The crystal structure of galgenbergite-(Ce), CaCe2(CO3)4•H2O

Science.gov (United States)

Walter, Franz; Bojar, Hans-Peter; Hollerer, Christine E.; Mereiter, Kurt

2013-04-01

Galgenbergite-(Ce) from the type locality, the railroad tunnel Galgenberg between Leoben and St. Michael, Styria, Austria, was investigated. There it occurs in small fissures of an albite-chlorite schist as very thin tabular crystals building rosette-shaped aggregates associated with siderite, ancylite-(Ce), pyrite and calcite. Electron microprobe analyses gave CaO 9.49, Ce2O3 28.95, La2O3 11.70, Nd2O3 11.86, Pr2O3 3.48, CO2 30.00, H2O 3.07, total 98.55 wt.%. CO2 and H2O calculated by stoichiometry. The empirical formula (based on Ca + REE ∑3.0) is C{{a}_{1.00 }}{{( {C{{e}_{1.04 }}L{{a}_{0.42 }}N{{d}_{0.42 }}P{{r}_{0.12 }}} )}_{2.00 }}{{( {C{{O}_3}} )}_4}\\cdot {{H}_2}O , and the simplified formula is CaC{{e}_2}{{( {C{{O}_3}} )}_4}\\cdot {{H}_2}O . According to X-ray single crystal diffraction galgenbergite-(Ce) is triclinic, space group Poverline{1},a=6.3916(5) , b = 6.4005(4), c = 12.3898(9) Å, α = 100.884(4), β = 96.525(4), γ = 100.492(4)°, V = 483.64(6) Å3, Z = 2. The eight strongest lines in the powder X-ray diffraction pattern are [ d calc in Å/( I)/ hkl]: 5.052/(100)/011; 3.011/(70)/0-22; 3.006/(66)/004; 5.899/(59)/-101; 3.900/(51)/1-12; 3.125/(46)/-201; 2.526/(42)/022; 4.694/(38)/-102. The infrared absorption spectrum reveals H2O (OH-stretching mode at 3,489 cm-1, HOH bending mode at 1,607 cm-1) and indicates the presence of distinctly non-equivalent CO3-groups by double and quadruple peaks of their ν1, ν2, ν3 and ν4 modes. The crystal structure of galgenbergite-(Ce) was refined with X-ray single crystal data to R1 = 0.019 for 2,448 unique reflections ( I > 2 σ( I)) and 193 parameters. The three cation sites of the structure Ca(1), Ce(2) and Ce(3) have a modest mixed site occupation by Ca and small amount of REE (Ce, La, Pr, Nd) and vice versa. The structure is based on double layers parallel to (001), which are composed of Ca(1)Ce(2)(CO3)2 single layers with an ordered chessboard like arrangement of Ca and Ce, and with a roof tile

The Environment Analysis in the CE-3 Landing Region

Science.gov (United States)

Mu, L.; Liu, J.; Zeng, X.; Gao, X.; Yan, W.; Zou, X.; Li, C.

2014-12-01

To understand the environment and select detecting objects for the Yutu Rover, NAOC used the DEM and DOM data obtained by CE-2, geological data released by USGS, and high resolution image captured by CE-3 and LRO-NAC to analyze the topographical characteristic, geologic age, Geomorphological feathers and new dust distribution in two scale levels. The first level is 45km×75km, and another one is 4km×4km. The center of the study region is the CE-3 landing site (19.51°W, 44.12°N). The following is the initial conclusions: (1) CE-3 landed on a relatively flat region in the Mare Imbrium with an elevation of -2615m. The geological age of the landing site belongs to young Eratoshenian. 10km to the north of the landing site is the older Mare Imbrium stratum, and the location of the landing site is just on the intersection area of these two stratums. (2) The landing site lies on the edge of a lunar mountain with a decline tendency from west to east, and the topographic slope and roughness of the landing region is low, which is the typical characteristic of lunar mare. There is a big crater with diameter of 430 meters in the west of the landing site, and lots of stones in different colors on the rim of this crater, shown in the Figure2. (3) By comparing the images captured by LRO-NAC before and after the landing, much lunar dust was blown away by the engine plume during the landing of CE-3. The change scope is about 60m with from east-west and 135m length from south-north. The direction of landing is from south-north, so the length is larger than the width, shown in the figure 3. (4) In the initial stage, the Yutu Rover was suggested to move in south direction and late in north direction, which would get more scientific data and result.

Recovery Ce from Ce - TBP Used Oxalic Acid

International Nuclear Information System (INIS)

Purwani, MV; Subagiono, R.; Suyanti

2007-01-01

Recovery or stripping Ce from Ce - TBP product of monazite sand used oxalic acid. Ce - TBP as organic phase and oxalic acid as aqueous phase and as strong precipitant compound to precipitate metal element. The stripping product as Ce - oxalic precipitate. The influence parameter were percentage of oxalic acid, volume ratio of Ce-TBP with oxalic acid, time and rate of stripping. At stripping of 25 ml Ce - TBP used oxalic acid, the optimum condition were achieve at using 5% oxalic acid, volume ratio of Ce - TBP : 5% oxalic acid = 1 : 1, time of stripping 7.5 minute and rate of stripping 150 rpm. At the optimum condition was obtained the recovery efficiency was 100%. (author)

Update History of This Database - tRNADB-CE | LSDB Archive [Life Science Database Archive metadata

Lifescience Database Archive (English)

Full Text Available switchLanguage; BLAST Search Image Search Home About Archive Update History Data List Contact us tRNAD...11/08/25 License is updated. 2010/03/29 tRNADB-CE English archive site is opened. 2008/7/1 tRNADB-CE( http:/...Download License Update History of This Database Site Policy | Contact Us Update History of This Database - tRNADB-CE | LSDB Archive ...

Photocatalytic activity of Ce-modified SBA-15 for the degradation of ...

Indian Academy of Sciences (India)

transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and N2 adsorption/desorption analysis. ... water.7,8,18 Existence of different sites of cerium ions and ... hydrocarbons.21 In this study, Ce-SBA-15 and Ce-Al-SBA-.

Preparation and luminescence properties of Ce3+ and Ce3+/Tb(3+)-activated Y4Si2O7N2 phosphors.

Science.gov (United States)

Xia, Zhiguo; Wu, Weiwei

2013-09-28

Ce(3+) and Ce(3+)/Tb(3+)-activated Y4Si2O7N2 phosphors are synthesized by the solid-state method, which can be efficiently excited by near ultraviolet (UV) light emitting diode (LED) chips. The PL spectrum of Y4Si2O7N2:Ce(3+) shows a broad hump between 380 and 650 nm, assigned to the electron transition from the 4f energy level to different 5d sub levels of the Ce(3+) ions at different Y(3+) sites. The color of the Y4Si2O7N2:Ce(3+) phosphor can shift from blue to green by introducing Tb(3+). In addition, the energy transfer process from Ce(3+) to Tb(3+) in the Y4Si2O7N2 host was investigated and discussed in terms of both the luminescence spectra and decay curves. The energy transfer critical distance has been calculated and evaluated by the concentration quenching method. Therefore, the Ce(3+) and Ce(3+)/Tb(3+)-activated Y4Si2O7N2 phosphors can serve as key materials for phosphor-converted white-light UV-LEDs.

Oxidation of Ce(III) in Foam Decontaminant by Ozone

Energy Technology Data Exchange (ETDEWEB)

Jung, Chong Hun; Yoon, I. H.; Choi, W. K.; Moon, J. K.; Yang, H. B. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, J. S. [Gachon University, Seongnam (Korea, Republic of)

2016-10-15

A nanoparticle-based foam decontaminant is composed of a surfactant and nanoparticles for the generation and maintenance of foam, and a chemical decontamination agent made of Ce(IV) dissolved in nitric acid. Ce(IV) will be reduced to Ce(III) through the decontamination process. Oxidizing cerium(III) can be reused as a decontamination agent, Ce(IV). Oxidation treatment technology by ozone uses its strong oxidizing power. It can be regarded as an environmentally friendly process, because ozone cannot be stored and transported like other industrial gases (because it quickly decays into diatomic oxygen) and must therefore be produced on site, and used ozone can decompose immediately. The ozonation treatment of Ce(III) in foam decontaminant containing a surfactant is necessary for the effective regeneration of Ce(III). Thus, the present study was undertaken to determine the optimal conditions for ozonation treatment in the regeneration of Ce(III) into Ce(IV) in the nanoparticle-based foam decontaminant containing surfactant. This study was undertaken to determine the optimal conditions for ozonation treatment in the regeneration of Ce(III) to Ce(IV) in nanoparticle-based foam decontaminant containing a TBS surfactant. The oxidation conversion rate of Ce(III) was increased with an increase in the flow rate of the gas mixture and ozone injection amount. The oxidation time required for the 100% oxidation conversion of Ce(III) to Ce(IV) at a specific ozone injection amount can be predicted from these experimental data.

Oxidation of Ce(III) in Foam Decontaminant by Ozone

International Nuclear Information System (INIS)

Jung, Chong Hun; Yoon, I. H.; Choi, W. K.; Moon, J. K.; Yang, H. B.; Lee, J. S.

2016-01-01

A nanoparticle-based foam decontaminant is composed of a surfactant and nanoparticles for the generation and maintenance of foam, and a chemical decontamination agent made of Ce(IV) dissolved in nitric acid. Ce(IV) will be reduced to Ce(III) through the decontamination process. Oxidizing cerium(III) can be reused as a decontamination agent, Ce(IV). Oxidation treatment technology by ozone uses its strong oxidizing power. It can be regarded as an environmentally friendly process, because ozone cannot be stored and transported like other industrial gases (because it quickly decays into diatomic oxygen) and must therefore be produced on site, and used ozone can decompose immediately. The ozonation treatment of Ce(III) in foam decontaminant containing a surfactant is necessary for the effective regeneration of Ce(III). Thus, the present study was undertaken to determine the optimal conditions for ozonation treatment in the regeneration of Ce(III) into Ce(IV) in the nanoparticle-based foam decontaminant containing surfactant. This study was undertaken to determine the optimal conditions for ozonation treatment in the regeneration of Ce(III) to Ce(IV) in nanoparticle-based foam decontaminant containing a TBS surfactant. The oxidation conversion rate of Ce(III) was increased with an increase in the flow rate of the gas mixture and ozone injection amount. The oxidation time required for the 100% oxidation conversion of Ce(III) to Ce(IV) at a specific ozone injection amount can be predicted from these experimental data

NMR study of CeTe at low temperatures

Energy Technology Data Exchange (ETDEWEB)

Hinderer, J. [Laboratorium fuer Festkoerperphysik, ETH Zuerich, CH-8093 Zurich (Switzerland)]. E-mail: hinderer@phys.ethz.ch; Weyeneth, S.M. [Laboratorium fuer Festkoerperphysik, ETH Zuerich, CH-8093 Zurich (Switzerland); Weller, M. [Laboratorium fuer Festkoerperphysik, ETH Zuerich, CH-8093 Zurich (Switzerland); Gavilano, J.L. [Laboratorium fuer Festkoerperphysik, ETH Zuerich, CH-8093 Zurich (Switzerland); Felder, E. [Laboratorium fuer Festkoerperphysik, ETH Zuerich, CH-8093 Zurich (Switzerland); Hulliger, F. [Laboratorium fuer Festkoerperphysik, ETH Zuerich, CH-8093 Zurich (Switzerland); Ott, H.R. [Laboratorium fuer Festkoerperphysik, ETH Zuerich, CH-8093 Zurich (Switzerland)

2006-05-01

We present {sup 125}Te NMR measurements on CeTe powder at temperatures between 1 and 150K and in magnetic fields between 5 and 8T. CeTe is a rocksalt-type intermetallic compound. It orders antiferromagnetically at T{sub N}{approx}2.2K with a much reduced ordered moment [H.R. Ott, J.K. Kjems, F. Hulliger, Phys. Rev. Lett. 42 20 (1979) 1378]. From our low-temperature NMR spectra we infer the presence of at least three inequivalent Te sites at low temperatures. Considering the crystal structure this result is completely unexpected. The linewidths and the Knight shifts of the individual lines are significantly different and increase substantially with decreasing temperature. They follow the temperature dependence of the magnetic susceptibility above 20K. Above T{sub N}, hyperfine fields of 1.6, 0.8 and 0.0T at the three Te sites per Bohr magneton of Ce moment are deduced from Knight shift vs. magnetic susceptibility data. These values are typical for transferred hyperfine fields via conduction electrons.

Experimental and theoretical study about sulfur deactivation of Ni/ CeO{sub 2} and Rh/CeO{sub 2} catalysts

Energy Technology Data Exchange (ETDEWEB)

Ocsachoque, Marco A., E-mail: ocmarco@quimica.unlp.edu.ar [Centro de Investigación y Desarrollo en Ciencias Aplicadas “Dr Jorge J. Ronco”, (CONICET, CCT La Plata), Departamento de Química, Facultad de Cs Exactas (UNLP), Calle 48 N° 257, 1900 La Plata (Argentina); Eugenio Russman, Juan I.; Irigoyen, Beatriz [Instituto de Tecnologías del Hidrógeno y Energías Sostenibles (ITHES), Departamento de Ingeniería Química, Facultad de Ingeniería (UBA), Buenos Aires (Argentina); Gazzoli, Delia [Dipartimento di Chimia, Universitá di Roma “La Sapienza”, Roma (Italy); González, María G. [Centro de Investigación y Desarrollo en Ciencias Aplicadas “Dr Jorge J. Ronco”, (CONICET, CCT La Plata), Departamento de Química, Facultad de Cs Exactas (UNLP), Calle 48 N° 257, 1900 La Plata (Argentina)

2016-04-01

Sulfur deactivation of Ni/CeO{sub 2} and Rh/CeO{sub 2} catalysts were examined through an experimental and theoretical study. These catalysts were characterized by N{sub 2} adsorption, X-ray diffraction, temperature programmed reaction, thermogravimetric analysis, Uv–visible spectroscopy and Raman spectroscopy, and tested under the methane dry reforming reaction in the presence of H{sub 2}S. On the other hand, different possible interactions of sulfur with Rh, Ni or surface sites of the CeO{sub 2} support were evaluated by performing energy calculations with the density functional theory (DFT). Overall, the results indicate that tolerance to sulfur of Rh/CeO{sub 2} catalyst is higher than that of Ni/CeO{sub 2} one. In this sense, TPR measurements show that reduction of CeO{sub 2} is promoted by the presence of Rh. This effect, probably caused by hydrogen spillover to CeO{sub 2} support during the reduction of RhO{sub x} species, could be linked to a high oxygen donation capacity of Rh/CeO{sub 2} catalysts. Accordingly, the O{sup 2−} species existing on Rh/CeO{sub 2} catalysts, revealed by Raman spectra of these samples, could favor sulfur oxidation and prevent Rh–S interactions. Likewise, the theoretical calculations show that desorption of S–O species from Rh/CeO{sub 2} system is more favorable than that from Ni/CeO{sub 2} one. Therefore, our experimental and theoretical study about sulfur deactivation of Ni and Rh supported on CeO{sub 2} allow us to postulate that Rh can help to desorb SO{sub x} species formed on the support, retarding sulfur poisoning of the Rh/CeO{sub 2} catalysts. - Highlights: • CeO{sub 2} support can act as a sacrifice trap decreasing sulfur poisoning. • Theoretical calculations indicate an important nickel affinity with sulfur. • Rh would favor desorption of S–O species formed on the support. • The O{sup 2−} species present on the Rh–CeO{sub 2} sample favor sulfur removal.

Database Description - tRNADB-CE | LSDB Archive [Life Science Database Archive metadata

Lifescience Database Archive (English)

Full Text Available switchLanguage; BLAST Search Image Search Home About Archive Update History Data List Contact us tRNAD...B-CE Database Description General information of database Database name tRNADB-CE Alter...CC BY-SA Detail Background and funding Name: MEXT Integrated Database Project Reference(s) Article title: tRNAD... 2009 Jan;37(Database issue):D163-8. External Links: Article title: tRNADB-CE 2011: tRNA gene database curat...n Download License Update History of This Database Site Policy | Contact Us Database Description - tRNADB-CE | LSDB Archive ...

P-EXAFS investigations of Zn uptake by montmorillonite. The strong and weak sites concept in the 2SPNE SC/CE sorption model

International Nuclear Information System (INIS)

Daehn, R.; Baeyens, B.; Bradbury, M.H.

2012-01-01

Document available in extended abstract form only. The sorption of radioactive elements on the immobile components in the near- and far-fields of a deep geological radioactive waste repository is a significant process in retarding their aqueous phase transport and an important component in safety assessment studies. The development of robust and well-founded mechanistic sorption models to predict the uptake of radionuclides under different geochemical conditions would enhance the justification and defensibility of the sorption values used in safety studies and thereby represent a considerable contribution to the scientific basis for radioactive waste disposal. The 2 site proto-lysis non electrostatic surface complexation and cation exchange (2SPNE SC/CE) sorption model has been used over the past decade or so to quantitatively describe the uptake of metals with oxidation states from II to VI on 2:1 clay minerals; montmorillonite and illite (Bradbury and Baeyens, 1997). One of the main features in this model is that there are two broad categories of amphoteric edge sorption sites; the so called strong (≡SSOH) and weak (≡SW1OH) sites. Because of their different sorption characteristics, it was expected that the coordination environments of the surface complexes on the two site types would be different. Although the 2SPNE SC/CE model uses different mechanistic uptake processes to describe sorption, it can only be described as a 'quasi mechanistic' model because the exact nature of the surface binding sites and surface complexes is not known. In order to check the 'strong site / weak site' sorption sites hypothesis in the 2SPNE SC/CE sorption model, it was essential to perform polarised extended X-ray absorption fine structure (P-EXAFS) measurements on an uptake system, in which it was possible to obtain good spectra particularly at the low metal loadings (∼2 mmol kg-1 or less) corresponding to occupancies dominated by strong sites. The Zn-montmorillonite system

Core-level XPS studies of Ce and La intermetallic compounds and their implications for the 4f levels of Ce compounds

International Nuclear Information System (INIS)

Freiburg, C.; Fuggle, J.C.; Hillebrecht, F.U.; Zolnierek, Z.; Laesser, R.

1983-01-01

The 3d core hole X-ray photoelectron spectra (XPS) of approximately 30 intermetallic compounds of La and Ce are reported. Transitions to final states with approximately f 0 , f 1 and f 2 character are observed in some Ce compounds (f 0 and f 1 for La compounds). The results are discussed in terms of the current ideas of the influence of f-counts and f-levels hybridization on core level lineshapes. We cannot find an explanatoin of the observed spectra consisted with the ''promotial model'' where the 4f-count varies and 4f electron was thought to be entirely promoted to the Ce 5d6s valence bands in some compounds. There may be some small charge transfer from the f level, however. In conjunction with ideas on screening processes in XPS the observed lineshapes suggest coupling of the 4f electrons to other states is strongest in those compounds previously thought to have f 0 character. This coupling increases despite a large increase in the Ce-Ce distance when Ce is diluted with Ni or Pd. Thus it cannot be due to direct f-f interaction and must be attributed to coupling with the other valence electrons; possibly those centred on the partner sites. (orig./EZ) [de

Ab initio study of solid CeIn3 at high pressures

Directory of Open Access Journals (Sweden)

M. Ilkhani

2008-06-01

Full Text Available   Electric field gradients (EFG’s at the In sites and spin magnetic moments at the Ce sites were calculated for the case of solid CeIn3. The calculations were performed by increasing pressure gradually from -5 to +22 GPa within the density functional theory (DFT using the augmented plane waves plus local orbital (APW+lo method employing the well-known PBE-GGA+U and WC-GGA+U schemes. The results almost show a linear reduction of spin magnetic moments of Ce by gradually increasing the pressure from -5 GPa to 22 GPa. However, from our results one can see that the calculated electric field gradients at the In site are growing up by increasing the pressure. We have compared the EFG’s at zero pressure with experimental and theoretical results of the others. The comparison shows that at ambient pressure our EFG’s are more consistent with experiment than the results of the other groups. Our result shows that the calculated spin magnetic moments are suppressed in the vicinity of some quantum critical point.

Highly porous CeO2 nanostructures prepared via combustion synthesis for supercapacitor applications

DEFF Research Database (Denmark)

Kadirvelayutham, Prasanna; Santhoshkumar, P.; Jo, Yong Nam

2017-01-01

We report highly porous CeO2 nanostructures (CeO2 NSs) suitable for supercapacitor applications, synthesized using a fast and cost effective combustion approach. Due to its prominent valence states of Ce3+/Ce4+, CeO2 has emerged as a promising pseudocapacitive material. The drawback of using CeO2...... as a supercapacitor electrode is its poor electrical conductivity. We overcame this drawback of CeO2 by creating oxygen vacancies on its surface, which act to enhance its electrical conductivity. The physical interpretation of the as-synthesized CeO2 NSs shows that they have dense active sites and diffusion pathways...... that enhance the performance of the electrode in a supercapacitor. Electrodes prepared using the synthesized CeO2 NSs exhibited the initial specific capacitance of 134.6 F g-1 and superior cycling stability of 92.5% after 1000 cycles at a constant current density of 1 A g-1, indicating their potential...

SELF-ASSEMBLY CE OXIDE/ORGANOPOLYSILOXANE COMPOSITE COATINGS.

Energy Technology Data Exchange (ETDEWEB)

SUGAMA,T.; SABATINI,R.; GAWLIK,K.

2005-01-01

A self-assembly composite synthesis technology was used to put together a Ce(OH){sub 3}-dispersed poly-acetamide-acetoxyl methyl-propylsiloxane (PAAMPA) organometallic polymer. Three spontaneous reactions were involved; condensation, amidation, and acetoxylation, between the Ce acetate and aminopropylsilane triol (APST) at 150 C. An increase in temperature to 200 C led to the in-situ phase transformation of Ce(OH){sub 3} into Ce{sub 2}O{sub 3} in the PAAMPA matrix. A further increase to 250 C caused oxidative degradation of the PAAMPA, thereby generating copious fissures in the composite. We assessed the potential of Ce(OH){sub 3}/ and Ce{sub 2}O{sub 3}/ PAAMPA composite materials as corrosion-preventing coatings for carbon steel and aluminum. The Ce{sub 2}O{sub 3} composite coating displayed better performance in protecting both metals against NaCl-caused corrosion than did the Ce(OH){sub 3} composite. Using this coating formed at 200 C, we demonstrated that the following four factors played an essential role in further mitigating the corrosion of the metals: First was a minimum susceptibility of coating's surface to moisture; second was an enhanced densification of the coating layer; third was the retardation of the cathodic oxygen reduction reaction at the metal's corrosion sites due to the deposition of Ce{sub 2}O{sub 3} as a passive film over the metal's surface; and, fourth was its good adherence to metals. The last two factors contributed to minimizing the cathodic delamination of coating film from the metal's surface. We also noted that the affinity of the composite with the surface of aluminum was much stronger than that with steel. Correspondingly, the rate of corrosion of aluminum was reduced as much as two orders of magnitude by a nanoscale thick coating. In contrast, its ability to reduce the corrosion rate of steel was lower than one order of magnitude.

Measurement of Ce(IV) Concentration in Foam Decontaminant containing Fluorosurfactant

Energy Technology Data Exchange (ETDEWEB)

Jung, Chong Hun; Yang, H. B.; Yoon, I. H.; Choi, W. K.; Moon, J. K. [KAERI, Daejeon (Korea, Republic of); Lee, J. S. [Gachon University, Seongnam (Korea, Republic of)

2016-05-15

To improve the stability of the foam, surfactants and inorganic materials such as nanoparticles can be added. A nanoparticle-based foam decontaminant is composed of a surfactant and nanoparticles for the generation and maintenance of foam, and a chemical decontamination agent made of Ce(IV) dissolved in nitric acid. Ce(IV) will be reduced to Ce(III) through the decontamination process. Oxidizing the cerium (III) can be reused as a decontamination agent, Ce(IV). Oxidation treatment technology by ozone uses its strong oxidizing power. It can be regarded as an environmentally friendly process, because ozone cannot be stored and transported like other industrial gases (because it quickly decays into diatomic oxygen) and must therefore be produced on site, and used ozone can be decomposed immediately. A concentration analysis of Ce(IV) in foam decontaminant containing a surfactant is necessary prior to the derivation of optimal conditions for the regeneration of Ce(III) through ozonation treatment. A UV spectrometric method using the absorbance or potentiometric method with a potential difference in Ce(III)/Ce(IV), or a potentiometric titration method using Fe (II), can be used for a Ce(IV) concentration analysis. A UV spectrometric method has a problem receiving the influence of the surfactant, and a potentiometric method is difficult to use because of the problem of an insignificant change in the potential difference value of the Ce(III)/Ce(IV). Thus, the present study was undertaken to determine whether the potentiometric titration method can be used for an analysis of the Ce(IV) concentration in the nanoparticle-based foam decontaminant containing surfactant. It will be effectively used for the Ce(IV) concentration measurement, in relation to the subsequent research on the derivation of optimal conditions for the regeneration of Ce(III) through ozonation treatment.

Diffusion of hydrogen in Pd-(Ce, Y, B) alloys

International Nuclear Information System (INIS)

Sakamoto, Y.; Kaneko, H.; Tsukahara, T.; Hirata, S.

1987-01-01

The study has been carried out to determine the diffusivity of hydrogen in Pd alloys containing Ce, Y and B in atom fractions up to θ/sub μ/ = 0.1 by an electrochemical permeation method, and to examine the lattice dilation effect on the diffusivity in these alloys. Ce and Y have been chosen because the solid solubility of both in Pd is about 13 at% in spite of the very large atomic size-factor difference between Pd and the solutes, and thus the expansion of the Pd lattice by Ce and Y is much larger than by Ag. Furthermore, it is of interest that the partial enthalpy of the dissolved hydrogen at infinite dilution ΔH 0 /sub H/ for Ce and Y is much smaller than for Pd. On the other hand, B atom also expands the Pd lattice in a way similar to Y, and sometimes B atoms may dissolve in the octahedral interstitial sites in the same way as hydrogen atoms

Comparison of Efficiencies and Mechanisms of Catalytic Ozonation of Recalcitrant Petroleum Refinery Wastewater by Ce, Mg, and Ce-Mg Oxides Loaded Al2O3

Directory of Open Access Journals (Sweden)

Chunmao Chen

2017-02-01

Full Text Available The use of catalytic ozonation processes (COPs for the advanced treatment of recalcitrant petroleum refinery wastewater (RPRW is rapidly expanding. In this study, magnesium (Mg, cerium (Ce, and Mg-Ce oxide-loaded alumina (Al2O3 were developed as cost efficient catalysts for ozonation treatment of RPRW, having performance metrics that meet new discharge standards. Interactions between the metal oxides and the Al2O3 support influence the catalytic properties, as well as the efficiency and mechanism. Mg-Ce/Al2O3 (Mg-Ce/Al2O3-COP reduced the chemical oxygen demand by 4.7%, 4.1%, 6.0%, and 17.5% relative to Mg/Al2O3-COP, Ce/Al2O3-COP, Al2O3-COP, and single ozonation, respectively. The loaded composite metal oxides significantly increased the hydroxyl radical-mediated oxidation. Surface hydroxyl groups (–OHs are the dominant catalytic active sites on Al2O3. These active surface –OHs along with the deposited metal oxides (Mg2+ and/or Ce4+ increased the catalytic activity. The Mg-Ce/Al2O3 catalyst can be economically produced, has high efficiency, and is stable under acidic and alkaline conditions.

Satellite line mapping in Eu3+–Ce3+ and Pr3+–Ce3+ codoped Y2SiO5

International Nuclear Information System (INIS)

Serrano, D.; Karlsson, J.; Zheng, L.; Dong, Y.; Ferrier, A.; Goldner, P.; Walther, A.; Rippe, L.; Kröll, S.

2016-01-01

In this work we perform a high-resolution spectroscopic investigation of Eu 3+ –Ce 3+ and Pr 3+ –Ce 3+ codoped Y 2 SiO 5 crystals. Satellite line spectra were recorded at low temperatures around the Eu 3+ : 7 F 0 → 5 D 0 and the Pr 3+ : 3 H 4 → 1 D 2 transitions. It is observed that the incorporation of Ce 3+ as a codopant notably changes the Eu 3+ and Pr 3+ satellite line patterns. Satellite lines measured in singly doped Eu 3+ :Y 2 SiO 5 were found at the same spectral positions in Eu 3+ –Ce 3+ codoped crystals. These coincident lines were concluded to be due to pairs of Eu 3+ ions. Extra satellite lines appeared in the codoped crystals, which were assigned to Ce 3+ related structures such as Ce 3+ –Eu 3+ pairs. The analysis of the Pr 3+ satellite line spectra presents further challenges. Satellite lines associated to Pr 3+ pairs show weaker intensity, presumably due to the efficient quenching of the Pr 3+1 D 2 emission through cross-relaxation paths ( 1 D 2 → 1 G 4 ; 3 H 4 → 3 F 4 ). The investigation of the Eu 3+ and Pr 3+ satellite line patterns in Y 2 SiO 5 is particularly interesting for their exploitation in rare-earth based quantum computation schemes. - Highlights: • We recorded Eu and Pr satellite lines in Y 2 SiO 5 with and without Ce as a codopant. • The presence of Ce leads to the appearance of extra satellite lines in the spectra. • The satellite lines are associated to minor crystal sites such as ion pairs. • Less than 100 ion pairs were detected per satellite line. • The exploitation of the satellite line structure is proposed for quantum computing.

CE and nanomaterials - Part II: Nanomaterials in CE.

Science.gov (United States)

Adam, Vojtech; Vaculovicova, Marketa

2017-10-01

The scope of this two-part review is to summarize publications dealing with CE and nanomaterials together. This topic can be viewed from two broad perspectives, and this article is trying to highlight these two approaches: (i) CE of nanomaterials, and (ii) nanomaterials in CE. The second part aims at summarization of publications dealing with application of nanomaterials for enhancement of CE performance either in terms of increasing the separation resolution or for improvement of the detection. To increase the resolution, nanomaterials are employed as either surface modification of the capillary wall forming open tubular column or as additives to the separation electrolyte resulting in a pseudostationary phase. Moreover, nanomaterials have proven to be very beneficial for increasing also the sensitivity of detection employed in CE or even they enable the detection (e.g., fluorescent tags of nonfluorescent molecules). © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Li4SrCa(SiO4)2:Ce3+, a highly efficient near-UV and blue emitting orthosilicate phosphor

International Nuclear Information System (INIS)

Zhang, Jilin; Zhang, Weilu; Qiu, Zhongxian; Zhou, Wenli; Yu, Liping; Li, Zhiqiang; Lian, Shixun

2015-01-01

High quantum efficiency is a vital parameter of phosphors for practical application. An efficient near-UV and blue emitting phosphor Li 4 SrCa(SiO 4 ) 2 :Ce 3+ was synthesized by a traditional solid-state reaction, and luminescent properties were studied in detail. The Ce 3+ -activated phosphor can emit both a near-UV light centred at 345 nm and a blue light peaking at 420 nm when Ce 3+ occupies the Sr and Ca site, respectively. The internal quantum efficiency (IQE) of Li 4 SrCa(SiO 4 ) 2 :0.03Ce 3+ is as high as 97% under the excitation at 288 nm, while the external quantum efficiency (EQE) is 66%. The IQE and EQE values of Li 4 SrCa(SiO 4 ) 2 :0.03Ce 3+ under the excitation at 360 nm are 82% and 31%, respectively. - Highlights: • Phosphor Li 4 SrCa(SiO 4 ) 2 :Ce 3+ emits a near-UV (345 nm) and a blue light (420 nm). • Emission band at 345 nm originates from Ce 3+ on Sr site. • Emission band at 420 nm belongs to Ce 3+ on Ca site. • Internal quantum efficiency is 97% for Li 4 SrCa(SiO 4 ) 2 :0.03Ce 3+ excited at 288 nm

Preparation and characterization of Ce-doped ZnO nanofibers by an electrospinning method

Directory of Open Access Journals (Sweden)

Jong-Pil Kim

2011-02-01

Full Text Available ZnO and Ce-doped ZnO Nanofibers on (111 Pt/SiO2/Si substrates were produced using an electrospinning technique. The as-prepared composite fibres were subjected to high-temperature calcination to produce inorganic fibers. After calcining at a temperature of 500 °C, the average diameter of the ZnO and Ce-doped ZnO nanofibers were determined to be 170 nm and 225 nm, respectively. The average grain size of the ZnO and Ce-doped ZnO nanofibers were about 50 nm and 57 nm, respectively. The microstructure, chemical bonding state and photoluminescence of the produced ZnO and Ce-doped ZnO nanofibers were investigated. The Ce-doped ZnO nanofiber can be assigned to the presence of Ce ions on substitutional sites of Zn ions and the Ce3+ state from X-ray photoelectron spectra. Compared with PL spectra of ZnO nanofibers, the peak position of the UV emission of the Ce-doped ZnO nanofibers is sharply suppressed while the green emission band is highly enhanced.

Photocatalytic degradation mechanisms of self-assembled rose-flower-like CeO2 hierarchical nanostructures

International Nuclear Information System (INIS)

Sabari Arul, N.; Mangalaraj, D.; Whan Kim, Tae

2013-01-01

Hierarchical rose-flower-like CeO 2 nanostructures were formed by using solvothermal and thermal annealing processes. The CeCO 3 OH thin film was transformed into CeO 2 roses due to thermal annealing. CeO 2 nanostructured roses exhibited excellent photocatalytic activity with a degradation rate of 65% for the azo dye acid orange 7 (AO7) under ultraviolet illumination. The fitting of the absorbance maximum versus time showed that the degradation of AO7 obeyed pseudo-first-order reaction kinetics. The enhancement of the photocatalytic activity for the CeO 2 roses was attributed to the high adsorptivity resulting from the surface active sites and special 4f electron configuration.

Pyrazolates advance cerium chemistry: a CeIII/CeIV redox equilibrium with benzoquinone.

Science.gov (United States)

Werner, Daniel; Deacon, Glen B; Junk, Peter C; Anwander, Reiner

2017-05-16

Two stable cerium(iv) 3,5-dialkylpyrazolate complexes are presented, namely dimeric [Ce(Me 2 pz) 4 ] 2 (Me 2 pz = 3,5-dimethylpyrazolate) and monomeric Ce(tBu 2 pz) 4 (tBu 2 pz = 3,5-di-tert-butylpyrazolate) along with their trivalent counterparts [Ce(Me 2 pz) 3 ] and [Ce(tBu 2 pz) 3 ] 2 . All complexes were obtained from protonolysis reactions employing the silylamide precursors Ce[N(SiHMe 2 ) 2 ] 4 and Ce[N(SiMe 3 ) 2 ] 3 . Treatment of homoleptic Ce IV and Ce III Me 2 pz complexes with 1,4-hydroquinone (H 2 hq) or 1,4-benzoquinone (bq), respectively, ultimately gave the same trimetallic Ce III species via a cerium redox equilibrium. The Ce III complex Ce 3 (Me 2 pz) 5 (pchd) 2 (L) (pchd = 1,4-bis(3,5-dimethylpyrazol-1-yl)cyclohex-2,5-diene-1,4-diolato; L = Me 2 pzH or (thf) 2 ) results from a di-1,4-pyrazolyl attack on pre-coordinated bq. The reduction of bq by [Ce(Me 2 pz) 3 (thf)] 2 , and re-oxidation by the resulting Ce IV species was supported by UV-vis spectroscopic investigations. Comparisons with the redox-innocent complexes [Ln(Me 2 pz) 3 (thf)] 2 (Ln = La and Pr) revealed far less selective reactions with bq, giving hexametallic and octametallic rare-earth metal side products containing 2-Me 2 pz substituted hq ligands.

EPR study of concentration dependence in Ce, Ce : La and Ce:Y doped SrF2

NARCIS (Netherlands)

Dankert, O.; Vainchtein, David; Datema, H.C.; den Hartog, Hendrik

1995-01-01

Experimental results of an EPR-study of the concentration dependence of the doubly integrated intensity and linewidth of the signals associated with tetragonal Ce3+-F--dipoles in Sr1-xCexF2+x, Sr-1-0.005-x Ce0.005LaxF2+0.005+x and Sr-1-0.005-x Ce0.005YxF2+0.005+x are presented. Both show a nonlinear

Coherence Kondo gap in CeNiSn and CeRhSb

International Nuclear Information System (INIS)

Takabatake, T.; Nakamoto, G.; Tanaka, H.; Bando, Y.; Fujii, H.; Nishigori, S.; Goshima, H.; Suzuki, T.; Fujita, T.; Oguro, I.; Hiraoka, T.; Malik, S.K.

1994-01-01

CeNiSn and CeRhSb are Kondo-lattice compounds showing the behavior of a small-gap semiconductor at temperatures below 7 K. We review and discuss the magnetic, transport and specific-heat measurements performed on single crystals of CeNiSn and polycrystals of CeRhSb. Prerequisites for gap formation are deduced from the effects of substitution and application of a magnetic field and pressure on the gapped state. ((orig.))

Luminescence and scintillation properties of YAG:Ce single crystal and optical ceramics

CERN Document Server

Mihóková, E; Mareš, J A; Beitlerová, A; Vedda, A; Nejezchleb, K; Blažek, K; D’Ambrosio, C

2007-01-01

We use various techniques to study optical and scintillation properties of Ce-doped yttrium aluminum garnet, Y3Al5O12 (YAG:Ce), in the form of a high-quality industrial single crystal. This was compared to optical ceramics prepared from YAG:Ce nanopowders. We present experimental data in the areas of optical absorption, radioluminescence, scintillation decay, photoelectron yield, thermally stimulated luminescence and radiation-induced absorption. The results point to an interesting feature—the absence of antisite (YAl, i.e. Y at the Al site) defects in optical ceramics. The scintillation decay of the ceramics is faster than that of the single crystal, but its photoelectron yield (measured with 1 μs integration time) is about 30–40% lower. Apart from the photoelectron yield value the YAG:Ce optical ceramic is fully comparable to a high quality industrial YAG:Ce single crystal and can become a competitive scintillator material.

Magnetic and transport properties of Ce 6MnSb 15

Science.gov (United States)

Godart, Claude; Rogl, Peter; Alleno, Eric; Gonçalves, António P.; Rouleau, Olivier

2006-05-01

In our effort to look for new Ce/Yb-based compounds with large unit cell, we studied Ce 6MnSb 15. Rietveld refinements of X-ray powder diffraction confirm that the material crystallizes in orthorhombic structure La 6MnSb 15-type, Imm2 space group, with 2 Ce sites (8e and 4d) and lattice parameters a=15.1643 Å, b=19.3875 Å and c=4.2794 Å, which closely agree with those already published. Magnetic susceptibility results show a paramagnetic behavior and no magnetic order down to 2 K in contrast to antiferromagnetic order previously reported at 7 K. Resistivity shows a metallic behavior and the Seebeck coefficient is very low, typically -2 μV/K.

Influence of Ce-H bonding on the physical properties of the hydrides CeCoSiH1.0 and CeCoGeH1.0

International Nuclear Information System (INIS)

Chevalier, B; Matar, S F; Menetrier, M; Marcos, J Sanchez; Fernandez, J Rodriguez

2006-01-01

The hydrides CeCoSiH 1.0 and CeCoGeH 1.0 which crystallize like the parent antiferromagnetic compounds CeCoSi and CeCoGe in the tetragonal CeFeSi-type structure, have been investigated by specific heat and thermoelectric power measurements and 1 H nuclear magnetic resonance (NMR). CeCoSiH 1.0 is an intermediate valence compound whereas CeCoGeH 1.0 can be considered as a nearly trivalent cerium compound. This behaviour is corroborated by the occurrence of a slight broadening of the 1 H NMR signal in the sequence CeCoSiH 1.0 → CeCoGeH 1.0 . The band structure calculations performed on these hydrides reveal the existence of strong bonding Ce-H interaction, found to be larger in CeCoSiH 1.0 than in CeCoGeH 1.0

Oxidative Ce"3"+ sequestration by fungal manganese oxides with an associated Mn(II) oxidase activity

International Nuclear Information System (INIS)

Zheng, Haisu; Tani, Yukinori; Naitou, Hirotaka; Miyata, Naoyuki; Tojo, Fuyumi

2016-01-01

"+ oxidation by BMOs produces nano-sized crystalline cerianite, and subsequent auto-catalytic Ce"3"+ oxidation efficiently occurs using dissolved oxygen as the oxidizing agent. Pretreatment of newly formed BMOs with La"3"+ solution resulted in decreased rate constants for primary Ce"3"+ oxidation by BMO due to site blocking by La"3"+ sorption. The results presented herein increase our understanding of the role of BMO in oxidative Ce"3"+ sequestration process(es) through enzymatic and abiotic paths in natural environments and provide supporting evidence for the potential application of BMOs towards the recovery of Ce"3"+ from contaminated waters. - Highlights: • Biogenic Mn oxides (BMOs) readily sequester Ce"3"+. • Self-regeneration by an associated Mn(II) oxidase suppresses Mn"2"+ release. • Primary Ce"3"+ oxidation by BMOs produces nano-sized cerianite (CeO_2). • Nano-sized CeO_2 induces auto-catalytic oxidation of Ce"3"+ by dissolved oxygen. • Coexisting La"3"+ slows Ce"3"+ oxidation rate by blocking of the reaction sites.

Local structure around Sn in CeCoIn5-xSnx

International Nuclear Information System (INIS)

Daniel, M.; Han, S.-W.; Booth, C.H.; Cornelius, A.L.; Bauer, E.D.; Sarrao, J.L.

2004-01-01

The local structure around Sn dopants in CeCoIn 5-x Sn z has been probed by extended x-ray absorption fine structure (EXAFS) technique. The fit results for both x = 0.12 and x = 0.18 clearly indicate the dopant Sn atoms predominantly occupying the planar In(1) site. These results are consistent with the quasi-two-dimensional electronic properties of CeCoIn 5 and is discussed in relation to the observed bulk properties

Effects of strong interactions between Ti and ceria on the structures of Ti/CeO2.

Science.gov (United States)

Yao, Xiao-Dan; Zhu, Kong-Jie; Teng, Bo-Tao; Yu, Cao-Ming; Zhang, Yun-Lei; Liu, Ya; Fan, Maohong; Wen, Xiao-Dong

2016-11-30

The effects of strong interactions between Ti and ceria on the structures of Ti/CeO 2 (111) are systematically investigated by density functional theory calculation. To our best knowledge, the adsorption energy of a Ti atom at the hollow site of CeO 2 is the highest value (-7.99 eV) reported in the literature compared with those of Au (-0.88--1.26 eV), Ag (-1.42 eV), Cu (-2.69 eV), Pd (-1.75 eV), Pt (-2.62 eV) and Sn (-3.68 eV). It is very interesting to find that Ti adatoms disperse at the hollow site of CeO 2 (111) to form surface TiO x species, instead of aggregating to form Ti metal clusters for the Ti-CeO 2 interactions that are much stronger than those of Ti-Ti ones. Ti adatoms are completely oxidized to Ti 4+ ions if they are monatomically dispersed on the next near hollow sites of CeO 2 (111) (xTi-NN-hollow); while Ti 3+ ions are observed when they locate at the near hollow sites (xTi-N-hollow). Due to the electronic repulsive effects among Ti 3+ ions, the adsorption energies of xTi-N-hollow are slightly weaker than those of xTi-NN-hollow. Simultaneously, the existence of unstable Ti 3+ ions on xTi-N-hollow also leads to the restructuring of xTi-N-hollow by surface O atoms of ceria transferring to the top of Ti 3+ ions, or oxidation by O 2 adsorption and dissociation. Both processes improve the stability of the xTi/CeO 2 system by Ti 3+ oxidation. Correspondingly, surface TiO 2 -like species form. This work sheds light into the structures of metal/CeO 2 catalysts with strong interactions between the metal and the ceria support.

Towards understanding the electronic structure of Fe-doped CeO2 nanoparticles with X-ray spectroscopy.

Science.gov (United States)

Wang, Wei-Cheng; Chen, Shih-Yun; Glans, Per-Anders; Guo, Jinghua; Chen, Ren-Jie; Fong, Kang-Wei; Chen, Chi-Liang; Gloter, Alexandre; Chang, Ching-Lin; Chan, Ting-Shan; Chen, Jin-Ming; Lee, Jyh-Fu; Dong, Chung-Li

2013-09-21

This study reports on the electronic structure of Fe-doped CeO2 nanoparticles (NPs), determined by coupled X-ray absorption spectroscopy and X-ray emission spectroscopy. A comparison of the local electronic structure around the Ce site with that around the Fe site indicates that the Fe substitutes for the Ce. The oxygen K-edge spectra that originated from the hybridization between cerium 4f and oxygen 2p states are sensitive to the oxidation state and depend strongly on the concentration of Fe doping. The Ce M(4,5)-edges and the Fe L(2,3)-edges reveal the variations of the charge states of Ce and Fe upon doping, respectively. The band gap is further obtained from the combined absorption-emission spectrum and decreased upon Fe doping, implying Fe doping introduces vacancies. The oxygen vacancies are induced by Fe doping and the spectrum reveals the charge transfer between Fe and Ce. Fe(3+) doping has two major effects on the formation of ferromagnetism in CeO2 nanoparticles. The first, at an Fe content of below 5%, is that the formation of Fe(3+)-Vo-Ce(3+) introduces oxygen deficiencies favoring ferromagnetism. The other, at an Fe content of over 5%, is the formation of Fe(3+)-Vo-Fe(3+), which favors antiferromagnetism, reducing the Ms. The defect structures Fe(3+)-Vo-Ce(3+) and Fe(3+)-Vo-Fe(3+) are crucial to the magnetism in these NPs and the change in Ms can be described as the effect of competitive interactions of magnetic polarons and paired ions.

Volta potential of clad AA2024 aluminium after exposure to CeCl3 solution

International Nuclear Information System (INIS)

Andreatta, F.; Druart, M.-E.; Marin, E.; Cossement, D.; Olivier, M.-G.; Fedrizzi, L.

2014-01-01

Highlights: • Alkaline etch of clad AA2024 enhances precipitation of Ce compounds. • Exposure to CeCl 3 solution decreases Volta potential of alkaline etched substrate. • Ce compounds reduce the driving force for initiation of localized attack. - Abstract: AA2024 clad with AA1050 was immersed in CeCl 3 solution to promote deposition of cerium species. The deposition occurs on the entire sample surface for the alkaline etched substrate, while it is very limited for the degreased substrate. The surface potential (Volta potential) was investigated by scanning Kelvin probe force microscopy after different immersion times in CeCl 3 solution. The preferential deposition of Ce compounds at Al–Fe intermetallic sites progressively reduces their Volta potential difference relative to the matrix in the alkaline etched substrate. This reduces the susceptibility to localized attack of the intermetallics as proven by potentiodynamic polarization measurements

Synthesis and physico-chemical characterization of CeO2/ZrO2-SO42- mixed oxides

International Nuclear Information System (INIS)

Hernandez E, J. M.; Silva R, R.; Garcia A, R.; Garcia S, L. A.; Handy, B. E.; Cardenas G, G.; Cueto H, A.

2012-01-01

Environmentally friendly solid-acid catalysts CeO 2 /ZrO 2 -SO 4 2- were prepared by the sol gel method varying CeO 2 content (10, 20 and 30 wt %) and using sulfation in situ, maintaining the sulfate ions amount present in the materials at 20 wt %. ZrO 2 and ZrO 2 -SO 4 2- were also prepared for comparison proposes using the same synthesis method. The materials were characterized by X-ray diffraction, nitrogen physisorption, potentiometric titration with n-butylamine, decomposition of 2-propanol and n-pentane isomerization. The specific surface area of ZrO 2 -SO 4 2- was high (160 m 2 /g) compared with the unmodified ZrO 2 (80 m 2 /g), however this area decreased with increasing the CeO 2 content (37-100 m 2 /g). There was no significant effect of CeO 2 on the tetragonal structure of ZrO 2 -SO 4 2- . The variation of acid sites amount runs parallel to the change of specific surface area. The acid sites amount decreased with increasing cerium oxide content. The decomposition of 2-propanol results fundamentally in the formation of dehydration products such as propylene and diisopropyl ether, both involving acid sites. In addition, a good performance during the n-pentane isomerization was observed for these materials. The selectivity towards isopentane reaches 84% when the Pt/CeO 2 /ZrO 2 -SO 4 2- catalyst with the highest CeO 2 content was used. (Author)

Site dependence of the Kondo scale in CePd{sub 1-x}Rh{sub x} evidenced by thermopower

Energy Technology Data Exchange (ETDEWEB)

Stockert, Ulrike; Hartmann, Stefanie; Deppe, Micha; Caroca-Canales, Nubia; Geibel, Christoph; Steglich, Frank [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Sereni, Julian [Division Bajas Temperaturas, Centro Atomico Bariloche (Argentina)

2015-07-01

CePd{sub 1-x}Rh{sub x} undergoes a continuous evolution from ferromagnetic order in CePd to an intermediate-valence (IV) ground state for CeRh. Close to the disappearance of magnetic order at x{sub cr} ∼ 0.87 unusual behavior of the ac susceptibility and the specific heat was observed. It was explained with a broad distribution of local Kondo temperatures T{sub K} from below 2 K to above 50 K due to the disorder introduced by Pd-Rh exchange. The thermopower S is very sensitive to Kondo scattering even for diluted 4f systems. In Ce compounds a large positive maximum in S(T) is usually observed around T{sub K}. We studied S(T) in CePd{sub 1-x}Rh{sub x} in order to evaluate the presence of Kondo scattering and the involved energy scales. Pure CeRh shows typical IV behavior with a large maximum at 220 K and small values at low T. Already 5 % Pd substitution leads to a strong enhancement of the low-T thermopower. Even larger values are found around x{sub cr}, while the high-T maximum shifts only moderately. Our results are in line with the existence of low (local) Kondo scales in the presence of IV behavior at high Rh content x > x{sub cr}. For lower Rh content a decreasing (average) Kondo scale is found.

Luminescence and color center distributions in K3YB6O12:Ce3+ phosphor

International Nuclear Information System (INIS)

Yang, Li; Wan, Yingpeng; Weng, Honggen; Huang, Yanlin; Chen, Cuili; Seo, Hyo Jin

2016-01-01

Polycrystalline Ce 3+ -doped K 3 YB 6 O 12 (1–14 mol%) phosphors were prepared by facile chemical sol–gel synthesis. The phase formation of the phosphors was confirmed by x-ray powder diffraction (XRD) analysis. The photoluminescence excitation spectra (PLE), emission spectra (PL) and the luminescence decay curves were tested. Under the near-UV light, the phosphors present the emission from blue color to yellowish green due to the allowed 4 f  –5 d transitions of Ce 3+ ions. The absolute quantum efficiency (QE) of K 3 YB 6 O 12 :Ce 3+ can reach 53% under the excitation of near-UV light. The luminescence thermal quenching of the phosphor was investigated by the temperature-dependent spectra. The crystallographic site of Ce 3+ ions in the lattice was identified and discussed on the basis of luminescence characteristics and structural data. There is only one isolated Ce 3+ center occupying the Y(II) sites in the lightly doped samples presenting a typical doublet emission profile. While the Ce 3+ multi-centers could be created with the enhancement of the doping levels, which could induce the distinct red-shift of the spectra due to the dipole–dipole interactions. The result in this work could be useful for the further investigation of other rare earth ions in this host. (paper)

Download - tRNADB-CE | LSDB Archive [Life Science Database Archive metadata

Lifescience Database Archive (English)

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Lattice dynamics of γ--Ce

International Nuclear Information System (INIS)

Gould, T.A.

1978-08-01

The phonon and magnetic measurements described in the thesis produced the following significant results concerning the lattice dynamical and magnetic properties of γ-Ce. The phonon spectrum is relatively soft, which is consistent with results obtained for CeSn 3 . The L [110] and T [111] branches of the dispersion curve are anomalous. The C 11 and C 44 elastic constants are quite close in value. No discrete magnetic excitations were observed. The magnetic scattering is qualitatively similar to the results from Ce 0 . 74 Th 0 . 26 , however, GAMMA/sub Ce/ less than GAMMA/sub Ce-Th/. The various lattice dynamical and magnetic similarities among γ-Ce, CeSn 3 , and Ce 0 . 74 Th 0 . 26 are mixed valence compounds. Therefore, a complete theoretical description of the observed properties of Ce and its compounds may provide a basis for understanding a whole class of mixed valence materials

Dopant concentration dependence of radiation-induced positive hysteresis of Ce:GSO and Ce:GSOZ

International Nuclear Information System (INIS)

Yanagida, Takayuki; Fujimoto, Yutaka; Watanabe, Kenichi

2014-01-01

Positive hysteresis and radiation tolerance to high-dose radiation exposure were investigated for Ce 0.5, 1, and 1.5%-doped Gd 2 SiO 5 (GSO) and for Zr co-doped GSO with the same Ce concentrations (GSOZ). When they were irradiated by 200–800 Gy 60 Co in 200 Gy steps, all Ce-doped GSO samples exhibited light yield enhancement (positive hysteresis). On the other hand, the light yield of GSOZ decreased greatly. Ce 0.5%-doped GSO showed the highest positive hysteresis, with ∼20% light yield enhancement. When the Ce concentration was increased, the positive hysteresis became weaker. - Highlights: • Positive hysteresis Ce 0.5, 1, and 1.5% doped GSO and GSOZ are studied. • Ce 0.5, 1, and 1.5% doped GSO show the positive hysteresis by 2–8 M rad 60 Co irradiation. • Ce 0.5, 1, and 1.5% doped GSOZ do not show the positive hysteresis. • By Zn co-doping, radiation tolerance of GSO becomes weaker. • By dense Ce doping, radiation tolerance of GSO and GSOZ are improved

Tuning Ce distribution for high performanced Nd-Ce-Fe-B sintered magnets

Energy Technology Data Exchange (ETDEWEB)

Fan, Xiaodong [School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048 (China); Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201 (China); Guo, Shuai; Chen, Kan; Chen, Renjie; Lee, Don [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201 (China); You, Caiyin, E-mail: caiyinyou@xaut.edu.cn [School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048 (China); Yan, Aru, E-mail: aruyan@nimte.ac.cn [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201 (China)

2016-12-01

A dual-alloy method was applied to tune the distribution of Ce for enhancing the performance of Nd-Ce-Fe-B sintered magnets with a nominal composition of (Nd{sub 0.75}Ce{sub 0.25}){sub 30.5}Fe{sub bal}Al{sub 0.1}Cu{sub 0.1}B. In comparison to the single alloy of (Nd{sub 0.75}Ce{sub 0.25}){sub 30.5}Fe{sub bal}Al{sub 0.1}Cu{sub 0.1}B, the coercivity was enhanced from 10.3 kOe to 12.1 kOe and the remanence was increased from 13.1 kG to 13.3 kG for the magnets with a dual-alloy method. In addition, the remanence temperature coefficient α and coercivity temperature coefficient β were also slightly improved for the magnet with the dual alloys. The results of microstructure characterizations show the uniform distribution of Ce for the magnet with a single alloy, and the coexistence of the Ce-rich and Ce-lean regions for the magnet with the dual alloys. In combinations with the nucleation of reversal domains and magnetic recoil curves, the property enhancement of magnets with a dual-alloy method was well explained. - Highlights: • Improved magnetic properties were obtained in dual-alloy magnet. • This is due to the tuning of Ce distribution and the change in microstructure. • The magnetic hardening effect can be observed in dual-alloy magnet.

First-principles studies of Ce and Eu doped inorganic scintillator gamma ray detectors

Science.gov (United States)

Canning, Andrew; Chaudhry, Anurag; Boutchko, Rostyslav; Derenzo, Stephen

2011-03-01

We have performed DFT based band structure calculations for new Ce and Eu doped wide band gap inorganic materials to determine their potential as candidates for gamma ray scintillator detectors. These calculations are based on determining the 4f ground state level of the Ce and Eu relative to the valence band of the host as well as the position of the Ce and Eu 5d excited state relative to the conduction band of the host. Host hole and electron traps as well as STEs (self trapped excitons) can also limit the transfer of energy from the host to the Ce or Eu site and therefore limit the light output. We also present calculations for host hole traps and STEs to compare the energies to the Ce and Eu excited states. The work was supported by the U.S. Department of Homeland Security and carried out at the Lawrence Berkeley National Laboratory under U.S. Department of Energy Contract No. DE-AC02- 05CH11231.

Fabrication of Nano-CeO2 and Application of Nano-CeO2 in Fe Matrix Composites

International Nuclear Information System (INIS)

Tiebao, W.; Chunxiang, C.; Xiaodong, W.; Guobin, L.

2010-01-01

It is expatiated that nano-CeO2 is fabricated by the direct sedimentation method. The components and particles diameter of nano-CeO2 powders are analyzed by XRD and SEM . The thermodynamic analysis and acting mechanism of nano-CeO2 with Al in Fe matrix composites are researched, which shows that the reaction is generated between CeO2 and Al in the composite, that is, 3CeO2+4Al - 2Al2O3+3[Ce], which obtains Al2O3 and active [Ce] during the sintering process. The active [Ce] can improve the performance of CeO2/Fe matrix composites. The suitable amount of CeO2 is about 0.05% in CeO2/Fe matrix composites. SEM fracture analysis shows that the toughness sockets in nano-CeO2/Fe matrix composites are more than those in no-added nano-CeO2 composites, which can explain that adding nano-CeO2 into Fe matrix composite, the toughness of the composite is improved significantly. Applied nano-CeO2 to Fe matrix diamond saw blades shows that Fe matrix diamond saw blade is sharper and of longer cutting life than that with no-added nano-CeO2.

The high-pressure phase of CePtAl

International Nuclear Information System (INIS)

Heymann, Gunter; Heying, Birgit; Rodewald, Ute C.; Janka, Oliver; Univ. Oldenburg

2017-01-01

The intermetallic aluminum compound HP-CePtAl was synthesized by arc melting of the elements with subsequent high-pressure/high-temperature treatment at 1620 K and 10.5 GPa in a multianvil press. The compound crystallizes in the hexagonal MgZn_2-type structure (P6_3/mmc) with lattice parameters of a=552.7(1) and c=898.8(2) pm refined from powder X-ray diffraction data. With the help of single crystal investigations (wR=0.0527, 187 F"2 values, 13 variables), the proposed structure type was confirmed and the mixed Pt/Al site occupations could be refined. Magnetic susceptibility measurements showed a disappearance of the complex magnetic ordering phenomena, which are observed in NP-CePtAl.

The high-pressure phase of CePtAl

Energy Technology Data Exchange (ETDEWEB)

Heymann, Gunter [Univ. Innsbruck (Austria). Inst. fuer Allgemeine, Anorganische und Theoretische Chemie; Heying, Birgit; Rodewald, Ute C. [Univ. Muenster (Germany). Inst. fuer Anorganische und Analytische Chemie; Janka, Oliver [Univ. Muenster (Germany). Inst. fuer Anorganische und Analytische Chemie; Univ. Oldenburg (Germany). Inst. fuer Chemie

2017-03-01

The intermetallic aluminum compound HP-CePtAl was synthesized by arc melting of the elements with subsequent high-pressure/high-temperature treatment at 1620 K and 10.5 GPa in a multianvil press. The compound crystallizes in the hexagonal MgZn{sub 2}-type structure (P6{sub 3}/mmc) with lattice parameters of a=552.7(1) and c=898.8(2) pm refined from powder X-ray diffraction data. With the help of single crystal investigations (wR=0.0527, 187 F{sup 2} values, 13 variables), the proposed structure type was confirmed and the mixed Pt/Al site occupations could be refined. Magnetic susceptibility measurements showed a disappearance of the complex magnetic ordering phenomena, which are observed in NP-CePtAl.

Growth and Characterization of Ce- Substituted Nd₂Fe₁₄¹¹B Single Crystals

Energy Technology Data Exchange (ETDEWEB)

Susner, M. A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Conner, B. S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Saparov, B. I. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; McGuire, M. A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Crumlin, E. J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source; Veith, G. M. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source; Cao, H. B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division; Shanavas, K. V. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Parker, D. S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Chakoumakos, B. C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division; Sales, B. C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division

2015-08-31

Single crystals of (Nd_1-xCe_x)₂Fe₁₄B are grown out of Fe-(Nd,Ce) flux. Chemical and structural analysis of the crystals indicates that (Nd_1-xCe_x)₂Fe₁₄B forms a solid solution until at least x = 0.38 with a Vegard-like variation of the lattice constants with x. Refinements of single crystal neutron diffraction data indicate that Ce has a slight site preference (7:3) for the 4g rare earth site over the 4f site. Furthermore, magnetization measurements show that for x = 0.38 the saturation magnetization at 400 K, a temperature important to applications, falls from 29.8 for the parent Nd₂Fe₁₄B to 27.6 μ_B/f.u., the anisotropy field decreases from 5.5 T to 4.7 T, and the Curie temperature decreases from 586 to 543 K. First principles calculations carried out within density functional theory are used to explain the decrease in magnetic properties due to Ce substitution. Although the presence of the lower-cost and more abundant Ce slightly affects these important magnetic characteristics, this decrease is not large enough to affect a multitude of applications. Ce-substituted Nd₂Fe₁₄B is therefore a potential high-performance permanent magnet material with substantially reduced Nd content.

Structural and dielectric studies of Ce doped BaSnO3 perovskite nanostructures

Science.gov (United States)

Angel, S. Lilly; Deepa, K.; Rajamanickam, N.; Jayakumar, K.; Ramachandran, K.

2018-04-01

Undoped and Cerium (Ce) doped BaSnO3(BSO) nanostructures were synthesized by co-precipitation method. The cubic structure and perovskite phase were confirmed by X-ray diffraction (XRD). The crystallite size of BSO is 41nm and when Ce ion concentration is increased, the crystallite sizesdecreased. The nanocube, nanocuboids and nanorods are observed from SEM analysis. The purity of the undoped and doped samples are confirmed by EDS spectrum. For larger defects, wide band gap was obtained from UV-Vis and PL spectrum. The dielectric constants are increased at low frequencies when Ce impurities are introduced in the BSO matrix at Sn site.

75As-NQR study of the hybridization gap semiconductor CeOs4As12

International Nuclear Information System (INIS)

Yogi, M; Niki, H; Higa, N; Kawata, T; Sekine, C

2016-01-01

We performed an 75 As nuclear quadrupole resonance (NQR) measurement on CeOs 4 As 12 . The 75 As-NQR spectrum shape demonstrates that the Ce-site filling fraction of our high-pressure synthesized sample is close to unity. A presence of the c — f hybridization gap is confirmed from the temperature dependence of the nuclear spin-lattice relaxation rate 1/T 1 . An increase of 1/T 1 below ∼3 K indicates a development of the spin fluctuations. The 1/T 1 for CeOs 4 As 12 shows similar behavior as that for CeOs 4 Sb 12 with different magnitude of the c — f hybridization gap. An absence of phase transition in CeOs 4 As 12 may be caused by the increase of the c — f hybridization, which increases the gap magnitude and reduces the residual density of state inside the gap. (paper)

Biological reduction-deposition and luminescent properties of nanostructured CePO{sub 4}@NaCe(SO{sub 4}){sub 2}(H{sub 2}O) and CePO{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Yu, Xiaoniu [School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China); Research Institute of Green Construction Materials, Southeast University, Nanjing 211189 (China); Qian, Chunxiang, E-mail: cxqian@seu.edu.cn [School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China); Research Institute of Green Construction Materials, Southeast University, Nanjing 211189 (China)

2016-03-01

Nano-sized CePO{sub 4}@NaCe(SO{sub 4}){sub 2}(H{sub 2}O) and CePO{sub 4} with hexagonal phase have been prepared by simply varying the reactant P/Ce molar ratio in bacterial liquid. The phase composition of two samples was checked via Fourier transform infrared spectroscopy (FTIR), energy dispersive analysis of X-rays (EDS) and X-ray diffraction (XRD) analyses, displaying the presence of CePO{sub 4}@NaCe(SO{sub 4}){sub 2}(H{sub 2}O) and CePO{sub 4} with average crystallite size are 32.34 and 15.61 nm, respectively. The scanning electron microscopy (SEM) images show that nano-clusters and sphere-like in shape with a narrow diameter distribution were observed in two samples. The transmission electron microscopy (TEM) photographs further indicate obtained CePO{sub 4}@NaCe(SO{sub 4}){sub 2}(H{sub 2}O) and CePO{sub 4} nanoparticles correspond to nanosheets and nanorods, respectively. The emission spectra of CePO{sub 4}@NaCe(SO{sub 4}){sub 2}(H{sub 2}O) and CePO{sub 4} display a broad band of 300–380 nm range with the strongest emission at 342 nm in the violet region. - Highlights: • A new method was found to synthesize CePO{sub 4}@NaCe(SO{sub 4}){sub 2}(H{sub 2}O) and CePO{sub 4} nanoparticles. • CePO{sub 4}@NaCe(SO{sub 4}){sub 2}(H{sub 2}O) nanoparticles have good luminescent properties. • Size and luminescent properties of two samples have been studied and compared.

