WorldWideScience

Sample records for determining oxidant mixing

  1. Plutonium oxides and uranium and plutonium mixed oxides. Carbon determination

    International Nuclear Information System (INIS)

    Anon.

    Determination of carbon in plutonium oxides and uranium plutonium mixed oxides, suitable for a carbon content between 20 to 3000 ppm. The sample is roasted in oxygen at 1200 0 C, the carbon dioxide produced by combustion is neutralized by barium hydroxide generated automatically by coulometry [fr

  2. Studies on O/M ratio determination in uranium oxide, plutonium oxide and uranium-plutonium mixed oxide

    International Nuclear Information System (INIS)

    Sampath, S.; Chawla, K.L.

    1975-01-01

    Thermogravimetric studies were carried out in unsintered and sintered samples of uranium oxide, plutonium oxide and uranium-plutonium mixed oxide under different atmospheric conditions (air, argon and moist argon/hydrogen). Moisture loss was found to occur below 200 0 C for uranium dioxide samples, upto 700 0 C for sintered plutonium dioxide and negligible for sintered samples. The O/M ratios for non-stoichiometric uranium dioxide (sintered and unsintered), plutonium dioxide and mixed uranium and plutonium oxides (sintered) could be obtained with a precision of +- 0.002. Two reference states UOsub(2.000) and UOsub(2.656) were obtained for uranium dioxide and the reference state MOsub(2.000) was used for other cases. For unsintered plutonium dioxide samples, accurate O/M ratios could not be obtained of overlap of moisture loss with oxygen loss/gain. (author)

  3. Determination of the oxygen-metal-ratio of uranium-americium mixed oxides

    International Nuclear Information System (INIS)

    Bartscher, W.

    1982-01-01

    During the dissolution of uranium-americium mixed oxides in phosphoric acid under nitrogen tetravalent uranium is oxidized by tetravalent americium. The obtained hexavalent uranium is determined by constant potential coulometry. The coulombs measured are equivalent to the oxygen in excess of the minimum composition of UO 2 x AmO 1 . 5 . The total uranium content of the sample is determined in a subsequent coulometric titration. The oxygen-metal ratio of the sample can be calculated for a given uranium-americium ratio. An excess of uranium dioxide is necessary in order to suppress the oxidation of water by tetravalent americium. The standard deviation of the method is 0.0017 O/M units. (orig.) [de

  4. Fluorine and chlorine determination in mixed uranium-plutonium oxide fuel and plutonium dioxide

    International Nuclear Information System (INIS)

    Elinson, S.V.; Zemlyanukhina, N.A.; Pavlova, I.V.; Filatkina, V.P.; Tsvetkova, V.T.

    1981-01-01

    A technique of fluorine and chlorine determination in the mixed uranium-plutonium oxide fuel and plutonium dioxide, based on their simultaneous separation by means of pyrohydrolysis, is developed. Subsequently, fluorine is determined by photometry with alizarincomplexonate of lanthanum or according to the weakening of zirconium colouring with zylenol orange. Chlorine is determined using the photonephelometric method according to the reaction of chloride-ion interaction with silver nitrate or by spectrophotometric method according to the reaction with mercury rhodanide. The lower limit of fluorine determination is -6x10 -5 %, of chlorine- 1x10 -4 % in the sample of 1g. The relative mean quadratic deviation of the determination result (Ssub(r)), depends on the character of the material analyzed and at the content of nx10 -4 - nx10 -3 mass % is equal to from 0.05 to 0.32 for fluorine and from 0.11 to 0.35 for chlorine [ru

  5. Determination of rare earth elements, hafnium and cadmium in sintered pellets of mixed thorium and uranium oxides by neutron activation

    International Nuclear Information System (INIS)

    Cardoso, S.N.M.

    1987-01-01

    This work shows the development of a method for determination of the rare-earth elements (Eu, Sm, Dy and Gd), Hf and Cd contents in sinterized U and Th mixed oxides by neutron activation analysis. The sample is dissolved in nitric/fluoridric (0,1% HF) medium, to dryness and redissolved in 6N HCl solution. The Hf is extracted into organic phase (0,5 M TTA/benzene), irradiated and analysed through 181 Hf isotope energy peak. The aqueous phase is treated with NH 4 OH for the precipitation of hidroxides. Then, these are dissolved in 6N HNO 3 solution. The extraction of U and Th is made in two steps, one with TBP/CCl 4 and another with 0,5 M TTA/C 6 H 6 . Then the rare-earth elements and Cd are irradiated and determined by gamma spectrometry. (author) [pt

  6. Determination of the O/M ratios of polynary uranium oxides by Ce(IV)-Fe(II) back titration after dissolution in mixed sulphuric and phosphoric acids

    International Nuclear Information System (INIS)

    Fujino, T.; Sato, N.; Yamada, K.

    1996-01-01

    Uranium (IV) in polynary uranium oxides is determined after the solid has been dissolved in a warm mixed solution of sulphuric and phosphoric acids containing excess Ce(IV). The latter is titrated with a Fe(II) standard solution using ferroin as indicator. This method is especially effective for (mixed) uranium oxides which are difficult to dissolve in hot Ce(IV) sulphuric acid. The standard deviation of the determined x value in polynary oxides is estimated to be below ± 0.004 for samples of 10-30 mg. (orig.)

  7. Determination of the O/M ratios of polynary uranium oxides by Ce(IV)-Fe(II) back titration after dissolution in mixed sulphuric and phosphoric acids.

    Science.gov (United States)

    Fujino, T; Sato, N; Yamada, K

    1996-01-01

    Uranium (IV) in polynary uranium oxides is determined after the solid has been dissolved in a warm mixed solution of sulphuric and phosphoric acids containing excess Ce(IV). The latter is titrated with a Fe(II) standard solution using ferroin as indicator. This method is especially effective for (mixed) uranium oxides which are difficult to dissolve in hot Ce(IV) sulphuric acid. The standard deviation of the determined x value in polynary oxides is estimated to be below +/- 0.004 for samples of 10-30 mg.

  8. Direct Determination of Oxidation States of Uranium in Mixed-Valent Uranium Oxides Using Total Reflection X-ray Fluorescence X-ray Absorption Near-Edge Spectroscopy.

    Science.gov (United States)

    Sanyal, Kaushik; Khooha, Ajay; Das, Gangadhar; Tiwari, M K; Misra, N L

    2017-01-03

    Total reflection X-ray fluorescence (TXRF)-based X-ray absorption near-edge spectroscopy has been used to determine the oxidation state of uranium in mixed-valent U 3 O 8 and U 3 O 7 uranium oxides. The TXRF spectra of the compounds were measured using variable X-ray energies in the vicinity of the U L 3 edge in the TXRF excitation mode at the microfocus beamline of the Indus-2 synchrotron facility. The TXRF-based X-ray absorption near-edge spectroscopy (TXRF-XANES) spectra were deduced from the emission spectra measured using the energies below and above the U L 3 edge in the XANES region. The data processing using TXRF-XANES spectra of U(IV), U(V), and U(VI) standard compounds revealed that U present in U 3 O 8 is a mixture of U(V) and U(VI), whereas U in U 3 O 7 is mixture of U(IV) and U(VI). The results obtained in this study are similar to that reported in literature using the U M edge. The present study has demonstrated the possibility of application of TXRF for the oxidation state determination and elemental speciation of radioactive substances in a nondestructive manner with very small amount of sample requirement.

  9. The oxidative pulverisation of mixed oxide fuels

    International Nuclear Information System (INIS)

    Rance, Peter; Beznosyuk, Vassily

    2005-01-01

    An investigation of the oxidation of mixed uranium-plutonium oxide (MOx) fuels containing from 5-30% plutonium (heavy metal basis) in air and oxygen atmospheres has been undertaken. MOx pellets prepared by a co-precipitation process were oxidised at temperatures from 600 to 1200degC, samples were reduced back to the MO 2 state and then re-oxidised. Weight changes were monitored during each procedure and the phases present in the products from each treatment were analysed using X-ray diffraction (XRD). Samples containing up to 10% Pu were oxidised sufficiently to cause pulverisation of the fuel matrix by a single oxidation treatment at 600degC whereas samples containing higher plutonium contents required a cycle of oxidation-reduction-oxidation cause them to become fragmented. XRD data suggests the formation of plutonium-rich and plutonium-lean grains during the reduction cycle and it is suggested that the oxidation of plutonium-lean grains during re-oxidation step is responsible for the break up of the pellets during this step. (author)

  10. Determination of strychnine, brucine, strychnine N-oxide, and brucine N-oxide in plasma samples after the oral administration of processed semen strychni extract by high-performance liquid chromatography with ultrasound-assisted mixed cloud point extraction.

    Science.gov (United States)

    Guo, Jun; Meng, Hua; Li, Huang Huang; Wang, Qiao Feng

    2016-07-01

    A sensitive and efficient mixed cloud point extraction combined with high-performance liquid chromatography was developed for the simultaneous separation and determination of four alkaloids (strychnine, strychnine N-oxide, brucine, and brucine N-oxide) in plasma after the oral administration of processed semen strychni extract. Tergitol TMN-6 and cetyl-trimethyl ammonium bromide were chosen as the mixed surfactants, and ultrasound was employed to enhance the extraction efficiency. Some important parameters affecting the mixed cloud point extraction efficiency, such as the content of Tergitol TMN-6 and cetyl-trimethyl ammonium bromide, pH, salt effect, extraction temperature, and ultrasound time were studied and optimized. Under optimum conditions, the linear range of four alkaloids was from 1.0 to 1000 ng/mL. All correlation coefficients of the calibration curves were higher than 0.9993. The intraday and interday precision were below 8.65% and the limits of detection for the four alkaloids were less than 1.0 ng/mL (S/N = 3). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. [Ammonia oxidation kinetics of ammonia oxidizer mixed culture under the conditions of O2 and trace NO2 mixed gasses].

    Science.gov (United States)

    Zhang, Dai-Jun; Zu, Bo; Ren, Hong-Yang; Zhang, Ping; Cong, Li-Ying; Yan, Qing

    2008-01-01

    The kinetics of the NO2-dependent ammonia oxidation was developed for ammonia oxidizer mixed culture when there was no molecular oxygen in the batch tests. The kinetics parameters were determined, where the half saturate coefficient of NO2 was 0.821 micromol x L(-1), inhibition coefficient of NO2 concentration was 1.721 micromol x L(-1), and the maximum ammonia oxidation rate were 0.144 mg x (mg x h)(-1). After adding the volume fraction of O2 was 2% to trace NO2, the ammonia oxidation rates increased obviously. The maximum ammonia oxidation rate, 0.198 mg x (mg x h)(-1) occurred under the condition of the mixed gasses containing the volume fraction of O2 was 2% and 50 x 10(-6) NO2. Under the condition of mixed gasses containing the volume fraction of O2 was 21% to trace NO2, the ammonia oxidation rates further increased greatly. The maximum ammonia oxidation rate, 0.477 mg x (mg x h)(-1) occurred when the volume fraction of O2 was 21% and 100 x 10(-6) NO2 in the mixed gas, which is 3 times higher than the general aerobic ammonia oxidation rate. The function for NO2 apparently to enhance ammonia oxidation was suggested. The kinetics model of ammonia oxidation under the conditions of O2 and trace NO2 mixed gasses was developed. The model was validated by the results of ammonia oxidation experiments under the conditions of the mixed gasses containing 2% O2 and trace NO2. The mechanism for NO2 to enhance ammonia oxidation under the conditions of O2 and trace NO2 mixed gasses was discussed.

  12. Ion and mixed conducting oxides as catalysts

    NARCIS (Netherlands)

    Gellings, P.J.; Bouwmeester, Henricus J.M.

    1992-01-01

    This paper gives a survey of the catalytic properties of solid oxides which display oxygen ion or mixed (i.e. ionic + electronic) conductivity. Particular consideration is given to the oxidation-reduction reactions of gas phase components, but attention is also devoted to oxygen exchange between gas

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

    International Nuclear Information System (INIS)

    Santiago, T.N.

    1980-10-01

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

  14. Selective propene oxidation on mixed metal oxide catalysts

    International Nuclear Information System (INIS)

    James, David William

    2002-01-01

    Selective catalytic oxidation processes represent a large segment of the modern chemical industry and a major application of these is the selective partial oxidation of propene to produce acrolein. Mixed metal oxide catalysts are particularly effective in promoting this reaction, and the two primary candidates for the industrial process are based on iron antimonate and bismuth molybdate. Some debate exists in the literature regarding the operation of these materials and the roles of their catalytic components. In particular, iron antimonate catalysts containing excess antimony are known to be highly selective towards acrolein, and a variety of proposals for the enhanced selectivity of such materials have been given. The aim of this work was to provide a direct comparison between the behaviour of bismuth molybdate and iron antimonate catalysts, with additional emphasis being placed on the component single oxide phases of the latter. Studies were also extended to other antimonate-based catalysts, including cobalt antimonate and vanadium antimonate. Reactivity measurements were made using a continuous flow microreactor, which was used in conjunction with a variety of characterisation techniques to determine relationships between the catalytic behaviour and the properties of the materials. The ratio of Fe/Sb in the iron antimonate catalyst affects the reactivity of the system under steady state conditions, with additional iron beyond the stoichiometric value being detrimental to the acrolein selectivity, while extra antimony provides a means of enhancing the selectivity by decreasing acrolein combustion. Studies on the single antimony oxides of iron antimonate have shown a similarity between the reactivity of 'Sb 2 O 5 ' and FeSbO 4 , and a significant difference between these and the Sb 2 O 3 and Sb 2 O 4 phases, implying that the mixed oxide catalyst has a surface mainly comprised of Sb 5+ . The lack of reactivity of Sb 2 O 4 implies a similarity of the surface with

  15. Mixed iron-manganese oxide nanoparticles

    NARCIS (Netherlands)

    Lai, Jriuan; Shafi, Kurikka V.P.M.; Ulman, Abraham; Loos, Katja; Yang, Nan-Loh; Cui, Min-Hui; Vogt, Thomas; Estournès, Claude; Locke, Dave C.

    2004-01-01

    Designing nanoparticles for practical applications requires knowledge and control of how their desired properties relate to their composition and structure. Here, we present a detailed systematic study of mixed iron-manganese oxide nanoparticles, showing that ultrasonication provides the high-energy

  16. Electron donating and acid-base properties of cerium oxide and its mixed oxides with alumina

    International Nuclear Information System (INIS)

    Sugunan, S.; Jalaja, J.M.

    1994-01-01

    The electron donating properties of cerium oxide activated at 300, 500 and 800 degC and of its mixed oxides with alumina were examined based on the adsorption of electron acceptors exhibiting different electron affinities. The surface acidity/basicity of the oxides was determined by titrimetry; the H 0,max values are given. The limit of electron transfer from the oxide surface lies within the region of 1.77 and 2.40 eV in terms of the electron affinity of the electron acceptor. Cerium oxide promotes the electron donor nature of alumina while leaving the limit of electron transfer unchanged. 2 tabs., 4 figs., 13 refs

  17. Alternative oxidation technologies for organic mixed waste

    International Nuclear Information System (INIS)

    Borduin, L.C.; Fewell, T.

    1998-01-01

    The Mixed Waste Focus Area (MWFA) is currently supporting the development and demonstration of several alternative oxidation technology (AOT) processes for treatment of combustible mixed low-level wastes. AOTs have been defined as technologies that destroy organic material without using open-flame reactions. AOTs include both thermal and nonthermal processes that oxidize organic wastes but operate under significantly different physical and chemical conditions than incinerators. Nonthermal processes currently being studied include Delphi DETOX and acid digestion at the Savannah River Site (SRS), and direct chemical oxidation at Lawrence Livermore National Laboratory (LLNL). All three technologies are at advanced stages of development or are entering the demonstration phase. Nonflame thermal processes include catalytic chemical oxidation, which is being developed and deployed at Lawrence Berkeley National Laboratory (LBNL), and steam reforming, a commercial process being supported by the Department of Energy (DOE). Although testing is complete on some AOT technologies, most require additional support to complete some or all of the identified development objectives. Brief descriptions, status, and planned paths forward for each of the technologies are presented

  18. 40 CFR 721.4610 - Mixed metal oxides (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Mixed metal oxides (generic). 721.4610... Substances § 721.4610 Mixed metal oxides (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as mixed metal oxides (PMN P-98-0002...

  19. Mixed alumina and cobalt containing plasma electrolytic oxide coatings

    Science.gov (United States)

    Yar-Mukhamedova, G. Sh; Ved', M. V.; Karakurkchi, A. V.; Sakhnenko, N. D.

    2017-06-01

    Principles of plasma electrolytic oxidation of the AL25 aluminum alloy in diphosphate alkali solutions containing cobalt(2+) cations are discussed. It has been established that a variation in the concentration of the electrolyte components provides the formation of mixed-oxide coatings consisting of the basic matrix materials and the cobalt oxides of different content. An increase in the cobalt oxide content in the coating is achieved by the variation in electrolysis current density as well as the treatment time due to both the electrochemical and thermo-chemical reactions at substrate surface and in spark region. Current density intervals that provide micro-globular surface formation and uniform cobalt distribution in the coating are determined. The composition and morphology of the surface causes high catalytic properties of synthesized materials, which confirmed the results of testing in model reaction CO and benzene oxidation as well as fuel combustion for various modes of engine operation.

  20. Investigation of Mixed Oxide Catalysts for NO Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Szanyi, Janos; Karim, Ayman M.; Pederson, Larry R.; Kwak, Ja Hun; Mei, Donghai; Tran, Diana N.; Herling, Darrell R.; Muntean, George G.; Peden, Charles HF; Howden, Ken; Qi, Gongshin; Li, Wei

    2014-12-09

    The oxidation of engine-generated NO to NO2 is an important step in the reduction of NOx in lean engine exhaust because NO2 is required for the performance of the LNT technology [2], and it enhances the activities of ammonia selective catalytic reduction (SCR) catalysts [1]. In particular, for SCR catalysts an NO:NO2 ratio of 1:1 is most effective for NOx reduction, whereas for LNT catalysts, NO must be oxidized to NO2 before adsorption on the storage components. However, NO2 typically constitutes less than 10% of NOx in lean exhaust, so catalytic oxidation of NO is essential. Platinum has been found to be especially active for NO oxidation, and is widely used in DOC and LNT catalysts. However, because of the high cost and poor thermal durability of Pt-based catalysts, there is substantial interest in the development of alternatives. The objective of this project, in collaboration with partner General Motors, is to develop mixed metal oxide catalysts for NO oxidation, enabling lower precious metal usage in emission control systems. [1] M. Koebel, G. Madia, and M. Elsener, Catalysis Today 73, 239 (2002). [2] C. H. Kim, G. S. Qi, K. Dahlberg, and W. Li, Science 327, 1624 (2010).

  1. effects of mixed of mixed of mixed alkaline earth oxides in potash

    African Journals Online (AJOL)

    eobe

    2 DEPARTMENT OF MECHANICAL ENGINEERING, UNIVERSITY OF UYO,UYO, AKWA-IBOM STATE, NIGERIA. E-mail address mail address mail addresses: 1 oyeahama1@yahoo.com, 2 memetie@yahoo.com. ABSTRACT. The aim of this work is to investigate the effects of mixed alkaline earth oxide. The aim of this work ...

  2. Heterogeneous Partial (ammOxidation and Oxidative Dehydrogenation Catalysis on Mixed Metal Oxides

    Directory of Open Access Journals (Sweden)

    Jacques C. Védrine

    2016-01-01

    Full Text Available This paper presents an overview of heterogeneous partial (ammoxidation and oxidative dehydrogenation (ODH of hydrocarbons. The review has been voluntarily restricted to metal oxide-type catalysts, as the partial oxidation field is very broad and the number of catalysts is quite high. The main factors of solid catalysts for such reactions, designated by Grasselli as the “seven pillars”, and playing a determining role in catalytic properties, are considered to be, namely: isolation of active sites (known to be composed of ensembles of atoms, Me–O bond strength, crystalline structure, redox features, phase cooperation, multi-functionality and the nature of the surface oxygen species. Other important features and physical and chemical properties of solid catalysts, more or less related to the seven pillars, are also emphasized, including reaction sensitivity to metal oxide structure, epitaxial contact between an active phase and a second phase or its support, synergy effect between several phases, acid-base aspects, electron transfer ability, catalyst preparation and activation and reaction atmospheres, etc. Some examples are presented to illustrate the importance of these key factors. They include light alkanes (C1–C4 oxidation, ethane oxidation to ethylene and acetic acid on MoVTe(SbNb-O and Nb doped NiO, propene oxidation to acrolein on BiMoCoFe-O systems, propane (ammoxidation to (acrylonitrile acrylic acid on MoVTe(SbNb-O mixed oxides, butane oxidation to maleic anhydride on VPO: (VO2P2O7-based catalyst, and isobutyric acid ODH to methacrylic acid on Fe hydroxyl phosphates. It is shown that active sites are composed of ensembles of atoms whose size and chemical composition depend on the reactants to be transformed (their chemical and size features and the reaction mechanism, often of Mars and van Krevelen type. An important aspect is the fact that surface composition and surface crystalline structure vary with reaction on stream until

  3. Synthesis and characterization of composites of mixed oxides of iron ...

    Indian Academy of Sciences (India)

    article/fulltext/boms/034/04/0843-0851. Keywords. Nanocomposites; polymer matrix; neodymium oxide; spinel ferrites; quadrupole splitting; Scherrer equation. Abstract. Nanocomposites of mixed oxides of iron and neodymium in polymer matrix of ...

  4. Sol-Gel/Hydrothermal Synthesis of Mixed Metal Oxide

    African Journals Online (AJOL)

    Mixed metal oxides of titanium and zinc nanocomposites were prepared through sol-gel method under hydrothermal condition ... Keywords: Nanocomposites, Titanium dioxide, Zinc oxide, Particle sizes, Optical property, X-Ray Diffraction. ABSTRACT. 321 ... doping with other semiconductors like zinc oxide, aluminium oxide ...

  5. Microstructure and thermophysical characterization of mixed oxide fuels

    Energy Technology Data Exchange (ETDEWEB)

    Freibert, Franz J [Los Alamos National Laboratory; Salich, Tarik A [Los Alamos National Laboratory; Schwartz, Daniel S [Los Alamos National Laboratory; Hampel, Fred G [Los Alamos National Laboratory; Mitchell, Jeremy N [Los Alamos National Laboratory; Davis, Charles C [Los Alamos National Laboratory; Neuman, Angelique D [Los Alamos National Laboratory; Willson, Steve P [Los Alamos National Laboratory; Dunwoody, John T [Los Alamos National Laboratory

    2009-01-01

    Pre-irradiated thermodynamic and microstructural properties of nuclear fuels form the necessary set of data against which to gauge fuel performance and irradiation damage evolution. This paper summarizes recent efforts in mixed-oxide and minor actinide-bearing mixed-oxide ceramic fuels fabrication and characterization at Los Alamos National Laboratory. Ceramic fuels (U{sub 1-x-y-z}u{sub x}Am{sub y}Np{sub z})O{sub 2} fabricated in the compositional ranges of 0.19 {le} x {le} 0.3 Pu, 0 {le} y {le} 0.05 Am, and O {le} z {le} O.03 Np exhibited a uniform crystalline face-centered cubic phase with an average grain size of 14{micro}m; however, electron microprobe analysis revealed segregation of NpO{sub 2} in minor actinide-bearing fuels. Immersion density and porosity analysis demonstrated an average density of 92.4% theoretical for mixed-oxide fuels and an average density of 89.5 % theoretical density for minor actinide-bearing mixed-oxide fuels. Examined fuels exhibited mean thermal expansion value of 12.56 x 10{sup -6} C{sup -1} for temperature range (100 C < T < 1500 C) and ambient temperature Young's modulus and Poisson's ratio of 169 GPa and of 0.327, respectively. Internal dissipation as determined from mechanical resonances of these ceramic fuels has shown promise as a tool to gauge microstructural integrity and to interrogate fundamental properties.

  6. Mediated electrochemical oxidation of mixed wastes

    International Nuclear Information System (INIS)

    Chiba, Z.

    1993-04-01

    The Mediated Electrochemical Oxidation (MEO) process was studied for destroying low-level combustible mixed wastes at Rocky Flats Plant. Tests were performed with non-radioactive surrogate materials: Trimsol for contaminated cutting oils, and reagent-grade cellulose for contaminated cellulosic wastes. Extensive testing was carried out on Trimsol in both small laboratory-scale apparatus and on a large-scale system incorporating an industrial-size electrochemical cell. Preliminary tests were also carried out in the small-scale system with cellulose. Operating and system parameters that were studied were: use of a silver-nitric acid versus a cobalt-sulfuric acid system, effect of electrolyte temperature, effect of acid concentration, and effect of current density. Destruction and coulombic efficiencies were calculated using data obtained from continuous carbon dioxide monitors and total organic carbon (TOC) analysis of electrolyte samples. For Trimsol, the best performance was achieved with the silver-nitrate system at high acid concentrations, temperatures, and current densities. Destruction efficiencies of 99% or greater, and coulombic efficiencies up to 70% were obtained. For the cellulose, high destruction efficiencies and reasonable coulombic efficiencies were obtained for both silver-nitrate and cobalt-sulfate systems

  7. Iron-tellurium-selenium mixed oxide catalysts for the selective oxidation of propylene to acrolein

    International Nuclear Information System (INIS)

    Patel, B.M.; Price, G.L.

    1990-01-01

    This paper reports on iron-tellurium-selenium mixed oxide catalysts prepared by coprecipitation from aqueous solution investigated for the propylene to acrolein reaction in the temperature range 543-773 K. Infrared spectroscopy, electron dispersive X-ray analysis, X-ray diffraction, and isotopic tracer techniques have also been employed to characterize this catalytic system. Properties of the Fe-Te-Se mixed oxide catalysts have been compared with Fe-Te mixed oxides in an effort to deduce the functionality of Se. The selenium in the Fe-Te-Se-O catalyst has been found to be the hydrocarbon activating site. The activation energies for the acrolein and carbon dioxide formation are 71 and 54 kJ/mol, respectively. Reactions carried out with 18 O 2 have shown lattice oxygen to be primarily responsible for the formation of both acrolein and carbon dioxide. The initial and rate-determining step for acrolein formation is hydrogen abstraction as determined by an isotope effect associated with the C 3 D 6 reaction. No isotope effect is observed for carbon dioxide formation from C 3 D 6 suggesting that CO 2 is formed by parallel, not consecutive, oxidation of propylene

  8. Cladding dimensional changes in mixed oxide fuel pins

    International Nuclear Information System (INIS)

    Makenas, B.J.; Jost, J.W.; Hales, J.W.

    1980-01-01

    Several types of stainless steel (304, 316, 316-20% Cold Worked, and 316 Titanium stabilized 20% CW) have been used as cladding for mixed oxide (U, Pu)O 2 fuel pins irradiated in EBR-II. All of the materials have performed satisfactorily in their respective experimental subassemblies but significant differences in swelling and inelastic strain behavior have been found at high fast fluences among the different materials and among different heats of the same material. Cladding diameter increases were measured for 622 developmental and FFTF reference design fuel pins which were irradiated in 19 experimental subassemblies. Fuel pin diameters were determined from multiangle axial trace profilometry measurements

  9. Investigation of the oxidative dehydrogenation of n-butenes over mixed tin-antimony oxides

    Energy Technology Data Exchange (ETDEWEB)

    Varga, K.; Halasz, J.; Hernadi, K.; Fejes, P.

    1985-01-01

    The oxidative of n-butenes in the gaseous phase over mixed oxide catalysts SnO/sub 2/-SbO/sub 4/ was investigated in a pulse reactor and in a recirculatory flow reactor at 523-673 K. Over catalysts containing more than 50% tin, practically the total quantity of converted 1-butene was transformed into butadiene. The reaction of 2-butene depended to a considerable extent on the composition of the catalyst. The lowest conversion was found for the mixed oxide with Sn:Sb = 1:1, but in the formation of butadiene this was the most selective catalysts. The selectivity decreased appreciably as the reaction temperature rose. From measurements in the recirculatory flow reactor, apparent rate constants and activation energies of reactions were determined; the latter values for 1-butene and 2-butene, were 105 and 70 kJ mol/sup -1/, respectively. This difference was explained by the dissimilarity of the rate-determining steps in the two reactions. The oxidation of 2-butene precedes isomerization to 1-butene on surface acid sites, with subsequent conversion to butadiene on oxidation centers via a ..pi..-allyl surface intermediate.

  10. Synthesis and characterization of composites of mixed oxides of iron ...

    Indian Academy of Sciences (India)

    2016-08-26

    Aug 26, 2016 ... Nanocomposites of mixed oxides of iron and neodymium in polymer matrix of anilineformaldehyde are reported. The composites have been obtained by treating the aqueous solution of aniline, hydrochloric acid and formaldehyde with halide of iron and neodymium oxide. The infra-red spectra show broad ...

  11. Synthesis and characterization of composites of mixed oxides of iron ...

    Indian Academy of Sciences (India)

    Administrator

    Nanocomposites of mixed oxides of iron and neodymium in polymer matrix of aniline- formaldehyde are reported. The composites have been obtained by treating the aqueous solution of aniline, hydrochloric acid and formaldehyde with halide of iron and neodymium oxide. The infra-red spectra show broad peaks at ~ 590 ...

  12. A structural analysis of W-Sb mixed oxide catalyst

    International Nuclear Information System (INIS)

    Lim, Y.S.; Jung, S.H.; Hong, S.-T.; Jung, S.M.; Kim, J.; Chae, J.H.; Lee, W.-H.

    2005-01-01

    An investigation on the structure of W-Sb mixed oxide catalyst, W 12 Sb x O y (x = 1, 3, 5), is proposed. The W-Sb mixed oxide powders were prepared by the calcination of aqueous precursors, antimony tartrate and ammoniummetatungstate, and characterized with scanning electron microscope, X-ray diffractometer, and transmission electron microscope. At low content of Sb (x = 1), the W-Sb mixed oxide powder consisted of polyhedral particles, and their crystal structure was triclinic WO 3 . At higher content (x = 3, 5), majority of the oxide powders were bar-shaped particles, consisting of triclinic WO 3 and tetragonal WO 3 . With electron diffraction pattern and simulation, Sb incorporation into the cuboctahedral sites of perovskite-like WO 3 was proved and its effect on the phase transition from triclinic to tetragonal was discussed

  13. An investigation of mixed cation oxide glasses

    International Nuclear Information System (INIS)

    Brook, H.C.

    1999-02-01

    This study has been undertaken with several purposes in mind. Firstly, the author wished to ascertain whether EXAFS would show the mixed alkali (MAE) in a mixed alkali glass in shell parameters other than those for the first shell, as well as being a structural probe. Secondly, it was desired to see whether borate glasses show the MAE in EXAFS. Thirdly, the author attempted to ascertain whether cations of different charges would show an effect similar to the MAE. Fourthly, to use NMR as a second structure probe in an attempt to gain a better understanding of the structure. Fifthly, to perform electrical conductivity experiments to try to link the conductivity behaviour with structural changes. Finally, to attempt to develop a generalised explanation of the origins of the MAE and the variations in physical properties in glasses. (author)

  14. Description of a reference mixed oxide fuel fabrication plant (MOFFP)

    International Nuclear Information System (INIS)

    1978-01-01

    In order to evaluate the environment impact, due to the Mixed Oxide Fuel Fabrication Plants, work has been initiated to describe the general design and operating conditions of a reference Mixed Oxide Fuel Fabrication Plant (MOFFP) for the 1990 time frame. The various reference data and basic assumptions for the reference MOFFP plant have been defined after discussion with experts. The data reported in this document are only made available to allow an evaluation of the environmental impact due to a reference MOFFP plant. These data have therefore not to be used as recommandation, standards, regulatory guides or requirements

  15. Selective oxidation of isobutane on V–Mo–O mixed oxide catalysts

    Directory of Open Access Journals (Sweden)

    GHEORGHITA MITRAN

    2008-01-01

    Full Text Available Four V–Mo–O mixed metal oxides were prepared, characterized and tested for the selective oxidation of isobutane in the temperature range 350–550 °C, at atmospheric pressure. Isobutane was mainly oxidized to iso-butene and carbon oxides. The systems with low vanadium contents showed low activities but high isobutene selectivities, while the systems with high vanadium contents showed high activities with high carbon oxides selectivities. The effects of temperature, contact time and the molar ratio iso-butane to oxygen on the conversion of isobutane and the selectivity of the oxidation were studied.

  16. Effects of Mixed Alkaline Earth Oxides in Potash Silicate Glass ...

    African Journals Online (AJOL)

    The aim of this work is to investigate the effects of mixed alkaline earth oxide in potash silicate glasses with regards to their physical properties. More recently; there has been an increase in the demand for light weight glasses which retains their physical and chemical properties for both domestic and industrial applications.

  17. Dissolution of mixed oxide spent fuel from FBR

    International Nuclear Information System (INIS)

    Sanyoshi, H.; Nishina, H.; Toyota, O.; Yamamoto, R.; Nemoto, S.; Okamoto, F.; Togashi, A.; Kawata, T.; Hayashi, S.

    1991-01-01

    At the Tokai Works of the Power Reactor and Nuclear Fuel Development Corporation (PNC), the Chemical Processing Facility (CPF) has been continuing operation since 1982 for laboratory scale hot experiments on reprocessing of FBR mixed oxide fuel. As a part of these experiments, dissolution experiments have been performed to define the key parameters affecting dissolution rates such as concentration of nitric acid, temperature and burnup and also to confirm the amount of insoluble residue. The dissolution rate of the irradiated fuel was determined to be in proportion to the 1.7 power of the nitric acid concentration. The activation energy determined from the experiments varied from 6 to 11 kcal/mol depending on the method of dissolution. The dissolution rate decreased as the fuel burnup increased in low nitric acid media below 5 mol/l. However, it was found that the effect of the burnup became negligible in a high concentration of nitric acid media. The amount of insoluble residue and its constituents were evaluated by changing the dissolution condition. (author)

  18. Factors affecting radium removal using mixed iron-manganese oxides

    Energy Technology Data Exchange (ETDEWEB)

    Mott, H.V. Singh, S.; Kondapally, V.R. (South Dakota School of Mines and Technology, Rapid City, SD (United States))

    1993-10-01

    Batch experiments confirmed that sorption of radium by a mixed iron-manganese oxide solid phase shows promise for treating radium-contaminated water. The capacities of these mixed oxides for sorption of radium depend on the composition of the solid phase, the pH of the aqueous solution, and the presence of competing cations. The removal of the oxide-radium complexes from aqueous suspension by manganese greensand filtration was also investigated. It was found that influent radium concentrations of 100 pCi/L were reduced to 2--9 pCi/L by this process. Additional study of the fate of radium in manganese greensand filters is recommended before this procedure is used for drinking water treatment.

  19. Photochemical oxidation: A solution for the mixed waste dilemma

    Energy Technology Data Exchange (ETDEWEB)

    Prellberg, J.W.; Thornton, L.M.; Cheuvront, D.A. [Vulcan Peroxidation Systems, Inc., Tucson, AZ (United States)] [and others

    1995-12-31

    Numerous technologies are available to remove organic contamination from water or wastewater. A variety of techniques also exist that are used to neutralize radioactive waste. However, few technologies can satisfactorily address the treatment of mixed organic/radioactive waste without creating unacceptable secondary waste products or resulting in extremely high treatment costs. An innovative solution to the mixed waste problem is on-site photochemical oxidation. Liquid-phase photochemical oxidation has a long- standing history of successful application to the destruction of organic compounds. By using photochemical oxidation, the organic contaminants are destroyed on-site leaving the water, with radionuclides, that can be reused or disposed of as appropriate. This technology offers advantages that include zero air emissions, no solid or liquid waste formation, and relatively low treatment cost. Discussion of the photochemical process will be described, and several case histories from recent design testing, including cost analyses for the resulting full-scale installations, will be presented as examples.

  20. Factors affecting radium removal using mixed iron-manganese oxides

    International Nuclear Information System (INIS)

    Mott, H.V. Singh, S.; Kondapally, V.R.

    1993-01-01

    Batch experiments confirmed that sorption of radium by a mixed iron-manganese oxide solid phase shows promise for treating radium-contaminated water. The capacities of these mixed oxides for sorption of radium depend on the composition of the solid phase, the pH of the aqueous solution, and the presence of competing cations. The removal of the oxide-radium complexes from aqueous suspension by manganese greensand filtration was also investigated. It was found that influent radium concentrations of 100 pCi/L were reduced to 2--9 pCi/L by this process. Additional study of the fate of radium in manganese greensand filters is recommended before this procedure is used for drinking water treatment

  1. Experiences of ZAMG on mixing height determination

    Energy Technology Data Exchange (ETDEWEB)

    Piringer, M. [Zentralanstalt fuer Meteorologie und Geodynamik, ZAMG, Vienna (Austria)

    1997-10-01

    Temperature inversions in the boundary layer occur quite often, esp. in mountainous terrain by which Austria is covered to a large extent, and can lead to enhanced pollution at the surface because the air volume available for dilution is then vertically limited. The Department of Environmental Meteorology of ZAMG therefore set up several field programs in the past to study such conditions at a variety of sites in Austria, using tethersondes and Sodars. Early investigations aimed at comparing Sodar echo profiles to the tethersonde temperature profiles to derive mixing heights from the Sodar echo structure. More recently, evolving from KONGEX, the `convective boundary layer experiment`, mixing heights calculated for Vienna by the OML model were compared to those derived from radiosonde and tethersonde potential temperature profiles. Results of these investigations will be presented, focussing on the problems when using the different methods. New efforts to derive mixing heights from data were also undertaken and are discussed separately. (au)

  2. Co-Mn-Al Mixed Oxides as Catalysts for Ammonia Oxidation to N2O.

    Czech Academy of Sciences Publication Activity Database

    Ludvíková, Jana; Jablońska, M.; Jirátová, Květa; Chmielarz, L.; Balabánová, Jana; Kovanda, F.; Obalová, L.

    2016-01-01

    Roč. 42, č. 3 (2016), s. 2669-2690 ISSN 0922-6168 R&D Projects: GA ČR GA14-13750S Institutional support: RVO:67985858 Keywords : Co-Mn-Al mixed oxides * catalytic ammonia oxidation * N2O production * mechanochemical production Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.369, year: 2016

  3. Fission gas behavior in mixed-oxide fuel during transient overpower

    International Nuclear Information System (INIS)

    Randklev, E.H.; Treibs, H.A.; Mastel, B.; Baldwin, D.L.

    1979-01-01

    Fission gas behavior can be important in determining fuel pin and core performance during a reactor transient. The results are presented of examinations characterizing the changes in microstructural distribution and retention of fission gas in fuel for a series of transient overpower (50 cents/s) tested mixed-oxide fuel pins and their steady state siblings

  4. Catalytic soot oxidation over Ce- and Cu-doped hydrotalcites-derived mesoporous mixed oxides.

    Science.gov (United States)

    Wang, Zhongpeng; Wang, Liguo; He, Fang; Jiang, Zheng; Xiao, Tiancun; Zhang, Zhaoliang

    2014-09-01

    Ce- and Cu-doped hydrotalcites derived mixed oxides were prepared through co-precipitation and calcination method, and their catalytic activities for soot oxidation with O2 and O2/NO were investigated. The solids were characterized by XRD, TG-DTG, BET, H2-TPR, in situ FTIR and TPO techniques. All the catalysts precursors showed the typical diffraction patterns of hydrotalcite-like materials having layered structure. The derived mixed oxides exhibited mesoporous properties with specific surface area of 45-160 m2/g. After both Ce and Cu incorporated, mixed crystalline phases of CuO (tenorite), CeO2 (fluorite) and MgAl2O4 (spinel) were formed. As a result, the NO(x) adsorption capacity of this catalyst was largely increased to 201 μmol/g, meanwhile, it was also the most effective to convert NO into NO2 in the sorption process due to the enhanced reducibility. The in situ FTIR spectra revealed that NO(x) were stored mainly as chelating bidentate and monodentate nitrate. The interaction effect between Cu and Ce in the mixed oxide resulted in different NO(x) adsorption behavior. Compared with the non-catalyzed soot oxidation, soot conversion curves over the mixed oxides catalysts shift to low temperature in O2. The presence of NO in the gas phase significantly enhanced the soot oxidation activity with ignition temperature decreased to about 320 degrees C, which is due to NO conversion to NO2 over the catalyst followed by the reaction of NO2 with soot. This explains the cooperative effect of Ce and Cu in the mixed oxide on soot oxidation with high activity and 100% selectivity to CO2 formation.

  5. The determination of the mixing height. Current progress and problems

    Energy Technology Data Exchange (ETDEWEB)

    Gryning, S.E.; Beyrich, F.; Batchvarova, E. [eds.

    1997-10-01

    This report contains extended abstracts of presentations given at a EURASAP Workshop on The Determination of the Mixing Height - Current Progress and Problems. The Workshop, initiated from discussions with Peter Builtjes, was held at Risoe National Laboratory 1-3 October 1997 within the framework of EURASAP (European Association for the Sciences of Air Pollution). The specific topics and chairpersons of the Workshop were: Theoretical Considerations (Sven-Erik Gryning), Mixing Height Estimation from Turbulence Measurements and In-Situ Soundings (Douw Steyn), Mixing Height Determination from NWP-Models (Han van Dop), Climatology and Global Aspects (Werner Klug), Mixing Height Determination from Remote Systems (Werner Klug), Verification of Mixing Height Parameterizations and Models (Frank Beyrich), Mixing Height over Complex Terrain (Ekaterina Batchvarova), Internal Boundary Layers: Mixing Height in Coastal Areas and Over Cities (Allen White). The discussion at the end of the Workshop was chaired by Robert Bornstein. (au)

  6. The oxidation of trichloroethylene over different mixed oxides derived from hydrotalcites

    OpenAIRE

    BLANCH RAGA, NEUS; Palomares Gimeno, Antonio Eduardo; Martínez Triguero, Luis Joaquín; Puche Panadero, Marta; Fetter, Geolar; Bosch, Pedro

    2014-01-01

    The activity of different Mg(Fe/Al), Ni(Fe/Al) and Co(Fe/Al) mixed oxides based on hydrotalcite-like compounds have been studied for the catalytic oxidation of trichloroethylene. It has been shown that the Co catalysts are more active than the Ni catalyst, being the Mg catalysts the less active ones. The activity of all the catalysts improves when iron is substituted by aluminum in the catalyst composition. The best results have been obtained with the CoAl mixed oxide derived from...

