WorldWideScience

Sample records for fluorite

  1. Coloring of synthetic fluorite

    International Nuclear Information System (INIS)

    Birsoy, R.

    1980-01-01

    A synthetic fluorite of the Harshaw Chemical Company is analyzed for rare earth elements, yttrium, and sodium. Samples of this fluorite are irradiated with X-rays, γ-rays, neutrons, electrons, protons, and α-particles at different energies, and their absorption spectra are analyzed. Analyzing the thermal bleaching of these radiation-coloured fluorites shows that both, impurities and radiation play a part in the coloration of synthetic fluorite. However, the main contribution comes from the radiation induced lattice defects. In the visible region spectra, the colour centre of the 5800 to 5900 A absorption band is probably mainly related with large aggregates of F-centres. The 5450 and the 5300 A absorption bands are mainly related to monovalent and divalent ion impurities and their association with lattice defects. The 3800 A absorption band seems to be related with F-centre aggregates. However, the contribution from the rare earth elements related complex color centres also plays some part for the production of this absorption band. These results indicate that the color centres of different origin can absorb light at the same wavelength. (author)

  2. Thermoluminescence in fluorite: sensitization mechanism

    International Nuclear Information System (INIS)

    Cruz, M.T. da; Watanabe, S.; Mayhugh, M.R.

    1974-01-01

    The sensitization of the major glow peaks (approximately to 100 and 200 0 C) in fluorite correlates with population of traps causing higher temperature glow peaks. When considered with supralinearity results, it is concluded that either the sensitization results from an increase in trap-filling efficiencies, or the deeper traps are not filled during irradiation

  3. Thermoluminescence in fluorite: sensitization mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Cruz, M.T. da; Watanabe, S; Mayhugh, M R

    1974-11-01

    The sensitization of the major glow peaks (approximately to 100 and 200/sup 0/ C) in fluorite correlates with population of traps causing higher temperature glow peaks. When considered with supralinearity results, it is concluded that either the sensitization results from an increase in trap-filling efficiencies, or the deeper traps are not filled during irradiation.

  4. Selective adsorption of benzhydroxamic acid on fluorite rendering selective separation of fluorite/calcite

    Science.gov (United States)

    Jiang, Wei; Gao, Zhiyong; Khoso, Sultan Ahmed; Gao, Jiande; Sun, Wei; Pu, Wei; Hu, Yuehua

    2018-03-01

    Fluorite, a chief source of fluorine in the nature, usually coexists with calcite mineral in ore deposits. Worldwide, flotation techniques with a selective collector and/or a selective depressant are commonly preferred for the separation of fluorite from calcite. In the present study, an attempt was made to use benzhydroxamic acid (BHA) as a collector for the selective separation of fluorite from calcite without using any depressant. Results obtained from the flotation experiments for single mineral and mixed binary minerals revealed that the BHA has a good selective collecting ability for the fluorite when 50 mg/L of BHA was used at pH of 9. The results from the zeta potential and X-ray photoelectron spectroscopy (XPS) indicated that the BHA easily chemisorbs onto the fluorite as compared to calcite. Crystal chemistry calculations showed the larger Ca density and the higher Ca activity on fluorite surface mainly account for the selective adsorption of BHA on fluorite, leading to the selective separation of fluorite from calcite. Moreover, a stronger hydrogen bonding with BHA and the weaker electrostatic repulsion with BHA- also contribute to the stronger interaction of BHA species with fluorite surface.

  5. Elements-admixtures of fluorite. Research technique

    International Nuclear Information System (INIS)

    Fayziev, A.R.

    2002-01-01

    Present article is devoted to elements-admixtures of fluorite and research techniques used. As a material for researches the mono mineral samples of fluorite of various geologic deposits and ores were used. The determination of sodium and potassium was conducted by means of flame photometry. Strontium, uranium, thorium, lead and rubidium were determined by means of quantitative X-ray spectroscopic analysis. The barium analysis was conducted by means of quantitative method. The manganese analysis was conducted by means of electron paramagnetic resonance.

  6. Elasticity of fluorite at high temperatures

    Science.gov (United States)

    Eke, J.; Tennakoon, S.; Mookherjee, M.

    2017-12-01

    Fluorite (CaF2) is a simple halide with cubic space group symmetry (Fm-3m) and is often used as an internal pressure calibrant in moderate high-pressure/high-temperature experiments [1]. In order to gain insight into the elastic behavior of fluorite, we have conducted Resonant Ultrasound Spectroscopy (RUS) on a single crystal of fluorite with rectangular parallelepiped geometry. Using single crystal X-ray diffraction, we aligned the edges of the rectangular parallelepiped with [-1 1 1], [-1 1 -2], and [-1 -1 0] crystallographic directions. We conducted the RUS measurements up to 620 K. RUS spectra are influenced by the geometry, density, and the full elastic moduli tensor of the material. In our high-temperature RUS experiments, the geometry and density were constrained using thermal expansion from previous studies [2]. We determined the elasticity by minimizing the difference between observed resonance and calculated Eigen frequency using Rayleigh-Ritz method [3]. We found that at room temperature, the single crystal elastic moduli for fluorite are 170, 49, and 33 GPa for C11, C12, and C44 respectively. At room temperatures, the aggregate bulk modulus (K) is 90 GPa and the shear modulus (G) is 43 GPa. We note that the elastic moduli and sound wave velocities decrease linearly as a function of temperature with dVP /dT and dVS /dT being -9.6 ×10-4 and -5.0 ×10-4 km/s/K respectively. Our high-temperature RUS results are in good agreement with previous studies on fluorite using both Ultrasonic methods and Brillouin scattering [4,5]. Acknowledgement: This study is supported by US NSF awards EAR-1639552 and EAR-1634422. References: [1] Speziale, S., Duffy, T. S. 2002, Phys. Chem. Miner., 29, 465-472; [2] Roberts, R. B., White, G. K., 1986, J. Phys. C: Solid State Phys., 19, 7167-7172. [3] Migliori, A., Maynard, J. D., 2005, Rev. Sci. Instrum., 76, 121301. [4] Catlow, C. R. A., Comins, J. D., Germano, F. A., Harley, R. T., Hayes, W., 1978, J. Phys. C Solid State Phys

  7. Conclusion - Admixture elements as indicators of fluorite genesis

    International Nuclear Information System (INIS)

    Fayziev, A.R.

    2002-01-01

    The information obtained during scientific researches was generalized and analyzed. It was defined that studying of qualitative composition and quantitative content revealed the geochemical features of fluorite.

  8. The use of natural fluorite as a dosemeter

    International Nuclear Information System (INIS)

    Mafra Neto, F.

    1980-01-01

    The possibility of the use of natural fluorite as a dosimeter for X and gama radiations was studied. Its main characteristics such as sensitivity, linearity, fading, standard-deviation, energy dependency, and so on were examined. By the experimental tests, made in the medical area of radiotherapy, we state fluorite as an excellent dosimeter. (Author) [pt

  9. Lattice shear distortions in fluorite structure oxides

    International Nuclear Information System (INIS)

    Faber, J. Jr.; Mueller, M.H.; Hitterman, R.L.

    1979-01-01

    Crystallographic shear distortions have been observed in fluorite structure, single crystals of UO 2 and Zr(Ca)O 2 /sub-x/ by neutron-diffraction techniques. These distortions localize on the oxygen sublattice and do not require the presence of an external strain. The internal rearrangement mode in UO 2 is a transverse, zone boundary q vector = 2π/a (0.5, 0.0) deformation with amplitude 0.014 A. In Zr(Ca)O/sub 2-x/, the mode is a longitudinal, q vector = 2-/a (0,0,0.5) deformation with amplitude 0.23 A. Cation-anion elastic interactions dominate in selecting the nature of the internal distortion

  10. Geo economical studies of Mina Florencia (Fluorite)

    International Nuclear Information System (INIS)

    Gomez Rifas, C.; Mari, C.; Theune, C.; Bosse, R.

    1982-01-01

    This report describes the works of Prospecting of Fluorite in Mina Florencia, in Maldonado Province. The project began in January of 1981, with the elaboration of a regional geologic cartography scale 1/20.000 of an area of 90,85 kilometers and cartography detailed scale 1/5.000 of the immediate area to Mina Florencia (6 kilometer that demonstrated the existence other veins of similar characteristic of the mine in exploration. Later on they were carried out geophysical studies (resistividad and electromagnetism, under the direction of the geophysical Fritz R. Haut of the BGR). The main geophysical anomalies inside the mining concession was studied by mechanical well, which results were showed in this report.

  11. Selective Flotation of Calcite from Fluorite: A Novel Reagent Schedule

    Directory of Open Access Journals (Sweden)

    Zhiyong Gao

    2016-10-01

    Full Text Available Fluorite is an important strategic mineral. In general, fluorite ores will contain a certain amount of calcite gangue mineral. Thus, they need to be separated from each other. For an economic separation, a reverse flotation process is used to float calcite gangue from fluorite. However, little information on the separation is available. In this study, a novel reagent schedule using citric acid (CA as the depressant, sodium fluoride (NaF as the regulator and sulfoleic acid (SOA as the collector, was developed to separate calcite from fluorite. The results demonstrated a high selectivity for the flotation of calcite from fluorite using this new reagent schedule. The best selective separation for a single mineral and mixed binary minerals was obtained when 200 mg/L of NaF, 50 mg/L of CA, and 6 mg/L of SOA were used at pH 9. In addition, a batch flotation experiment was carried out using a run-of-mine feed material. Selective separation was achieved with 85.18% calcite removal while only 11.2% of fluorite was lost. An attempt was made to understand the effect of the new reagent schedule on the flotation of calcite. The results from both microflotation and bench scale flotation demonstrated a great potential for industrial application using this novel reagent schedule to upgrade fluorite ore.

  12. Configurational Model for Conductivity of Stabilized Fluorite Structure Oxides

    DEFF Research Database (Denmark)

    Poulsen, Finn Willy

    1981-01-01

    The formalism developed here furnishes means by which ionic configurations, solid solution limits, and conductivity mechanisms in doped fluorite structures can be described. The present model differs markedly from previous models but reproduces qualitatively reality. The analysis reported...

  13. Study of thermophysical and anharmonic properties of fluorite compounds

    International Nuclear Information System (INIS)

    Singh, R.K.; Pandey, N.K.

    1983-01-01

    An extensive study is made of thermophysical and anharmonic properties of fluorite compounds using an interionic potential, which consists of a long-range Coulomb and three-body interactions and the short-range overlap repulsion and van der Waals attraction. The agreement achieved between experimental and theoretical results on third-order elastic constants and pressure derivatives of second order elastic constants are generally better than those obtained by others. This potential succeeds in predicting various thermophysical properties, like compressibility and its pressure and temperature derivatives, thermal expansion and Grueneisen parameters of seven crystals of fluorite structure. (author)

  14. Optical storage media based on fluorite activated crystals

    International Nuclear Information System (INIS)

    Mokienko, I.Yu.; Poletimov, A.E.; Shcheulin, A.S.

    1991-01-01

    Earlier studied mechanisms of photo- and thermotransformations of defects in pure and activated additively coloured crystals with fluorite structure are considered to suggest several methods of reversible optical recording of images, characterized by high resistance to high-power laser radiation and mechanical deformation

  15. [Assessment of Soil Fluorine Pollution in Jinhua Fluorite Ore Areas].

    Science.gov (United States)

    Ye, Qun-feng; Zhou, Xiao-ling

    2015-07-01

    The contents of. soil total fluorine (TF) and water-soluble fluorine (WF) were measured in fluorite ore areas located in Jinhua City. The single factor index, geoaccumulation index and health risk assessment were used to evaluate fluorine pollution in soil in four fluorite ore areas and one non-ore area, respectively. The results showed that the TF contents in soils were 28. 36-56 052. 39 mg.kg-1 with an arithmetic mean value of 8 325.90 mg.kg-1, a geometric mean of 1 555. 94 mg.kg-1, and a median of 812. 98 mg.kg-1. The variation coefficient of TF was 172. 07% . The soil WF contents ranged from 0. 83 to 74. 63 mg.kg-1 with an arithmetic mean value of 16. 94 mg.kg-1, a geometric mean of 10. 59 mg.kg-1, and a median of 10. 17 mg.kg-1. The variation coefficient of WF was 100. 10%. The soil TF and WF contents were far higher than the national average level of the local fluorine epidemic occurrence area. The fluoride pollution in soil was significantly affected by human factors. Soil fluorine pollution in Yangjia, Lengshuikeng and Huajie fluorite ore areas was the most serious, followed by Daren fluorite ore area, and in non-ore area there was almost no fluorine pollution. Oral ingestion of soils was the main exposure route. Sensitivity analysis of model parameters showed that children's weight exerted the largest influence over hazard quotient. Furthermore, a significant positive correlation was found among the three kinds of evaluation methods.

  16. (100) faceted anion voids in electron irradiated fluorite

    International Nuclear Information System (INIS)

    Johnson, E.

    1979-01-01

    High fluence electron irradiation of fluorite crystals in the temperature range 150 to 320 K results in formation of a simple cubic anion void superlattice. Above 320 K the damage structure changes to a random distribution of large [001] faceted anion voids. This voidage behaviour, similar to that observed in a range of irradiated metals, is discussed in terms points defect rather than conventional colour centre terminology. (Auth.)

  17. Size of oxide vacancies in fluorite and perovskite structured oxides

    DEFF Research Database (Denmark)

    Chatzichristodoulou, Christodoulos; Norby, Poul; Hendriksen, Peter Vang

    2015-01-01

    An analysis of the effective radii of vacancies and the stoichiometric expansion coefficient is performed on metal oxides with fluorite and perovskite structures. Using the hard sphere model with Shannon ion radii we find that the effective radius of the oxide vacancy in fluorites increases...... with increasing ion radius of the host cation and that it is significantly smaller than the radius of the oxide ion in all cases, from 37% smaller for HfO2 to 13 % smaller for ThO2. The perovskite structured LaGaO3 doped with Sr or Mg or both is analyzed in some detail. The results show that the effective radius...... of an oxide vacancy in doped LaGaO3 is only about 6 % smaller than the oxide ion. In spite of this the stoichiometric expansion coefficient (a kind of chemical expansion coefficient) of the similar perovskite, LaCrO3, is significantly smaller than the stoichiometric expansion coefficient of the fluorite...

  18. Application of mathematical statistics methods to study fluorite deposits

    International Nuclear Information System (INIS)

    Chermeninov, V.B.

    1980-01-01

    Considered are the applicability of mathematical-statistical methods for the increase of reliability of sampling and geological tasks (study of regularities of ore formation). Compared is the reliability of core sampling (regarding the selective abrasion of fluorite) and neutron activation logging for fluorine. The core sampling data are characterized by higher dispersion than neutron activation logging results (mean value of variation coefficients are 75% and 56% respectively). However the hypothesis of the equality of average two sampling is confirmed; this fact testifies to the absence of considerable variability of ore bodies

  19. Importance of surface structure on dissolution of fluorite

    DEFF Research Database (Denmark)

    Godinho, Jose; Piazolo, Sandra; Balic Zunic, Tonci

    2014-01-01

    forming the initial surface and its inclination to the closest stable planes, which are specific for each surface orientation. During an initial dissolution regime dissolution rates decrease significantly, even though the total surface area increases. During a second dissolution regime, some surfaces...... by the relative stability of the planes and type of edges that constitute a surface needs to be considered. Significant differences between dissolution rates calculated based on surface area alone, and based on surface reactivity are expected for materials with the fluorite structure....

  20. Factors influencing the determination of fluorite by means of neutron activation analysis

    International Nuclear Information System (INIS)

    Lutze, H.

    1975-01-01

    Proceeding from the necessity of a rapid analysis of fluorite by neutron activation of an unprepared drill core the influence of interfering elements, of inhomogeneous fluorite distribution, of the sample volume and of moisture are examined. Recommendations are given to overcome these interferences. (author)

  1. Radiation stability of fluorite-type nuclear oxides

    Energy Technology Data Exchange (ETDEWEB)

    Garrido, Frederico [Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, CNRS-IN2P3-Universite Paris-Sud, Batiments 104-108, 91405 Orsay Campus (France)], E-mail: Frederico.Garrido@csnsm.in2p3.fr; Vincent, Laetitia [Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, CNRS-IN2P3-Universite Paris-Sud, Batiments 104-108, 91405 Orsay Campus (France); Nowicki, Lech [Andrzej Soltan Institute for Nuclear Studies, Hoza 69, 00-681 Warsaw (Poland); Sattonnay, Gael [Laboratoire d' Etudes des Materiaux Hors-Equilibre, Institut de Chimie Moleculaire et des Materiaux d' Orsay, UMR 8182, Universite Paris-Sud, Batiment 410, 91405 Orsay Cedex (France); Thome, Lionel [Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, CNRS-IN2P3-Universite Paris-Sud, Batiments 104-108, 91405 Orsay Campus (France)

    2008-06-15

    Oxides with the fluorite-type structure are radiation tolerant materials. They are widely used or envisaged in hostile nuclear environments, such as nuclear fuels or inert transmutation matrices for actinide burning. Study of the radiation stability of this class of solids in various radiative fields is of major importance. Two issues which may affect the stability of materials are considered in this work: the production of radiation damage (ballistic contribution); the modification of the matrix composition by doping (chemical contribution). Both contributions may drastically affect the solid stability. Urania and zirconia single crystals were chosen as fluorite-type canonical systems. They were implanted with low-energy inert gases (He or Xe). The damage in-growth, due to both ballistic and chemical contributions, was investigated by in situ RBS/C experiments in the channelling mode and TEM. Two main steps in the disordering kinetics were observed for both inert gases. Relevant key parameters were found to be: the number of displaced lattice atoms created by the slowing-down of energetic ions during the implantation process; the concentration of noble gas atoms in the solid which cause the formation of large stress fields surrounding gas aggregates.

  2. High-pressure phase transformations of fluorite-type dioxides

    International Nuclear Information System (INIS)

    Lin-Gun Liu

    1980-01-01

    Phase transformations in six fluorite-type dioxides ('TbO 2 ', PbO 2 , 'PrO 2 ', CeO 2 , UO 2 and ThO 2 in the order of increasing cation size, where the quotation marks indicate non-stoichiometric materials) have been investigated in the diamond-anvil press coupled with laser heating. Together with earlier work, the results show that the post-fluorite phase transformations of these dioxides fall into two groups. The smaller cation group (HfO 2 , ZrO 2 and 'TbO 2 ') transforms to a cotunnite or a distorted cotunnite-type structure at pressures in the vicinity of 100 kbar and at about 1000 0 C. The larger cation group (from PbO 2 to ThO 2 ) is believed to transform to a different type of orthorhombic modification at high pressures. It is plausible that this high-pressure phase may possess a Ni 2 Si-related structure, as was observed in ThO 2 and 'PrO 2 ' at pressures greater than 150 and 200 kbar, respectively. (orig./ME)

  3. Evaluation of Sulfonate-Based Collectors with Different Hydrophobic Tails for Flotation of Fluorite

    Directory of Open Access Journals (Sweden)

    Renji Zheng

    2018-02-01

    Full Text Available This investigation aims to demonstrate the effects of hydrophobic tails on the affinity and relevant flotation response of sulfonate-based collectors for fluorite. For this purpose, a series of alkyl sulfonates with different hydrophobic tails, namely sodium decanesulfonate (C10, sodium dodecylsulfate (C12, sodium hexadecanesulfonate (C16, and sodium dodecylbenzenesulfonate (C12B were applied. The flotation tests showed that C12 and C12B had a better collecting performance than C10 and C16 at pH < 10, and the flotation recovery of fluorite was higher when adopting C12B as a collector compared with C12 with a strong base. The adsorption behaviors of collectors on the fluorite surface were studied through zeta potential, Fourier transform infrared (FTIR, and X-ray photoelectron spectroscopy (XPS analyses. It was found that the affinity of alkyl sulfonates for fluorite was enhanced with the increase of the alkyl chain length from C10 to C16. The existence of phenyl in the hydrophobic tail of sulfonates could improve its activity for fluorite by reducing its surface tension. The abnormal phenomenon C16 with a high affinity for fluorite had a low collecting performance for fluorite mainly due to its overlong alkyl chain, resulting in low solubility in pulp, which restrained its interaction with fluorite. We concluded that C12B was the most applicable collector for fluorite among these reagents due to its high activity, high solubility, and low cost, which was further substantiated by calculating their molecular frontier orbital energy.

  4. Application of X-ray technique to characterization of fluorite sample

    International Nuclear Information System (INIS)

    Cancado, R.Z.L.; Luz Ferreira, O. da.

    1986-01-01

    This investigation had the purpose of characterizing fluorite veins of ''Mineracao Sartor'', in Itaborai region/RJ, which is an excelent geographic position in relation to the consuming market. These studies have in view to give subsidy to future works to the best fluorite utilization. They realized tests with X-rays diffractometer and spectrometer, polarizing microscope and with a mounting of electric circuit to measure the type of semiconductivity. (C.M.C.T.R.) [pt

  5. Trace-element and Sr-Nd isotopic evidence for the origin of the Sardinian fluorite mineralization (Italy)

    International Nuclear Information System (INIS)

    Castorina, F.; Masi, U.; Padalino, G.; Palomba, M.

    2008-01-01

    The fluorite-bearing hydrothermal mineralization in Sardinia mainly occurs within Paleozoic volcanic and metasedimentary rocks. Only 3 occurrences are located in volcanic and siliciclastic Cenozoic rocks. Most Sardinian fluorites exhibit relatively high rare earth and Y (REY) contents, strong positive Y anomalies, slightly negative Ce and generally positive Eu anomalies. These features indicate that the REY were mobilized mainly from non-carbonate rocks. Neither Sr nor Nd isotopes can be used to date radiometrically the Sardinian fluorites. However, the measured Sr-isotope ratios of the fluorites hosted by Paleozoic rocks fit mixing lines in the 1000/Sr versus 87 Sr/ 86 Sr plot once recalculated at 280 Ma, suggesting that the age inferred for the correction probably represents that of the formation of the fluorite mineralization. Mixing likely occurred between diluted surficial waters and brines circulating mainly through the Lower Paleozoic metasedimentary basement. The Cenozoic fluorites exhibit chemical and isotopic features similar to those of the Paleozoic fluorites, except the Nuraghe Onigu fluorite displaying a possible contribution of Sr from Cenozoic magmatic rocks. The initial ε Nd values of the Paleozoic fluorites fit the age proposed for the formation of the deposits. Moreover, the values suggest that radiogenic Nd was provided to the fluids from the Ordovician siliciclastic basement, except for 3 deposits where the potential source rocks of Nd were mainly Ordovician acidic magmatic rocks. The initial ε Nd values of the Cenozoic fluorites suggest a provenance of Nd essentially from the leaching of Variscan granitoids

  6. Rare Earths in fluorite deposits of Elika Formation (East of Mazandaran Province

    Directory of Open Access Journals (Sweden)

    Zahra Mehraban

    2016-07-01

    Full Text Available Introduction The Central Alborz in eastern Mazandaran province is host to the most important carbonate-hosted fluorite deposits in Iran, such as Pachi-Miana, Sheshroodbar, Era and Kamarposht. In these deposits, mineralization occurs in the upper parts of the middle Triassic Elika formation (Vahabzadeh et al., 2009 and references therein. These deposits have long been studied, and various models are presented for ore genesis. Nevertheless, ore genesis in these deposits is still unclear. The present study of the geochemistry of the REEs of these deposits is intended to improve genetic models. Materials and methods Three hundred samples were taken from above mentioned deposits. Samples were categorized into 5 groups: (1 fluorite ore types, (2 ore-stage calcite, (3 carbonate host rocks, (4 basaltic rock around the deposits, and (5 shale of the Shemshak formation. Fourteen pure fluorite samples, 4 samples of pure calcite, 4 samples of carbonate host rock, 1 sample of basalt and 1 sample of shale were analyzed for REEs by ICP-MS at West Lab in Australia. Results Analytical data on fluorite from the Elika deposits show very low REE concentrations (0.5-18ppm, in calcite(0.5-3ppm in carbonate host rocks – limestone (1.8-7ppm, and in dolomitic limestone 6.5ppm, compared with upper Triassic basalt (43ppm and shale (261ppm. REE in fluorite of these deposits are strongly enriched (10 3 to 10 6 times relative to normal sea water, ore stage calcite and carbonate host rocks, especially for mid-REEs (Eu, Gd and heavy REEs (Lu, Yb, La/Yb=~0.05. Also, LREEs depletion (La/Sm= 2-10 and HREEs (La/Yb=0.01-0.08 relatively enrichment of fluorites compared with limestone (La/Sm=2.5-4, La/Yb=0.1-1.5 and dolomitic limestone (La/Sm=4.28, La/Yb=0.07-0.4 host rocks as well as positive Eu anomaly are the most important REEs signatures in fluorites. Fluorite elsewhere in the world with low total REE conten thas been interpreted to have a sedimentary origin (Ronchi et al

  7. Spectroscopic and computer modelling studies of mixed-cation superionic fluorites

    CSIR Research Space (South Africa)

    Netshisaulu, TT

    2005-10-19

    Full Text Available into the local environments of the Cd and Pb cations (as a function of composition and temperature) in CdF2 (xPbF(2)) mixed-cation superionic fluorites. A high degree of disorder is shown around both cations. However, the extent of disorder is even larger around...

  8. Naturally irradiated fluorite as a historic violet pigment: Raman spectroscopic and X-ray diffraction study

    Czech Academy of Sciences Publication Activity Database

    Čermáková, Zdeňka; Bezdička, Petr; Němec, I.; Hradilová, J.; Šrein, V.; Blažek, Jan; Hradil, David

    2015-01-01

    Roč. 46, č. 2 (2015), s. 236-243 ISSN 0377-0486 R&D Projects: GA ČR GAP103/12/2211 Institutional support: RVO:61388980 ; RVO:67985556 Keywords : fluorite * pigment * fluorescence bands * diffraction lines broadening * irradiation Subject RIV: CA - Inorganic Chemistry Impact factor: 2.395, year: 2015

  9. Investigation of thermally induced anion disorder in fluorites using neutron scattering techniques

    DEFF Research Database (Denmark)

    Hutchings, M T; Clausen, Kurt Nørgaard; Dickens, M H

    1984-01-01

    Some materials with the fluorite structures show a pronounced specific heat anomaly well below their melting temperature. This anomaly is a consequence of lattice disorder and is associated with the onset of fast-ion conduction. This paper presents the results of a series of experiments in which...

  10. Intricate disorder in defect fluorite/pyrochlore: a concord of chemistry and crystallography

    Czech Academy of Sciences Publication Activity Database

    Simeone, D.; Thorogood, G.J.; Huo, D.; Luneville, L.; Baldinozzi, G.; Petříček, Václav; Porcher, F.; Ribis, J.; Mazerolles, L.; Largeau, L.; Berar, J.F.; Surble, S.

    2017-01-01

    Roč. 7, Jun (2017), 1-7, č. článku 3727. ISSN 2045-2322 Institutional support: RVO:68378271 Keywords : disorder * atomic scale * metallic allys * oxides * fluorite/pyrochlore Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 4.259, year: 2016

  11. High-pressure U3O8 with the fluorite-type structure

    International Nuclear Information System (INIS)

    Zhang, F.X.; Lang, M.; Wang, J.W.; Li, W.X.; Sun, K.; Prakapenka, V.; Ewing, R.C.

    2014-01-01

    A new high-pressure phase of U 3 O 8 , which has a fluorite-type structure, forms at pressures greater than ∼8.1 GPa that was confirmed by in situ x-ray diffraction (XRD) measurements. The fluorite-type U 3 O 8 is stable at pressures at least up to ∼40 GPa and temperatures to 1700 K, and quenchable to ambient conditions. Based on the XRD analysis, there is a huge volume collapse (>20%) for U 3 O 8 during the phase transition and the quenched high-pressure phase is 28% denser than the initial orthorhombic phase at ambient conditions. The high-pressure phase has a very low compressibility comparing with the starting orthorhombic phase. - Graphical abstract: α-U 3 O 8 is in a layered structure with orthorhombic symmetry, at high pressures, it transformed to a fluorite-type cubic structure. There are a lot of defects in the cubic structure, and it is a new kind of hyperstoichiometric uranium oxide, which is stable at ambient conditions. - Highlights: • A new fluorite-type high-pressure phase was found in hyperstoichometric UO 2 +x (x∼0.8). • The new high-pressure structure is quenchable to ambient conditions. • Pressure driven phase transition in orthorhombic U 3 O 8 was first found

  12. Fluid Evolution During Mineralization of Atashkuh Fluorite-Barite (±Sulfide Deposit, South of Delijan

    Directory of Open Access Journals (Sweden)

    Seyed Javad Moghaddasi

    2016-07-01

    Full Text Available Introduction More than 30 fluorite occurrences with approximately 1.35 million tons of reserves have been recognized in Iran (Ghorbani, 2013. The Atashkuh fluorite-barite (±sulfide deposit is one of four occurrences located south of the city of Delijan in Markazi province, about 80 km SE of Arak city. The Atashkuh deposit occurs between the central Iran structural zone on the north and the Sanandaj-Sirjan structural zone on the south. The geology of the area is dominated by folded and faulted Jurassic carbonates and shales (Thiele et al., 1968. The lower Jurassic shale and calcareous sandstone of the Shemshak Formation and the Middle to Upper Jurassic dolomite of the Badamu Formation are the main host rocks for the fluorite veins. In this study, 40 samples from fluorite veins and host rocks were collected, from which 25 thin sections and 8 doubly-polished thin sections were prepared. Micro-thermometric studies were conducted on primary fluid inclusions using the Linkam THM600 heating-freezing stage. In addition, 10 samples were analyzed by XRD. Results Fluid inclusion data indicate that the Atashkuh fluorite-barite (±sulfides veins were deposited as a result of mixing a primary multi-component Na-K(-Mg-Ca high-salinity brine (SH type inclusions with less saline calcium-rich connate water (LVHH type inclusions and pressure reduction of ore bearing fluids. Fluid inclusions containing halite in high-salinity brine, and hydrohalite in connate water show suggest a high-salinity brine and connate water before mixing. The main mineralization stage was followed by circulation of low temperature meteoric water, responsible for the late stage mineralization. The micro-thermometry results suggest that the main fluorite mineralization occurred at 250 °C and 150 Mpa pressure. Dolomitization and silicification are the main alteration types associated with the Atashkuh mineralization. The occurrence of chlorite, talc, illite and dolomitized host rock all

  13. The orthorhombic fluorite related compounds Ln/sub 3/RuO/sub 7/, Ln=Nd, Sm and Eu

    International Nuclear Information System (INIS)

    Van Berkel, F.P.F.; Ijdo, D.J.W.

    1986-01-01

    Fluorite-related Ru(V) compound with composition Ln/sub 3/RuO/sub 7/ have been found. These compounds with space group Cmcm adopt a superstructure of the cubic fluorite structure with a/sub orth/=2a/sub c/, b/sub orth/=c/sub orth/=a/sub c/√2. These compounds have the same structure as La/sub 3/NbO/sub 7/

  14. Measurements of CaF2 concentration in fluorite ore using thermoluminescence techniques

    International Nuclear Information System (INIS)

    Lembo, L.; Maestri, G.; Pimpinella, M.; Benzi, V.; Muntoni, C.

    1990-01-01

    Fluorite powder is produced by means of a flotation process on crude ore extracted by the mines. A full automation of the flotation plant would reduce the operating cost and improve the quality and recovery of fluorite production. However, taking into account that the efficiency of a flotation cycle is directly dependent on the CaF 2 content in the concentrate and tail products, this automation requires a quasi-real-time quantitative analysis of CaF 2 concentration in the floated pulp. The feasibility was studied of using a thermoluminescence technique as an on-line analysis method to measure the CaF 2 concentration during the flotation cycle. A first set of experimental conditions to determine CaF 2 content in acid-grade fluorspar has been already developed and the preliminary results so far obtained are presented. (author)

  15. Direct reading spectrochemical determination of aluminium, iron and silicon in fluorite

    International Nuclear Information System (INIS)

    Roca, M.

    1966-01-01

    A quantitative spectrochemical method for the determination of Al, Fe and Si in fluorite has been worked out. The sample was supported in a graphite electrode with crater of 5 mm. in diameter, 2,5 mm deep, and burned by a d.c. are in a direct reading spectrometer. The excitation of samples has been studied without dilution as well as using graphite powder as diluent in the ratios 1:1, 1:4, and 1:9; the latter factor was chosen. Ag, Ca, Co, Cr, Mo and Sn were tested as internal standards. It has not been found any significant inter element effect. It is necessary to use natural fluorite as base material for the standards. (Author) 5 refs

  16. Factors controlling the oxide ion conductivity of fluorite and perovskite structured oxides

    DEFF Research Database (Denmark)

    Mogensen, Mogens Bjerg; Lybye, D.; Bonanos, N.

    2004-01-01

    Many metal oxides of fluorite and perovskite related structures are oxide ion conductors, which have practical applications in devices such as oxygen sensors, solid oxide fuel cells (SOFC) and electrolysers. Several structural and thermodynamic parameters such as (1) critical radius of the pathway...... such parameters for fluorite and perovskite oxides by considering their sensitivities to the individual ionic radii. Based on experimental data available in the literature, it is argued that lattice distortion (lattice stress and deviation from cubic symmetry) due to ion radii mismatch determines the ionic...... conductivity to a very large extent, and that lattice distortion is of much greater importance than many other proposed parameters. In case of the perovskites, the charge of the B-site ion is also of major importance. (C) 2004 Published by Elsevier B.V....

  17. Solid thermoluminescent dosemeter of sodium tetraborate and brazilian fluorite sensible to thermal neutrons

    International Nuclear Information System (INIS)

    Fratin, L.; Cruz, M.T. da

    1987-01-01

    A solid termoluminescent dosemeter of sodium tetraborate and brazilian fluorite sensible to thermal neutrons is described. The nuclears reactions 1) 10 B + n → 7 Li + He + Q1 (6,1%) where: Q1=2,79 MeV and Eα1 = 1,758 MeV and 2) 10 B + n → 7 Li* + 4 He + Q2 (93,9%) where: Q2 = 2,316 MeV and E2α 2 = 1,474 MeV are responsible by the thermoluminescent response of the thermal neutrons dosemeters. The stages in the fabrication process of this dosemeter of which are:1) sodium tetraborate vitrification, 2) mixture and pressing 3) sintering are cited. The obtainment of a natural fluorite dosemeter with sodium chloride is also shown. (C.G.C.) [pt

  18. Effect of natural irradiation in fluorites: possible implications for nuclear waste management?

    Czech Academy of Sciences Publication Activity Database

    Vlček, V.; Skála, Roman; Goliáš, V.; Drahokoupil, Jan; Čížek, J.; Strnad, L.; Ederová, J.

    2012-01-01

    Roč. 57, č. 1 (2012), s. 45-52 ISSN 1802-6222 R&D Projects: GA ČR GA106/07/0805; GA AV ČR KAN300100801 Institutional research plan: CEZ:AV0Z30130516 Keywords : fluorite * irradiation * X-ray diffraction * differential scanning calorimetry * defects * real structure Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.804, year: 2012

  19. Kinetic characterization of the first peak of natural fluorite from low ...

    African Journals Online (AJOL)

    Fluorite samples were irradiated with a low dose-rate (40 μGys-1 ) β- irradiation source to a test dose of 1.2 mGy and the heating rates of β = 1,3 and 5o Cs were considered, in order to minimize the effect of temperature lag. The role of thermal quenching (W) was investigated by evaluating the activation energy using the ...

  20. Coagulation of fines in fluorite froth flotation; Coagulacion de finos en la flotacion de la fluorita

    Energy Technology Data Exchange (ETDEWEB)

    Sarquis, P. E.; Gonzalez, M.; Moyano, A.; Bazan, V.

    2011-07-01

    Fluorite, a valuable mineral in the metallurgical industry, can be found together with silicates, carbonates and oxides in ore deposits. Commercial concentrates with more than 95 % of CaF{sub 2} are obtained processing the mineral in flotation plants and using oleic acid as fluorite collector. Depressor reagents such as sodium silicate, tannin and sodium carbonate are commonly employed to allow the oleic acid selective performance. These reagents cause a dispersant effect separating the solid-liquid solution on tailing plants. Fine particles in the recovered water enter the circuit and affect the flotation efficiency. The effect of coagulant ions was studied as a method to clarify the returned water. The problem of the presence of these ions is related to its reactions with the collector by the formation of compounds and possibly on the selectivity. Variable quantities of Al{sup 3}+, Fe{sup 3}+ and Ca{sup 2}+ ions were added to the flotation to evaluate its effect on the fluorite recovery, in the selectivity and in solids content in recirculation water. Results show that some ions fail to improve water quality and are detrimental to flotation. On the contrary, some ions contribute to reduce fine content in suspension. Therefore, although there is a recovery reduction, such effect can be counteracted increasing the collector consumption a little. (Author) 21 refs.

  1. Selective Separation of Fluorite, Barite and Calcite with Valonea Extract and Sodium Fluosilicate as Depressants

    Directory of Open Access Journals (Sweden)

    Zijie Ren

    2017-02-01

    Full Text Available Fluorite, barite and calcite are important industry minerals. However, they often co-exist, presenting difficulty in selectively separating them due to their similar surface properties. In this study, valonea extract and sodium fluosilicate were used as depressants to selectively separate them by flotation, with sodium oleate as the collector. The single mineral flotation results showed that valonea extract displayed the strongest depression on calcite, while sodium fluosilicate displayed the strongest depression on barite. These two depressants allowed selective separation of the three minerals through sequential flotation. The flotation of mixed minerals showed that 94% of the calcite was successfully depressed by the valonea extract, and 95% recovery of the fluorite was achieved in the subsequent flotation with sodium fluosilicate depressing barite. The different depressant–mineral interactions were investigated via electro-kinetic studies and molecular dynamics (MD simulations using the Materials Studio 6.0 program. The valonea extract exhibited the strongest adsorption on the calcite surface, and sodium fluosilicate exhibited the strongest adsorption on the barite surface, which prevented oleate species from reacting with Ca2+ or Ba2+ surface sites. This study provides useful guidance for how to process fluorite, barite and calcite resources.

  2. The reasons for the color green fluorite Mehmandooye cover using UV spectroscopy and XRF results

    Science.gov (United States)

    Pirzadeh, Sara; Zahiri, Reza

    2016-04-01

    Fluorite mineral or fluorine with chemical formula CaF2 is most important mineralfluor in nature. This mineral crystallization to colors yellow, green, pink, blue, purple, colorless and sometimes black andin cubic system crystallized.assemi transparent and glass with polished.fluoritethe purity include 48/9% fluoreand 51/9% calcium. How the creation colors in minerals different greatly indebted to Kurt Nassau research from Bell Labs, Murray Hill, New Jersey.almostall the mechanisms that cause color in minerals, are the result of the interaction of light waves with the electrons The main factors affecting the color generation include the following: 1)the presence of a constructive element inherent (essential ingredient mineral composition) 2)The presence of a minor impurities (such a element as involved in latticesolid solution) 3) appearancedefects in the crystal structure 4) There are some physical boundaries with distances very small and delicate, like blades out of the solution (which may be the play of colors or Chatvyansy) 5) Mixing mechanical impurities dispersed in a host mineral Based on the results of the analysis, XRF and UV spectrum and also based on the results of ICP, because the color green fluorite examined, the focus color (F_center) and also the presence of some elementsintermediate (such as Y (yttrium). [1] Bill, H., Calas, G. Color centres associated rare earth ions and the origin of coloration in natural fluorites// PhysChem Min, (1978), v 3, pp. 117-131.

  3. The fluorite-pyrochlore transformation of Ho2-yNdyZr2O7

    International Nuclear Information System (INIS)

    Clements, Richard; Hester, James R.; Kennedy, Brendan J.; Ling, Chris D.; Stampfl, Anton P.J.

    2011-01-01

    Twelve members of the Ho 2-y Nd y Zr 2 O 7 series, prepared using conventional solid state methods, have been characterised by neutron powder diffraction. Ho 2 Zr 2 O 7 has a defect fluorite structure whereas Nd 2 Zr 2 O 7 is found to adopt the ordered pyrochlore structure with the composition induced fluorite-pyrochlore transformation occurring near y=1. Rietveld analysis on the neutron data for all the compositions reveals an increase in lattice parameter as a function of y across the entire series, with a small discontinuity associated with the transformation. The neutron profile results suggest that domains of pyrochlore-type initially begin to form before crystallising into a separate phase, and therefore that anion and cation ordering processes are distinct. There is a strong correlation between the extent of disorder in the anion sublattice and the x-parameter of 48f oxygen. These results point the way to a better understanding of the stability observed in pyrochlore structures. - Graphical abstract: Neutron diffraction profiles for Nd 2-y Ho y Zr 2 O 7 type oxides reveal details of the transformation from the ordered pyrochlore structure (y=0) to the disordered fluorite structure (y=2). Highlights: → Structures of twelve members of the Ho 2-y Nd y Zr 2 O 7 series studied using neutron powder diffraction. → Domains of pyrochlore-type materials form at low doping levels. → Higher doping stabilises the pyrochlore. → Anion and cation ordering processes are distinct.

  4. Geochemical characterization of rare earth elements from fluorite deposits of Tangua district - RJ

    International Nuclear Information System (INIS)

    Coelho, C.E.S.; Dardenne, M.A.

    1987-01-01

    The Tangua fluorite vein-type deposits are related to an alkaline complex of the same name, and situated in the District of Itaborai, in the State of Rio de Janeiro. The plutonic body of nepheline syenites (Tangua Massif) intrudes basement gneisses, with dykes and sills of trachitic and phonolitic nature of hundreds of meters in length and centimeters to tens of meters in thickness. The fluorite veins are emplaced both in gneisses and alkaline rocks (plutonic body and dykes) in NE-ENE structures created or reactivated during the opening of the South Atlantic Ocean. The geochemical study of rare earth elements reveals that these mineralizations show very low contents in these elements, and a relatively high fractionation spectres. In the deposit environment, four mineralization phases were differenciated, with the first one being considered as the initial solution; the second one characterized by a new europium rich-solution; the third one, representing the evolution of this new solution, but in a reducing environment, with precipitation of pyrite; and the last one, representing a new batch of the initial solution. As a consequence of the REE's and fluid inclusions studies, we are able to suggest an origen by weathering of the country rocks due to superficial meteorics solutions along faults and fractures, that when heated in deep environments, promote lixiviation of silica and fluorine and precipitate the fluorites when their ascending movement comes to an end. (author) [pt

  5. A kinetic study of the replacement of calcite marble by fluorite

    Science.gov (United States)

    Trindade Pedrosa, Elisabete; Boeck, Lena; Putnis, Christine V.; Putnis, Andrew

    2016-04-01

    Replacement reactions are relevant in any situation that involves the reequilibration between a solid and an aqueous fluid phase and are commonly controlled by an interface-coupled dissolution-precipitation mechanism (Putnis and Putnis, 2007). These reactions control many large-scale Earth processes whenever aqueous fluids are available, such as during metamorphism, metasomatism, and weathering. An important consequence of coupled dissolution-precipitation is the generation of porosity in the product phase that then allows the infiltration of the fluid within the mineral being replaced. Understanding the mechanism and kinetics of the replacement of carbonates by fluorite has application in earth sciences and engineering. Fluorite (CaF2) occurs in all kinds of rocks (igneous, sedimentary, and metamorphic) and its origin is commonly associated with hydrothermal fluids. Moreover, calcium carbonate has been suggested as a successful seed material for the sequestration of fluoride from contaminated waters (Waghmare and Arfin, 2015). The aim of the present work is to investigate aspects of the replacement of calcium carbonate by fluorite to better understand the mechanism and kinetics of this reaction. Small cubes (˜ 3 × 3 × 3 mm) of Carrara marble (CaCO3 > 99 %) were cut and reacted with a 4 M ammonium fluoride (NH4F) solution for different times (1 to 48 hours) and temperatures (60, 80, 100, and 140 ° C). The microstructure of the product phases was analysed using SEM. The kinetics of replacement was monitored from the Rietveld analysis of X-ray powder diffraction patterns of the products as a function of temperature and reaction time. After reaction, all samples preserved their size and external morphology (a pseudomorphic replacement) and the product phase (fluorite) was highly porous. The activation energy Ea (kJ/mol) of the replacement reaction was empirically determined by both model-fitting and model-free methods. The isoconversional method yielded an

  6. Hydrothermal uranium deposits containing molybdenum and fluorite in the Marysvale volcanic field, west-central Utah

    Science.gov (United States)

    Cunningham, C.G.; Rasmussen, J.D.; Steven, T.A.; Rye, R.O.; Rowley, P.D.; Romberger, S.B.; Selverstone, J.

    1998-01-01

    Uranium deposits containing molybdenum and fluorite occur in the Central Mining Area, near Marysvale, Utah, and formed in an epithermal vein system that is part of a volcanic/hypabyssal complex. They represent a known, but uncommon, type of deposit; relative to other commonly described volcanic-related uranium deposits, they are young, well-exposed and well-documented. Hydrothermal uranium-bearing quartz and fluorite veins are exposed over a 300 m vertical range in the mines. Molybdenum, as jordisite (amorphous MoS2, together with fluorite and pyrite, increase with depth, and uranium decreases with depth. The veins cut 23-Ma quartz monzonite, 20-Ma granite, and 19-Ma rhyolite ash-flow tuff. The veins formed at 19-18 Ma in a 1 km2 area, above a cupola of a composite, recurrent, magma chamber at least 24 ?? 5 km across that fed a sequence of 21- to 14-Ma hypabyssal granitic stocks, rhyolite lava flows, ash-flow tuffs, and volcanic domes. Formation of the Central Mining Area began when the intrusion of a rhyolite stock, and related molybdenite-bearing, uranium-rich, glassy rhyolite dikes, lifted the fractured roof above the stock. A breccia pipe formed and relieved magmatic pressures, and as blocks of the fractured roof began to settle back in place, flat-lying, concave-downward, 'pull-apart' fractures were formed. Uranium-bearing, quartz and fluorite veins were deposited by a shallow hydrothermal system in the disarticulated carapace. The veins, which filled open spaces along the high-angle fault zones and flat-lying fractures, were deposited within 115 m of the ground surface above the concealed rhyolite stock. Hydrothermal fluids with temperatures near 200??C, ??18OH2O ~ -1.5, ?? -1.5, ??DH2O ~ -130, log fO2 about -47 to -50, and pH about 6 to 7, permeated the fractured rocks; these fluids were rich in fluorine, molybdenum, potassium, and hydrogen sulfide, and contained uranium as fluoride complexes. The hydrothermal fluids reacted with the wallrock resulting in

  7. Surface modelling on heavy atom crystalline compounds: HfO2 and UO2 fluorite structures

    International Nuclear Information System (INIS)

    Evarestov, Robert; Bandura, Andrei; Blokhin, Eugeny

    2009-01-01

    The study of the bulk and surface properties of cubic (fluorite structure) HfO 2 and UO 2 was performed using the hybrid Hartree-Fock density functional theory linear combination of atomic orbitals simulations via the CRYSTAL06 computer code. The Stuttgart small-core pseudopotentials and corresponding basis sets were used for the core-valence interactions. The influence of relativistic effects on the structure and properties of the systems was studied. It was found that surface properties of Mott-Hubbard dielectric UO 2 differ from those found for other metal oxides with the closed-shell configuration of d-electrons

  8. Thermodynamic determination of fluorite phases of the ULnO4 type

    International Nuclear Information System (INIS)

    Paula, H.C.B.

    1981-12-01

    A method for the determination of structure and thermodynamical stability of fluorite phases of the ULnO 4 type is presented. Through the use of a solid body galvanic chain with CaO-doped ZrO 2 working as an oxygen ion conductor solid electrolyte, phase transformation temperatures are determined, as well as solubility enthalpies and entropies for ULnO 4 systems (Ln= Sm, Tb, Er, Ho, Tm, YB). X-ray analyses confirmed the electrochemical measurements. The emf measurement system is checked by using binary oxides with known composition and oxygen partial pressure. A comparison between stabilities of analysed compounds is also presented. (Author) [pt

  9. Ab-initio calculation for cation vacancy formation energy in anti-fluorite structure

    Science.gov (United States)

    Saleel, V. P. Saleel Ahammad; Chitra, D.; Veluraja, K.; Eithiraj, R. D.

    2018-04-01

    Lithium oxide (Li2O) has been suggested as a suitable breeder blanket material for fusion reactors. Li+ vacancies are created by neutron irradiation, forming bulk defect complex whose extra character is experimentally unclear. We present a theoretical study of Li2O using density functional theory (DFT) with a plane-wave basis set. The generalized gradient approximation (GGA) and local-density approximation (LDA) were used for exchange and correlation. Here we address the total energy for defect free, cation defect, cation vacancy and vacancy formation energy in Li2O crystal in anti-fluorite structure.

  10. Effect of electronegativity on the mechanical properties of metal hydrides with a fluorite structure

    International Nuclear Information System (INIS)

    Ito, Masato; Setoyama, Daigo; Matsunaga, Junji; Muta, Hiroaki; Kurosaki, Ken; Uno, Masayoshi; Yamanaka, Shinsuke

    2006-01-01

    Bulk titanium, yttrium, and zirconium hydrides, which have the same structure as that of fluorite-type fcc C 1, were produced and their mechanical properties were investigated. With an increase in the hydrogen content, the lattice parameters of titanium and zirconium hydrides increased, whereas those of yttrium hydride decreased. The elastic moduli of titanium and zirconium hydrides decreased by hydrogen addition, whereas those of yttrium hydride increased. There are linear relations between the electronegativities and hydrogen content dependence of the properties. Therefore, the mechanical properties of the metal hydrides are considered to be determined by a common rule based on the electronegativity

  11. Transmission electron microscopic study of pyrochlore to defect-fluorite transition in rare-earth pyrohafnates

    Energy Technology Data Exchange (ETDEWEB)

    Karthik, Chinnathambi, E-mail: Karthikchinnathambi@boisestate.edu [Department of Materials Science and Engineering, Boise State University, 1910 University drive, Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd, Idaho Falls, ID 83415 (United States); Anderson, Thomas J. [Department of Materials Science and Engineering, Boise State University, 1910 University drive, Boise, ID 83725 (United States); Gout, Delphine [Oak Ridge National Lab, Neutron Scattering Science Division, Oak Ridge, TN (United States); Ubic, Rick [Department of Materials Science and Engineering, Boise State University, 1910 University drive, Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd, Idaho Falls, ID 83415 (United States)

    2012-10-15

    A structural transition in rare earth pyrohafnates, Ln{sub 2}Hf{sub 2}O{sub 7} (Ln=Y, La, Pr, Nd, Tb, Dy, Yb and Lu), has been identified. Neutron diffraction showed that the structure transforms from well-ordered pyrochloric to fully fluoritic through the lanthanide series from La to Lu with a corresponding increase in the position parameter x of the 48f (Fd3{sup Macron }m) oxygen site from 0.330 to 0.375. As evidenced by the selected area electron diffraction, La{sub 2}Hf{sub 2}O{sub 7}, Pr{sub 2}Hf{sub 2}O{sub 7} and Nd{sub 2}Hf{sub 2}O{sub 7} exhibited a well-ordered pyrocholoric structure with the presence of intense superlattice spots, which became weak and diffuse (in Dy{sub 2}Hf{sub 2}O{sub 7} and Tb{sub 2}Hf{sub 2}O{sub 7}) before disappearing completely as the series progressed towards the Lu end. High resolution electron microscopic studies showed the breakdown of the pyrochlore ordering in the form of antiphase domains resulting in diffused smoke-like superlattice spots in the case of Dy{sub 2}Hf{sub 2}O{sub 7} and Tb{sub 2}Hf{sub 2}O{sub 7}. - Graphical abstract: Transmission electron microscopic studies showed the ordered pyrochlore to defect fluorite transition in rare-earth pyrohafnates to occur via the formation of anti-phase domains to start with. Highlights: Black-Right-Pointing-Pointer Pyrochlore to fluorite structural transition in rare earth pyrohafnates. Black-Right-Pointing-Pointer La{sub 2}Hf{sub 2}O{sub 7}, Pr{sub 2}Hf{sub 2}O{sub 7} and Nd{sub 2}Hf{sub 2}O{sub 7} showed well ordered pyrochlore structure. Black-Right-Pointing-Pointer Short range ordering in Dy{sub 2}Hf{sub 2}O{sub 7} and Tb{sub 2}Hf{sub 2}O{sub 7}. Black-Right-Pointing-Pointer Break down of pyrochlore ordering due to antiphase boundaries. Black-Right-Pointing-Pointer Rest of the series showed fluoritic structure.

  12. The structural basis of the fluorite-related rare earth higher oxides

    International Nuclear Information System (INIS)

    Kang, Z.C.; Eyring, LeRoy

    1996-01-01

    In this paper phenomenological structural principles, and rules for their application are advanced for predicting the ideal structures of the higher oxides of the rare earths. These principles allow to establish a generic formula incorporating all known phases, guide the correct modelling of the established structures and demonstrate that structures previously proposed but proven incorrect do not follow the structural principles. They also can be used to predict the structures not yet established for known phases, including polymorphs, and provide rationalization for phases fitting the generic formula that have not yet been found. The structural principles flow naturally from the fluorite substructure characteristic of all established phases. 39 refs., 5 tabs., 16 figs

  13. Stability of fluorite-type La{sub 2}Ce{sub 2}O{sub 7} under extreme conditions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, F.X., E-mail: zhangfx@umich.edu [Department of Earth and Environmental Sciences, The University of Michigan, Ann Arbor, MI 48109 (United States); State Key Laboratory of Metastable Materials Science & Technology, Yanshan University, Qinhuangdao, Hebei 066004 (China); Tracy, C.L. [Department of Materials Science and Engineering, The University of Michigan, Ann Arbor, MI 48109 (United States); Lang, M. [Department of Nuclear Engineering, University of Tennessee, Knoxville, TN 37966 (United States); Ewing, R.C. [Department of Geological Sciences, Stanford University, Stanford, CA 94305 (United States)

    2016-07-25

    The structural stability of fluorite-type La{sub 2}Ce{sub 2}O{sub 7} was studied at pressure up to ∼40 GPa and under hydrothermal conditions of ∼1 GPa and up to 350 °C, respectively, using synchrotron X-ray diffraction (XRD) and Raman scattering measurements. XRD measurements indicated that the fluorite-type La{sub 2}Ce{sub 2}O{sub 7} is not stable at pressures greater than 22.6 GPa and gradually transformed to a high-pressure phase. The high-pressure phase is not stable and changed back to the fluorite-type structure when pressure is released. The La{sub 2}Ce{sub 2}O{sub 7} fluorite is also not stable under hydrothermal conditions and began to react with water at 200–250 °C. Both Raman and XRD results suggest that lanthanum hydroxide La(OH){sub 3} and La{sup 3+}-doped CeO{sub 2} fluorite are the dominant products after hydrothermal treatment. - Graphical abstract: The fluorite-type La{sub 2}Ce{sub 2}O{sub 7} reacted with water at hydrothermal condition (1 GPa, and above 200 °C), and formed rare earth hydroxides. - Highlights: • La{sub 2}Ce{sub 2}O{sub 7} transforms to a metastable phase at pressure higher than 21 GPa. • La{sub 2}Ce{sub 2}O{sub 7} reacts with water at ∼1 GPa and above 200 °C. • The pressure-induced phase transition is reversible.

  14. INAA in the determination of the elemental constituents of a natural fluorite

    International Nuclear Information System (INIS)

    Balogun, F.A.; Tubosun, I.A.; Adesanmi, C.A.; Ajao, J.A.; Akanle, A.O.; Spyrou, N.M.; Ojo, J.O.

    1997-01-01

    A complementary use of the comparative and the semi-absolute variations of instrumental neutron activation analysis (INAA) has enabled us to determine 22 different elements in a sample of natural fluorite originating from the younger granite province of Nigeria. The mineral has a brownish purple appearance with some veinlets having a deep purple coloration. Of all the 22 elements measured, Fe (851.36 ppm), Sb (7.69 ppm), Ag (87.4 ppm), Hg (2.71 ppm) and Se (1.97 ppm) are found to be exclusive to the veinlets while Au (109.15 ppm), Co (2.15 ppm) and W (173.20 ppm) are concentrated in the main matrix of the fluorite. With the aid of the semi-absolute method, it was possible to measure the Au concentration in the IAEA Soil-7 reference material to be 56.83±5.87% ppm. A qualitative electron microprobe analysis (EMA) showed that the bulk of the matrix is composed mainly of Ca and F, as expected. (author)

  15. Relationship between uranium-molybdenum, fluorite and gold deposits within provinces of continental volcanicity

    International Nuclear Information System (INIS)

    Modnikov, I.S.; Skvortsova, K.V.; Chesnokov, L.V.

    1974-01-01

    The article gives a comparative description of and the age relationships between uranium-molybdenum, gold and fluorite mineralizations in the areas of development of adhesite-diorite and liparite-granite vulcanoplutonic formations, which are most fully and intensively manifest in the intra-anticlinal and median blocks of folded regions in the final stages of geosynclinal development or during the final stages of tectono-magmatic activation. These formations usually fill vulcano-tectonic depression structures - overlaid troughs and inherited delections. The geological and geochemical data are evidence of the close temporal link between the hydrothermal process of ore formation and the type and scale of manifestations of the vulcano-plutonic magmatism that is responsible for the general geochemical features of the ores of deposits of various types. The formation of gold, fluorite and uranium-molybdenum deposits occurred immediately after the completion of effusive and intrusive magmatism during a single metallogenic cycle. The spatial distribution of the ore fields and deposits depends chiefly on the peculiarities of the tectonic make-up of the depression structures, and also on the type and scale of the manifestations of vulcano-plutonic magmatism. (B.Ya.)

  16. Laser site selective spectroscopy of rare-earth defects in fluorites

    International Nuclear Information System (INIS)

    Murdoch, K.M.

    1998-01-01

    Full text: Rare-earth (R 3+ ) doped fluorites (CaF 2 , SrF 2 , and BaF 2 ) have long been a model system for investigating the defect chemistry of crystalline solids. The trivalent R 3+ ions substitute for the divalent cations of the host and are charge compensated by the inclusion of additional interstitial fluoride ions (F - j ). A variety of R 3+ centres arise, including cubic symmetry R 3+ sites remote from any F - j , single R 3+ ions associated with one neighbouring F - j , and clusters of R 3+ associated with multiple F - j . Additional R 3+ centres are produced by chemical modifications involving the substitution of host anions or cations. Numerous experimental studies have shown that the relative populations of these centres are determined by the size of the R 3+ ions, the R 3+ concentration in the crystal, the crystals thermal history, and any pressure treatments. A considerable volume of theoretical work has also been presented to interpret these results. Laser site selective spectroscopy has proved a powerful technique for probing the defect chemistry of R 3+ doped fluorites. Some of the important results and conclusions of these experiments will be reviewed. A detailed account, with references to the original studies, has also been published recently

  17. Genesis of rare-metal pegmatites and alkaline apatite-fluorite rocks of Burpala massi, Northern Baikal folded zone

    Science.gov (United States)

    Sotnikova, Irina; Vladykin, Nikolai

    2015-04-01

    Burpalinsky rare metal alkaline massif in the Northern Baikal folded zone in southern margin of Siberian Platform, is a of intrusion central type, created 287 Ma covering area of about 250 km2. It is composed of nepheline syenites and pulaskites grading to quartz syenites in the contacts. Veines and dykes are represented by shonkinites, sodalite syenite, leucocratic granophyres, alkali granites and numerous rare metal alkaline syenite pegmatites and two dykes of carbonatites. All rocks except for granites are cut by a large apatite-fluorite dyke rocks with mica and magnetite, which in turn is cut by alaskite granites dyke. The massif has been studied by A.M. Portnov, A.A. Ganzeev et al. (1992) Burpalinsky massif is highly enriched with trace elements, which are concentrated in pegmatite dykes. About 70 rare-metal minerals we found in massif. Zr-silicates: zircon, eudialyte, lovenite, Ti-lovenite, velerite, burpalite, seidozerite, Ca- seidozerite, Rosenbuschite, vlasovite, katapleite, Ca-katapleite, elpidite. Ti- minerals:- sphene, astrophyllite, ramsaite, Mn-neptunite bafertisite, chevkinite, Mn-ilmenite, pirofanite, Sr-perrerit, landauite, rutile, anatase, brookite; TR- minerals - loparite, metaloparite, britolite, rinkolite, melanocerite, bastnesite, parisite, ankilite, monazite, fluocerite, TR-apatite; Nb- minerals - pyrochlore, loparite. Other rare minerals leucophanite, hambergite, pyrochlore, betafite, torite, thorianite, tayniolite, brewsterite, cryolite and others. We have proposed a new scheme massif: shonkinites - nepheline syenites - alkaline syenite - quartz syenites - veined rocks: mariupolites, rare-metal pegmatites, apatite, fluorite rock alyaskite and alkaline granites and carbonatites (Sotnikova, 2009). Apatite-fluorite rocks are found in the central part of massif. This is a large vein body of 2 km length and a 20 m width cutting prevailing pulaskites. Previously, these rocks were regarded as hydrothermal low-temperature phase. New geological and

  18. The Improvement Effect of Dispersant in Fluorite Flotation: Determination by the Analysis of XRD and FESEM-EDX

    Directory of Open Access Journals (Sweden)

    Y. J. Li

    2015-01-01

    Full Text Available Different dispersants were added in the dispersion process to improve the efficiency of fluorite flotation. The types and dosage of dispersant on the improvement of fluorite flotation were investigated; when the sodium polyacrylate (SPA was used as the dispersant and its addition is 0.5%, the concentrate grade of CaF2 increased from 90% to 98% and the fluorite recovery increased from 81% to 85%. Methods of X-ray powder diffraction (XRD, field emission scanning electron microscopy (FESEM, and Energy dispersive X-ray spectrometer (EDX were used to characterize the sample. According to the analysis of results, the optimal sample consisted of CaF2 and very little CaCO3 in the size range of 0–5 μm. It could be concluded that the mechanism of improvement for the concentrate grade and recovery of CaF2 was attributed to the change of potential energy barrier which caused the separation of particles with different charge. All results indicate that SPA has a great potential to be an efficient and cost-effective dispersant for the improvement of fluorite flotation.

  19. Ion irradiation-induced diffusion in bixbyite-fluorite related oxides: Dislocations and phase transformation

    Energy Technology Data Exchange (ETDEWEB)

    Rolly, Gaboriaud, E-mail: Rolly.gaboriaud@univ-poitiers.fr [Institut Pprime, CNRS-University of Poitiers, SP2MI-BP 30179, 86962 Chasseneuil-Futuroscope (France); Fabien, Paumier [Institut Pprime, CNRS-University of Poitiers, SP2MI-BP 30179, 86962 Chasseneuil-Futuroscope (France); Bertrand, Lacroix [CSIC – University of Sevilla, Avenida Américo Vespucio, 49, 41092 Sevilla (Spain)

    2014-05-01

    Ion-irradiation induced diffusion and the phase transformation of a bixbyite-fluorite related rare earth oxide thin films are studied. This work is focused on yttrium sesquioxide, Y{sub 2}O{sub 3}, thin films deposited on Si (1 0 0) substrates using the ion beam sputtering technique (IBS). As-deposited samples were annealed ant then irradiated at cryogenic temperature (80 K) with 260 keV Xe{sup 2+} at different fluences. The irradiated thin oxide films are characterized by X-ray diffraction. A cubic to monoclinic phase transformation was observed. Analysis of this phenomenon is done in terms of residual stresses. Stress measurements as a function of irradiation fluences were realised using the XRD-sin{sup 2}ψ method. Stress evolution and kinetic of the phase transformation are compared and leads to the role-played by the nucleation of point and extended defects.

  20. Properties of complex tungstates, niobates, translated with fluorite-like structure

    International Nuclear Information System (INIS)

    Vetkina, S.N.; Zolin, V.F.; Sirotinkin, V.P.; Smirnov, S.A.

    1989-01-01

    Spectra of ternary tungstates, niobates and tantalates (MeLa 2 WO 7 , La 3 TO 7 ; Me=Ba, Sr; T=Ta, Nb) related to the layered fluorite group are analyzed. The laser pumping and time resolved luminescence are used for selecting spectra of unequivalent centers. The symmetry of the first center is near to the distorted cubic one. The vibrational spectra of europium in Eu 3 NbO 7 and SrLa 2 WO 7 are due to the chain-like structure of niobates and to the net-like structure of tantalates. The stimulated emission of Nd 3+ in powders of BaLa 2 WO 7 and La 3 NbO 7 is observed at wavelengths of 1.07 and 1.063 μm, respectively

  1. Thermal and chemical variations of the Nigerian Benue trough lead-zinc-barite-fluorite deposits

    Science.gov (United States)

    Ogundipe, Ibukun Emmanuel

    2017-08-01

    The Benue trough is an intra-continental rift initiated in the Cretaceous during the opening of the South Atlantic Ocean. Lead-zinc-barite-fluorite mineralization occurs along the 600 km axis of the trough in three discrete sub-basins which coincide with the lower, middle and upper mineral districts of the Benue Valley. Lithologically these sub-basins are dominated by black carbonaceous shale in the Lower Benue, platform carbonates in the Middle Benue and sandstones in the Upper Benue. Micro-thermometric analysis of fluid inclusions in sphalerite, fluorite, barite and quartz have shown that each mineral district has its own unique thermal and chemical imprint. For example, the temperature can be bracketed between 109 °C and 160 °C for lower Benue, 89 °C-144 °C for the Middle Benue and 176 °C-254 °C for the Upper Benue. Chemical differentiation also exists between each mineral district with the Lower Benue having 22 wt % equivalent NaCl while the Middle and Upper Benue have 18 and 16 wt % equivalent NaCl respectively. This study shows that inter-district thermal and chemical variations exist between the ore-stage sulfide and post-sulfide gangue minerals of the entire Benue Valley. Similarly, intra-district thermal and chemical variations have also been observed among all the paragenetic minerals of each district. The thermal variations may be as a result of variations in the geothermal gradient accompanying continental rifting from one district to the other. The variations in the chemistry between the Lower Benue and the Upper Benue paragenic minerals may be as a result of the distinct lithological differences across the Benue Trough.

  2. Diagenetic and post-diagenetic fabrics in the Kamarposht fluorite mine (east of Mazandaran province: Explainaton and genetic interpretation

    Directory of Open Access Journals (Sweden)

    Faezeh Nabiloo

    2017-11-01

    Full Text Available Introduction Upper part of Elika Formation (middle Triassic in the central Alborz as one of the most important fluorite districts in Iran is the host of some carbonate rock-hosted fluorite deposits such as Kamarposht, Pachi-Miana, Shashroodbar, Era (Alirezaee, 1989; Gorjizad, 1996; Rastad and Shariatmadar, 2001; Rajabi et al., 2013; Vahabzadeh et al., 2013; Zabihitabar and Shafiei, 2015. One of the main active fluorite mines in the central Alborz is Kamarposht which is located at the southeast of DoAb in the Mazandaran province. The Kamarposht mine has 75000 tons of ores and mining there has begun in 2005. The effects and evidences of underground mining in the northern and southern parts of this mine indicate high-grade and coarse-grained ore zones which have fluorite, galena and barite. Until now, basic economic geology studies in the Kamarposht mine including mineralogy, fabric and texture of mineralization for introducing a new fluorite mine in Iran have not been carried out. The present study is based on field observations and macroscopic as well as microscopic studies aimed at identification of morphology and mode of occurrence of the ore body, mineralogy and fabric of mineralization and discussion of as well as presentation of a new genetic model for the Kamarposht mine. Materials and methods For the present research study, field geology and sampling were carried out to collect 100 samples from various fluorite ore-types and carbonate host rocks. The samples prepared for thin section (n=55 and polished-thin sections (n=22. Results Field observations indicate that economic mineable ore zones of the Kamarposht mine are mainly hosted by dolomitic limestone and silicified carbonate horizons of the Elika Formation. The ore zones have fluorite, barite and galena which are mainly located in fractured and faulted zones as well as karstic cavities in the host horizons. Coarse grain and euhedral fluorites with various colors, significant presence of

  3. Formation, structure and magnetism of the metastable defect fluorite phases AVO3.5+x (A=In, Sc)

    International Nuclear Information System (INIS)

    Shafi, Shahid P.; Lundgren, Rylan J.; Cranswick, Lachlan M.D.; Bieringer, Mario

    2007-01-01

    We report the preparation and stability of ScVO 3.5+x and the novel phase InVO 3.5+x . AVO 3.5+x (A=Sc, In) defect fluorite structures are formed as metastable intermediates during the topotactic oxidation of AVO 3 bixbyites. The oxidation pathway has been studied in detail by means of thermogravimetric/differential thermal analysis and in-situ powder X-ray diffraction. The oxidation of the bixbyite phase follows a topotactic pathway at temperatures between 300 and 400 deg. C in air/carbon dioxide. The range of accessible oxygen stoichiometries for the AVO 3.5+x structures following this pathway are 0.00≤x≤0.22. Rietveld refinements against powder X-ray and neutron data revealed that InVO 3.54 and ScVO 3.70 crystallize in the defect fluorite structure in space group Fm-3 m (227) with a=4.9863(5) and 4.9697(3)A, respectively with A 3+ /V 4+ disorder on the (4a) cation site. Powder neutron diffraction experiments indicate clustering of oxide defects in all samples. Bulk magnetic measurements showed the presence of V 4+ and the absence of magnetic ordering at low temperatures. Powder neutron diffraction experiments confirmed the absence of a long range ordered magnetic ground state. - Graphical abstract: Topotactic oxidation of AVO 3 bixbyite to AVO 3.5 defect fluorite structure followed by in-situ powder X-ray diffraction. The upper structural diagram shows a six coordinated (A/V)-O 6 fragment in bixbyite, the lower structure illustrates the same seven-fold coordinated (A/V)-O 7 cubic environment in the defect fluorite structure

  4. General description of new equipment 'Fluorite-III' for Bor-Oendoer fluorate factory

    International Nuclear Information System (INIS)

    Bayar, V.; Basankhueue, O.; Ganzorig, J.; Dushan, P.; Lodoisamba, S.; Otgooloi, B.; Tsehlmehg, A.; Shagjjamba, D.

    1992-01-01

    A new equipment 'Fluorite-III' is described which is used to register and analyze three kinds of following informations: 1. Pulse count for determination of ore's concentration which is transferring by the factory conveyor. 2. Pulse count for determination of ore's thickness which is transferring also by the factory conveyor. 3. Information about that: Is the conveyor moving or not during our measurements. First and second kinds of information are registered by two detectors which is established on the different places from the factory conveyor. Constraction of these detectors are the same. Every one of them consists of a ''photo multiplier tube'' and a scintillator of ''sodium-iodine''. The third information is corresponding to the ''transistor and transistical logic'' level. Every counters data and the information about the conveyor should be transferred every time to the computer which is compatible with the IBM/PC for further treatment through the following devices: 1. Three State Buffer which is made from ''Generic Array Logic'' device. 2. Universal Asynchronous Receiver and Transmitter (UART) which is of type (AY 3-1015). 3. 20 milli-ampere current interface with optical isolators. Also in this way but in reverse order by these devices we can control all processes of the measurements from the computer. 1 fig

  5. Interacting Frenkel defects at high concentration and the superionic transition in fluorite crystals

    International Nuclear Information System (INIS)

    March, N.H.; Tosi, M.P.

    1980-11-01

    A spherical cell model is proposed to account for the explicit concentration dependence of Frenkel defects in an ionic system. In the model, the linearized Debye-Hueckel equation is soluble exactly, subject to the boundary condition that the electric field is zero at the cell boundary R, related to the concentration α of defects by R proportional to csup(-1/3). This screened field is used to calculate the chemical potential, which in turn leads to a condition for the instability of the interacting defect assembly. This condition allows one to calculate the enhancement of the concentration of defects above its Arrhenius value at the point of instability in terms of (a) the critical concentration csub(c), (b) a/R, where a is the radius of defect and (c) the Debye-Hueckel screening length kappasub(c). It is clear from the cell model that this enhancement factor is reduced somewhat in the relevant range of parameters in some of the fluorites from its value in extended Debye-Hueckel theory. It is anticipated that the instability discussed here should afford an upper bound to csub(c) at the superionic transition, within the range of validity of the model. The excess he at capacity csub(p) is also discussed briefly. (author)

  6. U-Th/He ages of fluorite mineralizations of the Tangua alkaline intrusion; Idades U-Th/He das mineralizacoes de fluorita da intrusao alcalina de Tangua

    Energy Technology Data Exchange (ETDEWEB)

    Geraldes, M.C.; Vargas, T., E-mail: geraldes@uerj.br, E-mail: vargas@uerj.br [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil). Faculdade de Geologia; Evans, N., E-mail: Noreen.Evans@csiro.au [CSIRO and Curtin University for Technology, Western Australia (Australia); Nummer, A.R., E-mail: nummer@ufrrj.br [Universidade Federal Rural do Rio de Janeiro (DEGEOC/IA/UFRRJ), RJ (Brazil)

    2015-07-01

    The Tangua massif is part of a group of alkaline complexes that occurs in an extensive zone of faults and E-W lineaments and includes the Brazilian Southeastern Rift. This work presents U-He ages of the fluorite mineralization. The Tangua alkaline massif is emplaced in coarse-grained biotite gneiss (Oriental Domain, central portion of the Ribeira belt). Cataclastic gneiss with intense weathering are restricted to the intrusion contacts. The alkaline body is comprised of pulaskites and umptekites, nephelinesyenites, foiaites, and pseudoleucite foiaites and is cut by phonolite dykes, trachytes and alkaline lamprophyres. In the locality of Barbosao, veins of fluorite occur, accompanied by silica and pyrite within trachyte dykes. These veins are parallel to the gneiss foliation (N 50 - 70 E) with an average thickness of 30 cm and the fluorite contains limonite and manganese oxides inclusions. The U-He ages range from <2Ma to 73Ma. The older age is coherent with 80-65 ma range of K-Ar ages reported in the literature. The veins of fluorite crosscut the lithologies associated with shear zones, and are important to economic exploration in the region. The petrographic and U-Th/He sating studies indicate the fluorite formation coeval to alkaline intrusion and meteoric water fluid circulation recently. (author)

  7. Synthesis of Fluorite (CaF2 Crystal from Gypsum Waste of Phosphoric Acid Factory in Silica Gel

    Directory of Open Access Journals (Sweden)

    Mohammad Misbah Khunur

    2012-06-01

    Full Text Available This paper report the synthesis and characterization of fluorite single crystal prepared from gypsum waste of phosphoric acid production in silica gel. Instead of its high calcium, gypsum was used to recycle the waste which was massively produces in the phosphoric acid production. The gypsum waste, the raw material of CaCl2 supernatant, was dissolved in concentrated HCl and then precipitated as calcium oxalate (CaC2O4 by addition of ammonium oxalate. The CaCl2 was obtained by dissolving the CaC2O4 with HCl 3M. The crystals were grown at room temperature in silica gel and characterized by AAS, FTIR and powder XRD. The optimum crystal growth condition, which is pH of gel, CaCl2 concentration and growth time, were investigated. The result shows that at optimum condition of pH 5.80, CaCl2 concentrations of 1.2 M, and growth time of 144 hours, colorless crystals with the longest size of 3 mm, were obtained (72.57%. Characterization of the synthesized crystal by AAS indicates that the obtained crystal has high purity. Meanwhile, analysis by FTIR spectra shows a Ca–F peak at 775 cm-1, and powder-XRD analysis confirms that the obtained crystal was fluorite (CaF2. © 2012 BCREC UNDIP. All rights reservedReceived: 11st April 2012; Revised: 4th June 2012; Accepted: 13rd June 2012[How to Cite: M.M. Khunur, A. Risdianto, S. Mutrofin, Y.P. Prananto. (2012. Synthesis of Fluorite (CaF2 Crystal from Gypsum Waste of Phosphoric Acid Factory in Silica Gel. Bulletin of Chemical Reaction Engineering & Catalysis, 7 (1: 71-77.  doi:10.9767/bcrec.7.1.3171.71-77 ][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.7.1.3171.71-77 ] | View in 

  8. Surface modelling on heavy atom crystalline compounds: HfO{sub 2} and UO{sub 2} fluorite structures

    Energy Technology Data Exchange (ETDEWEB)

    Evarestov, Robert [Department of Quantum Chemistry, St. Petersburg State University, 26 Universitetsky Prospect, Peterhof, St. Petersburg 198504 (Russian Federation)], E-mail: re1973@re1973.spb.edu; Bandura, Andrei; Blokhin, Eugeny [Department of Quantum Chemistry, St. Petersburg State University, 26 Universitetsky Prospect, Peterhof, St. Petersburg 198504 (Russian Federation)

    2009-01-15

    The study of the bulk and surface properties of cubic (fluorite structure) HfO{sub 2} and UO{sub 2} was performed using the hybrid Hartree-Fock density functional theory linear combination of atomic orbitals simulations via the CRYSTAL06 computer code. The Stuttgart small-core pseudopotentials and corresponding basis sets were used for the core-valence interactions. The influence of relativistic effects on the structure and properties of the systems was studied. It was found that surface properties of Mott-Hubbard dielectric UO{sub 2} differ from those found for other metal oxides with the closed-shell configuration of d-electrons.

  9. Conductivity and hydration trends in disordered fluorite and pyrochlore oxides: A study on lanthanum cerate–zirconate based compounds

    DEFF Research Database (Denmark)

    Besikiotis, Vasileios; Ricote, Sandrine; Jensen, Molly Hjorth

    2012-01-01

    In the present contribution we discuss the influence of order/disorder on the concentration and mobility of ionic charge carriers in undoped and acceptor (calcium) doped fluorite and pyrochlore structured lanthanum cerate–zirconate solid solutions: (La1−yCay)2(Ce1−xZrx)2O7−δ (y=0, 0.02, 0.10; x=0...... enthalpy becomes more exothermic with higher cerium content, i.e. with more disordered materials. The proton conductivity decreases upon acceptor substitution of La3+ with Ca2+ which is attributed to trapping of the charge carriers by the effectively negative acceptor....

  10. Atmospheric dust deposition on soils around an abandoned fluorite mine (Hammam Zriba, NE Tunisia).

    Science.gov (United States)

    Djebbi, Chaima; Chaabani, Fredj; Font, Oriol; Queralt, Ignasi; Querol, Xavier

    2017-10-01

    The present study focuses on the eolian dispersion and dust deposition, of major and trace elements in soils in a semi-arid climate, around an old fluorite (CaF 2 ) and barite (BaSO 4 ) mine, located in Hammam Zriba in Northern Tunisia. Ore deposits from this site contain a high amount of metal sulphides constituting heavy metal pollution in the surrounding environment. Samples of waste from the surface of mine tailings and agricultural topsoil samples in the vicinity of the mine were collected. The soil samples and a control sample from unpolluted area, were taken in the direction of prevailing northwest and west winds. Chemical analysis of these solids was performed using both X-ray fluorescence and X-ray diffraction. To determine the transfer from mine wastes to the soils, soluble fraction was performed by inductively coupled plasma and ionic chromatography. The fine grained size fraction of the un-restored tailings, still contained significant levels of barium, strontium, sulphur, fluorine, zinc and lead with mean percentages (wt%) of 30 (calculated as BaO), 13 (as SrO), 10 (as SO 3 ), 4 (F), 2 (Zn) and 1.2 (Pb). Also, high concentrations of cadmium (Cd), arsenic (As) and mercury (Hg) were found with an averages of 36, 24 and 1.2mgkg -1 , respectively. As a result of the eolian erosion of the tailings and their subsequent wind transport, the concentrations of Ba, Sr, S, F, Zn and Pb were extremely high in the soils near to the tailings dumps, with 5%, 4%, 7%, 1%, 0.8% and 0.2%, respectively. Concentration of major pollutants decreases with distance, but they were high even in the farthest samples. Same spatial distribution was observed for Cd, As and Hg. While, the other elements follow different spatial patterns. The leaching test revealed that most elements in the mining wastes, except for the anions, had a low solubility despite their high bulk concentrations. According the 2003/33/CE Decision Threshold, some of these tailings samples were considered as

  11. Continental basinal origin of ore fluids from southwestern Massif central fluorite veins (Albigeois, France): evidence from fluid inclusion and stable isotope analyses

    International Nuclear Information System (INIS)

    Munoz, M.; Boyce, A.J.; Courjault-Rade, P.; Fallick, A.E.; Tollon, F.