The role of charge transfer in the oxidation state change of Ce atoms in the TM13-CeO2(111) systems (TM = Pd, Ag, Pt, Au): a DFT + U investigation.

Science.gov (United States)

Tereshchuk, Polina; Freire, Rafael L H; Ungureanu, Crina G; Seminovski, Yohanna; Kiejna, Adam; Da Silva, Juarez L F

2015-05-28

Despite extensive studies of transition metal (TM) clusters supported on ceria (CeO2), fundamental issues such as the role of the TM atoms in the change in the oxidation state of Ce atoms are still not well understood. In this work, we report a theoretical investigation based on static and ab initio molecular dynamics density functional theory calculations of the interaction of 13-atom TM clusters (TM = Pd, Ag, Pt, Au) with the unreduced CeO2(111) surface represented by a large surface unit cell and employing Hubbard corrections for the strong on-site Coulomb correlation in the Ce f-electrons. We found that the TM13 clusters form pyramidal-like structures on CeO2(111) in the lowest energy configurations with the following stacking sequence, TM/TM4/TM8/CeO2(111), while TM13 adopts two-dimensional structures at high energy structures. TM13 induces a change in the oxidation state of few Ce atoms (3 of 16) located in the topmost Ce layer from Ce(IV) (itinerant Ce f-states) to Ce(III) (localized Ce f-states). There is a charge flow from the TM atoms to the CeO2(111) surface, which can be explained by the electronegativity difference between the TM (Pd, Ag, Pt, Au) and O atoms, however, the charge is not uniformly distributed on the topmost O layer due to the pressure induced by the TM13 clusters on the underlying O ions, which yields a decrease in the ionic charge of the O ions located below the cluster and an increase in the remaining O ions. Due to the charge flow mainly from the TM8-layer to the topmost O-layer, the charge cannot flow from the Ce(IV) atoms to the O atoms with the same magnitude as in the clean CeO2(111) surface. Consequently, the effective cationic charge decreases mainly for the Ce atoms that have a bond with the O atoms not located below the cluster, and hence, those Ce atoms change their oxidation state from IV to III. This increases the size of the Ce(III) compared with the Ce(IV) cations, which builds-in a strain within the topmost Ce layer, and

Magnetic and electronic properties in CeTSi3 and CeTGe3 (T: transition metal)

International Nuclear Information System (INIS)

Shimoda, T.; Okuda, Y.; Takeda, Y.; Ida, Y.; Miyauchi, Y.; Kawai, T.; Fujie, T.; Sugitani, I.; Thamizhavel, A.; Matsuda, T.D.; Haga, Y.; Takeuchi, T.; Nakashima, M.; Settai, R.; Onuki, Y.

2007-01-01

We investigated the magnetic properties of CeTSi 3 (T: Ru, Os, Co, Rh, Ir, Pd and Pt) and CeTGe 3 (T: Co, Rh and Ir) by measuring their electrical resistivity and magnetic susceptibility. CeRuSi 3 , CeOsSi 3 and CeCoSi 3 do not order magnetically, with a large Kondo temperature of about 200K. The other compounds order antiferromagnetically, and are very similar to each other in their magnetic and electronic properties, which is related to a large crystalline electric field (CEF) splitting energy of the 4f electron, about 500K in CeIrSi 3

What was the population of Great Zimbabwe (CE1000 - 1800)?

Science.gov (United States)

Chirikure, Shadreck; Moultrie, Thomas; Bandama, Foreman; Dandara, Collett; Manyanga, Munyaradzi

2017-01-01

The World Heritage Site of Great Zimbabwe is one of the most iconic and largest archaeological settlements in Africa. It was the hub of direct and indirect trade which internally connected various areas of southern Africa, and externally linked them with East Africa and the Near and Far East. Archaeologists believe that at its peak, Great Zimbabwe had a fully urban population of 20,000 people concentrated in approximately 2.9 square kilometres (40 percent of 720 ha). This translates to a population density of 6,897, which is comparable with that of some of the most populous regions of the world in the 21st century. Here, we combine archaeological, ethnographic and historical evidence with ecological and statistical modelling to demonstrate that the total population estimate for the site's nearly 800-year occupational duration (CE1000-1800), after factoring in generational succession, is unlikely to have exceeded 10,000 people. This conclusion is strongly firmed up by the absence of megamiddens at the site, the chronological differences between several key areas of the settlement traditionally assumed to be coeval, and the historically documented low populations recorded for the sub-continent between CE1600 and 1950.

What was the population of Great Zimbabwe (CE1000 - 1800?

Directory of Open Access Journals (Sweden)

Shadreck Chirikure

Full Text Available The World Heritage Site of Great Zimbabwe is one of the most iconic and largest archaeological settlements in Africa. It was the hub of direct and indirect trade which internally connected various areas of southern Africa, and externally linked them with East Africa and the Near and Far East. Archaeologists believe that at its peak, Great Zimbabwe had a fully urban population of 20,000 people concentrated in approximately 2.9 square kilometres (40 percent of 720 ha. This translates to a population density of 6,897, which is comparable with that of some of the most populous regions of the world in the 21st century. Here, we combine archaeological, ethnographic and historical evidence with ecological and statistical modelling to demonstrate that the total population estimate for the site's nearly 800-year occupational duration (CE1000-1800, after factoring in generational succession, is unlikely to have exceeded 10,000 people. This conclusion is strongly firmed up by the absence of megamiddens at the site, the chronological differences between several key areas of the settlement traditionally assumed to be coeval, and the historically documented low populations recorded for the sub-continent between CE1600 and 1950.

Structural and magnetic properties of Ce/Fe and Ce/FeCoV multilayers

Energy Technology Data Exchange (ETDEWEB)

Tixier, S; Boeni, P [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Mannix, D; Stirling, W G [Liverpool Univ. (United Kingdom); Lander, G H

1997-09-01

Ce/Fe and Ce/FeCoV multilayers have been grown by magnetron sputtering. The interfaces are well defined and the layers are crystalline down to an individual layer thickness of 20 A. Ce/FeCoV multilayers show sharper interfaces than Ce/Fe but some loss of crystallinity is observed. Hysteresis loops obtained by SQUID show different behaviour of the bulk magnetisation as a function of the layer thickness. Fe moments are found by Moessbauer spectroscopy to be perpendicular to the interfaces for multilayers with small periodicity. (author) 2 figs., 2 refs.

CO2 methanation on the catalyst of Ni/MCM-41 promoted with CeO2.

Science.gov (United States)

Wang, Xiaoliu; Zhu, Lingjun; Liu, Yincong; Wang, Shurong

2018-06-01

CO 2 as a raw feed combined with renewable hydrogen for the production of useful chemicals and alternative energy products is one of the solutions to environmental and energy problems. In this study, a series of Ni-xCeO 2 /MCM-41 catalysts with a nickel content of 20wt% were prepared through deposition precipitation method for CO 2 methanation. Different characterization methods, including BET, XRD, TEM, SEM, H 2 -TPR and H 2 -TPD were applied to help explore the influence mechanism of CeO 2 on Ni/MCM-41 in CO 2 methanation. It was found that all CeO 2 -promoted catalysts exhibited enhanced catalytic activity when compared to Ni/MCM-41. The catalyst modified with 20wt% CeO 2 showed the best catalytic performance, with CO 2 conversion and CH 4 selectivity of 85.6% and 99.8%, respectively, at the temperature of 380°C under atmospheric pressure. The synergetic effects among Ni 0 active sites, the promoter and the support, including nickel dispersion improvement and increased CO 2 adsorption sites due to the addition of CeO 2 , were considered as important factors for high reactivity of the promoted catalysts. The stability test showed that the promoted catalyst maintained its high reactivity after 30h. Copyright © 2017 Elsevier B.V. All rights reserved.

Mesoporous CeTiSiMCM-48 as novel photocatalyst for degradation of organic compounds

International Nuclear Information System (INIS)

Mureseanu, Mihaela; Parvulescu, Viorica; Radu, Teodora; Filip, Mihaela; Carja, Gabriela

2015-01-01

This work presents novel photocatalysts containing Ti and/or Ce embedded in the mesoporous silica framework (TiSiMCM-48, CeSiMCM-48 and CeTiSiMCM-48) that were prepared via a facile sol–gel process in the presence of ionic structure directing agents. The structural properties of the obtained materials were analyzed by X-ray diffraction (XRD), nitrogen adsorption-desorption, scanning and transmission electron microscopy (SEM, TEM), EDAX analysis, X-ray photoelectron microscopy (XPS), ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS) and Fourier transformation infrared spectroscopy (FT-IR). The results indicated that Ce and Ti were highly dispersed or incorporated into the framework of the cubic SiMCM-48, with an enhanced light-trapping effect both in the UV and Vis regions. When applied to the photocatalytic degradation of phenol, the best results were obtained for the bimetallic hybrid. The best activity of CeTiSiMCM-48 photocatalyst was ascribed to improved electron–hole pair separation efficiency and formation of more reactive oxygen species due to the presence of Ce 4+ /Ce 3+ . The mesoporous support increases the dispersability of the photoactive Ti 4+ or Ce 4+ /Ce 3+ species on the catalyst surface and the accessibility of the substrate to the active sites. Furthermore, the catalysts can be easily recovered and reused for four cycles without significant loss of activity. - Highlights: • Novel photocatalysts containing Ti and/or Ce embedded in the mesoporous MCM-48 silica. • Ce 4+ /Ce 3+ improved electron–hole pair separation and reactivity of oxygen species. • The mesoporous support increases the dispersability of the photoactive species. • The photocatalyst was highly active and stable for phenol degradation under UV irradiation. • TiCeSiMCM-48 can be recycled up to four cycles without significant loss of activity

Inhibition of human carboxylesterases hCE1 and hiCE by cholinesterase inhibitors.

Science.gov (United States)

Tsurkan, Lyudmila G; Hatfield, M Jason; Edwards, Carol C; Hyatt, Janice L; Potter, Philip M

2013-03-25

Carboxylesterases (CEs) are ubiquitously expressed proteins that are responsible for the detoxification of xenobiotics. They tend to be expressed in tissues likely to be exposed to such agents (e.g., lung and gut epithelia, liver) and can hydrolyze numerous agents, including many clinically used drugs. Due to the considerable structural similarity between cholinesterases (ChE) and CEs, we have assessed the ability of a series of ChE inhibitors to modulate the activity of the human liver (hCE1) and the human intestinal CE (hiCE) isoforms. We observed inhibition of hCE1 and hiCE by carbamate-containing small molecules, including those used for the treatment of Alzheimer's disease. For example, rivastigmine resulted in greater than 95% inhibition of hiCE that was irreversible under the conditions used. Hence, the administration of esterified drugs, in combination with these carbamates, may inadvertently result in decreased hydrolysis of the former, thereby limiting their efficacy. Therefore drug:drug interactions should be carefully evaluated in individuals receiving ChE inhibitors. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Two-photon excitation processes to near-ultraviolet states in Ce3+:CaF2

International Nuclear Information System (INIS)

Hamilton, D.S.

1982-11-01

The two-photon transition to the lowest Ce 3+ 5d state in Ce 3+ :CaF 2 has been investigated. At liquid helium temperatures, a no-phonon resonance line is observed and is accompanied by a vibrational sideband. The peak cross section for this transition is of order 1 x 10 -53 cm 4 s indicating strong parity mixing for the 5d levels. The no-phonon line shows a polarization anisotropy consistent with a tetragonal Ce 3+ site of C 4 /sub V/ symmetry. The phonon side band shows a different anisotropy than the no-phonon line and its polarization characteristics are a function of phonon frequency and temperature

Methanol steam reforming over Pd/ZnO and Pd/CeO{sub 2} catalysts

Energy Technology Data Exchange (ETDEWEB)

Ranganathan, Easwar S.; Bej, Shyamal K.; Thompson, Levi T. [University of Michigan, Department of Chemical Engineering, 3026 H.H. Dow Building, 2300 Hayward Avenue, Ann Arbor, MI 48109-2136 (United States)

2005-08-10

The goal of work described in this paper was to better understand the methanol steam reforming (MSR) activity and selectivity patterns of ZnO and CeO{sub 2} supported Pd catalysts. This reaction is being used to produce H{sub 2}-rich gas for a number of applications including hydrogen fuel cells. The Pd/ZnO catalysts had lower MSR rates but were more selective for the production of CO{sub 2} than the Pd/CeO{sub 2} catalysts. The CH{sub 3}OH conversion rates were proportional to the H{sub 2} chemisorption uptake suggesting that the rate determining step was catalyzed by Pd. The corresponding turnover frequencies averaged 0.8+/-0.3s{sup -1} and 0.4+/-0.2s{sup -1} at 230{sup o}C for the Pd/ZnO and Pd/CeO{sub 2} catalysts, respectively. The selectivities are explained based on the reaction pathways, and characteristics of the support. The key surface intermediate appeared to be a formate. The ZnO supported catalysts had a higher density of acidic sites and favored pathways where the intermediate was converted to CO{sub 2} while the CeO{sub 2} supported catalysts had a higher density of basic sites and favored the production of CO.

Reconstructing the landing trajectory of the CE-3 lunar probe by using images from the landing camera

International Nuclear Information System (INIS)

Liu Jian-Jun; Yan Wei; Li Chun-Lai; Tan Xu; Ren Xin; Mu Ling-Li

2014-01-01

An accurate determination of the landing trajectory of Chang'e-3 (CE-3) is significant for verifying orbital control strategy, optimizing orbital planning, accurately determining the landing site of CE-3 and analyzing the geological background of the landing site. Due to complexities involved in the landing process, there are some differences between the planned trajectory and the actual trajectory of CE-3. The landing camera on CE-3 recorded a sequence of the landing process with a frequency of 10 frames per second. These images recorded by the landing camera and high-resolution images of the lunar surface are utilized to calculate the position of the probe, so as to reconstruct its precise trajectory. This paper proposes using the method of trajectory reconstruction by Single Image Space Resection to make a detailed study of the hovering stage at a height of 100 m above the lunar surface. Analysis of the data shows that the closer CE-3 came to the lunar surface, the higher the spatial resolution of images that were acquired became, and the more accurately the horizontal and vertical position of CE-3 could be determined. The horizontal and vertical accuracies were 7.09 m and 4.27 m respectively during the hovering stage at a height of 100.02 m. The reconstructed trajectory can reflect the change in CE-3's position during the powered descent process. A slight movement in CE-3 during the hovering stage is also clearly demonstrated. These results will provide a basis for analysis of orbit control strategy, and it will be conducive to adjustment and optimization of orbit control strategy in follow-up missions

La Substitution and Pressure Studies on CeCoSi: A Possible Antiferroquadrupolar Ordering Induced by Pressure

Science.gov (United States)

Tanida, Hiroshi; Muro, Yuji; Matsumura, Takeshi

2018-02-01

The La-substitution and pressure effects on antiferromagnet CeCoSi with a tetragonal crystal structure were investigated in order to clarify the origin of the pressure induced ordered phase (PIOP) with an enormously high transition temperature of T0 ˜ 38 K. By substituting Ce with La, the PIOP shifts to high pressures, and the maximum value of T0 is suppressed, indicating that the PIOP originates from a Ce-Ce interaction. At T0, the magnetic susceptibility exhibits not a cusp, but an increase with decreasing temperature, as is frequently observed in antiferroquadrupolar (AFQ) ordering. Based on these results, we propose that a possible origin of the PIOP is an AFQ ordered phase of Ce-4f electron. Due to the lack of local inversion symmetry at the Ce sites, the AFQ order could be accompanied by odd parity multipolar moments. Since there is no clear evidence of successive transitions below T0, the remaining Kramers degeneracy could be lifted by the Kondo coupling.

Electron spin-resonance study on Ce{sup 3+} in BaLiF{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Yamaga, M. [Department of Electrical and Electronic Engineering, Faculty of Engineering, Gifu University, Gifu (Japan); Honda, M. [Faculty of Science, Naruto University of Education, Naruto (Japan); Shimamura, K.; Fukuda, T. [Institute for Materials Research, Tohoku University, Sendai (Japan); Yosida, T. [Nakanihon Automotive College, Kamo (Japan)

2000-07-10

Three distinct Ce{sup 3+} sites in BaLiF{sub 3} crystals estimated from the optical spectra are associated with configurations of Ce{sup 3+} accompanied by different charge compensators. This assignment is consistent with the electron spin-resonance (ESR) result that there are two tetragonal Ce{sup 3+} centres distorted along the [001] axis and two orthorhombic Ce{sup 3+} centres distorted along the [110] axis in the absence of the cubic centre. The configurations of the Ce{sup 3+} centres correspond to the substitution for Ba{sup 2+} ions along the [001] and [110] axes with Li{sup +} ions and the Ba{sup 2+}-ion vacancies along the [001] and [110] axes. The dominant component of the Ce{sup 3+} luminescence spectrum with the peak at {approx}320 nm and the large Stokes shift energy ({approx}8300 cm{sup -1}) is assigned as due to the substitution for a Ba{sup 2+} ion along the [001] axis with a Li{sup +} ion. As the ionic radius (0.74 A) of Li{sup +} is much smaller than that (1.60 A) of Ba{sup 2+}, the Li substitution produces more space, resulting in the large lattice relaxation in the 5d excited state of Ce{sup 3+}. (author)

Ce(III)/Ce(IV) in methanesulfonic acid as the positive half cell of a redox flow battery

International Nuclear Information System (INIS)

Leung, P.K.; Ponce de Leon, C.; Low, C.T.J.; Walsh, F.C.

2011-01-01

The characteristics of the Ce(III)/Ce(IV) redox couple in methanesulfonic acid were studied at a platinum disk electrode (0.125 cm 2 ) over a wide range of electrolyte compositions and temperatures: cerium (III) methanesulfonate (0.1-1.2 mol dm -3 ), methanesulfonic acid (0.1-5.0 mol dm -3 ) and electrolyte temperatures (295-333 K). The cyclic voltammetry experiments indicated that the diffusion coefficient of Ce(III) ions was 0.5 x 10 -6 cm 2 s -1 and that the electrochemical kinetics for the oxidation of Ce(III) and the reduction of Ce(IV) was slow. The reversibility of the redox reaction depended on the electrolyte composition and improved at higher electrolyte temperatures. At higher methanesulfonic acid concentrations, the degree of oxygen evolution decreased by up to 50% when the acid concentration increased from 2 to 5 mol dm -3 . The oxidation of Ce(III) and reduction of Ce(IV) were also investigated during a constant current batch electrolysis in a parallel plate zinc-cerium flow cell with a 3-dimensional platinised titanium mesh electrode. The current efficiencies over 4.5 h of the process Ce(III) to Ce(IV) and 3.3 h electrolysis of the reverse reaction Ce(IV) to Ce(III) were 94.0 and 97.6%, respectively. With a 2-dimensional, planar platinised titanium electrode (9 cm 2 area), the redox reaction of the Ce(III)/Ce(IV) system was under mass-transport control, while the reaction on the 3-dimensional mesh electrode was initially under charge-transfer control but became mass-transport controlled after 2.5-3 h of electrolysis. The effect of the side reactions (hydrogen and oxygen evolution) on the current efficiencies and the conversion of Ce(III) and Ce(IV) are discussed.

Geometrically frustrated magnetic structures of the heavy-fermion compound CePdAl studied by powder neutron diffraction

Energy Technology Data Exchange (ETDEWEB)

Doenni, A.; Fischer, P.; Zolliker, M. [Laboratory for Neutron Scattering, ETH Zuerich and Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Ehlers, G.; Maletta, H. [Hahn Meitner Institute Berlin, Glienicker Strasse 100, D-14092 Berlin (Germany); Kitazawa, H. [National Research Institute for Metals, Tsukuba, Ibaraki 305 (Japan)

1996-12-09

The heavy-fermion compound CePdAl with ZrNiAl-type crystal structure (hexagonal space group P6-bar2m) was investigated by powder neutron diffraction. The triangular coordination symmetry of magnetic Ce atoms on site 3f gives rise to geometrical frustration. CePdAl orders below T{sub N} = 2.7 K with an incommensurate antiferromagnetic propagation vector k=[1/2, 0, {tau}], {tau} approx. 0.35, and a longitudinal sine-wave (LSW) modulated spin arrangement. Magnetically ordered moments at Ce(1) and Ce(3) coexist with frustrated disordered moments at Ce(2). The experimentally determined magnetic structure is in agreement with group theoretical symmetry analysis considerations, calculated by the program MODY, which confirm that for Ce(2) an ordered magnetic moment parallel to the magnetically easy c-axis is forbidden by symmetry. Further low-temperature experiments give evidence for a second magnetic phase transition in CePdAl between 0.6 and 1.3 K. Magnetic structures of CePdAl are compared with those of the isostructural compound TbNiAl, where a non-zero ordered magnetic moment for the geometrically frustrated Tb(2) atoms is allowed by symmetry. (author)

Air, aqueous and thermal stabilities of Ce3+ ions in cerium oxide nanoparticle layers with substrates

KAUST Repository

Naganuma, Tamaki

2014-01-01

Abundant oxygen vacancies coexisting with Ce3+ ions in fluorite cerium oxide nanoparticles (CNPs) have the potential to enhance catalytic ability, but the ratio of unstable Ce3+ ions in CNPs is typically low. Our recent work, however, demonstrated that the abundant Ce3+ ions created in cerium oxide nanoparticle layers (CNPLs) by Ar ion irradiation were stable in air at room temperature. Ce valence states in CNPs correlate with the catalytic ability that involves redox reactions between Ce3+ and Ce4+ ions in given application environments (e.g. high temperature in carbon monoxide gas conversion and immersion conditions in biomedical applications). To better understand the mechanism by which Ce3+ ions achieve stability in CNPLs, we examined (i) extra-long air-stability, (ii) thermal stability up to 500 °C, and (iii) aqueous stability of Ce 3+ ions in water, buffer solution and cell culture medium. It is noteworthy that air-stability of Ce3+ ions in CNPLs persisted for more than 1 year. Thermal stability results showed that oxidation of Ce 3+ to Ce4+ occurred at 350 °C in air. Highly concentrated Ce3+ ions in ultra-thin CNPLs slowly oxidized in water within 1 day, but stability was improved in the cell culture medium. Ce 3+ stability of CNPLs immersed in the medium was associated with phosphorus adsorption on the Ce3+ sites. This study also illuminates the potential interaction mechanisms of stable Ce3+ ions in CNPLs. These findings could be utilized to understand catalytic mechanisms of CNPs with abundant oxygen vacancies in their application environments. © The Royal Society of Chemistry 2014.

Investigation of the hydrothermal crystallisation of the perovskite solid solution NaCe{sub 1−x}La{sub x}Ti{sub 2}O{sub 6} and its defect chemistry

Energy Technology Data Exchange (ETDEWEB)

Harunsani, Mohammad H. [Department of Chemistry, University of Warwick, Coventry CV4 7AL (United Kingdom); Woodward, David I. [Department of Physics, University of Warwick, Coventry CV4 7Al (United Kingdom); Peel, Martin D.; Ashbrook, Sharon E. [School of Chemistry, and EaStCHEM University of St. Andrews, North Haugh, St. Andrews, KY16 9ST (United Kingdom); Walton, Richard I., E-mail: r.i.walton@warwick.ac.uk [Department of Chemistry, University of Warwick, Coventry CV4 7AL (United Kingdom)

2013-11-15

Perovskites of nominal composition NaCe{sub 1−x}La{sub x}Ti{sub 2}O{sub 6} (0≤x≤1) crystallise directly under hydrothermal conditions at 240 °C. Raman spectroscopy shows distortion from the ideal cubic structure and Rietveld analysis of powder X-ray and neutron diffraction reveals that the materials represent a continuous series in rhombohedral space group R3-bar c. Ce L{sub III}-edge X-ray absorption near edge structure spectroscopy shows that while the majority of cerium is present as Ce{sup 3+} there is evidence for Ce{sup 4+}. The paramagnetic Ce{sup 3+} affects the chemical shift and line width of {sup 23}Na MAS NMR spectra, which also show with no evidence for A-site ordering. {sup 2}H MAS NMR of samples prepared in D{sub 2}O shows the inclusion of deuterium, which IR spectroscopy shows is most likely to be as D{sub 2}O. The deuterium content is highest for the cerium-rich materials, consistent with oxidation of some cerium to Ce{sup 4+} to provide charge balance of A-site water. - Graphical abstract: A multi-element A-site perovskite crystallises directly from aqueous, basic solutions at 240 °C; while the paramagnetic effect of Ce{sup 3+} on the {sup 23}Na NMR shows a homogeneous solid-solution, the incorporation of A-site water is also found from {sup 2}H NMR and IR, with oxidation of some cerium to charge balance proved by XANES spectroscopy. Display Omitted - Highlights: • Direct hydrothermal synthesis allows crystallisation of a perovskite solid-solution. • XANES spectroscopy shows some oxidation of Ce{sup 3+} to Ce{sup 4+}. • The paramagnetism of Ce{sup 3+} shifts and broadens the {sup 23}Na solid-state NMR. • The perovskite materials incorporate water as an A-site defect.

Luminescence properties and gamma-ray response of the Ce and Ca co-doped (Gd,Y)F3 single crystals

International Nuclear Information System (INIS)

Kamada, Kei; Yanagida, Takayuki; Fujimoto, Yutaka; Fukabori, Akihiro; Yoshikawa, Akira; Nikl, Martin

2011-01-01

The Ca0.5% and Ce1%, 3%, 7%, 10% co-doped Gd 0.5 Y 0.5 F 3 single crystals were grown by the μ-PD method. In the Ca0.5% and Ce3% co-doped sample, Ce 3+ -perturbed luminescence at 380 nm was observed with 32.4 ns photoluminescence decay time. The energy transfer in the sequence of the regular Ce 3+ → (Gd 3+ ) n → the perturbed Ce 3+ sites was evidenced through observation of decay time shortening of the regular Ce 3+ and Gd 3+ centers and the change between the Gd 3+ and Ce 3+ -perturbed emission intensity. The gamma-ray excited scintillation response of the Ca0.5%, Ce7% co-doped Gd 0.5 Y 0.5 F 3 sample was investigated with the help of the pulse height spectra and the light yield, energy resolution and non-proportionality was evaluated in the interval of energies of 59.4-1274 keV.

Substrate-dependent Au{sub x} cluster: A new insight into Au{sub x}/CeO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Zhu, Kong-Jie; Yang, Yan-Ju [School of Chemistry and Life Science, Zhejiang Normal University, Jinhua 321004 (China); Lang, Jia-Jian [School of Chemistry and Life Science, Zhejiang Normal University, Jinhua 321004 (China); Engineering Laboratory of Specialty Fibers and Nuclear Energy Materials, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201 (China); Teng, Bo-Tao, E-mail: tbt@zjnu.cn [School of Chemistry and Life Science, Zhejiang Normal University, Jinhua 321004 (China); Wu, Feng-Min [School of Chemistry and Life Science, Zhejiang Normal University, Jinhua 321004 (China); Du, Shi-Yu [Engineering Laboratory of Specialty Fibers and Nuclear Energy Materials, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201 (China); Wen, Xiao-Dong, E-mail: wxd@sxicc.ac.cn [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China)

2016-11-30

Graphical abstract: 2D Au{sub x} (x < 10) on CeO{sub 2}(110) are more stable than 3D ones, while the stability trend changes for x ≥ 10; Au{sub x} (x ≤ 4) prefer to monatomically disperse on CeO{sub 2}(100) and aggregate to 3D clusters for x > 4. - Highlights: • The stable structures of Au{sub x}/CeO{sub 2} are dependent of index surfaces of CeO{sub 2}. • Au{sub x} prefers to monatomically disperse on CeO{sub 2}(100) at low coverage. • Au{sub x} aggregates to 3D clusters on CeO{sub 2}(100) at high coverage. • 2D Au{sub x} (x < 10) are more stable than the 3D ones on CeO{sub 2}(110). • The effects on the stability of Au{sub x}/CeO{sub 2} are systematically discussed. - Abstract: To theoretically study the structures of metal clusters on oxides is very important and becomes one of the most challenging works in computational heterogeneous catalysis since many factors affect their structures and lead to various possibilities. In this work, it is very interesting to find that the stable structures and stability evolution of Au{sub x} clusters on ceria are varied with different index surfaces of CeO{sub 2}. The corresponding reasons in chemical, geometric and electronic properties are systematically explored. Au{sub x} (x = 1–4) clusters prefer to separately disperse at the O-O bridge sites on CeO{sub 2}(100) due to the low coordination number of surface O; while aggregate due to the strong Au–Au attractions when x is larger than 4. Owing to the uniform distribution of O-O bridge sites on CeO{sub 2}(111) and (100), the most stable configurations of Au{sub x} are 3D structures with bottom atoms more than top ones when x is larger than 4. However, 2D configurations of Au{sub x}/CeO{sub 2}(110) (x < 10) are more stable than the corresponding 3D structures due to the particular O-O arrangement on CeO{sub 2}(110). 3D Au{sub x} clusters across O-O-Y lines are suggested as the most stable configurations for Au{sub x}/CeO{sub 2}(110) (x ≥ 10). The present

Magnetism and superconductivity in a heavy-fermion superconductor, CePt3Si

International Nuclear Information System (INIS)

Takeuchi, T; Hashimoto, S; Yasuda, T; Shishido, H; Ueda, T; Yamada, M; Obiraki, Y; Shiimoto, M; Kohara, H; Yamamoto, T; Sugiyama, K; Kindo, K; Matsuda, T D; Haga, Y; Aoki, Y; Sato, H; Settai, R; Onuki, Y

2004-01-01

We have studied the magnetic and thermal properties of a single crystal of CePt 3 Si, which is a recently reported heavy-fermion superconductor with a superconducting transition temperature T c = 0.75 K and a Neel temperature T N = 2.2 K. The overall experimental data are principally explained on the basis of the crystalline electric field (CEF) scheme. Even in the antiferromagnetic state, the CEF model applies well to the characteristic features in the magnetization curve. These results indicate the existence of a localized magnetic moment at the Ce site, with a considerably reduced ordered moment of 0.16 μ B /Ce, and the strongly correlated conduction electrons are condensed into the superconducting state. We have also constructed the magnetic phase diagram including the superconducting phase for H parallel [110] and [001]. (letter to the editor)

Dielectric properties estimation of the lunar regolith at CE-3 landing site using lunar penetrating radar data

Science.gov (United States)

Feng, Jianqing; Su, Yan; Ding, Chunyu; Xing, Shuguo; Dai, Shun; Zou, Yongliao

2017-03-01

The second channel (CH2) of the Lunar Penetrating Radar (LPR) carried on the Chang'e-3 (CE-3) Yutu Rover was used to determine the thickness and structure of the lunar regolith. Accurately revealing the true structure beneath the surface requires knowledge of the dielectric permittivity of the regolith, which allows one to properly apply migration to the radar image. In contrast to simple assumptions in previous studies, this paper takes account of heterogeneity of the regolith and derives regolith's permittivity distribution laterally and vertically by a method widely used in data processing of terrestrial Ground Penetrating Radar (GPR). We find that regolith permittivity at the landing site increases with depth more quickly than previously recognized. At a depth of ∼2.5-3 m, the dielectric constant reaches the value of solid basalt. The radar image was migrated on the basis of the permittivity profile. We do not find any continuous distinct layers or an apparent regolith/rock interface in the migrated radargram, which implies that this area is covered by relatively young, poorly layered deposits.

The calculated magnetic, electronic and thermodynamic properties of Ce{sub 3}Co{sub 29}Si{sub 4}B{sub 10} compound

Energy Technology Data Exchange (ETDEWEB)

Huo, Jin-Rong [Institute of Applied Physics, Beijing University of Science and Technology, Beijing 100083 (China); Wang, Xiao-Xu [Institute of Applied Physics, Beijing University of Science and Technology, Beijing 100083 (China); Cloud Computing Department, Beijing Computing Center, Beijing 100084 (China); Hu, Yao-Wen [Department of Physics, Tsinghua University, Beijing 100084 (China); Zhang, Guo-Hua; Cheng, Hai-Xia; Li, Lu [Institute of Applied Physics, Beijing University of Science and Technology, Beijing 100083 (China); Qian, Ping, E-mail: qianping@ustb.edu.cn [Institute of Applied Physics, Beijing University of Science and Technology, Beijing 100083 (China)

2016-05-15

The magnetic moment, lattice parameter and atom fraction coordinates for Ce{sub 3}Co{sub 29}Si{sub 4}B{sub 10} are calculated by the first-principles GGA+U method, and the results indicate that the calculated and experimental values are basically accordant when U=2.6 eV. We study the interaction effect and orbital hybridization between Co and Ce atoms. The projected density of states at U=2.6 eV which provided by Co-2c, Ce-2b and Ce-4d sites are contrasted with else U values. Meanwhile the electron density of states for different sites and the distance between various atoms are exhibited. In addition, the thermodynamic properties of Ce{sub 3}Co{sub 29}Si{sub 4}B{sub 10} are evaluated by using a series of interatomic pair potentials. - Graphical abstract: Change of the total magnetic moment for Ce{sub 3}Co{sub 29}Si{sub 4}B{sub 10} along with the value of U. There is a sharply decline of the curve at U=2.6 eV and, at the moment, the total magnetic moment of the compound have a good agreement with the experimental data. - Highlights: • We research of quaternary rare earth and transition metal compounds. • We perform the calculation of magnetic moment and electronic structure by GGA+U method. • The orbital hybridization between Co and Ce atoms is displayed and analyzed. • Show the plot of projected density of states for different sites more clearly. • Calculate the thermodynamic property of rare-earth transition metal compound.

Comparison of Spectral and Scintillation Properties of LuAP:Ce and LuAP:Ce,Sc Single Crystals

Science.gov (United States)

Petrosyan, Ashot G.; Derdzyan, Marina; Ovanesyan, Karine; Shirinyan, Grigori; Lecoq, Paul; Auffray, Etiennette; Kronberger, Matthias; Frisch, Benjamin; Pedrini, Christian; Dujardin, Christophe

2009-10-01

Scintillation properties of LuAP:Ce and LuAP:Ce,Sc crystal series were studied under excitation by gamma-rays from a 137Cs source. Both series demonstrated comparable optical quality in terms of underlying absorption at 260 nm, slope of the optical edge and transmission in the range of emission. The light yield of LuAP:Ce crystals measured in 0.2 cm times 0.2 cm times 0.8 cm pixels increases linearly with the Ce concentration reaching at 0.58 at. % 6448 plusmn 322 ph/MeV and 9911 plusmn 496 ph/MeV in the long and in the short directions respectively (the light yield ratio is 65%) and shows no sign of light saturation. The energy resolution is found to depend, among other factors, on the uniformity of Ce concentration within the pixels and is improved to 7.1 plusmn 0.4% (I = 0.2 cm), 9.5 plusmn 0.5% (I = 0.8 cm). Intentional co-doping with Sc + ions was tested and resulted in increase of the Ce distribution coefficient to about 0.3. This enabled to increase the concentration of Ce in LuAP:Ce,Sc crystals up to 0.7 at. %, while conserving high optical quality. In contrast to LuAP:Ce, the light yield in LuAP:Ce,Sc crystals does not increase with Ce concentration, the photo peak being gradually suppressed. The involved mechanisms are discussed basing on measurements of the unit cell volumes, Ce concentration uniformity, x-ray rocking spectra, absorption spectra of pure and variously doped LuAP crystals, and emission spectra under different excitations.

Solid state speciation of uranium and its local structure in Sr2CeO4 using photoluminescence spectroscopy

Science.gov (United States)

Sahu, M.; Gupta, Santosh K.; Jain, D.; Saxena, M. K.; Kadam, R. M.

2018-04-01

An effort was taken to carry our speciation study of uranium ion in technologically important cerate host Sr2CeO4 using time resolved photoluminescence spectroscopy. Such studies are not relevant only to nuclear industry but can give rich insight into fundamentals of 5f electron chemistry in solid state systems. In this work both undoped and varied amount of uranium doped Sr2CeO4 compound is synthesized using complex polymerization method and is characterized systematically using X-ray diffraction (XRD), Raman spectroscopy, photoluminescence spectroscopy and scanning electron microscopy (SEM). Both XRD and Raman spectroscopy confirmed the formation of pure Sr2CeO4 which has tendency to decompose peritectically to SrCeO3 and SrO at higher temperature. Uranium doping is confirmed by XRD. Uranium exhibits a rich chemistry owing to its variable oxidation state from +3 to +6. Each of them exhibits distinct luminescence properties either due to f-f transitions or ligand to metal charge transfer (LMCT). We have taken Sr2CeO4 as a model host lattice to understand the photophysical characteristics of uranium ion in it. Emission spectroscopy revealed the stabilization of uranium as U (VI) in the form of UO66- (octahedral uranate) in Sr2CeO4. Emission kinetics study reflects that uranate ions are not homogeneously distributed in Sr2CeO4 and it has two different environments due to its stabilization at both Sr2+ as well as Ce4+ site. The lifetime population analysis interestingly pinpointed that majority of uranate ion resided at Ce4+ site. The critical energy-transfer distance between the uranate ion was determined based on which the concentration quenching mechanism was attributed to electric multipolar interaction. These studies are very important in designing Sr2CeO4 based optoelectronic material as well exploring it for actinides studies.

Microstructures, mechanical properties and corrosion resistances of extruded Mg-Zn-Ca-xCe/La alloys.

Science.gov (United States)

Tong, L B; Zhang, Q X; Jiang, Z H; Zhang, J B; Meng, J; Cheng, L R; Zhang, H J

2016-09-01

Magnesium alloys are considered as good candidates for biomedical applications, the influence of Ce/La microalloying on the microstructure, mechanical property and corrosion performance of extruded Mg-5.3Zn-0.6Ca (wt%) alloy has been investigated in the current study. After Ce/La addition, the conventional Ca2Mg6Zn3 phases are gradually replaced by new Mg-Zn-Ce/La-(Ca) phases (T1'), which can effectively divide the Ca2Mg6Zn3 phase. The Ca2Mg6Zn3/T1' structure in Mg-Zn-Ca-0.5Ce/La alloy is favorably broken into small particles during the extrusion, resulting in an obvious refinement of secondary phase. The dynamic recrystallized grain size is dramatically decreased after 0.5Ce/La addition, and the tensile yield strength is improved, while further addition reverses the effect, due to the grain coarsening. However, the corrosion resistance of extruded Mg-Zn-Ca alloy deteriorates after Ce/La addition, because the diameter of secondary phase particle is remarkably decreased, which increases the amount of cathodic sites and accelerates the galvanic corrosion process. Copyright © 2016 Elsevier Ltd. All rights reserved.

CeO2-stabilized tetragonal ZrO2 polycrystals (Ce-TZP ceramics)

International Nuclear Information System (INIS)

Andrade Nono, M.C. de.

1990-12-01

This work presents the development and the characterization of CeO 2 -stabilized tetragonal ZrO 2 polycrystals (Ce-TZP ceramics), since it is considered candidate material for applications as structural high performance ceramics. Sintered ceramics were fabricated from mixtures of powders containing different CeO 2 content prepared by conventional and nonconventional techniques. These powders and their resultant sintered ceramics were specified by chemical and physical characterization, compactation state and mechanical properties. The chemical characteristics were determined by chemical analysis and the physical characteristics were evaluated by phase content, particle and agglomerate size and aspect, and powder porosity. (author)

Electronic structure study of Co doped CeO2 nanoparticles using X-ray absorption fine structure spectroscopy

International Nuclear Information System (INIS)

Kumar, Shalendra; Gautam, Sanjeev; Song, T.K.; Chae, Keun Hwa; Jang, K.W.; Kim, S.S.

2014-01-01

Highlights: • The electronic structural of Co–CeO 2 nanoparticles is investigated using XAFS. • Ce M 5,4 , Ce L 3 and O K edge NEXAFS reveal that the Ce-ions are in +4 valence state. • The NEXAFS spectrum performed at Co L3,2-edge confirms Co-ion in 2+ state. • The EXAFS analysis also show that Co ions are occupying Ce position in doped CeO 2 . • The distances between Ce–O and Ce–Ce/Co in all shells decreases with Co doping. - Abstract: We investigated the electronic structure of well characterized Co doped CeO 2 nanoparticles using X-ray absorption fine structure (XAFS) spectroscopy. Near edge X-ray absorption fine structure (NEXAFS) spectra at Ce M 5,4 , Ce L 3 and O K-edge conclude that the Ce-ions are in +4 valence state in pure as well as in Co doped CeO 2 nanoparticles. The local structure around Ce-atom in Co doped CeO 2 nanoparticles was also determined using extended X-ray absorption fine structure (EXAFS) spectroscopy at Ce L 3 edge. The EXAFS analysis suggest that the inter-atomic distance of Ce–O, Ce–Ce/Co decreases with Co doping, which indicate a contraction of the lattice. The decease in Ce–O distance also reflect that there is a formation of oxygen vacancies in CeO 2 matrix. The Debye–Waller factor also shows the consistent behaviour for all the coordination shells. The atomic multiplet calculations for Co L 3,2 -edge was performed to determine the valence state, symmetry and field splitting, which reflect that Co-ions are in 2+ state and substituted at Ce-site with crystal field splitting of 10Dq=-0.57eV. The XAFS measurements reveal that the Co-ions occupy the Ce position in the CeO 2 host matrix and create a oxygen vacancy

Magnetic behaviour of new Ce compounds

Energy Technology Data Exchange (ETDEWEB)

Sampathkumaran, E V [Tata Inst. of Fundamental Research, Bombay (India); Mallik, R [Tata Inst. of Fundamental Research, Bombay (India)

1996-07-01

We report initial results of our investigation on the magnetic behaviour of some new Ce compounds. The compounds, CeIr{sub 2}B{sub 2}C and CeIr{sub 2}Ge{sub 2}, do not appear to exhibit bulk magnetic ordering down to 2 K. The alloys, Ce{sub 2}Pd{sub 2}In and Ce{sub 2}Cu{sub 2}In, order magnetically below 4 and 6 K, respectively, and a marginal change in the Pd(Cu)/In composition does not significantly influence the ordering temperatures. (orig.).

Optical and scintillation properties of Ce-doped LuLiF4 with different Ce concentrations

International Nuclear Information System (INIS)

Yanagida, Takayuki; Fujimoto, Yutaka; Fukuda, Kentaro; Chani, Valery

2013-01-01

The crystals of 0.1, 0.5, and 1 mol% Ce-doped LuLiF 4 (Ce:LLF) grown by the micro-pulling down (μ-PD) method were examined for their optical and scintillation properties. Ce:LLF crystals had ∼80% transparency at wavelengths longer than 300 nm. In photoluminescence spectra, they demonstrated intense emission peaks at 310 and 330 nm with the quantum yield of 60–90%. Ce 3+ 5d–4f emission peaks were also detected at similar wavelengths of 310 and 330 nm in the radioluminescence spectra obtained under X-ray excitation. According to pulse height spectra recorded under γ-ray irradiation, the absolute light yield of Ce 0.1, 0.5, and 1% were 3600±400, 3000±300, and 1700±200 ph/MeV, respectively. Decay time kinetics was also inspected using a pulse X-ray equipped streak camera system. The decay time components of Ce:LLF were ∼70 ns and ∼1 μs for all the samples

Production of 139Ce by the 139La(p,n)139Ce reaction

International Nuclear Information System (INIS)

Ishioka, Noriko S.; Sekine, Toshiaki; Izumo, Mishiroku; Hashimoto, Kazuyuki; Kobayashi, Katsutoshi; Matsuoka, Hiromitsu

2002-01-01

To produce a carrier-free 139 Ce to be used as an efficiency-calibration source for Ge detectors, a target-preparation method and a chemical separation method were studied. It was found that commercially available powders of lanthanum-oxide and lanthanum metal are applicable to a target material in the nuclear reaction 139 La(p,n) 139 Ce. In the separation of 139 Ce from an irradiated lanthanum target, a solvent-extraction method and an ion-exchange method gave final products in good chemical purity. (author)

Effect of yttrium on electron–phonon coupling strength of 5d state of Ce3+ ion in LYSO:Ce crystals

International Nuclear Information System (INIS)

Ding, Dongzhou; Liu, Bo; Wu, Yuntao; Yang, Jianhua; Ren, Guohao; Chen, Junfeng

2014-01-01

This paper aims at an improved understanding of luminescence properties of (Lu 1−x Y x ) 2 SiO 5 :Ce (x=0 at%, 26 at%, 45 at%, 66 at% and 100 at%). Photoluminescence emission and excitation spectra as well as Raman spectra of (Lu 1−x Y x ) 2 SiO 5 :Ce were investigated as a function of yttrium (shortened as Y) content in it. Obtained Huang–Rhys factor S indicates that the coupling between Ce1 (7-oxygen-coordinated), Ce2 (6-oxygen-coordinated) and LYSO lattice is intermediate and strong, respectively. Besides, it was found that: with the increase of Y content, crystal field strength around Ce1 and Ce2 decreases, Stokes shift of Ce1 and Ce2 presents an increase trend, and S of Ce2 tends to decrease. These phenomena were explained by geometrical influence of Y 3+ /Lu 3+ on the crystal field splitting of the 5d levels of Ce 3+ and coupling strength. With the increase of Y content, the evolution of S and coupling energy ħω of Ce1 present a slight increase and decrease trend respectively, while S and coupling energy ħω of Ce2 present an obvious decrease and increase trend, respectively. - Highlights: • Crystal field strength around Ce1 decreases with increase of Y content in LYSO:Ce. • A diagram of Huang–Rhys factor S against Y content in LYSO:Ce was constructed. • A diagram of coupling energy ħω against Y content in LYSO:Ce was constructed. • A diagram of Stokes shift against Y content in LYSO:Ce was constructed

Catalytic Oxidation of NO over MnOx–CeO2 and MnOx–TiO2 Catalysts

Directory of Open Access Journals (Sweden)

Xiaolan Zeng

2016-11-01

Full Text Available A series of MnOx–CeO2 and MnOx–TiO2 catalysts were prepared by a homogeneous precipitation method and their catalytic activities for the NO oxidation in the absence or presence of SO2 were evaluated. Results show that the optimal molar ratio of Mn/Ce and Mn/Ti are 0.7 and 0.5, respectively. The MnOx–CeO2 catalyst exhibits higher catalytic activity and better resistance to SO2 poisoning than the MnOx–TiO2 catalyst. On the basis of Brunauer–Emmett–Teller (BET, X-ray diffraction (XRD, and scanning transmission electron microscope with mapping (STEM-mapping analyses, it is seen that the MnOx–CeO2 catalyst possesses higher BET surface area and better dispersion of MnOx over the catalyst than MnOx–TiO2 catalyst. X-ray photoelectron spectroscopy (XPS measurements reveal that MnOx–CeO2 catalyst provides the abundance of Mn3+ and more surface adsorbed oxygen, and SO2 might be preferentially adsorbed to the surface of CeO2 to form sulfate species, which provides a protection of MnOx active sites from being poisoned. In contrast, MnOx active sites over the MnOx–TiO2 catalyst are easily and quickly sulfated, leading to rapid deactivation of the catalyst for NO oxidation. Furthermore, temperature programmed desorption with NO and O2 (NO + O2-TPD and in situ diffuse reflectance infrared transform spectroscopy (in situ DRIFTS characterizations results show that the MnOx–CeO2 catalyst displays much stronger ability to adsorb NOx than the MnOx–TiO2 catalyst, especially after SO2 poisoning.

Physico-chemical properties of (U,Ce)O2

International Nuclear Information System (INIS)

Yamada, K.; Yamanaka, S.; Katsura, M.

1998-01-01

The high-temperature X-ray diffraction analysis of (U,Ce)O 2 with CeO 2 contents ranging from 0 to 20 mol.% CeO 2 was performed to obtain the variation of the linear thermal expansion coefficient with the CeO 2 content. Ultrasonic pulse-echo measurements were also carried out from room temperature to 673 K to estimate the change in the mechanical properties of (U,Ce)O 2 with the CeO 2 content. The variation in the linear thermal expansion coefficient at the low CeO 2 content region is more steep than that expected from the linear thermal expansion coefficient of UO 2 and CeO 2 . The Young's and shear moduli of all (U,Ce)O 2 were found to decrease with rising temperature. This was due to the increase of the bond length accompanied by the thermal expansion. Although the lattice parameter decreased with CeO 2 content, the moduli of (U,Ce)O 2 were found to decrease with increasing CeO 2 content at room temperature. These results show that in the range from 0 to 20 mol.% of CeO 2 , as CeO 2 content increases, the bottom of the potential energy in (U,Ce)O 2 is shallower and broader. (orig.)

Luminescence, Energy Transfer and Tunable Color of Ce3+- and Tb3+-Activated Na3Gd(BO3)2 Phosphors

Science.gov (United States)

Zhang, Xinguo; Pan, Jialiang; Mo, Fuwang

2017-07-01

A series of blue Na3Gd(BO3)2:Ce3+ and blue-to-green color-tunable Na3Gd (BO3)2:Ce3+,Tb3+ phosphors were synthesized by the solid-state method. The luminescence, concentration quenching and energy transfer (ET) process of Na3Gd(BO3)2:Ce3+,Tb3+ were investigated. Both Ce3+ and Tb3+ occupy the Gd3+ site in the Na3Gd(BO3)2 host. Na3Gd(BO3)2:Ce3+ exhibits strong ultraviolet absorption and broadband blue emission. The Ce3+ sensitization effect on Tb3+ has been verified by the variation of PL/PLE spectra, the Ce3+ decay lifetimes and the energy transfer efficiency of Na3Gd(BO3)2:Ce3+,Tb3+ phosphors. The maximum Ce3+-Tb3+ ET efficiency has been calculated to be 95%. The emitting color of the obtained phosphors can be modulated from blue (0.179, 0.204) through bluish-green (0.271, 0.391) to green (0.349, 0.551) by properly changing the ratio of Ce3+/Tb3+.

Comparison between the Oxygen Reduction Reaction Activity of Pd₅Ce and Pt₅Ce

DEFF Research Database (Denmark)

Tripkovic, Vladimir; Zheng, Jian; Rizzi, Gian Andrea

2015-01-01

A set of electrochemical and X-ray spectroscopy measurements have been used conjointly with density functional theory (DFT) simulations to study the activity and stability of Pd5Ce for the oxygen reduction reaction. A polycrystalline Pd5Ce rod has been selected as a model catalyst to test if resu......-Pd5Ce is more facile, requires less atom rearrangement, than transformation from Pt5Ce to Pt3Ce, which might explain the kinetic stability of Pt5Ce at low temperatures....

Formic Acid Modified Co3O4-CeO2 Catalysts for CO Oxidation

Directory of Open Access Journals (Sweden)

Ruishu Shang

2016-03-01

Full Text Available A formic acid modified catalyst, Co3O4-CeO2, was prepared via facile urea-hydrothermal method and applied in CO oxidation. The Co3O4-CeO2-0.5 catalyst, treated by formic acid at 0.5 mol/L, performed better in CO oxidation with T50 obtained at 69.5 °C and T100 obtained at 150 °C, respectively. The characterization results indicate that after treating with formic acid, there is a more porous structure within the Co3O4-CeO2 catalyst; meanwhile, despite of the slightly decreased content of Co, there are more adsorption sites exposed by acid treatment, as suggested by CO-TPD and H2-TPD, which explains the improvement of catalytic performance.

Dependence of the Ce(iii)/Ce(iv) ratio on intracellular localization in ceria nanoparticles internalized by human cells

KAUST Repository

Ferraro, Daniela

2017-01-09

CeO2 nanoparticles (CNPs) have been investigated as promising antioxidant agents with significant activity in the therapy of diseases involving free radicals or oxidative stress. However, the exact mechanism responsible for CNP activity has not been completely elucidated. In particular, in situ evidence of modification of the oxidative state of CNPs in human cells and their evolution during cell internalization and subsequent intracellular distribution has never been presented. In this study we investigated modification of the Ce(iii)/Ce(iv) ratio following internalization in human cells by X-ray absorption near edge spectroscopy (XANES). From this analysis on cell pellets, we observed that CNPs incubated for 24 h showed a significant increase in Ce(iii). By coupling on individual cells synchrotron micro-X-ray fluorescence (μXRF) with micro-XANES (μXANES) we demonstrated that the Ce(iii)/Ce(iv) ratio is also dependent on CNP intracellular localization. The regions with the highest CNP concentrations, suggested to be endolysosomes by transmission electron microscopy, were characterized by Ce atoms in the Ce(iv) oxidation state, while a higher Ce(iii) content was observed in regions surrounding these areas. These observations suggest that the interaction of CNPs with cells involves a complex mechanism in which different cellular areas play different roles.

Dependence of the Ce(iii)/Ce(iv) ratio on intracellular localization in ceria nanoparticles internalized by human cells

KAUST Repository

Ferraro, Daniela; Tredici, Ilenia G.; Ghigna, Paolo; Castillio-Michel, Hiram; Falqui, Andrea; Di Benedetto, Cristiano; Alberti, Giancarla; Ricci, Vittorio; Anselmi-Tamburini, Umberto; Sommi, Patrizia

2017-01-01

CeO2 nanoparticles (CNPs) have been investigated as promising antioxidant agents with significant activity in the therapy of diseases involving free radicals or oxidative stress. However, the exact mechanism responsible for CNP activity has not been completely elucidated. In particular, in situ evidence of modification of the oxidative state of CNPs in human cells and their evolution during cell internalization and subsequent intracellular distribution has never been presented. In this study we investigated modification of the Ce(iii)/Ce(iv) ratio following internalization in human cells by X-ray absorption near edge spectroscopy (XANES). From this analysis on cell pellets, we observed that CNPs incubated for 24 h showed a significant increase in Ce(iii). By coupling on individual cells synchrotron micro-X-ray fluorescence (μXRF) with micro-XANES (μXANES) we demonstrated that the Ce(iii)/Ce(iv) ratio is also dependent on CNP intracellular localization. The regions with the highest CNP concentrations, suggested to be endolysosomes by transmission electron microscopy, were characterized by Ce atoms in the Ce(iv) oxidation state, while a higher Ce(iii) content was observed in regions surrounding these areas. These observations suggest that the interaction of CNPs with cells involves a complex mechanism in which different cellular areas play different roles.

Luminescence properties and gamma-ray response of the Ce and Ca co-doped (Gd,Y)F{sub 3} single crystals

Energy Technology Data Exchange (ETDEWEB)

Kamada, Kei, E-mail: k-kamada@furukawakk.co.jp [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai (Japan); Furukawa Co. Ltd. (Japan); Yanagida, Takayuki; Fujimoto, Yutaka; Fukabori, Akihiro [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai (Japan); Yoshikawa, Akira [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai (Japan); New Industry Creation Hatchery Center, Tohoku University, Sendai (Japan); Nikl, Martin [Institute of Physics AS CR (Czech Republic)

2011-12-11

The Ca0.5% and Ce1%, 3%, 7%, 10% co-doped Gd{sub 0.5}Y{sub 0.5}F{sub 3} single crystals were grown by the {mu}-PD method. In the Ca0.5% and Ce3% co-doped sample, Ce{sup 3+}-perturbed luminescence at 380 nm was observed with 32.4 ns photoluminescence decay time. The energy transfer in the sequence of the regular Ce{sup 3+}{yields} (Gd{sup 3+}){sub n}{yields} the perturbed Ce{sup 3+} sites was evidenced through observation of decay time shortening of the regular Ce{sup 3+} and Gd{sup 3+} centers and the change between the Gd{sup 3+} and Ce{sup 3+}-perturbed emission intensity. The gamma-ray excited scintillation response of the Ca0.5%, Ce7% co-doped Gd{sub 0.5}Y{sub 0.5}F{sub 3} sample was investigated with the help of the pulse height spectra and the light yield, energy resolution and non-proportionality was evaluated in the interval of energies of 59.4-1274 keV.

Synthesis and physico-chemical characterization of CeO{sub 2}/ZrO{sub 2}-SO{sub 4}{sup 2-} mixed oxides

Energy Technology Data Exchange (ETDEWEB)

Hernandez E, J. M.; Silva R, R.; Garcia A, R. [Instituto Tecnologico de Ciudad Madero, Div. de Estudios de Posgrado e Investigacion, Juventino Rosas y Jesus Urueta s/n, Col. Los Mangos, 89440 Ciudad Madero, Tamaulipas (Mexico); Garcia S, L. A. [IPN, Centro Interdisciplinario de Investigaciones y de Estudios sobre Medio Ambiente y Desarrollo, 30 de Junio No. 1520, Barrio La Laguna Ticoman, 07340 Mexico D. F. (Mexico); Handy, B. E.; Cardenas G, G. [Universidad Autonoma de San Luis Potosi, CIEP, Facultad de Ciencias Quimicas, Av. Dr. Manuel Nava No. 6, Zona Universitaria, 78210 SLP, San Luis Potosi (Mexico); Cueto H, A. [Universidad Autonoma Metropolitana, Unidad Azcapotzalco, Av. San Pablo No. 180, Col. Reynosa Tamaulipas, 02200 Mexico D. F. (Mexico)

2012-07-01

Environmentally friendly solid-acid catalysts CeO{sub 2}/ZrO{sub 2}-SO{sub 4}{sup 2-} were prepared by the sol gel method varying CeO{sub 2} content (10, 20 and 30 wt %) and using sulfation in situ, maintaining the sulfate ions amount present in the materials at 20 wt %. ZrO{sub 2} and ZrO{sub 2}-SO{sub 4}{sup 2-} were also prepared for comparison proposes using the same synthesis method. The materials were characterized by X-ray diffraction, nitrogen physisorption, potentiometric titration with n-butylamine, decomposition of 2-propanol and n-pentane isomerization. The specific surface area of ZrO{sub 2}-SO{sub 4}{sup 2-} was high (160 m{sup 2}/g) compared with the unmodified ZrO{sub 2} (80 m{sup 2}/g), however this area decreased with increasing the CeO{sub 2} content (37-100 m{sup 2}/g). There was no significant effect of CeO{sub 2} on the tetragonal structure of ZrO{sub 2}-SO{sub 4}{sup 2-}. The variation of acid sites amount runs parallel to the change of specific surface area. The acid sites amount decreased with increasing cerium oxide content. The decomposition of 2-propanol results fundamentally in the formation of dehydration products such as propylene and diisopropyl ether, both involving acid sites. In addition, a good performance during the n-pentane isomerization was observed for these materials. The selectivity towards isopentane reaches 84% when the Pt/CeO{sub 2}/ZrO{sub 2}-SO{sub 4}{sup 2-} catalyst with the highest CeO{sub 2} content was used. (Author)

Adduct formation in Ce(IV) thenolytrifluoroacetonate

International Nuclear Information System (INIS)

Anufrieva, S.I.; Polyakova, G.V.; Snezhko, N.I.; Pechurova, N.I.; Martynenko, L.I.; Spitsyn, V.I.

1982-01-01

The literature contains no information on adduct formation in Ce(IV) β-diketonates with additional ligands. Since tetrakis-β-diketonates of Ce(IV) have four six-membered chelate rings, we can suppose that the introduction of an additional monodentate or bidentate ligand into the coordination sphere of Ce(IV) β-diketonates would lead to an increase in the coordination number (CN) of the Ce(IV) to nine or ten. The possibility of realization of such a high CN for Ce(IV) has not been proved; a study of adduct formation by Ce(IV) tetrakis-β-diketonates is thus of theoretical interest. Such an investigation might also be of practical interest, because the introduction of an additional ligand into the coordination sphere of a rare-earth β-diketonate usually increases the solubility of the β-diketonate in nonpolar solvents and increases the volatility of the compound; such a modification of the properties is important for various practical purposes. The aim of our work was to study the possibility of separating solid adducts of Ce(IV) tetrakis-thenoyltrifluoroacetonate with certain oxygen-containing and nitrogen-containing donor monodentate and bidentate ligands, and also to investigate their properties. As the β-diketone we used thenoyltrifluoroacetone (HTTFA), since in a parallel investigation it was found that Ce(TTFA) 4 has a high oxidation-reduction stability

Surface and bulk 4f-photoemission spectra of CeIn3 and CeSn3

International Nuclear Information System (INIS)

Kim, H.; Tjernberg, O.; Chiaia, G.; Kumigashira, H.; Takahashi, T.; Duo, L.; Sakai, O.; Kasaya, M.; Lindau, I.

1997-01-01

Resonant photoemission spectroscopy was performed on CeIn 3 and CeSn 3 at the 4d-4f and 3d-4f core thresholds. Using the different surface sensitivity between the two photon energies, surface and bulk 4f-photoemission spectra were derived for both compounds. With the noncrossing approximation of the Anderson impurity model, the 4d-4f resonant spectra together with the surface and bulk spectra were self-consistently analyzed to obtain the microscopic parameters such as the 4f-electron energy and the hybridization strength with conduction electrons. The result shows a substantial difference in these parameters between the surface and the bulk, indicating that it is important to take into account the surface effect in analyzing photoemission spectra of Ce compounds. It is also found that the 4f surface core-level shift is different between CeIn 3 and CeSn 3 . copyright 1997 The American Physical Society

Optical and scintillation properties of Ce-doped LuLiF{sub 4} with different Ce concentrations

Energy Technology Data Exchange (ETDEWEB)

Yanagida, Takayuki, E-mail: yanagida@lsse.kyutech.ac.jp [Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu-ku, Kitakyushu, Fukuoka 808-0196 (Japan); Fujimoto, Yutaka [Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu-ku, Kitakyushu, Fukuoka 808-0196 (Japan); Fukuda, Kentaro [Tokuyama Corporation, Shibuya 3-chome, Shibuya-ku, Tokyo 150-8383 Japan (Japan); Chani, Valery [Tohoku Univ., 2-1-1 Katahira, Sendai 980-8577 (Japan)

2013-11-21

The crystals of 0.1, 0.5, and 1 mol% Ce-doped LuLiF{sub 4} (Ce:LLF) grown by the micro-pulling down (μ-PD) method were examined for their optical and scintillation properties. Ce:LLF crystals had ∼80% transparency at wavelengths longer than 300 nm. In photoluminescence spectra, they demonstrated intense emission peaks at 310 and 330 nm with the quantum yield of 60–90%. Ce{sup 3+} 5d–4f emission peaks were also detected at similar wavelengths of 310 and 330 nm in the radioluminescence spectra obtained under X-ray excitation. According to pulse height spectra recorded under γ-ray irradiation, the absolute light yield of Ce 0.1, 0.5, and 1% were 3600±400, 3000±300, and 1700±200 ph/MeV, respectively. Decay time kinetics was also inspected using a pulse X-ray equipped streak camera system. The decay time components of Ce:LLF were ∼70 ns and ∼1 μs for all the samples.

miRNA-mediated 'tug-of-war' model reveals ceRNA propensity of genes in cancers.

Science.gov (United States)

Swain, Arpit Chandan; Mallick, Bibekanand

2018-06-01

Competing endogenous RNA (ceRNA) are transcripts that cross-regulate each other at the post-transcriptional level by competing for shared microRNA response elements (MREs). These have been implicated in various biological processes impacting cell-fate decisions and diseases including cancer. There are several studies that predict possible ceRNA pairs by adopting various machine-learning and mathematical approaches; however, there is no method that enables us to gauge as well as compare the propensity of the ceRNA of a gene and precisely envisages which among a pair exerts a stronger pull on the shared miRNA pool. In this study, we developed a method that uses the 'tug of war of genes' concept to predict and quantify ceRNA potential of a gene for the shared miRNA pool in cancers based on a score represented by SoCeR (score of competing endogenous RNA). The method was executed on the RNA-Seq transcriptional profiles of genes and miRNA available at TCGA along with CLIP-supported miRNA-target sites to predict ceRNA in 32 cancer types which were validated with already reported cases. The proposed method can be used to determine the sequestering capability of the gene of interest as well as in ranking the probable ceRNA candidates of a gene. Finally, we developed standalone applications (SoCeR tool) to aid researchers in easier implementation of the method in analysing different data sets or diseases. © 2018 The Authors. Published by FEBS Press and John Wiley & Sons Ltd.

Surface Reduced CeO2 Nanowires for Direct Conversion of CO2 and Methanol to Dimethyl Carbonate: Catalytic Performance and Role of Oxygen Vacancy

Directory of Open Access Journals (Sweden)

Zhongwei Fu

2018-04-01

Full Text Available Ultralong 1D CeO2 nanowires were synthesized via an advanced solvothermal method, surface reduced under H2 atmosphere, and first applied in direct synthesis of dimethyl carbonate (DMC from CO2 and CH3OH. The micro morphologies, physical parameters of nanowires were fully investigated by transmission electron microscopy (TEM, X-ray diffraction (XRD, N2 adsorption, X-ray photoelectron spectrum (XPS, and temperature-programmed desorption of ammonia/carbon dioxide (NH3-TPD/CO2-TPD. The effects of surface oxygen vacancy and acidic/alkaline sites on the catalytic activity was explored. After reduction, the acidic/alkaline sites of CeO2 nanowires can be dramatically improved and evidently raised the catalytic performance. CeO2 nanowires reduced at 500 °C (CeO2_NW_500 exhibited notably superior activity with DMC yield of 16.85 mmol gcat−1. Furthermore, kinetic insights of initial rate were carried out and the apparent activation energy barrier of CeO2_NW_500 catalyst was found to be 41.9 kJ/mol, much tiny than that of CeO2_NW catalyst (74.7 KJ/mol.