  7. Design and synthesis of mixed oxides nanoparticles for biofuel applications

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Senniang [Iowa State Univ., Ames, IA (United States)

    2010-05-15

    The work in this dissertation presents the synthesis of two mixed metal oxides for biofuel applications and NMR characterization of silica materials. In the chapter 2, high catalytic efficiency of calcium silicate is synthesized for transesterfication of soybean oil to biodisels. Chapter 3 describes the synthesis of a new Rh based catalyst on mesoporous manganese oxides. The new catalyst is found to have higher activity and selectivity towards ethanol. Chapter 4 demonstrates the applications of solid-state Si NMR in the silica materials.

  8. Grain growth kinetics in uranium-plutonium mixed oxides

    International Nuclear Information System (INIS)

    Sari, C.

    1986-01-01

    Grain growth rates were investigated in uranium-plutonium mixed oxide specimens with oxygen-to-metal ratios 1.97 and 2.0. The specimens in the form of cylindrical pellets were heated in a temperature gradient similar to that existing in a fast reactor. The results are in agreement with the cubic rate law. The mean grain size D(μm) after annealing for time t (min) is represented by D 3 -D 0 3 =1.11x10 12 . exp(-445870/RT).t and D 3 -D 0 3 =2.55x10 9 .exp(-319240/RT).t for specimens with overall oxygen-to-metal ratios 1.97 and 2.0, respectively (activation energies expressed in J/mol). An example for the influence of the oxygen-to-metal ratio on the grain growth in mixed oxide fuel during operation in a fast reactor is also given. (orig.)

  9. Influence of vanadium oxidation states on the performance of V-Mg-Al mixed-oxide catalysts for the oxidative dehydrogenation of propane

    Energy Technology Data Exchange (ETDEWEB)

    Schacht, L. [IPN, Escuela Superior de Fisica y Matematicas, Departamento de Ciencia de Materiales, Av. IPN s/n, Edificio 9, Col. Lindavista, 07738 Mexico D. F. (Mexico); Navarrete, J.; Schacht, P.; Ramirez, M. A., E-mail: pschacha@imp.m [Instituto Mexicano del Petroleo, Programa de Ingenieria Molecular, Eje Central Lazaro Cardenas No. 152, 07730 Mexico D. F. (Mexico)

    2010-07-01

    V-Mg-Al mixed-oxide catalysts for oxidative dehydrogenation of propane were prepared by thermal decomposition of Mg-Al-layered double hydroxides with vanadium interlayer doping. The obtained catalysts were tested for the oxidative dehydrogenation of propane, obtaining good results in catalytic activity (conversion 16.55 % and selectivity 99.97 %) Results indicated that catalytic performance of these materials depends on how vanadium is integrated in the layered structure, which is determined by the Mg/Al ratio. Vanadium interlayer doping modifies the oxidation state of vanadium and consequently catalytic properties. Surface properties were studied by X-ray photoelectron spectroscopic and diffuse reflectance, UV-visible spectroscopy, and temperature programmed reduction. The analyses provided information about the oxidation state, before and after the reaction. From these results, it is suggested that selectivity to propylene and catalytic activity depend mainly of vanadium oxidation state. (Author)

  10. Determination of Stability from Multicomponent Pesticide Mixes.

    Science.gov (United States)

    Dorweiler, Kelly J; Gurav, Jagdish N; Walbridge, James S; Ghatge, Vishwas S; Savant, Rahul H

    2016-08-10

    A study was conducted to evaluate the stability of 528 pesticides, metabolites, and contaminants prepared in large multicomponent mixes to enhance laboratory efficiency by allowing maximum use of the useful shelf life of the mixtures. Accelerated aging at 50 °C simulated 6 month, 1 year, and 2 year storage periods at -20 °C. Initial mixture composition was based on the instrument of analysis. After preliminary stability data had been obtained, mixtures were reformulated and re-evaluated. In all, 344 compounds showed satisfactory stability across all treatment groups, 100 compounds showed statistically significant changes between the control and the 6 month simulated storage period (27 with losses >20%), and the remainder showed borderline stability or were tested in one protocol. Stability behavior for organophosphates agreed with the proposed reaction mechanism responsible for acetylcholinesterase inhibition. A small number of compounds increased in response over time, suggesting the occurrence of degradation of precursor pesticides into these respective compounds.

  11. 40 CFR 721.5315 - Nickel, cobalt mixed metal oxide (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Nickel, cobalt mixed metal oxide... Specific Chemical Substances § 721.5315 Nickel, cobalt mixed metal oxide (generic). (a) Chemical substance... nickel, cobalt mixed metal oxide. (PMN P-02-90) is subject to reporting under this section for the...

  12. Behavior of molybdenum in mixed-oxide fuel

    International Nuclear Information System (INIS)

    Giacchetti, G.; Sari, C.

    1976-01-01

    Metallic molybdenum, Mo--Ru--Rh--Pd alloys, barium, zirconium, and tungsten were added to uranium and uranium--plutonium oxides by coprecipitation and mechanical mixture techniques. This material was treated in a thermal gradient similar to that existing in fuel during irradiation to study the behavior of molybdenum in an oxide matrix as a function of the O/(U + Pu) ratio and some added elements. Result of ceramographic and microprobe analysis shows that when the overall O/(U + Pu) ratio is less than 2, molybdenum and Mo--Ru--Rh--Pd alloy inclusions are present in the uranium--plutonium oxide matrix. If the O/(U + Pu) ratio is greater than 2, molybdenum oxidizes to MoO 2 , which is gaseous at a temperature approximately 1000 0 C. Molybdenum oxide vapor reacts with barium oxide and forms a compound that exists as a liquid phase in the columnar grain region. Molybdenum oxide also reacts with tungsten oxide (tungsten is often present as an impurity in the fuel) and forms a compound that contains approximately 40 wt percent of actinide metals. The apparent solubility of molybdenum in uranium and uranium--plutonium oxides, determined by electron microprobe, was found to be less than 250 ppM both for hypo- and hyperstoichiometric fuels

  13. Ceria doped mixed metal oxide nanoparticles as oxidation catalysts: Synthesis and their characterization

    OpenAIRE

    Sultana, S.S.P.; Kishore, D.H.V.; Kuniyil, Mufsir; Khan, Mujeeb; Alwarthan, Abdulrahman; Prasad, K.R.S.; Labis, Joselito P.; Adil, S.F.

    2015-01-01

    Mixed metal nanoparticles (NPs) have attracted significant attention as catalysts for various organic transformations. In this study, we have demonstrated the preparation of nickel–manganese mixed metal oxide NPs doped with X% nano cerium oxide (X = 1, 3, 5 mol%) by a facile co-precipitation technique using surfactant and surfactant free methodologies. The as-synthesized materials were calcined at different temperatures (300 °C, 400 °C, and 500 °C), and were characterized using various spectr...

  14. Isotopic mixing in carbon monoxide catalyzed by zinc oxide

    International Nuclear Information System (INIS)

    Carnisio, G.; Garbassi, F.; Petrini, G.; Parravano, G.

    1978-01-01

    The rate of the isotopic mixing in CO has been studied at 300 0 C, for CO partial pressures from 6 to 100 Torr and a total pressure of 250 Torr on ZnO catalysts. Significant deviations from a first-order rate in p/sub co/ were found. The rate of oxygen exchange between ZnO and gas-phase CO was also measured and the results were employed to calculate the fraction of surface sites active for the CO isotopic mixing. Values on the order of 0.001 were found. The turnover rate and surface collision efficiency varied between 0.7 and 107 min -1 and 0.13 and 2.24 x 10 -8 , respectively. H 2 additions to CO increased the rate of isotopic mixing, whereas the rate of H 2 + D 2 was decreased by the presence of CO. The H 2 + D 2 rate was faster than that of isotopic mixing in CO, but as the ratio p/sub H 2 //p/sub co/ decreased the rates became about equal. It is argued that on ZnO samples, in which the rate of CO isotopic mixing and the rate of ZnO--CO oxygen exchange were influenced in a similar manner by the CO pressure, the isotopic mixing in CO took place via the ZnO oxygen, while oxide oxygen participation was not kinetically significant for ZnO samples in which the two reactions had different kinetics. The crucial factor controlling the path followed by the isotopic mixing in CO seems to be the surface Zn/O ratio, since a close correlation was found between the former and the reaction kinetics of the CO isotopic mixing reaction. Solid-state conditions which may vary the Zn/O surface ratio (foreign additions) are indicated. The implications of these findings to the problem of product selectivity from CO-H 2 mixtures reacting on metal oxide surfaces are discussed

  15. Irradiation creep of the mixed oxide UPuO2

    International Nuclear Information System (INIS)

    Combette, Patrick; Milet, Claude

    1976-01-01

    The irradiation creep under compression of the mixed oxide UO 2 -PuO 2 was studied up to fission yields of 6x10 13 fcm -3 s -1 , under stresses -2 , in the temperature range 700-900 deg C. The creep rate is proportional to the applied stress and fission yield, athermal in the studied temperature range and non-dependent of burnup (up to 30000MWjt -1 ). In a sample under compression, swelling is observed due to the formation of fission products during the irradiation and the swelling rate is of the same order that in a cladded fuel element [fr

  16. Analysis of the porosity distribution of mixed oxide pins

    International Nuclear Information System (INIS)

    Lieblich, M.; Lopez, J.

    1987-01-01

    In the frame of the Joint Irradiation Program IVO-FR2-Vg7 between the Centre of Nuclear Research of Karlsruhe (KfK), the irradiation of 30 mixed-oxide fuel rods in the FR2 experimental reactor was carried out. The pins were located in 10 single-walled NaK capsules. The behaviour of the fuel during its burnup was studied, mainly, the rest-porosity and cracking distribution in the pellet, partial densification, etc. In this work 3 pins from the capsule No. 165 were analyzed. The experimental results (pore and cracking profiles) were interpreted by the fuel rod code SATURN. (Author) 20 refs

  17. Ceria doped mixed metal oxide nanoparticles as oxidation catalysts: Synthesis and their characterization

    Directory of Open Access Journals (Sweden)

    S.S.P. Sultana

    2015-11-01

    Full Text Available Mixed metal nanoparticles (NPs have attracted significant attention as catalysts for various organic transformations. In this study, we have demonstrated the preparation of nickel–manganese mixed metal oxide NPs doped with X% nano cerium oxide (X = 1, 3, 5 mol% by a facile co-precipitation technique using surfactant and surfactant free methodologies. The as-synthesized materials were calcined at different temperatures (300 °C, 400 °C, and 500 °C, and were characterized using various spectroscopic techniques, including, FTIR and XRD. SEM analysis, TEM analysis and TGA were employed to evaluate the structural properties of the as-prepared catalyst. These were evaluated for their catalytic behaviour towards the conversion of benzyl alcohol to benzaldehyde, which was used as a model reaction with molecular oxygen as oxidant. Furthermore, the effect of the variation of the percentage of nano ceria doping and the calcination temperature on the performance of as-prepared mixed metal catalysts was also evaluated. The kinetic studies of the reactions performed employing gas chromatographic technique have revealed that the mixed metal oxide catalyst doped with 5% nano ceria displayed excellent catalytc activity, among various catalysts synthesized.

  18. Preparation of uniform nanoparticles of ultra-high purity metal oxides, mixed metal oxides, metals, and metal alloys

    Science.gov (United States)

    Woodfield, Brian F.; Liu, Shengfeng; Boerio-Goates, Juliana; Liu, Qingyuan; Smith, Stacey Janel

    2012-07-03

    In preferred embodiments, metal nanoparticles, mixed-metal (alloy) nanoparticles, metal oxide nanoparticles and mixed-metal oxide nanoparticles are provided. According to embodiments, the nanoparticles may possess narrow size distributions and high purities. In certain preferred embodiments, methods of preparing metal nanoparticles, mixed-metal nanoparticles, metal oxide nanoparticles and mixed-metal nanoparticles are provided. These methods may provide tight control of particle size, size distribution, and oxidation state. Other preferred embodiments relate to a precursor material that may be used to form nanoparticles. In addition, products prepared from such nanoparticles are disclosed.

  19. [Synthesis and characterization of mixed metal oxide pigments].

    Science.gov (United States)

    Ding, Jie; Yue, Shi-juan; Liu, Cui-ge; Wei, Yong-ju; Meng, Tao; Jiang, Han-jie; Shi, Yong-zheng; Xu, Yi-zhuang; Yu, Jiang; Wu, Jin-guang

    2012-03-01

    In the present work, aluminum chloride and various soluble salts of doping ions were dissolved in water. In addition, urea and polyvinyl pyrrolidone (PVP) were also dissolved in the above aqueous solution under supersonic treatments. Then the solutions were heated to induce the hydrolysis of urea so that soluble aluminum and doping ions convert into insoluble hydroxide or carbonate gels. After calcinations, the obtained gels change to mixed metal oxide pigments whose color is related to type and concentrations of the doping ions. XRD characterization demonstrates that the diffraction patterns of the products are the same as that of alpha-alumina. Diffuse reflectance spectra of samples of the samples in UV-Vis regions show that the absorption bands for d-d transitions of the doping ions undergo considerable change as the coordinate environments change. In addition, L*, a* and b* values of the pigments were measured by using UV-Vis densitometer. SEM results indicate that the size of the pigment powders is in the range 200-300 nm. The pigments are quite stable since no evidence of dissolution was observed after the synthesized pigment is soaked for 24 hours. ICP test shows that very little amount of doped metal occurs in the corresponding filtrate. The above results suggest that these new kinds of mixed metal oxide pigments are stable, non-toxic, environmental friendly and they may be applicable in molten spinning process and provide a new chance for non-aqueous printing and dyeing industry.

  20. Equipment to weld fuel rods of mixed oxides

    International Nuclear Information System (INIS)

    Aparicio, G.; Orlando, O.S.; Olano, V.R.; Toubes, B.; Munoz, C.A.

    1987-01-01

    Two welding outfits system T1G were designed and constructed to weld fuel rods with mixed oxides pellets (uranium and plutonium). One of them is connected to a glove box where the loading of sheaths takes place. The sheaths are driven to the welder through a removable plug pusher in the welding chamber. This equipment was designed to perform welding tests changing the parameters (gas composition and pressure, welding current, electrode position, etc.). The components of the welder, such as plug holder, chamber closure and peripheral accessories, were designed and constructed taking into account the working pressures in the machine, which is placed in a controlled area and connected to a glove box, where special safety conditions are necessary. The equipment to weld fuel bars is complemented by another machine, located in cold area, of the type presently used in the fuel elements factory. This equipment has been designed to perform some welding operations in sheaths and mixed oxide rods of the type Atucha I and II. Both machines have a programmed power supply of wide range and a vacuum, and pressurizing system that allows the change of parameters. Both systems have special features of handling and operation. (Author)

  1. Modeling of Cd(II) sorption on mixed oxide

    International Nuclear Information System (INIS)

    Waseem, M.; Mustafa, S.; Naeem, A.; Shah, K.H.; Hussain, S.Y.; Safdar, M.

    2011-01-01

    Mixed oxide of iron and silicon (0.75 M Fe(OH)3:0.25 M SiO/sub 2/) was synthesized and characterized by various techniques like surface area analysis, point of zero charge (PZC), energy dispersive X-rays (EDX) spectroscopy, Thermogravimetric and differential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FTIR) and X-rays diffraction (XRD) analysis. The uptake of Cd/sup 2+/ ions on mixed oxide increased with pH, temperature and metal ion concentration. Sorption data have been interpreted in terms of both Langmuir and Freundlich models. The Xm values at pH 7 are found to be almost twice as compared to pH 5. The values of both DH and DS were found to be positive indicating that the sorption process was endothermic and accompanied by the dehydration of Cd/sup 2+/. Further, the negative value of DG confirms the spontaneity of the reaction. The ion exchange mechanism was suggested to take place for each Cd/sup 2+/ ions at pH 5, whereas ion exchange was found coupled with non specific adsorption of metal cations at pH 7. (author)

  2. Fabrication and performance testing of CANDU mixed-oxide fuel

    International Nuclear Information System (INIS)

    Dimayuga, F.C.; Floyd, M.R.; Cox, D.S.

    2000-01-01

    AECL's mixed-oxide fuel fabrication activities are performed in the Recycle Fuel Fabrication Laboratories (RFFL) at the Chalk River Laboratories. Since the start-up of the RFFL in the mid-1970s, several fabrication campaigns have been conducted in the facility, producing various types of mixed-oxide (MOX) fuel, which were used for both irradiation and physics testing. More recently, CANDU fuel bundles containing 0.5 w-t % plutonium in natural uranium, produced in the RFFL, were successfully irradiated in the NRU reactor at powers up to 65 kW/m and to burnups ranging from 13 to 23 MW·d/kg HE. Two of the bundles had power histories that bound the normal powers and burnups of natural UO 2 CANDU fuel ( 2 fuel. Significantly more grain growth was observed than that expected for UO 2 fuel; however, this increase in grain growth had no effect on the overall performance of the fuel. Two other bundles operated to extended burnups of 19 to 23 MW·d/kg HE. Burnup extension above 15 MW·d/kg HE only had a small effect on FGR. (author)

  3. Mass transport in mixed conducting perovskite related oxides

    CERN Document Server

    Shaw, C K M

    2001-01-01

    mechanical and chemical stability of LSCN under practical operating temperatures have been measured and related to long term stability in typical SOFC assemblies. The phase stability and the effect of preparation conditions under different atmospheres on La sub 2 Ni sub 1 sub - sub x Co sub x O sub 4 sub + subdelta compounds were examined using high temperature X-ray diffraction. Fast oxygen uptake at low temperatures was observed in these studies indicating rapid oxygen diffusion, which was confirmed by isotope exchange investigations. The oxygen diffusion and surface exchange data obtained from IEDP-SIMS measurements of La sub 2 Ni sub 0 sub . sub 8 Co sub 0 sub . sub 2 O sub 4 sub + subdelta have enabled suppositions to be made regarding the reduction process and aided further interpretation of the defect model for these oxides. Mixed ionic electronic conducting oxides of the perovskite structure have attracted great interest in the field of solid oxide electrochemical devices. Their ability to allow poten...

  4. Spectrographic determination of impurities in beryllium oxide

    International Nuclear Information System (INIS)

    Paula Reino, L.C. de; Lordello, A.R.; Pereira, A.S.A.

    1986-03-01

    A method for the spectrographic determination of Al, B, Cd, Co, Cu, Cr, Fe, Mg, NaNi, Si and Zn in nuclear grade beryllium oxide has been developed. The determination of Co, Al, Na and Zn is besed upon a carrier distillation technique. Better results were obtained with 2% Ga 2 O 3 as carrier in beryllium oxide. For the elements B, Cd, Cu, Fe, Cr, Mg, Ni and Si the sample is loaded in a Scribner-Mullin shallow cup electrode, covered with graphite powder and excited in DC arc. The relative standard deviation values for different elements are in the range of 10 to 20%. The method fulfills requirements of precision and sensitivity for specification analysis of nuclear grade beryllium oxide.(Author) [pt

  5. Comparison of open cycles of uranium and mixed oxides of thorium-uranium using advanced reactors

    International Nuclear Information System (INIS)

    Gonçalves, Letícia C.; Maiorino, José R.

    2017-01-01

    A comparative study of the mass balance and production costs of uranium oxide fuels was carried out for an AP1000 reactor and thorium-uranium mixed oxide in a reactor proposal using thorium called AP-Th1000. Assuming the input mass values for a fuel load the average enrichment for both reactors as well as their feed mass was determined. With these parameters, the costs were calculated in each fuel preparation process, assuming the prices provided by the World Nuclear Association. The total fuel costs for the two reactors were quantitatively compared with 18-month open cycle. Considering enrichment of 20% for the open cycle of mixed U-Th oxide fuel, the total uranium consumption of this option was 50% higher and the cost due to the enrichment was 70% higher. The results show that the use of U-Th mixed oxide fuels can be advantageous considering sustainability issues. In this case other parameters and conditions should be investigated, especially those related to fuel recycling, spent fuel storage and reduction of the amount of transuranic radioactive waste

  6. Determination of mixing characterisitics in leaching tanks using ...

    African Journals Online (AJOL)

    The mixing characteristics in two gold leaching tanks each of volume 1.4 x 103 m3 were investigated with a pulse injection of 7.4 x 1010 Bq aqueous solution of 131I into the feed of the tanks to determine the flow model and mixing efficiency of the system. The flow patterns in the tanks connected in series were identical with ...

  7. Determinants of Treatment Outcome of Public-Private Mix ...

    African Journals Online (AJOL)

    Background: Determinants for non-compliance to antituberculosis treatment range from a poor correlation between patient and programme needs and priorities among other socio-economic factors. Objectives: This is to assess determinants of treatment outcome of public private mix tuberculosis control programme in ...

  8. Supported Mixed Oxide Catalysts for the Total Oxidation of Volatile Organic Compounds

    Czech Academy of Sciences Publication Activity Database

    Kovanda, F.; Jirátová, Květa

    2011-01-01

    Roč. 176, č. 1 (2011), s. 110-115 ISSN 0920-5861. [International Symposium on Air Pollution Abatement Catalysis (APAC) /2./. Cracow, 08.09.2010-10.09.2010] R&D Projects: GA ČR GAP106/10/1762; GA ČR GA106/09/1664 Institutional research plan: CEZ:AV0Z40720504 Keywords : layered double hydroxides * mixed oxides * ethanol total oxidation Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 3.407, year: 2011

  9. Local structures around the substituted elements in mixed layered oxides.

    Science.gov (United States)

    Akama, Shota; Kobayashi, Wataru; Amaha, Kaoru; Niwa, Hideharu; Nitani, Hiroaki; Moritomo, Yutaka

    2017-03-02

    The chemical substitution of a transition metal (M) is an effective method to improve the functionality of a material, such as its electrochemical, magnetic, and dielectric properties. The substitution, however, causes local lattice distortion because the difference in the ionic radius (r) modifies the local interatomic distances. Here, we systematically investigated the local structures in the pure (x = 0.0) and mixed (x = 0.05 or 0.1) layered oxides, Na(M 1-x M' x )O 2 (M and M' are the majority and minority transition metals, respectively), by means of extended X-ray absorption fine structure (EXAFS) analysis. We found that the local interatomic distance (d M-O ) around the minority element approaches that around the majority element to reduces the local lattice distortion. We further found that the valence of the minority Mn changes so that its ionic radius approaches that of the majority M.

  10. Emission computer tomography on a Dodewaard mixed oxide fuel pin

    International Nuclear Information System (INIS)

    Buurveld, H.A.; Dassel, G.

    1993-12-01

    A nondestructive technique as well as a destructive PIE technique have been used to verify the results obtained with a newly 8-e computer tomography (GECT) system. Multi isotope Scanning (MIS), electron probe micro analysis (EPMA) and GECT were used on a mixed oxide (MOX) fuel rod from the Dodewaard reactor with an average burnup of 24 MWd/kg fuel. GECT shows migration of Cs to the periphery of fuel pellets and to radial cracks and pores in the fuel, whereas MIS shows Cs migration to pellet interfaces. The EPMA technique appeared not to be useful to show migration of Cs but, it shows the distribution of fission products from Pu. EPMA clearly shows the distribution of fission products from Pu, but did not reveal the Cs-migration. (orig./HP)

  11. Yttrium bismuth titanate pyrochlore mixed oxides for photocatalytic hydrogen production

    Energy Technology Data Exchange (ETDEWEB)

    Merka, Oliver

    2012-10-18

    In this work, the sol-gel synthesis of new non-stoichiometric pyrochlore titanates and their application in photocatalytic hydrogen production is reported. Visible light response is achieved by introducing bismuth on the A site or by doping the B site by transition metal cations featuring partially filled d orbitals. This work clearly focusses on atomic scale structural changes induced by the systematical introduction of non-stoichiometry in pyrochlore mixed oxides and the resulting influence on the activity in photocatalytic hydrogen production. The materials were characterized in detail regarding their optical properties and their atomic structure. The pyrochlore structure tolerates tremendous stoichiometry variations. The non-stoichiometry in A{sub 2}O{sub 3} rich compositions is compensated by distortions in the cationic sub-lattice for the smaller Y{sup 3+} cation and by evolution of a secondary phase for the larger Bi{sup 3+} cation on the A site. For TiO{sub 2} rich compositions, the non-stoichiometry leads to a special vacancy formation in the A and optionally O' sites. It is shown that pyrochlore mixed oxides in the yttrium bismuth titanate system represent very active and promising materials for photocatalytic hydrogen production, if precisely and carefully tuned. Whereas Y{sub 2}Ti{sub 2}O{sub 7} yields stable hydrogen production rates over time, the bismuth richer compounds of YBiTi{sub 2}O{sub 7} and Bi{sub 2}Ti{sub 2}O{sub 7} are found to be not stable under irradiation. This drawback is overcome by applying a special co-catalyst system consisting of a precious metal core and a Cr{sub 2}O{sub 3} shell on the photocatalysts.

  12. Selective oxidation of propene on bismuth molybdate and mixed oxides of tin and antimony and of uranium and antimony

    International Nuclear Information System (INIS)

    Pendleton, P.; Taylor, D.

    1976-01-01

    Propene + 18 0 2 reactions have been studied in a static reaction system on bismuth molybdate and mixed oxides of tin and antimony and of uranium and antimony. The [ 16 0] acrolein content of the total acrolein formed and the proportion of 16 0 in the oxygen of the carbon dioxide by-product have been determined. The results indicate that for each catalyst the lattice is the only direct source of the oxygen in the aldehyde, and that lattice and/or gas phase oxygen is used in carbon dioxide formation. Oxygen anion mobility appears to be greater in the molybdate catalyst than in the other two. (author)

  13. Structural and theoretical studies of mixed metal oxides

    International Nuclear Information System (INIS)

    Butler, V.

    1982-10-01

    Diffuse neutron scattering studies were made first on powdered samples of uranium/cerium oxide and, secondly, on single crystals of stoichiometric and reduced thorium/cerium oxide. The powder studies show that at low dopant concentrations, the cation distribution is random but, as the dopant concentration increases, considerable short range ordering takes place on the cation sublattice. The presence of oxygen vacancies at high temperature, when the cations are mobile, does not appear to affect the distribution of the cations. Powder neutron diffraction was carried out on stoichiometric and reduced samples of uranium/cerium oxide and, for comparison, on a reduced sample of 20 mole% CeO 2 in ThO 2 . In the former samples, separation of a second phase occurs on reduction of samples containing >= 20 mole% CeO 2 and, at all dopant concentrations, the level of reduction achieved is well below the expected value. The thorium/cerium oxide sample, on the other hand, is single-phase and fully reduced. Calculations performed using computer simulation techniques show that, in doped CeO 2 and ZrO 2 , the radius of the dopant ion is extremely important in determining the magnitude of the dopant-vacancy interaction and hence the ionic conductivity of the material. The results are discussed. (author)

  14. A magnetic route to measure the average oxidation state of mixed-valent manganese in manganese oxide octahedral molecular sieves (OMS).

    Science.gov (United States)

    Shen, Xiong-Fei; Ding, Yun-Shuang; Liu, Jia; Han, Zhao-Hui; Budnick, Joseph I; Hines, William A; Suib, Steven L

    2005-05-04

    A magnetic route has been applied for measurement of the average oxidation state (AOS) of mixed-valent manganese in manganese oxide octahedral molecular sieves (OMS). The method gives AOS measurement results in good agreement with titration methods. A maximum analysis deviation error of +/-7% is obtained from 10 sample measurements. The magnetic method is able to (1) confirm the presence of mixed-valent manganese and (2) evaluate AOS and the spin states of d electrons of both single oxidation state and mixed-valent state Mn in manganese oxides. In addition, the magnetic method may be extended to (1) determine AOS of Mn in manganese oxide OMS with dopant "diamagnetic" ions, such as reducible V5+ (3d0) ions, which is inappropriate for the titration method due to interference of redox reactions between these dopant ions and titration reagents, such as KMnO4, (2) evaluate the dopant "paramagnetic" ions that are present as clusters or in the OMS framework, and (3) determine AOS of other mixed-valent/single oxidation state ion systems, such as Mo3+(3d3)-Mo4+(3d2) systems and Fe3+ in FeCl3.

  15. Preliminary comparison of three processes of AlN oxidation: dry, wet and mixed ones

    Directory of Open Access Journals (Sweden)

    Korbutowicz R.

    2016-03-01

    Full Text Available Three methods of AlN layers oxidation: dry, wet and mixed (wet with oxygen were compared. Some physical parameters of oxidized thin films of aluminum nitride (AlN layers grown on silicon Si(1 1 1 were investigated by means Energy-Dispersive X-ray Spectroscopy (EDS and Spectroscopic Ellipsometry (SE. Three series of the thermal oxidations processes were carried out at 1012 °C in pure nitrogen as carrying gas and various gas ambients: (a dry oxidation with oxygen, (b wet oxidation with water steam and (c mixed atmosphere with various process times. All the research methods have shown that along with the rising of the oxidation time, AlN layer across the aluminum oxide nitride transforms to aluminum oxide. The mixed oxidation was a faster method than the dry or wet ones.

  16. Selectivity of layered double hydroxides and their derivative mixed metal oxides as sorbents of hydrogen sulfide.

    Science.gov (United States)

    Othman, Mohamed A; Zahid, Waleed M; Abasaeed, Ahmed E

    2013-06-15

    In the context of finding high efficient sorbent materials for removing hydrogen sulfide (H2S) from air stream, a screening study was performed to find the best combination of metals for the synthesis of layered double hydroxides (LDHs) and their derivative mixed metal oxides. Based on selectivity of 998 natural mineral species of sulfur-containing compounds, Cu(2+), Ni(2+) and Zn(2+) were selected as divalent metals, and Fe(3+), Al(3+) and Cr(3+) as trivalent metals to synthesis the LDHs sorbents. 10 LDHs materials and their calcined mixed metal oxides, Ni(0.66)Al(0.34), Cu(0.35)Ni(0.32)Al(0.33), Zn(0.66)Al(0.34), Cu(0.36)Zn(0.32)Al(0.32), Ni(0.64)Fe(0.36), Cu(0.35)Ni(0.31)Fe(0.34), Ni(0.66)Cr(0.34), Cu(0.35)Ni(0.31)Cr(0.34), Zn(0.66)Cr(0.34), Cu(0.33)Zn(0.32)Cr(0.35) were synthesized, characterized chemically and physically, and then tested using breakthrough test to determine their sulfur uptake. Ni(0.64)Fe(0.36) mixed metal oxides was found to have the best uptake of hydrogen sulfide (136 mg H₂S/g). Regeneration of spent Ni(0.64)Fe(0.36) mixed metal oxides was studied using two different mixture solutions, NaCl/NaOH and acetate-buffer/NaCl/NaOH. The latter mixture successfully desorbed the sulfur from the Ni0.64Fe0.36 sorbent for 2 cycles of regeneration/sorption. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Physico-chemical characteristics of sulfated mixed oxides of Sn with some rare earth elements

    International Nuclear Information System (INIS)

    Jyothi, T.M.; Mirakar, S.P.; Sreekumar, K.; Sugunan, S.; Talawar, M.B.

    2000-01-01

    A series of binary mixed oxides of tin with three rare earth elements viz. La, Ce and Sm were prepared by coprecipitation method and sulfate treatment was performed by treating the mixed hydroxides with sulfuric acid or ammonium sulfate. The physico-chemical characterization has been done by XRD, BET-SA, SEM, EDX, TG-DTA and IR spectroscopy. Adsorption of n-butylamine was used to probe the acidic properties of the catalysts. The strength and distribution of acid sites depend on the mixed metal oxide composition, as well as on the preparation method. The rare earth modified sulfated tin oxide catalysis are more active in the oxidative dehydrogenation of cyclohexanol and cyclohexane, compared to the corresponding mixed oxide systems and sulfated tin oxide. Among the different sulfated oxide systems investigated, cerium promoted catalysts displayed a better selectivity towards dehydrogenation products. (author)

  18. Eco-friendly synthesis and characterization of Ni-Si nanoparticles mixed oxides as catalyst for partial oxidation of methane

    International Nuclear Information System (INIS)

    Fakhroueian, Z.; Farzaneh, F.

    2009-01-01

    The nanoparticles of Ni-Si mixed oxides were prepared by co-precipitation method using nickel nitrate; Ni(NO 3 ) 2 6H 2 O and tetraethyl orthosilicate. The products were characterized by X-ray diffraction, transmission electron microscopy, and hydrogen temperature program reduction (H 2 -TPR). The results revealed that Ni-Si mixed oxides particles were obtained with average particle size 1-2 nm. The Ni-Si nanoparticles mixed oxides successfully catalyzed the partial oxidation of methane to hydrogen and carbon monoxide (Syn gas) using a fixed-bed reactor with about 92% activity and high selectivity. No coke formation and deactivation of catalyst were observed during the course of reaction. Particularly significant is the similar reactivity of this catalyst with that of Ni-Ce-Zr mixed oxides

  19. Rational synthesis of multifunctional mixed metal oxides by hydrothermal techniques

    Science.gov (United States)

    Stampler, Evan Scott

    Low temperature (oxide chalcogenides, hexagonal rare-earth manganites, and silver delafossites with mixed cations on the B-site. These materials are of particular interest because they combine multiple functional properties, such as transparency and conductivity, or magnetism and ferroelectricity, in a single-phase material, thus enabling innovative technological applications. Phase-pure products were achieved by the appropriate combination of starting reagents, pH, and reaction temperature to control the solubility of the reactants. Phase-pure BiCuOS and BiCuOSe have been synthesized in high yield by a single-step hydrothermal reaction at low temperature (250°C) and pressure (oxidation of sulfide and selenide. BiCuOS (Eg = 1.09 eV) and BiCuOSe (Eg = 0.75 eV) have smaller band gaps compared to the p-type transparent conductor LaCuOS (Eg = 3.1 eV) but have significantly higher room temperature conductivities (sigma ≈ 0.08 S cm-1 and 3.3 S cm-1, respectively). The high molar solubility of Mn2O3 ([Mn 3+] ≈ 10-3 M) and the slightly amphoteric character of the late rare-earth sesquioxides were exploited in the hydrothermal synthesis of rare-earth manganites, LnMnO3 (Ln=Ho-Lu and Y). While alkaline conditions were necessary for the solubilization of manganese, a reaction temperature approximately 50°C above the transition temperature of the respective rare-earth trihydroxide (100-300°C) accelerated the transition to the more reactive and soluble rare-earth oxide hydroxide and the subsequent reaction to yield the LnMnO3 phase. The high solubility of Ag2O, [Ag+] ≈ 10 -2.5 M, enabled the synthesis of two new silver delafossite solid solutions with the formulae AgAl1-xGaxO2 and AgSc1-xInxO2 and five mixed B-site silver delafossites with the formulae AgBe0.5Ti0.5O2, AgMg0.5Ti0.5O2, AgNi0.5Ti 0.5O2, AgCu0.5Ti0.5O2, and AgZn0.5Ti0.5O2 at a reaction temperature of 210°C. The former were observed when the solubilities of both B-site trivalent cations were ≥ 10-5 M and

  20. Composition of the corrosion product oxide phases in the gaps of three LMFBR-type mixed oxide fuel pins

    International Nuclear Information System (INIS)

    Walker, C.T.

    1978-01-01

    Identification of the corrosion product oxide phases in the gaps of mixed oxide fuel pins clad with austenitic stainless steel is an important step in understanding the mechanisms of corrosion. Once the oxide is identified the reaction paths by which it is formed can be established. The corrosion product oxide will also be a reliable indication of the oxygen potential in the gap. A grey oxide phase which is recognised to contain the products of cladding corrosion is often observed in the gaps of mixed oxide fuel pins. Its main constituents are known to be chromium, caesium and oxygen, and recently the composition of the grey oxide phase in the gaps of three fuel pins was shown to be broadly similar, and it was proposed that the phase was essentially chromium oxide. (Auth.)

  1. Mixed conducting materials for partial oxidation of hydrocarbons

    Directory of Open Access Journals (Sweden)

    Frade, J. R.

    2004-06-01

    Full Text Available Thermodynamic calculations with additional conditions for the conservation of carbon and hydrogen were used to predict the gas composition obtained by partial oxidation of methane as a function of oxygen partial pressure and temperature; this was used to assess the stability and oxygen permeability requirements of mixed conducting membrane materials proposed for this purpose. A re-examination of known mixed conductors shows that most materials with highest permeability still fail to fulfil the requirements of stability under reducing conditions. Other materials possess sufficient stability but their oxygen permeability is insufficient. Different approaches were thus used to attempt to overcome those limitations, including changes in composition in the A and B site positions of ABO3 perovskites, and tests of materials with different structure types. Promising results were obtained mainly for some materials with perovskite or related K2NiF4-type structures. Limited stability of the most promising materials shows that one should rely mainly on kinetic limitations in the permeate side to protect the mixed conductor from severe reducing conditions.

    Se han usado cálculos termodinámicos con condiciones adicionales para la conservación del carbono e hidrógeno para predecir la composición del gas obtenido mediante la oxidación parcial del metano en función de la presión parcial de oxígeno y de la temperatura; esto se ha usado para asegurar los requerimientos de estabilidad y permeabilidad al oxígeno de los materiales conductores mixtos empleados como membrana para este propósito. Un nuevo exámen de los conductores mixtos conocidos muestra que la mayoría de los materiales con la mayor permeabilidad todavía fallan en el cumplimiento de los requerimientos de estabilidad bajo condiciones reductoras. Otros materiales poseen suficiente estabilidad, pero su permeabilidad al oxígeno es insuficiente. Por ello se han empleado diferentes

  2. Different Abilities of Eight Mixed Cultures of Methane-oxidizing Bacteria to Degrade TCE

    DEFF Research Database (Denmark)

    Broholm, Kim; Christensen, Thomas Højlund; Jensen, Bjørn K.

    1993-01-01

    The ability of eight mixed cultures of methane-oxidizing bacteria to degrade trichloroethylene (TCE) was examined in laboratory batch experiments. This is one of the first reported works studying TCE degradation by mixed cultures of methane-oxidizing bacteria at 10°C, a common temperature for soils...

  3. Modern methods of material accounting for mixed oxide fuel fabrication facility

    International Nuclear Information System (INIS)

    Eggers, R.F.; Pindak, J.L.; Brouns, R.J.; Williams, R.C.; Brite, D.W.; Kinnison, R.R.; Fager, J.E.

    1981-01-01

    The generic requirements loss detection, and response to alarms of a contemporary material control and accounting (MCandA) philosophy have been applied to a mixed oxide fuel fabrication plant to produce a detailed preliminary MCandA system design that is generally applicable to facilities of this type. This paper summarizes and discusses detailed results of the mixed oxide fuel fabrication plant study

  4. Reducibility of ceria-lanthana mixed oxides under temperature programmed hydrogen and inert gas flow conditions

    International Nuclear Information System (INIS)

    Bernal, S.; Blanco, G.; Cifredo, G.; Perez-Omil, J.A.; Pintado, J.M.; Rodriguez-Izquierdo, J.M.

    1997-01-01

    The present paper deals with the preparation and characterization of La/Ce mixed oxides, with La molar contents of 20, 36 and 57%. We carry out the study of the structural, textural and redox properties of the mixed oxides, comparing our results with those for pure ceria. For this aim we use temperature programmed reduction (TPR), temperature programmed desorption (TPD), nitrogen physisorption at 77 K, X-ray diffraction and high resolution electron microscopy. The mixed oxides are more easy to reduce in a flow of hydrogen than ceria. Moreover, in an inert gas flow they release oxygen in higher amounts and at lower temperatures than pure CeO 2 . The textural stability of the mixed oxides is also improved by incorporation of lanthana. All these properties make the ceria-lanthana mixed oxides interesting alternative candidates to substitute ceria in three-way catalyst formulations. (orig.)

  5. Antineutrino monitoring of burning mixed oxide plutonium fuels

    Science.gov (United States)

    Hayes, A. C.; Trellue, H. R.; Nieto, Michael Martin; Wilson, W. B.

    2012-02-01

    Background: Antineutrino monitoring of reactors is an enhanced nuclear safeguard that is being explored by several international groups. A key question is whether such a scheme could be used to verify the destruction of plutonium loaded in a reactor as mixed oxide (MOX) fuel.Purpose: To explore the effectiveness of antineutrino monitoring for the purposes of nuclear accountability and safeguarding of MOX plutonium, we examine the magnitude and temporal variation in the antineutrino signals expected for different loadings of MOX fuels.Methods: Reactor burn simulations are carried out for four different MOX fuel loadings and the antineutrino signals as a function of fuel burnup are computed and compared.Results: The antineutrino signals from reactor-grade and weapons-grade MOX are shown to be distinct from those from burning low enriched uranium, and this signal difference increases as the MOX plutonium fraction of the reactor core increases.Conclusion: Antineutrino monitoring could be used to verify the destruction of plutonium in reactors, although verifying the grade of the plutonium being burned is found to be more challenging.