    1999-01-01

    The most important fluorspar mining district in France is located in the Palaeozoic basement of the Albigeois in southwestern French Massif Central. The massive fluorite is hosted within large E-W striking fractures, crosscutting Cambro-Ordovician clastics, associated with large zones of hypersilicified tectonic breccia which form the wall of the mined deposits. Fluid inclusion data for pre-fluorite and fluorite stage fluids have salinities between 20-26 wt% NaCl equiv., with homogenisation temperatures between 85-170C. Furthermore, low first ice melting temperatures (around -50C) indicates the presence of significant CaCl 2 and possibly MgCl 2 together with NaCl. Calculated fluid δ 18 O for pre-fluorite quartz ranges from -9.1per thousand to -5.2per thousand, with δD between -55per thousand to -64per thousand, placing the data directly on the present day meteoric water line. Fluorite stage fluids have δ 18 O between +0.1per thousand to +3.2per thousand, and δD ranging from -53per thousand to -75per thousand, indicating an interacted meteoric fluid origin. Combining the fluid inclusion and stable isotope data illustrates that the main fluorite depositing fluid has characteristics typical of a basinal brine. The authors have no evidence that a magmatic system was involved in the deposit genesis. The proposed model highlights that mineralisation was related to major Mesozoic extensional events coinciding with the gradual opening of the Atlantic and Tethys oceans. In order to account for the chemistry of the fluids, and the siting of the deposits, the authors postulate a genetic relationship with local, continental, evaporite-bearing basins coincident with, and controlled by the E-W fractures. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  12. Investigation of lanthanide ions and other paramagnetic impurities in natural fluorite by electron paramagnetic resonance: examples of application to mining exploration and geochemistry

    International Nuclear Information System (INIS)

    Chatagnon, B.

    1981-01-01

    This research thesis reports the application to geology, and more particularly to geochemistry and mining exploration, of a physical method: the electron paramagnetic resonance (EPR). After a report of a bibliographical investigation on mineralogy and geochemistry of fluorite and lanthanides, as well as on paramagnetic centres observed by physicists in synthetic fluorite, the author reports an experimental work, and describes two examples of application of EPR: firstly, the exploration of radioactive ores, and secondly, with the joint use of neutron activation analysis, the characterization of the redox status of the hydrothermal solution which is at the origin of fluorinated mineralisation

  13. Damage evolution of ion irradiated defected-fluorite La 2 Zr 2 O 7 epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kaspar, Tiffany C.; Gigax, Jonathan G.; Shao, Lin; Bowden, Mark E.; Varga, Tamas; Shutthanandan, Vaithiyalingam; Spurgeon, Steven R.; Yan, Pengfei; Wang, Chongmin; Ramuhalli, Pradeep; Henager, Charles H.

    2017-05-01

    Pyrochlore-structure oxides, A2B2O7, may exhibit remarkable radiation tolerance due to the ease with which they can accommodate disorder by transitioning to a defected fluorite structure. The mechanism of defect formation was explored by evaluating the radiation damage behavior of high quality epitaxial La2Zr2O7 thin films with the defected fluorite structure, irradiated with 1 MeV Zr+ at doses up to 10 displacements per atom (dpa). The level of film damage was evaluated as a function of dose by Rutherford backscattering spectrometry in the channeling geometry (RBS/c) and scanning transmission electron microscopy (STEM). At lower doses, the surface of the La2Zr2O7 film amorphized, and the amorphous fraction as a function of dose fit well to a stimulated amorphization model. As the dose increased, the surface amorphization slowed, and amorphization appeared at the interface. Even at a dose of 10 dpa, the core of the film remained crystalline, despite the prediction of amorphization from the model. To inform future ab initio simulations of La2Zr2O7, the bandgap of a thick La2Zr2O7 film was measured to be indirect at 4.96 eV, with a direct transition at 5.60 eV.

  14. Solid State Structure-Reactivity Studies on Bixbyites, Fluorites and Perovskites Belonging to the Vanadate, Titanate and Cerate Families

    Science.gov (United States)

    Shafi, Shahid P.

    This thesis primarily focuses on the systematic understanding of structure-reactivity relationships in two representative systems: bixbyite and related structures as well as indium doped CeO2. Topotactic reaction routes have gained significant attention over the past two decades due to their potential to access kinetically controlled metastable materials. This has contributed substantially to the understanding of solid state reaction pathways and provided first insights into mechanisms. Contrary to the widely used ex-situ methods, in-situ techniques including powder x-ray diffraction and thermogravimetric-differential thermal analysis have been employed extensively throughout this work in order to follow the reaction pathways in real time. Detailed analysis of the AVO3 (A = In, Sc) bixbyite reactivity under oxidative conditions has been carried out and a variety of novel metastable oxygen defect phases have been identified and characterized. The novel metastable materials have oxygen deficient fluorite structures and consequently are potential ion conductors. Structural aspects of the topotactic vs. reconstructive transformations are illustrated with this model system. The structure-reactivity study of AVO3 phases was extended to AVO3 perovskite family. Based on the research methodologies and results from AVO3 bixbyite reactivity studies a generalized mechanistic oxidation pathway has been established with a non-vanadium phase, ScTiO3 bixbyite. However, there is stark contrast in terms of structural stability and features beyond this stability limit during AVO3 and ScTiO3 bixbyite reaction pathways. A series of complex reaction sequences including phase separation and phase transitions were identified during the investigation of ScTiO3 reactivity. The two-step formation pathway for the fluorite-type oxide ion conductor Ce1-xInxO2-delta (0 ≤ x ≤ 0.3) is being reported. The formation of the BaCe1-xInxO 3-delta perovskites and the subsequent CO2-capture reaction

  15. Accelerator-based analytical technique in the evaluation of some Nigeria's natural minerals: Fluorite, tourmaline and topaz

    Energy Technology Data Exchange (ETDEWEB)

    Olabanji, S.O. [Istituto Nazionale di Fisica Nucleare (INFN), Laboratori Nazionali di Legnaro (LNL), viale dell' Universita 2, 35020 Legnaro, Padova (Italy)]. E-mail: skayode2002@yahoo.co.uk; Ige, O.A. [Natural History Museum, Obafemi Awolowo University, Ile-Ife (Nigeria); Mazzoli, C. [Dipartimento di Mineralogia e Petrologia, Universita di Padova, 35100 Padova (Italy); Ceccato, D. [Istituto Nazionale di Fisica Nucleare (INFN), Laboratori Nazionali di Legnaro (LNL), viale dell' Universita 2, 35020 Legnaro, Padova (Italy); Dipartimento di Fisica, Universita di Padova, via Marzolo 8, 35100 Padova (Italy); Akintunde, J.A. [CERD, Obafemi Awolowo University, Ile-Ife (Nigeria); De Poli, M. [Istituto Nazionale di Fisica Nucleare (INFN), Laboratori Nazionali di Legnaro (LNL), viale dell' Universita 2, 35020 Legnaro, Padova (Italy); Moschini, G. [Istituto Nazionale di Fisica Nucleare (INFN), Laboratori Nazionali di Legnaro (LNL), viale dell' Universita 2, 35020 Legnaro, Padova (Italy); Dipartimento di Fisica, Universita di Padova, via Marzolo 8, 35100 Padova (Italy)

    2005-10-15

    For the first time, the complementary accelerator-based analytical technique of PIXE and electron microprobe analysis (EMPA) were employed for the characterization of some Nigeria's natural minerals namely fluorite, tourmaline and topaz. These minerals occur in different areas in Nigeria. The minerals are mainly used as gemstones and for other scientific and technological applications and therefore are very important. There is need to characterize them to know the quality of these gemstones and update the geochemical data on them geared towards useful applications. PIXE analysis was carried out using the 1.8 MeV collimated proton beam from the 2.5 MV AN 2000 Van de Graaff accelerator at INFN, LNL, Legnaro, Padova, Italy. The novel results which show many elements at different concentrations in these minerals are presented and discussed.

  16. Study of genesis in Qahr-Abad fluorite deposit using fluid inclusion, southeast of Saqqez, the Kurdistan province

    Directory of Open Access Journals (Sweden)

    Mehrdad Barati

    2017-07-01

    Full Text Available Introduction The Qahr-abad fluorite deposit is located in the area of 36°10′ 3′′ N and 46°34′ 21′′E within the Sanandaj-Sirjan district east of the Kurdistan province , Iran and it is located ~57 km southeast of the city of Saqqez (Kholghi Khasraghi, 1999. This deposit is developed as scatter lenses, veins, and veinlets (stockwork structure within carbonate rocks of Elika formation and controlled by the regional NW–SE trending Zagross thrust nappe system. Fault trends in this area are perpendicular to fault trends in the Zagros zone. The fault dips are nearly vertical and mineralization has occurred in the brecciation fault zone (Talaii, 2010. The rough geological instruction of the deposit has indicated that it is similar to worldwide Epithermal deposits. The mineralization occurs as replacement (type I/ open-space (type II vein fillings and bodies within Mesozoic lime stones (mostly Upper Triassic and Lower Jurassic members of the Elika Formation, where they crop out to form horst structures. The mineralization is typically associated with post Pliocene disjunctive faults, which in part appear to have served as channel ways for the fluorite forming fluids that are representative of the geological setting of the mineralized area. Fluorite occurs in several color variations such as green, violet, blue, white or colorless, and is accompanied by quartz, barite and calcite (Moslehi, 2013. Materials and methods The minerals sampled for the fluid inclusion study include fluorite from mineralization stages. Samples covered all ore types. Micro thermometry analyses for 23 samples were performed after careful microscopic observation of 35 sections and 30 doubly polished sections. Micro thermometry was undertaken using a Linkam THS600 heating-freezing stage, with a measurable temperature range of between −196 and +600 °C (precision of freezing data and homogenization temperature of ±0.2 °C. Micro thermometry was undertaken in the

  17. Nuclear magnetic resonance in superionic conductors with fluorite-type structure; Ressonancia magnetica nuclear em condutores superionicos de estrutura fluorita

    Energy Technology Data Exchange (ETDEWEB)

    Souto, Sergio Paulo Amaral

    1991-12-31

    The {sup 19} F NMR relaxation times T{sub 1} and T{sub 2} were measured in ternary and nonstoichiometric compounds with the fluorite-type structure. We have studied the Na{sub 0-4} Y{sub 0-6} F{sub 2-2} crystal in the temperature range 600 K to 900 K, where the crystal has not the fluorite structure. The T{sub 1} values were measured in 2 Larmor frequencies: 20.42 MHz and 34.24 MHz. The results for T{sub 1} were seem to be qualitatively similar to those measured in the system with two inequivalent sublattices. The T{sub 2} measurements, in the Pb{sub O84} Bi{sub 0-16} F{sub 2-16} crystal, were made during temperature cycles in the range of 300 K to 830 K. The difference in activation energy between cooling and heating half cycles, found to be approximately 0.08 eV, appear to be associated with the change in the clusters structure and not to the energy of defect formation. Finally, similar T{sub 2} measurements during temperature cycling was made in K{sub 0-4} Bi{sub 0-6} F{sub 2-2} : 2% Pb F{sub 2} crystal, in the temperature range 300 K to 800 K, but in this case no difference in the cooling and heating results was observed. We also measured, in the same temperature range, the T{sub 1} relaxation time in 3 Larmor frequencies: 11.71 MHz, 20.42 MHz and 34.24 Mhz. This results appear to indicate the existence of two hopping mechanism. (author). 132 refs., 68 figs.

  18. Direct reading spectrochemical determination of aluminium, iron and silicon in fluorite; Determinacion espectroquimica de lectura directa de aluminio, hierro y silicio en fluorita

    Energy Technology Data Exchange (ETDEWEB)

    Roca, M

    1966-07-01

    A quantitative spectrochemical method for the determination of Al, Fe and Si in fluorite has been worked out. The sample was supported in a graphite electrode with crater of 5 mm. in diameter, 2,5 mm deep, and burned by a d.c. are in a direct reading spectrometer. The excitation of samples has been studied without dilution as well as using graphite powder as diluent in the ratios 1:1, 1:4, and 1:9; the latter factor was chosen. Ag, Ca, Co, Cr, Mo and Sn were tested as internal standards. It has not been found any significant inter element effect. It is necessary to use natural fluorite as base material for the standards. (Author) 5 refs.

  19. Enabling the high capacity of lithium-rich anti-fluorite lithium iron oxide by simultaneous anionic and cationic redox

    Science.gov (United States)

    Zhan, Chun; Yao, Zhenpeng; Lu, Jun; Ma, Lu; Maroni, Victor A.; Li, Liang; Lee, Eungje; Alp, Esen E.; Wu, Tianpin; Wen, Jianguo; Ren, Yang; Johnson, Christopher; Thackeray, Michael M.; Chan, Maria K. Y.; Wolverton, Chris; Amine, Khalil

    2017-12-01

    Anionic redox reactions in cathodes of lithium-ion batteries are allowing opportunities to double or even triple the energy density. However, it is still challenging to develop a cathode, especially with Earth-abundant elements, that enables anionic redox activity for real-world applications, primarily due to limited strategies to intercept the oxygenates from further irreversible oxidation to O2 gas. Here we report simultaneous iron and oxygen redox activity in a Li-rich anti-fluorite Li5FeO4 electrode. During the removal of the first two Li ions, the oxidation potential of O2- is lowered to approximately 3.5 V versus Li+/Li0, at which potential the cationic oxidation occurs concurrently. These anionic and cationic redox reactions show high reversibility without any obvious O2 gas release. Moreover, this study provides an insightful guide to designing high-capacity cathodes with reversible oxygen redox activity by simply introducing oxygen ions that are exclusively coordinated by Li+.

  20. A molecular dynamics study on the oxygen diffusion in doped fluorites: the effect of the dopant distribution

    Energy Technology Data Exchange (ETDEWEB)

    Tarancon, A. [M2E/XaRMAE/IREC, Department of Advanced Materials for Energy Applications, Catalonia Institute for Energy Research (IREC), Josep Pla 2, Torre 2, B2, 08019 Barcelona (Spain); Morata, A.; Peiro, F. [MIND/XaRMAE/IN2UB, Department of Electronics, University of Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Dezanneau, G. [Laboratoire Structures, Proprietes et Modelisation des Solides, Grande Voie des Vignes, Ecole Centrale Paris, F-92295 Chatenay-Malabry Cedex (France)

    2011-02-15

    The effect of the dopant distribution on the oxygen diffusion in doped fluorites typically used for solid oxide fuel cells electrolyte applications has been analysed by using molecular dynamics simulations. The oxygen mass transport in both yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria has been studied and compared in the range of temperatures between 1,159 and 1,959 K. A new methodology based on the analysis of local environments is used to describe the diffusion process at an atomic scale. Preferred vacancy migration pathways, most suitable conduction models, energy landscapes and jump efficiency have been detailed for each material. Finally, a particular case of non-random distribution of dopants in YSZ is presented in order to quantitatively evaluate the effect of the dopant pattern on the mass transport properties and the potential of the methodology developed here for understanding and foreseeing real configurations at the nanoscale. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. A new anion-deficient fluorite-related superstructure of Bi{sub 28}V{sub 8}O{sub 62}

    Energy Technology Data Exchange (ETDEWEB)

    Đorđević, T., E-mail: tamara.djordjevic@univie.ac.at [Institut für Mineralogie und Kristallographie-Geozentrum, Universität Wien, Althansstr. 14, A-1090 Wien (Austria); Karanović, Lj., E-mail: ljika2002@yahoo.com [Laboratory for Crystallography, Faculty of Mining and Geology, University of Belgrade, Đušina 7, 11000 Belgrade (Serbia)

    2014-12-15

    New hydrothermally synthesized Bi{sub 28}V{sub 8}O{sub 62} was structurally characterized using single-crystal X-ray diffraction data. Bi{sub 28}V{sub 8}O{sub 62} crystallizes in the novel type of defect fluorite structure related to the face-centered cubic δ-Bi{sub 2}O{sub 3}. It is monoclinic, s. g. P2{sub 1}/c, and the relation to the fluorite subcell is given as a∼(3/2)a{sub F}+(3/2)c{sub F}; b∼ −b{sub F}; c∼2a{sub F} −4c{sub F} (F in subscript indicate the unit cell parameter of fluorite). Its structure is characterized by slabs of edge sharing OBi{sub 4} tetrahedra surrounded by the OBi{sub 3} triangles. As a part of these OBi{sub 3} triangles, two positionally disordered Bi{sup 3+} cations were observed in the marginal part of the slabs. The slabs are extending along b axis and are linked by inter-slab portion of the structure composed of VO{sub 4} tetrahedra and BiO{sub 6−x} coordination polyhedra, where x is a number of vacant oxygen sites. Raman spectra verified the coordination environment of vanadium atoms in the structure. - Graphical abstract: The [4{sup ¯}01] projection of two slabs and inter-slab part of the structure in one layer parallel to the (3{sup ¯}08)=(002{sup ¯}){sub F} plane (F in subscript indicate a fluorite type structure). The large green circles are Bi atoms. Small blue circles represent partly and fully occupied O sites, respectively. Pink (hatched black) are V1O{sub 4} and blue (hatched white) are V2O{sub 4} coordination tetrahedra. - Highlights: • Single crystals of Bi{sub 28}V{sub 8}O{sub 62} were grown using hydrothermal technique. • The crystal structure of Bi{sub 28}V{sub 8}O{sub 62} was solved using single-crystal XRD method. • Bi{sub 28}V{sub 8}O{sub 62} has an anion-deficient fluorite-related superstructure. • Raman spectrum confirmed the coordination environment of vanadium atoms. • Relation to the structurally related compound was discussed.

  2. Magnetic interactions in praseodymium ruthenate Pr{sub 3}RuO{sub 7} with fluorite-related structure

    Energy Technology Data Exchange (ETDEWEB)

    Inabayashi, Masaki; Doi, Yoshihiro; Wakeshima, Makoto; Hinatsu, Yukio, E-mail: hinatsu@sci.hokudai.ac.jp

    2017-06-15

    Solid solutions Pr{sub 3}(Ru{sub 1-x}Ta{sub x})O{sub 7} (0≤x≤1.0) and (Pr{sub 1-x}Y{sub x}){sub 3}RuO{sub 7} (0≤x≤0.7) were obtained as a single phase compound. They crystallize in an orthorhombic superstructure derived from that of the cubic fluorite with space group Cmcm. The results of the Rietveld analysis for X-ray diffraction profiles of Pr{sub 3}(Ru{sub 1-x}Ta{sub x})O{sub 7} showed that Ru and Ta atoms are randomly situated at the six-coordinate 4b site. For (Pr{sub 1-x}Y{sub x}){sub 3}RuO{sub 7}, with increasing the concentration of Y ions (x value), the smaller Y ions occupy selectively the seven-coordinate 8g site rather than the eight-coordinate 4a site. Through magnetic susceptibility measurements for Pr{sub 3}(Ru{sub 1-x}Ta{sub x})O{sub 7}, the antiferromagnetic transition temperatures decrease linearly with increasing x value, and at x=0.75 no magnetic ordering was found down to 1.8 K, indicating the magnetic interaction is not one-dimensional, but three-dimensional. On the other hand, the antiferromagnetic transition temperature for (Pr{sub 1-x}Y{sub x}){sub 3}RuO{sub 7} decreases with increasing x value, but above x≥0.50 it becomes constant (~12 K). This result indicates that Pr{sup 3+} ions at the seven-coordinate site greatly contribute to the antiferromagnetic interactions observed in (Pr{sub 1-x}Y{sub x}){sub 3}RuO{sub 7}. Density functional calculations of Pr{sub 3}RuO{sub 7} demonstrate that the electronic structure gives insulating character and that oxygen 2p orbitals hybridize strongly with Ru 4d orbitals in the valence band (VB). Near the top of VB, the Pr 4 f orbitals at the seven-coordinated site also show a weak hybridization with the O(1) 2p orbitals. The Ru-O(1)-Pr superexchange pathway take part in three-dimensional magnetic interaction and play an important role in an enhancement of long-range magnetic ordering. - Graphical abstract: The spin densities and the spin polarization of Pr{sub 3}RuO{sub 7} are shown

  3. Determination of enrichment processes and radon concentration in underground mines of fluorite and coal in Santa Catarina state: criteria for radiation risk assessment

    International Nuclear Information System (INIS)

    Santos, Carlos Eduardo Lima dos

    2008-01-01

    The inhalation of radon present in underground mines can imply in the deposition of its descendants in the lungs, which may cause harm to the lungs tissues and induce cancer. Concentration of radon not greater than 500 Bq/m 3 in the environment of underground mines is considered to be acceptable internationally and concentrations above 1500 Bq/m 3 require protective measures for the miners. The objectives of this research work are to determine the enrichment processes and the concentrations of radon in air, as well as the resulting doses due to the presence of this radionuclide in three underground mines of fluorite and three underground mines of coal in the State of Santa Catarina. The concentration of radon was measured employing two types of detectors of nuclear tracks (SSNTD), the LEXAN and the CR-39. This detection method consists in counting, with the help of a microscope, tracks resulting from the interaction of alpha particles with the film, due to the penetration of Rn-222 in the interior of the detector chamber and its decaying process. Contents of radium in collected samples of rocks, minerals and underground water were determined and compared with the corresponding radon concentration found in the underground air. It was observed that the coal mines showed low concentrations of radon, which can be explained by the low concentration of radium in rocks (sandstones and siltites in the foot wall and hang wall) and in the coal that composes the mining environment or, yet still, due to the good ventilation system. The average dose to the workers of the coal mines was estimated as 0.7 mSv/a, value inferior to the limit of 1 mSv/a established by the Brazilian Nuclear Energy Commission (CNEN) for members of the public, and corresponding to a risk of fatal cancer after 50 years of work under this condition of 0.2%. On the other hand, the fluorite mines showed much higher concentrations of radon and superior to 1000 Bq/m 3 . The inefficiency of the ventilation

  4. Determination of enrichment processes and the concentrations of radon in underground mines of fluorite and coal in Santa Catarina state: criteria for evaluation of radiological risks

    International Nuclear Information System (INIS)

    Santos, Carlos Eduardo Lima dos

    2008-01-01

    The inhalation of radon present in underground mines can imply in the deposition of its descendent in the lungs, which may cause harm to the lungs tissues and induce cancer. Concentration of radon not greater than 500 Bq/m3 in the environment of underground mines is considered to be acceptable internationally and concentrations above 1500 Bq/m3 require protective measures for the miners. The objectives of this research work are to determine the enrichment processes and the concentrations of radon in air, as well as the resulting doses due to the presence of this radionuclide in three underground mines of fluorite and three underground mines of coal in the State of Santa Catarina. The concentration of radon was measured employing two types of detectors of nuclear tracks (SSNTD), the LEXAN and the CR-39. This detection method consists in counting, with the help of a microscope, tracks resulting from the interaction of alpha particles with the film, due to the penetration of Rn-222 in the interior of the detector chamber and its decaying process. Contents of radium in collected samples of rocks, minerals and underground water were determined and compared with the corresponding radon concentration found in the underground air. It was observed that the coal mines showed low concentrations of radon, which can be explained by the low concentration of radium in rocks (sandstones and siltites in the footwall and hang wall) and in the coal that composes the mining environment or, yet still, due to the good ventilation system. The average dose to the workers of the coal mines was estimated as 0.7 mSv/a, value inferior to the limit of 1 mSv/a established by the Brazilian Nuclear Energy Commission (CNEN) for members of the public, and corresponding to a risk of fatal cancer after 50 years of work under this condition of 0.2%. On the other hand, the fluorite mines showed much higher concentrations of radon and superior to 1000 Bq/m3. The inefficiency of the ventilation system

  5. Magnetic properties and structural transitions of fluorite-related rare earth osmates Ln3OsO7 (Ln=Pr, Tb)

    International Nuclear Information System (INIS)

    Hinatsu, Yukio; Doi, Yoshihiro

    2013-01-01

    Ternary rare-earth osmates Ln 3 OsO 7 (Ln=Pr, Tb) have been prepared. They crystallize in an ortho-rhombic superstructure of cubic fluorite with space group Cmcm. Both of these compounds undergo a structural phase transition at 130 K (Ln=Pr) and 580 K (Ln=Tb). These compounds show complex magnetic behavior at low temperatures. Pr 3 OsO 7 exhibits magnetic transitions at 8 and 73 K, and Tb 3 OsO 7 magnetically orders at 8 and 60 K. The Os moments become one-dimensionally ordered, and when the temperature is furthermore decreased, it provokes the ordering in the Ln 3+ sublattice that simultaneously becomes three-dimensionally ordered with the Os sublattice. - Graphical abstract: Ternary rare-earth osmates Ln 3 OsO 7 (Ln=Pr, Tb) have been prepared. They crystallize in an orthorhombic superstructure of cubic fluorite with space group Cmcm. Both of these compounds undergo a structural phase transition at 130 K (Ln=Pr) and 580 K (Ln=Tb). These compounds show complex magnetic behavior at low temperatures. Pr 3 OsO 7 exhibits magnetic transitions at 8 and 73 K, and Tb 3 OsO 7 magnetically orders at 8 and 60 K. Highlights: ► Ternary rare-earth osmates Ln 3 OsO 7 (Ln=Pr, Tb) with an ordered defect-fluorite structure have been prepared. ► Both of these compounds undergo a structural phase transition at 130 K (Ln=Pr) and 580 K (Ln=Tb). ► These compounds show complex magnetic behavior at low temperatures due to magnetic ordering of Ln and Os.

  6. Magnetic properties and structural transitions of fluorite-related rare earth osmates Ln{sub 3}OsO{sub 7} (Ln=Pr, Tb)

    Energy Technology Data Exchange (ETDEWEB)

    Hinatsu, Yukio, E-mail: hinatsu@sci.hokudai.ac.jp [Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Doi, Yoshihiro [Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan)

    2013-02-15

    Ternary rare-earth osmates Ln{sub 3}OsO{sub 7} (Ln=Pr, Tb) have been prepared. They crystallize in an ortho-rhombic superstructure of cubic fluorite with space group Cmcm. Both of these compounds undergo a structural phase transition at 130 K (Ln=Pr) and 580 K (Ln=Tb). These compounds show complex magnetic behavior at low temperatures. Pr{sub 3}OsO{sub 7} exhibits magnetic transitions at 8 and 73 K, and Tb{sub 3}OsO{sub 7} magnetically orders at 8 and 60 K. The Os moments become one-dimensionally ordered, and when the temperature is furthermore decreased, it provokes the ordering in the Ln{sup 3+} sublattice that simultaneously becomes three-dimensionally ordered with the Os sublattice. - Graphical abstract: Ternary rare-earth osmates Ln{sub 3}OsO{sub 7} (Ln=Pr, Tb) have been prepared. They crystallize in an orthorhombic superstructure of cubic fluorite with space group Cmcm. Both of these compounds undergo a structural phase transition at 130 K (Ln=Pr) and 580 K (Ln=Tb). These compounds show complex magnetic behavior at low temperatures. Pr{sub 3}OsO{sub 7} exhibits magnetic transitions at 8 and 73 K, and Tb{sub 3}OsO{sub 7} magnetically orders at 8 and 60 K. Highlights: Black-Right-Pointing-Pointer Ternary rare-earth osmates Ln{sub 3}OsO{sub 7} (Ln=Pr, Tb) with an ordered defect-fluorite structure have been prepared. Black-Right-Pointing-Pointer Both of these compounds undergo a structural phase transition at 130 K (Ln=Pr) and 580 K (Ln=Tb). Black-Right-Pointing-Pointer These compounds show complex magnetic behavior at low temperatures due to magnetic ordering of Ln and Os.

  7. The ionic conductivity and defect structure of fluorite-type solid solutions Basub(1-x)Usub(x)Fsub(2+2x)

    International Nuclear Information System (INIS)

    Ouwerkerk, M.

    1986-01-01

    The crystal growth and the characterization of the solid solutions Msub(1-x)Usub(x)Fsub(2+2x) (M = Ca, Sr, Ba and Pb) are described. X-ray diffraction and X-ray fluorescence methods have been utilized to determine the U 4+ content of the solid solutions. The incorporation of UF 4 in PbF 2 is found to have a stabilizing effect on the β-PbF 2 (fluorite) structure. A study of the conductivity properties of Basub(1-x)Usub(x)Fsub(2+2x) and of Pbsub(1-x)Usub(x)Fsub(2+2x) is presented. The effect of an anion excess on the diffuse phase transition and the specific heat anomaly of single crystals Msub(1-x)Usub(x)Fsub(2+2x) was studied with impedance spectroscopy and calorimetric measurements. Finally, a study of the fluorite-type solid solutions Basub(1-x)Lasub(x)Fsub(2+x) and Basub(1-x)Usub(x)Fsub(2+2x) using the Thermally Stimulated Depolarization Current (TSDC) technique is presented. (Auth.)

  8. Magnetic properties and structural transitions of fluorite-related rare earth osmates Ln3OsO7 (Ln=Pr, Tb)

    Science.gov (United States)

    Hinatsu, Yukio; Doi, Yoshihiro

    2013-02-01

    Ternary rare-earth osmates Ln3OsO7 (Ln=Pr, Tb) have been prepared. They crystallize in an ortho-rhombic superstructure of cubic fluorite with space group Cmcm. Both of these compounds undergo a structural phase transition at 130 K (Ln=Pr) and 580 K (Ln=Tb). These compounds show complex magnetic behavior at low temperatures. Pr3OsO7 exhibits magnetic transitions at 8 and 73 K, and Tb3OsO7 magnetically orders at 8 and 60 K. The Os moments become one-dimensionally ordered, and when the temperature is furthermore decreased, it provokes the ordering in the Ln3+ sublattice that simultaneously becomes three-dimensionally ordered with the Os sublattice.

  9. Formation of defect-fluorite structured NdNiOxHy epitaxial thin films via a soft chemical route from NdNiO3 precursors.

    Science.gov (United States)

    Onozuka, T; Chikamatsu, A; Katayama, T; Fukumura, T; Hasegawa, T

    2016-07-26

    A new phase of oxyhydride NdNiOxHy with a defect-fluorite structure was obtained by a soft chemical reaction of NdNiO3 epitaxial thin films on a substrate of SrTiO3 (100) with CaH2. The epitaxial relationship of this phase relative to SrTiO3 could be controlled by changing the reaction temperature. At 240 °C, NdNiOxHy grew with a [001] orientation, forming a thin layer of infinite-layer NdNiO2 at the interface between the NdNiOxHy and the substrate. Meanwhile, a high-temperature reaction at 400 °C formed [110]-oriented NdNiOxHy without NdNiO2.

  10. Properties of complex tungstates, niobates, translated with fluorite-like structure. Svojstva slozhnykh vol'framatov, niobatov, tantalatov s flyuoritopodobnoj strukturoj

    Energy Technology Data Exchange (ETDEWEB)

    Vetkina, S N; Zolin, V F; Sirotinkin, V P; Smirnov, S A

    1989-04-01

    Spectra of ternary tungstates, niobates and tantalates (MeLa{sub 2}WO{sub 7}, La{sub 3}TO{sub 7}; Me=Ba, Sr; T=Ta, Nb) related to the layered fluorite group are analyzed. The laser pumping and time resolved luminescence are used for selecting spectra of unequivalent centers. The symmetry of the first center is near to the distorted cubic one. The vibrational spectra of europium in Eu{sub 3}NbO{sub 7} and SrLa{sub 2}WO{sub 7} are due to the chain-like structure of niobates and to the net-like structure of tantalates. The stimulated emission of Nd{sup 3+} in powders of BaLa{sub 2}WO{sub 7} and La{sub 3}NbO{sub 7} is observed at wavelengths of 1.07 and 1.063 {mu}m, respectively.

  11. Electron paramagnetic resonance and neutron activation study of lanthanide ions behaviour in fluorite. Application to the geochemical study of Montroc and Burc veins (Tarn)

    International Nuclear Information System (INIS)

    Meary, Alain

    1983-01-01

    In order to obtain a better understanding of fluorite deposits, rare earth impurities have been analyzed for a large number of samples taken from cross-sections of several low temperature hydrothermal veins; two types of measurements have been used: Electron Paramagnetic Resonance (EPR) and Neutron Activation Analysis (NAA). This enabled us to measure a 'deficit of spins' relative to the total lanthanide concentration, this deficit reveals that the paramagnetic center observed by EPR is not the only mode of incorporation. For Gd no marked deficit is observed; that is the ratio of spin concentrations to total concentration [Gd 3+ ]/[Gd total ] is close to 1 in all the samples; on the other hand, the ratios [Eu 2+ ]/[Eu total ], [Ce 3- F i - ]/[Ce total ], and [Yb 3+ ]/ [Yb total ] exhibit large variations. The first result suggests that the major part of the lanthanides in the samples is incorporated in the crystal lattice and that clustering of lanthanides ions is not important. Deficit of spins observed for Ce and Nd are probably due to the dissociation of paramagnetic complexes Ce 3+ -F i - and Nd 3+ -F i - ; for Eu, it may be attributed to the oxidized state Eu 3+ . Moreover, the sign and the amplitude of the anomaly exhibited by Eu in the normalized lanthanides spectra may be correlated with the majority valence state of Eu in the crystal: a marked positive anomaly belongs to a deficit of paramagnetic divalent Eu and, inversely, if divalent Eu is the majority valence state, the Eu anomaly appears to be negative. The results obtained for the Montroc vein are consistent with a model involving discontinuous injections of hydrothermal solutions. They may be connected to variations of oxygen fugacity arising from cooling of these solutions and from precipitation of sulfides during fluorite precipitation. (author) [fr

  12. Study On Beneficiation Technology Of Dong Pao Rare-Earth-Barite-Fluorite With Two Product Plans About Content And Recovery Of Rare-Earth Fine Ores

    International Nuclear Information System (INIS)

    Duong Van Su; Truong Thi Ai; Bui Ba Duy; Bui Thi Bay; Nguyen Hong Ha; Le Thi Hong Ha; Doan Thi Mo; Doan Dac Ban; Nguyen Hoang Son

    2014-01-01

    The ore sample used in the research was taken from the F3 ore bodies and the sample of the F7, F9 and F16 ore bodies which contain the average of 5.98% TR 2 O 3 ; they are multi-metals ore which is difficult to enrich, highly weather with very complex ingredients. The process of the experiment is the ore is crushed, ground, screened and classified reasonably to -0.1 mm and divided into 3 particle size with the following technique: (1) -0.020 mm is primary sludge and the rare-earth fine ore; (2) 0.075-1 mm is gotten through the sludge concentrating table with the output is the 2 parts: the heavy part which is dried magnetic separator with high magnetism to get the rare-earth fine ore and the light one; (3) Light minerals, non-magnetic and ferromagnetic minerals group are ground together to 85% of them get size within -0.075 mm then mix it with 0.020-0.075 mm group. Using flotation separator, get barite-rare earth mixture and fluorite. After that, we separate this mixture by secondary flotation and get refined rare earth, barite and fluorite mineral. The result of the theme: (1) product plan A-rare-earth fine ore has TR 2 O 3 content archive 42.07% with recovery is 69.70%; (2) product plan B-rare-earth fine ore has TR 2 O 3 content archive 29.64% with recovery is 80.01%. (author)

  13. Electronic structures of (Pb sub 2 Cu)Sr sub 2 Eu sub x Ce sub n sub - sub x Cu sub 2 O sub 2 sub n sub + sub 6 (n=2, 3): Effect of fluorite blocks between adjacent CuO sub 2 layers

    CERN Document Server

    Arai, M

    2003-01-01

    The electronic structures of (Pb sub 2 Cu)Sr sub 2 Eu sub x Ce sub n sub - sub x Cu sub 2 O sub 2 sub n sub + sub 6 (n = 2, 3) compounds which have fluorite blocks between two adjacent CuO sub 2 layers have been studied by using ab-initio method. It is found that the anisotropy is enhanced by inserting the fluorite blocks. The Fermi velocity perpendicular to the CuO sub 2 layers decreases as the thickness of fluorite blocks increases. The Eu substitution is found to affect both the atomic positions and electronic structures. The distance between apical oxygen and copper becomes shorter by the Eu substitution. The energy bands derived from oxygens in the fluorite blocks approach Fermi energy as the content of Eu substitution increases. (author)

  14. Brine history indicated by argon, krypton, chlorine, bromine, and iodine analyses of fluid inclusions from the Mississippi Valley type lead-fluorite-barite deposits at Hansonburg, New Mexico

    Science.gov (United States)

    Böhlke, J.K.; Irwin, J.J.

    1992-01-01

    Argon, krypton, chlorine, bromine, and iodine were measured in a homogeneous population of high-salinity hydrothermal fluid inclusions from the Tertiary-age Mississippi Valley-type (MVT) lead-fluorite-barite deposits at Hansonburg, New Mexico to establish new types of evidence for the history of both the fluid and the major dissolved salts. Noble gases and halogens in fluid inclusions containing 10−10–10−9 L of brine (Cl= 3 molal) were analyzed by laser microprobe noble-gas mass spectrometry (lmngms) on neutron-irradiated samples.The concentrations of36Ar (4.7 × 10−8 molal) and84Kr1.8 × 10−9 molal) in the fluid inclusions are equal to those of fresh surface waters in equilibrium with air at approximately20 ± 5°. The mole ratios ofBr/Cl (1.2 × 10−4) andI/Cl (1–2 × 10−6) are among the lowest measured in any natural waters, similar to those of modern brines formed by dissolution of Permian NaCl-bearing evaporites in southeast New Mexico.40Ar/36Ar ratios (600) are twice that of air, and indicate that the fluid inclusions had excess radiogenic40Ar (1.4 × 10−5 molal) when trapped. The amount of excess40Ar appears to be too large to have been acquired with Cl by congruent dissolution of halite-bearing evaporites, and possibly too small to have been acquired with Pb by congruent dissolution of granitic basement rocks with Proterozoic KAr ages.From thelmngms data, combined with published Pb and S isotope data, we infer the following sequence of events in the history of the Hansonburg MVT hydrothermal brine: (1) the brine originated as relatively dilute meteoric water, and it did not gain or lose atmospheric Ar or Kr after recharge; (2) the originally dilute fluid acquired the bulk of its Cl and sulfate in the subsurface after recharge by dissolving halite-bearing Permian? marine evaporites; (3) the high salinity brine then acquired most of its Pb and excess radiogenic40Ar from interactions with aquifer rocks other than evaporites, possibly clastic

  15. Chemical ordering in substituted fluorite oxides: a computational investigation of Ho2Zr2O7 and RE2Th2O7 (RE=Ho, Y, Gd, Nd, La)

    OpenAIRE

    Jonathan M. Solomon; Jacob Shamblin; Maik Lang; Alexandra Navrotsky; Mark Asta

    2016-01-01

    Fluorite-structured oxides find widespread use for applications spanning nuclear energy and waste containment, energy conversion, and sensing. In such applications the host tetravalent cation is often partially substituted by trivalent cations, with an associated formation of charge-compensating oxygen vacancies. The stability and properties of such materials are known to be influenced strongly by chemical ordering of the cations and vacancies, and the nature of such ordering and associated e...

  16. Chemical ordering in substituted fluorite oxides: a computational investigation of Ho2Zr2O7 and RE2Th2O7 (RE=Ho, Y, Gd, Nd, La)

    Science.gov (United States)

    Solomon, Jonathan M.; Shamblin, Jacob; Lang, Maik; Navrotsky, Alexandra; Asta, Mark

    2016-12-01

    Fluorite-structured oxides find widespread use for applications spanning nuclear energy and waste containment, energy conversion, and sensing. In such applications the host tetravalent cation is often partially substituted by trivalent cations, with an associated formation of charge-compensating oxygen vacancies. The stability and properties of such materials are known to be influenced strongly by chemical ordering of the cations and vacancies, and the nature of such ordering and associated energetics are thus of considerable interest. Here we employ density-functional theory (DFT) calculations to study the structure and energetics of cation and oxygen-vacancy ordering in Ho2Zr2O7. In a recent neutron total scattering study, solid solutions in this system were reported to feature local chemical ordering based on the fluorite-derivative weberite structure. The calculations show a preferred chemical ordering qualitatively consistent with these findings, and yield values for the ordering energy of 9.5 kJ/mol-cation. Similar DFT calculations are applied to additional RE2Th2O7 fluorite compounds, spanning a range of values for the ratio of the tetravalent and trivalent (RE) cation radii. The results demonstrate that weberite-type order becomes destabilized with increasing values of this size ratio, consistent with an increasing energetic preference for the tetravalent cations to have higher oxygen coordination.

  17. High-throughput continuous hydrothermal flow synthesis of Zn-Ce oxides: unprecedented solubility of Zn in the nanoparticle fluorite lattice.

    Science.gov (United States)

    Kellici, Suela; Gong, Kenan; Lin, Tian; Brown, Sonal; Clark, Robin J H; Vickers, Martin; Cockcroft, Jeremy K; Middelkoop, Vesna; Barnes, Paul; Perkins, James M; Tighe, Christopher J; Darr, Jawwad A

    2010-09-28

    High-throughput continuous hydrothermal flow synthesis has been used as a rapid and efficient synthetic route to produce a range of crystalline nanopowders in the Ce-Zn oxide binary system. High-resolution powder X-ray diffraction data were obtained for both as-prepared and heat-treated (850 degrees C for 10 h in air) samples using the new robotic beamline I11, located at Diamond Light Source. The influence of the sample composition on the crystal structure and on the optical and physical properties was studied. All the nanomaterials were characterized using Raman spectroscopy, UV-visible spectrophotometry, Brunauer-Emmett-Teller surface area and elemental analysis (via energy-dispersive X-ray spectroscopy). Initially, for 'as-prepared' Ce(1-x)Zn(x)O(y), a phase-pure cerium oxide (fluorite) structure was obtained for nominal values of x=0.1 and 0.2. Biphasic mixtures were obtained for nominal values of x in the range of 0.3-0.9 (inclusive). High-resolution transmission electron microscopy images revealed that the phase-pure nano-CeO(2) (x=0) consisted of ca 3.7 nm well-defined nanoparticles. The nanomaterials produced herein generally had high surface areas (greater than 150 m(2) g(-1)) and possessed combinations of particle properties (e.g. bandgap, crystallinity, size, etc.) that were unobtainable or difficult to achieve by other more conventional synthetic methods.

  18. Phase transition of the orthorhombic fluorite-related compounds Ln{sub 3}IrO{sub 7} (Ln = Pr, Nd, Sm, Eu)

    Energy Technology Data Exchange (ETDEWEB)

    Hinatsu, Yukio, E-mail: hinatsu@sci.hokudai.ac.j [Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Doi, Yoshihiro; Nishimine, Hiroaki; Wakeshima, Makoto [Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Sato, Mineo [Department of Chemistry and Chemical Engineering, Faculty of Engineering, Niigata University, 8050 Ikarashi 2-nocho, Niigata 950-2181 (Japan)

    2009-12-04

    Rare earth iridium oxides Ln{sub 3}IrO{sub 7} (Ln = Pr, Nd, Sm, and Eu) were prepared and their structures were determined by X-ray diffraction measurements. At room temperature, Pr{sub 3}IrO{sub 7} crystallized in an orthorhombic superstructure of cubic fluorite with space group Cmcm. The differential thermal analysis (DTA) and specific heat measurements for Ln{sub 3}IrO{sub 7} (Ln = Pr, Nd, Sm, and Eu) showed a phase transition at 262, 342, 420, and 485 K, respectively. At low temperatures, Ln{sub 3}IrO{sub 7} crystallized in a monoclinic structure with the space group P2{sub 1}/n. The transition temperatures increased with decreasing the ionic radius of rare earths, which indicates that the transition is stress-induced and occurs with the lattice contraction on cooling. These results for Ln{sub 3}IrO{sub 7} were compared with the phase transitions observed for Ln{sub 3}MoO{sub 7}, Ln{sub 3}RuO{sub 7}, Ln{sub 3}ReO{sub 7}, and Ln{sub 3}OsO{sub 7}.

  19. Disorder–order phase transformation in a fluorite-related oxide thin film: In-situ X-ray diffraction and modelling of the residual stress effects

    International Nuclear Information System (INIS)

    Gaboriaud, R.J.; Paumier, F.; Lacroix, B.

    2016-01-01

    This work is focused on the transformation of the disordered fluorite cubic-F phase to the ordered cubic-C bixbyite phase, induced by isothermal annealing as a function of the residual stresses resulting from different concentrations of microstructural defects in the yttrium oxide, Y_2O_3. This transformation was studied using in-situ X-ray diffraction and was modelled using Kolmogorov–Johnson–Mehl–Avrami (KJMA) analysis. The degree of the disorder of the oxygen network was associated with the residual stress, which was a key parameter for the stability and the kinetics of the transition of the different phases that were present in the thin oxide film. When the degree of disorder/residual stress level is high, this transition, which occurs at a rather low temperature (300 °C), is interpreted as a transformation of phases that occurs by a complete recrystallization via the nucleation and growth of a new cubic-C structure. Using the KJMA model, we determined the activation energy of the transformation process, which indicates that this transition occurs via a one-dimensional diffusion process. Thus, we present the analysis and modelling of the stress state. When the disorder/residual stress level was low, a transition to the quasi-perfect ordered cubic-C structure of the yttrium oxide appeared at a rather high temperature (800 °C), which is interpreted as a classic recovery mechanism of the cubic-C structure. - Highlights: • Rare earth oxide thin films • XRD analysis • Phase transformation modelling • Residual stress effects • Crystallographic phase stability

  20. Disorder–order phase transformation in a fluorite-related oxide thin film: In-situ X-ray diffraction and modelling of the residual stress effects

    Energy Technology Data Exchange (ETDEWEB)

    Gaboriaud, R.J.; Paumier, F. [Institut Pprime, Department of Material Sciences, CNRS-University of Poitiers SP2MI-BP 30179, 86962 Futuroscope-Chasseneuil cedex (France); Lacroix, B. [CSIC, Institut de Ciencia de Materiales, University of Sevilla, Avenida Américo Vespucio, 49, 41092 Sevilla (Spain)

    2016-02-29

    This work is focused on the transformation of the disordered fluorite cubic-F phase to the ordered cubic-C bixbyite phase, induced by isothermal annealing as a function of the residual stresses resulting from different concentrations of microstructural defects in the yttrium oxide, Y{sub 2}O{sub 3}. This transformation was studied using in-situ X-ray diffraction and was modelled using Kolmogorov–Johnson–Mehl–Avrami (KJMA) analysis. The degree of the disorder of the oxygen network was associated with the residual stress, which was a key parameter for the stability and the kinetics of the transition of the different phases that were present in the thin oxide film. When the degree of disorder/residual stress level is high, this transition, which occurs at a rather low temperature (300 °C), is interpreted as a transformation of phases that occurs by a complete recrystallization via the nucleation and growth of a new cubic-C structure. Using the KJMA model, we determined the activation energy of the transformation process, which indicates that this transition occurs via a one-dimensional diffusion process. Thus, we present the analysis and modelling of the stress state. When the disorder/residual stress level was low, a transition to the quasi-perfect ordered cubic-C structure of the yttrium oxide appeared at a rather high temperature (800 °C), which is interpreted as a classic recovery mechanism of the cubic-C structure. - Highlights: • Rare earth oxide thin films • XRD analysis • Phase transformation modelling • Residual stress effects • Crystallographic phase stability.

  1. Crystal structure of fluorite-related Ln3SbO7 (Ln=La–Dy) ceramics studied by synchrotron X-ray diffraction and Raman scattering

    International Nuclear Information System (INIS)

    Siqueira, K.P.F.; Borges, R.M.; Granado, E.; Malard, L.M.; Paula, A.M. de; Moreira, R.L.; Bittar, E.M.; Dias, A.

    2013-01-01

    Ln 3 SbO 7 (Ln=La, Pr, Nd, Sm, Eu, Gd, Tb and Dy) ceramics were synthesized by solid-state reaction in optimized conditions of temperature and time to yield single-phase ceramics. The crystal structures of the obtained ceramics were investigated by synchrotron X-ray diffraction, second harmonic generation (SHG) and Raman scattering. All samples exhibited fluorite-type orthorhombic structures with different oxygen arrangements as a function of the ionic radius of the lanthanide metal. For ceramics with the largest ionic radii (La–Nd), the ceramics crystallized into the Cmcm space group, while the ceramics with intermediate and smallest ionic radii (Sm–Dy) exhibited a different crystal structure belonging to the same space group, described under the Ccmm setting. The results from SHG and Raman scattering confirmed these settings and ruled out any possibility for the non-centrosymmetric C222 1 space group describing the structure of the small ionic radii ceramics, solving a recent controversy in the literature. Besides, the Raman modes for all samples are reported for the first time, showing characteristic features for each group of samples. - Graphical abstract: Raman spectrum for La 3 SbO 7 ceramics showing their 22 phonon modes adjusted through Lorentzian lines. According to synchrotron X-ray diffraction and Raman scattering, this material belongs to the space group Cmcm. - Highlights: • Ln 3 SbO 7 ceramics belonging to the space groups Cmcm and Ccmm are synthesized. • SXRD, SHG and Raman scattering confirmed the orthorhombic structures. • Ccmm instead of C222 1 is the correct one based on SHG and Raman data

  2. Fluid evolution and mineralogy of Mn-Fe-barite-fluorite mineralizations at the contact of the Thuringian Basin, Thüringer Wald and Thüringer Schiefergebirge in Germany

    Directory of Open Access Journals (Sweden)

    Majzlan Juraj

    2016-02-01

    Full Text Available Numerous small deposits and occurrences of Mn-Fe-fluorite-barite mineralization have developed at the contact of the Thuringian Basin, Thüringer Wald and Thüringer Schiefergebirge in central Germany. The studied mineralizations comprise the assemblages siderite+ankerite-calcite-fluorite-barite and hematite-Mn oxides-calcite-barite, with the precipitation sequence in that order within each assemblage. A structural geological analysis places the origin of the barite veins between the Middle Jurassic and Early Cretaceous. Primary fluid inclusions contain water vapour and an aqueous phase with NaCl and CaCl2 as the main solutes, with salinities mostly between 24–27 mass. % CaCl2 eq. Th measurements range between 85 °C and 160 °C in barite, between 139 °C and 163 °C in siderite, and between 80 °C and 130 °C in fluorite and calcite. Stable isotopes (S, O point to the evaporitic source of sulphur in the observed mineralizations. The S,C,O isotopic compositions suggest that barite and calcite could not have precipitated from the same fluid. The isotopic composition of the fluid that precipitated barite is close to the sea water in the entire Permo–Mesozoic time span whereas calcite is isotopically distinctly heavier, as if the fluids were affected by evaporation. The fluid evolution in the siliciclastic/volcanic Rotliegend sediments (as determined by a number of earlier petrological and geochemical studies can be correlated with the deposition sequence of the ore minerals. In particular, the bleaching of the sediments by reduced Rotliegend fluids (basinal brines could be the event that mobilized Fe and Mn. These elements were deposited as siderite+ankerite within the Zechstein carbonate rocks and as hematite+Mn oxides within the oxidizing environment of the Permian volcanic and volcanoclastic rocks. A Middle-Jurassic illitization event delivered Ca, Na, Ba, and Pb from the feldspars into the basinal brines. Of these elements, Ba was

  3. Chemical ordering in substituted fluorite oxides: A computational investigation of Ho2 Zr2 O7 and RE2 Th2 O7 (RE=Ho, Y, Gd, Nd, La)

    OpenAIRE

    Solomon, JM; Shamblin, J; Lang, M; Navrotsky, A; Asta, M

    2016-01-01

    © 2016 The Author(s). Fluorite-structured oxides find widespread use for applications spanning nuclear energy and waste containment, energy conversion, and sensing. In such applications the host tetravalent cation is often partially substituted by trivalent cations, with an associated formation of charge-compensating oxygen vacancies. The stability and properties of such materials are known to be influenced strongly by chemical ordering of the cations and vacancies, and the nature of such ord...

  4. Ion mobility and conductivity in the M{sub 0.5–x}Pb{sub x}Bi{sub 0.5}F{sub 2+x} (M=K, Rb) solid solutions with fluorite structure

    Energy Technology Data Exchange (ETDEWEB)

    Kavun, V. Ya., E-mail: kavun@ich.dvo.ru [Institute of Chemistry FEBRAS, 159, Pr. 100-letya Vladivostoka, Vladivostok 690022 (Russian Federation); Uvarov, N.F. [Institute of Solid State Chemistry and Mechanochemistry, SB RAS, 18, Kutateladze Str., Novosibirsk 630128 (Russian Federation); Slobodyuk, A.B.; Polyantsev, M.M.; Merkulov, E.B. [Institute of Chemistry FEBRAS, 159, Pr. 100-letya Vladivostoka, Vladivostok 690022 (Russian Federation); Ulihin, A.S. [Institute of Solid State Chemistry and Mechanochemistry, SB RAS, 18, Kutateladze Str., Novosibirsk 630128 (Russian Federation); Goncharuk, V.K. [Institute of Chemistry FEBRAS, 159, Pr. 100-letya Vladivostoka, Vladivostok 690022 (Russian Federation)

    2017-05-15

    Ionic mobility and conductivity in the K{sub 0.5–x}Pb{sub x}Bi{sub 0.5}F{sub 2+x} and Rb{sub 0.5–x}Pb{sub x}Bi{sub 0.5}F{sub 2+x} (x=0.05, 0.09) solid solutions with the fluorite structure have been investigated using the methods of {sup 19}F NMR, X-ray diffraction and impedance spectroscopy. Types of ionic motions in the fluoride sublattice of solid solutions have been established and temperature ranges of their realization have been determined (150–450 K). Diffusion of fluoride ions is a dominating type of ionic motions in the fluoride sublattice of solid solutions under study above 350 K. Due to high ionic conductivity, above 10{sup –3} S/cm at 450 K, these solid solutions can be used as solid electrolytes in various electrochemical devices and systems. - Graphical abstract: Temperature dependence of the concentration of mobile (2, 4) and immobile (1, 3) F ions in the K{sub 0.5–x}Pb{sub x}Bi{sub 0.5}F{sub 2+x} solid solutions. - Highlights: • Studied the ion mobility, conductivity in M{sub 0.5–x}Pb{sub x}Bi{sub 0.5}F{sub 2+x} solid solutions (M=K, Rb). • An analysis of {sup 19}F NMR spectra made it possible to identify types of ion mobility. • The main type of ion motion above 300 K in solid solutions is a diffusion of ions F{sup –}. • The ionic conductivity of the solid solutions studied more than 10{sup –3} S/cm at 450 K.

  5. Thermally stimulated depolarization currents in the natural fluorite

    International Nuclear Information System (INIS)

    Valerio, Mario Ernesto Giroldo

    1986-01-01

    The present work deals with natural calcium fluoride from Criciuma, Santa Catarina. Thermally Stimulated Depolarization Currents (TSDC) can be used to determine the properties of dipole defects present in this crystal. The TSDC spectrum of this material shows three bands in the temperature range of 80 to 450 K. The first one, at 130 K, is due the dipoles formed by a trivalent impurity and an interstitial fluorine ion in the next nearest position of an impurity ion (nn R s 3+ -F i - ). The second one, at 102 k, is due to the presence of small aggregates of dipoles (like a dimer). The last band, at 360 k is due to the formation of Large Clusters. The continuous distribution model gave the best fit for these bands with mean activation energies of 0.41 eV, 0.595 eV and 1.02 eV for the first, second and third band respectively. Thermal treatments can modify the number of dipoles, dimers and clusters present in the crystal. The variation in the areas under each band can be used to measure this effect. In this work we used thermal treatments between 15 minutes and 10 hours and temperatures between 200 deg C and 500 deg C. For thermal treatments at 300 deg C, the dipoles and dimers are created and the clusters are destroyed as the time of thermal treatment increases. At 400 deg C the clusters are created and the dipoles and dimers and 350 deg C for the clusters. (author)

  6. Aging simulation of the tailings from Stava fluorite extraction by exposure to gamma rays

    Directory of Open Access Journals (Sweden)

    Gianluca Bella

    Full Text Available Abstract Tailings storage facilities are disposal systems for storing the waste products of the mining industry consisting of a slurry mixture made of soil, rock and water that remain after the mineral values have been removed from the patent ore. Tailings dams are supposed to last forever, so after their deposition, tailings can experience aging processes with physical and chemical changes depending on the interactions between local conditions and source mineralogy. The consequences of these aging processes are increased interlocking of particles and oxidation processes, sometimes making previously safely held contaminants available and mobile. Among the long-term aging processes, the natural ionizing radiation (from radioactive isotopes of the soils, cosmic rays, and also ultraviolet rays from the sun can be considered, as proposed in the current research. Furthermore, in many countries, tailings are beginning to be re-used as backfill, landscaping material or feedstock for cement and concrete. So if any, the long-term physical and chemical modifications could affect the hydraulic and mechanical behaviour of tailings with relevant economic consequences. For these reasons, wet and dry silty samples of tailings spilled out after the failure of the Stava tailings dam (Trentino Alto Adige, Italy were exposed to gamma rays, as an accelerated aging technique to simulate the natural ionizing radiation, and then characterized. The modifications on physical and chemical properties were observed and, despite certain chemical stability, some physical changes were observed, particularly in terms of size particle distribution, inner porosity of the particles and specific surface.

  7. Low temperature synthesis of fluorite-type Ce-based oxides of ...

    Indian Academy of Sciences (India)

    M MALATHI

    F-type oxides can be considered as multi-functional materials due to the ... The photoluminescence property of the rare earth ions was also studied, and the color coordinates were calculated using CIE ... active photocatalysts with a view to utilize solar light. Hence ... It consists of a cylindrical quartz double walled tube with.

  8. Thermally stimulated depolarization currents in the natural fluorite; Correntes de despolarizacao termicamente estimuladas na fluorita natural

    Energy Technology Data Exchange (ETDEWEB)

    Valerio, Mario Ernesto Giroldo

    1986-12-31

    The present work deals with natural calcium fluoride from Criciuma, Santa Catarina. Thermally Stimulated Depolarization Currents (TSDC) can be used to determine the properties of dipole defects present in this crystal. The TSDC spectrum of this material shows three bands in the temperature range of 80 to 450 K. The first one, at 130 K, is due the dipoles formed by a trivalent impurity and an interstitial fluorine ion in the next nearest position of an impurity ion (nn R{sub s}{sup 3+} -F{sub i}{sup -}). The second one, at 102 k, is due to the presence of small aggregates of dipoles (like a dimer). The last band, at 360 k is due to the formation of Large Clusters. The continuous distribution model gave the best fit for these bands with mean activation energies of 0.41 eV, 0.595 eV and 1.02 eV for the first, second and third band respectively. Thermal treatments can modify the number of dipoles, dimers and clusters present in the crystal. The variation in the areas under each band can be used to measure this effect. In this work we used thermal treatments between 15 minutes and 10 hours and temperatures between 200 deg C and 500 deg C. For thermal treatments at 300 deg C, the dipoles and dimers are created and the clusters are destroyed as the time of thermal treatment increases. At 400 deg C the clusters are created and the dipoles and dimers and 350 deg C for the clusters. (author) 60 refs., 41 figs., 1 tab.

  9. Nanometric solid solutions of the fluorite and perovskite type crystal structures: Synthesis and properties

    Directory of Open Access Journals (Sweden)

    Snežana Bošković

    2012-09-01

    Full Text Available In this paper a short review of our results on the synthesis of nanosized CeO2, CaMnO3 and BaCeO3 solid solutions are presented. The nanopowders were prepared by two innovative methods: self propagating room temperature synthesis (SPRT and modified glycine/nitrate procedure (MGNP. Different types of solid solutions with rare earth dopants in concentrations ranging from 0–0.25 mol% were synthesized. The reactions forming solid solutions were studied. In addition, the characteristics of prepared nanopowders, phenomena during sintering and the properties of sintered samples are discussed.

  10. Aging simulation of the tailings from Stava fluorite extraction by exposure to gamma rays

    Energy Technology Data Exchange (ETDEWEB)

    Bella, Gianluca; Barbero, Monica; Barpi, Fabrizio, E-mail: gianluca.bella@polito.it, E-mail: monica.barbero@polito.it, E-mail: fabrizio.barpi@polito.it [Politecnico di Torino - DISEG (Italy); Lameiras, Fernando Soares, E-mail: fsl@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Espósito, Terezinha de Jesus, E-mail: esposito@etg.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Transporte e Engenharia Geotécnica

    2017-10-15

    Tailings storage facilities are disposal systems for storing the waste products of the mining industry consisting of a slurry mixture made of soil, rock and water that remain after the mineral values have been removed from the patent ore. Tailings dams are supposed to last forever, so after their deposition, tailings can experience aging processes with physical and chemical changes depending on the interactions between local conditions and source mineralogy. The consequences of these aging processes are increased interlocking of particles and oxidation processes, sometimes making previously safely held contaminants available and mobile. Among the long-term aging processes, the natural ionizing radiation (from radioactive isotopes of the soils, cosmic rays, and also ultraviolet rays from the sun) can be considered, as proposed in the current research. Furthermore, in many countries, tailings are beginning to be re-used as backfill, landscaping material or feedstock for cement and concrete. So if any, the long-term physical and chemical modifications could affect the hydraulic and mechanical behaviour of tailings with relevant economic consequences. For these reasons, wet and dry silty samples of tailings spilled out after the failure of the Stava tailings dam (Trentino Alto Adige, Italy) were exposed to gamma rays, as an accelerated aging technique to simulate the natural ionizing radiation, and then characterized. The modifications on physical and chemical properties were observed and, despite certain chemical stability, some physical changes were observed, particularly in terms of size particle distribution, inner porosity of the particles and specific surface. (author)

  11. Thermally stimulated depolarization currents in the natural fluorite; Correntes de despolarizacao termicamente estimuladas na fluorita natural

    Energy Technology Data Exchange (ETDEWEB)

    Valerio, Mario Ernesto Giroldo

    1987-12-31

    The present work deals with natural calcium fluoride from Criciuma, Santa Catarina. Thermally Stimulated Depolarization Currents (TSDC) can be used to determine the properties of dipole defects present in this crystal. The TSDC spectrum of this material shows three bands in the temperature range of 80 to 450 K. The first one, at 130 K, is due the dipoles formed by a trivalent impurity and an interstitial fluorine ion in the next nearest position of an impurity ion (nn R{sub s}{sup 3+} -F{sub i}{sup -}). The second one, at 102 k, is due to the presence of small aggregates of dipoles (like a dimer). The last band, at 360 k is due to the formation of Large Clusters. The continuous distribution model gave the best fit for these bands with mean activation energies of 0.41 eV, 0.595 eV and 1.02 eV for the first, second and third band respectively. Thermal treatments can modify the number of dipoles, dimers and clusters present in the crystal. The variation in the areas under each band can be used to measure this effect. In this work we used thermal treatments between 15 minutes and 10 hours and temperatures between 200 deg C and 500 deg C. For thermal treatments at 300 deg C, the dipoles and dimers are created and the clusters are destroyed as the time of thermal treatment increases. At 400 deg C the clusters are created and the dipoles and dimers and 350 deg C for the clusters. (author) 60 refs., 41 figs., 1 tab.

  12. A wet-chemical approach to perovskite and fluorite-type nanoceramics: synthesis and processing

    NARCIS (Netherlands)

    Veldhuis, Sjoerd

    2015-01-01

    In thesis the low-temperature, wet-chemical approach to various functional inorganic oxide materials is described. The main focus of this research is to control the material’s synthesis from liquid precursor to metal oxide powder or thin film; while understanding its formation mechanism. In

  13. Activated crystals of fluorite type as photochromic mediums for recording of volumetric holograms

    International Nuclear Information System (INIS)

    Arkhangel'skaya, V.A.; Ashcheulov, Yu.V.; Perfilov, V.N.; Rejterov, V.M.; Sukhanov, V.I.; Feofilov, P.P.

    1975-01-01

    The paper is a study of the mechanism of photochromism and of the photochromic and holographic properties of fluorides of alkaline earth metals with one and two rare-earth activators. It is shown that the angular selectivity of ''thick'' (d approximately 2-5 mm) crystals is 2-3 angular minutes and that the optimum energy exposures, corresponding to the maximum diffraction efficiency values, are 0.1-1.0 J/cm 2 for singly-activated crystals and 1.0-10 J/cm 2 for crystals with two activators. The diffraction efficiencies of holograms of both types of crystals is in the range of approximately 0.1-0.2%. The experimental data are compared with calculations made for photochromic crystals with pigmentation centres. It is suggested that the materials studied can serve as a basis for measuring volumetric holograms. (author)

  14. Solid thermoluminescent dosemeter of sodium tetraborate and brazilian fluorite sensible to thermic neutrons

    International Nuclear Information System (INIS)

    Fratin, L.; Cruz, M.T. da

    1987-01-01

    The production of solid thermoluminescent dosemeters sensible to thermic neutrons is described. The stages of the production are described: vitrification of sodium tetraborate, mixture and cold pressing, syntherization. The obtention of a CaF 2 : natural dosemeter with NaCl which presents sensibility to gamma radiation similar to CaF 2 : natural dosemeter with Na 2 B 4 O 7 is studied. (M.A.C.) [pt

  15. Mode coupling analysis of coherent quasi-elastic neutron scattering from fluorite-type materials approaching the superionic transition

    International Nuclear Information System (INIS)

    Chaturvedi, D.K.; Tosi, M.P.

    1987-08-01

    Neutron scattering experiments on SrCl 2 , CaF 2 and PbF 2 have shown that intensity and width of the coherent diffuse quasi-elastic spectrum increase rapidly with temperature into the fast-ion conducting phase, the main feature in the integrated quasi-elastic intensity being a peak just beyond the (200) point along the (100) direction in scattering wave vector space. The Zwanzig-Mori memory function formalism is used in this work to analyze the quasi-elastic scattering cross section from charge density fluctuations in terms of anharmonic couplings between the vibrational modes of the crystal. The two- and three-mode channels are examined for compatibility with the quasi-elastic neutron scattering evidence, on the basis of (i) energy and momentum conservation and van Hove singularity arguments and (ii) measured phonon dispersion curves along the main symmetry directions in SrCl 2 , CaF 2 , SrF 2 and BaF 2 . The analysis identifies a specific microscopic role for the Raman-active optic branches. The eigenvectors of the relevant Raman-active and partner modes in the three-mode channel describe relative displacements of the two halogens in the unit cell superposed on relative displacements of the halogen and alkaline earth components. This microscopic picture is thus consistent with the superionic transition being associated with the onset of dynamic disorder in the anionic component of the crystal. (author). 13 refs, 2 tabs

  16. Influence of Gold on Ce-Zr-Co Fluorite-Type Mixed Oxide Catalysts for Ethanol Steam Reforming

    Directory of Open Access Journals (Sweden)

    Véronique Pitchon

    2012-02-01

    Full Text Available The effect of gold presence on carbon monoxide oxidation and ethanol steam reforming catalytic behavior of two Ce-Zr-Co mixed oxides catalysts with a constant Co charge and different Ce/Zr ratios was investigated. The Ce-Zr-Co mixed oxides were obtained by the pseudo sol-gel like method, based on metallic propionates polymerization and thermal decomposition, whereas the gold-supported Ce-Zr-Co mixed oxides catalysts were prepared using the direct anionic exchange. The catalysts were characterized using XRD, TPR, and EDXS-TEM. The presence of Au in doped Ce-Zr-Co oxide catalyst decreases the temperature necessary to reduce the cobalt and the cerium loaded in the catalyst and favors a different reaction pathway, improving the acetaldehyde route by ethanol dehydrogenation, instead of the ethylene route by ethanol dehydration or methane re-adsorption, thus increasing the catalytic activity and selectivity into hydrogen.

  17. phase formation and thermal stability of fcc (fluorite) Ce1-xTbxO2-d solid solutions

    NARCIS (Netherlands)

    de Vries, Karel Jan; de Vries, K.J.; Meng, G.Y.

    1998-01-01

    Ce1−xTbxO2−δ solid solutions (x = 0.3, 0.4, and 0.5) were synthesized by a coprecipitation method, using ammonia. The formation process of the solid solutions was studied as a function of temperature up to 1200°C by X-ray diffraction, thermogravimetric analysis, and differential scanning

  18. A novel nickel metal-organic framework with fluorite-like structure: Gas adsorption properties and catalytic activity in Knoevenagel condensation

    Czech Academy of Sciences Publication Activity Database

    Almáši, M.; Zeleňák, V.; Opanasenko, Maksym; Čejka, Jiří

    2014-01-01

    Roč. 43, č. 9 (2014), s. 3730-3738 ISSN 1477-9226 R&D Projects: GA ČR GBP106/12/G015 Institutional support: RVO:61388955 Keywords : zeolites * ligand * temperature Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.197, year: 2014

  19. Determination of thermodynamic properties and stability limit from fluorite phase of uranium and lanthanide mixed oxides, using galvanic cells with solid electrolytes

    International Nuclear Information System (INIS)

    Santiago, T.N.

    1980-10-01

    A method for thermodynamic properties determination for oxygen solubility in oxide systems at temperature interval 973 ≤ T [K] ≤ 1773 is described. A galvanic cell using as solid electrolytes zircon dioxide doped with 15% of calcium oxide is presented. This method was used for determining the phase change, temperature dependent, of uranium-lanthanides-oxygen Ln U O 4 stoichiometric system. (C.G.C.)

  20. A petrographic study of Precambrian quartzites from Goa coast

    Digital Repository Service at National Institute of Oceanography (India)

    Wagle, B.G.; Rajamanickam, G.V.

    tourmaline, topaz, zircon, rutile, fluorite, apatite and hornblende lead to a source of acidic composition. The introduction of tourmaline and fluorite in the wacke, the grade of metamorphism and the source of the wacke have been discussed...

  1. Optical properties of a new Bi{sub 38}Mo{sub 7}O{sub 78} semiconductor with fluorite-type δ-Bi{sub 2}O{sub 3} structure

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zuoshan; Bi, Shala; Wan, Yingpeng [State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Huang, Pengjie [College of Textile and Clothing Engineering, Soochow University, Suzhou 215006 (China); Zheng, Min, E-mail: zhengmin@suda.edu.cn [College of Textile and Clothing Engineering, Soochow University, Suzhou 215006 (China)

    2017-03-31

    Highlights: • Bi{sub 38}Mo{sub 7}O{sub 78} semiconductor nanoparticles were synthesized by sol-gel method. • Bi{sub 38}Mo{sub 7}O{sub 78} keeps the structural characteristics of the patrimonial δ-Bi{sub 2}O{sub 3} structure. • Bi{sub 38}Mo{sub 7}O{sub 78} show an efficient optical absorption in visible light. • Photocatalytic property was markedly enhanced for Bi{sub 38}Mo{sub 7}O{sub 78} nanoparticles. • The mechanism of this photocatalysis system was proposed. - Abstract: Bi{sup 3+}-containing inorganic materials usually show rich optical and electronic properties due to the hybridization between 6s and 6p electronic components together with the lone pair in Bi{sup 3+} ions. In this work, a new semiconductor of bismuth molybdate Bi{sub 38}Mo{sub 7}O{sub 78} (19Bi{sub 2}O{sub 3}·7MoO{sub 3}) was synthesized by the sol-gel film coating and the following heat process. The samples developed into nanoparticles with average size of 40 nm. The phase formation was verified via the XRD Rietveld structural refinement. Orthorhombic Bi{sub 38}Mo{sub 7}O{sub 78} can be regarded to be derived from the cubic δ-phase Bi{sub 2}O{sub 3} structure. The microstructure was investigated by SEM, EDX, TEM, BET and XPS measurements. The UV-vis absorption spectra showed that the band gap of Bi{sub 38}Mo{sub 7}O{sub 78} (2.38 eV) was greatly narrowed in comparison with Bi{sub 2}O{sub 3} (2.6 eV). This enhances the efficient absorption of visible light. Meanwhile, the conduction band of is wider and shows more dispersion, which greatly benefits the mobility of the light-induced charges taking part in the photocatalytic reactions. Bi{sub 38}Mo{sub 7}O{sub 78} nanoparticles possess efficient activities on the photodegradation of methylene blue (MB) solutions under the excitation of visible-light. The photocatalysis activities and mechanisms were discussed on the crystal structure characteristics and the measurements such as photoluminescence, exciton lifetime and XPS results.

  2. Heavily doped M1−xUxF2+2x fluorites studied by quasielastic neutron scattering(M=Ba) and specific heat measurements (M=Pb)

    DEFF Research Database (Denmark)

    Andersen, Niels Hessel; Clausen, Kurt Nørgaard; Kjems, Jørgen

    1983-01-01

    of doping is an increase of the thermally generated defect concentration; at high temperatures the effect is reversed. The microscopic defect structure of Ba0.9U0.1F2.2 has been studied by diffuse quasielastic neutron scattering experiments at room temperature. The experimental observations are in good......The thermal generation of defects in pure and doped Pb1−xUxF2+2x (x=0, 0.05and0.10) has been studied by specific heat measurements between 475 k and 875 k. A simple phenomenological mean field thermodynamic model has been developed and used to interpret the data. At low temperatures the result...

  3. Superionic conductors with the fluorite structure: a) Measurement of the ionic conductivity of SrF2 at high temperatures, b) Study of the thermodynamic properties at CaF2 by numerical simulation

    International Nuclear Information System (INIS)

    Evangelakis, Georges

    1989-01-01

    In this work we present the results of an experimental study concerning the superionic conductivity of SrF 2 and those obtained by an investigation of the thermodynamical properties of CaF 2 using molecular dynamics simulation in the superionic region. The conductivity measurements in SrF 2 have been performed at high temperatures (700-1350 K) and various frequencies (10 Hz-10 MHz). At each temperature a frequency dependence of the conductivity has been detected. The analysis of the results using complex impedance diagrams revealed that this dependence is not an intrinsic property of the material but is related to electrodes effects. The apparent activation energies associated to the different parts of the intrinsic and extrinsic conductivity regions have been determined. Unfortunately no clear conclusion relative to the conduction mechanism can be made there from. Computer simulations by molecular dynamics have been performed in CaF 2 modeled using a rigid ion potential. The diffusion coefficient, the specific heat, structure factors, mean square displacements of both anions and cations, as well as the temperature dependence of these quantities have been calculated. The good agreement found between calculated quantities and experimental results justified us in using the crude approximation of a rigid on potential. A direct computation of the superionic conductivity has been obtained for the first time using non-equilibrium molecular dynamics in the linear response regime. From the independent calculation of the diffusion coefficient and the conductivity, the Havens ratio has been deduced, Hr 0.34, in the superionic region. Its value suggests that the superionic conductivity of CaF 2 is due to a collective and correlated mechanism, a fact which has been confirmed by the MD trajectory analysis. (author) [fr

  4. Evaluation of aqueous geochemistry of fluoride enriched groundwater: A case study of the Patan district, Gujarat, Western India

    Directory of Open Access Journals (Sweden)

    Pankaj Kumar

    2017-10-01

    Saturation index for selected minerals suggests that most of the samples are oversaturated with calcite and undersaturated with fluorite. Calcite precipitation leads to the removal of Ca2+ from solution thus allowing more fluorite to dissolve. These released Ca2+ ions combine with CO32− ions to further enhance the precipitation of CaCO3.

  5. Manganese

    International Nuclear Information System (INIS)

    Fayziev, A.R.

    2002-01-01

    Present article is devoted to manganese content in fluoride. The manganese content of some geologic deposits of Tajikistan was determined by means of chemical analysis. The mono mineral samples of fluorite of 5 geologic deposits of various mineralogical and genetic type was studied. The manganese content in fluorite of geologic deposits of various mineralogical and genetic type was defined.

  6. Geochemical pattern of rare-earth elements from ore deposits of Sete Barras and Volta Grande-PR

    International Nuclear Information System (INIS)

    Ronchi, L.H.; Dardenne, M.A.

    1987-01-01

    The fluorite ore deposits of Volta Grande and Sete Barras in Parana show similar REE distribution patterns. Fluorite ores from other regions in Parana e Santa Catarina show marked differences in the REE pattern which suggest different modes of origin. (author) [pt

  7. Fabrication and characterization of oxide type fluorite with controlled porosity to study the mechanical behaviour of the fuel irradiated in storage conditions; Fabricacion y caracterizacion de oxidos tipo fluorita con porosidad controlada para estudiar el comportamiento mecanico del combustible irradiado en condiciones de almacenamiento

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, S.; Borjas, S.; Gutierrez, L.; Bonales, L. J.; Rodriguez, N.; Cobo, J. M.; Torres, Y.; Cobos, J.

    2014-07-01

    The objective of this research is to get pills with distribution of porosity to simulate mechanical properties in the irradiated fuel resulting from own burnt of the material to produce the release of fission gases. (Author)

  8. Studies on Structural and Morphological Properties of Multidoped Ceria Ce 0.8 Nd 0.0025 Sm 0.0025 Gd 0.005 Dy 0.095 Y 0.095 O 2 - δ ( x = 0.2 ) as Solid Solutions

    KAUST Repository

    Stojmenović, Marija; Pagnacco, Maja C.; Dodevski, Vladimir; Gulicovski, Jelena; Zunic, Milan; Bošković, Snežana

    2016-01-01

    spectroscopy results, single phase solid solutions of fluorite structure were evidenced regardless of the number of dopants and synthesis procedure. Both XRPD and TEM were analyses evidenced nanometer particle dimensions. The SPRT method results in obtaining

  9. High pressure phase transitions and compressibilities of Er2Zr2O7 and Ho2Zr2O7

    Science.gov (United States)

    Zhang, F. X.; Lang, M.; Becker, U.; Ewing, R. C.; Lian, J.

    2008-01-01

    Phase stability and compressibility of rare earth zirconates with the defect-fluorite structure were investigated by in situ synchrotron x-ray diffraction. A sluggish defect-fluorite to a cotunnitelike phase transformation occurred at pressures of ˜22 and ˜30GPa for Er2Zr2O7 and Ho2Zr2O7, respectively. Enhanced compressibility was found for the high pressure phase as a result of increasing cation coordination number and cation-anion bond length.

  10. High Pressure Phase Transitions and Compressibilities of Er2Zr2O7 and Ho2Zr2O7

    Energy Technology Data Exchange (ETDEWEB)

    Zhang,F.; Lang, M.; Becker, U.; Ewing, R.; Lian, J.

    2008-01-01

    Phase stability and compressibility of rare earth zirconates with the defect-fluorite structure were investigated by in situ synchrotron x-ray diffraction. A sluggish defect-fluorite to a cotunnitelike phase transformation occurred at pressures of {approx} 22 and {approx} 30 GPa for Er2Zr2O7 and Ho2Zr2O7, respectively. Enhanced compressibility was found for the high pressure phase as a result of increasing cation coordination number and cation-anion bond length.