Optical, luminescence and scintillation characteristics of non-stoichiometric LuAG:Ce ceramics

Czech Academy of Sciences Publication Activity Database

Liu, S.; Feng, X.; Mareš, Jiří A.; Babin, Vladimir; Nikl, Martin; Beitlerová, Alena; Shi, Y.; Zeng, Y.; Pan, Y.; D'Ambrosio, C.; Huang, Y.

2016-01-01

Roč. 169, Jan (2016), s. 72-77 ISSN 0022-2313 R&D Projects: GA ČR GAP204/12/0805 Institutional support: RVO:68378271 Keywords : non-stoichimetric LuAG:Ce ceramic s * radioluminescence * scintillation response * anti-site defects Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.686, year: 2016

Some regularities of Ce(3) and Ce(4) stabilization in their compounds with β-diketones

International Nuclear Information System (INIS)

Pechurova, N.I.; Martynenko, L.I.; Snezhko, N.I.; Anufrieva, S.I.

1985-01-01

Adduct formation of cerium (3) and cerium (4) β-diketonates (acetylacetonate, benzoylacetonate, dibenzoylmethanate and thenoyltrifluoroacetonate) with oxygen- and nitrogen-donor ligands (Q-α, α'-dipyridyl, o-phenanthroline, trioctylphosphine oxide and triphenylphosphine oxide) is studied. The compounds obtained as a results of the reactions are studied by means of IR-spectroscopic, derivatographic and X-ray phase methods. It is concluded that composition and thermodynamic stability of adducts of Ce(3) tris-β-diketonates are determined by correlation of donor properties of the basis and additional ligand and stability of adducts to oxidation - as well as by their solubility. Introduction of the additional ligand to the system Ce(4)-β-diketones even in the presence of air oxygen stabilizes Ce(3) and destabilizes Ce(4)

Unstable magnetic moments in Ce compounds

International Nuclear Information System (INIS)

Aarts, J.

1984-01-01

The problems which are connected with the appearance or disappearance of local moments in metals are well reflected in the magnetic behaviour of Ce intermetallic compounds. This work describes experiments on two Ce compounds which are typical examples of unstable moment systems. The first of these is CeAl 2 which at low temperatures, shows coexistence of antiferromagnetic order and the Kondo effect. Measurements are presented of the magnetization and the susceptibility in different magnetic field and temperature regions. An analysis of these measurements, using a model for the crystal field effects, shows the agreement between the measurements and the calculations to be reasonably good for CeAl 2 , but this agreement becomes worse upon decreasing Ce concentration. A phenomenological description of the observations is given. The second compound reported on is CeCu 2 Si 2 , the first 'heavy-fermion' superconductor to be investigated. The superconducting state is possibly formed by the quasi-particles of a non-magnetic many body singlet state, and not simply by the (sd) conduction electrons. This being a novel phenomenon, a number of experiments were performed to test this picture and to obtain a detailed description of the behaviour of CeCu 2 Si 2 . Measurements of the Meissner volume, confirmed the superconductivity to be intrinsic. (Auth.)

Ce decay curves in Ce, Tb co-doped LaF3 and the energy transfer mechanism

International Nuclear Information System (INIS)

Kroon, R.E.; Swart, H.C.; Ntwaeaborwa, O.M.; Seed Ahmed, H.A.A.

2014-01-01

Energy transfer phenomena can play an important role in the development of luminescent materials, and hosts co-doped with Ce 3+ and Tb 3+ ions continue to be actively studied. Several recent reports on Ce, Tb co-doped phosphors suggest different mechanisms for the energy transfer from Ce 3+ to Tb 3+ ions and further study is required to reach consensus on the mechanism or to understand why different mechanisms dominate in different hosts. A more direct method of analysis is proposed to distinguish between the different types of multipole energy transfer mechanisms. When applied to Ce, Tb co-doped LaF 3 , the experimental data shows a poor match to any of these models but is consistent with energy transfer through the exchange mechanism. The decay curves of Ce emission in Ce, Tb co-doped LaF 3 were also studied to obtain further insight on the energy transfer mechanism. Although the decrease in lifetime with increasing Tb concentration shows that energy transfer occurs through a non-radiative mechanism, the form of the decay curves does not correspond to what is expected for energy transfer via multipole interactions.

Impact of MicroRNA Levels, Target-Site Complementarity, and Cooperativity on Competing Endogenous RNA-Regulated Gene Expression.

Science.gov (United States)

Denzler, Rémy; McGeary, Sean E; Title, Alexandra C; Agarwal, Vikram; Bartel, David P; Stoffel, Markus

2016-11-03

Expression changes of competing endogenous RNAs (ceRNAs) have been proposed to influence microRNA (miRNA) activity and thereby regulate other transcripts containing miRNA-binding sites. Here, we find that although miRNA levels define the extent of repression, they have little effect on the magnitude of the ceRNA expression change required to observe derepression. Canonical 6-nt sites, which typically mediate modest repression, can nonetheless compete for miRNA binding, with potency ∼20% of that observed for canonical 8-nt sites. In aggregate, low-affinity/background sites also contribute to competition. Sites with extensive additional complementarity can appear as more potent, but only because they induce miRNA degradation. Cooperative binding of proximal sites for the same or different miRNAs does increase potency. These results provide quantitative insights into the stoichiometric relationship between miRNAs and target abundance, target-site spacing, and affinity requirements for ceRNA-mediated gene regulation, and the unusual circumstances in which ceRNA-mediated gene regulation might be observed. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Homoleptic Ce(III) and Ce(IV) Nitroxide Complexes: Significant Stabilization of the 4+ Oxidation State

Energy Technology Data Exchange (ETDEWEB)

Bogart, Justin A.; Lewis, Andrew J.; Medling, Scott A.; Piro, Nicholas A.; Carroll, Patrick J.; Booth, Corwin H.; Schelter, Eric J.

2014-06-25

Electrochemical experiments performed on the complex Ce-IV[2-((BuNO)-Bu-t)py](4), where [2-((BuNO)-Bu-t)py](-) = N-tert-butyl-N-2-pyridylnitroxide, indicate a 2.51 V stabilization of the 4+ oxidation state of Ce compared to [(Bu4N)-Bu-n](2)[Ce(NO3)(6)] in acetonitrile and a 2.95 V stabilization compared to the standard potential for the ion under aqueous conditions. Density functional theory calculations suggest that this preference for the higher oxidation state is a result of the tetrakis(nitroxide) ligand framework at the Ce cation, which allows for effective electron donation into, and partial covalent overlap with, vacant 4f orbitals with delta symmetry. The results speak to the behavior of CeO2 and related solid solutions in oxygen uptake and transport applications, in particular an inherent local character of bonding that stabilizes the 4+ oxidation state. The results indicate a cerium(IV) complex that has been stabilized to an unprecedented degree through tuning of its ligand-field environment.

Preparation and chemical properties of the skutterudites (Ce-Yb) yFe4-x(Co/Ni) xSb12

International Nuclear Information System (INIS)

Berardan, D.; Alleno, E.; Godart, C.; Rouleau, O.; Rodriguez-Carvajal, J.

2005-01-01

The double-filled skutterudites Ce y/2 Yb y/2 Fe 4-x Co x Sb 12 and Ce y/2 Yb y/2 Fe 4-x Ni x Sb 12 have been synthesized as single phase materials. The evolution of the lattice parameters and of the filling fractions with substitutions on the transition metal site have been studied by X-ray diffraction and electron probe microanalysis, respectively. Both results were compared to that of single filled series (Ce/Yb) y Fe 4-x (Co/Ni) x Sb 12 . It shows that double-filled skutterudites can be understood as a solid solution between single filled ones. The valence states of Ce and Yb in all series have been studied using X-ray absorption spectroscopy at the L 3 edges, and we discuss their relationships with structural parameters. Ce is always trivalent, whereas Yb valence state decreases as Yb fraction increases. No distortion of the environment or sub-position of Yb in the cage have been seen by neutron diffraction. The Seebeck coefficient has been measured using a home made apparatus from 120 K to 300 K. It shows a crossover from p- to n-type conductivity for Co or Ni rich skutterudites in the six series. We discuss the influence on the room temperature thermopower of valence states, filling fractions and substitution rate on the transition metal site. Thermopower seems to be only driven by charge carriers concentration

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The role of Ce(III) in BZ oscillating reactions

Science.gov (United States)

Nogueira, Paulo A.; Varela, Hamilton; Faria, Roberto B.

2012-03-01

Herein we present results on the oscillatory dynamics in the bromate-oxalic acid-acetone-Ce(III)/Ce(IV) system in batch and also in a CSTR. We show that Ce(III) is the necessary reactant to allow the emergence of oscillations. In batch, oscillations occur with Ce(III) and also with Ce(IV), but no induction period is observed with Ce(III). In a CSTR, no oscillations were found using a freshly prepared Ce(IV), but only when the cerium-containing solution was aged, allowing partial conversion of Ce(IV) to Ce(III) by reaction with acetone.

Promoting effect of CeO 2 on cyclohexanol conversion over CeO 2

Indian Academy of Sciences (India)

Abstract. CeO2-ZnO materials were prepared by amorphous citrate process and characterized by TGA, XRD, UV-DRS and surface area measurements. TGA showed that the citrate precursors decompose in the range 350-550°C producing CeO2-containing catalytic materials. XRD and DRS results indicated the formation of ...

Cerocene Revisited: The Electronic Structure of and Interconversion Between Ce2(C8H8)3 and Ce(C8H8)2

Energy Technology Data Exchange (ETDEWEB)

Walter, Marc D.; Booth, Corwin H.; Lukens, Wayne W.; Andersen, Richard A.

2009-02-02

New synthetic procedures for the preparation of Ce(cot)2, cerocene, from [Li(thf)4][Ce(cot)2], and Ce2(cot)3 in high yield and purity are reported. Heating solid Ce(cot)2 yields Ce2(cot)3 and COT while heating Ce2(cot)3 with an excess of COT in C6D6 to 65oC over four months yields Ce(cot)2. The solid state magnetic susceptibility of these three organocerium compounds shows that Ce(cot)2 behaves as a TIP (temperature independent paramagnet) over the temperature range of 5-300 K, while that of Ce2(cot)3 shows that the spin carriers are antiferromagnetically coupled below 10 K; above 10 K, the individual spins are uncorrelated, and [Ce(cot)2]- behaves as an isolated f1 paramagnet. The EPR at 1.5K for Ce2(cot)3 and [Ce(cot)2]- have ground state of MJ= +- 1/2. The LIII edge XANES of Ce(cot)2 (Booth, C.H.; Walter, M.D.; Daniel, M.; Lukens, W.W., Andersen, R.A., Phys. Rev. Lett. 2005, 95, 267202) and 2Ce2(cot)3 over 30-500 K are reported; the Ce(cot)2 XANES spectra show Ce(III) and Ce(IV) signatures up to a temperature of approximately 500 K, whereupon the Ce(IV) signature disappears, consistent with the thermal behavior observed in the melting experiment. The EXAFS of Ce(cot)2 and Ce2(cot)3 are reported at 30 K; the agreement between the molecular parameters for Ce(cot)2 derived from EXAFS and single crystal X-ray diffraction data are excellent. In the case of Ce2(cot)3 no X-ray diffraction data are known to exist, but the EXAFS are consistent with a"triple-decker" sandwich structure. A molecular rationalization is presented for the electronic structure of cerocene having a multiconfiguration ground state that is an admixture of the two configurations Ce(III, 4f1)(cot1.5-)2 and Ce(IV, 4f0)(cot2-)2; the multiconfigurational ground state has profound effects on the magnetic properties and on the nature of the chemical bond in cerocene and, perhaps, other molecules.

Coexistence of magnetic order and valence fluctuations in a heavy fermion system Ce{sub 2}Rh{sub 3}Sn{sub 5}

Energy Technology Data Exchange (ETDEWEB)

Gamza, Monika [Jeremiah Horrocks Institute, University of Central Lancashire, Preston (United Kingdom); MPI CPfS, Dresden (Germany); Institute of Physics, University of Silesia, Katowice (Poland); Gumeniuk, Roman [Institute of Experimental Physics, Freiberg University of Mining and Technology, Freiberg (Germany); MPI CPfS, Dresden (Germany); Schnelle, Walter; Burkhardt, Ulrich; Rosner, Helge [MPI CPfS, Dresden (Germany); Slebarski, Andrzej [Institute of Physics, University of Silesia, Katowice (Poland)

2016-07-01

While most Ce-based intermetallics contain either trivalent or intermediate-valent Ce ions, only for a few compounds a coexistence of both species has been reported. Here, we present a combined experimental and theoretical study based on thermodynamic measurements and spectroscopic data together with ab-initio electronic structure calculations aiming at exploring magnetic properties of Ce ions in two nonequivalent sites in Ce{sub 2}Rh{sub 3}Sn{sub 5}. Ce L{sub III} XAS spectra give direct evidence for valence fluctuations. Magnetization measurements show an onset of an antiferromagnetic order at T{sub N}∼2.5 K. The electronic structure calculations suggest that the magnetic ordering is related only to one Ce sublattice. This is in-line with a small entropy associated with the magnetic transition S{sub mag}∼0.35 R ln2 per Ce atom as revealed by the specific heat measurement. Furthermore, the temperature dependence of the magnetic susceptibility can be well described assuming that there are fluctuating moments of Ce{sup 3+} ions in one sublattice, whereas Ce atoms from the second sublattice are in a nonmagnetic intermediate valence state.

Glass forming ability of the Al-Ce-Ni system; Avaliacao da capacidade de formacao vitrea do sistema Al-Ce-Ni

Energy Technology Data Exchange (ETDEWEB)

Triveno Rios, C. [Engenharia Mecanica, Universidade Federal de Mato Grosso, Rondonopolis, MT (Brazil)], e-mail: triveno@ufmt.br; Surinach, S.; Baro, M.D. [Departamento de Engenharia de Materiais - Universidade Federal de Sao Carlos, SP (Brazil); Bolfarini, C.; Botta, W.J.; Kiminami, C.S. [Departamento de Fisica da Universidade Autonoma de Barcelona, Bellaterra (Spain)

2010-07-01

In the present work, the glass forming ability (GFA) and its compositional dependence on Al-Ni-Ce system alloys were investigated in function of several thermal parameters. Rapidly quenched Al{sub 85}Ni{sub 15}-{sub X}Ce{sub X} (X=4,5,6,7,10), Al{sub 90}Ni{sub 5}Ce{sub 5}, Al{sub 89}Ni{sub 2}.{sub 4}Ce{sub 8}.{sub 6}, Al{sub 80}Ni{sub 15.6}Ce{sub 4}.{sub 4} and Al{sub 78}Ni{sub 18.5}Ce{sub 3.5} amorphous ribbons were produced by melt-spinning and the structural transformation during heating was studied using a combination of X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results showed that the GFA and the thermal stability in the Al-rich corner of Al- Ni-Ce system alloys were enhanced by increasing the solute content and specifically the Ce content (author)

Mechanical properties of non-centrosymmetric CePt3Si and CePt3B

Science.gov (United States)

Rogl, G.; Legut, D.; Sýkora, R.; Müller, P.; Müller, H.; Bauer, E.; Puchegger, S.; Zehetbauer, M.; Rogl, P.

2017-05-01

Elastic moduli, hardness (both at room temperature) and thermal expansion (4.2-670 K) have been experimentally determined for polycrystalline CePt3Si and its prototype compound CePt3B as well as for single-crystalline CePt3Si. Resonant ultrasound spectroscopy was used to determine elastic properties (Young’s modulus E and Poisson’s ratio ν) via the eigenfrequencies of the sample and the knowledge of sample mass and dimensions. Bulk and shear moduli were calculated from E and ν, and the respective Debye temperatures were derived. In addition, ab initio DFT calculations were carried out for both compounds. A comparison of parameters evaluated from DFT with those of experiments revealed, in general, satisfactory agreement. Positive and negative thermal expansion values obtained from CePt3Si single crystal data are fairly well explained in terms of the crystalline electric field model, using CEF parameters derived recently from inelastic neutron scattering. DFT calculations, in addition, demonstrate that the atomic vibrations keep almost unaffected by the antisymmetric spin-orbit coupling present in systems with crystal structures having no inversion symmetry. This is opposite to electronic properties, where the antisymmetric spin-orbit interaction has shown to distinctly influence features like the superconducting condensate of CePt3Si.

Crystal growth and scintillation properties of multi-component oxide single crystals: Ce:GGAG and Ce:La-GPS

Energy Technology Data Exchange (ETDEWEB)

Yoshikawa, A., E-mail: yoshikawa@imr.tohoku.ac.jp [Institute for Materials Research (IMR), Tohoku University, Sendai 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai 980-8579 (Japan); C& A Corporation, 6-6-40 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579 (Japan); Kamada, K. [New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai 980-8579 (Japan); C& A Corporation, 6-6-40 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579 (Japan); Kurosawa, S. [Institute for Materials Research (IMR), Tohoku University, Sendai 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai 980-8579 (Japan); Shoji, Y. [Institute for Materials Research (IMR), Tohoku University, Sendai 980-8577 (Japan); C& A Corporation, 6-6-40 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579 (Japan); Yokota, Y. [New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai 980-8579 (Japan); Chani, V.I. [Institute for Materials Research (IMR), Tohoku University, Sendai 980-8577 (Japan); Nikl, M. [Institute of Physics, AS CR, Cukrovarnická 10, 162 53 Prague (Czech Republic)

2016-01-15

Crystal growth by micro-pulling-down, Czochralski, and floating zone methods and scintillation properties of Ce:Gd{sub 3}(Ga,Al){sub 5}O{sub 12} (Ce:GGAG) multi-component oxide garnets, and Ce:Gd{sub 2}Si{sub 2}O{sub 7} (Ce:GPS) or Ce:(La,Gd){sub 2}Si{sub 2}O{sub 7} (Ce:La-GPS) pyro-silicates are reviewed. GGAG crystals demonstrated practically linear dependences of some of the parameters including lattice constant, emission wavelength, and band gap on Ga content. However, emission intensity, light yield and energy resolution showed maxima for intermediate compositions. GGAG crystals had the highest light yield of 56,000 photon/MeV for Ga content of 2.7 atoms per garnet formula unit. Similarly the light yield and energy resolution of La-GPS showed the highest values of 40,000 photon/MeV and 4.4%@662 keV, respectively, for La-GPS containing 10% of La. Moreover, La-GPS demonstrated stable scintillation performance up to 200 °C.

The Asia-RiCE activity with data cube

Science.gov (United States)

Oyoshi, K.; Sobue, S.; LE Toan, T.; Lam, N. D.

2017-12-01

The Asia-RiCE initiative (http://www.asia-rice.org) has been organized to enhance rice production estimates through the use of Earth observation satellites data, and seeks to ensure that Asian rice crops are appropriately represented within GEO Global Agriculture Monitoring (GEO-GLAM) to support FAO Agriculture Market Information System (FAO-AMIS). Asia-RiCE is composed of national teams that are actively contributing to the Crop Monitor for AMIS and developing technical demonstrations of rice crop monitoring activities using both Synthetic Aperture Radar (SAR) data (Radarsat-2 from 2013; Sentinel-1 and ALOS-2 from 2015.From 2016 after the successful rice crop area and growing estimation using SAR in a technical demonstration site (provincial level), wall-to-wall (national scale) excurse as phase 2 has been implemented in Vietnam and Indonesia in cooperation with ministry of agriculture and space agencies. This paper reports this year activity of 2017 accomplishment and way forward, especially for analysis ready data (ARD) definition of SAR to ingest to CEOS data cube to provide national scale service in Vietnam and Indonesia.

Living target of Ce(III) action on horseradish cells: proteins on/in cell membrane.

Science.gov (United States)

Yang, Guangmei; Sun, Zhaoguo; Lv, Xiaofen; Deng, Yunyun; Zhou, Qing; Huang, Xiaohua

2012-12-01

Positive and negative effects of rare earth elements (REEs) in life have been reported in many papers, but the cellular mechanisms have not been answered, especially the action sites of REEs on plasma membrane are unknown. Proteins on/in the plasma membrane perform main functions of the plasma membrane. Cerium (Ce) is the richest REEs in crust. Thus, the interaction between Ce(III) and the proteins on/in the plasma membrane, the morphology of protoplast, and the contents of nutrient elements in protoplast of horseradish were investigated using the optimized combination of the fluorescence microscopy, fluorescence spectroscopy, circular dichroism, scanning electron microscopy, and X-ray energy dispersive spectroscopy. It was found that Ce(III) at the low concentrations (10, 30 μM) could interact with proteins on/in the plasma membrane of horseradish, leading to the improvement in the structure of membrane proteins and the plasma membrane, which accelerated the intra-/extra-cellular substance exchange and further promoted the development of cells. When horseradish was treated with Ce(III) at the high concentrations (60, 80 μM), Ce(III) also could interact with the proteins on/in the plasma membrane of horseradish, leading to the destruction in the structure of membrane proteins and the plasma membrane. These effects decelerated the intra-/extra-cellular substance exchange and further inhibited the development of cells. Thus, the interaction between Ce(III) and proteins on/in the plasma membrane in plants was an important reason of the positive and negative effects of Ce(III) on plants. The results would provide some references for understanding the cellular effect mechanisms of REEs on plants.

Crystal structure, energy transfer and tunable luminescence properties of Ca8ZnCe(PO4)7:Eu2+,Mn2+ phosphor

Science.gov (United States)

Ding, Chong; Tang, Wanjun

2018-02-01

Single-phased Ca8ZnCe(PO4)7:Eu2+,Mn2+ phosphors with whitlockite-type structure have been prepared via the combustion-assisted synthesis technique. The XRD pattern show that the as-obtained phosphors crystallize in a trigonal phase with space group of R-3c (161). Ca8ZnCe(PO4)7 host is full of sensitizers (Ce3+) and the Ce3+ emission at different lattice sites has been discussed. The efficient energy transfers from Ce3+ ions to Eu2+/Mn2+ ions and from Eu2+ to Mn2+ have been validated. Under UV excitation, the emitting color of Ca8ZnCe(PO4)7:Eu2+/Mn2+ samples can be modulated from violet blue to green and from violet blue to red-orange by the energy transfers of Ce3+→Eu2+ and Ce3+→Mn2+, respectively. Additionally, white emission has been obtained through adjusting the relative concentrations of Eu2+ and Mn2+ ions in the Ca8ZnCe(PO4)7 host under UV excitation. These results indicate that as-prepared Ca8ZnCe(PO4)7:Eu2+,Mn2+ may be a potential candidate as color-tunable white light-emitting phosphors.

A new 3DOM Ce-Fe-Ti material for simultaneously catalytic removal of PM and NOx from diesel engines.

Science.gov (United States)

Cheng, Ying; Liu, Jian; Zhao, Zhen; Song, Weiyu; Wei, Yuechang

2018-01-15

A new 3DOM material was designed and synthesized for the simultaneous removal of PM (soot particulates) and NOx from diesel engine exhausts. The catalytic purification taking place over the material with double efficacy is cost-efficient. The contact between solid PM and catalyst active site has been process intensified by 3DOM unique structure. 3DOM Ce 0.7 Fe 0.2 Ti 0.1 O 2 catalyst possess a high SCR activity and an excellent selectivity to N 2 , giving a maximum concentration of CO 2 at 385°C for PM combustion and 100% NO conversion in the temperature range of 281-425°C. The dual redox cycles (Fe 3+ +Ce 3+ ↔Fe 2+ +Ce 4+ ,Fe 3+ +Ti 3+ ↔Fe 2+ +Ti 4+ ) and the excellent reducibility and sufficient acid sites of catalysts play key roles for the highly catalytic performance. Copyright © 2017 Elsevier B.V. All rights reserved.

Radio- and photoluminescence properties of Ce/Tb co-doped glasses with huntite-like composition

Science.gov (United States)

Lorenzi, Roberto; Golubev, Nikita V.; Ziaytdinova, Mariyam Z.; Jarý, Vítězslav; Babin, Vladimir; Malashkevich, Georgii E.; Paleari, Alberto; Sigaev, Vladimir N.; Fasoli, Mauro; Nikl, Martin

2018-04-01

Optical properties of yttria-aluminoborate (YAB) glasses with general composition 10(CexTbyY(1-x-y))-30Al2O3-60B2O3 are investigated and compared with data available on YAB crystals with huntite-like structure. Ce doped samples show optical features ascribable to preferential location of rare earth ions in sites with specific geometry similar to that observed in crystalline structures. Samples prepared with Tb ions as emission activator and Ce ions as sensitizer have been studied within the framework of non-radiative energy transfer. The resulting Förster radius is of 4.6 ± 0.5 Å comparable with that observed in Ce/Tb co-doped YAl3(BO3)4 crystals. The investigated materials possess radio- and photoluminescence emission efficiencies and performances comparable to that of crystalline counterparts with the advantage of having easiness of preparation and workability typical of glassy systems.

A Permselective CeOx Coating Improves the Stability of Oxygen Evolution Electrocatalysts

KAUST Repository

Obata, Keisuke

2017-12-05

Highly active NiFeOx electrocatalysts for the oxygen evolution reaction (OER) suffer gradual deactivation with time due to the loss of Fe species from the active sites into solution during catalysis. Here, we describe the anodic deposition of a CeOx layer that prevents the loss of such Fe species from the OER catalysts, achieving a highly stable performance. The CeOx layer does not affect the OER activity of the catalyst underneath but exhibits unique permselectivity, allowing the permeation of OH- and O2 through while preventing the diffusion of redox ions through the layer to function as a selective O2-evolving electrode. The use of such permselective protective layer provides a new strategy for improving the durability of electrocatalysts.

A Permselective CeOx Coating Improves the Stability of Oxygen Evolution Electrocatalysts

KAUST Repository

Obata, Keisuke; Takanabe, Kazuhiro

2017-01-01

Highly active NiFeOx electrocatalysts for the oxygen evolution reaction (OER) suffer gradual deactivation with time due to the loss of Fe species from the active sites into solution during catalysis. Here, we describe the anodic deposition of a CeOx layer that prevents the loss of such Fe species from the OER catalysts, achieving a highly stable performance. The CeOx layer does not affect the OER activity of the catalyst underneath but exhibits unique permselectivity, allowing the permeation of OH- and O2 through while preventing the diffusion of redox ions through the layer to function as a selective O2-evolving electrode. The use of such permselective protective layer provides a new strategy for improving the durability of electrocatalysts.

Transitions between localized and itinerant antiferromagnetism in the Ce(Pb,In) sub 3 and Ce(Pb,Tl) sub 3 systems

Energy Technology Data Exchange (ETDEWEB)

Rahman, S; Timlin, J; Crow, J E; Mihalisin, T; Schlottmann, P [Temple Univ., Philadelphia, PA (United States)

1990-01-01

CePb{sub 3} is an itinerant heavy fermion antiferromagnetic displaying an incommensurate magnetic structure and an extremely small ordered moment. CeIn{sub 3} and CeTl{sub 3}, on the other hand are well-localized, simple antiferromagnets with the full moments expected for crystal field doublet Ce{sup 3+} ion systems. The authors have performed specific heat, sysceptibility and resistivity measurements for both the Ce(Pb,In){sub 3} and Ce(Pb,Tl){sub 3} systems. These systems remain cubic Cu{sub 3}Au structures across the entire series. They display extremely interesting T{sub N} behavior which suggests that a continuous transition from itinerant to localized antiferromagnetic behavior occurs for the Ce(Pb,Tl){sub 3} system. In the Ce (Pb,In){sub 3} system both types of antiferromagnetism are present but they are separated by a concentration range ({approximately}10-40% Pb) over which antiferromagnetism does not exist. The behavior of these systems cannot be accounted for by a Kondo necklace approach that neglects the coherence of a heavy fermion lattice and resulting itinerant antiferromagnetism.

Superconductivity and anomalous normal state in the CePd2Si2/CeNi2Ge2 system

International Nuclear Information System (INIS)

Grosche, F.M.; Lister, S.J.S.; Carter, F.V.; Saxena, S.S.; Haselwimmer, R.K.W.; Mathur, N.D.; Julian, S.R.; Lonzarich, G.G.

1997-01-01

The unconventional nonmagnetic metal CeNi 2 Ge 2 is characterised at ambient pressure by temperature dependences of the specific heat and of the resistivity which deviate strongly from standard Fermi-liquid predictions and are reminiscent of the behaviour observed in its sibling system CePd 2 Si 2 above the critical pressure at which magnetic order is suppressed. We have explored the CePd 2 Si 2 /CeNi 2 Ge 2 phase diagram in a series of resistivity measurements under high hydrostatic pressure, p. At p>15 kbar, a new superconducting transition appears below 220 mK in CeNi 2 Ge 2 and shifts to higher temperatures with increasing pressure, reaching ∝400 mK at p∝26 kbar. (orig.)

Redox potentials and kinetics of the Ce 3+/Ce 4+ redox reaction and solubility of cerium sulfates in sulfuric acid solutions

Science.gov (United States)

Paulenova, A.; Creager, S. E.; Navratil, J. D.; Wei, Y.

Experimental work was performed with the aim of evaluating the Ce 4+/Ce 3+ redox couple in sulfuric acid electrolyte for use in redox flow battery (RFB) technology. The solubility of cerium sulfates in 0.1-4.0 M sulfuric acid at 20-60 °C was studied. A synergistic effect of both sulfuric acid concentration and temperature on the solubility of cerous sulfate was observed. The solubility of cerous sulfate significantly decreased with rising concentration of sulfuric acid and rising temperature, while the solubility of ceric sulfate goes through a significant maximum at 40 °C. Redox potentials and the kinetics of the cerous/ceric redox reaction were also studied under the same temperature-concentration conditions. The redox potentials were measured using the combined redox electrode (Pt-Ag/AgCl) in equimolar Ce 4+/Ce 3+ solutions (i.e.[Ce 3+]=[Ce 4+]) in sulfuric acid electrolyte. The Ce 3+/Ce 4+ redox potentials significantly decrease (i.e. shift to more negative values) with rising sulfuric acid concentration; a small maximum is observed at 40 °C. Cyclic voltammetric experiments confirmed slow electrochemical kinetics of the Ce 3+/Ce 4+ redox reaction on carbon glassy electrodes (CGEs) in sulfuric acid solutions. The observed dependencies of solubilities, the redox potentials and the kinetics of Ce 3+/Ce 4+ redox reaction on sulfuric acid concentration are thought to be the result of inequivalent complexation of the two redox species by sulfate anions: the ceric ion is much more strongly bound to sulfate than is the cerous ion. The best temperature-concentration conditions for the RFB electrolytes appear to be 40 °C and 1 M sulfuric acid, where the relatively good solubility of both cerium species, the maximum of redox potentials, and the more or less satisfying stability of CGE s were found. Even so, the relatively low solubility of cerium salts in sulfuric acid media and slow redox kinetics of the Ce 3+/Ce 4+ redox reaction at carbon indicate that the Ce 3+/Ce

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Isolated centres versus defect associates in Sm3+-doped CeO2: a spectroscopic investigation

International Nuclear Information System (INIS)

Tiseanu, Carmen; Avram, Daniel; Cojocaru, Bogdan; Parvulescu, Vasile I; Vela-Gonzalez, Andrea V; Sanchez-Dominguez, Margarita

2013-01-01

The interactions between Sm 3+ and oxygen vacancies in CeO 2 are probed by the use of tuneable laser excited time-resolved photoluminescence and Raman spectroscopies. It is found that Sm 3+ (with doping concentrations of 0.1, 0.3, 1 and 5 wt%) substitutes largely for Ce 4+ in sites with cubic symmetry and the corresponding emission is sensitized via the Ce 4+ –O 2− charge-transfer band of CeO 2 . It is established from the photoluminescence spectra measured at long delay after the laser pulse that the local environment around cubic Sm 3+ centres is not changed with concentration and ceria size. In addition to cubic symmetry Sm 3+ centres, low-symmetry Sm 3+ centres tentatively assigned to the Sm 3+ –oxygen vacancy associates of nearest-neighbour type are also observed. Their emission is preferentially excited via the weak f–f absorption transitions of Sm 3+ . A relatively strong concentration-induced quenching of Sm 3+ emission was inferred from the decrease in the average emission lifetimes from 2.1 ms (0.1 wt%) to 0.87 ms (5 wt%). The local environments of Sm 3+ and Eu 3+ in CeO 2 are also compared on the basis of their emission spectra and decays. (paper)

Synthesis, Characterization and Properties of CeO2-doped TiO2 Composite Nanocrystals

Directory of Open Access Journals (Sweden)

Oman ZUAS

2013-12-01

Full Text Available Pure TiO2 and CeO2-doped TiO2 (3 % CeO2-97 %TiO2 composite nanocrystals were synthesized via co-precipitation method and characterized using TGA, XRD, FTIR, DR-UV-vis and TEM. The XRD data revealed that the phase structure of the synthesized samples was mainly in pure anatase having crystallite size in the range of 7 nm – 11 nm. Spherical shapes with moderate aggregation of the crystal particles were observed under the TEM observation. The presence of the CeO2 at TiO2 site has not only affected morphologically but also induced the electronic property of the TiO2 by lowering the band gap energy from 3.29 eV (Eg-Ti to 3.15 eV (Eg-CeTi. Performance evaluation of the synthesized samples showed that both samples have a strong adsorption capacity toward Congo red (CR dye in aqueous solution at room temperature experiment, where  the capacity of the CeTi was higher than the Ti sample. Based on DR-UV data, the synthesized samples obtained in this study may also become promising catalysts for photo-assisted removal of synthetic dye in aqueous solution. DOI: http://dx.doi.org/10.5755/j01.ms.19.4.2732

Direct observation of multivalent states and 4 f →3 d charge transfer in Ce-doped yttrium iron garnet thin films

Science.gov (United States)

Vasili, H. B.; Casals, B.; Cichelero, R.; Macià, F.; Geshev, J.; Gargiani, P.; Valvidares, M.; Herrero-Martin, J.; Pellegrin, E.; Fontcuberta, J.; Herranz, G.

2017-07-01

Due to their large magneto-optic responses, rare-earth-doped yttrium iron garnets, Y3F e5O12 (YIG), are highly regarded for their potential in photonics and magnonics. Here, we consider the case of Ce-doped YIG (Ce-YIG) thin films, in which substitutional C e3 + ions are magnetic because of their 4 f1 ground state. In order to elucidate the impact of Ce substitution on the magnetization of YIG, we have carried out soft x-ray spectroscopy measurements on Ce-YIG films. In particular, we have used the element specificity of x-ray magnetic circular dichroism to extract the individual magnetization curves linked to Ce and Fe ions. Our results show that Ce doping triggers a selective charge transfer from Ce to the Fe tetrahedral sites in the YIG structure. This, in turn, causes a disruption of the electronic and magnetic properties of the parent compound, reducing the exchange coupling between the Ce and Fe magnetic moments and causing atypical magnetic behavior. Our work is relevant for understanding magnetism in rare-earth-doped YIG and, eventually, may enable a quantitative evaluation of the magneto-optical properties of rare-earth incorporation into YIG.

Ce-doped nanoparticles of TiO2: Rutile-to-brookite phase transition and evolution of Ce local-structure studied with XRD and XANES

International Nuclear Information System (INIS)

Kityakarn, Sutasinee; Worayingyong, Attera; Suramitr, Anwaraporn; Smith, M.F.

2013-01-01

The crystal and electronic structural changes undergone by TiO 2 nanoparticles when Ce is introduced were studied using X-ray diffraction (XRD) and X-ray absorption near-edge spectroscopy (XANES). A small amount of Ce (less than 1% molar concentration) resulted in i/a significant reduction of the average size of the TiO 2 nanoparticles and ii/a phase transition in which brookite replaced rutile as the minority phase component (anatase was the majority phase component at all Ce concentrations studied up to 10% molar concentration). The Ce L3 edge XANES revealed changes in the local environment of Ce impurities. As Ce concentration was increased the fraction of Ce that have formal valence of +3 decreased and, for the remaining Ce with valence +4, the 4f orbitals became less-strongly hybridized with the p-orbitals of oxygen neighbors. The results have implications for photocatalytic and gas sensing properties of Ce-doped TiO 2 . - Highlights: ► Ce-doping: TiO 2 nanoparticles shrink and minority phase changes rutile-> brookite. ► XANES reveals phase change for arbitrarily small particles (while XRD fails). ► As Ce added: fraction of Ce +3 dopants falls, hybridization of Ce +4 with O weakens

In situ DRIFTS investigation of NH3-SCR reaction over CeO2/zirconium phosphate catalyst

Science.gov (United States)

Zhang, Qiulin; Fan, Jie; Ning, Ping; Song, Zhongxian; Liu, Xin; Wang, Lanying; Wang, Jing; Wang, Huimin; Long, Kaixian

2018-03-01

A series of ceria modified zirconium phosphate catalysts were synthesized for selective catalytic reduction of NO with ammonia (NH3-SCR). Over 98% NOx conversion and 98% N2 selectivity were obtained by the CeO2/ZrP catalyst with 20 wt.% CeO2 loading at 250-425 °C. The interaction between CeO2 and zirconium phosphate enhanced the redox abilities and surface acidities of the catalysts, resulting in the improvement of NH3-SCR activity. The in situ DRIFTS results indicated that the NH3-SCR reaction over the catalysts followed both Eley-Rideal and Langmuir-Hinshelwood mechanisms. The amide (sbnd NH2) groups and the NH4+ bonded to Brønsted acid sites were the important intermediates of Eley-Rideal mechanism.

Synthesis and characterization of Ce doped MFI zeolite

International Nuclear Information System (INIS)

Kalita, Banani; Talukdar, Anup K.

2012-01-01

Highlights: ► Cerium was incorporated into the tetrahedral position of MFI zeolite structure. ► Unit cell volume increases with an increase of Ce content in the framework of MFI. ► A band at 310 nm in the UV–vis spectra indicates Ce incorporation in MFI structure. ► The mass loss (%) in the region 373–423 K decreases with increase of Ce in MFI. - Abstract: Ce doped MFI (mobil five) zeolites with different Si to (Ce + Al) and different Ce to Al ratios were synthesized by a hydrothermal synthesis method. All the samples were characterized by different techniques such as X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), UV–vis diffuse reflectance spectroscopy (DRS) and scanning electron microscopy (SEM). The results showed that almost pure MFI phase was obtained in all cases with incorporation of cerium metal into the framework. The increase in unit cell parameters observed with an increase in Ce content is indicative of incorporation of Ce into the framework structure of microporous material MFI. Corroboration of the framework incorporation of Ce into the MFI zeolite structure was also obtained from the UV–vis DRS spectra by the presence of an absorption band at 280 nm. TGA and SEM of the samples provide complementary evidence for Ce incorporation into the framework MFI structure.

Catalytic reforming of toluene as tar model compound: effect of Ce and Ce-Mg promoter using Ni/olivine catalyst.

Science.gov (United States)

Zhang, Ruiqin; Wang, Huajian; Hou, Xiaoxue

2014-02-01

Tar produced by biomass gasification as a route of renewable energy must be removed before the gas can be used. This study was undertaken using toluene as a model tar compound for evaluating its steam reforming conversion with three Ni-based catalysts, Ni/olivine, Ni-Ce/olivine and Ni-Ce-Mg/olivine. Effects of Ce and Mg promoters on the reaction activity and coke deposition were studied. Overall the performance of Ce and Mg promoted Ni/olivine catalysts is better than that of only Ce promoter and Ni/olivine alone. The experimental results indicate that Ni-Ce-Mg/olivine catalysts could improve the resistance to carbon deposition, enhance energy gases yield and resist 10ppm H2S poison at 100mLmin(-1) for up to 400min. Furthermore, the activity of catalysts was related to the steam/carbon (S/C) ratios; at S/C ratio=5, T=790°C, space velocity=782h(-1) and t=2h, the Ni-Ce-Mg/olivine system yielded 89% toluene conversion, 5.6Lh(-1) product gas rate, 62.6mol% H2 content and 10% (mol useful gas mol(-1) toluene) energy yield. Moreover, at low S/C ratio, it had higher reaction activity and better ability to prevent coking. There is a small amount of carbon deposition in the form of amorphous carbon after 7h. Various characterization techniques such as XRD, FTIR and thermogravimetric were performed to investigate the coke deposition of Ni/olivine, Ni-Ce/olivine and Ni-Ce-Mg/olivine. It is suggested that 3% Ni-1% Ce-1% Mg/olivine was the most promising catalyst due to its minimum coke amount and the lower activation energy of coke burning. Copyright © 2014. Published by Elsevier Ltd.

Anomalous behavior of the magnetic hyperfine field at 140Ce impurities at La sites in LaMnSi2

Science.gov (United States)

Domienikan, C.; Bosch-Santos, B.; Cabrera-Pasca, G. A.; Saxena, R. N.; Carbonari, A. W.

2018-05-01

Magnetic hyperfine field has been measured in the orthorhombic intermetallic compound LaMnSi2 with perturbed angular correlation (PAC) spectroscopy using radioactive 140La(140Ce) nuclear probes. Magnetization measurements were also carried out in this compound with MPSM-SQUID magnetometer. Samples of LaMnSi2 compound were prepared by arc melting the component metals with high purity under argon atmosphere followed by annealing at 1000°C for 60 h under helium atmosphere and quenching in water. X-ray analysis confirmed the samples to be in a single phase with correct crystal structure expected for LaMnSi2 compound. The radioactive 140La (T1/2 = 40 h) nuclei were produced by direct irradiation of the sample with neutrons in the IEA-R1 nuclear research reactor at IPEN with a flux of ˜ 1013 n cm-2s-1 for about 3 - 4 min. The PAC measurements were carried out with a six BaF2 detector spectrometer at several temperatures between 10 K and 400 K. Temperature dependence of the hyperfine field, Bhf was found to be anomalous. A modified two-state model explained this anomalous behavior where the effective magnetic hyperfine field at 140Ce is believed to have two contributions, one from the unstable localized spins at Ce impurities and another from the magnetic Mn atoms of the host. The competition of these two contributions explains the anomalous behavior observed for the temperature dependence of the magnetic hyperfine field at 140Ce. The ferromagnetic transition temperature (TC) of LaMnSi2 was determined to be 400(1) K confirming the magnetic measurements.

Tetragonal zirconia ceramics in Zr O2-Ce O2 system (Ce-TZP): preparation, characterization and mechanical properties

International Nuclear Information System (INIS)

Andrade Nono, M.C. de.

1992-01-01

This paper describes and discusses the results achieved in a study about Ce-TZP ceramics prepared from conventional powder mixtures of Zr O 2 and Ce O 2 (with composition in the range of 8 to 16 mol% Ce O 2 ). Physical and chemical characteristics were related with the powder compaction behavior and with the sintering state. The sintered ceramics showed a level of high porosity (≅ 4%), mainly due to the fairly adequate powder characteristics and compaction. The crystalline phases were analysed from X-rays diffraction data and showed that these ceramics can present tetragonal-to-monoclinic stress induced transformation. The bending strength, fracture toughness and Vickers hardness results were influenced by Ce O 2 content microstructure and sintering temperature. These Ce-TZP ceramics showed mechanical strength results comparable to those published in the international literature. (author)

Chemically abrupt interface between Ce oxide and Fe films

International Nuclear Information System (INIS)

Lee, H.G.; Lee, D.; Kim, S.; Kim, S.G.; Hwang, Chanyong

2005-01-01

A chemically abrupt Fe/Ce oxide interface can be formed by initial oxidation of an Fe film followed by deposition of Ce metal. Once a Ce oxide layer is formed on top of Fe, it acts a passivation barrier for oxygen diffusion. Further deposition of Ce metal followed by its oxidation preserve the abrupt interface between Ce oxide and Fe films. The Fe and Ce oxidation states have been monitored at each stage using X-ray photoelectron spectroscopy

Redox behavior of Ce(IV)/Ce(III) in the presence of nitrilotriacetic acid: a surrogate study for An(IV)/An(III) redox behavior

International Nuclear Information System (INIS)

Suzuki, Y.; Nankawa, T.; Ohnuki, T.; Francis, A.J.

2010-01-01

Using cyclic voltammetry, we investigated the redox behavior of Ce(IV)/Ce(III), which is a surrogate for An(IV)/An(III) (An = actinides), in a solution of nitrilotriacetic acid (NTA) at 25 C. The cyclic voltammogram of Ce in a 0.1 M NTA solution at pH 6 showed a reversible one-electron redox reaction for Ce(IV)/Ce(III) at 0.51 V vs. Ag/AgCl. This redox potential was much lower than that obtained in 1 M nitric acid, indicating that Ce(IV) was preferentially stabilized by complexation with NTA. The redox potential in the NTA solution was independent of the Ce concentration from 2 to 20 mM, NTA concentration from 5 to 200 mM and pH between 3 and 7. These results indicated that no polymerization and no additional coordination of NTA and OH to the Ce(III)-NTA complex took place during the redox reaction. As the speciation calculation of Ce(III) in the NTA solution showed that the predominant species was Ce III (nta) 2 3 (H 3 nta = NTA), the redox reaction of the Ce-NTA complex was expressed by the following: Ce IV (nta) 2 2- + e - ↔ Ce III (nta) 2 3 . The logarithm of the stability constant of Ce IV (nta) 2 2- was calculated to be 38.6 ± 0.8 for I = 0 from the redox potential shift of Ce(IV)/Ce(III) in the NTA solution. The value was in good accordance with the stability constant of the Np IV (nta) 2 2- complex, demonstrating that the aqueous coordination chemistry of Ce(IV) with NTA is quite similar to that of An(IV). These results strongly suggest that a negative shift of the Pu(IV)/Pu(III) redox potential in the NTA solution should make Pu(IV) more stable than Pu(III) even in a reducing environment. (orig.)

Synthesis of CeS and interactions with molten metals

International Nuclear Information System (INIS)

Krikorian, O.H.; Curtis, P.G.

1988-01-01

Hot-pressed and sintered discs of single-phase CeS were tested for interaction with molten aluminium, uranium, and iron to determine the conditions under which reaction first begins and the nature of the reaction. Aluminium begins to react with CeS at ∼ 1190 K, slowly dissolving cerium and forming a thin layer of Ce 3 S 4 at the reaction interface. At 1363 K, aluminium wets and spreads over the CeS surface and dissolves ∼ 01 at% Ce. Ce 3 Al 11 precipitates out in the aluminium phase on cooldown. Uranium does not react with CeS at 1673 K, but at 1873 K it wets and spreads on CeS and dissolves ∼ 100 atom ppm S, which precipitates out as US on cooldown. Iron wets CeS at 1873 K and 1973 K but does not spread or interact. Because of the desirable containment characteristics of CeS and similar sulfides for molten metals, we recommend their use in a number of applications. (author)

(EC+β+) decay of 130Ce

International Nuclear Information System (INIS)

Xu Shuwei; Zhang Tianmei; Xie Yuanxiang; Ma Ruichang; Ge Yuanxiu; Guo Yingxiang; Wang Chunfang; Li Zhankui; Guo Bing; Xing Jianping; Guo Tianrui; Zhu Shaofei; Xu Wang; Du Jinzhou

1996-01-01

The nuclide 130 Ce was produced by a ( 16 O, 4n) reaction on an enriched 118 Sn target. Reaction products were transported to a shielded location by using a helium-jet tape transport system. A 22.9 min activity in chemically separated cerium sample was identified as 130 Ce. The (EC+β + ) decay scheme of 130 Ce was proposed for the first time. This scheme includes 108 γ-lines, 107 γ-lines among them being new. More than 13 1 + low-lying states of 130 La are populated in the decay of 130 Ce. Two new isomers with half-life of 77±10 ns and 17±5 ns were observed by means of delayed γ-γ coincidence measurements. (orig.). With 5 figs., 3 tabs

Microstructure and fatigue behaviors of a biomedical Ti–Nb–Ta–Zr alloy with trace CeO2 additions

International Nuclear Information System (INIS)

Song, Xiu; Wang, Lei; Niinomi, Mitsuo; Nakai, Masaaki; Liu, Yang; Zhu, Miaoyong

2014-01-01

The new β-type Ti–29Nb–13Ta–4.6Zr (TNTZ) alloy containing trace amounts of CeO 2 additions has been designed as a biomedical implant with improved fatigue properties achieved by keeping Young's modulus to a low value. The results show that the microstructure is refined by the addition of CeO 2 ; the β grain size becomes a little larger when Ce content increases from 0.05% to 0.10%. This occurs because dispersed CeO 2 particles can act as nucleation sites for β grains; thus, the effect of rare earth oxides on microstructure refinement mainly depends on the size and dispersion of the rare earth oxides. Young's moduli of TNTZ with CeO 2 additions are maintained as low as those of TNTZ without CeO 2 , while the fatigue limit is highly improved. The 0.10% Ce alloy exhibits the best fatigue strength among the experimental alloys; its fatigue strength is increased by 66.7% compared to that of pure TNTZ. The mechanism by which rare earth oxides affect fatigue performance is dominated by dispersion strengthening. The stiff rare earth oxides can hinder the movement of dislocations, resulting in resistance to the formation of fatigue cracks. Rare earth oxides also change the crack propagation direction and the crack propagation route, effectively decreasing the crack propagation rate

Influence of interstitial solutions (H, N) on cerium electronic state in Ce-Fe intermetallic compounds: X-ray Absorption Spectroscopy (XAS) study

International Nuclear Information System (INIS)

Chaboy, J.; Marcelli, A.; Bozukov, L.

1995-03-01

It is presented an x-ray absorption spectroscopy (XAS) investigation performed at the L-edges of the rare-earth and at the K-edge of iron in the R-Fe intermetallic compounds (La, Ce) 2 Fe 14 BH χ and Ce 2 Fe 17 (H,N) χ , to elucidate the role of the interstitial doping into the electronic and magnetic properties of these systems. Comparison with x-ray circular magnetic dichroism (XCMD) experiments has been carried out to clarify the localization of 4f magnetic moment at the Ce sites upon hydriding. Both XAS and XCMD results evidence the interplay between the structural and magnetic changes, that are associated to the modification of the hybridization between the Fe(3d) and Ce(5d) bands

Proximity effect of Pb on CeCu6 and La0.05Ce0.95Cu6

International Nuclear Information System (INIS)

Chen, T.P.; Tipparachi, U.; Yang, H.D.; Wang, J.T.; Chen, B.; Chen, J.C.J.

1999-01-01

Heavy fermion materials have attracted a great deal of attention since 1979. These materials which contain a rare earth (U, or Ce, etc.) element exhibit unusual behavior at low temperature. The effective mass m* of the Landau quasiparticles is found to be orders of magnitude higher than that of a bare electron. Some of the Heavy Fermion materials become superconductors at low temperature. The pairing of electrons in these superconductors may not be of s symmetry like those in BCS type superconductors. The mismatch in electronic mass and the difference in pairing state between the light conventional superconducting electrons and the heavy fermion electrons have brought the coupling between light electrons (BCS type) and the heavy fermion electrons into question. Proximity effect of Pb on CeCu 6 , Pb on La 0.05 Ce 0.95 Cu 6 , and Pb on Cu was used to investigate the coupling between the conventional superconducting electrons of Pb and the heavy electrons in CeCu 6 or La 0.05 Ce 0.95 Cu 6 . In this experiment proximity effect was found between Pb and CeCu 6 , as well as between Pb and La 0.05 Ce 0.95 Cu 6 . However, the proximity effect is small when compared with that between Pb and Cu. This indicates a much shorter extrapolation length in the heavy fermion materials than in Cu. Such a phenomenon can be explained by the mismatch in effective mass between the superconducting Pb electrons and the heavy fermion electrons

CE Challenges : Work to Do

NARCIS (Netherlands)

Stjepandic, J; Verhagen, W.J.C.; Wognum, P.M.

2015-01-01

CE has been used for more than two decades now. Despite many successes and advantages, there are still many challenges to be addressed. These challenges are both technical and organisational. In the paper we will address the current challenges of CE. Many challenges

What was the population of Great Zimbabwe (CE1000 – 1800)?

Science.gov (United States)

Moultrie, Thomas; Bandama, Foreman; Dandara, Collett; Manyanga, Munyaradzi

2017-01-01

The World Heritage Site of Great Zimbabwe is one of the most iconic and largest archaeological settlements in Africa. It was the hub of direct and indirect trade which internally connected various areas of southern Africa, and externally linked them with East Africa and the Near and Far East. Archaeologists believe that at its peak, Great Zimbabwe had a fully urban population of 20,000 people concentrated in approximately 2.9 square kilometres (40 percent of 720 ha). This translates to a population density of 6,897, which is comparable with that of some of the most populous regions of the world in the 21st century. Here, we combine archaeological, ethnographic and historical evidence with ecological and statistical modelling to demonstrate that the total population estimate for the site’s nearly 800-year occupational duration (CE1000–1800), after factoring in generational succession, is unlikely to have exceeded 10,000 people. This conclusion is strongly firmed up by the absence of megamiddens at the site, the chronological differences between several key areas of the settlement traditionally assumed to be coeval, and the historically documented low populations recorded for the sub-continent between CE1600 and 1950. PMID:28614397

Broadband Luminescence in Rare Earth Doped Sr2SiS4: Relating Energy Levels of Ce3+ and Eu2+

Directory of Open Access Journals (Sweden)

Anthony B. Parmentier

2013-08-01

Full Text Available Sr2SiS4:Ce3+ is an efficient blue-emitting (460 nm phosphor, excitable with light of wavelengths up to 420 nm. From the excitation spectrum, we construct the energy level scheme and use it to check the predictive power of the Dorenbos model, relating the positions of the Ce3+ energy levels with those of Eu2+ in the same host. For strontium thiosilicate, this method gives excellent results and allows us to determine which of two available crystallographic sites is occupied by cerium. We use the Dorenbos method for extracting information on the coordination of Ce3+ from the observed crystal field splitting.

78 FR 75557 - CE FLNG, LLC, CE Pipeline, LLC; Notice of Intent To Prepare an Environmental Impact Statement for...

Science.gov (United States)

2013-12-12

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. PF13-11-000] CE FLNG, LLC, CE Pipeline, LLC; Notice of Intent To Prepare an Environmental Impact Statement for the Planned CE FLNG Project, Request for Comments on Environmental Issues, and Notice of Public Scoping Meeting The staff of the Federal Energy Regulatory Commission ...

Inverted opal luminescent Ce-doped silica glasses

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R. Scotti

2006-01-01

Full Text Available Inverted opal Ce-doped silica glasses (Ce : Si molar ratio 1 ⋅ 10−3 were prepared by a sol-gel method using opals of latex microspheres as templates. The rare earth is homogeneously dispersed in silica host matrix, as evidenced by the absence of segregated CeO2, instead present in monolithic Ce-doped SG with the same cerium content. This suggests that the nanometric dimensions of bridges and junctions of the host matrix in the inverted opal structures favor the RE distribution avoiding the possible segregation of CeO2.

Synthesis and structural characterization of Ce-doped bismuth titanate

International Nuclear Information System (INIS)

Pavlovic, Nikolina; Srdic, Vladimir V.

2009-01-01

Ce-modified bismuth titanate nanopowders Bi 4-x Ce x Ti 3 O 12 (x ≤ 1) have been synthesized using a coprecipitation method. DTA/TG, FTIR, XRD, SEM/EDS and BET methods were used in order to investigate the effect of Ce-substitution on the structure, morphology and sinterability of the obtained powders. The phase structure investigation revealed that after calcinations at 600 deg. C powder without Ce addition exhibited pure bismuth titanate phase; however, powders with Ce (x = 0.25, 0.5 and 0.75) had bismuth titanate pyrochlore phase as the second phase. The strongest effect of Ce addition on the structure was noted for the powder with the highest amount of Ce (x = 1) having a cubic pyrochlore structure. The presence of pure pyrochlore phase was explained by its stabilization due to the incorporation of cerium ions in titanate structure. Ce-modified bismuth titanate ceramic had a density over 95% of theoretical density and the fracture in transgranular manner most probably due to preferable distribution of Ce in boundary region

Photoluminescence properties of Tb3Al5O12:Ce3+ garnet synthesized by the metal organic decomposition method

Science.gov (United States)

Onishi, Yuya; Nakamura, Toshihiro; Adachi, Sadao

2017-02-01

Tb3Al5O12:Ce3+ garnet (TAG:Ce3+) phosphor was synthesized by the metal organic decomposition (MOD) method and subsequent calcination at Tc = 800-1200°C for 1 h in air. The effects of Ce3+ concentration on the phosphor properties were investigated in detail using X-ray diffraction (XRD) analysis, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, and PL decay measurements. The maximum intensity in the Ce3+ yellow emission was observed at the Ce3+ concentration of ∼0.20%. PLE and PL decay measurements suggested an evidence of the energy transfer from Tb3+ to Ce3+. Calcination temperature dependence of the XRD and PL intensities yielded an energy of ∼1.5 eV both for the TAG formation in the MOD process and for the optical activation of Ce3+ in its lattice sites. Temperature dependences of the PL intensity for the TAG:Ce3+ yellow-emitting and K2SiF6:Mn4+ red-emitting phosphors were also examined for the future solid-state lighting applications at T = 20-500 K in 10-K steps. The data of TAG:Ce3+ were analyzed using a theoretical model with considering a reservoir level of Et ∼9 meV, yielding a quenching energy of Eq ∼0.35 eV, whereas the K2SiF6:Mn4+ red-emitting phosphor data yielded a value of Eq ∼1.0 eV. The schematic energy-level diagrams for Tb3+ and Ce3+ were proposed for the sake of a better understanding of these ions in the TAG host.

Synthesis, extraction and electronic structure of Ce@C2n

Science.gov (United States)

Liu, Bing-Bing; Zou, Guang-Tian; Yang, Hai-Bin; Yu, San; Lu, Jin-Shan; Liu, Zi-Yang; Liu, Shu-Ying; Xu, Wen-Guo

1997-11-01

In view of the growing interest in endohedral lanthanide fullerenes, Ce, as a typical+ 4 oxidation state lanthanide element, has been systematically studied. The synthesis, extraction and electronic structure of Ce @ C2n are investigated. Soot containing Ce@C2n was synthesized in high yield by carbonizing CeO2-containing graphite rods and are back-burning the CeC2-enriched cathode deposit in a DC arc plasma apparatus. Ce@C2n dominated by Ce@C82, can be efficiently extracted from the insoluble part of the soot after toluene Soxhlet extraction by pyridine at high temperature and high pressure in a closed vessel. About 60% Ce@C2n(2n = 82, 80, 78, 76) and 35% Ce@C82 can be enriched in the pyridine extract. This fact is identified by desorption electron impact mass spectrometry (DEI MS). The electronic structure of Ce@C2n is analyzed by using X-ray photoemission spectroscopy (XPS) of pyridine-free film. It is suggested that the encapsulated Ce atom is in a charge state close to+ 3 and was effectively protected from reaction with water and oxygen by the enclosing fullerene cage. Unlike theoretical expectation, the electronic state of Ce@C82 is formally described as Ce+3@C3-82.

Effect of CeO2 addition on electrical and optical properties of lithium borate glasses

International Nuclear Information System (INIS)

Gedam, R.S.; Ramteke, D.D.

2011-01-01

Rare earth (RE) ions play an important role in modern technology as an active ion in many optical materials. RE-doped glasses were used in many optical devices because of abundant number of the absorption and emission bands arising from the transitions between the RE elements energy levels. Among all rare earth, glasses containing CeO 2 are extensively studied for scintillating applications. Radiation length of CeO 2 containing lithium silicate glasses decreases and absorption edge in transmittance shift towards longer wavelength. In the present study an attempt has been made to verify similar results in borate containing glasses. Therefore glass series 15Li 2 O-xCeO 2 -(85''x)B 2 O 3 where x= 0.25, 0.5, 0.75, 1 mol% was prepared by conventional melt quench technique. Their electrical and optical properties have been investigated. It is observed that the conductivity of these glasses decreases while density, glass transition temperature and refractive index increases with the addition of CeO 2 . The conductivity of the glasses is mostly controlled by the activation energy. Since the lithium fraction in the present series is kept constant, the decrease in conductivity for glasses may be attributed to the reduction in the number of available vacant sites for the mobile lithium ions when boron is substituted with CeO 2 . The radiation length was determined using density values and it was found to decrease with the addition of CeO 2 . The absorption coefficient a were determined near the absorption edge of different photon energy for all glass samples and plot of (αhν) 1/2 Vs. hν (Tauc's plot) is shown. It is observed that the optical band gap energy (E g Opt ) decreases with the addition of CeO 2

Evaluation of critical distances for energy transfer between Pr{sup 3+} and Ce{sup 3+} in yttrium aluminium garnet

Energy Technology Data Exchange (ETDEWEB)

Zeng, Peng; Wei, Xiantao; Yin, Min; Chen, Yonghu, E-mail: yhuchen@ustc.edu.cn [Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, School of Physical Sciences, University of Science and Technology of China, No. 96 Jinzhai Road, Hefei, Anhui 230026 (China); Zhou, Shaoshuai [Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, School of Physical Sciences, University of Science and Technology of China, No. 96 Jinzhai Road, Hefei, Anhui 230026 (China); Department of Physics, Qufu Normal University, Qufu, Shandong 273165 (China)

2016-09-07

A series of Pr{sup 3+}/Ce{sup 3+} doped yttrium aluminium garnet (Y{sub 3}Al{sub 5}O{sub 12} or simply YAG) phosphors were synthesized to investigate the energy transfer between Pr{sup 3+} and Ce{sup 3+} for their potential application in a white light-emitting diode and quantum information storage and processing. The excitation and emission spectra of YAG:Pr{sup 3+}/Ce{sup 3+} were measured and analyzed, and it revealed that the reabsorption between Pr{sup 3+} and Ce{sup 3+} was so weak that it can be ignored, and the energy transfer from Pr{sup 3+} (5d) to Ce{sup 3+} (5d) and Ce{sup 3+} (5d) to Pr{sup 3+} ({sup 1}D{sub 2}) did occur. By analyzing the excitation and the emission spectra, the energy transfer from Pr{sup 3+} (5d) to Ce{sup 3+} (5d) and Ce{sup 3+} (5d) to Pr{sup 3+} ({sup 1}D{sub 2}) was examined in detail with an original strategy deduced from fluorescence dynamics and the Dexter energy transfer theory, and the critical distances of energy transfer were derived to be 7.9 Å and 4.0 Å for Pr{sup 3+} (5d) to Ce{sup 3+} (5d) and Ce{sup 3+} (5d) to Pr{sup 3+} ({sup 1}D{sub 2}), respectively. The energy transfer rates of the two processes of various concentrations were discussed and evaluated. Furthermore, for the purpose of sensing a single Pr{sup 3+} state with a Ce{sup 3+} ion, the optimal distance of Ce{sup 3+} from Pr{sup 3+} was evaluated as 5.60 Å, where the probability of success reaches its maximum value of 78.66%, and meanwhile the probabilities were evaluated for a series of Y{sup 3+} sites in a YAG lattice. These results will be of valuable reference for achievement of the optimal energy transfer efficiency in Pr{sup 3+}/Ce{sup 3+} doped YAG and other similar systems.

Ferroelectric relaxor Ba(TiCe)O3

International Nuclear Information System (INIS)

Chen Ang; Zhi Jing; Yu Zhi

2002-01-01

The dielectric behaviour of Ba(Ti 1-y Ce y )O 3 solid solutions (y=0-0.3) has been studied. A small amount of Ce doping (y=0.02) has weak influence on the dielectric behaviour of Ba(Ti 1-y Ce y )O 3 . With increasing Ce concentration, three phase transitions of pure BaTiO 3 are pinched into one rounded dielectric peak with frequency dispersion, and the relaxation time follows the Vogel-Fulcher relation. The evolution from a normal ferroelectric to a ferroelectric relaxor is emphasized. High strains (S=∼0.1-0.19%) with a small hysteresis under ac fields are obtained in ferroelectric relaxors Ba(Ti 1-y Ce y )O 3 . The physical mechanism of the relaxation process, the pinching effect of the phase transitions and their influence on the ferroelectric and electrostrictive behaviour are discussed. (author)

NMR study of CeCoSi3

International Nuclear Information System (INIS)

Iwamoto, Y.

1995-01-01

Low-temperature susceptibility, NMR and NQR of the 59 Co signal in CeCoSi 3 have been measured. CeCoSi 3 showed a superconducting transition at 0.7-1.2K. From NQR measurement, the nuclear quadrupole frequency and the full width at half maximum (FWHM) of 59 Co in CeCoSi 3 were estimated to be about 1.08MHz and 0.08MHz, respectively. The 59 Co nuclear spin-lattice relaxation rate (1/T 1 ) in CeCoSi 3 was proportional to the temperature (T) as the Fermi liquid state above the superconducting transition temperature (T c ), and then rapidly decreased below T c . ((orig.))