  6. Sensitivity analysis of characteristics of spent mixed oxide fuel

    International Nuclear Information System (INIS)

    Hagura, Naoto; Yoshida, Tadashi

    2008-01-01

    Prediction error was evaluated for decay heat and nuclide generation in spent mixed oxide (MOX) fuels on the basis of error files in JENDL-3.3. This computational analysis was performed using SWAT code system, ORIGEN2 code, and ERRORJ code. The results of nuclide generation error evaluation were compared with some discrepancies in the calculated values to experimental values (C/E ratio) which were already published and were obtained by analysis of post irradiated experiments (PIE) data. Though the discrepancies of some C/E values, especially those of americium and curium isotopes, ranged from a half to twice, the present error evaluation based on the error file of nuclide generation became 10% or less. We conclude that the discrepancy between calculation and the PIE data is almost factor 5 larger than that evaluated from the covariance data in JENDL-3.3. Therefore the practical error value of total decay heat should be 20% or more on 1 σ basis. (authors)

  7. Investigation of the Carbon Monoxide Gas Sensing Characteristics of Tin Oxide Mixed Cerium Oxide Thin Films

    Directory of Open Access Journals (Sweden)

    Muhammad B. Haider

    2012-02-01

    Full Text Available Thin films of tin oxide mixed cerium oxide were grown on unheated substrates by physical vapor deposition. The films were annealed in air at 500 °C for two hours, and were characterized using X-ray photoelectron spectroscopy, atomic force microscopy and optical spectrophotometry. X-ray photoelectron spectroscopy and atomic force microscopy results reveal that the films were highly porous and porosity of our films was found to be in the range of 11.6–21.7%. The films were investigated for the detection of carbon monoxide, and were found to be highly sensitive. We found that 430 °C was the optimum operating temperature for sensing CO gas at concentrations as low as 5 ppm. Our sensors exhibited fast response and recovery times of 26 s and 30 s, respectively.

  8. Studies on mixed metal oxides solid solutions as heterogeneous catalysts

    Directory of Open Access Journals (Sweden)

    H. R. Arandiyan

    2009-03-01

    Full Text Available In this work, a series of perovskite-type mixed oxide LaMo xV1-xO3+δ powder catalysts (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0, with 0.5 < δ < 1.5, prepared by the sol-gel process and calcined at 750ºC, provide an attractive and effective alternative means of synthesizing materials with better control of morphology. Structures of resins obtained during the gel formation process by FT-IR spectroscopy and XRD analysis showed that all the LaMo xV1-xO3+δ samples are single phase perovskite-type solid solutions. The surface area (BET between 2.5 - 5.0 m²/g (x = 0.1 and 1.0 respectively increases with increasing Mo ratio in the samples. They show high purity, good chemical homogeneity, and lower calcinations temperatures as compared with the solid-state chemistry route. SEM coupled to EDS and thermogravimetric analysis/differential thermal analyses (TGA/DTA have been carried out in order to evaluate the homogeneity of the catalyst. Finally, the experimental studies show that the calcination temperature and Mo content exhibited a significant influence on catalytic activity. Among the LaMo xV1-xO3+δ samples, LaMo0.7V0.3O4.2 showed the best catalytic activity for the topic reaction and the best activity and stability for ethane reforming at 850ºC under 8 bar.

  9. Some alternatives to the mixed oxide fuel cycle

    Energy Technology Data Exchange (ETDEWEB)

    Deonigi, D.E.; Eschbach, E.A.; Goldsmith, S.; Pankaskie, P.J.; Rohrmann, C.A.; Widrig, R.D.

    1977-02-01

    While on initial examination each of the six fuel cycle concepts (tandem cycle, extended burnup, fuel rejuvenation, coprocessing, partial reprocessing, and thorium) described in the report may have some potential for improving safeguards, none of the six appears to have any other major or compelling advantages over the mixed oxide (MOX) fuel cycle. Compared to the MOX cycle, all but coprocessing appear to have major disadvantages, including severe cost penalties. Three of the concepts-tandem, extended burnup, and rejuvenation--share the basic problems of the throwaway cycle (GESMO Alternative 6): without reprocessing, high-level waste volumes and costs are substantially increased, and overall uranium utilization decreases for three reasons. First, the parasitic fission products left in the fuel absorb neutrons in later irradiation steps reducing the overall neutronic efficiencies of these cycles. Second, discarded fuel still has sufficient fissile values to warrant recycle. Third, perhaps most important, the plutonium needed for breeder start-up will not be available; without the breeder, uranium utilization would drop by about a factor of sixty. Two of the concepts--coprocessing and partial reprocessing--involve variations of the basic MOX fuel cycle's chemical reprocessing step to make plutonium diversion potentially more difficult. These concepts could be used with the MOX fuel cycle or in conjunction with the tandem, extended burnup and rejuvenation concepts to eliminate some of the problems with those cycles. But in so doing, the basic impetus for those cycles--elimination of reprocessing for safeguards purposes--no longer exists. Of all the concepts considered, only coprocessing--and particularly the ''master blend'' version--appears to have sufficient promise to warrant a more detailed study. The master blend concept could possibly make plutonium diversion more difficult with minimal impact on the reprocessing and MOX fuel

  10. Some alternatives to the mixed oxide fuel cycle

    International Nuclear Information System (INIS)

    Deonigi, D.E.; Eschbach, E.A.; Goldsmith, S.; Pankaskie, P.J.; Rohrmann, C.A.; Widrig, R.D.

    1977-02-01

    While on initial examination each of the six fuel cycle concepts (tandem cycle, extended burnup, fuel rejuvenation, coprocessing, partial reprocessing, and thorium) described in the report may have some potential for improving safeguards, none of the six appears to have any other major or compelling advantages over the mixed oxide (MOX) fuel cycle. Compared to the MOX cycle, all but coprocessing appear to have major disadvantages, including severe cost penalties. Three of the concepts-tandem, extended burnup, and rejuvenation--share the basic problems of the throwaway cycle (GESMO Alternative 6): without reprocessing, high-level waste volumes and costs are substantially increased, and overall uranium utilization decreases for three reasons. First, the parasitic fission products left in the fuel absorb neutrons in later irradiation steps reducing the overall neutronic efficiencies of these cycles. Second, discarded fuel still has sufficient fissile values to warrant recycle. Third, perhaps most important, the plutonium needed for breeder start-up will not be available; without the breeder, uranium utilization would drop by about a factor of sixty. Two of the concepts--coprocessing and partial reprocessing--involve variations of the basic MOX fuel cycle's chemical reprocessing step to make plutonium diversion potentially more difficult. These concepts could be used with the MOX fuel cycle or in conjunction with the tandem, extended burnup and rejuvenation concepts to eliminate some of the problems with those cycles. But in so doing, the basic impetus for those cycles--elimination of reprocessing for safeguards purposes--no longer exists. Of all the concepts considered, only coprocessing--and particularly the ''master blend'' version--appears to have sufficient promise to warrant a more detailed study. The master blend concept could possibly make plutonium diversion more difficult with minimal impact on the reprocessing and MOX fuel fabrication operations

  11. Effect of Sr on the properties of Ce–Zr–La mixed oxides

    Directory of Open Access Journals (Sweden)

    RICHUAN RAO

    2006-03-01

    Full Text Available Ce–Zr–La–Sr mixed oxides, with different Sr contents, were prepared by the sol–gel method. In a flow-system microreactor, the reduction properties and the oxygen storage capacity (OSC of the Ce–Zr–La–Sr mixed oxides were investigated by a temperature programmed reduction (TPR and a pulse technique. It was shown that the properties of the Ce–Zr–La mixed oxides depend on the Sr content and that the optimum Sr content in the Ce–Zr–La–Sr mixed oxide is 3 mol%. The Ce–Zr–La–Sr mixed oxides doped with 3 mol% Sr (Ce0.52Zr0.4La0.05Sr0.03O1.945 has the largest specific surface area and better reduction properties and oxygen storage capacity in comparison to the other investigated samples. The XRD results of the Ce–Zr–La–Sr mixed oxides showed that their X-ray diffraction patterns are well in agreement with that of fluorite-type CeO2 with Sr ions incorporated into the Ce–Zr–La mixed oxide structures. With increasing calcination temperature, the intensity of the X-ray diffraction peaks increased, but no new peaks were observed. All of these indicate that the synthesized samples had good thermal stability.

  12. Determination of equivalent mixing height and atmospheric stability assessment

    International Nuclear Information System (INIS)

    Simon, J.; Bulko, M.; Holy, K.

    2007-01-01

    Atmospheric stability is an indicator that reflects the intensity of boundary layer mixing processes. This feature of the atmosphere is especially important since it defines dispersive atmospheric conditions and provides information on how effectively the anthropogenic pollution will be transferred to the higher levels of the atmosphere. The assessment of atmospheric dispersiveness plays a crucial role in the protection of air quality and public health in big cities. The presented paper deals with determination of atmospheric stability via so called Equivalent Mixing Height (EMH) quantity using a radioactive noble gas 222 Rn. A method of deriving a link between 222 Rn activity concentration, eddy diffusion coefficient and EMH using fluid mechanics is also outlined in this work. (authors)

  13. Efficient room temperature oxidation of cyclohexane over highly active hetero-mixed WO3/V2O5 oxide catalyst

    CSIR Research Space (South Africa)

    Makgwane, PR

    2014-09-01

    Full Text Available An efficient room temperature catalyzed oxidation of cyclohexane to cyclohexanone (K) and cyclohexanol (A) was achieved over hetero-mixed tungsten–vanadia (WO(sub3)/V(sub2)O(sub5)) using H(sub2)O(sub2) oxidant. WO(sub3)/V(sub2)O(sub5) exhibited high...

  14. Co3O4-CeO2 mixed oxide-based catalytic materials for diesel soot oxidation

    Czech Academy of Sciences Publication Activity Database

    Dhakad, M.; Mitshuhashi, T.; Rayalu, S.; Doggali, P.; Bakardjieva, Snejana; Šubrt, Jan; Fino, D.; Haneda, H.; Labhsetwar, N.

    2008-01-01

    Roč. 132, 1-4 (2008), s. 188-193 ISSN 0920-5861 R&D Projects: GA MŠk LC523 Institutional research plan: CEZ:AV0Z40320502 Keywords : soot oxidation * diesel particulate * Co3O4-CeO2 type mixed oxide Subject RIV: CA - Inorganic Chemistry Impact factor: 3.004, year: 2008

  15. Continuous precipitation of mineral products: influence of mixing conditions on the co-precipitation of cerium-zirconium mixed oxides

    International Nuclear Information System (INIS)

    Di Patrizio, Nicolas

    2015-01-01

    An automated experimental set-up with rapid mixers is used to study the influence of mixing conditions on the co-precipitation of cerium-zirconium mixed oxides. The intensity of mixing is controlled by the inlet flow rates of the reacting solutions. An engulfment model is used to estimate a mixing time from the measurement of a segregation index by the Villermaux-Dushman reaction system. Three geometries of Hartridge Roughton mixers are compared. Mixing performance is better when a separate mixing chamber upstream of a narrower outlet pipe is present. A better mixing decreases the maximal reducibility temperature of the material and increases the crystal strains of the particles calcined at 1100 C. This is probably due to a better homogenization of the particles content. The important incorporation of nitrates in the particle at the outlet of the mixers shows precipitation occurs while the mixing process is not finished. This experimental result was confirmed by numerical simulation and an estimation of sur-saturations during the mixing process. (author)

  16. Heat capacity measurements and XPS studies on uranium-lanthanum mixed oxides

    International Nuclear Information System (INIS)

    Venkata Krishnan, R.; Mittal, V.K.; Babu, R.; Senapati, Abhiram; Bera, Santanu; Nagarajan, K.

    2011-01-01

    Research highlights: → Heat capacity measurements were carried out on (U 1-y La y )O 2±x (y = 0.2, 0.4, 0.6, and 0.8) using differential scanning calorimeter (DSC) in the temperature range 298-800 K. → Enthalpy increment measurements were carried out on the above solid solution using high temperature drop calorimetry in the temperature range 800-1800 K. → Chemical states of U and La in the solid solutions of mixed oxides were determined using X-ray photoelectron spectroscopy (XPS). → The anomalous increase in the heat capacity is attributed to certain thermal excitation process namely Frenkel pair defect of oxygen. → From the XPS investigation, it is observed that the O/M ratio at the surface is higher than that to the bulk. → In uranium rich mixed oxide samples, the surface O/M is greater than 2 whereas that in La rich mixed oxides, it is less than 2, though the bulk O/M in all the samples are less than 2. - Abstract: Heat capacity measurements were carried out on (U 1-y La y )O 2±x (y = 0.2, 0.4, 0.6, and 0.8) using differential scanning calorimeter (DSC) in the temperature range 298-800 K. Enthalpy increment measurements were carried out on the above solid solutions using high temperature drop calorimetry in the temperature range 800-1800 K. Chemical states of U and La in the solid solutions of mixed oxides were determined using X-ray photoelectron spectroscopy (XPS). Oxygen to metal ratios of (U 1-y La y )O 2±x were estimated from the ratios of different chemical states of U present in the sample. Anomalous increase in the heat capacity is observed for (U 1-y La y )O 2±x (y = 0.4, 0.6 and 0.8) with onset temperatures in the range of 1000-1200 K. The anomalous increase in the heat capacity is attributed to certain thermal excitation process, namely, Frenkel pair defect of oxygen. The heat capacity value of (U 1-y La y )O 2±x (y = 0.2, 0.4, 0.6, and 0.8) at 298 K are 65.3, 64.1, 57.7, 51.9 J K -1 mol -1 , respectively. From the XPS investigations

  17. Characterization of the acid strength of SiO[sub 2]-ZrO[sub 2] mixed oxides

    Energy Technology Data Exchange (ETDEWEB)

    Bosman, H.J.M.; Kruissink, E.C.; Spoel, J. van der; Brink, F. van den (DSM Research B.V., Gelenee (Netherlands))

    1994-08-01

    The preparation of SiO[sub 2]-ZrO[sub 2] mixed oxides and the single oxides SiO[sub 2] and ZrO[sub 2] from H[sub 2]SiF[sub 6] and/or H[sub 2]ZrF[sub 6] is described. The catalysts are characterized using Hammett colour indicators, temperature programmed desorption of ammonia, XRD, XPS, and infrared spectroscopy. New IR bands and absence of XRD crystallinity show mixing of SiO[sub 2] and ZrO[sub 2] on an atomic scale in the amorphous coprecipitate. However, as could be concluded from the difference between surface concentrations of Zr and Si measured with XPS and the mean bulk concentrations, the ZrO[sub 2] precipitates somewhat more quickly than SiO[sub 2]. The acid strength of the SiO[sub 2]-ZrO[sub 2] mixed oxides corresponds to an H[sub 0] value between -11.4 and 13.8 (super-acidity). There is a fair correlation between the surface concentration of strong acid sites, determined from NH[sub 3] TPD, and the performance in the acid catalyzed dehydration of cyclohexanol to cyclohexene. In addition to the concentration of acid sites, their acid strength is an important factor determining the performance of the SiO[sub 2]-ZrO[sub 2] catalysts in the dehydration of cyclohexanol. The acid strength needed for the dehydration of cyclohexanol corresponds to H[sub 0] [<=] +2.8. Chemically mixed SiO[sub 2]-ZrO[sub 2] oxides contain strong acid sites as opposed to the single oxides SiO[sub 2] and ZrO[sub 2], which contain only weak acid sites. XPS shows an oxygen depletion on the surface of the mixed oxides, which indicates that the strong acid sites are of the Lewis type. 27 refs., 11 figs., 4 tabs.

  18. Plutonium-uranium mixed oxide characterization by coupling micro-X-ray diffraction and absorption investigations

    Science.gov (United States)

    Degueldre, C.; Martin, M.; Kuri, G.; Grolimund, D.; Borca, C.

    2011-09-01

    Plutonium-uranium mixed oxide (MOX) fuels are currently used in nuclear reactors. The potential differences of metal redox state and microstructural developments of the matrix before and after irradiation are commonly analysed by electron probe microanalysis. In this work the structure and next-neighbor atomic environments of Pu and U oxide features within unirradiated homogeneous MOX and irradiated (60 MW d kg -1) MOX samples was analysed by micro-X-ray fluorescence (μ-XRF), micro-X-ray diffraction (μ-XRD) and micro-X-ray absorption fine structure (μ-XAFS) spectroscopy. The grain properties, chemical bonding, valences and stoichiometry of Pu and U are determined from the experimental data gained for the unirradiated as well as for irradiated fuel material examined in the center of the fuel as well as in its peripheral zone (rim). The formation of sub-grains is observed as well as their development from the center to the rim (polygonization). In the irradiated sample Pu remains tetravalent (>95%) and no (oxidation in the rim zone. Any slight potential plutonium oxidation is buffered by the uranium dioxide matrix while locally fuel cladding interaction could also affect the redox of the fuel.

  19. Mixing height determination using remote sensing systems. General remarks

    Energy Technology Data Exchange (ETDEWEB)

    Beyrich, F. [BTU Cottbus, LS Umweltmeteorologie, Cottbus (Germany)

    1997-10-01

    Remote sensing systems can be considered today as a real alternative to classical soundings with respect to the MH (mixing height) determination. They have the basic advantage to allow continuous monitoring of the ABL (atmospheric boundary layer). Some technical issues which limit their operational use at present should be solved in the near future (frequency allocation, eye safety, costs). Taking into account specific operating conditions and the formulated-above requirements of a sounding system to be used for MH determination it becomes obvious that none of the available systems meets all of them, i.e., the `Mixing height-meter` does not exist. Therefore, reliable MH determination under a wide variety of conditions can be achieved only by integrating different instruments into a complex sounding system. The S-profiles provide a suitable data base for MH estimation from all types of remote sensing instruments. The criteria to deduce MH-values from these profiles should consider the structure type and the evolution stage of the ABL as well as the shape of the profiles. A certain kind of harmonization concerning these criteria should be achieved. MH values derived automatically from remote sensing data appear to be not yet reliable enough for direct operational use, they should be in any case critically examined by a trained analyst. Contemporary mathematical methods (wavelet transforms, fuzzy logics) are supposed to allow considerable progress in this field in the near future. (au) 19 refs.

  20. Magnetic properties of mesoporous cobalt-silica-alumina ternary mixed oxides

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Nabanita [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Seikh, Md. Motin [Department of Chemistry, Visva-Bharati University, Santiniketan, West Bengal (India); Bhaumik, Asim, E-mail: msab@iacs.res.in [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India)

    2013-02-15

    Mesoporous cobalt-silica-alumina mixed oxides with variable cobalt content have been synthesized through slow evaporation method by using Pluronic F127 non-ionic surfactant as template. N{sub 2} sorption analysis of the template-free mixed oxide samples revealed that these mesoporous materials have high BET surface areas together with large mesopores. Powder XRD, TEM, EDS, FT IR and EPR spectroscopic analysis have been employed to understand the nature of the mesophases, bonding and composition of the materials. Low temperature magnetic measurements of these mixed oxide materials show the presence of ferromagnetic correlation at elevated temperature though at low temperature paramagnetic to ferrimagnetic transition is observed. Highlights: Black-Right-Pointing-Pointer Mesoporous cobalt-silica-alumina ternary mixed oxides. Black-Right-Pointing-Pointer High surface area and mesoporosity in magnetic materials. Black-Right-Pointing-Pointer Ferromagnetic correlation at elevated temperature. Black-Right-Pointing-Pointer Low temperature paramagnetic to ferrimagnetic transition.

  1. Single crystal particles of a mesoporous mixed transition metal oxide with a wormhole structure.

    Science.gov (United States)

    Lee, B; Lu, D; Kondo, J N; Domen, K

    2001-10-21

    A new type of mesoporous mixed transition metal oxide of Nb and Ta (NbTa-TIT-1) has been prepared through a two-step calcination, which consists of single crystal particles with wormhole mesoporous structure.

  2. Different Abilities of Eight Mixed Cultures of Methane-oxidizing Bacteria to Degrade TCE

    DEFF Research Database (Denmark)

    Broholm, Kim; Christensen, Thomas Højlund; Jensen, Bjørn K.

    1993-01-01

    methanol, but only for a limited time period of about 5 days. Several explanations for the discontinued degradation of TCE are given. An experiment carried out to re-activate the methane-oxidizing bacteria after 8 days of growth on methanol by adding methane did not immediately result in degradation......The ability of eight mixed cultures of methane-oxidizing bacteria to degrade trichloroethylene (TCE) was examined in laboratory batch experiments. This is one of the first reported works studying TCE degradation by mixed cultures of methane-oxidizing bacteria at 10°C, a common temperature for soils...... and groundwaters. Only three of the eight mixed cultures were able to degrade TCE, or to degrade TCE fast enough to result in a significant removal of TCE within the experimental time, when the cultures used methane as growth substrate. The same three mixed cultures were able to degrade TCE when they oxidized...

  3. Insight into the photocatalytic activity of ZnCr-CO3 LDH and derived mixed oxides

    Czech Academy of Sciences Publication Activity Database

    Paušová, Š.; Krysa, J.; Jirkovský, Jaromír; Forano, C.; Mailhot, G.; Prevot, V.

    2015-01-01

    Roč. 170, JUL 01 (2015), s. 25-33 ISSN 0926-3373 Institutional support: RVO:61388955 Keywords : photocatalysis * layered double hydroxides * mixed oxides Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 8.328, year: 2015

  4. Development of an engineered safeguards system concept for a mixed-oxide fuel fabrication facility

    International Nuclear Information System (INIS)

    Chapman, L.D.; de Montmollin, J.M.; Deveney, J.E.; Fienning, W.C.; Hickman, J.W.; Watkins, L.D.; Winblad, A.E.

    1976-08-01

    An initial concept of an Engineered Safeguards System for a representative commercial mixed-oxide fuel fabrication facility is presented. Computer simulation techniques for evaluation and further development of the concept are described. An outline of future activity is included

  5. Titanium oxide modification with oxides of mixed cobalt valence for photo catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Alanis O, R.; Jimenez B, J., E-mail: jaime.jimenez@inin.gob.m [ININ, Departamento de Quimica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2010-07-01

    In the present work, heterogenous photo catalysis, a technique often used for organic compound degradation toxic in water, was used. The photo catalyst most often used in this technique is TiO{sub 2}, which due to its physical and chemical properties, can degrade a great number of organic compounds. In addition, in recent years it has been verified that the doping of semiconductors with metals or metallic oxides increases the photo catalytic activity of these semiconductors, which is why it was proposed for doping by the impregnating method using commercial TiO{sub 2} synthesized by the Degussa company (TiO{sub 2} Degussa P25) with and oxide of mixed cobalt valence (Co{sub 3}O{sub 4}) synthesized using the sol-gel method. The synthesized photo catalyst TiO{sub 2}/Co{sub 3}O{sub 4} was characterized by the techniques of X-ray diffraction, scanning electronic microscopy, Raman spectroscopy and finally, photo catalytic tests by means of the degradation of methylene blue. (Author)

  6. Titanium oxide modification with oxides of mixed cobalt valence for photo catalysis

    International Nuclear Information System (INIS)

    Alanis O, R.; Jimenez B, J.

    2010-01-01

    In the present work, heterogenous photo catalysis, a technique often used for organic compound degradation toxic in water, was used. The photo catalyst most often used in this technique is TiO 2 , which due to its physical and chemical properties, can degrade a great number of organic compounds. In addition, in recent years it has been verified that the doping of semiconductors with metals or metallic oxides increases the photo catalytic activity of these semiconductors, which is why it was proposed for doping by the impregnating method using commercial TiO 2 synthesized by the Degussa company (TiO 2 Degussa P25) with and oxide of mixed cobalt valence (Co 3 O 4 ) synthesized using the sol-gel method. The synthesized photo catalyst TiO 2 /Co 3 O 4 was characterized by the techniques of X-ray diffraction, scanning electronic microscopy, Raman spectroscopy and finally, photo catalytic tests by means of the degradation of methylene blue. (Author)

  7. Argonne National Laboratory's photo-oxidation organic mixed waste treatment system - installation and startup testing

    International Nuclear Information System (INIS)

    Shearer, T.L.; Nelson, R.A.; Torres, T.; Conner, C.; Wygmans, D.

    1997-01-01

    This paper describes the installation and startup testing of the Argonne National Laboratory (ANL-E) Photo-Oxidation Organic Mixed Waste Treatment System. This system will treat organic mixed (i.e., radioactive and hazardous) waste by oxidizing the organics to carbon dioxide and inorganic salts in an aqueous media. The residue will be treated in the existing radwaste evaporators. The system is installed in the Waste Management Facility at the ANL-E site in Argonne, Illinois. 1 fig

  8. Influence of Precipitation Method on Acid-Base Catalyzed Reactions over Mg-Zr Mixed Oxides

    OpenAIRE

    Kozlowski, J.; Behrens, M.; Schlögl, R.; Davis, R.

    2013-01-01

    To examine the promotional effect that zirconia has on magnesia in catalysis, mixed oxides were prepared by coprecipitation under controlled-pH conditions or rising-pH conditions. The resulting mixed oxides were characterized by using NH3 and CO2 adsorption microcalorimetry, X-ray diffraction, and scanning electron microscopy. The samples were also tested as catalysts for transesterification of tributyrin with methanol, coupling of acetone, and conversion of ethanol to ethene, ethanal, and bu...

  9. Feasibility Study of 1/3 Thorium-Plutonium Mixed Oxide Core

    OpenAIRE

    Cheuk Wah Lau; Henrik Nylén; Klara Insulander Björk; Urban Sandberg

    2014-01-01

    Thorium-plutonium mixed oxide (Th-MOX) fuel has become one of the most promising solutions to reduce a large and increasing plutonium stockpile. Compared with traditional uranium-plutonium mixed oxide (U-MOX) fuels, Th-MOX fuel has higher consumption rate of plutonium in LWRs. Besides, thorium based fuels have improved thermomechanical material properties compared with traditional U-MOX fuels. Previous studies on a full Th-MOX core have shown reduced efficiency in reactivity control mechanism...

  10. Autoradiographic measurement of Pu distribution in mixed-oxide nuclear fuel

    International Nuclear Information System (INIS)

    Green, D.R.; Rasmussen, D.E.; Gray, W.H.

    1976-09-01

    The autoradiographic method described was developed for rapid, economical determination of the Pu distribution and microhomogeneity in mixed oxide fuel. High Pu concentration regions of any size down to 13 microns in diameter can be reproducibly resolved using this method. The new method uses computerized scanning and analysis, and includes automatic self-calibration to virtually elimate variations resulting from photographic film and processing. The speed of this new method allows analysis of enough data to ensure statistical reliability of occurrence frequencies, even for sparse populations of Pu-rich regions with diameters greater than 60 microns. Determination of these occurrence frequencies is an important factor in controlling fuel quality to ensure safe, efficient operation in a Liquid Metal Fast Breeder Reactor

  11. Molten carbonate fuel cell cathode with mixed oxide coating

    Science.gov (United States)

    Hilmi, Abdelkader; Yuh, Chao-Yi

    2013-05-07

    A molten carbonate fuel cell cathode having a cathode body and a coating of a mixed oxygen ion conductor materials. The mixed oxygen ion conductor materials are formed from ceria or doped ceria, such as gadolinium doped ceria or yttrium doped ceria. The coating is deposited on the cathode body using a sol-gel process, which utilizes as precursors organometallic compounds, organic and inorganic salts, hydroxides or alkoxides and which uses as the solvent water, organic solvent or a mixture of same.

  12. Determination of oxygen nonstoichiometry and diffusivity in mixed conducting oxides by oxygen Coulometric titration. II. Oxygen nonstoichiometry and defect model for La0.8Sr0.2CoO3-d

    NARCIS (Netherlands)

    Lankhorst, M.H.R.; Lankhorst, M.H.R.; Bouwmeester, Henricus J.M.

    1997-01-01

    The oxygen nonstoichiometry of La0.8Sr0.2CoO3-delta has been determined as a function of oxygen partial pressure and temperature using a high-temperature coulometric titration cell. For each measured value of the oxygen chemical potential, the oxygen nonstoichiometry is found to be nearly

  13. Phase stability and oxygen transport properties of mixed ionic-electronic conducting oxides

    NARCIS (Netherlands)

    Yoo, C.-Y.

    2012-01-01

    The application of mixed ionic-electronic conducting oxides as oxygen separation membrane for the production of oxygen offers significant advantages over conventional cryogenic distillation. Perovskite- and fluorite-type oxides are promising candidates for such application. The research described in

  14. Effect of cobalt loading on the solid state properties and ethyl acetate oxidation performance of cobalt-cerium mixed oxides.

    Science.gov (United States)

    Konsolakis, M; Carabineiro, S A C; Marnellos, G E; Asad, M F; Soares, O S G P; Pereira, M F R; Órfão, J J M; Figueiredo, J L

    2017-06-15

    Cobalt-cerium mixed oxides were prepared by the wet impregnation method and evaluated for volatile organic compounds (VOCs) abatement, using ethyl acetate (EtAc) as model molecule. The impact of Co content on the physicochemical characteristics of catalysts and EtAc conversion was investigated. The materials were characterized by various techniques, including N 2 adsorption at -196°C, scanning electron microscopy (SEM), X-ray diffraction (XRD), H 2 -temperature programmed reduction (H 2 -TPR) and X-ray photoelectron spectroscopy (XPS) to reveal the structure-activity relationship. The obtained results showed the superiority of mixed oxides compared to bare CeO 2 and Co 3 O 4 , demonstrating a synergistic effect. The optimum oxidation performance was achieved with the sample containing 20wt.% Co (Co/Ce atomic ratio of ca. 0.75), in which complete conversion of EtAc was attained at 260°C. In contrast, temperatures above 300°C were required to achieve 100% conversion over the single oxides. Notably, a strong relationship between both the: (i) relative population, and (ii) facile reduction of lattice oxygen with the ethyl acetate oxidation activity was found, highlighting the key role of loosely bound oxygen species on VOCs oxidation. A synergistic Co-Ce interaction can be accounted for the enhanced reducibility of mixed oxides, linked with the increased mobility of lattice oxygen. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Preparation of mixed oxides (Th,U)O{sub 2}: an evaluation of different techniques; Estudos de diferentes rotas de preparacao de oxidos binarios de torio e uranio

    Energy Technology Data Exchange (ETDEWEB)

    Ayoub, Jamil Mahmoud Said

    1999-07-01

    An evaluation of different ways of obtaining (Th-U)O{sub 2} mixed oxides is described. Coprecipitation, mechanical mixing of uranium and thorium powders, and the sol-gel technique were studied in order to get a large spectrum of knowledge of the process performance. The use of ultrasonic waves for the homogenization of the hydroxide mixture and microwave heating for powder drying was also investigated. Sol-gel showed the best results regarding the specific area for obtained samples. Oxide drying by microwave is an effective method to get mixed oxides for fuel fabrication. Neither coprecipitation nor mechanical mixing of the thorium and uranium oxide powders is suitable for the purpose. The obtained data are less than 70% than those achieved when sol-gel process is performed. Electronic microscopy, X-ray fluorescence and diffraction, thermogravimetry, specific gravidity and specific area determination (BET) used for sample characterization were convenient and accomplished good results. (author)

  16. High purity samarium oxide from mixed rare earth carbonates

    International Nuclear Information System (INIS)

    Queiroz, Carlos A. da S.; Seneda, Jose A.; Vasconcellos, Mari E. de; Pedreira Filho, Walter dos R.

    2013-01-01

    A simple and economical chemical process for the production of highly pure samarium oxides is discussed. The raw material, which was used in the form of rare earth carbonates was produced industrially from the chemical treatment of Brazilian monazite. Ion exchange chromatography was performed using a strong cationic resin that is typically employed in water treatment processes to fractionate rare earth elements (REE) without the use of retention ions. Under these conditions, 99.9% pure Sm 2 O 3 was eluted using the ammonium salt of ethylenediaminetetraacetic acid (EDTA) at a controlled pH. The EDTA-samarium complex was separated from EDTA and then precipitated as oxalate and fired to samarium oxide. Molecular absorption spectrophotometry was used to monitor the samarium content during the proposed process, and sector field inductively coupled plasma mass spectrometry was used to certify the purity of the samarium oxide. Typical samarium oxide obtained from the proposed procedure contained the following contaminants in micrograms per gram: Sc (20.90); Y (11.80); La (8.4); Ce (4.3); Pr (2.5); Nd (5.1); Eu (94); Gd (114); Tb (3.6); Dy (2.5), Ho (2.3); Er (3.0); Tm (2.3); Yb (38,2); Lu (25.6). The high-purity samarium oxides produced in the present study can be used as an alternative to imported products in research and development applications. (author)

  17. Analysis impurity elements in mixed U-Th Oxide with emission spectrograph

    International Nuclear Information System (INIS)

    Simbolon, Sahat; Aryadi

    1996-01-01

    Analysis impurity elements of boron and cadmium in mixed U-Th oxide with emission spectrograph was done. Mixed U-Th oxide standard containing impurity elements was made by mixing 90 % uranium oxide and 10 % thorium oxide that was known concentration of each impurity elements. Thorax film plate was used to replace film SA1 as a film standard and carrier distillation of AgCI, Ga 2 O 3 and LiF was used during the excitation with DC arc. The most sensitive wavelength of impurity elements of boron and cadmium were used for analysis, on 249.77 nm and 228.8 nm respectively. Grating 590 groves/mm was used. Limit of detection for boron and cadmium was calculated by use standard error of estimation of each calibration curve. It was found detection limit of boron 0.19 ppm and cadmium 0.35 ppm

  18. Modification of Co-Mn-Al Mixed Oxide with Potassium and Its Effect on Deep Oxidation of VOC

    Czech Academy of Sciences Publication Activity Database

    Jirátová, Květa; Mikulová, Jana; Klempa, Jan; Grygar, Tomáš; Bastl, Zdeněk; Kovanda, F.

    2009-01-01

    Roč. 361, 1-2 (2009), s. 106-116 ISSN 0926-860X R&D Projects: GA ČR GA104/07/1400 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z40320502; CEZ:AV0Z40400503 Keywords : mixed oxide catalysts * VOC total oxidation * potassium promoter Subject RIV: CC - Organic Chemistry Impact factor: 3.564, year: 2009

  19. Mixed conductivity in erbia-stabilized bismuth oxide

    NARCIS (Netherlands)

    Vinke, I.C.; Vinke, I.C.; Boukamp, Bernard A.; de Vries, K.J.; de Vries, Karel Jan; Burggraaf, Anthonie; Burggraaf, A.J.

    1992-01-01

    The mixed conducting solid solution 0.75Bi2O3−0.25Tb4O7 (BT40) was studied by impedance techniques using ionically blocking electrodes. These measurements confirmed the p-type electronic conductivity suggested in literature. In air at temperatures between 600 and 900 K the ionic transference number

  20. Novel synthesis of manganese and vanadium mixed oxide (V2O5/OMS-2) as an efficient and selective catalyst for the oxidation of alcohols in liquid phase

    International Nuclear Information System (INIS)

    Mahdavi, Vahid; Soleimani, Shima

    2014-01-01

    Graphical abstract: Oxidation of various alcohols is studied in the liquid phase over new composite mixed oxide (V 2 O 5 /OMS-2) catalyst using tert-butyl hydroperoxide (TBHP). The activity of V 2 O 5 /OMS-2 samples was considerably increased with respect to OMS-2 catalyst and these samples are found to be suitable for the selective oxidation of alcohols. - Highlights: • V 2 O 5 /K-OMS-2 with different V/Mn molar ratios prepared by the impregnation method. • Oxidation of alcohols was studied in the liquid phase over V 2 O 5 /K-OMS-2 catalyst. • V 2 O 5 /K-OMS-2 catalyst had excellent activity for alcohol oxidation. • Benzyl alcohol oxidation using excess TBHP followed a pseudo-first order kinetic. • The selected catalyst was reused without significant loss of activity. - Abstract: This work reports the synthesis and characterization of mixed oxide vanadium–manganese V 2 O 5 /K-OMS-2 at various V/Mn molar ratios and prepared by the impregnation method. Characterization of these new composite materials was made by elemental analysis, BET, XRD, FT-IR, SEM and TEM techniques. Results of these analyses showed that vanadium impregnated samples contained mixed phases of cryptomelane and crystalline V 2 O 5 species. Oxidation of various alcohols was studied in the liquid phase over the V 2 O 5 /K-OMS-2 catalyst using tert-butyl hydroperoxide (TBHP) and H 2 O 2 as the oxidant. Activity of the V 2 O 5 /K-OMS-2 samples was increased considerably with respect to K-OMS-2 catalyst due to the interaction of manganese oxide and V 2 O 5 . The kinetic of benzyl alcohol oxidation using excess TBHP over V 2 O 5 /K-OMS-2 catalyst was investigated at different temperatures and a pseudo-first order reaction was determined with respect to benzyl alcohol. The effects of reaction time, oxidant/alcohol molar ratio, reaction temperature, solvents, catalyst recycling potential and leaching were investigated

  1. The underwater coincidence counter for plutonium measurements in mixed-oxide fuel assemblies manual

    International Nuclear Information System (INIS)

    Eccleston, G.W.; Menlove, H.O.; Abhold, M.; Baker, M.; Pecos, J.

    1999-01-01

    This manual describes the Underwater Coincidence Counter (UWCC) that has been designed for the measurement of plutonium in mixed-oxide (MOX) fuel assemblies prior to irradiation. The UWCC uses high-efficiency 3 He neutron detectors to measure the spontaneous-fission and induced-fission rates in the fuel assembly. Measurements can be made on MOX fuel assemblies in air or underwater. The neutron counting rate is analyzed for singles, doubles, and triples time correlations to determine the 240 Pu effective mass per unit length of the fuel assembly. The system can verify the plutonium loading per unit length to a precision of less than 1% in a measurement time of 2 to 3 minutes. System design, components, performance tests, and operational characteristics are described in this manual

  2. A safeguards approach applicable to A plutonium mixed oxide powder plant

    International Nuclear Information System (INIS)

    Ismail, B.

    1988-01-01

    This report describes a safeguards approach possible to apply in a plutonium mixed oxide powder plant which handles large amounts of plutonium in the light of experience gained in some other plutonium bulk handling facilities in the nuclear fuel cycle under IAEA safeguards. The approach is based on performing two routine verifications of the nuclear material per month without interrupting the process operations in the plant combined with continual flow verifications for ongoing process and transfer operations; and two physical inventory verifications per year. The total annual effort to cover all the verifications was estimated to be in the range of 150 to 240 man day. The analysis of the approach showed that with further advances in the Non destructive assay measurement techniques for the determination of plutonium content in solutions and MOX powder would lead to development of the approach towards increase in effectiveness and decrease in the verification effort. 2 fig., 4 tab

  3. Rapid mixing chemical oxidative polymerization: an easy route to ...

    Indian Academy of Sciences (India)

    Administrator

    bon nanomaterial suspensions (Gedela et al 2012); here, the problems of poor solvability and/or dispersion of the constituent materials in the solvents used in synthesis protocols can be overcome. In this study, an easy method. (in situ chemical oxidative polymerization) to synthesize small diameter carbon nanotubes ...

  4. Enhanced Fe 2+ oxidation by mixed culture originated from hot ...

    African Journals Online (AJOL)

    For maximum oxidation efficiency and minimum amount of jarosite, a total of 30 experimental runs were conducted and the experimental data fitted to the experimental quadratic model. The analysis of variance (ANOVA) demonstrated that the model was highly significant. Three dimensional plots were illustrated to depict ...

  5. Surface Chemistry of Nano-Structured Mixed Metal Oxide Films

    Science.gov (United States)

    2012-12-11

    dehydration . Steady-state reactive molecular beam scattering (RMBS) shows that dehydration is the dominant reaction pathway on clean Mo(1 1 0), while C–Mo(1 1...photoelectrochemical water oxidation performance under simulated solar irradiation of hematite (α-Fe2O3) films synthesized by coevaporation of pure Si and Fe

  6. Mixed drink increased carbohydrate oxidation but not performance ...

    African Journals Online (AJOL)

    Kathryn van Boom

    It is well-established that consuming exogenous carbohydrate during prolonged physical activity improves performance.[1,2] The role of exogenous carbohydrate intake is hypothesised to provide additional substrate for oxidation[3] specifically influencing performance by decreasing endogenous liver glycogen utilisation ...

  7. Mixed drink increased carbohydrate oxidation but not performance ...

    African Journals Online (AJOL)

    ... improvement in 40 km time trial time between an isocaloric GP-only or a GP and fructose drink, and no differences in any of the measured variables other than exogenous carbohydrate oxidation at 90 minutes during the pre-time trial steady state ride. Keywords: multiple carbohydrate, cycling, endurance, glucose, fructose ...

  8. Synthesis, characterization and thermal expansion studies on thorium-praseodymium mixed oxide solid solutions

    International Nuclear Information System (INIS)

    Panneerselvam, G.; Antony, M.P.; Srinivasan, T.G.; Vasudeva Rao, P.R.