  11. Lattice thermal expansion and solubility limits of neodymium-doped ceria

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jinhua, E-mail: jhzhang1212@126.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); State Key laboratory of Geological Process and Mineral Resources, China University of Geosciences, Wuhan 430074 (China); Ke, Changming [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Wu, Hongdan [College of Resources and Enviromental Engineering, Wuhan University of Science and Technology, Wuhan 430081 (China); Yu, Jishun [State Key laboratory of Geological Process and Mineral Resources, China University of Geosciences, Wuhan 430074 (China); Wang, Jingran [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China)

    2016-11-15

    Nd{sub x}Ce{sub 1−x}O{sub 2−0.5x} (x=0–1.0) powders were prepared by reverse coprecipitation-calcination method and characterized by XRD. The crystal structure of product powders transformed from single fluorite structure to the complex of fluorite and C-type cubic structure, and finally to trigonal structure with the increase of x-value. An empirical equation simulating the lattice parameter of neodymium doped ceria was established based on the experimental data. The lattice parameters of the fluorite structure solid solutions increased with extensive adoption of Nd{sup 3+}, and the heating temperature going up. The average thermal expansion coefficients of neodymium doped ceria with fluorite structure are higher than 13.5×10{sup −6} °C{sup −1} from room temperature to 1200 °C. - Graphical abstract: The crystal structure of Nd{sub x}Ce{sub 1−x}O{sub 2−0.5x} (x=0–1.0) powders transformed from single fluorite structure to the complex of fluorite and C-type cubic structure, and finally to trigonal structure with the increase of x-value.

  12. Mineralogical and geochemical characteristics of uranium-rich fluoriteinEl-Missikat mineralized granite,Central Eastern Desert, Egypt

    Directory of Open Access Journals (Sweden)

    Mohamed Fahmy Raslan

    2009-12-01

    Full Text Available A unique, highly radioactive variety of fluor it emineral has been recorded in the uranium occurrence of El-Missikat sheared granite pluton. In this occurrence, the uranium assumes different forms, including its presence as discrete, visible, secondary minerals, rare uraninite and its association with the jasperoid and silica veinlets. However,in some other parts of the sheared zone, the uranium was found to be solely incorporated with fluorite crystals,filling veinlet sand fractures with out any other manife station.This paper focuses ont her elevant mineralogical and geochemical characteristics of this unique fluorite variety.In addition to an investigation with binocular and polarizing microscopes, the separated fluorite grains were analyzed usingan environmental scanning electronmicroscope(ESEM and a field-emission scanning electron microscope.In addition to this,some fluorite crystals were subjected to electron microprobe analyses. While the fluorite accounted for as much as 20% of the sheared granite samples studied, it was found to range from 82 to 96 % in the different size fractions of the separated heavy mineral content. In some parts of the separated fluorite crystals,uranium inquantities of up to 2200 ppm was found to be heterogeneously distributed in the fluoritelattice,regardless of its coloration.

  13. Lattice thermal expansion and solubility limits of neodymium-doped ceria

    International Nuclear Information System (INIS)

    Zhang, Jinhua; Ke, Changming; Wu, Hongdan; Yu, Jishun; Wang, Jingran

    2016-01-01

    Nd x Ce 1−x O 2−0.5x (x=0–1.0) powders were prepared by reverse coprecipitation-calcination method and characterized by XRD. The crystal structure of product powders transformed from single fluorite structure to the complex of fluorite and C-type cubic structure, and finally to trigonal structure with the increase of x-value. An empirical equation simulating the lattice parameter of neodymium doped ceria was established based on the experimental data. The lattice parameters of the fluorite structure solid solutions increased with extensive adoption of Nd 3+ , and the heating temperature going up. The average thermal expansion coefficients of neodymium doped ceria with fluorite structure are higher than 13.5×10 −6 °C −1 from room temperature to 1200 °C. - Graphical abstract: The crystal structure of Nd x Ce 1−x O 2−0.5x (x=0–1.0) powders transformed from single fluorite structure to the complex of fluorite and C-type cubic structure, and finally to trigonal structure with the increase of x-value.

  14. Electronic, elastic, acoustic and optical properties of cubic TiO2: A DFT approach

    International Nuclear Information System (INIS)

    Mahmood, Tariq; Cao, Chuanbao; Tahir, Muhammad; Idrees, Faryal; Ahmed, Maqsood; Tanveer, M.; Aslam, Imran; Usman, Zahid; Ali, Zulfiqar; Hussain, Sajad

    2013-01-01

    The electronic, elastic, acoustic and optical properties of cubic phases TiO 2 fluorite and pyrite are investigated using the first principles calculations. We have employed five different exchange–correlation functions within the local density and generalized gradient approximations using the ultrasoft plane wave pseudopotential method. The calculated band structures of cubic-TiO 2 elucidate that the TiO 2 fluorite and pyrite are direct and indirect semiconductors in contrast to the previous findings. From our studied properties such as bulk and shear moduli, elastic constants C 44 and Debye temperature for TiO 2 fluorite and pyrite, we infer that both the cubic phases are not superhard materials and the pyrite phase is harder than fluorite. The longitudinal and transversal acoustic wave speeds for both phases in the directions [100], [110] and [111] are determined using the pre-calculated elastic constants. In addition, we also calculate the optical properties such as dielectric function, absorption spectrum, refractive index and energy loss function using the pre-optimized structure. On the observation of optical properties TiO 2 fluorite phase turn out to be more photocatalytic than pyrite

  15. Evolution of mineralizing brines in the east Tennessee Mississippi Valley-type ore field

    Energy Technology Data Exchange (ETDEWEB)

    Kesler, S.E.; Gesink, J.A.; Haynes, F.M. (Univ. of Michingan, Ann Arbor (USA))

    1989-05-01

    The east Tennessee Mississippi Valley-type (MVT) ore field contains barite-fluorite and sphalterite deposits in a continuous paleoaquifer consisting of breccia zones in the Upper Cambrian-Lower Ordovician Knox Group. Paragenetic observations and fluid inclusion compositions in these deposits indicate that the Knox paleoaquifer was invaded first by Ca-rich brines (Ca:Na about 1) that deposited fluorite and barite, and later by Na-Ca brines (Ca:Na = 0.1 to 0.5) that deposited sphalerite. Geologic relation sindicate that these brines were derived from the southeast, in the area of the Middle Ordovician Servier foreland shale basin, and that imposed by fluorite solubility indicate further that all original connate water in the Sevier basin was required to deposit the estimated flourite reserves of the ore field.Thus, the later, sphalerite-depositing brines represent recycled meteoric water from the Sevier basin or connate brines from underlying (Cambrian) shales.

  16. Composite catalyst for carbon monoxide and hydrocarbon oxidation

    Science.gov (United States)

    Liu, Wei; Flytzani-Stephanopoulos, Maria

    1996-01-01

    A method and composition for the complete oxidation of carbon monoxide and/or hydrocarbon compounds. The method involves reacting the carbon monoxide and/or hydrocarbons with an oxidizing agent in the presence of a metal oxide composite catalyst. The catalyst is prepared by combining fluorite-type oxygen ion conductors with active transition metals. The fluorite oxide, selected from the group consisting of cerium oxide, zirconium oxide, thorium oxide, hafnium oxide, and uranium oxide, and may be doped by alkaline earth and rare earth oxides. The transition metals, selected from the group consisting of molybdnum, copper, cobalt, maganese, nickel, and silver, are used as additives. The atomic ratio of transition metal to fluorite oxide is less than one.

  17. The structural priciples that underlie the higher oxides of the rare earths

    International Nuclear Information System (INIS)

    Kang, Z.C.; Zhang, J.; Eyring, L.

    1996-01-01

    The structural principle that accounts for the anion-deficient, fluorite-related homologous series of higher rare earth oxides has awaited the determination of a sufficient number of their structures to test hypotheses. Recent structure refinement of five additional members has permitted extraction of a number of generalizations concerning their crystallization behavior. These general principles are outlined. Furthermore, based on the fluorite structure itself, a phenomenological structural principle is outlined that (1) unifies all known and possible phases in these fluorite-related systems under one generic formula, (2) models all known structures correctly and (3) enables modeling of any unknown structure or polymorph in the series. All that is required are electron diffraction patterns adequate to determine the supercell and a knowledge of its composition. (orig.)

  18. Depressing effect of phenoxyl acetic acids on flotation of minerals containing Ca2+/Mg2+ gangues

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Phenoxyl acetic acids were applied to determine their depressing effect on minerals containing Ca2+/Mg2+ gangues. Calcite,mixture of calcite and fluorite, and nickel ore were used in the flotation. And the depression mechanism was studied by the determination of contact angle, zeta potential, adsorptive capacity of collector, and IR analysis as well. It is found that 0.1 mmol/L of phenoxyl acetic acid derived from pyrogallol or gallic acid exhibits strong depressing ability on calcite in almost zero yields at pH value of 9.8, and calcite can be depressed in the flotation of calcite/fluorite mixture for approximate 87% yield of fluorite. The flotation result of practical nickel ore containing serpentine indicates that these two depressants may also show better depression performance to serpentine than traditional depressants such as sodium fluosilicate and carboxylmethyl cellulose. Analysis for the depression mechanism reveals that there exists strong chemical interaction between the depressants and minerals.

  19. SANDIA MOUNTAIN WILDERNESS, NEW MEXICO.

    Science.gov (United States)

    Hedlund, D.C.; Kness, R.F.

    1984-01-01

    Geologic and mineral-resource investigations in the Sandia Mountains in New Mexico indicate that a small part of the area has a probable mineral-resource potential. Most of the mineral occurrences are small barite-fluorite veins that occur along faults on the eastern slope of the range. The barite veins in the Landsend area and in the Tunnel Spring area are classed as having a probable mineral-resource potential. Fluorite veins which occur at the La Luz mine contain silver-bearing galeana and the area near this mine is regarded as having a probable resource potential for silver. No energy resources were identified in this study.

  20. Development and simulation of various methods for neutron activation analysis

    International Nuclear Information System (INIS)

    Otgooloi, B.

    1993-01-01

    Simple methods for neutron activation analysis have been developed. The results on the studies of installation for determination of fluorine in fluorite ores directly on the lorry by fast neutron activation analysis have been shown. Nitrogen in organic materials was shown by N 14 and N 15 activation. The description of the new equipment 'FLUORITE' for fluorate factory have been shortly given. Pu and Be isotope in organic materials, including in wheat, was measured. 25 figs, 19 tabs. (Author, Translated by J.U)

  1. Pressure derivatives of the second-order elastic constants of strontium, barium, and lead nitrate

    International Nuclear Information System (INIS)

    Bedi, S.S.; Verma, M.P.

    1980-01-01

    An interpretation is given of the measured results on the pressure derivatives of second-order elastic constants (SOEC) of strontium barium, and lead nitrate crystallizing in the fluorite type structure from the Lundquist potential. Potential parameters are determined from the experimental values of SOEC and the equilibrium condition

  2. Advanced waste forms research and development. Final report, October 1, 1978-September 30, 1979

    International Nuclear Information System (INIS)

    McCarthy, G.J.

    1979-08-01

    Research on supercalcine-ceramics was conducted with the objectives of characterizing the phases and of applying them to fluorine-containing Thorex wastes. This report is concerned with quantitative phase analysis of complex ceramics using x-ray powder diffraction methods and with scanning transmission electron microscopy of these ceramics and its correlation with fluorite structure solid solution phase diagrams

  3. Coherent dynamics of the localized vibrational modes of hydrogen in CaF2

    NARCIS (Netherlands)

    Wells, J. P. R.; Rella, C. W.; Bradley, I. V.; Galbraith, I.; Pidgeon, C. R.

    2000-01-01

    We report the observation of giant quantum coherence effects in the localized modes of ionized hydrogen in synthetic fluorite. Infrared free induction decay experiments on the substitutional H+ center thew dramatic modulations at negative delay times due to interference between multiple vibrational

  4. Study of the temperature dependence of the structureof KY3F10

    DEFF Research Database (Denmark)

    Friese, K; Krüger, H; Kahlenberg, V

    2006-01-01

    KY3F10 (Fm¯3m, Z = 8) is an anion-excess fluorite-related superstructure, which is employed as a room-temperature laser, when doped with rare-earths. Earlier conductivity measurements have revealed two thermally activated processes below and above 600 K. In this work we studied the high-temperatu...

  5. Phosphorites from the error seamount, Northern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P

    are algal foraminiferal limestones of shallow water origin. X-ray diffraction study shows that calcite is the dominant mineral followed by francolite, fluorite and goethite. P 2O5 concentration of the phosphorite varies between 18.0 and 21.5%. It appears...

  6. Shock Compression Response of Calcium Fluoride (CaF2)

    Science.gov (United States)

    Root, Seth

    2017-06-01

    The fluorite crystal structure is a textbook lattice that is observed for many systems, such as CaF2, Mg2 Si, and CeO2. Specifically, CaF2 is a useful material for studying the fluorite system because it is readily available as a single crystal. Under static compression, CaF2 is known to have at least three solid phases: fluorite, cotunnite, and a Ni2 In phase. Along the Hugoniot CaF2 undergoes a fluorite to cotunnite phase transition, however, at higher shock pressures it is unknown whether CaF2 undergoes another solid phase transition or melts directly from the cotunnite phase. In this work, we conducted planar shock compression experiments on CaF2 using Sandia's Z-machine and a two-stage light gun up to 900 GPa. In addition, we use density functional theory (DFT) based quantum molecular dynamics (QMD) simulations to provide insight into the CaF2 state along the Hugoniot. In collaboration with: Michael Desjarlais, Ray Lemke, Patricia Kalita, Scott Alexander, Sandia National Laboratories. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL850.

  7. Basement and alluvial aquifers of Malawi: An overview of ...

    African Journals Online (AJOL)

    Elizabeth B Mapoma

    2014-02-17

    Feb 17, 2014 ... Rowland HAL, Gault AG, Lythgoe P, Polya DA (2008) Geochemistry of aquifer sediments and arsenic-rich groundwaters from Kandal. Province, Cambodia. Appl. Geochem. 23: 3029–3046. Sajidu SM, Masumbu FFF, Fabiano E, Ngongondo C (2007). Drinking water quality and identification of fluoritic areas ...

  8. Facile hydrothermal synthesis of CeO 2 nanopebbles

    Indian Academy of Sciences (India)

    Cerium oxide (CeO2) nanopebbles have been synthesized using a facile hydrothermal method. X-ray diffraction pattern (XRD) and transmission electron microscopy analyses confirm the presence of CeO2 nanopebbles. XRD shows the formation of cubic fluorite CeO2 and the average particle size estimated from the ...

  9. Niobium-Thorium-Strontium-Rare Earth Element Mineralogy and Preliminary Sulphur Isotope Geochemistry of the Eaglet Property, East-Central British Columbia (NTS 093A/10W)

    Czech Academy of Sciences Publication Activity Database

    Hora, Z. D.; Langrová, Anna; Pivec, Edvín; Žák, Karel

    2010-01-01

    Roč. 2009, č. 1 (2010), s. 93-96 ISSN 0381-243X Institutional research plan: CEZ:AV0Z30130516 Keywords : fluorite * celestite * pyrochlore * thorite * titanbetafite * bastnaesite * sulphur isotopes * Eaglet deposit * MINFILE 093A46 Subject RIV: DD - Geochemistry http://www.empr.gov.bc.ca/Mining/Geoscience/PublicationsCatalogue/Fieldwork/Documents/2009/08_Hora_2009.pdf

  10. Diffuse neutron scattering from anion-excess strontium chloride

    DEFF Research Database (Denmark)

    Goff, J.P.; Clausen, K.N.; Fåk, B.

    1992-01-01

    The defect structure and diffusional processes have been studied in the anion-excess fluorite (Sr, Y)Cl2.03 by diffuse neutron scattering techniques. Static cuboctahedral clusters found at ambient temperature break up at temperatures below 1050 K, where the anion disorder is highly dynamic. The a...

  11. Technical Cooperation. Project No. 77.210.9. Geological German Mission in Uruguay. Final report

    International Nuclear Information System (INIS)

    Roth, W.

    1983-01-01

    This report shows the result of work carried out in the framework of the German mission in Uruguay. The main results obtained were the general inventory of non metallic raw as well as important raw materials investigation such as bentonite, limestone, fluorite, graphite, talc and materials for construction

  12. Simulation; an everyday tool for research in chemical kinetics

    International Nuclear Information System (INIS)

    Nakhle, M.; Roux, P.; Thomas de Montpreville, C.

    1985-08-01

    In order to make apparent the facilities offered by the NEPTUNIX package in solving some complex problems in chemical kinetics, the paper deals with its application to a particular example taken from material science: assistance to the validation of mechanisms governing colloids growth in a fluorite crystal when it is irradiated by an electron beam

  13. Void lattices

    International Nuclear Information System (INIS)

    Chadderton, L.T.; Johnson, E.; Wohlenberg, T.

    1976-01-01

    Void lattices in metals apparently owe their stability to elastically anisotropic interactions. An ordered array of voids on the anion sublattice in fluorite does not fit so neatly into this scheme of things. Crowdions may play a part in the formation of the void lattice, and stability may derive from other sources. (Auth.)

  14. Determination of fluoride ions by measuring ionic activities and using selective electrode

    International Nuclear Information System (INIS)

    Angelini, J.M.G.; Castro Miquelino, F.L. de

    1984-01-01

    Fluorides interfere adversely in electroplating baths of printed circuits and in other environments where it promotes corrosion. A calibration curve for its determination was drawn with standards of known concentrations. As the concentration of the fluorite ions in the sample did not follow the linearity of the curve, it was measured by means of the standard addition method. (C.L.B.) [pt

  15. Doklad aktivity nizkoteplotních Ca-Na-Cl solanek ve feldspatizovaných granitech živcového ložiska Krásno (masiv Krudum)

    Czech Academy of Sciences Publication Activity Database

    Dolníček, Z.; René, Miloš

    2012-01-01

    Roč. 19, 1/2 (2012), s. 153-156 ISSN 1212-6209 R&D Projects: GA ČR GA205/09/0540 Institutional research plan: CEZ:AV0Z30460519 Keywords : granite * alteration * fluorite Subject RIV: DB - Geology ; Mineralogy

  16. Synthesis and structural characterization of (Bi2O3)1–x (Y2O3)x and ...

    Indian Academy of Sciences (India)

    Unknown

    Keywords. Fast ion conductors; fluorite structure; fuel cell materials. 1. Introduction. Fast ion conductors have been a subject of extensive re- search because of their interesting physical properties as ... potential of enormous commercial and ecologi- cal benefits provided suitable high performance material can be developed.

  17. Lattice dynamics of ThO2

    International Nuclear Information System (INIS)

    Gupta, M.K.; Goel, Prabhatasree; Mittal, R.; Choudhury, N.; Chaplot, S.L.

    2012-01-01

    Thorium oxide finds application in nuclear industry. It is also used as a solid state electrolyte and an optical component material. ThO 2 is found in fluorite Fm3m structure. Actinide oxides are found to undergo superionic transition at elevated temperatures, when oxygen atoms start showing liquid like diffusion behaviour

  18. P-T path fluid evolution in the Gross Spitzkoppe granite stock, Namibia

    Directory of Open Access Journals (Sweden)

    Stephen Frindt

    2002-01-01

    Full Text Available The Gross Spitzkoppe granite stock (GSS is a zoned 30 km^2 epizonal intrusion that consists of three main granites: 1 medium-grained biotite granite (marginal, 2 a coarse-grained biotite granite, and 3 a central, porphyritic granite. The stock contains pegmatites as banded marginal stockscheiders and isolated pockets composed of large alkali feldspar and quartz, dark mica, interstitial fluorite, and euhedral topaz and beryl crystals. In the porphyritic granite there are local wolframite-bearing greisens and hydrothermal fluorite and topaz-rich veins.Fluid inclusion studies were conducted on: 1 topaz and quartz crystals from the marginal stockscheider; 2 quartz, topaz, fluorite and beryl crystals from isolated pegmatites; 3 topaz from a miarolitic pegmatite; 4 beryl and quartz veins from greisenized porphyritic granite; and 5 fluorite from a late fluorite vein inthe coarse-grained biotite granite. Preliminary data indicate the presence of three compositionally distinct primary and pseudosecondary inclusion types that are of late magmatic-hydrothermal origin.Type 1. Low salinity (0–10 eq. wt% NaCl H2O (± CO2 inclusions that homogenize to the liquid phase in the temperature range of 300 to 550˚C. These inclusions are from quartz, topaz and beryl. Inclusions in fluorite from the fluorite vein homogenize at ~170˚C and have a salinity of ca. 1–2 eq. wt% NaCl.Type 2. Saline (25–30 eq. wt% NaCl halite-bearing H2O (± CO2 inclusions that homogenize to the liquid phase in the temperature range of 300 to 400˚C. These inclusions are from quartz.Type 3. Low salinity (0–3 eq. wt% NaCl H2O-CO2 inclusions that homogenize to vapor phase in the temperature range of 330 to 550˚C. These inclusions are from quartz and topaz.Hydrothermal fluids from greisen minerals are represented by type 1 and type 2 H2O inclusions. They are predominantly of low salinity (~8 eq. wt% NaCl and homogenize to the liquid phase in the temperature range of 300 to 500

  19. The Li–Si–(O)–N system revisited: Structural characterization of Li{sub 21}Si{sub 3}N{sub 11} and Li{sub 7}SiN{sub 3}O

    Energy Technology Data Exchange (ETDEWEB)

    Casas-Cabanas, M. [CIC energiGUNE, Parque Tecnológico de Álava, Albert Einstein 48, ED.CIC, 01510 Miñano (Spain); Santner, H. [Institut de Ciència de Materials de Barcelona (CSIC) Campus UAB, 08193 Bellaterra, Catalonia (Spain); Palacín, M.R., E-mail: rosa.palacin@icmab.es [Institut de Ciència de Materials de Barcelona (CSIC) Campus UAB, 08193 Bellaterra, Catalonia (Spain)

    2014-05-01

    A systematic study of the Li–Si–(O)–N system is presented. The synthetic conditions to prepare Li{sub 2}SiN{sub 2}, Li{sub 5}SiN{sub 3}, Li{sub 18}Si{sub 3}N{sub 10}, Li{sub 21}Si{sub 3}N{sub 11} and Li{sub 7}SiN{sub 3}O are described and the structure of the last two compounds has been solved for the first time. While Li{sub 21}Si{sub 3}N{sub 11} crystallizes as a superstructure of the anti-fluorite structure with Li and Si ordering, Li{sub 7}SiN{sub 3}O exhibits the anti-fluorite structure with both anion and cation disorder. - Graphical abstract: A systematic study of the Li–Si–(O)–N system is presented. Li{sub 21}Si{sub 3}N{sub 11} crystallizes as a superstructure of the anti-fluorite structure with Li and Si ordering, Li{sub 7}SiN{sub 3}O exhibits the anti-fluorite structure with both anion and cation disorder. - Highlights: • Li{sub 2}SiN{sub 2}, Li{sub 5}SiN{sub 3}, Li{sub 18}Si{sub 3}N{sub 10}, Li{sub 21}Si{sub 3}N{sub 11} and Li{sub 7}SiN{sub 3}O are prepared. • The structures of Li{sub 21}Si{sub 3}N{sub 11} and Li{sub 7}SiN{sub 3}O are presented. • Li{sub 21}Si{sub 3}N{sub 11} exhibits an anti-fluorite superstructure with Li and Si ordering.

  20. The pressure-induced structural response of rare earth hafnate and stannate pyrochlore from 0.1-50 GPa

    Science.gov (United States)

    Turner, K. M.; Rittman, D.; Heymach, R.; Turner, M.; Tracy, C.; Mao, W. L.; Ewing, R. C.

    2017-12-01

    Complex oxides with the pyrochlore (A2B2O7) and defect-fluorite ((A,B)4O7) structure-types undergo structural transformations under high-pressure. These compounds are under consideration for applications including as a proposed waste-form for actinides generated in the nuclear fuel cycle. High-pressure transformations in rare earth hafnates (A2Hf2O7, A=Sm, Eu, Gd, Dy, Y, Yb) and stannates (A2Sn2O7, A=Nd, Gd, Er) were investigated to 50 GPa by in situ Raman spectroscopy and synchrotron x-ray diffraction (XRD). Rare-earth hafnates form the pyrochlore structure for A=La-Tb and the defect-fluorite structure for A=Dy-Lu. Lanthanide stannates form the pyrochlore structure. Raman spectra revealed that at ambient pressure all compositions have pyrochlore-type short-range order. Stannate compositions show a larger degree of pyrochlore-type short-range ordering relative to hafnates. In situ high-pressure synchrotron XRD showed that rare earth hafnates and stannates underwent a pressure-induced phase transition to a cotunnite-like (Pnma) structure that begins between 18-25 GPa in hafnates and between 30-33 GPa in stannates. The phase transition is not complete at 50 GPa, and upon decompression, XRD indicates that all compositions transform to defect-fluorite with an amorphous component. In situ Raman spectroscopy showed that disordering in stannates and hafnates occurs gradually upon compression. Pyrochlore-structured hafnates retain short-range order to a higher pressure (30 GPa vs. <10 GPa) than defect-fluorite-structured hafnates. Hafnates and stannates decompressed from 50 GPa show Raman spectra consistent with weberite-type structures, also reported in irradiated stannates. The second-order Birch-Murnaghan equation of state fit gives a bulk modulus of 250 GPa for hafnate compositions with the pyrochlore structure, and 400 GPa for hafnate compositions with the defect-fluorite structure. Stannates have a lower bulk modulus relative to hafnates (between 80-150 GPa

  1. The use of fluoride as a natural tracer in water and the relationship to geological features: Examples from the Animas River Watershed, San Juan Mountains, Silverton, Colorado

    Science.gov (United States)

    Bove, D.J.; Walton-Day, K.; Kimball, B.A.

    2009-01-01

    Investigations within the Silverton caldera, in southwestern Colorado, used a combination of traditional geological mapping, alteration-assemblage mapping, and aqueous geochemical sampling that showed a relationship between geological and hydrologic features that may be used to better understand the provenance and evolution of the water. Veins containing fluorite, huebnerite, and elevated molybdenum concentrations are temporally and perhaps genetically associated with the emplacement of high-silica rhyolite intrusions. Both the rhyolites and the fluorite-bearing veins produce waters containing elevated concentrations of F-, K and Be. The identification of water samples with elevated F/Cl molar ratios (> 10) has also aided in the location of water draining F-rich sources, even after these waters have been diluted substantially. These unique aqueous geochemical signatures can be used to relate water chemistry to key geological features and mineralized source areas. Two examples that illustrate this relationship are: (1) surface-water samples containing elevated F-concentrations (> 1.8 mg/l) that closely bracket the extent of several small high-silica rhyolite intrusions; and (2) water samples containing elevated concentrations of F-(> 1.8 mg/ l) that spatially relate to mines or areas that contain late-stage fluorite/huebnerite veins. In two additional cases, the existence of high F-concentrations in water can be used to: (1) infer interaction of the water with mine waste derived from systems known to contain the fluorite/huebnerite association; and (2) relate changes in water quality over time at a high elevation mine tunnel to plugging of a lower elevation mine tunnel and the subsequent rise of the water table into mineralized areas containing fluorite/huebnerite veining. Thus, the unique geochemical signature of the water produced from fluorite veins indicates the location of high-silica rhyolites, mines, and mine waste containing the veins. Existence of high F

  2. The Structure and Magnetic Properties of Pr 3MO7 with M = Nb, Ta, and Sb

    Science.gov (United States)

    Vente, J. F.; Helmholdt, R. B.; IJdo, D. J. W.

    1994-01-01

    The crystal structure of the fluorite-related praseodymium compounds with the composition Pr 3MO7, M = Nb, Ta, and Sb, have been determined using Rietveld refinement from X-ray and neutron powder diffraction data at 293 and 4 K. The structure described is orthorhombic with space group Cmcm (No. 63). It is a superstructure of the cubic fluorite structure with unit cell parameters a orth ≈ 2a c, b orth ≈ c orth ≈ a c2, as in La 3NbO 7. This structure consists of chains of corner linked MO 6 octahedra parallel with the c-axis. The magnetic susceptibility was measured between 4 and 300 K. The compounds obey the Curie-Weiss law including a Van Vleck temperature independent term. Pr 3SbO 7 shows a small deviation from this law below 25 K.

  3. A neutron diffraction study of the superionic transition in (Ca sub 1 sub - sub x Y sub x)F sub 2 sub + sub x with x=0.06

    CERN Document Server

    Hofmann, M; Wilson, C C; McIntyre, G J

    1997-01-01

    We have investigated the high-temperature superionic transition of the anion-excess fluorite (Ca sub 1 sub - sub x Y sub x)F sub 2 sub + sub x with x=0.06 using both monochromatic and time-of-flight Laue single-crystal neutron diffraction. The measured Bragg intensities indicate that the cuboctahedral defect clusters found at ambient temperature start to break up into smaller fragments even below the superionic transition temperature, T sub c approx 1200 K. Information concerning the local defect configuration at T = 1173 K has been provided by modelling the measured distribution of the coherent elastic diffuse scattering within the (11-bar0) plane of reciprocal space. The high-temperature defects are of the 'Willis' type and strongly resemble the short-lived Frenkel clusters found in the pure fluorites such as CaF sub 2 above T sub c. (author)

  4. Study of the R-(Zr,W)-(O,N) (R = Y, Nd, Sm, Gd, Yb) oxynitride system

    Energy Technology Data Exchange (ETDEWEB)

    Tessier, Franck, E-mail: Franck.Tessier@univ-rennes1.fr [UMR CNRS 6226 ' Sciences Chimiques de Rennes' , equipe ' Verres et Ceramiques' , Universite de Rennes 1, 35042 Rennes cedex (France); Maillard, Pascal [UMR CNRS 6226 ' Sciences Chimiques de Rennes' , equipe ' Verres et Ceramiques' , Universite de Rennes 1, 35042 Rennes cedex (France); Orhan, Emmanuelle [Laboratoire Science des Procedes Ceramiques et Traitements de Surface, UMR CNRS 6638, Universite de Limoges, 123 Avenue Albert Thomas, 87060 Limoges cedex (France); Chevire, Francois [UMR CNRS 6226 ' Sciences Chimiques de Rennes' , equipe ' Verres et Ceramiques' , Universite de Rennes 1, 35042 Rennes cedex (France)

    2010-02-15

    The replacement of tantalum by the couple Zr/W within the RTa-O-N systems (R = Y, Nd, Sm, Gd, Yb), enables the preparation of novel oxide and oxynitride phases in the R-Zr-W-O-N system. R{sub 2}Zr{sub 2-x}W{sub x}O{sub 7+x} oxides exhibit the fluorite-type (x < 0.9) and scheelite (x {approx} 1) structures. Corresponding oxynitride compositions are of the fluorite-type and show different colors, for example in the case of ytterbium: pale yellow (x = 0.2 or 0.25), green (x = 0.5-0.8) and brown for the tungsten-rich samples (x = 0.9, 1). Photocatalytic activity measurements have been performed to investigate the overall water splitting behavior of these colored phases.

  5. Thermal expansion data

    International Nuclear Information System (INIS)

    Taylor, D.

    1984-01-01

    This paper gives regression data for a modified second order polynomial fitted to the expansion data of, and percentage expansions for dioxides with (a) the fluorite and antifluorite structure: AmO 2 , BkO 2 , CeO 2 , CmO 2 , HfO 2 , Li 2 O, NpO 2 , PrO 2 , PuO 2 , ThO 2 , UO 2 , ZrO 2 , and (b) the rutile structure: CrO 2 , GeO 2 , IrO 2 , MnO 2 , NbO 2 , PbO 2 , SiO 2 , SnO 2 , TeO 2 , TiO 2 and VO 2 . Reduced expansion curves for the dioxides showed only partial grouping into iso-electronic series for the fluorite structures and showed that the 'law of corresponding states' did not apply to the rutile structures. (author)

  6. Glasses obtained from industrial wastes

    International Nuclear Information System (INIS)

    Bortoluzzi, D.; Oliveira Fillho, J.; Uggioni, E.; Bernardin, A.M.

    2009-01-01

    This paper deals with the study of the vitrification mechanism as an inertization method for industrial wastes contaminated with heavy metals. Ashes from coal (thermoelectric), wastes from mining (fluorite and feldspar) and plating residue were used to compose vitreous systems planed by mixture design. The chemical composition of the wastes was determined by XRF and the formulations were melted at 1450 deg C for 2h using 10%wt of CaCO 3 (fluxing agent). The glasses were poured into a mold and annealed (600 deg C). The characteristic temperatures were determined by thermal analysis (DTA, air, 20 deg C/min) and the mechanical behavior by Vickers microhardness. As a result, the melting temperature is strongly dependent on silica content of each glass, and the fluorite residue, being composed mainly by silica, strongly affects Tm. The microhardness of all glasses is mainly affected by the plating residue due to the high iron and zinc content of this waste. (author)

  7. Glasses obtained from industrial wastes; Vidros obtidos a partir de residuos industriais

    Energy Technology Data Exchange (ETDEWEB)

    Bortoluzzi, D.; Oliveira Fillho, J.; Uggioni, E. [Universidade do Extremo Sul Catarinense (UNESC), Criciuma, SC (Brazil). Curso de Engenharia de Materiais; Bernardin, A.M., E-mail: amb@unesc.ne [Servico Nacional de Aprendizagem Industrial (SENAI), Tijucas, SC (Brazil). Tecnologia em Ceramica

    2009-07-01

    This paper deals with the study of the vitrification mechanism as an inertization method for industrial wastes contaminated with heavy metals. Ashes from coal (thermoelectric), wastes from mining (fluorite and feldspar) and plating residue were used to compose vitreous systems planed by mixture design. The chemical composition of the wastes was determined by XRF and the formulations were melted at 1450 deg C for 2h using 10%wt of CaCO{sub 3} (fluxing agent). The glasses were poured into a mold and annealed (600 deg C). The characteristic temperatures were determined by thermal analysis (DTA, air, 20 deg C/min) and the mechanical behavior by Vickers microhardness. As a result, the melting temperature is strongly dependent on silica content of each glass, and the fluorite residue, being composed mainly by silica, strongly affects Tm. The microhardness of all glasses is mainly affected by the plating residue due to the high iron and zinc content of this waste. (author)

  8. National reports on raw materials economy. Vol. 6

    International Nuclear Information System (INIS)

    Haude, H.; Weber, R.

    1975-06-01

    A review is given of the ore deposits, mine production, and use of mineral resources in Argentina (oil, gas, asphalt, oil shale, coal, uranium, thorium, iron, manganese, chrome, tungsten, vanadium, copper, lead, zinc, tin, antimony, gold, silver, aluminium, beryllium, boron, sulfur, and fluorite). Argentina is dependent on imports of nearly all mineral resources. Only exports of zinc, tungsten, fluorite, and borate have been possible and the only other significant production has been of energy resources, iron, manganese, and lead. The extreme concentration of population in the east, the great distances to the Andes in the west, and the as yet inadequate transport network with the west has limited the mining activity up to the present. As part of industrial development, the government has made great efforts to increase the supply of raw materials through intensive prospecting and use of Argentina's own natural resources. Newly discovered ore deposits confirm that extensive parts of the country are prospective for mineral resources. (orig.) [de

  9. A density-functional and molecular-dynamics study on the physical properties of yttrium-doped tantalum oxynitride

    International Nuclear Information System (INIS)

    Wolff, H.; Schilling, H.; Lerch, M.; Dronskowski, R.

    2006-01-01

    Fluorite-type phases in the system Y-Ta-O-N have been studied using both first-principle electronic-structure calculations and molecular-dynamic simulations to validate the structural data and to explain unusual asymmetric reflection profiles observed in the experimental X-ray diffraction patterns. We provide evidence that the compounds may be macroscopically described as to represent cubic fluorite-type defect structures despite the fact that DFT calculations clearly show that all crystallographic unit cells appear as triclinically distorted. Additionally, we find that there is a minute (but hardly significant) tendency for anionic ordering at absolute zero temperature but none under reaction conditions. - Graphical abstract: Structural result of a room-temperature molecular-dynamic simulation of a supercell of Y 0.125 Ta 0.875 O 0.875 N□ 0.125

  10. Structures of Bi14WO24 and Bi14MoO24 from neutron powder diffraction data

    International Nuclear Information System (INIS)

    Ling, C.D.; Withers, R.L.; Thompson, J.G.; Schmid, S.

    1999-01-01

    The (isomorphous) structures of Bi 14 WO 24 , tetradecabismuth tungsten tetracosaoxide, and Bi 14 MoO 24 , tetradecabismuth molybdenum tetracosaoxide, have been solved and refined using neutron powder diffraction data in the space group I4/m. The metal-atom array is fully ordered in terms of composition, and in terms of atomic positions deviates only slightly from a fluorite-type δ-Bi 2 O 3 -related parent structure. Three independent O-atom sites (accounting for 70 out of 78 O atoms in the unit cell) are also very close to fluorite-type parent positions. The remaining two O-atom sites, which coordinate W, exhibit partial occupancies and displacive disorder, neither of which could be better modelled by lowering of symmetry. The W site is coordinated by four O atoms in highly distorted tetrahedral coordination, the tetrahedron necessarily being orientationally disordered on that site. Nonetheless, the structure appears to be chemically reasonable. (orig.)

  11. An insight into the local O{sub h} {yields}T{sub d} instability in BaF{sub 2}:Mn{sup 2+}

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Fernandez, P; Aramburu, J A; Barriuso, M T; Moreno, M, E-mail: morenom@unican.e

    2010-11-01

    While most complexes in fluorite-type lattices (CaF{sub 2}, SrF{sub 2}, CdF{sub 2}) containing Mn{sup 2+} impurities remain cubic at all temperatures, electron paramagnetic resonance (EPR) measurements have shown that the one in BaF{sub 2} is tetrahedral below 50K. This surprising behaviour is intrinsic to the centre and not associated to any close defect or pure lattice phase-transition. Through the use of density functional (DFT) calculations we show that the distortion is linked to the unexpected low force constant along the tetrahedral distortion mode with a{sub 2u} symmetry in these complexes and the large metal-ligand distance existing in BaF{sub 2}:Mn{sup 2+}. Ultimately, these facts reflect that, for substitutional impurities in fluorite-type crystals, the ligand-ligand interaction is dominant over the metal-ligand one.

  12. Investigation of radon level in Chongqing

    International Nuclear Information System (INIS)

    Pan Chunzhen; Liu Jialie; Du Hengyan; Wang Ling; Li Yiwei

    2009-01-01

    Contents of radon in air in the urban district, building fields,diggings and hotel in Chongqing were investigated. Result shows that the mean concentration of radon is 10.8 Bq/m 3 in air in the urban district, and the mean concentration of radon is 1193 Bq/m 3 in soils on building fields. Radon level is obviously different in each of diggings, with the highest being in fluorite mine and the second in plumbum and zinc mine. The statistical mean value of radon concentration of 10 typles of diggings investigated is 65.2 Bq/m 3 , while the mean concentration of radon in fluorite mine is 369 Bq/m 3 , which is 35 times higher than in the urban area. The mean concentration of radon is 32.9 Bq/m 3 in eight hotels. (authors)

  13. Pressure and temperature phase diagram of Gd{sub 2}Ti{sub 2}O{sub 7} under irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Catillon, G. [Université Paris-Est, G2I, EA4119, 5 Blvd. Descartes, F-77454 Marne la Vallée Cedex 2 (France); Chartier, A., E-mail: alain.chartier@cea.fr [CEA, DEN, DMN, SCCME, F-91191 Gif-Sur-Yvette Cedex (France)

    2014-11-21

    The pressure and temperature phase diagram of Gd{sub 2}Ti{sub 2}O{sub 7} under irradiation are calculated by means of molecular dynamics calculations. The critical temperature for amorphization obeys a linear law with pressure. Gd{sub 2}Ti{sub 2}O{sub 7} under irradiation transits towards the fluorite above this temperature and amorphizes below. The configuration of the Ti interstitial reveals to be the key of the amorphizability of Gd{sub 2}Ti{sub 2}O{sub 7}. Its stability depends upon disorder and pressure. Low pressure promotes the stabilization of Ti linked-polyhedra that drive the system to the amorphous state under irradiation. Conversely, high pressure activates its destabilization to interstitials that recombine with vacancies, driving the system to the fluorite structure under irradiation.

  14. Experimental study and thermodynamic assessment of the ZrO2-DyO1.5 system

    International Nuclear Information System (INIS)

    Wang, Chong; Zinkevich, M.; Aldinger, F.; Stuttgart Univ.

    2007-01-01

    The phase equilibria and thermodynamic properties in the ZrO 2 -DyO 1.5 system have been studied using the experimental methods of X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, differential thermal analysis and high temperature drop calorimetry. The tetragonal + fluorite and fluorite + C-Dy 2 O 3 phase equilibria between 1400 C and 1700 C have been determined, together with the enthalpy increments of the materials with 30 mol.% and 50 mol.% DyO 1.5 in the temperature range 200-1400 C. Furthermore, the martensitic transformation temperatures (A s ,M s ) have been measured for the samples with 1 and 2 mol.% DyO 1.5 . Finally, thermodynamic assessment has been carried out using the experimental results obtained and literature data. (orig.)

  15. Polycrystalline dosimetric discs of natural CaF2

    International Nuclear Information System (INIS)

    Okuno, E.; Ferreira, M.M.; Cruz, M.T.; Watanabe, S.

    1977-01-01

    A new method to prepare TL dosimeters in solid discs form, by the application of cold press in a mixture of KCL and fluorite in powder form, is investigated. By this method, it is possible to obtain thousands of dosimeters without difficulty much more uniform than that obtained from monocrystal ingots. The results show that the new dosimeters present the same properties as the fluorite in powder form, with the advantage that it is easier to handle in routine work. The ratio of 2 to 1 for KCL mass to CaF 2 mass presents good Tl sensitivity to ionizing radiation and sufficient mechanical resistivity. The minimum detectable exposure is approximately 10 mR. 83% from 442 CaF 2 solid discs gave TL response within 10% of mean value. Energy dependence is also presented [pt

  16. Eaglet property, southeastern British Columbia: Re-Os geochronology, sulphur isotopes, and thermobarometry

    Czech Academy of Sciences Publication Activity Database

    Hora, Z. D.; Stein, H.; Žák, Karel; Dobeš, P.

    2018-01-01

    Roč. 2017, č. 1 (2018), s. 157-166 ISSN 0381-243X Institutional support: RVO:67985831 Keywords : Eaglet deposit * MINFILE 093A 046 * fluorite * celestite * molybdenite * sulphur isotopes * Re-Os geochronology * fluid inclusion microthermobarometry Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology http://cmscontent.nrs.gov.bc.ca/geoscience/PublicationsCatalogue/Fieldwork/Documents/2017/P2018-1.pdf

  17. Theory of diffusion of rare gases in solids

    International Nuclear Information System (INIS)

    Lidiard, A.B.

    1980-01-01

    This paper reviews the basic theoretical description of the solubility and diffusion of rare gas atoms in crystalline solids. It then shows how this description can be used in conjunction with atomistic calculations to understand experimental observations. This understanding is particularly good for ionic compounds and a brief summary of the present situation is given for three main classes, namely those with the rocksalt structure, the fluorite structure and the caesium chloride structure. (author)

  18. REDUPP. Second annual report

    International Nuclear Information System (INIS)

    Zetterstroem Evins, L.; Vaehaenen, M.

    2013-05-01

    Understanding the interactions between solid surface and fluid during the dissolution process is essential for developing a model for spent fuel dissolution. This project aims to enhance the understanding of the dissolution process of fluorite-type materials; these have the same crystal structure as nuclear fuel. CaF 2 , CeO 2 , ThO 2 and UO 2 are here used in dissolution studies during which the evolution of the solution and surface is monitored as the dissolution proceeds. For the UO 2 -experiments, the effect of natural groundwater on the dissolution of a surface emitting alpha radiation is investigated. The goal is to use the experimental results in combination with first-principles modelling to formulate a model describing the surfaces of dissolving fluorite-type materials. The project is on-going and this report presents the progress after two years. The experimental results reported here point towards effects of surface area and surface area to volume ratios, exposed grain boundaries, and bulk vs. 'local' solubility. The importance of well-controlled analytical conditions and high-resolution measurements are emphasized, in order to distinguish differences between effects of remnant fines, amorphous precipitates, grain boundaries, surface defects and crystallographic orientation of the exposed surfaces. The progress with regards to modelling shows that a surface model is formulated which can predict the surface formation energies of all crystal planes of the fluorite structure. It has been shown that this quantity can be related with the experimental surface stability during dissolution, and that for any material with the fluorite structure the same relation between computed surface stability and experimental stability (dissolution rate) will hold. The work on setting up a model of the dissolution process is ongoing; this kind of modelling is computationally very demanding as it requires a combination of molecular dynamics simulations and ab initio electronic

  19. Electrical impedance studies of uranium oxide

    International Nuclear Information System (INIS)

    Hampton, R.N.

    1986-11-01

    The thesis presents data on the electrical properties of uranium oxide at temperatures from 1700K to 4.2K, and pressures between 25 K bar and 70 K bar. The impedance data were analysed using the technique of complex plane representation to establish the conductivity and dielectric constant of uranium dioxide. The thermophysical data were compared with previously reported experimental and theoretical work on uranium dioxide and other fluorite structured oxides. (U.K.)

  20. Uranium prospecting in alkaline mountain chimneys of Serra Negra and Salitre - Minas Gerais, Brasil

    International Nuclear Information System (INIS)

    Souza Filho, J.G.C.

    1974-01-01

    The occurence of radioactive minerals such as apatite and pyrochlore, in the alkaline chimneys of Serra Negra and Salitre (Minas Gerais, Brazil), is discussed. Also mentioned are other minerals of interest associated with the alkaline magma such as columbite, fluorite, monazite, zircon, baddeleyite, etc, which in favourable conditions may occur in deposits of great economical value, and which may present high contents of rare earths, thorium and uranium

  1. Acoustic phonon dispersion of CoSi2

    International Nuclear Information System (INIS)

    Weiss, L.; Rumyantsev, A.Yu.; Ivanov, A.S.

    1985-01-01

    The acoustical phonon dispersion curves of CoSi 2 are measured at room temperature along the main symmetry directions by means of coherent one-phonon scattering of thermal neutrons. The dispersion curves are compared with those of Ge, Si, and the fluorite structure types as CaF 2 and UO 2 . From the slope of the phonon dispersion curves at the GAMMA-point the elastic constants have been obtained

  2. Some remarks on NAA in geochemical research

    International Nuclear Information System (INIS)

    Geisler, M.

    1985-01-01

    A review is given of certain applications of NAA in geology. The emphasis is placed on reactor activation and the efficiency of NAA in gelogical research. The statements made are illustrated by a few examples showing the determination of rare elements in granites and fluorites, measurement of osmium and intercomparisons of accuracy of NAA by comparing results of the same sample analyzed by several laboratories

  3. Defining chemical expansion: the choice of units for the stoichiometric expansion coefficient

    DEFF Research Database (Denmark)

    Marrocchelli, Dario; Chatzichristodoulou, Christodoulos; Bishop, Sean R.

    2014-01-01

    Chemical expansion refers to the spatial dilation of a material that occurs upon changes in its composition. When this dilation is caused by a gradual, iso-structural increase in the lattice parameter with composition, it is related to the composition change by the stoichiometric expansion coeffi...... are provided for changes in oxygen content in fluorite, perovskite, and Ruddlesden-Popper (K2NiF4) phase materials used in solid oxide fuel cells....

  4. The effect of B-site substitution on structural transformation and ionic conductivity in Ho2(ZryTi1−y)2O7

    International Nuclear Information System (INIS)

    Shafique, Muhammad; Kennedy, Brenden J.; Iqbal, Yaseen; Ubic, Rick

    2016-01-01

    Compounds in the pyrochlore system Ho 2 (Zr y Ti 1−y ) 2 O 7 exhibit an order-disorder transition from pyrochlore to a defect-fluorite type structure. Compositions in this system were prepared via mechanical milling, followed by a two-step sintering process. Structural characterization was carried out via Rietveld refinements using neutron powder diffraction data, supported by X-ray diffraction to determine the phase and location of the pyrochlore-fluorite transformation. Unit-cell parameters were determined for the whole series using Rietveld refinements as well as the Nelson–Riley function. The neutron refinement results confirmed that the cation disorder was independent of the anion Frenkel disorder. The relation between the x-parameter in the oxygen 48f position and anion Frenkel disorder was found to be linear for the pyrochlore structure. The ionic conductivity studies were undertaken via AC impedance analysis to determine the electronic behaviour and its relation to the structural change in the temperature range 300°C–700 °C. The trends in ionic conductivity and activation energy were explained structurally via neutron powder diffraction and X-ray diffraction data. The pyrochlore-fluorite boundary composition (at y = 0.5) exhibited the lowest activation energy and highest ionic conductivity. - Highlights: • Ho 2 (Zr y Ti 1-y ) 2 O 7 structure changed from ordered pyrochlore to defect-fluorite at y = 0.6. • Ho 2 (Zr 0.5 Ti 0.5 ) 2 O 7 exhibited high ionic conductivity and low activation energy. • Doping improved stability in ionic conductivity behaviour at lower temperature.

  5. Co-adsorption of surfactants and water at inorganic solid surfaces.

    Science.gov (United States)

    Cooper, Timothy G; de Leeuw, Nora H

    2002-07-21

    Computer simulations of the co-adsorption of water and methanoic acid at a range of surface features of calcite and fluorite minerals have shown that the relative adsorption energies for the two minerals are reversed when solvent effects are included in the calculations, a finding which is important in the search for effective surfactant reagents in flotation techniques, which are used extensively in the mining and pharmaceutical industries and in environmental remediation processes.

  6. Oxygen potentials of transuranium oxides

    International Nuclear Information System (INIS)

    Haruyoshi Otobe; Mituso Akabori; Arai Yasuo; Kazuo Minato

    2008-01-01

    The oxygen potentials of pyrochlore-type Pu 2 Zr 2 O 7+y , fluorite-type (Pu 0.5 Zr 0.5 )O 2-x and AmO 2-x have been measured by the electromotive force (EMF) method with a zirconia solid-electrolyte. The oxygen potentials of these oxides were reviewed. The phase relations, microstructure, equilibrium state of these oxides were discussed, referring to the isothermal curve of the oxygen potentials. (authors)

  7. Gradient composite metal-ceramic foam as supportive component for planar SOFCs and MIEC membranes

    International Nuclear Information System (INIS)

    Smorygo, Oleg; Mikutski, Vitali; Marukovich, Alexander; Sadykov, Vladislav; Usoltsev, Vladimir; Mezentseva, Natalia; Borodinecs, Anatolijs; Bobrenok, Oleg

    2011-01-01

    A novel approach to the design of planar gradient porous supports for the thin-film SOFCs and MIEC membranes is described. The support's thermal expansion is controlled by the creation of a two-component composite metal-ceramic foam structure. Thin MIEC membranes and SOFCs were prepared on the composite supports by the layerwise deposition of composite functional layers including complex fluorites and perovskites. Lab-scale studies demonstrated promising performance of both MIEC membrane and SOFC.

  8. Gradient composite metal-ceramic foam as supportive component for planar SOFCs and MIEC membranes

    Science.gov (United States)

    Smorygo, Oleg; Mikutski, Vitali; Marukovich, Alexander; Sadykov, Vladislav; Usoltsev, Vladimir; Mezentseva, Natalia; Borodinecs, Anatolijs; Bobrenok, Oleg

    2011-06-01

    A novel approach to the design of planar gradient porous supports for the thin-film SOFCs and MIEC membranes is described. The support's thermal expansion is controlled by the creation of a two-component composite metal-ceramic foam structure. Thin MIEC membranes and SOFCs were prepared on the composite supports by the layerwise deposition of composite functional layers including complex fluorites and perovskites. Lab-scale studies demonstrated promising performance of both MIEC membrane and SOFC.

  9. A study of point defects in UO 2+x and their impact upon fuel properties

    OpenAIRE

    Ma , Yue

    2017-01-01

    Uranium dioxide is an oxygen excess, non-stoichiometric, fluorite material which exists over a wide range of compositions. At temperatures and oxygen activities that are relevant to its in-reactor behaviour, it has been reported that various types of point defects and clusters thereof may exist with different charge states and different compositions on both the anion and cation sublattices. These defects have a major influence on certain key engineering properties such as cation self -diffusi...

  10. Thin film ionic conductors based on cerium oxide

    International Nuclear Information System (INIS)

    Haridoss, P.; Hellstrom, E.; Garzon, F.H.; Brown, D.R.; Hawley, M.

    1994-01-01

    Fluorite and perovskite structure cerium oxide based ceramics are a class of materials that may exhibit good oxygen ion and/or protonic conductivity. The authors have successfully deposited thin films of these materials on a variety of substrates. Interesting orientation relationships were noticed between cerium oxide films and strontium titanate bi-crystal substrates. Near lattice site coincidence theory has been used to study these relationships

  11. Thermal expansion studies on uranium-neodymium mixed oxide solid solutions

    International Nuclear Information System (INIS)

    Panneerselvam, G.; Venkata Krishnan, R.; Antony, M.P.; Nagarajan, K.

    2012-01-01

    Uranium-Neodymium mixed oxides solid solutions (U 1-y Nd y ) O 2 (y=0.2-0.95) were prepared by combustion synthesis using citric acid as fuel. Structural characterization and computation of lattice parameter was carried out from room temperature X-ray diffraction measurements. Single-phase fluorite structure was observed up to y=0.80. For solid solutions with y>0.80 additional Nd 2 O 3 lines were visible

  12. Incorporation of uranium in pyrochlore oxides and pressure-induced phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, F.X., E-mail: zhangfx@umich.edu [Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Lang, M.; Tracy, C.; Ewing, R.C. [Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Gregg, D.J.; Lumpkin, G.R. [Institute of Materials Engineering, ANSTO, Locked Bag 2001, Kirrawee DC 2232, NSW (Australia)

    2014-11-15

    Uranium-doped gadolinium zirconates with pyrochlore structure were studied at ambient and high-pressure conditions up to 40 GPa. The bonding environment of uranium in the structure was determined by x-ray photoelectron and Raman spectroscopies and x-ray diffraction. The uranium valence for samples prepared in air is mainly U{sup 6+}, but U{sup 4+} is present in pyrochlores fabricated in an argon atmosphere. Rietveld refinement of the XRD pattern suggests that uranium ions in pyrochlores are on the 16d site in 6-fold coordination with oxygen. At pressures greater than 22 GPa, the pyrochlore structure transformed to a cotunnite-type phase. The cotunnite high-pressure phase transformed to a defect fluorite structure on the release of pressure. - Graphical abstract: In U-bearing pyrochlore, U ions mainly occupy the 16d site and replace the smaller Zr{sup 4+}, part of the oxygen will occupy the 8b site, which is empty to most pyrochlores. At pressure of 22 GPa, the pyrochlore lattice is not stable and transforms to a cotunnite-type structure. The high-pressure structure is not stable and transform to a fluorite or back to the pyrochlore structure when pressure is released. - Highlights: • We found that U ions mainly occupy the smaller cation site in U-bearing pyrochlore. • Pyrochlore structure is not stable at pressure of more than 20 GPa. • The quenched sample has a pyrochlore or a disordered fluorite structure.

  13. CaSO4:Dy and/or Tm: study of its properties for dosimetry application

    International Nuclear Information System (INIS)

    Ferreira, M.M.

    1979-01-01

    In order obtain in practical and cheap solid state dosimeter with high sensitivity, a technique initially developed to cold press a mixture of suitable materials in their powder form sensitive to radiation. The material initially used was natural CaF 2 (fluorite) for this salt was extensively studied in radiation dosimetry since it shows a thermoluminescent (TL) effect after radiation. However, natural calcium fluorite shows two main disadvantages: its high senstivity to room light and the impossibility to control its impurity content due to its natural origin. Calcium sulphate was thus used as a good substitute of fluorite. Rare earths doped calcium sulphate shows a high TL sensitivity and is not disturbed by light. It is also easily obtained in the laboratory under controlled conditions so to get reproducible impurity content. The best dosimeters that can be produced with rare earth doped calcium sulphate are CaSO 4 :Dy and CaSO 4 :Tm. Calcium sulphate, simultaneously doped with Tm and Dy was produced and 100% increase was obtained in the TL sensitivity when compared with the individually are earth doped calcium sulphate. (Author) [pt

  14. Structural Phase Transition and Compressibility of CaF2 Nanocrystals under High Pressure

    Directory of Open Access Journals (Sweden)

    Jingshu Wang

    2018-05-01

    Full Text Available The structural phase transition and compressibility of CaF2 nanocrystals with size of 23 nm under high pressure were investigated by synchrotron X-ray diffraction measurement. A pressure-induced fluorite to α-PbCl2-type phase transition starts at 9.5 GPa and completes at 20.2 GPa. The phase-transition pressure is lower than that of 8 nm CaF2 nanocrystals and closer to bulk CaF2. Upon decompression, the fluorite and α-PbCl2-type structure co-exist at the ambient pressure. The bulk modulus B0 of the 23 nm CaF2 nanocrystals for the fluorite and α-PbCl2-type phase are 103(2 and 78(2 GPa, which are both larger than those of the bulk CaF2. The CaF2 nanocrystals exhibit obviously higher incompressibility compare to bulk CaF2. Further analysis demonstrates that the defect effect in our CaF2 nanocrystals plays a dominant role in the structural stability.

  15. Mineral characterisation of Don Pao rare earth deposit in Vietnam

    International Nuclear Information System (INIS)

    XuanBen, T.

    1998-01-01

    Full text: The Don Pao Rare Earth Deposit was discovered in 1959 in Phon Tho district, about 450km North-West of Hanoi capital. Geological work was conducted between 1959-95, resulting in 60 ore bodies of various sizes being identified. The ore bodies are irregularly shaped nests, lenses and veins hosted in the shear zone, at the margin of a Paeleogene aged syenite massif. The mineral composition of Don Pao Deposit is very complex, consisting of more than 50 minerals. Among them, basnaesite, parisite, fluorite and barite are the main constituent minerals of the ore. All the minerals were identified by the modern methods of mineralogical studies. Based on the constituent mineral ratios, four ore types have been distinguished in the deposit: 1. Rare earth ore containing over 5 percent of RE 2 O 3 . 2. Rare Earth-Barite ore containing 0.5 to 30 percent of RE 2 O 3 . 3. Rare Earth-Barite-Fluorite ore containing 1 to 5 percent of RE 2 O 3 . 4. Rare Earth bearing Fluorite ore containing 1 to 5 percent of RE 2 O 3 . According to the benefication test, the ores in Don Pao can be enriched to a concentrate of 60 percent of RE 2 O 3 with a recover of 75 percent

  16. Study of the gamma spectrum of 16N with a BGO detector, for the purpose of calibration and of determining the fluorine grade of mineral samples

    International Nuclear Information System (INIS)

    Castro-Garcia, M.P.; Alonso-Sanchez, T.; Rey-Ronco, M.A.

    2013-01-01

    The study of 16 N's gamma spectrum has two main uses: calibrating gamma detectors in a high energy range, and determining the fluorine grade of mineral samples of fluorite. This article examines and compares the gamma ray spectrum of 16 N as recorded by a Bi 4 GeO 12 detector, as well as the resolution of this detector at high energy levels, and the signal-background relationship of an experimental laboratory cyclic activation unit. 16 N is the product of the reaction 9-F-19(n,α)7-N-16, which takes place during the neutron activation of mineral samples of fluorspar, and its production depends, among other factors, upon the grade of fluorite. The technique used in this study is cyclic-type neutron activation for recording delayed gamma rays, carried out with an americium-beryllium neutron source with an activity of 1 Ci. Lastly, a correlation is established between the area below the peak amount of 16 N emitted by the sample, and the sample's fluorite grade. (author)

  17. X-ray diffraction study of the Y{sub 2}Ti{sub 2}O{sub 7} pyrochlore disordering sequence under irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Soulié, Aurélien, E-mail: aurelien.soulie@cea.fr [CEA, DEN, Service de Recherches de Métallurgie Physique, Université Paris-Saclay, F-91191 Gif sur Yvette (France); CEA, DEN, Service de Recherches de Métallurgie Appliqué, Université Paris-Saclay, F-91191 Gif sur Yvette (France); Menut, Denis [CEA, DEN, Service de Recherches de Métallurgie Appliqué, Université Paris-Saclay, F-91191 Gif sur Yvette (France); Crocombette, Jean-Paul [CEA, DEN, Service de Recherches de Métallurgie Physique, Université Paris-Saclay, F-91191 Gif sur Yvette (France); Chartier, Alain [CEA, DEN, Service de la Corrosion et du Comportement des Matériaux dans leur Environnement, Laboratoire de Modélisation, de Thermodynamique et de Thermochimie, Université Paris-Saclay, F-91191 Gif sur Yvette (France); Sellami, Neila [Univ. Paris Sud, ICMMO-SP2M, Bât. 410, F-91405 Orsay (France); Sattonnay, Gaël [Univ. Paris-Sud, CSNSM, CNRS, IN2P3, Bât. 108, F-91405 Orsay (France); Monnet, Isabelle [CIMAP, CEA, CNRS, Université de Caen, BP 5133, F-14070 Caen Cedex 5 (France); and others

    2016-11-15

    The disordering sequence of Y{sub 2}Ti{sub 2}O{sub 7} pyrochlore, a nano-oxide phase that strengthens ODS steels under irradiation is studied in the experimental and modeling framework. XRD analysis has been performed considering both swift heavy ion and low energy/low mass ion irradiations. The simulation within molecular dynamics of Frenkel pair accumulation proves able to reproduce the variation of the amorphization fluence with temperature. XRD patterns calculated from the simulations reproduce well the patterns observed experimentally in the literature. Both experiments and calculations point to a first transition from pyrochlore to fluorite before an eventual amorphization. For swift heavy ion irradiations with 93 MeV Xe ions, tracks of direct impact amorphization are visible by HRTEM. Advanced refinement shows that one third of the pyrochlore impacted by an ion transforms into fluorite, while two third are directly amorphized. - Highlights: • A comparison between swift heavy ion and low energy/low mass ion irradiation of Y{sub 2}Ti{sub 2}O{sub 7} pyrochlore is performed. • Simulations of the irradiation with Molecular dynamics reproduce the amorphization dose at low energy/mass ion irradiation. • Advanced refinement of X-ray diffraction patterns gives the evolution of phase fractions in pyrochlore under irradiation. • The disordering sequence a transition from pyrochlore to defect fluorite before an eventual amorphization.

  18. Key insights on the structural characterization of textured Er{sub 2}O{sub 3}-ZrO{sub 2} nano-oxides prepared by a surfactant-free solvothermal route

    Energy Technology Data Exchange (ETDEWEB)

    Julian-Lopez, Beatriz, E-mail: julian@qio.uji.es [Departamento de Quimica Inorganica y Organica, Universitat Jaume I, Avda. Vicente Sos Baynat s/n, 12071 Castellon (Spain); Luz, Veronica de la; Gonell, Francisco; Cordoncillo, Eloisa [Departamento de Quimica Inorganica y Organica, Universitat Jaume I, Avda. Vicente Sos Baynat s/n, 12071 Castellon (Spain); Lopez-Haro, Miguel; Calvino, Jose J. [Departamento de Ciencia de los Materiales e Ingenieria Metalurgica y Quimica Inorganica, Facultad de Ciencias, Universidad de Cadiz, Campus Rio San Pedro, Puerto Real, 11510 Cadiz (Spain); Escribano, Purificacion [Departamento de Quimica Inorganica y Organica, Universitat Jaume I, Avda. Vicente Sos Baynat s/n, 12071 Castellon (Spain)

    2012-04-05

    Highlights: Black-Right-Pointing-Pointer Structural resolution of fluorite vs. pyrochlore in small nanocrystals. Black-Right-Pointing-Pointer Simple template-free solvothermal synthesis of Er{sub 2}O{sub 3}-ZrO{sub 2} nanooxides. Black-Right-Pointing-Pointer Good control over size, morphology and surface properties (280 m{sup 2} g{sup -1}). - Abstract: Zirconia-mixed oxides can exhibit cubic fluorite and pyrochlore structure. Their discrimination is not easy in nanooxides with a crystal size close to that of a few unit cells. In this work, high resolution transmission electron microscopy (HRTEM) has been employed to provide key insights on the structural characterization of a nanometric and porous mixed Er{sub 2}O{sub 3}-ZrO{sub 2} oxide. The material was prepared by a simple template-free solvothermal route that provided nanocrystalline powders at low temperature (170 Degree-Sign C) with spherical morphology, and high surface area ({approx}280 m{sup 2} g{sup -1}). The porosity was mainly originated from the assembling of organic complexing agents used in the synthesis to limit the crystal growth and to control hydrolysis and condensation reaction rates. The samples were characterized by thermal analysis, X-ray diffraction, scanning electron microscopy and N{sub 2} adsorption measurements. A detailed study by HRTEM was conducted on microtomed samples. It was observed that the material was made of nanocrystals packed into spherical agglomerates. HRTEM simulations indicated that it is not possible to identify the pyrochlore phase in nanoparticles with diameter below 2 nm. In our samples, the analysis of the HRTEM lattice images by means of fast Fourier transform (FFT) techniques revealed well defined spots that can be assigned to different planes of a cubic fluorite-type phase, even in the raw material. Raman spectroscopy was also a powerful technique to elucidate the crystalline phase of the materials with the smallest nanoparticles. HREM and Raman results evidenced

  19. Key insights on the structural characterization of textured Er2O3–ZrO2 nano-oxides prepared by a surfactant-free solvothermal route

    International Nuclear Information System (INIS)

    Julián-López, Beatriz; Luz, Verónica de la; Gonell, Francisco; Cordoncillo, Eloisa; López-Haro, Miguel; Calvino, Jose J.; Escribano, Purificación

    2012-01-01

    Highlights: ► Structural resolution of fluorite vs. pyrochlore in small nanocrystals. ► Simple template-free solvothermal synthesis of Er 2 O 3 –ZrO 2 nanooxides. ► Good control over size, morphology and surface properties (280 m 2 g −1 ). - Abstract: Zirconia-mixed oxides can exhibit cubic fluorite and pyrochlore structure. Their discrimination is not easy in nanooxides with a crystal size close to that of a few unit cells. In this work, high resolution transmission electron microscopy (HRTEM) has been employed to provide key insights on the structural characterization of a nanometric and porous mixed Er 2 O 3 –ZrO 2 oxide. The material was prepared by a simple template-free solvothermal route that provided nanocrystalline powders at low temperature (170 °C) with spherical morphology, and high surface area (∼280 m 2 g −1 ). The porosity was mainly originated from the assembling of organic complexing agents used in the synthesis to limit the crystal growth and to control hydrolysis and condensation reaction rates. The samples were characterized by thermal analysis, X-ray diffraction, scanning electron microscopy and N 2 adsorption measurements. A detailed study by HRTEM was conducted on microtomed samples. It was observed that the material was made of nanocrystals packed into spherical agglomerates. HRTEM simulations indicated that it is not possible to identify the pyrochlore phase in nanoparticles with diameter below 2 nm. In our samples, the analysis of the HRTEM lattice images by means of fast Fourier transform (FFT) techniques revealed well defined spots that can be assigned to different planes of a cubic fluorite-type phase, even in the raw material. Raman spectroscopy was also a powerful technique to elucidate the crystalline phase of the materials with the smallest nanoparticles. HREM and Raman results evidenced that the material is constituted, irrespective of the temperature of the final calcination step, by an ensemble of randomly

  20. A model for the oxygen potential of oxide fuels at high burnup

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, P; Piron, J P [CEA Centre d` Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France); Baron, D [Direction des Etudes et Recherches, Electricite de France, Moret-dur-Loing (France)

    1997-08-01

    Using Lindemer`s analysis as a starting point, a comprehensive description of the chemical state of the fluorite fuel matrix along with the most abundant fission products has been developed. The model was then implemented within the framework of an upgraded version of the SOLGASMIX program known as SAGE. In addition to approximately seventy solid compounds, three different mixture phases are modelled. The first one is the gaseous phase and comprises roughly sixty different compounds. The second is made up of noble metals such as Mo, Ru, Tc, Pd. The third mixture phase is a representation of the fluorite fuel matrix. Since SAGE is a code which calculates chemical equilibria by minimizing the Gibbs energy of the system, it is essential that reliable free energies of formation be used as data. This is relatively straightforward with regard to most compounds and thermochemical data are readily available in the open literature. As regards the fluorite phase however, the basic hypothesis is that it is possible to model the effect of defects such as interstitials (in the hyperstoichiometric phase) and vacancies (in the hypostoichiometric phase) by assuming the existence of hypothetical solute compounds such as U{sub 2}O{sub 4.5} that stabilize the hyperstoichiometric phase. As rare earths (Re) of valence two or three are dissolved in the matrix, the hypothetical compounds Re{sub 4/3}O{sub 2} and URe{sub 2}O{sub 6} are chosen to reflect the behavior of the ternay system. This description accurately predicts the hypostoichiometric region of the phase diagram but underestimate the increase in oxygen potential in the hyperstoichiometric region. 26 refs, 10 figs, 1 tab.

  1. Mineralogical Characterization of The Alteration Facies at Gabal El-Missikat Area, Central Eastern Desert, Egypt

    International Nuclear Information System (INIS)

    El-Sherif, A.M.

    2013-01-01

    The present study deals with the petrographical, mineralogical and geochemical characteristics of the alteration facies zones recognized around the shear zone at Gabal El-Missikat area, Central Eastern Desert, Egypt. Petrographically, the fresh granitic samples are composed mainly of quartz, K-feldspars (microcline and microcline perthite), plagioclase, biotite. The secondary minerals are sericite, kaolinite, muscovite, chlorite and epidote as well as zircon, apatite, fluorite, titanite and iron oxides as accessory minerals. Two alteration facies zones are recognized and namely as propylitic and advanced argillic. The propylitic facies zone is composed mainly of sericite with minor kaolinite, muscovite, quartz, relics of plagioclases, chlorite and rare epidote as well as zircon, hematite, goethite, magnetite, ilmenite, ilmenorutile, rutile, titanite, apatite, columbite and fluorite and secondary uranium minerals, the advanced argillic facies zone is composed mainly of kaolinite with minor sericite, quartz, muscovite, chlorite and rare epidote as well as zircon, hematite, goethite, magnetite, ilmenite, ilmenorutile, rutile, titanite, apatite and garnet of spessartine type as accessory minerals. The identified minerals in the studied two alteration facies zones can be grouped into three mineral groups which are: the primary minerals (pyrite, magnetite, galena, columbite and gold), the secondary minerals (uranophane, kasolite and wulfenite) and the gangue minerals (anhydrite, barite, celestine, hematite, goethite and fluorite). The identified mineral assemblage of the studied propylitic alteration facies zone may be attributed to strongly alkaline hydrothermal solutions at ph value of more than 7 with temperature varying between 350 and 450°C, while the advanced argillic alteration facies zone is essentially associated with strongly acidic hydrothermal solutions at ph value less than 7 with temperature varying between 150 and 400°C

  2. Study of fluid inclusions in rodioactive mineralized pegmatites, dara area northern eastern desert, Egypt

    International Nuclear Information System (INIS)

    Ali, B.H.; Abdel Warith, A.

    2003-01-01

    Numerous pegmatite pockets of un zoned and zoned types are the most important rock types from the radioactive point of view. They occur at the marginal parts and higher topographic level of G.Dara younger granites. Zoned pegmatites are composed of extremely coarse-grained milky quartz core, intermediate zone and wall zone. The alteration zone is found at the contact between quartz core and intermediate zone. It is recorded the highest radioactive values due to their mineral composition, as a result of alteration processes associated with radioactive minerals. Only two alteration zones (P1 and P2) has been studied in this paper. The late magmatic alteration process (hematization, kaolinization, chloritization and fluortization) of the pegmatite resulted in the formation of chlorite, fluorite, clay minerals and carbonates (calcite) in the alteration zones as mineral assemblage. opaque minerals are found as pyrite, iron oxyhydroxide and garnet. Fluid inclusion studies by microthermometry were carried out on authigenic minerals (such as quartz and fluorite) in alteration zones (primary fluid inclusions). This study revealed that, at least two stages of the post-magmatic hydrothermal alteration are involved. The first stages of high temperature, low saline fluids are involved. The first stage is of high temperature, low saline fluids which characterized with hematization and/or chloritization resulted from fluid-rock interaction with late magmatic fluids that very probably mixed with external low salinity fluids along brittle structure. The second stage is of low temperature the main role in re high saline fluids characterized the fluoritized alteration due to consequent reaction with wall rocks and mixing with meteoric water. Mixing of low salinity meteoric water with hot a sending saline hydrothermal solution leads to ph change and continuous interaction with wall rock

  3. A model for the oxygen potential of oxide fuels at high burnup

    International Nuclear Information System (INIS)

    Garcia, P.; Piron, J.P.; Baron, D.

    1997-01-01

    Using Lindemer's analysis as a starting point, a comprehensive description of the chemical state of the fluorite fuel matrix along with the most abundant fission products has been developed. The model was then implemented within the framework of an upgraded version of the SOLGASMIX program known as SAGE. In addition to approximately seventy solid compounds, three different mixture phases are modelled. The first one is the gaseous phase and comprises roughly sixty different compounds. The second is made up of noble metals such as Mo, Ru, Tc, Pd. The third mixture phase is a representation of the fluorite fuel matrix. Since SAGE is a code which calculates chemical equilibria by minimizing the Gibbs energy of the system, it is essential that reliable free energies of formation be used as data. This is relatively straightforward with regard to most compounds and thermochemical data are readily available in the open literature. As regards the fluorite phase however, the basic hypothesis is that it is possible to model the effect of defects such as interstitials (in the hyperstoichiometric phase) and vacancies (in the hypostoichiometric phase) by assuming the existence of hypothetical solute compounds such as U 2 O 4.5 that stabilize the hyperstoichiometric phase. As rare earths (Re) of valence two or three are dissolved in the matrix, the hypothetical compounds Re 4/3 O 2 and URe 2 O 6 are chosen to reflect the behavior of the ternay system. This description accurately predicts the hypostoichiometric region of the phase diagram but underestimate the increase in oxygen potential in the hyperstoichiometric region. 26 refs, 10 figs, 1 tab

  4. Selective catalytic reduction of sulfur dioxide to elemental sulfur. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Liu, W.; Flytzani-Stephanopoulos, M.; Sarofim, A.F.

    1995-06-01

    This project has investigated new metal oxide catalysts for the single stage selective reduction of SO{sub 2} to elemental sulfur by a reductant, such as CO. Significant progress in catalyst development has been made during the course of the project. We have found that fluorite oxides, CeO{sub 2} and ZrO{sub 2}, and rare earth zirconates such as Gd{sub 2}Zr{sub 2}O{sub 7} are active and stable catalysts for reduction Of SO{sub 2} by CO. More than 95% sulfur yield was achieved at reaction temperatures about 450{degrees}C or higher with the feed gas of stoichiometric composition. Reaction of SO{sub 2} and CO over these catalysts demonstrated a strong correlation of catalytic activity with the catalyst oxygen mobility. Furthermore, the catalytic activity and resistance to H{sub 2}O and CO{sub 2} poisoning of these catalysts were significantly enhanced by adding small amounts of transition metals, such as Co, Ni, Co, etc. The resulting transition metal-fluorite oxide composite catalyst has superior activity and stability, and shows promise in long use for the development of a greatly simplified single-step sulfur recovery process to treat variable and dilute SO{sub 2} concentration gas streams. Among various active composite catalyst systems the Cu-CeO{sub 2} system has been extensively studied. XRD, XPS, and STEM analyses of the used Cu-CeO{sub 2} catalyst found that the fluorite crystal structure of ceria was stable at the present reaction conditions, small amounts of copper was dispersed and stabilized on the ceria matrix, and excess copper oxide particles formed copper sulfide crystals of little contribution to catalytic activity. A working catalyst consisted of partially sulfated cerium oxide surface and partially sulfided copper clusters. The overall reaction kinetics were approximately represented by a first order equation.

  5. Rare Mineralogy in Alkaline Ultramafic Rocks, Western Kentucky Fluorspar District

    Science.gov (United States)

    Anderson, W.

    2017-12-01

    The alkaline ultramafic intrusive dike complex in the Western Kentucky Fluorspar District contains unusual mineralogy that was derived from mantle magma sources. Lamprophyre and peridotite petrologic types occur in the district where altered fractionated peridotites are enriched in Rare Earth Elements (REE) and some lamprophyre facies are depleted in incompatible elements. Unusual minerals in dikes, determined by petrography and X-ray diffraction, include schorlomite and andradite titanium garnets, astrophyllite, spodumene, niobium rutile, wüstite, fluoro-tetraferriphlogopite, villiaumite, molybdenite, and fluocerite, a REE-bearing fluoride fluorescent mineral. Mixing of MVT sphalerite ore fluids accompanies a mid-stage igneous alteration and intrusion event consistent with paragenetic studies. The presence of lithium in the spodumene and fluoro-tetraferriphlogopite suggests a lithium phase in the mineral fluids, and the presence of enriched REE in dikes and fluorite mineralization suggest a metasomatic event. Several of these rare minerals have never been described in the fluorspar district, and their occurrence suggests deep mantle metasomatism. Several REE-bearing fluoride minerals occur in the dikes and in other worldwide occurrences, they are usually associated with nepheline syenite and carbonatite differentiates. There is an early and late stage fluoride mineralization, which accompanied dike intrusion and was also analyzed for REE content. One fluorite group is enriched in LREE and another in MREE, which suggests a bimodal or periodic fluorite emplacement. Whole-rock elemental analysis was chondrite normalized and indicates that some of the dikes are slightly enriched in light REE and show a classic fractionation enrichment. Variations in major-element content; high titanium, niobium, and zirconium values; and high La/Yb, Zr/Y, Zr/Hf, and Nb/Ta ratios suggest metasomatized lithospheric-asthenospheric mantle-sourced intrusions. The high La/Yb ratios in some

  6. Topotactic oxidation pathway of ScTiO3 and high-temperature structure evolution of ScTiO3.5 and Sc4Ti3O12-type phases.

    Science.gov (United States)

    Shafi, Shahid P; Hernden, Bradley C; Cranswick, Lachlan M D; Hansen, Thomas C; Bieringer, Mario

    2012-02-06

    The novel oxide defect fluorite phase ScTiO(3.5) is formed during the topotactic oxidation of ScTiO(3) bixbyite. We report the oxidation pathway of ScTiO(3) and structure evolution of ScTiO(3.5), Sc(4)Ti(3)O(12), and related scandium-deficient phases as well as high-temperature phase transitions between room temperature and 1300 °Cusing in-situ X-ray diffraction. We provide the first detailed powder neutron diffraction study for ScTiO(3). ScTiO(3) crystallizes in the cubic bixbyite structure in space group Ia3 (206) with a = 9.7099(4) Å. The topotactic oxidation product ScTiO(3.5) crystallizes in an oxide defect fluorite structure in space group Fm3m (225) with a = 4.89199(5) Å. Thermogravimetric and differential thermal analysis experiments combined with in-situ X-ray powder diffraction studies illustrate a complex sequence of a topotactic oxidation pathway, phase segregation, and ion ordering at high temperatures. The optimized bulk synthesis for phase pure ScTiO(3.5) is presented. In contrast to the vanadium-based defect fluorite phases AVO(3.5+x) (A = Sc, In) the novel titanium analogue ScTiO(3.5) is stable over a wide temperature range. Above 950 °C ScTiO(3.5) undergoes decomposition with the final products being Sc(4)Ti(3)O(12) and TiO(2). Simultaneous Rietveld refinements against powder X-ray and neutron diffraction data showed that Sc(4)Ti(3)O(12) also exists in the defect fluorite structure in space group Fm3m (225) with a = 4.90077(4) Å. Sc(4)Ti(3)O(12) undergoes partial reduction in CO/Ar atmosphere to form Sc(4)Ti(3)O(11.69(2)).