Magnetic behavior of the alloys (Ce{sub 1-x}Y{sub x}){sub 2}PdSi{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Mallik, R [Tata Inst. of Fundamental Res., Colaba, Mumbai (India); Sampathkumaran, E V [Tata Inst. of Fundamental Res., Colaba, Mumbai (India)

1996-11-01

The results of X-ray diffraction (Cu K{sub {alpha}}), electrical resistivity ({rho}), heat capacity (C) and magnetic susceptibility ({chi}) measurements are reported for a new pseudoternary solid solution, (Ce{sub 1-x}Y{sub x}){sub 2}PdSi{sub 3} (x=0.0, 0.2, 0.5, 0.8, 1.0). The X-ray diffraction patterns indicate that single phase alloys can be formed in a derived version of the AlB{sub 2}-type hexagonal structure for x{>=}0.2, while for x=0.0, apparently there is an additional weak phase. In the case of the alloy Ce{sub 2}PdSi{sub 3}, the majority of Ce ions do not exhibit magnetic ordering down to 1.4 K, though magnetic ordering at 7 K from one of the two crystallographically inequivalent sites cannot be ruled out. For other compositions, no magnetic ordering is observed above 1.4 K. The Kondo effect is operative in all these alloys, with the strength of the Kondo effect increasing with the compression of the lattice by the gradual replacement of Ce by Y. The C/T exhibits a low temperature enhancement in all Ce containing alloys. (orig.).

Distribution and Translocation of 141Ce (III) in Horseradish

Science.gov (United States)

Guo, Xiaoshan; Zhou, Qing; Lu, Tianhong; Fang, Min; Huang, Xiaohua

2007-01-01

Background and Aims Rare earth elements (REEs) are used in agriculture and a large amount of them contaminate the environment and enter foods. The distribution and translocation of 141Ce (III) in horseradish was investigated in order to help understand the biochemical behaviour and toxic mechanism of REEs in plants. Method The distribution and translocation of 141Ce (III) in horseradish were investigated using autoradiography, liquid scintillation counting (LSC) and electron microscopic autoradiography (EMARG) techniques. The contents of 141Ce (III) and nutrient elements were analysed using an inductively coupled plasma-atomic emission spectrometer (ICP-AES). Results The results from autoradiography and LSC indicated that 141Ce (III) could be absorbed by horseradish and transferred from the leaf to the leaf-stalk and then to the root. The content of 141Ce (III) in different parts of horseradish was as follows: root > leaf-stalk > leaf. The uptake rates of 141Ce (III) in horseradish changed with the different organs and time. The content of 141Ce (III) in developing leaves was greater than that in mature leaves. The results from EMARG indicated that 141Ce (III) could penetrate through the cell membrane and enter the mesophyll cells, being present in both extra- and intra-cellular deposits. The contents of macronutrients in horseradish were decreased by 141Ce (III) treatment. Conclusions 141Ce (III) can be absorbed and transferred between organs of horseradish with time, and the distribution was found to be different at different growth stages. 141Ce (III) can enter the mesophyll cells via apoplast and symplast channels or via plasmodesmata. 141Ce (III) can disturb the metabolism of macronutrients in horseradish. PMID:17921527

Traducerea: între ce se poate traduce și ce trebuie tradus

Directory of Open Access Journals (Sweden)

Magda Jeanrenaud

2016-02-01

Full Text Available Pornind de la o tulburătoare interpretare a lui Jacques Derrida, studiul de față își propune să investigheze și încearcă să explice blocajul ce intervine în versiunile englezești, franceze și românești (semnate de Antoine Berman, Alexis Nouss, Steven Rendall, Catrinel Pleșu etc. ale celebrului text al lui Walter Benjamin, Die Aufgabe des Übersetzers, atunci cînd traducătorii transpun în cele trei limbi țintă cele două citate cuprinse în acesta: un citat din Mallarmé, lăsat netradus de Benjamin însuși, și un altul, din Pannwitz. Într-un fel sau altul, ambele citate au o formă discursivă ce lasă să se întrevadă o sintaxă ce se abate deliberat de la normă, ca și cum ar fi deja niște „traduceri”. Analiza mai pune în evidență și comportamentul (cumva o dominantă a psihologiei traducătorilor? celor ce au transpus textul benjaminian, comportament marcat de obsesia lizibilității văzută ca o trăsătură congenitală a oricărei traduceri, chiar și atunci cînd textul original nu tinde spre aceasta. De unde și dilema, dureroasă, legată de spinoasa chestiune a intenționalității textului (nu doar de tradus...

Floods of December 1966 in southwestern Utah

Science.gov (United States)

Butler, Elmer; Mundorff, J.C.

1970-01-01

Severe floods occurred in parts of southwestern Utah on December 5-6, 1966, as a result of precipitation of about 1 inch to more than 12 inches during December 3-6. The flood on the Virgin River was the greatest since the first settlers arrived in 1860.The peak discharge of the Virgin River at Virgin, Utah, was 22,830 cubic feet per second on December 6; this exceeded the previous maximum discharge of 13,500 cubic feet per second on March 3, 1938, and September 17, 1961, and probably has a recurrence interval of 100 years. At eight other gage sites in the flood area, the peak discharge in December 1966 was the highest of record; the recurrence intervals of some of the peak discharges may be 100 years. The flood peaks were generally of short duration and most streams receded to near base flow within 24 hours.The dissolved-solids content was significantly lower in the Virgin River at Virgin than at St. George, about 25 miles downstream; the water was of the calcium sulfate type at both sites. Data for the Santa Clara River above Winsor Dam and the Santa Clara River near Santa Clara show a significant increase in dissolved solids between the two sites. The water above Winsor Dam was of the calcium bicarbonate type, and the water near Santa Clara was of the calcium bicarbonate sulfate type.The suspended-sediment discharge, during the period December 5-8, 1966, at Santa Clara River above Winsor Dam, near Santa Clara was about foyer times greater than all the suspended-sediment discharge during the preceding 3 years ; the suspended-sediment discharge of the Virgin River at Virgin was greater during the 4-day period than during any one of the preceding 3 years.Nearly all the flood damage in the area occurred in the Virgin River basin. According to the Soil Conservation Service, total damage in the Dixie Soil Conservation District in Washington County was about $835,000; 60 percent of the damage was caused by floodwater and 40 percent by deposited sediment.

Resonant photoemission study of CeRu4Sb12

International Nuclear Information System (INIS)

Ishii, Hiroyoshi; Miyahara, Tsuneaki; Takayama, Yasuhiro; Shiozawa, Hidetsugu; Obu, Kenji; Matsuda, Tatsuma D.; Aoki, Yuji; Sugawara, Hitoshi; Sato, Hideyuki

2005-01-01

We have measured the Ce 4d-4f and Ce 3d-4f resonant photoemission spectra of CeRu 4 Sb 12 . The Ce 4f spectra show the spectral features corresponding to a weakly hybridized system. The number of 4f electrons is estimated to be ∼1.0

Ethanol Sensor of CdO/Al2O3/CeO2 Obtained from Ce-DOPED Layered Double Hydroxides with High Response and Selectivity

Science.gov (United States)

Xu, Dongmei; Guan, Meiyu; Xu, Qinghong; Guo, Ying; Wang, Yao

2013-04-01

In this paper, Ce-doped CdAl layered double hydroxide (LDH) was first synthesized and the derivative CdO/Al2O3/CeO2 composite oxide was prepared by calcining Ce-doped CdAl LDH. The structure, morphology and chemical state of the Ce doped CdAl LDH and CdO/Al2O3/CeO2 were also investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), solid state nuclear magnetic resonance (SSNMR), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The gas sensing properties of CdO/Al2O3/CeO2 to ethanol were further studied and compared with CdO/Al2O3 prepared from CdAl LDH, CeO2 powder as well as the calcined Ce salt. It turns out that CdO/Al2O3/CeO2 sensor shows best performance in ethanol response. Besides, CdO/Al2O3/CeO2 possesses short response/recovery time (12/72 s) as well as remarkable selectivity in ethanol sensing, which means composite oxides prepared from LDH are very promising in gas sensing application.

Luminescent and scintillation properties of the Ce3+ doped Y3−xLuxAl5O12:Ce single crystalline films

International Nuclear Information System (INIS)

Zorenko, Yu.; Gorbenko, V.; Zorenko, T.; Popielarski, P.; Mosińska, L.; Fedorov, A.

2016-01-01

The work is related to the investigation of scintillation and luminescent properties of single crystalline films (SCF) of solid solutions of Ce 3+ doped Y 3−x Lu x Al 5 O 12 :Ce garnets with x value in the 0–3 range. We have shown a possibility of realization of high-energy shift of the Ce 3+ ion emission spectrum in these garnets up to 22 nm. We have also found that the light yield of the radioluminescence under α-particle excitation of LuAG:Ce SCF can exceed by 1.3 times the corresponding values for the YAG:Ce SCF counterpart. For investigation of the luminescent properties of Y 3−x Lu x Al 5 O 12 :Ce SCF at different x values the luminescent spectroscopy of these SCFs under excitation by synchrotron radiation in the VUV range was performed. - Highlights: • Single crystalline films of Y 3−x Lu x Al 5 O 12 garnets at x=0–3.0 were grown by LPE method onto YAG substrates. • Lattice constant of Y 3−x Lu x Al 5 O 12 :Ce film and the film/substrate misfit changed linearly with increasing of Lu content in the x=0–3.0 range. • High-energy shift of the Ce 3+ emission up to 22 nm in Y 3−x Lu x Al 5 O 12 film with increasing of Lu content in the x=0–3.0 range. • Light yield of Y 3−x Lu x Al 5 O 12 :Ce film decreases in the x=0–1.8 range and increases in the x=1.8–3.0 range. • Scintillation LY of Lu 3 Al 5 O 12 :Ce film can exceed by 1.3 times the LY for YAG:Ce film counterpart.

Ce3 - xMgxCo9 : Transformation of a Pauli Paramagnet into a Strong Permanent Magnet

Science.gov (United States)

Lamichhane, Tej N.; Taufour, Valentin; Palasyuk, Andriy; Lin, Qisheng; Bud'ko, Sergey L.; Canfield, Paul C.

2018-02-01

We report on the synthesis of single-crystal and polycrystalline samples of Ce3 -xMgxCo9 solid solution (0 ≤x ≲1.4 ) and characterization of their structural and magnetic properties. The crystal structure remains rhombohedral in the whole composition range and Mg partially replaces Ce in the 6 c site of the CeCo3 structure. Ferromagnetism is induced by Mg substitutions starting as low as x =0.18 and reaching a Curie temperature as high as 450 K for x =1.35 . Measurements on single crystals with x =1.34 and TC=440 K indicate an axial magnetic anisotropy with an anisotropy field of 6 T and a magnetization of 6 μB/f .u . at 300 K. Coercicity is observed in the polycrystalline samples consistent with the observed axial magnetic anisotropy. Our discovery of ferromagnetism with large axial magnetic anisotropy induced by substituting a rare-earth element by Mg is a very promising result in the search of inexpensive permanent-magnet materials and suggests that other nonmagnetic phases, similar to CeCo3 , may also conceal nearby ferromagnetic phases.

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.

Electro-regeneration of Ce(IV) in real spent Cr-etching solutions

International Nuclear Information System (INIS)

Chen, Te-San; Huang, Kuo-Lin

2013-01-01

Highlights: • An electrochemical process is used to regenerate Ce(IV) in real (hazardous) spent TFT-LCD Cr-etching solutions. • The Ce(IV) yield on tested anodes was in order BDD > Pt > DSA. • A Neosepta CMX separator was better than Nafion ones to be used in the process. • The activation energy on Pt was 10.7 kJ/mol. • The obtained parameters are useful to design reactors for 100% Ce(IV) regeneration in real spent Cr-etching solutions. -- Abstract: This paper presents the electro-regeneration of Ce(IV) in real (hazardous) spent thin-film transistor liquid-crystal display (TFT-LCD) Cr-etching solutions. In addition to Ce(III) > Ce(IV) in diffusivity, a quasi-reversible behavior of Ce(III)/Ce(IV) was observed at both boron-doped diamond (BDD) and Pt disk electrodes. The Ce(IV) yield on Pt increased with increasing current density, and the best current efficiency (CE) was obtained at 2 A/2.25 cm 2 . The performance in terms of Ce(IV) yield and CE of tested anodes was in order BDD > Pt > dimensional stable anode (DSA). At 2 A/2.25 cm 2 on Pt and 40 °C for 90 min, the Ce(IV) yield, CE and apparent rate constant (k) for Ce(III) oxidation were 81.4%, 21.8% and 3.17 × 10 −4 s −1 , respectively. With the increase of temperature, the Ce(IV) yield, CE, and k increased (activation energy = 10.7 kJ/mol), but the specific electricity consumption decreased. The Neosepta CMX membrane was more suitable than Nafion-117 and Nafion-212 to be used as the separator of the Ce(IV) regeneration process. The obtained parameters are useful to design divided batch reactors for the Ce(IV) electro-regeneration in real spent Cr-etching solutions

Loparite-(Ce) from the Khibiny Alkaline Pluton, Kola Peninsula, Russia

Science.gov (United States)

Konopleva, N. G.; Ivanyuk, G. Yu.; Pakhomovsky, Ya. A.; Yakovenchuk, V. N.; Mikhailova, Yu. A.

2017-12-01

Data on the occurrence, morphology, anatomy, composition, and formation conditions of loparite-(Ce) in the Khibiny alkaline pluton are given. Loparite-(Ce), (Na,Ce,Sr)(Ce,Th)(Ti,Nb)2O6, resulted from metasomatic alteration and assimilation of metamorphic host rocks at the contact with foyaite as well as foyaite on the contact with foidolite. This alteration was the highest in pegmatite, and albitite developed there. A decrease in temperature resulted in enrichment of the perovskite and tausonite endmembers in loparite-(Ce) owing to a decrease in the loparite and lueshite endmembers. La and Ce sharply predominate among rare earth elements in the composition of loparite-(Ce).

Single-crystal FCC and DHCP phases in Ce/Pr superlattices

International Nuclear Information System (INIS)

Lee, S.; Goff, J.P.; Ward, R.C.C.; Wells, M.R.; McIntyre, G.J.

2002-01-01

Cerium usually comprises a mixture of polycrystalline FCC and DHCP allotropes. Single-crystal Ce has been stabilised in Ce/Pr superlattices grown using molecular beam epitaxy. It is found that FCC or DHCP phases can be obtained depending on superlattice composition and growth conditions. Low-temperature neutron scattering was performed on Ce/Pr samples using the triple-axis spectrometer D10 at the ILL. Such measurements revealed one sample, [Ce 20 Pr 20 ] 60 , to be a single crystal with a DHCP unit cell; while another, [Ce 30 Pr 10 ] 56 , was a mixture of FCC and DHCP phases. Antiferromagnetic ordering of magnetic moments was observed in the DHCP sample (T N =11.1 K) with a magnetic structure similar to that found in bulk β-Ce. Surprisingly, the magnetic ordering was found to be confined to single Ce blocks. Furthermore, it was found that, at low temperatures, the lattice contraction observed for bulk FCC Ce was suppressed in Ce/Pr superlattices. (orig.)

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 ...

Unraveling the oxygen vacancy structures at the reduced Ce O2(111 ) surface

Science.gov (United States)

Han, Zhong-Kang; Yang, Yi-Zhou; Zhu, Beien; Ganduglia-Pirovano, M. Verónica; Gao, Yi

2018-03-01

Oxygen vacancies at ceria (Ce O2 ) surfaces play an essential role in catalytic applications. However, during the past decade, the near-surface vacancy structures at Ce O2(111 ) have been questioned due to the contradictory results from experiments and theoretical simulations. Whether surface vacancies agglomerate, and which is the most stable vacancy structure for varying vacancy concentration and temperature, are being heatedly debated. By combining density functional theory calculations and Monte Carlo simulations, we proposed a unified model to explain all conflicting experimental observations and theoretical results. We find a novel trimeric vacancy structure which is more stable than any other one previously reported, which perfectly reproduces the characteristics of the double linear surface oxygen vacancy clusters observed by STM. Monte Carlo simulations show that at low temperature and low vacancy concentrations, vacancies prefer subsurface sites with a local (2 × 2) ordering, whereas mostly linear surface vacancy clusters do form with increased temperature and degree of reduction. These results well explain the disputes about the stable vacancy structure and surface vacancy clustering at Ce O2(111 ) , and provide a foundation for the understanding of the redox and catalytic chemistry of metal oxides.

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

Tunable colorimetric performance of Al{sub 2}O{sub 3}-YAG:Ce{sup 3+} eutectic crystal by Ce{sup 3+} concentration

Energy Technology Data Exchange (ETDEWEB)

Sai, Qinglin, E-mail: saiql@siom.ac.cn; Xia, Changtai, E-mail: xia_ct@siom.ac.cn

2017-06-15

Ce-doped Al{sub 2}O{sub 3}-YAG eutectics with different percentage of Ce were successfully grown by the optical floating zone technique. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the structure. The results show that they have typical eutectic structure of interpenetrating sapphire and garnet phases with the tens of microns lamella spacing. The photoluminescence spectra of the eutectics showed that they have wide excitation band, and samples with 1.6 mol% Ce-doped has the highest emission intensity. The eutectic-packaged LED has high luminous efficiency and its color can be modulated by changing Ce concentration. The results reveal that Ce-doped Al{sub 2}O{sub 3}-YAG eutectic is a promising phosphor for white LED applications.

CeO2-ZrO2 ceramic compounds

International Nuclear Information System (INIS)

Melo, F.C.L.; Cairo, C.A.C.; Devezas, T.C.; Nono, M.C.A.

1988-01-01

In order to study the mechanical properties of tetragonal polycrystal zirconia stabilized with ceria various powder compositions with different CeO 2 content were made. Modulus of rupture for those compounds was measured. Tetragonal retained phase was determined for samples of CeO 2 -ZrO 2 ceramics with and without superficial mechanical treatment. The experimental results allowed us to evaluate the effects of CeO 2 content and sintering temperature in the mechanical properties and tetragonal transformed phase (t→ m) in ceramics of CeO 2 -ZrO 2 systems. (author) [pt

Positron annihilation studies in the Nd-Ce-Cu-O superconductor

International Nuclear Information System (INIS)

Sundar, C.S.; Bharathi, A.; Jean, Y.C.; Hor, P.H.; Meng, R.L.; Huang, Z.J.; Chu, C.W.

1990-01-01

In the superconducting Nd 1.85 Ce 0.15 CuO 3.98 , the positron lifetime is observed to decrease from 211 to 205 ps in the temperature range of 150--50 K, whereas in the nonsuperconducting Nd 1.85 Ce 0.15 CuO 4 , having a lifetime value of 231 ps, no significant temperature dependence of lifetime is observed. The difference in the lifetimes of the superconducting and nonsuperconducting samples and their temperature dependencies are understood in terms of positron interaction with the vacancies in the system. Doppler-broadened line shapes of energy spectra are found to show similar results as lifetime measurements. Theoretical calculations are used to show that the oxygen vacancies are weaker traps compared with the vacancies at the Cu and Nd sites. The observed decrease in lifetime in the superconducting sample is interpreted in terms of an increase in the fraction of positrons trapped at the oxygen vacancies as the temperature is lowered. Plausible reasons for the temperature independence of lifetime across T c in the superconducting sample are discussed

Toxicity of inhaled 144CeCl3 in beagle dogs

International Nuclear Information System (INIS)

Muggenburg, B.A.; Hahn, F.F.; Boecker, B.B.; McClellan, R.O.; Pickrell, J.A.

1980-01-01

The metabolism, dosimetry and effects of inhaled 144 CeCl 3 in beagle dogs are being studied to assess the biological consequences of inhaling 144 Ce. Studies have shown that the 144 Ce deposited in the lung as 144 CeCl 3 is translocated at a moderately rapid rate to liver and skeleton and that significant radiation doses are accumulated by all three organs. Fifty-five dogs that inhaled 144 CeCl 3 and 17 control dogs are being observed for their life span. The 144 Ce-exposed dogs had long-term retained burdens that ranged from 2.6 to 360 μCi 144 Ce/kg body weight. Fifty-three of the dogs exposed to 144 CeCl 3 have died and twelve control dogs have died. Serial observations are continuing on the two surviving exposed dogs and five control dogs

Spin glass and ferromagnetic properties of Ce(Cu_1_-_xNi_x)_4Mn alloys: Multicritical points in the magnetic phase diagram

International Nuclear Information System (INIS)

Synoradzki, K.; Toliński, T.

2016-01-01

We report on the CeNi_4Mn (ferromagnet FM) - CeCu_4Mn (spin-glass SG) transformation leading to a complex magnetic phase diagram (MPD). It is verified that all the Ce(Cu_1_-_xNi_x)_4Mn alloys are isostructural and the transformation is governed only by the Cu-Ni substitution. MPD is built based on the magnetic dc/ac susceptibility measurements and reveals SG formation as well as the region of the coexistence of the FM and SG state in the middle range of the Ni concentration. The complex MPD is explained by clusters formation and a competition of interactions between various crystallographic sites of the hexagonal CaCu_5-type structure, mainly the 3g-3g and 3g-2c interactions. The predominance of the SG state is confirmed by the analysis of the frequency dependence of the ac magnetic susceptibility components and the relaxation of the remanent magnetization. Additionally, the presence of two multicritical points is observed. - Highlights: • We fully characterized the magnetic properties of Ce(Cu_1_-_xNi_x)_4Mn alloys. • We show the presence of complex magnetic behaviour due to atomic-site disorder. • Magnetic phase diagram revels mixed-phase ground state. • Two multicritical points on magnetic phase diagram occurs.

Physical, biochemical and genetic characterization of enterocin CE5-1 produced by Enterococcus faecium CE5-1 isolated from Thai indigenous chicken intestinal tract

Directory of Open Access Journals (Sweden)

Kraiyot Saelim

2015-06-01

Full Text Available Enterocin CE5-1 produced by Enterococcus faecium CE5-1 isolated from the chicken gastrointestinal tract was active in the wide range of pH 2-10 and temperature 30-100°C and sensitive to proteolytic enzymes and -amylase. It remained active after storage at -20°C for 2 months. Moreover, enterocin CE5-1 showed antibacterial activity against lactobacilli, bacilli, listeria, staphylococci and enterococci, especially antibiotic-resistant enterococci. In vitro study of enterocin CE5-1 decreased the population of Ent. faecalis VanB from 6.03 to 4.03 log CFU/ml. The lethal mode of action of enterocin CE5-1 appeared to be pore and filament formation in the cell wall. PCR sequencing analysis revealed the presence of two open reading frames (ORFs, containing enterocin CE5-1 (entCE5-1 and enterocin immunity (entI gene. Therefore, enterocin CE5-1 from Ent. faecium CE5-1 could possibly be used as an antimicrobial agent to control foodborne pathogen, spoilage bacteria and antibiotic-resistant enterococci in foods, feeds and the environments.

Itinerant f-electron behavior in Ce and U compounds

International Nuclear Information System (INIS)

Crabtree, G.W.

1985-04-01

The experimentally observed Fermi surface properties in URh 3 , UIr 3 , UGe 3 , CeSn 3 , CeB 6 , U 3 As 4 , U 3 P 4 , and CeSb are reviewed. For the compounds with no magnetic order, band structure models of the Fermi surface geometry are confirmed and f-ligand hybridization is found to be dominant. For CeB 6 , U 3 As 4 , and U 3 P 4 the experiments show that both local moments and f hybridization are important. In CeSb new data can be explained by a purely local model with no f-hybridization

Structure and phase composition of Al-Ce-Cu system alloys in range of quasi-binary Al-Al8CeCu4 section

International Nuclear Information System (INIS)

Belov, N.A.; Khvan, A.V.

2007-01-01

The phase diagram of the Al-Cu-Ce system in the quasibinary section area of Al-Al 8 CeCu 4 has been investigated by metallographic, thermal, micro-X-ray spectral and X-ray structural analyses. The parameters of the eutectic reaction L→(Al)+CeCu 4 Al 8 : T=610 Deg C were found out; the composition was 14% Cu and 7% Ce. This eutectics is of a disperse structure and the ternary compound contained is capable of fragmentation and spheroidizing in the heating process (starting from 540 Deg C). It was demonstrated that the area of optimal (Al)+CeCu 4 Al 8 eutectics-based alloy compositions was within the narrow limits. That is related to the fact that at a comparatively little variation of the Cu:Ce=2 ratio solidus sharply decreases and, as a result, the crystallization interval considerably extends [ru

How to Attain an Ultralow Interfacial Tension and a Three-Phase Behavior with a Surfactant Formulation for Enhanced Oil Recovery: A Review. Part 2. Performance Improvement Trends from Winsor's Premise to Currently Proposed Inter- and Intra-Molecular Mixtures.

Science.gov (United States)

Salager, Jean-Louis; Forgiarini, Ana M; Márquez, Laura; Manchego, Lisbeth; Bullón, Johnny

2013-01-01

The minimum interfacial tension occurrence along a formulation scan at the so-called optimum formulation is discussed to be related to the interfacial curvature. The attained minimum tension is inversely proportional to the domain size of the bicontinuous microemulsion and to the interfacial layer rigidity, but no accurate prediction is available. The data from a very simple ternary system made of pure products accurately follows the correlation for optimum formulation, and exhibit a linear relationship between the performance index as the logarithm of the minimum tension at optimum, and the formulation variables. This relation is probably too simple when the number of variables is increased as in practical cases. The review of published data for more realistic systems proposed for enhanced oil recovery over the past 30 years indicates a general guidelines following Winsor's basic studies concerning the surfactant-oil-water interfacial interactions. It is well known that the major performance benefits are achieved by blending amphiphilic species at the interface as intermolecular or intramolecular mixtures, sometimes in extremely complex formulations. The complexity is such that a good knowledge of the possible trends and an experienced practical know-how to avoid trial and error are important for the practitioner in enhanced oil recovery.

Microstructures and luminescent properties of Ce-doped transparent mica glass-ceramics

International Nuclear Information System (INIS)

Taruta, Seiichi; Iwasaki, Yoshitomo; Nishikiori, Hiromasa; Yamakami, Tomohiko; Yamaguchi, Tomohiro; Kitajima, Kunio; Okada, Kiyoshi

2012-01-01

Highlights: ► Ce-doped transparent glass-ceramics and their parent glasses. ► TEM and STEM images for the microstructures. ► Each mica crystal did not contain Ce uniformly. ► Emission due to Ce 3+ ions in the glass phase and/or Ce 3+ ions in the mica crystals. - Abstract: Transparent mica glass-ceramics were prepared by heating parent glasses that had been doped with 0.5–15 mol% CeO 2 . During the melting and heat treatment, Ce 4+ ions in the specimens were reduced to Ce 3+ ions, and one or both of these ion species were then replaced with Li + ions in the interlayers of the separated mica crystals. However, scanning transmission electron microscope (STEM) and Z-contrast imaging revealed that the mica crystals did not contain the same amount of Ce. On excitation at 254 nm, the parent glasses and glass-ceramics emitted blue light, which originated from the 5d to 4f transition of the Ce 3+ ions. The emission of the glass-ceramic containing a smaller amount of Ce was attributed to the Ce 3+ ions in both the glass phase and the mica crystals, whereas that of the glass-ceramics containing a larger amount of Ce was caused mainly by Ce 3+ ions in the mica crystals. The dependence of the emission band of the parent glasses on the amount of Ce was a unique feature of the Ce-doped transparent mica glass-ceramics and was not observed in previous studies of Eu-doped parent glasses and mica glass-ceramics.

Metallic oxides supported in CeO{sub 2} and CeO{sub 2}-La{sub 2} O{sub 3} for low temperature shift reaction; Oxidos metalicos suportados em CeO{sub 2} e CeO{sub 2}-La{sub 2} O{sub 3} para reacao shift a baixa temperatura

Energy Technology Data Exchange (ETDEWEB)

Maluf, Silvia Salua; Assaf, Elisabete Moreira [Universidade de Sao Paulo (USP), Sao Carlos, SP (Brazil). Inst. de Quimica]. E-mail: sil_maluf@iqsc.usp.br

2008-07-01

This work studied copper and zinc oxides supported in CeO{sub 2} and CeO{sub 2}/La{sub 2}O{sub 3}. The catalytic tests for low temperature shift reaction, carried out for samples, showed the Cu-Ce catalyst presents the highest value of CO conversion (50%) and after the Cu-Ce-La catalysts (30%). The other catalysts showed CO conversion in range of 15%. This behavior is related with surface area, and also with the amount of Cu in the surface of samples (author)

Electron traps and scintillation mechanism in YAlO3:Ce and LuAlO3:Ce scintillators

International Nuclear Information System (INIS)

Wojtowicz, A.J.; Glodo, J.; Drozdowski, W.; Przegietka, K.R.

1998-01-01

In this paper we present the results of thermoluminescence, isothermal decay and scintillation light yield measurements on two isostructural scintillator materials, YAlO 3 :Ce and LuAlO 3 :Ce. In addition to the variety of deep traps identified by thermoluminescence and isothermal decays, scintillation light yield experiments demonstrate the presence in both materials of a number of relatively shallow traps. While the deep traps may reduce the scintillation light yield, they do not influence the kinetics of the process. The shallow traps, on the other hand, by interfering with the process of radiative recombination of charge carriers via Ce 3+ ions, can strongly affect not only the yield of the scintillation process but its kinetics as well. The presence of shallow traps provides a consistent explanation for a number of poorly understood relationships between the two scintillator materials, including a higher room temperature scintillation light yield and longer scintillation decay time in YAlO 3 :Ce, and a longer scintillation rise time in LuAlO 3 :Ce. Theoretical analysis indicates that elimination of these traps would make the two materials nearly identical in scintillator performance. Although the specific identity of all traps remains elusive, the performance of both scintillator materials is now, in practical terms, fully understood. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

Photocatalytic activity of the binary composite CeO{sub 2}/SiO{sub 2} for degradation of dye

Energy Technology Data Exchange (ETDEWEB)

Phanichphant, Sukon [Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Nakaruk, Auppatham [Department of Industrial Engineering, Faculty of Engineering, Naresuan University, Phitsanulok 65000 (Thailand); Centre of Excellence for Innovation and Technology for Water Treatment, Naresuan University, Phitsanulok 65000 (Thailand); Channei, Duangdao, E-mail: duangdaoc@nu.ac.th [Department of Chemistry, Faculty of Science, Naresuan University, Phitsanulok 65000 (Thailand); Research Center for Academic Excellence in Petroleum, Petrochemicals and Advanced Materials, Naresuan University, Phitsanulok 65000 (Thailand)

2016-11-30

Highlights: • The enhanced photocatalytic activity of the CeO{sub 2}/SiO{sub 2} composite can be explained by the presence of the SiO{sub 2} adsorbent, which effectively increased the surface area of the CeO{sub 2}. • The increased surface area of CeO{sub 2} should be helpful to facilitate more effective adsorption sites, which enhances the photocatalytic degradation of organic pollutant significantly. • SiO{sub 2} modification is effective in separating the photogenerated electrons and holes, which is of great importance for photocatalytic activity. • SiO{sub 2} acted as a carrier for CeO{sub 2} attachment and avoided the agglomeration of CeO{sub 2} particles. - Abstract: In this study, CeO{sub 2} photocatalyst was modified by composite with SiO{sub 2} to increase efficiency and improve photocatalytic activity. The as-prepared SiO{sub 2} particles have been incorporated into the precursor mixture of CeO{sub 2} by homogeneous precipitation and subsequent calcination process. The phase compositions of CeO{sub 2} before and after compositing with SiO{sub 2} were identified by X-ray diffraction (XRD). The morphology and particle size of CeO{sub 2}/SiO{sub 2} composite was analyzed by high resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). The results showed SiO{sub 2} spheres with the particle size approximately 100–120 nm, and a uniform layer of CeO{sub 2} nanoparticles with a diameter of about 5–7 nm that were fully composite to the surfaces of SiO{sub 2}. The X-ray photoelectron spectroscopy (XPS) technique was carried out in order to characterize the change in valence state and composite characteristic by shifted peaks of binding energies. The photocatalytic activity was studied through the degradation of Rhodamine B in aqueous solution under visible light exposure. The highest photocatalytic efficiency of CeO{sub 2}/SiO{sub 2} composite was also obtained. To explain the high photocatalytic

Thermodynamic stability studies of Ce-Sb compounds with Fe

Science.gov (United States)

Xie, Yi; Zhang, Jinsuo; Benson, Michael T.; Mariani, Robert D.

2018-02-01

Lanthanide fission products can migrate to the fuel periphery and react with cladding, causing fuel-cladding chemical interaction (FCCI). Adding a fuel additive dopant, such as Sb, can bind lanthanide, such as Ce, into metallic compounds and thus prevent migration. The present study focuses on the thermodynamic stability of Ce-Sb compounds when in contact with the major cladding constituent Fe by conducting diffusion couple tests. Ce-Sb compounds have shown high thermodynamic stability as they did not react with Fe. When Fe-Sb compounds contacted with Ce, Sb was separated out of Fe-Sb compounds and formed the more stable Ce-Sb compounds.

Evidence for a second-order phase transition around 350 K in Ce3Rh4Sn13

Science.gov (United States)

Kuo, C. N.; Chen, W. T.; Tseng, C. W.; Hsu, C. J.; Huang, R. Y.; Chou, F. C.; Kuo, Y. K.; Lue, C. S.

2018-03-01

We report an observation of a phase transition in Ce3Rh4Sn13 with the transition temperature T*≃350 K by means of synchrotron x-ray powder diffraction, specific heat, electrical resistivity, Seebeck coefficient, thermal conductivity, as well as 119Sn nuclear magnetic resonance (NMR) measurements. The phase transition has been characterized by marked features near T* in all measured physical quantities. The lack of thermal hysteresis in the specific heat indicates a second-order phase transition in nature. From the NMR analysis, the change in the transferred hyperfine coupling constant for two tin sites has been resolved. The obtained result has been associated with the reduction in the averaged interatomic distance between Ce and Sn atoms, particularly for the Sn2 atoms. It indicates that the movement of the Sn2 atoms, which deforms the high-temperature structure, shortens the Ce-Sn2 bond length at low temperatures. We therefore provide a concise picture that the observed second-order phase transition at T* of Ce3Rh4Sn13 should be characterized by a structural modulation essentially due to lattice distortions arising from phonon instability.

Resistance to {gamma} irradiation of LaBr{sub 3}:Ce and LaCl{sub 3}:Ce single crystals

Energy Technology Data Exchange (ETDEWEB)

Normand, S. [CEA-Recherche Technologique, DETECS/SSTM CE Saclay F-91191 Gif Sur Yvette Cedex (France)]. E-mail: stephane.normand@cea.fr; Iltis, A. [Saint-Gobain Crystals, 104 Route de Larchant, 77140 St Pierre les Nemours (France); Bernard, F. [Saint-Gobain Crystals, 104 Route de Larchant, 77140 St Pierre les Nemours (France); Domenech, T. [CEA-Recherche Technologique, DETECS/SSTM CE Saclay F-91191 Gif Sur Yvette Cedex (France); Delacour, P. [CEA-Recherche Technologique, DETECS/SSTM CE Saclay F-91191 Gif Sur Yvette Cedex (France)

2007-03-11

LaBr{sub 3}:Ce (Brillance 380) and LaCl{sub 3}:Ce (Brillance 350) both exhibit a very good energy resolution and energy linearity response. They are also more sensitive to {gamma}-rays than NaI(Tl) detectors, due to their higher density. The aim of this work is to determine the behaviour of those new single crystals in comparison with NaI(Tl) under severe {gamma}-ray irradiation. Therefore we have irradiated three 25 by 25 mm cylinder crystals encapsulated in air-tight aluminium housing with {sup 60}Co beam. Crystals were tested as stand-alone material not to test the impact of radiation to our photomultiplier tube (PMT). Only encapsulated crystals (alone, without PMTs) were irradiated during several periods to achieve the final 3.4 kGy integrated dose. Intermediate measurements of {sup 137}Cs spectrum were done in order to evaluate the impact of the dose on the studied crystal performances. The radiation hardness of LaBr{sub 3}:Ce and LaCl{sub 3}:Ce was then compared to NaI(Tl). We show in this paper that up to 3.4 kGy no permanent modification of the energy resolution nor colour change is observed for LaBr{sub 3}:Ce and LaCl{sub 3}:Ce crystals. The light output also seems quite stable. This is in stark contrast with the behaviour of NaI:Tl which exhibits continuously decreasing light output, colour change and worsening of energy resolution for doses above 5 Gy.

In situ IR studies of Co and Ce doped Mn/TiO{sub 2} catalyst for low-temperature selective catalytic reduction of NO with NH{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Qiu, Lu; Pang, Dandan; Zhang, Changliang; Meng, Jiaojiao; Zhu, Rongshu; Ouyang, Feng, E-mail: ouyangfh@hit.edu.cn

2015-12-01

Highlights: • A SCR mechanistic pathway over Mn–Co–Ce/TiO{sub 2} is proposed. • The cobalt oxide produces lots of Brønsted acid sites, which favor to the adsorption of coordinated NH{sub 3} through NH{sub 3} migration. • Ce addition improves amide ions formation to reach best NO reduction selectivity. • At low-temperature coordinated NH{sub 3} reacts with NO{sub 2}{sup −}, or amide reacts with NO (ad) or NO (g) to form N{sub 2}. At high temperature, the reaction also occurs between coordinated NH{sub 3} and nitrate species. - Abstract: The Mn–Co–Ce/TiO{sub 2} catalyst was prepared by wet co-impregnation method for selective catalytic reduction of NO by NH{sub 3} in the presence of oxygen. The adsorption and co-adsorption of NH{sub 3}, NO and O{sub 2} on catalysts were investigated by in situ FTIR spectroscopy. The results suggested that addition of cobalt and cerium oxides increased the numbers of acid and redox sites. Especially, the cobalt oxide produced lots of Brønsted acid sites, which favor to the adsorption of coordinated NH{sub 3} through NH{sub 3} migration. Ce addition improved amide ions formation to reach best NO reduction selectivity. A mechanistic pathway over Mn–Co–Ce/TiO{sub 2} was proposed. At low-temperature SCR reaction, coordinated NH{sub 3} reacted with NO{sub 2}{sup −}, and amide reacted with NO (ad) or NO (g) to form N{sub 2}. NO{sub 2} was related to the formation of nitrite on Co-contained catalysts and the generation of −NH{sub 2}{sup −} on Ce-contained catalysts. At high temperature, the other branch reaction also occurred between the coordinated NH{sub 3} and nitrate species, resulting in N{sub 2}O yield increase.

Ni-CeO2 Cermets Synthesis by Solid State Sintering of Ni/CeO2 Multilayer

Directory of Open Access Journals (Sweden)

Aleksandras ILJINAS

2013-12-01

Full Text Available Nickel and gadolinium doped cerium oxide (GDC cermet is intensively investigated for an application as an anode material for solid oxide fuel cells based on various electrolytes. The purpose of the present investigation is to analyze morphology, microstructure, and optical properties of deposited and annealed for one hour in the temperatures from 500 ºC to 900 ºC Ni/CeO2 multilayer thin films deposited by sputtering. The crystallographic structure of thin films was investigated by X-ray diffraction. The morphology of the film cross-section was investigated with scanning electron microscope. The elemental analysis of samples was investigated by energy-dispersive X-ray spectroscopy. The fitting of the optical reflectance data was made using Abeles matrix method that is used for the design of interference coatings. The film cross-section of the post-annealed samples consisted of four layers. The first CeO2 layer (on Si had the same fine columnar structure with no features of Ni intermixing. The part of Ni (middle-layer after annealing was converted to NiO with grain size exceeding 100 nm. The CeO2 layer deposited on Ni was divided into two layers. Lower layer had small grains not exceeding 25 nm and consisting of NiO and CeO2 mixture. Upper layer consisted of CeO2 columns with approximate thickness of 50 nm. Ni sample annealed at 600 ºC was fully oxidized. The NiO thickness and refraction index were almost steady after annealing in various temperatures. The approximation of experimental reflectance data was successful only for the samples with one transparent homogeneous layer. The reflectance of the Ni/CeO2 samples annealed at intermediate temperatures could not be fitted using one-layer or three-layer model. That may show that a simplified model could not be implemented.  The real system has complicated distribution of refraction index. DOI: http://dx.doi.org/10.5755/j01.ms.19.4.3073

A pressure study of CePt{sub 3}B

Energy Technology Data Exchange (ETDEWEB)

Rauch, Daniela; Suellow, Stefan [Institute of Condensed Matter Physics, University of Technology Braunschweig, Braunschweig (Germany); Hartwig, Steffen [Institute of Condensed Matter Physics, University of Technology Braunschweig, Braunschweig (Germany); BENSC, Helmholtz Zentrum Berlin, Berlin (Germany); Hidaka, Hiroyuki; Yamazaki, Seigo; Amitsuka, Hiroshi [Department of Physics, Hokkaido University, Sapporo (Japan); Bauer, Ernst [Institute of Solid State Physics, Vienna University of Technology, Vienna (Austria)

2013-07-01

CePt{sub 3}B is isostructural to the non-centro symmetric heavy-fermion superconductor CePt{sub 3}Si. In contrast to the latter system, CePt{sub 3}B exhibits a complex magnetically ordered state at low temperatures, with an antiferromagnetic phase below T{sub N}=7.8 K and a weakly ferromagnetic transition below T{sub C}∼5 K. CePt{sub 3}B can be understand as a low pressure variant of CePt{sub 3}Si. Here we report a study of CePt{sub 3}B by means of high pressure magnetization measurements, this way in particular accessing the pressure evolution of the ferromagnetic transition temperature T{sub C}. From our investigation up to about 40 kbar we observe an almost constant transition temperature T{sub C} with pressure. This behavior we discuss in the context of alloying studies on this material.

Correlated electronic structure of CeN

Energy Technology Data Exchange (ETDEWEB)

Panda, S.K., E-mail: swarup.panda@physics.uu.se [Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala (Sweden); Di Marco, I. [Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala (Sweden); Delin, A. [Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala (Sweden); KTH Royal Institute of Technology, School of Information and Communication Technology, Department of Materials and Nano Physics, Electrum 229, SE-164 40 Kista (Sweden); KTH Royal Institute of Technology, Swedish e-Science Research Center (SeRC), SE-100 44 Stockholm (Sweden); Eriksson, O., E-mail: olle.eriksson@physics.uu.se [Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala (Sweden)

2016-04-15

Highlights: • The electronic structure of CeN is studied within the GGA+DMFT approach using SPTF and Hubbard I approximation. • 4f spectral functions from SPTF and Hubbard I are coupled to explain the various spectroscopic manifestations of CeN. • The calculated XPS and BIS spectra show good agreement with the corresponding experimental spectra. • The contribution of the various l-states and the importance of cross-sections for the photoemission process are analyzed. - Abstract: We have studied in detail the electronic structure of CeN including spin orbit coupling (SOC) and electron–electron interaction, within the dynamical mean-field theory combined with density-functional theory in generalized gradient approximation (GGA+DMFT). The effective impurity problem has been solved through the spin-polarized T-matrix fluctuation-exchange (SPTF) solver and the Hubbard I approximation (HIA). The calculated l-projected atomic partial densities of states and the converged potential were used to obtain the X-ray-photoemission-spectra (XPS) and Bremstrahlung Isochromat spectra (BIS). Following the spirit of Gunnarsson–Schonhammer model, we have coupled the SPTF and HIA 4f spectral functions to explain the various spectroscopic manifestations of CeN. Our computed spectra in such a coupled scheme explain the experimental data remarkably well, establishing the validity of our theoretical model in analyzing the electronic structure of CeN. The contribution of the various l-states in the total spectra and the importance of cross sections are also analyzed in detail.

Adsorption mechanism and kinetics of azo dye chemicals on oxide nanotubes: a case study using porous CeO_2 nanotubes

International Nuclear Information System (INIS)

Wu, Junshu; Wang, Jinshu; Du, Yucheng; Li, Hongyi; Jia, Xinjian

2016-01-01

Metal oxide nanotubes are believed to be promising materials with adsorption functionality for water purification due to their synergistic effect of the overall microscale morphology for easy separation and nanoscale surface characters providing enough surface active absorption sites. This work shows the synthesis of uniform hierarchical porous CeO_2 nanotubes via nanowire-directed templating method and describes the adsorption behavior of CeO_2 nanotubes for a typical azo dye Congo red which has resistance to oxidation and decoloration in natural conditions. Fourier transform infrared spectroscopy spectra provided the evidence that Congo red was successfully coated on the surface of CeO_2 nanotubes by both bidentate-type bridge link of Ce"4"+ cations from sulfonate SO_3"− groups and the electrostatic attraction between the protonated surface generated by oxygen vacancies and dissociated sulfonate groups. The adsorption kinetic data fitted well to the pseudo-second-order kinetic equation, whereas the Langmuir isotherm equation exhibited better correlation with the experimental data. The calculated maximum adsorption capacity from the isothermal model was 362.32 mg/g. In addition, the prepared CeO_2 nanotubes exhibited good recyclability and reusability as highly efficient adsorbents for Congo red removal after regeneration. These favorable performances enable the obtained CeO_2 nanotubes to be promising materials for dye removal from aqueous solution.Graphical AbstractCeO_2 nanotubes composed of crystallized nanoparticles exhibit well adsorption ability for a typical azo dye Congo red.

Luminescence and Tb3+-Ce3+-Eu3+ ion energy transfer in single-crystalline films of Tb3Al5O12:Ce,Eu garnet

International Nuclear Information System (INIS)

Zorenko, Y.; Gorbenko, V.; Voznyak, T.; Batentschuk, M.; Osvet, A.; Winnacker, A.

2008-01-01

The paper is devoted to investigation of the processes of excitation energy transfer between the host cations (Tb 3+ ions) and the activators (Ce 3+ and Eu 3+ ions) in single-crystalline films of Tb 3 Al 5 O 12 :Ce,Eu (TbAG:Ce,Eu) garnet which is considered as a promising luminescent material for the conversion of LED's radiation. The cascade process of excitation energy transfer is shown to be realized in TbAG:Ce,Eu: (i) from Tb 3+ ions to Ce 3+ and Eu 3+ ions; (ii) from Ce 3+ ions to Eu 3+ ions by means of dipole-dipole interaction and through Tb 3+ ion sublattice

Scintillation response of BaF2 and YAlO3:Ce (YAP:Ce) to energetic ions

International Nuclear Information System (INIS)

Slunga, E.; Cederwall, B.; Ideguchi, E.; Kerek, A.; Klamra, W.; Marel, J. van der; Novak, D.; Norlin, L.-O.

2001-01-01

The scintillation response of BaF 2 and YAP:Ce to protons, α particles, 16 O and 28 Si ions in the 5-30 MeV range has been investigated. The ratio between the fast and slow parts of the scintillator signal for BaF 2 has been used to separate protons, α particles and heavier ions, and the dependence of this ratio on the particle energy has been studied. The time constants and intensities of the two components of the YAP:Ce signal were measured, as were the time constant and intensity of the weak component of the slow part of the BaF 2 signal. Furthermore, the dependence of the light yield on the particle energy has been investigated for both BaF 2 and YAP:Ce

Determination of the differences in oxidation potentials for the Pr3+/Pr2+ and Ce3+/Ce2+ pairs in halide melts

International Nuclear Information System (INIS)

Mikheev, N.B.; Auerman, L.N.; Rumer, I.A.; D'yachkova, R.A.

1983-01-01

Cocrystallization has been used with the (PrOCl)/sub s. ph/ - (PrCl 2 , PrCl 3 , SrCl 2 ) melt system to examine the dependence of the cerium(III) cocrystallization coefficient on the X/sub Pr 2+ /X/sub Pr 3+ / ratio in the melt. Measurement has been made in this way of the difference in oxidation potentials for the pairs Pr 3+ /Pr 2+ and Ce 3+ /Ce 2+ : ΔE/sub Pr 3+ /Pr 2+0 -E/sub Ce 3+ /Ce 2+ / 0 , which is 0.08 +/- 0.04 V for chloride

Optical spectroscopy and luminescence quenching of LuI3:Ce3+

International Nuclear Information System (INIS)

Birowosuto, M.D.; Dorenbos, P.; Haas, J.T.M. de; Eijk, C.W.E. van; Kraemer, K.W.; Guedel, H.U.

2006-01-01

Optical spectroscopy of LuI 3 doped with Ce 3+ using ultraviolet and visible light excitation is reported. LuI 3 host excitation and emission and 4f-5d excitation and emission of Ce 3+ are observed. An empirical model based on crystal field splitting was used to estimate the energy of the highest 4f-5d excitation band. The crystal field splitting and centroid shift were compared to those of LuCl 3 :Ce 3+ and LuBr 3 :Ce 3+ . Temperature dependence of X-ray excited luminescence spectra shows thermal quenching, whereas that of the decay curve of Ce 3+ emission excited at the lowest 5d band of Ce 3+ does not indicate the presence of quenching of Ce 3+ emission for temperature below 625K. The quenching in LuI 3 :Ce 3+ therefore occurs before the 5d Ce 3+ emission takes place

Luminescence and scintillation properties of LuPO4-Ce nanoparticles

International Nuclear Information System (INIS)

Vistovskyy, V.; Malyy, T.; Pushak, A.; Vas’kiv, A.; Shapoval, A.; Mitina, N.; Gektin, A.; Zaichenko, A.; Voloshinovskii, A.

2014-01-01

Study of the spectral-luminescence parameters of LuPO 4 -Ce nanoparticles upon the excitation by X-ray quanta and synchrotron radiation with photon energies of 4–25 eV was performed. Nanoparticles with mean size about a=35 nm and nanoparticles with size less than 12 nm reveal the different structures of cerium centers. Luminescence efficiency of LuPO 4 -Ce nanoparticles of a 4 -Ce nanoparticles studied using synchrotron and X-ray excitation. • Different structure of Ce 3+ -centers has been revealed for LuPO 4 -Ce nanoparticles. • Luminescence of LuPO 4 -Ce with size less than 12 nm is strongly quenched upon the X-ray excitation

The highest spin discrete levels in 131,132Ce

International Nuclear Information System (INIS)

Paul, E S; Choy, P T W; Andreoiu, C; Boston, A J; Evans, A O; Fox, C; Gros, S; Nolan, P J; Rainovski, G; Sampson, J A; Scraggs, H C; Walker, A; Appelbe, D E; Joss, D T; Simpson, J; Gizon, J; Astier, A; Buforn, N; Prevost, A; Redon, N; Stezowski, O; Nyako, B M; Sohler, D; Timar, J; Zolnai, L; Bazzacco, D; Lunardi, S; Petrache, C M; Bednarczyk, P; Curien, D; Kintz, N; Ragnarsson, I

2006-01-01

The three superdeformed (SD) bands in 132 Ce and the two SD bands in 131 Ce have been extended to higher spin following experiments with the EUROBALL IV spectrometer. The two SD bands in 131 Ce have been linked together. However, despite the relatively high population intensity of the bands (up to 5% of the respective channel), it has not been possible to unambiguously link any of the five SD bands into the low-spin, normally deformed structures of 131,132 Ce

Using Ce to modify inclusion in spring steel

Directory of Open Access Journals (Sweden)

Wang Q.

2017-01-01

Full Text Available The effect of rare earth metals addition on the Al2O3 inclusions in spring steel used in fastener of high speed railway was investigated by metallographic examination, SEM-EDS and composition analysis. To deform those harmful inclusions to improve material performance，the evolution process of Al2O3 inclusions was investigated through the surface and line scanning. Ce metal modifying Al2O3 is a stepwise reduction process based on a formation of ring shape Ce-riched band around the Al2O3 inclusions during reaction process. Through experiment and thermodynamic calculation, an evolvement rule about Al2O3 inclusions change after Ce addition is obtained, i.e. Al2O3→Ce2O3-Al2O3→Ce2O2S. Changing the inclusions from Al2O3 to rare earth inclusions could improve the resistance to pitting corrosion based on potentiodynamic anodic polarization test.

Electronic and optical properties of layered RE{sub 2}Ti{sub 2}O{sub 7} (RE = Ce and Pr) from first principles

Energy Technology Data Exchange (ETDEWEB)

Sayede, A. [Universite Lille Nord de France, F-59000 Lille (France); Khenata, R. [Laboratoire de Physique Quantique et de Modlisation Mathmatique, Universite de Mascara, Mascara, 29000 (Algeria); Chahed, A.; Benhelal, O. [Condensed Matter and Sustainable Development Laboratory, Djillali Liabes University of Sidi Bel-Abbes, Sidi Bel-Abbes 22000 (Algeria)

2013-05-07

We have studied the structural and electronic properties of Ce{sub 2}Ti{sub 2}O{sub 7} (CeTO) and Pr{sub 2}Ti{sub 2}O{sub 7} (PrTO) by first-principles density functional theory calculations. The computed structural parameters are in fairly good agreement with the available experimental findings. Band structure calculations using the GGA+U approach predict an insulating ground state for the herein studied compounds. The insulating band gaps of 2.00 eV and 2.83 eV are found for CeTO and PrTO, respectively. The analysis of the density of states reveals that the strongly localized RE 4f levels act as charge-trapping sites, predicting a lower photocatalytic activity for CeTO. We have also calculated the optical properties for both CeTO and PrTO. Based on these properties, it is predicted that these titanates are insensitive to ultra-violet radiation, while they are more sensitive to frequencies of the radiation in visible and early UV regions.

Room temperature ferromagnetism in Fe-doped CeO2 nanoparticles.

Science.gov (United States)

Maensiri, Santi; Phokha, Sumalin; Laokul, Paveena; Seraphin, Supapan

2009-11-01

RT ferromagnetism was observed in nanoparticles of Fe-doped CeO2 (i.e., Ce(0.97)Fe(0.03)O2) synthesized by a sol-gel method. The undoped and Fe-doped CeO2 were characterized by XRD, Raman spectroscopy, TEM, and VSM. The undoped samples and Ce(0.97)Fe(0.03)O2 precursor exhibit a diamagnetic behavior. The 673 K-calcined Ce(0.97)Fe(0.03)O2 sample is paramagnetic whereas 773 and 873 K-calcined Ce(0.97)Fe(0.03)O2 samples are ferromagnetism having the magnetizations of 4.65 x 10(-3) emu/g and 6.20 x 10(-3) emu/g at 10 kOe, respectively. Our results indicate that the ferromagnetic property is intrinsic to the Fe-doped CeO2 system and is not a result of any secondary magnetic phase or cluster formation.

Synthesis and luminescence of CePO4 and CePO4:Tb hollow and core-shell microspheres composed of single-crystal nanorods

International Nuclear Information System (INIS)

Guan Mingyun; Sun Jianhua; Han Min; Xu Zheng; Tao Feifei; Yin Gui; Wei Xianwen; Zhu Jianmin; Jiang Xiqun

2007-01-01

Lanthanide phosphate microspheres composed of single-crystal CePO 4 and CePO 4 :Tb nanorods were successfully synthesized, respectively, using the functionalized composite aggregate as a template, which is composed of P123, H 6 P 4 O 13 and Ce 3+ , and also as a resource of reaction species with high chemical potential. The shape and the phase structure of the CePO 4 nanocrystal can be easily controlled via adjusting reaction temperature, monomer concentration and annealing temperature. SEM images show the spherical superstructure composed of nanorods. HRTEM and SAED images reveal the single-crystalline nature of nanorod and TEM images show the hollow interiors of the superstructure. XRD patterns indicate that the crystal structure of the nanorods is hexagonal before and monoclinic after annealing. The formation mechanism was proposed. Strong UV and green luminescence were observed for the CePO 4 and CePO 4 :Tb microspheres, respectively. The synthesis method can be extended to the fabrication of NRHS and core-shell microspheres of other rare-earth or doped LnPO 4 materials for wide applications

Electrochemical characterization of Pt-CeO{sub 2}/C and Pt-Ce{sub x}Zr{sub 1-x}O{sub 2}/C catalysts for ethanol electro-oxidation

Energy Technology Data Exchange (ETDEWEB)

Bai, Yuxia; Qiu, Xinping; Xi, Jingyu; Wang, Jianshe; Li, Jinfeng; Zhu, Wentao; Chen, Liquan [Key Laboratory of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084 (China); Wu, Jianjun [Key Laboratory of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084 (China); Department of Chemistry, Shijiazhuang College, Shijiazhuang 050801 (China)

2007-04-24

Pt-CeO{sub 2}/C and a series of Pt-Ce{sub x}Zr{sub 1-x}O{sub 2}/C catalyst powders with different Ce/Zr ratio were prepared and evaluated in terms of the electrochemical activity for ethanol electro-oxidation using cyclic voltammetry (CV), steady state polarization experiments and CO-stripping technique at room temperature. XRD results show that Ce{sub x}Zr{sub 1-x}O{sub 2} and Pt coexist in the Pt-Ce{sub x}Zr{sub 1-x}O{sub 2}/C catalyst and Ce{sub x}Zr{sub 1-x}O{sub 2} has no effect on the crystalline lattice of Pt. TEM results show that the Pt and Ce{sub x}Zr{sub 1-x}O{sub 2} particles dispersed uniformly over the surface of the carbon black. Cyclic voltammetry results show that the mass activity and specific activity of Pt-CeO{sub 2}/C for ethanol electro-oxidation is higher than that of Pt/C. The structure and Ce/Zr ratio of Pt-Ce{sub x}Zr{sub 1-x}O{sub 2}/C has effect on the catalytic activity of catalysts. CO-stripping voltammetry showed that the inclusion of CeO{sub 2} and Ce{sub x}Zr{sub 1-x}O{sub 2} favors the CO oxidation at lower potential. (author)

Tetragonal Ce-based Ce-Sm(Fe, Co, Ti){sub 12} alloys for permanent magnets

Energy Technology Data Exchange (ETDEWEB)

Martin-Cid, Andres; Salazar, Daniel [BCMaterials, Bizkaia Science and Tecnology Park, 48160 Derio (Spain); Gabay, Aleksandr M.; Hadjipanayis, George C. [Department of Physics and Astronomy, University of Delaware, Newark, DE, 19716 (United States); Barandiaran, Jose Manuel [BCMaterials, Bizkaia Science and Tecnology Park, 48160 Derio (Spain); Department of Electricity and Electronics, University Basque Country (UPV/EHU), 48080 Bilbao (Spain)

2016-12-15

Abundance and relatively low cost of Ce provide a great incentive for its use in rare-earth permanent magnets. It has been recently reported that the tetragonal Ce(Fe,Co,Ti)12 compounds may exhibit application-worthy intrinsic magnetic properties. In this work the effect of the α-Fe phase formation due to the evaporation of Sm during alloy fabrication has been studied, as a previous step in the attempt to convert the intrinsic magnetic properties into functional properties of a permanent magnet. Ce{sub 0.5}Sm{sub 0.5}Fe{sub 9}Co{sub 2}Ti alloys based on the ThMn12-type crystal structure have been synthesized via melt-spinning with different Sm content. Coercive fields between 2.8 and 1.4 kOe have been found for α-Fe phase contents between 8 and 46% in volume, showing the influence of the α-Fe phase on the coercivity and exchange coupling between the hard and soft phase. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Method for removing trace contaminants from multicurie amounts of 144Ce

International Nuclear Information System (INIS)

Wagner, J.A.; Kanapilly, G.M.

1976-01-01

Removal of contaminants from stock solutions of 144 Ce(III) was required for large quantities of 144 Ce prior to incorporation into fused aluminosilicate particles for inhalation toxicology studies. Since available procedures for purification of 144 Ce could not be readily adapted to our laboratory conditions and requirements, a simple procedure was developed to purify 144 Ce in multicurie quantities of 144 Ce(III). This procedure consists of separation of 144 Ce from contaminants by precipitation and filtrations at different pH. Its simplicity and efficacy in providing a stock solution that would readily exchange into montmorillonite clay was demonstrated when it was used during the preparation of large amounts of 144 Ce in fused aluminosilicate particles

ARC Cache: A solution for lightweight Grid sites in ATLAS

CERN Document Server

Garonne, Vincent; The ATLAS collaboration

2016-01-01

Many Grid sites have the need to reduce operational manpower, and running a storage element consumes a large amount of effort. In addition, setting up a new Grid site including a storage element involves a steep learning curve and large investment of time. For these reasons so-called storage-less sites are becoming more popular as a way to provide Grid computing resources with less operational overhead. ARC CE is a widely-used and mature Grid middleware which was designed from the start to be used on sites with no persistent storage element. Instead, it maintains a local self-managing cache of data which retains popular data for future jobs. As the cache is simply an area on a local posix shared filesystem with no external-facing service, it requires no extra maintenance. The cache can be scaled up as required by increasing the size of the filesystem or adding new filesystems. This paper describes how ARC CE and its cache are an ideal solution for lightweight Grid sites in the ATLAS experiment, and the integr...

The poisoning effect of PbO on Mn-Ce/TiO{sub 2} catalyst for selective catalytic reduction of NO with NH{sub 3} at low temperature

Energy Technology Data Exchange (ETDEWEB)

Zhou, Lingling [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China); Li, Caiting, E-mail: ctli@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China); Zhao, Lingkui; Zeng, Guangming; Gao, Lei; Wang, Yan; Yu, Ming’e [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China)

2016-12-15

Highlights: • The poisoning effects of PbO-doped Mn-Ce/TiO{sub 2} catalysts for low temperature NH{sub 3}-SCR were investigated. • Low concentration of Mn{sup 4+} and chemisorbed oxygen (O{sub b}) were not favorable for the generation of intermediates. • The decreased Ce{sup 3+} and less reducible of manganese oxides hindered the redox cycle (Mn{sup 3+} + Ce{sup 4+} ↔ Mn{sup 4+} + Ce{sup 3+}). • The doping of PbO not only altered acid sites but also inhibited ammonia adsorption as well as activation. • The poisoning of PbO resulted in the decrease of ad-NO{sub x} species (only a spot of bidentate nitrates remained). - Abstract: Lead oxide (PbO) as one of the typical heavy metals in flue gas from power plants has strong accumulation as well as poisoning effects on SCR catalysts. In this paper, a series of PbO-doped Mn-Ce/TiO{sub 2} catalysts were synthesized by impregnation method. The poisoning effects of PbO over Mn-Ce/TiO{sub 2} samples for selective catalytic reduction of NO by NH{sub 3} were investigated based on catalytic activity test and characterizations. The NO conversion of Mn-Ce/TiO{sub 2} was greatly decreased after the addition of PbO. It was obvious that the NO conversion efficiency of Mn-Ce/TiO{sub 2} catalyst declined from 96.75% to about 40% at 200 °C when Pb:Mn molar ratio reached 0.5. Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Hydrogen temperature programmed reduction (H{sub 2}-TPR), Ammonia temperature programmed desorption (NH{sub 3}-TPD) and Fourier transform infrared spectroscopy (FT-IR) were carried out to study the deactivation reasons of PbO poisoned catalysts. Manganese oxides’ crystallization, less reducible of manganese and cerium oxides, the decreasing of surface area, Mn{sup 4+} as well as Ce{sup 3+} concentration and chemisorbed oxygen (O{sub b}) after the introduction of PbO, all of these resulted in a poor SCR performance

Anodized porous titanium coated with Ni-CeO{sub 2} deposits for enhancing surface toughness and wear resistance

Energy Technology Data Exchange (ETDEWEB)

Zhou, Xiaowei, E-mail: zhouxiaowei901@163.com; Ouyang, Chun

2017-05-31

Highlights: • Structural design of anodized nanoporous Ti was introduced for bonding pinholes to achieve a metallurgical bonding interface. • Anodized porous Ti substrate was activated by electroless Ni-P film to be acted as transitional layer to deposit Ni-CeO{sub 2} nanocomposite coatings. • An analytical model was validated for predicting the Ce-rich worn products as a self-lubricant phase for monitoring wear mechanisms. - Abstract: In order to make large improvements of surface toughness and wear resistance for pure titanium (Ti) substrate, anodic titanium oxide (ATO) surface with nanoporous structure was coated with the Ni-CeO{sub 2} nanocomposite coatings. Regarding TiO{sub 2} barrier layer on Ti surface to inhibit its electrochemical activity, pre-treatments were successively processed with anodizing, sensitizing, activating, and then followed by electroless Ni-P film to be acted as an activated layer for electroplating Ni-CeO{sub 2} deposits. The existing Pd atoms around ATO nanopores were expected as the heterogeneous nucleation sites for supporting the growing locations of electroless Ni-P film. The innovative of interface design using porous structure was introduced for bonding pinholes to achieve a metallurgical adhesion interface between Ti substrate and surface coatings. Besides the objectives of this work were to elucidate how effects by the adding CeO{sub 2} nanoparticles on modifying microstructures and wear mechanisms of Ni-CeO{sub 2} nanocomposite coatings. Many efforts of XRD, FE-SEM, TEM and Nanoindentation tests were devoted to comparing different wear behaviors of Ni-CeO{sub 2} coatings relative to pure nickel. Results indicated that uniform-distributed Ti nanopores with an average diameter size of ∼200 nm was achieved using the Phosphate-type anodizing solution at DC 150 V. A worn surface without fatigue cracks was observed for TAO surface coated with Ni-CeO{sub 2} deposits, showing the existing Ce-rich worn products to be acted as a

Sonocatalytic degradation of diclofenac with FeCeOx particles in water.