    2010-01-01

    Full text: Thorium-praseodymium mixed oxide solid solutions containing 15, 25, 40 and 55 mole percent of praseodymia were synthesized by mixing the solutions of thorium nitrate in water and praseodymium oxide (Pr 6 O 11 ) in conc. HNO 3 . Subsequently, their hydroxides were co-precipitated by the addition of aqueous ammonia. Further the precipitate was dried at 50 deg C, calcined at 600 deg C for 4 hours and sintered at 1200 deg C for 6 h in air. X-ray diffraction measurements were performed for phase identification and lattice parameter derivation. Single-phase fluorite structure was observed for all the compositions. Bulk and theoretical densities of solid solutions were also determined by immersion and X-ray techniques. Thermal expansion coefficients and percentage linear thermal expansion of the solid solutions were determined using high temperature X-ray diffraction technique in the temperature range 300 to 1700 K for the first time. The room temperature lattice constants estimated for above compositions are 0.5578, 0.5565, 0.5545 and 0.5526 nm, respectively. The mean linear thermal expansion coefficients for the solid solutions are 15.48 x 10 -6 K -1 , 18.35 x 10 -6 K -1 , 22.65 x 10 -6 K -1 and 26.95 x 10 -6 K -1 , respectively. The percentage linear thermal expansions in this temperature range are 1.68, 1.89, 2.21 and 2.51 respectively. It is seen that the solid solutions are stable up to 1700 K. It is also seen that the effect and nature of the dopant are the important parameters influencing the thermal expansion of the ThO 2 . The lattice parameter of the solid solutions exhibited a decreasing trend with respect to praseodymia addition. The percentage linear thermal expansion of the solid solutions increases steadily with increasing temperature

  9. Development of Mixed Ion-Electron Conducting Metal Oxides for Solid Oxide Fuel Cells

    Science.gov (United States)

    Kan, Wang Hay

    A solid oxide fuel cell (SOFC) is an energy conversion device, which directly converts chemical fuels (e.g., H2, C xHy) into electricity and heat with high efficiency up to 90%. The by-product of CO2 can be safely sequestrated or subsequently chemically transformed back into fuels (e.g., CO, CH 4) by electrolysis using renewable energy sources such as solar and wind. The state-of-the-art Ni-YSZ anode is de-activated in the presence of ppm level of H2S and forming coke in hydrocarbons. Currently, mixed ion and electron conductors (MIECs) are considered as alternatives for Ni-YSZ in SOFCs. The key goal of the research was to develop mixed ion-electron conducting metal oxides based on B-site disordered perovskite-type Ba(Ca,Nb)1-x MxO3-delta (M = Mn, Fe, Co), the B-site 1:1 ordered perovskite-type (M = Mn, Fe, Co) and the Sr2PbO4-type Sr2Ce1-xPrxO4 for SOFCs. Ba2(Ca,Nb)2-xMxO6-delta was chemically stable in 30 ppm levels of H2S at 600 °C for 24 h and in pure CO2 at 800 °C for 24 h. The thermal expansion coefficients (TEC) of the as-prepared ordered perovskites was found to be comparable to Zr0.84Y0.16O1.92 (YSZ). The near-surface concentration of Fe2+ in Ba2Ca 0.67Fe0.33NbO6-delta was found to be about 3 times higher than that in the bulk sample. The electrochemical performance of Ba2Ca0.67M0.33NbO6-delta was assessed by ac impedance spectroscopy using a YSZ supported half-cell. The area specific polarization resistance (ASR) of all samples was found to decrease with increasing temperature. The ASR for H2 gas oxidation can be correlated to the higher concentration of low valence Fe2+ species near-surface (nano-scale). BaCa0.335M0.165Nb0.5O3-delta crystallizes in the B-site disordered primitive perovskite (space group Pm-3m) at 900 °C in air, which can be converted into the B-site 1:2 ordered perovskite (space group P-3m1) at 1200 °C and the B-site 1:1 ordered double perovskite phase (space group Fm-3m ) at 1300 °C. The chemical stability of the perovskites in CO

  10. Reduction of mixed oxide spinels: nickel ferrite and alumina doped nickel ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Allender, J.; De Jonghe, L. C.

    1976-01-01

    When oxide ceramics are used in a hydrogen environment at elevated temperatures they will be reduced at a rate which can depend on a variety of parameters. The presence of minor amounts of alloying elements, e.g., can significantly alter the reduction rate. Since practical oxide ceramics generally contain mixed oxides of two or more metals, an understanding of the reduction behavior of mixed oxides, as well as an understanding of the effects of minor alloying elements in this, is important as a guide to extending the usefulness of oxide ceramics, and may serve to help in selecting raw materials that contain elements beneficial in improving resistance to reduction. In this paper, how the hydrogen reduction of nickel ferrites at 1000/sup 0/C is affected by the presence of 3.5 cation mole % aluminum in solid solution is studied.

  11. Study of Ce-Cu mixed oxide catalysts by in situ electrical conductivity measurements.

    Science.gov (United States)

    Popescu, Ionel; Piumetti, Marco; Bensaid, Samir; Marcu, Ioan-Cezar

    2017-12-06

    Three Ce-Cu mixed oxides, namely Ce 0.95 Cu 0.05 , Ce 0.6 Cu 0.4 and Ce 0.15 Cu 0.85 , along with pure CeO 2 and CuO were characterized by in situ electrical conductivity measurements. Their electrical conductivity was studied as a function of temperature and oxygen partial pressure, and was followed with time during successive exposure to air, nitrogen and different gaseous mixtures containing propane as a VOC model molecule, under conditions close to those of their catalytic applications. CeO 2 and CuO appeared to be n-type and p-type semiconductors, respectively, while the semiconducting behavior of the Ce-Cu mixed oxides depended on the oxide composition. The semiconductive and redox properties of the samples were correlated with their catalytic behavior in CO oxidation, ethene total oxidation and soot combustion.

  12. Establishment of cooperation basis of joint research on the mixed waste molten salt oxidation technology

    International Nuclear Information System (INIS)

    Yang, Hee Chul; Cho, Y. J.; Kim, J. H.; Yoo, J. H.; Yun, H. C.; Lee, D. G.

    2005-08-01

    Molten salt oxidation, MSO for short, is a robust technology that can effectively treat mixed waste (radioactive waste including hazardous metals or organics). It can safely and economically treat the difficult wastes such as not-easily destroyable toxic organic waste, medical waste, chemical warfare and energetic materials such as propellant and explosives, all of which are not easily treated by an incinerator or other currently existing thermal treatment system. Therefore, molten salt oxidation technology should be developed and utilized to treat a lot of niche waste stored in the nuclear and environmental industries. So, if we put the MSO technology to practical use by Korea-Vietnam joint research, we can reduce R and D fund for MSO technology by ourselves and we can expect an export of the outcome of nuclear R and D in Korea. For Establishment of cooperation basis of joint research concerning molten salt oxidation technology between KOREA and VIETNAM, in this research, We invited two Vietnamese researchers and we introduced our experimental scale molten salt oxidation system in order to let them understand molten salt oxidation technology. We also visited Viet man and we consulted about molten salt oxidation process. We held seminar on the mixed waste molten salt oxidation technology, discussed on the joint research on the mixed waste molten salt oxidation technology and finally we wrote MOU for joint research

  13. Establishment of cooperation basis of joint research on the mixed waste molten salt oxidation technology

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Hee Chul; Cho, Y. J.; Kim, J. H.; Yoo, J. H.; Yun, H. C.; Lee, D. G

    2005-08-01

    Molten salt oxidation, MSO for short, is a robust technology that can effectively treat mixed waste (radioactive waste including hazardous metals or organics). It can safely and economically treat the difficult wastes such as not-easily destroyable toxic organic waste, medical waste, chemical warfare and energetic materials such as propellant and explosives, all of which are not easily treated by an incinerator or other currently existing thermal treatment system. Therefore, molten salt oxidation technology should be developed and utilized to treat a lot of niche waste stored in the nuclear and environmental industries. So, if we put the MSO technology to practical use by Korea-Vietnam joint research, we can reduce R and D fund for MSO technology by ourselves and we can expect an export of the outcome of nuclear R and D in Korea. For Establishment of cooperation basis of joint research concerning molten salt oxidation technology between KOREA and VIETNAM, in this research, We invited two Vietnamese researchers and we introduced our experimental scale molten salt oxidation system in order to let them understand molten salt oxidation technology. We also visited Viet man and we consulted about molten salt oxidation process. We held seminar on the mixed waste molten salt oxidation technology, discussed on the joint research on the mixed waste molten salt oxidation technology and finally we wrote MOU for joint research.

  14. Application of Ni-Oxide@TiO₂ Core-Shell Structures to Photocatalytic Mixed Dye Degradation, CO Oxidation, and Supercapacitors.

    Science.gov (United States)

    Lee, Seungwon; Lee, Jisuk; Nam, Kyusuk; Shin, Weon Gyu; Sohn, Youngku

    2016-12-20

    Performing diverse application tests on synthesized metal oxides is critical for identifying suitable application areas based on the material performances. In the present study, Ni-oxide@TiO₂ core-shell materials were synthesized and applied to photocatalytic mixed dye (methyl orange + rhodamine + methylene blue) degradation under ultraviolet (UV) and visible lights, CO oxidation, and supercapacitors. Their physicochemical properties were examined by field-emission scanning electron microscopy, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, and UV-visible absorption spectroscopy. It was shown that their performances were highly dependent on the morphology, thermal treatment procedure, and TiO₂ overlayer coating.

  15. Spectrographic determination of impurities in high-purity tantalum oxide and niobium oxide

    International Nuclear Information System (INIS)

    Anderson, S.T.G.; Russell, G.M.

    1990-01-01

    The development of spectrographic methods by direct current arc excitation and carrier distillation for the determination of impurities in tantalum and niobium oxides are described. Iron, silicon, aluminium, titanium, calcium, silver, tin, magnesium, and manganese can be determined in tantalum oxide and niobium oxide in concentrations ranging from 3 to 300 p.p.m. Niobium can be determined in tantalum oxide in concentrations ranging from 10 to 300 p.p.m. Tantalum cannot be determined in niobium oxide, and tungsten cannot be determined in either matrix as a result of the absence of sensitive lines in the spectra of these elements. Relative standard deviations of analyte element concentrations are in the region of 0,18 for tantalum oxide samples, and 0,13 for niobium oxide samples. A detailed laboratory method is included. 4 figs., 4 tabs., 3 refs

  16. Homogeneous Cobalt/Vanadium Complexes as Precursors for Functionalized Mixed Oxides in Visible-Light-Driven Water Oxidation.

    Science.gov (United States)

    Pavliuk, Mariia V; Mijangos, Edgar; Makhankova, Valeriya G; Kokozay, Vladimir N; Pullen, Sonja; Liu, Jia; Zhu, Jiefang; Styring, Stenbjörn; Thapper, Anders

    2016-10-20

    The heterometallic complexes (NH 4 ) 2 [Co(H 2 O) 6 ] 2 [V 10 O 28 ]⋅4 H 2 O (1) and (NH 4 ) 2 [Co(H 2 O) 5 (β-HAla)] 2 [V 10 O 28 ]⋅4 H 2 O (2) have been synthesized and used for the preparation of mixed oxides as catalysts for water oxidation. Thermal decomposition of 1 and 2 at relatively low temperatures (oxides CoV 2 O 6 /V 2 O 5 (3) and Co 2 V 2 O 7 /V 2 O 5 (4). The complexes (1, 2) and heterogeneous materials (3, 4) act as catalysts for photoinduced water oxidation. A modification of the thermal decomposition procedure allowed the deposition of mixed metal oxides (MMO) on a mesoporous TiO 2 film. The electrodes containing Co/V MMOs in TiO 2 films were used for electrocatalytic water oxidation and showed good stability and sustained anodic currents of about 5 mA cm -2 at 1.72 V versus relative hydrogen electrode (RHE). This method of functionalizing TiO 2 films with MMOs at relatively low temperatures (oxides with different functionality for applications in, for example, artificial photosynthesis. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Study of the catalytic activity of mixed non-stoichiometric uranium-thorium oxides in carbon monoxide oxidation

    International Nuclear Information System (INIS)

    Brau, G.

    1969-06-01

    The aim of this work has been to study the catalytic properties of non-stoichiometric uranium-thorium oxides having the general formula U x Th 1-x O 2+y , for the oxidation of carbon monoxide. The preparation of pure, homogeneous, isotropic solids having good structural stability and a surface area as high as possible calls for a strict control of the conditions of preparation of these oxides right from the preparation of 'mother salts': the mixed oxalates U x Th 1-x (C 2 O 4 ) 2 , 2H 2 O. A study has been made of their physico-chemical properties (overall and surface chemical constitution, texture, structure, electrical conductivity), as well as of their adsorption properties with respect to gaseous species occurring in the catalytic reaction. This analysis has made it possible to put forward a reaction mechanism based on successive oxidations and reductions of the active surface by the reactants. A study of the reactions kinetics has confirmed the existence of this oxidation-reduction mechanism which only occurs for oxides having a uranium content of above 0.0014. The carbon dioxide produced by the reaction acts as an inhibitor by blocking the sites on which carbon monoxide can be adsorbed. These non-stoichiometric mixed oxides are a particularly clear example of catalysis by oxygen exchange between the solid and the gas phase. (author) [fr

  18. Biological behavior of mixed sodium and plutonium oxide aerosols

    International Nuclear Information System (INIS)

    Metivier, H.

    1976-01-01

    New risks from sodium cooled fast breeders are due to solubilization of plutonium dioxide by sodium oxides. The resulting chemical forms of higher valency stage are more transportable than PuO 2 . Bone burden is about 100 times as high as observed with PuO 2 . Diffusion is fast, therapy must be started within 6 h. DTPA is still effective, however chelation efficiency is lower than in the case of Pu IV-DTPA chelation [fr

  19. Thermal diffusivity and conductivity of thorium- uranium mixed oxides

    Science.gov (United States)

    Saoudi, M.; Staicu, D.; Mouris, J.; Bergeron, A.; Hamilton, H.; Naji, M.; Freis, D.; Cologna, M.

    2018-03-01

    Thorium-uranium oxide pellets with high densities were prepared at the Canadian Nuclear Laboratories (CNL) by co-milling, pressing, and sintering at 2023 K, with UO2 mass contents of 0, 1.5, 3, 8, 13, 30, 60 and 100%. At the Joint Research Centre, Karlsruhe (JRC-Karlsruhe), thorium-uranium oxide pellets were prepared using the spark plasma sintering (SPS) technique with 79 and 93 wt. % UO2. The thermal diffusivity of (Th1-xUx)O2 (0 ≤ x ≤ 1) was measured at CNL and at JRC-Karlsruhe using the laser flash technique. ThO2 and (Th,U)O2 with 1.5, 3, 8 and 13 wt. % UO2 were found to be semi-transparent to the infrared wavelength of the laser and were coated with graphite for the thermal diffusivity measurements. This semi-transparency decreased with the addition of UO2 and was lost at about 30 wt. % of UO2 in ThO2. The thermal conductivity was deduced using the measured density and literature data for the specific heat capacity. The thermal conductivity for ThO2 is significantly higher than for UO2. The thermal conductivity of (Th,U)O2 decreases rapidly with increasing UO2 content, and for UO2 contents of 60% and higher, the conductivity of the thorium-uranium oxide fuel is close to UO2. As the mass difference between the Th and U atoms is small, the thermal conductivity decrease is attributed to the phonon scattering enhanced by lattice strain due to the introduction of uranium in ThO2 lattice. The new results were compared to the data available in the literature and were evaluated using the classical phonon transport model for oxide systems.

  20. Contribution to the determination of total hydrogen in oxide nuclear fuels

    International Nuclear Information System (INIS)

    Bartscher, W.; Kutter, H.

    1979-01-01

    Normally the total hydrogen content of a fast breeder mixed oxide fuel is calculated from the results of the determinations of free hydrogen and water. Thermodynamic considerations, coupled with kinetic results for room temperature and 1000 0 C and taken from the literature indicate, that the normal method for the determination of water by heating in a carrier gas stream and subsequent coulometric determination of the expelled water must give low results. A modification of this method involving the introduction of a copper oxide furnace into the system for the oxidation of hydrogen has been studied. The resulting method for the determination of total hydrogen gives about ten times higher values than those calculated from the normal water determination. These total hydrogen values and the oxygen to metal ratios which are obtained by gravimetric methods and not corrected for the water content, reflect more realistically the in-pile conditions in the fuel pin. (Auth.)

  1. Solvent-Free Selective Oxidation of Toluene with O2 Catalyzed by Metal Cation Modified LDHs and Mixed Oxides

    Directory of Open Access Journals (Sweden)

    Xiaoli Wang

    2016-01-01

    Full Text Available A series of metal cation modified layered-double hydroxides (LDHs and mixed oxides were prepared and used to be the selective oxidation of toluene with O2. The results revealed that the modified LDHs exhibited much higher catalytic performance than their parent LDH and the modified mixed oxides. Moreover, the metal cations were also found to play important roles in the catalytic performance and stabilities of modified catalysts. Under the optimal reaction conditions, the highest toluene conversion reached 8.7% with 97.5% of the selectivity to benzyldehyde; moreover, the catalytic performance remained after nine catalytic runs. In addition, the reaction probably involved a free-radical mechanism.

  2. Determination of Neutrino mixing parameters after SNO oscillation evidence

    CERN Document Server

    Aliani, P; Picariello, M; Ferrari, R; Torrente-Lujan, E

    2003-01-01

    An updated analysis of all available neutrino oscillation evidence in Solar experiments (SK day and night spectra, global rates from Homestake, SAGE and GALLEX) including the latest SNO CC and NC data is presented. Assuming that the shape of the SNO CC energy spectrum is undistorted and using the information provided by SNO we obtain, for the fraction of electron neutrinos remaining in the solar beam at energies $\\gsim 5$ MeV: $\\phi_{CC}/\\phi_{NC}=0.34^{+0.05}_{-0.04},$ which is nominally $\\sim 30\\sigma$ away from the standard value. The fraction of oscillating neutrinos which into active ones is computed to be: $ (\\Phi_{NC}-\\Phi_{CC})/(\\Phi_{SSM}-\\Phi_{CC})=0.92^{+0.39}_{-0.20} $ nearly $5\\sigma$ deviations from the pure sterile oscillation case. The data is still compatible with an important fraction of sterile component in the solar beam (up to 20% of the total). In the framework of two active neutrino oscillations we determine individual neutrino mixing parameters and their errors in the region of no spec...

  3. Thermal performance of fresh mixed-oxide fuel in a fast flux LMR [liquid metal reactor

    International Nuclear Information System (INIS)

    Ethridge, J.L.; Baker, R.B.

    1985-01-01

    A test was designed and irradiated to provide power-to-melt (heat generation rate necessary to initiate centerline fuel melting) data for fresh mixed-oxide UO 2 -PuO 2 fuel irradiated in a fast neutron flux under prototypic liquid metal reactor (LMR) conditions. The fuel pin parameters were selected to envelope allowable fabrication ranges and address mass production of LMR fuel using sintered-to-size techniques. The test included fuel pins with variations in fabrication technique, pellet density, fuel-to-cladding gap, Pu concentration, and fuel oxygen-to-metal ratios. The resulting data base has reestablished the expected power-to-melt in mixed-oxide fuels during initial reactor startup when the fuel temperatures are expected to be the highest. Calibration of heat transfer models of fuel pin performance codes with these data are providing more accurate capability for predicting steady-state thermal behavior of current and future mixed-oxide LMR fuels

  4. Mixing height determination from the momentum balance of the neutral or stable PBL

    Energy Technology Data Exchange (ETDEWEB)

    Bergmann, J.C. [Risoe National Lab., Roskilde (Denmark)

    1997-10-01

    The mixing height is defined by the top of the layer of turbulent mixing. This height is equal to the height H of turbulent vertical momentum transport (fiction) in neutral or stable stratification. In very stable cases, the wave induced momentum transport must be excluded if the waves do not have mixing effects (e.g. break) within the frictional layer. Thus the conditions provided by the momentum balance determine the mixing height in most cases of mechanical turbulence. Mixing is a time dependent process and depends also on the height of release of substance to be mixed. It depends on the specific form of the exchange coefficient function whether the mixing time for the mixed layer is finite of infinite. If this time is infinite, an additional mixing time criterion for a substance released close to the ground must be applied for the determination of the corresponding mixing height. (au)

  5. High temperature oxidation behaviour of nanostructured cermet coatings in a mixed CO2 - O2 environment

    Science.gov (United States)

    Farrokhzad, M. A.; Khan, T. I.

    2014-06-01

    Nanostructured ceramic-metallic (cermet) coatings composed of nanosized ceramic particles (α-Al2O3 and TiO2) dispersed in a nickel matrix were co-electrodeposited and then oxidized at 500°C, 600°C and 700°C in a mixed gas using a Thermo-gravimetric Analysis (TGA) apparatus. The mixed gas was composed of 15% CO2, 10% O2 and 75% N2. This research investigates the effects of CO2 and O2 partial pressures on time-depended oxidation rates for coatings and compared them to the results from atmospheric oxidation under similar temperatures. The increase in partial pressure of oxygen due to the presence of CO2 at each tested temperature was calculated and correlated to the oxidation rate of the coatings. The results showed that the presence of CO2 in the system increased the oxidation rate of cermet coatings when compared to atmospheric oxidation at the same temperature. It was also shown that the increase in the oxidation rate is not the result of CO2 acting as the primary oxidant but as a secondary oxidant which results in an increase of the total partial pressure of oxygen and consequently higher oxidation rates. The WDS and XRD analyses results showed that the presence of nanosized TiO2 particles in a nickel matrix can improve oxidation behaviour of the coatings by formation of Ni-Ti compounds on oxidizing surface of the coating which was found beneficiary in reducing the oxidation rates for cermet coatings.

  6. Thorium-based mixed oxide fuel in a pressurized water reactor: A feasibility analysis with MCNP

    Science.gov (United States)

    Tucker, Lucas Powelson

    This dissertation investigates techniques for spent fuel monitoring, and assesses the feasibility of using a thorium-based mixed oxide fuel in a conventional pressurized water reactor for plutonium disposition. Both non-paralyzing and paralyzing dead-time calculations were performed for the Portable Spectroscopic Fast Neutron Probe (N-Probe), which can be used for spent fuel interrogation. Also, a Canberra 3He neutron detector's dead-time was estimated using a combination of subcritical assembly measurements and MCNP simulations. Next, a multitude of fission products were identified as candidates for burnup and spent fuel analysis of irradiated mixed oxide fuel. The best isotopes for these applications were identified by investigating half-life, photon energy, fission yield, branching ratios, production modes, thermal neutron absorption cross section and fuel matrix diffusivity. 132I and 97Nb were identified as good candidates for MOX fuel on-line burnup analysis. In the second, and most important, part of this work, the feasibility of utilizing ThMOX fuel in a pressurized water reactor (PWR) was first examined under steady-state, beginning of life conditions. Using a three-dimensional MCNP model of a Westinghouse-type 17x17 PWR, several fuel compositions and configurations of a one-third ThMOX core were compared to a 100% UO2 core. A blanket-type arrangement of 5.5 wt% PuO2 was determined to be the best candidate for further analysis. Next, the safety of the ThMOX configuration was evaluated through three cycles of burnup at several using the following metrics: axial and radial nuclear hot channel factors, moderator and fuel temperature coefficients, delayed neutron fraction, and shutdown margin. Additionally, the performance of the ThMOX configuration was assessed by tracking cycle length, plutonium destroyed, and fission product poison concentration.

  7. Ni–Ta–O mixed oxide catalysts for the low temperature oxidative dehydrogenation of ethane to ethylene

    KAUST Repository

    Zhu, Haibo

    2015-09-01

    The "wet" sol-gel and "dry" solid-state methods were used to prepare Ni-Ta-O mixed oxide catalysts. The resulting Ni-Ta oxides exhibit high activity and selectivity for the low temperature oxidative dehydrogenation of ethane to ethylene. The Ta/(Ni + Ta) atomic ratios (varying from 0 to 0.11 in "wet" sol-gel method, and from 0 to 0.20 in "dry" solid-state method) as well as the preparation methods used in the synthesis, play important roles in controlling catalyst structure, activity, selectivity and stability in the oxidative dehydrogenation of ethane. Electron microscopy characterizations (TEM, EELS mapping, and HAADF-STEM) clearly demonstrate that the Ta atoms are inserted into NiO crystal lattice, resulting in the formation of a new Ni-Ta oxide solid solution. More Ta atoms are found to be located at the lattice sites of crystal surface in sol-gel catalyst. While, a small amount of thin layer of Ta2O5 clusters are detected in solid-state catalyst. Further characterization by XRD, N2 adsorption, SEM, H2-TPR, XPS, and Raman techniques reveal different properties of these two Ni-Ta oxides. Due to the different properties of the Ni-Ta oxide catalysts prepared by two distinct approaches, they exhibit different catalytic behaviors in the ethane oxidative dehydrogenation reaction at low temperature. Thus, the catalytic performance of Ni-Ta-O mixed oxide catalysts can be systematically modified and tuned by selecting a suitable synthesis method, and then varying the Ta content. ©2015 Elsevier Inc. All rights reserved.

  8. Anodic ammonia oxidation to nitrogen gas catalyzed by mixed biofilms in bioelectrochemical systems

    International Nuclear Information System (INIS)

    Zhan, Guoqiang; Zhang, Lixia; Tao, Yong; Wang, Yujian; Zhu, Xiaoyu; Li, Daping

    2014-01-01

    In this paper we report ammonia oxidation to nitrogen gas using microbes as biocatalyst on the anode, with polarized electrode (+600 mV vs. Ag/AgCl) as electron acceptor. In batch experiments, the maximal rate of ammonia-N oxidation by the mixed culture was ∼ 60 mg L −1 d −1 , and nitrogen gas was the main products in anode compartment. Cyclic voltammetry for testing the electroactivity of the anodic biofilms revealed that an oxidation peak appeared at +600 mV (vs. Ag/AgCl), whereas the electrode without biofilms didn’t appear oxidation peak, indicating that the bioanode had good electroactivities for ammonia oxidation. Microbial community analysis of 16S rRNA genes based on high throughput sequencing indicated that the combination of the dominant genera of Nitrosomonas, Comamonas and Paracocus could be important for the electron transfer from ammonia oxidation to anode

  9. Demonstration of a Mixed Oxide Process for Control of Corrosion and Microbiological Growth in Cooling Towers

    Science.gov (United States)

    2009-08-01

    placing a bed of quartz rocks in the bottom of the brine tank, where the salt precipitate can settle and dissolve into solution over time. The subse...developing the brine may negatively impact system performance. If food-grade table salt is used, it must be mixed in a brine tank containing a settling bed...oxidant solution is not a desalinization device for making fresh water from salt water, but instead uses salt water in making the on- site oxidant

  10. Magnetic behavior of Mg-Al-Zn-Fe mixed oxides from precursors layered double hydroxide

    Energy Technology Data Exchange (ETDEWEB)

    Oliva, M.I., E-mail: marcosivanoliva@gmail.com [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, M. Allende y H. de la Torre Ciudad Universitaria, 5000 Cordoba (Argentina); IFFAM AF (CONICET - FaMAF UNC), M. Allende y H. de la Torre Ciudad Universitaria, 5000 Cordoba (Argentina); Heredia, A. [CITeQ - Facultad R. Cordoba, Universidad Tecnologica Nacional Maestro Lopez esq. Cruz Roja Argentina, CP 5016 Cordoba (Argentina); Zandalazini, C.I. [Centro Laser de Ciencias Moleculares. INFIQC-FCQ-Grupo de Ciencia de Materiales-FaMAF-Universidad Nacional de Cordoba, Ciudad Universitaria, CP5000 Cordoba, Argentina CONICET (Argentina); Crivello, M. [CITeQ - Facultad R. Cordoba, Universidad Tecnologica Nacional Maestro Lopez esq. Cruz Roja Argentina, CP 5016 Cordoba (Argentina); Corchero, E. [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, M. Allende y H. de la Torre Ciudad Universitaria, 5000 Cordoba (Argentina)

    2012-08-15

    Mixed oxides of Mg-Al-Zn-Fe were obtained by calcination of layered double hydroxides (LDH) prepared by coprecipitation reaction with hydrothermal treatment. The structural characterization of precursors and oxides was carried out by X rays diffraction, showing increases of ZnO phase with the increase of the zinc content. Magnetic behavior was studied by vibrating sample magnetometer (VSM) and by a superconducting quantum interference device (SQUID) showing both paramagnetic and super paramagnetic behavior depending on both particles size and composition.

  11. Alkali Metals as Promoters in Co-Mn-Al Mixed Oxide for N2O Decomposition

    Czech Academy of Sciences Publication Activity Database

    Obalová, L.; Karásková, K.; Wach, A.; Kustrowski, P.; Mamulová-Kutláková, K.; Michalik, S.; Jirátová, Květa

    462-463, JUL 10 (2013), s. 227-235 ISSN 0166-9834 R&D Projects: GA TA ČR TA01020336 Grant - others:MŠMT(CZ) CZ.1.05/2.1.00/03/0100; MŠMT(CZ) CZ.1.07/2.3.00/20.0074 Institutional support: RVO:67985858 Keywords : layered double hydroxides * hydrothermal reaction * mixed oxides * supported catalysts * ethanol total oxidation Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  12. Clay and oxide destabilization induced by mixed alum/macromolecular flocculation aids.

    Science.gov (United States)

    Pefferkorn, E

    2006-06-30

    The review points out typical differences and analogies of the bulk characteristics of aluminum ion complexed polyelectrolytes and of their adsorption behaviors when such systems were supplied to inorganic colloids such as oxides and clays. It reports some particular investigations that were carried out in aqueous media to determine (i) the nature of the interactions existing between clay or oxides, aluminum ions and polyelectrolytes and (ii) the effects on the interfacial characteristics and the colloid stability related to the relative concentrations of these different constituents. The investigations concerned the synthetic alumina/polyacrylic acid systems and the natural kaolinite/humic acid systems, as well as partly the mixed alumina/humic acid systems. Different adsorption features and destabilization kinetics were determined to develop within these systems. One of the main constraints of the investigation arose from the presence of three interacting components which developed amphoteric and amphipatic interactions, the latter being generated by the hydrophobic moieties induced by the aluminum ions/carboxylic acid groups ion-pairing. The investigations concerned the extent and the rate of transfer of hydrogen, aluminum ions and polyelectrolytes from the bulk solution to the solid surface. Electrical surface charge characteristics were expressed in terms of the zeta potential of the colloid/polymer complexes. The colloid stability of the systems was determined as a function of time at short and long terms. The variation as a function of time of the number and weight average masses was correlated with the variation with time of the zeta potential. All these systems were determined to reach the kinetic and thermodynamic equilibrium only slowly. Despite the fact that the supply of mixed coagulants provoked the initial aggregation and the subsequent fragmentation processes for both systems, the mechanisms responsible for the two processes were found to be

  13. Decommissioning of a mixed oxide fuel fabrication facility

    International Nuclear Information System (INIS)

    Buck, S.; Colquhoun, A.

    1990-01-01

    Decommissioning of the coprecipitation plant, which made plutonium/uranium oxide fuel, is a lead project in the BNFL Sellafield decommissioning programme. The overall programme has the objectives of gaining data and experience in a wide range of decommissioning operations and hence in this specific project to pilot the decommissioning of plant heavily contaminated with plutonium and other actinides. Consequently the operations have been used to test improvements in temporary containment, contamination control and decontamination methods and also to develop in situ plutonium assay, plutonium recovery and size-reduction methods. Finally the project is also yielding data on manpower requirements, personnel radiation uptake and waste arisings to help in the planning of future decommissioning projects

  14. Redox kinetics of ceria-based mixed oxides in selective hydrogen combustion.

    Science.gov (United States)

    Blank, Jan Hendrik; Beckers, Jurriaan; Collignon, Paul F; Rothenberg, Gadi

    2007-12-03

    Ceria-based mixed oxides, in which about 10 mol % of the cerium is replaced by another metal, catalyze the selective combustion of hydrogen from a mixture of hydrogen, propane, and propene at 550 degrees C. This makes them attractive catalysts for the oxidative dehydrogenation of propane. Hydrogen combustion shifts the equilibrium to the products side, supplies energy for the endothermic dehydrogenation, and simplifies product separation. The type of metal added has an important effect on the catalytic properties. To gain insight into the process, a set consisting of six mixed oxides was synthesized and the catalytic properties and redox behavior were tested. The mixed oxides generally release more oxygen than plain ceria. Mixed oxides containing Bi, Cu, Fe, Pd or Ca release between 1.6 and 2.0 mg of oxygen per 100 mg sample (compared to only 1.2 mg for plain ceria). This result is important for reactions in which the catalyst acts as an oxygen reservoir, such as selective hydrogen combustion. The temperature at which oxygen is released is generally lower for the mixed oxides, and varies from 110 degrees C (for Cu-CeO2) to 550 degrees C (for Ca-CeO2), which enables catalytic applications over a wide temperature range. The reduction rate at 550 degrees C is related to the reduction onset of the catalysts. Those catalysts with a relatively low reduction temperature, such as Cu-, Mn-, Bi-, and Pb-CeO2, show a high reduction rate, whereas those with a high reduction temperature, such as Ca-CeO2, Fe-CeO2, and plain ceria, reduce at a slower rate. The latter catalysts also have a low selectivity towards hydrogen combustion. The influence of the catalyst composition and crystallite size on the activity and selectivity is discussed.

  15. Determination of copper oxidizing power in superconducting yttrium ceramics

    International Nuclear Information System (INIS)

    Pontaler, R.P.; Lebed', N.B.

    1989-01-01

    A new photometric method for determining the formal copper degree of oxidation and oxygen deficiency in superconducting high-temperature oxides containing yttrium, barium and copper is developed. The method is based on oxidation of Co(2) complex with EDTA by Cu(3) ions in acetrate buffer solution with pH 4.2-4.7 and allows one to determine 1-10% of Cu(3). Relative standard deviation when determining Cu(3) makes up 0.03-0.05. Using a qualitative reaction with the application of sodium vanadate hydrochloride solution the absence of peroxide compound in superconducting yttrium ceramics is ascertained

  16. Dissolution test for homogeneity of mixed oxide fuel pellets

    International Nuclear Information System (INIS)

    Lerch, R.E.

    1979-08-01

    Experiments were performed to determine the relationship between fuel pellet homogeneity and pellet dissolubility. Although, in general, the amount of pellet residue decreased with increased homogeneity, as measured by the pellet figure of merit, the relationship was not absolute. Thus, all pellets with high figure of merit (excellent homogeneity) do not necessarily dissolve completely and all samples that dissolve completely do not necessarily have excellent homogeneity. It was therefore concluded that pellet dissolubility measurements could not be substituted for figure of merit determinations as a measurement of pellet homogeneity. 8 figures, 3 tables

  17. Dynamics and Thermochemistry of Oxygen Uptake by a Mixed Ce-Pr Oxide

    Science.gov (United States)

    Sinev, M. Yu.; Fattakhova, Z. T.; Bychkov, V. Yu.; Lomonosov, V. I.; Gordienko, Yu. A.

    2018-03-01

    The dynamics of oxygen uptake by mixed Ce0.55Pr0.45O2-x oxide is studied in a pulsed oxygen supply mode using in situ high-temperature heat flow differential scanning calorimetry. It is stated that the oxidation proceeds in two regimes: a fast one at the beginning of the oxidation process, and a slow one, which is controlled by the diffusion of oxygen through the bulk of the solid at the later stages of the process. Analysis of the shape of calorimetric profiles reveals some processes, accompanied by heat release, that occur in the sample in the absence of oxygen in the gas phase. These could be due to both the redistribution of consumed oxygen in the oxide lattice and the lattice relaxation associated with the transformation of phases with different arrangements of oxygen vacancies in them. The heat effect (which diminishes from 60 to 40 kJ/mol in the course of oxygen uptake) associated with the oxidation of the reduced form of mixed Ce-Pr oxide, corresponds to the oxidation of praseodymium ions from (3+) to (4+).

  18. Fabrication of iron-cerium mixed oxide: an efficient photocatalyst for ...

    African Journals Online (AJOL)

    We report herein the fabrication of nanostructured and mesoporous iron-cerium mixed oxides for photocatalytic application. Phase, electronic structure and other properties of the products were characterized by both low-angle and wide-angle X-ray diffraction, diffuse reflectance spectroscopy, transmission electron ...

  19. A study of oxygen transport in mixed conducting oxides using isotopic exchange and conductivity relaxation

    NARCIS (Netherlands)

    den Otter, M.W.

    2000-01-01

    Mixed conducting oxygen ion conductors can be applied as membranes for the separation of oxygen from air, as electrodes for both oxygen pumps and solid oxide fuel cells. In these applications, oxygen molecules dissociate on the surface of the material. The atomic oxygen species pick up two electrons

  20. Sol-gel/hydrothermal synthesis of mixed metal oxide of Titanium and ...

    African Journals Online (AJOL)

    Mixed metal oxides of titanium and zinc nanocomposites were prepared through sol-gel method under hydrothermal condition using titanium oxy-(1, 2 - pentadione) and zinc acetate without hazardous additives. The resulting composites were characterized by X-Ray Diffractometer (XRD), Scanning Electron Microscope ...

  1. Supported Layered Double Hydroxide-Related Mixed Oxides and Their Application in the Total Oxidation of Volatile Organic Compounds

    Czech Academy of Sciences Publication Activity Database

    Kovanda, F.; Jirátová, Květa

    2011-01-01

    Roč. 53, č. 2 (2011), s. 305-316 ISSN 0169-1317 R&D Projects: GA ČR GAP106/10/1762; GA ČR GA106/09/1664 Institutional research plan: CEZ:AV0Z40720504 Keywords : layered double hydroxides * hydrothermal reaction * mixed oxides Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.474, year: 2011

  2. Microwave assisted synthesis of manganese mixed oxide nanostructures using plastic templates

    Science.gov (United States)

    Leyva, A. G.; Stoliar, P.; Rosenbusch, M.; Lorenzo, V.; Levy, P.; Albonetti, C.; Cavallini, M.; Biscarini, F.; Troiani, H. E.; Curiale, J.; Sanchez, R. D.

    2004-11-01

    The synthesis method for obtaining sub-micrometric structures of rare earth manganese-based mixed oxide compounds is described. Pore wetting of porous polycarbonate templates with the liquid precursor was followed by a two-stage thermal treatment to obtain single phase La 0.325Pr 0.300Ca 0.375MnO 3 hollow and solid structures, with external diameter determined by the sacrificial template pore size. The first thermal stage, a microwave assisted denitration process, determines the shape of the structures. The second treatment, performed at 1073 K, allows to obtain the crystallographic structure of the compound. A variety of techniques (scanning and transmission electron microscopy, scanning probe microscopy) allowed to fully characterize the microstructure and morphology of these self-standing manganite nanostructures. For 1 μm pore size templates we obtained tubes, with external diameter around 800 nm and wall thickness around 150 nm; densely packed nanoparticles sized 20-50 nm are the building blocks of the walls. For pore size below 0.1 μm, solid nanowires were obtained, the size of constituent crystallites being around 10 nm. Overall obtained material exhibits ferromagnetic ordering below 200 K.

  3. Portable calorimeter system for nondestructive assay of mixed-oxide fuels

    International Nuclear Information System (INIS)

    Roche, C.T.; Perry, R.B.; Lewis, R.N.; Jung, E.A.; Haumann, J.R.

    1978-04-01

    Calorimetric assay provides a precise, nondestructive method to determine sample Pu content based on the heat emitted by decaying radionuclides. This measurement, in combination with a gamma-spectrometer analysis of sample isotopic content, yields the total sample Pu mass. The technique is applicable to sealed containers and is essentially independent of sample matrix configuration and elemental composition. Conventional calorimeter designs employ large water-bath heat sinks and lack the portability needed by inspection personnel. The ANL air-chamber isothermal calorimeters are low-thermal-capacitance devices which eliminate the need for large constant-temperature heat sinks. These instruments are designed to use a feedback system that applies power to maintain the sample chamber at a constant electrical resistance and, therefore, at a constant temperature. The applied-power difference between a Pu-containing sample and a blank determines the radioactive-decay power. The operating characteristics of a calorimeter designed for assaying mixed-oxide powders, fuel pellets, and Pu-containing solutions are discussed. This device consists of the calorimeter, sample preheatr, and a microprocessor-controlled data-acquisition system. The small-sample device weighs 18 kg and has a measurement cycle of 20 min, with a precision of 0.1% at 10 mW. A 100-min gamma-ray measurement gives the specific power with a precision of better than 1% for samples containing 1 to 2 g of plutonium

  4. Storage capacity and oxygen mobility in mixed oxides from transition metals promoted by cerium

    International Nuclear Information System (INIS)

    Perdomo, Camilo; Pérez, Alejandro; Molina, Rafael; Moreno, Sonia

    2016-01-01

    Highlights: • Ce addition to the catalysts improves the availability of oxygen in the materials. • Mixed oxide with Co and Cu exhibits the best oxygen transport properties. • Co presence improves O 2 mobility in the catalysts. • The presence of Cu in the solids improves redox properties. - Abstract: The oxygen mobility and storage capacity of Ce-Co/Cu-MgAl or Ce–MgAl mixed oxides, obtained by hydrotalcite precursors, were evaluated using Toluene-temperature-programmed-reaction, 18 O 2 isotopic exchange and O 2 -H 2 titration. The presence of oxygen vacancies-related species was evaluated by means of Electron Paramagnetic Resonance. A correlation was found between the studied properties and the catalytic activity of the oxides in total oxidation processes. It was evidenced that catalytic activity depends on two related processes: the facility with which the solid can be reduced and its ability to regenerate itself in the presence of molecular oxygen in the gas phase. These processes are enhanced by Cu-Co cooperative effect in the mixed oxides. Additionally, the incorporation of Ce in the Co-Cu catalysts improved their oxygen transport properties.

  5. Effect of cooling rate on achieving thermodynamic equilibrium in uranium-plutonium mixed oxides

    Science.gov (United States)

    Vauchy, Romain; Belin, Renaud C.; Robisson, Anne-Charlotte; Hodaj, Fiqiri

    2016-02-01

    In situ X-ray diffraction was used to study the structural changes occurring in uranium-plutonium mixed oxides U1-yPuyO2-x with y = 0.15; 0.28 and 0.45 during cooling from 1773 K to room-temperature under He + 5% H2 atmosphere. We compare the fastest and slowest cooling rates allowed by our apparatus i.e. 2 K s-1 and 0.005 K s-1, respectively. The promptly cooled samples evidenced a phase separation whereas samples cooled slowly did not due to their complete oxidation in contact with the atmosphere during cooling. Besides the composition of the annealing gas mixture, the cooling rate plays a major role on the control of the Oxygen/Metal ratio (O/M) and then on the crystallographic properties of the U1-yPuyO2-x uranium-plutonium mixed oxides.