  7. Topotactic synthesis of a new BiS2-based superconductor Bi2(O,F)S2

    OpenAIRE

    Okada, Tomoyuki; Ogino, Hiraku; Shimoyama, Jun-ichi; Kishio, Kohji

    2015-01-01

    A new BiS2-based superconductor Bi2(O,F)S2 was discovered. This is a layered compound consisting of alternate stacking structure of rock-salt-type BiS2 superconducting layer and fluorite-type Bi(O,F) blocking layer. Bi2(O,F)S2 was obtained as the main phase by topotactic fluorination of undoped Bi2OS2 using XeF2, which is the first topotactic synthesis of an electron-doped superconductor via reductive fluorination. With increasing F-content, a- and c-axis length increased and decreased, respe...

  8. Topotactic synthesis of a new BiS2-based superconductor Bi2(O,F)S2

    Science.gov (United States)

    Okada, Tomoyuki; Ogino, Hiraku; Shimoyama, Jun-ichi; Kishio, Kohji

    2015-02-01

    A new BiS2-based superconductor, Bi2(O,F)S2, was discovered. It is a layered compound consisting of alternately stacked structure of rock-salt-type BiS2 superconducting layers and fluorite-type Bi(O,F) blocking layers. Bi2(O,F)S2 was obtained as the main phase by topotactic fluorination of undoped Bi2OS2 using XeF2. This is the first topotactic synthesis of an electron-doped superconductor via reductive fluorination. With increasing F-content, a- and c-axis lengths increased and decreased, respectively, and Tc increased to 5.1 K.

  9. Uranium-contaminated soils: Ultramicrotomy and electron beam analysis

    International Nuclear Information System (INIS)

    Buck, E.C.; Dietz, N.L.; Bates, J.K.; Cunnane, J.C.

    1994-01-01

    Uranium contaminated soils from the Fernald Operation Site, Ohio, have been examined by a combination of optical microscopy, scanning electron microscopy with backscattered electron detection (SEM/BSE), and analytical electron microscopy (AEM). A method is described for preparing of transmission electron microscopy (TEM) thin sections by ultramicrotomy. By using these thin sections, SEM and TEM images can be compared directly. Uranium was found in iron oxides, silicates (soddyite), phosphates (autunites), and fluorite. Little uranium was associated with clays. The distribution of uranium phases was found to be inhomogeneous at the microscopic level

  10. Carbothermic reduction of pyrolusite for obtaining carbon bearing ferromanganese and slags, adequated to the development of welding materials

    International Nuclear Information System (INIS)

    Cruz-Crespo, A.; Garcia-Sanchez, L. L.; Quintana-Puchol, R.; Perdomo Gonzalez, L.; Gomez-Perez, C. R.; Jimenez-Vielsa, G. E.; Cores-Sanchez, A.

    2004-01-01

    The high carbon ferromanganese obtained by means of carbothermic reduction in an electric arc furnace of direct current is proposed. the ideal composition of slag oxides to achieve a flux to be used in the submerged arc welding (SAW) is established. Calculation for charge components (pyrolusite, coke, steel wool, lime, rutile and fluorite) for no fluxes technology for FeMn is carried out taking into account the welding fluxes characteristics of the SiO 2 -MnO-CaO system. Change materials reduction experiments to obtain FeMn and slag are used to develop a SAW flux. (Author) 21 refs

  11. C60 and U ion irradiation of Gd2TixZr2-xO7 pyrochlore

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jiaming; Toulemonde, Marcel; Lang, Maik; Costantini, Jean Marc; Della-Negra, Serge; Ewing, Rodney C.

    2015-08-01

    Gd2TixZr2-xO7 (x = 0 to 2) pyrochlore was irradiated by 30 MeV C60 clusters, which provide an extremely high ionizing energy density. Here, high-resolution transmission electron microscopy revealed a complex ion-track structure in Gd2Ti2O7 and Gd2TiZrO7, consisting of an amorphous core and a shell of a disordered, defect-fluorite structure.

  12. Fluorine concentrations of ore fluids in the Illinois-Kentucky district: Evidence from SEM-EDS analysis of fluid inclusion decrepitates

    Science.gov (United States)

    Kenderes, Stuart M.; Appold, Martin S.

    2017-08-01

    The Illinois-Kentucky district is an atypical occurrence of Mississippi Valley-type (MVT) mineralization that consists predominantly of fluorite rather than metal sulfide minerals. A long-standing assumption for the predominance of fluorite in the Illinois-Kentucky district is that the ore fluids there were anomalously rich in dissolved fluorine compared to typical sedimentary brines and other MVT ore fluids. This hypothesis is based on the unusual close temporal and spatial association of fluorine-rich ultramafic igneous rocks to MVT mineralization in the district, high K and Sr concentrations in the igneous rocks and in MVT ore-hosted fluid inclusions, a significant mantle 3He/4He component in ore-hosted fluid inclusions, and reaction path models that show titration of a HF-rich fluid into sedimentary brine is capable of producing a fluorite-dominated MVT ore mineral assemblage. The purpose of the present study was to test this hypothesis more directly by determining the fluorine concentration of the Illinois-Kentucky ore fluid through SEM-EDS analysis of evaporative solute mounds resulting from thermal decrepitation of fluid inclusions hosted in sphalerite. All 26 evaporative solute mounds from Illinois-Kentucky sphalerite samples analyzed contained detectable concentrations of fluorine of 1-4 weight percent. Based on calibration to standard solutions and previously published fluid inclusion major element concentrations, these solute mound fluorine concentrations correspond to fluid inclusion fluorine concentrations of about 680-4300 ppm, indicating that the Illinois-Kentucky ore fluids were quite rich in fluorine compared to typical sedimentary brines, which have fluorine concentrations mainly on the order of 1's to 10's of ppm. In contrast, solute mounds from sphalerite-hosted fluid inclusions from the Tri-State district did not contain fluorine in excess of the detection limit. The detection limit equates to an aqueous fluorine concentration between 87 and

  13. A Study of F-center in the Ionic Crystal by Using The Quantum Dot Model Potential

    Directory of Open Access Journals (Sweden)

    Hashem Abood Kassim

    2018-02-01

    Full Text Available This work presents a study of the electronic structure of F-center in the crystal of NaCl, CsCl and fluorite structure by using quantum dot model potential. This model employs the semi-continuum method due to Simpson and specifies the F-center as a quantum dot partially confined within finite potential. The energy levels and transition energy of the F-center are calculated analytically by using this new model potential and including the effect of continuum medium due to the coulomb tail and using the strong perturbation approach

  14. A deposit model for carbonatite and peralkaline intrusion-related rare earth element deposits: Chapter J in Mineral deposit models for resource assessment

    Science.gov (United States)

    Verplanck, Philip L.; Van Gosen, Bradley S.; Seal, Robert R.; McCafferty, Anne E.

    2014-01-01

    Carbonatite and alkaline intrusive complexes, as well as their weathering products, are the primary sources of rare earth elements. A wide variety of other commodities have been exploited from carbonatites and alkaline igneous rocks including niobium, phosphate, titanium, vermiculite, barite, fluorite, copper, calcite, and zirconium. Other elements enriched in these deposits include manganese, strontium, tantalum, thorium, vanadium, and uranium. Carbonatite and peralkaline intrusion-related rare earth element deposits are presented together in this report because of the spatial, and potentially genetic, association between carbonatite and alkaline rocks. Although these rock types occur together at many locations, carbonatite and peralkaline intrusion-related rare earth element deposits are not generally found together.

  15. Some particularities of impurity center structure in concentrated solid solutions MeF2-GdF3, where Me-Ca2+, Sr2+ and Ba2+

    International Nuclear Information System (INIS)

    Karelin, V.V.; Orlov, Yu.N.; Bozhevol'nov, V.E.; Ivanov, L.N.

    1981-01-01

    The monocrystalline CaF 2 -GdF 3 , SrF 2 -GdF 3 and BaF 2 -GdF 3 systems are studied using the methods of EPR, photo-, radio-, cathode- and thermoluminescence. It is shown that the structure of fluorite solid solutions changes considerably with the growth of the rare earth component concentration. At that, in the systems investigated at least three concentration regions can be singled out: (up to 1%; from 1 to 15%, and > 15% GdF 3 ) which are characterized by their certain selection of impurity centres [ru

  16. Simulation experiments and solar wind sputtering

    International Nuclear Information System (INIS)

    Griffith, J.E.; Papanastassiou, D.A.; Russell, W.A.; Tombrello, T.A.; Weller, R.A.

    1978-01-01

    In order to isolate the role played by solar wind sputtering from other lunar surface phenomena a number of simulation experiments were performed, including isotope abundance measurements of Ca sputtered from terrestrial fluorite and plagioclase by 50-keV and 130-keV 14 N beams, measurement of the energy distribution of U atoms sputtered with 80-keV 40 Ar, and measurement of the fraction of sputtered U atoms which stick on the surfaces used to collect these atoms. 10 references

  17. Zn-Pb Ores of Mississippi Valley Type in the Lycksele-Storuman District, Northern Sweden: A Possible Rift-Related Cambrian Mineralisation Event

    Directory of Open Access Journals (Sweden)

    Kjell Billström

    2012-06-01

    Full Text Available The epigenetic Zn-Pb deposits in the Lycksele-Storuman ore district, northern Sweden, are hosted by Paleoproterozoic basement near the margin of the Caledonian mountains. A paleogeographic reconstruction suggests that platform sediments, including Cambrian shales, overlaid the mineralised basement. The mineralisation type, containing sphalerite, galena, calcite and fluorite, is confined to veins and breccias and interpreted to be of Mississippi Valley Type (MVT style. There is no appreciable wall rock alteration. Fluid inclusion work reveals coexisting aqueous and hydrocarbon fluids. Ore deposition is interpreted to have occurred during mixing of two fluids; a cool (

  18. Sequential evolution of different phases in metastable Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 (0.0 ≤ x ≤ 2.0) system: crucial role of reaction conditions.

    Science.gov (United States)

    Shukla, Rakesh; Sayed, Farheen N; Phapale, Suhas; Mishra, Ratikant; Tyagi, Avesh K

    2013-07-15

    The Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 (0.0 ≤ x ≤ 2.0) series was synthesized by the gel combustion method. This system exhibited the presence of a fluorite-type phase, along with a narrow biphasic region, depending upon the Ce/Gd content in the sample. Thermal stability of these new compounds under oxidizing and reducing conditions has been investigated. The products obtained on decomposition of Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 in oxidizing and reducing conditions were found to be entirely different. It was observed that in air the fluorite-type solid solutions of Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 composition undergo phase separation into perovskite GdAlO3 and fluorite-type solid solutions of Gd-Ce-Zr-O or Ce-Zr-Al-O depending upon the extent of Ce and Al substitution. On the other hand, Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 samples on heating under reducing conditions show a phase separation to CeAlO3 perovskite and a defect-fluorite of Gd2Zr2O7. The extent of metastability for a typical composition of Gd(1.2)Ce(0.8)Zr(1.2)Al(0.8)O7 (nano), Gd(1.2)Ce(0.8)Zr(1.2)Al(0.8)O(6.6) (heated under reduced conditions), Gd(1.2)Ce(0.8)Zr(1.2)Al(0.8)O7 (heated in air at 1200 °C) has been experimentally determined employing a high temperature Calvet calorimeter. On the basis of thermodynamic stability data, it could be inferred that the formation of a more stable compound in the presence of two competing cations (i.e., Gd(3+) and Ce(3+)) is guided by the crystallographic stability.

  19. Improvement of graphite crystal analyzer for light elements on X-ray fluorescence holography measurement

    Science.gov (United States)

    Happo, Naohisa; Hada, Takuma; Kubota, Atsushi; Ebisu, Yoshihiro; Hosokawa, Shinya; Kimura, Koji; Tajiri, Hiroo; Matsushita, Tomohiro; Hayashi, Kouichi

    2018-05-01

    Using a graphite crystal analyzer, focused monochromatic fluorescent X-rays can be obtained on an X-ray fluorescence holography (XFH) measurement. To measure the holograms of elements lighter than Ti, we improved a cylindrical-type crystal analyzer and constructed a small C-shaped analyzer. Using the constructed C-shaped analyzer, a Ca Kα hologram of a fluorite single crystal was obtained, from which we reconstructed a clear atomic image. The XFH measurements for the K, Ca, and Sc elements become possible using the presently constructed analyzer.

  20. Leaching of sodium carbonate cakes by nitric acid

    International Nuclear Information System (INIS)

    Troyanker, L.S.; Nikonov, V.N.

    1977-01-01

    The interaction has been studied of soda cakes of fluorite-rare-earth concentrate with nitric acid. The effect of a number of factors on extraction of REE into a nitric solution has been considered: the final acidity of the pulp, the duration of leaching, and the ratio between solid and liquid phases. The effect of adding aluminium nitrate into the pulp has also been studied. It has been shown that three-stage counterflow leaching of soda cakes with nitric acid increases REE extraction approximately by 10%

  1. Neutron scattering studies of solid electrolytes

    International Nuclear Information System (INIS)

    Shapiro, S.M.

    1976-01-01

    The role which neutron scattering can play in determining the nature of the disorder and the conducting mechanism in the solid electrolytes is discussed. First, some of the general formalism for elastic and inelastic neutron scattering is reviewed, and the quantities which can be measured are pointed out. Then the application of neutron scattering to the studies of three different problems is examined; the anion disorder in the fluorite system, the dynamical behavior in beta-alumina, and the cation diffusion in αAgI are discussed. 8 figures

  2. Quantitative X-ray diffraction analysis of alumina, silicon carbide and zirconium carbide in ceramic composites

    International Nuclear Information System (INIS)

    Veiga, Sonia M.B.; Bressiani, Jose Carlos; Veiga, Marcello M.; Chaklader, Asoke C.D.

    1995-01-01

    The x-ray diffraction technique has been successfully applied to determine the phases formed in a carbo thermal synthesis of ceramic composites (Al 2 O 3 -Si C and Al 2 O 3 -Si C-Zr C) using kaolinite, cyanite and zircon as precursors. The powder method using fluorite as internal standard has shown reliable results to estimate accurately phases in composites (relative error as low as 5%). In addition, quantitative X-ray analysis allows an indirect evaluation of Si O (gas) losses from the system during the carbo thermal reaction. (author)

  3. Short-term 222Rn activity concentration changes in underground spaces with limited air exchange with the atmosphere

    Science.gov (United States)

    Fijałkowska-Lichwa, L.; Przylibski, T. A.

    2011-04-01

    The authors investigated short-time changes in 222Rn activity concentration occurring yearly in two underground tourist facilities with limited air exchange with the atmosphere. One of them is Niedźwiedzia (Bear) Cave in Kletno, Poland - a natural space equipped with locks ensuring isolation from the atmosphere. The other site is Fluorite Adit in Kletno, a section of a disused uranium mine. This adit is equipped with a mechanical ventilation system, operated periodically outside the opening times (at night). Both sites are situated within the same metamorphic rock complex, at similar altitudes, about 2 km apart. The measurements conducted revealed spring and autumn occurrence of convective air movements. In Bear Cave, this process causes a reduction in 222Rn activity concentration in the daytime, i.e. when tourists, guides and other staff are present in the cave. From the point of view of radiation protection, this is the best situation. For the rest of the year, daily concentrations of 222Rn activity in the cave are very stable. In Fluorite Adit, on the other hand, significant variations in daily 222Rn activity concentrations are recorded almost all year round. These changes are determined by the periods of activity and inactivity of mechanical ventilation. Unfortunately this is inactive in the daytime, which results in the highest values of 222Rn activity concentration at the times when tourists and staff are present in the adit. Slightly lower concentrations of radon in Fluorite Adit are recorded in the winter season, when convective air movements carry a substantial amount of radon out into the atmosphere. The incorrect usage of mechanical ventilation in Fluorite Adit results in the most unfavourable conditions in terms of radiation protection. The staff working in that facility are exposed practically throughout the year to the highest 222Rn activity concentrations, both at work (in the adit) and at home (outside their working hours). Therefore, not very well

  4. Defect structure of yttria-stabilized zirconia and its influence on the ionic conductivity at elevated temperatures

    DEFF Research Database (Denmark)

    Goff, J.P.; Hayes, W.; Hull, S.

    1999-01-01

    The defect structure of cubic fluorite structured yttria-stabilized zirconia (ZrO2)(1-x)(Y2O3)(x) has been investigated over the composition range 0.100(3)less than or equal to x less than or equal to 0.241 (10) and temperatures T(K) up to 2780(10) K, using single-crystal specimens. Analysis of n......, we propose that the anomalous decrease in the ionic conductivity with increasing x is a consequence of the decreasing mobility of the isolated defects, possibly due to blockage by the increasing number of static aggregates....

  5. Performance of cubic ZrO{sub 2} doped CeO{sub 2}: First-principles investigation on elastic, electronic and optical properties of Ce{sub 1−x} Zr{sub x}O{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Dong [State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Kunming 650093, Yunnan (China); Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, Yunnan (China); Zeng, Chunhua, E-mail: zchh2009@126.com [State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Kunming 650093, Yunnan (China); Faculty of Science, Kunming University of Science and Technology, Kunming 650093, Yunnan (China); Wang, Hua, E-mail: wanghuaheat@hotmail.com [State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Kunming 650093, Yunnan (China); Luo, Hongchun [Faculty of Science, Kunming University of Science and Technology, Kunming 650093, Yunnan (China); Cheng, Xianming [State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Kunming 650093, Yunnan (China); Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, Yunnan (China); Xiang, Chao [College of Mechanical and Electrical Engineering, Yangtze Normal University, Fuling 408100, Chongqing (China); Wei, Yonggang; Li, Kongzhai; Zhu, Xing [State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Kunming 650093, Yunnan (China); Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, Yunnan (China)

    2016-06-25

    The structural, elastic, electronic and optical properties of Ce{sub 1−x} Zr{sub x}O{sub 2} (x = 0, 0.25, 0.5, 0.75, 1) fluorite type oxides are studied by researchers using the method of density functional theory (DFT) + U method. The calculated equilibrium lattice parameter, cell volume, elastic and optical properties for CeO{sub 2} and ZrO{sub 2} are all in good agreement with the available experimental data and other theoretical results. It is found that Ce substituted by Zr leads to the formation of the pseudo-cubic fluorite-type structure. With doping concentration × increasing, the lattice parameter, cell volume and the bond length of d{sub Ce−O} and d{sub Zr−O} decrease linearly. It is interesting to find that the hardness of materials increase with Zr concentration increasing. For Ce{sub 0.75} Zr{sub 0.25} O{sub 2}, we also find that its ductility is good. Meanwhile, the range of the conduction band energy in the doped system becomes wider than that in the undoped system. The overlapping band phenomenon occur for all substitutions in Ce{sub 1−x} Zr{sub x}O{sub 2} (from x = 0.25 to x = 0.75), especially for the structure of Ce{sub 0.5} Zr{sub 0.5} O{sub 2} and Ce{sub 0.25} Zr{sub 0.75} O{sub 2}, its second band gaps almost disappear. Based on the dielectric functions obtained, it is shown that the static dielectric constant ε{sub 0} and refractive index n{sub 0} obviously decrease with Zr concentration increasing. After discussing, we know that CeO{sub 2} is suitable as a useful high-refractive index film material in single and multilayered optical coatings, whereas ZrO{sub 2} can be used as gate-dielectric materials in metal-oxide semiconductor (MOS) devices, in metallurgy and as a thermal barrier coating in engines. - Highlights: • Structural, and optical properties of fluorite type oxides are studied; • Ce substituted by Zr leads to formation of pseudo-cubic fluorite-type structure; • Hardness of materials are increased with Zr

  6. Neutron dosimetry using thermoluminescent material and KBr

    International Nuclear Information System (INIS)

    Sahyun, A.

    1979-01-01

    It is investigated the misture of natural CaF 2 and KBr as thermal neutron dosimeter compared to pure fluorite. Firstly, it was found that a 50 - 50 mixture in weight produces the highest TL sensitivity when irradiated with thermal neutrons. Second, it was shown experimentally that for TL reading within 30 to 40 hours after irradiation, the radioisotopes 42 K, 80 Br and 80 sub(m)Br contribute predominantly, while for periods longer than 4 to 5 days, 82 Br also contributes significantly. It is in question, the minimum detectable fluence is of the order of 10 9 n/cm 2 . (Autor) [pt

  7. Method of crude ore defluoridation in hydrometallurgy of beryllium, affording fluorosilicic acid

    International Nuclear Information System (INIS)

    Samojlov, V.I.; Borsuk, A.N.; Zherin, I.I.

    2006-01-01

    Results of laboratory and industrial tests conducted at Ul'ba Metallurgical Plant on leaching bertrandite - phenacite - fluorite flotation concentrate containing ∼4 wt. % beryllium in a rotary furnace using sulfuric acid are presented. The technology is shown to provide a 7.8% reduction in the net cost of beryllium production (1 kg) in the form of technical-grade Be(OH) 2 by obviating the need of smelting beryllium concentrates and alkali fluxes. Besides, the technology permits concomitant production of H 2 SiF 6 , its commercial sales promoting a 17.6% reduction in beryllium production net cost [ru

  8. Band Gap Transition Studies of U:ThO2 Using Cathodoluminescence

    Science.gov (United States)

    2014-03-27

    regarding x-ray fluorescence. 2.1 Atomic Properties of Ux:Th1−xO2 Thorium and uranium dioxide are metal oxides with the fluorite crystal structure...thorium oxide is a material upon which few studies have been performed. The goal of this research is to determine how the insertion of uranium atoms into...doped thorium oxide crystal, 041 TU, with uranium mass concentration of 22.7% before chemical cleaning. Mass pre-cleaning: 0.341 g. 7 Figure 1.5

  9. Rare earth silicate (Ce, La, Nd, Ca, Th) SiO4 and cheralite (Th, Ca, Ce, La) (Psi)O4 are the responsible minerals for the anomalies of Morro de Ferro

    International Nuclear Information System (INIS)

    Fujimori, K.

    1982-01-01

    The Rare Earth silicate (La, Ce, Nd, Ca, Th)SiO 4 and cheralite (identified by Prof. Freeborn on a sample prepared from drilling core) were recognized as the most probable radioactive minerals that gave origin to high radioactive anomaly at Morro do Ferro hill together with coffinite, thorite, pyrochlore, apatite, etc., that are found in small quantity. The acids produced by decomposition of pyrite and fluorite have etched these radioactive minerals giving the high radioactive anomaly caracterized by high grade desiquilibrium of 232 Th serie. (Author) [pt

  10. Reducción carbotérmica de pirolusita para la obtención de ferromanganeso y escoria, adecuados al desarrollo de materiales de soldadura

    OpenAIRE

    Cruz-Crespo, A.; García-Sánchez, L. L.; Quintana-Puchol, R.; Perdomo-González, L.; Gómez-Pérez, C. R.; Jiménez-Vielsa, G. E.; Cores-Sánchez, A.

    2004-01-01

    The high carbon ferromanganese obtained by means of carbothermic reduction in an electric arc furnace of direct current is proposed. The ideal composition of slag oxides to achieve a flux to be used in the submerged arc welding (SAW) is established. Calculation for charge components (pirolusite, coke, steel wool, lime, rutile and fluorite) for no fluxes technology for FeMn is carried out taking into account the welding fluxes characteristics of the SiO2-MnO-CaO system. ...

  11. Disclosure of domain structure in cubic CaxZr1-xO2-x, 0x15 ≤ x ≤ 0x20, by Talbot image enhancement of high-resolution electron micrographs

    International Nuclear Information System (INIS)

    Rossell, H.J.; Wilson, I.J.; Sellar, J.R.

    1991-01-01

    High-resolution electron microscope images have been recorded of several cystalline samples of calcia-stabilized zirconia (Ca-CSZ) and of the fluorite-related superstructure phase φ 1 (CaZr 4 O 9 ). The contrast of the CSZ images has been enhanced markedly by the light-optical Talbot self-imaging technique. Is is demonstrated that the CSZ crystals contain a coherent dispersion of microdomains approximately 30 A in diameter, and that the structure of the microdomains is that of φ 1 . (orig.)

  12. Conductivity and thermodynamic characteristic of superionic transition in strontium chloride

    International Nuclear Information System (INIS)

    Voronin, B.M.; Prisyazhnyj, V.D.

    1989-01-01

    Electric conductivity of strontium polycrystalline chloride in the wide temperature range including melting point is measured. Reciprocally caused anomalous behaviour of kinetic and thermodynamic properties, which relates to peculiarities of salt transition to a superionic state is established in the region of high temperatures. Thermodynamic functions corresponding to crystal anion sublattice disordering are determined and characterized. Comparative analysis of data on strontium chloride and other structural-like salts testifies about step-by-step washing-out character of superionic transition, and the depth of transition (the degree of disordering) reached at melting points relates regularly to relative sizes of cations and anions in the fluorite lattice

  13. Controlled hydrothermal synthesis of CeO{sub 2} nanospheres and their excellent magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Xiaofei [Suzhou University, Anhui Key Laboratory of Spintronics and Nanomaterials Research, Suzhou, Anhui (China)

    2017-04-15

    Monodisperse spherical CeO{sub 2} nanostructures with irregular and rough surfaces have successfully been synthesized via a facile hydrothermal technology. XRD, SEM, XPS, Raman scattering, and M-H curves were employed to characterize the samples. The results showed that the spherical CeO{sub 2} nanostructures have a cubic fluorite structure and that there are Ce{sup 3+} ions and oxygen vacancies in the surface of the samples. The M-H curve of CeO{sub 2} nanospheres exhibits excellent room-temperature ferromagnetism (RT-FM), which is likely ascribed to the effects of the Ce{sup 3+} ions and oxygen vacancies. (orig.)

  14. Rapid, cool sintering of wet processed yttria-stabilized zirconia ceramic electrolyte thin films

    OpenAIRE

    Park, Jun-Sik; Kim, Dug-Joong; Chung, Wan-Ho; Lim, Yonghyun; Kim, Hak-Sung; Kim, Young-Beom

    2017-01-01

    Here we report a photonic annealing process for yttria-stabilized zirconia films, which are one of the most well-known solid-state electrolytes for solid oxide fuel cells (SOFCs). Precursor films were coated using a wet-chemical method with a simple metal-organic precursor solution and directly annealed at standard pressure and temperature by two cycles of xenon flash lamp irradiation. The residual organics were almost completely decomposed in the first pre-annealing step, and the fluorite cr...

  15. Computed phase equilibria for burnable neutron absorbing materials for advanced pressurized heavy water reactors

    Energy Technology Data Exchange (ETDEWEB)

    Corcoran, E.C. [Department of Chemistry and Chemical Engineering, Royal Military College of Canada, P.O. Box 17000, St. Forces, Kingston, Ont., K7K 7B4 (Canada)], E-mail: emily.corcoran@rmc.ca; Lewis, B.J.; Thompson, W.T. [Department of Chemistry and Chemical Engineering, Royal Military College of Canada, P.O. Box 17000, St. Forces, Kingston, Ont., K7K 7B4 (Canada); Hood, J. [Atomic Energy of Canada Ltd., Sheridan Park, 2251 Speakman Drive, Mississauga, Ont., L5K 1B2 (Canada); Akbari, F.; He, Z. [Atomic Energy of Canada Ltd., Chalk River Laboratories, Chalk River, Ont., K0J 1J0 (Canada); Reid, P. [Atomic Energy of Canada Ltd., Sheridan Park, 2251 Speakman Drive, Mississauga, Ont., L5K 1B2 (Canada)

    2009-03-31

    Burnable neutron absorbing materials are expected to be an integral part of the new fuel design for the Advanced CANDU [CANDU is as a registered trademark of Atomic Energy of Canada Limited.] Reactor. The neutron absorbing material is composed of gadolinia and dysprosia dissolved in an inert cubic-fluorite yttria-stabilized zirconia matrix. A thermodynamic model based on Gibbs energy minimization has been created to provide estimated phase equilibria as a function of composition and temperature. This work includes some supporting experimental studies involving X-ray diffraction.

  16. Pair Distribution Function Analysis of Structural Disorder by Nb5+ Inclusion in Ceria: Evidence for Enhanced Oxygen Storage Capacity from Under-Coordinated Oxide.

    Science.gov (United States)

    Hiley, Craig I; Playford, Helen Y; Fisher, Janet M; Felix, Noelia Cortes; Thompsett, David; Kashtiban, Reza J; Walton, Richard I

    2018-02-07

    Partial substitution of Ce 4+ by Nb 5+ is possible in CeO 2 by coinclusion of Na + to balance the charge, via hydrothermal synthesis in sodium hydroxide solution. Pair distribution function analysis using reverse Monte Carlo refinement reveals that the small pentavalent substituent resides in irregular coordination positions in an average fluorite lattice, displaced away from the ideal cubic coordination toward four oxygens. This results in under-coordinated oxygen, which explains significantly enhanced oxygen storage capacity of the materials of relevance to redox catalysis used in energy and environmental applications.

  17. Carbothermic reduction of pyrolusite for obtaining carbon bearing ferromanganese and slags, adequated to the development of welding materials; Reduccion carbotermica de pirolusita para la obtencion de ferromanganeso y escoria, adecuados al desarrollo de materiales de soldadura

    Energy Technology Data Exchange (ETDEWEB)

    Cruz-Crespo, A.; Garcia-Sanchez, L. L.; Quintana-Puchol, R.; Perdomo Gonzalez, L.; Gomez-Perez, C. R.; Jimenez-Vielsa, G. E.; Cores-Sanchez, A.

    2004-07-01

    The high carbon ferromanganese obtained by means of carbothermic reduction in an electric arc furnace of direct current is proposed. the ideal composition of slag oxides to achieve a flux to be used in the submerged arc welding (SAW) is established. Calculation for charge components (pyrolusite, coke, steel wool, lime, rutile and fluorite) for no fluxes technology for FeMn is carried out taking into account the welding fluxes characteristics of the SiO{sub 2}-MnO-CaO system. Change materials reduction experiments to obtain FeMn and slag are used to develop a SAW flux. (Author) 21 refs.

  18. Synthesis, Characterization and Thermal Diffusivity of Holmium and Praseodymium Zirconates

    OpenAIRE

    Stopyra M.; Niemiec D.; Moskal G.

    2016-01-01

    A2B2O7 oxides with pyrochlore or defected fluorite structure are among the most promising candidates for insulation layer material in thermal barrier coatings. The present paper presents the procedure of synthesis of holmium zirconate Ho2Zr2O7 and praseodymium zirconate Pr2Zr2O7 via Polymerized-Complex Method (PCM). Thermal analysis of precursor revealed that after calcination at relatively low temperature (700°C) fine-crystalline, single-phase material is obtained. Thermal diffusivity was me...

  19. Transmission electron microscopic study of reduced Ca2UO5

    International Nuclear Information System (INIS)

    Krasevec, V.; Prodan, A.; Holc, J.; Kolar, D.

    1983-01-01

    Structural changes of Ca 2 UO 5 during reduction in hydrogen were studied by transmission electron microscopy. It was shown that monoclinic Ca 2 UO 5 changes into triclinic Ca 4 U 2 O 9 . They are related, respectively, to the fluorite and the bixbyite (C-M 2 O 3 ) structures, so that the product is a superstructure of the latter. Reduction occurs along the (100)/sub t/ planes originating from the (006)/sub m/ planes of the parent structure by diminishing the coordination number of the Ca cation from 7 to 6. 5 figures

  20. Investigation of interaction of zirconium and hafnium tetrafluorides with strontium fluoride

    International Nuclear Information System (INIS)

    Ratnikova, I.D.; Korenev, Yu.M.; Novoselova, A.V.

    1980-01-01

    Diagrams of the condensated state of systems SrF 2 -EF 4 have been plotted, where E represents Zr, Hf. In these systems, three intermediate compounds of Sr 3 EF 10 , Sr 2 EF 8 and Sr EF 6 compositions are formed. All those compounds melt incongruently at temperatures of 982, 865 and 750 deg C, respectively - zirconium salt; at temperatures of 1000, 900 and 820 deg C - hafnium salts. Fluoro-metallates of composition 2:1, and 1:1, exist in two polymorphic forms. Tetrafluorides were found to dissolve in strontium fluoride: they form solid solutions having fluorite structure

  1. Californium oxygen system for 1.50 < O/Cf < 1.72

    International Nuclear Information System (INIS)

    Turcotte, R.P.; Haire, R.G.

    1975-01-01

    The californium-oxygen system was studied as a function of temperature, oxygen pressure, and stoichiometry by manometric and x-ray diffraction methods. The results establish rhombohedral Cf 7 O 12 as the stable compound obtained by heating Cf 2 O 3 in air. The isobaric oxidation-reduction cycles Cf 2 O 3 → Cf 7 O 12 → Cf 2 O 3 , observed in constant rate of heating (cooling) experiments, occur with large hysteresis. A close parallel to other fluorite related lanthanide and actinide oxide systems is established. (auth)

  2. The emerald deposits of ultramafic rocks of Capoeirana and Belmont, State of Minas Gerais, Brazil

    International Nuclear Information System (INIS)

    Abreu Machado, G.; Schorscher, H.

    1998-01-01

    The emerald deposits of Capoeirana and Belmont, State of Minas Gerais (MG), Brazil, occur vithin an area comprising a deeply weathered Archean Metavulcano-Sedimentary Sequence (SVS) in tectonic contact with the Borrachudos Metagranitoids (GB) and Fluorite bearing Foliated Metagranitoids (MGF). The SVS is formed by intercalation s of ultramafic schists and amphibolites, basic to intermediate amphibolites, vulcanoclastic, metapelitic and calcsilicate schists and gneisses, banded iron formation and metacherts. The metaultramafic rocks include minor chromitite cumulates and occur at the base of the SVS. When metasomatized in the shear zones adjoining GB and MGF they host emerald mineralizations. (author)

  3. Interface formation and defect structures in epitaxial La2Zr2O7 thin films on (111) Si

    International Nuclear Information System (INIS)

    Seo, J.W.; Fompeyrine, J.; Guiller, A.; Norga, G.; Marchiori, C.; Siegwart, H.; Locquet, J.-P.

    2003-01-01

    We have studied the growth of epitaxial La 2 Zr 2 O 7 thin films on (111) Si. Although the interface structure can be strongly affected by the Si oxidation during the deposition process, epitaxial growth of La 2 Zr 2 O 7 was obtained. A detailed study by means of transmission electron microscopy reveals two types of structures (pyrochlore and fluorite) with the same average chemical composition but strong differences in reactivity and interface formation. The structural complexity of the ordered pyrochlore structure seems to prevent excess oxygen diffusion and interfacial SiO 2 formation

  4. Lattice contraction and lattice deformation of UO{sub 2} and ThO{sub 2} doped with Gd{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Baena, Angela [Belgian Nuclear Research Centre (SCK-CEN), Institute for Nuclear Materials Science, Boeretang 200, B-2400 Mol (Belgium); KU Leuven, Department of Chemistry, Celestijnenlaan 200F, P.O. Box 2404, B-3001 Heverlee (Belgium); Cardinaels, Thomas; Govers, Kevin; Pakarinen, Janne [Belgian Nuclear Research Centre (SCK-CEN), Institute for Nuclear Materials Science, Boeretang 200, B-2400 Mol (Belgium); Binnemans, Koen [KU Leuven, Department of Chemistry, Celestijnenlaan 200F, P.O. Box 2404, B-3001 Heverlee (Belgium); Verwerft, Marc, E-mail: marc.verwerft@sckcen.be [Belgian Nuclear Research Centre (SCK-CEN), Institute for Nuclear Materials Science, Boeretang 200, B-2400 Mol (Belgium)

    2015-12-15

    The lattice deformations in two doped fluorite systems, (U{sub 1−x}Gd{sub x})O{sub 2.00} and (Th{sub 1−x}Gd{sub x})O{sub 2−x/2}, have been reassessed by precise X-ray and electron diffraction investigations and the results were interpreted using the Bond Valence Sum (BVS) approach. For the (U{sub 1−x}Gd{sub x})O{sub 2.00} system, the experimental findings and theoretical assessment confirm earlier work: the lattice keeps its fluorite structure with a unit cell parameter that contracts linearly with dopant concentration. The lattice contraction in the (Th{sub 1−x}Gd{sub x})O{sub 2−x/2} system has for the first time been analyzed up to the solubility limit. Similar as for (U{sub 1−x}Gd{sub x})O{sub 2.00}, the (Th{sub 1−x}Gd{sub x})O{sub 2−x/2} solid solution contracts linearly as a function of dopant concentration but additionally, it develops a superstructure which is closely related to the parent fluorite structure. An excess anion bixbyite trial model is proposed to describe this superstructure. - Highlights: • Lattice deformations of (U{sub 1−x}Gd{sub x})O{sub 2.00} & (Th{sub 1−x}Gd{sub x})O{sub 2−x/2} are not identical. • (U{sub 1−x}Gd{sub x})O{sub 2.00} retains its fluorite structure. • (Th{sub 1−x}Gd{sub x})O{sub 2−x/2} forms an excess-anion bixbyite structure. • (U{sub 1−x}Gd{sub x})O{sub 2.00} and (Th{sub 1−x}Gd{sub x})O{sub 2−x/2} contractions were evaluated with high precision.

  5. Color tunability in green, red and infra-red upconversion emission in Tm{sup 3+}/Yb{sup 3+}/Ho{sup 3+} co-doped CeO{sub 2} with potential application for improvement of efficiency in solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, Luiz G.A.; Rocha, Leonardo A.; Buarque, Juliana M.M. [Laboratório de Materiais Inorgânicos Fotoluminescentes e Polímeros Biodegradáveis (LAFOP), Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João Del Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, 36301-160 São João Del Rei, MG (Brazil); Gonçalves, Rogéria Rocha [Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, USP, Av. Bandeirantes, 3900, 14040-901 Ribeirão Preto, SP (Brazil); Nascimento Jr, Clébio S. [Laboratório de Química Teórica e Computacional – (LQTC), Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, 36301-160 São João del-Rei, MG (Brazil); and others

    2015-03-15

    The preparation of Tm{sup 3+}/Yb{sup 3+}/Ho{sup 3+} co-doped CeO{sub 2} prepared by the precipitation method using ammonium hydroxide as a precursor is presented. By X-ray diffraction the materials show the phase-type of fluorite structure and the crystallite sizes were calculated by the Scherrer's equation. No other phase was observed evincing that the rare earth ions were inserted into the fluorite phase as substitutional or interstitial dopants. The microstrain calculated by the Williamson–Hall method do not show significant changes in their values, indicating that the inclusion of rare earths does not causes structural changes in the CeO{sub 2} used as a host matrix. All material showed intense upconversion emission at red and green region under excitation with diode laser at 980 nm. The color of emission changes from green to red with increasing excitation power pump. The materials showed suitable photoluminescent properties for applications as a laser source, solar cells, and great emitter at 800 nm. - Highlights: • Tm{sup 3+}/Yb{sup 3+}/Ho{sup 3+} co-doped CeO{sub 2} prepared by the simple way. • Intense upconversion emission regions and the tunability of emission color by the laser power pump. • The materials showed suitable photoluminescent properties for different applications.

  6. TEM and HRTEM study of oxide particles in an Al-alloyed high-Cr oxide dispersion strengthened ferritic steel with Hf addition

    Energy Technology Data Exchange (ETDEWEB)

    Dou, Peng, E-mail: doup@tsinghua.edu.cn [School of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Kimura, Akihiko, E-mail: kimura@iae.kyoto-u.ac.jp [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Kasada, Ryuta, E-mail: r-kasada@iae.kyoto-u.ac.jp [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Okuda, Takanari, E-mail: okuda.takanari@kki.kobelco.com [Kobelco Research Institute, 1-5-5 Takatsukadai, Nishi-ku, Kobe, Hyogo 651-2271 (Japan); Inoue, Masaki, E-mail: inoue.masaki@jaea.go.jp [Advanced Nuclear System R& D Directorate, Japan Atomic Energy Agency, 4002 Narita, O-arai, Ibaraki 311-1393 (Japan); Ukai, Shigeharu, E-mail: s-ukai@eng.hokudai.ac.jp [Graduate School of Engineering, Hokkaido University, N13, W8, Kita-ku, Sapporo 060-8628 (Japan); Ohnuki, Somei, E-mail: ohnuki@eng.hokudai.ac.jp [Graduate School of Engineering, Hokkaido University, N13, W8, Kita-ku, Sapporo 060-8628 (Japan); Fujisawa, Toshiharu, E-mail: fujisawa@esi.nagoya-u.ac.jp [EcoTopia Science Institute, Nagoya University, Furo, Chikusa-ku, Nagoya 464-8603 (Japan); Abe, Fujio, E-mail: ABE.Fujio@nims.go.jp [Structural Metals Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Jiang, Shan, E-mail: js93518@gmail.com [School of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Yang, Zhigang, E-mail: zgyang@tsinghua.edu.cn [Key Laboratory of Advanced Materials (MOE), School of Materials Sciences and Engineering, Tsinghua University, Beijing 100084 (China)

    2017-03-15

    The nanoparticles in an Al-alloyed high-Cr oxide dispersion strengthened (ODS) ferritic steel with Hf addition, i.e., SOC-16 (Fe-15Cr-2W-0.1Ti-4Al-0.62Hf-0.35Y{sub 2}O{sub 3}), have been examined by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Relative to an Al-alloyed high-Cr ODS ferritic steel without Hf addition, i.e., SOC-9 (Fe-15.5Cr-2W-0.1Ti-4Al-0.35Y{sub 2}O{sub 3}), the dispersion morphology and coherency of the oxide nanoparticles in SOC-16 were significantly improved. Almost all the small nanoparticles (diameter <10 nm) in SOC-16 were found to be consistent with cubic Y{sub 2}Hf{sub 2}O{sub 7} oxides with the anion-deficient fluorite structure and coherent with the bcc steel matrix. The larger particles (diameter >10 nm) were also mainly identified as cubic Y{sub 2}Hf{sub 2}O{sub 7} oxides with the anion-deficient fluorite structure. The results presented here are compared with those of SOC-9 with a brief discussion of the underlying mechanisms of the unusual thermal and irradiation stabilities of the oxides as well as the superior strength, excellent irradiation tolerance and extraordinary corrosion resistance of SOC-16.

  7. Spectroscopic studies on surface reactions between minerals and reagents in flotation systems

    International Nuclear Information System (INIS)

    Giesekke, E.W.

    1981-01-01

    A study of the adsorbed species at the interface between the minerals and the aqueous solution is reported in the hope that it will contribute to a better understanding of selective mineral flotation by various reagents. The results of infrared spectroscopic studies are cited from the author's investigation on the fluorite-sodium oleate and fluorite-linoleate systems. Electron-spectroscopic techniques, e.g., electron spectroscopy for chemical analysis (ESCA) have also been useful in the identification of adsorbed species on mineral surfaces. Some experimental data from the literature are discussed. These studies have the disadvantage that they are not in situ investigations of the interface between the mineral and the aqueous solution. The potential use of other spectroscopic techniques are discussed, photo-acoustic, Raman, and electron-spin-resonance spectroscopy being considered as possible alternatives. It is suggested that the relatively small surface areas of minerals used in flotation (i.e. smaller than 2m 2 .g- 1 ) impose severe restrictions on the use of such techniques

  8. The fluoride in the groundwater of Guarani Aquifer System: the origin associated with black shales of Paraná Basin

    Science.gov (United States)

    Kern, M. L.; Vieiro, A. P.; Machado, G.

    2008-09-01

    This work presents petrological and geochemical results of the black shales interval from Permian and Devonian strata of the Paraná Basin, Brazil and its relationships with fluoride of groundwater from Guarani Aquifer System. The Guarani Aquifer, located in South Brazil, Uruguay, Paraguay and Argentine, presents contents of fluoride higher than the Brazilian accepted potability limits. Several hypotheses have been presented for the origin of the fluoride in the groundwater of the Guarani Aquifer. Microcrystalline fluorite was registered in black shales of Ponta Grossa and Irati formations from Paraná Basin. The results shown in this work suggest that fluoride present in groundwater of Guarani Aquifer can be originated in deeper groundwater that circulates in Ponta Grossa and Irati formations. The interaction of the groundwater coming from deeper black shales with the groundwater-bearing Aquifer Guarani System occurs through regional fragile structures (faults and fractures) that constitute excellent hydraulic connectors between the two sedimentary packages. The microcrystalline fluorite registered in Ponta Grossa and Irati Formations can be dissolved promoting fluoride enrichment in groundwater of these black shales and Guarani Aquifer System.

  9. Contribution to the study of mechanical properties of nuclear fuel: atomistic modelling of the deformation of uranium dioxide

    International Nuclear Information System (INIS)

    Fossati, P.

    2012-01-01

    Mechanical properties of nuclear fuel are a complex problem, involving many coupled mechanisms occurring at different length scales. We used Molecular Dynamics models to bring some light on some of these mechanisms at the atomic scale. We devised a procedure to calculate transition pathways between some UO 2 polymorphs, and then carried out dynamics simulations of these transitions. We confirmed the stability of the cotunnite structure at high pressure using various empirical potentials, the fluorite structure being the most stable at room pressure. Moreover, we showed a reconstructive phase transition between the fluorite and cotunnite structures. We also showed the importance of the major deformation axis on the kind of transition that occur under tensile conditions. Depending on the loading direction, a scrutinyite or rutile phase can appear. We then calculated the elastic behaviour of UO 2 using different potentials. The relative agreement between them was used to produce a set of parameters to be used as input in mesoscale models. We also simulated crack propagation in UO 2 single crystals. These simulations showed secondary phases nucleation at crack tips, and hinted at the importance thereof on crack propagation at higher length-scales. We then described some properties of edge dislocations in UO 2 . The core structures were compared for various glide planes. The critical resolved shear stress was calculated for temperatures up to 2000 K. These calculations showed a link between lattice disorder at the dislocations core and the dislocations mobility. (author)

  10. Pyrochlore as nuclear waste form. Actinide uptake and chemical stability

    Energy Technology Data Exchange (ETDEWEB)

    Finkeldei, Sarah Charlotte

    2015-07-01

    Radioactive waste is generated by many different technical and scientific applications. For the past decades, different waste disposal strategies have been considered. Several questions on the waste disposal strategy remain unanswered, particularly regarding the long-term radiotoxicity of minor actinides (Am, Cm, Np), plutonium and uranium. These radionuclides mainly arise from high level nuclear waste (HLW), specific waste streams or dismantled nuclear weapons. Although many countries have opted for the direct disposal of spent fuel, from a scientific and technical point of view it is imperative to pursue alternative waste management strategies. Apart from the vitrification, especially for trivalent actinides and Pu, crystalline ceramic waste forms are considered. In contrast to glasses, crystalline waste forms, which are chemically and physically highly stable, allow the retention of radionuclides on well-defined lattice positions within the crystal structure. Besides polyphase ceramics such as SYNROC, single phase ceramics are considered as tailor made host phases to embed a specific radionuclide or a specific group. Among oxidic single phase ceramics pyrochlores are known to have a high potential for this application. This work examines ZrO{sub 2} based pyrochlores as potential nuclear waste forms, which are known to show a high aqueous stability and a high tolerance towards radiation damage. This work contributes to (1) understand the phase stability field of pyrochlore and consequences of non-stoichiometry which leads to pyrochlores with mixed cationic sites. Mixed cationic occupancies are likely to occur in actinide-bearing pyrochlores. (2) The structural uptake of radionuclides themselves was studied. (3) The chemical stability and the effect of phase transition from pyrochlore to defect fluorite were probed. This phase transition is important, as it is the result of radiation damage in ZrO{sub 2} based pyrochlores. ZrO{sub 2} - Nd{sub 2}O{sub 3} pellets

  11. Homogeneously dispersed CeO2 nanoparticles on exfoliated hexaniobate nanosheets

    Science.gov (United States)

    Marques, Thalles M. F.; Strayer, Megan E.; Ghosh, Anupama; Silva, Alexandre; Ferreira, Odair P.; Fujisawa, Kazunori; Alves da Cunha, Jose R.; Abreu, Guilherme J. P.; Terrones, Mauricio; Mallouk, Thomas E.; Viana, Bartolomeu C.

    2017-12-01

    Hexaniobate nanosheets derived from the parent compound K4Nb6O17 have been decorated with CeO2 nanoparticles by ion exchange with aqueous cerium (IV) solution. Very homogeneous CeO2 nanoparticle decoration of the hexaniobate sheets can be achieved by this method and the resulting composites may absorb visible light. HRTEM images show that ∼3.0 nm diameter CeO2 nanoparticles adhere to hexaniobate nanosheets that are exfoliated and then restacked prior to Ce deposition. The interfacial interaction between CeO2 nanoparticles and nanosheets would be due to an electrostatic attraction mechanism. Raman and XRD measurements have given strong evidence that CeO2 nanoparticles have fluorite structure. EDS, FTIR and XPS results suggest almost complete exchange of TBA+ and K+ by Ce4+. Cerium ion exchange on the acid exchanged parent compound, H2.9K1.1Nb6O17, revealed that the extent of Ce ion exchange is much greater in case of nanosheets, which may be rationalized by the larger surface area available after exfoliation. XPS measurements show that the ratio of Ce4+/Ce3+ is around 4.4, in agreement with the formation of fluorite structure (CeO2). Thus, these CeO2 nanoparticle/nanosheet composites may be useful for catalytic processes.

  12. Characterization of BaBi2Ta2O9 prepared through amorphous precursor

    International Nuclear Information System (INIS)

    Maczka, M.; Kepinski, L.; Hermanowicz, K.; Dacko, S.; Czapla, Z.; Hanuza, J.

    2011-01-01

    Research highlights: → Formation of Bi-layered BaBi 2 Ta 2 O 9 proceeds via an intermediate fluorite phase. → Mechanochemical activation lowers the synthesis temperature by 150-200 deg. C. → The lateral size of the synthesized plate-like crystallites is about 100-200 nm. → Properties of the synthesized crystallites are different from the bulk material. - Abstract: Formation of ferroelectric BaBi 2 Ta 2 O 9 by annealing of an amorphous precursor prepared by high energy milling in ball mill has been studied by X-ray, scanning electron microscopy (SEM), Raman, infrared spectroscopy (IR), diffuse reflectivity and dielectric measurements. Our results show that formation of Bi-layered BaBi 2 Ta 2 O 9 proceeds via an intermediate fluorite phase. Mechanochemical activation allows obtaining BaBi 2 Ta 2 O 9 at short time and much lower temperatures than those required in a conventional solid state reaction. The lateral size of the plate-like crystallites is about 100-200 nm and properties of the synthesized particles are different compared to the bulk material.

  13. A salt diapir-related Mississippi Valley-type deposit: the Bou Jaber Pb-Zn-Ba-F deposit, Tunisia: fluid inclusion and isotope study

    Science.gov (United States)

    Bouhlel, Salah; Leach, David L.; Johnson, Craig A.; Marsh, Erin; Salmi-Laouar, Sihem; Banks, David A.

    2016-08-01

    The Bou Jaber Ba-F-Pb-Zn deposit is located at the edge of the Bou Jaber Triassic salt diapir in the Tunisia Salt Diapir Province. The ores are unconformity and fault-controlled and occur as subvertical column-shaped bodies developed in dissolution-collapse breccias and in cavities within the Late Aptian platform carbonate rocks, which are covered unconformably by impermeable shales and marls of the Fahdene Formation (Late Albian-Cenomanian age). The host rock is hydrothermally altered to ankerite proximal to and within the ore bodies. Quartz, as fine-grained bipyramidal crystals, formed during hydrothermal alteration of the host rocks. The ore mineral assemblage is composed of barite, fluorite, sphalerite, and galena in decreasing abundance. The ore zones outline distinct depositional events: sphalerite-galena, barite-ankerite, and fluorite. Fluid inclusions, commonly oil-rich, have distinct fluid salinities and homogenization temperatures for each of these events: sphalerite-galena (17 to 24 wt% NaCl eq., and Th from 112 to 136 °C); ankerite-barite (11 to 17 wt% NaCl eq., and Th from 100 to 130 °C); fluorite (19 to 21 wt% NaCl eq., Th from 140 to 165 °C). The mean temperature of the ore fluids decreased from sphalerite (125 °C) to barite (115 °C) and increased during fluorite deposition (152 °C); then decreased to ˜110 °C during late calcite precipitation. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of fluid inclusions in fluorite are metal rich (hundreds to thousands ppm Pb, Zn, Cu, Fe) but the inclusions in barite are deficient in Pb, Zn, Cu, Fe. Inclusions in fluorite have Cl/Br and Na/Br ratios of several thousand, consistent with dissolution of halite while the inclusions analysed in barite have values lower than seawater which are indicative of a Br-enriched brine derived from evaporation plus a component of halite dissolution. The salinity of the barite-hosted fluid inclusions is less than obtained simply by the

  14. Inhibition of Neuroblastoma cancer cells viability by ferromagnetic Mn doped CeO_2 monodisperse nanoparticles mediated through reactive oxygen species

    International Nuclear Information System (INIS)

    Abbas, Fazal; Jan, Tariq; Iqbal, Javed; Haider Naqvi, M. Sajjad; Ahmad, Ishaq

    2016-01-01

    Here we report the Mn doping induced effects on structural, Raman, optical, magnetic and anticancer properties of CeO_2 nanoparticles prepared via soft chemical route. Structural and microstructural results infer that the synthesized nanoparticles have single phase cubic fluorite structure of CeO_2 and that Mn doping results in enhancement of the structural defects. Scanning electron microscopy results reveal the formation of monodisperse nanoparticles having average particle size ranging from 30 to 41 nm. The optical absorbance spectroscopy analysis discloses the band gap energy tailoring of CeO_2 nanoparticles via Mn doping. Room temperature ferromagnetism (RTFM) has been found in both as-prepared and Mn doped CeO_2 nanoparticles. This RTFM of the synthesized nanoparticles have been attributed to the Mn ions and surface defects such as oxygen vacancies. Finally, the influence of Mn dopant on the cell viability and reactive oxygen species (ROS) generation levels of CeO_2 nanoparticles in the presence of healthy and cancerous cells have been studied. It has been observed that the differential cytotoxicity of the synthesized nanoparticles is strongly correlated with level of ROS generation. - Highlights: • Mn doped CeO_2 nanoparticles with cubic fluorite structure were synthesized. • Mn dopant significantly tailored the band gap of CeO_2 nanoparticles. • The synthesized nanoparticles exhibited room temperature ferromagnetic behavior. • The cytotoxicity of these nanoparticles was reported for the first time. • The synthesized nanoparticles exhibited differential cytotoxicity.

  15. Contribution to the study of french pitchblendes

    International Nuclear Information System (INIS)

    Geffroy, J.; Sarcia, J.A.

    1955-01-01

    The authors first review the characteristics of uraninite-pitchblende, as deduced of present literature. They set apart from typical pitchblende a black oxide aspect, which probably corresponds to neo-formations, and a 'para-pitchblende' aspect, which they relate to deep sur-oxidation of normal pitchblende. They insist on the easy replacement of pitchblende by silica. and give indications as to changes in vein stones (fluorite, quartz, etc...). A detailed study of paragenesis and successions in french uranium districts follows (including discussion of uranium of uranium-bearing coals). The authors attempt to classify french pitchblende veins. They are chiefly epithermal and poor in satellite ores. Three types of deposits are identified: massive - pitchblende type, silica type, fluorite type. These deposits, as those of Portugal, are included in granite, Central-European peri-batholitic types where uranium associates which Ni, Co, Bi and Ag, are in France both rare and poor. Finally, the authors attempt to bring out in the european Hercynian area a particular distribution of paragenetic types. (authors) [fr

  16. Characterizing the relationship between hyperstoichiometry, defect structure and local corrosion kinetics of uranium dioxide

    International Nuclear Information System (INIS)

    He Heming; Qin, Z.; Shoesmith, D.W.

    2010-01-01

    The ability of the UO 2 fluorite structure to accommodate large amounts of interstitial oxygen in various lattice sites leads to the formation of hyper-stoichiometric phases. The defect structures occurring in hyper-stoichiometric UO 2+x over the range 0.02 ≤ x ≤ 0.1 have been characterized by SEM/EDX and Raman analyses. The results demonstrate that as the nominal stoichiometry increases from 2.002 to 2.1, the diversity of defective structures existing on the UO 2+ surface also increases. Scanning electrochemical microscopy (SECM) measurements combined with a theoretical model were used to determine the rate constant for the reduction of the redox mediator ferrocene methanol, acting as a cathodic oxidant to corrode the four UO 2+x specimens. The rate constant was found to vary with location on the surface. Stoichiometric locations, with a well defined fluorite structure, exhibited very low corrosion rates. Higher rates were observed at more non-stoichiometric locations with the highest rates being obtained on locations exhibiting tetragonal distortions as their composition approached UO 2.33 . The distribution of rates increases with the degree of nominal non-stoichiometry as the diversity of microstructures existing on the UO 2+x surface increases.

  17. New halides of neodymium and their crystal structures

    International Nuclear Information System (INIS)

    Loechner, U.

    1980-01-01

    The crystal structures of the peritectic phases NdClsub(2.27) (t-phase) and NdClsub(2.37) (rh-phase) were determined. The structure of the rh-phase was solved, from the t-phase only the elementary cell could be determined because no single crystals of sufficient quality were obtained. Jutting out feature of the rh-phase which has to be formulated as Nd 14 Cl 32 O is a polyeder cluster of 6 quadratic antiprisms the inner cubo octahedric cavity of which is occupied by an oxygen atom. The linkage of these polyeder cluster ensues only under each other along the triple axis of the rhomboedric system over 3 upper and 3 lower common borders each. Therewith for the first time a superlattice of the fluorite-type was found in which this unit exclusively occurs. The type of linkage of polyeder clusters causes the occurrence of an exceptional polyeder around the twovalent Nd ions which can be looked at as a zwitter polyeder of icosahedron and cube and therefore coordinates tenfold the twovalent neodymium. The strict order of chemically and crystallografically clearly differentiated cations is expressed by a hexagonal-rhomboedric superstructure of the fluorite-aristotyp with a doubled c-axis. The phase diagram of the system Nd-NdBr 3 was determined and a structure proposition was worked out for the first Vernier phase in there with n=4 of the series Lnsub(n)Xsub(2n+1). (SPI)

  18. Pyrochlore as nuclear waste form. Actinide uptake and chemical stability

    International Nuclear Information System (INIS)

    Finkeldei, Sarah Charlotte

    2015-01-01

    Radioactive waste is generated by many different technical and scientific applications. For the past decades, different waste disposal strategies have been considered. Several questions on the waste disposal strategy remain unanswered, particularly regarding the long-term radiotoxicity of minor actinides (Am, Cm, Np), plutonium and uranium. These radionuclides mainly arise from high level nuclear waste (HLW), specific waste streams or dismantled nuclear weapons. Although many countries have opted for the direct disposal of spent fuel, from a scientific and technical point of view it is imperative to pursue alternative waste management strategies. Apart from the vitrification, especially for trivalent actinides and Pu, crystalline ceramic waste forms are considered. In contrast to glasses, crystalline waste forms, which are chemically and physically highly stable, allow the retention of radionuclides on well-defined lattice positions within the crystal structure. Besides polyphase ceramics such as SYNROC, single phase ceramics are considered as tailor made host phases to embed a specific radionuclide or a specific group. Among oxidic single phase ceramics pyrochlores are known to have a high potential for this application. This work examines ZrO 2 based pyrochlores as potential nuclear waste forms, which are known to show a high aqueous stability and a high tolerance towards radiation damage. This work contributes to (1) understand the phase stability field of pyrochlore and consequences of non-stoichiometry which leads to pyrochlores with mixed cationic sites. Mixed cationic occupancies are likely to occur in actinide-bearing pyrochlores. (2) The structural uptake of radionuclides themselves was studied. (3) The chemical stability and the effect of phase transition from pyrochlore to defect fluorite were probed. This phase transition is important, as it is the result of radiation damage in ZrO 2 based pyrochlores. ZrO 2 - Nd 2 O 3 pellets with pyrochlore and defect

  19. BIOQUIMICO PLASMÁTICO DE CÃES: EFEITOS DOS DIFERENTES ANTICOAGULANTES EM COMPARAÇÃO COM O SORO

    Directory of Open Access Journals (Sweden)

    Bianca Ressetti da Silva

    2015-06-01

    Full Text Available Different types of anticoagulants are used in the routine of a veterinary clinic, which are chosen based on the exam to be performed. Agitated, aggressive, of hard contention and small size animals can be a limiting factor when it is wished to separate samples into tubes with different anticoagulants. Therefore, this study had as the objective evaluate the effects of anticoagulants: EDTA, sodium citrate and sodium fluorite associated with EDTA, in the results of routine plasma biochemistry performed in dogs and compare it with serum. Blood samples of 10 clinically healthy dogs were collected and placed in different tubes with each anticoagulant and one without to obtain serum. Albumin, alanine aminotransferase (ALT, calcium, total cholesterol, creatine, phosphorus, glucose, total protein (PT and urea concentrations were measured by spectophotometric. It was found that plasma obtained with EDTA anticoagulant resulted in dosage alterations for glucose, cholesterol and calcium. Samples obtained with sodium citrate presented results lower than serum in all analyzed parameters, except for ALT. The anticoagulant sodium 34 Colloquium Agrariae, v. 11, n.1, Jan-Jun. 2015, p.33-41. DOI: 10.5747/ca.2015.v11.n1.a116 fluorite with EDTA only didn’t result in statistical differences when compared to serum in the parameters of urea and glucose. Thus, serum is the most trustworthy sample to determine the biochemical profile of dogs, however some biochemical’s can be performed with plasma with EDTA such as creatine, ALT, urea, albumin, PT and phosphorus.

  20. Color change of gemstones by exposure to gamma rays

    Energy Technology Data Exchange (ETDEWEB)

    Lima, Giovanna L.C. de; Lameiras, Fernando S., E-mail: giovannalarissa17@hotmail.com, E-mail: fsl@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2015-07-01

    A gem is appreciated by collectors and, when polished, widely used for jewelry manufacturing. For example, when quartz naturally or artificially acquires a color it becomes a gemstone (smoky quartz, morion, citrine, amethyst, or prasyolite). The presence of chromophore elements in a quartz sample was analysed by Fourier transform infrared spectrometry (FTIR). With a semi-quantitative analysis of the absorption FTIR spectra, it was possible to predict if colorless quartz has the potential to develop color when exposed to ionizing radiation and heat. Specific absorption bands show the presence of chromophore elements in quartz such as aluminum, iron, hydrogen, sodium, or lithium. Considering the ratio of the heights of the absorption bands of these elements, it was possible to predict the color quartz can develop. Samples of irradiated dark and light violet fluorites were analyzed by FTIR and energy-dispersive X-rays spectroscopy. The light violet samples has higher content of calcium relative to fluorine, as well higher content of hydroxyl, probably replacing fluorine in crystal lattice. Hydroxyls cannot be precursors of F color centers, which are the cause of violet color in fluorite, explaining the light violet color of hydroxyl-rich samples. (author)

  1. A salt diapir-related Mississippi Valley-type deposit: The Bou Jaber Pb-Zn-Ba-F deposit, Tunisia: Fluid inclusion and isotope study

    Science.gov (United States)

    Bouhlel, Salah; Leach, David; Johnson, Craig A.; Marsh, Erin; Salmi-Laouar, Sihem; Banks, David A.

    2016-01-01

    The Bou Jaber Ba-F-Pb-Zn deposit is located at the edge of the Bou Jaber Triassic salt diapir in the Tunisia Salt Diapir Province. The ores are unconformity and fault-controlled and occur as subvertical column-shaped bodies developed in dissolution-collapse breccias and in cavities within the Late Aptian platform carbonate rocks, which are covered unconformably by impermeable shales and marls of the Fahdene Formation (Late Albian–Cenomanian age). The host rock is hydrothermally altered to ankerite proximal to and within the ore bodies. Quartz, as fine-grained bipyramidal crystals, formed during hydrothermal alteration of the host rocks. The ore mineral assemblage is composed of barite, fluorite, sphalerite, and galena in decreasing abundance. The ore zones outline distinct depositional events: sphalerite-galena, barite-ankerite, and fluorite. Fluid inclusions, commonly oil-rich, have distinct fluid salinities and homogenization temperatures for each of these events: sphalerite-galena (17 to 24 wt% NaCl eq., and Th from 112 to 136 °C); ankerite-barite (11 to 17 wt% NaCl eq., and Th from 100 to 130 °C); fluorite (19 to 21 wt% NaCl eq., Th from 140 to 165 °C). The mean temperature of the ore fluids decreased from sphalerite (125 °C) to barite (115 °C) and increased during fluorite deposition (152 °C); then decreased to ∼110 °C during late calcite precipitation. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of fluid inclusions in fluorite are metal rich (hundreds to thousands ppm Pb, Zn, Cu, Fe) but the inclusions in barite are deficient in Pb, Zn, Cu, Fe. Inclusions in fluorite have Cl/Br and Na/Br ratios of several thousand, consistent with dissolution of halite while the inclusions analysed in barite have values lower than seawater which are indicative of a Br-enriched brine derived from evaporation plus a component of halite dissolution. The salinity of the barite-hosted fluid inclusions is less than obtained

  2. Structure and mechanical properties of swift heavy ion irradiated tungsten-bearing delta-phase oxides Y{sub 6}W{sub 1}O{sub 12} and Yb{sub 6}W{sub 1}O{sub 12}

    Energy Technology Data Exchange (ETDEWEB)

    Tang, M., E-mail: mtang@lanl.gov [Materials Science and Technology Division, Mail-Stop G755, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Wynn, T.A. [Materials Physics and Application Division, Mail-Stop K771, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Patel, M.K.; Won, J. [Materials Science and Technology Division, Mail-Stop G755, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Monnet, I. [CIMAP, CEA-CNRS-ENSICAEN-Universite de Caen Normandie, Bd Henri Becquerel, BP 5133, F-14070, Caen Cedex 5 (France); Pivin, J.C. [Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, CNRS-IN2P3-Universite Paris Sud, UMR 8609, Bat. 108, 91405 Orsay (France); Mara, N.A. [Materials Physics and Application Division, Mail-Stop K771, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Sickafus, K.E. [Materials Science and Technology Division, Mail-Stop G755, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2012-06-15

    We report on the relationship between structure and mechanical properties of complex oxides whose structures are derivatives of fluorite, following irradiation with swift heavy ion (92 MeV Xe) which approximately simulates fission product irradiation, where the electronic energy loss dominates. The two compounds of interest in this paper are Y{sub 6}W{sub 1}O{sub 12} and Yb{sub 6}W{sub 1}O{sub 12}. These compounds possess an ordered, fluorite derivative crystal structure known as the delta ({delta}) phase, a rhombohedral structure belonging to space group R3{sup Macron}. Structural changes induced by irradiation were examined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD investigations indicated an irradiation-induced amorphization in these compounds. This result is consistent with our previous study on Y{sub 6}W{sub 1}O{sub 12} under displacive radiation environment in which the nuclear energy loss is dominant. High resolution TEM also revealed that individual ion tracks was amorphized. The mechanical properties of both irradiated compounds, were determined by cross-sectional nano-indentation measurements as a function of ion penetration depth. The decreases in Young's modulus, E, and hardness, H (both by about 40% at the irradiated surface) suggest amorphization beyond simple defect accumulation occurs under this irradiation condition.

  3. Studies on Structural and Morphological Properties of Multidoped Ceria Ce0.8Nd0.0025Sm0.0025Gd0.005Dy0.095Y0.095O2-δ (x=0.2 as Solid Solutions

    Directory of Open Access Journals (Sweden)

    Marija Stojmenović

    2016-01-01

    Full Text Available The nanopowdery solid solutions of multidoped ceria Ce0.8Nd0.0025Sm0.0025Gd0.005Dy0.095Y0.095O2-δ (x=0.2 with the fluorite type crystal structure of CeO2 were synthesized for the first time. Two synthesis procedures were applied: the modified glycine-nitrate procedure (MGNP method and room temperature self-propagating reaction (SPRT method. All nanopowders were characterized by XRPD analysis, Raman spectroscopy, low temperature nitrogen physisorption, TEM, and SEM methods. According to the XRPD and Raman spectroscopy results, single phase solid solutions of fluorite structure were evidenced regardless of the number of dopants and synthesis procedure. Both XRPD and TEM were analyses evidenced nanometer particle dimensions. The SPRT method results in obtaining sample with higher specific surface area, smaller crystallite and particles sizes, and the same values of the lattice parameter in comparison to pure CeO2. Raman spectroscopy was confirmed to the oxygen vacancies introduced into the ceria lattice when Ce4+ ions were replaced with cations (dopants of lower valence state (3+, which may indicate the potential improvement of ionic conductivity. Additionally, the presence of oxygen vacancies in the lattice ceria, as well as very developed grain boundaries, gives a new possibility for potential application of obtained nanopowders in the area of room temperature ferromagnetism as spintronics.

  4. Chemical thermodynamic representations of and

    International Nuclear Information System (INIS)

    Besmann, T.M.; Lindemer, T.B.

    1985-01-01

    All available oxygen potential-temperature-composition data for the calcium fluorite-structure sup(**) phase were retrieved from the literature and utilized in the development of a binary solid solution representation of the phase. The data and phase relations are found to be best described by a solution of [Pusub(4/3)O 2 ] and [PuO 2 ] with a temperature dependent interaction energy. The fluorite-structure is assumed to be represented by a combination of the binaries and , and thus treated as a solution of [Pusub(4/3)O 2 ], [PuO 2 ], [UO 2 ], and either [U 2 Osub(4.5)] or [U 3 O 7 ]. The resulting equations well reproduce the large amount of oxygen potential-temperature-composition data for the mixed oxide system, all of which were also retrieved from the literature. These models are the first that appear to display the appropriate oxygen potential-temperature-composition and phase relation behavior over the entire range of existence for the phases. (orig.)

  5. Recycling of electric arc furnace (EAF dust for use in steel making process

    Directory of Open Access Journals (Sweden)

    José Alencastro de Araújo

    2014-07-01

    Full Text Available The EAF dust is listed as hazardous waste from specific source, K061, according to ABNT 10004:2004 and constitutes one of the major problems of electrical steel plant. This work suggests recycling of the EAF dust by sintering of a composite, pre-cast agglomerate (PCA consisting of EAF dust agglomerate to coke particles, mill scale and ceramic fluorite into pellets. The work was divided into three stages, in the first stage the technical viability of using only solid waste industrial to produce a PCA was observed, in the second phase, the main effects between the components of the PCA to obtain the optimal formulation was tested. In the third phase the intensity of the variables, coke and fluorite ceramics, for removing zinc of PCA was checked. Every stage was chemically analyzed by X-ray fluorescence spectrometer and X-ray diffraction. The first two stages of the production PCA were carried out in a pilot plant sintering downstream and the third phase in a pilot plant upstream. As a result of the process two by-products were obtained, the pre-cast agglomerated, PCA, with total iron content exceeding 70%, object of the process of sintering and zinc dust, containing more than 50% zinc resulting from volatilization of this metal during the sintering process and collected by bag filter. In addition, approximately 90% of lead and cadmium contained in the initial EAF dust was extracted.

  6. Color change of gemstones by exposure to gamma rays

    International Nuclear Information System (INIS)

    Lima, Giovanna L.C. de; Lameiras, Fernando S.

    2015-01-01

    A gem is appreciated by collectors and, when polished, widely used for jewelry manufacturing. For example, when quartz naturally or artificially acquires a color it becomes a gemstone (smoky quartz, morion, citrine, amethyst, or prasyolite). The presence of chromophore elements in a quartz sample was analysed by Fourier transform infrared spectrometry (FTIR). With a semi-quantitative analysis of the absorption FTIR spectra, it was possible to predict if colorless quartz has the potential to develop color when exposed to ionizing radiation and heat. Specific absorption bands show the presence of chromophore elements in quartz such as aluminum, iron, hydrogen, sodium, or lithium. Considering the ratio of the heights of the absorption bands of these elements, it was possible to predict the color quartz can develop. Samples of irradiated dark and light violet fluorites were analyzed by FTIR and energy-dispersive X-rays spectroscopy. The light violet samples has higher content of calcium relative to fluorine, as well higher content of hydroxyl, probably replacing fluorine in crystal lattice. Hydroxyls cannot be precursors of F color centers, which are the cause of violet color in fluorite, explaining the light violet color of hydroxyl-rich samples. (author)

  7. Panorama of mining activities in France during 1993-1994

    International Nuclear Information System (INIS)

    Michel, J.C.; Bornuat, M.; Heinry, C.; Le Berre, P.

    1995-01-01

    Demand, and thus prices and activities, in the French mining sector continued to suffer from the effects of the 1993 recession. The moderate economic recovery seen in 1994 has not had an immediate impact on the mining industry partly because of previously built up stocks, but some encouraging signs have appeared: a clear resumption of oil exploration, the anti-dumping measures of the European Union, and a new Chinese pricing policy particularly concerning tungsten, antimony and fluorite. In general, French mining continued its decline as illustrated by the closures of further iron, uranium and zinc mines and the loss of all tungsten, bauxite, lead, zinc and germanium mines. The very marked decrease in zinc, silver, uranium, iron and coal production reflects the programmed closure of certain mines. In detail, the balance is more varied and the situation and outlook are not as bleak for all mineral substances: decline is moderate for potassium, barite and fluorite; oil and gas in France and nickel in new Caledonia are stable; sulphur, talc, salt, kaolin, feldspar and silica production have recorded a slight growth while gold is in clear progression. However, these positive aspects cannot counter-balance the lack of significant new resources (hydrocarbons, potassium) and of sufficient exploration effort relative to the stakes (metal ore mines). The end of the National Mineral Inventory in 1993 and the very long procedures for mining permits obtention do not favor national or international private investment. (J.S.). 14 figs., 11 tabs

  8. Structure and bulk modulus of Ln-doped UO{sub 2} (Ln = La, Nd) at high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Rittman, Dylan R., E-mail: drittman@stanford.edu [Department of Geological Sciences, Stanford University, Stanford, CA 94305 (United States); Park, Sulgiye; Tracy, Cameron L. [Department of Geological Sciences, Stanford University, Stanford, CA 94305 (United States); Zhang, Lei [Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California Davis, Davis, CA 95616 (United States); Department of Chemical Engineering and Materials Science, University of California Davis, Davis, CA 95616 (United States); Palomares, Raul I.; Lang, Maik [Department of Nuclear Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Navrotsky, Alexandra [Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California Davis, Davis, CA 95616 (United States); Department of Chemical Engineering and Materials Science, University of California Davis, Davis, CA 95616 (United States); Mao, Wendy L. [Department of Geological Sciences, Stanford University, Stanford, CA 94305 (United States); Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Ewing, Rodney C. [Department of Geological Sciences, Stanford University, Stanford, CA 94305 (United States)

    2017-07-15

    The structure of lanthanide-doped uranium dioxide, Ln{sub x}U{sub 1-x}O{sub 2-0.5x+y} (Ln = La, Nd), was investigated at pressures up to ∼50–55 GPa. Samples were synthesized with different lanthanides at different concentrations (x ∼ 0.2 and 0.5), and all were slightly hyperstoichiometric (y ∼ 0.25–0.4). In situ high-pressure synchrotron X-ray diffraction was used to investigate their high-pressure phase behavior and determine their bulk moduli. All samples underwent a fluorite-to-cotunnite phase transformation with increasing pressure. The pressure of the phase transformation increased with increasing hyperstoichiometry, which is consistent with results from previous computational simulations. Bulk moduli are inversely proportional to both the ionic radius of the lanthanide and its concentration, as quantified using a weighted cationic radius ratio. This trend was found to be consistent with the behavior of other elastic properties measured for Ln-doped UO{sub 2}, such as Young's modulus. - Highlights: •Ln-doped UO{sub 2} transforms from fluorite to cotunnite at high pressure. •Transition pressure increases with increasing hyperstoichiometry. •Bulk modulus decreases with increasing Ln-dopant radius and concentration.

  9. TEM and HRTEM study of oxide particles in an Al-alloyed high-Cr oxide dispersion strengthened ferritic steel with Hf addition

    International Nuclear Information System (INIS)

    Dou, Peng; Kimura, Akihiko; Kasada, Ryuta; Okuda, Takanari; Inoue, Masaki; Ukai, Shigeharu; Ohnuki, Somei; Fujisawa, Toshiharu; Abe, Fujio; Jiang, Shan; Yang, Zhigang

    2017-01-01

    The nanoparticles in an Al-alloyed high-Cr oxide dispersion strengthened (ODS) ferritic steel with Hf addition, i.e., SOC-16 (Fe-15Cr-2W-0.1Ti-4Al-0.62Hf-0.35Y 2 O 3 ), have been examined by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Relative to an Al-alloyed high-Cr ODS ferritic steel without Hf addition, i.e., SOC-9 (Fe-15.5Cr-2W-0.1Ti-4Al-0.35Y 2 O 3 ), the dispersion morphology and coherency of the oxide nanoparticles in SOC-16 were significantly improved. Almost all the small nanoparticles (diameter <10 nm) in SOC-16 were found to be consistent with cubic Y 2 Hf 2 O 7 oxides with the anion-deficient fluorite structure and coherent with the bcc steel matrix. The larger particles (diameter >10 nm) were also mainly identified as cubic Y 2 Hf 2 O 7 oxides with the anion-deficient fluorite structure. The results presented here are compared with those of SOC-9 with a brief discussion of the underlying mechanisms of the unusual thermal and irradiation stabilities of the oxides as well as the superior strength, excellent irradiation tolerance and extraordinary corrosion resistance of SOC-16.

  10. Intergranular fracture in UO2: derivation of traction-separation law from atomistic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Yongfeng Zhang; Paul C Millett; Michael R Tonks; Xian-Ming Bai; S Bulent Biner

    2013-10-01

    In this study, the intergranular fracture behavior of UO2 was studied by molecular dynamics simulations using the Basak potential. In addition, the constitutive traction-separation law was derived from atomistic data using the cohesive-zone model. In the simulations a bicrystal model with the (100) symmetric tilt E5 grain boundaries was utilized. Uniaxial tension along the grain boundary normal was applied to simulate Mode-I fracture. The fracture was observed to propagate along the grain boundary by micro-pore nucleation and coalescence, giving an overall intergranular fracture behavior. Phase transformations from the Fluorite to the Rutile and Scrutinyite phases were identified at the propagating crack tips. These new phases are metastable and they transformed back to the Fluorite phase at the wake of crack tips as the local stress concentration was relieved by complete cracking. Such transient behavior observed at atomistic scale was found to substantially increase the energy release rate for fracture. Insertion of Xe gas into the initial notch showed minor effect on the overall fracture behavior.