Science.gov (United States)

Chong, Shan; Zhang, Guangming; Wei, Zhongheng; Zhang, Nan; Huang, Ting; Liu, Yucan

2017-01-01

This paper studies the sonocatalytic degradation of diclofenac in water using FeCeO x -catalyzed ultrasound. The effects of pre-adsorption and gas addition were investigated. Nitrogen adsorption/desorption, SEM, XRD, Raman and XPS analyses of FeCeO x before and after sonication were characterized. The proposed mechanism was based on the microstructure changes of FeCeO x and reactive-species-scavenging performances. The results show that FeCeO x has excellent performance in catalyzing an ultrasonic system in water, and 80% of diclofenac was removed in 30min ([Diclofenac]=20mg/L, FeCeO x amount=0.5g/L, pH=6, ultrasonic density=3.0W/cm 3 , ultrasonic frequency=20kHz, temperature=298K). The Fe, Ce, and O elements remained highly dispersed in the structure of FeCeO x , and the solid solution structure of FeCeO x remained stable after the reaction. Ce (III) was gradually oxidized to Ce (IV) and Fe (III) was gradually reduced to Fe (II) after the reaction, which indicates that Fe and Ce ions with different valences coexisted in dynamic equilibrium. The amount of oxygen vacancies in FeCeO x significantly decreased after the reaction, which indicates that oxygen vacancy participated in the ultrasonic process. Singlet oxygen 1 O 2 was the primary reactive species in the degradation process, and the hydroxyl radicals OH and superoxide radical anion O 2 - also participated in the reaction. FeCeO x had excellent chemical stability with negligible leaching ions in the ultrasonic process. Copyright © 2016 Elsevier B.V. All rights reserved.

The role of calcification for staging cystic echinococcosis (CE)

Energy Technology Data Exchange (ETDEWEB)

Hosch, Waldemar; Kauffmann, Guenter W. [University Hospital Heidelberg, Department of Radiology, Heidelberg (Germany); Stojkovic, Marija; Junghanss, Thomas [University Hospital of Heidelberg, Section of Clinical Tropical Medicine, Heidelberg (Germany); Jaenisch, Thomas [University Hospital of Heidelberg, Section of Clinical Tropical Medicine, Heidelberg (Germany); University Hospital of Heidelberg, Section of Biostatistics and Epidemiology, Heidelberg (Germany)

2007-10-15

The prevalence of calcified cysts and the significance of calcification as a sign of cyst inactivity in cystic echinococcosis (CE) was evaluated. Seventy-eight patients (36 females, 42 males, mean age 40.8 {+-} 16.9 years) with CE, having a total of 137 abdominal cysts (116 hepatic, three splenic, one renal and 17 peritoneal cysts), were diagnosed and followed-up by ultrasound during and after albendazole treatment or as part of the watch-and-wait approach recording changes in the cyst wall and content. In 48 patients with 94 cysts, computed tomography (CT) imaging was additionally available and was correlated with ultrasound findings. Cyst wall calcification was classified into (1) ''sprinkled'', (2) ''eggshell-like'', and (3) ''circular''. Calcification of the cyst wall and/or cyst content was detected in 67 echinococcal cysts (48.9% of all cysts) in 39 patients (15 females, 24 males, mean age 40.8 {+-} 14.8 years). Of the total of 67 calcified cysts, only 23 were compatible with WHO type CE5, 18 with WHO type CE4. Judged by cyst content, the remaining 26 were of WHO type CE1, CE2 and CE3 (n = 1, n = 8, and n = 17, respectively). During a mean period of 34.3 months ({+-}21.3 months) the majority of cysts (n = 32) did not exhibit any change in cyst content and wall properties. Fourteen cysts showed signs of progressive involution, five cysts (all of WHO type CE3) of renewed activity defined by recurring fluid collection. In 16 cysts, no follow-up was available due to surgery or drop out. Calcification of the cyst is not restricted to the inactive WHO cyst types CE4 and CE5, but occurs in all stages and in up to 50% of cysts. The completeness and, most importantly, the stability of consolidation of cyst content over time predicts cyst inactivity more reliably. (orig.)

Solid-solution stability and preferential site-occupancy in (R-R′)2Fe14B compounds

International Nuclear Information System (INIS)

Colin, C. V.; Dempsey, N. M.; Ito, M.; Yano, M.; Suard, E.; Givord, D.

2016-01-01

The rare-earth (R) uniaxial anisotropy of R 2 Fe 14 B compounds with magnetic R atoms (e.g., Nd or Pr) is at the origin of the exceptional hard magnetic properties achieved in magnets based on these compounds. The uniaxial anisotropy found in Ce 2 Fe 14 B is attributed mainly to the magnetism of Fe. Ce is the most abundant R element and there has been much recent effort to fabricate magnets in which Ce is partially substituted for Nd. In the present neutron study of (R 1−x Ce x ) 2 Fe 14 B (R = La or Nd), Ce is found to enter the R 2 Fe 14 B phase over the entire composition range. The crystallographic parameters decrease with increasing Ce content and the Ce atoms preferentially occupy the smaller 4f sites. It is concluded that Ce in these (RR′) 2 Fe 14 B compounds essentially maintains the intermediate valence character found in Ce 2 Fe 14 B. It is proposed that, in this intermediate valence state, Ce weakly contributes to uniaxial anisotropy, thus making a link with the fact that significant coercivity is preserved in Ce-substituted NdFeB magnets.

CE-MS fingerprinting of Laurencia complex algae (Rhodophyta).

Science.gov (United States)

Machín-Sánchez, María; Asensio-Ramos, María; Hernández-Borges, Javier; Gil-Rodríguez, María Candelaria

2014-03-01

The use of CE-ESI-MS has been considered as a new chemical strategy for the possible discernment of genera and species of the Laurencia complex. After the selection of the CE-MS and the extraction conditions, a total of 28 specimens of the complex, including different species of four genera (Laurencia, Laurenciella, Palisada, and Osmundea) collected from five intertidal locations on the Island of Tenerife (Canary Islands, Spain) were analyzed. CE-MS fingerprints revealed that CE-MS can be used as a useful tool for these studies in order to assess similarities and differences between them and that it constitutes an important starting point for further studies in the field. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Y/Gd-free yellow Lu{sub 3}Al{sub 5}O{sub 12}:Ce{sup 3+} phosphor for white LEDs

Energy Technology Data Exchange (ETDEWEB)

Park, Kwangwon [Department of Display Science and Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of); Kim, Taehoon; Yu, Youngmoon [LED-Marine Convergence Technology R& BD Center, Pukyong National University, Busan 608−739 (Korea, Republic of); Seo, Kwangil [L-Stone Co. Ltd., Bucheon 421−807 (Korea, Republic of); Kim, Jongsu, E-mail: jsukim@pknu.ac.kr [Department of Display Science and Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of)

2016-05-15

Solid solubility limit of Ce{sup 3+} ions into Lu-based garnet, Lu{sub 3(1−x)}Ce{sub 3x}Al{sub 5}O{sub 12}, was determined as below 6.7 mol% (3x<0.2 mol) through Raman spectra and X−ray diffraction patterns. Above the solid solubility limit (3x≥0.2 mol), Lu{sub 3(1−x)}Ce{sub 3x}Al{sub 5}O{sub 12} phosphors showed the significant redshift to the yellow spectral region without Y{sup 3+} and Gd{sup 3+} ions. The redshift was explained in terms of the local compressive strain at the Ce{sup 3+} sites. The optimized sample (3x=0.4 mol) had a dominant emission wavelength of 548 nm, color coordinate of CIEx=0.421, CIEy=0.548, quantum efficiency of 80%, absorbance of 91%, lumen maintenance of 90% and high color stability at 473 K under 450 nm excitation wavelength, suggesting substitutability for the commercial yellow (Y, Gd){sub 3}(Al, Ga){sub 5}O{sub 12}:Ce{sup 3+} phosphor. The measured decay times at higher Ce{sup 3+} concentration are significantly shortened at higher temperature than that of those at lower Ce{sup 3+} concentration. The yellow Lu{sub 2.6}Ce{sub 0.4}Al{sub 5}O{sub 12} and a commercial red (Sr, Ca)AlSiN{sub 3}:Eu{sup 2+} phosphor were applied to the pc-WLED, it gave an excellent luminous efficiency (138 lm/W) with a slightly lower color rendering index (Ra=76.4) under correlated color temperature of 6500 K compared to those of the (Y, Gd){sub 3}(Al, Ga){sub 5}O{sub 12}:Ce{sup 3+}-based one (136 lm/W, Ra=78.7). Especially, the quantities of the used phosphors were significantly decreased by 20% for the yellow LuAG:Ce and by 40% for the red (Sr, Ca)AlSiN{sub 3}:Eu{sup 2+}. Thus, the Y/Gd−free pure LuAG:Ce yellow phosphors can be used as alternative to the commercial yellow YAG:Ce phosphor.

Novel Ni-Ce-Zr/Al2O3 Cellular Structure for the Oxidative Dehydrogenation of Ethane

Directory of Open Access Journals (Sweden)

Juan Pablo Bortolozzi

2017-11-01

Full Text Available A novel γ-alumina-supported Ni-Ce-Zr catalyst with cellular structure was developed for oxidative dehydrogenation of ethane (ODHE. First, powdered samples were synthesized to study the effect of both the total metal content and the Ce/Zr ratio on the physicochemical properties and performance of these catalysts. All synthesized powdered samples were highly active and selective for ODHE with a maximum ethylene productivity of 6.94 µmolethylene gact cat−1 s−1. According to the results, cerium addition increased the most reducible nickel species population, which would benefit ethane conversion, whereas zirconium incorporation would enhance ethylene selectivity through the generation of higher amounts of the least reducible nickel species. Therefore, the modification of active site properties by addition of both promoters synergistically increases the productivity of the Ni-based catalysts. The most efficient formulation, in terms of ethylene productivity per active phase amount, contained 15 wt% of the mixed oxide with Ni0.85Ce0.075Zr0.075 composition. This formulation was selected to synthesize a Ni-Ce-Zr/Al2O3 structured body by deposition of the active phase onto a homemade γ-alumina monolith. The structured support was manufactured by extrusion of boehmite-containing dough. The main properties of the Ni0.85Ce0.075Zr0.075 powder were successfully preserved after the shaping procedure. In addition, the catalytic performance of the monolithic sample was comparable in terms of ethylene productivity to that of the powdered counterpart.

The equiatomic intermetallics REPtCd (RE = La, Ce, Pr, Nd, Eu) and magnetic properties of CeAuCd

Energy Technology Data Exchange (ETDEWEB)

Johnscher, Michael; Niehaus, Oliver; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Tappe, Frank [Hochschule Hamm-Lippstadt, Hamm (Germany)

2015-06-01

The cadmium intermetallics REPtCd (RE = La, Ce, Pr, Nd, Eu) and CeAuCd were synthesized by induction-melting of the elements in sealed niobium ampoules followed by annealing in muffle furnaces. The samples were characterized by powder X-ray diffraction. The structures of CePtCd (ZrNiAl type, P anti 62m, a = 763.8(6), c = 409.1(4) pm, wR2 = 0.0195, 298 F{sup 2} values, 14 variables) and EuPtCd (TiNiSi type, Pnma, a = 741.3(2), b = 436.4(1), c = 858.0(4) pm, wR2 = 0.0385, 440 F{sup 2} values, 20 variables) were refined from single-crystal data. The REPtCd structures exhibit three-dimensional networks of corner- and edge-sharing Cd rate at Pt{sub 2/6}Pt{sub 2/3} and Cd rate at Pt{sub 4/4} tetrahedra, which leave cages for the rare earth atoms. Temperature-dependent magnetic susceptibility data of CeAuCd reveal a paramagnetic to antiferromagnetic phase transition at T{sub N} = 3.7(5) K.

The equiatomic intermetallics REPtCd (RE = La, Ce, Pr, Nd, Eu) and magnetic properties of CeAuCd

International Nuclear Information System (INIS)

Johnscher, Michael; Niehaus, Oliver; Poettgen, Rainer

2015-01-01

The cadmium intermetallics REPtCd (RE = La, Ce, Pr, Nd, Eu) and CeAuCd were synthesized by induction-melting of the elements in sealed niobium ampoules followed by annealing in muffle furnaces. The samples were characterized by powder X-ray diffraction. The structures of CePtCd (ZrNiAl type, P anti 62m, a = 763.8(6), c = 409.1(4) pm, wR2 = 0.0195, 298 F 2 values, 14 variables) and EuPtCd (TiNiSi type, Pnma, a = 741.3(2), b = 436.4(1), c = 858.0(4) pm, wR2 = 0.0385, 440 F 2 values, 20 variables) were refined from single-crystal data. The REPtCd structures exhibit three-dimensional networks of corner- and edge-sharing Cd rate at Pt 2/6 Pt 2/3 and Cd rate at Pt 4/4 tetrahedra, which leave cages for the rare earth atoms. Temperature-dependent magnetic susceptibility data of CeAuCd reveal a paramagnetic to antiferromagnetic phase transition at T N = 3.7(5) K.

The Role of Neodymium in the Optimization of a Ni/CeO2 and Ni/CeZrO2 Methane Dry Reforming Catalyst

Directory of Open Access Journals (Sweden)

Alfonsina Pappacena

2018-04-01

Full Text Available The development of a sustainable economy based on the use of renewable resources and the reduction of greenhouse gases emissions is an important mandate in modern societies to minimize the global warming. The CO2-reforming of methane through a conversion of CO2 and CH4 to syngas is a suitable process for this purpose and there is growing interest in the development of new catalysts for this process’ application at an industrial scale. This study is the first to investigate methane dry reforming activity of nickel supported on CeO2 and CeO2–ZrO2 solid solutions doped with neodymium. The supports were synthesized using a surfactant-assisted co-precipitation method and characterized through several analytical techniques to understand the role of synthesis parameters in the distribution of the dopant as well as in the properties of the supports. Co-doping with Zr and Nd resulted in an enhancement of dry reforming activity of ceria due to a higher dispersion of Ni and changes in the strength of basic sites. It was also shown that the addition of Nd helped to mitigate coking issues by increasing the mobility of surface oxygen in ceria and ceria–zirconia oxides and, accordingly, the rate of oxidation of carbonaceous deposits.

CONFIRMATORY SURVEY RESULTS FOR PORTIONS OF THE ABB COMBUSTION ENGINEERING SITE IN WINDSOR, CONNECTICUT DURING THE FALL OF 2011

Energy Technology Data Exchange (ETDEWEB)

Wade C. Adams

2011-12-09

From the mid-1950s until mid-2000, the Combustion Engineering, Inc. (CE) site in Windsor, Connecticut (Figure A-1) was involved in the research, development, engineering, production, and servicing of nuclear fuels, systems, and services. The site is currently undergoing decommissioning that will lead to license termination and unrestricted release in accordance with the requirements of the License Termination Rule in 10 CFR Part 20, Subpart E. Asea Brown Boveri Incorporated (ABB) has been decommissioning the CE site since 2001.

Confirmatory Survey Results For Portions Of The ABB Combustion Engineering Site In Windsor, Connecticut During The Fall Of 2011

International Nuclear Information System (INIS)

Adams, Wade C.

2011-01-01

From the mid-1950s until mid-2000, the Combustion Engineering, Inc. (CE) site in Windsor, Connecticut (Figure A-1) was involved in the research, development, engineering, production, and servicing of nuclear fuels, systems, and services. The site is currently undergoing decommissioning that will lead to license termination and unrestricted release in accordance with the requirements of the License Termination Rule in 10 CFR Part 20, Subpart E. Asea Brown Boveri Incorporated (ABB) has been decommissioning the CE site since 2001.

Sr2CeO4: Electronic and structural properties

International Nuclear Information System (INIS)

Rocha, Leonardo A.; Schiavon, Marco A.; Nascimento, Clebio S.; Guimarães, Luciana; Góes, Márcio S.; Pires, Ana M.; Paiva-Santos, Carlos O.

2014-01-01

Highlights: • Sr 2 CeO 4 it was obtained from the heat treatment of Ce 3+ -doped strontium oxalate. • Rietveld analysis made it possible to obtain information about crystalline structure. • Experimental band gap value was compared with theoretical obtained by Sparkle/PM7. • The materials obtained shows intense photoluminescence and scintillator properties. - Abstract: This work presents on the preparation and photoluminescent properties of Sr 2 CeO 4 obtained from the heat treatment of Ce(III)-doped strontium oxalate (10, 25 and 33 mol%). The oxalate precursors were heat treated at 1100 °C for 12 h. The structure of this photoluminescent material was evaluated by the Rietveld method. The route used in this work to prepare the materials showed to be viable when compared to other synthesis reported in the literature. The Sr 2 CeO 4 material showed a broad and intense band emission with a maximum around 485 nm. The quantitative phase analysis showed that the Sr 2 CeO 4 photoluminescent phase is the majority one compared to the impurity phases of SrCeO 3 and SrCO 3 . From all results it was possible to verify a complete elimination of the CeO 2 phase for the sample obtained from the heat treatment of oxalate precursor containing 33 mol% of cerium(III). The material showed excellent properties for possible candidate as scintillator materials, and in the improvement of efficiency of solar cells when excited in the UV–vis region. The CIE chromaticity diagram it is also reported in this work

Preparation and characterization of Ce-doped HfO2 nanoparticles

International Nuclear Information System (INIS)

Gálvez-Barboza, S.; González, L.A.; Puente-Urbina, B.A.; Saucedo-Salazar, E.M.; García-Cerda, L.A.

2015-01-01

Highlights: • Ce-doped HfO 2 nanoparticles were prepared by a modified solgel method. • Ce-doped HfO 2 nanoparticles have a semispherical shape with sizes between 6 and 11.5 nm. • The samples doped with 10% in weight of Ce directly crystallized in a cubic structure. • A quick, straightforward and effective route for the preparation of Ce-doped nanoparticles. - Abstract: A modified solgel method to synthesize Ce-doped HfO 2 nanoparticles was carried out using a precursor material prepared with cerium nitrate, hafnium chloride, citric acid and ethylene glycol. The obtained precursor material was calcined at 500 and 700 °C for 2 h in air. The influence of the concentration of Ce and the calcination temperature was studied to observe the structural and morphological changes of the obtained materials. For the characterization, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman scattering (RS) were employed. The XRD patterns shown that the Ce-doped HfO 2 undergoes a structural transformation from monoclinic to cubic phase, which is significantly dependent on the Ce content and calcination temperature. TEM images have also confirmed the existence of semispherical nanoparticles with sizes between 6 and 11.5 nm

Physical, biochemical and genetic characterization of enterocin CE5-1 produced by Enterococcus faecium CE5-1 isolated from Thai indigenous chicken intestinal tract

OpenAIRE

Kraiyot Saelim; Sireewan Kaewsuwan; Akio Tani; Suppasil Maneerat

2015-01-01

Enterocin CE5-1 produced by Enterococcus faecium CE5-1 isolated from the chicken gastrointestinal tract was active in the wide range of pH 2-10 and temperature 30-100°C and sensitive to proteolytic enzymes and -amylase. It remained active after storage at -20°C for 2 months. Moreover, enterocin CE5-1 showed antibacterial activity against lactobacilli, bacilli, listeria, staphylococci and enterococci, especially antibiotic-resistant enterococci. In vitro study of enterocin CE5-1 decr...

The formation of intermetallic compounds during interdiffusion of Mg–Al/Mg–Ce diffusion couples

International Nuclear Information System (INIS)

Dai, Jiahong; Jiang, Bin; Li, Xin; Yang, Qingshan; Dong, Hanwu; Xia, Xiangsheng; Pan, Fusheng

2015-01-01

Graphical abstract: Al–Ce intermetallic compounds (IMCs) formed in Mg–Al/Mg–Ce diffusion couples. During the whole diffusion process, Al was the dominant diffusing species, and it substituted for Mg atoms of the Mg–Ce substrate. Five Al–Ce IMCs of Al 4 Ce, Al 11 Ce 3 , Al 3 Ce, Al 2 Ce, and AlCe were formed via the reaction of Al and Ce. - Highlights: • Al–Ce IMCs formation in the Mg–Al/Mg–Ce diffusion couples was studied. • Formation of Al 4 Ce as the first phase was rationalized using the Gibbs free energy. • The activation energy for the growth of the diffusion reaction zones was 36.6 kJ/mol. - Abstract: The formation of Al–Ce intermetallic compounds (IMCs) during interdiffusion of Mg–Al/Mg–Ce diffusion couples prepared by solid–liquid contact method was investigated at 623 K, 648 K and 673 K for 24 h, 48 h and 72 h, respectively. During the whole diffusion process, Al was the dominant diffusing species, and it substituted for Mg of the Mg–Ce substrate. Five Al–Ce IMCs of Al 4 Ce, Al 11 Ce 3 , Al 3 Ce, Al 2 Ce and AlCe were formed via the reaction of Al and Ce. The formation of Al 4 Ce as the first kind of IMC was rationalized on the basis of an effective Gibbs free energy model. The activation energy for the growth of the total diffusion reaction layer was 36.6 kJ/mol

Experimental investigation and thermodynamic calculation of the Zn–Fe–Ce system

Energy Technology Data Exchange (ETDEWEB)

Lu, Longfei; Wu, Changjun [Jiangsu Key Laboratory of Materials Surface Science and Technology, Changzhou University, Jiangsu 213164 (China); Jiangsu Collaborative Innovation Center of Photovolatic Science and Engineering, Changzhou University, Jiangsu 213164 (China); Wang, Jianhua, E-mail: wangjh@cczu.edu.cn [Jiangsu Key Laboratory of Materials Surface Science and Technology, Changzhou University, Jiangsu 213164 (China); Jiangsu Collaborative Innovation Center of Photovolatic Science and Engineering, Changzhou University, Jiangsu 213164 (China); Liu, Ya; Tu, Hao; Su, Xuping [Jiangsu Key Laboratory of Materials Surface Science and Technology, Changzhou University, Jiangsu 213164 (China); Jiangsu Collaborative Innovation Center of Photovolatic Science and Engineering, Changzhou University, Jiangsu 213164 (China)

2015-11-05

The 450 °C and 600 °C isothermal sections of the Zn–Fe–Ce system were investigated using equilibrated alloys and diffusion couples. The samples were analyzed by Scanning Electron Microscopy equipped with Energy Dispersive X-ray Spectrometer analysis and X-ray power diffraction. 15 and 13 three-phase regions were identified to exist at 450 °C and 600 °C, respectively. No ternary compound was found. Ce can not dissolve into all the Zn–Fe binary compounds and the solubilities of Fe in all the Zn–Ce binary phases were limited. All the Zn–Fe compounds can equilibrate with CeZn{sub 11} and all the Ce–Zn compounds (except CeZn) can equilibrate with α-Fe. Furthermore, thermodynamic extrapolation of the Zn–Fe–Ce system was carried out and showed good agreement well with detected phase relationships. - Highlights: • 450 °C and 600 °C sections of the Zn–Fe–Ce system were constructed. • No ternary compound exists. • Ce can not dissolve into all the Zn–Fe compounds. • All the Fe–Zn compounds can equilibrate with CeZn{sub 11}. • Thermodynamic extrapolation results agree with experimental data.

Mechanochemical and combustion synthesis of CeB{sub 6}

Energy Technology Data Exchange (ETDEWEB)

Akguen, Baris [Roketsan Missiles Inc., Ankara (Turkey); Sevinc, Naci; Topkaya, Yavuz [Middle East Technical Univ., Ankara (Turkey). Dept. of Metallurgical and Materials Engineerung; Camurlu, H. Erdem [Akdeniz Univ., Antalya (Turkey). Dept. of Mechanical Engineering

2013-04-15

CeB{sub 6} powder was prepared via combustion synthesis (CS) and mechanochemical processing (MCP) methods starting from CeO{sub 2}, B{sub 2}O{sub 3} and Mg powder mixtures. In CS, reactant mixtures were ignited in a preheated pot furnace under argon atmosphere. Products contained CeB{sub 6}, MgO and Mg{sub 3}B{sub 2}O{sub 6}, as revealed by X-ray diffraction analysis. After leaching in 1 M HCl for 15h, MgO was removed but Mg{sub 3}B{sub 2}O{sub 6} could not be removed from the products. Ball milling of products in ethanol prior to leaching made the removal of Mg{sub 3}B{sub 2}O{sub 6} possible by leaching. Yield of CeB{sub 6} was 68.6% in CS. MCP was performed in a stainless steel vial with a planetary ball mill at 300 rpm for 30h. MCP products contained CeB{sub 6}, MgO and small amount of Fe. Leaching in 1 M HCl for 30min was sufficient to remove MgO. Yield of CeB{sub 6} was 84.4% in MCP. According to scanning electron microscopy examinations, particles of CeB6 prepared by CS and MCP had submicrometer size. Average particle sizes were determined as 290nm and 240nm, respectively.

Solid-solution stability and preferential site-occupancy in (R-R')2Fe14B compounds

Science.gov (United States)

Colin, C. V.; Ito, M.; Yano, M.; Dempsey, N. M.; Suard, E.; Givord, D.

2016-06-01

The rare-earth (R) uniaxial anisotropy of R2Fe14B compounds with magnetic R atoms (e.g., Nd or Pr) is at the origin of the exceptional hard magnetic properties achieved in magnets based on these compounds. The uniaxial anisotropy found in Ce2Fe14B is attributed mainly to the magnetism of Fe. Ce is the most abundant R element and there has been much recent effort to fabricate magnets in which Ce is partially substituted for Nd. In the present neutron study of (R1-xCex)2Fe14B (R = La or Nd), Ce is found to enter the R2Fe14B phase over the entire composition range. The crystallographic parameters decrease with increasing Ce content and the Ce atoms preferentially occupy the smaller 4f sites. It is concluded that Ce in these (RR')2Fe14B compounds essentially maintains the intermediate valence character found in Ce2Fe14B. It is proposed that, in this intermediate valence state, Ce weakly contributes to uniaxial anisotropy, thus making a link with the fact that significant coercivity is preserved in Ce-substituted NdFeB magnets.

Adsorption process of fluoride from drinking water with magnetic core-shell Ce-Ti@Fe3O4 and Ce-Ti oxide nanoparticles.

Science.gov (United States)

Abo Markeb, Ahmad; Alonso, Amanda; Sánchez, Antoni; Font, Xavier

2017-11-15

Synthesized magnetic core-shell Ce-Ti@Fe 3 O 4 nanoparticles were tested, as an adsorbent, for fluoride removal and the adsorption studies were optimized. Adsorption capacity was compared with the synthesized Ce-Ti oxide nanoparticles. The adsorption equilibrium for the Ce-Ti@Fe 3 O 4 adsorbent was found to occur in cycles of adsorption-desorption. Although the nanoparticles suffer slight structure modifications after their reusability, they keep their adsorption capacity. Likewise, the efficiency of the Ce-Ti@Fe 3 O 4 was demonstrated when applied to real water to obtain a residual concentration of F - below the maximum contaminated level, 1.5mg/L (WHO, 2006). Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis, characterization and magnetic properties of NiFe{sub 2−x}Ce{sub x}O{sub 4} nanoribbons by electrospinning

Energy Technology Data Exchange (ETDEWEB)

Li, Jianan; Jing, Panpan; Zhang, Xinlei; Cao, Derang; Wei, Jinwu; Pan, Lining [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Liu, Zhenlin [Analysis and researching center of Gansu province, Lanzhou 730000 (China); Wang, Jianbo [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Key Laboratory for Special Function Materials and Structural Design of the Ministry of the Education, Lanzhou University, Lanzhou 730000 (China); Liu, Qingfang, E-mail: liuqf@lzu.edu.cn [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

2017-03-01

NiFe{sub 2−x}Ce{sub x}O{sub 4} (x = 0–0.03) nanoribbons have been successfully fabricated using electrospinning technique and followed by calcining in air at 500 °C. The crystalline, morphologies and compositions of NiFe{sub 2−x}Ce{sub x}O{sub 4} nanoribbons are characterized by X-ray diffraction, selected area electron diffraction, transmission electron microscope, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy (EDX). The results show that the components, mean crystallite sizes and morphologies change along with the content of Ce{sup 3+}. A formation mechanism of NiFe{sub 2-x}Ce{sub x}O{sub 4} nanoribbons is proposed. The magnetic hysteresis loops of NiFe{sub 2−x}Ce{sub x}O{sub 4} nanoribbons reveals that the coercivity changes from 165 Oe to 64 Oe and saturation magnetizations change from 40.97 emu/g to 25.05 emu/g at room temperature. Morevover, the Mössbauer spectra of {sup 57}Fe in NiFe{sub 2−x}Ce{sub x}O{sub 4} nanoribbons is discussed in detail. It is believed that this work will play important role in magnetic application with the advantage of excellent magnetic properties, efficient functionalization and relatively low cost. - Highlights: • The NiFe{sub 2−x}Ce{sub x}O{sub 4} nanoribbons have been fabricated using electrospinning technique. • Ce{sup 3+} ions occupy B sites by replacing Fe{sup 3+} ions. • The coercivity changes from 165 Oe to 64 Oe. • The saturation magnetizations change from 40.97 emu/g to 25.05 emu/g.

Methanol conversion to light olefins over nanostructured CeAPSO-34 catalyst: Thermodynamic analysis of overall reactions and effect of template type on catalytic properties and performance

Energy Technology Data Exchange (ETDEWEB)

Aghamohammadi, Sogand [Chemical Engineering Faculty, Sahand University of Technology, P.O. Box 51335-1996, Sahand New Town, Tabriz (Iran, Islamic Republic of); Reactor and Catalysis Research Center (RCRC), Sahand University of Technology, P.O. Box 51335-1996, Sahand New Town, Tabriz (Iran, Islamic Republic of); Haghighi, Mohammad, E-mail: haghighi@sut.ac.ir [Chemical Engineering Faculty, Sahand University of Technology, P.O. Box 51335-1996, Sahand New Town, Tabriz (Iran, Islamic Republic of); Reactor and Catalysis Research Center (RCRC), Sahand University of Technology, P.O. Box 51335-1996, Sahand New Town, Tabriz (Iran, Islamic Republic of); Charghand, Mojtaba [Chemical Engineering Faculty, Sahand University of Technology, P.O. Box 51335-1996, Sahand New Town, Tabriz (Iran, Islamic Republic of); Reactor and Catalysis Research Center (RCRC), Sahand University of Technology, P.O. Box 51335-1996, Sahand New Town, Tabriz (Iran, Islamic Republic of)

2014-02-01

Graphical abstract: In this research nanostructured CeAPSO-34 was synthesized to explore the effect of TEAOH and morpholine on its physiochemical properties and MTO performance. Prepared catalysts were characterized with XRD, FESEM, BET, FTIR and NH3-TPD techniques. The results indicated that the nature of the template determines the physiochemical properties of CeAPSO-34 due to different rate of crystal growth. The catalyst obtained by using morpholine showed longer life time as well as sustaining light olefins selectivity at higher values. Furthermore, a comprehensive thermodynamic analysis of overall reactions network was carried out to address the major channels of methanol to olefins conversion. - Highlights: • Introduction of Ce into SAPO-34 framework. • Comparison of CeAPSO-34 synthesized using morpholine and TEAOH. • The nature of the template determines the physiochemical properties of CeAPSO-34. • Morpholine enhances catalyst lifetime in MTO process. • Presenting a complete reaction network for MTO process. - Abstract: TEAOH and morpholine were employed in synthesis of nanostructured CeAPSO-34 molecular sieve and used in methanol to olefins conversion. Prepared samples were characterized by XRD, FESEM, EDX, BET, FTIR and NH{sub 3}-TPD techniques. XRD patterns reflected the higher crystallinity of the catalyst synthesized with morpholine. The FESEM results indicated that the nature of the template determines the morphology of nanostructured CeAPSO-34 due to different rate of crystal growth. There was a meaningful difference in the strength of both strong and weak acid sites for CeAPSO-34 catalysts synthesized with TEAOH and morpholine templates. The catalyst synthesized with morpholine showed higher desorption temperature of both weak and strong acid sites evidenced by NH{sub 3}-TPD characterization. The catalyst obtained using morpholine template had the longer lifetime and sustained desired light olefins at higher values. A comprehensive

Methanol conversion to light olefins over nanostructured CeAPSO-34 catalyst: Thermodynamic analysis of overall reactions and effect of template type on catalytic properties and performance

International Nuclear Information System (INIS)

Aghamohammadi, Sogand; Haghighi, Mohammad; Charghand, Mojtaba

2014-01-01

Graphical abstract: In this research nanostructured CeAPSO-34 was synthesized to explore the effect of TEAOH and morpholine on its physiochemical properties and MTO performance. Prepared catalysts were characterized with XRD, FESEM, BET, FTIR and NH3-TPD techniques. The results indicated that the nature of the template determines the physiochemical properties of CeAPSO-34 due to different rate of crystal growth. The catalyst obtained by using morpholine showed longer life time as well as sustaining light olefins selectivity at higher values. Furthermore, a comprehensive thermodynamic analysis of overall reactions network was carried out to address the major channels of methanol to olefins conversion. - Highlights: • Introduction of Ce into SAPO-34 framework. • Comparison of CeAPSO-34 synthesized using morpholine and TEAOH. • The nature of the template determines the physiochemical properties of CeAPSO-34. • Morpholine enhances catalyst lifetime in MTO process. • Presenting a complete reaction network for MTO process. - Abstract: TEAOH and morpholine were employed in synthesis of nanostructured CeAPSO-34 molecular sieve and used in methanol to olefins conversion. Prepared samples were characterized by XRD, FESEM, EDX, BET, FTIR and NH 3 -TPD techniques. XRD patterns reflected the higher crystallinity of the catalyst synthesized with morpholine. The FESEM results indicated that the nature of the template determines the morphology of nanostructured CeAPSO-34 due to different rate of crystal growth. There was a meaningful difference in the strength of both strong and weak acid sites for CeAPSO-34 catalysts synthesized with TEAOH and morpholine templates. The catalyst synthesized with morpholine showed higher desorption temperature of both weak and strong acid sites evidenced by NH 3 -TPD characterization. The catalyst obtained using morpholine template had the longer lifetime and sustained desired light olefins at higher values. A comprehensive thermodynamic

Photodynamic Processes in Fluoride Crystals Doped with Ce3+

Directory of Open Access Journals (Sweden)

Pavlov V.V.

2015-01-01

Full Text Available Integrated studies of photoelectric phenomena and their associated photodynamic processes in LiCaAlF6, LiLuF4, LiYF4, LiY0,5Lu0,5F4, SrAlF5 crystals doped with Ce3+ ions have been carried out using the combination of the methods of optical and dielectric spectroscopy. The numerical values of the basic parameters of photodynamic processes and their spectral dependence in 240 – 310 nm spectral range are evaluated. It has been shown that the most probable process, which leads to the photoionization of Ce3+ ions in LiYxLu1-xF4:Ce3+ (x=0; 0,5; 1 and LiCaAlF6:Ce3+ crystals, is excited-state absorption to the states of mixed configurations of Ce3+ ions localized near/in the conduction band of crystal.

Characterizations of electrodeposited Ni–CeO{sub 2} nanocomposite coatings

Energy Technology Data Exchange (ETDEWEB)

Kasturibai, S., E-mail: s.kasturibai@yahoo.co.in [Department of Chemistry, Alagappa Government Arts College, Karaikudi 630 003, Tamilnadu (India); Advanced Nanocomposite Coatings Laboratory, Department of Industrial Chemistry, School of Chemical Sciences, Alagappa University, Karaikudi 630 003, Tamilnadu (India); Kalaignan, G. Paruthimal, E-mail: pkalaignan@yahoo.com [Advanced Nanocomposite Coatings Laboratory, Department of Industrial Chemistry, School of Chemical Sciences, Alagappa University, Karaikudi 630 003, Tamilnadu (India)

2014-10-15

The expansion of current machinery requires metallic materials with better surface properties. In the present investigation, CeO{sub 2} reinforced nickel nanocomposite coatings were deposited on mild steel substrate by direct current electrodeposition process employing nickel acetate bath. The effect of incorporation of CeO{sub 2} particles in the Ni nanocomposite coatings on the micro hardness and corrosion behaviour has been evaluated. Smooth and compact nanocomposite deposits containing well-distributed cerium oxide particles were obtained. The crystallite structure was fcc for electrodeposited nickel and Ni–CeO{sub 2} nanocomposite coatings. It has been observed that, the presence of CeO{sub 2} nanoparticles favours the [111] and [200] texture of nickel matrix. The co-deposition of CeO{sub 2} nanoparticles with nickel was found to be favoured at applied current density of 8 A dm{sup −2}. The micro hardness values of the nickel nanocomposite coatings (725 HV) was higher than that of pure nickel (265 HV).The decrease in I{sub corr} values and increase in Constant Phase Element values were investigated in 3.5% NaCl solution which showed the higher corrosion resistant nature of Ni–CeO{sub 2} coatings. - Highlights: • Ni–CeO{sub 2} composite coatings have electrodeposited from eco-friendly acetate bath. • Inclusion of CeO{sub 2} in the composite coating has refined the crystallite size. • Micro hardness values have increased with CeO{sub 2} content in the composite coatings. • The negative shift of E{sub corr} confirming cathodic protective nature of coatings.

Hydrogen Production from Methanol Steam Reforming over TiO2 and CeO2 Pillared Clay Supported Au Catalysts

Directory of Open Access Journals (Sweden)

Rongbin Zhang

2018-01-01

Full Text Available Abstract: Methanol steam reforming is a promising process for the generation of hydrogen. In this study, Au catalysts supported on modified montmorillonite were prepared and their catalytic activity for methanol steam reforming was investigated at 250–500 °C. The physical and chemical properties of the as-prepared catalysts were characterized by Brunauer–Emmet–Teller method (BET, X-ray diffraction (XRD, transmission electron microscopic (TEM, scanning electron microscopy (SEM, X-ray photoelectron spectroscopy (XPS, Inductively Coupled Plasma (ICP, and thermogravimetrc analysis (TGA. For the catalysts examined, Au-Ti-Ce/Na-ABen exhibits the best catalytic performance with methanol conversion of 72% and H2 selectivity of 99% at 350 °C. This could be attributed to Au, Ce, and Ti species which form a solid solution and move into the interlayer space of the bentonite leading to a high surface area, large average pore volume, large average pore diameter, and small Au particle size. We considered that the synergistic effect of the crosslinking agent, the Ce species, and the Au active sites were responsible for the high activity of Au-Ti-Ce/Na-ABen catalyst for methanol steam reforming.

Information System through ANIS at CeSAM

Science.gov (United States)

Moreau, C.; Agneray, F.; Gimenez, S.

2015-09-01

ANIS (AstroNomical Information System) is a web generic tool developed at CeSAM to facilitate and standardize the implementation of astronomical data of various kinds through private and/or public dedicated Information Systems. The architecture of ANIS is composed of a database server which contains the project data, a web user interface template which provides high level services (search, extract and display imaging and spectroscopic data using a combination of criteria, an object list, a sql query module or a cone search interfaces), a framework composed of several packages, and a metadata database managed by a web administration entity. The process to implement a new ANIS instance at CeSAM is easy and fast : the scientific project has to submit data or a data secure access, the CeSAM team installs the new instance (web interface template and the metadata database), and the project administrator can configure the instance with the web ANIS-administration entity. Currently, the CeSAM offers through ANIS a web access to VO compliant Information Systems for different projects (HeDaM, HST-COSMOS, CFHTLS-ZPhots, ExoDAT,...).

Scintillation and optical stimulated luminescence of Ce-doped CaF2

International Nuclear Information System (INIS)

Yanagida, Takayuki; Fujimoto, Yutaka; Watanabe, Kenichi; Fukuda, Kentaro; Kawaguchi, Noriaki; Miyamoto, Yuka; Nanto, Hidehito

2014-01-01

Scintillation and optical stimulated luminescence of Ce 0.1–20% doped CaF 2 crystals prepared by Tokuyama Corp. were investigated. In X-ray induced scintillation spectra, luminescence due to Ce 3+ 5d–4f transition appeared around 320 nm with typically 40 ns decay time. By 241 Am 5.5 MeV α-ray irradiation, 0.1% doped one showed the highest scintillation light yield and the light yield monotonically decreased with Ce concentrations. Optically stimulated luminescence after X-ray irradiation was observed around 320 nm under 550 or 830 nm stimulation in all samples. As a result, intensities of optically stimulated luminescence were proportional to Ce concentrations. Consequently, scintillation and optically stimulated luminescence resulted to have a complementary relation in Ce-doped CaF 2 system. - Highlights: • Optical, scintillation, and OSL properties of Ce 0.1–20% doped CaF 2 were studied. • Scintillation light yield exhibited inverse proportionality to Ce concentrations. • OSL intensities showed proportionality to Ce concentrations. • Complementary relation of scintillation and OSL was experimentally confirmed

Raman spectroscopic studies on CeVO4 at high pressures

International Nuclear Information System (INIS)

Rao, Rekha; Garg, Alka B.; Wani, B.N.

2011-01-01

Raman scattering investigations of CeVO 4 at high pressures is reported. Polycrystalline CeVO 4 was prepared by solid state reaction of CeO 2 and V 2 O 5 . High pressure Raman spectroscopic measurements were carried out as per experimental details given

Activation of surface lattice oxygen in single-atom Pt/CeO ₂ for low-temperature CO oxidation

Energy Technology Data Exchange (ETDEWEB)

Nie, Lei; Mei, Donghai; Xiong, Haifeng; Peng, Bo; Ren, Zhibo; Pereira Hernandez, Xavier I.; DelaRiva, Andrew; Wang, Meng; Engelhard, Mark H.; Kovarik, Libor; Datye, Abhaya K.; Wang, Yong

2017-12-14

While single-atom catalysts can provide high catalytic activity and selectivity, application in industrial catalysts demands long term performance and the ability to regenerate the catalysts. We have investigated the factors that lead to improved catalytic activity of a Pt/CeO2 catalyst for low temperature CO oxidation. Single-atom Pt/CeO2 becomes active for CO oxidation under lean condition only at elevated temperatures, because CO is strongly bound to ionic Pt sites. Reducing the catalyst, even under mild conditions, leads to onset of CO oxidation activity even at room temperature. This high activity state involves the transformation of mononuclear Pt species to sub-nanometer sized Pt particles. Under oxidizing conditions, the Pt can be restored to its stable, single-atom state. The key to facile regeneration is the ability to create mobile Pt species and suitable trapping sites on the support, making this a prototypical catalyst system for industrial application of single-atom catalysis.

Anisotropic p-f mixing mechanism explaining anomalous magnetic properties in Ce monopnictides

International Nuclear Information System (INIS)

Takahashi, H.; Kasuya, T.

1985-01-01

An anomalously small crystal-field splitting in the paramagnetic region in CeSb and CeBi compared with those in CeP and CeAs is explained by the mixing mechanism between the occupied 4f states and the valence band holes. In the paramagnetic regions, the above p-f mixing gives the effective crystal-field splitting, which is estimated to nearly cancel the normal splittings extrapolated from CeP and CeAs in good agreement with experiment. The formula for the second-order transition temperature, at which the population ratio of the 4f GAMMA 8 states begins to be unbalanced, is also derived. In CeBi the second-order transition may occur, while in CeSb the first-order transition should occur in agreement with experiments. (author)

Performance evaluation of LaBr3: Ce scintillator

International Nuclear Information System (INIS)

Xie Ming; Lin Li; Liu Shihao; Xiao Peng; Xie Qingguo

2012-01-01

The cerium doped lanthanum bromide crystal (LaBr 3 : Ce) is a new kind of scintillator with many advantages such as good energy resolution, high light output, short decay time, good proportionality response. These properties make the LaBr 3 : Ce attractive substantial interest to use in the radiation detection. The energy resolution were investigated with Φ25 × 25 mm LaBr 3 : Ce coupled to a Hamamatsu R8900 photomultiplier tube. Energy resolution of 3.6% (FWHM) have been achieved for 511 keV photons ( 18 F source) at room temperature. Decay time constant of 20 ns have been acquired with a Hamamatsu fast-time-response R9800 photomultiplier tube. The results approve the excellent characterizations of LaBr 3 : Ce and imply its enormous potentiality in the radiation detectors of gamma-ray spectroscopy and PET. (authors)

Doping of Czochralski-grown bulk β-Ga2O3 single crystals with Cr, Ce and Al

Science.gov (United States)

Galazka, Zbigniew; Ganschow, Steffen; Fiedler, Andreas; Bertram, Rainer; Klimm, Detlef; Irmscher, Klaus; Schewski, Robert; Pietsch, Mike; Albrecht, Martin; Bickermann, Matthias

2018-03-01

We experimentally evaluated segregation of Cr, Ce and Al in bulk β-Ga2O3 single crystals grown by the Czochralski method, as well as the impact of these dopants on optical properties. The segregation of Cr and Ce and their incorporation into the β-Ga2O3 crystal structure strongly depends on O2 concentration in the growth atmosphere which has a noticeable impact on decomposition of Ga2O3 and Cr2O3, as well as on the charge state of Cr and Ce. Effective segregation coefficients for Cr are in the range of 3.1-1.5 at 7-24 vol% O2, while for Ce they are roughly below 0.01 at 1.5-34 vol% O2. The effective segregation coefficient for Al is 1.1 at 1.5-21 vol% O2. Both dopants Ce and Al have a thermodynamically stabilizing effect on β-Ga2O3 crystal growth by supressing decomposition. While Ce has no impact on the optical transmittance in the ultraviolet and visible regions, in Cr doped crystals we observe three absorption bands due to Cr3+ on octahedral Ga sites, one in the ultraviolet merging with the band edge absorption of β-Ga2O3 and two in the visible spectrum, for which we estimate the absorption cross sections. Al doping also does not induce dopant related absorption bands but clearly shifts the absorption edge as one expects for a solid-solution crystal Ga2(1-x)Al2xO3 still in the monoclinic phase. For the highest doping concentration (Ga1.9Al0.1O3) we estimate an increase of the energy gap by 0.11 eV.

Crystal structure and anisotropic magnetic properties of new ferromagnetic Kondo lattice compound Ce(Cu,Al,Si){sub 2}

Energy Technology Data Exchange (ETDEWEB)

Maurya, A.; Thamizhavel, A.; Dhar, S.K. [Department of Condensed Matter Physics & Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005 (India); Provino, A.; Pani, M.; Costa, G.A. [Department of Chemistry, University of Genova, Via Dodecaneso 31, 16146 Genova (Italy); Institute SPIN-CNR, Corso Perrone 24, 16152 Genova (Italy)

2017-03-15

Single crystals of the new compound CeCu{sub 0.18}Al{sub 0.24}Si{sub 1.58} have been grown by high-temperature solution growth method using a eutectic Al-Si mixture as flux. This compound is derived from the binary CeSi{sub 2} (tetragonal α-ThSi{sub 2}-type, Pearson symbol tI12, space group I4{sub 1}/amd) obtained by partial substitution of Si by Cu and Al atoms but showing full occupation of the Si crystal site (8e). While CeSi{sub 2} is a well-known valence-fluctuating paramagnetic compound, the CeCu{sub 0.18}Al{sub 0.24}Si{sub 1.58} phase orders ferromagnetically at T{sub C}=9.3 K. At low temperatures the easy-axis of magnetization is along the a-axis, which re-orients itself along the c-axis above 30 K. The presence of hysteresis in the magnetization curve, negative temperature coefficient of resistivity at high temperatures, reduced jump in the heat capacity and a relatively lower entropy released up to the ordering temperature, and enhanced Sommerfeld coefficient (≈100 mJ/mol K{sup 2}) show that CeCu{sub 0.18}Al{sub 0.24}Si{sub 1.58} is a Kondo lattice ferromagnetic, moderate heavy fermion compound. Analysis of the high temperature heat capacity data in the paramagnetic region lets us infer that the crystal electric field split doublet levels are located at 178 and 357 K, respectively, and Kondo temperature (8.4 K) is of the order of T{sub C} in CeCu{sub 0.18}Al{sub 0.24}Si{sub 1.58}.

Treatment on outliers in UBJ-SARIMA models for forecasting dengue cases on age groups not eligible for vaccination in Baguio City, Philippines

Science.gov (United States)

Magsakay, Clarenz B.; De Vera, Nora U.; Libatique, Criselda P.; Addawe, Rizavel C.; Addawe, Joel M.

2017-11-01

Dengue vaccination has become a breakthrough in the fight against dengue infection. This is however not applicable to all ages. Individuals from 0 to 8 years old and adults older than 45 years old remain susceptible to the vector-borne disease dengue. Forecasting future dengue cases accurately from susceptible age groups would aid in the efforts to prevent further increase in dengue infections. For the age groups of individuals not eligible for vaccination, the presence of outliers was observed and was treated using winsorization, square root, and logarithmic transformations to create a SARIMA model. The best model for the age group 0 to 8 years old was found to be ARIMA(13,1,0)(1,0,0)12 with 10 fixed variables using square root transformation with a 95% winsorization, and the best model for the age group older than 45 years old is ARIMA(7,1,0)(1,0,0)12 with 5 fixed variables using logarithmic transformation with 90% winsorization. These models are then used to forecast the monthly dengue cases for Baguio City for the age groups considered.

Adsorption mechanism and kinetics of azo dye chemicals on oxide nanotubes: a case study using porous CeO{sub 2} nanotubes

Energy Technology Data Exchange (ETDEWEB)

Wu, Junshu; Wang, Jinshu, E-mail: wangjsh@bjut.edu.cn; Du, Yucheng; Li, Hongyi; Jia, Xinjian [Beijing University of Technology, School of Materials Science and Engineering (China)

2016-07-15

Metal oxide nanotubes are believed to be promising materials with adsorption functionality for water purification due to their synergistic effect of the overall microscale morphology for easy separation and nanoscale surface characters providing enough surface active absorption sites. This work shows the synthesis of uniform hierarchical porous CeO{sub 2} nanotubes via nanowire-directed templating method and describes the adsorption behavior of CeO{sub 2} nanotubes for a typical azo dye Congo red which has resistance to oxidation and decoloration in natural conditions. Fourier transform infrared spectroscopy spectra provided the evidence that Congo red was successfully coated on the surface of CeO{sub 2} nanotubes by both bidentate-type bridge link of Ce{sup 4+} cations from sulfonate SO{sub 3}{sup −} groups and the electrostatic attraction between the protonated surface generated by oxygen vacancies and dissociated sulfonate groups. The adsorption kinetic data fitted well to the pseudo-second-order kinetic equation, whereas the Langmuir isotherm equation exhibited better correlation with the experimental data. The calculated maximum adsorption capacity from the isothermal model was 362.32 mg/g. In addition, the prepared CeO{sub 2} nanotubes exhibited good recyclability and reusability as highly efficient adsorbents for Congo red removal after regeneration. These favorable performances enable the obtained CeO{sub 2} nanotubes to be promising materials for dye removal from aqueous solution.Graphical AbstractCeO{sub 2} nanotubes composed of crystallized nanoparticles exhibit well adsorption ability for a typical azo dye Congo red.

VUV-UV–vis photoluminescence of Ce{sup 3+} and Ce{sup 3+}-Eu{sup 2+} energy transfer in Ba{sub 2}MgSi{sub 2}O{sub 7}

Energy Technology Data Exchange (ETDEWEB)

Yan, Jing; Liu, Chunmeng; Zhou, Weijie [MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, KLGHEI of Environment and Energy Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou 510275 (China); Huang, Yan; Tao, Ye [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039 (China); Liang, Hongbin, E-mail: cesbin@mail.sysu.edu.cn [MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, KLGHEI of Environment and Energy Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou 510275 (China)

2017-05-15

A series of Ce{sup 3+} doped and Ce{sup 3+}-Eu{sup 2+} co-doped Ba{sub 2}MgSi{sub 2}O{sub 7} phosphors was prepared via a high-temperature solid-state reaction technique. The photoluminescence properties, which include synchrotron radiation VUV-UV excitation spectra, emission spectra and concentration effect, thermal stability of Ce{sup 3+} are investigated. Hence the energies of the crystal field split 5d excited states of Ce{sup 3+} are determined. Due to spectral overlap, the energy transfer from sensitizer Ce{sup 3+} to activator Eu{sup 2+} in Ba{sub 2}MgSi{sub 2}O{sub 7}:Ce{sup 3+}, Eu{sup 2+} occurs, and the mechanism is demonstrated to be an electric dipole−dipole interaction. - Highlights: •The energies of five crystal field split 5d states of Ce{sup 3+} in Ba{sub 2}MgSi{sub 2}O{sub 7} were determined by synchrotron radiation VUV-UV excitation spectrum. •The concentration effect, thermal stability of Ce{sup 3+} were investigated. •The energy transfer from Ce{sup 3+} to Eu{sup 2+} and its influence on luminescence decays of Ce{sup 3+} and Eu{sup 2+} were studied.

Effect of Box-Cox transformation on power of Haseman-Elston and maximum-likelihood variance components tests to detect quantitative trait Loci.

Science.gov (United States)

Etzel, C J; Shete, S; Beasley, T M; Fernandez, J R; Allison, D B; Amos, C I

2003-01-01

Non-normality of the phenotypic distribution can affect power to detect quantitative trait loci in sib pair studies. Previously, we observed that Winsorizing the sib pair phenotypes increased the power of quantitative trait locus (QTL) detection for both Haseman-Elston (HE) least-squares tests [Hum Hered 2002;53:59-67] and maximum likelihood-based variance components (MLVC) analysis [Behav Genet (in press)]. Winsorizing the phenotypes led to a slight increase in type 1 error in H-E tests and a slight decrease in type I error for MLVC analysis. Herein, we considered transforming the sib pair phenotypes using the Box-Cox family of transformations. Data were simulated for normal and non-normal (skewed and kurtic) distributions. Phenotypic values were replaced by Box-Cox transformed values. Twenty thousand replications were performed for three H-E tests of linkage and the likelihood ratio test (LRT), the Wald test and other robust versions based on the MLVC method. We calculated the relative nominal inflation rate as the ratio of observed empirical type 1 error divided by the set alpha level (5, 1 and 0.1% alpha levels). MLVC tests applied to non-normal data had inflated type I errors (rate ratio greater than 1.0), which were controlled best by Box-Cox transformation and to a lesser degree by Winsorizing. For example, for non-transformed, skewed phenotypes (derived from a chi2 distribution with 2 degrees of freedom), the rates of empirical type 1 error with respect to set alpha level=0.01 were 0.80, 4.35 and 7.33 for the original H-E test, LRT and Wald test, respectively. For the same alpha level=0.01, these rates were 1.12, 3.095 and 4.088 after Winsorizing and 0.723, 1.195 and 1.905 after Box-Cox transformation. Winsorizing reduced inflated error rates for the leptokurtic distribution (derived from a Laplace distribution with mean 0 and variance 8). Further, power (adjusted for empirical type 1 error) at the 0.01 alpha level ranged from 4.7 to 17.3% across all tests

The γ rays sensitivity measurement of CeF3 scintillator detector

International Nuclear Information System (INIS)

Hu Mengchun; Zhou Dianzhong; Li Rurong; Wang Zhentong; Yang Hongqiong; Zhang Jianhua; Hu Qingyuan; Peng Taiping

2003-01-01

The CeF 3 is an abio-scintillator developed in recent years, which are insensitive to neutron and sensitive to gamma rays and respond quickness. The relationship of CeF 3 scintillation detector gamma rays sensitivity with the change of crystal thickness was measured. The CeF 3 scintillation detector is composed by high liner current photomultiplier tube of CHφT3, CHφT5 and CeF 3 scintillator. The detector gamma rays sensitivity of purple photocell and common photocell with CeF 3 scintillator were measured too

A permselective CeO{sub x} coating to improve the stability of oxygen evolution electrocatalysts

Energy Technology Data Exchange (ETDEWEB)

Obata, Keisuke; Takanabe, Kazuhiro [King Abdullah University of Science and Technology (KAUST), KAUST Catalysis Center (KCC) and Physical Sciences and Engineering Division PSE, Thuwal (Saudi Arabia)

2018-02-05

Highly active NiFeO{sub x} electrocatalysts for the oxygen evolution reaction (OER) suffer gradual deactivation with time owing to the loss of Fe species from the active sites into solution during catalysis. The anodic deposition of a CeO{sub x} layer prevents the loss of such Fe species from the OER catalysts, achieving a highly stable performance. The CeO{sub x} layer does not affect the OER activity of the catalyst underneath but exhibits unique permselectivity, allowing the permeation of OH{sup -} and O{sub 2} through while preventing the diffusion of redox ions through the layer to function as a selective O{sub 2}-evolving electrode. The use of such a permselective protective layer provides a new strategy for improving the durability of electrocatalysts. (copyright 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

2D NiFe/CeO2 Basic-Site-Enhanced Catalyst via in-Situ Topotactic Reduction for Selectively Catalyzing the H2 Generation from N2H4·H2O.

Science.gov (United States)

Wu, Dandan; Wen, Ming; Gu, Chen; Wu, Qingsheng

2017-05-17

An economical catalyst with excellent selectivity and high activity is eagerly desirable for H 2 generation from the decomposition of N 2 H 4 ·H 2 O. Here, a bifunctional two-dimensional NiFe/CeO 2 nanocatalyst with NiFe nanoparticles (∼5 nm) uniformly anchored on CeO 2 nanosheets supports has been successfully synthesized through a dynamic controlling coprecipitation process followed by in-situ topotactic reduction. Even without NaOH as catalyst promoter, as-designed Ni 0.6 Fe 0.4 /CeO 2 nanocatalyst can show high activity for selectively catalyzing H 2 generation (reaction rate (mol N2H4 mol -1 NiFe h -1 ): 5.73 h -1 ). As ceria is easily reducible from CeO 2 to CeO 2-x , the surface of CeO 2 could supply an extremely large amount of Ce 3+ , and the high-density electrons of Ce 3+ can work as Lewis base to facilitate the absorption of N 2 H 4 , which can weaken the N-H bond and promote NiFe active centers to break the N-H bond preferentially, resulting in the high catalytic selectivity (over 99%) and activity for the H 2 generation from N 2 H 4 ·H 2 O.

CE APPROVAL IN ELECTRICAL HOUSEHOLD APPLIANCES AND A CASE STUDY

Directory of Open Access Journals (Sweden)

Nazmi EKREN

2009-01-01

Full Text Available Due to the reason for rapidly developing technology, increasing competition medium, and awareness of the consumers, nowadays, the exigency of production with good quality has gained more and more significance. Certification of the quality and safety of the products to the consumers is compulsory in terms of producers. There are some documents to certify safety of the products. One of them is CE certificate. In this paper, basic information about CE mark is given and CE standards and tests required for electrical household appliances are mentioned. As an application, one of an electrical household appliance, toaster grill is treated and examined. To obtain CE certificate for toaster grill, required tests are made according to EN60335-2-9 and CE certificate is obtained.

Luminescence of Ce3+ doped LaPO4 nanophosphors upon Ce3+ 4f-5d and band-to-band excitation

International Nuclear Information System (INIS)

Stryganyuk, G.; Trots, D.M.; Voloshinovskii, A.; Shalapska, T.; Zakordonskiy, V.; Vistovskyy, V.; Pidzyrailo, M.; Zimmerer, G.

2008-01-01

Luminescence spectral-kinetic studies have been performed for pure and Ce-doped LaPO 4 micro- and nanosized phosphates using synchrotron radiation for the excitation within 5-20 eV energy range at T=8-300 K. Mechanisms for the excitation of Ce 3+ 5d-4f emission as well as the quenching processes are discussed. The influence of surface defects has been considered to modify considerably the luminescent properties of nanosized phosphors upon the excitation in the energy range of Ce 3+ 4f-5d transitions and LaPO 4 host absorption

HumanViCe: Host ceRNA network in virus infected cells in human

Directory of Open Access Journals (Sweden)

Suman eGhosal

2014-07-01

Full Text Available Host-virus interaction via host cellular components has been an important field of research in recent times. RNA interference mediated by short interfering RNAs and microRNAs (miRNA, is a widespread anti-viral defence strategy. Importantly, viruses also encode their own miRNAs. In recent times miRNAs were identified as key players in host-virus interaction. Furthermore, viruses were shown to exploit the host miRNA networks to suite their own need. The complex cross-talk between host and viral miRNAs and their cellular and viral targets forms the environment for viral pathogenesis. Apart from protein-coding mRNAs, non-coding RNAs may also be targeted by host or viral miRNAs in virus infected cells, and viruses can exploit the host miRNA mediated gene regulatory network via the competing endogenous RNA effect. A recent report showed that viral U-rich non-coding RNAs called HSUR, expressed in primate virus herpesvirus saimiri (HVS infected T cells, were able to bind to three host miRNAs, causing significant alteration in cellular level for one of the miRNAs. We have predicted protein coding and non protein-coding targets for viral and human miRNAs in virus infected cells. We identified viral miRNA targets within host non-coding RNA loci from AGO interacting regions in three different virus infected cells. Gene ontology (GO and pathway enrichment analysis of the genes comprising the ceRNA networks in the virus infected cells revealed enrichment of key cellular signalling pathways related to cell fate decisions and gene transcription, like Notch and Wnt signalling pathways, as well as pathways related to viral entry, replication and virulence. We identified a vast number of non-coding transcripts playing as potential ceRNAs to the immune response associated genes; e.g. APOBEC family genes, in some virus infected cells. All these information are compiled in HumanViCe, a comprehensive database that provides the potential ceRNA networks in virus

Pd/CeO2/SiC Chemical Sensors

Science.gov (United States)

Lu, Weijie; Collins, W. Eugene

2005-01-01

The incorporation of nanostructured interfacial layers of CeO2 has been proposed to enhance the performances of Pd/SiC Schottky diodes used to sense hydrogen and hydrocarbons at high temperatures. If successful, this development could prove beneficial in numerous applications in which there are requirements to sense hydrogen and hydrocarbons at high temperatures: examples include monitoring of exhaust gases from engines and detecting fires. Sensitivity and thermal stability are major considerations affecting the development of high-temperature chemical sensors. In the case of a metal/SiC Schottky diode for a number of metals, the SiC becomes more chemically active in the presence of the thin metal film on the SiC surface at high temperature. This increase in chemical reactivity causes changes in chemical composition and structure of the metal/SiC interface. The practical effect of the changes is to alter the electronic and other properties of the device in such a manner as to degrade its performance as a chemical sensor. To delay or prevent these changes, it is necessary to limit operation to a temperature sensor structures. The present proposal to incorporate interfacial CeO2 films is based partly on the observation that nanostructured materials in general have potentially useful electrical properties, including an ability to enhance the transfer of electrons. In particular, nanostructured CeO2, that is CeO2 with nanosized grains, has shown promise for incorporation into hightemperature electronic devices. Nanostructured CeO2 films can be formed on SiC and have been shown to exhibit high thermal stability on SiC, characterized by the ability to withstand temperatures somewhat greater than 700 C for limited times. The exchanges of oxygen between CeO2 and SiC prevent the formation of carbon and other chemical species that are unfavorable for operation of a SiC-based Schottky diode as a chemical sensor. Consequently, it is anticipated that in a Pd/CeO2/SiC Schottky

Study of the growth of CeO2 nanoparticles onto titanate nanotubes

Science.gov (United States)

Marques, Thalles M. F.; Ferreira, Odair P.; da Costa, Jose A. P.; Fujisawa, Kazunori; Terrones, Mauricio; Viana, Bartolomeu C.

2015-12-01

We report the study of the growth of CeO2 nanoparticles on the external walls and Ce4+ intercalation within the titanate nanotubes. The materials were fully characterized by multiple techniques, such as: Raman spectroscopy, infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The ion exchange processes in the titanate nanotubes were carried out using different concentrations of Ce4+ in aqueous solution. Our results indicate that the growth of CeO2 nanoparticles grown mediated by the hydrolysis in the colloidal species of Ce and the attachment onto the titanate nanotubes happened and get it strongly anchored to the titanate nanotube surface by a simple electrostatic interaction between the nanoparticles and titanate nanotubes, which can explain the small size and even distribution of nanoparticles on titanate supports. It was demonstrated that it is possible to control the amount and size of CeO2 nanoparticles onto the nanotube surface, the species of the Ce ions intercalated between the layers of titanate nanotubes, and the materials could be tuned for using in specific catalysis in according with the amount of CeO2 nanoparticles, their oxygen vacancies/defects and the types of Ce species (Ce4+ or Ce3+) present into the nanotubes.