  6. Fabrication of uranium–americium mixed oxide pellet from microsphere precursors: Application of CRMP process

    Energy Technology Data Exchange (ETDEWEB)

    Remy, E. [Radiochemistry and Processes Department, CEA, Nuclear Energy Division, F-30207 Bagnols-sur-Cèze (France); Picart, S., E-mail: sebastien.picart@cea.fr [Radiochemistry and Processes Department, CEA, Nuclear Energy Division, F-30207 Bagnols-sur-Cèze (France); Delahaye, T. [Fuel Cycle Technology Department, CEA, Nuclear Energy Division, F-30207 Bagnols-sur-Cèze (France); Jobelin, I. [Radiochemistry and Processes Department, CEA, Nuclear Energy Division, F-30207 Bagnols-sur-Cèze (France); Lebreton, F.; Horlait, D. [Fuel Cycle Technology Department, CEA, Nuclear Energy Division, F-30207 Bagnols-sur-Cèze (France); Bisel, I. [Radiochemistry and Processes Department, CEA, Nuclear Energy Division, F-30207 Bagnols-sur-Cèze (France); Blanchart, P. [Heterogeneous Materials Research Group, Centre Européen de la Céramique, F-87068 Limoges (France); Ayral, A. [Institut Européen des Membranes, CNRS-ENSCM-UM2, CC47, University Montpellier 2, F-34095 Montpellier cedex 5 (France)

    2014-10-15

    Highlights: • Dust free process for (U,Am)O{sub 2} transmutation target fabrication. • Synthesis of U{sub 0.9}Am{sub 0.1}O{sub 2} mixed oxide microspheres from ion exchange resin. • Fabrication of dense U{sub 0.9}Am{sub 0.1}O{sub 2} pellet with 95% TD from mixed oxide microspheres. - Abstract: Mixed uranium–americium oxides are one of the materials envisaged for Americium Bearing Blankets dedicated to transmutation in fast neutron reactors. Recently, several processes have been developed in order to validate fabrication flowchart in terms of material specifications such as density and homogeneity but also to suggest simplifications for lowering industrial costs and hazards linked to dust generation of highly contaminating and irradiating compounds. This study deals with the application of an innovative route using mixed oxide microspheres obtained from metal loaded resin bead calcination, called Calcined Resin Microsphere Pelletization (CRMP). The synthesis of mixed oxide microsphere precursor of U{sub 0.9}Am{sub 0.1}O{sub 2±δ} is described as well as its characterisation. The use of this free-flowing precursor allows the pressing and sintering of one pellet of U{sub 0.9}Am{sub 0.1}O{sub 2±δ}. The ceramic obtained was characterised and results showed that its microstructure is dense and homogeneous and its density attains 95% of the theoretical density. This study validates the scientific feasibility of the CRMP process applied to the fabrication of uranium and americium-containing materials.

  7. DETERMINATION OF MIXED STABILITY CONSTANTS OF LEAD(II ...

    African Journals Online (AJOL)

    A method involving the use of paper ionophoresis is described for the study of equilibria in mixed – ligand complex systems in solution. The technique is based on the movement of a spot of metal ion under an electric field with the complexants added to the background electrolyte at pH 8.5. The stability constants of the ...

  8. Measurement of oxygen thermomigration in a hypostoichiometric mixed oxide

    International Nuclear Information System (INIS)

    Norris, D.I.R.; Coleman, S.C.; Kay, P.

    1978-08-01

    A method of determining oxygen to metal ratios in hypostoichiometric (U, Ce)Osub(2-x) by means of lattice parameter measurement and its application to thermomigration experiments is described. The technique is shown to compare favourably with other methods when a simple structure prevails. It is found that oxygen redistributes down an imposed temperature gradient, confirming theoretical predictions, and that the measured Arrhenius slope decreases as the cerium valency decreases. This effect is more marked than in (U, Pu)Osub(2-x). The results are attributable to solid state transport of oxygen vacancies and suggest that immobile complexes incorporating some oxygen deficiency are more easily formed in (U, Ce)Osub(2-x) than in (U, Pu)Osub(2-x). (author)

  9. Selective oxidation of benzene and cyclohexane using amorphous microporous mixed oxides; Selektive Oxidation von Benzol und Cyclohexan mit amorphen mikroporoesen Mischoxiden

    Energy Technology Data Exchange (ETDEWEB)

    Stoeckmann, M.

    2000-07-01

    Phenol was to be produced by direct oxidation of benzene with environment-friendly oxidants like hydrogen peroxide, oxygen, or ozone. Catalysts were amorphous microporous mixed oxides whose properties can be selected directly in the sol-gel synthesis process. Apart from benzene, also cyclohexane was oxidized with ozone using AMM catalysts in order to get more information on the potential of ozone as oxidant in heterogeneously catalyzed reactions. [German] Ziel dieser Arbeit war die Herstellung von Phenol durch die Direktoxidation von Benzol mit umweltfreundlichen Oxidationsmitteln wie Wasserstoffperoxid, Sauerstoff oder Ozon. Als Katalysatoren dienten amorphe mikroporoese Mischoxide, da deren Eigenschaften direkt in der Synthese durch den Sol-Gel-Prozess gezielt eingestellt werden koennen. Neben Benzol wurde auch Cyclohexan mit Ozon unter der Verwendung von AMM-Katalysatoren oxidiert, um das Potential von Ozon als Oxiationsmittel in heterogen katalysierten Reaktionen naeher zu untersuchen. (orig.)

  10. Selection of mixed conducting oxides for oxidative dehydrogenation of propane with pulse experiments

    NARCIS (Netherlands)

    Crapanzano, S.D.; Babych, Igor V.; Lefferts, Leonardus

    2010-01-01

    In this study, propane pulse experiments at 550 °C are used as a method to select suitable oxides for further operation of catalytic dense membrane reactor (CDMR) for oxidative dehydrogenation of propane. Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF), La2NiO4+δ (LN) and PrBaCo2O5+δ (PBC) powders were used as

  11. Synthesis and characterization of brannerite wasteforms for the immobilization of mixed oxide fuel residues

    Energy Technology Data Exchange (ETDEWEB)

    Bailey, D.J.; Stennett, M.C.; Hyatt, N.C. [Immobilisation Science Laboratory, Department of Materials Science and Engineering, University of Sheffield, Sheffield, S1 3JD (United Kingdom)

    2016-07-01

    A possible method for the reduction of civil Pu stockpiles is the reuse of Pu in mixed oxide fuel (MOX). During MOX fuel production, residues unsuitable for further recycle will be produced. Due to their high actinide content MOX residues require immobilization within a robust host matrix. Although it is possible to immobilize actinides in vitreous wasteforms; ceramic phases, such as brannerite (UTi{sub 2}O{sub 6}), are attractive due to their high waste loading capacity and relative insolubility. A range of uranium brannerite, formulated Gd{sub x}U{sub 1-x}Ti{sub 2}O{sub 6}, were prepared using a mixed oxide route. Charge compensation of divalent and trivalent cations was expected to occur via the oxidation of U{sup 4+} to higher valence states (U{sup 5+} or U{sup 6+}). Gd{sup 3+} was added to act as a neutron absorber in the final Pu bearing wasteform. X-ray powder diffraction of synthesised specimens found that phase distribution was strongly affected by processing atmosphere (air or Ar). In all cases prototypical brannerite was formed accompanied by different secondary phases dependent on processing atmosphere. Microstructural analysis (SEM) of the sintered samples confirmed the results of the X-ray powder diffraction. The preliminary results presented here indicate that brannerite is a promising host matrix for mixed oxide fuel residues. (authors)

  12. Cu-Mn-Ce ternary mixed-oxide catalysts for catalytic combustion of toluene.

    Science.gov (United States)

    Lu, Hanfeng; Kong, Xianxian; Huang, Haifeng; Zhou, Ying; Chen, Yinfei

    2015-06-01

    Cu-Mn, Cu-Mn-Ce, and Cu-Ce mixed-oxide catalysts were prepared by a citric acid sol-gel method and then characterized by XRD, BET, H2-TPR and XPS analyses. Their catalytic properties were investigated in the toluene combustion reaction. Results showed that the Cu-Mn-Ce ternary mixed-oxide catalyst with 1:2:4 mole ratios had the highest catalytic activity, and 99% toluene conversion was achieved at temperatures below 220°C. In the Cu-Mn-Ce catalyst, a portion of Cu and Mn species entered into the CeO2 fluorite lattice, which led to the formation of a ceria-based solid solution. Excess Cu and Mn oxides existed on the surface of the ceria-based solid solution. The coexistence of Cu-Mn mixed oxides and the ceria-based solid solution resulted in a better synergetic interaction than the Cu-Mn and Cu-Ce catalysts, which promoted catalyst reducibility, increased oxygen mobility, and enhanced the formation of abundant active oxygen species. Copyright © 2015. Published by Elsevier B.V.

  13. Soft chemical control of the crystal and magnetic structure of a layered mixed valent manganite oxide sulfide

    Directory of Open Access Journals (Sweden)

    Jack N. Blandy

    2015-04-01

    Full Text Available Oxidative deintercalation of copper ions from the sulfide layers of the layered mixed-valent manganite oxide sulfide Sr2MnO2Cu1.5S2 results in control of the copper-vacancy modulated superstructure and the ordered arrangement of magnetic moments carried by the manganese ions. This soft chemistry enables control of the structures and properties of these complex materials which complement mixed-valent perovskite and perovskite-related transition metal oxides.

  14. Reaction pathways for catalytic gas-phase oxidation of glycerol over mixed metal oxides

    Energy Technology Data Exchange (ETDEWEB)

    Suprun, W.; Glaeser, R.; Papp, H. [Leipzig Univ. (Germany). Inst. of Chemical Technology

    2011-07-01

    Glycerol as a main by-product from bio-diesel manufacture is a cheap raw material with large potential for chemical or biochemical transformations to value-added C3-chemicals. One possible way of glycerol utilization involves its catalytic oxidation to acrylic acid as an alternative to petrochemical routes. However, this catalytic conversion exhibits various problems such as harsh reaction conditions, severe catalyst coking and large amounts of undesired by-products. In this study, the reaction pathways for gas-phase conversion of glycerol over transition metal oxides (Mo, V und W) supported on TiO{sub 2} and SiO{sub 2} were investigated by two methods: (i) steady state experiments of glycerol oxidation and possible reactions intermediates, i.e., acrolein, 3-hydroxy propionaldehyde and acetaldehyde, and (ii) temperature-programmed surface reaction (TPSR) studies of glycerol conversion in the presence and in the absence of gas-phase oxygen. It is shown that the supported W-, V and Mo-oxides possess an ability to catalyze the oxidation of glycerol to acrylic acid. These investigations allowed us to gain a deeper insight into the reaction mechanism. Thus, based on the obtained results, three possible reactions pathways for the selective oxidation of glycerol to acrylic acid on the transition metal-containing catalysts are proposed. The major pathways in presence of molecular oxygen are a fast successive destructive oxidation of glycerol to CO{sub x} and the dehydration of glycerol to acrolein which is a rate-limiting step. (orig.)

  15. Some recent results on the correlation of nano-structural and redox properties in ceria-zirconia mixed oxides

    Energy Technology Data Exchange (ETDEWEB)

    Bernal, S. [Departamento de Ciencia de los Materiales, Ingenieria Metalurgica y Quimica Inorganica, Facultad de Ciencias, Universidad de Cadiz, Campus Rio San Pedro, E-11510 Puerto Real (Cadiz) (Spain)], E-mail: serafin.bernal@uca.es; Blanco, G.; Calvino, J.J.; Hernandez, J.C.; Perez-Omil, J.A.; Pintado, J.M.; Yeste, M.P. [Departamento de Ciencia de los Materiales, Ingenieria Metalurgica y Quimica Inorganica, Facultad de Ciencias, Universidad de Cadiz, Campus Rio San Pedro, E-11510 Puerto Real (Cadiz) (Spain)

    2008-02-28

    Some recent results on the redox behaviour of thermally aged ceria-zirconia mixed oxides with Ce/Zr molar ratios typically ranging from 50/50 to 70/30 are briefly reviewed. In accordance with them, a tentative model allowing us to correlate ageing conditions, surface and bulk nano-structural properties of the oxides, and changes occurred in their redox behaviour is proposed. As revealed by the analysis of appropriate chemical studies and the nano-structural information provided with High Resolution Transmission (HREM) and High Angle Annular Dark Field-Scanning Transmission (HAADF-STEM) electron microscopies, the presence/absence of a pyrochlore-related {kappa}-phase in the aged oxides plays a key role in determining their redox response. In the low-temperature region (T{sub red} {<=} 773 K), the enhanced reducibility exhibited by the oxide resulting from a high-temperature reduction/mild re-oxidation ageing cycle (SR-MO sample) is interpreted as due to kinetic reasons, the occurrence of the {kappa}-like phase in its surface being responsible for a faster H{sub 2} chemisorption, the rate controlling step of the overall reduction process. By contrast, in the high-temperature range (T{sub red} {>=} 973 K), the observed differences of reducibility would have a thermodynamic origin, which may be correlated with the total amount of {kappa}-like phase present in the aged sample.

  16. Mesoscopic Diffusion of Poly(ethylene oxide) in Pure and Mixed Solvents.

    Science.gov (United States)

    Zheng, Xiong; Anisimov, Mikhail A; Sengers, Jan V; He, Maogang

    2018-04-05

    We present results from an experimental dynamic light-scattering study of poly(ethylene oxide) (PEO) in both a pure solvent (water) and a mixed solvent (tert-butanol + water). The concentration dependence of the diffusive relaxation of the PEO molecules is found to be typical of polymers in a good solvent. However, the mesoscopic diffusive behavior of PEO in the mixed solvent is very different, indicating an initial collapse and subsequent reswelling of PEO caused by co-nonsolvency. Furthermore, in the solutions of PEO with very large molecular weights, we found additional hydrodynamic modes indicating the presence of PEO clusters and aggregates similar to those found by some other investigators.

  17. Detection of nitrogen dioxide using mixed tungsten oxide-based thick film semiconductor sensor.

    Science.gov (United States)

    Su, P-G; Ren-Jang, Wu; Fang-Pei, Nieh

    2003-03-10

    The thick film semiconductor sensor for NO(2) gas detection was fabricated by screen-printing method using a mixed WO(3)-based as sensing material. The sensing characteristics, such as response time, response linearity, sensitivity, working range, cross sensitivity, and long-term stability were further studied by using a WO(3)-based mixed with different metal oxides (SnO(2), TiO(2) and In(2)O(3)) and doped with noble metals (Au, Pd and Pt) as sensing materials was observed. The highest sensitivity for low concentrations (SnO(2)-Au as sensing material.

  18. XPS determination of Mn oxidation states in Mn (hydr)oxides

    International Nuclear Information System (INIS)

    Ilton, Eugene S.; Post, Jeffrey E.; Heaney, Peter J.; Ling, Florence T.; Kerisit, Sebastien N.

    2016-01-01

    Graphical abstract: - Highlights: • Systematic fitting the XPS Mn3p, Mn2p, and Mn3s to determine oxidation states of Mn (hydr)oxides. • Analysis of using the Mn3s multiplet splitting for determining valence of Mn(hydr)oxides. • Provided an easy to implement method for determining Mn oxidation states using XPS. - Abstract: Hydrous manganese oxides are an important class of minerals that help regulate the geochemical redox cycle in near-surface environments and are also considered to be promising catalysts for energy applications such as the oxidation of water. A complete characterization of these minerals is required to better understand their catalytic and redox activity. In this contribution an empirical methodology using X-ray photoelectron spectroscopy (XPS) is developed to quantify the oxidation state of hydrous multivalent manganese oxides with an emphasis on birnessite, a layered structure that occurs commonly in soils but is also the oxidized endmember in biomimetic water-oxidation catalysts. The Mn2p 3/2 , Mn3p, and Mn3s lines of near monovalent Mn(II), Mn(III), and Mn(IV) oxides were fit with component peaks; after the best fit was obtained the relative widths, heights and binding energies of the components were fixed. Unknown multivalent samples were fit such that binding energies, intensities, and peak-widths of each oxidation state, composed of a packet of correlated component peaks, were allowed to vary. Peak-widths were constrained to maintain the difference between the standards. Both average and individual mole fraction oxidation states for all three energy levels were strongly correlated, with close agreement between Mn3s and Mn3p analyses, whereas calculations based on the Mn2p 3/2 spectra gave systematically more reduced results. Limited stoichiometric analyses were consistent with Mn3p and Mn3s. Further, evidence indicates the shape of the Mn3p line was less sensitive to the bonding environment than that for Mn2p. Consequently, fitting the

  19. Phase stability and oxygen transport properties of mixed ionic-electronic conducting oxides

    OpenAIRE

    Yoo, C.-Y.

    2012-01-01

    The application of mixed ionic-electronic conducting oxides as oxygen separation membrane for the production of oxygen offers significant advantages over conventional cryogenic distillation. Perovskite- and fluorite-type oxides are promising candidates for such application. The research described in this thesis is mainly focused on i) crystal chemistry and phase stability of either Zr- or Nb-substituted Ba0.5Sr0.5Co0.8Fe0.2O3-¿ (BSCF), and those of the parent perovskite phase, and ii) oxygen ...

  20. Thermochemical Properties of the Lattice Oxygen in W,Mn-Containing Mixed Oxide Catalysts for the Oxidative Coupling of Methane

    Science.gov (United States)

    Lomonosov, V. I.; Gordienko, Yu. A.; Sinev, M. Yu.; Rogov, V. A.; Sadykov, V. A.

    2018-03-01

    Mixed NaWMn/SiO2 oxide, samples containing individual components (Na, W, Mn) and their double combinations (Na-W, Na-Mn, W-Mn) supported on silica were studied by temperature programmed reduction (TPR) and desorption (TPD), and heat flow calorimetry during their reoxidation with molecular oxygen in pulse mode. The NaWMn/SiO2 mixed oxide was shown to contain two different types of reactive lattice oxygen. The weakly-bonded oxygen can be reversibly released from the oxide in a flow of inert gas in the temperature range of 575‒900°C, while the strongly-bonded oxygen can be removed during the reduction of the sample with hydrogen at 700-900°C. The measured thermal effect of oxygen consumption for these two oxygen forms are 185 and 350 kJ/mol, respectively. The amount of oxygen removed at reduction ( 443 μmol/g) considerably exceeded the amount desorbed in an inert gas flow ( 56 μmol/g). The obtained results suggest that the reversible oxygen desorption is due to the redox process in which manganese ions are involved, while during the temperature programmed reduction, mainly oxygen bonded with tungsten is removed.

  1. Oxidation kinetic analysis of a mixed uranium dicarbide and graphite compound

    Energy Technology Data Exchange (ETDEWEB)

    Marchand, M., E-mail: mickael.marchand@cea.fr [Commissariat à l’Energie Atomique et aux énergies alternatives, CEA, CADARACHE, DEN, DEC, SPUA/Laboratoire des Combustibles Uranium, 13108 Saint Paul-lez-Durance Cedex (France); Fiquet, O., E-mail: olivier.fiquet@cea.fr [Commissariat à l’Energie Atomique et aux énergies alternatives, CEA, CADARACHE, DEN, DEC, SPUA/Laboratoire des Combustibles Uranium, 13108 Saint Paul-lez-Durance Cedex (France); Brothier, M. [Commissariat à l’Energie Atomique et aux énergies alternatives, CEA, CADARACHE, DEN, DEC, SPUA/Laboratoire des Combustibles Uranium, 13108 Saint Paul-lez-Durance Cedex (France)

    2013-06-15

    Highlights: ► Experimental study of uranium carbides and graphite powder oxidations. ► Single rate limiting step identification by extensive kinetic analysis. ► Pseudo-steady-state validation during chemical conversion. ► Combination of TGA, TDA, XRD and gas phase chromatography results. -- Abstract: The oxidation of a mixed uranium dicarbide and graphite powder has been investigated by simultaneous thermal gravimetric (TGA) and differential thermal (DTA) analyses coupled with gas phase chromatography. For isothermal oxidation conditions with temperatures below 330 °C, only the UC{sub 2} chemical phase is progressively oxidised into U{sub 3}O{sub 8} oxides. Parabolic weight gain curves as a function of oxidation over time were obtained. A detailed kinetic study is proposed to establish a pseudo-steady-state during the oxidation process. Using an experimental method based on the sudden temperature increases, a single rate-limiting step has been validated and then modelled by a 3D diffusion law. An apparent activation energy calculated from the Arrhenius representation has been evaluated at −35 kJ/mol, thus describing the diffusion of oxygen through the oxide layer.

  2. Strain Field in Ultrasmall Gold Nanoparticles Supported on Cerium-Based Mixed Oxides. Key Influence of the Support Redox State.

    Science.gov (United States)

    López-Haro, Miguel; Yoshida, Kenta; Del Río, Eloy; Pérez-Omil, José A; Boyes, Edward D; Trasobares, Susana; Zuo, Jian-Min; Gai, Pratibha L; Calvino, José J

    2016-05-03

    Using a method that combines experimental and simulated Aberration-Corrected High Resolution Electron Microscopy images with digital image processing and structure modeling, strain distribution maps within gold nanoparticles relevant to real powder type catalysts, i.e., smaller than 3 nm, and supported on a ceria-based mixed oxide have been determined. The influence of the reduction state of the support and particle size has been examined. In this respect, it has been proven that reduction even at low temperatures induces a much larger compressive strain on the first {111} planes at the interface. This increase in compression fully explains, in accordance with previous DFT calculations, the loss of CO adsorption capacity of the interface area previously reported for Au supported on ceria-based oxides.

  3. Sol-gel synthesis and characterization of mesoporous iron-titanium mixed oxide for catalytic application

    Energy Technology Data Exchange (ETDEWEB)

    Parida, K.M., E-mail: paridakulamani@yahoo.com [Colloids and Materials Chemistry Department, Institute of Minerals and Materials Technology, Bhubaneswar 751013, Orissa (India); Pradhan, Gajendra Kumar [Colloids and Materials Chemistry Department, Institute of Minerals and Materials Technology, Bhubaneswar 751013, Orissa (India)

    2010-10-01

    A mixed phase of mesoporous iron-titanium mixed oxide (ITMO) has been successfully synthesized by simple sol-gel technique by taking iron (II) sulphate and Ti-isopropoxide as the precursors and sodium dodecyl sulphate (SDS) as the surfactant. The prepared catalysts were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), diffuse reflectance UV-vis spectra (UV-vis DRS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic absorption spectroscopy (AAS), N{sub 2} adsorption-desorptions isotherm, temperature programmed desorption (TPD) and gas chromatography (GC). Low-angle XRD (LAXRD) as well as surface area analysis confirms the mesoporosity nature of the catalysts. The phase and crystallinity were revealed by XRD study. The crystallinity of the catalysts increased with increase in calcinations temperature. Catalysts screening were performed for oxidation of cyclohexane to cyclohexanol and cyclohexanone.

  4. Formation of peripheral porosity regions around urania in zirconia-urania mixed oxide powder compact sintering

    International Nuclear Information System (INIS)

    Das, P.; Choudhury, R.

    1992-01-01

    Sintering studies of zirconia-urania mixed oxide powder compacts (in stages of 5% urania up to a maximum of 20% addition) were carried out at temperatures between 1000-1400deg C for various soaking periods. The formation of a peripheral porosity region around comparatively coarser urania particle was a characteristic feature in this mixed oxide sintered compact. At even a higher sintering temperature (1800deg C), where extensive solid solution formation takes place, this porosity region demarcates the solutionized particles from the host zirconia apparently acting as a discontinuity in the system. Relative shrinkage difference between the dissimilar particles probably contributes to the porosity regions around the minor second phase at a lower temperature while at higher temperature generation of 'Kirkendall porosity' may be responsible for such an effect. (orig.)

  5. General features of conceptual design for the pilot plant to manufacture fuel rods from mixed oxides

    International Nuclear Information System (INIS)

    Quesada, C.A.; Adelfang, P.; Esteban, A.; Aparicio, G.; Friedenthal, M.; Orlando, O.S.

    1987-01-01

    This paper conceptually describes: 1) the processes in the manufacturing lines; 2) the distribution of quality controls and glove boxes in manufacturing lines; 3) the Control and Radiological Safety Room; 4) the Dressing Room; 5) the requirements of the ventilation system. The plant will be located in the first floor of the Radiochemical Processes Laboratory building, occupying a surface of 600 m 2 . The necessary equipment for the following manufacturing lines will be provided: a) conversion from Pu(NO3)4 to PuO 2 (through Pu(III)oxalate); b) manufacture of homogeneous of mixed oxides of U and Pu; c) manufacture of (U,Pu)O 2 pellets; d) manufacture of fuel rods of mixed uranium and plutonium oxides. (Author)

  6. A gravimetric method for the determination of oxygen in uranium oxides and ternary uranium oxides by addition of alkaline earth compounds

    International Nuclear Information System (INIS)

    Fujino, Takeo; Tagawa, Hiroaki; Adachi, Takeo; Hashitani, Hiroshi

    1978-01-01

    A simple gravimetric determination of oxygen in uranium oxides and ternary uranium oxides is described. In alkaline earth uranates which are formed by heating in air at 800-1100 0 C, uranium is in the hexavalent state over certain continuous ranges of alkaline earth-to-uranium ratios. Thus, if an alkaline earth uranate or a compound containing an alkaline earth element, e.g. MgO, is mixed with the oxide sample and heated in air under suitable conditions, oxygen can be determined from the weight change before and after the reaction. The standard deviation of the O:U ratio for a UOsub(2+x) test sample is +-0.0008-0.001, if a correction is applied for atmospheric moisture absorbed during mixing. (Auth.)

  7. Coordinated safeguards for materials management in a mixed-oxide fuel facility

    Energy Technology Data Exchange (ETDEWEB)

    Shipley, J.P.; Cobb, D.D.; Dietz, R.J.; Evans, M.L.; Schelonka, E.P.; Smith, D.B.; Walton, R.B.

    1977-02-01

    A coordinated safeguards system is described for safeguarding strategic quantities of special nuclear materials in mixed-oxide recycle fuel fabrication facilities. The safeguards system is compatible with industrial process requirements and combines maximum effectiveness consistent with modest cost and minimal process interference. It is based on unit process accounting using a combination of conventional and state-of-the-art NDA measurement techniques. The effectiveness of the system against single and multiple thefts is evaluated using computer modeling and simulation techniques.

  8. Coordinated safeguards for materials management in a mixed-oxide fuel facility

    International Nuclear Information System (INIS)

    Shipley, J.P.; Cobb, D.D.; Dietz, R.J.; Evans, M.L.; Schelonka, E.P.; Smith, D.B.; Walton, R.B.

    1977-02-01

    A coordinated safeguards system is described for safeguarding strategic quantities of special nuclear materials in mixed-oxide recycle fuel fabrication facilities. The safeguards system is compatible with industrial process requirements and combines maximum effectiveness consistent with modest cost and minimal process interference. It is based on unit process accounting using a combination of conventional and state-of-the-art NDA measurement techniques. The effectiveness of the system against single and multiple thefts is evaluated using computer modeling and simulation techniques

  9. K‑Doped Co−Mn−Al Mixed Oxide Catalyst for N2O Abatement from\

    Czech Academy of Sciences Publication Activity Database

    Pacultová, K.; Karásková, K.; Kovanda, F.; Jirátová, Květa; Šrámek, J.; Kustrovski, P.; Kotarba, A.; Chromčáková, Ž.; Kočí, K.; Obalová, L.

    2016-01-01

    Roč. 55, č. 26 (2016), s. 7076-7084 ISSN 0888-5885 R&D Projects: GA ČR GA14-13750S; GA TA ČR TA01020336 Institutional support: RVO:67985858 Keywords : Co-Mn-Al mixed oxide * N2O decomposition * HNO3 pilot plant Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.843, year: 2016

  10. Fabrication experience with mixed-oxide LWR fuels at the BELGONUCLEAIRE plant

    International Nuclear Information System (INIS)

    Vanhellemont, G.

    1979-01-01

    For nearly 20 years BELGONUCLEAIRE has been involved in a steadily growing effort to increase its production of mixed oxides. This programme has ranged from basic research and process development through a pilot-scale unit to today's mixed-oxide fuel fabrication plant at Dessel, which has been in operation for just over 5 years. The reference fabrication flow sheet includes UO 2 , PuO 2 and a scraped powder preparation, sintered ground pellets as well as rod fabrication and assembling. With regard to quality, attention is especially paid to the process monitoring and quality controls at the qualification step and during the routine production. Entirely different types of thermal UO 2 -PuO 2 fuel pellets, rods and assemblies have been manufactured for PWR and BWR operation. For these fabrications, some diagrams of the results with regard to the required technical specifications are presented. Special emphasis is placed on the occasional deviations of some finished products from the specifications and on the solutions applied to avoid such problems. Concerning the actual capacity of the mixed-oxide fuel fabrication plant, several limiting factors due to the nature of plutonium itself are discussed. Taking into account all these ambient limitations, a reference PWR mixed-oxide fuel output of nominally 18 t/a is obtained. The industrial feasibility of UO 2 -PuO 2 fuel fabrication has been thoroughly demonstrated by the present BELGONUCLEAIRE plant. The experience obtained has led to progressive improvements of the fabrication process and adaptation of the product controls in order to ensure the requested quality levels. (author)

  11. Simulated physical inventory verification exercise at a mixed-oxide fuel fabrication facility

    International Nuclear Information System (INIS)

    Reilly, D.; Augustson, R.

    1985-01-01

    A physical inventory verification (PIV) was simulated at a mixed-oxide fuel fabrication facility. Safeguards inspectors from the International Atomic Energy Agency (IAEA) conducted the PIV exercise to test inspection procedures under ''realistic but relaxed'' conditions. Nondestructive assay instrumentation was used to verify the plutonium content of samples covering the range of material types from input powders to final fuel assemblies. This paper describes the activities included in the exercise and discusses the results obtained. 5 refs., 1 fig., 6 tabs

  12. Vanadium Oxidation State Determination by X-Ray Absorption Spectroscopy

    Science.gov (United States)

    Duchesne, Marc A.; Nakano, Jinichiro; Hu, Yongfeng; MacLennan, Aimee; Hughes, Robin W.; Bennett, James; Nakano, Anna

    Vanadium is found in slags produced during metal refinement and fossil fuel combustion/gasification. The oxidation state of vanadium in slag has technological and environmental implications. For example, it may affect slag flow and refractory wear inside reactors, as well as leachability and toxicity of industrial by-products. Determination of vanadium's oxidation state in crystalline phases can be achieved via the widely adopted X-ray diffraction (XRD) technique. However, this technique does not provide information on vanadium in amorphous phases. The objective of this research is to determine the oxidation state of vanadium in petroleum coke gasification samples and laboratory samples using X-ray absorption spectroscopy (XAS) with Canadian Light Source's soft X-ray micro-characterization beamline (SXRMB). Linear combination fitting of XAS spectra with reference samples allowed quantitative determination of vanadium speciation.

  13. Molten salt oxidation of mixed waste: Preliminary bench-scale experiments without radioactivity

    International Nuclear Information System (INIS)

    Haas, P.A.; Rudolph, J.C.; Bell, J.T.

    1994-06-01

    Molten salt oxidation (MSO) is a process in which organic wastes are oxidized by sparging them with air through a bed of molten sodium carbonate (bp 851 degrees C) at ≥ 900 degrees C. This process is readily applicable to the mixed waste because acidic products from Cl, S, P, etc., in the waste, along with most metals and most radionuclides, are retained within the melt as oxides or salts. Rockwell International has studied the application of MSO to various wastes, including some mixed waste. A unit used by Rockwell to study the mixed waste treatment is presently in use at Oak Ridge National Laboratory (ORNL). ORNL's studies to date have concentrated on chemical flowsheet questions. Concerns that were studied included carbon monoxide (CO) emissions, NO x , emissions, and metal retention under a variety of conditions. Initial experiments show that CO emissions increase with increasing NaCl content in the melt, increasing temperature, and increasing airflow. Carbon monoxide content is especially high (> 2000 ppm) with high chlorine content (> 10%). Thermal NO x , emissions are relatively low ( x , The metal contents of the melt and of knockout pot samples of condensed salt show high volatilities of Cs as CsCl. Average condensed salt concentrations were 60% for barium and 100% for strontium and cobalt. The cerium disappeared -- perhaps from deposition on the alumina reactor walls

  14. Fabrication of uranium-americium mixed oxide pellet from microsphere precursors: Application of CRMP process

    Science.gov (United States)

    Remy, E.; Picart, S.; Delahaye, T.; Jobelin, I.; Lebreton, F.; Horlait, D.; Bisel, I.; Blanchart, P.; Ayral, A.

    2014-10-01

    Mixed uranium-americium oxides are one of the materials envisaged for Americium Bearing Blankets dedicated to transmutation in fast neutron reactors. Recently, several processes have been developed in order to validate fabrication flowchart in terms of material specifications such as density and homogeneity but also to suggest simplifications for lowering industrial costs and hazards linked to dust generation of highly contaminating and irradiating compounds. This study deals with the application of an innovative route using mixed oxide microspheres obtained from metal loaded resin bead calcination, called Calcined Resin Microsphere Pelletization (CRMP). The synthesis of mixed oxide microsphere precursor of U0.9Am0.1O2±δ is described as well as its characterisation. The use of this free-flowing precursor allows the pressing and sintering of one pellet of U0.9Am0.1O2±δ. The ceramic obtained was characterised and results showed that its microstructure is dense and homogeneous and its density attains 95% of the theoretical density. This study validates the scientific feasibility of the CRMP process applied to the fabrication of uranium and americium-containing materials.

  15. Basic design requirements for the containment system of a mixed oxide fuel fabrication plant

    International Nuclear Information System (INIS)

    Cardinale, A.; Grillo, P.

    1980-01-01

    This paper describes the updated basic design requirements for the containment system of a mixed oxide fuel fabrication plant. The design has been developed on the basis of safety goals, taking into account the environmental compatibility under both normal and accident conditions. The different sources of risk, which might cause a mixed oxide release to the environment, are analysed with regard to the system performances. In particular, this paper describes both the operational containment leakages and the basic accidents that could occur, such as a fire causing primary containment unavailability. In each possible accident situation a fault tree analysis was developed with the aim of defining the availability requirements of the most important components relevant to nuclear safety. The study points out that nuclear safety goals are attained using industrial process components, while a higher quality level is required only for components performing protection functions. Finally, a general discussion is carried out to prove the attainment of the previously stated goals, on the basis of the evaluation of releases and of their probability. The conclusion reached was that the environmental impact of a mixed oxide fuel fabrication plant can be kept at a very low level. (author)

  16. Promoting effects of thoria on the nickel-manganese mixed oxide catalysts for the aerobic oxidation of benzyl alcohol

    Directory of Open Access Journals (Sweden)

    S.S.P. Sultana

    2017-05-01

    Full Text Available Due to the recent advancement in the development of various characterization techniques, mixed metal oxide (MMO based catalysts have gained tremendous attention in the field of catalysis. In this study, we demonstrated the synthesis of a series of novel MMO based catalysts by a facile co-precipitation method. The detailed structure and composition of thoria promoted NiMnO catalysts was investigated using various microscopic and spectroscopic techniques such as, SEM, EDAX, XRD, TGA, BET and TPR. In order to study the effect of the content of thorium oxide on the catalytic activity of the as-prepared material various samples were prepared by the addition of low quantities of thorium oxide with 1%, 3% and 5% on NiMnO. The catalytic performances of the as-prepared catalysts were evaluated towards the aerobic oxidation of benzyl alcohol using molecular oxygen as oxidant. Furthermore, in order to investigate the effect of the calcination temperatures on the catalytic activities of the as-prepared materials, the samples were calcined at three different temperatures at 300 °C, 400 °C and 500 °C. The catalysts displayed significant enhancement in catalytic activity towards the catalytic conversion of benzyl alcohol (C6H5CH2OH to benzaldehyde (C6H5CHO. Detailed kinetic studies of the reactions using gas chromatography have revealed that the variation of calcination temperature and the percentage of thoria had significant effect on the catalytic performances of the materials. Among all synthesized catalysts ThO2-(5%-NiMnO catalyst calcined at 400 °C exhibited the highest catalytic performance and stability for the selective oxidation of alcohols.

  17. Selective oxidations on vanadiumoxide containing amorphous mixed oxides (AMM-V) with tert.-butylhydroperoxide

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Y.; Hunnius, M.; Storck, S.; Maier, W.F. [Max-Planck-Institut fuer Kohlenforschung, Muelheim an der Ruhr (Germany)

    1998-12-31

    The catalytic oxygen transfer properties of vanadium containing zeolites and vanadium based sol-gel catalysts with hydrogen peroxides are well known. The severe problem of vanadium leaching caused by the presence of the by-product water has been addressed. To avoid any interference with homogeneously catalyzed reactions, our study focusses on selective oxidations in a moisture-free medium with tert.-butylhydroperoxide. We have investigated the catalytic properties of amorphous microporous materials based on SiO{sub 2}, TiO{sub 2}, ZrO{sub 2} and Al{sub 2}O{sub 3} as matrix material and studied the effects of surface polarity on the oxidation of 1-octene and cyclohexane. (orig.)

  18. Electrochemical investigation of mixed metal oxide nanocomposite electrode for low temperature solid oxide fuel cell

    Science.gov (United States)

    Abbas, Ghazanfar; Raza, Rizwan; Ashfaq Ahmad, M.; Ajmal Khan, M.; Jafar Hussain, M.; Ahmad, Mukhtar; Aziz, Hammad; Ahmad, Imran; Batool, Rida; Altaf, Faizah; Zhu, Bin

    2017-10-01

    Zinc-based nanostructured nickel (Ni) free metal oxide electrode material Zn0.60/Cu0.20Mn0.20 oxide (CMZO) was synthesized by solid state reaction and investigated for low temperature solid oxide fuel cell (LTSOFC) applications. The crystal structure and surface morphology of the synthesized electrode material were examined by XRD and SEM techniques respectively. The particle size of ZnO phase estimated by Scherer’s equation was 31.50 nm. The maximum electrical conductivity was found to be 12.567 S/cm and 5.846 S/cm in hydrogen and air atmosphere, respectively at 600∘C. The activation energy of the CMZO material was also calculated from the DC conductivity data using Arrhenius plots and it was found to be 0.060 and 0.075 eV in hydrogen and air atmosphere, respectively. The CMZO electrode-based fuel cell was tested using carbonated samarium doped ceria composite (NSDC) electrolyte. The three layers 13 mm in diameter and 1 mm thickness of the symmetric fuel cell were fabricated by dry pressing. The maximum power density of 728.86 mW/cm2 was measured at 550∘C.

  19. Dry recovery test of plutonium-uranium mixed oxide fuel pellets

    International Nuclear Information System (INIS)

    Kinugasa, Manabu; Kawamata, Kazuhiko; Kashima, Sadamitsu

    1981-01-01

    The oxidation conditions for pulverizing directly Pu-U mixed oxide pellets without mechanical crushing were examined to simplify the process and to reduce radiation exposure during the dry recovery of highly enriched Pu pellets. The specimens used were the Pusub(0.3) Usub(0.7) Osub(2-x) pellets with different density, which were sintered at 1650 deg C for 2 hours under an atmosphere of 5 % H 2 - N 2 . The oxidation experiment was carried out under several conditions. The oxidation products were examined by weight gain, X-ray diffraction, appearance pictures, SEM photographs and so on. From these studies, it can be concluded that the oxidation in NO 2 diluted with air was very powerful, but if only the coarse spalling of Pusub(0.3) Usub(0.7) O 2 sintered pellets is required, it is sufficient to oxidize them in air for 1 hr in a temperature range from 400 to 600 deg C. (Asami, T.)

  20. Adsorption studies of Cd(II) onto Al{sub 2}O{sub 3}/Nb{sub 2}O{sub 5} mixed oxide dispersed on silica matrix and its on-line preconcentration and determination by flame atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Mendonca Costa, Lucimara [Programa de Pos-Graduacao em Quimica da Universidade Federal de Alfenas, Rua Gabriel Monteiro da Silva, 700, Alfenas-MG, CEP 37130-000 (Brazil); Ribeiro, Emerson Schwingel [Instituto de Quimica, Universidade Federal do Rio de Janeiro, Rio de Janeiro-RJ, CEP 21941-909 (Brazil); Segatelli, Mariana Gava [Departamento de Quimica, Universidade Estadual de Londrina, Rod. Celso Garcia Cid, PR 445 Km 380, Campus Universitario, Londrina-PR, CEP 86051-990 (Brazil); Nascimento, Danielle Raphael do [Instituto de Quimica, Universidade Federal do Rio de Janeiro, Rio de Janeiro-RJ, CEP 21941-909 (Brazil); Midori de Oliveira, Fernanda [Departamento de Quimica, Universidade Estadual de Londrina, Rod. Celso Garcia Cid, PR 445 Km 380, Campus Universitario, Londrina-PR, CEP 86051-990 (Brazil); Tarley, Cesar Ricardo Teixeira, E-mail: tarley@uel.br [Programa de Pos-Graduacao em Quimica da Universidade Federal de Alfenas, Rua Gabriel Monteiro da Silva, 700, Alfenas-MG, CEP 37130-000 (Brazil); Departamento de Quimica, Universidade Estadual de Londrina, Rod. Celso Garcia Cid, PR 445 Km 380, Campus Universitario, Londrina-PR, CEP 86051-990 (Brazil)

    2011-05-15

    The present study describes the adsorption characteristic of Cd(II) onto Nb{sub 2}O{sub 5}/Al{sub 2}O{sub 3} mixed oxide dispersed on silica matrix. The characterization of the adsorbent has been carried out by infrared spectroscopy (IR), scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), energy dispersive X-ray fluorescence analysis (EDXRF) and specific surface area (S{sub BET}). From batch experiments, adsorption kinetic of Cd(II) was described by a pseudo-second-order kinetic model. The Langmuir linear isotherm fitted to the experimental adsorption isotherm very well, and the maximum adsorption capacity was found to be 17.88 mg g{sup -1}. Using the effective material, a method for Cd(II) preconcentration at trace level was developed. The method was based on on-line adsorption of Cd(II) onto SiO{sub 2}/Al{sub 2}O{sub 3}/Nb{sub 2}O{sub 5} at pH 8.64, in which the quantitative desorption occurs with 1.0 mol L{sup -1} hydrochloric acid towards FAAS detector. The experimental parameters related to the system were studied by means of multivariate analysis, using 2{sup 4} full factorial design and Doehlert matrix. The effect of SO{sub 4}{sup 2-}, Cu{sup 2+}, Zn{sup 2+} and Ni{sup 2+} foreign ions showed no interference at 1:100 analyte:interferent proportion. Under the most favorable experimental conditions, the preconcentration system provided a preconcentration factor of 18.4 times, consumption index of 1.08 mL, sample throughput of 14 h{sup -1}, concentration efficiency of 4.35 min{sup -1}, linear range from 5.0 up to 35.0 {mu}g L{sup -1} and limits of detection and quantification of 0.19 and 0.65 {mu}g L{sup -1} respectively. The feasibility of the proposed method for Cd(II) determination was assessed by analysis of water samples, cigarette sample and certified reference materials TORT-2 (Lobster hepatopancreas) and DOLT-4 (Dogfish liver).