  11. Studies on Structural and Morphological Properties of Multidoped Ceria Ce 0.8 Nd 0.0025 Sm 0.0025 Gd 0.005 Dy 0.095 Y 0.095 O 2 - δ ( x = 0.2 ) as Solid Solutions

    KAUST Repository

    Stojmenović, Marija

    2016-04-17

    The nanopowdery solid solutions of multidoped ceria Ce0.8Nd0.0025Sm0.0025Gd0.005Dy0.095Y0.095 () with the fluorite type crystal structure of CeO2 were synthesized for the first time. Two synthesis procedures were applied: the modified glycine-nitrate procedure (MGNP method) and room temperature self-propagating reaction (SPRT method). All nanopowders were characterized by XRPD analysis, Raman spectroscopy, low temperature nitrogen physisorption, TEM, and SEM methods. According to the XRPD and Raman spectroscopy results, single phase solid solutions of fluorite structure were evidenced regardless of the number of dopants and synthesis procedure. Both XRPD and TEM were analyses evidenced nanometer particle dimensions. The SPRT method results in obtaining sample with higher specific surface area, smaller crystallite and particles sizes, and the same values of the lattice parameter in comparison to pure CeO2. Raman spectroscopy was confirmed to the oxygen vacancies introduced into the ceria lattice when Ce4+ ions were replaced with cations (dopants) of lower valence state (3+), which may indicate the potential improvement of ionic conductivity. Additionally, the presence of oxygen vacancies in the lattice ceria, as well as very developed grain boundaries, gives a new possibility for potential application of obtained nanopowders in the area of room temperature ferromagnetism as spintronics.

  12. Rare earth element and yttrium geochemistry applied to the genetic study of cryolite ore at the Pitinga Mine (Amazon, Brazil

    Directory of Open Access Journals (Sweden)

    Orlando R.R. Minuzzi

    2008-12-01

    Full Text Available This work aims at the geochemical study of Pitinga cryolite mineralization through REE and Y analyses in disseminated and massive cryolite ore deposits, as well as in fluorite occurrences. REE signatures in fluorite and cryolite are similar to those in the Madeira albite granite. The highest ΣREE values are found in magmatic cryolite (677 to 1345 ppm; ΣREE is lower in massive cryolite. Average values for the different cryolite types are 10.3 ppm, 6.66 ppm and 8.38 ppm (for nucleated, caramel and white types, respectively. Disseminated fluorite displays higher ΣREE values (1708 and 1526ppm than fluorite in late veins(34.81ppm. Yttrium concentration is higher in disseminated fluorite and in magmatic cryolite. The evolution of several parameters (REEtotal, LREE/HREE, Y was followed throughout successive stages of evolution in albite granites and associated mineralization. At the end of the process, late cryolite was formed with low REEtotal content. REE data indicate that the MCD was formed by, and the disseminated ore enriched by (additional formation of hydrothermal disseminated cryolite, hydrothermal fluids, residual from albite granite. The presence of tetrads is poorly defined, although nucleated, caramel and white cryolite types show evidence for tetrad effect.Este trabalho enfoca a geoquímica de elementos terras raras (ETR e de Y no minério criolítico disseminado, no depósito criolítico maciço e na fluorita associada na mina Pitinga. As assinaturas de ETR na criolita e fluorita são similares àquelas do granito Madeira. Os maiores valores de SETR são encontrados na criolita magmática disseminada (677 a 1.345 ppm; SETR é menor na criolita maciça, com valores médios de 10,3 ppm, 6,66 ppm e 8,38 ppm, respectivamente, nos tipos de criolita nucleada, caramelo e branca. A fluorita magmática disseminada apresenta os valores mais altos de SETR (1.708 e 1.526 ppm, contrastando com a fluorita de veio tardio(34,81 ppm. A concentra

  13. Late-stage anhydrite-gypsum-siderite-dolomite-calcite assemblages record the transition from a deep to a shallow hydrothermal system in the Schwarzwald mining district, SW Germany

    Science.gov (United States)

    Burisch, Mathias; Walter, Benjamin F.; Gerdes, Axel; Lanz, Maximilian; Markl, Gregor

    2018-02-01

    The majority of hydrothermal vein systems of economic interest occur at relatively shallow crustal levels, although many of them formed at significantly greater depths. Their present position is a consequence of uplift and erosion. Although, many aspects of their formation are well constrained, the temporal chemical evolution of such systems during uplift and erosion is still poorly understood. These vein minerals comprise calcite, dolomite-ankerite, siderite-magnesite, anhydrite and gypsum forming the last gangue assemblages in Jurassic and Tertiary sulphide-fluorite-quartz-barite veins of the Schwarzwald mining district, SW Germany. Mineral textures of samples from nine localities reveal that in these sequences, mineral precipitation follows a recurring pattern: early calcite is followed by anhydrite or gypsum, siderite and/or dolomite. This succession may repeat up to three times. In-situ (LA-ICP-MS) U-Pb age dating of 15 carbonates from three subsequent generations of the late-stage vein assemblage yield robust ages between 20 and 0.6 Ma. Each mineral sequence forms in a distinctive period of about 2-5 Ma. These ages clearly relate these late-stage mineral phases to the youngest geological episode of the Schwarzwald, which is associated with the Cenozoic Rhine Graben rifting and basement uplift. Based on thermodynamic modelling, the formation of the observed mineral assemblages required an deeply sourced Mg-, Fe- and SO4-rich fluid (b), which was episodically mixed with a shallow crustal HCO3-rich fluid (a). As a consequence of fluid mixing, concentrations of Mg, Fe and SO4 temporarily increased and initiated the formation of the observed sulphate-carbonate mineral sequences. This discontinuous large-scale vertical fluid mixing was presumably directly related to episodes of active tectonics associated with the Cenozoic strike-slip regime of the Upper Rhine Graben. Analogously, episodic fluid mixing is a major key in the formation of older (Jurassic to early

  14. Separation of lanthanides through hydroxyapatite; Separacion de lantanidos mediante hidroxiapatita

    Energy Technology Data Exchange (ETDEWEB)

    Garcia M, F.G

    2006-07-01

    With the objective of obtaining from an independent way to each one of the lanthanides {sup 151} Pm, {sup 161} Tb, {sup 166} Ho and {sup 177} Lu free of carrier and with high specific activities starting from the indirect irradiation via, it intends in this work to determine the viability of separation of the couples Nd/Pm, Dy/Ho, Gd/Tb and Yb/Lu, by means of ion exchange column chromatography, using hydroxyapatite (HAp) and fluorite like absorbent material in complexing media. It is important to mention that have registered separation studies among lanthanides of the heavy group with those of the slight group, using the same mass and, in comparison with this work, quantities different from the father were used and of the son, also, that the separation studies were carried out among neighboring lanthanides. In this investigation, it was determined the effect that its have the complexing media: KSCN, sodium tartrate, sodium citrate, EDTA and aluminon, their pH and concentration, in the adsorption of the lanthanides in both minerals, in order to determine the chromatographic conditions for separation of the couples Nd/Pm, Dy/Ho, Gd/Tb and Yb/Lu. The work consists of five chapters, in the first one they are presented a theoretical introduction of the characteristics more important of the lanthanides, the hydroxyapatite and the fluorite; in the second, it is deepened in the ion exchange, as well as the two techniques (XRD and High Vacuum Electron Microscopy) to make the characterization of LnCI{sub 3} (Ln = Nd, Gd, Dy or Yb) synthesized. The third chapter, it describes the methodology continued in our experimental work; in the room, its are presented the obtained results of the static and dynamic method to determine the viability of separation of neighboring lanthanides; and finally, the five chapter shows the conclusions. In this study, it is concludes that the separation among neighboring lanthanides cannot be carried out in the minerals and used media; because

  15. Phase Behavior and Equations of State of the Actinide Oxides

    Science.gov (United States)

    Chidester, B.; Pardo, O. S.; Panero, W. R.; Fischer, R. A.; Thompson, E. C.; Heinz, D. L.; Prescher, C.; Prakapenka, V. B.; Campbell, A.

    2017-12-01

    The distribution of the long-lived heat-producing actinide elements U and Th in the deep Earth has important implications for the dynamics of the mantle and possibly the energy budget of Earth's core. The low shear velocities of the Large Low-Shear Velocity Provinces (LLSVPs) on the core-mantle boundary suggests that these regions are at least partially molten and may contain concentrated amounts of the radioactive elements, as well as other large cations such as the rare Earth elements. As such, by exploring the phase behavior of actinide-bearing minerals at extreme conditions, some insight into the mineralogy, formation, and geochemical and geodynamical effects of these regions can be gained. We have performed in situ high-pressure, high-temperature synchrotron X-ray diffraction experiments and calculations on two actinide oxide materials, UO2 and ThO2, to determine their phase behavior at the extreme conditions of the lower mantle. Experiments on ThO2 reached 60 GPa and 2500 K, and experiments on UO2 reached 95 GPa and 2500 K. We find that ThO2 exists in the fluorite-type structure to 20 GPa at high temperatures, at which point it transforms to the high-pressure cotunnite-type structure and remains thus up to 60 GPa. At room temperature, an anomalous expansion of the fluorite structure is observed prior to the transition, and may signal anion sub-lattice disorder. Similarly, UO2 exists in the fluorite-type structure at ambient conditions and up to 28 GPa at high temperatures. Above these pressures, we have observed a previously unidentified phase of UO2 with a tetragonal structure as the lower-temperature phase and the cotunnite-type phase at higher temperatures. Above 78 GPa, UO2 undergoes another transition or possible dissociation into two separate oxide phases. These phase diagrams suggest that the actinides could exist as oxides in solid solution with other analogous phases (e.g. ZrO2) in the cotunnite-type structure throughout much of Earth's lower mantle.

  16. Carbonatites in China: A review for genesis and mineralization

    Directory of Open Access Journals (Sweden)

    Cheng Xu

    2010-10-01

    Full Text Available Carbonatites are commonly related to the accumulation of economically valuable substances such as REE, Cu, and P. The debate over the origin of carbonatites and their relationship to associated silicate rocks has been ongoing for about 45 years. Worldwide, the rocks characteristically display more geochemical enrichments in Ba, Sr and REE than sedimentary carbonate rocks. However, carbonatite’s geochemical features are disputed because of secondary mineral effects. Rock-forming carbonates from carbonatites at Qinling, Panxi region, and Bayan Obo in China show REE distribution patterns ranging from LREE enrichment to flat patterns. They are characterized by a Sr content more than 10 times higher than that of secondary carbonates. The coarse- and fine-grained dolomites from Bayan Obo H8 dolomite marbles also show similar high Sr abundance, indicating that they are of igneous origin. Some carbonates in Chinese carbonatites show REE (especially HREE contents and distribution patterns similar to those of the whole rocks. These intrusive carbonatites display lower platinum group elements and stronger fractionation between Pt and Ir relative to high-Si extrusive carbonatite. This indicates that most intrusive carbonatites may be carbonate cumulates. Maoniuping and Daluxiang in Panxi region are large REE deposits. Hydrothermal fluorite ore veins occur outside of the carbonatite bodies and are emplaced in wallrock syenite. The fluorite in Maoniuping has Sr and Nd isotopes similar to carbonatite. The Daluxiang fluorite shows Sr and REE compositions different from those in Maoniuping. The difference is reflected by both the carbonatites and rock-forming carbonates, indicating that REE mineralization is related to carbonatites. The cumulate processes of carbonate minerals make fractionated fluids rich in volatiles and LREE as a result of low partition coefficients for REE between carbonate and carbonatite melt and an increase from LREE to HREE. The

  17. Remarkable changes in the photoluminescent properties of Y2Ce2O7:Eu(3+) red phosphors through modification of the cerium oxidation states and oxygen vacancy ordering.

    Science.gov (United States)

    Raj, Athira K V; Prabhakar Rao, P; Sreena, T S; Sameera, S; James, Vineetha; Renju, U A

    2014-11-21

    A new series of red phosphors based on Eu(3+)-doped yttrium cerate [Y1.9Ce2O7:0.1Eu(3+), Y2Ce1.9O7:0.1Eu(3+) and Y2Ce2-xO7:xEu(3+) (x = 0.05, 0.10, 0.15, 0.20, 0.25 and 0.50)] was prepared via a conventional solid-state method. The influence of the substitution of Eu(3+) at the aliovalent site on the photoluminescent properties was determined by powder X-ray diffraction, FT Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy with energy-dispersive spectroscopy, UV-visible absorption spectroscopy, photoluminescence spectroscopy and lifetime measurements. The substitution of Eu(3+) at the Ce(4+) site induces a structural transition from a defect fluorite to a C-type structure, which increases the oxygen vacancy ordering and the distortion of the Eu(3+) environment, and decreases the formation of Ce(3+) states. In contrast, phosphors with isovalent substitution at the Y(3+) site exhibit the biphasic nature of defect fluorite and a C-type structure, thereby increasing the number of Ce(3+) oxidation states. These modifications resulted in remarkable changes in the photoluminescent properties of Y2Ce1.9O7:0.1Eu(3+) red phosphors, with emission intensities 3.8 times greater than those of the Ce0.9O2:0.1Eu(3+) and Y1.9Ce2O7:0.1Eu(3+). The photoluminescent properties of Y2Ce2-xO7:xEu(3+) were studied at different Eu(3+) concentrations under excitation with blue light. These phosphors emit intense red light due to the (5)D0-(7)F2 transition under excitation at 466 nm and no concentration quenching is observed with up to 50 mol% Eu(3+). They show increased lifetimes in the range 0.62-0.72 ms at Eu(3+) concentrations. The cation ordering linked to the oxygen vacancy ordering led to the uniform distribution of Eu(3+) ions in the lattice, thus allowing higher doping concentrations without quenching and consequently increasing the lifetime of the (5)D0 states. Our results demonstrate that significant improvements in

  18. Separation of lanthanides through hydroxyapatite

    International Nuclear Information System (INIS)

    Garcia M, F.G.

    2006-01-01

    With the objective of obtaining from an independent way to each one of the lanthanides 151 Pm, 161 Tb, 166 Ho and 177 Lu free of carrier and with high specific activities starting from the indirect irradiation via, it intends in this work to determine the viability of separation of the couples Nd/Pm, Dy/Ho, Gd/Tb and Yb/Lu, by means of ion exchange column chromatography, using hydroxyapatite (HAp) and fluorite like absorbent material in complexing media. It is important to mention that have registered separation studies among lanthanides of the heavy group with those of the slight group, using the same mass and, in comparison with this work, quantities different from the father were used and of the son, also, that the separation studies were carried out among neighboring lanthanides. In this investigation, it was determined the effect that its have the complexing media: KSCN, sodium tartrate, sodium citrate, EDTA and aluminon, their pH and concentration, in the adsorption of the lanthanides in both minerals, in order to determine the chromatographic conditions for separation of the couples Nd/Pm, Dy/Ho, Gd/Tb and Yb/Lu. The work consists of five chapters, in the first one they are presented a theoretical introduction of the characteristics more important of the lanthanides, the hydroxyapatite and the fluorite; in the second, it is deepened in the ion exchange, as well as the two techniques (XRD and High Vacuum Electron Microscopy) to make the characterization of LnCI 3 (Ln = Nd, Gd, Dy or Yb) synthesized. The third chapter, it describes the methodology continued in our experimental work; in the room, its are presented the obtained results of the static and dynamic method to determine the viability of separation of neighboring lanthanides; and finally, the five chapter shows the conclusions. In this study, it is concludes that the separation among neighboring lanthanides cannot be carried out in the minerals and used media; because practically these lanthanides

  19. Remote Sensing, Geology and Geochemistry on the GVIII Uranium Mineralization, Gabal Gattar, North Eastern Desert, Egypt

    International Nuclear Information System (INIS)

    Elkholy, D.M.; Elhusseiny, M.O.; Saleh, W.H.; Elzalaky, M.A.

    2012-01-01

    GVIII- uranium occurrence of Gabal Gattar is located at the intersection of Lat. 27° 05' 56 a nd Long. 33° 16' 33 t o the south of GH-uranium occurrence. This occurrence is hosted in the alkali feldspar granite of Gabal Gattar. It is dissected by NNE-SSW, ENE-WSW and NW-SE faults and fractures. The granite is strongly altered in the zones of these faults and fractures. This granite is composed of K-feldspars, quartz, plagioclase and biotite as essential minerals and zircon, apatite, fluorite as accessories. The secondary minerals are chlorite, sericite, muscovite and iron oxides. The main alterations along the fault and fracture zones are hematitization, silicification, kaolintiization, chloritization and fluoritization that increase at the zones of intersection.The Advanced Spacebome Thermal Emission and Reflection Radiometer (ASTER) discriminated and mapped the hematitized zones in the studied granitic rocks predicting iron oxides as pathfinder minerals that be helpful in localizing high uranium concentration. The compilated and integrated data as alteration zones, geological and structural features using Geographic Information System (GIS) played an important role in correlating, manipulating, visualizing and extracting the information getting a better result for interpretation and evaluation of this occurrence. The study granite is geochemically, alkali- feldspar granite to syenogranite originated from weakly peraluminous magma of alkaline affinity and of within plate tectonic setting due to crustal relaxation. This granite shows many geochemical characterestics similar to the A-type granite, high contents of SiO 2 , (Na 2 O + K 2 O), Rb, Nb, Y, low contents of MgO, CaO and Sr and apparently F-rich granite.Radiometric measurements of GVIII U-occurrence show that the study granite records uranium values between 15 and 28 ppm, while the anomalies record uranium values range from 400 to more than 30000 ppm. Surfacial yellow secondary uranium

  20. Radioactive ores from Agostinho field, Pocos de Caldas (MG), Brazil

    International Nuclear Information System (INIS)

    Fujimori, K.

    1974-01-01

    Aiming to characterize the radioactive minerals of Campo Agostinho, Pocos de Caldas - Brazil, the survey of all natural radiactive elements and their geochemical behaviors, decays and radioactive equilibrium was done. Several models of radioactive instability of the minerals or the radioactive samples were proposed to characterize the geochemistry and the mineralization of radioactive elements. The complete isotopic analysis of the elements was done by high resolution gamma spectrometry, using a Ge(Li) detector, at the temperature of liquid nitrogen, coupled to a multichannel analyser. The sample in radioactive equilibrium of Atomic Energy Comission of United States - A.S. n.6, NBL - New Brunswick Laboratory, was considered as standard sample. Fluorite, zircons, pirite, molibinite, rutile, anatase, niobophyllite, and in small ratio (bellow 0.1%) uranothorianite, coffinite, pyrochlore, monazite and apatite. (M.C.K.) [pt

  1. Molecular dynamics simulation of dislocations in uranium dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Fossati, Paul [CEA, DEN, DPC, SCCME, F-91191 Gif-sur-Yvette Cedex (France); Van Brutzel, Laurent, E-mail: laurent.vanbrutzel@cea.fr [CEA, DEN, DPC, SCCME, F-91191 Gif-sur-Yvette Cedex (France); Devincre, Benoît [LEM, CNRS-ONERA, 29 avenue de la Division Leclerc, F-92322 Châtillon Cedex (France)

    2013-11-15

    The plasticity of the fluorite structure in UO{sub 2} is investigated with molecular dynamics simulation and empirical potential. The stacking fault energies and the dislocation core structures with Burgers vector a/2 〈110〉 are systematically calculated. All dislocation core structures show a significant increase of the oxygen sub-lattice disorder at temperatures higher than 1500 K. The threshold stress for dislocation glide is found to decrease with increasing temperature but its values is always very high, several GPa at 0 K and several hundred of MPa at 2000 K. A relation between the dislocation mobility dependence with temperature and the increase of the oxygen sub-lattice disorder in the dislocation cores is established.

  2. Sorption of Sr and Cs on rocks and minerals. Pt. 1

    International Nuclear Information System (INIS)

    Torstenfelt, B.; Andersson, K.; Allard, B.

    1981-09-01

    The sorption of Sr 90 and Cs 137 on some common Swedish rocks (granite, gneiss, and diabase) and eleven different major rock-forming minerals (quartz, orthoclase, apatite, fluorite, biotite, muscovite, hematite, magnetite, hornblende, calcite, and serpentine) has been studied, using a batch technique. A comparison with the retention obtained in column experiments has been made. The water phase in all experiments has been an artificial groundwater with a composition corresponding to Swedish natural deep groundwaters. The influence of parameters, such as pH (4-11), contact time (1 day-6 months), nuclide concentration (normally 10 -7 M, variations up to 0.1 M has been made), liquid to solid ratio, particle size (three fractions between 0.045 and 0.500 mm) has been studied. An attempt to predict the distribution coefficient for rocks, using known data for the rock-forming minerals gave too low values in all cases. (Auth.)

  3. Uranium-contaminated soils: Ultramicrotomy and electron beam analysis

    International Nuclear Information System (INIS)

    Buck, E.C.; Dietz, N.L.; Bates, J.K.; Cunnane, J.C.

    1994-02-01

    Uranium-contaminated soils from the U.S. Department of Energy (DOE) Fernald Site, Ohio, have been examined by a combination of scanning electron microscopy with backscattered electron imaging (SEM/BSE) and analytical electron microscopy (AEM). The inhomogeneous distribution of particulate uranium phases in the soil required the development of a method for using ultramicrotomy to prepare transmission electron microscopy (TEM) thin sections of the SEM mounts. A water-miscible resin was selected that allowed comparison between SEM and TEM images, permitting representative sampling of the soil. Uranium was found in iron oxides, silicates (soddyite), phosphates (autunites), and fluorite (UO 2 ). No uranium was detected in association with phyllosilicates in the soil

  4. Characterization of composite metal-ceramic of nickel-oxide cerium doped gadolinium

    International Nuclear Information System (INIS)

    Silva, M.L.A. da; Varela, M.C.R.S.

    2016-01-01

    Composite nickel doped cerium oxide are used in SOFC anode materials. In this study we evaluated the effect of the presence of gadolinium on the properties of composite nickel and ceria and. The supports were synthesized by sol-gel method. The impregnation with nickel nitrate was taken sequentially, followed by calcination. The materials were characterized by X-ray diffraction, measurement of specific surface area, temperature programmed reduction, Raman spectroscopy. The presence of gadolinium retained the fluorite structure of ceria by forming a solid solution, also not influencing significantly on the specific surface area of the support. On the other hand, there was a decrease in the area catalysts, which can be attributed to sintering of nickel. Furthermore, addition of gadolinium favored the formation of intrinsic and extrinsic vacancies in cerium oxide, which leads to an increase in the ionic conductivity of the solid, desirable property for an SOFC anode catalyst. (author)

  5. International Uranium Resources Evaluation Project (IUREP) orientation phase mission summary report: Thailand

    International Nuclear Information System (INIS)

    1985-01-01

    The IURBP Orientation Phase Mission assesses the Speculative Uranium Resources in Thailand to be within the range of 1 500 to 38 500 tonnes U. Geological environments which are considered by the Mission to be favourable for uranium occurrences include the following: sandstones of Jurassic to Triassic age; Tertiary sedimentary basins (northern Thailand); Tertiary sedimentary basins (southern Thailand); associated with fluorite deposits; granitic rocks; black shales and graphitic slates of the Palaeozoic; associated with sedimentary phosphate deposits; and associated with monazite sands. Physical conditions in Thailand, including a wet tropical climate, dense forest growth and rugged terrain in some areas and relative inaccessibility, make exploration difficult and costly. There is currently no ready accessibility to detailed topographic and geological maps and other basic data. This lack of availability is a severe constraint to systematic exploration. The lack of skilled personnel experienced in uranium studies and the low level of technical support is a serious hindrance to exploration in Thailand. (author)

  6. Atomic structure of CaF2/MnF2-Si(1 1 1) superlattices from X-ray diffraction

    International Nuclear Information System (INIS)

    Alcock, Simon G.; Nicklin, C.L.; Howes, P.B.; Norris, C.A.; Kyutt, R.N.; Sokolov, N.S.; Yakovlev, N.L.

    2007-01-01

    X-ray reflectivity and non-specular crystal truncation rod scans have been used to determine the three-dimensional atomic structure of the buried CaF 2 -Si(1 1 1) interface and ultrathin films of MnF 2 and CaF 2 within a superlattice. We show that ultrathin films of MnF 2 , below a critical thickness of approximately four monolayers, are crystalline, pseudomorphic, and adopt the fluorite structure of CaF 2 . High temperature deposition of the CaF 2 buffer layer produces a fully reacted, CaF 2 -Si(1 1 1) type-B interface. The mature, 'long' interface is shown to consist of a partially occupied layer of CaF bonded to the Si substrate, followed by a distorted CaF layer. Our atomistic, semi-kinematical scattering method extends the slab reflectivity method by providing in-plane structural information

  7. Synthesis and crystal structure of the first Sc-Nb-O-N phases

    Energy Technology Data Exchange (ETDEWEB)

    Orthmann, Steven; Lerch, Martin [Institut fuer Chemie, Technische Universitaet Berlin (Germany)

    2017-11-17

    Synthesis of phase-pure materials in the system Sc-Nb-O-N is challenging. In this contribution we report on the preparation of the first scandium niobium oxide nitrides via reaction of water-saturated gaseous ammonia or an ammonia-oxygen mixture with amorphous scandium niobium oxides. Two new phases were obtained: rutile-type ScNb{sub 4}O{sub 7}N{sub 3}, which crystallizes in space group P4{sub 2}/mnm, and an anion-deficient fluorite-type Sc{sub 2}Nb(O,N,⬜){sub 6} phase crystallizing in space group Fm anti 3m. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Enhancement of the chemical stability in confined δ-Bi2O3

    DEFF Research Database (Denmark)

    Sanna, Simone; Esposito, Vincenzo; Andreasen, Jens Wenzel

    2015-01-01

    Bismuth-oxide-based materials are the building blocks for modern ferroelectrics1, multiferroics2, gas sensors3, light photocatalysts4 and fuel cells5,6. Although the cubic fluorite δ-phase of bismuth oxide (δ-Bi2O3) exhibits the highest conductivity of known solid-state oxygen ion conductors5, its...... instability prevents use at low temperature7–10. Here we demonstrate the possibility of stabilizing δ-Bi2O3 using highly coherent interfaces of alternating layers of Er2O3-stabilized δ-Bi2O3 and Gd2O3-doped CeO2. Remarkably, an exceptionally high chemical stability in reducing conditions and redox cycles...

  9. Synthesis of nc-UO{sub 2} by controlled precipitation in aqueous phase

    Energy Technology Data Exchange (ETDEWEB)

    Jovani-Abril, R., E-mail: raqueljovaniabril@gmail.com [European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O.Box 2340, D-76125 Karlsruhe (Germany); Gibilaro, M. [Laboratoire de Génie Chimique (LGC), Université de Toulouse, UMR CNRS 5503, 31062 Toulouse cedex 9 (France); Janßen, A.; Eloirdi, R.; Somers, J.; Spino, J.; Malmbeck, R. [European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O.Box 2340, D-76125 Karlsruhe (Germany)

    2016-08-15

    Nanocrystalline UO{sub 2} has been produced through controlled precipitation from an electrolytically reduced U(IV) solution. The reduction process of U(VI) to U(IV) was investigated by cyclic voltammetry in combination with absorption spectrophotometry. Precipitation was achieved by controlled alkalinisation following closely the solubility line of U(IV) in aqueous media. The highest starting concentration used was 0.5 M uranylnitrate which yielded, with the equipment used, around 10 g material pro batch. The produced nc-UO{sub 2} was characterised by transmission electron microscopy (TEM) and x-ray diffraction (XRD) and exhibited the typical UO{sub 2+x} fcc fluorite structure with an average crystallite size of 3.9 nm.

  10. Uranium districts defined by reconnaissance geochemistry in South Greenland

    International Nuclear Information System (INIS)

    Armour-Brown, A.; Steenfelt, A.; Kunzendorf, H.

    1983-01-01

    A reconnaissance exploration survey over 14 000 km 2 of Precambrian terrain in South Greenland using stream-sediment and stream-water samples delineated a central uranium district of 2000 km 2 with enhanced uranium levels and smaller anomalous zones in the south of the field area. Limited follow-up work located 8 pitchblende occurrences in this extensive district. The pitchblende is in veins which contain quartz, calcite, iron oxide, fluorite and minor sulphides. The isotopic (U-Pb) age of the pitchblende, which ranges from 1180-1090 Ma, corresponds to the late stages of Gardar alkaline igneous activity. It is concluded, therefore, that the reconnaissance geochemistry reflects a district-wide hydrothermal event related to the late volatile differentiates derived from the highly fractionated alkaline magma. A combination of primary and secondary features have complemented each other in enhancing the geochemical reconnaissance data and emphasized its importance but has not materially altered the interpretation. (Auth.)

  11. Characterization of composite metal-ceramic of nickel-oxide cerium doped gadolinium; Caracterizacao de compositos ceramica-metal de niquel e oxido de cerio dopado com gadolinio

    Energy Technology Data Exchange (ETDEWEB)

    Silva, M.L.A. da, E-mail: maria.andrade@pro.unifacs.br [Universidade Salvador (UNIFACS), BA (Brazil). Escola de Engenharia, Arquitetura e TI; Universidade Federal da Bahia (UFBA), BA (Brazil); Varela, M.C.R.S. [Universidade Federal da Bahia (UFBA), BA (Brazil)

    2016-07-01

    Composite nickel doped cerium oxide are used in SOFC anode materials. In this study we evaluated the effect of the presence of gadolinium on the properties of composite nickel and ceria and. The supports were synthesized by sol-gel method. The impregnation with nickel nitrate was taken sequentially, followed by calcination. The materials were characterized by X-ray diffraction, measurement of specific surface area, temperature programmed reduction, Raman spectroscopy. The presence of gadolinium retained the fluorite structure of ceria by forming a solid solution, also not influencing significantly on the specific surface area of the support. On the other hand, there was a decrease in the area catalysts, which can be attributed to sintering of nickel. Furthermore, addition of gadolinium favored the formation of intrinsic and extrinsic vacancies in cerium oxide, which leads to an increase in the ionic conductivity of the solid, desirable property for an SOFC anode catalyst. (author)

  12. Solid thermoluminescent dosemeter of sodium tetraborate and brazilian fluoride sensitive to thermal neutrons

    International Nuclear Information System (INIS)

    Fratin, L.

    1988-01-01

    The techniques of compacting sodium tetraborate and natural fluoride mixtures were studied in this work, with the aim of producing a solid dosimeter sensitive to thermal neutrons. The production procedure involves the vitrification of the sodium tetraborate, the grinding, mixture, cold pressing and the sinterization of the pellets. A special arrangement was built for irradiation where paraffin was used as moderator for neutrons from a 241 Am-Be source. Two different mass ratios of sodium tetraborate and flourite showed a linear thermoluminescent response to the neutron fluence in the range of 1.0 to 7.0 x 10 8 n (sub)tcm -2 . Solid dosimeters, manufactured from natural fluorite and sodium chloride, showed a response to gamma radiation similar to the response of the dosimeters sensitive to neutrons. These dosimeters are need to identify the proportion of thermoluminescent response due to gamma radiation present in a neutron field. (author) [pt

  13. Equilibrium structure of δ-Bi2O3 from first principles

    International Nuclear Information System (INIS)

    Music, Denis; Konstantinidis, Stephanos; Schneider, Jochen M

    2009-01-01

    Using ab initio calculations, we have systematically studied the structure of δ-Bi 2 O 3 (fluorite prototype, 25% oxygen vacancies) probing and combined and oxygen vacancy ordering, random distribution of oxygen vacancies with two different statistical descriptions as well as local relaxations. We observe that the combined and oxygen vacancy ordering is the most stable configuration. Radial distribution functions for these configurations can be classified as discrete (ordered configurations) and continuous (random configurations). This classification can be understood on the basis of local structural relaxations. Up to 28.6% local relaxation of the oxygen sublattice is present in the random configurations, giving rise to continuous distribution functions. The phase stability obtained may be explained with the bonding analysis. Electron lone-pair charges in the predominantly ionic Bi-O matrix may stabilize the combined and oxygen vacancy ordering.

  14. Why is AgBr not a superionic conductor

    International Nuclear Information System (INIS)

    Andreoni, W.; Tosi, M.P.

    1982-03-01

    The behaviour of AgCl and AgBr is contrasted with that of fluorite-type crystals, which also are Frenkel conductors at low temperatures but undergo a diffuse transition to a superionic phase before melting. Concentrating on AgBr for which the relevant defect parameters are better known, a Debye-Hueckel model for the interactions between defects, modified for saturation of screening at high defect concentrations, is used to show that both Frenkel and Schottky disorder are present and rapidly increasing with temperature in the hot solid, with the Schottky component rapidly overtaking the Frenkel component. It is suggested that this defect behaviour frustrates a superionic transition and leads to melting accompanied by an anomalous ionic conductivity in the premelting region. The model is tested by a comparison with data on the Frenkel defect concentration in superionic PbF 2 . (author)

  15. Deposition and characterisation of epitaxial oxide thin films for SOFCs

    KAUST Repository

    Santiso, José

    2010-10-24

    This paper reviews the recent advances in the use of thin films, mostly epitaxial, for fundamental studies of materials for solid oxide fuel cell (SOFC) applications. These studies include the influence of film microstructure, crystal orientation and strain in oxide ionic conducting materials used as electrolytes, such as fluorites, and in mixed ionic and electronic conducting materials used as electrodes, typically oxides with perovskite or perovskite-related layered structures. The recent effort towards the enhancement of the electrochemical performance of SOFC materials through the deposition of artificial film heterostructures is also presented. These thin films have been engineered at a nanoscale level, such as the case of epitaxial multilayers or nanocomposite cermet materials. The recent progress in the implementation of thin films in SOFC devices is also reported. © 2010 Springer-Verlag.

  16. Electron microprobe investigations of ore minerals of the Altenberg tin deposit (Erzgebirge, GDR). 3

    International Nuclear Information System (INIS)

    Foerster, H.J.; Hunger, H.J.; Grimm, L.

    1987-01-01

    Members of the scheelite-powellite solid solution series filling thin fractures or mantling wolframite were found in association with fluorite within a small polymineralic quartz vein traversing a topaz-protolithionite-quartz greisen. The composition of the mixed-crystal series determined by means of an automated ARL SEMQ energy-dispersive electron microprobe is characterized by a great variability and heterogeneity which has not previously been reported from any specimen nor from this special mode of occurrence yet. With an amount of powellite component between 3.2 and 58 mole percent, the molybdoscheelites from Altenberg show the today known extent of complete miscibility in the natural scheelite-powellite series. Final remarks deal with the possibilities of using the mineral series, together with some other tungsten minerals, as an indicator of the physicochemical conditions of ore formation. (author)

  17. The origin of barium in the Cambrian–Vendian aquifer system, North Estonia

    Directory of Open Access Journals (Sweden)

    Mokrik, Robert

    2009-09-01

    Full Text Available Identification of the barium occurrence and its origin is made on the basis of the groundwater chemistry study. High Ba content has been detected in the Cambrian–Vendian aquifer system in the coastal vicinity of the Gulf of Finland in Estonia and St Petersburg. The dissolution of Ba from witherite as the primary source was derived from the analysis of the aqueous solution equilibrium with Ba-related minerals. It is reflected in the chemical composition of groundwater and influenced by the galenite–calcite–fluorite polymetallic mineralization in Vendian sandstones. The dissolution and re-deposition of carbonates and baryte are confirmed by mineral saturation states for an aqueous solution and distribution of other species in the groundwater of the Cambrian–Vendian aquifer system in North Estonia.

  18. Structure and activity of tellurium-cerium oxide acrylonitrile catalysts

    International Nuclear Information System (INIS)

    Bart, J.C.J.; Giordano, N.

    1982-01-01

    Ammoxidation of propylene to acrylonitrile (ACN) was investigated over various silica-supported (Te,Ce)O catalysts at 360 and 440 0 C. The binary oxide system used consists of a single nonstoichiometric fluorite-type phase α-(Ce,Te)O 2 up to about 80 mole% TeO 2 and a tellurium-saturated solid solution β-(Ce,Te)O 2 at higher tellurium concentrations. The ACN yield varies almost linearly with the tellurium content of (Ce,Te)O 2 . The β-(Ce,Te)O 2 phase is the most active component of the system (propylene conversion and ACN selectivity at 440 C of 76.7 and 74%, respectively) and is slightly more selective to ACN than α-Te0 2 . Tellurium reduces the overoxidation properties of cerium and selective oxidation occurs through Te(IV)-bonded oxygen

  19. Structural, Mechanical and Thermodynamic Properties under Pressure Effect of Rubidium Telluride: First Principle Calculations

    Directory of Open Access Journals (Sweden)

    Bidai K.

    2017-06-01

    Full Text Available First-principles density functional theory calculations have been performed to investigate the structural, elastic and thermodynamic properties of rubidium telluride in cubic anti-fluorite (anti-CaF2-type structure. The calculated ground-state properties of Rb2Te compound such as equilibrium lattice parameter and bulk moduli are investigated by generalized gradient approximation (GGA-PBE that are based on the optimization of total energy. The elastic constants, Young’s and shear modulus, Poisson ratio, have also been calculated. Our results are in reasonable agreement with the available theoretical and experimental data. The pressure dependence of elastic constant and thermodynamic quantities under high pressure are also calculated and discussed.

  20. M3FT-15OR0202212: SUBMIT SUMMARY REPORT ON THERMODYNAMIC EXPERIMENT AND MODELING

    Energy Technology Data Exchange (ETDEWEB)

    McMurray, Jake W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Brese, Robert G. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Silva, Chinthaka M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Besmann, Theodore M. [Univ. of South Carolina, Columbia, SC (United States)

    2015-09-01

    Modeling the behavior of nuclear fuel with a physics-based approach uses thermodynamics for key inputs such as chemical potentials and thermal properties for phase transformation, microstructure evolution, and continuum transport simulations. Many of the lanthanide (Ln) elements and Y are high-yield fission products. The U-Y-O and U-Ln-O ternaries are therefore key subsystems of multi-component high-burnup fuel. These elements dissolve in the dominant urania fluorite phase affecting many of its properties. This work reports on an effort to assess the thermodynamics of the U-Pr-O and U-Y-O systems using the CALPHAD (CALculation of PHase Diagrams) method. The models developed within this framework are capable of being combined and extended to include additional actinides and fission products allowing calculation of the phase equilibria, thermochemical and material properties of multicomponent fuel with burnup.

  1. Mineralogy of Non-Silicified Fossil Wood

    Directory of Open Access Journals (Sweden)

    George E. Mustoe

    2018-03-01

    Full Text Available The best-known and most-studied petrified wood specimens are those that are mineralized with polymorphs of silica: opal-A, opal-C, chalcedony, and quartz. Less familiar are fossil woods preserved with non-silica minerals. This report reviews discoveries of woods mineralized with calcium carbonate, calcium phosphate, various iron and copper minerals, manganese oxide, fluorite, barite, natrolite, and smectite clay. Regardless of composition, the processes of mineralization involve the same factors: availability of dissolved elements, pH, Eh, and burial temperature. Permeability of the wood and anatomical features also plays important roles in determining mineralization. When precipitation occurs in several episodes, fossil wood may have complex mineralogy.

  2. Occurrence model for volcanogenic beryllium deposits: Chapter F in Mineral deposit models for resource assessment

    Science.gov (United States)

    Foley, Nora K.; Hofstra, Albert H.; Lindsey, David A.; Seal, Robert R.; Jaskula, Brian W.; Piatak, Nadine M.

    2012-01-01

    Current global and domestic mineral resources of beryllium (Be) for industrial uses are dominated by ores produced from deposits of the volcanogenic Be type. Beryllium deposits of this type can form where hydrothermal fluids interact with fluorine and lithophile-element (uranium, thorium, rubidium, lithium, beryllium, cesium, tantalum, rare earth elements, and tin) enriched volcanic rocks that contain a highly reactive lithic component, such as carbonate clasts. Volcanic and hypabyssal high-silica biotite-bearing topaz rhyolite constitutes the most well-recognized igneous suite associated with such Be deposits. The exemplar setting is an extensional tectonic environment, such as that characterized by the Basin and Range Province, where younger topaz-bearing igneous rock sequences overlie older dolomite, quartzite, shale, and limestone sequences. Mined deposits and related mineralized rocks at Spor Mountain, Utah, make up a unique economic deposit of volcanogenic Be having extensive production and proven and probable reserves. Proven reserves in Utah, as reported by the U.S. Geological Survey National Mineral Information Center, total about 15,900 tons of Be that are present in the mineral bertrandite (Be4Si2O7(OH)2). At the type locality for volcanogenic Be, Spor Mountain, the tuffaceous breccias and stratified tuffs that host the Be ore formed as a result of explosive volcanism that brought carbonate and other lithic fragments to the surface through vent structures that cut the underlying dolomitic Paleozoic sedimentary rock sequences. The tuffaceous sediments and lithic clasts are thought to make up phreatomagmatic base surge deposits. Hydrothermal fluids leached Be from volcanic glass in the tuff and redeposited the Be as bertrandite upon reaction of the hydrothermal fluid with carbonate clasts in lithic-rich sections of tuff. The localization of the deposits in tuff above fluorite-mineralized faults in carbonate rocks, together with isotopic evidence for the

  3. Strontium isotope evolution of pore water and calcite in the Topopah Spring Tuff, Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    Marshall, Brian D.; Futa, Kiyoto

    2001-01-01

    Pore water in the Topopah Spring Tuff has a narrow range of (delta) 87 Sr values that can be calculated from the (delta) 87 Sr values of the rock considering advection through and reaction with the overlying nonwelded tuffs of the PTn. This model can be extended to estimate the variation of (delta) 87 Sr in the pore water through time; this approximates the variation of (delta) 87 Sr measured in calcite fracture coatings. In samples of calcite where no silica can be dated by other methods, strontium isotope data may be the only method to determine ages. In addition, other Sr-bearing minerals in the calcite and opal coatings, such as fluorite, may be dated using the same model

  4. The XPS study of the structure of uranium-containing ceramics

    Directory of Open Access Journals (Sweden)

    Teterin Anton Yu.

    2010-01-01

    Full Text Available The samples of the (Ca0.5GdU0.5Zr2O7 and (Ca0.5GdU0.5(ZrTiO7 ceramics with the fluorite and pyrochlore structures used as matrixes for the long-lived high-level radioactive waste disposal were studied with the X-ray photoelectron spectroscopy method. On the basis of the X-ray photoelectron spectroscopy parameters of the outer and core electrons from the binding energy range of 0-1250 eV the oxidation states of the included metal ions were determined, the quantitative elemental and ionic analysis was done, and the orderliness (monophaseness was evaluated. The obtained data agree with the X-ray diffraction and the scanning electron microscopy results.

  5. Fluorescent minerals - A potential source of UV protection and visible light for the growth of green algae and cyanobacteria in extreme cosmic environments

    Science.gov (United States)

    Omairi, Tareq; Wainwright, Milton

    2015-07-01

    We propose that green algae (Chlorella variabilis and Dunaliella tertiolecta) and cyanobacteria (Synechococcus elongatus and Nostoc commune) can grow inside fluorescent rock minerals which convert damaging UV light to visible light, thereby allowing these organisms to survive and thrive in UV-rich environments without (or with limited) visible light, which would otherwise be inimical to them. The four microorganisms were incubated inside fluorescent rocks composed of fluorite, calcite and pyrite. The resultant growth was then measured following exposure to UV radiation, with the use of optical density and measurement of chlorophyll concentration. Results show that the microorganisms were shielded from harmful UV in these semi-transparent rocks, while at the same time benefiting from the fact that the minerals converted UV to visible light; this have been shown by a statistically significant increase in their growth, which although lower than when the cells were incubated in sunlight, was significantly higher than in controls incubated in the dark.

  6. Studies on powder processing and sintering behaviour of ZrO2-9.0 mol% Y2O3 ceramics

    International Nuclear Information System (INIS)

    Ghosh, A.; Gonal, M.R.; Upadhyaya, D.D.; Ram Prasad

    1998-01-01

    In the present investigation the synthesis and densification behaviour of ZrO 2 -9.0 mol% Y 2 O 3 ceramics has been described. Powder preparation was based on the co-precipitation method. It was found that variation in the precipitation conditions and washing steps of the precipitated gels resulted in powder of different agglomerate sizes. The effect of different precipitations and washing conditions on the crystallite size of the 600 deg C calcined powders were examined by x-ray diffraction. The powders produced were essentially of the cubic fluorite phase. The ball-milled powders were analyzed for particle size distribution. Densification behaviour of the bodies made by slip casting has also been studied. (author)

  7. The mechanical properties and hydration characteristics of cement pastes containing added-calcium coal gangue

    Energy Technology Data Exchange (ETDEWEB)

    Dongxu Li; Xuyan Song [Nanjing University of Technology, Nanjing (China). College of Material Science and Engineering

    2008-04-15

    The mechanical properties of several kinds of coal gangue calcined with limestone were researched so as to find the optimum way of calcinations with limestone. The microstructure and property of hydration process of cement pastes containing added-calcium coal gangue were analyzed by means of scanning electron microscope (SEM) and the method of mercury in trusion poremeasurement. When the proper amounst of gypsum and fluorite were taken as mineralizers in the course of calcinations of added-calcium coal gangue, the activity of coal gangue can be effectively improved. The results of mechanical property and structural characteristics such as hydration, hydration products and microstructure etc. of cement pastes containing added-calcium coal gangue are consistent.

  8. Groundwater fluoride contamination: A reappraisal

    Directory of Open Access Journals (Sweden)

    Amlan Banerjee

    2015-03-01

    Full Text Available Dissolution of fluorite (CaF2 and/or fluorapatite (FAP [Ca5(PO43F], pulled by calcite precipitation, is thought to be the dominant mechanism responsible for groundwater fluoride (F− contamination. Here, one dimensional reactive–transport models are developed to test this mechanism using the published dissolution and precipitation rate kinetics for the mineral pair FAP and calcite. Simulation results correctly show positive correlation between the aqueous concentrations of F− and CO32− and negative correlation between F− and Ca2+. Results also show that precipitation of calcite, contrary to the present understanding, slows down the FAP dissolution by 106 orders of magnitude compared to the FAP dissolution by hydrolysis. For appreciable amount of fluoride contamination rock–water interaction time must be long and of order 106 years.

  9. Structural Characteristics of Bimetallic Catalysts Supported on Nano-Ceria

    Directory of Open Access Journals (Sweden)

    J. F. Bozeman

    2011-01-01

    Full Text Available Cu-Pt bimetal catalysts supported on nanocrystalline CeO2 (nano-ceria are synthesized via the low-cost sol-gel approach followed by impregnation processing. The average particle size of the catalytic composites is 63 nm. Ceria nanopowders sequentially impregnated in copper solution and then in Pt solution transformed into Pt-skin-structured Cu-Pt/ceria nanocomposite, based on the surface elemental and bulk compositional analyses. The ceria supporter has a fluorite structure, but the structure of Cu and Pt catalytic contents, not detected by X-ray diffraction spectroscopy due to the low loading level, is yet conclusive. The bimetallic catalytic nanocomposites may potentially serve as sulfur-tolerant anode in solid oxide fuel cells.

  10. Minerals from Macedonia: XV. Sivec mineral assemble

    International Nuclear Information System (INIS)

    Boev, Blazho; Jovanovski, Gligor; Makreski, Petre; Bermanec, Vladimir

    2005-01-01

    The paper presents investigations carried out on the collected minerals from the Sivec deposit. It is situated in the vicinity of the town of Prilep, representing a rare occurrence of sugary white dolomite marbles. The application of suitable methods of exploitation of decorative-dimension stones makes possible to obtain large amounts of commercial blocks well known in the world. Despite the existence of dolomite marbles, a series of exotic minerals are typical in Sivec mineralization. Among them, the most significant are: calcite, fluorite, rutile, phlogopite, corundum, diaspore, almandine, kosmatite (clintonite or margarite), clinochlore, muscovite, quartz, pyrite, tourmaline and zoisite. An attempt to identify ten collected minerals using the FT IR spectroscopy is performed. The identification of the minerals was based on the comparison of the infrared spectra of our specimens with the corresponding literature data for the mineral species originating all over the world. The coloured pictures of all studied silicate minerals are presented as well. (Author)

  11. THERMODYNAMIC AND KINETIC PARAMETERS OF MIXTURES DESULFURIZING THE MADE WITH CaO, MgO, SiO2 AND CaF2

    Directory of Open Access Journals (Sweden)

    Felipe Nylo de Aguiar

    2012-09-01

    Full Text Available This paper presents an analysis of the kinetics and thermodynamics of marble residue mixtures utilisation on desulfurization of pig iron. The desulfurization was carried out using lime, marble residue, fluorite and pig iron. Different mixtures of these materials were added into a bath of pig iron at 1,450°C. Metal samples were collected via vacuum samplers at times of 5, 10, 15, 20 and 30 minutes, in order to check the variation of sulfur content. Based on the results of chemical analysis of the metal and the desulfurizer mixture, the sulfide capacity of mixtures, the sulfur partition coefficient and the sulfur mass transport coefficient values were calculated.The results show the technical feasibility of using marble waste as desulfurizer agent.

  12. A study of the disorder in heavily doped Ba1-xLaxF2+x by neutron scattering, ionic conductivity and specific heat measurements

    DEFF Research Database (Denmark)

    Andersen, Niels Hessel; Clausen, Kurt Nørgaard; Kjems, Jørgen

    1986-01-01

    The ionic disorder in single crystals of the fluorite-type solid solutions Ba1-xLaxF2+x (with x=0.209 and x=0.492) has been studied in the temperature range from room temperature to 800 degrees C by diffuse neutron scattering, ionic conductivity, and specific heat measurements. From the diffuse...... neutron scattering it was found that the disorder was dominated by 222 clusters, which at low temperatures (T>10-10s), in agreement with NMB results which suggest a jump frequency below 75 MHz. The temperatures at which the steepest slopes are found in the loss of correlations and in the conductivity...... coincide at approximately 650 degrees C. At this temperature no clear anomaly is observed in the specific heat. Based on these findings the authors propose a conduction mechanisms where F- ions are moving through the lattice by means of rearrangements of the 222 clusters....

  13. Evaluation of dilatometric techniques for studies of sintering kinetics

    International Nuclear Information System (INIS)

    El-Sayed Ali, M.; Toft Soerensen, O.

    1985-04-01

    The kinetics of the initial sintering stage of CeO 2 is evaluated by three different techniques: constant heating rate dilatometry, constant shrinkage rate dilatometry and a new technique recently introduced by the authors called Stepwise Isothermal Dilatometry (SID). Comparative measurements with these techniques showed that too high activation energies were obtained with the two first techniques, both of which can be termed as nonisothermal, whereas activation energies comparable to those reported for cation diffusion in other fluorite oxides were obtained with the latter technique. Of the three techniques SID is thus considered to be the most accurate for studies of the sintering kinetics. In contrast to the two nonisothermal techniques SID has the further advantage that both the controlling mechanism and its activation energy can be determined in a single experiment. From the SID-measurement it was concluded that the initial sintering stage of CeO 2 is controlled by grain-boundary diffusion. (author)

  14. Rapid, cool sintering of wet processed yttria-stabilized zirconia ceramic electrolyte thin films.

    Science.gov (United States)

    Park, Jun-Sik; Kim, Dug-Joong; Chung, Wan-Ho; Lim, Yonghyun; Kim, Hak-Sung; Kim, Young-Beom

    2017-09-29

    Here we report a photonic annealing process for yttria-stabilized zirconia films, which are one of the most well-known solid-state electrolytes for solid oxide fuel cells (SOFCs). Precursor films were coated using a wet-chemical method with a simple metal-organic precursor solution and directly annealed at standard pressure and temperature by two cycles of xenon flash lamp irradiation. The residual organics were almost completely decomposed in the first pre-annealing step, and the fluorite crystalline phases and good ionic conductivity were developed during the second annealing step. These films showed properties comparable to those of thermally annealed films. This process is much faster than conventional annealing processes (e.g. halogen furnaces); a few seconds compared to tens of hours, respectively. The significance of this work includes the treatment of solid-state electrolyte oxides for SOFCs and the demonstration of the feasibility of other oxide components for solid-state energy devices.

  15. SrWO4 at high pressures

    International Nuclear Information System (INIS)

    Grzechnik, A.; Crichton, W.A.; Hanfland, M.

    2005-01-01

    Room-temperature high-pressure behaviour of SrWO 4 scheelite (I4 1 /a, Z=4) has been studied to 20.7 GPa in a diamond anvil cell using synchrotron angle-dispersive X-ray powder diffraction. Above 10 GPa, it transforms to the fergusonite structure (I2/a, Z=4). Both scheelite and fergusonite types are ordered superstructures of fluorite (Fm anti 3m, Z=4). There is no significant volume collapse at the scheelite-fergusonite phase transition. However, the compression data including both phases of strontium tungstate cannot be fitted by a common Birch-Murnaghan equation of state. An onset of decomposition into component oxides occurs at about 15 GPa. The pressure-induced transformations are irreversible. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. SrWO{sub 4} at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Grzechnik, A. [Departamento de Fisica de la Materia Condensada, Universidad del Pais Vasco, Apdo. 644, Bilbao 48080 (Spain); European Synchrotron Radiation Facility, B.P. 220, 38043 Grenoble cedex (France); Crichton, W.A.; Hanfland, M. [European Synchrotron Radiation Facility, B.P. 220, 38043 Grenoble cedex (France)

    2005-11-01

    Room-temperature high-pressure behaviour of SrWO{sub 4} scheelite (I4{sub 1}/a, Z=4) has been studied to 20.7 GPa in a diamond anvil cell using synchrotron angle-dispersive X-ray powder diffraction. Above 10 GPa, it transforms to the fergusonite structure (I2/a, Z=4). Both scheelite and fergusonite types are ordered superstructures of fluorite (Fm anti 3m, Z=4). There is no significant volume collapse at the scheelite-fergusonite phase transition. However, the compression data including both phases of strontium tungstate cannot be fitted by a common Birch-Murnaghan equation of state. An onset of decomposition into component oxides occurs at about 15 GPa. The pressure-induced transformations are irreversible. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Solid state chemistry of rare earth oxides. Final report, September 1, 1950--July 31, 1977

    International Nuclear Information System (INIS)

    Eyring, L.

    1977-07-01

    Work under Contract E(11-1)-1109 and its antecedents has been primarily for the purpose of obtaining detailed thermodynamic, kinetic and structural information on the complex rare earth oxides of praseodymium and terbium. These systems exhibit homologous series of ordered phases, order-disorder transformations, wide-range nonstoichiometric phases, chemical hysteresis in two-phase regions and many other solid state reaction phenomena. Fluorite-related materials of importance to ERDA occur as nuclear fuels, radiation power sources, insulators and solid electrolytes. The rare earth oxides serve directly as model systems for such similar materials and, in a more general sense, they serve as models of solids in general since they exhibit nearly the full range of solid state properties

  18. Transmutation of americium and curium incorporated in zirconia-based host materials

    International Nuclear Information System (INIS)

    Raison, P.E.

    2001-01-01

    Presented are studies involving the incorporation of americium and curium in zirconia-based materials. First explored was the pseudo ternary system AmO 2 -ZrO 2 -Y 2 O 3 . It was determined that selected Y-CSZ materials can incorporate significant quantities of americium oxide and remain cubic single-phase. The cell parameters of these fluorite-type products were established to be linear with the AmO 2 content. The Cm 2 O 3 -ZrO 2 system was also investigated. It was found that at 25 mol% of CmO 1.5 , the Cm(III) stabilized zirconia in its cubic form (a = 5.21 ±0.01 Angstrom). At higher and lower concentrations, diphasic materials were encountered. At 50 mol% of CmO 1.5 , a pyrochlore oxide - Cm 2 Zr 2 O 7 - is formed (a = 10.63 ±0.02 Angstrom). (author)

  19. Progress report - Physical and Environmental Sciences - Physics Division, 1996 January 1 to December 31

    International Nuclear Information System (INIS)

    Powell, B.M.

    1997-04-01

    This document is the last Progress Report for the Neutron and Condensed Matter Science Branch, at Chalk River Labs of Atomic Energy of Canada Limited. The materials science program continued to include measurements of stress as a major component, but the determination of phase diagrams for specific alloys was also a prominent activity. Studies were made of two types of unusual magnetic materials. The magnetic properties of several oxide pyrochlore were investigated and spin waves were measured in the magnetic semiconductor, chalcopyrite. The crystal structures of the deuterated anti fluorite were determined and the reorientation of the ammonium ion was refined in detail. Differential scanning calorimetry measurements were used to investigate whether spontaneous phase separation into chiral domains occurs for mixtures of DPPC of opposite chirality. A new Neutron Velocity Selector was commissioned

  20. Progress report - Physical and Environmental Sciences - Physics Division, 1996 January 1 to December 31

    Energy Technology Data Exchange (ETDEWEB)

    Powell, B.M. (ed.)

    1997-04-01

    This document is the last Progress Report for the Neutron and Condensed Matter Science Branch, at Chalk River Labs of Atomic Energy of Canada Limited. The materials science program continued to include measurements of stress as a major component, but the determination of phase diagrams for specific alloys was also a prominent activity. Studies were made of two types of unusual magnetic materials. The magnetic properties of several oxide pyrochlore were investigated and spin waves were measured in the magnetic semiconductor, chalcopyrite. The crystal structures of the deuterated anti fluorite were determined and the reorientation of the ammonium ion was refined in detail. Differential scanning calorimetry measurements were used to investigate whether spontaneous phase separation into chiral domains occurs for mixtures of DPPC of opposite chirality. A new Neutron Velocity Selector was commissioned.

  1. Phase composition of murataite ceramics for excess weapons plutonium immobilization

    International Nuclear Information System (INIS)

    Sobolev, I.A.; Stefanovsky, S.V.; Myasoedov, B.F.; Kullako, Y.M.; Yudintsev, S.V.

    2000-01-01

    Among the host phases for actinides immobilization, murataite (cubic, space group Fm3m) with the general formula A 4 B 2 C 7 O 22-x (A=Ca, Mn, Na, Ln, An; B=Mn, Ti, Zr, An IV ; C=Ti, Al, Fe; 0< x<1.5) is a promising matrix due to high isomorphic capacity and low leaching of actinides. One feature of murataite actinide zoning is an order-of-magnitude difference in concentration between the core and the rim. [1,2] Investigation of murataite ceramics in detail has shown occurrence of several murataite varieties with three-, five-, and eight-fold fluorite unit cells. [1-3] The goal of the present step of work is to study an effect of waste elements on phase composition of murataite ceramic and isomorphic capacity of waste elements

  2. Synthesis and characterization of Ce{sub 1-x}SmXO{sub 2-(x/2)} as solid electrolyte for application in IT-SOFCs; Sintese e caracterizacao de Ce{sub 1-x}SmXO{sub 2-(x/2)} como eletrolito solido para aplicacao em IT-SOFCs

    Energy Technology Data Exchange (ETDEWEB)

    Nicodemo, J.P.; Martinelli, A.E.; Nascimento, R.M. [Universidade Federal do Rio Grande do Norte (DECM/UFRN), Natal, RN (Brazil). Dept. de Engenharia de Materiais], e-mail: juli_pivotto@yahoo.com.br; Melo, D.M.A. [Universidade Federal do Rio Grande do Norte (DQ/UFRN), Natal, RN (Brazil). Dept. de Quimica; Cela, B. [Universidade Federal do Rio Grande do Norte (PPGCEM/UFRN), Natal, RN (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais; Macedo, D.A. [Universidade Federal do Rio Grande do Norte (PPGEM/UFRN), Natal, RN (Brazil). Programa de Pos-Graduacao em Engenharia Mecanica

    2008-07-01

    Mixed rare earth doped CeO{sub 2} oxide-based have been extensively studied for use in solid electrolytes for fuel cells. Ceramics-based CeO{sub 2} have high ionic conductivity and enable the operation of solid oxide fuel cells (SOFCs) in intermediate temperatures, in the range of 500 to 750 deg C. In this work, was investigated the Sm{sub 2}O{sub 3} doped CeO{sub 2} by Pechini method to obtain Ce{sub 0,9}Sm{sub 0,1}O{sub 1,95}. The resulting powders were characterized by the chemical composition (EDS) and crystallographic (XRD), thermal analysis (TG/ATD and DTG), and particles morphology (SEM). After calcinations of 500 and 700 deg C for 2 hours were obtained nanosized powders with crystalline structure of cubic phase type fluorite fully formed. (author)

  3. Grain-boundary oxidation of used CANDU fuel exposed to dry air at 150 degrees C for a prolonged period

    International Nuclear Information System (INIS)

    Hocking, W.H.; Behnke, R.; Duclos, A.M.

    1995-01-01

    The grain-boundary chemistry of used CANDU fuel exposed to dry air at 150 degrees C for a prolonged period has been investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). High degrees of surface oxidation have been determined using the chemical-shift effects for the uranium photoelectron emission, but these must be largely restricted to thin films. The observed distribution of segregated fission products implies an absence of major fuel restructuring and SEM examinations revealed mainly subtle changes in the UO 2 grain structure. These findings are consistent with metallographic evidence of pervasive grain-boundary attack, despite only slight bulk alteration of the fluorite-lattice structure. (author)

  4. {sup 4}He channelling studies of U{sub 4}O{sub 9}

    Energy Technology Data Exchange (ETDEWEB)

    Garrido, Frederico [Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, CNRS-IN2P3-Universite Paris-Sud, Batiments 104-108, 91405 Orsay (France)]. E-mail: garrido@csnsm.in2p3.fr; Nowicki, Lech [The Andrzej Soltan Institute for Nuclear Studies, Hoza 69, 00-681 Warsaw (Poland); Stonert, Anna [Andrzej Soltan Institute for Nuclear Studies, Hoza 69, 00-681 Warsaw (Poland); Pietraszko, Adam [Institute for Low Temperature and Structural Research, Polish Academy of Science, 50-422 Wroclaw (Poland); Wendler, Elke [Institut fuer Festkoerperphysik, Friedrich-Schiller Universitaet Jena, 07743 Jena (Germany)

    2006-08-15

    UO{sub 2} and U{sub 4}O{sub 9} single crystals were investigated by means of the {sup 4}He backscattering/channelling technique and the use of the 3032-keV elastic scattering resonance on {sup 16}O. Angular scans obtained for U{sub 4}O{sub 9} were interpreted in the framework of a recently published U{sub 4}O{sub 9} model. It was shown that the U{sub 4}O{sub 9} channelling data can be explained by the aggregation of some O atoms in cuboctahedral clusters, and the displacement of other (U and O) atoms from the UO{sub 2}-type sites. Basing on the combined use of the channelling technique and Monte Carlo simulations we suggest that the displacements of U atoms from their fluorite sites are larger than those determined by the neutron diffraction analysis.

  5. High ionic conductivity in confined bismuth oxide-based heterostructures

    Directory of Open Access Journals (Sweden)

    Simone Sanna

    2016-12-01

    Full Text Available Bismuth trioxide in the cubic fluorite phase (δ-Bi2O3 exhibits the highest oxygen ionic conductivity. In this study, we were able to stabilize the pure δ-Bi2O3 at low temperature with no addition of stabilizer but only by engineering the interface, using highly coherent heterostructures made of alternative layers of δ-Bi2O3 and Yttria Stabilized Zirconia (YSZ, deposited by pulsed laser deposition. The resulting [δ-Bi2O3/YSZ] heterostructures are found to be stable over a wide temperature range (500-750 °C and exhibits stable high ionic conductivity over a long time comparable to the value of the pure δ-Bi2O3, which is approximately two orders of magnitude higher than the conductivity of YSZ bulk.

  6. Geochemical interpretation of groundwaters from Finnsjoen, Sweden

    International Nuclear Information System (INIS)

    Puigdomenech, I.

    1987-01-01

    Computer calculations with aqueous speciation models (WATEQ3 and EQ3NR) give a picture of the water-rock interactions. The mineral saturation indices of calcite, strontianite, rhodochrosite, and siderite show that the concentration levels of Ca 2+ , Sr 2+ , Mn 2+ and Fe 2+ are probably fixed by the aqueous carbonate system and its minerals. However, unreasonably high saturation indices of calcite (up to + 1.7) confirm the uncertainties in the pH-values. Computer simulations with the EQ6 code show that CO 2 (g) outgassing/ingassing might have contributed errors in the pH measurements during the sampling procedure. EQ6 simulations also show that mixing of waters from different aquifers might have induced transient over- or undersaturation of carbonate minerals. Equilibrium between groundwaters and fluorite and barite appear to fix the concentrations of F - and Ba 2+ respectively. (orig./DG)

  7. Development of optical apparatus with remote analysis in nuclear industry

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sung Ho; Cha, Byung Heon; Ko, Do Kyeong; Cha, Hyeong Ky

    1999-12-01

    Optical apparatus with remote analysis was developed. It is composed with Dye laser, optical fiber and optical transmitter, and optical corrector. Laser light is arming in untested sample, and there is back scattered fluorescence. Material is identified by detecting and analysis of this fluorescence. Liquid and solid dye laser was carry out. The maximum efficiency was up to 34 percent. and the divergency and bandwidth of laser light are 2 mrad and 4.2 GHz, respectively. A dye laser with two wavelength was also carry out. 3 inch optical transmitter with fluorite lens was developed and the spatial resolution was less than 2 arc sec. And large optical corrector with 6 inch was developed and that mirror was coated by enhanced aluminum. Thus the efficiency was up to 92 percent. (author)

  8. Investigation of nozzle shape effect on Sm0.1Ce0.9O1.95 thin film prepared by electrostatic spray deposition

    International Nuclear Information System (INIS)

    Ksapabutr, Bussarin; Panapoy, Manop; Choncharoen, Kittikhun; Wongkasemjit, Sujitra; Traversa, Enrico

    2008-01-01

    Dense samarium doped ceria (SDC) thin films are deposited using electrostatic spray deposition (ESD) technique. The influences of nozzle shape on the distribution of liquid jet at the nozzle tip and the morphology of the deposited SDC films are elucidated. Geometries of three nozzles employed are flat, sawtooth and wedge tips. From the observation of jet formation, the nozzle in flat shape gives the highest distribution of emitted droplets. The deposited films are characterized using a combination of XRD, SEM and AFM techniques. XRD results reveal that the single-phase fluorite structure forms at a relatively low deposition temperature of 400 o C. The flat spray tip provides the most uniform and smooth thin films, and also presents the lowest agglomeration of particles on thin-film surface

  9. Neutron-diffraction study of the crystal structure of the superconductor TiSr2(Eu0.8Ce0.2)2Cu2Oz

    International Nuclear Information System (INIS)

    Ishigaki, T.; Ogasawara, Y.; Oikawa, K.; Hoshikawa, A.; Kamiyama, T.

    2004-01-01

    TiSr 2 (RE 1-x Ce x ) 2 Cu 2 O z superconductors (T c ∼20 K) have a 1222-structure with fluorite blocks. Neutron diffraction has been performed on the Eu-containing compound TiSr 2 (Eu 0.8 Ce 0.2 ) 2 Cu 2 O z , with natural Eu, and its crystal structure was refined. The neutron powder diffraction experiment was carried out on the VEGA diffractometer at KENS. The sample was contained in a thin flat cell of 0.5 mm thickness in order to reduce the large absorption effects of natural Eu. The absorption correction for the flat sample was taken into account in the Rietveld refinement. The results show that the O(1) atom in the Ti-layer is shifted from the 4c-site to the split site (8j), and that the concentration is deficient (g∼0.19)

  10. First-Principles Modeling of ThO2 Solid Solutions with Oxides of Trivalent Cations

    Science.gov (United States)

    Alexandrov, Vitaly; Asta, Mark; Gronbech-Jensen, Niels

    2010-03-01

    Solid solutions formed by doping ThO2 with oxides of trivalent cations, such as Y2O3 and La2O3, are suitable for solid electrolyte applications, similar to doped zirconia and ceria. ThO2 has also been gaining much attention as an alternative to UO2 in nuclear energy applications, the aforementioned trivalent cations being important fission products. In both cases the mixing energetics and short-range ordering/clustering are key to understanding structural and transport properties. Using first-principles atomistic calculations, we address intra- and intersublattice interactions for both cation and anion sublattices in ThO2-based fluorite-type solid solutions and compare the results with similar modeling studies for related trivalent-doped zirconia systems.

  11. Petrology, geochemistry and source characteristics of the Burpala alkaline massif, North Baikal

    Directory of Open Access Journals (Sweden)

    N.V. Vladykin

    2017-07-01

    Full Text Available The Burpala alkaline massif contains rocks with more than 50 minerals rich in Zr, Nb, Ti, Th, Be and rare earth elements (REE. The rocks vary in composition from shonkinite, melanocratic syenite, nepheline and alkali syenites to alaskite and alkali granite and contain up to 10% LILE and HSFE, 3.6% of REE and varying amounts of other trace elements (4% Zr, 0.5% Y, 0.5% Nb, 0.5% Th and 0.1% U. Geological and geochemical data suggest that all the rocks in the Burpala massif were derived from alkaline magma enriched in rare earth elements. The extreme products of magma fractionation are REE rich pegmatites, apatite–fluorite bearing rocks and carbonatites. The Sr and Nd isotope data suggest that the source of primary melt is enriched mantle (EM-II. We correlate the massif to mantle plume impact on the active margin of the Siberian continent.

  12. Preliminary study of the uranium favorability of the Jornada Del Muerto Basin and adjacent areas, South Central New Mexico

    International Nuclear Information System (INIS)

    Templain, C.J.; Dotterrer, F.E.

    1978-06-01

    Data indicate that possible uranium host rocks include the Precambrian rocks, the Ordovician Bat Cave Formation and Cable Canyon Sandstone, the Permian Abo Formation, Lower Cretaceous Dakota Sandstone, and the Upper Cretaceous-lower Tertiary McRae Formation. The Cenozoic sequence contains possible host beds; little is known, however, about its stratigraphy. Secondary uranium mineralization is found associated with faults in the Jornada area. All fault zones there are possible sites for uranium deposition. Possible sources for uranium in the Jornada del Muerto area include uraniferous Precambrian rocks, tuffaceous beds in the McRae Formation, and the Tertiary Datil and Thurman Formations. Hydrothermal solutions may have deposited the veinlike fluorite deposits, of which the purple varieties were found to be radioactive during this study

  13. Magmatism and mineralization ages from northeast area of La Sierra de San Luis, Argentina

    International Nuclear Information System (INIS)

    Ulacco, Jose H

    2001-01-01

    Three igneous rock groups, characterized as pre, sin and post-kinematics, have intruded the crystalline basement of Sierra de San Luis, Argentina. The ore deposits are associated with Devonian to Carboniferous epizonal granite stocks and batholiths in an area underlain by metamorphic rocks. This granitoids are characterized as post-kinematics magmatism. Model lead ages on the ore deposits (338,8 - 292,1 Ma) are strongly supported by K-Ar ages of the intrusives. The bulk of the north Sierra de San Luis ore deposits are genetically related to late Carboniferous granite plutons. The ore bodies are tungsten veins with greisen envelopes, lead veins, epithermal fluorite veins and REE and Th deposit. A generalized scheme of ore bodies related to granites is proposed. The ore deposits and their lithotectonic setting are characteristic of Gondwana metallogenetic Epoch in the Sierra de San Luis (au)

  14. Raman study of Ba-doped ceria nanopowders

    Directory of Open Access Journals (Sweden)

    Radović M.

    2007-01-01

    Full Text Available A series of Ce1-xBaxO2-y (5£x£0.20 nanometric powders were synthesized by selfpropagating room temperature synthesis. XRD and Raman scattering measurements were used to characterize the samples at room temperature. All the samples are solid solutions with fluorite type structure with an average crystallite size about 5 nm. The redshift and asymmetric broadening of the Raman F2g mode can be well explained with combined confinement and strain effects because of the nanocrystalline powders nature. The appearance of the additional peaks at ~ 560 cm-1 and ~ 600 cm-1, are attributed to extrinsic and intrinsic O2- vacancies in ceria lattice. Raman spectra of temperature treated Ce0.80Ba0.20O2-d sample revealed the instability of this system.

  15. Dislocation motion and high temperature plasticity of binary and ternary oxides

    International Nuclear Information System (INIS)

    Bretheau, T.; Castaing, J.; Rabier, J.; Veyssiere, P.

    1979-01-01

    Literature dealing with the plasticity of single crystal oxides deformed at elevated temperatures and the associated mobility of dislocations is reviewed. The experimental approach to the subject is examined critically by selecting oxides and deforming samples and by studying their specific mechanical behaviour, characterizing the deformation substructures and modelling the rate controlling processes. Since oxides with the simple rocksalt structure (Mg0, Ni0, Co0, Fe0,...) are not representative of all oxides, examples of other structures are also examined in detail, including Ti0 2 and Cu 2 0 oxides with fluorite (Zr0 2 , U0 2 ), with corundum (A1 2 0 3 ) and with spinel (MgA1 2 0 4 ternary) structures. Occasionally work on more exotic compounds like Y 2 0 3 or some with the garnet structure is included. (UK)

  16. Preparation of thin layer materials with macroporous microstructure for SOFC applications

    International Nuclear Information System (INIS)

    Marrero-Lopez, D.; Ruiz-Morales, J.C.; Pena-Martinez, J.; Canales-Vazquez, J.; Nunez, P.

    2008-01-01

    A facile and versatile method using polymethyl methacrylate (PMMA) microspheres as pore formers has been developed to prepare thin layer oxide materials with controlled macroporous microstructure. Several mixed oxides with fluorite and perovskite-type structures, i.e. doped zirconia, ceria, ferrites, manganites, and NiO-YSZ composites have been prepared and characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption and mercury porosimetry. The synthesised materials are nanocrystalline and present a homogeneous pore distribution and relatively high specific surface area, which makes them interesting for SOFC and catalysis applications in the intermediate temperature range. - Graphical abstract: Thin films materials of mixed oxides with potential application in SOFC devices have been prepared with macroporous microstructure using PMMA microspheres as pore formers. Display Omitted

  17. Characteristics of mesozoic magmatic rocks in western Zhejiang and their relation with uranium mineralization

    International Nuclear Information System (INIS)

    Zhou Jiazhi

    2000-01-01

    The author summarizes characteristics of Mesozoic (Yangshanian Period) acid-intermediate volcanics, sub-volcanics and basic intrusive from aspects of formation time of rock series, petrogenic sequence, chemical composition, rock -controlling factors and petrogenic environments. It is suggested that these rocks were originated from different source areas of crust and mantle. Based on the time-space relation between different types uranium deposits and magmatic rocks, the author proposes that: the earlier stage (Earlier Cretaceous) U-hematite ores were originated from acid volcanic magmatism of crustal source, but the later stage (Late Cretaceous) pitchblende-polymetallic sulfide and pitchblende-purple fluorite rich ores were derived from basic magmatism of mantle source. Finally, the author proposes prospecting criteria of the above two types of uranium deposits

  18. Synthesis and characterization of charge-substituted garnets YCaLnGa5O12 (Ln = Ce,Pr,Tb)

    International Nuclear Information System (INIS)

    Gramsch, S.A.

    1993-01-01

    A low temperature method is described for the preparation of the new garnet compounds YCaLnGa 5 O l2 (Ln=Ce, Pr, Th). In this set of compounds (Ca 2+ + Ln 4+ ) replaces 2 Y 3+ in the parent gallium based garnet Y 3 Ga 5 O l2 in order to stabilize as effectively as possible the Ln 4+ species in the eight-coordinate ''A'' site of the garnet structure. Characterization of the oxides by x-ray powder diffraction and thermogravimetric analysis is discussed with regard to the structural relationship of the substituted compound to the parent material. The tetravalent ions Pr 4+ and Tb 4+ exhibit increased thermal stability in reducing conditions as compared to the Ln 4+ states in the fluorite (LnO 2 ) and perovskite (BaLnO 3 ) type structures. This result is discussed with reference to the complex crystal chemistry of these systems

  19. Mineral potential for incompatible element deposits hosted in pegmatites, alkaline rocks, and carbonatites in the Islamic Republic of Mauritania (phase V, deliverable 87): Chapter Q in Second projet de renforcement institutionnel du secteur minier de la République Islamique de Mauritanie (PRISM-II)

    Science.gov (United States)

    Taylor, Cliff D.; Giles, Stuart A.

    2015-01-01

    Review of PRISM-I documents and the National inventory of mineral occurrences suggests that resources of U, Th, Nb, Ta, Be, rare earth elements (REEs) and fluorite are known in Mauritania and have been exploited in the past at the Bou Naga alkaline complex. Several different deposit types are indicated by the available data. Pegmatitic veins are recorded in several areas of the Archean and Paleoproterozoic portions of the Rgueïbat Shield and are prospective for resources of Li, Be, Nb, Ta, U, Th, and REEs. Over 150 beryl pegmatites are known in the Khnefissat and Inkebden areas of the Chami greenstone belt, and additional concentrations of pegmatites are known in the Guelb Nich Sud area of the Sebkhet Nich greenstone belt and in the northeastern part of the Amsaga Complex. Due to the small size of these deposits, they are unlikely to be economic unless additional value can be gained by processing contained minerals for their industrial uses.

  20. High ionic conductivity in confined bismuth oxide-based heterostructures

    DEFF Research Database (Denmark)

    Sanna, Simone; Esposito, Vincenzo; Christensen, Mogens

    2016-01-01

    Bismuth trioxide in the cubic fluorite phase (δ-Bi2O3) exhibits the highest oxygen ionic conductivity. In this study, we were able to stabilize the pure -Bi2O3 at low temperature with no addition of stabilizer but only by engineering the interface, using highly coherent heterostructures made...... of alternative layers of δ-Bi2O3 and Yttria Stabilized Zirconia (YSZ), deposited by pulsed laser deposition. The resulting [δ-Bi2O3=YSZ] heterostructures are found to be stable over a wide temperature range (500-750 °C) and exhibits stable high ionic conductivity over a long time comparable to the value...... of the pure δ-Bi2O3, which is approximately two orders of magnitude higher than the conductivity of YSZ bulk....

  1. Neutron diffraction and TSDC on Ba1−xUxF2+2x solid electrolytes

    DEFF Research Database (Denmark)

    Ouwerkerk, M.; Andersen, N. H.; Veldkamp, F. F.

    1986-01-01

    The defect structure of fluorite-type Ba1−xUxF2+2x solid solutions, which exhibit fast fluoride ion conductivity, has been investigated by quasi-elastic diffuse neutron scattering (QDNS) experiments, and thermally stimulated depolarisation current (TSDC) measurements. A comparison with model...... calculations reveals (212) clusters to dominate the defect structure. From 10 to 400K TSDS spectra reveal for x Conductivity parameters calculated from the latter relaxation compare very well with those...... obtained from a.c. ionic conductivity studies. The low-temperature relaxation at 29.5 K is ascribed to depolarisation steps of (212) clusters. Evidence for the relaxation of a minor amount of (UBaFi)x dipoles is found. A direct indication of the freedom of orientation of a (212) cluster is obtained from...

  2. Degradation effects in the one-band-tunneling Au/CaF{sub 2}/n-Si(111) MIS structures

    Energy Technology Data Exchange (ETDEWEB)

    Vexler, M.I.; Suturin, S.M.; Tyaginov, S.E.; Banshchikov, A.G. [A.F. Ioffe Physical-Technical Institute of the Russian Academy of Sciences, 26 Polytechnicheskaya Str., 194021 St.-Petersburg (Russian Federation); Sokolov, N.S. [A.F. Ioffe Physical-Technical Institute of the Russian Academy of Sciences, 26 Polytechnicheskaya Str., 194021 St.-Petersburg (Russian Federation)], E-mail: nsokolov@fl.ioffe.ru

    2008-10-01

    High quality Au/CaF{sub 2}/n-Si(111) metal-insulator-semiconductor structures with thin (< 2.5 nm) epitaxial fluorite layers were fabricated. Damage of such structures due to electrical overload has been investigated in this work. Current-voltage characteristics of these structures before and in process of degradation are measured. A mechanism explaining the pronounced breakdown at reverse bias is suggested. This mechanism relies on the potentially possible bistability arising from the one-band character of tunneling in the studied devices. Some comparisons with the degradation scenario in SiO{sub 2}-based samples are made. Wear-out fields for CaF{sub 2} films are estimated. The changes in behaviour of fresh and damaged structures under visible light irradiation are treated.