Preparation and Oxidation Performance of Y and Ce-Modified Cr Coating on open-cell Ni-Cr-Fe Alloy Foam by the Pack Cementation

Science.gov (United States)

Pang, Q.; Hu, Z. L.; Wu, G. H.

2016-12-01

Metallic foams with a high fraction of porosity, low density and high-energy absorption capacity are a rapidly emerging class of novel ultralight weight materials for various engineering applications. In this study, Y-Cr and Ce-Cr-coated Ni-Cr-Fe alloy foams were prepared via the pack cementation method, and the effects of Y and Ce addition on the coating microstructure and oxidation performance were analyzed in order to improve the oxidation resistance of open-cell nickel-based alloy foams. The results show that the Ce-Cr coating is relatively more uniform and has a denser distribution on the surface of the nickel-based alloy foam. The surface grains of the Ce-Cr-coated alloy foam are finer compared to those of the Y-Cr-coated alloy foam. An obvious Ce peak appears on the interface between the coating and the alloy foam strut, which gives rise to a "site-blocking" effect for the short-circuit transport of the cation in the substrate. X-ray diffraction analysis shows that the Y-Cr-coated alloy foam mainly consists of Cr, (Fe, Ni) and (Ni, Cr) phases in the surface layer. The Ce-Cr-coated alloy foam is mainly composed of Cr and (Ni, Cr) phases. Furthermore, the addition of Y and Ce clearly lead to an improvement in the oxidation resistance of the coated alloy foams in the temperature range of 900-1000 °C. The addition of Ce is especially effective in enhancing the diffusion of chromium to the oxidation front, thus, accelerating the formation of a Cr2O3 layer.

Hybrid Density Functional Study of the Local Structures and Energy Levels of CaAl2O4:Ce3.

Science.gov (United States)

Lou, Bibo; Jing, Weiguo; Lou, Liren; Zhang, Yongfan; Yin, Min; Duan, Chang-Kui

2018-05-03

First-principles calculations were carried out for the electronic structures of Ce 3+ in calcium aluminate phosphors, CaAl 2 O 4 , and their effects on luminescence properties. Hybrid density functional approaches were used to overcome the well-known underestimation of band gaps of conventional density functional approaches and to calculate the energy levels of Ce 3+ ions more accurately. The obtained 4f-5d excitation and emission energies show good consistency with measured values. A detailed energy diagram of all three sites is obtained, which explains qualitatively all of the luminescent phenomena. With the results of energy levels calculated by combining the hybrid functional of Heyd, Scuseria, and Ernzerhof (HSE06) and the constraint occupancy approach, we are able to construct a configurational coordinate diagram to analyze the processes of capture of a hole or an electron and luminescence. This approach can be applied for systematic high-throughput calculations in predicting Ce 3+ activated luminescent materials with a moderate computing requirement.

Effect of poling process on piezoelectric properties of BCZT - 0.08 wt.% CeO{sub 2} lead-free ceramics

Energy Technology Data Exchange (ETDEWEB)

Chandrakala, E.; Praveen, J. Paul; Das, Dibakar, E-mail: ddse@uohyd.ernet.in [School of Engineering Sciences & Technology, University of Hyderabad, Hyderabad 500046 (India)

2016-05-06

The properties of lead free piezoelectric materials can be tuned by suitable doping in the A and B sites of the perovskite structure. In the present study, cerium has been identified as a dopant to investigate the piezoelectric properties of lead-free BCZT system. BCZT – 0.08 wt.%CeO{sub 2} lead-free ceramics have been synthesized using sol-gel technique and the effects of CeO{sub 2} dopant on their phase structure and piezoelectric properties were investigated systematically. Poling conditions, such as temperature, electric field, and poling time have been optimized to get enhanced piezoelectric response. The optimized poling conditions (50°C, 3Ec and 30min) resulted in high piezoelectric charge coefficient d{sub 33} ~ 670pC/N, high electromechanical coupling coefficient k{sub p} ~ 60% and piezoelectric voltage coefficient g{sub 33} ~ 14 mV.m/N for BCZT – 0.08wt.% CeO{sub 2} ceramics.

Luminescence from Ce in sol-gel SiO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Kroon, R.E., E-mail: KroonRE@ufs.ac.za [Department of Physics, University of the Free State, IB51, Box 339, Bloemfontein 9300 (South Africa); Seed Ahmed, H.A.A.; Ntwaeaborwa, O.M. [Department of Physics, University of the Free State, IB51, Box 339, Bloemfontein 9300 (South Africa); Koao, L.F. [Department of Physics, University of the Free State (Qwaqwa Campus), Private Bag X13, Phuthaditjhaba 9866 (South Africa); Nagpure, I.M.; Gusowski, M.A. [Department of Physics, University of the Free State, IB51, Box 339, Bloemfontein 9300 (South Africa); Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, Box 77000, Port Elizabeth 6031 (South Africa); Swart, H.C. [Department of Physics, University of the Free State, IB51, Box 339, Bloemfontein 9300 (South Africa)

2012-05-15

The sol-gel process provides an attractive low temperature alternative to the melt process for producing Ce-doped silica, but reports of the emission wavelength have not been consistent. In this paper, luminescence measurements using a variety of excitation methods, including cathodoluminescence not yet reported by other researchers, are compared and evaluated in the light of previously published data. Several papers report luminescence around 350 nm but emission near this wavelength was not found from our samples. This luminescence originates from Ce that has not yet been incorporated in the silica and is found in samples that have not undergone high temperature annealing. Our photoluminescence results from samples annealed in a reducing atmosphere suggest that emission from Ce incorporated in the silica lattice occurs near 455 nm, and some indication of the emission from Ce in amorphous clusters at 400 nm is also found. However, our results also confirm earlier indications that intrinsic defects in silica can create photoluminescence near both these wavelengths, which can make identification of the luminescence due to Ce difficult. Finally, it has been found that samples which have been annealed in air, and therefore display poor photoluminescence because most of the Ce occurs in the tetravalent form, are luminescent under electron beam excitation. It is suggested that during cathodoluminescence measurements Ce{sup 4+} ions capture electrons to form excited Ce{sup 3+} ions from which the luminescence originates.

Complex impedance study on nano-CeO2 coating TiO2

International Nuclear Information System (INIS)

Zhang Mei; Wang Honglian; Wang Xidong; Li Wenchao

2006-01-01

Titanium dioxide (TiO 2 ) nanoparticles and cerium dioxide (CeO 2 ) nanoparticles coated titanium dioxide (TiO 2 ) nanoparticles (CeO 2 -TiO 2 nanoparticles) have been successfully synthesized by sol-gel method. The complex impedance of the materials was investigated. The grain resistance, boundary resistance and activation energy of the nanoparticles were calculated according to Arrhenius equation. According to calculating results, the active capacity of pure TiO 2 nanoparticles has been improved because of nano-CeO 2 coating. An optimal CeO 2 content of 4.9 mol% was achieved. The high resolution electron microscopy images of CeO 2 -TiO 2 nanoparticles showed that TiO 2 nanoparticles, as a core, were covered by CeO 2 nanoparticles. The average size of CeO 2 coating TiO 2 nanoparticles was about 70 nm. Scanning electron microscopy observation indicted that CeO 2 nanoparticle coating improved the separation, insulation, and stability the CeO 2 -TiO 2 nanoparticles, which was benefit to the activity of materials

Ce doped NiO nanoparticles as selective NO2 gas sensor

Science.gov (United States)

Gawali, Swati R.; Patil, Vithoba L.; Deonikar, Virendrakumar G.; Patil, Santosh S.; Patil, Deepak R.; Patil, Pramod S.; Pant, Jayashree

2018-03-01

Metal oxide gas sensors are promising portable gas detection devices because of their advantages such as low cost, easy production and compact size. The performance of such sensors is strongly dependent on material properties such as morphology, structure and doping. In the present study, we report the effect of cerium (Ce) doping on nickel oxide (NiO) nano-structured thin film sensors towards various gases. Bare NiO and Ce doped NiO nanoparticles (Ce:NiO) were synthesized by sol-gel method. To understand the effect of Ce doping in nickel oxide, various molar percentages of Ce with respect to nickel were incorporated. The structure, phase, morphology and band-gap energy of as-synthesized nanoparticles were studied by XRD, SEM, EDAX and UV-vis spectroscopy. Thin film gas sensors of all the samples were prepared and subjected to various gases such as LPG, NH3, CH3COCH3 and NO2. A systematic and comparative study reveals an enhanced gas sensing performance of Ce:NiO sensors towards NO2 gas. The maximum sensitivity for NO2 gas is around 0.719% per ppm at moderate operating temperature of 150 °C for 0.5% Ce:NiO thin film gas sensor. The enhanced gas sensing performance for Ce:NiO is attributed to the distortion of crystal lattice caused by doping of Ce into NiO.

Down-conversion luminescence from (Ce, Yb) co-doped oxygen-rich silicon oxides

International Nuclear Information System (INIS)

Heng, C. L.; Wang, T.; Su, W. Y.; Wu, H. C.; Yin, P. G.; Finstad, T. G.

2016-01-01

We have studied down-conversion photoluminescence (PL) from (Ce, Yb) co-doped “oxygen rich” silicon oxide films prepared by sputtering and annealing. The Ce"3"+ ∼510 nm PL is sensitive to the Ce concentration of the films and is much stronger for 3 at. % Ce than for 2 at. % Ce after annealing at 1200 °C. The PL emission and excitation spectroscopy results indicate that the excitation of Yb"3"+ is mainly through an energy transfer from Ce"3"+ to Yb"3"+, oxide defects also play a role in the excitation of Yb"3"+ after lower temperature (∼800 °C) annealing. The Ce"3"+ 510 nm photon excites mostly only one Yb"3"+ 980 nm photon. Temperature-dependent PL measurements suggest that the energy transfer from Ce"3"+ to Yb"3"+ is partly thermally activated.

A comparative study of LaBr3(Ce(3+)) and CeBr3 based gamma-ray spectrometers for planetary remote sensing applications.

Science.gov (United States)

Kozyrev, A; Mitrofanov, I; Owens, A; Quarati, F; Benkhoff, J; Bakhtin, B; Fedosov, F; Golovin, D; Litvak, M; Malakhov, A; Mokrousov, M; Nuzhdin, I; Sanin, A; Tretyakov, V; Vostrukhin, A; Timoshenko, G; Shvetsov, V; Granja, C; Slavicek, T; Pospisil, S

2016-08-01

The recent availability of large volume cerium bromide crystals raises the possibility of substantially improving gamma-ray spectrometer limiting flux sensitivities over current systems based on the lanthanum tri-halides, e.g., lanthanum bromide and lanthanum chloride, especially for remote sensing, low-level counting applications or any type of measurement characterized by poor signal to noise ratios. The Russian Space Research Institute has developed and manufactured a highly sensitive gamma-ray spectrometer for remote sensing observations of the planet Mercury from the Mercury Polar Orbiter (MPO), which forms part of ESA's BepiColombo mission. The Flight Model (FM) gamma-ray spectrometer is based on a 3-in. single crystal of LaBr3(Ce(3+)) produced in a separate crystal development programme specifically for this mission. During the spectrometers development, manufacturing, and qualification phases, large crystals of CeBr3 became available in a subsequent phase of the same crystal development programme. Consequently, the Flight Spare Model (FSM) gamma-ray spectrometer was retrofitted with a 3-in. CeBr3 crystal and qualified for space. Except for the crystals, the two systems are essentially identical. In this paper, we report on a comparative assessment of the two systems, in terms of their respective spectral properties, as well as their suitability for use in planetary mission with respect to radiation tolerance and their propensity for activation. We also contrast their performance with a Ge detector representative of that flown on MESSENGER and show that: (a) both LaBr3(Ce(3+)) and CeBr3 provide superior detection systems over HPGe in the context of minimally resourced spacecraft and (b) CeBr3 is a more attractive system than LaBr3(Ce(3+)) in terms of sensitivities at lower gamma fluxes. Based on the tests, the FM has now been replaced by the FSM on the BepiColombo spacecraft. Thus, CeBr3 now forms the central gamma-ray detection element on the MPO spacecraft.

Synergy of CuO and CeO2 combination for mercury oxidation under low-temperature selective catalytic reduction atmosphere

KAUST Repository

Li, Hailong

2016-07-19

Synergy for low temperature Hg0 oxidation under selective catalytic reduction (SCR) atmosphere was achieved when copper oxides and cerium oxides were combined in a CuO-CeO2/TiO2 (CuCeTi) catalyst. Hg0 oxidation efficiency as high as 99.0% was observed on the CuCeTi catalyst at 200 °C, even the gas hourly space velocity was extremely high. To analyze the synergistic effect, comparisons of catalyst performance in the presence of different SCR reaction gases were systematically conducted over CuO/TiO2 (CuTi), CeO2/TiO2 (CeTi) and CuCeTi catalysts prepared by sol-gel method. The interactions between copper oxides and cerium oxides in CuCeTi catalyst yielded more surface chemisorbed oxygen, and facilitated the conversion of gas-phase O2 to surface oxygen, which are favorable for Hg0 oxidation. Copper oxides in the combination interacted with NO forming more chemisorbed oxygen for Hg0 oxidation in the absence of gas-phase O2. Cerium oxides in the combination promoted Hg0 oxidation through enhancing the transformations of NO to NO2. In the absence of NO, NH3 exhibited no inhibitive effect on Hg0 oxidation, because enough Lewis acid sites due to the combination of copper oxides and cerium oxides scavenged the competitive adsorption between NH3 and Hg0. In the presence of NO, although NH3 lowered Hg0 oxidation rate through inducing reduction of oxidized mercury, complete recovery of Hg0 oxidation activity over the CuCeTi catalyst was quickly achieved after cutting off NH3. This study revealed the synergistic effect of the combination of copper oxides and cerium oxides on Hg0 oxidation, and explored the involved mechanisms. Such knowledge would help obtaining maximum Hg0 oxidation co-benefit from SCR units in coal-fired power plants.

LiCaAlF sub 6 :Ce crystal: a new scintillator

CERN Document Server

Gektin, A V; Neicheva, S; Gavrilyuk, V; Bensalah, A; Fukuda, T; Shimamura, K

2002-01-01

Scintillation properties of LiCaAlF sub 6 :Ce crystal, well known as the effective UV laser material, is reported. Ce sup 3 sup + emission at 286-305 nm with a single exponential decay time of 35 ns provides a scintillation pulse. Radiation damage in pure and Ce-doped crystals is studied. In contrast to the majority of fluoride crystals, cerium is responsible for the ultradeep traps formation revealing thermostimulated luminescence. Overlapping of color center absorption and Ce sup 3 sup + ion emission bands limits the scintillation efficiency of LiCaAlF sub 6 :Ce at high radiation doses.

Interfacing HTCondor-CE with OpenStack

Science.gov (United States)

Bockelman, B.; Caballero Bejar, J.; Hover, J.

2017-10-01

Over the past few years, Grid Computing technologies have reached a high level of maturity. One key aspect of this success has been the development and adoption of newer Compute Elements to interface the external Grid users with local batch systems. These new Compute Elements allow for better handling of jobs requirements and a more precise management of diverse local resources. However, despite this level of maturity, the Grid Computing world is lacking diversity in local execution platforms. As Grid Computing technologies have historically been driven by the needs of the High Energy Physics community, most resource providers run the platform (operating system version and architecture) that best suits the needs of their particular users. In parallel, the development of virtualization and cloud technologies has accelerated recently, making available a variety of solutions, both commercial and academic, proprietary and open source. Virtualization facilitates performing computational tasks on platforms not available at most computing sites. This work attempts to join the technologies, allowing users to interact with computing sites through one of the standard Computing Elements, HTCondor-CE, but running their jobs within VMs on a local cloud platform, OpenStack, when needed. The system will re-route, in a transparent way, end user jobs into dynamically-launched VM worker nodes when they have requirements that cannot be satisfied by the static local batch system nodes. Also, once the automated mechanisms are in place, it becomes straightforward to allow an end user to invoke a custom Virtual Machine at the site. This will allow cloud resources to be used without requiring the user to establish a separate account. Both scenarios are described in this work.

Facile hydrothermal synthesis of CeO2 nanopebbles

Indian Academy of Sciences (India)

Administrator

However, to the best of our knowledge the reports on the synthesis of CeO2 ... The base pressure of the XAS chamber was in the range of 10–8 Pa. A Shimadzu ... scopy was investigated to confirm the crystalline quality of CeO2 nanopebbles.

Study of structural and transport properties of nanostructured CeO{sub 2}, Ce{sub 1-x}Ru{sub x}O{sub 2} and Ce{sub 1-x}In{sub x}O{sub 2} thin films

Energy Technology Data Exchange (ETDEWEB)

Rangel, R.; Chavez-Chavez, L. [Division de Estudios de Posgrado, Facultad de Ingenieria Quimica, Universidad Michoacana de S.N.H. (Mexico); Martinez, E. [Centro de Investigacion en Materiales Avanzados, S.C. (CIMAV), Nuevo Leon (Mexico); Bartolo-Perez, P. [Departamento de Fisica Aplicada, CINVESTAV-IPN, Merida, Yucatan (Mexico)

2012-06-15

The present work reports for the first time thin films prepared from Ce{sub 1-x}M{sub x}O{sub 2-{delta}} (M = Ru, In) solid solutions for application as gas sensors. The CeO{sub 2}, Ce{sub 0.95}Ru{sub 0.05}O{sub 2} and Ce{sub 0.95}In{sub 0.05}O{sub 2} thin films were prepared by means of the RF sputtering process onto Si (111) substrates. The deposition conditions were carried out at 500 C varying the deposition time. Targets were prepared via sol-gel process starting from C{sub 6}H{sub 9}O{sub 6}In, Ru{sub 3}(CO){sub 12} and Ce(C{sub 2}H{sub 3}O{sub 2}){sub 3} . 1.5H{sub 2}O compounds and using a ceramic method to consolidate them. The samples were characterized by means of XRD, SEM, and AFM. Their thickness was measured using a profilometer. The results herein obtained regarding the microstructure and transport properties indicate that these materials can be used as gas sensors. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Ultraviolet and near-infrared luminescence of LaBO3:Ce3+,Yb3+

Science.gov (United States)

Wei, Heng-Wei; Shao, Li-Ming; Jiao, Huan; Jing, Xi-Ping

2018-01-01

Ce3+ or Yb3+ singly doped LaBO3 and Ce3+-Yb3+ co-doped LaBO3 were prepared by conventional solid state reactions at 1100 °C and their photoluminescence (PL) properties were investigated. The emission spectrum of LaBO3:Ce3+,Yb3+ contains both the Ce3+ ultraviolet (UV) emissions (355 nm and 380 nm) and the Yb3+ near infrared (NIR) emission (975 nm) when excited by the UV light at 270 nm. By using the data of the Ce3+ decay curves and the PL intensities of both Ce3+ and Yb3+, the energy transfer efficiency (η) from Ce3+ to Yb3+, the actual energy transfer efficiency (AE) and the quantum efficiency (Q) of the Yb3+ emission were calculated. In the Ce3+-Yb3+ co-doped LaBO3, Ce3+ can transfer its absorbed energy to Yb3+ efficiently (η can be over 60%), and Yb3+ shows the Q value over 50% when it accepts the energy from Ce3+, which results in the low AE value ∼30%. The energy transfer process from Ce3+ to Yb3+ may be understood by the charge transfer mechanism: Ce3+ + Yb3+ ↔ Ce4+ + Yb2+. Particularly the Ce3+-Yb3+ co-doped LaBO3 phosphor gives the emissions mainly in the UV range and the NIR range with a portion of visible emissions in eye-insensitive range. This unique property may be suitable for applications in anti-counterfeiting techniques and public security affairs.

Implementace OpenVPN na platformě Windows CE

OpenAIRE

Ešner, Oldřich

2008-01-01

Motivací pro vznik této diplomové práce, která navazuje na stejnojmenný semestrální projekt, byl převod aplikace pro tvorbu virtuálních privátních sítí OpenVPN z operačního systému Windows XP na platformu Windows CE Embedded 6.0. Práce pojednává obecně o virtuálních privátních sítích, a podrobněji o jedné z jejich implementací - OpenVPN. Uvádí základní vlastnosti operačního systému Windows CE, dále popisuje princip ovladačů zařízení v operačních systémech na bázi Windows NT, používaný Windows...

Investigating the capability of ToF-SIMS to determine the oxidation state of Ce

Science.gov (United States)

Seed Ahmed, H. A. A.; Swart, H. C.; Kroon, R. E.

2018-04-01

The capability of time of flight secondary ion mass spectrometry (ToF-SIMS) to determine the oxidation state of Ce ions doped in a phosphor was investigated. Two samples of SiO2:Ce (4 mol%) with known Ce3+/Ce4+ relative concentrations were subjected to ToF-SIMS measurements. The spectra were very similar and no significant differences in the relative peak intensities were observed that would readily allow one to distinguish Ce3+ from Ce4+. Although ToF-SIMS was therefore not useful to distinguish the charge state of Ce ions doped in this phosphor material, the idea in principle was also tested on two other samples, namely CeF3 and CeF4 These contain Ce as part of the host (i.e. much higher concentration) and are fluorides, which is significant because ToF-SIMS has previously been reported to be able to distinguish Eu2+ from Eu3+ in Eu doped Sr5(PO4)3F phosphor. The spectrum of CeF4 contained a small peak related to Ce4+ which was not observed in the CeF3 spectrum, yet the peak related to the Ce3+ ions was found to be much more intense in the spectrum of CeF4 than CeF3, showing that the ToF-SIMS signals cannot be directly interpreted as retaining the charge state of the ions in the original material. Nevertheless, the significant differences in the Ce-related peaks in the ToF-SIMS spectra from CeF3 and CeF4 show that the charge state of Ce may be distinguished. This study shows that while in principle ToF-SIMS may be used to distinguish the charge state of Ce ions, this depends on the sample and it would not be easy to interpret the spectra without a standard or reference.

A novel gamma-ray detector with submillimeter resolutions using a monolithic MPPC array with pixelized Ce:LYSO and Ce:GGAG crystals

Energy Technology Data Exchange (ETDEWEB)

Kato, T., E-mail: katou.frme.8180@asagi.waseda.jp [Research Institute for Science and Engineering, Waseda University, 3-4-1, Ohkubo, Shinjuku, Tokyo (Japan); Kataoka, J.; Nakamori, T.; Miura, T.; Matsuda, H.; Kishimoto, A. [Research Institute for Science and Engineering, Waseda University, 3-4-1, Ohkubo, Shinjuku, Tokyo (Japan); Sato, K.; Ishikawa, Y.; Yamamura, K.; Nakamura, S.; Kawabata, N. [Solid State Division, Hamamatsu Photonics K. K., 1126-1, Ichino-cho, Hamamatsu, Shizuoka (Japan); Ikeda, H. [ISAS/JAXA, 3-1-1, Yoshinodai, Chuo-ku, Sagamihara-shi, Kanagawa (Japan); Yamamoto, S. [Kobe City College of Technology, 8-3, Gakuenhigashimati, Nishi-ku, Kobe-shi, Hyougo 651-2194 (Japan); Kamada, K. [Materials Research Laboratory, Furukawa Co., Ltd., 1-25-13, Kannondai, Tsukuba, Ibaraki 305-0856 (Japan)

2013-01-21

We have developed a large-area monolithic Multi-Pixel Photon Counter (MPPC) array consisting of 4×4 channels with a three-side buttable package. Each channel has a photosensitive area of 3×3 mm{sup 2} and 3600 Geiger mode avalanche photodiodes (APDs). For typical operational gain of 7.5×10{sup 5} at +20 °C, gain fluctuation over the entire MPPC device is only ±5.6%, and dark count rates (as measured at the 1 p.e. level) amount to ≤400kcps per channel. We first fabricated a gamma-ray camera consisting of the MPPC array with one-to-one coupling to a Ce-doped (Lu,Y){sub 2}(SiO{sub 4})O (Ce:LYSO) crystal array (4×4 array of 3×3×10 mm{sup 3} crystals). Energy and time resolutions of 11.5±0.5% (FWHM at 662 keV) and 493±22ps were obtained, respectively. When using the charge division resistor network, which compiles signals into four position-encoded analog outputs, the ultimate positional resolution is estimated as 0.19 mm in both X and Y directions, while energy resolution of 10.2±0.4% (FWHM) was obtained. Finally, we fabricated submillimeter Ce:LYSO and Ce-doped Gd{sub 3}Ga{sub 3}Al{sub 2}O{sub 12} (Ce:GGAG) scintillator matrices each consisting of 1.0×1.0, 0.7×0.7 and 0.5×0.5 mm{sup 2} pixels, to further improve the spatial resolution. In all types of Ce:LYSO and Ce:GGAG matrices, each crystal was clearly resolved in the position histograms when irradiated by a {sup 137}Cs source. The energy resolutions for 662 keV gamma-rays for each Ce:LYSO and Ce:GGAG scintillator matrix were ≤14.3%. These results suggest excellent potential for its use as a high spatial medical imaging device, particularly in positron emission tomography (PET). -- Highlights: ► We developed a newly designed large-area monolithic MPPC array. ► We obtained fine gain uniformity, and good energy and time resolutions when coupled to the LYSO scintillator. ► We fabricated gamma-ray camera consisting of the MPPC array and submillimeter pixelized LYSO and GGAG scintillators. ► In

Preparation and characterization of Ce-doped HfO{sub 2} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Gálvez-Barboza, S. [Centro de Investigación en Química Aplicada, Departamento de Materiales Avanzados, Blvd. Enrique Reyna Hermosillo #140, C.P. 25294 Saltillo, Coahuila (Mexico); Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Av. Industria Metalúrgica # 1062 Parque Industrial, C.P. 25900 Ramos Arizpe, Coahuila (Mexico); González, L.A. [Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Av. Industria Metalúrgica # 1062 Parque Industrial, C.P. 25900 Ramos Arizpe, Coahuila (Mexico); Puente-Urbina, B.A.; Saucedo-Salazar, E.M. [Centro de Investigación en Química Aplicada, Departamento de Materiales Avanzados, Blvd. Enrique Reyna Hermosillo #140, C.P. 25294 Saltillo, Coahuila (Mexico); García-Cerda, L.A., E-mail: luis.garcia@ciqa.edu.mx [Centro de Investigación en Química Aplicada, Departamento de Materiales Avanzados, Blvd. Enrique Reyna Hermosillo #140, C.P. 25294 Saltillo, Coahuila (Mexico)

2015-09-15

Highlights: • Ce-doped HfO{sub 2} nanoparticles were prepared by a modified solgel method. • Ce-doped HfO{sub 2} nanoparticles have a semispherical shape with sizes between 6 and 11.5 nm. • The samples doped with 10% in weight of Ce directly crystallized in a cubic structure. • A quick, straightforward and effective route for the preparation of Ce-doped nanoparticles. - Abstract: A modified solgel method to synthesize Ce-doped HfO{sub 2} nanoparticles was carried out using a precursor material prepared with cerium nitrate, hafnium chloride, citric acid and ethylene glycol. The obtained precursor material was calcined at 500 and 700 °C for 2 h in air. The influence of the concentration of Ce and the calcination temperature was studied to observe the structural and morphological changes of the obtained materials. For the characterization, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman scattering (RS) were employed. The XRD patterns shown that the Ce-doped HfO{sub 2} undergoes a structural transformation from monoclinic to cubic phase, which is significantly dependent on the Ce content and calcination temperature. TEM images have also confirmed the existence of semispherical nanoparticles with sizes between 6 and 11.5 nm.

FIRST-PRINCIPLES PHASE DIAGRAM OF THE Ce-Th SYSTEM

International Nuclear Information System (INIS)

Landa, A; Soderlind, P

2005-01-01

Actinide physics has seen a remarkable focus the last decade or so due to the combination of improved experimental diamond-anvil-cell techniques and the development of fast computers and more advanced theory. All f-electron systems are expected to have multiphase phase diagrams due to the sensitivity of the f-electron band to external influences such as pressure and temperature. For instance, compression of an f-electron metal generally causes the occupation of f-states to change due to the shift of these bands relative to others. This can in some cases, as in the Ce-Th system, cause the crystal to adopt a lower symmetry structure at elevated pressures. Here we study the phase stabilities of Ce, Th, and the Ce-Th system as a function of compression. Theoretically, both Ce and Th metals are rather well described within the DFT, although a proper treatment of the Ce-Th alloys has not yet been presented. In the present paper we revisit this problem by applying the modern theory of random alloys based on the coherent potential approximation (CPA)

Surface nucleation and independent growth of Ce(OH)4 within confinement space on modified carbon black surface to prepare nano-CeO2 without agglomeration

Science.gov (United States)

Zhang, Xinyue; Xia, Chunhui; Li, Kaitao; Lin, Yanjun

2018-04-01

Highly dispersed negative carboxyl groups can be formed on carbon black (CB) surface modified with strong nitric acid. Therefore positive cations can be uniformly absorbed by carboxyl groups and precipitated within a confinement space on modified CB surface to prepare highly dispersed nanomaterials. In this paper, the formation and dispersion status of surface negative carboxyl groups, adsorption status of Ce3+, surface confinement nucleation, crystallization and calcination process were studied by EDS, SEM, and laser particle size analysis. The results show that the carboxyl groups formed on modified CB surface are highly dispersed, and Ce3+ cations can be uniformly anchored by carboxyl groups. Therefore, highly dispersed Ce3+ can react with OH- within a confinement surface region to form positive nano-Ce(OH)4 nuclei which also can be adsorbed by electrostatic attraction. After independent growth of Ce(OH)4 without agglomeration, highly dispersed CeO2 nanoparticles without agglomeration can be prepared together with the help of effectively isolates by CO2 released in the combustion of CB.

The magnetic properties of Ce/Pd surface alloys investigated using DFT

KAUST Repository

Shuttleworth, I.G.

2014-06-01

The surface alloys that form between Ce and Pd(1 1 1), Pd(1 0 0) and both unreconstructed and missing-row type Pd(1 1 0) at low Ce coverage ( θCe=19ML) have shown permanent magnetism that is mediated in part by an RKKY-like delocalized Ce 6s-Pd 5s interaction. The Pd 4d states are significantly affected by alloying and their behavior cannot be explained by a purely spin-dependent Hamiltonian. Experimental observations of changes to the Pd 4d states are explained and the implications of Ce/Pd magnetism in reforming catalysis are discussed. © 2014 Elsevier B.V. All rights reserved.

The magnetic properties of Ce/Pd surface alloys investigated using DFT

KAUST Repository

Shuttleworth, I.G.

2014-01-01

The surface alloys that form between Ce and Pd(1 1 1), Pd(1 0 0) and both unreconstructed and missing-row type Pd(1 1 0) at low Ce coverage ( θCe=19ML) have shown permanent magnetism that is mediated in part by an RKKY-like delocalized Ce 6s-Pd 5s interaction. The Pd 4d states are significantly affected by alloying and their behavior cannot be explained by a purely spin-dependent Hamiltonian. Experimental observations of changes to the Pd 4d states are explained and the implications of Ce/Pd magnetism in reforming catalysis are discussed. © 2014 Elsevier B.V. All rights reserved.

Assessing Hubbard-corrected AM05+U and PBEsol+U density functionals for strongly correlated oxides CeO_2 and Ce_2O_3

International Nuclear Information System (INIS)

Weck, Philippe F.; Kim, Eunja

2016-01-01

The structure–property relationships of bulk CeO_2 and Ce_2O_3 have been investigated using AM05 and PBEsol exchange–correlation functionals within the frameworks of Hubbard-corrected density functional theory (DFT+U) and density functional perturbation theory (DFPT+U). Compared with conventional PBE+U, RPBE+U, PW91+U and LDA+U functionals, AM05+U and PBEsol+U describe experimental crystalline parameters and properties of CeO_2 and Ce_2O_3 with superior accuracy, especially when +U is chosen close to its value derived by the linear-response approach. Lastly, the present findings call for a reexamination of some of the problematic oxide materials featuring strong f- and d-electron correlation using AM05+U and PBEsol+U.

Construction of g-C3N4/CeO2/ZnO ternary photocatalysts with enhanced photocatalytic performance

Science.gov (United States)

Yuan, Yuan; Huang, Gui-Fang; Hu, Wang-Yu; Xiong, Dan-Ni; Zhou, Bing-Xin; Chang, Shengli; Huang, Wei-Qing

2017-07-01

Promoting the spatial separation of photoexcited charge carriers is of paramount significance for photocatalysis. In this work, binary g-C3N4/CeO2 nanosheets are first prepared by pyrolysis and subsequent exfoliation method, then decorated with ZnO nanoparticles to construct g-C3N4/CeO2/ZnO ternary nanocomposites with multi-heterointerfaces. Notably, the type-II staggered band alignments existing between any two of the constituents, as well as the efficient three-level transfer of electron-holes in unique g-C3N4/CeO2/ZnO ternary composites, leads to the robust separation of photoexcited charge carriers, as verified by its photocurrent increased by 8 times under visible light irradiation. The resulting g-C3N4/CeO2/ZnO ternary nanocomposites unveil appreciably increased photocatalytic activity, faster than that of pure g-C3N4, ZnO and g-C3N4/CeO2 by a factor of 11, 4.6 and 3.7, respectively, and good stability toward methylene blue (MB) degradation. The remarkably enhanced photocatalytic activity of g-C3N4/CeO2/ZnO ternary heterostructures can be interpreted in terms of lots of active sites of nanosheet shapes and the efficient charge separation owing to the resulting type-II band alignment with more than one heterointerface and the efficient three-level electron-hole transfer. A plausible mechanism is also elucidated via active species trapping experiments with various scavengers, which indicating that the photogenerated holes and •OH radicals play a crucial role in photodegradation reaction under visible light irradiation. This work suggest that the rational design and construction of type II multi-heterostructures is powerful for developing highly efficient and reusable visible-light photocatalysts for environmental purification and energy conversion.

Crystal growth and magnetic properties of equiatomic CeAl

Science.gov (United States)

Das, Pranab Kumar; Thamizhavel, A.

2015-03-01

Single crystal of CeAl has been grown by flux method using Ce-Al self-flux. Several needle like single crystals were obtained and the length of the needle corresponds to the [001] crystallographic direction. Powder x-ray diffraction revealed that CeAl crystallizes in orthorhombic CrB-type structure with space group Cmcm (no. 63). The magnetic properties have been investigated by means of magnetic susceptibility, isothermal magnetization, electrical transport, and heat capacity measurements. CeAl is found to order antiferromagnetically with a Neel temperature TN = 10 K. The magnetization data below the ordering temperature reveals two metamagentic transitions for fields less than 20 kOe. From the inverse magnetic susceptibility an effective moment of 2.66 μB/Ce has been estimated, which indicates that Ce is in its trivalent state. Electrical resistivity data clearly shows a sharp drop at 10 K due to the reduction of spin disorder scattering of conduction electrons thus confirming the magnetic ordering. The estimated residual resistivity ratio (RRR) is 33, thus indicating a good quality of the single crystal. The bulk nature of the magnetic ordering is also confirmed by heat capacity data. From the Schottky anomaly of the heat capacity we have estimated the crystal field level splitting energies of the (2J + 1) degenerate ground state as 25 K and 175 K respectively for the fist and second excited states.

Laser clad Ni-base alloy added nano- and micron-size CeO 2 composites

Science.gov (United States)

Zhang, Shi Hong; Li, Ming Xi; Cho, Tong Yul; Yoon, Jae Hong; Lee, Chan Gyu; He, Yi Zhu

2008-07-01

Micron-size Ni-base alloy (NBA) powders are mixed with both 1.5 wt% (%) micron-CeO 2 (m-CeO 2) and also 1.0-3.0% nano-CeO 2 (n-CeO 2) powders. These mixtures are coated on low carbon steel (Q235) by 2.0 kW CO 2 laser cladding. The effects on microstructures, microhardness and wear resistance of the coating by the addition of m- and n-CeO 2 powders to NBA (m- and n-CeO 2/NBA) have been investigated. Addition to the primary phases of γ-Ni, Cr 23C 6 and Ni 3B of NBA coating, CeNi 3 shows up both in m- and n-CeO 2/NBA coatings and CeNi 5 appears only in n-CeO 2/NBA coating. Directional dendrite and coarse equiaxed dendrite are grown in m-CeO 2/NBA coating from interface to central zone, whereas multi-oriented dendrite and fine equiaxed dendrite growth by addition of n-CeO 2. The microhardness and wear resistance of coatings are greatly improved by CeO 2 powder addition, and compared to the addition of 1.0% and 3.0%, 1.5% n-CeO 2/NBA is the best. Hardness and wear resistance of the coating improves with decreasing CeO 2 size from micron to nano.

{sup 115}In NQR studies of CeRhIn{sub 5} and CeCoIn{sub 5} under high pressure

Energy Technology Data Exchange (ETDEWEB)

Kohori, Y. [Department of Physics, Faculty of Science, Chiba University, Chiba 263-8522 (Japan)]. E-mail: kohori@faculty.chiba-u.jp; Taira, H. [Graduate School of Science and Technonogy, Chiba University, Chiba 263-8522 (Japan); Fukazawa, H. [Graduate School of Science and Technonogy, Chiba University, Chiba 263-8522 (Japan); Kohara, T. [Graduate School of Material Science, University of Hyogo, Hyogo 678-1297 (Japan); Iwamoto, Y. [Division of Cargo and Transportation Science, Kobe University, Kobe 658-0022 (Japan); Matsumoto, T. [National Institite of Material Science, Tsukuba 305-0044 (Japan); Maple, M.B. [Department of Physics and Institute for Pure and Applied Physical Science, University of California, San Diego, La Jolla, CA 92093, USA (United States)

2006-02-09

We have carried out{sup 115}In nuclear quadrupole resonance (NQR) measurements in CeRhIn{sub 5} and CeCoIn{sub 5} under presure P. The nuclear spin-lattice relaxation rates, 1/T{sub 1}, of{sup 115}In indicated that the anisotropic superconductivity with line nodes occurred near an antiferromagnetic state. The application of P suppressed the antiferromagnetic, AF, spin fluctuations and moves the system away from the AF state to the non-magnetic Fermi liquid state. The P dependence of 1/T{sub 1} in the superconducting state of CeCoIn{sub 5} shows that the magnitude of the superconducting energy gap scales with its T{sub C} up to 3.0 GPa.

Heteroaggregation, transformation and fate of CeO2 nanoparticles in wastewater treatment

International Nuclear Information System (INIS)

Barton, Lauren E.; Auffan, Melanie; Olivi, Luca; Bottero, Jean-Yves; Wiesner, Mark R.

2015-01-01

Wastewater Treatment Plants (WWTPs) are a key pathway by which nanoparticles (NPs) enter the environment following release from NP-enabled products. This work considers the fate and exposure of CeO 2 NPs in WWTPs in a two-step process of heteroaggregation with bacteria followed by the subsequent reduction of Ce(IV) to Ce(III). Measurements of NP association with solids in sludge were combined with experimental estimates of reduction rate constants for CeO 2 NPs in Monte Carlo simulations to predict the concentrations and speciation of Ce in WWTP effluents and biosolids. Experiments indicated preferential accumulation of CeO 2 NPs in biosolids where reductive transformation would occur. Surface functionalization was observed to impact both the distribution coefficient and the rates of transformation. The relative affinity of CeO 2 NPs for bacterial suspensions in sludge appears to explain differences in the observed rates of Ce reduction for the two types of CeO 2 NPs studied. - Highlights: • We combine experimental and computational methods to track CeO 2 NPs through WWTPs. • We investigate the importance of environmental transformations on NP exposure. • We estimate the concentrations of CeO 2 NPs and reductive transformation byproducts. - CeO 2 nanoparticles that are released to the waste stream will preferentially associate with the solid phase (∼96%), where they will undergo significant transformation (∼50%)

Properties and practical application of thin CeOx films

Directory of Open Access Journals (Sweden)

Maksimchuk N. V.

2010-10-01

Full Text Available The properties of CeOx films produced by various methods have been investigated. According to the comparative analisys “metallic mirror oxidation” method allows to produce films with significantly better characteristics than the «explosive evaporation» method. Though the latter method yields higher photosensitivity of CeOx films and structures on their base. In the process the optimal value of the substrate temperature was determined. Obtained data expand the CeOx application potential in microelectronic sensor sphere.

Investigation of the physical, optical, and photocatalytic properties of CeO2/Fe-doped InVO4 composite

Science.gov (United States)

Chaison, Jindaporn; Wetchakun, Khatcharin; Wetchakun, Natda

2017-12-01

The CeO2/Fe-doped InVO4 composites with various Fe concentrations (0.5, 1.0, 2.0, 5.0 and 6.0 mol%) was synthesized by homogeneous precipitation and hydrothermal methods. The as-synthesized samples were characterized by powder X-ray diffraction (XRD), Brunauer Emmett and Teller (BET)-specific surface area, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and UV-visible diffuse reflectance spectroscopy (DRS). Fe-doping into InVO4 crystal induces the distortion of the crystalline structure, the transformation of InVO4 morphology, and the new energy subband level generation of Fe between the CB and VB edge of InVO4. The electron excitation from the VB to Fe orbitals results in the decreased band gap and the extended absorption of visible-light, and thus enhances its photocatalytic performance. Visible-light-driven photocatalytic degradation of Rhodamine B (RhB) dye in water was used to evaluate the photocatalytic performance of CeO2/Fe-doped InVO4 composites. The results revealed that there is an optimum Fe (5.0 mol %) doping level. The composite with the optimum doping level obtains high photocatalytic activity of CeO2/Fe-doped InVO4 composite compared to pure CeO2 and pure InVO4 host. The increase of photocatalytic activity of CeO2/Fe-doped InVO4 composite was ascribed to the surface area, crystal defect, and band gap energy. Moreover, the photocatalytic enhancement is also because iron ions act as a trapping site, which results in the higher separation efficiency of photogenerated electrons and holes pairs in the CeO2/InVO4 composite. The evaluation of radical scavengers confirmed that hydroxyl radical was the main active species during the photodegradation of RhB. These synergistic effects are responsible for the enhanced photocatalytic activity of CeO2/Fe-doped InVO4 composite. Furthermore, the possible enhanced photocatalytic mechanism

Fermi-surface topology of the heavy-fermion system Ce2PtIn8

Science.gov (United States)

Klotz, J.; Götze, K.; Green, E. L.; Demuer, A.; Shishido, H.; Ishida, T.; Harima, H.; Wosnitza, J.; Sheikin, I.

2018-04-01

Ce2PtIn8 is a recently discovered heavy-fermion system structurally related to the well-studied superconductor CeCoIn5. Here we report on low-temperature de Haas-van Alphen-effect measurements in high magnetic fields in Ce2PtIn8 and Pr2PtIn8 . In addition, we performed band-structure calculations for localized and itinerant Ce-4 f electrons in Ce2PtIn8 . Comparison with the experimental data of Ce2PtIn8 and of the 4 f -localized Pr2PtIn8 suggests the itinerant character of the Ce-4 f electrons. This conclusion is further supported by the observation of effective masses in Ce2PtIn8 , which are strongly enhanced with up to 26 bare electron masses.

Ce activated potassium bromide phosphor for lyoluminescence dosimetry of ionizing radiation

International Nuclear Information System (INIS)

Bhujbal, P.M.; Dhoble, S.J.

2013-01-01

The lyoluminescence (LL) properties of gamma irradiated KBr:Ce phosphor are reported in this paper. The samples were prepared by wet chemical route. The prepared material was characterized by lyoluminescence technique. LL in KBr:Ce have been recorded for different gamma doses. The nature of variation of peak LL intensity is found to be sublinear with gamma irradiation dose, and the peak LL intensity is found to be dependent on concentrations of added Ce in the samples. Negligible fading in the prepared KBr:Ce (0.5 mol%) sample is observed. -- Highlights: • The LL intensities are found to be dependent on concentrations of Ce ion. • The LL intensities are found to be dependent on gamma rays radiation dose. • Dose response of KBr:Ce (0.5 mol%) is observed linear between 0.08 and 1.00 kGy. • The prepared material may be useful for ionizing radiation dosimetry

Room-temperature synthesis and characterization of porous CeO2 thin films

International Nuclear Information System (INIS)

Chu, Dewei; Masuda, Yoshitake; Ohji, Tatsuki; Kato, Kazumi

2012-01-01

CeO 2 thin films with hexagonal-shaped pores were successfully prepared by a facile electrodeposition at room temperature combined with an etching process. By using electrodeposited ZnO nanorods as a soft template, the morphology, and microstructure of the CeO 2 could be controlled. TEM observation indicated that as-prepared CeO 2 film is composed of nanocrystals with average size of several nanometers, while XPS analysis showed the coexistence of Ce 3+ and Ce 4+ in the film. The photoluminescence properties of CeO 2 films were measured, which showed much higher sensitivity compared to bare substrate. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Highly active and durable Ca-doped Ce-SBA-15 catalyst for biodiesel production

International Nuclear Information System (INIS)

Thitsartarn, Warintorn; Maneerung, Thawatchai; Kawi, Sibudjing

2015-01-01

In this work, Ca-doped Ce-incorporated SBA-15 (Ca/CeS) catalyst was successfully synthesized by using direct synthesis of Ce-incorporated SBA-15 followed by impregnation of CaO (calcium oxide). The maximum Si/Ce molar ratio that Ce atoms can be incorporated successfully into the mesoporous framework was found to be 5 (CeS-5). After the impregnation of 30 wt. % Ca, the obtained 30Ca/CeS-5 catalysts showed the superior catalytic performance for transesterification reaction of palm oil with methanol and also the higher catalytic activity as compared to other supported catalysts, i.e. CaO/CeO 2 and CaO–CeO 2 /SBA-15. This can be attributed to the well-dispersion of CaO on the CeS-5 support surface. Furthermore, it was found that the leaching of Si, Ce and Ca from the catalyst into biodiesel produced was negligible (i.e. <1 ppm after 7 cycles), indicating the strong interaction between CaO and CeS-5 support. As a result, the 30Ca/CeS-5 catalyst can be reused at least 15 cycles with insignificant decrease in catalytic activity, offering the efficient CaO-based catalyst for biodiesel production. - Highlights: • Mesoporous Ca-based catalyst was successfully developed for biodiesel production. • Catalyst exhibited high activity towards transesterification (FAME yield > 98%). • Catalyst can be effectively re-used at least 15 cycles. • Extremely low catalyst contaminant (<1 ppm) was presented

Effect of cerium on the corrosion behaviour of sintered (Nd,Ce)FeB magnet

Energy Technology Data Exchange (ETDEWEB)

Yang, Lijing [CAS Key Laboratory of Magnetic Materials and Devices, Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Bi, Mengxue [CAS Key Laboratory of Magnetic Materials and Devices, Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Nano Science and Technology Institute, University of Science and Technology of China, Hefei 230026 (China); Jiang, Jianjun; Ding, Xuefeng [CAS Key Laboratory of Magnetic Materials and Devices, Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Zhu, Minggang; Li, Wei [Functional Materials Research Institute, Central Iron & Steel Research Institute, Beijing 100081 (China); Lv, Zhongshan [Ningbo Shuo Teng new material Co., Ltd., Cixi 315301 (China); Song, Zhenlun, E-mail: songzhenlun@nimte.ac.cn [CAS Key Laboratory of Magnetic Materials and Devices, Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

2017-06-15

Highlights: • A little Ce could promote the magnets for a better corrosion resistance. • With increased Ce contents, the corrosion resistances of magnets decrease. • As the corrosion developed, the magnetic properties decreased. - Abstract: For the balanced consumption of rare-earth elements, cerium (Ce) was partially used for NdFeB magnets instead of Nd. The corrosion behaviour of the (Nd,Ce)FeB magnet with different Ce contents in 3.5% NaCl solution was investigated by SEM, XRD, EDS and electrochemical tests. After immersion, the weight loss was calculated and the magnetic properties of the samples were measured. Results showed that Ce affected the corrosion of the (Nd,Ce)FeB magnet. Compared with the NdFeB magnet without Ce but of the same grade as the magnetic energy product, (Nd,Ce)FeB magnet showed better corrosion resistance. With increased Ce content, the corrosion resistances and magnetic properties of (Nd,Ce)FeB magnets were investigated.

An Update on NiCE Support for BISON

Energy Technology Data Exchange (ETDEWEB)

McCaskey, Alex [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Billings, Jay Jay [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Deyton, Jordan H. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Wojtowicz, Anna [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2015-09-01

The Nuclear Energy Advanced Modeling and Simulation program (NEAMS) from the Department of Energy s Office of Nuclear Energy has funded the development of a modeling and simulation workflow environment to support the various codes in its nuclear energy scientific computing toolkit. This NEAMS Integrated Computational Environment (NiCE) provides extensible tools and services that enable efficient code execution, input generation, pre-processing visualizations, and post-simulation data analysis and visualization for a large portion of the NEAMS Toolkit. A strong focus for the NiCE development team throughout FY 2015 has been support for the Multiphysics Object Oriented Simulation Environment (MOOSE) and the NEAMS nuclear fuel performance modeling application built on that environment, BISON. There is a strong desire in the program to enable and facilitate the use of BISON throughout nuclear energy research and industry. A primary result of this desire is the need for strong support for BISON in NiCE. This report will detail improvements to NiCE support for BISON. We will present a new and improved interface for interacting with BISON simulations in a variety of ways: (1) improved input model generation, (2) embedded mesh and solution data visualizations, and (3) local and remote BISON simulation launch. We will also show how NiCE has been extended to provide support for BISON code development.

The CE3R Network: current status and future perspectives

Science.gov (United States)

Lenhardt, Wolfgang; Pesaresi, Damiano; Živčić, Mladen; Costa, Giovanni; Kuk, Kresimir; Bondár, István; Duni, Llambro; Spacek, Petr

2016-04-01

In order to improve the monitoring of seismic activities in the border regions and to enhance the collaboration between countries and seismological institutions in Central Europe, the Environment Agency of the Slovenian Republic (ARSO), the Italian National Institute for Oceanography and Experimental Geophysics (OGS), the University of Trieste (UniTS) and the Austrian Central Institute for Meteorology and Geodynamics (ZAMG) established in 2001 the "South Eastern Alps Transfrontier Seismological Network". In May 2014 ARSO, OGS, UniTS and ZAMG agreed to formalize the transfrontier network, to name it "Central and East European Earthquake Research Network", (CE3RN or CE3R Network) in order to locate it geographically since cross-border networks can be established in other areas of the world and to expand their cooperation, including institutions in other countries. The University of Zagreb (UniZG) joined CE3RN in October 2014. The Kövesligethy Radó Seismological Observatory (KRSZO) of the Hungarian Academy of Sciences joined CE3RN in October 2015. The Institute of Geosciences, Energy, Water and Environment (IGEWE) of the Polytechnic University of Tirana joined CE3RN in November 2015. The Institute of Physics of the Earth (IPE) of the Masaryk University in Brno joined CE3RN in November 2015. CE3RN Parties intend to formalize and possibly extend their ongoing cooperation in the field of seismological data acquisition, exchange and use for seismological and earthquake engineering and civil protection purposes. The purpose of this cooperation is to retain and expand the existing cross-border network, specify the rules of conduct in the network management, improvements, extensions and enlargements, enhance seismological research in the region, and support civil protection activities. Since the formal establishment of CE3RN, several common projects have been completed, like the SeismoSAT project for the seismic data center connection over satellite funded by the Interreg

Structure and Chemical Bond of Thermoelectric Ce-Co-Sb Skutterudites

Institute of Scientific and Technical Information of China (English)

无

2001-01-01

The correlations among composition,structure,chemical bond and thermoelectric property of skutterudites CoSb3 and CeCo5Fe3Sb12 have been studied by using density function and discrete variation (DFT-DVM) method.Three models for this study were proposed and calculated by which the "rattling" pattern was described.Model 1 is with Ce in the center,model 2 is with Ce away the center and near to Sb,and model 3 is also with Ce away the center but near to Fe.The calculated results show that in model 3,the ionic bond is the strongest,but the covalent bond is the weakest.Due to the different changes between ionic and covalent bond,there is less difference in the stability among the models 1,2 and 3.Therefore,these different models can exist at the same time,or can translate from one to another more easily.In other words,the "rattling" pattern has taken place.Unfilled model of CoSb3,without Ce and Fe,is called model 4.The covalent bond of Co-Sb or Fe-Sb in models 1,2 and 3 is weaker than that of Co-Sb in model 4,as some electrical cloud of Sb takes part in the covalent bond of Ce-Sb in the filled models.The result is consistent with the experimental result that the thermal conductivity of CeCo5Fe3Sb12 is lower than that of CoSb3,and the thermoelectric property of CeCo5Fe3Sb12 is superior to that of CoSb3.

Adsorption and Reaction of Acetone over CeOX(111) Thin Films

International Nuclear Information System (INIS)

Mullins, David R.; Senanayake, Sanjaya D.; Gordon, Wesley O.; Overbury, Steven H.

2009-01-01

This study reports the interaction of acetone (CH3COCH3), the simplest ketone, with well ordered CeO2(111) thin film surfaces. The fully oxidized CeO2(111) surface shows a weak interaction with acetone with the sole desorption product (TPD) being acetone at 210 K. The chemisorbed molecule binds to the surface as the ?1-acetone species rather than through a bridge-bonded dioxy-configuration. Exposure of a CeO2(111) surface to acetone at 600K removes oxygen as CO and results in the conversion of Ce4+ to Ce3+. Acetone chemisorbs strongly on reduced CeO2-x(111) with molecular acetone desorbing near 500 K. Decomposition also occurs with H2 desorbing between 450 and 600 K and C reacting with O in the ceria to desorb above 650 K. A stable species exists from 200 to 500 K on the reduced surface that has three unique types of C. High resolution C 1s XPS spectra indicate these are Ce-CH2, C-CH3 and C-O species. C k-edge NEXAFS indicates the presence of C(double b ond)C and C(double b ond)O bonds. It is postulated that the intermediate is a carbanion bonded through both O and C atoms to Ce cations.

Preparation and Characterization of Graphite Waste/CeO2 Composites

Science.gov (United States)

Kusrini, E.; Utami, C. S.; Nasruddin; Prasetyanto, E. A.; Bawono, Aji A.

2018-03-01

In this research, the chemical modification of graphite waste with CeO2 was developed and characterized. Graphite waste was pretreated with mechanical to obtain the size 200 mesh (75 μm), and thermal methods at 110°C oven for 6 hours. Here, we demonstrate final properties of graphite before modification (GBM), activated graphite (GA) and graphite/CeO2 composite with variation of 0.5, 1 and 2 g of CeO2 (G0.5; G1; G2). The effect of CeO2 concentration was observed. The presence of cerium in modified graphite samples (G0.5; G1; G2) were analyzed using SEM-EDX. The results show that the best surface area was found in G2 is 26.82 m2/g. The presence of CeO2 onto graphite surface does not significantly increase the surface area of composites.

Selective Synthesis of Mesoporous and Nanorod CeVO4 without Template

International Nuclear Information System (INIS)

Zhu Ling; Li Qin; Li Jiayan; Liu Xiangdong; Meng Jian; Cao Xueqiang

2007-01-01

A simple and efficient method has been established for the selective synthesis of mesoporous and nanorod CeVO 4 with different precursors by sonochemical method. CeVO 4 nanorod can be simply synthesized by ultrasound irradiation of Ce(NO 3 ) 3 and NH 4 VO 3 in aqueous solution without any surfactant or template. While mesoporous CeVO 4 with high specific surface area can be prepared with Ce(NO 3 ) 3 , V 2 O 5 and NaOH in the same way. Mesoporous CeVO 4 has a specific surface area of 122 m 2 g -1 and an average pore size of 5.2 nm; CeVO 4 nanorods have a diameter of about 5 nm, and a length of 100-150 nm. The ultrasound irradiation and ammonia in the reactive solution are two key factors in the formation of such rod-like products. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG) and differential thermal analyses (DTA), UV/vis absorption spectroscopy and Brunauer-Emmett-Teller (BET) were applied for characterization of the as-prepared products

Luminescence properties of Y3Al5O12:Ce nanoceramics

International Nuclear Information System (INIS)

Zorenko, Yu.; Voznyak, T.; Gorbenko, V.; Zych, E.; Nizankovski, S.; Dan'ko, A.; Puzikov, V.

2011-01-01

Comparative analysis of the luminescent properties of Y 3 Al 5 O 12 :Ce (YAG:Ce) transparent optical ceramics (OS) with those of single crystal (SC) and single crystalline film (SCF) analogues has been performed under excitation by pulsed synchrotron radiation in the fundamental absorption range of YAG host. It has been shown that the properties of YAG:Ce OC are closer to the properties of the SCF counterpart, where Y Al antisite defects are completely absent, rather than to the properties of SC of this garnet with large concentration of Y Al antisite defects. At the same time, the luminescence spectra of YAG:Ce OC show weak emission bands in the 200-470 nm range related to Y Al antisite defects and charged oxygen vacancies (F + and F centers). YAG:Ce OS also possesses significantly larger contribution of slow components in the Ce 3+ luminescence decay under high-energy excitation in comparison with SC and SCF of this garnet due to the involvement of antisite defects, charged oxygen vacancies as well as boundaries of grains in the energy transfer processes from the host to the Ce 3+ ions.

Effect of cerium on the corrosion behaviour of sintered (Nd,Ce)FeB magnet

Science.gov (United States)

Yang, Lijing; Bi, Mengxue; Jiang, Jianjun; Ding, Xuefeng; Zhu, Minggang; Li, Wei; Lv, Zhongshan; Song, Zhenlun

2017-06-01

For the balanced consumption of rare-earth elements, cerium (Ce) was partially used for NdFeB magnets instead of Nd. The corrosion behaviour of the (Nd,Ce)FeB magnet with different Ce contents in 3.5% NaCl solution was investigated by SEM, XRD, EDS and electrochemical tests. After immersion, the weight loss was calculated and the magnetic properties of the samples were measured. Results showed that Ce affected the corrosion of the (Nd,Ce)FeB magnet. Compared with the NdFeB magnet without Ce but of the same grade as the magnetic energy product, (Nd,Ce)FeB magnet showed better corrosion resistance. With increased Ce content, the corrosion resistances and magnetic properties of (Nd,Ce)FeB magnets were investigated.

CeBr3 as a room-temperature, high-resolution gamma-ray detector

International Nuclear Information System (INIS)

Guss, Paul; Reed, Michael; Yuan Ding; Reed, Alexis; Mukhopadhyay, Sanjoy

2009-01-01

Cerium bromide (CeBr 3 ) has become a material of interest in the race for high-resolution gamma-ray spectroscopy at room temperature. This investigation quantified the potential of CeBr 3 as a room-temperature, high-resolution gamma-ray detector. The performance of CeBr 3 crystals was compared to other scintillation crystals of similar dimensions and detection environments. Comparison of self-activity of CeBr 3 to cerium-doped lanthanum tribromide (LaBr 3 :Ce) was performed. Energy resolution and relative intrinsic efficiency were measured and are presented.

Study of the magnetic properties of CeCu{sub 2}(Si{sub 1-x}Ge{sub x}){sub 2} by means of neutron scattering; Untersuchung der magnetischen Eigenschaften von CeCu{sub 2}(Si{sub 1-x}Ge{sub x}){sub 2} mittels Neutronenstreuung

Energy Technology Data Exchange (ETDEWEB)

Faulhaber, Enrico

2008-07-01

In 1979 the first heavy-fermion superconductor CeCu{sub 2}Si{sub 2} was discovered by Steglich et al. The system is near a quantum critical point (QCP), where the magnetic order is just suppressed. The distance to the QCP can be varied with hydrostatic pressure as well as by germanium substitution on the silicon site. Next to the superconductivity in CeCu{sub 2}Si{sub 2} one finds distinct magnetic phases while increasing the germanium content. CeCu{sub 2}Si{sub 2} shows a magnetic order of a spin-density-type below T{sub N}-0.8 K, whereas the heavy fermion system CeCu{sub 2}Ge{sub 2} orders below T{sub N}=4.1 K as an antiferromagnet. The focus of this thesis is on neutron-diffraction in the system CeCu{sub 2}(Si{sub 1-x}Ge{sub x}){sub 2}. Starting with a sample with a high germanium content of x=0.45, the magnetic structures are investigated in detail. Following a step-by-step approach, samples with reduced x are investigated subsequently to figure out the properties of pure CeCu{sub 2}Si{sub 2}, which were not accessible before. Furthermore, the complex interaction between magnetism and superconductivity is investigated in detail. Using a specially designed setup, the ac-susceptibility could be recorded simultaneously during the neutron diffraction experiments. Due to the direct correlation between antiferromagnetic signals and diamagnetic features, the microscopic coexistence of superconductivity and magnetic order can be ruled out. Instead, a phase separation on the microscopic scale is found. (orig.)

Solid-solution stability and preferential site-occupancy in (R-R′){sub 2}Fe{sub 14}B compounds

Energy Technology Data Exchange (ETDEWEB)

Colin, C. V.; Dempsey, N. M. [CNRS, Inst NEEL, F-38000 Grenoble (France); Univ. Grenoble Alpes, Inst NEEL, F-38000 Grenoble (France); Ito, M. [CNRS, Inst NEEL, F-38000 Grenoble (France); Univ. Grenoble Alpes, Inst NEEL, F-38000 Grenoble (France); Advanced Material Engineering Div., Toyota Motor Corporation, Susono 410-1193 (Japan); Yano, M. [Advanced Material Engineering Div., Toyota Motor Corporation, Susono 410-1193 (Japan); Suard, E. [Institut Laue-Langevin, CS 20156-38042 Grenoble cedex 9 (France); Givord, D. [CNRS, Inst NEEL, F-38000 Grenoble (France); Univ. Grenoble Alpes, Inst NEEL, F-38000 Grenoble (France); Instituto de Fisica, Universidade Federal do Rio de Janeiro, 21941-972 Rio de Janeiro (Brazil)

2016-06-13

The rare-earth (R) uniaxial anisotropy of R{sub 2}Fe{sub 14}B compounds with magnetic R atoms (e.g., Nd or Pr) is at the origin of the exceptional hard magnetic properties achieved in magnets based on these compounds. The uniaxial anisotropy found in Ce{sub 2}Fe{sub 14}B is attributed mainly to the magnetism of Fe. Ce is the most abundant R element and there has been much recent effort to fabricate magnets in which Ce is partially substituted for Nd. In the present neutron study of (R{sub 1−x}Ce{sub x}){sub 2}Fe{sub 14}B (R = La or Nd), Ce is found to enter the R{sub 2}Fe{sub 14}B phase over the entire composition range. The crystallographic parameters decrease with increasing Ce content and the Ce atoms preferentially occupy the smaller 4f sites. It is concluded that Ce in these (RR′){sub 2}Fe{sub 14}B compounds essentially maintains the intermediate valence character found in Ce{sub 2}Fe{sub 14}B. It is proposed that, in this intermediate valence state, Ce weakly contributes to uniaxial anisotropy, thus making a link with the fact that significant coercivity is preserved in Ce-substituted NdFeB magnets.

Study of magnetic properties of TGa6 with T = Ce, Pr, Nd, Tb, Ho, Dy and of solid solutions Ce(Ga1-x Alx)2

International Nuclear Information System (INIS)

Jerjini, M.

1987-10-01

At low temperature TGa 6 compounds are ordered with a Neel temperature of about 10 K. Magnetic structures are antiferromagnetic for T = Pr or Nd or modulated for T = Tb, Ho or Dy. Ce presents an abnormal behavior in CeGa 6 . Neutron inelastic scattering allows the determination of energy levels in the crystal field of cerium ion and evidences hybridation of 4f and valence electrons. Three magnetic transitions for T 6 . Study of CeGa 6 and solid solutions. Ce(Ga (1-x) Al x ) 2 shows that aluminium insertion reinforces the Kondo effect. For x = O.1 an incommensurable structure subsists at very low temperature. CeGa 2 is ordered with 3 magnetic structures. Magnetic moment is reduced with Al. The study of crystal field by neutron scattering shows that hybridation effects are more important for the compound with x = 0.1 [fr

CE-SAM: a conversational interface for ISR mission support

Science.gov (United States)

Pizzocaro, Diego; Parizas, Christos; Preece, Alun; Braines, Dave; Mott, David; Bakdash, Jonathan Z.

2013-05-01

There is considerable interest in natural language conversational interfaces. These allow for complex user interactions with systems, such as fulfilling information requirements in dynamic environments, without requiring extensive training or a technical background (e.g. in formal query languages or schemas). To leverage the advantages of conversational interactions we propose CE-SAM (Controlled English Sensor Assignment to Missions), a system that guides users through refining and satisfying their information needs in the context of Intelligence, Surveillance, and Reconnaissance (ISR) operations. The rapidly-increasing availability of sensing assets and other information sources poses substantial challenges to effective ISR resource management. In a coalition context, the problem is even more complex, because assets may be "owned" by different partners. We show how CE-SAM allows a user to refine and relate their ISR information needs to pre-existing concepts in an ISR knowledge base, via conversational interaction implemented on a tablet device. The knowledge base is represented using Controlled English (CE) - a form of controlled natural language that is both human-readable and machine processable (i.e. can be used to implement automated reasoning). Users interact with the CE-SAM conversational interface using natural language, which the system converts to CE for feeding-back to the user for confirmation (e.g. to reduce misunderstanding). We show that this process not only allows users to access the assets that can support their mission needs, but also assists them in extending the CE knowledge base with new concepts.