  1. Denitrification rate determined by nitrate disapperance is higher than determined by nitrous oxide production with acetylene blockage

    DEFF Research Database (Denmark)

    Yu, Kewei; Struwe, Sten; Kjøller, Annelise

    2008-01-01

    A mixed beech and spruce forest soil was incubated under potential denitrification assay (PDA) condition with 10% acetylene (C2H2) in the headspace of soil slurry bottles. Nitrous oxide (N2O) concentration in the headspace, as well as nitrate, nitrite and ammonium concentrations in the soil...... slurries were monitored during the incubation. Results show that nitrate disappearance rate was higher than N2O production rate with C2H2 blockage during the incubation. Sum of nitrate, nitrite, and N2O with C2H2 blockage could not recover the original soil nitrate content, showing an N imbalance...... in such a closed incubation system. Changes in nitrite and ammonium concentration during the incubation could not account for the observed faster nitrate disappearance rate and the N imbalance. Non-determined nitric oxide (NO) and N2 production could be the major cause, and the associated mechanisms could vary...

  2. DETERMINATION OF MIXED STABILITY CONSTANTS OF LEAD(II ...

    African Journals Online (AJOL)

    a

    day human diet are 0.06-0.5 mg and 0.001-0.002 mg, respectively [15]. The ionophoretic technique had been introduced in 1964 for investigating the formation of complexes and determination of the stability constants of mononuclear complexes [16, 17]. The procedure was to study the mobility of a metal cation spot on a ...

  3. Mixed colloidal suspensions of reduced graphene oxide and layered metal oxide nanosheets: useful precursors for the porous nanocomposites and hybrid films of graphene/metal oxide.

    Science.gov (United States)

    Lee, Yu Ri; Kim, In Young; Kim, Tae Woo; Lee, Jang Mee; Hwang, Seong-Ju

    2012-02-20

    Homogeneously mixed colloidal suspensions of reduced graphene oxide, or RGO, and layered manganate nanosheets have been synthesized by a simple addition of the exfoliated colloid of RGO into that of layered MnO(2). The obtained mixed colloidal suspensions with the RGO/MnO(2) ratio of ≤0.3 show good colloidal stability without any phase separation and a negatively charged state with a zeta (ζ) potential of -30 to -40 mV. The flocculation of these mixed colloidal suspensions with lithium cations yields porous nanocomposites of Li/RGO-layered MnO(2) with high electrochemical activity and a markedly expanded surface area of around 70-100 m(2)  g(-1). Relative to the Li/RGO and Li/layered MnO(2) nanocomposites (≈116 and ≈167 F g(-1)), the obtained Li/RGO-layered MnO(2) nanocomposites deliver a larger capacitance of approximately 210 F g(-1) with good cyclability of around 95-97 % up to the 1000th cycle, thus indicating the positive effect of hybridization on the electrode performances of RGO and lithium manganate. Also, an electrophoretic deposition of the mixed colloidal suspensions makes it possible to easily fabricate uniform hybrid films composed of graphene and manganese oxide. The obtained films show a distinct electrochemical activity and a homogeneous distribution of RGO and MnO(2). The present experimental findings clearly demonstrate that the utilization of the mixed colloidal suspensions as precursors provides a facile and universal methodology to synthesize various types of graphene/metal oxide hybrid materials. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Mixed Oxides of Transition Metals as Catalysts for Total Ethanol Oxidation

    Czech Academy of Sciences Publication Activity Database

    Ludvíková, Jana; Jirátová, Květa; Kovanda, F.

    2012-01-01

    Roč. 66, č. 6 (2012), s. 589-597 ISSN 0366-6352. [International Conference of the Slovak Society of Chemical Engineering /38./. Tatranské Matliare, 23.05.2011-27.05.2011] R&D Projects: GA ČR GAP106/10/1762; GA ČR GD203/08/H032 Institutional research plan: CEZ:AV0Z40720504 Keywords : volatile organic compound * total oxidation * layered double hydroxidesLDH precursors Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 0.879, year: 2012

  5. A Mixed-Oxide Assembly Design for Rapid Disposition of Weapons Plutonium in Pressurized Water Reactors

    International Nuclear Information System (INIS)

    Alonso, Gustavo; Adams, Marvin L.

    2002-01-01

    We have created a new mixed-oxide (MOX) fuel assembly design for standard pressurized water reactors (PWRs). Design goals were to maximize the plutonium throughput while introducing the lowest perturbation possible to the control and safety systems of the reactor. Our assembly design, which we call MIX-33, offers some advantages for the disposition of weapons-grade plutonium; it increases the disposition rate by 8% while increasing the worth of control material, compared to a previous Westinghouse design. The MIX-33 design is based upon two ideas: the use of both uranium and plutonium fuel pins in the same assembly, and the addition of water holes in the assembly. The main result of this paper is that both of these ideas are effective at increasing Pu throughput and increasing the worth of control material. With this new design, according to our analyses, we can transition smoothly from a full low-enriched-uranium (LEU) core to a full MIX-33 core while meeting the operational and safety requirements of a standard PWR. Given an interruption of the MOX supply, we can transition smoothly back to full LEU while meeting safety margins and using standard LEU assemblies with uniform pinwise enrichment distribution. If the MOX supply is interrupted for only one cycle, the transition back to a full MIX-33 core is not as smooth; high peaking could cause power to be derated by a few percent for a few weeks at the beginning of one transition cycle

  6. Mixed ionic liquids/graphene-supported platinum nanoparticles as an electrocatalyst for methanol oxidation

    International Nuclear Information System (INIS)

    Shi, Guoyu; Wang, Zonghua; Xia, Jianfei; Bi, Sai; Li, Yue; Zhang, Feifei; Xia, Lin; Li, Yanhui; Xia, Yanzhi; Xia, Linhua

    2014-01-01

    Graphical abstract: A kind of mixed ionic liquids (ILs) of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4], IL1) and hexafluorophosphate ([bmim][PF6], IL2) was introduced to the functionalization of graphene (GN) nanosheets, which was used to the synthesis of platinum nanoparticles (Pt NPs) to obtain the Pt/IL1-IL2/GN nanocomposite. The as-prepared Pt/IL1-IL2/GN composites exhibited highly electrocatalytic activity (764.3 mA mg − 1Pt at 0.6 V vs. SCE) and stability toward methanol oxidation, demonstrating their promising potential as the anode catalyst for direct methanol fuel cells (DMFCs). - Highlights: • Pt/mixed ionic liquids/graphene composite catalyst was easily synthesized. • The special phase equilibrium characteristics exerted by the peculiar interactions between different ILs can promote the homogeneous growth of small Pt nanoparticles. • The as-made catalyst exhibited enhanced electro-catalytic performance for methanol oxidation. - Abstract: A kind of mixed ionic liquids (ILs) of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF 4 ], IL 1 ) and hexafluorophosphate ([bmim][PF 6 ], IL 2 ) was introduced to the functionalization of graphene (GN) nanosheets, which was used to the synthesis of platinum nanoparticles (Pt NPs) to obtain the Pt/IL 1 -IL 2 /GN nanocomposite. The interaction between mixed ILs and GN achieved a stable performance due to the excellent electronic and interfacial property of the fabricated nanocomposites, which was favorable for effective loading of Pt NPs on the IL 1 -IL 2 /GN support. The as-prepared Pt/IL 1 -IL 2 /GN composites exhibited highly electrocatalytic activity (764.3 mA mg −1 Pt at 0.6 V vs. SCE) and stability toward methanol oxidation, demonstrating their promising potential as the anode catalyst for direct methanol fuel cells (DMFCs)

  7. Spectrographic determination of impurities in copper and copper oxide

    International Nuclear Information System (INIS)

    Sabato, S.F.; Lordello, A.R.

    1990-11-01

    An emission spectrographic method for the determination of Al, Bi, Ca, Cd, Cr, Fe, Ge, Mg, Mn, Mo, Ni, Pb, Sb, Si, Sn and Zn in copper and copper oxide is described. Two mixtures (Graphite and ZnO: graphite and GeO sub(2)) were used as buffers. The standard deviation lies around 10%. (author)

  8. Determination of Ammonia Oxidizing Bacteria and Nitrate Oxidizing Bacteria in Wastewater and Bioreactors

    Science.gov (United States)

    Francis, Somilez Asya

    2014-01-01

    The process of water purification has many different physical, chemical, and biological processes. One part of the biological process is the task of ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB). Both play critical roles in the treatment of wastewater by oxidizing toxic compounds. The broad term is nitrification, a naturally occurring process that is carried out by AOB and NOB by using oxidation to convert ammonia to nitrite and nitrite to nitrate. To monitor this biological activity, bacterial staining was performed on wastewater contained in inoculum tanks and biofilm samples from bioreactors. Using microscopy and qPCR, the purpose of this experiment was to determine if the population of AOB and NOB in wastewater and membrane bioreactors changed depending on temperature and hibernation conditions to determine the optimal parameters for AOB/NOB culture to effectively clean wastewater.

  9. Status of plutonium recycle from mixed oxide fuel fabrication wastes (U,Pu)O2 facility activities

    International Nuclear Information System (INIS)

    Quesada, Calixto A.; Adelfang, Pablo; Greiner, G.; Orlando, Oscar S.; Mathot, Sergio R.

    1999-01-01

    Within the specific subject of mixed oxides corresponding to the Fuel Cycle activities performed at CNEA, the recovery of plutonium from wastes originated during tests and pre-fabrication stages is performed. (author)

  10. Mixed Waste Focus Area alternative oxidation technologies development and demonstration program

    International Nuclear Information System (INIS)

    Borduin, L.C.; Fewell, T.; Gombert, D.; Priebe, S.

    1998-01-01

    The Mixed Waste Focus Area (MWFA) is currently supporting the development and demonstration of several alternative oxidation technology (AOT) processes for treatment of combustible mixed low-level wastes. The impetus for this support derives from regulatory and political hurdles frequently encountered by traditional thermal techniques, primarily incinerators. AOTs have been defined as technologies that destroy organic material without using open-flame reactions. Whether thermal or nonthermal, the processes have the potential advantages of relatively low-volume gaseous emissions, generation of few or no dioxin/furan compounds, and operation at low enough temperatures that metals (except mercury) and most radionuclides are not volatilized. Technology development and demonstration are needed to confirm and realize the potential of AOTs and to compare them on an equal basis with their fully demonstrated thermal counterparts. AOTs include both thermal and nonthermal processes that oxidize organic wastes but operate under significantly different physical and chemical conditions than incinerators. Nonthermal processes currently being studied include Delphi DETOX and acid digestion at the Savannah River Site, and direct chemical oxidation at Lawrence Livermore National Laboratory. All three technologies are at advanced stages of development or are entering the demonstration phase. Nonflame thermal processes include catalytic chemical oxidation, which is being developed and deployed at Lawrence Berkeley National Laboratory, and team reforming, a commercial process being supported by Department of Energy. Related technologies include two low-flow, secondary oxidation processes (Phoenix and Thermatrix units) that have been tested at MSE, Inc., in Butte, Montana. Although testing is complete on some AOT technologies, most require additional support to complete some or all of the identified development objectives. Brief descriptions, status, and planned paths forward for each

  11. Catalytic activity of calcium-based mixed metal oxides nanocatalysts in transesterification reaction of palm oil

    Science.gov (United States)

    Hassan, Noraakinah; Ismail, Kamariah Noor; Hamid, Ku Halim Ku; Hadi, Abdul

    2017-12-01

    Nowadays, biodiesel has become the forefront development as an alternative diesel fuel derived from biological sources such as oils of plant and fats. Presently, the conventional transesterification of vegetable oil to biodiesel gives rise to some technological problem. In this sense, heterogeneous nanocatalysts of calcium-based mixed metal oxides were synthesized through sol-gel method. It was found that significant increase of biodiesel yield, 91.75 % was obtained catalyzed by CaO-NbO2 from palm oil compared to pure CaO of 53.99 % under transesterification conditions (methanol/oil ratio 10:1, reaction time 3 h, catalyst concentration 4 wt%, reaction temperature 60 °C, and mixing speed of 600 rpm). The phase structure and crystallinity as well as the texture properties of the prepared catalysts were characterized by X-ray Diffraction (XRD) and the textural properties were characterized by N2 adsorption-desorption analysis. Sol-gel method has been known as versatile method in controlling the structural and chemical properties of the catalyst. Calcium-based mixed oxide synthesized from sol-gel method was found to exist as smaller crystallite size with high surface area.

  12. Electrochemical behaviour of manganese & ruthenium mixed oxide@ reduced graphene oxide nanoribbon composite in symmetric and asymmetric supercapacitor

    Science.gov (United States)

    Ahuja, Preety; Ujjain, Sanjeev Kumar; Kanojia, Rajni

    2018-01-01

    This paper reports the interaction of 3d-4d transition metal mixed oxide as simultaneous existence of M(3d) and M(4d) expectedly enhance the electrochemical performance of the resulting composite. Electrochemical performance of MnO2-RuO2 nanoflakes reduced graphene oxide nanoribbon composite (MnO2-RuO2@GNR) is intensively explored in symmetric and asymmetric supercapacitor assembly. In situ incorporation of graphene oxide nanoribbon (GONR) during synthesis provides efficient binding sites for growth of MnO2-RuO2 nanoflakes via their surface functionalities. The interconnected MnO2-RuO2 nanoflakes via GNR form a network with enhanced diffusion kinetics leading to efficient supercapacitor performance. Fabricated asymmetric supercapacitor reveals energy density 60 Wh kg-1 at power density 14 kW kg-1. Based on the analysis of impedance data in terms of complex power, quick response time of supercapacitor reveals excellent power delivery of the device. Improved cycling stability after 7000 charge discharge cycles for symmetric and asymmetric supercapacitor highlights the buffering action of GNR and can be generalized for next generation high performance supercapacitor.

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

    Directory of Open Access Journals (Sweden)

    Véronique Pitchon

    2012-02-01

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

  14. Low-temperature synthesis of Mn-based mixed metal oxides with novel fluffy structures as efficient catalysts for selective reduction of nitrogen oxides by ammonia.

    Science.gov (United States)

    Meng, Bo; Zhao, Zongbin; Chen, Yongsheng; Wang, Xuzhen; Li, Yong; Qiu, Jieshan

    2014-10-21

    A series of Mn-based mixed metal oxide catalysts (Co-Mn-O, Fe-Mn-O, Ni-Mn-O) with high surface areas were prepared via low temperature crystal splitting and exhibited extremely high catalytic activity for the low-temperature selective catalytic reduction of nitrogen oxides with ammonia.

  15. Co-Mn-Al Mixed Oxides on Anodized Aluminum Supports and Their Use as Catalysts in the Total Oxidation of Ethanol

    Czech Academy of Sciences Publication Activity Database

    Kovanda, F.; Jirátová, Květa; Ludvíková, Jana; Raabová, H.

    2013-01-01

    Roč. 464, AUG 15 (2013), s. 181-190 ISSN 0926-860X R&D Projects: GA ČR GAP106/10/1762 Institutional support: RVO:67985858 Keywords : layered double hydroxides * hydrothermal reaction * mixed oxides * supported catalysts * ethanol total oxidation Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 3.674, year: 2013

  16. Feasibility Study of 1/3 Thorium-Plutonium Mixed Oxide Core

    Directory of Open Access Journals (Sweden)

    Cheuk Wah Lau

    2014-01-01

    Full Text Available Thorium-plutonium mixed oxide (Th-MOX fuel has become one of the most promising solutions to reduce a large and increasing plutonium stockpile. Compared with traditional uranium-plutonium mixed oxide (U-MOX fuels, Th-MOX fuel has higher consumption rate of plutonium in LWRs. Besides, thorium based fuels have improved thermomechanical material properties compared with traditional U-MOX fuels. Previous studies on a full Th-MOX core have shown reduced efficiency in reactivity control mechanisms, stronger reactivity feedback, and a significantly lower fraction of delayed neutrons compared with a traditional uranium oxide (UOX core. These problems complicate the implementation of a full Th-MOX core in a similar way as for a traditional U-MOX core. In order to reduce and avoid some of these issues, the introduction of a lower fraction of Th-MOX fuel in the core is proposed. In this study, one-third of the assemblies are Th-MOX fuel, and the rest are traditional UOX fuel. The feasibility study is based on the Swedish Ringhals-3 PWR. The results show that the core characteristics are more similar to a traditional UOX core, and the fraction of delayed neutrons is within acceptable limits. Moreover, the damping of axial xenon oscillations induced by control rod insertions is almost 5 times more effective for the 1/3 Th-MOX core compared with the standard core.

  17. Determination of plutonium and uranium in mixed nuclear fuel by means of potentiostatic and amperostatic coulometry

    International Nuclear Information System (INIS)

    Kuperman, A.Ya.; Moiseev, I.V.; Galkina, V.N.; Yakushina, G.S.; Nikitskaya, V.N.

    1977-01-01

    Product solution occurs in HClO 4 + HNO 3 mixing. In prepared plutonium (6) and uranium (6) perchloric acid solution Cl and Cr (6), Mn (7,6,3) foreign oxidizers are selectively reduced with formic and malonic acids. Potentiostatic variant of method is based on successive reduction of Pu(6) to Pu(3) and U(6) to U(4) in 4.5M HCl, containing 5x10 -4 M bismuth (3). In using amperostatic variant of method plutonium and uranium are determined separately. In sulfur-phosphoric acid media plutonium (6) is titrated to Pu(4) with continuously generated iron (2) ions. Uranium (6) in phosphoric acid media is initially reduced to U(4) with Fe(2), and then after Fe(2) excess reduction with nitric acid it is titrated to uranium (6) with continuously electrogenerated manganese (3) ions or vanadium (5). To obtain equivalent point in plutonium (6) and uranium (4) titration amperometric method is used. Coefficient of variation is 0.2-0.3 % rel

  18. Mixed

    Directory of Open Access Journals (Sweden)

    Pau Baya

    2011-05-01

    Full Text Available Remenat (Catalan (Mixed, "revoltillo" (Scrambled in Spanish, is a dish which, in Catalunya, consists of a beaten egg cooked with vegetables or other ingredients, normally prawns or asparagus. It is delicious. Scrambled refers to the action of mixing the beaten egg with other ingredients in a pan, normally using a wooden spoon Thought is frequently an amalgam of past ideas put through a spinner and rhythmically shaken around like a cocktail until a uniform and dense paste is made. This malleable product, rather like a cake mixture can be deformed pulling it out, rolling it around, adapting its shape to the commands of one’s hands or the tool which is being used on it. In the piece Mixed, the contortion of the wood seeks to reproduce the plasticity of this slow heavy movement. Each piece lays itself on the next piece consecutively like a tongue of incandescent lava slowly advancing but with unstoppable inertia.

  19. Polyethylene encapsulation of molten salt oxidation mixed low-level radioactive salt residues

    International Nuclear Information System (INIS)

    Lageraaen, P.R.; Kalb, P.D.; Grimmett, D.L.; Gay, R.L.; Newman, C.D.

    1995-01-01

    A limited scope treatability study was conducted for polyethylene encapsulation of salt residues generated by a Molten Salt Oxidation (MSO) technology demonstration at the Energy Technology Engineering Center (ETEC), operated by Rockwell International for the US Department of Energy (DOE). During 1992 and 1993, ETEC performed a demonstration with a prototype MSO unit and treated approximately 50 gallons of mixed waste comprised of radioactively contaminated oils produced by hot cell operations. A sample of the mixed waste contaminated spent salt was used during the BNL polyethylene encapsulation treatability study. A nominal waste loading of 50 wt % was successfully processed and waste form test specimens were made for Toxicity Characteristic Leaching Procedure (TCLP) testing. The encapsulated product was compared with base-line TCLP results for total chromium and was found to be well within allowable EPA guidelines

  20. Methodologies For Characterising Mixed Conducting Oxides For Oxygen Membrane And SOFC Cathode Application

    DEFF Research Database (Denmark)

    Hendriksen, Peter Vang; Søgaard, Martin; Plonczak, Pawel

    2012-01-01

    Two methods for detailed characterization of the process of oxygen exchange between the gas phase and a mixed conducting solid oxide are discussed. First, the use of solid electrolyte probes for measuring the change in oxygen activity over the surface of a mixed conductor is presented...... and advantages of the technique discussed. Secondly, the use of thin film model electrodes is treated. Studies of thin films applied by PLD on both sides of a YSZ single crystal are presented for three different film materials; La0.85Sr0.15MnO3, La0.6Sr0.4Fe0.8Co0.2O3 and La0.6Sr0.4CoO3. Variations in electrode...

  1. Mixed-component sulfone-sulfoxide tagged zinc IRMOFs:In situ ligand oxidation, carbon dioxide, and water sorption studies

    OpenAIRE

    Bryant, Macguire R; Burrows, Andrew D; Kepert, Cameron J; Southon, Peter D; Qazvini, Omid T; Telfer, Shane G; Richardson, Christopher

    2017-01-01

    Reported here are the syntheses and adsorption properties of a series of single- and mixed-component zinc IRMOFs derived from controlled ratios of sulfide and sulfone functionalized linear biphenyldicarboxylate (bpdc) ligands. During MOF synthesis the sulfide moieties undergo in situ oxidation, giving rise to sulfoxide functionalized ligands, which are incorporated to give mixed-component sulfoxide–sulfone functionalized MOFs. The single- and mixed-component systems all share the IRMOF-9 stru...

  2. Thorium/uranium mixed oxide nano-crystals: Synthesis, structural characterization and magnetic properties

    International Nuclear Information System (INIS)

    Hudry, Damien; Griveau, Jean-Christophe; Apostolidis, Christos; Colineau, Eric; Rasmussen, Gert; Walter, Olaf; Wang, Di; Venkata Sai Kiran Chakravadhaluna; Courtois, Eglantine; Kubel, Christian

    2014-01-01

    One of the primary aims of the actinide community within nano-science is to develop a good understanding similar to what is currently the case for stable elements. As a consequence, efficient, reliable and versatile synthesis techniques dedicated to the formation of new actinide-based nano-objects (e.g., nano-crystals) are necessary. Hence, a 'library' dedicated to the preparation of various actinide based nano-scale building blocks is currently being developed. Nano-scale building blocks with tunable sizes, shapes and compositions are of prime importance. So far, the non-aqueous synthesis method in highly coordinating organic media is the only approach which has demonstrated the capability to provide size and shape control of actinide-based nano-crystals (both for thorium and uranium, and recently extended to neptunium and plutonium). In this paper, we demonstrate that the non-aqueous approach is also well adapted to control the chemical composition of the nano-crystals obtained when mixing two different actinides. Indeed, the controlled hot co-injection of thorium acetylacetonate and uranyl acetate (together with additional capping agents) into benzyl ether can be used to synthesize thorium/uranium mixed oxide nano-crystals covering the full compositional spectrum. Additionally, we found that both size and shape are modified as a function of the thorium/uranium ratio. Finally, the magnetic properties of the different thorium/uranium mixed oxide nano-crystals were investigated. Contrary to several reports, we did not observe any ferromagnetic behavior. As a consequence, ferromagnetism cannot be described as a universal feature of nano-crystals of non-magnetic oxides as recently claimed in the literature. (authors)

  3. Removal of inhaled industrial mixed oxide aerosols from Beagle dogs by lung lavage and chelation therapy

    International Nuclear Information System (INIS)

    Muggenburg, B.A.; Mewhinney, J.A.; Eidson, A.F.; Guilmette, R.A.

    1978-01-01

    An experiment was conducted in 15 adult Beagle dogs to evaluate lung lavage and chelation therapy for the removal of inhaled particles of mixed actinide oxides. The dogs were divided into three groups of five dogs each. Each group was exposed to an aerosol from a different industrial process. Group 1 was exposed to mixed oxide material which had been calcined at 750 0 C collected from a ball milling process. Group 2 was exposed to mixed oxide material from a centerless grinding operation which had been previously heat treated to 1750 0 C. The third group was exposed to 239 PuO 2 not containing uranium from a V-blending procedure which had been heat treated at 850 0 C. After exposure, three dogs in each group were given ten lung lavages and 18 intravenous injections of calcium trisodium diethylenetriaminepentaacetate (DTPA). All dogs were sacrificed 64 days after inhalation exposure. The tissues were radioanalyzed for plutonium and americium. Fluorimetric analyses for uranium in the tissues are in progress. The urine, feces and lavage fluid are also being analyzed for plutonium, americium and uranium. The distribution of plutonium and americium expressed as percentages of the sacrifice body burden was similar in the tissues of the treated and unteated dogs. The lungs contained most of the radionuclides with a small amount in the liver, skeleton and tracheobronchial lymph nodes. The percentage of the sacrifice body burden of americium and plutonium that was present in the lung was less in the treated dogs and was higher in the TBLN's and skeleton than in the untreated dogs. The ratio of Pu/Am was higher in the lungs than in the original material obtained from the industrial sites suggesting a shorter retention time for americium than plutonium to 64 days in the dog

  4. Mediated electrochemical oxidation as an alternative to incineration for mixed wastes

    International Nuclear Information System (INIS)

    Chiba, Z.; Schumacher, B.; Lewis, P.; Murguia, L.

    1995-02-01

    Mediated Electrochemical Oxidation (MEO) is an aqueous process which oxidizes organics electrochemically at low temperatures and ambient pressures. The process can be used to treat mixed wastes containing hazardous organics by destroying the organic components of the wastes. The radioactive components of the wastes are dissolved in the electrolyte where they can be recovered if desired, or immobilized for disposal. The process of destroying organics is accomplished via a mediator, which is in the form of metallic ions in solution. At Lawrence Livermore National Laboratory (LLNL) we have worked with worked with several mediators, including silver, cobalt and cerium. We have tested mediators in nitric as well as sulfuric acids. We have recently completed extensive experimental studies on cobalt-sulfuric acid and silver-nitric acid systems for destroying the major organic components of Rocky Flats Plant combustible mixed wastes. Organics tested were: Trimsol (a cutting oil), cellulose (including paper and cloth), rubber (latex), plastics (Tyvek, polyethylene and polyvinyl chloride) and biomass (bacteria). The process was capable of destroying almost all of the organics tested, attaining high destruction efficiencies at reasonable coulombic efficiencies. The only exception was polyvinyl chloride, which was destroyed very slowly resulting in poor coulombic efficiencies. Besides the process development work mentioned above, we are working on the design of a pilot-plant scale integrated system to be installed in the Mixed Waste Management Facility (MWMF) at LLNL. The system will also be completely integrated with upstream and downstream processes (for example, feed preparation, off-gas and water treatment, and final forms encapsulation). The conceptual design for the NEO-MWMF system has been completed and preliminary design work has been initiated. Demonstration of the process with low-level mixed wastes is expected to commence in 1998

  5. Tunable catalytic properties of bi-functional mixed oxides in ethanol conversion to high value compounds

    Energy Technology Data Exchange (ETDEWEB)

    Ramasamy, Karthikeyan K.; Gray, Michel J.; Job, Heather M.; Smith, Colin D.; Wang, Yong

    2016-04-10

    tA highly versatile ethanol conversion process to selectively generate high value compounds is pre-sented here. By changing the reaction temperature, ethanol can be selectively converted to >C2alcohols/oxygenates or phenolic compounds over hydrotalcite derived bi-functional MgO–Al2O3cata-lyst via complex cascade mechanism. Reaction temperature plays a role in whether aldol condensationor the acetone formation is the path taken in changing the product composition. This article containsthe catalytic activity comparison between the mono-functional and physical mixture counterpart to thehydrotalcite derived mixed oxides and the detailed discussion on the reaction mechanisms.

  6. Neutronic feasibility of PWR core with mixed oxide fuels in the Republic of Korea

    International Nuclear Information System (INIS)

    Kim, Y.J.; Joo, H.K.; Jung, H.G.; Sohn, D.S.

    1997-01-01

    Neutronic feasibility of a PWR core with mixed oxide (MOX) fuels has been investigated as part of the feasibility study for recycling spent fuels in Korea. A typical 3-loop PWR with 900 MWe capacity is selected as reference plant to develop equilibrium core designs with low-leakage fuel management scheme, while incorporating various MOX loading. The fuel management analyses and limited safety analyses show that, safely stated, MOX recycling with 1/3 reload fraction can be accommodated for both annual and 18 month fuel cycle schemes in Korean PWRs, without major design modifications on the reactor systems. (author). 12 refs, 4 figs, 3 tabs

  7. Detailed description of an SSAC at the facility level for mixed oxide fuel fabrication facilities

    International Nuclear Information System (INIS)

    Jones, R.J.

    1985-09-01

    The purpose of this document is to provide a detailed description of a system for the accounting for and control of nuclear material in a mixed oxide fuel fabrication facility which can be used by a facility operator to establish his own system to comply with a national system for nuclear material accounting and control and to facilitate application of IAEA safeguards. The scope of this document is limited to descriptions of the following SSAC elements: (1) Nuclear Material Measurements; (2) Measurement Quality; (3) Records and Reports; (4) Physical Inventory Taking; (5) Material Balance Closing

  8. Application of a mixed metal oxide catalyst to a metallic substrate

    Science.gov (United States)

    Sevener, Kathleen M. (Inventor); Lohner, Kevin A. (Inventor); Mays, Jeffrey A. (Inventor); Wisner, Daniel L. (Inventor)

    2009-01-01

    A method for applying a mixed metal oxide catalyst to a metallic substrate for the creation of a robust, high temperature catalyst system for use in decomposing propellants, particularly hydrogen peroxide propellants, for use in propulsion systems. The method begins by forming a prepared substrate material consisting of a metallic inner substrate and a bound layer of a noble metal intermediate. Alternatively, a bound ceramic coating, or frit, may be introduced between the metallic inner substrate and noble metal intermediate when the metallic substrate is oxidation resistant. A high-activity catalyst slurry is applied to the surface of the prepared substrate and dried to remove the organic solvent. The catalyst layer is then heat treated to bind the catalyst layer to the surface. The bound catalyst layer is then activated using an activation treatment and calcinations to form the high-activity catalyst system.

  9. The maximum specific hydrogen-producing activity of anaerobic mixed cultures: definition and determination.

    Science.gov (United States)

    Mu, Yang; Yang, Hou-Yun; Wang, Ya-Zhou; He, Chuan-Shu; Zhao, Quan-Bao; Wang, Yi; Yu, Han-Qing

    2014-06-10

    Fermentative hydrogen production from wastes has many advantages compared to various chemical methods. Methodology for characterizing the hydrogen-producing activity of anaerobic mixed cultures is essential for monitoring reactor operation in fermentative hydrogen production, however there is lack of such kind of standardized methodologies. In the present study, a new index, i.e., the maximum specific hydrogen-producing activity (SHAm) of anaerobic mixed cultures, was proposed, and consequently a reliable and simple method, named SHAm test, was developed to determine it. Furthermore, the influences of various parameters on the SHAm value determination of anaerobic mixed cultures were evaluated. Additionally, this SHAm assay was tested for different types of substrates and bacterial inocula. Our results demonstrate that this novel SHAm assay was a rapid, accurate and simple methodology for determining the hydrogen-producing activity of anaerobic mixed cultures. Thus, application of this approach is beneficial to establishing a stable anaerobic hydrogen-producing system.

  10. Silica-based composite and mixed-oxide nanoparticles from atmospheric pressure flame synthesis

    Science.gov (United States)

    Akurati, Kranthi K.; Dittmann, Rainer; Vital, Andri; Klotz, Ulrich; Hug, Paul; Graule, Thomas; Winterer, Markus

    2006-08-01

    Binary TiO2/SiO2 and SnO2/SiO2 nanoparticles have been synthesized by feeding evaporated precursor mixtures into an atmospheric pressure diffusion flame. Particles with controlled Si:Ti and Si:Sn ratios were produced at various flow rates of oxygen and the resulting powders were characterized by BET (Brunauer-Emmett-Teller) surface area analysis, XRD, TEM and Raman spectroscopy. In the Si-O-Ti system, mixed oxide composite particles exhibiting anatase segregation formed when the Si:Ti ratio exceeded 9.8:1, while at lower concentrations only mixed oxide single phase particles were found. Arrangement of the species and phases within the particles correspond to an intermediate equilibrium state at elevated temperature. This can be explained by rapid quenching of the particles in the flame and is in accordance with liquid phase solubility data of Ti in SiO2. In contrast, only composite particles formed in the Sn-O-Si system, with SnO2 nanoparticles predominantly found adhering to the surface of SiO2 substrate nanoparticles. Differences in the arrangement of phases and constituents within the particles were observed at constant precursor mixture concentration and the size of the resultant segregated phase was influenced by varying the flow rate of the oxidant. The above effect is due to the variation of the residence time and quenching rate experienced by the binary oxide nanoparticles when varying the oxygen flow rate and shows the flexibility of diffusion flame aerosol reactors.

  11. Calcium-based mixed oxide catalysts for methanolysis of Jatropha curcas oil to biodiesel

    International Nuclear Information System (INIS)

    Taufiq-Yap, Y.H.; Lee, H.V.; Hussein, M.Z.; Yunus, R.

    2011-01-01

    Calcium-based mixed oxides catalysts (CaMgO and CaZnO) have been investigated for the transesterification of Jatropha curcas oil (JCO) with methanol, in order to evaluate their potential as heterogeneous catalysts for biodiesel production. Both CaMgO and CaZnO catalysts were prepared by coprecipitation method of the corresponding mixed metal nitrate solution in the presence of a soluble carbonate salt at ∼ pH 8-9. The catalysts were characterized by X-ray diffraction (XRD), temperature programmed desorption of CO 2 (CO 2 -TPD), scanning electron microscopy (SEM) and N 2 adsorption (BET). The conversion of JCO by CaMgO and CaZnO were studied and compared with calcium oxide (CaO), magnesium oxide (MgO) and zinc oxide (ZnO) catalysts. Both CaMgO and CaZnO catalysts showed high activity as CaO and were easily separated from the product. CaMgO was found more active than CaZnO in the transesterification of JCO with methanol. Under the suitable transesterification conditions at 338 K (catalyst amount = 4 wt. %, methanol/oil molar ratio = 15, reaction time = 6 h), the JCO conversion of more than 80% can be achieved over CaMgO and CaZnO catalysts. Even though CaO gave the highest activity, the conversion of JCO decreased significantly after reused for forth run whereas the conversion was only slightly lowered for CaMgO and CaZnO after sixth run.

  12. Vaporization of actinide oxides in thermal treatment processes for mixed waste

    International Nuclear Information System (INIS)

    Ebbinghaus, B.B.; Krikorian, O.H.; Adamson, M.G.

    1994-01-01

    The purpose of this study is to evaluate the volatilities of U, Pu, and Am in thermal treatment processes for mixed wastes. The thermodynamics of vaporization U and Pu oxides in the presence of oxygen and water vapor and of U oxide in the presence of oxygen and chlorine were studied. Experimental studies of U oxide volatilities by previous authors have also been reviewed. For species where data are unavailable estimation methods were used to obtain free energies of formation of the gaseous species, The data are applied to thermal treatment processes in general and then more specifically to conditions representative of the Rocky Flats Plant Fluidized Bed Unit. (RFP FBU), molten salt oxidizer, and an incinerator. U volatilities are greatest ranging from 2.67 x 10 -7 gU/h in the RFP FBU to 4. 00 gU/h for typical incinerator conditions. Pu volatilities are almost 5 orders of magnitude less than U and Am volatilities are about 3 orders of magnitude less than Pu

  13. Nanotubular Iridium-Cobalt Mixed Oxide Crystalline Architectures Inherited from Cobalt Oxide for Highly Efficient Oxygen Evolution Reaction Catalysis.

    Science.gov (United States)

    Yu, Areum; Lee, Chongmok; Kim, Myung Hwa; Lee, Youngmi

    2017-10-11

    Here, we report the unique transformation of one-dimensional tubular mixed oxide nanocomposites of iridium (Ir) and cobalt (Co) denoted as Ir x Co 1-x O y , where x is the relative Ir atomic content to the overall metal content. The formation of a variety of Ir x Co 1-x O y (0 ≤ x ≤ 1) crystalline tubular nanocomposites was readily achieved by electrospinning and subsequent calcination process. Structural characterization clearly confirmed that Ir x Co 1-x O y polycrystalline nanocomposites had a tubular morphology consisting of Ir/IrO 2 and Co 3 O 4 , where Ir, Co, and O were homogeneously distributed throughout the entire nanostructures. The facile formation of Ir x Co 1-x O y nanotubes was mainly ascribed to the inclination of Co 3 O 4 to form the nanotubes during the calcination process, which could play a critical role in providing a template of tubular structure and facilitating the formation of IrO 2 by being incorporated with Ir precursors. Furthermore, the electroactivity of obtained Ir x Co 1-x O y nanotubes was characterized for oxygen evolution reaction (OER) with rotating disk electrode voltammetry in 1 M NaOH aqueous solution. Among diverse Ir x Co 1-x O y , Ir 0.46 Co 0.54 O y nanotubes showed the best OER activity (the least-positive onset potential, greatest current density, and low Tafel slope), which was even better than that of commercial Ir/C. The Ir 0.46 Co 0.54 O y nanotubes also exhibited a high stability in alkaline electrolyte. Expensive Ir mixed with cheap Co at an optimum ratio showed a greater OER catalytic activity than pure Ir oxide, one of the most efficient OER catalysts.

  14. A CFD model for determining mixing and mass transfer in a high power agitated bioreactor

    DEFF Research Database (Denmark)

    Bach, Christian; Albæk, Mads O.; Stocks, Stuart M.

    Prediction of mixing and mass transfer in agitated systems is a vital tool for process development and scale up in industrial biotechnology. In particular key process parameters such as mixing time and kLa are essential for bioprocess development [1]. In this work the mixing and mass transfer...... performance of a high power agitated pilot scale bioreactor has been characterized using a novel combination of computational fluid dynamics (CFD) and experimental investigations. The effect of turbulence inside the vessel was found to be most efficiently described by using the k-ε model with regards...... to computational effort and required accuracy for industrial application. Mixing time was determined by carrying out sodium chloride tracer experiments at various bulk viscosities and agitation speeds, while tracking the conductivity. The mixing performance was predicted with one-phase CFD simulations and showed...

  15. Mechanisms of oxidative stress and alterations in gene expression by Libby six-mix in human mesothelial cells

    Directory of Open Access Journals (Sweden)

    Hillegass Jedd M

    2010-09-01

    Full Text Available Abstract Background Exposures to an amphibole fiber in Libby, Montana cause increases in malignant mesothelioma (MM, a tumor of the pleural and peritoneal cavities with a poor prognosis. Affymetrix microarray/GeneSifter analysis was used to determine alterations in gene expression of a human mesothelial cell line (LP9/TERT-1 by a non-toxic concentration (15×106 μm2/cm2 of unprocessed Libby six-mix and negative (glass beads and positive (crocidolite asbestos controls. Because manganese superoxide dismutase (MnSOD; SOD2 was the only gene upregulated significantly (p 6 μm2/cm2 and toxic concentrations (75×106 μm2/cm2 of Libby six-mix. Results Exposure to 15×106 μm2/cm2 Libby six-mix elicited significant (p SOD2; 4-fold at 8 h and 111 gene changes at 24 h, including a 5-fold increase in SOD2. Increased levels of SOD2 mRNA at 24 h were also confirmed in HKNM-2 normal human pleural mesothelial cells by qRT-PCR. SOD2 protein levels were increased at toxic concentrations (75×106 μm2/cm2 of Libby six-mix at 24 h. In addition, levels of copper-zinc superoxide dismutase (Cu/ZnSOD; SOD1 protein were increased at 24 h in all mineral groups. A dose-related increase in SOD2 activity was observed, although total SOD activity remained unchanged. Dichlorodihydrofluorescein diacetate (DCFDA fluorescence staining and flow cytometry revealed a dose- and time-dependent increase in reactive oxygen species (ROS production by LP9/TERT-1 cells exposed to Libby six-mix. Both Libby six-mix and crocidolite asbestos at 75×106 μm2/cm2 caused transient decreases (p HO-1 in LP9/TERT-1 and HKNM-2 cells. Conclusions Libby six-mix causes multiple gene expression changes in LP9/TERT-1 human mesothelial cells, as well as increases in SOD2, increased production of oxidants, and transient decreases in intracellular GSH. These events are not observed at equal surface area concentrations of nontoxic glass beads. Results support a mechanistic basis for the importance of SOD2

  16. Catalysts with Cu base supported in mixed oxides to generate H2: reformed of methanol in oxidant atmosphere

    International Nuclear Information System (INIS)

    Aguila M, M.M.; Perez H, R.; Rodriguez L, V.

    2006-01-01

    In this work, the characterization of Cu supported in CeO 2 -ZrO 2 , for to generate H 2 starting from the one reformed of methanol with water vapor and oxygen is presented. The sol-gel technique and classic impregnation for the obtaining of the supports and catalysts respectively were used. The materials were characterized by XRD, SEM, adsorption- desorption of N 2 and TPR. The catalytic materials presented crystalline phases associated with the zircon (tetragonal and monoclinic phase) and the ceria (cubic phase) depending on the CeO 2 /ZrO 2 relationship. The morphology of the catalysts was analyzed by SEM being observed semispheric particles for the rich materials in ZrO 2 and added planars in the rich materials in CeO 2 . The ceria addition to the zircon favors the specific area of the mixed oxides CeO 2 -ZrO 2 and it promotes the reducibility of the copper oxide at low temperatures. The rich catalysts in ceria also showed high activity in the methanol transformation and bigger selectivity toward the production of H 2 . This result is associated with the presence of copper species that decrease to low temperature present in the rich catalysts in ceria and that they are not present in the rich catalysts in zircon. (Author)

  17. Phototherapy with blue and green mixed-light is as effective against unconjugated jaundice as blue light and reduces oxidative stress in the Gunn rat model.