  3. Ionic/Electronic Conductivity, Thermal/Chemical Expansion and Oxygen Permeation in Pr and Gd Co-Doped Ceria PrxGd0.1Ce0.9-xO1.95-δ

    DEFF Research Database (Denmark)

    Cheng, Shiyang; Chatzichristodoulou, Christodoulos; Søgaard, Martin

    2017-01-01

    Pr. A series of compositions of PrxGd0.1Ce0.9-xO1.95-δ (x = 0, 0.02, 0.05, 0.08, 0.15, 0.25, 0.3 and 0.4) was prepared by solid state reaction. X-ray powder diffraction (XPD) indicates that Pr is completely dissolved in the fluorite structure up to 40 at.%. Pronounced nonlinear thermal expansion...... behavior was observed as a function of temperature, due to the simultaneous contributions of both thermal and chemical expansion. The electronic and ionic conductivities were measured as a function of temperature and oxygen partial pressure. Within the range from 10 to 15 at.% Pr, a drastic drop...

  4. First-principles study of dielectric properties of cerium oxide

    International Nuclear Information System (INIS)

    Yamamoto, Takenori; Momida, Hiroyoshi; Hamada, Tomoyuki; Uda, Tsuyoshi; Ohno, Takahisa

    2005-01-01

    We have theoretically investigated the dielectric properties of fluorite CeO 2 as well as hexagonal and cubic Ce 2 O 3 by using first-principles pseudopotentials techniques within the local density approximation. Calculated electronic and lattice dielectric constants of CeO 2 are in good agreement with previous theoretical and experimental results. For Ce 2 O 3 , the hexagonal phase has a lattice dielectric constant comparable to that of CeO 2 , whereas the cubic phase has a much smaller one. We have concluded that the enhancement of the dielectric constant in CeO 2 epitaxially grown on Si is not due to its lattice expansion experimentally observed nor regular formation of oxygen vacancies in CeO 2

  5. The complexity of the CaF2:Yb system: evidence that CaF2:Yb2+ is not an impurity trapped exciton system

    Science.gov (United States)

    Mackeen, Cameron; Bridges, Frank; Kozina, Michael; Mehta, Apurva; Reid, M. F.; Wells, J.-P. R.; BarandiaráN, Zoila

    Fluorite crystal structures doped with rare-earth elements exhibit an anomalous redshifted luminescence upon UV excitation, generally attributed to the relaxation of impurity trapped excitons (ITE). We find that the intensity of this luminescence decreases as the total concentration of Yb 2+ increases in unexposed samples, which is in conflict with the currently accepted ITE model. Further, using x-ray absorption spectroscopy and UV-vis studies of CaF2:Yb, we find a large (but reversible) Yb valence reduction upon x-ray exposure at 200 K - from mostly 3+ to 2+. This valence reduction is stable for long time periods at low T ITE model; the data appear more consistent with an intervalence charge transfer (IVCT) model. It is likely that many similar ITE systems have also been misidentified.

  6. Crystal structures of orthorhombic, hexagonal, and cubic compounds of the Sm(x)Yb(2−x)TiO5 series

    International Nuclear Information System (INIS)

    Aughterson, Robert D.; Lumpkin, Gregory R.; Reyes, Massey de los; Sharma, Neeraj; Ling, Christopher D.; Gault, Baptiste; Smith, Katherine L.; Avdeev, Maxim; Cairney, Julie M.

    2014-01-01

    A series of single phase compounds with nominal stoichiometry Sm (x) Yb (2−x) TiO 5 (x=2, 1.4, 1, 0.6, and 0) have been successfully fabricated to generate a range of crystal structures covering the most common polymorphs previously discovered in the Ln 2 TiO 5 series (Ln=lanthanides and yttrium). Four of the five samples have not been previously fabricated in bulk, single phase form so their crystal structures are refined and detailed using powder synchrotron and single crystal x-ray diffraction, neutron diffraction and transmission electron microscopy. Based on the phase information from diffraction data, there are four crystal structure types in this series; orthorhombic Pnma, hexagonal P6 3 /mmc, cubic (pyrochlore-like) Fd-3m and cubic (fluorite-like) Fm-3m. The cubic materials show modulated structures with variation between long and short range ordering and the variety of diffraction techniques were used to describe these complex crystal structure types. - Graphical abstract: A high resolution image of the compound Sm 0.6 Yb 1.4 TiO 5 showing contrast from lattice fringes and the corresponding fast Fourier transform (FFT) of the HREM image with pyrochlore related diffraction spots marked “P” and fluorite marked “F”. The crystal is oriented down the [1 1 0] zone axis based on the Fd-3m structure. The ideal crystal structure (no vacancies) of the cubic, pyrochlore-like (Sm 0.6 Yb 1.4 TiO 5 ). - Highlights: • First fabrication of bulk single-phase material with stoichiometry Sm 2 TiO 5 . • Systematic study of crystal structure types within Ln 2 TiO 5 series (Ln=lanthanides). • A novel technique using IFFT of HREM images to study cubic structures

  7. Hydrogen separation through tailored dual phase membranes with nominal composition BaCe0.8Eu0.2O3-δ:Ce0.8Y0.2O2-δ at intermediate temperatures

    Science.gov (United States)

    Ivanova, Mariya E.; Escolástico, Sonia; Balaguer, Maria; Palisaitis, Justinas; Sohn, Yoo Jung; Meulenberg, Wilhelm A.; Guillon, Olivier; Mayer, Joachim; Serra, Jose M.

    2016-11-01

    Hydrogen permeation membranes are a key element in improving the energy conversion efficiency and decreasing the greenhouse gas emissions from energy generation. The scientific community faces the challenge of identifying and optimizing stable and effective ceramic materials for H2 separation membranes at elevated temperature (400-800 °C) for industrial separations and intensified catalytic reactors. As such, composite materials with nominal composition BaCe0.8Eu0.2O3-δ:Ce0.8Y0.2O2-δ revealed unprecedented H2 permeation levels of 0.4 to 0.61 mL·min-1·cm-2 at 700 °C measured on 500 μm-thick-specimen. A detailed structural and phase study revealed single phase perovskite and fluorite starting materials synthesized via the conventional ceramic route. Strong tendency of Eu to migrate from the perovskite to the fluorite phase was observed at sintering temperature, leading to significant Eu depletion of the proton conducing BaCe0.8Eu0.2O3-δ phase. Composite microstructure was examined prior and after a variety of functional tests, including electrical conductivity, H2-permeation and stability in CO2 containing atmospheres at elevated temperatures, revealing stable material without morphological and structural changes, with segregation-free interfaces and no further diffusive effects between the constituting phases. In this context, dual phase material based on BaCe0.8Eu0.2O3-δ:Ce0.8Y0.2O2-δ represents a very promising candidate for H2 separating membrane in energy- and environmentally-related applications.

  8. Laboratory testing of glasses for Lockheed Idaho Technology Co. - fiscal year 1994 report

    International Nuclear Information System (INIS)

    Ellison, A.J.G.; Wolf, S.F.; Bates, J.K.

    1995-04-01

    The purpose of this project is to measure the intermediate and long-term durability of vitrified waste forms developed by Lockheed Idaho Technology Co. (LITCO) for the immobilization of calcined radioactive wastes at Idaho National Engineering Laboratory. Two vitreous materials referred to as Formula 127 and Formula 532, have been subjected to accelerated durability tests to measure their long-term performance. Formula 127 consists of a glass matrix containing 5-10 vol % fluorite (CaF 2 ) as a primary crystalline phase. It shows low releases of glass components to solution in 7-, 28-, 70-, and 140-day Product Consistency Tests performed at 2000 m -1 at 90 degrees C. In these tests, release rates for glass-forming components were similar to those found for durable waste glasses. The Ca and F released by the glass as it corrodes appear to reprecipitate as fluorite. Formula 532 consists of a glass matrix containing 5-10 vol % of an Al-Si-rich primary crystalline phase. The release rates for components other than aluminum are relatively low, but aluminum is released at a much higher rate than is typical for durable waste glasses. Secondary crystalline phases form relatively early during the corrosion of Formula 532 and appear to consist almost entirely of the Al-Si-rich primary phase (or a crystal with the same Al:Si ratio) and a sodium-bearing zeolite. Future test results are expected to highlight the relative importance of primary and secondary crystalline phases to the rate of corrosion of Formula 127 and Formula 532

  9. Hydrogeochemistry of co-occurring geogenic arsenic, fluoride and iodine in groundwater at Datong Basin, northern China

    Energy Technology Data Exchange (ETDEWEB)

    Pi, Kunfu; Wang, Yanxin, E-mail: yx.wang@cug.edu.cn; Xie, Xianjun, E-mail: xjxie@cug.edu.cn; Su, Chunli; Ma, Teng; Li, Junxia; Liu, Yaqing

    2015-12-30

    Highlights: • Co-mobilization of As, F and I was identified at Datong Basin. • Both As and I are released via reductive dissolution of Fe minerals. • Some amounts of As and I may be sequestered by FeS precipitates. • Intensive evaporation promotes retention of As but mobilization of F and I. - Abstract: Abnormal levels of co-occurring arsenic (As), fluorine (F) and iodine (I) in groundwater at Datong Basin, northern China are geochemically unique. Hydrochemical, {sup 18}O and {sup 2}H characteristics of groundwater were analyzed to elucidate their mobilization processes. Aqueous As, F and I ranged from 5.6 to 2680 μg/L, 0.40 to 3.32 mg/L and 10.1 to 186 μg/L, respectively. High As, F and I groundwater was characterized by moderately alkaline, high HCO{sub 3}{sup −}, Fe(II), HS{sup −} and DOC concentrations with H{sub 3}AsO{sub 3}, F{sup −} and I{sup −} as the dominant species. The plots of δ{sup 18}O values and Cl/Br ratios versus Cl{sup −} concentration demonstrate build-up of more oxidizing conditions and precipitation of carbonate minerals induced by vertical recharge and intensive evaporation facilitate As retention to Fe (hydr) oxides, but enhance F and I mobilization from host minerals. Under reducing conditions, As and I can be simultaneously released via reductive dissolution of Fe (hydr) oxides and reduction of As(V) and I(V) while F migration may be retarded due to effects of dissolution-precipitation equilibria between carbonate minerals and fluorite. With the prevalence of sulfate-reducing condition and lowering of HCO{sub 3}{sup −} concentration, As and I may be sequestered by Fe(II) sulfides and F is retained to fluorite and on clay mineral surfaces.

  10. Order-disorder phase transformations in quaternary pyrochlore oxide system: Investigated by X-ray diffraction, transmission electron microscopy and Raman spectroscopic techniques

    International Nuclear Information System (INIS)

    Radhakrishnan, A.N.; Prabhakar Rao, P.; Sibi, K.S.; Deepa, M.; Koshy, Peter

    2009-01-01

    Order-disorder transformations in a quaternary pyrochlore oxide system, Ca-Y-Zr-Ta-O, were studied by powder X-ray diffraction (XRD) method, transmission electron microscope (TEM) and FT-NIR Raman spectroscopic techniques. The solid solutions in different ratios, 4:1, 2:1, 1:1, 1:2, 1:4, 1:6, of CaTaO 3.5 and YZrO 3.5 were prepared by the conventional high temperature ceramic route. The XRD results and Rietveld analysis revealed that the crystal structure changed from an ordered pyrochlore structure to a disordered defect fluorite structure as the ratios of the solid solutions of CaTaO 3.5 and YZrO 3.5 were changed from 4:1 to 1:4. This structural transformation in the present system is attributed to the lowering of the average cation radius ratio, r A /r B as a result of progressive and simultaneous substitution of larger cation Ca 2+ for Y 3+ at A sites and smaller cation Ta 5+ for Zr 4+ at B sites. Raman spectroscopy and TEM analysis corroborated the XRD results. - Graphical abstract: Selected area electron diffraction (SAED) patterns showed highly ordered diffraction maxima with characteristic superlattice weak diffraction spots of the pyrochlore structure for (a) Ca 0.6 7Y 1.33 Zr 1.33 Ta 0.33 O 7 (C2YZT2) and bright diffraction maxima arranged in a ring pattern of the fluorite structure for (b) Ca 0.29 7Y 1.71 Zr 1.71 Ta 0.29 O 7 (CY6Z6T).

  11. The Bairendaba silver polymetallic deposit in Inner Mongolia, China: characteristics of ore-forming fluid and genetic type of ore deposit

    Science.gov (United States)

    Wang, Ying; Xie, Yuling; Wu, Haoran

    2018-02-01

    Bairendaba silver-polymetallic deposit is located in the middle south of the Xing Meng orogenic belt, and in the silver-polymetallic metallogenic belt on the west slope of the southern of Great Xing’an Range. Based on studying of the fluid inclusion, we discuss the characteristics of ore-forming fluid and the metallic genesis of the Bairendaba silver-polymetallic deposit. By means of the analysis of the fluid inclusions, homogenization temperature, salinity and composition were studied in quartz and fluorite. The result is as the follows: with homogenization temperatures of fluid inclusions in quartz veins being 196∼312 °C, the average 244.52 °C, and fluid salinity 2.90∼9.08 wt%NaCl; with homogenization temperatures of fluid inclusions in fluorite being 127∼306 °C, the average 196.92 °C, and fluid salinity 2.90∼9.34 wt% NaCl. The ore-forming fluid is mainly composed of water and the gas. The results of laser Raman analysis show that the gas phase is mainly CH4. It shows that the ore-forming fluid is characterized by medium-low temperature and low-salinity system. The temperature of ore-forming fluid is from high to low, and the salinity from high to low, and the meteoric water or metamorphic water is added during deposit. According to the geological characteristics of the mining area, it is considered that the genetic type of the ore deposit should be the fault-controlled and the medium-low temperature hydrothermal deposit related to magmatic hydrothermal activities.

  12. Chemistry of reference waters of the crystalline basement of Northern Switzerland for safety assessment studies

    International Nuclear Information System (INIS)

    Pearson, F.J. Jr.; Scholtis, A.

    1993-08-01

    The chemistry of groundwater in formations being considered as host rocks for nuclear waste repositories must be known to assess the performance of those repositories, and as media for laboratory experiments. Two potential repository siting areas in the crystalline basement of northern Switzerland are being assessed. This report gives the chemistry of water in both areas for reference use in this assessment. The western area is in the region defined by the Kaisten, Leuggern, Boettstein, and Zurzach boreholes. The western reference water is based on samples from the Leuggern, Boettstein, and Zurzach boreholes. Kaisten water is of higher salinity (1.3 g/l). The concentration ranges of the reference water include Kaisten values, however. High quality samples and analyses, particularly from long term sampling at Zurzach and Leuggern, define the concentration ranges of many trace elements. The definition of this water assumes saturation with respect to calcite, baryte, fluorites, chalcedony, and kaolinite. The reference pe is based on the assumption that dissolved iron concentrations are controlled by the solubility of the mineral goethite, and is consistent with other redox indicators such as the measured Pt-electrode potential and the ratio of dissolved As(V) to As(III). The eastern area is characterized by the Siblingen boreholes. The eastern reference water is a Na-HCO 3 -SO 4 -(Cl) type with a total dissolved solids content of about 0.5 g/l. Only three samples taken during borehole drilling are available to define this water, so it can be specified in less detail and with less precision than the western water. Its definition assumes saturation with respect to calcite, baryte, and fluorites. The samples permit only a broad definition of its oxidation potential and content of redox-sensitive metals such as Fe, As, Mn, and U. Trace element data for the most part are lacking. (author) figs., tabs., 28 refs

  13. Sr isotope geochemistry of East Alpine mineral deposits and mass spectrometric analyses of fluid inclusions

    International Nuclear Information System (INIS)

    Grum, W.

    1995-05-01

    Strontium isotope geochemistry and deformational history of selected carbonate-hosted deposits from different tectonic positions in the Eastern Alps were studied. In this context an equipment has been constructed to analyze the composition of volatile components of fluid inclusions (FI). Based on the results of Sr-isotopic investigations two groups of deposits are discriminated: Deposits formed by formation waters and/or metamorphogenic fluids: Tux (magnesite, scheelite), Otterzug (barite), Lassing (magnesite), Rabenwald (talc), Laussa and Mooseck (fluorite). The mineralizing fluids are derived from different sedimentary rock series and therefore 87 Sr/ 86 Sr-ratios vary between 0.707 and 0.719. Deposits situated along fault zones: Lassing (talc), Gasteiner Tal (Silberpfennig area; gold), Schlaining (stibnite) and Waldenstein (specularite). Sr isotope ratios of the mineralizing fluids from Lassing, Waldenstein and Schlaining ranges from 0.7112 to 0.7127 and are therefore thought to have scavenged the East Alpine crystalline. The mineralizing solutions of the Gasteiner Tal deposit may either have equilibrated with low radiogenic sedimentary or with (ultra-)basic rocks. A cracking chamber has been constructed in order to open FI by cracking for mass spectrometric analysis of volatile components. Gases are analysed using a quadrupole mass spectrometer. The desorption of gas from metal and sample surfaces during cracking can be neglected. The amount of gas released from the mineral lattices was studied. With that fast method ore bearing from barren host rocks have been distinguished by different composition of the FI at the Brixlegg barite mineralization (Eastern Alps). Within the Galway fluorite deposit (Ireland) different fluids were involved and mass spectrometric analysis were carried out to characterize these different fluids and to identify their origin. (author)

  14. SHRIMP U-Pb zircon dating of Pedras Grandes Suite, southern Santa Catarina State, Brazil

    Directory of Open Access Journals (Sweden)

    Andréa R. Jelinek

    2005-03-01

    Full Text Available Two major magmatic pulses of the granitic Florianópolis Batholith in Santa Catarina State, southern Brazil, occurred between 613±5Ma and 595±5 Ma, during the Neoproterozoic Brasiliano Cycle. These ages were obtained by U-Pb isotopic determinations with the sensitive high mass-resolution ion microprobe on igneous zircons from Pedras Grandes Suite in Santa Catarina State. Euhedral zircons remained unaltered close to a fluorite vein deposited at 180?C or more. These ages suggest a northern limit for the Pedras Grandes Suite, explaining the spatial relationship between the fluorite veins and the source rock.Dois dos principais pulsos da atividade granítica no Batólito Florianópolis em Santa Catarina ocorreram entre 613 ±5 Ma e 595 ±5 Ma, durante o Neoproterozóico do Ciclo Brasiliano. Estas idades foram obtidas a partir dedeterminações isotópicas U-Pb em cristais de zircão da Suite Pedras Grandes por "Sensitive high-resolution íon microprobe" - SHRIMP II. Os cristais de zircão permaneceram inalterados mesmo mediante condições hidrotermais com temperaturas iguais e, até mesmo, superiores a 180ºC. Estas idades sugerem a delimitação norte do Maciço Pedras Grandes, explicando a relação espacial existente entre os filões de fluorita e a rocha fonte destas mineralizações.

  15. Preparation of extractive resins for producing terbium-161

    International Nuclear Information System (INIS)

    De la Cruz B, C. C.; Monroy G, F.

    2009-10-01

    This paper presents the development of a methodology for extractive resins preparation to base of HDEHP, which allows to separation of Tb from Gd generating an own technology of preparation of these resins. The study included the extractive resins preparation from 6 different supports: kieselguhr Dg, alumina, red volcanic rock, chiluca, quarry and fluorite; two treatment types of of supports and varied concentrations of HDEHP extractant (di(2-etil hexyl) orthophosphoric acid), in order to determine which resin has improved efficiency of Gd and Tb separation, and radionuclide purity of 161 Tb. Resins were prepared to base of kieselguhr to determine the most appropriate silicon deposition process. Two silicon deposition treatments were realized: treatment I , by contact with silicon deposition solution (dimethyldichlorosilane / heptane 1:30) and treatment II by contact with vapors of dimethyldichlorosilane in vacuum. The extractant retention was carried out to different concentrations of HDEHP / acetone: 1:4, 1:8, 1:15, 1:20, 1:30 and 1:40. According to the results, there is not direct relation of HDEHP concentration used in extractive resins preparation to base of kieselguhr over the efficiency of Gd and Tb separation and of radionuclide purity of 161 Tb. The effect of support in the efficiency of Gd and Tb separation was studied to prepare resins with the supports kieselguhr, alumina, quarry, chiluca, volcanic rock and fluorite, using the silicon deposition treatment II for the supports and a concentration of HDEHP / acetone 1:20, for extractant retention. Only resins based on kieselguhr could separate to Gd from Tb quantitatively, the resin at a concentration of HDEHP / Acetone 1:20 was the best results obtained in Gd and Tb separation, achieving a separation efficiency greater than 90% and a radionuclide purity higher than 99%. (Author)

  16. The interfacial orientation relationship of oxide nanoparticles in a hafnium-containing oxide dispersion-strengthened austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Yinbin, E-mail: miao2@illinois.edu [Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Mo, Kun [Nuclear Engineering Division, Argonne National Laboratory, Lemont, IL 60493 (United States); Cui, Bai [Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588 (United States); Department of Material Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Chen, Wei-Ying [Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Miller, Michael K.; Powers, Kathy A. [Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37830 (United States); McCreary, Virginia; Gross, David [Department of Material Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Almer, Jonathan [X-ray Science Division, Argonne National Laboratory, Lemont, IL 60493 (United States); Robertson, Ian M. [Department of Material Science and Engineering, University of Wisconsin-Madison, Madison, WA 53706 (United States); Department of Material Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Stubbins, James F. [Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States)

    2015-03-15

    This work reports comprehensive investigations on the orientation relationship of the oxide nanoparticles in a hafnium-containing austenitic oxide dispersion-strengthened 316 stainless steel. The phases of the oxide nanoparticles were determined by a combination of scanning transmission electron microscopy–electron dispersive X-ray spectroscopy, atom probe tomography and synchrotron X-ray diffraction to be complex Y–Ti–Hf–O compounds with similar crystal structures, including bixbyite Y{sub 2}O{sub 3}, fluorite Y{sub 2}O{sub 3}–HfO{sub 2} solid solution and pyrochlore (or fluorite) Y{sub 2}(Ti,Hf){sub 2−x}O{sub 7−x}. High resolution transmission electron microscopy was used to characterize the particle–matrix interfaces. Two different coherency relationships along with one axis-parallel relation between the oxide nanoparticles and the steel matrix were found. The size of the nanoparticles significantly influences the orientation relationship. The results provide insight into the relationship of these nanoparticles with the matrix, which has implications for interpreting material properties as well as responses to radiation. - Highlights: • The oxide nanoparticles in a hafnium-containing austenitic ODS were characterized. • The nanoparticles are Y–Hf–Ti–O enriched phases according to APT and STEM–EDS. • Two coherency and an axis-parallel orientation relationships were found by HR-TEM. • Particle size has a prominent effect on the orientation relationship (OR). • Formation mechanism of the oxide nanoparticles was discussed based on the ORs.

  17. Hydrogeochemistry of co-occurring geogenic arsenic, fluoride and iodine in groundwater at Datong Basin, northern China

    International Nuclear Information System (INIS)

    Pi, Kunfu; Wang, Yanxin; Xie, Xianjun; Su, Chunli; Ma, Teng; Li, Junxia; Liu, Yaqing

    2015-01-01

    Highlights: • Co-mobilization of As, F and I was identified at Datong Basin. • Both As and I are released via reductive dissolution of Fe minerals. • Some amounts of As and I may be sequestered by FeS precipitates. • Intensive evaporation promotes retention of As but mobilization of F and I. - Abstract: Abnormal levels of co-occurring arsenic (As), fluorine (F) and iodine (I) in groundwater at Datong Basin, northern China are geochemically unique. Hydrochemical, "1"8O and "2H characteristics of groundwater were analyzed to elucidate their mobilization processes. Aqueous As, F and I ranged from 5.6 to 2680 μg/L, 0.40 to 3.32 mg/L and 10.1 to 186 μg/L, respectively. High As, F and I groundwater was characterized by moderately alkaline, high HCO_3"−, Fe(II), HS"− and DOC concentrations with H_3AsO_3, F"− and I"− as the dominant species. The plots of δ"1"8O values and Cl/Br ratios versus Cl"− concentration demonstrate build-up of more oxidizing conditions and precipitation of carbonate minerals induced by vertical recharge and intensive evaporation facilitate As retention to Fe (hydr) oxides, but enhance F and I mobilization from host minerals. Under reducing conditions, As and I can be simultaneously released via reductive dissolution of Fe (hydr) oxides and reduction of As(V) and I(V) while F migration may be retarded due to effects of dissolution-precipitation equilibria between carbonate minerals and fluorite. With the prevalence of sulfate-reducing condition and lowering of HCO_3"− concentration, As and I may be sequestered by Fe(II) sulfides and F is retained to fluorite and on clay mineral surfaces.

  18. Fluorine geochemistry in bedrock groundwater of South Korea

    International Nuclear Information System (INIS)

    Chae, Gi-Tak; Yun, Seong-Taek; Mayer, Bernhard; Kim, Kyoung-Ho; Kim, Seong-Yong; Kwon, Jang-Soon; Kim, Kangjoo; Koh, Yong-Kwon

    2007-01-01

    High fluoride concentrations (median = 4.4 mg/L) in deep bedrock groundwater of South Korea prevent the usage of it as a drinking water source. The hydrogeochemistry of deep thermal groundwaters (N = 377) in diverse bedrocks has been studied in order to evaluate the geologic and geochemical controls on fluoride concentrations in groundwater. The groundwater samples were clustered geologically, and the average and median concentrations of fluoride were compared by the Mann-Whitney U test. The order of median fluoride concentration with respect to geology is as follows: metamorphic rocks ≥ granitoids ≥ complex rock >> volcanic rocks ≥ sedimentary rocks. This result indicates that the geological source of fluoride in groundwater is related to the mineral composition of metamorphic rocks and granitoids. With respect to groundwater chemistry, the fluoride concentration was highest in Na-HCO 3 type groundwater and lowest in Ca-HCO 3 type groundwater. Ionic relationships also imply that the geochemical behavior of fluoride in groundwater is related to the geochemical process releasing Na and removing Ca ions. The thermodynamic relationship between the activities of Ca and F indicates that fluoride concentration is controlled by the equilibrium of fluorite (CaF 2 ). In other words, the upper limits of fluoride concentration are determined by the Ca ion; i.e., Ca concentrations play a crucial role in fluoride behavior in deep thermal groundwater. The result of this study suggests that the high fluoride in groundwater originates from geological sources and fluoride can be removed by fluorite precipitation when high Ca concentration is maintained. This provides a basis for a proper management plan to develop the deep thermal groundwater and for treatment of high fluoride groundwater frequently found in South Korea

  19. Effect of synthesis conditions on the nanopowder properties of Ce{sub 0.9}Zr{sub 0.1}O{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Zimicz, M.G.; Fabregas, I.O.; Lamas, D.G. [CINSO (Centro de Investigaciones en Solidos) CONICET-CITEFA J.B. de La Salle 4397, 1603 Villa Martelli, Pcia. de Buenos Aires (Argentina); Larrondo, S.A., E-mail: susana@di.fcen.uba.ar [Laboratorio de Procesos Cataliticos, Departamento de Ingenieria Quimica, Facultad de Ingenieria, Universidad de Buenos Aires, Pabellon de Industrias, Ciudad Universitaria, 1428 Buenos Aires (Argentina)

    2011-06-15

    Graphical abstract: . The synthesis of nanocrystalline Ce{sub 0.9}Zr{sub 0.1}O{sub 2} powders via the gel-combustion method, using different fuels, and following either stoichiometric or non-stoichiometric pH-controlled routes is investigated. Research highlights: {yields} All samples exhibited the fluorite-type crystal structure, nanometric average crystallite size and negligible carbon content. {yields} Synthesis conditions strongly affect the average crystallite size, the degree of agglomeration, the specific surface area and the pore volume. {yields} Our results indicate that, by controlling the synthesis conditions it is possible to obtain solids with custom-made morphological properties. -- Abstract: In this work, the synthesis of nanocrystalline Ce{sub 0.9}Zr{sub 0.1}O{sub 2} powders via the gel-combustion method, using different fuels, and following either stoichiometric or non-stoichiometric pH-controlled routes is investigated. The objective is to evaluate the effect of synthesis conditions on the textural and morphological properties, and the crystal structure of the synthesized materials. The solids were characterized by nitrogen physisorption, Scanning Electron Microscopy (SEM), X-ray powder diffraction (XPD), and Carbon-Hydrogen-Nitrogen Elemental Analysis (CHN). All the powders exhibited nanometric crystallite size, fluorite-type structure and negligible carbon content. Synthesis conditions strongly affect the average crystallite size, the degree of agglomeration, the specific surface area and the pore volume. Our results indicate that, by controlling the synthesis conditions it is possible to obtain solids with custom-made morphological properties.

  20. Inhibition of Neuroblastoma cancer cells viability by ferromagnetic Mn doped CeO{sub 2} monodisperse nanoparticles mediated through reactive oxygen species

    Energy Technology Data Exchange (ETDEWEB)

    Abbas, Fazal; Jan, Tariq [Laboratory of Nanoscience and Technology (LNT), Department of Physics, International Islamic University Islamabad (Pakistan); Iqbal, Javed, E-mail: javed.saggu@iiu.edu.pk [Laboratory of Nanoscience and Technology (LNT), Department of Physics, International Islamic University Islamabad (Pakistan); Haider Naqvi, M. Sajjad [Department of Biochemistry, University of Karachi, Karachi (Pakistan); Ahmad, Ishaq [Experimental Physics Labs, National Center for Physics, Islamabad (Pakistan)

    2016-04-15

    Here we report the Mn doping induced effects on structural, Raman, optical, magnetic and anticancer properties of CeO{sub 2} nanoparticles prepared via soft chemical route. Structural and microstructural results infer that the synthesized nanoparticles have single phase cubic fluorite structure of CeO{sub 2} and that Mn doping results in enhancement of the structural defects. Scanning electron microscopy results reveal the formation of monodisperse nanoparticles having average particle size ranging from 30 to 41 nm. The optical absorbance spectroscopy analysis discloses the band gap energy tailoring of CeO{sub 2} nanoparticles via Mn doping. Room temperature ferromagnetism (RTFM) has been found in both as-prepared and Mn doped CeO{sub 2} nanoparticles. This RTFM of the synthesized nanoparticles have been attributed to the Mn ions and surface defects such as oxygen vacancies. Finally, the influence of Mn dopant on the cell viability and reactive oxygen species (ROS) generation levels of CeO{sub 2} nanoparticles in the presence of healthy and cancerous cells have been studied. It has been observed that the differential cytotoxicity of the synthesized nanoparticles is strongly correlated with level of ROS generation. - Highlights: • Mn doped CeO{sub 2} nanoparticles with cubic fluorite structure were synthesized. • Mn dopant significantly tailored the band gap of CeO{sub 2} nanoparticles. • The synthesized nanoparticles exhibited room temperature ferromagnetic behavior. • The cytotoxicity of these nanoparticles was reported for the first time. • The synthesized nanoparticles exhibited differential cytotoxicity.

  1. Nd{sup 3+}-substituted (Zr{sub 1−x}Ce{sub x})O{sub 2} (0.0 ≤ x ≤ 1.0) system: Synthesis, structural and thermophysical investigations

    Energy Technology Data Exchange (ETDEWEB)

    Nandi, Chiranjit [Radiometallurgy Division, Bhabha Atomic Research Centre, HBNI, Mumbai 400085 (India); Grover, V., E-mail: Vinita@barc.gov.in [Chemistry Division, Bhabha Atomic Research Centre, HBNI, Mumbai 400085 (India); Sahu, M. [Radioanalytical Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Krishnan, K. [Fuel Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Guleria, A. [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Kaity, Santu; Prakash, Amrit [Radiometallurgy Division, Bhabha Atomic Research Centre, HBNI, Mumbai 400085 (India); Tyagi, A.K. [Chemistry Division, Bhabha Atomic Research Centre, HBNI, Mumbai 400085 (India)

    2016-10-15

    In order to mimic co-loading of Pu and Am in zirconia, Nd{sub 0.20}[Zr{sub 1−x}Ce{sub x}]{sub 0.80}O{sub 1.90} (0.0 ≤ x ≤ 1.0) system was synthesized and thoroughly characterized by X-ray diffraction (XRD) and Raman spectroscopy. The entire system was found to be single-phasic fluorite-type and most interesting result is stabilization of multi-phasic ceria-zirconia system in a single-phasic system by substituting Nd{sup 3+}. Raman spectroscopy revealed entirely different nature of defects prevalent in the solid solutions possessing F-type structure across the composition range. The heat capacity of representative compositions was measured by heat flux-type differential scanning calorimeter. Specific heat capacity of the solid solutions was found to increase with decreasing CeO{sub 2} content. Different thermodynamic functions such as enthalpy increment, entropy and Gibbs energy functions were determined using heat capacity values. The lattice thermal expansion (298–1273 K) behaviour of the few selected compositions revealed a gradual increase in thermal expansion coefficient with increasing CeO{sub 2} content. - Highlights: • Single-phasic fluorite-type solid solution obtained across the composition range. • Multi-phasic CeO{sub 2}-ZrO{sub 2} system converted into single-phasic by Nd{sup 3+} substitution. • Different local structures and defects in Ce-rich and Zr-rich regions. • Lattice thermal expansion coefficient increases with increasing CeO{sub 2} content. • Thermal expansion behaviour is a manifestation of decreasing melting point.

  2. REDUPP First Annual Report

    Energy Technology Data Exchange (ETDEWEB)

    Zetterstrom Evins, L. [Svensk Kaernbraenslehantering AB (SKB), Stockholm (Sweden); Vahanen, M. (eds.)

    2012-06-15

    The REDUPP project aims to investigate how surfaces of solids with a fluorite structure change with time during dissolution. Laboratory experiments are performed to monitor dissolution of CaF{sub 2}, CeO{sub 2}, ThO{sub 2} and UO{sub 2}, in connection with ab initio calculations. Another aspect of the project involves investigating if using natural groundwater in the leaching tests has an effect on the measured dissolution rate of UO{sub 2}. The preliminary results after one project year are documented here. Samples have been prepared as sintered pellets with similar microstructures as UO{sub 2}. For the UO{sub 2} study, pellets doped with U-233 are used. Preliminary dissolution data show the expected trends for pH and temperature dissolution kinetics dependence. Studies on CeO{sub 2} monolith samples indicate that there is a crystallographic control on leaching, and that the grain boundaries are preferentially attacked. Measurable Th concentrations are achieved in pre-tests for ThO{sub 2} dissolution where the effect of carbonate complexation is also observed. The preliminary results of the studies performed on U-233-doped UO{sub 2} samples in natural groundwater are in agreement with previous results, and show no observable effect of trace elements or level of alpha radiolysis. In the modelling work, the stabilities of surfaces corresponding to different crystal planes have been computed, and work is in progress to develop a model involving stepped surfaces. Preliminary results show that only a few energies of reference planes need to be computed, and all other surface energies can be accurately estimated from a linear relation. The goal is to develop a model of how the surfaces of fluorite-structures evolve during dissolution. (orig.)

  3. Distillation Separation of Hydrofluoric Acid and Nitric Acid from Acid Waste Using the Salt Effect on Vapor-Liquid Equilibrium

    Science.gov (United States)

    Yamamoto, Hideki; Sumoge, Iwao

    2011-03-01

    This study presents the distillation separation of hydrofluoric acid with use of the salt effect on the vapor-liquid equilibrium for acid aqueous solutions and acid mixtures. The vapor-liquid equilibrium of hydrofluoric acid + salt systems (fluorite, potassium nitrate, cesium nitrate) was measured using an apparatus made of perfluoro alkylvinylether. Cesium nitrate showed a salting-out effect on the vapor-liquid equilibrium of the hydrofluoric acid-water system. Fluorite and potassium nitrate showed a salting-in effect on the hydrofluoric acid-water system. Separation of hydrofluoric acid from an acid mixture containing nitric acid and hydrofluoric acid was tested by the simple distillation treatment using the salt effect of cesium nitrate (45 mass%). An acid mixture of nitric acid (5.0 mol · dm-3) and hydrofluoric acid (5.0 mol · dm-3) was prepared as a sample solution for distillation tests. The concentration of nitric acid in the first distillate decreased from 5.0 mol · dm-3 to 1.13 mol · dm-3, and the concentration of hydrofluoric acid increased to 5.41 mol · dm-3. This first distillate was further distilled without the addition of salt. The concentrations of hydrofluoric acid and nitric acid in the second distillate were 7.21 mol · dm-3 and 0.46 mol · dm-3, respectively. It was thus found that the salt effect on vapor-liquid equilibrium of acid mixtures was effective for the recycling of acids from acid mixture wastes.

  4. The role of pegmatites and acid fluids for REE/HFSE mobilization in the Strange Lake peralkaline granitic pluton, Canada

    Science.gov (United States)

    Gysi, A. P.; Williams-Jones, A.

    2012-12-01

    The Strange Lake pluton in Canada is a mid-Proterozoic peralkaline granitic intrusion that is host to a world-class rare earth element (REE), yttrium (Y) and high-field strength element (HFSE) deposit containing more than 50 Mt ore at >1.5 wt.% REE and >3 wt.% Zr. The highest REE/HFSE concentrations are found in pegmatite-rich zones characterized by intense alteration. Previous studies of Strange Lake and other peralkaline and alkaline intrusions, such as Khan Bogd (Mongolia) and Tamazeght (Morocco) plutons have shown that hydrothermal alteration may play an important role in the mobility of the REE/HFSE. However, the fluid chemistry and conditions of alteration (i.e., P, T, pH, fO2, ligand activity) in these systems still need to be constrained to evaluate the importance and scale of such hydrothermal mobilization. We present new data from the B-zone, a pegmatite-rich zone located in NW Strange Lake. The pegmatites are generally zoned and form two main types. The border-type pegmatites consist of quartz, K-feldspar and hematized aegirine, whereas volatile-rich pegmatites consist of hydrothermal quartz and fluorite. Transitions between both types were also observed, with the K-feldspar being partly altered and replaced by Al-Si-rich phyllosilicates. The heavy (H)REE and Zr were primarily concentrated in zirconosilicates such as elpidite, now pseudomorphed by zircon or gittinsite, whereas light (L)REE and Y were concentrated in REE-F-(CO2)-minerals such as fluocerite and bastnäsite. Textural and mineralogical observations indicate that these minerals are primary and were partly to completely leached upon fluid-rock interaction in the pegmatites. Secondary phases include Ca-F-Y-rich minerals, mainly hydrothermal fluorite, that fill vugs and replaced primary REEHFSE minerals. The presence of hydrothermal fluorite veins, micro-veins, vugs and micro-breccia in the most altered parts of the B-zone are interpreted to reflect interaction of the rocks with a F-rich fluid

  5. Jubilite: A 4-,8-connected Cubic Structural Pattern in Space Group Pm3

    Directory of Open Access Journals (Sweden)

    Eduardo A. Castro

    2005-05-01

    Full Text Available Abstract: In the course of investigating structural modifications of the 3-,4-connected net known as the Pt3O4 structure-type (waserite, a novel 4-,8-connected structure-type was discovered. This lattice is generated by replacing the 3-connected trigonal planar vertices of the Pt3O4 structure-type with 4-connected tetrahedral vertices, to achieve a structure which possesses a generic empirical formula of JK6L8. In such a topological modification, the four 3-fold axes of the parent cubic, Pm3n, Pt3O4 structure-type are retained. Thus the 4-connected tetrahedral vertices are oriented so as to preserve cubic symmetry in the resulting Pm3, JK6L8 (jubilite lattice. The unit cell contains a single 8-connected cubecentered vertex, six 4-connected distorted square planar vertices and eight 4-connected distorted tetrahedral vertices. It is a Wellsean structure with a Wells point symbol given by (4166484(42826(43838 and a Schläfli symbol of (53/4, 4.2667. This latter index reveals a decrease in the lattice’s polygonality and concomitant increase in the connectivity through the transformation from waserite to jubilite. The topology of the parent waserite lattice (Pt3O4 corresponds to that of the Catalan structures with the Wells point symbol (843(834, which has the Schläfli symbol (8, 3.4285. Finally, it can be seen that a sequence of structure-types starting with waserite (Pt3O4 and moving to jubilite (JK6L8 and finally to fluorite (CaF2 represents a continuous crystallographic structural transformation in which the symmetry and topology undergo concomitant changes from one structure-type (waserite to the other structure-types. The topology of the fluorite lattice, represented by the Wells point symbol (424(462, and the Schläfli symbol (4, 51/3, indicates a discontinuous topological transformation from the intermediate jubilite lattice; like the discontinuous topological transformation from Pt3O4 to JK6L8; in which the

  6. Coagulación de finos en la flotación de la fluorita

    Directory of Open Access Journals (Sweden)

    Sarquís, P. E.

    2011-06-01

    Full Text Available Fluorite, a valuable mineral in the metallurgical industry, can be found together with silicates, carbonates and oxides in ore deposits. Commercial concentrates with more than 95 % of CaF2 are obtained processing the mineral in flotation plants and using oleic acid as fluorite collector. Depressor reagents such as sodium silicate, tannin and sodium carbonate are commonly employed to allow the oleic acid selective performance. These reagents cause a dispersant effect separating the solid-liquid solution on tailing plants. Fine particles in the recovered water enter the circuit and affect the flotation efficiency. The effect of coagulant ions was studied as a method to clarify the returned water. The problem of the presence of these ions is related to its reactions with the collector by the formation of compounds and possibly on the selectivity. Variable quantities of Al3+, Fe3+ and Ca2+ ions were added to the flotation to evaluate its effect on the fluorite recovery, in the selectivity and in solids content in recirculation water. Results show that some ions fail to improve water quality and are detrimental to flotation. On the contrary, some ions contribute to reduce fine content in suspension. Therefore, although there is a recovery reduction, such effect can be counteracted increasing the collector consumption a little.

    La fluorita es un mineral de mucha importancia en la industria metalúrgica. Se presenta acompañada de silicatos, carbonatos y óxidos. Para la obtención de concentrados comerciales, más de 95 % de CaF2, el mineral se procesa en plantas de flotación donde se usa ácido oleico como colector de la fluorita. Para que el ácido oleico actúe selectivamente es común el uso de reactivos depresores: silicato de sodio, tanino y carbonato de sodio. Estos agentes tienen un efecto dispersante que se evidencia en la separación de sólido-líquido sobre las colas de las

  7. Thermal history of the unsaturated zone at Yucca Mountain, Nevada, USA

    International Nuclear Information System (INIS)

    Whelan, Joseph F.; Neymark, Leonid A.; Moscati, Richard J.; Marshall, Brian D.; Roedder, Edwin

    2008-01-01

    Secondary calcite, silica and minor amounts of fluorite deposited in fractures and cavities record the chemistry, temperatures, and timing of past fluid movement in the unsaturated zone at Yucca Mountain, Nevada, the proposed site of a high-level radioactive waste repository. The distribution and geochemistry of these deposits are consistent with low-temperature precipitation from meteoric waters that infiltrated at the surface and percolated down through the unsaturated zone. However, the discovery of fluid inclusions in calcite with homogenization temperatures (T h ) up to ∼80 deg. C was construed by some scientists as strong evidence for hydrothermal deposition. This paper reports the results of investigations to test the hypothesis of hydrothermal deposition and to determine the temperature and timing of secondary mineral deposition. Mineral precipitation temperatures in the unsaturated zone are estimated from calcite- and fluorite-hosted fluid inclusions and calcite δ 18 O values, and depositional timing is constrained by the 207 Pb/ 235 U ages of chalcedony or opal in the deposits. Fluid inclusion T h from 50 samples of calcite and four samples of fluorite range from ∼35 to ∼90 deg. C. Calcite δ 18 O values range from ∼0 to ∼22 per mille (SMOW) but most fall between 12 and 20 per mille . The highest T h and the lowest δ 18 O values are found in the older calcite. Calcite T h and δ 18 O values indicate that most calcite precipitated from water with δ 18 O values between -13 and -7 per mille , similar to modern meteoric waters. Twenty-two 207 Pb/ 235 U ages of chalcedony or opal that generally postdate elevated depositional temperatures range from ∼9.5 to 1.9 Ma. New and published 207 Pb/ 235 U and 230 Th/Uages coupled with the T h values and estimates of temperature from calcite δ 18 O values indicate that maximum unsaturated zone temperatures probably predate ∼10 Ma and that the unsaturated zone had cooled to near-present-day temperatures

  8. Mixing of fluids in hydrothermal ore-forming (Sn,W) systems: stable isotope and rare earth elements data

    Science.gov (United States)

    Sushchevskaya, T. M.; Popova, J. A.; Velivetskaya, T. A.; Ignatiev, A. V.; Matveeva, S. S.; Limantseva, O. A.

    2012-04-01

    Experimental and physico-chemical modeling data witness to important role of mixing of different type of fluids during tin and tungsten ore formation in hydrothermal systems. Mixing of magmatogeneous fluids, exsolved from granite melts, with exogenic, initially meteoric waters in hydrothermal ore-forming systems may change chemical composition of ore-forming fluid, causing cassiterite and/or wolframite precipitation (Heinrich, 1990; Sushchevskaya, Ryzhenko, 2002). We studied the process of genetically different fluids mixing for two economic Sn-W deposits, situated in the Iultin ore region (North-East of Russia, Chukotka Penninsula). The Iultin and Svetloe deposits are located in the apical parts of close situated leucogranite stocks, formed at the final stage of the Iultin complex emplacement. Both deposits are composed of a series of quartz veins among the flyschoid rocks (T 1-2), cut by the dikes (K1) of lamprophyre, granodiorite porphyre and alpite. The veins of the deposits are dominated by the productive quartz-wolframite-cassiterite-arsenopyrite-muscovite mineral assemblage. Topaz, beryl, fluorite, and albite occur sporadically. The later sulfide (loellingite-stannite-chalcopyrite) and quartz-fluorite-calcite assemblages show insignificant development. The preore quartz veinlets in host hornfels contain disseminated iron sulfides, chalcopyrite, muscovite. Isotopic (H, O, Ar) study of minerals, supplemented by oxygen isotope data of host granites and metamorphic rocks gave us possibility to conclude, that at the Iultin and the Svetloye deposits fluid mixing was fixed on the early stages of deposit formation and could be regarded as probable cause of metal (W, Sn) precipitation. During postore time the intensive involvement of isotopically light exogenic waters have changed: a) the initial character of oxygen isotope zonality; b) the initial hydrogen isotope composition of muscovites, up to meteoric calculated values for productive fluid (while the δ18O

  9. Cachoeira Uranium Deposit, Lagoa Real, Bahia, Brazil – Kinematic, compositional and fluid evolution

    International Nuclear Information System (INIS)

    Pires, F.; Miano, S.

    2014-01-01

    The Cachoeira uranium albitite-type deposit occurs in a steep dip shear zone aligned with several other similar uranium deposits in the Lagoa Real Province. Uranium resources are estimated as about 90,000 t U_3O_8 [~76,000 t U] grading 2500 ppm U_3O_8 [~2100 ppm U]. Uraniferous albitite occupies a 15 m-thick strongly mylonitized shear zone structurally enclosed within “zebra” biotite gneiss. Uranium albitite mineralization forms cigar-shaped (prolate) and secondarily pancake-shaped (oblate) bodies composed of albite-hornblende-garnet-uraninite-magnetite ore grading to quartz-free skarntype rock with fluorite-kyanite-calcite-quartz concordant veins and pockets formed by late hydrothermal process. Brown chalcedony was the latest mineral to form. Fine-grained, disseminated uraninite is distributed and concentrated in the mafic portions of the gneiss consisting of hornblende andradite- sphene-apatite-epidote forming 30% and albite portions consisting of 70% of the albitite, which allows its gravitational treatment, thus decreasing acid leaching. While the host rock was severely affected by K-metasomatism the uraninite zone was deposited together with hornblende by Na- and Ca-metasomatism. Another reaction involves garnet crystallization exclusively together with uraninite, which liberates sílica and oxygen, differently from previous reaction which consumes silica and oxygen. Both reactions involve magnetite. The destabilization of biotite at the ore zone implies in the formation of GSPO-biotite overgrowing the LPO-biotite previously formed at host rock, due to the excess of K in the system. Magnetite is absent. The reaction represents the K-metasomatism at the host zebra gneiss: biotite + plagioclase + pyroxene + UO_2Cl"+ + Ca_2"+ = hornblende + uraninite + kyanite + quartz. The excess of Ca is allocated in the sphene, apatite and epidote structures. Consumption of Ca results in rutile deposition. As fluid composition was complex F and CO_2 were enriched in the

  10. Thermal history of the unsaturated zone at Yucca Mountain, Nevada, USA

    Energy Technology Data Exchange (ETDEWEB)

    Whelan, Joseph F. [U.S. Geological Survey, Box 25046, M.S. 963, Denver Federal Center, Denver, CO 80225 (United States)], E-mail: jfwhelan@usgs.gov; Neymark, Leonid A.; Moscati, Richard J.; Marshall, Brian D. [U.S. Geological Survey, Box 25046, M.S. 963, Denver Federal Center, Denver, CO 80225 (United States); Roedder, Edwin [Department of Earth and Planetary Science, Harvard University, Cambridge, MA 02138 (United States)

    2008-05-15

    Secondary calcite, silica and minor amounts of fluorite deposited in fractures and cavities record the chemistry, temperatures, and timing of past fluid movement in the unsaturated zone at Yucca Mountain, Nevada, the proposed site of a high-level radioactive waste repository. The distribution and geochemistry of these deposits are consistent with low-temperature precipitation from meteoric waters that infiltrated at the surface and percolated down through the unsaturated zone. However, the discovery of fluid inclusions in calcite with homogenization temperatures (T{sub h}) up to {approx}80 deg. C was construed by some scientists as strong evidence for hydrothermal deposition. This paper reports the results of investigations to test the hypothesis of hydrothermal deposition and to determine the temperature and timing of secondary mineral deposition. Mineral precipitation temperatures in the unsaturated zone are estimated from calcite- and fluorite-hosted fluid inclusions and calcite {delta}{sup 18}O values, and depositional timing is constrained by the {sup 207}Pb/{sup 235}U ages of chalcedony or opal in the deposits. Fluid inclusion T{sub h} from 50 samples of calcite and four samples of fluorite range from {approx}35 to {approx}90 deg. C. Calcite {delta}{sup 18}O values range from {approx}0 to {approx}22 per mille (SMOW) but most fall between 12 and 20 per mille . The highest T{sub h} and the lowest {delta}{sup 18}O values are found in the older calcite. Calcite T{sub h} and {delta}{sup 18}O values indicate that most calcite precipitated from water with {delta}{sup 18}O values between -13 and -7 per mille , similar to modern meteoric waters. Twenty-two {sup 207}Pb/{sup 235}U ages of chalcedony or opal that generally postdate elevated depositional temperatures range from {approx}9.5 to 1.9 Ma. New and published {sup 207}Pb/{sup 235}U and {sup 230}Th/Uages coupled with the T{sub h} values and estimates of temperature from calcite {delta}{sup 18}O values indicate

  11. Uranyl and/or rare-earth mellitates in extended organic-inorganic networks: A unique case of hetero-metallic cation-cation interaction with U-VI=O-Ln(III) bonding (Ln = Ce, Nd)

    International Nuclear Information System (INIS)

    Volkringer, Christophe; Henry, Natacha; Grandjean, Stephane; Loiseau, Thierry

    2012-01-01

    A series of uranyl and lanthanide (trivalent Ce, Nd) mellitates (mel) has been hydrothermally synthesized in aqueous solvent. Mixtures of these 4f and 5f elements also revealed the formation of a rare case of lanthanide-uranyl coordination polymers. Their structures, determined by XRD single-crystal analysis, exhibit three distinct architectures. The pure lanthanide mellitate Ln 2 (H 2 O) 6 (mel) possesses a 3D framework built up from the connection of isolated LnO 6 (H 2 O) 3 polyhedra (tri-capped trigonal prism) through the mellitate ligand. The structure of the uranyl mellitate (UO 2 ) 3 (H 2 O) 6 - (mel).11.5H 2 O is lamellar and consists of 8-fold coordinated uranium atoms linked to each other through the organic ligand giving rise to the formation of a 2D 3 6 net. The third structural type, (UO 2 ) 2 Ln(OH)(H 2 O) 3 (mel).2.5H 2 O, involves direct oxygen bondings between the lanthanide and uranyl centers, with the isolation of a hetero-metallic dinuclear motif. The 9-fold coordinated Ln cation, LnO 5 (OH)(H 2 O) 3 , is linked to the 7-fold coordinated uranyl (UO 2 )O-4(OH) (pentagonal bipyramid) via one μ 2 -hydroxo group and one μ 2 -oxo group. The latter is shared between the uranyl bonding (U=O = 1.777(4)1.779(6) angstrom) and a long Ln-O bonding (Ce-O = 2.822(4) angstrom; Nd-O = 2.792(6) angstrom). This unusual linkage is a unique illustration of the so-called cation cation interaction associating 4f and 5f metals. The dinuclear motif is then further connected through the mellitate ligand, and this generates organic inorganic layers that are linked to each other via discrete uranyl (UO 2 )O 4 units (square bipyramid), which ensure the three-dimensional cohesion of the structure. The mixed U-Ln carboxylate is thermally decomposed from 260 to 280 degrees C and then transformed into the basic uranium oxide (U 3 O 8 ) together with U-Ln oxide with the fluorite structural type ('(Ln,U)O 2 '). At 1400 degrees C, only fluorite type '(Ln,U)O 2 ' is formed with

  12. Anomalous thermodynamic behaviour of novel compounds: inelastic neutron scattering and lattice dynamics studies

    International Nuclear Information System (INIS)

    Mittal, R.

    2014-01-01

    The understanding of the thermodynamic properties of solids has important applications in diverse areas like condensed matter physics, materials science, mineralogy, geophysics, etc. We have been extensively investigating anomalous thermodynamic properties of compounds using the techniques of inelastic neutron scattering and lattice dynamics. We would present some of the results from our recent studies. Studies of materials exhibiting anomalous thermal expansion are of interest due to their fundamental scientific importance and potential applications in ceramic, optical and electronic industry etc. We have studied the thermodynamic properties of negative thermal expansion (NTE) compounds ZrW 2 O 8 , HfW 2 O 8 , ZrMo 2 O 8 , ZrV 2 O 7 , HfV 2 O 7 , Zn(CN) 2 , Cu 2 O, Ag 2 O, Ag 3 Co(CN) 6 and Ag 3 Fe(CN) 6 . Our calculations predicted that large softening of the phonon spectrum involving librational and translational modes below 10 MeV would be responsible for anomalous thermal expansion behaviour. High pressure inelastic neutron scattering experiments carried by us on cubic ZrW 2 O 8 , ZrMo 2 O 8 and Zn(CN) 2 confirmed the phonon softening. Our studies indicate that unusual phonon softening of low energy modes is able to account for the thermal expansion behaviour in these compounds. Superionic conduction in fluorite-structured (anti-fluorite, Li 2 O) oxides (MO 2 , M= U, Th) have applications in energy storage, conversion and nuclear industry. The possible role of phonon in initiation of diffusion has been studied in Li 2 O. We found that in the superionic regime lithium atoms may exhibit macroscopic movement along (100) direction. The microscopic modeling or simulation is found to play a pivotal role in understanding the conduction processes at high temperatures in Li 2 O. We have also studied zircon structured compounds MSiO 4 (M=Zr, Hf, Th, U), RPO 4 , (R=rare earth atom). The compounds are known to transform to the scheelite (body centered tetragonal, I4 1 /a

  13. Calibration of the Fluorine, Chlorine and Hydrogen Content of Apatites With the ChemCam LIBS Instrument

    Science.gov (United States)

    Meslin, P.-Y.; Cicutto, L.; Forni, O.; Drouet, C.; Rapin, W.; Nachon, M.; Cousin, A.; Blank, J. G.; McCubbin, F. M.; Gasnault, O.; hide

    2016-01-01

    Determining the composition of apatites is important to understand the behavior of volatiles during planetary differentiation. Apatite is an ubiquitous magmatic mineral in the SNC meteorites. It is a significant reservoir of halogens in these meteorites and has been used to estimate the halogen budget of Mars. Apatites have been identified in sandstones and pebbles at Gale crater by ChemCam, a Laser-Induced Breakdown Spectroscometer (LIBS) instrument onboard the Curiosity rover. Their presence was inferred from correlations between calcium, fluorine (using the CaF molecular band centered near 603 nm, whose detection limit is much lower that atomic or ionic lines and, in some cases, phosphorus (whose detection limit is much larger). An initial quantification of fluorine, based on fluorite (CaF2)/basalt mixtures and obtained at the LANL laboratory, indicated that the excess of F/Ca (compared to the stoichiometry of pure fluorapatites) found on Mars in some cases could be explained by the presence of fluorite. Chlorine was not detected in these targets, at least above a detection limit of 0.6 wt% estimated from. Fluorapatite was later also detected by X-ray diffraction (with CheMin) at a level of approx.1wt% in the Windjana drill sample (Kimberley area), and several points analyzed by ChemCam in this area also revealed a correlation between Ca and F. The in situ detection of F-rich, Cl-poor apatites contrasts with the Cl-rich, F-poor compositions of apatites found in basaltic shergottites and in gabbroic clasts from the martian meteorite NWA 7034, which were also found to be more Cl-rich than apatites from basalts on Earth, the Moon, or Vesta. The in situ observations could call into question one of the few possible explanations brought forward to explain the SNC results, namely that Mars may be highly depleted in fluorine. The purpose of the present study is to refine the calibration of the F, Cl, OH and P signals measured by the ChemCam LIBS instrument, initiated

  14. Contribution to the study of french pitchblendes; Contribution a l'etude des pechblendes francaises

    Energy Technology Data Exchange (ETDEWEB)

    Geffroy, J [Commissariat a l' Energie Atomique, Lab. de Mineralogie, Centre de Chatillon (France). Centre d' Etudes Nucleaires; Sarcia, J A [Commissariat a l' Energie Atomique, Div. de la Crouzille, Haute Vienne (France). Centre d' Etudes Nucleaires

    1955-07-01

    The authors first review the characteristics of uraninite-pitchblende, as deduced of present literature. They set apart from typical pitchblende a black oxide aspect, which probably corresponds to neo-formations, and a 'para-pitchblende' aspect, which they relate to deep sur-oxidation of normal pitchblende. They insist on the easy replacement of pitchblende by silica. and give indications as to changes in vein stones (fluorite, quartz, etc...). A detailed study of paragenesis and successions in french uranium districts follows (including discussion of uranium of uranium-bearing coals). The authors attempt to classify french pitchblende veins. They are chiefly epithermal and poor in satellite ores. Three types of deposits are identified: massive - pitchblende type, silica type, fluorite type. These deposits, as those of Portugal, are included in granite, Central-European peri-batholitic types where uranium associates which Ni, Co, Bi and Ag, are in France both rare and poor. Finally, the authors attempt to bring out in the european Hercynian area a particular distribution of paragenetic types. (authors) [French] Les auteurs recapitulent d'abord les caracteres et les occurences de l'uraninite - pechblende, tels qu'ils peuvent etre degages de l'actuelle bibliographie. Ils exposent ensuite les faits qui du point de vue mineralogique seulement ressortent de l'etude mineralogique et chalcographique des pechblendes francaises et de leurs satellites. Ils distinguent de la pechblende-type un facies oxyde noir; correspondant probablement a une neoformation, et un facies parapechblende, qui est rapporte a une sur oxydation hypogene de la pechblende proprement dite. Ils insistent sur le facile remaniement de la pechblende par la slice; et donnent quelques precisions sur les modifications des gangues (fluorine, quartz, etc...). Suit l'etude detaillee des parageneses et des successions dans les districts uraniferes francais: Divisions du Limousin, de Grury, de Lachaux et de

  15. Bi1−xNbxO1.5+x (x=0.0625, 0.12) fast ion conductors: Structures, stability and oxide ion migration pathways

    International Nuclear Information System (INIS)

    Tate, Matthew L.; Hack, Jennifer; Kuang, Xiaojun; McIntyre, Garry J.; Withers, Ray L.; Johnson, Mark R.; Radosavljevic Evans, Ivana

    2015-01-01

    A combined experimental and computational study of Bi 1−x Nb x O 1.5+x (x=0.0625 and 0.12) has been carried out using laboratory X-ray, neutron and electron diffraction, impedance measurements and ab-initio molecular dynamics. We demonstrate that Bi 0.9375 Nb 0.0625 O 1.5625 , previously reported to adopt a cubic fluorite-type superstructure, can form two different polymorphs depending on the synthetic method: a metastable cubic phase is produced by quenching; while slower cooling yields a stable material with a tetragonal √2×√2×1 superstructure, which undergoes a reversible phase transition into the cubic form at ~680 °C on subsequent reheating. Neutron diffraction reveals that the tetragonal superstructure arises mainly from ordering in the oxygen sublattice, with Bi and Nb remaining disordered, although structured diffuse scattering observed in the electron diffraction patterns suggests a degree of short-range ordering. Both materials are oxide ion conductors. On thermal cycling, Bi 0.88 Nb 0.12 O 1.62 exhibits a decrease in conductivity of approximately an order of magnitude due to partial transformation into the tetragonal phase, but still exhibits conductivity comparable to yttria-stabilised zirconia (YSZ). Ab-initio molecular dynamics simulations performed on Bi 0.9375 Nb 0.0625 O 1.5625 show that oxide ion diffusion occurs by O 2− jumps between edge- and corner-sharing OM 4 groups (M=Bi, Nb) via tetrahedral □M 4 and octahedral □M 6 vacancies. - Graphical abstract: Oxide ion migration in tetragonal Bi 0.9375 Nb 0.0625 O 1.5625 occurs by O 2− jumps between edge- and corner-sharing OM 4 groups (M=Bi, Nb) via tetrahedral M 4 and octahedral M 6 vacancies. - Highlights: • Bi 0.9375 Nb 0.0625 O 1.5625 adopts a tetragonal √2×√2×1 fluorite superstructure. • Superstructure is due to ordering in the O-sublattice, with Bi/Nb disordered. • Bi 0.9375 Nb 0.0625 O 1.5625 is a good oxide ion conductor. • O 2− jump between OM 4 groups (M

  16. XRD monitoring of α self-irradiation in uranium-americium mixed oxides.

    Science.gov (United States)

    Horlait, Denis; Lebreton, Florent; Roussel, Pascal; Delahaye, Thibaud

    2013-12-16

    The structural evolution under (241)Am self-irradiation of U(1-x)Am(x)O(2±δ) transmutation fuels (with x ≤ 0.5) was studied by X-ray diffraction (XRD). Samples first underwent a preliminary heat treatment performed under a reducing atmosphere (Ar/H2(4%)) aiming to recover the previously accumulated structural defects. Over all measurements (carried out over up to a full year and for integrated doses up to 1.5 × 10(18) α-decay events·g(-1)), only fluorite U(1-x)Am(x)O(2±δ) solid solutions were observed. Within a few days after the end of the heat treatment, each of the five studied samples was slowly oxidized as a consequence of their move to air atmosphere, which is evidenced by XRD by an initial sharp decrease of the unit cell parameter. For the compounds with x ≤ 0.15, this oxidation occurred without any phase transitions, but for U0.6Am0.4O(2±δ) and U0.5Am0.5O(2±δ), this process is accompanied by a transition from a first fluorite solid solution to a second oxidized one, as the latter is thermodynamically stable in ambient conditions. In the meantime and after the oxidation process, (241)Am α self-irradiation caused a structural swelling up to ∼0.8 vol %, independently of the sample composition. The kinetic constants of swelling were also determined by regression of experimental data and are, as expected, dependent on x and thus on the dose rate. The normalization of these kinetic constants by sample α-activity, however, leads to very close swelling rates among the samples. Finally, evolutions of microstrain and crystallite size were also monitored, but for the considered dose rates and cumulated doses, α self-irradiation was found, within the limits of the diffractometer used, to have almost no impact on these characteristics. Microstrain was found to be influenced instead by the americium content in the materials (i.e., by the impurities associated with americium starting material and the increase of cationic charge heterogeneity with

  17. Cavity-based secondary mineralization in volcanic tuffs of Yucca Mountain, Nevada: a new type of the polymineral vadose speleothem, or a hydrothermal deposit?

    Directory of Open Access Journals (Sweden)

    Dublyansky Yuri V.

    2005-07-01

    Full Text Available Secondary minerals (calcite, chalcedony, quartz, opal, fluorite, heulandite, strontianite residing in open cavities in the Miocenerhyolite tuffs of Yucca Mountain, Nevada have been interpreted by some researchers as "speleothemic" formations, deposited as aresult of downward infiltration of meteoric waters (DOE, 2001, Whelan et al., 2002. The major mineral of the paragenesis, calcite,shows spectacular trend of the textural and crystal morphology change: from anhedral granular occurrences, through (optionalplatelet, bladed and scepter varieties, to euhedral blocky morphologies. The trend is consistent with the overall decrease in thesupesaturation of the mineral forming solution. Stable isotope properties of calcite evolve from 13C-enriched (δ13C = +4 to +9 ‰ PDBat early stages of growth to 13C-depleted (-5 to -10 ‰ at late stages. The non-cyclic character of the isotope record and extremevariations of isotopic values argue against the meteoric origin of mineral forming fluids. The δ13C >4 ‰ PDB require isotope partitioningbetween dissolved CO2 and CH4, which is only possible in reducing anoxic environment, but not in aerated vadose zone.Fluid inclusions studied in calcite, quartz and fluorite revealed that the minerals were deposited from thermal solutions. Thetemperatures were higher at early stages of mineral growth (60 to 85oC and declined with time. Most late-stage calcites containonly all-liquid inclusions, suggesting temperatures less than ca. 35-50oC. Minerals collected close to the major fault show the highesttemperatures. Gases trapped in fluid inclusions are dominated by CO2 and CH4; Raman spectrometry results suggest the presenceof aromatic/cyclic hydrocarbon gases. The gas chemistry, thus, also indicates reduced (anoxic character of the mineral formingfluids.Secondary minerals at Yucca Mountain have likely formed during the short-term invasion(s of the deep-seated aqueous fluidsinto the vadose zone. Following the invasion

  18. Ceria-Based Anodes for Next Generation Solid Oxide Fuel Cells

    Science.gov (United States)

    Mirfakhraei, Behzad

    Mixed ionic and electronic conducting materials (MIECs) have been suggested to represent the next generation of solid oxide fuel cell (SOFC) anodes, primarily due to their significantly enhanced active surface area and their tolerance to fuel components. In this thesis, the main focus has been on determining and tuning the physicochemical and electrochemical properties of ceria-based MIECs in the versatile perovskite or fluorite crystal structures. In one direction, BaZr0.1Ce0.7Y0.1 M0.1O3-delta (M = Fe, Ni, Co and Yb) (BZCY-M) perovskites were synthesized using solid-state or wet citric acid combustion methods and the effect of various transition metal dopants on the sintering behavior, crystal structure, chemical stability under CO2 and H 2S, and electrical conductivity, was investigated. BZCY-Ni, synthesized using the wet combustion method, was the best performing anode, giving a polarization resistance (RP) of 0.4 O.cm2 at 800 °C. Scanning electron microscopy and X-ray diffraction analysis showed that this was due to the exsolution of catalytic Ni nanoparticles onto the oxide surface. Evolving from this promising result, the effect of Mo-doped CeO 2 (nCMO) or Ni nanoparticle infiltration into a porous Gd-doped CeO 2 (GDC) anode (in the fluorite structure) was studied. While 3 wt. % Ni infiltration lowered RP by up to 90 %, giving 0.09 O.cm2 at 800 °C and exhibiting a ca. 5 times higher tolerance towards 10 ppm H2, nCMO infiltration enhanced the H2 stability by ca. 3 times, but had no influence on RP. In parallel work, a first-time study of the Ce3+ and Ce 4+ redox process (pseudocapacitance) within GDC anode materials was carried out using cyclic voltammetry (CV) in wet H2 at high temperatures. It was concluded that, at 500-600 °C, the Ce3+/Ce 4+ reaction is diffusion controlled, probably due to O2- transport limitations in the outer 5-10 layers of the GDC particles, giving a very high capacitance of ca. 70 F/g. Increasing the temperature ultimately

  19. The role of hydrothermal processes in concentrating high-field strength elements in the Strange Lake peralkaline complex, northeastern Canada

    Science.gov (United States)

    Salvi, Stefano; Williams-Jones, Anthony E.

    1996-06-01

    The middle-Proterozoic peralkaline pluton at Strange Lake, Quebec/Labrador, comprises hypersolvus to subsolvus phases which are unusually enriched in Zr, Y, REEs, Nb, Be, and F, as exotic alkali and alkaline-earth silicate minerals. The highest concentrations of these elements are in subsolvus granite, which underwent intense low temperature (≤200°C) hydrothermal alteration involving hematization and the replacement of alkali high-field strength element (HFSE) minerals by calcic equivalents. This alteration is interpreted to have been caused by meteoric or formational waters. High temperature (≥ 350°C) alteration, attributed to orthomagmatic fluids, is evident in other parts of the subsolvus granite by the replacement of arfvedsonite by aegirine. Comparisons of the chemical compositions of fresh and altered rocks indicate that rocks subjected to high temperature alteration were chemically unaffected, except for depletion in Zr, Y, and HREEs. These elements were appreciably enriched in rocks that underwent low temperature alteration. Other elements affected by low temperature alteration include Ca and Mg, which were added and Na, which was removed. Available data on HFSE speciation in aqueous fluids and the chemistry of the pluton, suggest that the HFSEs were transported as fluoride complexes. If this was the case, the low temperature fluid could not have been responsible for HFSE transport, because the high concentration of Ca and low solubility of fluorite would have buffered F - activity to levels too low to permit significant complexation. We propose that HFSE mineralization and accompanying alteration were the result of mixing, in the apical parts of the pluton, of a F-rich, essentially Ca-free orthomagmatic fluid containing significant concentrations of HFSEs, with an externally derived meteoric-dominated fluid, enriched in Ca as a result of interaction with calc-silicate gneisses and gabbros. According to this interpretation, the latter fluid was

  20. Fluorine

    Science.gov (United States)

    Hayes, Timothy S.; Miller, M. Michael; Orris, Greta J.; Piatak, Nadine M.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

    2017-12-19

    Fluorine compounds are essential in numerous chemical and manufacturing processes. Fluorspar is the commercial name for fluorite (isometric CaF2), which is the only fluorine mineral that is mined on a large scale. Fluorspar is used directly as a fluxing material and as an additive in different manufacturing processes. It is the source of fluorine in the production of hydrogen fluoride or hydrofluoric acid, which is used as the feedstock for numerous organic and inorganic chemical compounds.The United States was the world’s leading producer of fluorspar until the mid-1950s. In the mid-1970s, the U.S. fluorspar mining industry began to decline because of foreign competition. By 1982, there was essentially only a single U.S. producer left, and that company ceased mining in 1996. Consumption of fluorspar in the United States peaked in the early 1970s, which was also the peak period of U.S. steel production. Since then, U.S. fluorspar consumption has decreased substantially; the United States has nonetheless increased its imports of downstream fluorine compounds, such as, in order of tonnage imported, hydrofluoric acid, aluminum fluoride, and cryolite. This combination of no U.S. production (until recently) and high levels of consumption has made the United States the world’s leading fluorspar-importing country, in all its various forms.The number of fluorspar-exporting countries has decreased substantially in recent decades, and, as a result, the United States has become dependent on just a few countries to supply its needs. In 2013, the United States imported the majority of its fluorspar from three countries, which were, in descending order of the amount imported, Mexico, China, and South Africa.Geologically, in igneous systems, fluorine is one of a number of elements that are “incompatible.” These incompatible elements become concentrated in the residual magma while the common silicates crystallize upon magma ascent and cooling, leading to relatively high

  1. Short-term Rn-222 concentration changes in underground spaces with limited air exchange

    Science.gov (United States)

    Fijałkowska-Lichwa, Lidia; Przylibski, Tadeusz A.

    2010-05-01

    Authors conducted research on radon concentration in two underground structures located in the vicinity of Kletno (Sudety Mts., SW Poland), which are accessible for visitors. One of these structures is Niedźwiedzia (Bear) Cave, and the second one is the part of former uranium mine - Fluorite Adit. Both selected underground structures are characterized by almost constant temperature, changing within the range from +5 to +7° C and also constant relative humidity, close to 100%. Both these parameters testify that air exchange with the atmosphere is very limited. Air exchange is limited particularly in Niedźwiedzia Cave, which microclimate is protected i.e. by applying of locks at the entrance and exit of tourist route. The measurements were conducted between 16.05.2008. and 15.11.2009., by the use of a new Polish equipment - SRDN-3 devices with semiconductor detector. SRDN-3 device records every hour radon concentration as well as atmospheric parameters - relative humidity and temperature. At the same time authors conducted measurements of basic parameters in the open atmosphere close to Niedźwiedzia Cave. Obtained results of atmospheric parameters measurements may be used for both underground structures; because they are located within the distance of about 1 km. Atmospheric parameters were measured by the use of automatic weather station VantagePro2. On the base of conducted research authors corroborate, that the differences of radon concentration in both underground structures reach three orders of magnitude during a year. In Niedźwiedzia Cave these values are in the range from below 88 Bq/m3 (detection limit of the SRDN-3 device) up to 12 kBq/m3. Related values in Fluorite Adit are between < 88 Bq/m3 and 35 kBq/m3. It was observed also the different course of daily radon concentration changes in both structures. Additionally, authors registered that daily course of radon concentration changes differs due to season of the year. Such changes are observed in

  2. Chemical Equilibrium and Mineral Saturation in Waters from Oil Wells of the Activo Luna Field, Tabasco, Mexico; Equilibrio quimico y grado de saturacion de minerales en aguas de pozos petroleros de Activo Luna, Tabasco, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Barragan R, Rosa Maria; Arellano G, Victor M.; Portugal M, Enrique; Torres R, Vicente [Instituto de Investigaciones Electricas (Mexico); Torres Alvarado, Ignacio [Universidad Nacional Autonoma de Mexico (Mexico); Ascencio C, Fernando; Martinez A; Ana E [Petroleos Mexicanos (Mexico)

    2001-09-01

    Chemical equilibrium of formation waters from seven oil wells of the Activo Luna field (Tabasco, Mexico) was modelled. Saturation indices of characteristic hydrothermal minerals were calculated at ambient and reservoir conditions in order to predict scaling potential of deep and surface installations. The salinity of waters was found to be in the range from 43,000 (well Escuintle 2) to 250,000 (well Lune 3B) mg/kg as total dissolved solids. The water samples were classified as sodium-chioride type. Ionic strength for the solutions was found to be between 0.75 and 6.5. Activity coefficients were estimated by virial (Pitzer equations) methods using the GEOCHEMIST WORKENCH (GWB) software. Minerals such as anhydrite, halite, alunite, fluorite and barite were found to be supersaturated at reservoir conditions. A solid scale sample obtained from well Luna-3B was analysed. Analysis indicate the presence of calcite, anhydrite, fluorite and sphalerite which suggest the occurrence of temperatures of at least 180 Celcius degrees with acidic conditions and high chemical corrosion potential. [Spanish] Se modelo el equilibrio quimico de aguas de formacion producidas por siete pozos petroleros pertenecientes al Activo Luna, en el estado de Tabasco, Mexico, se calcularon los indices de saturacion de minerales caracteristicos tanto en las condiciones ambiente como en las de yacimiento, con el proposito de apoyar el control de incrustaciones en las instalaciones superficiales y profundas. La salinidad de las salmueras se encontro en el rango de 43,000 (pozos Escuintle 2) a 250,000 (pozos Luna 3B) mg/kg de solidos disueltos totales y las muestras se clasificaron como del tipo clorurado-sodico. La fuerza ionica de las soluciones varia entre 0.75 y 6.5 molar, por lo que los coeficientes de actividad de la modelacion de equilibrio quimico se estimaron por metodos viriales empleando las ecuaciones de Pitzer mediante el programa GEOCHEMIST WORKBENCH (GWB). Minerales como anhidrita, halita

  3. Wadi Ladid Al-JI,Dan Alkali Feldspar Granites and Associated Pegmatites, North Eastern Eser, Egypt:Geology,Mineralogy and Radioactivity

    International Nuclear Information System (INIS)

    Abu Steet, A.A.; Ayoub, R.R.; Bakhit, A.F.