Blue emitting KSCN:xCe phosphor for solid state lighting

Energy Technology Data Exchange (ETDEWEB)

Chikte, Devayani, E-mail: devi.awade@gmail.com [G.N. Khalsa College, Matunga, Mumbai 400019 (India); Omanwar, S.K. [Department of Physics, S.G.B. Amravati University, Amravati (India); Moharil, S.V. [Department of Physics, R.T.M. Nagpur University, Nagpur 440010 (India)

2014-01-15

The intense blue emitting phosphor KSCN:xCe (x=0.005, 0.01, 0.02, 0.04) is synthesized by a simple, time saving, economical method of re-crystallization through aqueous solution at 353 K. Photoluminescence measurements showed that the said phosphor exhibits emission with good intensity peaking at 450 nm corresponding to d→f transitions of Ce{sup 3+} ion. The excitation spectra monitored at 450 nm shows small peak at 282 nm and broad intense excitation band peaking at 350 nm. The latter lies in near ultraviolet (350–410 nm) emission of UV LED. The phosphor KSCN:0.02Ce{sup 3+} shows CIE 1931 color coordinates as (0.1484, 0.0602) whereas the commercial blue phosphor BAM:Eu{sup 2+} shows the color co-ordinates as (0.1417, 0.1072), respectively, indicating better color purity for KSCN: 0.02Ce{sup 3+} compared to the BAM:Eu{sup 2+} phosphor. The color coordinates of KSCN: 0.02Ce{sup 3+} phosphor (0.1484, 0.0602) are nearer to the color coordinate for blue color suggested by the color systems EBUPAL/SECAM, sRGB Blue as well as Adobe blue(0.15, 0.06). -- Highlights: • Novel phosphor KSCN:xCe prepared for the first time. • Method is simple, time saving, economical, easy to handle. • Intense, blue, Characteristic Ce{sup 3+} emission at 450 nm. • nUV excitation, suitable for solid state lighting.

Levels in 146Ce and the N = 88 isotones

International Nuclear Information System (INIS)

Gowdy, G.M.; Chrien, R.E.; Chu, Y.Y.

1981-01-01

An investigation of the level structure of 146 Ce following the beta decay of the low-spin isomer of 146 La has been carried out at the ISOL facility TRISTAN at Brookhaven National Laboratory. The half-life for the low spin isomer was found to be 6.0 +- 0.4s. A partial level scheme for 146 Ce below 2 MeV is given. The level energies and some B(E2) values extracted from our data have been compared with IBA-2 calculations done entirely with extrapolated parameters from neighboring Z nuclei in order to check the predictive power of the model. Systematics of the Z = 58 isotopes and N = 88 isotones indicate that although 146 Ce is more deformed than its isotones with Z greater than or equal to 60, the transition to the well-deformed region can probably more correctly be thought to occur after 146 Ce, between N = 88 and N = 90, as it does for Z greater than or equal to 60. The abrupt onset of deformation present in the higher Z isotopes is not seen in the Ce isotopes where the trend is found to be rather smooth throughout

Nanocrystalline Mn-Mo-Ce Oxide Anode Doped Rare Earth Ce and Its Selective Electro-catalytic Performance

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SHI Yan-hua

2017-09-01

Full Text Available The anode oxide of nanocrystalline Mn-Mo-Ce was prepared by anode electro-deposition technology, and its nanostructure and selective electro-catalytic performance were investigated using the SEM, EDS, XRD, HRTEM, electrochemical technology and oxygen evolution efficiency testing. Furthermore, the selective electro-catalytic mechanism of oxygen evolution and chlorine depression was discussed. The results show that the mesh-like nanostructure Mn-Mo-Ce oxide anode with little cerium doped is obtained, and the oxygen evolution efficiency for the anode in the seawater is 99.51%, which means a high efficiency for the selective electro-catalytic for the oxygen evolution. Due to the structural characteristics of γ-MnO2, the OH- ion is preferentially absorbed, while Cl- absorption is depressed. OH- accomplishes the oxygen evolution process during the valence transition electrocatalysis of Mn4+/Mn3+, completing the selective electro-catalysis process. Ce doping greatly increases the reaction activity, and promotes the absorption and discharge; the rising interplanar spacing between active (100 crystalline plane promotes OH- motion and the escape of newborn O2, so that the selective electro-catalytic property with high efficient oxygen evolution and chlorine depression is achieved from the nano morphology effect.

Effects of Surfactants on the Performance of CeO2 Humidity Sensor

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Chunjie Wang

2014-01-01

Full Text Available Nanosized CeO2 powders were synthesized via hydrothermal method with different types of surfactants (polyethylene glycol (PEG, cetyltrimethylammonium bromide (CTAB, and sodium dodecylbenzenesulfonate (SDBS. X-ray diffraction, Raman spectroscopy, and transmission electron microscopy were utilized to characterize the phase structures and morphologies of the products. The sample with CTAB as surfactant (CeO2-C has the largest specific surface area and the smallest particle size among these three samples. The humidity sensor fabricated by CeO2-C shows higher performance than those used CeO2-P and CeO2-S. The impedance of the CeO2-C sensor decreases by about five orders of magnitude with relative humidity (RH changing from 15.7 to 95%. The response and recovery time are 7 and 7 s, respectively. These results indicate that the performance of CeO2 humidity sensors can be improved effectively by the addition of cationic surfactant.

Numerical error in electron orbits with large ωceδt

International Nuclear Information System (INIS)

Parker, S.E.; Birdsall, C.K.

1989-01-01

We have found that running electrostatic particle codes relatively large ω ce Δt in some circumstances does not significantly affect the physical results. We first present results from a single particle mover finding the correct first order drifts for large ω ce Δt. We then characterize the numerical orbit of the Boris algorithm for rotation when ω ce Δt much-gt 1. Next, an analysis of the guiding center motion is given showing why the first order drift is retained at large ω ce Δt. Lastly, we present a plasma simulation of a one dimensional cross field sheath, with large and small ω ce Δt, with very little difference in the results. 15 refs., 7 figs., 1 tab

The Absolute Reflectance and New Calibration Site of the Moon

Science.gov (United States)

Wu, Yunzhao; Wang, Zhenchao; Cai, Wei; Lu, Yu

2018-05-01

How bright the Moon is forms a simple but fundamental and important question. Although numerous efforts have been made to answer this question such as use of sophisticated electro-optical measurements and suggestions for calibration sites, the answer is still debated. An in situ measurement with a calibration panel on the surface of the Moon is crucial for obtaining the accurate absolute reflectance and resolving the debate. China’s Chang’E-3 (CE-3) “Yutu” rover accomplished this type of measurement using the Visible-Near Infrared Spectrometer (VNIS). The measurements of the VNIS, which were at large emission and phase angles, complement existing measurements for the range of photometric geometry. The in situ reflectance shows that the CE-3 landing site is very dark with an average reflectance of 3.86% in the visible bands. The results are compared with recent mission instruments: the Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC), the Spectral Profiler (SP) on board the SELENE, the Moon Mineralogy Mapper (M3) on board the Chandrayaan-1, and the Chang’E-1 Interference Imaging Spectrometer (IIM). The differences in the measurements of these instruments are very large and indicate inherent differences in their absolute calibration. The M3 and IIM measurements are smaller than LROC WAC and SP, and the VNIS measurement falls between these two pairs. When using the Moon as a radiance source for the on-orbit calibration of spacecraft instruments, one should be cautious about the data. We propose that the CE-3 landing site, a young and homogeneous surface, should serve as the new calibration site.

On the response of Y 3Al 5O 12: Ce (YAG: Ce) powder scintillating screens to medical imaging X-rays

Science.gov (United States)

Kandarakis, I.; Cavouras, D.; Sianoudis, I.; Nikolopoulos, D.; Episkopakis, A.; Linardatos, D.; Margetis, D.; Nirgianaki, E.; Roussou, M.; Melissaropoulos, P.; Kalivas, N.; Kalatzis, I.; Kourkoutas, K.; Dimitropoulos, N.; Louizi, A.; Nomicos, C.; Panayiotakis, G.

2005-02-01

The aim of this study was to examine Y 3Al 5O 12:Ce (also known as YAG:Ce) powder scintillator under X-ray imaging conditions. This material shows a very fast scintillation decay time and it has never been used in X-ray medical imaging. In the present study various scintillator layers (screens) with coating thickness ranging from 13 to 166 mg/cm 2 were prepared in our laboratory by sedimentation of Y 3Al 5O 12: Ce powder. Optical emission spectra and light emission efficiency (spectrum area over X-ray exposure) of the layers were measured under X-ray excitation using X-ray tube voltages (80-120 kVp) often employed in general medical radiography and fluoroscopy. Spectral compatibility with various optical photon detectors (photodiodes, photocathodes, charge coupled devices, films) and intrinsic conversion efficiency values were determined using emission spectrum data. In addition, parameters related to X-ray detection, energy absorption efficiency and K-fluorescence characteristic emission were calculated. A theoretical model describing radiation and light transfer through scattering media was used to fit experimental data. Intrinsic conversion efficiency (η≈0.03-0.05) and light attenuation coefficients (σ≈26.5 cm/g) were derived through this fitting. Y 3Al 5O 12:Ce showed peak emission in the wavelength range 530-550 nm. The light emission efficiency was found to be maximum for the 107 mg/cm 2 layer. Due to its "green" emission spectrum, Y 3Al 5O 12:Ce showed excellent compatibility (of the order of 0.9) with the sensitivity of many currently used photodetectors. Taking into account its very fast response Y 3Al 5O 12:Ce could be considered for application in X-ray imaging especially in various digital detectors.

On the response of Y3Al5O12: Ce (YAG: Ce) powder scintillating screens to medical imaging X-rays

International Nuclear Information System (INIS)

Kandarakis, I.; Cavouras, D.; Sianoudis, I.; Nikolopoulos, D.; Episkopakis, A.; Linardatos, D.; Margetis, D.; Nirgianaki, E.; Roussou, M.; Melissaropoulos, P.; Kalivas, N.; Kalatzis, I.; Kourkoutas, K.; Dimitropoulos, N.; Louizi, A.; Nomicos, C.; Panayiotakis, G.

2005-01-01

The aim of this study was to examine Y 3 Al 5 O 12 :Ce (also known as YAG:Ce) powder scintillator under X-ray imaging conditions. This material shows a very fast scintillation decay time and it has never been used in X-ray medical imaging. In the present study various scintillator layers (screens) with coating thickness ranging from 13 to 166mg/cm 2 were prepared in our laboratory by sedimentation of Y 3 Al 5 O 12 : Ce powder. Optical emission spectra and light emission efficiency (spectrum area over X-ray exposure) of the layers were measured under X-ray excitation using X-ray tube voltages (80-120kVp) often employed in general medical radiography and fluoroscopy. Spectral compatibility with various optical photon detectors (photodiodes, photocathodes, charge coupled devices, films) and intrinsic conversion efficiency values were determined using emission spectrum data. In addition, parameters related to X-ray detection, energy absorption efficiency and K-fluorescence characteristic emission were calculated. A theoretical model describing radiation and light transfer through scattering media was used to fit experimental data. Intrinsic conversion efficiency (ηC ∼0.03-0.05) and light attenuation coefficients (σ∼26.5cm 2 /g) were derived through this fitting. Y 3 Al 5 O 12 :Ce showed peak emission in the wavelength range 530-550nm. The light emission efficiency was found to be maximum for the 107mg/cm 2 layer. Due to its 'green' emission spectrum, Y 3 Al 5 O 12 :Ce showed excellent compatibility (of the order of 0.9) with the sensitivity of many currently used photodetectors. Taking into account its very fast response Y 3 Al 5 O 12 :Ce could be considered for application in X-ray imaging especially in various digital detectors

The Fermi surface of CeSb

International Nuclear Information System (INIS)

Crabtree, G.W.; Aoki, H.; Joss, W.; Hulliger, F.

1987-01-01

This paper uses accurate Fermi surface measurements as a test of hybridization models in CeSb. Detailed measurements of the Fermi surface geometry and effective masses are presented which show a number of unusual properties associated with the magnetic structure and anisotropy. Measurements are compared with predictions of a band structure in which the f-electron is assumed to be local, interacting with the conduction electrons only through anisotropic Coulomb and exchange interactions. This model reproduces all the unusual features observed in the measurements and suggests that hybridization is not essential to describing the electronic properties of CeSb

Photoluminescence analysis of Ce3+:Zn2SiO4 & Li++ Ce3+:Zn2SiO4: phosphors by a sol-gel method

Science.gov (United States)

Babu, B. Chandra; Vandana, C. Sai; Guravamma, J.; Rudramadevi, B. Hemalatha; Buddhudu, S.

2015-06-01

Here, we report on the development and photoluminescence analysis of Zn2SiO4, Ce3+:Zn2SiO4 & Li+ + Ce3+: Zn2SiO4 novel powder phosphors prepared by a sol-gel technique. The total amount of Ce3+ ions was kept constant in this experiment at 0.05 mol% total doping. The excitation and emission spectra of undoped (Zn2SiO4) and Ce3+ doped Zn2SiO4 and 0.05 mol% Li+ co-doped samples have been investigated. Cerium doped Zn2SiO4 powder phosphors had broad blue emission corresponding to the 2D3/2→2FJ transition at 443nm. Stable green-yellow-red emission has been observed from Zn2SiO4 host matrix and also we have been observed the enhanced luminescence of Li+ co-doped Zn2SiO4:Ce3+. Excitation and emission spectra of these blue luminescent phosphors have been analyzed in evaluating their potential as luminescent screen coating phosphors.

Intermediate Ce{sup 3+} defect level induced photoluminescence and third-order nonlinear optical effects in TiO{sub 2}-CeO{sub 2} nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Divya, S.; Nampoori, V.P.N.; Radhakrishnan, P.; Mujeeb, A. [Cochin University of Science and Technology, International School of Photonics, Cochin, Kerala (India)

2014-02-15

We report on the linear and nonlinear optical studies of TiO{sub 2}-CeO{sub 2} nanocomposites. It was found that the band gap of the nanocomposite can be tuned by varying Ce/Ti content. Nonlinear absorption characteristics of these samples were studied by employing open aperture Z-scan technique using an Nd:YAG laser (532 nm, 7 ns, 10 Hz). It has been observed that as the CeO{sub 2} amount increases, band gap of the nanocomposites decreases and the reason proposed for the change in band gap is the smudging of localised states of Ce{sup 3+} into the forbidden energy gap, thus acting as the intermediate state. Fluorescence studies confirmed the above argument. Nonlinear investigation revealed that with increase in the CeO{sub 2} amount, the two-photon absorption coefficient increased due to the modification of TiO{sub 2} dipole symmetry. Suitable candidature of the nanocomposites for the fabrication of nonlinear optical devices was proved by determining the optical limiting threshold. (orig.)

/sup 144/Ce in tissue of beagle dogs after inhalation of CeCl/sub 3/ with special emphasis on endocrine glands and reproductive organs

Energy Technology Data Exchange (ETDEWEB)

Cuddihy, R G; Boecker, B B; McClellan, R O; Kanapilly, G M [Lovelace Foundation for Medical Education and Research, Albuquerque, N.Mex. (USA)

1976-01-01

Beagle dogs inhaled aerosols containing /sup 144/CeCl/sub 3/. Deposition of /sup 144/Ce in tissues was determined in serially sacrificed dogs to characterize radiation dose patterns at early times after exposure. Uptakes of /sup 144/Ce in endocrine glands and reproductive organs were also measured; radiation doses were calculated and those doses were compared with the doses to the major organs of deposition - lung, liver and skeleton. Integrated radiation doses in pituitary and adrenal glands, pancreas, ovaries, testes, prostate and uterus were less than 2 % of those in lung and liver, while the thyroid dose was about 30 % of the dose in liver. These findings were consistent with previously reported biological responses in beagle dogs exposed to high levels of /sup 144/CeCl/sub 3/ wherein no radiation effects related to endocrine glands or the reproductive system have been observed. Use of these results in predicting the dosimetry of /sup 144/Ce in exposed humans re-emphasized the importance of radiation damage to lung, liver, skeleton and gastrointestinal tract compared to other organ systems.

Nonstoichiometry and stability in water of undoped SrCeO3

Directory of Open Access Journals (Sweden)

Jurado, J. R.

2003-10-01

Full Text Available Strontium cerate is the parent phase of an important class of proton-conducting perovskites with various potential technological applications. Phase formation and structure of SrCeO3 with Sr:Ce nonstoichiometry have been investigated for the series, Sr1±xCeO3±δ (0.98 ≤ x ≤ 1.04. Analyses by EPMA (electron probe micro analysis and X-ray diffraction (XRD indicate that, for samples sintered at 1350°C, the main phase is Sr-rich for all x. The accommodation of excess SrO in the bulk phase and/or intergranular regions is discussed. The stability of nominally stoichiometric SrCeO3 was examined in an atmosphere of high water vapour partial pressure (pH2O for 2 hours, degrading to Sr(OH2.H2O and CeO2 for pH2O ≥ 3.6atm.La fase SrCeO3 da origen a una importante familia de perovskitas conductoras protónicas con potenciales aplicaciones tecnológicas. En este trabajo se estudia la formación de la fase y la estructura de SrCeO3 con la relación Sr:Ce no estequiométrica para la serie Sr1±xCeO3±δ (0.98 ≤ x ≤ 1.04. Los análisis por microsonda (EPMA y difracción de rayos X (DRX indican que en las muestras sinterizadas a 1350°C, la fase principal es rica en estroncio para todo valor de x. Se discute la posible ubicación del exceso de SrO tanto en la región intergranular como en el propio grano. También se examina la estabilidad de la composición con estequiometría nominal SrCeO3 en una atmosfera con una alta presión de vapor de agua (pH2O, observándose que la degradación a Sr(OH2.H2O y CeO2 ocurre a pH2O ≥ 3.6atm (expuesto durante 2 horas.

Synthesis, characterization, and ecotoxicity of CeO{sub 2} nanoparticles with differing properties

Energy Technology Data Exchange (ETDEWEB)

Alam, Bushra [Aero Shade Technologies Inc (United States); Philippe, Allan, E-mail: philippe@uni-landau.de; Rosenfeldt, Ricki R.; Seitz, Frank [University of Koblenz-Landau, Group of Environmental and Soil Chemistry, Institute for Environmental Sciences (Germany); Dey, Sonal [SUNY Polytechnic Institute, Colleges of Nanoscale Science and Engineering (United States); Bundschuh, Mirco; Schaumann, Gabriele E. [University of Koblenz-Landau, Group of Environmental and Soil Chemistry, Institute for Environmental Sciences (Germany); Brenner, Sara A. [SUNY Polytechnic Institute, Colleges of Nanoscale Science and Engineering (United States)

2016-10-15

CeO{sub 2} nanoparticles with various characteristics find an increasing number of applications in the electronic, medical, and other industries and are therefore likely released in the environment. This calls for investigations linking the physicochemical properties of these particles with their potential environmental impacts. In this study, CeO{sub 2} nanoparticle powders were prepared using three different precursors [Ce(NO{sub 3}){sub 3}, CeCl{sub 3}, and Ce(CH{sub 3}COO){sub 3}] and annealing temperatures (300, 500, and 700 °C). This procedure resulted in nine different types of nanoparticles with differing size (5–90 nm), morphology, surface Ce{sup 3+}/Ce{sup 4+} ratio, and slightly different crystal structures as characterized using transmission electron microscopy, dynamic light scattering, X-ray photoelectron spectroscopy, and X-ray diffraction measurements with Rietveld refinement. These CeO{sub 2} nanoparticles underwent toxicity testing at concentrations up to 64 mg L{sup −1} using Daphnia magna. Toxic effects were observed for three particle types with EC50 values between 5 and 64 mg L{sup −1}. No clear correlation was observed between the physicochemical properties (size, shape, oxygen occupancy, Ce{sup 3+}/Ce{sup 4+} ratio) of the nanoparticles and their toxicity. However, toxicity was correlated with the amount of Ce remaining suspended in the test medium after 24 h. This indicated that toxic effects may depend on the colloidal stability of CeO{sub 2} nanoparticles during the first day of exposure. Therefore, being readily suspended and remaining stable for several days in the aquatic media increases the likelihood that CeO{sub 2} nanoparticles will cause unwanted adverse effects.

Luminescence properties of LiPrxCe1-xP4O12

International Nuclear Information System (INIS)

Shalapska, T.; Stryganyuka, G.; Trotsc, D.; Demkiv, T.; Gektin, A.; Voloshinovskii, A.; Dorenbos, P.

2010-01-01

LiPr 1-x Ce x P 4 O 12 (x=0, 0.002, 0.02; 0.1) powder samples were prepared using the melt solution technique. Luminescent parameters of LiPr 1-x Ce x P 4 O 12 phosphors have been investigated under ultraviolet-vacuum ultraviolet (3-12 eV) synchrotron radiation and X-rays excitation at room and near liquid He temperatures. Excitation luminescence spectra of Ce 3+ emission, luminescent spectra and decay curves from the lower excited state levels of the 4f 1 5d 1 and 5d 1 electronic configuration of the Pr 3+ and Ce 3+ , respectively, clearly indicate energy transfer from Pr 3+ to Ce 3+ . Energy migration proceeds via the Pr-sublattice followed by nonradiation transfer from Pr 3+ to Ce 3+ ions.

ETUDE PAR DFT+U DE L’INTERACTION Ni-CeO2

Directory of Open Access Journals (Sweden)

Z CHAFI

2010-12-01

Full Text Available L’étude de l’interaction Ni-CeO2 a été entreprise en utilisant une méthode ab initio basée sur la DFT+U. Dans une première étape, les valeurs du paramètre d’Hubbard, Ueff, ont été déterminées après ajustement du paramètre de maille et de l’énergie de gap du volume de l’oxyde de cérium. Elles sont respectivement de 3 et 5 eV pour les approximations GGA et LDA. Nous avons ensuite étudié d’une part la possibilité d’insérer le nickel atomique dans le volume de CeO2. D’autre part, nous avons testé les effets de l’insertion et l’adsorption de Ni dans les surfaces les plus stables (111 et (110 de CeO2. Les résultats des calculs DFT+U sont en bon accord avec ceux que nous avons précédemment trouvé en utilisant un calcul DFT concernant les sites favorables de l’atome de nickel et le nombre de liaisons. Toutefois, l’approximation LDA+5 eV, a permis d’obtenir des énergies plus favorables ainsi que des distances comparables à celles observées expérimentalement à l’interface métal/oxyde dans les catalyseurs Ni/CeO2 synthétisés sous irradiation. Une expansion du volume est observée lors de l’insertion du nickel dans le volume de l’oxyde de cérium. Concernant l’adsorption sur les surfaces, la meilleure énergie est trouvée dans le cas où l’atome de nickel est situé en position bridge entre deux atomes d’oxygène sur la surface (110. Finalement, les calculs montrent que le nickel s’insère plus facilement dans la surface (110 avec une meilleure énergie d’insertion, obtenue par l’approximation LDA+5 eV, de 4,071 eV.

Ethylene Glycol Adsorption and Reaction over CeOX(111) Thin Films

Energy Technology Data Exchange (ETDEWEB)

T Chen; D Mullins

2011-12-31

This study reports the interaction of ethylene glycol with well-ordered CeO{sub x}(111) thin film surfaces. Ethylene glycol initially adsorbs on fully oxidized CeO{sub 2}(111) and reduced CeO{sub 2-x}(111) through the formation of one C-O-Ce bond and then forms a second alkoxy bond after annealing. On fully oxidized CeO{sub 2}(111) both recombination of ethylene glycol and water desorption occur at low temperature leaving stable -OCH{sub 2}CH{sub 2}O- (ethylenedioxy) intermediates and oxygen vacancies on the surface. This ethylenedioxy intermediate goes through C-C bond scission to produce formate species which then react to produce CO and CO{sub 2}. The formation of water results in the reduction of the ceria. On a reduced CeO{sub 2-x}(111) surface the reaction selectivity shifts toward a dehydration process. The ethylenedioxy intermediate decomposes by breaking a C-O bond and converts into an enolate species. Similar to the reaction of acetaldehyde on reduced CeO{sub 2-x}(111), the enolate reacts to produce acetaldehyde, acetylene, and ethylene. The loss of O from ethylene glycol leads to a small amount of oxidation of the reduced ceria.

Experimental and theoretical investigations for site preference and anisotropic size change of RE{sub 11}Ge{sub 4}In{sub 6−x}M{sub x} (RE = La, Ce; M = Li, Ge; x = 1, 1.96)

Energy Technology Data Exchange (ETDEWEB)

Jeon, Beom-Yong; Jeon, Jieun [Department of Chemistry, Chungbuk National University, Cheongju, Chungbuk 361-763 (Korea, Republic of); Lee, Junseong [Department of Chemistry, Chonnam National University, Gwangju, Chonnam 500-757 (Korea, Republic of); Kim, Jongsik [Department of Chemistry, Dong-A University, Pusan 604-714 (Korea, Republic of); You, Tae-Soo [Department of Chemistry, Chungbuk National University, Cheongju, Chungbuk 361-763 (Korea, Republic of)

2015-01-25

Graphical abstract: Reported is experimental and theoretical studies to understand the site-preference between anionic elements and the anisotropic size-change of the 3-D anionic frameworks of two polar intermetallic compounds in the RE{sub 11}Ge{sub 4}In{sub 6−x}M{sub x} (RE = La, Ce; M = Li, Ge; x = 1, 1.96) phase. Indium atoms with a smaller electronegativity prefer to occupy the “dumbbell-site” having the smaller QVAL value, and the anisotropic size-change of the anionic framework in La{sub 11}Ge{sub 4}In{sub 5.00(1)}Li{sub 1.00} is rationalized by using various COHP curves analyses. - Highlights: • Site-preference between anions was elucidated by the QVAL value of each site. • Ten models with different atomic orderings were examined by coloring problems. • COHP curves explained the anisotropic size-change of La{sub 11}Ge{sub 4}In{sub 5.00(1)}Li{sub 1.00}. - Abstract: Two polar intermetallic compounds in the RE{sub 11}Ge{sub 4}In{sub 6−x}M{sub x} (RE = La, Ce; M = Li, Ge; x = 1, 1.96) series have been synthesized by conventional high-temperature reactions and characterized by both single-crystal and powder X-ray diffractions. Both compounds crystallized in the tetragonal crystal system (space group I4/mmm, Z = 4, Pearson symbol tI84) with nine crystallographically independent atomic positions in the asymmetric unit and adopted the Sm{sub 11}Ge{sub 4}In{sub 6}-type structure, which can be considered as an ordered version of the Ho{sub 11}Ge{sub 10}-type. The lattice parameters are a = 11.8370(4) Å and c = 17.2308(7) Å for La{sub 11}Ge{sub 4}In{sub 5.00(1)}Li{sub 1.00}; a = 11.8892(4) Å, c = 16.5736(7) Å for Ce{sub 11}Ge{sub 5.96(3)}In{sub 4.04}. The overall crystal structures of two isotypic compounds can be described as a combination of the cage-shaped 3-dimensional (3-D) anionic framework and three different types of cationic polyhedra filling the inside of the 3-D frameworks. Anionic elements consisting of the frameworks indicate the

Novel hydrogen decrepitation behaviors of (La, Ce)-Fe-B strips

Science.gov (United States)

Jin, Jiaying; Bai, Guohua; Zhang, Yujing; Peng, Baixing; Liu, Yongsheng; Ma, Tianyu; Yan, Mi

2018-05-01

La and Ce substitution for Nd in the 2:14:1-type sintered magnet is of commercial interest to reduce the material cost and to balance the utilization of rare earth (RE) sources. As hydrogen decrepitation (HD) is widely utilized to prepare the magnetic powders during magnets fabrication, incorporating La and Ce into the Nd-Fe-B permanent magnets, however, may exert complex influences on the decrepitation behavior. In the present work, through a comparative study of the HD behaviors between the (La, Ce)-Fe-B strips and the conventional Nd-Fe-B ones, we find that similar to the Nd-Fe-B system, increasing hydrogen pressures from 2.5 to 5.5 MPa do not break the 2:14:1 tetragonal structure of (La, Ce)-Fe-B strips. The enhanced hydrogen absorption behaviors are observed with increasing pressure, which are still inferior to that of the Nd-Fe-B strips. This should be ascribed to the higher oxygen affinity of La and Ce than that of Nd, leading to the decreased amount of active RE-rich phase and limited hydrogen diffusion channel. As a result, the hydrogen absorption of 2:14:1 matrix phase is significantly suppressed, dramatically weakening the exothermic effect. This finding suggests that La and Ce with stable 2:14:1 tetragonal structure upon HD process are promising alternatives for Nd, despite that more precise oxygen control is necessary for the microstructure modification and magnetic performance enhancement of (La, Ce)-Fe-B sintered magnets.

Investigation into kinetics of redox interaction in the system Ce(4). beta. -diketonate-additional ligand

Energy Technology Data Exchange (ETDEWEB)

Anufrieva, S.I.; Snezhko, N.I.; Pechurova, N.I.; Martynenko, L.N.; Spitsyn, V.I. (Moskovskij Gosudarstvennyj Univ. (USSR))

1981-07-01

The rate of reduction of ..beta..-diketonate complexes of Ce(4) to Ce(3) ..beta..-diketonates in benzene solution in the presence and in the absence of additional ligands is studied using spectrophotometry. The rate of reduction of Ce(4) ..beta..-diketonates increases in the series Ce(TTFA)/sub 4/<Ce(DPM)/sub 4/<Ce(DBM)/sub 4/<Ce(BA)/sub 4/<Ce(AA)/sub 4/ (TTFA - thenoyltrifluoroacetone, DPM- --dipivaloylmethane, DBM - dibenzoylmethane, BA benzoylacetone, AA - acetylacetone). The studied phosphorus-containing additional ligands as to their effect on the rate of Ce (4) reduction can be arranged in the following order: trioctylphosphine oxide>triphenylphosphine oxide>tributyl phosphate.

Non-aqueous CE-MS of cinchona alkaloids - characterizationof a novel CE-ESI-MS interface

DEFF Research Database (Denmark)

Hansen, Frederik André; Hansen, Steen Honoré; Petersen, Nickolaj J.

We have recently in our group at the University of Copenhagen developed a robust and simple sheatless CE-ESI-MS interface (capillary electrophoresis – electrospray ionization-mass spectrometry). In this presentation the interface is characterized and compared with HPLC-MS for studying...... a submicron fracture in the capillary close the ESI tip. The fracture provides a zero dead volume and excellent conducting properties due to the large amount of ions in the electric double layer. Electric current exceeding the upper limit of CE instrumentation of up to 300 µA can easily be obtained....... Furthermore, the increased conductivity of the buffer in the fracture generates field free pumping of the analytes towards the ESI spray tip. In this study the device was used to analyze the four major alkaloids (diastereomeric pairs of quinine/quinidine and cinchonine/cinchonidine) in Cinchona bark samples...

Molecular genotyping of Echinococcus granulosus using formalin-fixed paraffin-embedded preparations from human isolates in unusual tissue sites.

Science.gov (United States)

Hizem, A; M'rad, S; Oudni-M'rad, M; Mestiri, S; Hammedi, F; Mezhoud, H; Zakhama, A; Mokni, M; Babba, H

2016-07-01

Cystic echinococcosis (CE) caused by Echinococcus granulosus remains a serious problem worldwide for issues relating to public health and the economy. The most predominantly affected sites are the liver and the lungs, but other organs such as the heart, the spleen and the peritoneum can also be infected. Access to cysts from uncommon sites has limited genomic and molecular investigations. In the present study, genotypes of E. granulosus sensu lato were identified from formalin-fixed paraffin-embedded tissues (FF-PETs) implicated in human CE. Tissue samples were obtained from 57 patients with histologically confirmed CE. DNA samples were analysed using Egss 1 polymerase chain reaction (PCR) specific to the mitochondrial 12S rRNA gene of E. granulosus sensu stricto. All cysts were typed as E. granulosus sensu stricto with up to 35% of the liver and 16.6% of lungs being the most frequently infected, and up to 48.4% of samples being from rare sites. No correlation was found between cyst site and either the gender or the age of patients. This study demonstrates the possibility of exploiting atypical cysts using FF-PET samples and highlights the predominance of E. granulosus sensu stricto species in the Tunisian population, even in unusual infection sites.

Magnetism and superconductivity of CePt3Si and Ce1+xPt3+ySi1+z

International Nuclear Information System (INIS)

Motoyama, Gaku; Yamamoto, Suguru; Takezoe, Hiroaki; Oda, Yasukage; Ueda, Ko-ichi; Kohara, Takao

2006-01-01

We measured the dc magnetization, electrical resistivity, and ac magnetic susceptibility of a series of polycrystalline CePt 3 Si samples whose compositions vary slightly from the stoichiometric composition. The sample that showed the most distinct anitiferromagnetic transition at 2.2K was found to be Ce 1.01 Pt 3 Si annealed. This sample showed a clear bulk antiferromagnetic order at 2.2 K even in both electrical resistivity and dc magnetization measurements, although the characteristic change in dc magnetization at 2.2 K was found to be small and to be easily masked in other magnetic anomalies if they exist. Moreover, it had the largest residual resistivity ratio. We concluded that Ce 1.01 Pt 3 Si annealed has the intrinsic bulk properties of ideal CePt 3 Si. In addition, we revealed that some anomalies arise as a result of the variation in composition. One is a ferromagnetic anomaly at 3.0 K in the Pt-rich samples, and the other is an antiferromagnetic anomaly at 4.0 K in the Pt-poor samples. The two magnetic anomalies seemed to appear in small domains in the samples that exhibited an antiferromagnetic order at 2.2 K. To reveal the relationship between these magnetisms and superconductivity, we measured ac magnetic susceptibility down to ∼14mK. We found that the superconducting transition temperature is suppressed by the ferromagnetic anomaly. (author)

Properties of Ce-doped ITO films deposited on polymer substrate by DC magnetron sputtering

International Nuclear Information System (INIS)

Kang, Y.M.; Kwon, S.H.; Choi, J.H.; Cho, Y.J.; Song, P.K.

2010-01-01

Ce-doped indium tin oxide (ITO:Ce) films were deposited on flexible polyimide substrates by DC magnetron sputtering using ITO targets containing various CeO 2 contents (CeO 2 : 0, 0.5, 3.0, 4.0, 6.0 wt.%) at room temperature and post-annealed at 200 o C. The crystallinity of the ITO films decreased with increasing Ce content, and it led to a decrease in surface roughness. In addition, a relatively small change in resistance in dynamic stress mode was obtained for ITO:Ce films even after the annealing at high temperature (200 o C). The minimum resistivity of the amorphous ITO:Ce films was 3.96 x 10 -4 Ωcm, which was deposited using a 3.0 wt.% CeO 2 doped ITO target. The amorphous ITO:Ce films not only have comparable electrical properties to the polycrystalline films but also have a crystallization temperature > 200 o C. In addition, the amorphous ITO:Ce film showed stable mechanical properties in the bended state.

Room-temperature ferromagnetism in pure and Co doped CeO2 powders

International Nuclear Information System (INIS)

Wen Qiye; Zhang Huaiwu; Song Yuanqiang; Yang Qinghui; Zhu Hao; Xiao, John Q

2007-01-01

We report the room-temperature (RT) ferromagnetism (FM) observed in pure and Co doped CeO 2 powder. An insulating nonmagnetic CeO 2 single crystal, after grinding into fine powder, shows an RT-FM with a small magnetization of 0.0045 emu g -1 . However, the CeO 2 powder became paramagnetic after oxygen annealing, which strongly suggests an oxygen vacancy meditated FM ordering. Furthermore, by doping Co into CeO 2 powder the FM can significantly enhance through a F-centre exchange (FCE) coupling mechanism, in which both oxygen vacancies and magnetic ions are involved. As the Co content increases, the FM of Co doped CeO 2 initially increases to a maximum 0.47 emu g -1 , and then degrades very quickly. The complex correlation between the Co content and saturation magnetization was well interpreted by supposing the coexistence of three subsets of Co ions in CeO 2 . Our results reveal that the large RT-FM observed in Co doped CeO 2 powder originates from a combination effect of oxygen vacancies and transition metal doping

Mechanochemical synthesis of ultrafine Ce2S3 powder

International Nuclear Information System (INIS)

Tsuzuki, T.; McCormick, P.G.

1998-01-01

Full text: Rare earth sulphides have been receiving an increasing attraction for various applications including infrared window materials and magneto-optical devices. In particular, Ce 2 S 3 has been under intensive study for use as a red pigment to replace toxic cadmium sulfoselenide. The conventional method for synthesising Ce 2 S 3 is the sulphidization of the element or sesquioxide with hydrogen sulphide gas. However, the method usually requires a high-temperature process (>1000 deg C), and hence coarse particles larger than the optimal size of ∼ 2 S 3 powder by mechanochemical processing using X-ray diffraction spectroscopy, BET surface area analysis and transmission electron microscopy. Mechanical milling of the mixture of a cerium salt and an alkali/alkali-earth sulphide powders led to a solid state displacement reaction in a steady-state manner, forming Ce 2 S 3 nanoparticles in a salt by-product matrix. After a simple washing process to remove the salt by-product, ultrafine Ce 2 S 3 particles with sizes of 20 - 200 nm having an orthorhombic structure were obtained. Using a diluent and mechanically alloyed CaS nanoparticles in the starting powder, particles of only a cubic γ-Ce 2 S 3 phase with sizes of 10 - 80 nm were formed

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)

miRSponge: a manually curated database for experimentally supported miRNA sponges and ceRNAs.

Science.gov (United States)

Wang, Peng; Zhi, Hui; Zhang, Yunpeng; Liu, Yue; Zhang, Jizhou; Gao, Yue; Guo, Maoni; Ning, Shangwei; Li, Xia

2015-01-01

In this study, we describe miRSponge, a manually curated database, which aims at providing an experimentally supported resource for microRNA (miRNA) sponges. Recent evidence suggests that miRNAs are themselves regulated by competing endogenous RNAs (ceRNAs) or 'miRNA sponges' that contain miRNA binding sites. These competitive molecules can sequester miRNAs to prevent them interacting with their natural targets to play critical roles in various biological and pathological processes. It has become increasingly important to develop a high quality database to record and store ceRNA data to support future studies. To this end, we have established the experimentally supported miRSponge database that contains data on 599 miRNA-sponge interactions and 463 ceRNA relationships from 11 species following manual curating from nearly 1200 published articles. Database classes include endogenously generated molecules including coding genes, pseudogenes, long non-coding RNAs and circular RNAs, along with exogenously introduced molecules including viral RNAs and artificial engineered sponges. Approximately 70% of the interactions were identified experimentally in disease states. miRSponge provides a user-friendly interface for convenient browsing, retrieval and downloading of dataset. A submission page is also included to allow researchers to submit newly validated miRNA sponge data. Database URL: http://www.bio-bigdata.net/miRSponge. © The Author(s) 2015. Published by Oxford University Press.

Luminescence Properties of Ca19Ce(PO4)14:A (A = Eu3+/Tb3+/Mn2+) Phosphors with Abundant Colors: Abnormal Coexistence of Ce4+/3+-Eu3+ and Energy Transfer of Ce3+ → Tb3+/Mn2+ and Tb3+-Mn2.

Science.gov (United States)

Shang, Mengmeng; Liang, Sisi; Lian, Hongzhou; Lin, Jun

2017-06-05

A series of Eu 3+ /Tb 3+ /Mn 2+ -ion-doped Ca 19 Ce(PO 4 ) 14 (CCPO) phosphors have been prepared via the conventional high-temperature solid-state reaction process. Under UV radiation, the CCPO host presents a broad blue emission band from Ce 3+ ions, which are generated during the preparation process because of the formation of deficiency. The Eu 3+ -doped CCPO phosphors can exhibit magenta to red-orange emission as a result of the abnormal coexistence of Ce 3+ /Ce 4+ /Eu 3+ and the metal-metal charge-transfer (MMCT) effect between Ce 3+ and Eu 3+ . When Tb 3+ /Mn 2+ are doped into the hosts, the samples excited with 300 nm UV light present multicolor emissions due to energy transfer (ET) from the host (Ce 3+ ) to the activators with increasing activator concentrations. The emitting colors of CCPO:Tb 3+ phosphors can be tuned from blue to green, and the CCPO:Mn 2+ phosphors can emit red light. The ET mechanism from the host (Ce 3+ ) to Tb 3+ /Mn 2+ is demonstrated to be a dipole-quadrapole interaction for Ce 3+ → Tb 3+ and an exchange interaction for Ce 3+ → Mn 2+ in CCPO:Tb 3+ /Mn 2+ . Abundant emission colors containing white emission were obtained in the Tb 3+ - and Mn 2+ -codoped CCPO phosphors through control of the levels of doped Tb 3+ and Mn 2+ ions. The white-emitted CCPO:Tb 3+ /Mn 2+ phosphor exhibited excellent thermal stability. The photoluminescence properties have shown that these materials might have potential for UV-pumped white-light-emitting diodes.

CE microchips: an opened gate to food analysis.

Science.gov (United States)

Escarpa, Alberto; González, María Cristina; Crevillén, Agustín González; Blasco, Antonio Javier

2007-03-01

CE microchips are the first generation of micrototal analysis systems (-TAS) emerging in the miniaturization scene of food analysis. CE microchips for food analysis are fabricated in both glass and polymer materials, such as PDMS and poly(methyl methacrylate) (PMMA), and use simple layouts of simple and double T crosses. Nowadays, the detection route preferred is electrochemical in both, amperometry and conductivity modes, using end-channel and contactless configurations, respectively. Food applications using CE microchips are now emerging since food samples present complex matrices, the selectivity being a very important challenge because the total integration of analytical steps into microchip format is very difficult. As a consequence, the first contributions that have recently appeared in the relevant literature are based primarily on fast separations of analytes of high food significance. These protocols are combined with different strategies to achieve selectivity using a suitable nonextensive sample preparation and/or strategically choosing detection routes. Polyphenolic compounds, amino acids, preservatives, and organic and inorganic ions have been studied using CE microchips. Thus, new and exciting future expectations arise in the domain of food analysis. However, several drawbacks could easily be found and assumed within the miniaturization map.

32 CFR Appendix B to Part 247 - CE Publications

Science.gov (United States)

2010-07-01

... dining at a restaurant or attending a musical performance) of a commercial organization whose primary... potentially become the CE contractor. Upon evaluation of the competing proposals by the Source Selection Advisory Committee (SSAC) and selection of a winner by the selecting official, the CE contract shall be...

Room-temperature synthesis and characterization of porous CeO{sub 2} thin films

Energy Technology Data Exchange (ETDEWEB)

Chu, Dewei; Masuda, Yoshitake; Ohji, Tatsuki; Kato, Kazumi [National Institute of Advanced Industrial Science and Technology (AIST), Anagahora, Shimoshidami, Moriyama-ku, Nagoya (Japan)

2012-01-15

CeO{sub 2} thin films with hexagonal-shaped pores were successfully prepared by a facile electrodeposition at room temperature combined with an etching process. By using electrodeposited ZnO nanorods as a soft template, the morphology, and microstructure of the CeO{sub 2} could be controlled. TEM observation indicated that as-prepared CeO{sub 2} film is composed of nanocrystals with average size of several nanometers, while XPS analysis showed the coexistence of Ce{sup 3+} and Ce{sup 4+} in the film. The photoluminescence properties of CeO{sub 2} films were measured, which showed much higher sensitivity compared to bare substrate. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Luminescence characteristics of Pb2+ centres in undoped and Ce3+-doped Lu3Al5O12 single-crystalline films and Pb2+→Ce3+ energy transfer processes

International Nuclear Information System (INIS)

Babin, V.; Gorbenko, V.; Makhov, A.; Mares, J.A.; Nikl, M.; Zazubovich, S.; Zorenko, Yu.

2007-01-01

At 4.2-350 K, the steady-state and time-resolved emission and excitation spectra and luminescence decay kinetics were studied under excitation in the 2.5-15 eV energy range for the undoped and Ce 3+ -doped Lu 3 Al 5 O 12 (LuAG) single-crystalline films grown by liquid phase epitaxy method from the PbO-based flux. The spectral bands arising from the single Pb 2+ -based centres were identified. The processes of energy transfer from the host lattice to Pb 2+ and Ce 3+ ions and from Pb 2+ to Ce 3+ ions were investigated. Competition between Pb 2+ and Ce 3+ ions in the processes of energy transfer from the LuAG crystal lattice was evidenced especially in the exciton absorption region. Due to overlap of the 3.61 eV emission band of Pb 2+ centres with the 3.6 eV absorption band of Ce 3+ centres, an effective nonradiative energy transfer from Pb 2+ ions to Ce 3+ ions takes place, resulting in the appearance of slower component in the luminescence decay kinetics of Ce 3+ centres and decrease of the Ce 3+ -related luminescence intensity

SP@CE - An SP-based programming model for consumer electronics streaming applications

NARCIS (Netherlands)

Varbanescu, Ana Lucia; Nijhuis, Maik; Escribano, Arturo González; Sips, Henk; Bos, Herbert; Bal, Henri

2007-01-01

Efficient programming of multimedia streaming applications for Consumer Electronics (CE) devices is not trivial. As a solution for this problem, we present SP@CE, a novel programming model designed to balance the specific requirements of CE streaming applications with the simplicity and efficiency

Application of CE-ICP-MS and CE-ESI-MS/MS for identification of Zn-binding ligands in Goji berries extracts.

Science.gov (United States)

Ruzik, Lena; Kwiatkowski, Piotr

2018-06-01

The identification of groups of ligands binding metals is a crucial issue for the better understanding of their bioaccessibility. In the current study, we have intended an approach for identification of Zn-binding ligands based on using capillary electrophoresis combined with inductively coupled plasma mass spectrometry (CE-ICP-MS) and tandem electrospray ionization mass spectrometry (CE-ESI-MS/MS). The approach, which featured the use of the coupling of capillary electrophoresis with inductively coupled plasma mass spectrometry allows to separate and observe zinc ions present in complexes with respect to their size and charge and to identify nine compounds with zinc isotopic profile. CE-ICP-MS provides us with information about presence of zinc species and elemental information about zinc distribution. CE-ESI-MS/MS provide us with information about the most favorable Zn binding ligands: amino acids, flavonols, stilbenoids, fenolic acids and carotenoids. The presented work is the continuation of previous studies based on using LC-ESI-MS/MS, though, now we presented a new solutions with the possibility of changing detectors without changing the separation techniques, what is important without re-optimizing the method. The new presented method allows to identify the zinc-binding ligands in shorter time. Copyright © 2018 Elsevier B.V. All rights reserved.

Scintillation properties of selected oxide monocrystals activated with Ce and Pr

Science.gov (United States)

Wojtowicz, Andrzej J.; Drozdowski, Winicjusz; Wisniewski, Dariusz; Lefaucheur, Jean-Luc; Galazka, Zbigniew; Gou, Zhenhui; Lukasiewicz, Tadeusz; Kisielewski, Jaroslaw

2006-01-01

In the last 10-15 years there has been a significant effort toward development of new, more efficient and faster materials for detection of ionizing radiation. A growing demand for better scintillator crystals for detection of 511 keV gamma particles has been due mostly to recent advances in modern imaging systems employing positron emitting radionuclides for medical diagnostics in neurology, oncology and cardiology. While older imaging systems were almost exclusively based on BGO and NaI:Tl crystals the new systems, e.g., ECAT Accel, developed by Siemens/CTI, are based on recently discovered and developed LSO (Lu 2SiO 5:Ce, Ce-activated lutetium oxyorthosilicate) crystals. Interestingly, despite very good properties of LSO, there still is a strong drive toward development of new scintillator crystals that would show even better performance and characteristics. In this presentation we shall review spectroscopic and scintillator characterization of new complex oxide crystals, namely LSO, LYSO, YAG, LuAP (LuAlO 3, lutetium aluminate perovskite) and LuYAP activated with Ce and Pr. The LSO:Ce crystals have been grown by CTI Inc (USA), LYSO:Ce, LuAP:Ce and LuYAP:Ce crystals have been grown by Photonic Materials Ltd., Scotland (PML is the only company providing large LuAP:Ce crystals on a commercial scale), while YAG:Pr and LuAP:Pr crystals have been grown by Institute of Electronic Materials Technology (Poland). All these crystals have been characterized at Institute of Physics, N. Copernicus University (Poland). We will review and compare results of measurements of radioluminescence, VUV spectroscopy, scintillation light yields, scintillation time profiles and low temperature thermoluminescence performed on these crystals. We will demonstrate that all experiments clearly indicate that there is a significant room for improvement of LuAP, LuYAP and YAG. While both Ce-activated LSO and LYSO perform very well, we also note that LuYAP:Ce, LuAP:Ce and YAG:Pr offer some

Optical properties of CeO 2 thin films

Indian Academy of Sciences (India)

Cerium oxide (CeO2) thin films have been prepared by electron beam evaporation technique onto glass substrate at a pressure of about 6 × 10-6 Torr. The thickness of CeO2 films ranges from 140–180 nm. The optical properties of cerium oxide films are studied in the wavelength range of 200–850 nm. The film is highly ...

Facile preparation of self-healing superhydrophobic CeO2 surface by electrochemical processes

Science.gov (United States)

Nakayama, Katsutoshi; Hiraga, Takuya; Zhu, Chunyu; Tsuji, Etsushi; Aoki, Yoshitaka; Habazaki, Hiroki

2017-11-01

Herein we report simple electrochemical processes to fabricate a self-healing superhydrophobic CeO2 coating on Type 304 stainless steel. The CeO2 surface anodically deposited on flat stainless steel surface is hydrophilic, although high temperature-sintered and sputter-deposited CeO2 surface was reported to be hydrophobic. The anodically deposited hydrophilic CeO2 surface is transformed to hydrophobic during air exposure. Specific accumulation of contaminant hydrocarbon on the CeO2 surface is responsible for the transformation to hydrophobic state. The deposition of CeO2 on hierarchically rough stainless steel surface produces superhydrophobic CeO2 surface, which also shows self-healing ability; the surface changes to superhydrophilic after oxygen plasma treatment but superhydrophobic state is recovered repeatedly by air exposure. This work provides a facile method for preparing a self-healing superhydrophobic surface using practical electrochemical processes.

The investigation of Ce doped ZnO crystal: The electronic, optical and magnetic properties

Science.gov (United States)

Wen, Jun-Qing; Zhang, Jian-Min; Qiu, Ze-Gang; Yang, Xu; Li, Zhi-Qin

2018-04-01

The electronic, optical and magnetic properties of Ce doped ZnO crystal have been studied by using first principles method. The research of formation energies show that Ce doped ZnO is energetically stable, and the formation energies reduce from 6.25% to 12.5% for Ce molar percentage. The energy band is still direct band gap after Ce doped, and band gap increases with the increase of Cesbnd Ce distance. The Fermi level moves upward into conduction band and the DOS moves to lower energy with the increase of Ce concentration, which showing the properties of n-type semiconductor. The calculated optical properties imply that Ce doped causes a red-shift of absorption peaks, and enhances the absorption of the visible light. The transition from ferromagnetic to antiferromagnetic has been found in Ce doped ZnO.

Diclofenac degradation in water by FeCeOx catalyzed H2O2: Influencing factors, mechanism and pathways.

Science.gov (United States)

Chong, Shan; Zhang, Guangming; Zhang, Nan; Liu, Yucan; Huang, Ting; Chang, Huazhen

2017-07-15

The degradation of diclofenac in a like Fenton system, FeCeO x -H 2 O 2 , was studied in details. The influencing factors, reaction kinetics, reaction mechanism and degradation pathways of diclofenac were investigated. The optimum conditions were at a solution pH of 5.0, H 2 O 2 concentration of 3.0mmol/L, diclofenac initial concentration of 0.07mmol/L, FeCeO x dosage of 0.5g/L, and 84% degradation of diclofenac was achieved within 40min. The kinetics of FeCeO x catalyzed H 2 O 2 process involved adsorption-dominating and degradation-dominating stages and fitted pseudo-second order model and pseudo-first order model, respectively. Singlet oxygen 1 O 2 was the primary intermediate oxidative species in the degradation process; superoxide radical anion O 2 - also participated in the reaction. The surface cerium and iron sites and the oxygen vacancies in the FeCeO x catalyst were proposed to play an important role in H 2 O 2 decomposition and active species generation. The detected intermediates were identified as hydroxylated derivatives (m/z of 310, 326 and 298), quinone imine compounds (m/z of 308, 278 and 264) and hydroxyl phenylamine (m/z of 178). The majority intermediates were hydroxylated derivatives and the minority was hydroxyl phenylamine. The degradation pathways were proposed to involve hydroxylation, decarboxylation, dehydrogenation and CN bond cleavage. Copyright © 2017 Elsevier B.V. All rights reserved.

Nuclear magnetic resonance investigation of the heavy fermion system Ce2CoAl7Ge4

Science.gov (United States)

Dioguardi, A. P.; Guzman, P.; Rosa, P. F. S.; Ghimire, N. J.; Eley, S.; Brown, S. E.; Thompson, J. D.; Bauer, E. D.; Ronning, F.

2017-12-01

We present nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements performed on single crystalline Ce2CoAl7Ge4 , a member of a recently discovered family of heavy fermion materials Ce2M Al7Ge4 (M =Co , Ir, Ni, or Pd). Previous measurements indicated a strong Kondo interaction as well as magnetic order below TM=1.8 K . Our NMR spectral measurements show that the Knight shift K is proportional to the bulk magnetic susceptibility χ at high temperatures. A clear Knight shift anomaly (K ¬∝χ ) is observed at coherence temperatures T*˜17.5 K for H0∥c ̂ and 10 K for H0∥a ̂ at the 59Co site, and T*˜12.5 K at the 27Al(3) site for H0∥a ̂ characteristic of the heavy fermion nature of this compound. At high temperatures, the 59Co NMR spin-lattice relaxation rate T1-1 is dominated by spin fluctuations of the 4 f local moments with a weak metallic background. The spin fluctuations probed by 59Co NMR are anisotropic and larger in the basal plane than in the c direction. Furthermore, we find (T1T K ) -1∝T-1 /2 at the 59Co site as expected for a Kondo system for T >T* and T >TK . 59Co NQR T1-1 measurements at low temperatures indicate slowing down of spin fluctuations above the magnetic ordering temperature TM˜1.8 K . A weak ferromagnetic character of fluctuations around q =0 is evidenced by an increase of χ T versus T above the magnetic ordering temperature. We also find good agreement between the observed and calculated electric field gradients at all observed sites.

Building novel Ag/CeO2 heterostructure for enhancing photocatalytic activity

International Nuclear Information System (INIS)

Leng, Qiang; Yang, Dezhi; Yang, Qi; Hu, Chenguo; Kang, Yue; Wang, Mingjun; Hashim, Muhammad

2015-01-01

Highlights: • Ag nanoparticle is designed to building Schottky heterojunction on CeO 2 nanocube. • The photocatalytic activity of Ag/CeO 2 heterostructure is much enhanced. • 95.33% of MB can be effectively degraded within half an hour. • Ag as acceptor of photoelectrons blocks the recombination of electron–hole pairs. - Abstract: Stable and recyclable photocatalysts with high efficiency to degrade organic contamination are important and widely demanded under the threat of the environment pollution. Ag/CeO 2 heterostructure is designed as a photocatalyst to degrade organic dye under the simulated sunlight. The catalytic activity of CeO 2 nanocubes (NCs) to degrade methylene blue (MB) is obviously enhanced when Ag nanoparticles (NPs) are deposited on the surface of them. The weight ratio of Ag and CeO 2 in forming high efficiency catalyst, the amount of Ag/CeO 2 catalyst used in degradation process, and the dye concentration and pH value of the initial MB solution are examined systematically. 95.33% of MB can be effectively degraded within half an hour when 50 mg of Ag/CeO 2 catalyst in an optimal weight ratio of 1:3, is added to the 100 mL of MB solution (c 0 = 1 × 10 −5 mol L −1 , pH 6.2). The mechanism of the enhanced catalytic activity of Ag/CeO 2 heterostructure is discussed. The photocatalytic degradation rate is found to obey pseudo-first-order kinetics equations according to Langmuir–Hinshelwood model. The intermediate products in different stages during the degradation of MB are analyzed

Analysis of the geomorphology surrounding the Chang'e-3 landing site

Science.gov (United States)

Li, Chun-Lai; Mu, Ling-Li; Zou, Xiao-Duan; Liu, Jian-Jun; Ren, Xin; Zeng, Xing-Guo; Yang, Yi-Man; Zhang, Zhou-Bin; Liu, Yu-Xuan; Zuo, Wei; Li, Han

2014-12-01

Chang'e-3 (CE-3) landed on the Mare Imbrium basin in the east part of Sinus Iridum (19.51°W, 44.12°N), which was China's first soft landing on the Moon and it started collecting data on the lunar surface environment. To better understand the environment of this region, this paper utilizes the available high-resolution topography data, image data and geological data to carry out a detailed analysis and research on the area surrounding the landing site (Sinus Iridum and 45 km×70 km of the landing area) as well as on the topography, landform, geology and lunar dust of the area surrounding the landing site. A general topographic analysis of the surrounding area is based on a digital elevation model and digital elevation model data acquired by Chang'e-2 that have high resolution; the geology analysis is based on lunar geological data published by USGS; the study on topographic factors and distribution of craters and rocks in the surrounding area covering 4 km×4 km or even smaller is based on images from the CE-3 landing camera and images from the topographic camera; an analysis is done of the effect of the CE-3 engine plume on the lunar surface by comparing images before and after the landing using data from the landing camera. A comprehensive analysis of the results shows that the landing site and its surrounding area are identified as typical lunar mare with flat topography. They are suitable for maneuvers by the rover, and are rich in geological phenomena and scientific targets, making it an ideal site for exploration.

An Update on Improvements to NiCE Support for RELAP-7

Energy Technology Data Exchange (ETDEWEB)

McCaskey, Alex [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Wojtowicz, Anna [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Deyton, Jordan H. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Patterson, Taylor C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Billings, Jay Jay [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2015-01-01

The Multiphysics Object-Oriented Simulation Environment (MOOSE) is a framework that facilitates the development of applications that rely on finite-element analysis to solve a coupled, nonlinear system of partial differential equations. RELAP-7 represents an update to the venerable RELAP-5 simulator that is built upon this framework and attempts to model the balance-of-plant concerns in a full nuclear plant. This report details the continued support and integration of RELAP-7 and the NEAMS Integrated Computational Environment (NiCE). RELAP-7 is fully supported by the NiCE due to on-going work to tightly integrate NiCE with the MOOSE framework, and subsequently the applications built upon it. NiCE development throughout the first quarter of FY15 has focused on improvements, bug fixes, and feature additions to existing MOOSE-based application support. Specifically, this report will focus on improvements to the NiCE MOOSE Model Builder, the MOOSE application job launcher, and the 3D Nuclear Plant Viewer. This report also includes a comprehensive tutorial that guides RELAP-7 users through the basic NiCE workflow: from input generation and 3D Plant modeling, to massively parallel job launch and post-simulation data visualization.

Isolation and functional characterization of CE1 binding proteins

Directory of Open Access Journals (Sweden)

Yu Ji-hyun

2010-12-01

Full Text Available Abstract Background Abscisic acid (ABA is a plant hormone that controls seed germination, protective responses to various abiotic stresses and seed maturation. The ABA-dependent processes entail changes in gene expression. Numerous genes are regulated by ABA, and promoter analyses of the genes revealed that cis-elements sharing the ACGTGGC consensus sequence are ubiquitous among ABA-regulated gene promoters. The importance of the core sequence, which is generally known as ABA response element (ABRE, has been demonstrated by various experiments, and its cognate transcription factors known as ABFs/AREBs have been identified. Although necessary, ABRE alone is not sufficient, and another cis-element known as "coupling element (CE" is required for full range ABA-regulation of gene expression. Several CEs are known. However, despite their importance, the cognate transcription factors mediating ABA response via CEs have not been reported to date. Here, we report the isolation of transcription factors that bind one of the coupling elements, CE1. Results To isolate CE1 binding proteins, we carried out yeast one-hybrid screens. Reporter genes containing a trimer of the CE1 element were prepared and introduced into a yeast strain. The yeast was transformed with library DNA that represents RNA isolated from ABA-treated Arabidopsis seedlings. From the screen of 3.6 million yeast transformants, we isolated 78 positive clones. Analysis of the clones revealed that a group of AP2/ERF domain proteins binds the CE1 element. We investigated their expression patterns and analyzed their overexpression lines to investigate the in vivo functions of the CE element binding factors (CEBFs. Here, we show that one of the CEBFs, AtERF13, confers ABA hypersensitivity in Arabidopsis, whereas two other CEBFs enhance sugar sensitivity. Conclusions Our results indicate that a group of AP2/ERF superfamily proteins interacts with CE1. Several CEBFs are known to mediate defense or

Isolation and functional characterization of CE1 binding proteins.

Science.gov (United States)

Lee, Sun-ji; Park, Ji Hye; Lee, Mi Hun; Yu, Ji-hyun; Kim, Soo Young

2010-12-16

Abscisic acid (ABA) is a plant hormone that controls seed germination, protective responses to various abiotic stresses and seed maturation. The ABA-dependent processes entail changes in gene expression. Numerous genes are regulated by ABA, and promoter analyses of the genes revealed that cis-elements sharing the ACGTGGC consensus sequence are ubiquitous among ABA-regulated gene promoters. The importance of the core sequence, which is generally known as ABA response element (ABRE), has been demonstrated by various experiments, and its cognate transcription factors known as ABFs/AREBs have been identified. Although necessary, ABRE alone is not sufficient, and another cis-element known as "coupling element (CE)" is required for full range ABA-regulation of gene expression. Several CEs are known. However, despite their importance, the cognate transcription factors mediating ABA response via CEs have not been reported to date. Here, we report the isolation of transcription factors that bind one of the coupling elements, CE1. To isolate CE1 binding proteins, we carried out yeast one-hybrid screens. Reporter genes containing a trimer of the CE1 element were prepared and introduced into a yeast strain. The yeast was transformed with library DNA that represents RNA isolated from ABA-treated Arabidopsis seedlings. From the screen of 3.6 million yeast transformants, we isolated 78 positive clones. Analysis of the clones revealed that a group of AP2/ERF domain proteins binds the CE1 element. We investigated their expression patterns and analyzed their overexpression lines to investigate the in vivo functions of the CE element binding factors (CEBFs). Here, we show that one of the CEBFs, AtERF13, confers ABA hypersensitivity in Arabidopsis, whereas two other CEBFs enhance sugar sensitivity. Our results indicate that a group of AP2/ERF superfamily proteins interacts with CE1. Several CEBFs are known to mediate defense or abiotic stress response, but the physiological functions

Cerium(IV) carboxymethylcellulose (CMC−Ce ) as an efficient and ...

Indian Academy of Sciences (India)

chemsci

nucleotides (Figure 1).1,2 Many pyridine derivatives po- ... neous catalyst, no attention so far has been paid to using ... Schematic illustration of the preparation and possible structure of CMC–CeIV. ... C to constant weight to provide the ..... Purposed mechanism for CMC−CeIVcatalyzed formation of 2,4,6-triarylpyridines.

Particle-specific toxicity and bioavailability of cerium oxide (CeO{sub 2}) nanoparticles to Arabidopsis thaliana

Energy Technology Data Exchange (ETDEWEB)

Yang, Xinping; Pan, Haopeng [College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China); Wang, Peng, E-mail: p.wang3@uq.edu.au [College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China); The University of Queensland, School of Agriculture and Food Sciences, St. Lucia, Queensland 4072 (Australia); Zhao, Fang-Jie [College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China); Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ (United Kingdom)

2017-01-15

Highlights: • The phytotoxicity and uptake of CeO{sub 2} NPs were examined in Arabidopsis. • CeO{sub 2} NPs stimulated plant growth at low doses but were toxic at high doses. • The toxicity was due to the NPs per se, rather than from the dissolved Ce ions. • A similar up-translocation factor was found for CeO{sub 2} NPs, bulk CeO{sub 2} and Ce ions. - Abstract: The use of manufactured cerium oxide nanoparticles (CeO{sub 2}-NPs) in consumer products has increased markedly over the past decade, and their release into natural ecosystems is unavoidable. This study investigated the phytotoxicity and uptake of CeO{sub 2}-NPs in Arabidopsis thaliana grown in an agar medium. Although low concentrations of CeO{sub 2}-NPs had stimulatory effects on plant growth, at higher concentrations, CeO{sub 2}-NPs reduced growth and had adverse effects on the antioxidant systems and photosystem. Importantly, the toxicity resulted from the nanoparticles per se, rather than from the dissolved Ce ions. CeO{sub 2}-NPs were taken up and subsequently translocated to shoot tissues, and transmission electron microscopy (TEM) showed the presence of a large number of needle-like particle aggregations in the intercellular regions and the cytoplasm of leaf cells. The up-translocation factor to shoots was independent of the concentrations of Ce in the roots and the supplied forms of Ce (i.e. CeO{sub 2}-NPs, CeO{sub 2}-bulk, and ionic Ce), suggesting that endocytosis is likely to be a general mechanism responsible for the translocation of these Ce compounds. These findings provide important information regarding the toxicity and uptake of CeO{sub 2}-NPs in plants, which needs to be considered in environmental risk assessment for the safe use and disposal of CeO{sub 2}-NPs.