    OpenAIRE

    Uchida, Yumiko; Morimoto, Yukihiro; Uchiike, Takao; Kamamoto, Tomoyuki :4/0000339; Hayashi, Tamaki; Arai, Ikuyo; Nishikubo, Toshiya; Takahashi, Yukihiro

    2015-01-01

    OBJECTIVE:Phototherapy using blue light-emitting diodes (LED) is effective against neonatal jaundice. However, green light phototherapy also reduces unconjugated jaundice. We aimed to determine whether mixed blue and green light can relieve jaundice with minimal oxidative stress as effectively as either blue or green light alone in a rat model.METHODS:Gunn rats were exposed to phototherapy with blue (420-520 nm), filtered blue (FB; 440-520 nm without

  18. Application of cylinder symmetry to iron and titanium oxidation by oxygen or hydrogen-water vapour mixes

    International Nuclear Information System (INIS)

    Raynaud, Pierre

    1980-01-01

    This research thesis addresses the study of the oxidation reaction in the case of corrosion of iron by oxygen, hydrogen sulphide or hydrogen-water vapour mixes, and in the case of oxidation of titanium and of titanium nitride by hydrogen-water vapour mixes. It first addresses the corrosion of iron by oxygen with an experiment performed in cylinder symmetry: description of operational conditions, discussion of kinetic curves, development of a law of generation of multiple layers in cylinder symmetry, analytical exploitation of experimental results. The second part addresses the oxidation of iron by hydrogen-water vapour mixes: experimental conditions, influence of temperature on kinetics, micrographic study (oxide morphology, coating morphology, interpretation of differences with the case of plane symmetry), discussion of the influence of cylinder symmetry on oxidation kinetics. The third part addresses the oxidation of titanium by hydrogen-water vapour mixes: global kinetic evolution, reaction products and micrographic examination, morphology and texture studies, discussion of the oxidation mechanism and of cylinder symmetry [fr

  19. Phototherapy with blue and green mixed-light is as effective against unconjugated jaundice as blue light and reduces oxidative stress in the Gunn rat model.

    Science.gov (United States)

    Uchida, Yumiko; Morimoto, Yukihiro; Uchiike, Takao; Kamamoto, Tomoyuki; Hayashi, Tamaki; Arai, Ikuyo; Nishikubo, Toshiya; Takahashi, Yukihiro

    2015-07-01

    Phototherapy using blue light-emitting diodes (LED) is effective against neonatal jaundice. However, green light phototherapy also reduces unconjugated jaundice. We aimed to determine whether mixed blue and green light can relieve jaundice with minimal oxidative stress as effectively as either blue or green light alone in a rat model. Gunn rats were exposed to phototherapy with blue (420-520 nm), filtered blue (FB; 440-520 nm without 1.00), respectively. Blue plus green phototherapy is as effective as blue phototherapy and it attenuates irradiation-induced oxidative stress. Combined blue and green spectra might be effective against neonatal hyperbilirubinemia. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  20. Mixed oxides derived from layered double hydroxides as novel catalysts for phenol photodegradation

    Science.gov (United States)

    Puscasu, C. M.; Carja, G.; Mureseanu, M.; Zaharia, C.

    2017-08-01

    The removal of organic pollutants is nowadays a very challenging aspect of the environmental research. There are strong interests to develop novel semiconducting photocatalysts able to efficiently promote advanced oxidation reactions. The development of photocatalysts based on the mixtures of mixed oxides derived from layered double hydroxides (LDHs) - a family of naturally occurring anionic clays - might offer novel environmental-friendly solutions for the cost effective removal of organic pollutants. This work presents ZnO/ZnAl2O4, ZnO/Zn2TiO4 and ZnO/ZnCr2O4 as novel photocatalytic formulations for phenol degradation under UV irradiation. They were obtained by the controlled thermal treatment of the layered double hydroxides matrices (LDHs), as precursors materials, type ZnM-LDH (M = Al3+, Cr3+ or Ti4+). The LDHs were synthesized by the co-precipitation method at a constant pH. Controlled calcination at 650°C gives rise to solutions of mixed metal oxides. The structural and nanoarchitectonics characteristics of the studied catalysts were described by: XRD, SEM/TEM and TG/DTG techniques. Results show that in the photocatalytic process of the phenol degradation from aqueous solutions, ZnO/ZnCr2O4 and ZnO/ZnAl2O4 showed the best performance degrading ∼98% of phenol after 3.5 hs and 5 hs, respectively; while ZnO/Zn2TiO4 has degraded almost 80 % after 7.5 hs of UV irradiation. These results open new opportunities in the development of new cost effective photoresponsive formulations able to facilitate the photo-degradation of the organic pollution as “green” solution for removal of dangerous pollutants.

  1. Results of the irradiation of mixed UO2 - PuO2 oxide fuel elements

    International Nuclear Information System (INIS)

    Mikailoff, H.; Mustelier, J.P.; Bloch, J.; Ezran, L.; Hayet, L.

    1966-01-01

    In order to study the behaviour of fuel elements used for the first charge of the reactor Rapsodie, a first batch of eleven needles was irradiated in the reactor EL3 and then examined. These needles (having a shape very similar lo that of the actual needles to be used) were made up of a stack of sintered mixed-oxide pellets: UO 2 containing about 10 per cent of PuO 2 . The density was 85 to 97 per cent of the theoretical, value. The diametral gap between the oxide and the stainless steel can was between 0,06 and 0,27 mm. The specific powers varied from 1230 to 2700 W/cm 3 and the can temperature was between 450 and 630 C. The maximum burn-up attained was 22000 MW days/tonne. Examination of the needles (metrology, radiography and γ-spectrography) revealed certain macroscopic changes, and the evolution of the fuel was shown by micrographic studies. These observations were used, together with flux measurements results, to calculate the temperature distribution inside the fuel. The volume of the fission gas produced was measured in some of the samples; the results are interpreted taking into account the temperature distribution in the oxide and the burn-up attained. Finally a study was made both of the behaviour of a fuel element whose central part was molten during irradiation, and of the effect of sodium which had penetrated into some of the samples following can rupture. (author) [fr

  2. Voltametric determination of O:U relation in uranium oxide

    International Nuclear Information System (INIS)

    Carvalho, F.M.S. de; Abrao, A.

    1988-07-01

    Uranium oxide samples are dissolved in hot concentrated H 3 PO 4 - H 2 SO 4 mixture and the solution diluted with 1M H 2 SO 4 . One aliquot of such solution (A) is used to record the first voltamogram which gives the U(VI) content. To a second aliquot HNO 3 and H 2 O 2 is added to oxidise uranium to the hexavalent state (B) and the second voltamogram is recorded from 0.0 to 0.4 V X SCE. The O:U ratio in the original sample is calculated by the expression: O/U = 2.000 + [U (VI) soln.A/% U(VI) soln. B]. The method provides an accurate means for determining O to U ratios in high-purity uranium dioxide, fuel pellets and a variety of oxides prepared for developmental work on ceramic fuel materials. (author) [pt

  3. Copper enhances the activity and salt resistance of mixed methane-oxidizing communities.

    Science.gov (United States)

    van der Ha, David; Hoefman, Sven; Boeckx, Pascal; Verstraete, Willy; Boon, Nico

    2010-08-01

    Effluents of anaerobic digesters are an underestimated source of greenhouse gases, as they are often saturated with methane. A post-treatment with methane-oxidizing bacterial consortia could mitigate diffuse emissions at such sites. Semi-continuously fed stirred reactors were used as model systems to characterize the influence of the key parameters on the activity of these mixed methanotrophic communities. The addition of 140 mg L(-1) NH (4) (+) -N had no significant influence on the activity nor did a temperature increase from 28 degrees C to 35 degrees C. On the other hand, addition of 0.64 mg L(-1) of copper(II) increased the methane removal rate by a factor of 1.5 to 1.7 since the activity of particulate methane monooxygenase was enhanced. The influence of different concentrations of NaCl was also tested, as effluents of anaerobic digesters often contain salt levels up to 10 g NaCl L(-1). At a concentration of 11 g NaCl L(-1), almost no methane-oxidizing activity was observed in the reactors without copper addition. Yet, reactors with copper addition exhibited a sustained activity in the presence of NaCl. A colorimetric test based on naphthalene oxidation showed that soluble methane monooxygenase was inhibited by copper, suggesting that the particulate methane monooxygenase was the active enzyme and thus more salt resistant. The results obtained demonstrate that the treatment of methane-saturated effluents, even those with increased ammonium (up to 140 mg L(-1) NH (4) (+) -N) and salt levels, can be mitigated by implementation of methane-oxidizing microbial consortia.

  4. Relationship between transport properties and phase transformations in mixed-conducting oxides

    International Nuclear Information System (INIS)

    Deng, Z.Q.; Yang, W.S.; Liu, W.; Chen, C.S.

    2006-01-01

    To elucidate the relationship between transport properties and phase transformations in mixed-conducting oxides, Sr 0.9 Ca 0.1 Co 0.89 Fe 0.11 O 3- δ (SCCFO) and SrCoO 3- δ (SCO) were chosen as the model materials and have been investigated in detail. Oxygen permeation measurements verified that both oxides are well permeable to oxygen at elevated temperatures, e.g., at 900 deg. C during a cooling procedure, oxygen permeation rates as large as 1.5 and 2.0 mL/min/cm 2 could be obtained with disk-shaped SCCFO and SCO membranes of thickness 1.5 mm, respectively. But when cooled to critical temperatures, the oxygen permeability of these kinds of oxides diminished sharply, which could be recovered by increasing the temperature again to certain values. Abrupt changes on electrical conductivity were also observed for both oxides around the same region of temperature as that of oxygen permeability. As indicated by high-temperature X-ray diffraction and thermal analysis, the SCCFO and SCO systems undergo phase transformation between a low-temperature orthorhombic brownmillerite structure (B) or a hexagonal 2H-type structure (H) and a high-temperature cubic perovskite structure (C), respectively. The present results suggest the observed abrupt changes in transport properties versus temperature are attributed to such phase transformation, which may be directly associated with the order-disorder transition of oxygen vacancies. Moreover, compared to the B/C transformation that mainly involves an order-disorder transition on the oxygen sublattice, the H/C one necessarily also involves the cooperative long-range reorganization on the cation sublattice. Therefore it occurs at a higher temperature and absorbs more heat quantity than those of B/C transformation

  5. Structure, activity and kinetics of supported molybdenum oxide and mixed molybdenum-vanadium oxide catalysts prepared by flame spray pyrolysis for propane OHD

    DEFF Research Database (Denmark)

    Høj, Martin; Kessler, Thomas; Beato, Pablo

    2013-01-01

    reflectance UV-vis spectroscopy and evaluated as catalysts for the oxidative dehydrogenation (ODH) of propane. The results show that samples with high specific surface areas between 122 and 182 m2/g were obtained, resulting in apparent MoOx and VOx surface densities from 0.7 to 7.7 nm -2 and 1.5 to 1.9 nm-2......, respectively. Raman spectroscopy, UV-vis spectroscopy and XRD confirmed the high dispersion of molybdenum and vanadia species on γ-Al2O3 as the main crystalline phase. Only at the highest loading of 15 wt% Mo, with theoretically more than monolayer coverage, some crystalline molybdenum oxide was observed....... For the mixed molybdenum-vanadium oxide catalysts the surface species were separate molybdenum oxide and vanadium oxide monomers at low loadings of molybdenum, but with increasing molybdenum loading interactions between surface molybdenum and vanadium oxide species were observed with Raman spectroscopy...

  6. Determination of the oxidizing capacity of manganese ores.

    Science.gov (United States)

    Prasad, R

    1974-09-01

    An accurate method is described for determining the amount of active oxygen in manganese ores, based on the oxidation-reduction reaction between the ore and arsenic(III) in presence of ammonium molybdate, followed by the back-titration of excess of arsenic(III) with cerium(IV), using osmium tetroxide as catalyst and Disulphine Blue V as indicator. A survey has been made of the applicability of this method to various pyrolusite ores containing less than 0.2% phosphorus. Aluminium(III), copper(II), iron(III), manganese(II), and molybdenum(VI) do not interfere. Up to 30% phosphorus(V) causes no interference.

  7. Determining the reversibility of oxidation-reduction reactions in groundwater

    International Nuclear Information System (INIS)

    Runnells, D.D.

    1985-01-01

    This report summarizes initial developmental work done under contract to the BWIP in FY-85 to determine the reversibility of oxidation-reduction reactions in a basalt groundwater system. None of the data reported is considered licensable because all the work was performed, with the BWIP's consent, without an approved QA plan. Three electrochemical techniques are currently being utilized in the project. These are cyclic scanning voltammetry, chronocoulometry, and potentiometry. Using cyclic scanning voltammetry, which is the major experimental technique being used, information about the degree of reversibility of both the homogeneous redox reaction in solution and the heterogeneous reaction at the electrode surface can be obtained. 29 refs., 19 figs

  8. High temperature oxidation behaviour of nanostructured cermet coatings in a mixed CO2 – O2 environment

    International Nuclear Information System (INIS)

    Farrokhzad, M A; Khan, T I

    2014-01-01

    Nanostructured ceramic-metallic (cermet) coatings composed of nanosized ceramic particles (α-Al 2 O3 and TiO 2 ) dispersed in a nickel matrix were co-electrodeposited and then oxidized at 500°C, 600°C and 700°C in a mixed gas using a Thermo-gravimetric Analysis (TGA) apparatus. The mixed gas was composed of 15% CO 2 , 10% O 2 and 75% N 2 . This research investigates the effects of CO 2 and O 2 partial pressures on time-depended oxidation rates for coatings and compared them to the results from atmospheric oxidation under similar temperatures. The increase in partial pressure of oxygen due to the presence of CO 2 at each tested temperature was calculated and correlated to the oxidation rate of the coatings. The results showed that the presence of CO 2 in the system increased the oxidation rate of cermet coatings when compared to atmospheric oxidation at the same temperature. It was also shown that the increase in the oxidation rate is not the result of CO2 acting as the primary oxidant but as a secondary oxidant which results in an increase of the total partial pressure of oxygen and consequently higher oxidation rates. The WDS and XRD analyses results showed that the presence of nanosized TiO 2 particles in a nickel matrix can improve oxidation behaviour of the coatings by formation of Ni-Ti compounds on oxidizing surface of the coating which was found beneficiary in reducing the oxidation rates for cermet coatings

  9. Study of reactions between fuel (mixed oxide (UPu)Osub(2-x)) and cladding (stainless-steel) in reactors: influence of iodine compounds

    International Nuclear Information System (INIS)

    Aubert, Michel.

    1976-03-01

    The influence of iodine compounds on the development of the oxide-cladding reaction was examined. The action of iodine, cesium and cesium iodide on type 316 stainless was determined in the presence or absence of uranium oxide or mixed uranium-plutonium oxide type fuel in a closed system, isothermal or with a temperature gradient. The study of the stainless steel iodine reactions was developed in particular. These experiments showed that cesium combines with uranium oxide to give cesium uranate Cs 2 U 2 O 7 ; it is not unreasonable to suppose that cesium urano-plutonate Cs 2 (U,Pu) 2 O 7 could be formed inside the pile. It was then shown that cesium iodide in the presence of sufficiently non-stoichiometric mixed oxide could contribute towards the degradation of the stainless steel cladding. Under these conditions the reaction is accompained by a transport of manganese, chromium and iron into the hot parts of the fuel by a Van-Arkel type mechanism. This might explain the presence of metallic precipitates in the fuel, but the role assigned to molybdenum iodide in the same phenomenon is considered unlikely. Finally it is proposed to deposit a thin layer of manganese metal on the inner surface of the cladding in order to minimize the action of fission products (CsI, Te) [fr

  10. Spatial and temporal variability of nitrous oxide emissions in a mixed farming landscape of Denmark

    DEFF Research Database (Denmark)

    Schelde, Kirsten; Cellier, P; Bertolini, T

    2012-01-01

    Nitrous oxide (N2O) emissions from agricultural land are variable at the landscape scale due to variability in land use, management, soil type, and topography. A field experiment was carried out in a typical mixed farming landscape in Denmark, to investigate the main drivers of variations in N2O...... emissions, measured using static chambers. Measurements were made over a period of 20 months, and sampling was intensified during two weeks in spring 2009 when chambers were installed at ten locations or fields to cover different crops and topography and slurry was applied to three of the fields. N2O...... emissions during spring 2009 were relatively low, with maximum values below 20 ng N m−2 s−1. This applied to all land use types including winter grain crops, grasslands, meadows, and wetlands. Slurry application to wheat fields resulted in short-lived two-fold increases in emissions. The moderate N2O fluxes...

  11. Fabrication of 0.5-inch diameter FBR mixed oxide fuel pellets

    International Nuclear Information System (INIS)

    Rasmussen, D.E.; Benecke, M.W.; McCord, R.B.

    1979-01-01

    Large diameter (0.535 inch) mixed oxide fuel pellets for Fast Breeder Reactor application were successfully fabricated by the cold-press-and-sinter technique. Enriched UO 2 , PuO 2 -UO 2 , and PuO 2 -ThO 2 compositions were fabricated into nominally 90% theoretical density pellets for the UO 2 and PuO 2 -UO 2 compositions, and 88% and 93% T.D. for the PuO 2 -ThO 2 compositions. Some processing adjustments were required to achieve satisfactory pellet quality and density. Furnace heating rate was reduced from 200 to 50 0 C/h for the organic binder burnout cycle for the large, 0.535-inch diameter pellets to eliminate pellet cracking during sintering. Additional preslugging steps and die wall lubrication during pressing were used to eliminate pressing cracks in the PuO 2 -ThO 2 pellets

  12. Fuel-cladding mechanical interaction effects in fast reactor mixed oxide fuel

    International Nuclear Information System (INIS)

    Boltax, A.; Biancheria, A.

    1977-01-01

    Thermal and fast reactor irradiation experiments on mixed oxide fuel pins under steady-state and power change conditions reveal evidence for significant fuel-cladding mechanical interaction (FCMI) effects. Analytical studies with the LIFE-III fuel performance code indicate that high cladding stresses can be produced by general and local FCMI effects. Also, evidence is presented to show that local cladding strains can be caused by the accumulation of cesium at the fuel-cladding interface. Although it is apparent that steady-state FCMI effects have not given rise to cladding breaches in current fast reactors, it is anticipated that FCMI may become more important in the future because of interest in: higher fuel burnups; increased power ramp rates; load follow operation; and low swelling cladding alloys. (author)

  13. Technical specification: Mixed-oxide pellets for the light-water reactor irradiation demonstration test

    International Nuclear Information System (INIS)

    Cowell, B.S.

    1997-06-01

    This technical specification is a Level 2 Document as defined in the Fissile Materials Disposition Program Light-Water Reactor Mixed-oxide Fuel Irradiation Test Project Plan. It is patterned after the pellet specification that was prepared by Atomic Energy of Canada, Limited, for use by Los Alamos National Laboratory in fabrication of the test fuel for the Parallex Project, adjusted as necessary to reflect the differences between the Canadian uranium-deuterium reactor and light-water reactor fuels. This specification and the associated engineering drawing are to be utilized only for preparation of test fuel as outlined in the accompanying Request for Quotation and for additional testing as directed by Oak Ridge National Laboratory or the Department of Energy

  14. Optical refractive index and static permittivity of mixed Zr-Si oxide thin films prepared by ion beam induced CVD

    Energy Technology Data Exchange (ETDEWEB)

    Ferrer, F.J. [Centro Nacional de Aceleradores, Av. Thomas A. Edison, 7, 41092 Sevilla (Spain)], E-mail: fjferrer@us.es; Frutos, F. [E.T.S. de Ingenieria Informatica, Avda. Reina Mercedes, s/n, 41012 Sevilla (Spain); Garcia-Lopez, J. [Centro Nacional de Aceleradores, Av. Thomas A. Edison, 7, 41092 Sevilla (Spain); Gonzalez-Elipe, A.R.; Yubero, F. [Insituto de Ciencia de Materiales de Sevilla, c/ Americo vespucio, no. 49, 41092 Sevilla (Spain)

    2007-12-03

    Mixed oxides Zr{sub x}Si{sub 1-x}O{sub 2} (0 < x < 1) thin films have been prepared at room temperature by decomposition of (CH{sub 3}CH{sub 2}O){sub 3}SiH and Zr[OC(CH{sub 3}){sub 3}]{sub 4} volatile precursors induced by mixtures of O{sub 2}{sup +} and Ar{sup +} ions. The films were flat and amorphous independently of the Si/Zr ratio and did not present phase segregation of the pure single oxides (SiO{sub 2} and ZrO{sub 2}). A 10-23 at.% of H and 1-5 at.% of C atoms remained incorporated in the films depending on the mixture ratio of the Si and Zr precursors and the composition of the bombarding gas used during the deposition process. These impurities are mainly forming hydroxyl and carboxylic groups. Optical refractive index and static permittivity of the films were determined by reflection NIR-Vis spectroscopy and C-V electrical characterization, respectively. It is found that the refractive index increases non-linearly from 1.45 to 2.10 as the Zr content in the thin films increases. The static permittivity also increases non-linearly from {approx} 4 for pure SiO{sub 2} to {approx} 15 for pure ZrO{sub 2}. Optical and electrical characteristics of the films are justified by their impurity content and the available theories.

  15. Evaluation of tubular reactor designs for supercritical water oxidation of U.S. Department of Energy mixed waste

    International Nuclear Information System (INIS)

    Barnes, C.M.

    1994-12-01

    Supercritical water oxidation (SCWO) is an emerging technology for industrial waste treatment and is being developed for treatment of the US Department of Energy (DOE) mixed hazardous and radioactive wastes. In the SCWO process, wastes containing organic material are oxidized in the presence of water at conditions of temperature and pressure above the critical point of water, 374 C and 22.1 MPa. DOE mixed wastes consist of a broad spectrum of liquids, sludges, and solids containing a wide variety of organic components plus inorganic components including radionuclides. This report is a review and evaluation of tubular reactor designs for supercritical water oxidation of US Department of Energy mixed waste. Tubular reactors are evaluated against requirements for treatment of US Department of Energy mixed waste. Requirements that play major roles in the evaluation include achieving acceptable corrosion, deposition, and heat removal rates. A general evaluation is made of tubular reactors and specific reactors are discussed. Based on the evaluations, recommendations are made regarding continued development of supercritical water oxidation reactors for US Department of Energy mixed waste

  16. Comparison of the redox activities of sol-gel and conventionally prepared Bi-Mo-Ti mixed oxides

    Energy Technology Data Exchange (ETDEWEB)

    Wildberger, M.; Grundwaldt, J.D.; Mallat, T.; Baiker, A. [Lab. of Technical Chemistry, Swiss Federal Inst. of Technology, ETH-Zentrum, Zuerich (Switzerland)

    1998-12-31

    Novel sol-gel Bi-Mo-Ti oxides have been prepared and characterized by XRD, XPS, FT-Raman and HRTEM. The surface Bi{sup 3+} and Mo{sup 6+} species of some xerogels and an aerogel could be reduced and oxidized at room temperature, whereas the conventionally prepared reference materials were not reduced by H{sub 2} below 300 C. The unusual redox properties, under very mild conditions, are likely due to the unique morphology of Bi-Mo-oxides stabilized by titania. During butadiene oxidation to furan at above 400 C to sol-gel mixed oxides restructured considerably and their performance was barely better than that of titania-supported Bi-Mo oxides. (orig.)

  17. Mediated electrochemical oxidation treatment for Rocky Flats combustible low-level mixed waste. Final report, FY 1993 and 1994

    International Nuclear Information System (INIS)

    Chiba, Z.; Lewis, P.R.; Murguia, L.C.

    1994-09-01

    Mediated Electrochemical Oxidation (MEO) is an aqueous process which destroys hazardous organics by oxidizing a mediator at the anode of an electrochemical cell; the mediator in turn oxidizes the organics within the bulk of the electrolyte. With this process organics can be nearly completely destroyed, that is, the carbon and hydrogen present in the hydrocarbon are almost entirely mineralized to carbon dioxide and water. The MEO process is also capable of dissolving radioactive materials, including difficult-to-dissolve compounds such as plutonium oxide. Hence, this process can treat mixed wastes, by destroying the hazardous organic components of the waste, and dissolving the radioactive components. The radioactive material can be recovered if desired, or disposed of as non-mixed radioactive waste. The process is inherently safe, since the hazardous and radioactive materials are completely contained in the aqueous phase, and the system operates at low temperatures (below 80 degree C) and at ambient pressures

  18. Removal of Hazardous Pollutants from Wastewaters: Applications of TiO2-SiO2 Mixed Oxide Materials

    Directory of Open Access Journals (Sweden)

    Shivatharsiny Rasalingam

    2014-01-01

    Full Text Available The direct release of untreated wastewaters from various industries and households results in the release of toxic pollutants to the aquatic environment. Advanced oxidation processes (AOP have gained wide attention owing to the prospect of complete mineralization of nonbiodegradable organic substances to environmentally innocuous products by chemical oxidation. In particular, heterogeneous photocatalysis has been demonstrated to have tremendous promise in water purification and treatment of several pollutant materials that include naturally occurring toxins, pesticides, and other deleterious contaminants. In this work, we have reviewed the different removal techniques that have been employed for water purification. In particular, the application of TiO2-SiO2 binary mixed oxide materials for wastewater treatment is explained herein, and it is evident from the literature survey that these mixed oxide materials have enhanced abilities to remove a wide variety of pollutants.

  19. Mixed fuel strategy for carbon deposition mitigation in solid oxide fuel cells at intermediate temperatures.

    Science.gov (United States)

    Su, Chao; Chen, Yubo; Wang, Wei; Ran, Ran; Shao, Zongping; Diniz da Costa, João C; Liu, Shaomin

    2014-06-17

    In this study, we propose and experimentally verified that methane and formic acid mixed fuel can be employed to sustain solid oxide fuel cells (SOFCs) to deliver high power outputs at intermediate temperatures and simultaneously reduce the coke formation over the anode catalyst. In this SOFC system, methane itself was one part of the fuel, but it also played as the carrier gas to deliver the formic acid to reach the anode chamber. On the other hand, the products from the thermal decomposition of formic acid helped to reduce the carbon deposition from methane cracking. In order to clarify the reaction pathways for carbon formation and elimination occurring in the anode chamber during the SOFC operation, O2-TPO and SEM analysis were carried out together with the theoretical calculation. Electrochemical tests demonstrated that stable and high power output at an intermediate temperature range was well-maintained with a peak power density of 1061 mW cm(-2) at 750 °C. With the synergic functions provided by the mixed fuel, the SOFC was running for 3 days without any sign of cell performance decay. In sharp contrast, fuelled by pure methane and tested at similar conditions, the SOFC immediately failed after running for only 30 min due to significant carbon deposition. This work opens a new way for SOFC to conquer the annoying problem of carbon deposition just by properly selecting the fuel components to realize their synergic effects.

  20. Mixed alkali effect on the spectroscopic properties of alkali-alkaline earth oxide borate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Srinivas, G., E-mail: srinu123g@gmail.com; Ramesh, B.; Shareefuddin, Md.; Chary, M. N.; Sayanna, R. [Department of Physics, Osmania University, Hyderabad, Telangana, India. (India)

    2016-05-06

    The mixed alkali and alkaline earth oxide borate glass with the composition xK{sub 2}O - (25-x) Li{sub 2}O-12.5BaO-12.5MgO-50B{sub 2}O{sub 3} (x = 0, 5, 10, 15, 20 and 25mol %) and doped with 1mol% CuO were prepared by the melt quenching technique. From the optical absorption spectra the optical band gap, electronic polarizability(α{sub 0}2-), interaction parameter (A), theoretical and experimental optical basicity (Λ) values were evaluated. From the Electron Paramagnetic Resonance (EPR) spectral data the number of spins (N) and susceptibility (χ) were evaluated. The values of (α{sub 0}2-), and (Λ) increases with increasing of K{sub 2}O content and electronic polarizability and interaction parameter show opposite behaviuor which may be due to the creation of non-bridging oxygens and expansion of borate network. The reciprocal of susceptibility (1/χ) and spin concentration (N) as a function of K{sub 2}O content, varied nonlinearly which may be due to creation of non-bridging oxygens in the present glass system. This may be attributed to mixed alkali effect (MAE).

  1. Tunable Mixed Ionic/Electronic Conductivity and Permittivity of Graphene Oxide Paper for Electrochemical Energy Conversion.

    Science.gov (United States)

    Bayer, Thomas; Bishop, Sean R; Perry, Nicola H; Sasaki, Kazunari; Lyth, Stephen M

    2016-05-11

    Graphene oxide (GO) is a two-dimensional graphitic carbon material functionalized with oxygen-containing surface functional groups. The material is of interest in energy conversion, sensing, chemical processing, gas barrier, and electronics applications. Multilayer GO paper has recently been applied as a new proton conducting membrane in low temperature fuel cells. However, a detailed understanding of the electrical/dielectric properties, including separation of the ionic vs electronic contributions under relevant operating conditions, has so far been lacking. Here, the electrical conductivity and dielectric permittivity of GO paper are investigated in situ from 30 to 120 °C, and from 0 to 100% relative humidity (RH) using impedance spectroscopy. These are related to the water content, measured by thermogravimetric analysis. With the aid of electron blocking measurements, GO is demonstrated to be a mixed electronic-protonic conductor, and the ion transference number is derived for the first time. For RH > 40%, conductivity is dominated by proton transport (with a maximum of 0.5 mS/cm at 90 °C and 100% RH). For RH permittivity of GO paper increases with decreasing humidity, from ∼10 at 100% RH to several 1000 at 10% RH. These results underline the potential of GO for application not only as a proton conducting electrolyte but also as a mixed conducting electrode material under appropriate conditions. Such materials are highly applicable in electrochemical energy conversion and storage devices such as fuel cells and electrolyzers.

  2. Highly efficient electrochemical responses on single crystalline ruthenium-vanadium mixed metal oxide nanowires.

    Science.gov (United States)

    Chun, Sung Hee; Choi, Hyun-A; Kang, Minkyung; Koh, Moonjee; Lee, Nam-Suk; Lee, Sang Cheol; Lee, Minyung; Lee, Youngmi; Lee, Chongmok; Kim, Myung Hwa

    2013-09-11

    Highly efficient single crystalline ruthenium-vanadium mixed metal oxide (Ru1-xVxO2, 0≤x≤1) nanowires were prepared on a SiO2 substrate and a commercial Au microelectrode for the first time through a vapor-phase transport process by adjusting the mixing ratios of RuO2 and VO2 precursors. Single crystalline Ru1-xVxO2 nanowires show homogeneous solid-solution characteristics as well as the distinct feature of having remarkably narrow dimensional distributions. The electrochemical observations of a Ru1-xVxO2 (x=0.28 and 0.66)-decorated Au microelectrode using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) demonstrate favorable charge-transfer kinetics of [Fe(CN)6]3-/4- and Ru(NH3)6(3+/2+) couples compared to that of a bare Au microelectrode. The catalytic activity of Ru1-xVxO2 for oxygen and H2O2 reduction at neutral pH increases as the fraction of vanadium increases within our experimental conditions, which might be useful in the area of biofuel cells and biosensors.

  3. Optimization of Cs Content in Co-Mn-Al Mixed Oxide as Catalyst for N2O Decomposition.

    Czech Academy of Sciences Publication Activity Database

    Chromčáková, Ž.; Obalová, L.; Kustrowski, P.; Drozdek, M.; Karásková, K.; Jirátová, Květa; Kovanda, F.

    2015-01-01

    Roč. 41, č. 12 (2015), s. 9319-9332 ISSN 0922-6168. [Pannonian Symposium on Catalysis /12./. Třešť, 16.09.2014-20.09.2014] R&D Projects: GA ČR GA14-13750S Institutional support: RVO:67985858 Keywords : nitrous oxide * mixed oxide catalysts * cesium promoter * layered double hydroxides Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.833, year: 2015

  4. EBSD and TEM Characterization of High Burn-up Mixed Oxide Fuel

    International Nuclear Information System (INIS)

    Teague, Melissa C; Gorman, Brian P.; Miller, Brandon D; King, Jeffrey

    2014-01-01

    Understanding and studying the irradiation behavior of high burn-up oxide fuel is critical to licensing of future fast breeder reactors. Advancements in experimental techniques and equipment are allowing for new insights into previously irradiated samples. In this work dual column focused ion beam (FIB)/scanning electron microscope (SEM) was utilized to prepared transmission electron microscope samples from mixed oxide fuel with a burn-up of 6.7% FIMA. Utilizing the FIB/SEM for preparation resulted in samples with a dose rate of <0.5 mRem/h compared to approximately 1.1 R/h for a traditionally prepared TEM sample. The TEM analysis showed that the sample taken from the cooler rim region of the fuel pellet had approximately 2.5x higher dislocation density than that of the sample taken from the mid-radius due to the lower irradiation temperature of the rim. The dual column FIB/SEM was additionally used to prepared and serially slice approximately 25 um cubes. High quality electron back scatter diffraction (EBSD) were collected from the face at each step, showing, for the first time, the ability to obtain EBSD data from high activity irradiated fuel

  5. Water gas shift reaction over Cu catalyst supported by mixed oxide materials for fuel cell application

    Directory of Open Access Journals (Sweden)

    Tepamatr Pannipa

    2016-01-01

    Full Text Available The water gas shift activities of Cu on ceria and Gd doped ceria have been studied for the further enhancement of hydrogen purity [1] after the steam reforming of ethanol. The catalytic properties of commercial catalysts were also studied to compare with the as-prepared catalysts. Copper-containing cerium oxide materials are shown in this work to be suitable for the high temperature. Copper-ceria is a stable high-temperature shift catalyst, unlike iron-chrome catalysts that deactivate severely in CO2-rich gases. We found that 5%Cu/10%GDC(D has much higher activity than other copper ceria based catalysts. The finely dispersed CuO species is favorable to the higher activity, which explained the activity enhancement of this catalyst. The kinetics of the WGS reaction over Cu catalysts supported by mixed oxide materials were measured in the temperature range 200-400 °C. An independence of the CO conversion rate on CO2 and H2 was found.

  6. Influence of oxygen-metal ratio on mixed-oxide fuel performance

    International Nuclear Information System (INIS)

    Lawrence, L.A.; Leggett, R.D.

    1979-04-01

    The fuel oxygen-to-metal ratio (O/M) is recognized as an important consideration for performance of uranium--plutonium oxide fuels. An overview of the effects of differing O/M's on the irradiation performance of reference design mixed-oxide fuel in the areas of chemical and mechanical behavior, thermal performance, and fission gas behavior is presented. The pellet fuel has a nominal composition of 75 wt% UO 2 + 25 wt% PuO 2 at a pellet density of approx. 90% TD. for nominal conditions this results in a smeared density of approx. 85%. The cladding in all cases is 20% CW type 316 stainless steel with an outer diameter of 5.84 to 6.35 mm. O/M has been found to significantly influence fuel pin chemistry, mainly FCCI and fission product and fuel migration. It has little effect on thermal performance and overall mechanical behavior or fission gas release. The effects of O/M (ranging from 1.938 to 1.984) in the areas of fuel pin chemistry, to date, have not resulted in any reduction in fuel pin performance capability to goal burnups of approx. 8 atom% or more

  7. Conversion of Syngas-Derived C2+ Mixed Oxygenates to C3-C5 Olefins over ZnxZryOz Mixed Oxides Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Colin D.; Lebarbier, Vanessa M.; Flake, Matthew D.; Ramasamy, Karthikeyan K.; Kovarik, Libor; Bowden, Mark E.; Onfroy, Thomas; Dagle, Robert A.

    2016-04-01

    In this study we report on a ZnxZryOz mixed oxide type catalyst capable of converting a syngas-derived C2+ mixed oxygenate feedstock to isobutene-rich olefins. Aqueous model feed comprising of ethanol, acetaldehyde, acetic acid, ethyl acetate, methanol, and propanol was used as representative liquid product derived from a Rh-based mixed oxygenate synthesis catalyst. Greater than 50% carbon yield to C3-C5 mixed olefins was demonstrated when operating at 400-450oC and 1 atm. In order to rationalize formation of the products observed feed components were individually evaluated. Major constituents of the feed mixture (ethanol, acetaldehyde, acetic acid, and ethyl acetate) were found to produce isobutene-rich olefins. C-C coupling was also demonstrated for propanol feedstock - a minor constituent of the mixed oxygenate feed - producing branched C6 olefins, revealing scalability to alcohols higher than ethanol following an analogous reaction pathway. Using ethanol and propanol feed mixtures, cross-coupling reactions produced mixtures of C4, C5, and C6 branched olefins. The presence of H2 in the feed was found to facilitate hydrogenation of the ketone intermediates, thus producing straight chain olefins as byproducts. While activity loss from coking is observed complete catalyst regeneration is achieved by employing mild oxidation. For conversion of the mixed oxygenate feed a Zr/Zn ratio of 2.5 and a reaction temperature of 450oC provides the best balance of stability, activity, and selectivity. X-ray diffraction and scanning transmission electron microscopy analysis reveals the presence of primarily cubic phase ZrO2 and a minor amount of the monoclinic phase, with ZnO being highly dispersed in the lattice. The presence of ZnO appears to stabilize the cubic phase resulting in less monoclinic phase as the ZnO concentration increases. Infrared spectroscopy shows the mixed oxide acid sites are characterized as primarily Lewis type acidity. The direct relationship between

  8. Determination of aggregate morphological properties using laser and their effects on rutting of asphalt mixes

    CSIR Research Space (South Africa)

    Anochie-Boateng, Joseph

    2013-11-01

    Full Text Available A new and innovative three-dimensional (3-D) laser based technique was employed to accurately determine the morphological (shape) properties of aggregates used in asphalt mixes. The objective of this paper is to investigate the influence of shape...

  9. Application of Ni-Oxide@TiO2 Core-Shell Structures to Photocatalytic Mixed Dye Degradation, CO Oxidation, and Supercapacitors

    Directory of Open Access Journals (Sweden)

    Seungwon Lee

    2016-12-01

    Full Text Available Performing diverse application tests on synthesized metal oxides is critical for identifying suitable application areas based on the material performances. In the present study, Ni-oxide@TiO2 core-shell materials were synthesized and applied to photocatalytic mixed dye (methyl orange + rhodamine + methylene blue degradation under ultraviolet (UV and visible lights, CO oxidation, and supercapacitors. Their physicochemical properties were examined by field-emission scanning electron microscopy, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, and UV-visible absorption spectroscopy. It was shown that their performances were highly dependent on the morphology, thermal treatment procedure, and TiO2 overlayer coating.

  10. Amorphous Mixed-Valence Vanadium Oxide/Exfoliated Carbon Cloth Structure Shows a Record High Cycling Stability.

    Science.gov (United States)

    Song, Yu; Liu, Tian-Yu; Yao, Bin; Kou, Tian-Yi; Feng, Dong-Yang; Liu, Xiao-Xia; Li, Yat

    2017-04-01

    Previous studies show that vanadium oxides suffer from severe capacity loss during cycling in the liquid electrolyte, which has hindered their applications in electrochemical energy storage. The electrochemical instability is mainly due to chemical dissolution and structural pulverization of vanadium oxides during charge/discharge cyclings. In this study the authors demonstrate that amorphous mixed-valence vanadium oxide deposited on exfoliated carbon cloth (CC) can address these two limitations simultaneously. The results suggest that tuning the V 4+ /V 5+ ratio of vanadium oxide can efficiently suppress the dissolution of the active materials. The oxygen-functionalized carbon shell on exfoliated CC can bind strongly with VO x via the formation of COV bonding, which retains the electrode integrity and suppresses the structural degradation of the oxide during charging/discharging. The uptake of structural water during charging and discharging processes also plays an important role in activating the electrode material. The amorphous mixed-valence vanadium oxide without any protective coating exhibits record-high cycling stability in the aqueous electrolyte with no capacitive decay in 100 000 cycles. This work provides new insights on stabilizing vanadium oxide, which is critical for the development of vanadium oxide based energy storage devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Determination of mixing quality in biogas plant digesters using tracer tests and computational fluid dynamics

    Directory of Open Access Journals (Sweden)

    Luděk Kamarád

    2013-01-01

    Full Text Available The total electricity demand of investigated biogas plants (BGP makes up 7–8 % of the total electricity produced. Nearly 40 % of this energy is consumed just for mixing in digesters and the energy demand for mixing in some biogas plants can be even higher. Therefore, optimal mixing in anaerobic digesters is a basic condition for efficient plant operation and biogas production. The use of problematic substrates (e.g. grass silage or other fibrous substrates, installation of unsuitable mixing systems or inconvenient mixing intervals may lead to mixing problems. Knowledge about mixing in biogas digesters is still insufficient, so the objective of this study was to fill the information gaps in the literature by determining the minimal retention time of substrates fed into anaerobic digesters and to describe substrate distribution and washing out rates from investigated digesters. Two full-scale biogas plant digesters (2000 m3 and 1500 m3 using different mixing systems and substrates were investigated. To characterize the substrate distribution, lithium hydroxide monohydrate solutions were used for tracer tests at concentrations of 47.1 mg Li+ / kg TS and 46.6 mg Li+ / kg TS in digester. The tracer concentration in the digester effluents was measured during two hydraulic retention times and compared. Although the tracer was detected in the digester effluent at nearly the same time in both cases, the tracer tests showed very different distribution curves. The tracer concentration in effluent B grew much slower than in effluent A and no significant short circuiting streams were detected. Although the data calculated by computational fluid dynamics methods (CFD showed a very good agreement with the full scale results, full comparison was not possible.

  12. Oxidation-sulfidation behavior of Ni aluminide in oxygen-sulfur mixed-gas atmospheres

    International Nuclear Information System (INIS)

    Natesan, K.