    2013-01-01

    This article deals with the geology, structure, mineralogy and radioactivity of the alkali feldspar granites at wadi Ladid al-Ji,dan, north Eastern Desert of Egypt. Geologically, the area consists mainly of alkali feldspar granites. These granites are medium to coarse grained, pink to red in colour and form numbers of moderate to relatively high elevated outcrops. These rocks are altered in some parts due to secondary processes especially along the fault zones and contacts. The area displays primary and secondary structures. Primary structures comprise layering, volcanic flows, vesicular tops of lavas and volcanic bombs. The secondary structures are represented by exfoliation, joints and faults. The granites are dissected by several sets of joints predominating in the N-S direction, dipping 84°-88° mainly to west; E-W direction, dipping 70°-75° mainly to south and NW-SE direction, dipping 80°-82° to SW direction. The majority of joints are tension ones. These tension joints are commonly filled with quartz, feldspars, epidote, iron oxides, manganese oxides and aplite. The studied area is dissected by major regional faults. Along the fault zones; the granites are marked by fault breccia and alteration features, especially silicification, hematitization, kaolinitization and chloritization. The area is cutting by faults trending mainly in N-S, NE-SW and NNW-SSE directions. The average uranium and thorium contents of the alkali feldspar granites are 12 and 23 ppm and reaches up to 36 and 37 ppm in the normal pegmatites. In the anomalous pegmatites the maximum values recorded are 91 and 72 ppm. Generally, the averages of uranium and thorium contents in the studied pegmatites are higher than that of the world and Egyptian uraniferous pegmatites. The high uranium content in alkali feldspar granites is related to the presence of some accessory minerals such as zircon, fluorite and apatite but the high uranium content in the pegmatites is related to the presence of

  4. Nano-crystals of cerium–hafnium binary oxide: Their size-dependent structure

    Energy Technology Data Exchange (ETDEWEB)

    Raitano, Joan M. [Department of Applied Physics and Applied Mathematics, Materials Science and Engineering Program, Columbia University, New York, NY 10027 (United States); Khalid, Syed [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973 (United States); Marinkovic, Nebojsa [Chemical Engineering Department, Columbia University, 500 W 120th St, Mudd 801, New York, NY 10027 (United States); Chan, Siu-Wai, E-mail: sc174@columbia.edu [Department of Applied Physics and Applied Mathematics, Materials Science and Engineering Program, Columbia University, New York, NY 10027 (United States)

    2015-09-25

    Highlights: • (1 − x)CeO{sub 2}–xHfO{sub 2} was precipitated (0 < x < 1) and calcined in air. • For x ⩽ 0.14, crystallites ⩽140 nm in size exhibit only the fluorite structure. • This low hafnia solubility is attributable to no auto-reduction (Ce{sup 3+} = 0). • The low solubility is also due to the high temperature required for homogenization. • Coarsening is lessened as Hf{sup 4+} ions slow cation diffusion in these crystallites. - Abstract: Cerium oxide (CeO{sub 2}, “ceria”) and hafnium oxide (HfO{sub 2}, “hafnia”) were aqueously co-precipitated and subsequently calcined to allow for homogenization. The size of the (1−x)CeO{sub 2}–xHfO{sub 2} crystallites, determined by the Scherrer equation, varied from 140 nm for x = 0 to 15 nm for x = 0.73. For x ⩽ 0.14, only cubic structures are visible in X-ray diffractograms, and the lattice parameters are consistent with the values expected for structurally cubic solid solutions of hafnia in ceria. At x = 0.26, tetragonal and monoclinic phases nucleated with the former not being observed in the bulk phase diagram for ceria–hafnia. Therefore, the solubility limit of the cubic structure is between x = 0.14 and x = 0.26 for 40–61 nm crystallites, the sizes of these respective compositions. More specifically, for the 40 nm crystallites of x = 0.26 (1 − x)CeO{sub 2}–xHfO{sub 2}, 15% of the hafnia remains in a structurally cubic solid solution with ceria based on the observed cubic lattice parameter. The compositional domain for the cubic fluorite structure in this study is narrower than other nanostructured (1 − x)CeO{sub 2}–xHfO{sub 2} studies, especially studies with crystallite sizes less than 10 nm, but wider than observed in the bulk and helps to expand the size regime over which the relationship between crystallite size and phase stability is known. The extent of this cubic-structure domain is mainly attributable to the intermediate crystallite size and the roughly zero Ce{sup 3

  5. The Morro do Resende orthogneiss: mineralogy, petrography, geochemistry and geochronology; Ortognaisse Morro do Resende: mineralogia, petrografia, geoquimica e geocronologia

    Energy Technology Data Exchange (ETDEWEB)

    Vasconcelos, Fabiana Franco de; Avila, Ciro Alexandre; Bongiolo, Everton Marques; Camara, Beatriz de Oliveira; Menezes, Victor Hugo Riboura; Cunha, Fernanda Caetano de Mattos, E-mail: fma3003@globo.com, E-mail: avila@mn.ufrj.br, E-mail: ebongiolo@geologia.ufrj.br, E-mail: camara_b@hotmail.com, E-mail: vmenezes92@gmail.com, E-mail: fefemattos@gmail.com [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil); Neumann, Reiner, E-mail: reiner.neumann@gmail.com [Centro de Tecnologia Mineral (CETEM), Rio de Janeiro, RJ (Brazil); Teixeira, Wilson; Barbosa, Natali, E-mail: wteixeir@usp.br, E-mail: natali@usp.br [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Instituto de Geociencias

    2017-01-15

    The Morro do Resende orthogneiss is a hololeucocratic to leucocratic, fine-grained body with monzogranitic to granodioritic composition, cropping out near the Volta Grande mine in Nazareno County, State of Minas Gerais, Brazil. It bears xenoliths of metamafic rocks of the Rio das Mortes metavolcano-sedimentary sequence and yields a U-Pb SHRIMP crystallization age of 2174 ± 4 Ma, relating it to one of the magmatic pulses of the Mineiro Belt. The primary mineralogy includes quartz, albite, microcline, biotite, allanite, zircon, magnetite, titanite and apatite, while sericite, epidote, zoisite, clinozoisite, carbonate and chlorite are metamorphic minerals. Maghemite, barite, fluorite, monazite, xenotime, garnet and REE fluorides (possibly gagarinite) are hydrothermal, as they fill the fractures, intergrow or replace the primary and metamorphic minerals. Fluid interaction was not homogeneous throughout the body. Metamorphic paragenesis points to greenschist facies conditions, which could be related to the Paleoproterozoic II event of the Mineiro Belt, which lasted from 2131 to 2101 Ma. The Morro do Resende orthogneiss is distinguished by significant REE enrichment, as well as a negative Eu anomaly linked to the magmatic crystallization and a negative Ce anomaly related to oxidizing hydrothermal fluids circulation. (author)

  6. Mineralogy, stable isotopes (δ18O and δ34S and 40Ar-39Ar geochronology studies on the hydrothermal carapace of the Igarapé Manteiga W-Sn Deposit, Rondônia

    Directory of Open Access Journals (Sweden)

    Thais Marcela Fernandes do Nascimento

    Full Text Available ABSTRACT: The Igarapé Manteiga W-Sn deposit is formed by a granite stock that intrudes in the Paleoproterozoic basement. The mineralization is encapsulated in an alumino-siliceous hydrothermal carapace formed by greisen, vein-veinlets and breccia, developed in the apex zone of a granite stock. At this site, wolframite, cassiterite and sulfides-minerals, as well as siderite, monazite, xenotime, hematite and others, are spread out or in massive clusters associated with quartz, topaz, zinnwaldite and fluorite. Wolframite is not zoned and relatively rich in Fe, and poor in Nb and Ta. Cassiterite exhibits growth-zones with light-yellow to dark-orange colors, and is rich in Ta, and poor in Ti, W, Mn and U. Oxygen and sulfur (δ18O and δ34S isotope data on the ore- and sulfide-minerals indicates that it is a magmatic source, with closing temperatures from 230°C to 480°C. The hydrothermal phase was cyclical and protractedly active, promoting greisenization and hydrofracturing. The lowering of temperature and the change in the composition of fluids (from oxidized to reduced controlled the precipitation of the hydrothermal mineral assemblage. The 40Ar-39Ar analyses reveal a plateau age of 988 Ma, interpreted as the closure time for the hydrothermal processes responsible for mineralization, which is linked to the final magmatic evolution of the Rondônia Intrusive Suite (995-991 Ma.

  7. The ionic conductivity and dielectric properties of Ba{sub 1−x}Sn{sub x}F{sub 2} solid solutions prepared by mechanochemical milling

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Mohamad M., E-mail: mmohamad@kfu.edu.sa [Department of Physics, College of Science, King Faisal University, Al-Ahsaa 31982 (Saudi Arabia); Department of Science and Mathematics, Faculty of Education in The New Valley, Assiut University, El-Kharga 72511 (Egypt); Yamane, Yohei; Yamada, Koji [Department of Applied Molecular Chemistry, College of Industrial Technology, Nihon University, Narashino, Chiba 275-8575 (Japan)

    2013-09-01

    Highlights: • New Ba{sub 1−x}Sn{sub x}F{sub 2} compositions have been synthesized by the mechanochemical milling. • Considerably higher ionic conductivity is obtained when increasing SnF{sub 2} content. • The increased conductivity is due to the enhanced mobility of fluoride ions -- Abstract: Solid solutions of Ba{sub 1−x}Sn{sub x}F{sub 2} fluoride ion conductors, with x = 0.1–0.4, have been synthesized by the mechanochemical milling technique for the first time. All of the prepared materials crystallize in the cubic fluorite-type structure, which indicates that the solid solution can be synthesized in the studied composition range by the mechanochemical milling technique at ambient temperature and pressure. The ionic conduction of the investigated materials has been studied by impedance spectroscopy. The ionic conductivity increased considerably, by up to six orders of magnitude compared to pure un-milled BaF{sub 2}, with increasing SnF{sub 2} content. From the analysis of the conductivity spectra of the investigated materials it is found that the concentration of mobile fluoride ions is independent of temperature with almost the same values for the investigated materials. The present results suggest that the enhanced mobility of mobile ions is the origin of the higher ionic conductivity. The dielectric properties and the associated relaxation phenomena of the current materials are also described.

  8. Topotactic oxidative and reductive control of the structures and properties of layered manganese oxychalcogenides.

    Science.gov (United States)

    Hyett, Geoffrey; Barrier, Nicolas; Clarke, Simon J; Hadermann, Joke

    2007-09-12

    Topotactic modification, by both oxidation and reduction, of the composition, structures, and magnetic properties of the layered oxychalcogenides Sr4Mn3O7.5Cu2Ch2 (Ch=S, Se) is described. These Mn3+ compounds are composed of alternating perovskite-type strontium manganese oxide slabs separated by anti-fluorite-type copper chalcogenide layers and are intrinsically oxide deficient in the central layer of the perovskite slabs. The systems are unusual examples of perovskite-related compounds that may topotactically be both oxidized by fluorination and reduced by deintercalation of oxygen from the oxide-deficient part of the structure. The compounds exhibit antiferromagnetic ordering of the manganese magnetic moments in the outer layers of the perovskite slabs, while the other moments, in the central layers, exhibit spin-glass-like behavior. Fluorination has the effect of increasing the antiferromagnetic ordering temperature and the size of the ordered moment, whereas reduction destroys magnetic long-range order by introducing chemical disorder which leads to both further disorder and frustration of the magnetic interactions in the manganese oxide slab.

  9. Evaluation of uranium dioxide thermal conductivity using molecular dynamics simulations

    International Nuclear Information System (INIS)

    Kim, Woongkee; Kaviany, Massoud; Shim, J. H.

    2014-01-01

    It can be extended to larger space, time scale and even real reactor situation with fission product as multi-scale formalism. Uranium dioxide is a fluorite structure with Fm3m space group. Since it is insulator, dominant heat carrier is phonon, rather than electrons. So, using equilibrium molecular dynamics (MD) simulation, we present the appropriate calculation parameters in MD simulation by calculating thermal conductivity and application of it to the thermal conductivity of polycrystal. In this work, we investigate thermal conductivity of uranium dioxide and optimize the parameters related to its process. In this process, called Green Kubo formula, there are two parameters i.e correlation length and sampling interval, which effect on ensemble integration in order to obtain thermal conductivity. Through several comparisons, long correlation length and short sampling interval give better results. Using this strategy, thermal conductivity of poly crystal is obtained and comparison with that of pure crystal is made. Thermal conductivity of poly crystal show lower value that that of pure crystal. In further study, we broaden the study to transport coefficient of radiation damaged structures using molecular dynamics. Although molecular dynamics is tools for treating microscopic scale, most macroscopic issues related to nuclear materials such as voids in fuel materials and weakened mechanical properties by radiation are based on microscopic basis. Thus, research on microscopic scale would be expanded in this field and many hidden mechanism in atomic scales will be revealed via both atomic scale simulations and experiments

  10. Study on Surface Structure of U1-yGdyO2-x Using Raman Spectroscopy

    International Nuclear Information System (INIS)

    Lee, Jeong Mook; Kim, Jan Dee; Youn, Young Sang; Kim, Jong Goo; Ha, Yeong Keong; Kim, Jong Yun

    2016-01-01

    To understand the structural character of the spent nuclear fuel, rare earth element (REE) doped UO 2±x have been studied as simulated spent fuel. The REE doping effect has influence on the phase stability in U-FP-O system, thermal conductivity and the relevant fuel performance. Raman spectroscopy has been used to investigate surface structure of the nuclear fuel materials, because of its sensitivity, convenience and non-destructive sample preparation. The Raman studies on trivalent-doped UO 2 directly show the defect due to oxygen vacancy that could be created by loss of oxygen for charge compensation. This defect has significant effect on the kinetics of fuel oxidation. In this study, we have been investigated the effect on Gd-doping on the UO 2 structure with Raman spectroscopy to characterize the defect structure of nuclear fuel material. The oxygen deficiencies of pellets were estimated by the relation between the doping concentration and a lattice parameter evaluated from XRD spectra. The Raman spectra of U 1-y GdyO 2-x solid solution pellets show the distorted fluorite structure with defect structure due to oxygen vacancies with increasing Gd contents.

  11. Lattice parameters and electrical resistivity of Ceria-Yttria solid solutions

    International Nuclear Information System (INIS)

    Rey, Jose Fernando Queiruga

    2002-01-01

    Ce0 2 :u mol% Y 2 O 3 (u=0, 4, 6, 8, 10 and 12) solid solutions were prepared by the conventional powder mixture technique. The main purposes of this work are: the study of the dependence of the lattice parameter of the Ceria cubic phase on the Yttria content, comparing the experimental data with data calculated according to the existing theoretical models; to determine the dependence of the ionic conductivity on the Yttria content; and to study the stability of the cubic fluorite phase after extensive thermal treatments (aging) of the Ceria-Yttria specimens. The results show that the lattice parameter of the solid solutions follows the Vegard's law and can be described by the two reported theoretical models. The 8 mol% Yttria-doped Ceria was found to present the largest value of ionic conductivity. Preliminary results show that a large decrease is found for only 1 h aging at 700 deg C and that the ionic conductivity decreases for ceramic specimens aged for times up to 10 h. (author)

  12. Structure reconstruction of TiO2-based multi-wall nanotubes: first-principles calculations.

    Science.gov (United States)

    Bandura, A V; Evarestov, R A; Lukyanov, S I

    2014-07-28

    A new method of theoretical modelling of polyhedral single-walled nanotubes based on the consolidation of walls in the rolled-up multi-walled nanotubes is proposed. Molecular mechanics and ab initio quantum mechanics methods are applied to investigate the merging of walls in nanotubes constructed from the different phases of titania. The combination of two methods allows us to simulate the structures which are difficult to find only by ab initio calculations. For nanotube folding we have used (1) the 3-plane fluorite TiO2 layer; (2) the anatase (101) 6-plane layer; (3) the rutile (110) 6-plane layer; and (4) the 6-plane layer with lepidocrocite morphology. The symmetry of the resulting single-walled nanotubes is significantly lower than the symmetry of initial coaxial cylindrical double- or triple-walled nanotubes. These merged nanotubes acquire higher stability in comparison with the initial multi-walled nanotubes. The wall thickness of the merged nanotubes exceeds 1 nm and approaches the corresponding parameter of the experimental patterns. The present investigation demonstrates that the merged nanotubes can integrate the two different crystalline phases in one and the same wall structure.

  13. An anti CuO{sub 2}-type metal hydride square net structure in Ln{sub 2}M{sub 2}As{sub 2}H{sub x} (Ln = La or Sm, M = Ti, V, Cr, or Mn)

    Energy Technology Data Exchange (ETDEWEB)

    Mizoguchi, Hiroshi; Park, SangWon; Hosono, Hideo [Tokyo Institute of Technology, Yokohama (Japan). Materials Research Center for Element Strategy; Hiraka, Haruhiro; Ikeda, Kazutaka; Otomo, Toshiya [High-Energy Accelerator Research Organization (KEK), Tsukuba (Japan). Inst. of Materials Structure Science

    2015-03-02

    Using a high pressure technique and the strong donating nature of H{sup -}, a new series of tetragonal La{sub 2}Fe{sub 2}Se{sub 2}O{sub 3}-type layered mixed-anion arsenides, Ln{sub 2}M{sub 2}As{sub 2}H{sub x}, was synthesized (Ln=La or Sm, M=Ti, V, Cr, or Mn; x∼3). In these compounds, an unusual M{sub 2}H square net, which has anti CuO{sub 2} square net structures accompanying two As{sup 3-} ions, is sandwiched by (LaH){sub 2} fluorite layers. Notably, strong metal-metal bonding with a distance of 2.80 Aa was confirmed in La{sub 2}Ti{sub 2}As{sub 2}H{sub 2.3}, which has metallic properties. In fact, these compounds are situated near the boundary between salt-like ionic hydrides and transition-metal hydrides with metallic characters.

  14. An anti CuO{sub 2}-type metal hydride square net structure in Ln{sub 2}M{sub 2}As{sub 2}H{sub x} (Ln = La or Sm, M = Ti, V, Cr, or Mn)

    Energy Technology Data Exchange (ETDEWEB)

    Mizoguchi, Hiroshi; Park, SangWon; Hosono, Hideo [Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Hiraka, Haruhiro; Ikeda, Kazutaka; Otomo, Toshiya [Institute of Materials Structure Science, High-Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 (Japan)

    2015-03-02

    Using a high pressure technique and the strong donating nature of H{sup -}, a new series of tetragonal La{sub 2}Fe{sub 2}Se{sub 2}O{sub 3}-type layered mixed-anion arsenides, Ln{sub 2}M{sub 2}As{sub 2}H{sub x}, was synthesized (Ln=La or Sm, M=Ti, V, Cr, or Mn; x∼3). In these compounds, an unusual M{sub 2}H square net, which has anti CuO{sub 2} square net structures accompanying two As{sup 3-} ions, is sandwiched by (LaH){sub 2} fluorite layers. Notably, strong metal-metal bonding with a distance of 2.80 Aa was confirmed in La{sub 2}Ti{sub 2}As{sub 2}H{sub 2.3}, which has metallic properties. In fact, these compounds are situated near the boundary between salt-like ionic hydrides and transition-metal hydrides with metallic characters. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Design of high quality doped CeO2 solid electrolytes with nanohetero structure

    International Nuclear Information System (INIS)

    Mori, T.; Ou, D.R.; Ye, F.; Drennan, J.

    2006-01-01

    Doped cerium (CeO 2 ) compounds are fluorite related oxides which show oxide ionic conductivity higher than yttria-stabilized zirconia in oxidizing atmosphere. As a consequence of this, a considerable interest has been shown in application of these materials for low (400-650 o C) temperature operation of solid oxide fuel cells (SOFCs). In this paper, our experimental data about the influence of microstructure at the atomic level on electrochemical properties were reviewed in order to develop high quality doped CeO 2 electrolytes in fuel cell applications. Using this data in the present paper, our original idea for a design of nanodomain structure in doped CeO 2 electrolytes was suggested. The nanosized powders and dense sintered bodies of M doped CeO 2 (M:Sm,Gd,La,Y,Yb, and Dy) compounds were fabricated. Also nanostructural features in these specimens were introduced for conclusion of relationship between electrolytic properties and domain structure in doped CeO 2 . It is essential that the electrolytic properties in doped CeO 2 solid electrolytes reflect in changes of microstructure even down to the atomic scale. Accordingly, a combined approach of nanostructure fabrication, electrical measurement and structure characterization was required to develop superior quality doped CeO 2 electrolytes in the fuel cells. (author)

  16. Southern complex: geology, geochemistry, mineralogy, and mineral chemistry of selected uranium- and thorium-rich granites

    International Nuclear Information System (INIS)

    Hoffman, M.A.

    1987-01-01

    Four major rock groups are defined in the Southern Complex: the Bell Creek Granite (BCG), the Clotted Granitoids (CGR), the Albite Granite (AGR), and the Migmatite Complex. Metatexites of the Migmatite Complex are the oldest rocks and include paleosome of a metasedimentary and metavolcanic protolith represented by Banded Iron Formation, Banded Amphibolite, and Banded Gneisses, and interlayered or crosscutting leucogranites. The CGR span the range from metatexite to diatexite and represent in-situ partial melting of metapelitic layers in the protolith during intrusion of the BCG. The BCG cuts the migmatites, is locally cut by the CGR, and was derived by partial melting of a dominantly metasedimentary protolith at some depth below the presently exposed migmatites during a regional tectonothermal event. The Albite Granite is a 2km diameter, muscovite-fluorite-columbite-bearing intrusive stock that cuts all other major units. The thorium history of the BCG is a function of the history of monazite. The thorium history of the CGR is also dominated by monazite but the thorium content of this unit cannot be entirely accounted for by original restite monazite. The uranium history of the BCG and CGR was dominated by magmatic differentiation and post magmatic, metamorphic and supergene redistributions and is largely independent of the thorium history. The thorium and uranium history of the AGR was dominated by magmatic/deuteric processes unlike the BCG and CGR

  17. Effects of quartz on crystallization behavior of mold fluxes and microstructural characteristics of flux film.

    Science.gov (United States)

    Lei, Liu; Xiuli, Han; Mingduo, Li; Di, Zhang

    2018-01-01

    Mold fluxes are mainly prepared using cement clinker, quartz, wollastonite, borax, fluorite, soda ash and other mineral materials. Quartz, as one of the most common and essential materials, was chosen for this study to analyze itseffects on crystallization temperature, critical cooling rate, crystal incubation time, crystallization ratio and phases of flux film. We used the research methods of process mineralogy with the application of the single hot thermocouple technique, heat flux simulator, polarizing microscope, X-ray diffraction, etc. Results: By increasing the quartz content from 16 mass% to 24 mass%, the crystallization temperature, critical cooling rate and crystallization ratio of flux film decreased, and the crystal incubation time was extended. Meanwhile, the mineralogical structure of the flux film changed, with a large amount of wollastonite precipitation and a significant decrease in the cuspidine content until it reached zero. This showed a steady decline in the heat transfer control capacity of the flux film. The reason for the results above is that, by increasing the quartz content, the silicon-oxygen tetrahedron network structure promoted a rise in viscosity and restrained ion migration, inhibiting crystal nucleation and growth, leading to the weakening of the crystallization and a decline in the crystallization ratio.

  18. Oxide-ion and proton conducting electrolyte materials for clean energy applications: structural and mechanistic features.

    Science.gov (United States)

    Malavasi, Lorenzo; Fisher, Craig A J; Islam, M Saiful

    2010-11-01

    This critical review presents an overview of the various classes of oxide materials exhibiting fast oxide-ion or proton conductivity for use as solid electrolytes in clean energy applications such as solid oxide fuel cells. Emphasis is placed on the relationship between structural and mechanistic features of the crystalline materials and their ion conduction properties. After describing well-established classes such as fluorite- and perovskite-based oxides, new materials and structure-types are presented. These include a variety of molybdate, gallate, apatite silicate/germanate and niobate systems, many of which contain flexible structural networks, and exhibit different defect properties and transport mechanisms to the conventional materials. It is concluded that the rich chemistry of these important systems provides diverse possibilities for developing superior ionic conductors for use as solid electrolytes in fuel cells and related applications. In most cases, a greater atomic-level understanding of the structures, defects and conduction mechanisms is achieved through a combination of experimental and computational techniques (217 references).

  19. Atmospheric fluoride pollution. Part II

    Energy Technology Data Exchange (ETDEWEB)

    Hasegawa, T; Yamazaki, Y

    1969-01-01

    In East Osaka, agricultural crops either died or showed poor growth in the neighborhood of a factory producing white cosmetic bottles. Since fluorite was used as a material and there was no damage before the establishment of the factory, it was suspected that fluorine compounds were causing the damage. Quantitative analysis was performed on the agricultural crops and the exhaust gas as well as the dust particles in order to determine the fluorine content. Gas samplers were used to collect the dusts from the surrounding atmosphere. The fluorine content of dust near the factory was about 93 mg per cubic meter per day, and in some parts, as high as 1.54 mq per cubic meter per day. Relatively larger quantities of fluorine were measured at the southwestern and southeastern area of the factory, corresponding to the general wind pattern. Rice and soy beans from the neighborhood of the factory showed concentrations of fluorine and, especially in the leaves of the damaged crops, the concentrations were several hundred times higher than those of the undamaged leaves.

  20. Study on Surface Structure of U1-yGdyO2-x Using Raman Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jeong Mook; Kim, Jan Dee; Youn, Young Sang; Kim, Jong Goo; Ha, Yeong Keong; Kim, Jong Yun [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    To understand the structural character of the spent nuclear fuel, rare earth element (REE) doped UO{sub 2±x} have been studied as simulated spent fuel. The REE doping effect has influence on the phase stability in U-FP-O system, thermal conductivity and the relevant fuel performance. Raman spectroscopy has been used to investigate surface structure of the nuclear fuel materials, because of its sensitivity, convenience and non-destructive sample preparation. The Raman studies on trivalent-doped UO{sub 2} directly show the defect due to oxygen vacancy that could be created by loss of oxygen for charge compensation. This defect has significant effect on the kinetics of fuel oxidation. In this study, we have been investigated the effect on Gd-doping on the UO{sub 2} structure with Raman spectroscopy to characterize the defect structure of nuclear fuel material. The oxygen deficiencies of pellets were estimated by the relation between the doping concentration and a lattice parameter evaluated from XRD spectra. The Raman spectra of U{sub 1-y}GdyO{sub 2-x} solid solution pellets show the distorted fluorite structure with defect structure due to oxygen vacancies with increasing Gd contents.

  1. Thermodynamic modeling of mineralogical phases formed by continuous casting powders

    International Nuclear Information System (INIS)

    Romo-Castaneda, Julio; Cruz-Ramirez, Alejandro; Romero-Serrano, Antonio; Vargas-Ramirez, Marissa; Hallen-Lopez, Manuel

    2011-01-01

    A great amount of mineralogical phases were predicted and represented in stability phase diagrams, which were obtained by the use of the thermodynamic software FACTSage considering both the chemical composition and the melting temperature of the mould flux. Melting-solidification tests on commercial mould flux glasses for thin slab casting of steel revealed the existence of cuspidine (Ca 4 Si 2 O 7 F 2 ) as the main mineralogical phase formed during the flux solidification by X-ray powder diffraction (XRD). This phase directly influences the heat transfer phenomena from the strand to the mould and it is obtained with higher fluorite content (22% CaF 2 ). Cuspidine is desirable only in fluxes to produce medium carbon (included peritectic grade) steels, because it reduces the heat flux from the strand to the mould, thus controlling the shrinkage rate during the flux solidification. The experimental results are in agreement with those obtained by the thermodynamic software. The stability phase diagrams could be used as an important tool in the flux design for continuous casting process.

  2. Thermodynamic modeling of mineralogical phases formed by continuous casting powders

    Energy Technology Data Exchange (ETDEWEB)

    Romo-Castaneda, Julio [Metallurgy and Materials Department, Instituto Politecnico Nacional-ESIQIE, Apdo. P. 118-431, 07051 Mexico D.F. (Mexico); Cruz-Ramirez, Alejandro, E-mail: alcruzr@ipn.mx [Metallurgy and Materials Department, Instituto Politecnico Nacional-ESIQIE, Apdo. P. 118-431, 07051 Mexico D.F. (Mexico); Romero-Serrano, Antonio; Vargas-Ramirez, Marissa; Hallen-Lopez, Manuel [Metallurgy and Materials Department, Instituto Politecnico Nacional-ESIQIE, Apdo. P. 118-431, 07051 Mexico D.F. (Mexico)

    2011-01-10

    A great amount of mineralogical phases were predicted and represented in stability phase diagrams, which were obtained by the use of the thermodynamic software FACTSage considering both the chemical composition and the melting temperature of the mould flux. Melting-solidification tests on commercial mould flux glasses for thin slab casting of steel revealed the existence of cuspidine (Ca{sub 4}Si{sub 2}O{sub 7}F{sub 2}) as the main mineralogical phase formed during the flux solidification by X-ray powder diffraction (XRD). This phase directly influences the heat transfer phenomena from the strand to the mould and it is obtained with higher fluorite content (22% CaF{sub 2}). Cuspidine is desirable only in fluxes to produce medium carbon (included peritectic grade) steels, because it reduces the heat flux from the strand to the mould, thus controlling the shrinkage rate during the flux solidification. The experimental results are in agreement with those obtained by the thermodynamic software. The stability phase diagrams could be used as an important tool in the flux design for continuous casting process.

  3. High-throughput continuous hydrothermal synthesis of an entire nanoceramic phase diagram.

    Science.gov (United States)

    Weng, Xiaole; Cockcroft, Jeremy K; Hyett, Geoffrey; Vickers, Martin; Boldrin, Paul; Tang, Chiu C; Thompson, Stephen P; Parker, Julia E; Knowles, Jonathan C; Rehman, Ihtesham; Parkin, Ivan; Evans, Julian R G; Darr, Jawwad A

    2009-01-01

    A novel High-Throughput Continuous Hydrothermal (HiTCH) flow synthesis reactor was used to make directly and rapidly a 66-sample nanoparticle library (entire phase diagram) of nanocrystalline Ce(x)Zr(y)Y(z)O(2-delta) in less than 12 h. High resolution PXRD data were obtained for the entire heat-treated library (at 1000 degrees C/1 h) in less than a day using the new robotic beamline I11, located at Diamond Light Source (DLS). This allowed Rietveld-quality powder X-ray diffraction (PXRD) data collection of the entire 66-sample library in <1 day. Consequently, the authors rapidly mapped out phase behavior and sintering behaviors for the entire library. Out of the entire 66-sample heat-treated library, the PXRD data suggests that 43 possess the fluorite structure, of which 30 (out of 36) are ternary compositions. The speed, quantity and quality of data obtained by our new approach, offers an exciting new development which will allow structure-property relationships to be accessed for nanoceramics in much shorter time periods.

  4. Synthesis and characterization of new oxides and oxynitrides of niobium; Synthese und Charakterisierung neuer Oxide und Oxidnitride des Niobs

    Energy Technology Data Exchange (ETDEWEB)

    Orthmann, Steven

    2017-11-02

    By different synthesis routes the first oxide nitrides in the series scandium-niobium-oxygen-nitrogen could be synthesized and characterized. ScNb{sub 4}O{sub 7}N{sub 3}, which crystallizes in the rutile-type structure, exhibit a band gap of 2.62 eV after a short oxidation. Furthermore anion-deficit NbSc{sub 2}(O,N,□){sub 6} with fluorite-type structure could be synthesized. UV-Vis measurements point to a band gap of 3.36 eV after a short oxidation of the product. In the series zirconium-niobium-oxygen-nitrogen new oxides and oxide nitrides could be synthesized. By replacing zirconium with hafnium isotopical compounds with comparable composition could be obtained. The crystal structure of these new compounds is discussed respecting magnetism and the results of electron microscopy and neutron diffraction. By partially substitution of niobium with magnesium or zinc three additional oxide nitrides with the compositions Mg{sub 2}Nb{sub 4}O{sub 2}N{sub 5}, Zn{sub 2}NbO{sub 0,3}N{sub 2,8}, and ZnNb{sub 3}O{sub 0,1}N{sub 4,5}, showing a tetragonal Nb{sub 4}N{sub 5}-type structure, could be synthesized.

  5. Recovery of rare earth minerals, with emphasis on flotation process

    International Nuclear Information System (INIS)

    Houot, R.; Cuif, J.P.; Mottot, Y.; Samama, J.C.

    1991-01-01

    Bastnasite and monazite are the two major minerals used commercially to supply most of the rare earths. Monazite is often a by-product of the concentration of heavy minerals of zirconium and titanium in beach sands. Thus, the methods of concentration are gravity (spirals, Reichert cones and shaking tables), ending with magnetism, electrostatic and in certain cases, flotation. The two main deposits of bastnasite are Mountain Pass (U.S.A.) and Bayan Obo (China). The rock bastnasite content is within 15% and the recovery of rare earth minerals is made through flotation. The flowsheets are complex enough because the existence of accompanying minerals such as quartz, iron components, barite, fluorite, calcite, etc. The conditioning is done by heating and the frequently employed collector is a fatty acid associated with selective agents, as sodium silicate or fluosilicate, lignin sulphonate, sodium carbonate, aluminium salts, etc. Recent studies tempt to introduce the use of phosphoric esters, dicarboxilic, sulphonic and/or sulphosuccinic acids. Concentrates with 60% REO are then treated with acidic solution to eliminate residual calcite. The possibility of obtaining products enriched with rare earths are also noted: these are ores of uranium (Elliot Lake), pyrochlore, apatite, and other complex ores with euxenite, fergusonite or loparite. (author) 10 figs., 6 tabs., 57 refs

  6. Oxygen exchange and transport in dual phase ceramic composite electrodes.

    Science.gov (United States)

    Druce, John; Téllez, Helena; Ishihara, Tatsumi; Kilner, John A

    2015-01-01

    Composites consisting of a perovskite-based electronic or mixed conductor with a fluorite-structured ionic conductor are often used as electrodes in solid oxide electrochemical energy conversion devices. After sintering the materials, there is often evidence for inter-reaction between the two phases, or inter-diffusion of cations or impurities between the two phases. We studied the (18)O exchange properties of a composite consisting of CGO and LSCF in a 50 : 50 ratio. High resolution ToF-SIMS mapping reveals that the (18)O fraction at the very outer surface of grains of the CGO phase is much higher than expected from D* and k* values for the single-phase parent material. Surface compositional analysis by ToF-SIMS and low energy ion scattering (LEIS) spectroscopy suggests that the surfaces of the CGO grains in the composite do not show the impurities which typically segregate to the surface in single-phase CGO. Thus, the "cleaning" of impurities from the CGO surface by dissolution into the perovskite phase may be one explanation for the apparent enhanced surface exchange for CGO in these composites.

  7. Assessment of industrial minerals and rocks in the controlled area

    International Nuclear Information System (INIS)

    Castor, S.B.; Lock, D.E.

    1996-01-01

    Yucca Mountain in Nye County, Nevada, is a potential site for a permanent repository for high-level nuclear waste in Miocene ash flow tuff. The Yucca Mountain controlled area occupies approximately 98 km 2 that includes the potential repository site. The Yucca Mountain controlled area is located within the southwestern Nevada volcanic field, a large area of Miocene volcanism that includes at least four major calderas or cauldrons. It is sited on a remnant of a Neogene volcanic plateau that was centered around the Timber Mountain caldera complex. The Yucca Mountain region contains many occurrences of valuable or potentially valuable industrial minerals, including deposits with past or current production of construction aggregate, borate minerals, clay, building stone, fluorspar, silicate, and zeolites. The existence of these deposits in the region and the occurrence of certain mineral materials at Yucca Mountain, indicate that the controlled area may have potential for industrial mineral and rock deposits. Consideration of the industrial mineral potential within the Yucca Mountain controlled area is mainly based on petrographic and lithologic studies of samples from drill holes in Yucca Mountain. Clay minerals, zeolites, fluorite, and barite, as minerals that are produced economically in Nevada, have been identified in samples from drill holes in Yucca Mountain

  8. Thermoluminescence spectra of natural CaF2 irradiated by 10MeV electrons

    International Nuclear Information System (INIS)

    Manrique, J.; Angulo, S.; Pardo, M.P.; Gastesi, R.; De la Cruz, A.; Perez, A.

    2006-01-01

    The spectra of thermoluminescence from natural and electron-irradiated fluorite in the 350-800nm spectral range were studied between room temperature and 500 o C. The sample came from Asturias (Spain) and was analyzed by X-ray diffractometry and inductively coupled plasma-mass spectrometry. Glow peaks appeared at 115, 205 and 310 o C. Main emissions occurred at 475, 575, 650 and 745nm, attributed to the Dy +3 ion and, at 410nm, from electron-hole recombination. The fractional glow technique and the general order model were employed to study the emission at 575nm in detail. The results showed that the 115 and 205 o C glow peaks originate at traps with activation energies of 1.6 and 1.9eV, respectively, on the kinetic order of 1.5 and 1.3 and frequency factors of 1.7x10 19 and 2.7x10 19 s -1 , respectively. Spectrally resolved fading produced by storage was observed, and we concluded that the emission was due to large defect complexes. The dosimetric study showed that there was saturation at doses higher than 2kGy

  9. The effect of hydrothermal treatment on samaria and gadolinia doped ceria powders synthesized by coprecipitation

    International Nuclear Information System (INIS)

    Arakaki, Alexander Rodrigo; Yoshito, Walter Kenji; Ussui, Valter; Lazar, Dolores Ribeiro Ricci

    2009-01-01

    One of the main applications of ceria-based (CeO 2 ) ceramics is the manufacturing of Intermediate Temperature Solid Oxide Fuel Cells electrolytes. In order to improve ionic conductivity and densification of these materials various powder synthesis routes have been studied. In this work powders with composition Ce 0.8 (SmGd) 0.2 O 1.9h ave been synthesized by coprecipitation and hydrothermal treatment. A concentrate of rare earths containing 90wt% of CeO 2 and other containing 51% of Sm 2 O 3 and 30% of Gd 2 O 3 , both prepared from monazite processing, were used as precursor materials. The powders were characterized by X-ray diffraction, scanning and transmission electron microscopy, agglomerate size distribution by laser scattering and specific surface area by gas adsorption. Ceramic sinterability was evaluated by dilatometry and density measurements by Archimedes method. High specific surface area powders (~100m 2 /g) and cubic fluorite structure were obtained after hydrothermal treatment around 200 deg C. Ceramic densification was improved when compared to the one prepared from powders calcined at 800 deg C. (author)

  10. Analysis of synchrotron X-ray diffraction patterns from fluorotic enamel samples

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, Ana P.G.; Braz, Delson, E-mail: anapaulagalmeida@gmail.co [Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Lab. de Instrumentacao Nuclear; Colaco, Marcos V.; Barroso, Regina C., E-mail: cely@uerj.b [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil). Inst. de Fisica; Porto, Isabel M., E-mail: belporto@ig.com.b [Universidade Estadual de Campinas (UNICAMP), Piracicaba, SP (Brazil). Faculdade de Odontologia; Gerlach, Raquel F., E-mail: rfgerlach@forp.usp.b [Universidade de Sao Paulo (USP), Ribeirao Preto, SP (Brazil). Faculdade de Odontologia; Droppa Junior, Roosevelt, E-mail: rdroppa@lnls.b [Associacao Brasileira de Tecnologia de Luz Sincrotron (ABTLuS), Campinas, SP (Brazil)

    2009-07-01

    With the introduction of fluoride as the main anticaries agent used in preventive dentistry, and perhaps an increase in fluoride in our food chain, dental fluorosis has become an increasing world-wide problem. Visible signs of fluorosis begin to become obvious on the enamel surface as opacities, implying some porosity in the tissue. The mechanisms that conduct the formation of fluorotic enamel are unknown, but should involve modifications in the basics physical-chemistry reactions of demineralisation and remineralisation of the enamel of the teeth, which is the same reaction of formation of the enamel's hydroxyapatite (HAp) in the maturation phase. The increase of the amount of fluoride inside of the apatite will result in gradual increase of the lattice parameters. The hexagonal symmetry seems to work well with the powder diffraction data, and the crystal structure of HAp is usually described in space group P63/m. The aim of this work is to characterize the healthy and fluorotic enamel in human tooth using technique Synchrotron X-ray diffraction in order to determine the crystal structure and crystallinity of on fluoroapatite (FAp) crystal present in fluoritic enamel. All the scattering profile measurements was carried out at the X-ray diffraction beamline (XRD1) at the National Synchrotron Light Laboratory - LNLS, Campinas, Brazil. (author)

  11. NMR study of the structure and ion transport in the M1-xRxF2+x diamagnetic solid electrolytes

    International Nuclear Information System (INIS)

    Matsulv, A.N.; Nuznik, V.M.; Livshits, A.I.; Fedorov, P.P.; Sobolev, B.P.

    1988-01-01

    Monocrystalline samples of Sr 0.75 La 0.25 F 2.25 and Ba 0.75 Y 0.25 F 2.25 solid electrolytes, which belong to diamagnetic fluorite-like solid solutions, are investigated using 19 F continuous NMR method at 48 MHz frequency. Comparison of theoretical calculations and experimental data has allowed to attach component-spectra to two structural positions - F l main lattice one and F i interstitial one. A technique is suggested, and evaluation of density of structural positions is made on the basis of orientational dependences of spectra secondary moment. Change of spectra form and dispersion on heating is characteristic one for samples with ion diffusive movement. Analysis of experimental data has allowed to determine, that anionic systems of solid solutions are dinamically heterogeneous. At 290-470 K temperatures the florine ions of both types (F l and F i ) contribute to the ionic conductivity. Within this temperature range movement of the bulk of fluorine ions is more, than 10 4 Hz. Measurements, conducted for Sr 0.75 La 0.25 F 2.25 have shown, that fluorine ions in the interstitial positions are more mobile, than in the lattice ones

  12. Molecular dynamics studies of superionic conductors

    International Nuclear Information System (INIS)

    Rahman, A.

    1979-01-01

    Over the last fifteen years computer modeling of liquids and solids has become a useful method of understanding the structural and dynamical correlations in these systems. Some characteristics of the method are presented with an example from work on homogeneous nucleation in monoatomic liquids; the interaction potential determines the structure: a Lennard--Jones system nucleates a close packed structure while an alkali metal potential nucleates a bcc packing. In the study of ionic systems like CaF 2 the Coulomb interaction together with the short range repulsion is enough to produce a satisfactory model for the motion of F - ions in CaF 2 at approx. 1600 0 K. Analysis of this motion shows that F - ions reside at their fluorite sites for about 6 x 10 -12 s and that the diffusion is mainly due to F - jumps in the 100 direction. The motion can be analyzed in terms of the generation and annihilation of anti-Frenkel pairs. The temperature dependence of the F - diffusion constant at two different densities has also been calculated. The computer model does not correspond with experiment in this regard

  13. Modular automation in PET tracer manufacturing: application of an autosynthesizer to the production of 2-deoxy-2-[18F] fluoro-D-glucose

    International Nuclear Information System (INIS)

    Alexoff, D.L.; Russell, J.A.G.; Shiue, C.Y.; Wolf, A.P.; Fowler, J.S.; MacGregor, R.R.

    1986-01-01

    A compact autosynthesizer was developed and used successfully for the production of 2-deoxy-2-[ 18 F]fluoro-D-glucose [ 18 FDG] from gaseous acetyl hypo[ 18 F]fluorite. The autosynthesizer performs a sequence of general purpose synthesis procedures named Synthesis Unit Operations (SUOs). Each SUO is controlled through execution of a digital control algorithm with a BASIC language subroutine. This automatic synthesis system is based on two industry standard microcomputer architectures, the IBM PC and STD Bus, and it becomes a component of an evolving distributed microprocessor network of task-dedicated subsystems suitable for automated manufacturing of several useful radiotracers. The yield of 18 FDG product using the autosynthesizer and remote manually controlled purification procedures is approx. 20% EOB. Radiochemical purity of this product as measured by thin layer chromatography was 96-99%. Chemical purity of the product was measured to be approx. 96%. 2-Deoxy-2-fluoro-D-mannose impurity from this method was determined to be approx. 4%. (author)

  14. A robust NiO-Sm0.2Ce0.8O1.9 anode for direct-methane solid oxide fuel cell

    KAUST Repository

    Tian, Dong

    2015-07-02

    In order to directly use methane without a reforming process, NiO-Sm0.2Ce0.8O1.9 (NiO-SDC) nanocomposite anode are successfully synthesized via a one-pot, surfactant-assisted co-assembly approach for direct-methane solid oxide fuel cells. Both NiO with cubic phase and SDC with fluorite phase are obtained at 550 °C. Both NiO nanoparticles and SDC nanoparticles are highly monodispersed in size with nearly spherical shapes. Based on the as-synthesized NiO-SDC, two kinds of single cells with different micro/macro-porous structure are successfully fabricated. As a result, the cell performance was improved by 40%-45% with the new double-pore NiO-SDC anode relative to the cell performance with the conventional NiO-SDC anode due to a wider triple-phase-boundary (TPB) area. In addition, no significant degradation of the cell performance was observed after 60 hours, which means an increasing of long term stability. Therefore, the as-synthesized NiO-SDC nanocomposite is a promising anode for direct-methane solid oxide fuel cells.

  15. Study on Dy0.45Ba0.05Sr0.5Co0.8Fe0.2O3-δ-Ce0.85Gd0.15O1.95 composite cathode material for intermediate temperature solid oxide fuel cell

    Science.gov (United States)

    Kautkar, Pranay R.; Acharya, Smita A.

    2018-05-01

    xDy0.45Ba0.05Sr0.5Co0.8Fe0.2O3-δ - xCe0.85Gd0.15O1.95 (x = 50 %) composite cathode supported on Ce0.85Gd0.15O1.95 (GDC15) electrolyte are studied for applications in IT-SOFCs. Results attribute that Dy0.45Ba0.05Sr0.5Co0.8Fe0.2O3-δ material is chemically compatible with Ce0.85Gd0.15O1.95 (GDC15). Rietveld refined X-ray diffraction patterns notify orthorhombic (space group:Pbnm) symmetry for Dy0.45 Ba0.05Sr0.5Co0.8Fe0.2O3-δ and fluorite type structure (space group: Fm-3m) symmetry for GDC15. The polarization resistance (Rp) of composite cathode reduces to the minimum value of 1.35 Ω cm2 at 650 °C in air. Area specific resistance (ASR) of composite cathode has found 0.67 Ω.cm2 at 650°C respectively. Result shows that the surface diffusion of the dissociative adsorbed oxygen at electrode/electrolyte interface on the composite cathode.

  16. Study on the leaching behavior of actinides from nuclear fuel debris

    Science.gov (United States)

    Kirishima, Akira; Hirano, Masahiko; Akiyama, Daisuke; Sasaki, Takayuki; Sato, Nobuaki

    2018-04-01

    For the prediction of the leaching behavior of actinides contained in the nuclear fuel debris generated by the Fukushima Daiichi nuclear power plant accident in Japan, simulated fuel debris consisting of a UO2-ZrO2 solid solution doped with 137Cs, 237Np, 236Pu, and 241Am tracers was synthesized and investigated. The synthesis of the debris was carried out by heat treatment at 1200 °C at different oxygen partial pressures, and the samples were subsequently used for leaching tests with Milli-Q water and seawater. The results of the leaching tests indicate that the leaching of actinides depends on the redox conditions under which the debris was generated; for example, debris generated under oxidative conditions releases more actinide nuclides to water than that generated under reductive conditions. Furthermore, we found that, as Zr(IV) increasingly substituted U(IV) in the fluorite crystal structure of the debris, the actinide leaching from the debris decreased. In addition, we found that seawater leached more actinides from the debris than pure water, which seems to be caused by the complexation of actinides by carbonate ions in seawater.

  17. The Timber Mountain magmato-thermal event: An intense widespread culmination of magmatic and hydrothermal activity at the southwestern Nevada volcanic field

    International Nuclear Information System (INIS)

    Jackson, M.R. Jr.

    1988-05-01

    Eruption of the Rainier Mesa and Ammonia Tanks Members Timber Mountain Tuff at about 11.5 and 11.3 Ma, respectively, resulted in formation of the timber Mountain (TM) caldera; new K-Ar ages show that volcanism within and around the TM caldera continued for about 1 m.y. after collapse. Some TM age magmatic activity took place west and southeast of the TM caldera in the Beatty -- Bullfrog Hills and Shoshone Mountain areas, suggesting that volcanic activity at the TM caldera was an intense expression of an areally extensive magmatic system active from about 11.5 to 10Ma. Epithermal Au-Ag, Hg and fluorite mineralization and hydrothermal alteration are found in both within and surrounding the Timber Mountain -- Oasis Valley caldera complex. New K-Ar ages date this hydrothermal activity between about 13 and 10 Ma, largely between about 11.5 and 10 Ma, suggesting a genetic relation of hydrothermal activity to the TM magmatic system

  18. Hydrothermal mobilization of pegmatite-hosted REE and Zr at Strange Lake, Canada: A reaction path model

    Science.gov (United States)

    Gysi, Alexander P.; Williams-Jones, Anthony E.

    2013-12-01

    Petrological and geochemical observations of pegmatites in the Strange Lake pluton, Canada, have been combined with numerical simulations to improve our understanding of fluid-rock interaction in peralkaline granitic systems. In particular, they have made it possible to evaluate reaction paths responsible for hydrothermal mobilization and mineralization of rare earth elements (REE) and Zr. The focus of the study was the B-Zone in the northwest of the pluton, which contains a pegmatite swarm and is the target of exploration for an economically exploitable REE deposit. Many of the pegmatites are mineralogically zoned into a border consisting of variably altered primary K-feldspar, arfvedsonite, quartz, and zirconosilicates, and a core rich in quartz, fluorite and exotic REE minerals. Textural relationships indicate that the primary silicate minerals in the pegmatites were leached and/or replaced during acidic alteration by K-, Fe- and Al-phyllosilicates, aegirine, hematite, fluorite and/or quartz, and that primary zirconosilicates (e.g., elpidite) were replaced by gittinsite and/or zircon. Reaction textures recording coupled dissolution of silicate minerals and crystallization of secondary REE-silicates indicate hydrothermal mobilization of the REE. The mobility of the light (L)REE was limited by the stability of REE-F-(CO2)-minerals (basnäsite-(Ce) and fluocerite-(Ce)), whereas zirconosilicates and secondary gadolinite-group minerals controlled the mobility of Zr and the heavy (H)REE. Hydrothermal fluorite and fluorite-fluocerite-(Ce) solid solutions are interpreted to indicate the former presence of F-bearing saline fluids in the pegmatites. Numerical simulations show that the mobilization of REE and Zr in saline HCl-HF-bearing fluids is controlled by pH, ligand activity and temperature. Mobilization of Zr is significant in both saline HF- and HCl-HF-bearing fluids at low temperature (250 °C). In contrast, the REE are mobilized by saline HCl-bearing fluids

  19. Ionoluminscence of partially-stabilized zirconia for thermal barrier coatings

    International Nuclear Information System (INIS)

    Rebollo, N.R.; Ruvalcaba-Sil, J.L.; Miranda, J.

    2007-01-01

    Ionoluminescence is explored as an alternative technique to study the high temperature phase stability of zirconia-based oxides. The evolution of an initially metastable single tetragonal phase towards de-stabilization is investigated for three single-doped zirconia compositions with Y, Yb and Gd. The differences in de-stabilization paths are identified using X-ray diffraction and ionoluminescence; elemental analysis is also performed using particle-induced X-ray emission. X-ray diffraction studies reveal a different scenario for each of the compositions selected; the differences are strongly influenced by the thermodynamic driving forces associated to the fluorite-to-tetragonal displacive transformation. Ionoluminescence studies indicate a significant increment on the signal intensity for de-stabilized samples, relative to previous annealing stages. There are also more subtle differences in the luminescent response from the samples at intermediate annealing stages also related to phase changes. This study provides a basis to characterize phase evolution in single-doped zirconia compositions for thermal insulation applications using luminescence

  20. Order-disorder phase transformation in ion-irradiated rare earth sesquioxides

    International Nuclear Information System (INIS)

    Tang, M.; Valdez, J. A.; Sickafus, K. E.; Lu, P.

    2007-01-01

    An order-to-disorder (OD) transformation induced by ion irradiation in rare earth (RE) sesquioxides, Dy 2 O 3 , Er 2 O 3 , and Lu 2 O 3 , was studied using grazing incidence x-ray diffraction and transmission electron microscopy. These sesquioxides are characterized by a cubic C-type RE structure known as bixbyite. They were irradiated with heavy Kr ++ ions (300 keV) and light Ne + ions (150 keV) at cryogenic temperature (∼120 K). In each oxide, following a relatively low ion irradiation dose of ∼2.5 displacements per atom, the ordered bixbyite structure was transformed to a disordered, anion-deficient fluorite structure. This OD transformation was found in all three RE sesquioxides (RE=Dy, Er, and Lu) regardless of the ion type used in the irradiation. The authors discuss the irradiation-induced OD transformation process in terms of anion disordering, i.e., destruction of the oxygen order associated with the bixbyite structure

  1. Ion irradiation induced order-to-disorder transformations in δ-phase Sc4-xZr3+xO12+x/2

    International Nuclear Information System (INIS)

    Zhang, J.; Wang, Y.Q.; Tang, M.; Valdez, J.A.; Sickafus, K.E.

    2010-01-01

    The purpose of this study is to investigate the role of stoichiometry on crystal structure transformations in derivative fluorite compounds known as delta (δ) phase. In this study, polycrystalline δ-phase ceramic pellets were prepared with stoichiometries given by Sc 4-x Zr 3+x O 12+x/2 (x = 0, 0.77 and 1.20) . The pressed and polished pellets were then irradiated under cryogenic conditions with 200 keV Ne + ions to fluences ranging from 1-5 x 10 14 Ne/cm 2 . An order-to-disorder (O-D) transformation was observed for all compositions, as determined using grazing incidence X-ray diffraction (GIXRD). However, the transformation threshold dose was found to systematically decrease with increasing ZrO 2 content: ∼0.2, ∼0.16, and ∼0.08 dpa for Sc 4-x Zr 3+x O 12+x/2 with x = 0, 0.77, and 1.20, respectively. These irradiation-induced phase transformation results are discussed in terms of the crystal structure of the δ-phase.

  2. Assessing the hydrogeochemical processes affecting groundwater pollution in arid areas using an integration of geochemical equilibrium and multivariate statistical techniques.

    Science.gov (United States)

    El Alfy, Mohamed; Lashin, Aref; Abdalla, Fathy; Al-Bassam, Abdulaziz

    2017-10-01

    Rapid economic expansion poses serious problems for groundwater resources in arid areas, which typically have high rates of groundwater depletion. In this study, integration of hydrochemical investigations involving chemical and statistical analyses are conducted to assess the factors controlling hydrochemistry and potential pollution in an arid region. Fifty-four groundwater samples were collected from the Dhurma aquifer in Saudi Arabia, and twenty-one physicochemical variables were examined for each sample. Spatial patterns of salinity and nitrate were mapped using fitted variograms. The nitrate spatial distribution shows that nitrate pollution is a persistent problem affecting a wide area of the aquifer. The hydrochemical investigations and cluster analysis reveal four significant clusters of groundwater zones. Five main factors were extracted, which explain >77% of the total data variance. These factors indicated that the chemical characteristics of the groundwater were influenced by rock-water interactions and anthropogenic factors. The identified clusters and factors were validated with hydrochemical investigations. The geogenic factors include the dissolution of various minerals (calcite, aragonite, gypsum, anhydrite, halite and fluorite) and ion exchange processes. The anthropogenic factors include the impact of irrigation return flows and the application of potassium, nitrate, and phosphate fertilizers. Over time, these anthropogenic factors will most likely contribute to further declines in groundwater quality. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Synthesis, Optical and Electrochemical Properties of Y2O3 Nanoparticles Prepared by Co-Precipitation Method.

    Science.gov (United States)

    Saravanan, Thulasingam; Raj, Srinivasan Gokul; Chandar, Nagamuthu Raja Krishna; Jayavel, Ramasamy

    2015-06-01

    Y2O3 nanoparticles were synthesized by co-precipitation route using yttrium nitrate hexahydrate and ammonium hydroxide as precursors. The prepared sample was calcined at 500 degrees C and subjected to various characterization studies like thermal analysis (TG/DTA), X-ray diffraction (XRD), transmission electron microscope (TEM), UV-visible (UV-Vis) and photoluminescence (PL) spectroscopy. The XRD pattern showed the cubic fluorite structure of Y2O3 without any impurity peaks, revealing high purity of the prepared sample. TEM images revealed that the calcined Y2O3 nanoparticles consist of spherical-like morphology with an average particle size of 12 nm. The absorption spectrum of calcined samples shows blue-shift compared to the as-prepared sample, which was further confirmed by PL studies. The possible formation mechanism of Y2O3 nanoparticles has been discussed based on the experimental results. Electrochemical behavior of Y2O3 nanoparticles was studied by cyclic voltammetry to assess their suitability for supercapacitor applications.

  4. METALLOGENY OF EOCENE SYNCOLLISIONAL GRANITES OF MOTAJICA AND PROSARA MOUNTAINS

    Directory of Open Access Journals (Sweden)

    Ivan Jurković

    2004-12-01

    Full Text Available The geological setting is dominated by Eocene (48.7 Ma syncollisional granitoids in the form of a small pluton in the Motajica Mt. and in the form of numerous sills and dykes in the Prosara Mt. Microelement paragenesis of these magmatites, pegmatites, greisens and quartz veins are distinguished by U, Th, Ce, Y, P, Nb, Ta, B, Li, F, Be, Sn, Mo, W, Fe, Cu, Pb. These elements and 87Sr/86Sr and 18O isotopic values indicate the mantle origin of magma contaminated by relatively sterile lithospheric rocks. The most probable hypothesis of such a hybrid magma formation is the "slab break-off model". Deep erosion of Motajica granitoid pluton opened its acrobatholitic and epibatholitic level with numerous, but small pegmatite deposits (beryllites, tourmalinites, emeraldites and sylexites with piezoelectric quartz. Greisenization marked by strong silicification and muscovitization affected less than 1% of pluton. It is characterized by minor and accessory molybdenite, wolframite, huebnerite, scheelite, fluorite. Hydrothermal occurrences, galena and Fe minerals have only a mineralogical significance. Economically significant are numerous autochthonous kaolin deposits formed in Pliocene-Pleistocene time. Prosara apomagmatic granitoids, exclusively granite dykes are metallogenetically sterile.

  5. Mineralogy and Radioactivity of Some Pegmatite Bodies, Southeastern Sinai, Egypt

    International Nuclear Information System (INIS)

    Elnahas, H.A.

    2012-01-01

    The area under consideration constitutes the extreme eastern part of the Kid metamorphic belt in Sinai Peninsula. The Neoproterozoic rock units exposed there comprise gneisses, migmatites, old granitoids and monzogranites. Most of the pegmatite bodies encountered in the monzogranite rocks occur as plug-like bodies and veins of variable dimensions. These studied pegmatites are mainly of the simple unzoned type. They are composed of intergrowths of smoky quartz and pink K-feldspar with some accumulations of micas which host most of radioactive mineralizations. Radiomertrically, the concentration of eU ranges between 41 and 117ppm with an average of 73ppm, while eTh varies between 160 and 433ppm with an average of 223ppm. The Ra content reaches up to 94ppm with an average of 62ppm. The radioelements variation diagrams illustrate that the distribution of radioelements is due to both magmatic origin and hydrothermal redistribution. The high level of radioactivity in the studied granitic pegmatites is mainly resulted from the presence of ishikawaite, thorite, uranothorite, thorianite, zircon, fiptafite and fluorite. Most of the studied radioactive minerals commonly occur in the metamict state. Other accessory minerals like anatase, hematite and magnetite are also recorded. The study reports for the first time the presence of Ishikawaite-Th, where Th prevails U. Ishikawaite-Th grains contain exsolution intergrowths of ishikawaite-U and thorianite.

  6. Charge Distribution and Local Structure and Speciation in the UO2+x and PuO2+x Binary Oxides for x

    International Nuclear Information System (INIS)

    Conradson, Steven D.; Begg, Bruce D.; Clark, David L.; Den Auwer, Christophe J.; Ding, Mei; Dorhout, Peter K.; Espinosa-Faller, Francisco J.; Gordon, Pamela L.; Haire, Richard G.; Hess, Nancy J.; Hess, Ryan F.; Keogh, D. Webster; Lander, Gerard H.; Manara, Dario; Morales, Luis A.; Neu, Mary P.; Paviet-Hartmann, Patricia; Rebizant, Jean; Rondinella, Vincenzo V.; Runde, Wolfgang; Tait, C. Drew; Veirs, D. Kirk; Villella, Phillip M.; Wastin, Franck

    2005-01-01

    The local structure and chemical speciation of the mixed valence, fluorite-based oxides UO2+x (0.00pxp0.20) and PuO2+x/PuO2+x*y(OH)2y * zH2O have been determined by U/Pu LIII XAFS spectroscopy. The U spectra indicate (1) that the O atoms are incorporated as oxo groups at short (1.75A ? ) U?O distances consistent with U(VI) concomitant with a large range of U displacements that reduce the apparent number of U neighbors and (2) that the UO2 fraction remains intact implying that these O defects interact to form clusters and give the heterogeneous structure consistent with the diffraction patterns. The PuO2+x system, which does not show a separate phase at its x ? 0:25 endpoint, also displays (1) oxo groups at longer 1.9A ? distances consistent with Pu(V+d), (2) a multisite Pu?O distribution even when x is close to zero indicative of the formation of stable species with H2O and its hydrolysis products with O2*, and (3) a highly disordered, spectroscopically invisible Pu?Pu component. The structure and bonding in AnO2+x are therefore more complicated than have previously been assumed and show both similarities but also distinct differences among the different elements

  7. Charge Distribution and Local Structure and Speciation in the UO2+x and PuO2+x Binary Oxides for x <= 0.25

    Energy Technology Data Exchange (ETDEWEB)

    Conradson, Steven D.; Begg, Bruce D.; Clark, David L.; Den Auwer, Christophe J.; Ding, Mei; Dorhout, Peter K.; Espinosa-Faller, Francisco J.; Gordon, Pamela L.; Haire, Richard G.; Hess, Nancy J.; Hess, Ryan F.; Keogh, D. Webster; Lander, Gerard H.; Manara, Dario; Morales, Luis A.; Neu, Mary P.; Paviet-Hartmann, Patricia; Rebizant, Jean; Rondinella, Vincenzo V.; Runde, Wolfgang; Tait, C DREW.; Veirs, D. Kirk; Villella, Phillip M.; Wastin, Franck

    2005-02-01

    The local structure and chemical speciation of the mixed valence, fluorite-based oxides UO2+x (0.00pxp0.20) and PuO2+x/PuO2+x*y(OH)2y * zH2O have been determined by U/Pu LIII XAFS spectroscopy. The U spectra indicate (1) that the O atoms are incorporated as oxo groups at short (1.75A ? ) U?O distances consistent with U(VI) concomitant with a large range of U displacements that reduce the apparent number of U neighbors and (2) that the UO2 fraction remains intact implying that these O defects interact to form clusters and give the heterogeneous structure consistent with the diffraction patterns. The PuO2+x system, which does not show a separate phase at its x ? 0:25 endpoint, also displays (1) oxo groups at longer 1.9A ? distances consistent with Pu(V+d), (2) a multisite Pu?O distribution even when x is close to zero indicative of the formation of stable species with H2O and its hydrolysis products with O2*, and (3) a highly disordered, spectroscopically invisible Pu?Pu component. The structure and bonding in AnO2+x are therefore more complicated than have previously been assumed and show both similarities but also distinct differences among the different elements.

  8. Geological and geochronological evidence for the effect of Paleogene and Miocene uplift of the Northern Ordos Basin on the formation of the Dongsheng uranium district, China

    Science.gov (United States)

    Zhang, Chuang; Yi, Chao; Dong, Qian; Cai, Yu-Qi; Liu, Hong-Xu

    2018-02-01

    The Dongsheng uranium district, located in the northern part of the Ordos Basin, contains the largest known sandstone-hosted uranium deposit in China. This district contains (from west to east) the Daying, Nalinggou, and Dongsheng uranium deposits that host tens of thousands of metric tonnes of estimated recoverable uranium resources at an average grade of 0.05% U. These uranium orebodies are generally hosted by the lower member of the Zhiluo Formation and are dominantly roll or tabular in shape. The uranium deposits in this district formed during two stages of mineralization (as evidenced by U-Pb dating) that occurred at 65-60 and 25 Ma. Both stages generated coffinite, pitchblende, anatase, pyrite, and quartz, with or without sericite, chlorite, calcite, fluorite, and hematite. The post-Late Cretaceous uplift of the Northern Ordos Basin exposed the northern margins of the Zhiluo Formation within the Hetao depression at 65-60 Ma, introducing groundwater into the formation and generating the first stage of uranium mineralization. The Oligocene (∼25 Ma) uplift of this northern margin exposed either the entirety of the southern flank of the Hetao depression or only the clastic sedimentary part of this region, causing a second gravitational influx of groundwater into the Zhiluo Formation and forming the second stage of uranium mineralization.

  9. Synthesis and characterization of (Ba,Yb doped ceria nanopowders

    Directory of Open Access Journals (Sweden)

    Branko Matović

    2011-06-01

    Full Text Available Nanometric size (Ba, Yb doped ceria powders with fluorite-type structure were obtained by applying selfpropagating room temperature methods. Tailored composition was: Ce0.95−xBa0.05YbxO2−δ with fixed amount of Ba − 0.05 and varying Yb content “x” from 0.05 to 0.2. Powder properties such as crystallite and particle size and lattice parameters have been studied. Röntgen diffraction analyses (XRD were used to characterize the samples at room temperature. Also, high temperature treatment (up to 1550°C was used to follow stability of solid solutions. The mean diameters of the nanocrystals are determined from the full width at half maxima (FWHM of the XRD peaks. It was found that average diameter of crystallites is less than 3 nm. WilliamsonHall plots were used to separate the effect of the size and strain in the nanocrystals.

  10. Nanoscopic characterization of Pr2Zr2O7 at Zr sites

    International Nuclear Information System (INIS)

    Martinez, J.A.; Caracoche, M.C.; Rodriguez, A.M.; Rivas, P.C.; Bondioli, F.; Manfredini, T.; Ferrari, A.M.

    2005-01-01

    By using Perturbed Angular Correlation Spectroscopy, a suitable technique to explore internal fields at nanoscopic scale, the electric field gradients at Zr 4+ sites in the Pr 2 Zr 2 O 7 compound have been determined as a function of temperature. Three nonequivalent nanoconfigurations are present, which have been interpreted with the aid of point charge model calculations. Two of them correspond to pyrochlore - oxygen defective and perfect structures -, and the third one to the pyrochlore-related defect fluorite structure. The most abundant interaction is a disordered and fluctuating electric field gradient, which describes the oxygen defective pyrochlore. As temperature increases, its gradual and reversible transformation towards the perfect form is observed. Below 750 C the oxygen vacancies movement, which exhibits an activation energy of 0.14 eV, is assumed to be due to vacancies jumping among 48f equivalent sites. At higher temperatures the movement is interpreted as the fast diffusion of oxygen vacancies involving 48f and 8b sites, thus giving place to anionic disorder. The activation energy for this movement has been determined to be of 0.85 eV. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Fluoride in groundwater: toxicological exposure and remedies.

    Science.gov (United States)

    Jha, S K; Singh, R K; Damodaran, T; Mishra, V K; Sharma, D K; Rai, Deepak

    2013-01-01

    Fluoride is a chemical element that is found most frequently in groundwater and has become one of the most important toxicological environmental hazards globally. The occurrence of fluoride in groundwater is due to weathering and leaching of fluoride-bearing minerals from rocks and sediments. Fluoride when ingested in small quantities (dental health by reducing dental caries, whereas higher concentrations (>1.5 mg/L) may cause fluorosis. It is estimated that about 200 million people, from among 25 nations the world over, may suffer from fluorosis and the causes have been ascribed to fluoride contamination in groundwater including India. High fluoride occurrence in groundwaters is expected from sodium bicarbonate-type water, which is calcium deficient. The alkalinity of water also helps in mobilizing fluoride from fluorite (CaF2). Fluoride exposure in humans is related to (1) fluoride concentration in drinking water, (2) duration of consumption, and (3) climate of the area. In hotter climates where water consumption is greater, exposure doses of fluoride need to be modified based on mean fluoride intake. Various cost-effective and simple procedures for water defluoridation techniques are already known, but the benefits of such techniques have not reached the rural affected population due to limitations. Therefore, there is a need to develop workable strategies to provide fluoride-safe drinking water to rural communities. The study investigated the geochemistry and occurrence of fluoride and its contamination in groundwater, human exposure, various adverse health effects, and possible remedial measures from fluoride toxicity effects.

  12. Structure and thermal expansion of Lu2O3 and Yb2O3 up to the melting points

    Science.gov (United States)

    Pavlik, Alfred; Ushakov, Sergey V.; Navrotsky, Alexandra; Benmore, Chris J.; Weber, Richard J. K.

    2017-11-01

    Knowledge of thermal expansion and high temperature phase transformations is essential for prediction and interpretation of materials behavior under the extreme conditions of high temperature and intense radiation encountered in nuclear reactors. Structure and thermal expansion of Lu2O3 and Yb2O3 were studied in oxygen and argon atmospheres up to their melting temperatures using synchrotron X-ray diffraction on laser heated levitated samples. Both oxides retained the cubic bixbyite C-type structure in oxygen and argon to melting. In contrast to fluorite-type structures, the increase in the unit cell parameter of Yb2O3 and Lu2O3 with temperature is linear within experimental error from room temperature to the melting point, with mean thermal expansion coefficients (8.5 ± 0.6) · 10-6 K-1 and (7.7 ± 0.6) · 10-6 K-1, respectively. There is no indication of a superionic (Bredig) transition in the C-type structure or of a previously suggested Yb2O3 phase transformation to hexagonal phase prior to melting.

  13. Fluorescent minerals--A potential source of UV protection and visible light for the growth of green algae and cyanobacteria in extreme cosmic environments.

    Science.gov (United States)

    Omairi, Tareq; Wainwright, Milton

    2015-07-01

    We propose that green algae (Chlorella variabilis and Dunaliella tertiolecta) and cyanobacteria (Synechococcus elongatus and Nostoc commune) can grow inside fluorescent rock minerals which convert damaging UV light to visible light, thereby allowing these organisms to survive and thrive in UV-rich environments without (or with limited) visible light, which would otherwise be inimical to them. The four microorganisms were incubated inside fluorescent rocks composed of fluorite, calcite and pyrite. The resultant growth was then measured following exposure to UV radiation, with the use of optical density and measurement of chlorophyll concentration. Results show that the microorganisms were shielded from harmful UV in these semi-transparent rocks, while at the same time benefiting from the fact that the minerals converted UV to visible light; this have been shown by a statistically significant increase in their growth, which although lower than when the cells were incubated in sunlight, was significantly higher than in controls incubated in the dark. Copyright © 2015 The Committee on Space Research (COSPAR). Published by Elsevier Ltd. All rights reserved.

  14. Thermodynamic modeling of the CeO{sub 2}–CoO nano-phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sung S., E-mail: sungkim@wow.hongik.ac.kr

    2014-03-05

    Highlights: • The CeO{sub 2}–CoO nano-phase diagram was modeled thermodynamically. • The surface energies of the solution phases were modeled with Butler’s equation. • The present work agreed with the experimental work on the nanoparticle sintering. -- Abstract: A nano-phase diagram of the CeO{sub 2}–CoO system was modeled thermodynamically with experimental data available in the literatures. The surface energies of CeO{sub 2} and CoO unavailable in the literatures were estimated reasonably on the thermodynamic basis. Butler’s model was used to describe the surface energy and the surface composition of the solution phases and then the nano interaction parameters on the particle radius were assessed through the multiple linear regression method. A consistent set of optimized interaction parameters in the present system was derived for describing the Gibbs energy of liquid, fluorite, and halite solution phases as a function of particle radius. The eutectic temperatures calculated in the present work interpreted well the experimental data for the unusual low sintering temperature of the nanoparticles with the tri-modal particle size distribution. Furthermore, with the aid of the present result, the microstructure evolution in the CGO–CoO system during the nanoparticle sintering was described reasonably. It is concluded that the present modeling will be a good guide for the condition of the liquid phase sintering to obtain the rapid densification of the nanoparticles at lower temperatures.

  15. ROS mediated malignancy cure performance of morphological, optical, and electrically tuned Sn doped CeO2 nanostructures

    Science.gov (United States)

    Abbas, Fazal; Iqbal, Javed; Maqbool, Qaisar; Jan, Tariq; Ullah, Muhammad Obaid; Nawaz, Bushra; Nazar, Mudassar; Naqvi, M. S. Hussain; Ahmad, Ishaq

    2017-09-01

    To grapple with cancer, implementation of differentially cytotoxic nanomedicines have gained prime attention of the researchers across the globe. Now, ceria (CeO2) at nanoscale has emerged as a cut out therapeutic agent for malignancy treatment. Keeping this in view, we have fabricated SnxCe1-xO2 nanostructures by facile, eco-friendly, and biocompatible hydrothermal method. Structural examinations via XRD and FT-IR spectroscopy have revealed single phase cubic-fluorite morphology while SEM analysis has depicted particle size ranging 30-50nm for pristine and doped nanostructures. UV-Vis spectroscopy investigation explored that Sn doping significantly tuned the band gap (eV) energies of SnxCe1-xO2 nanostructures which set up the base for tremendous cellular reactive oxygen species (ROS) generations involved in cancer cells' death. To observe cytotoxicity, synthesized nanostructures were found selectively more toxic to neuroblastoma cell lines as compared to HEK-293 healthy cells. This study anticipates that SnxCe1-xO2 nanostructures, in future, might be used as nanomedicine for safer cancer therapy.

  16. The new insight into the structure-activity relation of Pd/CeO2-ZrO2-Nd2O3 catalysts by Raman, in situ DRIFTS and XRD Rietveld analysis.

    Science.gov (United States)

    Yang, X; Yang, L; Lin, J; Zhou, R

    2016-01-28

    Pd/CeO2-ZrO2-Nd2O3 (CZN) catalysts with different CeO2/ZrO2 molar ratios were synthesized and have been characterized by multiple techniques, e.g. XRD in combination with Rietveld refinement, UV-Raman, XPS and in situ DRIFTS. The XRD pattern of CZN with CeO2/ZrO2 molar ratios ≥1/2 can be indexed satisfactorily to the fluorite structure with a space group Fm3̄m, while the XRD patterns of CZ12 only display diffraction peaks of the tetragonal phase (S.G. P42/nmc). Nd addition can effectively stabilize the cubic structure of the CZN support and increase the enrichment of defect sites on the surface, which may be related to the better catalytic activity of Pd/CZN12 catalysts compared with Pd/CZ12. The presence of moderate ZrO2 can increase the concentration of O* active species, leading to accelerate the formation of nitrate species and thus enhance the catalytic activity of NOx and HC elimination. The Pd-dispersion decreases with the increasing Zr content, leading to the decreased CO catalytic activity, especially for the aged catalysts. The change regularity of the OSC value is almost the same with the in situ dynamic operational window, demonstrating that the in situ dynamic operational window is basically affected by the OSC value.

  17. Unusual behavior of uranium dioxide at high magnetic fields. Part I

    Science.gov (United States)

    Gofryk, K.; Jaime, M.; Zapf, V.; Harrison, N.; Saul, A.; Radtke, G.; Lashley, J. C.; Salamon, M.; Andersson, A. D.; Stanek, C.; Durakiewicz, T.; Smith, J. L.

    UO2 is a Mott-Hubbard insulator with well-localized 5 f-electrons and its crystal structure is the face-centered-cubic fluorite. It experiences a first-order antiferromagnetic phase transition at 30.8 K to a non-collinear antiferromagnetic structure that remains a topic of debate. It is believed that the first order nature of the transition results from the competition between the exchange interaction and the Jahn-Teller distortion of oxygen atoms. Despite extensive experimental and theoretical efforts the nature of the competing degrees of freedom and their couplings (such as spin-phonon coupling) are still unclear. Here we present results of our extensive thermodynamic investigations, on well-characterized and oriented single crystals of UO2, focusing on magnetization M(T,H) measurements in DC and pulsed magnetic fields to up 65 T at the NHMFL. Work supported by the Department of Energy, Office of Basic Energy Sciences, Materials Sciences, and Engineering Division. The NHMFL Pulsed Field Facility is supported by the NSF, the U.S. D.O.E., and the State of Florida through NSF cooperative Grant DMR.

  18. On the nature of the phase transition in uranium dioxide

    Science.gov (United States)

    Gofryk, K.; Mast, D.; Antonio, D.; Shrestha, K.; Andersson, D.; Stanek, C.; Jaime, M.

    Uranium dioxide (UO2) is by far the most studied actinide material as it is a primary fuel used in light water nuclear reactors. Its thermal and magnetic properties remain, however, a puzzle resulting from strong couplings between magnetism and lattice vibrations. UO2 crystalizes in the face-centered-cubic fluorite structure and is a Mott-Hubbard insulator with well-localized uranium 5 f-electrons. In addition, below 30 K, a long range antiferromagnetic ordering of the electric-quadrupole of the uranium moments is observed, forming complex non-collinear 3-k magnetic structure. This transition is accompanied by Jahn-Teller distortion of oxygen atoms. It is believed that the first order nature of the transition results from the competition between the exchange interaction and the Jahn-Teller distortion. Here we present results of our extensive thermodynamic investigations on well-characterized and oriented single crystals of UO2+x (x = 0, 0.033, 0.04, and 0.11). By focusing on the transition region under applied magnetic field we are able to study the interplay between different competing interactions (structural, magnetic, and electrical), its dynamics, and relationship to the oxygen content. We will discuss implications of these results. Work supported by the Department of Energy, Office of Basic Energy Sciences, Materials Sciences, and Engineering Division.

  19. Opto-electronic properties of bismuth oxide films presenting different crystallographic phases

    Energy Technology Data Exchange (ETDEWEB)

    Gomez, Celia L. [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Posgrado en Ciencia e Ingeniería de Materiales, UNAM, Unidad de Posgrado, Edificio C, Piso 1, Zona Cultural de CU, México, D.F. 04510 (Mexico); Depablos-Rivera, Osmary, E-mail: osmarydep@yahoo.com [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Posgrado en Ciencia e Ingeniería de Materiales, UNAM, Unidad de Posgrado, Edificio C, Piso 1, Zona Cultural de CU, México, D.F. 04510 (Mexico); Silva-Bermudez, Phaedra [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Instituto Nacional de Rehabilitación, Calz. México Xochimilco No. 289 Col. Arenal de Guadalupe, C.P.14389, Ciudad de México, D.F. (Mexico); Muhl, Stephen [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Zeinert, Andreas; Lejeune, Michael; Charvet, Stephane; Barroy, Pierre [Laboratoire de Physique de la Matière Condensée, Université de Picardie Jules Verne, 33 rue Saint Leu, 80039 Amiens Cedex 1 (France); Camps, Enrique [Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca S/N, kilómetro 36.5. La Marquesa, Municipio de Ocoyoacac, CP 52750, Estado de México (Mexico); Rodil, Sandra E. [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico)

    2015-03-02

    The optical, electrical and structural properties of bismuth oxide thin films deposited by radio frequency reactive magnetron sputtering were studied. The Bi{sub 2}O{sub 3} thin films were grown on Si and glass substrates under different power and substrate temperatures in an oxygen-enriched plasma leading to films with different crystalline phase as evidenced by X-ray diffraction and Raman spectroscopy. The optical properties of the films were measured using ellipsometric spectroscopy and optical transmission spectra. In order to parameterize the optical dispersion functions (n, k) of the films, the Tauc–Lorentz dispersion model was used. The optical bandgap was then assessed by different methods and the results are compared to the thermal variations of the electrical resistivity of the films. It was found that the refractive index, extinction coefficient and optical gap strongly depend on the deposition conditions and the crystalline phase; the fluorite defect cubic δ-Bi{sub 2}O{sub 3} phase showed the lowest optical gap and lower resistivity. - Highlights: • Different bismuth oxide phases were obtained by sputtering. • The power and substrate temperature were the two key parameters. • Room temperature delta-Bi{sub 2}O{sub 3} thin films were obtained. • The optical bandgap was around 1.5 and 2.2 eV, depending on the phase. • The bismuth oxide films presented activation energies around 1 eV.

  20. Gemstone deposits of Serbia

    Directory of Open Access Journals (Sweden)

    Miladinović Zoran

    2016-06-01

    Full Text Available Gemstone minerals in Serbia have never been regarded as an interesting and significant resource. Nevertheless, more than 150 deposits and occurrences have been recorded and some of them preliminarily explored in the last 50 years. The majority of deposits and occurrences are located within the Serbo-Macedonian metallogenic province and the most significant metallogenic units at the existing level of knowledge are the Fruska Gora ore district, Cer ore district, Sumadija metallogenic zone, Kopaonik metallogenic zone and Lece-Halkidiki metallogenic zone. The most important genetic type of deposits is hydrothermal, particularly in case of serpentinite/peridotite as host/parent rock. Placer deposits are also economically important. The dominant gemstones are silica minerals: chalcedony (Chrysoprase, carnelian, bluish chalcedony etc., jasper (picture, landscape, red etc., common opal (dendritic, green, milky white etc., silica masses (undivided, and quartz (rock crystal, amethyst etc.. Beside silica minerals significant gemstones in Serbia include also beryl (aquamarine, garnet (almandine and pyrope, tourmaline, fluorite, rhodochrosite, carbonate-silica breccia, carbonate-silica onyx, silicified wood, howlite, serpentinite, marble onyx, and kyanite. This paper aims to present an overview of Serbian gemstone deposits and occurrences and their position based on a simplified gemstone metallogenic map of Serbia, as well as genetic-industrial classification of gemstone deposits and gemstone varieties.

  1. Alteration history studies in the Exploratory Studies Facility, Yucca Mountain, Nevada, USA

    International Nuclear Information System (INIS)

    Levy, S.S.; Chipera, S.J.; Norman, D.I.