A comparative study of LaBr{sub 3}(Ce{sup 3+}) and CeBr{sub 3} based gamma-ray spectrometers for planetary remote sensing applications

Energy Technology Data Exchange (ETDEWEB)

Kozyrev, A., E-mail: kozyrev@mx.iki.rssi.ru; Mitrofanov, I.; Bakhtin, B.; Fedosov, F.; Golovin, D.; Litvak, M.; Malakhov, A.; Mokrousov, M.; Nuzhdin, I.; Sanin, A.; Tretyakov, V.; Vostrukhin, A. [Space Research Institute of the Russian Academy of Sciences (IKI), 84/32 Profsoyuznaya St., Moscow 117997 (Russian Federation); Owens, A.; Benkhoff, J. [European Space Agency, ESTEC, Keplerlaan, 2200 AG Noordwijk (Netherlands); Quarati, F. [AP, RST, FAME, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); Gonitec BV, J. Bildersstraat 60, 2596 EJ Den Haag (Netherlands); Timoshenko, G.; Shvetsov, V. [Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow Region 141980 (Russian Federation); Granja, C.; Slavicek, T.; Pospisil, S. [Institute of Experimental and Applied Physics, Czech Technical University in Prague, Horska 3a/22, 12800 Prague 2 (Czech Republic)

2016-08-15

The recent availability of large volume cerium bromide crystals raises the possibility of substantially improving gamma-ray spectrometer limiting flux sensitivities over current systems based on the lanthanum tri-halides, e.g., lanthanum bromide and lanthanum chloride, especially for remote sensing, low-level counting applications or any type of measurement characterized by poor signal to noise ratios. The Russian Space Research Institute has developed and manufactured a highly sensitive gamma-ray spectrometer for remote sensing observations of the planet Mercury from the Mercury Polar Orbiter (MPO), which forms part of ESA’s BepiColombo mission. The Flight Model (FM) gamma-ray spectrometer is based on a 3-in. single crystal of LaBr{sub 3}(Ce{sup 3+}) produced in a separate crystal development programme specifically for this mission. During the spectrometers development, manufacturing, and qualification phases, large crystals of CeBr{sub 3} became available in a subsequent phase of the same crystal development programme. Consequently, the Flight Spare Model (FSM) gamma-ray spectrometer was retrofitted with a 3-in. CeBr{sub 3} crystal and qualified for space. Except for the crystals, the two systems are essentially identical. In this paper, we report on a comparative assessment of the two systems, in terms of their respective spectral properties, as well as their suitability for use in planetary mission with respect to radiation tolerance and their propensity for activation. We also contrast their performance with a Ge detector representative of that flown on MESSENGER and show that: (a) both LaBr{sub 3}(Ce{sup 3+}) and CeBr{sub 3} provide superior detection systems over HPGe in the context of minimally resourced spacecraft and (b) CeBr{sub 3} is a more attractive system than LaBr{sub 3}(Ce{sup 3+}) in terms of sensitivities at lower gamma fluxes. Based on the tests, the FM has now been replaced by the FSM on the BepiColombo spacecraft. Thus, CeBr{sub 3} now forms

Improvement of photoluminescence intensity of Ce-doped Y{sub 3}Al{sub 5}O{sub 12} phosphor by Si{sub 3}N{sub 4} addition

Energy Technology Data Exchange (ETDEWEB)

Shyu, Jiin-Jyh, E-mail: jjshyu@ttu.edu.tw; Yang, Chia-Wei

2017-06-01

Yttrium aluminum garnet (Y{sub 3}Al{sub 5}O{sub 12}, YAG) has been widely used as a host for luminescent ions. The present paper describes the effects of Si{sub 3}N{sub 4} addition on the formation and photoluminescence properties of the Ce-doped YAG yellow phosphors. Phosphor powders with the nominal compositions of Y{sub 2.95}Ce{sub 0.05}Al{sub 5-m}Si{sub m}O{sub 12-m}N{sub m} (m = 0–0.6) were prepared by calcining the mixed raw materials at 1500 °C in nitrogen atmosphere. X-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscope, and transmission electron microscopy equipped with an energy dispersive x-ray spectrometer were used to characterize the structure of the calcined powders. The photoluminescence properties were measured with fluorescence spectrophotometry. It was found that in the range of m = 0–0.27, single phase YAG solid solution (s.s.) in which the Y, Al, and O sites are partially occupied by Ce, Si, and N ions, respectively. The nitrogen ions do not distribute homogeneously over the YAG lattice. The tendency to bond with nitrogen ion for the cations is (Y, Ce) > Si > Al. With the increase in the Si{sub 3}N{sub 4} content, the increase in both the Ce{sup 3+}/(Ce{sup 3+} + Ce{sup 4+}) ratio and the Ce-N bonds improve the intensity of the photoluminescent emission. At m = 0.27, the emission intensity reaches a maximum which is about 2.5 and 1.6 times of that for the Si{sub 3}N{sub 4}-free composition (m = 0) calcined in air and nitrogen, respectively. When the Si{sub 3}N{sub 4} content (m) is higher than 0.27, the emission intensity decreases due to the existence of residual Si{sub 3}N{sub 4} phase. - Highlights: • Addition of Si{sub 3}N{sub 4} can increase the emission intensity of YAG:Ce up to 2.5 times. • Increase in the Ce{sup 3+}/Ce{sup 4+} ratio and the number of Ce-N bonds improve the emission. • The tendency to bond with nitrogen ion for cations in YAG:Ce is (Y, Ce) > Si > Al. • The incomplete dissolution

Radiation streaming with SAM-CE

International Nuclear Information System (INIS)

De Gangi, N.; Cohen, M.O.; Waluschka, E.; Steinberg, H.A.

1980-01-01

The SAM-CE Monte Carlo code has been employed to calculate doses, due to neutron streaming, on the operating floor and other locations of the Millstone Unit II Nuclear Power Facility. Calculated results were compared against measured doses

The effect of Ce doping on the structure, surface morphology and magnetic properties of Dy doped-yttrium iron garnet films prepared by a sol–gel method

Energy Technology Data Exchange (ETDEWEB)

Arsad, A.Z.; Ibrahim, N.B., E-mail: baayah@ukm.edu.my

2016-07-15

Cerium substitute Y{sub 2.8−x}Dy{sub 0.2}Ce{sub x}Fe{sub 5}O{sub 12} (x=0, 0.2, 0.25, 0.3, 0.35) films have been prepared on quartz substrates by a simple sol–gel method and followed by a spin-coating technique. The crystalline structures, surface and magnetic properties of the films has been investigated by an X-ray diffractometer (XRD), a field emission scanning electron microscope (FESEM), an atomic force microscope (AFM) and a vibrating sample magnetometer (VSM). The XRD analysis revealed that the films have garnet structure. The lattice parameter increased as Ce content was increased up to 0.25 due to the Ce{sup 3+} ions completely substituted for Y{sup 3+} ions. For films x≥0.3, the lattice parameter decreased. The FESEM results showed that the average grains were small, ranging from 11 to 14 nm and the thickness of films increased with the increment of Ce contents. VSM results for both in and out-plane magnetic measurement showed the film with x=0 has the highest saturation magnetization (M{sub s}) values. With the increment of Ce contents, the M{sub s} of films decreased due to the substitution of Ce{sup 3+}, Dy{sup 3+} ions in the c-site. For films x≥0.3 the reduction of M{sub s} values was due to the presence of CeO{sub 2} in the film. The films with x=0–0.25 exhibited increases in H{sub c} values. The improvement of coercivity value, small grain size and high crystalline structure of film with x=0.25 has a potential to be used in magneto optical (MO) memory storage applications. - Highlights: • Ce-doped Y{sub 2.8−x}Dy{sub 0.2}Ce{sub x}Fe{sub 5}O{sub 12} films were prepared by the sol–gel method. • The solubility limit of Ce{sup 3+} ions in the film was x=0.25. • The average grain size ranging from 11 to 14 nm with the increment of Ce doping. • Increasing Ce contents degrades the saturation of magnetization of films. • Increasing Ce contents improve the coercivity of films.

Temperature and magnetic field dependence of magnetic correlations in the heavy fermion compound CeCu6

International Nuclear Information System (INIS)

Regnault, L.P.; Rossat-Mignod, J.; Jacoud, J.L.; Erkelens, W.A.C.; Rijksuniversiteit Leiden

1988-01-01

Inelastic neutron scattering experiments have been performed on the heavy fermion compound CeCu 6 at very low temperatures (T > 20 mK) and under magnetic fields up to 50 kOe. The analysis of the data shows that the magnetic scattering is the superposition of a single site contribution of Lorentzian type and of a broadened inelastic contribution associated with AF correlations. These correlations saturate below 1.5 - 2 K and are completely destroyed above 40 kOe

121Sb-NMR study of filled skutterudite CeOs4Sb12

International Nuclear Information System (INIS)

Yogi, M.; Niki, H.; Mukuda, H.; Kitaoka, Y.; Sugawara, H.; Sato, H.

2007-01-01

121 Sb nuclear magnetic resonance (NMR) of filled skutterudite compound CeOs 4 Sb 12 has been carried out to investigate a spin fluctuation below T∼25K. In spite of a powdered sample, many sharp peaks, similar to a data for single crystal, were observed because of an orientation of the sample from the anisotropy of the magnetization. A numerical calculation well reproduces resonance fields for Sb(1) sites with H parallel V zz . The nuclear spin-lattice relaxation rate divided by temperature 1/T 1 T shows continuous decrease with increasing magnetic field, indicating a suppression of the spin fluctuation by the field

Toxicity of 144Ce inhaled in a relatively insoluble form by beagle dogs

International Nuclear Information System (INIS)

Boecker, B.B.; Hahn, F.F.; Muggenburg, B.A.; Mauderly, J.L.; McClellan, R.O.; Pickrell, J.A.

1980-01-01

The metabolism, dosimetry and effects of 144 Ce inhaled in fused aluminosilicate particles are being investigated in the beagle dog to assess the long-term biological consequences of release of relatively insoluble aerosol forms of 144 Ce that could occur in nuclear accidents. The effects resulting from the relatively protracted radiation dose patterns to the lung from this form of 144 Ce are being compared with effects of other radiation dose patterns to the lung. One hundred eleven dogs were exposed to aerosols of 144 Ce in fused aluminosilicate particles to yield initial lung burdens of 0.0024 to 210 μCi/kg body weight and 15 control dogs were exposed to nonradioactive fused aluminosilicate particles. To date, 65 144 Ce-exposed and 2 control dogs have died or were euthanized at 143 to 4578 days after inhalation of 144 Ce. Prominent findings in the 144 Ce-exposed dogs were radiation pneumonitis in 17 dogs that died at early times and neoplastic disease in 39 of the 48 dogs that died 750 days or later. Observations are continuing on the 46 144 Ce-exposed and 13 control dogs remaining alive at this time, at least 3337 days after exposure

Stabilization of temperature during magnetic hyperthermia by Ce substituted magnetite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Shaw, S.K.; Alla, S.K. [Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India); Meena, S.S. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Mandal, R.K. [Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India); Prasad, N.K., E-mail: nandkp.met@iitbhu.ac.in [Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

2017-07-15

Highlights: • Ce{sub x}Fe{sub 3−x}O{sub 4} (0.01 ≤ x ≤ 0.5) nanoparticles below 15 nm were synthesized by microwave refluxing method. • The saturation magnetization decreased with increased Ce concentration. • The sample displayed stabilization of temperature near 42 °C during magnetic hyperthermia. - Abstract: We report here magnetic hyperthermia using nanoparticles of Ce{sub x}Fe{sub 3−x}O{sub 4} (x = 0.01, 0.05, 0.1, 0.3 and 0.5) during which temperature was found to be stabilizing near 42 °C. This happens despite of their high saturation magnetization (M{sub S}) and Curie temperature (T{sub C}) values. It was observed that by selecting an appropriate magnetic field the temperature can be rose exactly near the therapeutic temperature and thus it will help to selectively kill the cancerous cells leaving normal cells unaffected. These nanoparticles (size around 8–15 nm) were produced by single step microwave refluxing technique. X-ray diffraction (XRD) analysis demonstrates that samples were essentially single phase except for x = 0.5 sample. The X-ray photoelectron spectroscopy (XPS) study for the samples demonstrated that Ce was present in both Ce{sup 3+} and Ce{sup 4+} states. The saturation magnetization value of the samples decreased sharply from 62 Am{sup 2}/kg for x = 0.01 to 19 Am{sup 2}/kg for x = 0.1. This value further decreased with increased Ce doping.

DOTA-functionalized polylysine: a high number of DOTA chelates positively influences the biodistribution of enzymatic conjugated anti-tumor antibody chCE7agl.

Directory of Open Access Journals (Sweden)

Jürgen Grünberg

Full Text Available Site-specific enzymatic reactions with microbial transglutaminase (mTGase lead to a homogenous species of immunoconjugates with a defined ligand/antibody ratio. In the present study, we have investigated the influence of different numbers of 1,4,7,10-tetraazacyclododecane-N-N'-N''-N'''-tetraacetic acid (DOTA chelats coupled to a decalysine backbone on the in vivo behavior of the chimeric monoclonal anti-L1CAM antibody chCE7agl. The enzymatic conjugation of (DOTA1-decalysine, (DOTA3-decalysine or (DOTA5-decalysine to the antibody heavy chain (via Gln295/297 gave rise to immunoconjugates containing two, six or ten DOTA moieties respectively. Radiolabeling of the immunoconjugates with (177Lu yielded specific activities of approximately 70 MBq/mg, 400 MBq/mg and 700 MBq/mg with increasing numbers of DOTA chelates. Biodistribution experiments in SKOV3ip human ovarian cancer cell xenografts demonstrated a high and specific accumulation of radioactivity at the tumor site for all antibody derivatives with a maximal tumor accumulation of 43.6±4.3% ID/g at 24 h for chCE7agl-[(DOTA-decalysine]2, 30.6±12.0% ID/g at 24 h for chCE7agl-[(DOTA3-decalysine]2 and 49.9±3.1% ID/g at 48 h for chCE7agl-[(DOTA5-decalysine]2. The rapid elimination from the blood of chCE7agl-[(DOTA-decalysine]2 (1.0±0.1% ID/g at 24 h is associated with a high liver accumulation (23.2±4.6% ID/g at 24 h. This behavior changed depending on the numbers of DOTA moieties coupled to the decalysine peptide with a slower blood clearance (5.1±1.0 (DOTA3 versus 11.7±1.4% ID/g (DOTA5, p<0.005 at 24 h and lower radioactivity levels in the liver (21.4±3.4 (DOTA3 versus 5.8±0.7 (DOTA5, p<0.005 at 24 h. We conclude that the site-specific and stoichiometric uniform conjugation of the highly DOTA-substituted decalysine ((DOTA5-decalysine to an anti-tumor antibody leads to the formation of immunoconjugates with high specific activity and excellent in vivo behavior and is a valuable option for

Incommensurate and commensurate magnetic structures of the ternary germanide CeNiGe3

International Nuclear Information System (INIS)

Durivault, L; Bouree, F; Chevalier, B; Andre, G; Weill, F; Etourneau, J; Martinez-Samper, P; Rodrigo, J G; Suderow, H; Vieira, S

2003-01-01

The structural properties of CeNiGe 3 have been investigated via electron diffraction and neutron powder diffraction (NPD). This ternary germanide crystallizes in the orthorhombic SmNiGe 3 -type structure (Cmmm space group). Electrical resistivity, ac- and dc-magnetization measurements show that CeNiGe 3 orders antiferromagnetically below T N = 5.5(2) K and exclude the occurrence at low temperatures of a spin-glass state for CeNiGe 3 as previously reported. Specific heat measurements and NPD both reveal two magnetic transitions, observed at T N1 = 5.9(2) K and T N2 = 5.0(2) K. Between T N1 and T N2 , the Ce magnetic moments in CeNiGe 3 are ordered in a collinear antiferromagnetic structure associated with the k 1 = (100) wavevector and showing a relationship with the magnetic structure of the Ce 3 Ni 2 Ge 7 ternary germanide. Below T N2 , this k 1 = (100) commensurate magnetic structure coexists with an incommensurate helicoidal magnetic structure associated with k 2 = (00.409(1)1/2). This last magnetic structure is highly preponderant below T N2 (93(5)% in volume). At 1.5 K, the Ce atoms in CeNiGe 3 carry a reduced ordered magnetic moment (0.8(2) μ B ). This value, smaller than that obtained in Ce 3 Ni 2 Ge 7 , results from an important hybridization of the 4f(Ce) orbitals with those of the Ni and Ge ligands

Decays of 143La and 145Ce using KUR-ISOL

International Nuclear Information System (INIS)

Ukon, Hiroe; Shibata, Michihiro; Kawade, Kiyoshi; Yamamoto, Hiroshi; Katoh, Toshiro; Kawase, Yoichi; Okano, Kotoyuki; Ruan, J.Z.

1987-01-01

Accurate measurements of beta- and gamma-rays resulting from the decay of 143 La and 145 Ce are made with KUR-ISOL to develop their decay diagram. First, gamma-singles spectrometry is performed to determine the energy and intensity of gamma-rays resulting from the decay of 143 La and 145 Ce. About 30 and 7 peaks are newly identified for 143 La and 145 Ce, respectively, in their gamma-ray spectra. Another gamma-singles spectrometry is carried out using 60 cm 3 Ge(Li) and LEPS detectors to determine 620 keV gamma-ray emission rate in the decay of 143 La. The emission rate is calculated at 4.23 and 4.62 percent from measurements made with Ge(Li) and LEPS, respectively. Gamma-gamma coincidence spectrometry is performed using a 60 cm 3 Ge(Li)-142 cm 3 Ge(Li) or a 60 cm 3 Ge(Li)-LEPS detector. LEPS is then applied to beta-singles spectrometry to determine the maximum energy of the gamma-rays from 143 La and 145 Ce within an error of about 20 keV. The beta-ray end point is determined from the measurements. Decay diagrams of 143 La and 145 Ce are constructed based on these results. The intensity and multipolarity of 18.9, 23.4 and 42.3 keV gamma-rays in the decay of 143 La are determined. Energy and intensity of gamma-rays of 2.8 MeV or above are also determined for 143 La. Three low energy levels of 145 Ce is examined in comparison to the decay diagram of 143 La. 143 Ce is found to have an energy level structure similar to that of other nuclides of N = 85. (Nogami, K.)

Exposure of agricultural crops to nanoparticle CeO2 in biochar-amended soil.

Science.gov (United States)

Servin, Alia D; De la Torre-Roche, Roberto; Castillo-Michel, Hiram; Pagano, Luca; Hawthorne, Joseph; Musante, Craig; Pignatello, Joseph; Uchimiya, Minori; White, Jason C

2017-01-01

Biochar is seeing increased usage as an amendment in agricultural soils but the significance of nanoscale interactions between this additive and engineered nanoparticles (ENP) remains unknown. Corn, lettuce, soybean and zucchini were grown for 28 d in two different soils (agricultural, residential) amended with 0-2000 mg engineered nanoparticle (ENP) CeO 2  kg -1 and biochar (350 °C or 600 °C) at application rates of 0-5% (w/w). At harvest, plants were analyzed for biomass, Ce content, chlorophyll and lipid peroxidation. Biomass from the four species grown in residential soil varied with species and biochar type. However, biomass in the agricultural soil amended with biochar 600 °C was largely unaffected. Biochar co-exposure had minimal impact on Ce accumulation, with reduced or increased Ce content occurring at the highest (5%) biochar level. Soil-specific and biochar-specific effects on Ce accumulation were observed in the four species. For example, zucchini grown in agricultural soil with 2000 mg CeO 2  kg -1 and 350 °C biochar (0.5-5%) accumulated greater Ce than the control. However, for the 600 °C biochar, the opposite effect was evident, with decreased Ce content as biochar increased. A principal component analysis showed that biochar type accounted for 56-99% of the variance in chlorophyll and lipid peroxidation across the plants. SEM and μ-XRF showed Ce association with specific biochar and soil components, while μ-XANES analysis confirmed that after 28 d in soil, the Ce remained largely as CeO 2 . The current study demonstrates that biochar synthesis conditions significantly impact interactions with ENP, with subsequent effects on particle fate and effects. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Dosimeter properties of Ce and Eu doped LiCaAlF6

International Nuclear Information System (INIS)

Yanagida, Takayuki; Fujimoto, Yutaka; Watanabe, Kenichi; Fukuda, Kentaro

2014-01-01

Optical, scintillation properties, optical stimulated luminescence, and thermally stimulated luminescence of Ce 1, 3, and 5% doped and Eu 1, 1.5, and 2% doped LiCaAlF 6 crystals fabricated by Tokuyama Corp. were investigated. In transmittance, absorption was proportional to dopant concentrations and typical optical quantum yield of Ce and Eu-doped LiCaAlF 6 were 40 and 100%, respectively. Scintillation wavelength and decay time profiles were investigated under X-ray irradiation. Ce 3+ and Eu 2+ 5d-4f luminescence appeared around 300 nm and 370 nm with typical decay time of 40 ns and 1.5 μs, respectively. Optically stimulated luminescence of Ce-doped ones appeared under 405 nm stimulation with detectable intensity while those of Eu doped ones were quite weak. Thermally stimulated luminescence of Ce- and Eu-doped LiCaAlF 6 were enough strong and they exhibited good response function from 1 to 1000 mGy exposure. - Highlights: • Optical, scintillation, OSL, and TSL properties of Ce or Eu differently doped LiCaAlF6 were studied. • PL quantum yield of Ce and Eu doped LiCaAlF6 showed 40% and 100%, respectively. • OSL was observed in Ce-doped LiCaAlF6. • TSL was observed in both material systems and exhibited a good dose response from 1 to 1000 mGy

Estimation of human gonadal Pu and Ce concentrations from animal data

International Nuclear Information System (INIS)

Thomas, R.G.; Durbin, P.W.; McInroy, J.F.; Healy, J.W.

1989-01-01

Data were obtained from the literature for gonad and body weights and for the Pu or Ce content of the gonads and body at death for several laboratory animal species, five human Pu injection cases, and 731 human adults exposed environmentally to Pu in fallout. Data for Pu concentration in gonads, liver, and bone samples of 59 male and five female occupational Pu cases (including four completely analyzed whole bodies) were obtained from the U.S. Transuranium Registry. A logarithmic function was used to relate fractional Pu or Ce concentration in testes and ovaries to body weight of the animals and to predict fractional Pu or Ce concentrations in human gonads, [Pu]G . PuB-1 = aBWb, where [Pu]G or [Ce]G is the nuclide concentration in gonads (Bq g-1 of wet weight), PuB or CeB is the nuclide content of the body at death, and BW is body weight (kg). The fractional Pu and Ce concentrations in both the testes and ovaries are inverse and nearly linear functions of body weight. The regression lines of fractional Pu or Ce concentration in testes and ovaries have similar slopes (b = -1.07 +/- 0.14); however, the nuclide concentrations (coefficient a) in ovaries are six times greater than in testes. Extrapolation of the animal data yielded fractional Pu concentrations in human testes and ovaries that agree with those calculated for the occupational cases and those recommended by the International Commission on Radiological Protection. The good agreement between the fractional concentrations of Pu and Ce in the testes and in the ovaries suggests that these data can be substituted in metabolic models of chemically similar elements for which gonadal data are scarce

New limits on 2ε, εβ{sup +} and 2β{sup +} decay of {sup 136}Ce and {sup 138}Ce with deeply purified cerium sample

Energy Technology Data Exchange (ETDEWEB)

Belli, P.; Bernabei, R. [INFN Sezione Roma ' ' Tor Vergata' ' , Rome (Italy); Universita di Roma ' ' Tor Vergata' ' , Dipartimento di Fisica, Rome (Italy); Boiko, R.S. [Institute for Nuclear Research, Kyiv (Ukraine); National University of Life and Environmental Sciences of Ukraine, Kyiv (Ukraine); Cappella, F. [INFN Sezione Roma, Rome (Italy); Cerulli, R.; Laubenstein, M. [INFN, Laboratori Nazionali del Gran Sasso, Assergi (Italy); Danevich, F.A.; Kropivyansky, B.N.; Polischuk, O.G.; Tretyak, V.I. [Institute for Nuclear Research, Kyiv (Ukraine); Incicchitti, A. [INFN Sezione Roma, Rome (Italy); Universita di Roma ' ' La Sapienza' ' , Dipartimento di Fisica, Rome (Italy); Mokina, V.M. [Institute for Nuclear Research, Kyiv (Ukraine); INFN Sezione Roma, Rome (Italy)

2017-08-15

A search for double electron capture (2ε), electron capture with positron emission (εβ{sup +}), and double positron emission (2β{sup +}) in {sup 136}Ce and {sup 138}Ce was realized with a 465 cm{sup 3} ultra-low background HP Ge γ spectrometer over 2299 h at the Gran Sasso underground laboratory. A 627 g sample of cerium oxide deeply purified by liquid-liquid extraction method was used as a source of γ quanta expected in double β decay of the cerium isotopes. New improved half-life limits were set on different modes and channels of double β decay of {sup 136}Ce and {sup 138}Ce at the level of T{sub 1/2} > 10{sup 17}-10{sup 18} yr. (orig.)

Specific heat measurements of CePt{sub 3}Si and Ce{sub 1+x}Pt{sub 3+y}Si{sub 1+z}

Energy Technology Data Exchange (ETDEWEB)

Motoyama, G. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan)]. E-mail: motoyama@sci.u-hyogo.ac.jp; Watanabe, M. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Maeda, K. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Oda, Y. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Ueda, K. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Kohara, T. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan)

2007-03-15

We have measured the specific heat of a series of polycrystalline CePt{sub 3}Si and Ce{sub 1+x}Pt{sub 3+y}Si{sub 1+z} samples whose compositions vary slightly from the stoichiometric composition. We observed two peaks derived from magnetic anomalies on the specific heat measurements of the Ce{sub 1+x}Pt{sub 3+y}Si{sub 1+z} samples. One of the peaks relates to the antiferromagnetic phase transition at T{sub N}=2.2K. The other is a large peak at 2.7K observed for the sample that showed a ferromagnetic anomaly at 3.0K on the temperature dependence of the magnetization. Heat treatment had different effects between these anomalies.

Sorption of Fe3+ , Co2+ , Ce3+ , Cs+ and Ba2+ in zeolite X

International Nuclear Information System (INIS)

Martinez M, V.

1994-01-01

The sorption behavior of Fe 3+ , Co 2+ , Ce 3+ , Cs + , and Ba 2+ in aqueous solutions, was studied in presence of zeolite X. Solutions of Fe(NO 3 ) 3 . 9 H 2 O, Co(NO 3 ) 2 . 6 H 2 O, Ce(NO 3 ) 3 . 6 H 2 O, Cs NO 3 and Ba(NO 3 ) 2 were labelled with the respectively radioactive isotopes Fe 59 , Co 60 , Cs 134 , Ba 139 and Ce 141 . 20 ml. of each solution was left in contact with 200 mg. of zeolite for different periods. Later the zeolites were separated by centrifugation from the aqueous solutions and the radioactivity of the aqueous phases was measured with a NaI(Tl) solid-state well detector coupled to a single-channel Picker analyzer or with a Gel hyper pure solid-state detector coupled to a 2048 channel pulse height analyzer. When Cs + in the aqueous solutions was left in contact with zeolite X it was found that it does not occupy all cationic sites in the zeolite due to the ionic radium effect. A similar behavior was found for the divalent ions. In all cases, when the pH was not controlled, the zeolite lost part of its crystallinity and when the divalent ions were exchanged again by Na + , the zeolite recovered completely its crystallinity. During the sorption, the ionic radius, and the charge are important parameters as well as the pH. When the pH of the solution was adjusted between 6.5 - 7.0 the crystallinity was maintained in some cases. For Fe 3+ the crystallinity after the ion exchange was 94 % and when the pH was not adjusted the crystallinity was completely lost. It was found as well that the zeolite X induces the formation of H 3 O + which competes with the cations for the sites in the zeolite. (Author)

Scintillation properties of Ce-doped LuLiF{sub 4} and LuScBO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Yanagida, Takayuki, E-mail: t_yanagi@tagen.tohoku.ac.jp [IMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Fujimoto, Yutaka [IMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Kawaguchi, Noriaki [IMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Tokuyama Corporation, Shibuya 3-chome, Shibuya-ku, Tokyo 150-8383 (Japan); Yokota, Yuui [IMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Kamada, Kei [Materials Research Laboratory, Furukawa, Co. Ltd., 1-25-13 Kannondai, Tsukuba, Ibaragi 305-0856 (Japan); Totsuka, Daisuke [Nihon Kessho Kogaku Co., Ltd., 810-5 Nobe-cho, Tatebayashi, Gunma 374-0047 (Japan); Hatamoto, Shun-Ichi [Corporate Research and Development Center, Mitsui Mining and Smelting Co., Ltd., 1333-2 Haraichi, Ageo Saitama 362-0023 (Japan); Yoshikawa, Akira; Chani, Valery [IMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan)

2011-10-01

The crystals of 1 mol% Ce-doped LuLiF{sub 4} (Ce:LLF) grown by the micro-pulling down ({mu}-PD) method and 1 mol% Ce-doped LuScBO{sub 3} (Ce:LSBO) grown by the conventional Czochralski (Cz) method were examined for their scintillation properties. Ce:LLF and Ce:LSBO demonstrated {approx}80% transparency at wavelengths longer than 300 and 400 nm, respectively. When excited by {sup 241}Am {alpha}-ray to obtain radioactive luminescence spectra, Ce{sup 3+} 5d-4f emission peaks were detected at around 320 nm for Ce:LLF and at around 380 nm for Ce:LSBO. In Ce:LSBO, the host luminescence was also observed at 260 nm. By recording pulse height spectra under {gamma}-ray irradiation, the absolute light yield of Ce:LLF and Ce:LSBO was measured to be 3600{+-}400 and 4200{+-}400 ph/MeV, respectively. Decay time kinetics was also investigated using a pulse X-ray equipped streak camera system. The main component of Ce:LLF was {approx}320 ns and that of Ce:LSBO was {approx}31 ns. In addition, the light yield non-proportionality and energy resolution against the {gamma}-ray energy were evaluated.

Heat capacity measurement of CeNbO4(s)

International Nuclear Information System (INIS)

Bhojane, S.M.; Kulkarni, Jayanthi; Kulkarni, S.G.

2012-01-01

Molar heat capacity of CeNbO 4 (s) was determined using differential scanning calorimeter in the temperature range of 550 to 900 K. The molar heat capacity values were least squares analysed and the dependence of molar heat capacity with temperature for CeNbO 4 (s) can be given as, J K -1 mol -1 = 94.7320 + 0.0852T-1.6073 x 10 6 T -2 (550≤T(K)≤900) Cerium is commonly used as an inactive analogue to plutonium; also it is an important fission product with moderate yield. Various Nb alloys are used as cladding material in nuclear industry. Hosts of thermodynamic data are needed to understand the various phenomena that occur in a nuclear reactor. In the present study, the molar heat capacity of CeNbO 4 (s) has been determined using high temperature differential scanning calorimeter in temperature range 550 to 900 K. This is one of the important compounds in the ternary system of Ce-Nb-O

Speciation of the oxidation states of plutonium in aqueous solutions by UV/Vis spectroscopy, CE-ICP-MS and CE-RIMS

International Nuclear Information System (INIS)

Buerger, S.; Banik, N.L.; Buda, R.A.; Kratz, J.V.; Kuczewski, B.; Trautmann, N.

2007-01-01

For the speciation of the plutonium oxidation states in aqueous solutions, the online coupling of capillary electrophoresis (CE) with inductively coupled plasma mass spectrometry (ICP-MS) has been developed. Depending on the radius/electrical charge ratio, the oxidation states III, IV, V, and VI of plutonium are separated by CE, based on the different migration times through the capillary and are detected by ICP-MS. The detection limit is 20 ppb, i.e. 10 9 -10 10 atoms (10 -12 -10 -13 g) for one oxidation state with an uncertainty of the reproducibility of the migration times of ≤ 1% and ≤ 5% for the peak area. The redox kinetics of the different plutonium oxidation states in the presence of humic substances (humic and fulvic acid) have been studied. A relatively rapid reduction of Pu(VI) (10 to 1000 h) in contact with Gorleben fulvic or Aldrich humic acid could be observed, depending on the pH of the solution. Furthermore, at pH=1, a reduction to Pu(III) and Pu(IV) in a mixture of all four oxidation states in contact with Gorleben fulvic acid after one month has been observed. In order to improve the sensitivity of the CE method, the offline coupling of CE to resonance ionization mass spectrometry (RIMS) has been explored. First applications of this new speciation method are presented. (orig.)

Magnetic susceptibility of LaxCe1-xF3 single crystals

International Nuclear Information System (INIS)

Paradowski, M.L.; Pacyna, A.W.; Bombik, A.; Korczak, W.; Korczak, S.Z.

2000-01-01

The magnetic susceptibility of La x Ce 1-x F 3 single crystals, for 0 eff and paramagnetic Curie temperature θ p have been obtained, using the Curie-Weiss law in the temperature range 100-300 K. The interconfiguration excited energy E ex , the spin-fluctuation temperature T sf , and the g-values, corresponding to three Kramers doublets in the 2 F 5/2 ground multiplet of Ce 3+ ion in La x Ce 1-x F 3 have been determined, using quantum theory of paramagnetic susceptibility. The mixed-valent and crystal field effects influence significantly the g-values. The effect of the dilution of the paramagnetic Ce 3+ ions with diamagnetic La 3+ ions is also discussed

Preparation of Mn doped CeO_2 nanoparticles with enhanced ferromagnetism

International Nuclear Information System (INIS)

Ravi, S.; Winfred Shashikanth, F.

2017-01-01

Spherical-like CeO_2 and Mn-doped CeO_2 using 6-aminohexanoic acid as surfactant exhibit enhanced ferromagnetism. The optical absorption spectra reveal a red shift with a band gap of 2.51 eV. The mechanics of ferromagnetism and the red shift were analyzed. These results provide a promising platform for developing a dilute magnetic semiconductor in spintronics. - Highlights: • Pure and Mn-doped CeO_2 is prepared with aminohexanoic acid as capping. • They exhibit wide optical absorption with red-shift in their band gap. • Mn-doped CeO_2 nanoparticle exhibit hysteresis at room temperature. • Results were promising to use in spintronics and opto-electronics field.

Investigation of the 600 C isothermal section of the Fe-Al-Ce ternary system

Energy Technology Data Exchange (ETDEWEB)

Zheng, Huiyun; Yin, Fucheng [Xiangtan Univ., Hunan (China). School of Materials Science and Engineering; Xiangtan Univ., Hunan (China). Key Laboratory of Materials Design and Preparation Technology of Hunan Province; Li, Zhi [Xiangtan Univ., Hunan (China). School of Materials Science and Engineering; Xiangtan Univ., Hunan (China). Key Laboratory of Materials Design and Preparation Technology of Hunan Province; Xiangtan Univ., Hunan (China). Key Laboratory of Key Film Materials and Application for Equipment (Hunan province); Ji, Li [South China University of Technology, Guangdong (China). School of Materials Science and Engineering

2017-01-15

The isothermal section of the Fe-Al-Ce system at 600 C was determined by means of scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray powder diffraction. Twenty three-phase regions were confirmed experimentally, and two three-phase regions could be deduced in this section. Five ternary compounds, i. e., τ{sub 1}, τ{sub 2}, τ{sub 3}, τ{sub 5}, and τ{sub 6}, exist at 600 C. The Fe{sub 2}Ce phase contains 6.6 at.% Al in the Fe-Al-Ce system. The Fe solubility in α-Al, αAl{sub 11}Ce{sub 3}, αAl{sub 3}Ce, Al{sub 2}Ce, AlCe, and AlCe{sub 3} is approximately 1.7 at.%, 1.1 at.%, 1.2 at.%, 1.3 at.%, 5.8 at.%, and 0.1 at.%, respectively, and the solubility of Ce in α-Al, FeAl{sub 3}, Fe{sub 2}Al{sub 5}, FeAl{sub 2}, and FeAl is approximately 0.1 at.%, 1.2 at.%, 1.9 at.%, 0.9 at.%, and 3.7 at.%, respectively.

Evidence of complex magnetism in CePt3C

International Nuclear Information System (INIS)

Vejpravova, J.; Prokleska, J.; Danis, S.; Uhlirova, K.; Sechovsky, V.

2006-01-01

CePt 3 C has been synthesized and studied by powder X-ray diffraction (at RT), specific heat, resistivity and magnetization measurements at temperatures from RT down to 0.4K and in magnetic fields up to 10T. A possible scenario for the ground state of CePt 3 C based on the observed phenomena is proposed

Effects of Ce3+ concentration, beam voltage and current on the cathodoluminescence intensity of SiO2: Pr3+–Ce3+ nanophosphor

CSIR Research Space (South Africa)

Mhlongo, GH

2011-02-01

Full Text Available SiO2:Pr3+–Ce3+ phosphor powders were successfully prepared using a sol–gel process. The concentration of Pr3+ was fixed at 0.2 mol% while that of Ce3+ was varied in the range of 0.2–2 mol%. High resolution transmission electron microscopy (HRTEM...

Structure and photocatalytic activity studies of TiO2-supported over Ce-modified Al-MCM-41

International Nuclear Information System (INIS)

Krishna Reddy, Jakkidi; Durgakumari, Valluri; Subrahmanyam, Machiraju; Sreedhar, Bojja

2009-01-01

Ce-Al-MCM-41, TiO 2 /Al-MCM-41 and TiO 2 /Ce-Al-MCM-41 materials with varying contents of Ce (by impregnation) and TiO 2 loaded (by solid-state dispersion) on Al-MCM-41 support are prepared. The Ce modified and TiO 2 loaded composite systems are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra (DRS) and X-ray photoelectron spectroscopy (XPS) techniques. The DRS and XPS of low Ce content (0.2-0.5 wt.%) modified Al-MCM-41 samples are showing more characteristic of Ce 3+ species wherein cerium in interaction with Al-MCM-41 and that of high Ce (0.8, 3.0 wt.%) content modified samples are showing the characteristic of both Ce 4+ and Ce 3+ species. A series of Ce-modified Al-MCM-41 and TiO 2 loaded composite catalysts are evaluated for photocatalytic degradation of phenol under UV irradiation. Low Ce content in Ce 3+ state on Al-MCM-41 is showing good photoactivity in comparison with high Ce content samples and pure ceria. The composite TiO 2 /Ce-Al-MCM-41 is showing enhanced degradation activity due decreased rate of electron-hole recombination on TiO 2 surface by the redox properties of cerium. The photocatalyst TiO 2 /Ce-Al-MCM-41 with an optimum of 10 wt.% TiO 2 and 0.3 wt.% Ce is showing maximum phenol degradation activity. The possible mechanism of phenol degradation on the composite photocatalyst is proposed.

Phase Composition and Long-Term Conductivity of Acceptor Doped Ce(PO₃)₄ and CeP₂O₇ with Variable P/Metal Ratio and of CeP₂O₇-KH₂PO₄ Composite

DEFF Research Database (Denmark)

Chatzichristodoulou, Christodoulos; Hallinder, Jonathan; Lapina, Alberto

2013-01-01

The thermal evolution of the phase composition of CeP2O7 and Ce(PO3)4 with 10 mol% Y and Gd doping, respectively, was examined by in-situ powder X-ray diffraction and thermogravimetry with in-line mass spectroscopy. The phase composition depends critically on the P to metal ratio, the annealing...... temperature, humidity and time. CeP2O7 and Ce(PO3)4 were completely decomposed to CePO4 following a 1100 h long conductivity test at 155°C. The conductivity of 10 mol% Gd doped Ce(PO3)4 (synthesized with P:(Ce + Gd) = 5.0) reaches a value of 6.4·10−2 S·cm−1 at 150°C under wet conditions (pH2O = 0.2 atm...

Solid-state reaction synthesis and aqueous durability of Ce-doped zirconolite-rich ceramics

Energy Technology Data Exchange (ETDEWEB)

Wen, Guanjun [State Key Laboratory Cultivation Base for Nonmetal Composite and Functional Materials, Southwest University of Science and Technology, Mianyang, Sichuan 621010 (China); Zhang, Kuibao, E-mail: xiaobao320@163.com [State Key Laboratory Cultivation Base for Nonmetal Composite and Functional Materials, Southwest University of Science and Technology, Mianyang, Sichuan 621010 (China); Yin, Dan [State Key Laboratory Cultivation Base for Nonmetal Composite and Functional Materials, Southwest University of Science and Technology, Mianyang, Sichuan 621010 (China); Zhang, Haibin, E-mail: hbzhang@imr.ac.cn [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

2015-11-15

In this study, Ce-doped zirconolite-rich ceramics were prepared by solid-state reaction process using cerium as the surrogate of tetravalence actinide nuclide. The occupancy of Ce in the waste forms was investigated. The aqueous durability of Ce-doped zirconolite-rich ceramic was examined as well. The results show that zirconolite and pseudobrookite coexisted after being sintered at 1200 °C for 6 h. Meanwhile, perovskite is inevitable generated during the process. CeO{sub 2} can be successfully incorporated into the lattice structure of the zirconolite-rich ceramics. The maximum containing capacity of CeO{sub 2} is up to 14.95 wt% or y = 0.4. The normalized elemental leaching rates of Ce and Ca are fairly constant in low values of 1.2 × 10{sup −6} and 2.3 × 10{sup −2} g m{sup −2} d{sup −1} after 28 days. The normalized leaching rate of Fe is also in a low value of 2.9 × 10{sup −4} g m{sup −2} d{sup −1} after 7 days. - Highlights: • Ce-doped zirconolite-rich ceramic was produced at 1200 °C. • Pseudobrookite-type Fe{sub 2}TiO{sub 5} was employed to incorporate Fe element. • Ce{sup 3+} and Ce{sup 4+} coexisted in the Ce-doped zirconolite-rich waste form after being sintered at 1200 °C for 6 h. • The leaching rate of Ca was relatively higher than that of borosilicate glasses.

Structure and scintillation yield of Ce-doped Al–Ga substituted yttrium garnet

International Nuclear Information System (INIS)

Sidletskiy, Oleg; Kononets, Valerii; Lebbou, Kheirreddine; Neicheva, Svetlana; Voloshina, Olesya; Bondar, Valerii; Baumer, Vyacheslav; Belikov, Konstantin; Gektin, Alexander; Grinyov, Boris; Joubert, Marie-France

2012-01-01

Highlights: ► Range of Y 3 (Al 1−x Ga x ) 5 O 12 :Ce solid solution crystals are grown from melt by the Czochralski method. ► Light yield of mixed crystals reaches 130% of the YAG:Ce value at x ∼ 0.4. ► ∼1% of antisite defects is formed in YGG:Ce, but no evidence of this is obtained for the rest of crystals. -- Abstract: Structure and scintillation yield of Y 3 (Al 1−x Ga x ) 5 O 12 :Ce solid solution crystals are studied. Crystals are grown from melt by the Czochralski method. Distribution of host cations in crystal lattice is determined. Quantity of antisite defects in crystals is evaluated using XRD and atomic emission spectroscopy data. Trend of light output at Al/Ga substitution in Y 3 (Al 1−x Ga x ) 5 O 12 :Ce is determined for the first time. Light output in mixed crystals reaches 130% comparative to Ce-doped yttrium–aluminum garnet. Luminescence properties at Al/Ga substitution are evaluated.

Effect of Ce on performance and physicochemical properties of Pt-containing automotive emission control catalysts

International Nuclear Information System (INIS)

Nunan, J.G.; Silver, R.G.; Bradley, S.A.

1992-01-01

Present-day automotive emission control catalysts contain noble metals such as Pt, Pd and Rh all on an alumina support with a variety of promoters. Ce is one of the most important promoters. In this paper, the interaction between Pt and Ce is studied using TPR and STEM on a variety of catalysts. The degree of Pt/Ce interaction is increased by decreasing CeO 2 crystallite size, and to a lesser extent by increasing CeO 2 loading. Direct Pt/Ce interaction leads to a synergistic reduction of both Pt and surface Ce. This reduction qualitatively correlates with catalyst performance after activation in a reducing gas. It is proposed that this synergistic reduction of Pt and Ce is associated with observed improvements in catalyst performance using a non-oscillating exhaust gas

Light emission efficiency and imaging properties of YAP:Ce granular phosphor screens

International Nuclear Information System (INIS)

Kalivas, N.; Valais, I.; Nikolopoulos, D.; Konstantinidis, A.; Cavouras, D.; Kandarakis, I.; Gaitanis, A.; Nomicos, C.D.; Panayiotakis, G.

2007-01-01

Phosphor materials are used in medical imaging combined with radiographic film or other photodetectors. Cerium (Ce 3+ ) -doped scintillators are of particular interest for medical imaging, because of their very fast response. YAP:Ce scintillator-based image detectors have already been evaluated in single-crystal form and under conditions of positron emission tomography and synchrotron or γ-ray irradiation. Furthermore, YAP:Ce phosphor has been evaluated in conjunction with radiographic films. The present work reports experimental and theoretical data concerning the light output absolute luminescence efficiency (AE) of the YAP:Ce screens under irradiation conditions employed in medical X-ray projection imaging (i.e., in diagnostic radiology). projection imaging (i.e., in diagnostic radiology). YAP:Ce phosphor screens with surface densities ranging between 53 and 110 mg/cm 2 were prepared by sedimentation on fused silica substrates in our laboratory. The resulted surface density of the screens was determined by dividing the phosphor mass deposited on the screen surface with the area of the surface. Additionally this work addresses the imaging performance of YAP:Ce by estimation of the detective quantum efficiency (DQE), i.e., the square of the signal to noise ratio transfer. Absolute efficiency was found to decrease with X-ray tube voltage for for YAP:Ce phosphor. The highest experimental efficiency was obtained for the 53.7 mg/cm 2 and 88.0 mg/cm 2 YAP:Ce screens. The highest DQE value was found for the 88.0 mg/cm 2 screen irradiated at 60 kVp. (orig.)

Magnetic properties of nearly stoichiometric CeAuBi2 heavy fermion compound

International Nuclear Information System (INIS)

Adriano, C.; Jesus, C. B. R.; Pagliuso, P. G.; Rosa, P. F. S.; Grant, T.; Fisk, Z.; Garcia, D. J.

2015-01-01

Motivated by the interesting magnetic anisotropy found in the heavy fermion family CeTX 2 (T = transition metal and X = pnictogen), here, we study the novel parent compound CeAu 1−x Bi 2−y by combining magnetization, pressure dependent electrical resistivity, and heat-capacity measurements. The magnetic properties of our nearly stoichiometric single crystal sample of CeAu 1−x Bi 2−y (x = 0.92 and y = 1.6) revealed an antiferromagnetic ordering at T N  = 12 K with an easy axis along the c-direction. The field dependent magnetization data at low temperatures reveal the existence of a spin-flop transition when the field is applied along the c-axis (H c  ∼ 7.5 T and T = 5 K). The heat capacity and pressure dependent resistivity data suggest that CeAu 0.92 Bi 1.6 exhibits a weak heavy fermion behavior with strongly localized Ce 3+ 4f electrons. Furthermore, the systematic analysis using a mean field model including anisotropic nearest-neighbors interactions and the tetragonal crystalline electric field (CEF) Hamiltonian allows us to extract a CEF scheme and two different values for the anisotropic J RKKY exchange parameters between the Ce 3+ ions in this compound. Thus, we discuss a scenario, considering both the anisotropic magnetic interactions and the tetragonal CEF effects, in the CeAu 1−x Bi 2−y compounds, and we compare our results with the isostructural compound CeCuBi 2

Chemiluminescence of the Ce{sup 3+}* ions, and the {sup 1}ГђЕѕ{sub 2} and ({sup 1}ГђЕѕ{sub 2}){sub 2} molecular species of oxygen induced by active surface of the (NH{sub 4}){sub 2}Ce(NO{sub 3}){sub 6} crystals at reduction of Ce{sup 4+} to Ce{sup 3+} by water in heterogeneous system «(NH{sub 4}){sub 2}Ce(NO{sub 3}){sub 6}-C{sub 6}H{sub 6}-H{sub 2}O»

Energy Technology Data Exchange (ETDEWEB)

Bulgakov, Ramil G., E-mail: profbulgakov@yandex.ru [Laboratory of Negative Ions Mass Spectrometry, Institute of Molecule and Crystal Physics, Ufa Research Centre of the Russian Academy of Sciences, 71, Oktyabrya Prosp., 450054 Ufa (Russian Federation); Gazeeva, Dilara R., E-mail: galimovdi@mail.ru [Laboratory of High Energy Chemistry and Catalysis, Institute of Petrochemistry and Catalysis Russian Academy of Sciences, 141 Prosp. Oktyabrya, 450075 Ufa (Russian Federation); Galimov, Dim I. [Laboratory of High Energy Chemistry and Catalysis, Institute of Petrochemistry and Catalysis Russian Academy of Sciences, 141 Prosp. Oktyabrya, 450075 Ufa (Russian Federation)

2017-03-15

We have discovered an unusual new chemiluminescence (CL) in the title system, which is different from other known CL by unusual combination of various in nature emitters, namely, electronically excited state of the Ce{sup 3+}* ion (λ{sub max}=335 nm), singlet oxygen {sup 1}ГђЕѕ{sub 2} (emission near 1270 nm) and its dimer ({sup 1}ГђЕѕ{sub 2}){sub 2} (λ{sub max}=490, 645, 715 nm). The Ce{sup 3+}* ions and oxygen emitters {sup 1}O{sub 2} and ({sup 1}O{sub 2}){sub 2} are generated in the reaction of Ce{sup 4+} with water and hydrogen peroxide, respectively. CL is generated only in a heterogeneous system «(NH{sub 4}){sub 2}Ce(NO{sub 3}){sub 6}-C{sub 6}H{sub 6}-H{sub 2}O» and completely absent in a homogeneous solution (NH{sub 4}){sub 2}Ce(NO{sub 3}){sub 6} in water containing benzene. This is due to the fact that the redox processes and CL in the «(NH{sub 4}){sub 2}Ce(NO{sub 3}){sub 6}-C{sub 6}H{sub 6}-H{sub 2}O» system are induced by active surface of the (NH{sub 4}){sub 2}Ce(NO{sub 3}){sub 6} crystals. It is through the action of the active surface of the (NH{sub 4}){sub 2}Ce(NO{sub 3}){sub 6} crystals is carried out population of such a high energy level of 5d{sup 1} excited state of Ce{sup 3+}* ion (λ{sub max}=353 nm, 3.7 eV). Discovered CL is the first example of an experimental registration of the Ce{sup 3+}* ion emission in a chemical reaction, because formation of Ce{sup 3+}* ion previously assumed to be in a great many works on the study of CL in reactions of Ce{sup 4+} compounds with various reducing agents, including the reaction with water, initiated by light or catalysts. Possible mechanism generation of new CL in the system under study has been proposed in the paper. - Highlights: • A new chemiluminescence (CL) in the (NH{sub 4}){sub 2}Ce(NO{sub 3}){sub 2}-C{sub 6}H{sub 6}-H{sub 2}O system was discovered. • The emission of the Ce{sup 3+}* ion as a CL emitter has been registered for the first time. • Other emitters of this CL are

Siderophore-mediated oxidation of Ce and fractionation of HREE by Mn (hydr)oxide-coprecipitation and sorption on MnO2: Experimental evidence for negative Ce-anomalies in abiogenic manganese precipitates

Science.gov (United States)

Krämer, Dennis; Tepe, Nathalie; Bau, Michael

2014-05-01

We conducted experiments with Rare Earths and Yttrium (REY), where the REY were sorbed on synthetic manganese dioxide as well as on coprecipitating manganese (hydr)oxide in the presence and absence of the siderophore desferrioxamine-B (DFOB). Siderophores are a group of globally abundant biogenic complexing agents which are excreted by plants and bacteria to enhance the bioavailability of Fe in oxic environments. The model siderophore used in this study, DFOB, is a hydroxamate siderophore occurring in almost all environmental settings with concentrations in the nanomolar to millimolar range and is one of the most thoroughly studied siderophores. In the absence of siderophores and other organic ligands, trivalent Ce is usually surface-oxidized to tetravalent Ce during sorption onto manganese (hydr)oxides. Such Mn precipitates, therefore, often show positive Ce anomalies, whereas the ambient solutions exhibit negative Ce anomalies (Ohta and Kawabe, 2001). In marked contrast, however, REY sorption in the presence of DFOB produces negative Ce anomalies in the Mn precipitates and a distinct and characteristic positive Ce anomaly in the residual siderophore-bearing solution. Furthermore, the heavy REY with ionic radii larger than the radius of Sm are also almost completely prevented from sorption onto the Mn solid phases. Sorption of REY onto Mn (hydr)oxides in the presence of DFOB creates a distinct and pronounced fractionation of Ce and the heavy REY from the light and middle REY. Apart from Ce, which is oxidized in solution by the siderophore, the distribution of the other REY mimics the stability constants for multi-dentate complexes of REY with DFOB, as determined by Christenson & Schijf (2011). Heavier REY are forming stronger complexes (and are hence better "protected" from sorption) than light REY, excluding Ce. Preferential partitioning of Ce into the liquid phase during the precipitation of Mn (hydr)oxides has only rarely been described for natural Mn (hydr

Magnetic Phase Transitions of CeSb. I

DEFF Research Database (Denmark)

Fischer, Pernille Hertz; Lebech, Bente; Meier, G.

1978-01-01

The magnetic ordering of the anomalous antiferromagnet CeSb, which has a NaCl crystal structure, was determined in zero applied magnetic field by means of neutron diffraction investigations of single crystals and powder. Below the Neel temperature TN of (16.1+or-0.1)K, there exist six partially...... a first-order phase transition at TN. At approximately TN/2 there is a first-order phase transition to a FCC type IA low-temperature configuration. The unusual magnetic properties of CeSb, which result from anisotropic exchange and crystalline electric field effects, resemble those of certain actinide Na...

Analysis of the geomorphology surrounding the Chang'e-3 landing site

International Nuclear Information System (INIS)

Li Chun-Lai; Mu Ling-Li; Zou Xiao-Duan; Liu Jian-Jun; Ren Xin; Zeng Xing-Guo; Yang Yi-Man; Zhang Zhou-Bin; Liu Yu-Xuan; Zuo Wei; Li Han

2014-01-01

Chang'e-3 (CE-3) landed on the Mare Imbrium basin in the east part of Sinus Iridum (19.51°W, 44.12°N), which was China's first soft landing on the Moon and it started collecting data on the lunar surface environment. To better understand the environment of this region, this paper utilizes the available high-resolution topography data, image data and geological data to carry out a detailed analysis and research on the area surrounding the landing site (Sinus Iridum and 45 km×70 km of the landing area) as well as on the topography, landform, geology and lunar dust of the area surrounding the landing site. A general topographic analysis of the surrounding area is based on a digital elevation model and digital elevation model data acquired by Chang'e-2 that have high resolution; the geology analysis is based on lunar geological data published by USGS; the study on topographic factors and distribution of craters and rocks in the surrounding area covering 4 km×4 km or even smaller is based on images from the CE-3 landing camera and images from the topographic camera; an analysis is done of the effect of the CE-3 engine plume on the lunar surface by comparing images before and after the landing using data from the landing camera. A comprehensive analysis of the results shows that the landing site and its surrounding area are identified as typical lunar mare with flat topography. They are suitable for maneuvers by the rover, and are rich in geological phenomena and scientific targets, making it an ideal site for exploration

On the mechanism of nanoparticulate CeO{sub 2} toxicity to freshwater algae

Energy Technology Data Exchange (ETDEWEB)

Angel, Brad M., E-mail: Brad.Angel@csiro.au [Centre for Environmental Contaminants Research, CSIRO Land and Water Flagship, Locked Bag 2007, Kirrawee, NSW 2232 (Australia); Vallotton, Pascal [Digital Productivity Flagship, CSIRO, North Ryde, NSW 1670 (Australia); Apte, Simon C. [Centre for Environmental Contaminants Research, CSIRO Land and Water Flagship, Locked Bag 2007, Kirrawee, NSW 2232 (Australia)

2015-11-15

Highlights: • Nanoparticulate CeO{sub 2} less toxic than micron-sized CeO{sub 2}. • UV light filters prevented ROS generation by CeO{sub 2}. • ROS not toxic mechanism: CeO{sub 2} toxicity was similar in presence and absence of ROS. • Strong sorption of nanoparticulate CeO{sub 2} to Pseudokirchneriella subcapitata in synthetic fresh water. • CeO{sub 2} sorption to cells was prevented and toxicity mitigated in the presence of DOC. - Abstract: The factors affecting the chronic (72-h) toxicity of three nanoparticulate (10–34 nm) and one micron-sized form of CeO{sub 2} to the green alga, Pseudokirchneriella subcapitata were investigated. To characterise transformations in solution, hydrodynamic diameters (HDD) were measured by dynamic light scatter, zeta potential values by electrophoretic mobility, and dissolution by equilibrium dialysis. The protective effects of humic and fulvic dissolved organic carbon (DOC) on toxicity were also assessed. To investigate the mechanisms of algal toxicity, the CytoViva hyperspectral imaging system was used to visualise algal–CeO{sub 2} interactions in the presence and absence of DOC, and the role of reactive oxygen species (ROS) was investigated by ‘switching off’ ROS production using UV-filtered lighting conditions. The nanoparticulate CeO{sub 2} immediately aggregated in solution to HDDs measured in the range 113–193 nm, whereas the HDD and zeta potential values were significantly lower in the presence of DOC. Negligible CeO{sub 2} dissolution over the time course of the bioassay ruled out potential toxicity from dissolved cerium. The nanoparticulate CeO{sub 2} concentration that caused 50% inhibition of algal growth rate (IC50) was in the range 7.6–28 mg/L compared with 59 mg/L for micron-sized ceria, indicating that smaller particles were more toxic. The presence of DOC mitigated toxicity, with IC50s increasing to greater than 100 mg/L. Significant ROS were generated in the nanoparticulate CeO{sub 2

Electronic structure of heavy fermion system CePt2In7 from angle-resolved photoemission spectroscopy

International Nuclear Information System (INIS)

Shen Bing; Yu Li; Lyu Shou-Peng; Jia Xiao-Wen; Zhang Yan; Wang Chen-Lu; Hu Cheng; Ding Ying; Sun Xuan; Hu Yong; Liu Jing; Gao Qiang; Zhao Lin; Liu Guo-Dong; Liu Kai; Lu Zhong-Yi; Bauer, E D; Thompson, J D; Xu Zu-Yan; Chen Chuang-Tian

2017-01-01

We have carried out high-resolution angle-resolved photoemission measurements on the Ce-based heavy fermion compound CePt 2 In 7 that exhibits stronger two-dimensional character than the prototypical heavy fermion system CeCoIn 5 . Multiple Fermi surface sheets and a complex band structure are clearly resolved. We have also performed detailed band structure calculations on CePt 2 In 7 . The good agreement found between our measurements and the calculations suggests that the band renormalization effect is rather weak in CePt 2 In 7 . A comparison of the common features of the electronic structure of CePt 2 In 7 and CeCoIn 5 indicates that CeCoIn 5 shows a much stronger band renormalization effect than CePt 2 In 7 . These results provide new information for understanding the heavy fermion behaviors and unconventional superconductivity in Ce-based heavy fermion systems. (paper)

Scintillation characteristics of LiPO3:Ce3+ glass scintillators

International Nuclear Information System (INIS)

Shin, S. W.; Hwang, J. H.

2003-01-01

LiPO 3 :Ce 3+ glass scintillators doped with 0.5, 0.75, 1.0, 1.25 and 1.5wt% cerium as an activator were fabricated. For the best transparency of the LiPO 3 glasses, optimum heating conditions were investigated. Optimum heating temperature and time is 950 .deg. C and 90 min with 1wt% sugar add as reductant. The lattice structure of LiPO 3 :Ce 3+ glass scintillator was monoclinic, its lattice constants(a 0 , b 0 , c 0 ) being 16,490λ, 5.427λ and 13.120λ. Photo-refraction index of LiPO 3 :Ce 3 + measured by SE(Spectroscopic ellipsometry) was 1.45 ∼ 1.5 and its bandgap energy was 2.342 eV. The absorption spectral range of LiPO 3 :Ce 3+ measured by UV-VIS spectrophotometry was 350∼ 375nm and the spectral ranges of photoluminescence(PL) were 400∼450nm and 750∼900nm, its maximum PL intensity appeared at 417nm and 791nm. LiPO 3 :Ce 3 + glass scintillator doped with 0.75wt% cerium showed the best PL intensity. The PL intensity increased until cerium content reaches 0.75wt% above which ir decreased

Integrated chemical process for exothermic wave synthesis of high luminance YAG:Ce phosphors

International Nuclear Information System (INIS)

Won, C.W.; Nersisyan, H.H.; Won, H.I.; Youn, J.W.

2011-01-01

In this paper, high-luminance yellow-emitting Y 3 Al 5 O 12 :Ce 3+ phosphor (YAG:Ce) microparticles were prepared in a solid flame using a 1.425Y 2 O 3 +2.5Al 2 O 3 +0.15CeO 2 +k(KClO 3 +urea)+mNH 4 F precursor mixture (here k is the number of moles of the KClO 3 +urea red-ox mixture, and m is the number of moles of NH 4 F). The self-sustaining combustion process for the entire reaction sample was provided by the heat generated from the KClO 3 +urea mixture. Parametric studies demonstrated that the maximum temperature in the combustion wave varied from 885 to 1200 deg. C for k=2.0-3.0 mole and m=0-1.5 mole. X-ray analysis results showed that the product obtained in the solid flame consisted of Y 3 Al 5 O 12 :Ce 3+ and KCl phases. Therefore, after dissolving potassium chloride in distillated water, pure-phase YAG:Ce phosphor powder was obtained. The as-prepared YAG:Ce phosphor particles had diameters of 10-25 μm and good dispersity and exhibited luminescence properties comparable to those of YAG:Ce phosphor powders prepared by conventional high-temperature processing. - Highlights: → A new solid-flame strategy was developed for synthesizing high-luminance YAG:Ce phosphor. → Adding KClO 3 +CO(NH 2 ) 2 +NH 4 F mixture to oxide powders provides a low-temperature combustion process. → YAG:Ce phosphor particles 10-25 μm in diameter were obtained at 1000-1100 deg. C within tens of seconds. → As-prepared YAG:Ce emission intensity was 90.1-103.2% compared to that of the reference sample.

Electron paramagnetic resonance study of Ce doped partially stabilized ZrO2 crystals

Directory of Open Access Journals (Sweden)

Mikhail А. Borik

2017-09-01

Full Text Available ZrO2 (PSZ solid solutions crystals stabilized with yttrium and cerium oxides have been studied using electron paramagnetic resonance (EPR in the X and Q ranges. Zr3+ have been observed centers in the as-annealed ZrO2 crystals stabilized only by yttrium oxide (2.8 mol% Y2O3. Another type of paramagnetic-O-centers appear as a result of CeO2 addition to ZrO2 crystals along with yttrium oxide. To estimate the concentration of Ce3+ ions in PZS crystals, we recorded the EPR spectra in the presence of a reference at 7 K. Paramagnetic Ce3+ ions have been identified and their relative amount in the PSZ crystals before and after high-temperature heat treatment has been assessed. Annealing in air leads decreases the concentration of Ce3+ ions for all the test compositions and changes the color of the crystals from red to white. After annealing of the sample 2.0Y0.8Ce3Zr, the amount of paramagnetic Ce3+ ions decreased approximately twofold. Paramagnetic centers from Ce3+ have not been detected in the specimen with a low cerium content of 0.1 mol% after annealing which indicates the complete transition of Ce3+ to the Ce4+ state. We show that the forming cerium paramagnetic centers are bound by strong exchange interactions. No angular dependence of the EPR lines of the paramagnetic Ce3+ cations on the applied external magnetic field has been observed. Probable origin of the absence of angular dependence is that the impurity rare-earth ions are located close to one another, forming impurity clusters with an effective spin of Seff=1/2.

Scientific Objectives of China Chang E 4 CE-4 Lunar Far-side Exploration Mission