    1996-01-01

    By mid-1995, the Exploratory Studies Facility (ESF) extended about 1. 1 km from Exile Hill westward toward Yucca Mountain, mostly within densely welded, devitrfied Tiva Canyon Tuff. Secondary mineral occurrences in this unit include breccia cements of mordenite, a fibrous zeolite, and vapor-phase deposits of silica, alkali feldspar, apatite, hollandite, amphibole, and zircon. Calcite is also a common secondary mineral in faults and fractures. Studies of water and gas contents in fluid inclusions in calcites from a fault in nonwelded tuff and a fracture in densely welded tuff suggest mineral deposition under transient locally saturated conditions. Calcite in the nonwelded tuff incorporated air from the unsaturated tuff adjacent to the fault. A highly altered interval within pre-Pah Canyon tuffs just above the top of the Topopah Spring Tuff may be a fossil fumarole or other hydrothermal feature associated with cooling pyroclastic deposits, overprinted by later zeolitic alteration. The observed quartz, cristobalite, opal-CT, and fluorite have been widely identified as products of syngenetic devitrification and vapor-phase alteration in and above the Topopah Spring Tuff. Smectite, also an abundant secondary mineral at the ESF site, has been observed elsewhere at this stratigraphic level. Zeolitic alteration of nonwelded tuffs above the Topopah Spring Tuff, as seen in the ESF, has also been noted in drill core and outcrop at northeastern Yucca Mountain. The hydrologic and geochemical conditions that favored zeolitization only in certain areas of this stratigraphic interval have yet to be determined

  2. Lanthanum gallate and ceria composite as electrolyte for solid oxide fuel cells

    International Nuclear Information System (INIS)

    Li Shuai; Li Zhicheng; Bergman, Bill

    2010-01-01

    The composite of doped lanthanum gallate (La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 2.85 , LSGM) and doped ceria (Ce 0.8 Sm 0.2 O 1.9 , CSO) was investigated as an electrolyte for solid oxide fuel cell (SOFC). The LSGM-CSO composite was examined by X-ray diffraction (XRD) and impedance spectroscopy. It was found that the sintered LSGM-CSO composite contains mainly fluorite CeO 2 phase and a minority impurity phase, Sm 3 Ga 5 O 12 . The LSGM-CSO composite electrolyte shows a small grain boundary response in the impedance spectroscopy as compared to LSGM and CSO pellets. The composite electrolyte exhibits the highest conductivity in the temperature range of 250-600 o C, compared to LSGM and CSO. The LSGM-CSO composite can be expected to be an attractive intermediate temperature electrolyte material for solid oxide fuel cells.

  3. Diffusion pathway of mobile ions and crystal structure of ionic and mixed conductors. A brief review

    International Nuclear Information System (INIS)

    Yashima, Masatomo

    2009-01-01

    A brief review on the field of Solid State Ionics, including the diffusion pathway of mobile ions, crystal structure and materials, is presented. In the fluorite-structured ionic conductors such as ceria solid solution Ce 0.93 Y 0.07 O 1.96 , bismuth oxide solid solution δ-Bi 1.4 Yb 0.6 O 3 and copper iodide CuI, a similar curved diffusion pathway along the directions is observed. In the ionic and mixed conductors with the cubic ABO 3 perovskite-type structure such as lanthanum gallate and lanthanum cobaltite solid solutions, the mobile ions diffuse along a curved line keeping the interatomic distance between the B cation and O 2- anion to some degree. The structure and diffusion path of double-perovskite-type La 0.64 Ti 0.92 Nb 0.08 O 2.99 , K 2 NiF 4 -type (Pr 0.9 La 0.1 ) 2 (Ni 0.74 Cu 0.21 Ga 0.05 )O 4+δ , and apatite-type La 9.69 (Si 5.70 Mg 0.30 )O 26.24 are described. The diffusion paths of Li + ions in La 0.62 Li 0.16 TiO 3 and Li 0.6 FePO 4 are two- and one-dimensional, respectively. (author)

  4. Lanthanum gallate and ceria composite as electrolyte for solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Li Shuai, E-mail: shuail@kth.s [Department of Materials Science and Engineering, School of Industrial Engineering and Management, Royal Institute of Technology, SE 10044 Stockholm (Sweden); Li Zhicheng [School of Materials Science and Engineering, Central South University, 410083 Changsha, Hunan (China); Bergman, Bill [Department of Materials Science and Engineering, School of Industrial Engineering and Management, Royal Institute of Technology, SE 10044 Stockholm (Sweden)

    2010-03-04

    The composite of doped lanthanum gallate (La{sub 0.9}Sr{sub 0.1}Ga{sub 0.8}Mg{sub 0.2}O{sub 2.85}, LSGM) and doped ceria (Ce{sub 0.8}Sm{sub 0.2}O{sub 1.9}, CSO) was investigated as an electrolyte for solid oxide fuel cell (SOFC). The LSGM-CSO composite was examined by X-ray diffraction (XRD) and impedance spectroscopy. It was found that the sintered LSGM-CSO composite contains mainly fluorite CeO{sub 2} phase and a minority impurity phase, Sm{sub 3}Ga{sub 5}O{sub 12}. The LSGM-CSO composite electrolyte shows a small grain boundary response in the impedance spectroscopy as compared to LSGM and CSO pellets. The composite electrolyte exhibits the highest conductivity in the temperature range of 250-600 {sup o}C, compared to LSGM and CSO. The LSGM-CSO composite can be expected to be an attractive intermediate temperature electrolyte material for solid oxide fuel cells.

  5. Crystal structure and ion-diffusion pathway of inorganic materials through neutron diffraction

    International Nuclear Information System (INIS)

    Yashima, Masatomo

    2012-01-01

    The present brief review describes the application of neutron powder diffractometry and maximum-entropy method to the studies of crystal structure and diffusional pathways of mobile ions in ionic conducting ceramic materials. La 0.62 Li 0.16 TiO 3 and L i0.6 FePO 4 exhibit two- and one-dimensional networks of Li cation diffusional pathways, respectively. In the fluorite-structure ionic conductors such as celia solid solution Ce 0.93 Y 0.07 O 1.96 , bismuth oxide solid solution δ-Bi 1.4 Yb 0.6 O 3 and copper iodide CuI, a similar curved diffusion pathway along the directions is observed. In the cubic ABO 3 perovskite-type ionic conductor, lanthanum gallate solid solution, the mobile ions diffuse along a curved line keeping the interatomic distance between the B cation and O 2- anion. We have experimentally confirmed that the anisotropic thermal motions of the apex O2 atom and the interstitial O3 atoms are essential for the high oxygen permeability of the K 2 NiF 4 -type mixed conductor. Diffusion paths of proton are visualized along c axis in hexagonal hydroxyapatite. (author)

  6. A charge-optimized many-body potential for the U-UO2-O2 system

    Science.gov (United States)

    Li, Yangzhong; Liang, Tao; Sinnott, Susan B.; Phillpot, Simon R.

    2013-12-01

    Building on previous charge-optimized many-body (COMB) potentials for metallic α-U and gaseous O2, we have developed a new potential for UO2, which also allows the simulation of U-UO2-O2 systems. The UO2 lattice parameter, elastic constants and formation energies of stoichiometric and non-stoichiometric intrinsic defects are well reproduced. Moreover, this is the first rigid-ion potential that produces the correct deviation of the Cauchy relation, as well as the first classical interatomic potential that is able to determine the defect energies of non-stoichiometric intrinsic point defects in UO2 with an appropriate reference state. The oxygen molecule interstitial in the α-U structure is shown to decompose, with some U-O bonds approaching the natural bond length of perfect UO2. Finally, we demonstrate the capability of this COMB potential to simulate a complex system by performing a simulation of the α-U + O2 → UO2 phase transformation. We also identify a possible mechanism for uranium oxidation and the orientation of the resulting fluorite UO2 structure relative to the coordinate system of orthorhombic α-U.

  7. Thermochemistry of rare earth doped uranium oxides LnxU1-xO2-0.5x+y (Ln = La, Y, Nd)

    Science.gov (United States)

    Zhang, Lei; Navrotsky, Alexandra

    2015-10-01

    Lanthanum, yttrium, and neodymium doped uranium dioxide samples in the fluorite structure have been synthesized, characterized in terms of metal ratio and oxygen content, and their enthalpies of formation measured by high temperature oxide melt solution calorimetry. For oxides doped with 10-50 mol % rare earth (Ln) cations, the formation enthalpies from constituent oxides (LnO1.5, UO2 and UO3 in a reaction not involving oxidation or reduction) become increasingly exothermic with increasing rare earth content, while showing no significant dependence on the varying uranium oxidation state. The oxidation enthalpy of LnxU1-xO2-0.5x+y is similar to that of UO2 to UO3 for all three rare earth doped systems. Though this may suggest that the oxidized uranium in these systems is energetically similar to that in the hexavalent state, thermochemical data alone can not constrain whether the uranium is present as U5+, U6+, or a mixture of oxidation states. The formation enthalpies from elements calculated from the calorimetric data are generally consistent with those from free energy measurements.

  8. Energetics and Defect Interactions of Complex Oxides for Energy Applications

    Science.gov (United States)

    Solomon, Jonathan Michael

    The goal of this dissertation is to employ computational methods to gain greater insights into the energetics and defect interactions of complex oxides that are relevant for today's energy challenges. To achieve this goal, the development of novel computational methodologies are required to handle complex systems, including systems containing nearly 650 ions and systems with tens of thousands of possible atomic configurations. The systems that are investigated in this dissertation are aliovalently doped lanthanum orthophosphate (LaPO4) due to its potential application as a proton conducting electrolyte for intermediate temperature fuel cells, and aliovalently doped uranium dioxide (UO2) due to its importance in nuclear fuel performance and disposal. First we undertake density-functional-theory (DFT) calculations on the relative energetics of pyrophosphate defects and protons in LaPO4, including their binding with divalent dopant cations. In particular, for supercell calculations with 1.85 mol% Sr doping, we investigate the dopant-binding energies for pyrophosphate defects to be 0.37 eV, which is comparable to the value of 0.34 eV calculated for proton-dopant binding energies in the same system. These results establish that dopant-defect interactions further stabilize proton incorporation, with the hydration enthalpies when the dopants are nearest and furthest from the protons and pyrophosphate defects being -1.66 eV and -1.37 eV, respectively. Even though our calculations show that dopant binding enhances the enthalpic favorability of proton incorporation, they also suggest that such binding is likely to substantially lower the kinetic rate of hydrolysis of pyrophosphate defects. We then shift our focus to solid solutions of fluorite-structured UO 2 with trivalent rare earth fission product cations (M3+=Y, La) using a combination of ionic pair potential and DFT based methods. Calculated enthalpies of formation with respect to constituent oxides show higher

  9. Mineralogy, stable isotopes (δ18O and δ34S) and 40Ar-39Ar geochronology studies on the hydrothermal carapace of the Igarapé Manteiga W-Sn Deposit, Rondônia

    International Nuclear Information System (INIS)

    Nascimento, Thais Marcela Fernandes do; Souza, Valmir da Silva

    2017-01-01

    The Igarapé Manteiga W-Sn deposit is formed by a granite stock that intrudes in the Paleoproterozoic basement. The mineralization is encapsulated in an alumino-siliceous hydrothermal carapace formed by greisen, vein-veinlets and breccia, developed in the apex zone of a granite stock. At this site, wolframite, cassiterite and sulfides-minerals, as well as siderite, monazite, xenotime, hematite and others, are spread out or in massive clusters associated with quartz, topaz, zinnwaldite and fluorite. Wolframite is not zoned and relatively rich in Fe, and poor in Nb and Ta. Cassiterite exhibits growth-zones with light-yellow to dark-orange colors, and is rich in Ta, and poor in Ti, W, Mn and U. Oxygen and sulfur (δ 18 O and δ 34 S) isotope data on the ore- and sulfide-minerals indicates that it is a magmatic source, with closing temperatures from 230° C to 480° C. The hydrothermal phase was cyclical and protractedly active, promoting greisenization and hydrofracturing. The lowering of temperature and the change in the composition of fluids (from oxidized to reduced) controlled the precipitation of the hydrothermal mineral assemblage. The 40 Ar- 39 Ar analyses reveal a plateau age of 988 Ma, interpreted as the closure time for the hydrothermal processes responsible for mineralization, which is linked to the final magmatic evolution of the Rondônia Intrusive Suite (995-991Ma). (author)

  10. Synthesis and characterization of arsenic-doped cysteine-capped thoria-based nanoparticles

    International Nuclear Information System (INIS)

    Pereira, F. J.; Díez, M. T.; Aller, A. J.

    2013-01-01

    Thoria materials have been largely used in the nuclear industry. Nonetheless, fluorescent thoria-based nanoparticles provide additional properties to be applied in other fields. Thoria-based nanoparticles, with and without arsenic and cysteine, were prepared in 1,2-ethanediol aqueous solutions by a simple precipitation procedure. The synthesized thoria-based nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (ED-XRS), Raman spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and fluorescence microscopy. The presence of arsenic and cysteine, as well as the use of a thermal treatment facilitated fluorescence emission of the thoria-based nanoparticles. Arsenic-doped and cysteine-capped thoria-based nanoparticles prepared in 2.5 M 1,2-ethanediol solutions and treated at 348 K showed small crystallite sizes and strong fluorescence. However, thoria nanoparticles subjected to a thermal treatment at 873 K also produced strong fluorescence with a very narrow size distribution and much smaller crystallite sizes, 5 nm being the average size as shown by XRD and TEM. The XRD data indicated that, even after doping of arsenic in the crystal lattice of ThO 2 , the samples treated at 873 K were phase pure with the fluorite cubic structure. The Raman and FT-IR spectra shown the most characteristics vibrational peaks of cysteine together with other peaks related to the bonds of this molecule to thoria and arsenic when present

  11. Conductivity and structure of sub-micrometric SrTiO3-YSZ composites

    DEFF Research Database (Denmark)

    Ruiz Trejo, Enrique; Thydén, Karl Tor Sune; Bonanos, Nikolaos

    2016-01-01

    Sub-micrometric composites of SrTiO3-YSZ (1:1 volume) and samples of SrTiO3 were prepared by high temperature consolidation of precursors obtained by precipitation with NaOH. The structure development and morphology of the precursors were studied by XRD and SEM. The perovskite and fluorite phases...... in the composites are clearly formed at 600°C with no signs of reaction up to 1100°C; the nominally pure SrTiO3 can be formed at temperatures as low as 400°C. Composites with sub-micrometric grain sizes can be prepared successfully without reaction between the components, although a change in the cell parameter...... of the SrTiO3 is attributed to the presence of Na. The consolidated composites were studied by impedance spectroscopy between 200 and 400°C and at a fixed temperature of 600°C with a scan in the partial pressure of oxygen. The composites did not exhibit high levels of ionic conductivity in the grain...

  12. Effect of B-site cation stoichiometry on electrical fatigue of RuO2//Pb(ZrxTi1-x)O3//RuO2 capacitors

    International Nuclear Information System (INIS)

    Al-Shareef, H.N.; Tuttle, B.A.; Warren, W.L.; Headley, T.J.; Dimos, D.; Voigt, J.A.; Nasby, R.D.

    1996-01-01

    There have been numerous reports that Pb(Zr x Ti 1-x )O 3 (PZT) thin-film capacitors with RuO 2 electrodes and compositions near the morphotropic phase boundary exhibit minimal decrease in switched polarization with electric-field cycling. We show that the fatigue performance of RuO 2 //PZT//RuO 2 capacitors strongly depends on PZT film composition. Specifically, we demonstrate that the rate of polarization fatigue increases with increasing Ti content for PZT thin films of tetragonal crystal symmetry deposited on RuO 2 electrodes. As the Ti content of the PZT films increased, the film gain morphology changed from columnar to granular and the volume percent of a fluorite-type second phase decreased. These microstructural trends and the possibility that the electrode material acts as a sink for oxygen vacancies are discussed to explain the fatigue dependence on B-site cation ratio for PZT films with RuO 2 electrodes. copyright 1996 American Institute of Physics

  13. The electrode kinetics of the evolution and dissolution of oxygen at the urania-zirconia interfaces

    International Nuclear Information System (INIS)

    Badwal, S.P.S.; Bevan, D.J.M.; Bockris, J.O'M.

    1980-01-01

    In order to assess the potential of urania-yttria fluorite-type solid solutions as electrodes for high-temperature electrolysis of steam, oxygen evolution and dissolution reactions have been studied at the (Usub(0.7)Ysub(0.3))Osub (2+x)/YSZ interface. A current-interruption technique was used to separate overpotential and resistive potential drop. In oxygen and air the overpotential-current curves obey the Tafel law, suggesting that a charge-transfer process is rate determining. Activation energies of 120 kJ mole -1 and 165 kJ mole -1 were obtained for the cathodic reaction in oxygen and air respectively. The capacitance obtained from galvanostatic transients varied with potential, temperature, and oxygen partial pressure. The average value of n, the number of electrons involved in the overall charge-transfer reaction, was determined to be 4.01 from reversible potential measurements. The overpotential losses are small for porous electrodes at high psub(O 2 ). A mechanism for the oxygen transfer reaction has been proposed and its limitations discussed. (author)

  14. International Uranium Resources Evaluation Project (IUREP) national favourability studies: Thailand

    International Nuclear Information System (INIS)

    1977-08-01

    Thailand is a country with an area of 514?000 square kilometres situated in the centre of continental south-east Asia, The geology of Thailand is very varied with sedimentary formations ranging from Cambrian to Quaternary in age and including sandstones, shales, limestones of many varieties. Among the igneous rocks, granites are very important and rhyolites, tuffs diorites, basalts and ultrabasic rocks also exist. Tin is the most important mineral occurrence. Available information on the geology and mineral resources suggests that the country may contain significant resources of radioactive minerals. Favourable potential host types are; 1) uranium and thorium in monazite in beach sands and tin placer deposits; 2) uranium in sandstones, principally in Jurassic sandstones of the Khorat Plateau; 3) uranium in Tertiary lignite deposits; 4) uranium in veins in granites; 5) uranium related to fluorite deposits; 6) uranium in black shales and phosphates. Uranium mineralization in sedimentary rocks at Phu Wieng was discovered in 1970. The area has been radiometrically grid mapped and limited shallow drilling has shown continuity.of the narrow, carbonaceous, conglomeratic sandstone host bed. No uranium reserves or resources can be stated at the present time, but the favourable geology of the Khorat Plateau, the known uranium occurrence and the very small exploration coverage is possibly indicative of a good future potential. The Speculative Potential is estimated to be between 1000 and 10,000 tonnes uranium. (author)

  15. Synthesis, characterization and antibacterial activity of hybrid chitosan-cerium oxide nanoparticles: As a bionanomaterials.

    Science.gov (United States)

    Senthilkumar, R P; Bhuvaneshwari, V; Ranjithkumar, R; Sathiyavimal, S; Malayaman, V; Chandarshekar, B

    2017-11-01

    The hybrid chitosan cerium oxide nanoparticles were prepared for the first time by green chemistry approach using plant leaf extract. The intense peak observed around 292nm in the UV-vis spectrum indicate the formation of cerium oxide nanoparticles. The XRD pattern revealed that the hybrid chitosan-cerium oxide nanoparticles have a polycrystalline structure with cubic fluorite phase. The FTIR spectrum of prepared samples showed the formation of Ce-O bonds and chitosan main chains COC and CO. The FESEM image of hybrid chitosan cerium oxide nanoparticles revealed that the particles are spherical in shape with grains size varying from 23.12nm to 89.91nm. EDAX analysis confirmed the presence of Ce, O, C and N elements in the prepared sample. TEM images showed that the prepared hybrid chitosan-cerium oxide nanoparticles are predominantly uniform in size and most of the particles are spherical in shape with less agglomeration and the particles size varies from 3.61nm to 24.40nm. The prepared chitosan cerium oxide nanoparticles of 50μL concentration showed good antibacterial properties against test pathogens, which was confirmed by the FESEM analysis. The prepared small particle size facilitate that these hybrid ChiCO 2 NPs could effectively be used in biomedical applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Structure and Thermal Expansion of YSZ and La2Zr2O7 Above 1500°C from Neutron Diffraction on Levitated Samples

    International Nuclear Information System (INIS)

    Ushakov, Sergey V.; Neuefeind, Joerg C.

    2015-01-01

    High-temperature time-of-flight neutron diffraction experiments were performed in this paper on cubic yttria-stabilized zirconia (YSZ, 10 mol% YO 1.5 ) and lanthanum zirconate (LZ) prepared by laser melting. Three spheroids of each composition were aerodynamically levitated and rotated in argon flow and heated with a CO 2 laser. Unit cell, positional and atomic displacement parameters were obtained by Rietveld analysis. Below ~1650°C the mean thermal expansion coefficient (TEC) for YSZ is higher than for LZ (13 ± 1 vs. 10.3 ± 0.6) × 10 -6 /K. From ~1650°C to the onset of melting of LZ at ~2250°C, TEC for YSZ and LZ are similar and within (7 ± 2) × 10 -6 /K. LZ retains the pyrochlore structure up to the melting temperature with Zr coordination becoming closer to perfectly octahedral. Congruently melting LZ is La deficient. The occurrence of thermal disordering of oxygen sublattice (Bredig transition) in defect fluorite structure was deduced from the rise in YSZ TEC to ~25 × 10 -6 /K at 2350°C–2550°C with oxygen displacement parameters (U iso ) reaching 0.1 Å 2 , similar to behavior observed in UO 2 . Acquisition of powder-like high-temperature neutron diffraction data from solid-levitated samples is feasible and possible improvements are outlined. Finally, this methodology should be applicable to a wide range of materials for high-temperature applications.

  17. Radiation damage in natural materials: implications for radioactive waste forms

    International Nuclear Information System (INIS)

    Ewing, R.C.

    1981-01-01

    The long-term effect of radiation damage on waste forms, either crystalline or glass, is a factor in the evaluation of the integrity of waste disposal mediums. Natural analogs, such as metamict minerals, provide one approach for the evaluaton of radiation damage effects that might be observed in crystalline waste forms, such as supercalcine or synroc. Metamict minerals are a special class of amorphous materials which were initially crystalline. Although the mechanism for the loss of crystallinity in these minerals (mostly actinide-containing oxides and silicates) is not clearly understood, damage caused by alpha particles and recoil nuclei is critical to the metamictization process. The study of metamict minerals allows the evaluation of long-term radiation damage effects, particularly changes in physical and chemical properties such as microfracturing, hydrothermal alteration, and solubility. In addition, structures susceptible to metamictization share some common properties: (1) complex compositions; (2) some degree of covalent bonding, instead of being ionic close-packed MO/sub x/ structures; and (3) channels or interstitial voids which may accommodate displaced atoms or absorbed water. On the basis of these empirical criteria, minerals such as pollucite, sodalite, nepheline and leucite warrant careful scrutiny as potential waste form phases. Phases with the monazite or fluorite structures are excellent candidates

  18. Effect of oxygen partial pressure on the microstructural, optical and gas sensing characterization of nanostructured Gd doped ceria thin films deposited by pulsed laser deposition

    Directory of Open Access Journals (Sweden)

    Nagaraju P.

    2017-12-01

    Full Text Available Microstructural properties of 10 mol% gadolinium doped ceria (CeO2 thin films that were deposited on quartz substrate at substrate temperature of 1023 K by using pulsed laser deposition with different oxygen partial pressures in the range of 50–200 mTorr. The influence of oxygen partial pressure on microstructural, morphological, optical and gas sensing characterization of the thin films was systematically studied. The microstructure of the thin films was investigated using X-ray diffraction, atomic force microscopy and Raman spectroscopy. Morphological studies have been carried out using scanning electron microscope. The experimental results confirmed that the films were polycrystalline in nature with cubic fluorite structure. Optical properties of the thin films were examined using UV–vis spectrophotometer. The optical band gap calculated from Tauc’s relation. Gas sensing characterization has been carried at different operating temperatures (room temperature to 523 K for acetone gas. Response and recovery times of the sensor were calculated using transient response plot.

  19. Characterization of crystalline phases of (U,Er)O{sub 2} pellets by X-Ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Sansone, Alberto E.S.; Riella, Humberto G.; Carvalho, Elita F. U. de, E-mail: alberto.sansone@usp.br, E-mail: riella@enq.ufsc.br, E-mail: elitaucf@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2017-07-01

    Optimization of nuclear fuel for use in pressurized water reactors can be achieved by obtaining higher burnups. This, however, requires the excess reactivity caused by increasing the fuel's enrichment to be taken into account, which can be done by introducing burnable absorbers into the UO{sub 2} fuel pellets themselves. Some of the rare earth elements have thermal and mechanical properties that make them appropriate for use inside the reactor. In order to characterize the microstructure of erbium-doped UO{sub 2} fuel, sintered UO{sub 2}-Er{sub 2}O{sub 3} pellets were prepared, with Er{sub 2}O{sub 3} content ranging from 1:0 to 9:8wt%, and analyzed by X-ray diffraction to determine whether the composite formed solid solutions and, if so, evaluate the lattice parameter as a function of erbia concentration. While XRD analysis showed the Er{sub 2}O{sub 3} completely dissolved in the UO{sub 2} powder, it also evidenced the emergence of a second fluorite-type phase, whose phase fraction increases and lattice parameter decreases with increasing erbia concentration. Analysis of the diffraction patterns showed this emerging phase has the same crystalline structure as the host lattice, but with a smaller lattice parameter, and a smaller domain size. These results are compatible with the phenomenon of defect segregation, which consists in the formation of microdomains with a higher concentration of defects. (author)

  20. Mineralogical and chemical characteristics of marble of Bela Pola deposite

    International Nuclear Information System (INIS)

    Shijakova-Ivanova, Tena; Boev, Blazho; Panov, Zoran; Pavlov, Dejan

    2009-01-01

    This paper presents mineralogical characteristics of marbles from the Bela Pola deposit. We have made mineralogical-chemical analyses of marbles and associated minerals in them. The investigation was carried out at the Faculty of natural and technical sciences - Shtip. Marbles from Bela Pola are dolomite and dolomite-calcite types. Microscope investigations have shown that marbles from Bela Pola have granoblastic structure but at some places it can be found with porphyroblastic structures. Percentage on calcite and dolomite is: 94.08% dolomite, 6.25% is calcite in white marbles. On the other hand calcite is present with 93% in gray marbles. Except dolomite and calcite also appear the following accessoring minerals: quartz, fluorite, corundum and paragonite. In general, after summarizing all the facts, which have resulted from this research we could say that, the Bela Pola marbles are massive, compact and white with high quality. In accordance to all formerly mentioned features, this marbles can be classified in the commercial group of marbles suitable for external application or internal design

  1. Magnetic susceptibilities of Ca/sub y/U/sub 1-y/O/sub 2+x/ solid solutions

    International Nuclear Information System (INIS)

    Hinatsu, Y.; Fujino, T.

    1988-01-01

    Magnetic susceptibilities of Ca/sub y/U/sub 1-y/O/sub 2+x/ solid solutions with fluorite structure were measured from 4.2 K to room temperature. An antiferromagnetic transition was observed for all the solid solutions examined in this study (y ≤ 0.33). The Neel temperature of the oxygen-hypostoichiometric solid solutions (x 2 solid solutions, but different from that of (U,Th)O 2 solid solutions. The effective magnetic moment decreased with increasing calcium concentration, which indicates the oxidation of uranium in the solid solutions. From the analysis of the magnetic susceptibility data, it was found that the oxidation state of uranium was either tetravalent or pentavalent. The Neel temperature of the hyperstoichiometric solid solutions (x > 0) did not change appreciably with calcium concentrations. From the comparison of the magnetic susceptibility data of the hypostoichiometric solid solutions with those of the hyperstoichiometric solid solutions, the effect of oxygen vacancies is more significant than that of interstitial oxygens on the decrease of magnetic interactions between uranium ions

  2. Geochemical characterization and evaluation of groundwater suitability for domestic and agricultural utility in semi-arid region of Basara, Telangana State, South India

    Science.gov (United States)

    Adimalla, Narsimha; Venkatayogi, Sudarshan

    2018-03-01

    Hydrogeochemical investigations were carried out in semi-arid region of Basara to estimate the quality of groundwater for its suitability for domestic and agricultural purposes. For this region 34 groundwater samples were collected in different locations and analyzed for various ions, viz., Na+, Ca2+, Mg2+, K+, Cl-, HCO3 -, SO4 2-, CO3 2-, HCO3 -, NO3 - and F- to assess the water chemistry with sodium absorption ratio, %Na, residual sodium carbonate, magnesium hazard. The nitrate and fluoride concentrations were above the maximum permissible limit, while calcium, sodium, potassium and chloride were found below the desirable limits in most of the groundwater samples. The Wilcox diagram illustrates that 59% of the samples belong to excellent to good category, while the US Salinity Laboratory diagram indicates medium salinity/low sodium content in 64.70% of samples. In general, the geochemistry of groundwater in Basara region is influenced by the water rock processes through percolation and dissolution of rock forming minerals, while calculated values of saturation index for Anhydrite, Aragonite, Artinite, Brucite, Calcite, Fluorite, Gypsum, Dolomite and Magnesite of the groundwater samples were less than zero, indicating under-saturation. Chadha rectangular diagram for geochemical classification and hydrochemical processes of groundwater for Basara provinces indicates 50% of Na+-Cl-, 29% of Ca2+-Mg2+-Cl- and 18% of the water samples concentrate in the category of Na+-HCO3 - type.

  3. Structure of δ-Bi2O3 from density functional theory: A systematic crystallographic analysis

    International Nuclear Information System (INIS)

    Aidhy, Dilpuneet S.; Sinnott, Susan B.; Wachsman, Eric D.; Phillpot, Simon R.; Nino, Juan C.

    2009-01-01

    A systematic crystallographic analysis of the and vacancy-ordered structure of cubic δ-Bi 2 O 3 obtained from electronic-structure calculations is presented. The ordering of vacancies leads to a doubling of the unit-cell that results in a 2x2x2 fluorite super-structure, with an associated reduction in its space group symmetry from Fm3-barm to Fm3-bar. The Bi atoms present inside the vacancy-ordered oxygen sublattice have equal Bi-O bond lengths, whereas, those present inside the vacancy-ordered oxygen sublattice have three different pairs of Bi-O bond lengths. The specific ionic displacements and electronic charge configurations also depend on the nature of vacancy ordering in the oxygen sub-lattice. - Graphical abstract: 1/8 of a 2x2x2 δ-Bi 2 O 3 superstructure having Fm3-bar space group. Every oxygen (black) has three possible positions, only one of which is filled either by O1 (red) or O 2 (blue).

  4. The sedimentology, mineralogy and geochemistry of the Mooifontein deposit, Orange Free State

    International Nuclear Information System (INIS)

    Brynard, H.J.; Jakob, W.R.O.; Le Roux, J.P.

    1982-08-01

    The sedimentology, mineralogy and geochemistry of the Mooifontein deposit, which is situated north-west of Edenburg, Orange Free State, has been investigated. The orebody is located stratigraphically in the Adelaide Subgroup of the Karoo Sequence. Palaeocurrent and geological sections afford a picture of a fan-shaped distributary system and together with features such as small-scale channeling, cyclical deposition and an upward coarsening cycle, suggest a lacustrine-delta model of formation. The rocks constituting the deposit are feldspathic greywackes and feldspathic silt- and mudstones and can be divided into five texturally distinguishable groups. The mineralised lenses of the Mooifontein deposit attain a thickness of 7 m which can be split into two or three zones. The average grade of 0,85 kg U 3 O 8 /t is lower than that of the southern Karoo deposits (1 kg U 3 O 8 /t). The shallow depth of the orebody makes it amenable to open-cast mining. Molybdenum concentrations in the deposit are too low to be of economic significance. The sediments have low copper, vanadium and arsenic contents and the above-average calcite content of 9% will result in high acid consumption should an acid leaching process be used for uranium recovery. Both calcite and fluorite are unrelated to the uranium mineralisation. The deposit as a whole appears to have been little affected by post-genetic processes with only minor redistribution of uranium and moderate oxidation of organic carbon and sulphides

  5. The Morro do Resende orthogneiss: mineralogy, petrography, geochemistry and geochronology

    International Nuclear Information System (INIS)

    Vasconcelos, Fabiana Franco de; Avila, Ciro Alexandre; Bongiolo, Everton Marques; Camara, Beatriz de Oliveira; Menezes, Victor Hugo Riboura; Cunha, Fernanda Caetano de Mattos; Neumann, Reiner; Teixeira, Wilson; Barbosa, Natali

    2017-01-01

    The Morro do Resende orthogneiss is a hololeucocratic to leucocratic, fine-grained body with monzogranitic to granodioritic composition, cropping out near the Volta Grande mine in Nazareno County, State of Minas Gerais, Brazil. It bears xenoliths of metamafic rocks of the Rio das Mortes metavolcano-sedimentary sequence and yields a U-Pb SHRIMP crystallization age of 2174 ± 4 Ma, relating it to one of the magmatic pulses of the Mineiro Belt. The primary mineralogy includes quartz, albite, microcline, biotite, allanite, zircon, magnetite, titanite and apatite, while sericite, epidote, zoisite, clinozoisite, carbonate and chlorite are metamorphic minerals. Maghemite, barite, fluorite, monazite, xenotime, garnet and REE fluorides (possibly gagarinite) are hydrothermal, as they fill the fractures, intergrow or replace the primary and metamorphic minerals. Fluid interaction was not homogeneous throughout the body. Metamorphic paragenesis points to greenschist facies conditions, which could be related to the Paleoproterozoic II event of the Mineiro Belt, which lasted from 2131 to 2101 Ma. The Morro do Resende orthogneiss is distinguished by significant REE enrichment, as well as a negative Eu anomaly linked to the magmatic crystallization and a negative Ce anomaly related to oxidizing hydrothermal fluids circulation. (author)

  6. The ionic conductivity and local environment of cations in Bi9ReO17

    International Nuclear Information System (INIS)

    Thompson, M.; Herranz, T.; Santos, B.; Marco, J.F.; Berry, F.J.; Greaves, C.

    2010-01-01

    The influence of temperature on the structure of Bi 9 ReO 17 has been investigated using differential thermal analysis, variable temperature X-ray diffraction and neutron powder diffraction. The material undergoes an order-disorder transition at ∼1000 K on heating, to form a fluorite-related phase. The local environments of the cations in fully ordered Bi 9 ReO 17 have been investigated by Bi L III - and Re L III -edge extended X-ray absorption fine structure (EXAFS) measurements to complement the neutron powder diffraction information. Whereas rhenium displays regular tetrahedral coordination, all bismuth sites show coordination geometries which reflect the importance of a stereochemically active lone pair of electrons. Because of the wide range of Bi-O distances, EXAFS data are similar to those observed for disordered structures, and are dominated by the shorter Bi-O bonds. Ionic conductivity measurements indicate that ordered Bi 9 ReO 17 exhibits reasonably high oxide ion conductivity, corresponding to 2.9x10 -5 Ω -1 cm -1 at 673 K, whereas the disordered form shows higher oxide ion conductivity (9.1x10 -4 Ω -1 cm -1 at 673 K). - Graphical abstract: The structure of Bi 9 ReO 17 is discussed and related to the ionic conductivity of the ordered and disordered forms.

  7. Controllable deposition of gadolinium doped ceria electrolyte films by magnetic-field-assisted electrostatic spray deposition

    International Nuclear Information System (INIS)

    Ksapabutr, Bussarin; Chalermkiti, Tanapol; Wongkasemjit, Sujitra; Panapoy, Manop

    2013-01-01

    This paper describes a simple and low-temperature approach to fabrication of dense and crack-free gadolinium doped ceria (GDC) thin films with controllable deposition by a magnetic-field-assisted electrostatic spray deposition technique. The influences of external permanent magnets on the deposition of GDC films were investigated. The coating area deposited using two magnets with the same pole arrangement decreased in comparison with the case of no magnets, whereas the largest deposition area was obtained in the system of the opposite poles. Analysis of as-deposited films at 450 °C indicated the formation of uniform, smooth and dense thin films with a single-phase fluorite structure. The films produced in the system using same poles were thicker, smaller in crystallite size and smoother than those fabricated under other conditions. Additionally, the GDC film deposited using the same pole arrangement showed the maximum in electrical conductivity of about 2.5 × 10 −2 S/cm at a low operating temperature of 500 °C. - Highlights: • Magnetic-field-assisted electrostatic spray allows a controllable coating. • Dense, crack-free thin films were obtained at low process temperature of 450 °C. • Control of deposition, thickness and uniformity is easy to achieve simultaneously. • Films from the same pole were thicker, smaller in crystal size and smoother. • The maximum conductivity of doped ceria film was 2.5 × 10 −2 S/cm at 500 °C

  8. Detection and removal of fluorine in the waste gases of a steel smelter and measuring air quality in its surroundings

    Energy Technology Data Exchange (ETDEWEB)

    Graue, G; Nagel, H

    1968-01-01

    Plant damage in the Duisburg area was attributed to the action of fluoride supposedly originating in industrial waste gases, particularly of steel smelters. Air quality measurements were taken near a large steel smelter for a period of three years. After eliminating errors the total concentration of fluoride in the course of 3 years was established as between 2 and 6 mg/m/sup 2/ per day. Clearly, no free fluorine is emitted by steel smelters, although gaseous fluoride compounds can occur. Downstream from metallurgical furnaces, particularly where brown smoke is emitted, this fluoride is almost completely adsorbed by the dust. Ores and other raw materials in steel smelters are liable to contain fluorides, usually in the form of fluorite. Only a small proportion of this is liberated on the sintering band. However, since the sintering waste gases are acid, less fluoride is adsorbed by dust at this point and separated during dust collection. The use of desulfurization units downstream of the sintering bands could solve this problem. If, for the time being, nothing is done in this direction, it is because the fluoride contents of these gases do not play a significant role, due to the height of the stacks in use. This is supported by the results of extensive air purity measurements in the Duisburg region, in which fluoride levels between 1 and 3 ..mu..g were found per m/sup 3/ STP of air.

  9. Groundwater Quality of Southeastern Brazzaville, Congo

    Directory of Open Access Journals (Sweden)

    Matini Laurent

    2010-01-01

    Full Text Available The groundwater in southeastern Brazzaville (Congo was analyzed for their fluoride contents and others related parameters in rainy season. The fluoride contents in water samples (wells and spring can be gather in three classes in the study area: low, optimal, high. Fluoride concentration in water samples presents a low significant correlation with Ca2+. This suggests that fluoride in the groundwater come from fluoride-bearing minerals such as CaF2 (fluorite. Maps were drawn to show the geographical distribution of EC, Ca2+, Mg2+and F-. Factor analysis and cluster analysis were applied to the dataset. Factor analysis resulted in four factors explained 76.90% of the total groundwater quality variance. Factor 1 (hardness of the groundwater includes total hardness, the concentration of K+, Ca2+ and pH. Factor 2 (low mineralization of the groundwater includes concentrations of TDS, Cl--, SO42+ and EC. Factor 3 (anthropogenic activities with the impact of agricultural fertilizers, farming activities, domestic wastewater, septic tanks includes concentrations of Na+ and NO3-. Factor 4 (weathering of calcium minerals includes concentrations of F-. For cluster analysis, Ward’s method and the Euclidean distance were used. The findings of the cluster analysis are presented in the form of dendrogram of the well water sites (cases. The discriminating parameters between clusters have been highlighted from the Student test. In majority, they are in accordance with those highlighted by factor analysis.

  10. Oxidative Precipitation of Manganese from Acid Mine Drainage by Potassium Permanganate

    Directory of Open Access Journals (Sweden)

    Regeane M. Freitas

    2013-01-01

    Full Text Available Although oxidative precipitation by potassium permanganate is a widely recognised process for manganese removal, research dealing with highly contaminated acid mine drainage (AMD has yet to be performed. The present study investigated the efficiency of KMnO4 in removing manganese from AMD effluents. Samples of AMD that originated from inactive uranium mine in Brazil were chemically characterised and treated by KMnO4 at pH 3.0, 5.0, and 7.0. Analyses by Raman spectroscopy and geochemical modelling using PHREEQC code were employed to assess solid phases. Results indicated that the manganese was rapidly oxidised by KMnO4 in a process enhanced at higher pH. The greatest removal, that is, 99%, occurred at pH 7.0, when treated waters presented manganese levels as low as 1.0 mg/L, the limit established by the Brazilian legislation. Birnessite (MnO2, hausmannite (Mn3O4, and manganite (MnOOH were detected by Raman spectroscopy. These phases were consistently identified by the geochemical model, which also predicted phases containing iron, uranium, manganese, and aluminium during the correction of the pH as well as bixbyite (Mn2O3, nsutite (MnO2, pyrolusite (MnO2, and fluorite (CaF2 following the KMnO4 addition.

  11. Polyacrylamide-hydroxyapatite composite: Preparation, characterization and adsorptive features for uranium and thorium

    Science.gov (United States)

    Baybaş, Demet; Ulusoy, Ulvi

    2012-10-01

    The composite of synthetically produced hydroxyapatite (HAP) and polyacrylamide was prepared (PAAm-HAP) and characterized by BET, FT-IR, TGA, XRD, SEM and PZC analysis. The adsorptive features of HAP and PAAm-HAP were compared for UO22+ and Th4+. The entrapment of HAP into PAAm-HAP did not change the structure of HAP. Both structures had high affinity to the studied ions. The adsorption capacity of PAAm-HAP was than that of HAP. The adsorption dependence on pH and ionic intensity provided supportive evidences for the effect of complex formation on adsorption process. The adsorption kinetics was well compatible to pseudo second order model. The values of enthalpy and entropy changes were positive. Th4+ adsorption from the leachate obtained from a regional fluorite rock confirmed the selectivity of PAAm-HAP for this ion. In consequence, PAAm-HAP should be considered amongst favorite adsorbents for especially deposition of nuclear waste containing U and Th, and radionuclide at secular equilibrium with these elements.

  12. Recent progress in the development of anode materials for solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Cowin, Peter I.; Petit, Christophe T.G.; Lan, Rong; Tao, Shanwen [Department of Chemical and Process Engineering, University of Strathclyde, Glasgow G1 1XJ (United Kingdom); Irvine, John T.S. [School of Chemistry, University of St Andrews, St Andrews, Fife KY16 9ST (United Kingdom)

    2011-05-15

    The field of research into solid oxide fuel cell (SOFC) anode materials has been rapidly moving forward. In the four years since the last in-depth review significant advancements have been made in the reduction of the operating temperature and improvement of the performance of SOFCs. This progress report examines the developments in the field and looks to draw conclusions and inspiration from this research. A brief introduction is given to the field, followed by an overview of the principal previous materials. A detailed analysis of the developments of the last 4 years is given using a selection of the available literature, concentrating on metal-fluorite cermets and perovskite-based materials. This is followed by a consideration of alternate fuels for use in SOFCs and their associated problems and a short discussion on the effect of synthesis method on anode performance. The concluding remarks compile the significant developments in the field along with a consideration of the promise of future research. The recent progress in the development of anode materials for SOFCs based on oxygen ion conducting electrolytes is reviewed. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Mineralogy, stable isotopes (δ{sup 18}O and δ{sup 34}S) and {sup 40}Ar-{sup 39}Ar geochronology studies on the hydrothermal carapace of the Igarapé Manteiga W-Sn Deposit, Rondônia

    Energy Technology Data Exchange (ETDEWEB)

    Nascimento, Thais Marcela Fernandes do; Souza, Valmir da Silva, E-mail: thais.marcela@gmail.com, E-mail: valmirsouzaunb@gmail.com [Geosciences Postgraduate Program, Universidade Federal do Amazonas – UFAM, Manaus, AM (Brazil)

    2017-10-15

    The Igarapé Manteiga W-Sn deposit is formed by a granite stock that intrudes in the Paleoproterozoic basement. The mineralization is encapsulated in an alumino-siliceous hydrothermal carapace formed by greisen, vein-veinlets and breccia, developed in the apex zone of a granite stock. At this site, wolframite, cassiterite and sulfides-minerals, as well as siderite, monazite, xenotime, hematite and others, are spread out or in massive clusters associated with quartz, topaz, zinnwaldite and fluorite. Wolframite is not zoned and relatively rich in Fe, and poor in Nb and Ta. Cassiterite exhibits growth-zones with light-yellow to dark-orange colors, and is rich in Ta, and poor in Ti, W, Mn and U. Oxygen and sulfur (δ{sup 18}O and δ{sup 34}S) isotope data on the ore- and sulfide-minerals indicates that it is a magmatic source, with closing temperatures from 230° C to 480° C. The hydrothermal phase was cyclical and protractedly active, promoting greisenization and hydrofracturing. The lowering of temperature and the change in the composition of fluids (from oxidized to reduced) controlled the precipitation of the hydrothermal mineral assemblage. The {sup 40}Ar-{sup 39}Ar analyses reveal a plateau age of 988 Ma, interpreted as the closure time for the hydrothermal processes responsible for mineralization, which is linked to the final magmatic evolution of the Rondônia Intrusive Suite (995-991Ma). (author)

  14. Study on superstructure in ion co-doped BiFeO3 by using transmission electron microscopy

    Science.gov (United States)

    Pu, Shi-Zhou; Guo, Chao; Li, Mei-Ya; Chen, Zhen-Lian; Zou, Hua-Min

    2015-04-01

    La3+ and V5+ co-doped BiFeO3 ceramics are synthesized by rapid liquid sintering technique. The modulated structure in Bi0.85La0.15Fe0.97V0.03O3 is investigated by using transmission electron microscopy (TEM). Two kinds of superstructures are observed in the samples. One is the component modulated superstructure and twin-domain, which is generated by La3+ ordered substitution for Bi3+ and frequently appears. The chemical composition of the superstructure is explored by x-ray energy dispersive spectroscopy (EDS). The model of the ordered structure is proposed. Simulation based on the model is conducted. The second is the fluorite-type δ-Bi2O3 related superstructure. The relation between the ferroelectric property and the microstructure of the sample is also discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 51372174, 11074193, and 51132001) and the Fundamental Research Funds for the Central Universities.

  15. Photoemission properties of Eu-doped Zr1- x Ce x O2 (x = 0-0.2) nanoparticles prepared by hydrothermal method

    Science.gov (United States)

    Ozawa, Masakuni; Matsumoto, Masashi; Hattori, Masatomo

    2018-01-01

    Photoluminescent Eu-doped ZrO2 and Zr1- x Ce x O2 (x = 0-0.2) nanoparticles were prepared by a hydrothermal method. X-ray diffraction and Raman spectra indicated the formation of tetragonal crystals of ZrO2 and its solid solutions with a grain size of less than 10 nm diameter after heat treatment at 400 °C. The photoemission spectra of Zr1- x Ce x O2:Eu3+ nanocrystalline samples showed the typical emission of Eu3+ ions assigned to 5D0 → 7F1 (590 nm) and 5D0 → 7F2 (610 nm) transitions and additional emissions of 5D0 → 7F J with higher J of 3-5. Increasing the CeO2 concentration reduced the emission intensity, and the emission peak shift was affected by a local lattice distortion, i.e., CeO2 concentration. The present study provided fundamental knowledge that is expected to enable the fabrication of ZrO2-based nanocrystal phosphor materials and a measure for controlling the emission peak shift and intensity in oxide fluorite-based phosphor.

  16. A study of a ceria-zirconia-supported manganese oxide catalyst for combustion of Diesel soot particles

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez Escribano, V.; Fernandez Lopez, E.; del Hoyo Martinez, C. [Departamento de Quimica Inorganica, Facultad de Ciencias Quimicas, Pa. de la Merced s/n, E-37008 Salamanca (Spain); Gallardo-Amores, J.M. [Lab. Complutense de Altas Presiones, Departamento de Quimica Inorganica I, Universidad Complutense, Ciudad Universitaria, E-28040 Madrid (Spain); Pistarino, C.; Panizza, M.; Resini, C.; Busca, G. [Dipartimento di Ingegneria Chimica e di Processo, Universita di Genova, P.le J.F. Kennedy, Pad. D, I-16129 Genoa (Italy)

    2008-04-15

    A study has been conducted on the structural and morphological characterization of a Ce-Zr mixed oxide-supported Mn oxide as well as on its catalytic activity in the oxidation of particulate matter arising from Diesel engines. X-ray powder diffraction analysis (XRD) and FT-IR and FT-Raman spectroscopy evidence that the support is a fluorite-like ceria-zirconia solid solution, whereas the supported phase corresponds to the manganese oxide denoted as bixbyite ({alpha}-Mn{sub 2}O{sub 3}). Thermal analyses and FT-IR spectra in air at varying temperatures of soot mechanically mixed with the catalyst evidence that the combustion takes place to a total extent in the range 420-720 K, carboxylic species being detected as intermediate compounds. Moreover, the soot oxidation was studied in a flow reactor and was found to be selective to CO{sub 2}, with CO as by-product in the range 420-620 K. The amount of the generated CO decreases significantly with increasing O{sub 2} concentration in the feed. (author)

  17. Impact of stylolitization on diagenesis of a Lower Cretaceous carbonate reservoir from a giant oilfield, Abu Dhabi, United Arab Emirates

    Science.gov (United States)

    Paganoni, Matteo; Al Harthi, Amena; Morad, Daniel; Morad, Sadoon; Ceriani, Andrea; Mansurbeg, Howri; Al Suwaidi, Aisha; Al-Aasm, Ihsan S.; Ehrenberg, Stephen N.; Sirat, Manhal

    2016-04-01

    Bed-parallel stylolites are a widespread diagenetic feature in Lower Cretaceous limestone reservoirs, Abu Dhabi, United Arab Emirates (UAE). Diagenetic calcite, dolomite, kaolin and small amounts of pyrite, fluorite, anhydrite and sphalerite occur along and in the vicinity of the stylolites. Petrographic observations, negative δ18OVPDB, fluid inclusion microthermometry, and enrichment in 87Sr suggest that these cements have precipitated from hot basinal brines, which migrated along the stylolites and genetically related microfractures (tension gashes). Fluid migration was presumably related to lateral tectonic compression events related to the foreland basin formation. The low solubility of Al3 + in formation waters suggests that kaolin precipitation was linked to derivation of organic acids during organic matter maturation, probably in siliciclastic source rocks. The mass released from stylolitization was presumably re-precipitated as macro- and microcrystalline calcite cement in the host limestones. The flanks of the oilfield (water zone) display more frequent presence and higher amplitude of stylolites, lower porosity and permeability, higher homogenization temperatures and more radiogenic composition of carbonates compared to the crest (oil zone). This indicates that oil emplacement retards diagenesis. This study demonstrates that stylolitization plays a crucial role in fluid flow and diagenesis of carbonate reservoirs during basin evolution.

  18. Synthesis, crystal structure, and magnetic properties of pyrochlore-type Eu{sub 2}Ta{sub 2}(O,N){sub 7+δ}

    Energy Technology Data Exchange (ETDEWEB)

    Anke, Bjoern; Hund, Sophie; Lorent, Christian; Lerch, Martin [Institut fuer Chemie, Technische Universitaet Berlin (Germany); Janka, Oliver; Block, Theresa; Poettgen, Rainer [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster (Germany)

    2017-12-13

    Pyrochlore-type Eu{sub 2}Ta{sub 2}(O,N){sub 7+δ} phases were prepared by reaction of ammonia with an amorphous europium tantalum oxide precursor. {sup 151}Eu Moessbauer and EPR spectroscopy as well as magnetic susceptibility measurements point to the presence of exclusively Eu{sup 3+}. For phase-pure samples (X-ray powder diffraction), the nitrogen content varies between 1.0 and 1.8 wt %, leading to compositions in the range Eu{sub 2}Ta{sub 2}O{sub 7.1}N{sub 0.6} - Eu{sub 2}Ta{sub 2}O{sub 6.5}N{sub 1.0}. Pyrochlore-type phases are structurally derived from the fluorite type with 1/8 of the anions missing, resulting in an ideal composition A{sub 2}B{sub 2}X{sub 7}. In Eu{sub 2}Ta{sub 2}(O,N){sub 7+δ} the excess anions partly occupy these vacancies. The prepared phases are colorless with a direct optical bandgap of 4.3 eV and they show the typical Van Vleck paramagnetic behavior known for trivalent Eu atoms. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Hydrocarbon accumulation in deep fluid modified carbonate rock in the Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The activities of deep fluid are regionalized in the Tarim Basin. By analyzing the REE in core samples and crude oil, carbon isotope of carbon dioxide and inclusion temperature measurement in the west of the Tazhong Uplift in the western Tarim Basin, all the evidence confirms the existence of deep fluid. The deep fluid below the basin floor moved up into the basin through discordogenic fauit and volcanicity to cause corrosion and metaaomatosis of carbonate rock by exchange of matter and energy. The pore structure and permeability of the carbonate reservoirs were improved, making the carbonate reservoirs an excellent type of deeply buried modification. The fluorite ore belts discovered along the large fault and the volcanic area in the west of the Tazhong Uplift are the outcome of deep fluid action. Such carbonate reservoirs are the main type of reservoirs in the Tazhong 45 oilfield. The carbonate reservoirs in well YM 7 are improved obviously by thermal fluid dolomitization. The origin and territory of deep fluid are associated with the discordogenic fault and volcanicity in the basin. The discordogenic fault and volcanic area may be the pointer of looking for the deep fluid modified reservoirs. The primary characteristics of hydrocarbon accumulation in deep fluid reconstructed carbonate rock are summarized as accumulation near the large fault and volcano passage, late-period hydrocarbon accumulation after volcanic activity, and subtle trap reservoirs controlled by lithology.

  20. Synergic effect of the TiO2-CeO2 nanoconjugate system on the band-gap for visible light photocatalysis

    International Nuclear Information System (INIS)

    Contreras-García, M.E.; García-Benjume, M. Lorena; Macías-Andrés, Víctor I.; Barajas-Ledesma, E.; Medina-Flores, A.; Espitia-Cabrera, M.I.

    2014-01-01

    Graphical abstract: - Highlights: • Nanostructured TiO 2 -CeO 2 films are successfully synthesized by combining of sputtering and electrophoresis methods. • Synergic effect of CeO 2 on TiO 2 band gap was demonstrated, CeO 2 diminishes it from 3.125 to 2.74. • Morphologic characterization of the nanoconjugate TiO 2 -CeO 2 films by different microscopy techniques. - Abstract: The TiO 2 -CeO 2 photocatalytic system in films is proposed here, in order to obtain photocatalytic systems that can be excited by solar light. The films were obtained through the electrophoretic deposition (EPD) of TiO 2 -CeO 2 gel on sputtered Ti Corning glass substrates. The synergic effect of CeO 2 in TiO 2 films was analyzed as a function of the optical band gap reduction at different concentrations (1, 5, 10, and 15 mol%). The effect of two thermal treatments was also evaluated. The lowest band gap value was obtained for the sample with 5 mol% ceria that was thermally treated at 700 °C. The nanostructured films were characterized by Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high angle annular dark field (HAADF), high resolution transmission electron microscopy (HRTEM), and atomic force microscopy (AFM). The nanocomposites were formed by TiO 2 and CeO 2 nanoparticles in the anatase and fluorite type phases, respectively

  1. Crystal structure and charge density analysis of Li2NH by synchrotron X-ray diffraction

    International Nuclear Information System (INIS)

    Noritake, T.; Nozaki, H.; Aoki, M.; Towata, S.; Kitahara, G.; Nakamori, Y.; Orimo, S.

    2005-01-01

    Complex hydrides, such as lithium amide (LiNH 2 ) and lithium imide (Li 2 NH), have recently been noticed as one of the most promising materials for reversible hydrogen storage. In this paper, we reveal the bonding nature of hydrogen in Li 2 NH crystal by synchrotron powder X-ray diffraction measurement at room temperature. The crystal structure was refined by Rietveld method and the charge density distribution was analyzed by maximum entropy method (MEM). The Li 2 NH crystal is anti-fluorite type structure (space group Fm3-bar m) consisting of Li and NH. Hydrogen atom occupies randomly the 48h (Wyckoff notation) sites around N atom. The refined lattice constant is a=5.0742(2)A. The charge density distribution around NH anion in Li 2 NH is almost spherical. The number of electrons within the sphere around the Li and NH is estimated from the obtained charge density distribution. As the result, the ionic charge is expressed as [Li 0.99+ ] 2 [NH] 1.21- . Therefore, it is confirmed experimentally that Li 2 NH is ionically bonded

  2. Structure and defect studies of In2O3:Zn,Zr for higher stability TCO

    Science.gov (United States)

    Herwadkar, Aditi; Kim, Kwiseon

    2010-03-01

    The defects structures among the transparent conducting oxides (TCO) plays a major role in determining stability of the oxide over a temperature range and in tuning electrical and optical properties for the different TCO applications In2O3 crystallizes in the cubic bixbyite structure. The structure can be derived from the related fluorite structure by removing one fourth of the anions and allowing for small shifts of the ionic positions. In2O3 has two non-equivalent six-fold coordinated cation sites. For one of the sites, the cation is bounded by two structural vacancy along the body diagonal and for the other non-equivalent site the vacancies lie along the face diagonal. These vacancies are actually empty oxygen vacancy positions. Indium is in +3 charge state. ZnO on the other hand crystallizes to form wurtzite structure with four-fold coordination for Zn and is in +2 charge state where as the crystal structure of ZrO is rulite with Zr in +4 charge state and is four fold coordinated. Co-doping of Zn and Zr with each substituting the In atom satisfies the octet rule and is lower in energy then the individual substitutions with overall neutrality. The formation enthalpy as a function of pair (Zn, Zr) shows a minimum at experimental composition of In2(Zn,Zr)3O24. We in this work present the electronic structure optimization and study the defect states in this material.

  3. Properties of ceria doped with gadolinia via microwave-assisted hydrothermal synthesis

    International Nuclear Information System (INIS)

    Carregosa, J.D.C.; Oliveira, R.M.P.B.; Macedo, D.A.; Nascimento, R.M.

    2016-01-01

    The solid solution of CeO_2 doped with Gd"3"+ (CGO) is a promising candidate for electrolyte in Solid Oxide Full Cells (SOFCs) operating in intermediate and low temperatures. The reduction of the working temperature of these energy conversion devices is the great technological challenge to its marketing. In this work, nanocrystalline powders of Ce_1_-_xGd_xO_2_-_x_/_2 with x=0, x=0.1 e x=0.2 were obtained via microwave-hydrothermal synthesis at low temperature and times of synthesis (10 and 20 min at 120° C). The powders were analyzed by TG-DTA, DRX and dilatometry. The results showed characteristic peaks of the cubic fluorite-type structure, referring to the cerium oxide (CeO_2), without the presence of secondary peaks. It was also observed that the samples processed at levels of 10 and 20 minutes showed distinct behaviors in contrast to the concentrations of Gd"3"+. (author)

  4. STUDY OF BIREFRINGENCE INFLUENCE ON IMAGE QUALITY OF PHOTOLITHOGRAPHY SYSTEMS IN VIEW OF PARTIALLY-COHERENT LIGHT SOURCE

    Directory of Open Access Journals (Sweden)

    E. A. Nikulina

    2015-03-01

    Full Text Available Subject of study. A vector model for conversion of electromagnetic radiation in optical systems is considered, taking into account the influence of birefringence, as well as partially coherent illumination. Model. The proposed model is based on the representation of the complex amplitude of the monochromatic field through thesuperposition of basic plane waves. Transmitted light image with partially coherent illumination is performed by the sourceintegration method. Main results. The results of simulation for the point spread function are demonstrating the level of the birefringence influence on the image quality. In the presence of the wave aberration about 0.098 of the wavelength, the wave energy loss in the center of the Airy disk with an average birefringence of 4 nm/cm was 8%, and at 16 nm/cm it reached 30%. The calculation of the point spread function for a real sample of fluorite is given. The central peak of the PSF without birefringence was 0.722, with regard to birefringence it was equal to 0.701. Practical significance. The findings can be used in the development of photolithographic lenses, as well as for the manufacturing of any other optical systems that require consideration of the polarization properties of the materials.

  5. U-Pb, Pb-Pb, and K-Ar isotopic study and petrography of uraniferous phosphate-bearing rocks in the Thelon Formation, Dubawnt Group, Northwest Territories, Canada

    International Nuclear Information System (INIS)

    Miller, A.R.; Cumming, G.L.; Krstic, D.

    1989-01-01

    The Thelon Formation, uppermost unit of the Dubawnt Group, overlies a regionally extensive paleoweathered zone developed on a wide range of lithochronological units including formations in the lower Dubawnt Group. Authigenic uraniferous phosphate minerals, fluorapatite and goyazite, cementing Thelon conglomerate - sandstone and filling fractures in the underlying paleoweathered zone, were dated in an attempt to better constrain the age of Thelon sedimentation and diagenesis. The oldest age, 1720 ± 6 Ma, derived from phosphate-cemented sediments, is interpreted as a minimum age for diagenesis and therefore brackets initial Thelon sedimentation between emplacement of fluorite-bearing granites at 1753 Ma and authigenic phosphate cementation at 1720 Ma. Additional ages of 1685 ± 4 and 1647 Ma are interpreted as remobilization or subsequent cementation events. K-Ar ages on illite, 1386 ± 37 and 1266 ± 31 Ma, from the paleoweathered zone and basal conglomerate, respectively, are significantly younger than ages derived from coexisting phosphate. These K-Ar ages recorded hydrothermal events that may be related to processes associated with unconformity-type uranium mineralization at approximately 1400-1300 Ma. Ages from the Thelon Basin permit geochronologic correlations with the Athabasca and Hornby basins, long correlated on the basis of similarities in sedimentation, stratigraphy, and tectonic setting

  6. Petrographic characterization, geochemistry and age of the nepheline syenite of San Jose del Guaviare

    International Nuclear Information System (INIS)

    Arango Mejia, Maria Isabel; Zapata Garcia, Gilberto; Martens, Uwe

    2012-01-01

    The San Jose del Guaviare Nepheline Syenite includes two rock bodies that crop out 20 km SW of the town with the same name. The first of these bodies, which had already been reported by Vesga and Castillo (1972), is exposed in the La Pizarra area. The second body, which had not been previously reported, occurs in the Las Delicias area.Petrographic characterization shows that rocks correspond to nepheline syenite, nepheline monzosyenite, and feldspar + nepheline granofels. The main minerals in the rocks are microcline + nepheline + plagioclase + -- biotite + - arfvedsonite, and accessory phases include fluorite, sphene, apatite, garnet, zircon, epidote and calcite. Structures and textures are chiefly igneous in the la Pizarra body and mainly metamorphic (restitic) in the Las Delicias body. The geochemical character of the rocks is alkaline, and they correspond to within- the field of rocks formed in intraplate environment. The above features suggest that the San Jose del Guaviare syenite was formed by anatexis in a continental environment.U/Pb dating of zircon and 40Ar/39Ar (HS) dating of biotite indicates age 577.8+ -/0 6.3 - 9 Ma (Ediacaran) crystallization and 494+ - 5 Ma (late Cambrian) cooling.

  7. Fluoride ions vs removal technologies: A study

    Directory of Open Access Journals (Sweden)

    Jagvir Singh

    2016-11-01

    Full Text Available Literature reported that drinking water is a precious and scarce resource and it has to be protected and kept free from any kind of contamination. Further, it has to be used carefully without wasting. Literature also reported that fluoride bearing rocks are abundant in India, as a result, fluoride leaches out and contaminates the adjacent water and soil resources. A high concentration of fluoride ions in ground water increases up to more than 30 mg/L. This high concentration of fluoride ions causes many harmful and dangerous effects on our datum. Fluoride ions in larger quantities i.e. 20–80 mg/day taken over a period of 10–20 years result in crippling and skeletal fluorosis, severely damaging the bone. In the present scenario, there is a continuously increasing worldwide concern for the development of fluoride treatment technologies. Possibilities of reducing the high fluorine content in groundwater are by defluorination process/dilution with the surface water which is a very simple technique but the addition of Ca2+ ions to a solution in contact with fluorite when experimented in distilled water caused an appreciable decrease in fluoride concentration. In this review article, we emphasized the relationship between high concentrations of fluoride ions and their compounds and their health impact.

  8. Opto-electronic properties of bismuth oxide films presenting different crystallographic phases

    International Nuclear Information System (INIS)

    Gomez, Celia L.; Depablos-Rivera, Osmary; Silva-Bermudez, Phaedra; Muhl, Stephen; Zeinert, Andreas; Lejeune, Michael; Charvet, Stephane; Barroy, Pierre; Camps, Enrique; Rodil, Sandra E.

    2015-01-01

    The optical, electrical and structural properties of bismuth oxide thin films deposited by radio frequency reactive magnetron sputtering were studied. The Bi 2 O 3 thin films were grown on Si and glass substrates under different power and substrate temperatures in an oxygen-enriched plasma leading to films with different crystalline phase as evidenced by X-ray diffraction and Raman spectroscopy. The optical properties of the films were measured using ellipsometric spectroscopy and optical transmission spectra. In order to parameterize the optical dispersion functions (n, k) of the films, the Tauc–Lorentz dispersion model was used. The optical bandgap was then assessed by different methods and the results are compared to the thermal variations of the electrical resistivity of the films. It was found that the refractive index, extinction coefficient and optical gap strongly depend on the deposition conditions and the crystalline phase; the fluorite defect cubic δ-Bi 2 O 3 phase showed the lowest optical gap and lower resistivity. - Highlights: • Different bismuth oxide phases were obtained by sputtering. • The power and substrate temperature were the two key parameters. • Room temperature delta-Bi 2 O 3 thin films were obtained. • The optical bandgap was around 1.5 and 2.2 eV, depending on the phase. • The bismuth oxide films presented activation energies around 1 eV

  9. FORECASTING MODEL OF GHG EMISSION IN MANUFACTURING SECTORS OF THAILAND

    Directory of Open Access Journals (Sweden)

    Pruethsan Sutthichaimethee

    2017-01-01

    Full Text Available This study aims to analyze the modeling and forecasting the GHG emission of energy consumption in manufacturing sectors. The scope of the study is to analysis energy consumption and forecasting GHG emission of energy consumption for the next 10 years (2016-2025 and 25 years (2016-2040 by using ARIMAX model from the Input-output table of Thailand. The result shows that iron and steel has the highest value of energy consumption and followed by cement, fluorite, air transport, road freight transport, hotels and places of loading, coal and lignite, petrochemical products, other manufacturing, road passenger transport, respectively. The prediction results show that these models are effective in forecasting by measured by using RMSE, MAE, and MAPE. The results forecast of each model is as follows: 1 Model 1(2,1,1 shows that GHG emission will be increasing steadily and increasing at 25.17% by the year 2025 in comparison to 2016. 2 Model 2 (2,1,2 shows that GHG emission will be rising steadily and increasing at 41.51% by the year 2040 in comparison to 2016.

  10. Y3Fe5O12/Na,Bi,Sr-doped PZT particulate magnetoelectric composites

    Science.gov (United States)

    Lisnevskaya, I. V.; Bobrova, I. A.; Lupeiko, T. G.; Agamirzoeva, M. R.; Myagkaya, K. V.

    2016-05-01

    Magnetoelectric (ME) composites of Na, Bi, Sr substituted lead zirconate titanate (PZT) and yttrium iron garnet having representative formula (100-x) wt% Na,Bi,Sr-doped PZT (PZTNB-1)+x wt% Y3Fe5O12 (YIG) with x=10-90 were manufactured using powdered components obtained through sol-gel processes. It is shown that the decrease in sintering temperature provided by the use of finely dispersed PZTNB-1 and YIG powders allows to significantly reduce content of fluorite-like foreign phase based on zirconium oxide, which forms due to the interfacial interaction during heat treatment and becomes stabilized by yttrium oxide. Connectivity has considerable effect on the value of ME coefficient of composite ceramics. With the same x value, ΔE/ΔH characteristic decreases when changing from 0-3-type structured composites (PZT grains embedded in ferrite matrix) to 3-3-(interpenetrating network of two phases) and especially 3-0-type samples (YIG grains embedded in PZT matrix); in the last case this can be attributed to the substrate clamping effect when ferrite grains are clamped with piezoelectric matrix. ΔE/ΔH value of 0-3 composites with x=40-60 wt% was found to be ∼1.6 mV/(cm Oe).

  11. The dielectric track and thermoluminescent detectors applied to neutron dosimetry in personnel monitoring

    International Nuclear Information System (INIS)

    Mebhah, D.

    1984-03-01

    The personnal dosimeter for neutron based on the detection of fission fragments from 237 Np and 232 Th by a polycarbonate 10 gm, and lithium fluorite 6 LIF/ 7 LIF, allow to cover an energy spectrum from 0.05 eV to 14 MeV with a easy neutron gamma discrimination. In criticality dosimetry, the energy spectrum of the incident neutrons can be defined by two components: the fast component by E b exp(-ae) with E between 0.1 and 14 MeV, a and b determined by a combination of 237 Np and 232 Th track detector responses, and the epithermal component in 1/E, the thermal component having a minor contribution to the total equivalent dose. We took into account the body influence on the detectors response by introducing effective cross section. The equivalent dose obtained by this dosimeter is 20% overestimated in low doses dosimetry. The interpretation of the detectors responses is based on the definition of a factor and a calibration parameter for each zone in which the spectrum is constant. The knowledge of this parameter for individual dosimeters allows to account for the variations of the conditions of calibration

  12. Fundamental aspects of Am and Cm in zirconia-based materials. Investigations using X-ray diffraction and Raman spectroscopy

    International Nuclear Information System (INIS)

    Raison, P.E.; Haire, R.G.; Assefa, Z.

    2002-01-01

    We have investigated incorporation of americium and curium in selected zirconia-based materials. Fundamental aspects were explored via X-ray diffraction and Raman spectroscopy. First explored was the pseudo ternary system, AmO 2 -ZrO 2 -Y 2 O 3 . It was found that stable, cubic solid solutions (Am x Zr 1-x Y y )O 2-2/y can be obtained for selected compositions. The cell parameters of the cubic phases were established as being linear with the AmO 2 content. For the Cm 2 O 3 -ZrO 2 system, it was determined that diphasic materials are produced, except for two compositions: 25 mol% and 50 mol% of CmO 1.5 . For these compositions a single-phase cubic fluorite type solid solution (a=5.21A±0.01) and a pyrochlore oxide Cm 2 Zr 2 O 7 (a=10.63A±0.02) are formed, respectively. The stability of pyrochlore oxides is also being investigated as a function of self-irradiation, using shorter-lived isotopes, one being the californium pyrochlore 249 Cf 2 Zr 2 O 7 . We obtained evidence that after six months of storage the pyrochlore oxide is undergoing structural change. Additional studies are in progress. (author)

  13. Co-occurrence of arsenic and fluoride in groundwater of semi-arid regions in Latin America: genesis, mobility and remediation.

    Science.gov (United States)

    Alarcón-Herrera, María Teresa; Bundschuh, Jochen; Nath, Bibhash; Nicolli, Hugo B; Gutierrez, Melida; Reyes-Gomez, Victor M; Nuñez, Daniel; Martín-Dominguez, Ignacio R; Sracek, Ondra

    2013-11-15

    Several million people around the world are currently exposed to excessive amounts of arsenic (As) and fluoride (F) in their drinking water. Although the individual toxic effects of As and F have been analyzed, there are few studies addressing their co-occurrences and water treatment options. Several studies conducted in arid and semi-arid regions of Latin America show that the co-occurrences of As and F in drinking water are linked to the volcaniclastic particles in the loess or alluvium, alkaline pH, and limited recharge. The As and F contamination results from water-rock interactions and may be accelerated by geothermal and mining activities, as well as by aquifer over-exploitation. These types of contamination are particularly pronounced in arid and semi-arid regions, where high As concentrations often show a direct relationship with high F concentrations. Enrichment of F is generally related to fluorite dissolution and it is also associated with high Cl, Br, and V concentrations. The methods of As and F removal, such as chemical precipitation followed by filtration and reverse osmosis, are currently being used at different scales and scenarios in Latin America. Although such technologies are available in Latin America, it is still urgent to develop technologies and methods capable of monitoring and removing both of these contaminants simultaneously from drinking water, with a particular focus towards small-scale rural operations. Copyright © 2012 Elsevier B.V. All rights reserved.

  14. Geochemical criteria for distinguishing magmatic and metasomatic albite-enrichment in granitoids — examples from the Ta-Li granite Yichun (China) and the Sn-W deposit Tikus (Indonesia)

    Science.gov (United States)

    Schwartz, M. O.

    1992-03-01

    Two examples of albite-rich granitoids of different genesis are discussed: the Ta-Li granite at Yichun (China) exhibits dominantly igneous textures, and the sodium-enrichment zone in biotite granite of the Sn-W deposit at Tikus is characterized by metasomatic textures. The Yichun stock shows a magmatic evolution from biotite-muscovite granite to lepidolite granite with an increase of Na2O and F concentrations and a decrease of CaO and Sr concentrations. The composition of the different granite phases is close to pseudoternary minima in the haplogranite-H2O(-Li-F) system. The composition of the F-rich albitization zone at Tikus deviates strongly from the pseudoternary minima and shows a tendency to become monomineralic (nearly pure albitite). CaO and Sr concentrations are increased or remain unchanged with respect to the unaltered biotite granite at Tikus. Albitization produced by fluid-rock interaction in F-rich systems is characterized by that CaO or Sr released by the breakdown of plagioclase in the granite protolith, are fixed in newly formed fluorite or albite, respectively.

  15. Amphoteric oxide semiconductors for energy conversion devices: a tutorial review.

    Science.gov (United States)

    Singh, Kalpana; Nowotny, Janusz; Thangadurai, Venkataraman

    2013-03-07

    In this tutorial review, we discuss the defect chemistry of selected amphoteric oxide semiconductors in conjunction with their significant impact on the development of renewable and sustainable solid state energy conversion devices. The effect of electronic defect disorders in semiconductors appears to control the overall performance of several solid-state ionic devices that include oxide ion conducting solid oxide fuel cells (O-SOFCs), proton conducting solid oxide fuel cells (H-SOFCs), batteries, solar cells, and chemical (gas) sensors. Thus, the present study aims to assess the advances made in typical n- and p-type metal oxide semiconductors with respect to their use in ionic devices. The present paper briefly outlines the key challenges in the development of n- and p-type materials for various applications and also tries to present the state-of-the-art of defect disorders in technologically related semiconductors such as TiO(2), and perovskite-like and fluorite-type structure metal oxides.

  16. Chemical characteristics of the major thermal springs of Montana

    Energy Technology Data Exchange (ETDEWEB)

    Mariner, R.H.; Presser, T.S.; Evans, W.C.

    1976-07-01

    Twenty-one thermal springs in western Montana were sampled for chemical, isotope, and gas compositions. Most of the springs issue dilute to slightly saline sodium-bicarbonate waters of neutral to slightly alkaline pH. A few of the springs issue sodium-mixed anion waters of near neutral pH. Fluoride concentrations are high in most of the thermal waters, up to 18 miligrams per litre, while F/Cl ratios range from 3/1 in the dilute waters to 1/10 in the slightly saline waters. Most of the springs are theoretically in thermodynamic equilibrium with respect to calcite and fluorite. Nitrogen is the major gas escaping from most of the hot springs; however, Hunters Hot Springs issue principally methane. The deuterium content of the hot spring waters is typical of meteoric water in western Montana. Geothermal calculations based on silica concentrations and Na-K-Ca ratios indicate that most of the springs are associated with low temperature aquifers (less than 100/sup 0/C). Chalcedony may be controlling the silica concentrations in these low temperature aquifers even in ''granitic'' terranes.

  17. Synthesis, Characterization and Thermal Diffusivity of Holmium and Praseodymium Zirconates

    Directory of Open Access Journals (Sweden)

    Stopyra M.

    2016-06-01

    Full Text Available A2B2O7 oxides with pyrochlore or defected fluorite structure are among the most promising candidates for insulation layer material in thermal barrier coatings. The present paper presents the procedure of synthesis of holmium zirconate Ho2Zr2O7 and praseodymium zirconate Pr2Zr2O7 via Polymerized-Complex Method (PCM. Thermal analysis of precursor revealed that after calcination at relatively low temperature (700°C fine-crystalline, single-phase material is obtained. Thermal diffusivity was measured in temperature range 25-200°C, Ho2Zr2O7 exhibits lower thermal diffusivity than Pr2Zr2O7. Additionally, PrHoZr2O7 was synthesized. The powder in as-calcined condition is single-phase, but during the sintering decomposition of solid solution took place and Ho-rich phase precipitated. This material exhibited the best insulating properties among the tested ones.

  18. Properties of ceria doped with gadolinia via microwave-assisted hydrothermal synthesis; Propriedades de ceria dopada com gadolinia via sintese hidrotermal assistida por micro-ondas

    Energy Technology Data Exchange (ETDEWEB)

    Carregosa, J.D.C.; Oliveira, R.M.P.B. [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil); Macedo, D.A. [Universidade Federal da Paraiba (UFPB), Joao Pessoa, PB (Brazil); Nascimento, R.M., E-mail: jdcovello@hotmail.com [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil)

    2016-07-01

    The solid solution of CeO{sub 2} doped with Gd{sup 3+} (CGO) is a promising candidate for electrolyte in Solid Oxide Full Cells (SOFCs) operating in intermediate and low temperatures. The reduction of the working temperature of these energy conversion devices is the great technological challenge to its marketing. In this work, nanocrystalline powders of Ce{sub 1-x}Gd{sub x}O{sub 2-x/2} with x=0, x=0.1 e x=0.2 were obtained via microwave-hydrothermal synthesis at low temperature and times of synthesis (10 and 20 min at 120° C). The powders were analyzed by TG-DTA, DRX and dilatometry. The results showed characteristic peaks of the cubic fluorite-type structure, referring to the cerium oxide (CeO{sub 2}), without the presence of secondary peaks. It was also observed that the samples processed at levels of 10 and 20 minutes showed distinct behaviors in contrast to the concentrations of Gd{sup 3+}. (author)

  19. Reaction of cerium dioxide with alkali metal alkoxides

    International Nuclear Information System (INIS)

    Sato, Nobuaki; Fujino, Takeo

    1992-01-01

    The gas-solid reaction process using volatile alkali metal alkoxides has many advantages in producing the uranates (plutonates) which are expected to improve the dissolution behavior of the fuel into nitric acid. In this work, the reactions of CeO 2 , which was used as a non-radioactive stand-in of PuO 2 , with MOBu t (M = Li, K) under several conditions were examined. In the case of the M y Ce 1-y O 2-x synthesized by an aqueous method, the lattice parameter was slightly increased with increasing M concentration, y, up to 0.20. When the LiOBu t vapor reacted with CeO 2 , a new fluorite phase having a = 5.4935 A, y = 0.044, x = 0.30 was formed over 973 K. A similar compound (a = 5.4797 A, y = 0.035, x = 0.22) was observed by the reaction of CeO 2 with KOBu t . (author)

  20. Formation and decomposition of some rare earth (RE = La, Ce, Pr) hydroxides and oxides by homogeneous precipitation

    International Nuclear Information System (INIS)

    Ozawa, Masakuni; Onoe, Ryota; Kato, Hajime

    2006-01-01

    Formation and thermal decomposition of rare earth (RE = La, Ce, Pr) hydroxides and oxides by homogeneous precipitation using hexamethylenetetramine. The precipitatates were examined using thermal gravimetry and differential thermal analysis, infrared spectrometry and X-ray diffraction. The as-precipitated powders from the present process were La(OH) 3 , CeO 2 , Pr(OH) 3 . In the case of Ce, a cubic fluorite phase of cerium dioxide was directly obtained. The lanthanum trihydroxide decomposed to oxides via three steps. Two-step dehydration decomposition behavior at 340 and 500 o C was observed as La(OH) 3 → LaOOH + H 2 O and 2LaOOH → La 2 O 3 + H 2 O. The activation energy (ΔH) for dehydration was 240 and 244 kJ/mol, respectively. The additional decomposition of carbonate-containing species was observed at 670 o C with ΔH of 390 kJ/mol. Pr(OH) 3 did not show additional TGA profile of carbonate decomposition. Since no carbonate species form in solution during the HMT precipitation (hydrolysis of this molecule), the difference between La and Pr depends on the strength of basicity in the reaction with CO 2 after precipitation