    1988-01-01

    Oxidation-sulfidation studies were conducted with sheet samples of nickel aluminide, containing 23.5 at. % Al, 0.5 at. % Hf, and 0.2 at. % B, in an annealed condition and after preoxidation treatments. Continuous weight-change measurements were made by a thermogravimetric technique in exposure atmospheres of air, a low-pO/sub 2/ gas mixture, and low-pO/sub 2/ gas mixtures with several levels of sulfur. The air-exposed specimens developed predominantly nickel oxide; the specimen exposed to a low-pO/sub 2/ environment developed an aluminum oxide scale. As the sulfur content of the gas mixture increased, the alumina scale exhibited spallation and the alloy tended to form nickel sulfide as the reaction phase. The results indicated that the sulfidation reaction of nickel aluminide specimens (both bare and preoxidized) was determined by the rate of transport of nickel from the substrate through the scale to the gas/alumina scale interface, the mechanical integrity of the oxide scale, and the H/sub 2/S concentration in the exposure environment

  13. Development of a novel wet oxidation process for hazardous and mixed wastes

    International Nuclear Information System (INIS)

    Dhooge, P.M.

    1994-01-01

    Many DOE waste streams and remediates contain complex and variable mixtures of organic compounds, toxic metals, and radionuclides. These materials are often dispersed in organic or inorganic matrices, such as personal protective equipment, various sludges, soils, and water. The over all objective of the effort described here is to develop a novel catalytic wet oxidation process for the treatment of these multi-component wastes, with the aim of providing a versatile, non-thermal method which will destroy hazardous organic compounds while simultaneously containing and concentrating toxic and radioactive metals for recovery or disposal in a readily stabilized matrix. The DETOX process uses a unique combination of metal catalysts to increase the rate of oxidation of organic materials. The metal catalysts are in the form of salts dissolved in a dilute acid solution. A typical catalyst composition is 60% ferric chloride, 3--4% hydrochloric acid, 0.13% platinum ions, and 0.13% ruthenium ions in a water solution. The catalyst solution is maintained at 423--473 K. Wastes are introduced into contact with the solution, where their organic portion is oxidized to carbon dioxide and water. If the organic portion is chlorinated, hydrogen chloride will be produced as a product. The process is a viable alternative to incineration for the treatment of organic mixed wastes. Estimated costs for waste treatment using the process are from $2.50/kg to $25.00/kg, depending on the size of the unit and the amount of waste processed. Process units can be mobile for on-site treatment of wastes. Results from phase 1 and 2, design and engineering studies, are described

  14. Dissolution of thorium/uranium mixed oxide in nitric acid-hydrofluoric acid solution

    International Nuclear Information System (INIS)

    Filgueiras, S.A.C.

    1984-01-01

    The dissolution process of thorium oxide and mixed uranium-thorium oxide is studied, as a step of the head-end of the fuel reprocessing. An extensive bibliography was analysed, concerning the main aspects of the system, specially the most important process variables. Proposed mechanisms and models for the thorium oxide dissolution are presented. The laboratory tests were performed in two phases: at first, powdered thoria was used as the material to be dissolved. The objective was to know how changes in he concentrations of the dissolvent solution components HNO 3 , HF and Al(NO 3 ) 3 affect the dissolution rate. The tests were planned according to the fractional factorial method. Thes results showed that it is advantageous to work with powdered material, since the reaction occurs rapidly. And, if the Thorex solution (HNO 3 13M, HF 0.05M and Al(NO 3 ) 3 0.10M) is a suitable dissolvent, it was verified that it is possible to reduce the concentration of either nitric or fluoridric acid, without reducing the reaction rate to an undesirable value. It was also observed significant interaction between the components of the dissolvent solution. In the second phase of the tests, (Th, 5%U)O 2 sintered pellets were used. The main goals were to know the pellets dissolution behaviour and to compare the results for different pellets among themselves. It was observed that the metallurgical history of the material strongly influences its dissolution, specially the density and the microstructure. It was also studied how the (Th,U)O 2 mass/Thorex solution volume ratio affects the time needed to obtain an 1 M Th/liter solution. The activation energy for the reaction was obtained. (Author) [pt

  15. Effects of photochemical oxidation on the mixing state and light absorption of black carbon in the urban atmosphere of China

    Science.gov (United States)

    Wang, Qiyuan; Huang, Rujin; Zhao, Zhuzi; Cao, Junji; Ni, Haiyan; Tie, Xuexi; Zhu, Chongshu; Shen, Zhenxing; Wang, Meng; Dai, Wenting; Han, Yongming; Zhang, Ningning; Prévôt, André S. H.

    2017-04-01

    The relationship between the refractory black carbon (rBC) aerosol mixing state and the atmospheric oxidation capacity was investigated to assess the possible influence of oxidants on the particles’ light absorption effects at two large cities in China. The number fraction of thickly-coated rBC particles (F rBC) was positively correlated with a measure of the oxidant concentrations (OX = O3 + NO2), indicating an enhancement of coated rBC particles under more oxidizing conditions. The slope of a linear regression of F rBC versus OX was 0.58% ppb-1 for Beijing and 0.84% ppb-1 for Xi’an, and these relationships provide some insights into the evolution of rBC mixing state in relation to atmospheric oxidation processes. The mass absorption cross-section of rBC (MACrBC) increased with OX during the daytime at Xi’an, at a rate of 0.26 m2 g-1 ppb-1, suggesting that more oxidizing conditions lead to internal mixing that enhances the light-absorbing capacity of rBC particles. Understanding the dependence of the increasing rates of F rBC and MACrBC as a function of OX may lead to improvements of climate models that deal with the warming effects, but more studies in different cities and seasons are needed to gauge the broader implications of these findings.

  16. Transparent conductive electrodes of mixed TiO2−x–indium tin oxide for organic photovoltaics

    KAUST Repository

    Lee, Kyu-Sung

    2012-05-22

    A transparent conductive electrode of mixed titanium dioxide (TiO2−x)–indium tin oxide (ITO) with an overall reduction in the use of indium metal is demonstrated. When used in organic photovoltaicdevices based on bulk heterojunction photoactive layer of poly (3-hexylthiophene) and [6,6]-phenyl C61 butyric acid methyl ester, a power conversion efficiency of 3.67% was obtained, a value comparable to devices having sputtered ITO electrode. Surface roughness and optical efficiency are improved when using the mixed TiO2−x–ITO electrode. The consumption of less indium allows for lower fabrication cost of such mixed thin filmelectrode.

  17. Effect of preparation procedure on the formation of nanostructuredceria–zirconia mixed oxide catalysts for ethyl acetate oxidation:Homogeneous precipitation with urea vs template-assistedhydrothermal synthesis

    Czech Academy of Sciences Publication Activity Database

    Tsoncheva, T.; Ivanova, R.; Henych, Jiří; Dimitrov, M.; Kormunda, M.; Kovacheva, D.; Scotti, N.; Dal Santo, V.; Štengl, Václav

    2015-01-01

    Roč. 502, JUL (2015), s. 418-432 ISSN 0926-860X Institutional support: RVO:61388980 Keywords : Ceria–zirconia mixed oxides * Template -assisted hydrothermal method * Urea hydrolysis * Ethyl acetate oxidationa Subject RIV: CA - Inorganic Chemistry Impact factor: 4.012, year: 2015

  18. An ultrasonic-accelerated oxidation method for determining the oxidative stability of biodiesel.

    Science.gov (United States)

    Avila Orozco, Francisco D; Sousa, Antonio C; Domini, Claudia E; Ugulino Araujo, Mario Cesar; Fernández Band, Beatriz S

    2013-05-01

    Biodiesel is considered an alternative energy because it is produced from fats and vegetable oils by means of transesterification. Furthermore, it consists of fatty acid alkyl esters (FAAS) which have a great influence on biodiesel fuel properties and in the storage lifetime of biodiesel itself. The biodiesel storage stability is directly related to the oxidative stability parameter (Induction Time - IT) which is determined by means of the Rancimat® method. This method uses condutimetric monitoring and induces the degradation of FAAS by heating the sample at a constant temperature. The European Committee for Standardization established a standard (EN 14214) to determine the oxidative stability of biodiesel, which requires it to reach a minimum induction period of 6h as tested by Rancimat® method at 110°C. In this research, we aimed at developing a fast and simple alternative method to determine the induction time (IT) based on the FAAS ultrasonic-accelerated oxidation. The sonodegradation of biodiesel samples was induced by means of an ultrasonic homogenizer fitted with an immersible horn at 480Watts of power and 20 duty cycles. The UV-Vis spectrometry was used to monitor the FAAS sonodegradation by measuring the absorbance at 270nm every 2. Biodiesel samples from different feedstock were studied in this work. In all cases, IT was established as the inflection point of the absorbance versus time curve. The induction time values of all biodiesel samples determined using the proposed method was in accordance with those measured through the Rancimat® reference method by showing a R(2)=0.998. Copyright © 2012 Elsevier B.V. All rights reserved.

  19. Experimental and molecular dynamics study of thermo-physical and transport properties of ThO{sub 2}-5wt.%CeO{sub 2} mixed oxides

    Energy Technology Data Exchange (ETDEWEB)

    Somayajulu, P.S. [Radiometallurgy Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Ghosh, P.S., E-mail: psghosh@barc.gov.in [Material Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Banerjee, J. [Radiometallurgy Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Babu, K.L.N.C. [Metallic Fuels Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Danny, K.M. [Radiometallurgy Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Mandal, B.P. [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Mahata, T. [Powder Metallurgy Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Sengupta, P. [Material Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Sali, S.K. [Fuel Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Arya, A. [Material Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

    2015-12-15

    We have determined the thermo-physical (elastic modulus, specific heat, thermal expansion and thermal conductivity) and transport (ionic conductivity) properties of ThO{sub 2}-5wt.%CeO{sub 2} mixed oxide (MOX) using a combined experimental and theoretical methodology. The specific heat, ionic conductivity and elastic properties of ThO{sub 2}-5wt.%CeO{sub 2} pellets prepared by conventional powder metallurgy (POP) and coated agglomerate pelletization (CAP) routes (sintered in both air and Ar-8%H{sub 2} atmosphere) are compared with respect to homogeneity (CeO{sub 2} distribution in ThO{sub 2} matrix), microstructure, porosity and oxygen to metal ratio. The effects of inhomogeneity and pore distribution on thermal expansion and thermal conductivity of the mixed-oxide pellets are identified. Molecular dynamics (MD) simulations using the Coulomb-Buckingham-Morse-many-body model based interatomic potentials are used to predict elastic properties in the temperature range between 300 and 2000 K and thermodynamic properties, viz., enthalpy increment and specific heats of ThO{sub 2}. Finally, the thermal expansion coefficient and thermal conductivity of ThO{sub 2} and (Th,Ce)O{sub 2} mixed-oxides obtained from MD are compared with available experimental results.

  20. Experimental and molecular dynamics study of thermo-physical and transport properties of ThO2-5wt.%CeO2 mixed oxides

    Science.gov (United States)

    Somayajulu, P. S.; Ghosh, P. S.; Banerjee, J.; Babu, K. L. N. C.; Danny, K. M.; Mandal, B. P.; Mahata, T.; Sengupta, P.; Sali, S. K.; Arya, A.

    2015-12-01

    We have determined the thermo-physical (elastic modulus, specific heat, thermal expansion and thermal conductivity) and transport (ionic conductivity) properties of ThO2-5wt.%CeO2 mixed oxide (MOX) using a combined experimental and theoretical methodology. The specific heat, ionic conductivity and elastic properties of ThO2-5wt.%CeO2 pellets prepared by conventional powder metallurgy (POP) and coated agglomerate pelletization (CAP) routes (sintered in both air and Ar-8%H2 atmosphere) are compared with respect to homogeneity (CeO2 distribution in ThO2 matrix), microstructure, porosity and oxygen to metal ratio. The effects of inhomogeneity and pore distribution on thermal expansion and thermal conductivity of the mixed-oxide pellets are identified. Molecular dynamics (MD) simulations using the Coulomb-Buckingham-Morse-many-body model based interatomic potentials are used to predict elastic properties in the temperature range between 300 and 2000 K and thermodynamic properties, viz., enthalpy increment and specific heats of ThO2. Finally, the thermal expansion coefficient and thermal conductivity of ThO2 and (Th,Ce)O2 mixed-oxides obtained from MD are compared with available experimental results.

  1. The decomposition of mixed oxide Ag2Cu2O3: Structural features and the catalytic properties in CO and C2H4 oxidation

    Science.gov (United States)

    Svintsitskiy, Dmitry A.; Kardash, Tatyana Yu.; Slavinskaya, Elena M.; Stonkus, Olga A.; Koscheev, Sergei V.; Boronin, Andrei I.

    2018-01-01

    The mixed silver-copper oxide Ag2Cu2O3 with a paramelaconite crystal structure is a promising material for catalytic applications. The as-prepared sample of Ag2Cu2O3 consisted of brick-like particles extended along the [001] direction. A combination of physicochemical techniques such as TEM, XPS and XRD was applied to investigate the structural features of this mixed silver-copper oxide. The thermal stability of Ag2Cu2O3 was investigated using in situ XRD under different reaction conditions, including a catalytic CO + O2 mixture. The first step of Ag2Cu2O3 decomposition was accompanied by the appearance of ensembles consisting of silver nanoparticles with sizes of 5-15 nm. Silver nanoparticles were strongly oriented to each other and to the surface of the initial Ag2Cu2O3 bricks. Based on the XRD data, it was shown that the release of silver occurred along the a and b axes of the paramelaconite structure. Partial decomposition of Ag2Cu2O3 accompanied by the formation of silver nanoparticles was observed during prolonged air storage under ambient conditions. The high reactivity is discussed as a reason for spontaneous decomposition during Ag2Cu2O3 storage. The full decomposition of the mixed oxide into metallic silver and copper (II) oxide took place at temperatures higher than 300 °C regardless of the nature of the reaction medium (helium, air, CO + O2). Catalytic properties of partially and fully decomposed samples of mixed silver-copper oxide were measured in low-temperature CO oxidation and C2H4 epoxidation reactions.

  2. Technology, safety and costs of decommissioning a reference small mixed oxide fuel fabrication plant. Volume 1. Main report

    Energy Technology Data Exchange (ETDEWEB)

    Jenkins, C. E.; Murphy, E. S.; Schneider, K J

    1979-01-01

    Detailed technology, safety and cost information are presented for the conceptual decommissioning of a reference small mixed oxide fuel fabrication plant. Alternate methods of decommissioning are described including immediate dismantlement, safe storage for a period of time followed by dismantlement and entombment. Safety analyses, both occupational and public, and cost evaluations were conducted for each mode.

  3. Optimization of CeO2-ZrO2 mixed oxide catalysts for ethyl acetate combustion

    Czech Academy of Sciences Publication Activity Database

    Dimitrov, M.; Ivanova, R.; Štengl, Václav; Henych, Jiří; Kovacheva, D.; Tsoncheva, T.

    2015-01-01

    Roč. 47, č. 1 (2015), s. 323-329 ISSN 0324-1130 Institutional support: RVO:61388980 Keywords : nanosized CeO2-ZrO2 * mixed oxide phase * ethyl acetate combustion Subject RIV: CA - Inorganic Chemistry Impact factor: 0.229, year: 2015

  4. Thiophene Conversion and Ethanol Oxidation on SiO2-Supported 12-PMoV-Mixed Heteropoly Compounds

    Czech Academy of Sciences Publication Activity Database

    Spojakina, A. A.; Kostova, N. G.; Sow, Bineta; Stamenova, M. W.; Jirátová, Květa

    2001-01-01

    Roč. 65, 2-4 (2001), s. 315-321 ISSN 0920-5861 Institutional research plan: CEZ:AV0Z4072921 Keywords : thiophene conversion * ethanol oxidation * mixed heteropoly compounds Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.333, year: 2001

  5. Effect of Preparation Method on Catalytic Properties of Co-Mn-Al Mixed Oxides for N2O Decomposition.

    Czech Academy of Sciences Publication Activity Database

    Klyushina, A.; Pacultová, K.; Karásková, K.; Jirátová, Květa; Ritz, M.; Fridrichová, D.; Volodorskaja, A.; Obalová, L.

    2016-01-01

    Roč. 425, DEC 15 (2016), s. 237-247 ISSN 1381-1169 R&D Projects: GA ČR GA14-13750S Institutional support: RVO:67985858 Keywords : Co-Mn-Al mixed oxide * N2O decomposition * preparation methods Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 4.211, year: 2016

  6. Measurement and modelling of the defect chemistry and transport properties of ceramic oxide mixed ionic and electronic conductors

    DEFF Research Database (Denmark)

    Dalslet, Bjarke Thomas

    2008-01-01

    The subject of this thesis is ceramic mixed ionic and electronic conductors (MIECs). MIECs have potential uses, such as solid oxygen permeation membranes, as catalysts, and as components in fuel cells. The MIECs examined in this thesis are all oxide ion conducting materials. This thesis describes...

  7. General synthesis of vanadium-based mixed metal oxides hollow nanofibers for high performance lithium-ion batteries

    Science.gov (United States)

    Xiang, Juan; Yu, Xin-Yao; Paik, Ungyu

    2016-10-01

    Hollow nanostructured mixed metal oxides have recently been intensively investigated as electrode materials for energy storage and conversion due to their remarkable electrochemical properties. Although great efforts have been made, the synthesis of hollow nanostructured vanadium-based mixed metal oxides especially those with one dimensional structure is rarely reported. Vanadium-based mixed metal oxides are promising electrode materials for lithium-ion batteries with high capacity and good rate capability. Here, we develop a facile and general method for the synthesis of one dimensional MxV2O8 (M = Co, Ni, Fe) tubular structure through a simple single-spinneret electrospinning technique followed by a calcination process. As a demonstration, Co3V2O8 hollow nanofibers are evaluated as anode materials for lithium-ion batteries. As expected, benefiting from their unique one dimensional tubular structure, the as-synthesized Co3V2O8 exhibits excellent electrochemical properties for lithium storage. To be specific, it can deliver a high specific capacity of 900 mAh g-1 at 5 A g-1, and long cycling stability up to 2000 cycles. The present work makes a significant contribution to the design and synthesis of mixed metal oxides with one dimensional tubular structure, as well as their potential applications in electrochemical energy storage.

  8. Structure and growth of polymeric niobia-silica mixed-oxide sols for microporous molecular sieving membranes: A SAXS study

    NARCIS (Netherlands)

    Boffa, V.; Castricum, H.L.; Garcia, Ruben; Schmuhl, R.; Petukhov, Andrei V.; Blank, David H.A.; ten Elshof, Johan E.

    2009-01-01

    Branched polymeric niobia-silica (NS) mixed-oxide sols with a Nb:Si molar ratio between 0.33 and 0.8 were made by acid-catalyzed sol−gel synthesis and characterized using small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS). The growth rate of NS sols after addition of a niobium

  9. Measurement and modelling of the defect chemistry and transport properties of ceramic oxide mixed ionic and electronic conductors

    NARCIS (Netherlands)

    Dalslet, Bjarke Thomas

    2008-01-01

    The mixed ionic and electronic conducting fluorite and perovskite materials examined in this thesis are all oxide ion conducting materials. The defect chemistry and transport properties of a number of these materials are measured using: 1) a measurement technique using an oxygen pump and an

  10. A stochastic model of turbulent mixing with chemical reaction: Nitric oxide formulation in a plug-flow burner

    Science.gov (United States)

    Flagan, R. C.; Appleton, J. P.

    1973-01-01

    A stochastic model of turbulent mixing was developed for a reactor in which mixing is represented by n-body fluid particle interactions. The model was used to justify the assumption (made in previous investigations of the role of turbulent mixing on burner generated thermal nitric oxide and carbon monoxide emissions) that for a simple plug flow reactor, composition nonuniformities can be described by a Gaussian distribution function in the local fuel:air equivalence ratio. Recent extensions of this stochastic model to include the combined effects of turbulent mixing and secondary air entrainment on thermal generation of nitric oxide in gas turbine combustors are discussed. Finally, rate limited upper and lower bounds of the nitric oxide produced by thermal fixation of molecular nitrogen and oxidation of organically bound fuel nitrogen are estimated on the basis of the stochastic model for a plug flow burner; these are compared with experimental measurements obtained using a laboratory burner operated over a wide range of test conditions; good agreement is obtained.

  11. Determination of regional heat fluxes from the growth of the mixed layer

    Energy Technology Data Exchange (ETDEWEB)

    Gryning, S.E. [Risoe National Lab., Roskilde (Denmark); Batchvarova, E. [National Inst. of Meteorology and Hydrology, Sofia (Bulgaria)

    1997-10-01

    The distribution of surface sensible heat flux is a critical factor in producing and modifying the mesoscale atmospheric flows, turbulence and evaporation. Parameterizations that assume homogeneous land characteristics are inappropriate to represent the spatial variability often found in nature. One possibility to overcome this problem is to increase the resolution of the model grid which demands unrealistic computing resources and data for model initialization. Area averaged fluxes can be obtained from aircraft measurements. It is essential that the flights are performed at a height where the individual surface features are not felt. A large number of flights and appropriate pattern to meet the task are needed in order to achieve a fair statistics. The mixed layer grows in response to the regional turbulent fluxes including the aggregation and small scale processes. The region of influence in upwind direction is typically 20 times the height of the mixed layer for convective and 100 times the height of the mixed layer for atmospheric near neutral conditions. In this study we determine the regional integrated sensible heat flux from information on the evolution of the mixed layer over the area. The required information to use the method can be derived from wind speed and temperature profiles obtained by radio-soundings when performed frequently enough to provide a reasonably detailed structure of the development of the mixed-layer. The method is applied to estimate the regional heat flux over the NOPEX experimental area for three days during the campaign in 1994. (au)

  12. Indices of Paraoxonase and Oxidative Status Do Not Enhance the Prediction of Subclinical Cardiovascular Disease in Mixed-Ancestry South Africans

    Science.gov (United States)

    Macharia, M.; Kengne, A. P.; Blackhurst, D. M.; Erasmus, R. T.; Hoffmann, M.; Matsha, T. E.

    2014-01-01

    We evaluated the association of indices of paraoxonase (PON1) and oxidative status with subclinical cardiovascular disease (CVD) in mixed-ancestry South Africans. Participants were 491 adults (126 men) who were stratified by diabetes status and body mass index (BMI). Carotid intima-media thickness (CIMT) was used as a measure of subclinical CVD. Indices of PON1 and oxidative status were determined by measuring levels and activities (paraoxonase and arylesterase) of PON1, antioxidant activity (ferric reducing antioxidant power and trolox equivalent antioxidant capacity), and lipid peroxidation markers (malondialdehyde and oxidized LDL). Diabetic subjects (28.9%) displayed a significant decrease in PON1 status and antioxidant activity as well as increase in oxidized LDL and malondialdehyde. A similar profile was apparent across increasing BMI categories. CIMT was higher in diabetic than nondiabetic subjects (P < 0.0001) but showed no variation across BMI categories. Overall, CIMT correlated negatively with indices of antioxidant activity and positively with measures of lipid oxidation. Sex, age, BMI, and diabetes altogether explained 29.2% of CIMT, with no further improvement from adding PON1 and/or antioxidant status indices. Though indices of PON1 and oxidative status correlate with CIMT, their measurements may not be useful for identifying subjects at high CVD risk in this population. PMID:24799979

  13. Indices of Paraoxonase and Oxidative Status Do Not Enhance the Prediction of Subclinical Cardiovascular Disease in Mixed-Ancestry South Africans

    Directory of Open Access Journals (Sweden)

    M. Macharia

    2014-01-01

    Full Text Available We evaluated the association of indices of paraoxonase (PON1 and oxidative status with subclinical cardiovascular disease (CVD in mixed-ancestry South Africans. Participants were 491 adults (126 men who were stratified by diabetes status and body mass index (BMI. Carotid intima-media thickness (CIMT was used as a measure of subclinical CVD. Indices of PON1 and oxidative status were determined by measuring levels and activities (paraoxonase and arylesterase of PON1, antioxidant activity (ferric reducing antioxidant power and trolox equivalent antioxidant capacity, and lipid peroxidation markers (malondialdehyde and oxidized LDL. Diabetic subjects (28.9% displayed a significant decrease in PON1 status and antioxidant activity as well as increase in oxidized LDL and malondialdehyde. A similar profile was apparent across increasing BMI categories. CIMT was higher in diabetic than nondiabetic subjects (P<0.0001  but showed no variation across BMI categories. Overall, CIMT correlated negatively with indices of antioxidant activity and positively with measures of lipid oxidation. Sex, age, BMI, and diabetes altogether explained 29.2% of CIMT, with no further improvement from adding PON1 and/or antioxidant status indices. Though indices of PON1 and oxidative status correlate with CIMT, their measurements may not be useful for identifying subjects at high CVD risk in this population.

  14. Novel Montmorillonite/TiO2/MnAl-Mixed Oxide Composites Prepared from Inverse Microemulsions as Combustion Catalysts

    Directory of Open Access Journals (Sweden)

    Bogna D. Napruszewska

    2017-11-01

    Full Text Available A novel design of combustion catalysts is proposed, in which clay/TiO2/MnAl-mixed oxide composites are formed by intermixing exfoliated organo-montmorillonite with oxide precursors (hydrotalcite-like in the case of Mn-Al oxide obtained by an inverse microemulsion method. In order to assess the catalysts’ thermal stability, two calcination temperatures were employed: 450 and 600 °C. The composites were characterized with XRF (X-ray fluorescence, XRD (X-ray diffraction, HR SEM (high resolution scanning electron microscopy, N2 adsorption/desorption at −196 °C, and H2 TPR (temperature programmed reduction. Profound differences in structural, textural and redox properties of the materials were observed, depending on the presence of the TiO2 component, the type of neutralization agent used in the titania nanoparticles preparation (NaOH or NH3 (aq, and the temperature of calcination. Catalytic tests of toluene combustion revealed that the clay/TiO2/MnAl-mixed oxide composites prepared with the use of ammonia showed excellent activity, the composites obtained from MnAl hydrotalcite nanoparticles trapped between the organoclay layers were less active, but displayed spectacular thermal stability, while the clay/TiO2/MnAl-mixed oxide materials obtained with the aid of NaOH were least active. The observed patterns of catalytic activity bear a direct relation to the materials’ composition and their structural, textural, and redox properties.

  15. Mixed oxide fuels testing in the advanced test reactor to support plutonium disposition

    International Nuclear Information System (INIS)

    Ryskamp, J.M.; Sterbentz, J.W.; Chang, G.S.

    1995-09-01

    An intense worldwide effort is now under way to find means of reducing the stockpile of weapons-grade plutonium. One of the most attractive solutions would be to use WGPu as fuel in existing light water reactors (LWRs) in the form of mixed oxide (MOX) fuel - i.e., plutonia (PUO 2 ) mixed with urania (UO 2 ). Before U.S. reactors could be used for this purpose, their operating licenses would have to be amended. Numerous technical issues must be resolved before LWR operating licenses can be amended to allow the use of MOX fuel. These issues include the following: (1) MOX fuel fabrication process verification, (2) Whether and how to use burnable poisons to depress MOX fuel initial reactivity, which is higher than that of urania, (3) The effects of WGPu isotopic composition, (4) The feasibility of loading MOX fuel with plutonia content up to 7% by weight, (5) The effects of americium and gallium in WGPu, (6) Fission gas release from MOX fuel pellets made from WGPu, (7) Fuel/cladding gap closure, (8) The effects of power cycling and off-normal events on fuel integrity, (9) Development of radial distributions of burnup and fission products, (10) Power spiking near the interfaces of MOX and urania fuel assemblies, and (11) Fuel performance code validation. We have performed calculations to show that the use of hafnium shrouds can produce spectrum adjustments that will bring the flux spectrum in ATR test loops into a good approximation to the spectrum anticipated in a commercial LWR containing MOX fuel while allowing operation of the test fuel assemblies near their optimum values of linear heat generation rate. The ATR would be a nearly ideal test bed for developing data needed to support applications to license LWRs for operation with MOX fuel made from weapons-grade plutonium. The requirements for planning and implementing a test program in the ATR have been identified

  16. Dual Electrospray Pyrolysis for Mixed Metal Oxide (and Carbon) Composite Nanoparticle Synthesis with Applications in Energy Storage

    Science.gov (United States)

    Tang, Justin; Liu, Wen; Wang, Hailiang; Gomez, Alessandro

    We present a novel approach to synthesizing mixed metal oxide nanoparticles with a continuous, scalable aerosol flow process using the electrospray. The electrospray is a liquid atomization technique that generates a monodisperse population of highly charged liquid droplets over a broad size range (nanometric to tens of microns). Each liquid droplet serves as a micro-reactor, containing a payload of suitable precursors (such as metal nitrides), allowing for precise control over particle composition and size. By using two electrosprays of opposite polarities, the two highly charged droplets plumes are electrostatically mixed to produce a charge-neutral aerosol. Electrostatically driven droplet-droplet collisions can also be used to control morphology to some degree. This aerosol is passed through a tubular furnace via carrier gas, pyrolizing the precursors to synthesize nanomaterials. We apply this approach to manganese oxide, cobalt oxide, and carbon composite nanoparticles for use in energy storage applications.

  17. Physical and spectroscopic studies of Cr{sup 3+} doped mixed alkaline earth oxide borate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Samdani, E-mail: samdanimohd82@gmail.com [Department of Engineering, Salalah College of Technology, Salalah (Oman); Ramadevudu, G. [Department of Physics, Vasavi College of Engineering, Ibrahimbagh, Hyderabad 500031, Telangana (India); Chary, M. Narasimha; Shareefuddin, Md. [Department of Physics, Osmania University, Hyderabad 500007, Telangana (India)

    2017-01-15

    A series of mixed alkaline earth oxide glasses xMgO-(30-x)BaO-69.8B{sub 2}O{sub 3}-0.2Cr{sub 2}O{sub 3} were prepared and studied using electron paramagnetic resonance (EPR), optical absorption, Raman spectroscopy and photoluminescence experimental techniques. The optical absorption spectra revealed the characteristic octahedral symmetry of Cr{sup 3+}ions through three broad band transitions {sup 4}A{sub 2g}(F)→ {sup 4}T{sub 2g}(F), {sup 4}A{sub 2g}(F)→ {sup 4}T{sub 1g}(F), and {sup 4}A{sub 2g}(F)→ {sup 2}T{sub 1g}(P). The crystal field (Dq) and Racah parameters (B and C), the optical band gap and Urbach energies of the glass samples were also reported along with the physical properties like density and molar volume. In the EPR spectra three resonance signals corresponding to Cr3+ ions were observed. A broad signal with g = 5.110 was observed which belongs to the isolated Cr3+ centers localized in the strongly distorted octahedral (rhombic) sites of the glass network, a narrow signal (g = 1.960) corresponding to the Cr{sup 3+} centers in the weekly distorted (cubic) sites of the glass network, and a third very broad signal (g = 2.210) was also observed corresponding to Cr{sup 3+}- Cr{sup 3+} paired centers coupled by magnetic dipolar interaction. Another resonance signal with effective value g ≈ 4.220 was attributed to Fe{sup 3+} ions impurity. The number of spins (N) participating in the resonance and susceptibility (χ) values at room temperature were reported and their values varied in a non-linear manner with the composition exhibiting mixed oxide effect. The estimated molecular bonding coefficients (α) values indicated stronger ionic contribution. The Raman spectral investigations were carried out. The Photoluminescence spectra bands near 690 and 750 nm correspond to the Cr{sup 3+} centers in high and low field sites respectively. - Highlights: • Spectroscopic studies were made on alkaline earth borate glasses. • Three resonance signals

  18. Structural and microstructural changes in the zirconium-indium mixed oxide system during the thermal treatment

    Science.gov (United States)

    Štefanić, G.; Štefanić, I. I.; Musić, S.; Ivanda, M.

    2011-05-01

    The zirconium-indium mixed oxide systems on both the zirconium- and the indium-rich side of the concentration range were prepared by co-precipitation from aqueous solutions of the corresponding salts, followed by washing and heat-treatment. The thermal behavior (up to 1000 °C) of the dried samples was examined by X-ray powder diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray spectrometry, differential thermal analysis and thermogravimetric measurements. The obtained results show that the increase in the amount of the second phase causes an increase of both the crystallization temperature of the amorphous precursors of ZrO 2, from 435 °C (0 mol.% of InO 1.5) to 476 °C (˜62 mol.% of InO 1.5), and of the topotactic transition temperature of cubic In(OH) 3 to cubic In 2O 3, from 259 °C (0 mol.% of ZrO 2) to 290 °C (˜25 mol.% of ZrO 2). The amorphous precursors of ZrO 2 phase exhibit an extended capability to incorporate In 3+ ions (more than 60 mol.%). With a rise in temperature the maximum solubility of In 3+ ions in the ZrO 2 lattice decreases from ˜55 mol.% in the crystallization products obtained after calcination at 400 °C to ˜10 mol.% after calcination at 1000 °C. The results of phase analysis indicate that the incorporation of In 3+ ions partially stabilized both the tetragonal and cubic ZrO 2 polymorphs. The maximum solubility of Zr 4+ ions in the starting In(OH) 3 lattice was estimated at ˜10 mol.%. Thermal treatment causes a small increase of Zr 4+ ion solubility limits, estimated at ˜15 mol.% in the cubic In 2O 3 lattice after calcination at 1000 °C. Precise lattice parameter measurements, by using Le Bail refinements of the powder diffraction patterns with added silicon as an internal standard, show that the incorporation of In 3+ ions caused a very small decrease of the cubic ZrO 2 lattice, while the incorporation of Zr 4+ ions had a negligible

  19. Studies on carboxylated graphene oxide incorporated polyetherimide mixed matrix ultrafiltration membranes

    Energy Technology Data Exchange (ETDEWEB)

    Kaleekkal, Noel Jacob, E-mail: noeljacob89@gmail.com [Membrane Laboratory, Department of Chemical Engineering, ACT, Anna University, Chennai, 600025 (India); Thanigaivelan, A., E-mail: thanichemstar@gmail.com [Membrane Laboratory, Department of Chemical Engineering, ACT, Anna University, Chennai, 600025 (India); Rana, Dipak, E-mail: rana@uottawa.ca [Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis Pasteur Private, Ottawa, Ontario, K1N 6N5 (Canada); Mohan, D., E-mail: mohantarun@gmail.com [Membrane Laboratory, Department of Chemical Engineering, ACT, Anna University, Chennai, 600025 (India)

    2017-01-15

    In this work the graphene oxide prepared by the modified Hummers’ method was effectively carboxylated. These carboxylated graphene oxide (c-GO) microsheets was characterized by X-ray diffraction analysis, Raman shift, zeta potential, and their morphology was observed using a high resolution scanning/transmission electron microscopy. Polyetherimide mixed matrix membranes (MMMs) were fabricated by the non-solvent induced phase separation technique with varying concentration of this microsheet. The presence of these microsheets on the membrane surface was confirmed by Fourier transform infrared spectroscopy, Raman spectroscopy and could also be confirmed visually by optical images. The membranes were further characterized; they showed a greater water flux, higher porosity, and sufficient thermal stability. Incorporation of these microsheets improved the hydrophilicity of the membrane confirmed by the lower contact angle values, which in turn explained the lower interfacial free energy, the increase in work of adhesion, the higher solid-vapor free energy and the spreading coefficient. Membranes loaded with 0.3 wt% of c-GO showed a flux recovery of 94% and only a small flux decline even after 180 min of filtration of humic acid (HA) solution. The efficiency of these membranes in removal of HA, toxic metal ions was also investigated. The bacterial anti-adhesion property of c-GO in the membranes was also explored using Escherichia coli, as a model bio-foulant. The charge of the microsheets and their unique architecture imparts higher hydrophilicity and greater fouling resistance along with improved permeation flux when incorporated into the polymer matrix. - Highlights: • Novel membranes by incorporating carboxylated GO into polyetherimide matrix. • Modified membranes exhibited greater porosity, flux and high humic acid rejection. • Nanoplatelets improved the flux recovery ratio to >94%. • Liquid phase polymer based retention utilized for toxic heavy metal

  20. Oxidative stabilization of mixed mayonnaises made with linseed oil and saturated medium-chain triglyceride oil

    DEFF Research Database (Denmark)

    Raudsepp, Piret; Brüggemann, Dagmar A.; Lenferink, Aufried

    2014-01-01

    storage was lower in mixed mayonnaise compared to LSO mayonnaise, while in mixed oil mayonnaise the level of peroxides was constantly low. Mixed oil mayonnaise had a lower rate of oxygen consumption than mixed mayonnaise, LSO mayonnaise having the highest rate. The decay of water-soluble nitroxyl radicals...

  1. A titration method for determining individual oxidant concentration in the dual sodium persulfate and hydrogen peroxide oxidation system.

    Science.gov (United States)

    Liang, Chenju; He, Boyu

    2018-05-01

    The use of a dual oxidation system, which combines sodium persulfate (Na 2 S 2 O 8 , SPS) and hydrogen peroxide (H 2 O 2 , HP) is increasing as an in-situ chemical oxidation (ISCO) process for soil and groundwater remediation. An analytical method was assessed in this study for determining individual oxidant concentration in order to understand the interactions, and variations in the concentrations, of SPS and HP in aqueous systems containing both SPS and HP. The iodometric titration method was demonstrated to be capable of measuring total oxidant (SPS + HP) concentration; while the ceric sulfate titration method can be used specifically for measuring HP in the dual oxidation system without interfering with the iodometric titration. Therefore, SPS concentration can be deduced by subtraction of the HP concentration from the total oxidant concentration. Direct iodometric titration for determination of total oxidant at concentration above 20 mM exhibited <8% concentration. Based on the results of indirect determination of SPS in the dual oxidation system, an approximate 10% concentration variation was expected. This research may serve as a reference for measuring oxidant variations in this ISCO dual oxidant application. Copyright © 2018. Published by Elsevier Ltd.

  2. Method of CO and/or CO.sub.2 hydrogenation to higher hydrocarbons using doped mixed-metal oxides

    Science.gov (United States)

    Shekhawat, Dushyant; Berry, David A.; Haynes, Daniel J.; Abdelsayed, Victor; Smith, Mark W.; Spivey, James J.

    2017-03-21

    A method of hydrogenation utilizing a reactant gas mixture comprising a carbon oxide and a hydrogen agent, and a hydrogenation catalyst comprising a mixed-metal oxide containing metal sites supported and/or incorporated into the lattice. The mixed-metal oxide comprises a pyrochlore, a brownmillerite, or mixtures thereof doped at the A-site or the B-site. The metal site may comprise a deposited metal, where the deposited metal is a transition metal, an alkali metal, an alkaline earth metal, or mixtures thereof. Contact between the carbon oxide, hydrogen agent, and hydrogenation catalyst under appropriate conditions of temperature, pressure and gas flow rate generate a hydrogenation reaction and produce a hydrogenated product made up of carbon from the carbon oxide and some portion of the hydrogen agent. The carbon oxide may be CO, CO.sub.2, or mixtures thereof and the hydrogen agent may be H.sub.2. In a particular embodiment, the hydrogenated product comprises olefins, paraffins, or mixtures thereof.

  3. Method of CO and/or CO.sub.2 hydrogenation using doped mixed-metal oxides

    Energy Technology Data Exchange (ETDEWEB)

    Shekhawat, Dushyant; Berry, David A.; Haynes, Daniel J.; Abdelsayed, Victor; Smith, Mark W.; Spivey, James J.

    2015-10-06

    A method of hydrogenation utilizing a reactant gas mixture comprising a carbon oxide and a hydrogen agent, and a hydrogenation catalyst comprising a mixed-metal oxide containing metal sites supported and/or incorporated into the lattice. The mixed-metal oxide comprises a perovskite, a pyrochlore, a fluorite, a brownmillerite, or mixtures thereof doped at the A-site or the B-site. The metal site may comprise a deposited metal, where the deposited metal is a transition metal, an alkali metal, an alkaline earth metal, or mixtures thereof. Contact between the carbon oxide, hydrogen agent, and hydrogenation catalyst under appropriate conditions of temperature, pressure and gas flow rate generate a hydrogenation reaction and produce a hydrogenated product made up of carbon from the carbon oxide and some portion of the hydrogen agent. The carbon oxide may be CO, CO.sub.2, or mixtures thereof and the hydrogen agent may be H.sub.2. In a particular embodiment, the hydrogenated product comprises an alcohol, an olefin, an aldehyde, a ketone, an ester, an oxo-product, or mixtures thereof.

  4. B0s mixing at the Z0 resonance determined with the RICH technique

    International Nuclear Information System (INIS)

    Haider, S.M.

    1995-01-01

    After the description of the Barrel RICH detector of the DELPHI experiment the determination of the integrated B s mixing parameter χ s by means of the decay modes B s →D s lν, B s →D s X, and B s →φlνX. A final value of χ s =0.33±0.42 is obtained. (HSI)

  5. International safeguards for a modern MOX (mixed-oxide) fuel fabrication facility

    Energy Technology Data Exchange (ETDEWEB)

    Pillay, K.K.S.; Stirpe, D.; Picard, R.R.

    1987-03-01

    Bulk-handling facilities that process plutonium for commercial fuel cycles offer considerable challenges to nuclear materials safeguards. Modern fuel fabrication facilities that handle mixed oxides of plutonium and uranium (MOX) often have large inventories of special nuclear materials in their process lines and in storage areas for feed and product materials. In addition, the remote automated processing prevalent at new MOX facilities, which is necessary to minimize radiation exposures to personnel, tends to limit access for measurements and inspections. The facility design considered in this study incorporates all these features as well as state-of-the-art measurement technologies for materials accounting. Key elements of International Atomic Energy Agency (IAEA) safeguards for such a fuel-cycle facility have been identified in this report, and several issues of primary importance to materials accountancy and IAEA verifications have been examined. We have calculated detection sensitivities for abrupt and protracted diversions of plutonium assuming a single materials balance area for all processing areas. To help achieve optimal use of limited IAEA inspection resources, we have calculated sampling plans for attributes/variables verification. In addition, we have demonstrated the usefulness of calculating sigma/sub (MUF-D)/ and detection probabilities corresponding to specified material-loss scenarios and resource allocations. The data developed and the analyses performed during this study can assist both the facility operator and the IAEA in formulating necessary safeguards approaches and verification procedures to implement international safeguards for special nuclear materials.

  6. Survey of Worldwide Light Water Reactor Experience with Mixed Uranium-Plutonium Oxide Fuel

    International Nuclear Information System (INIS)

    Cowell, B.S.; Fisher, S.E.

    1999-01-01

    The US and the Former Soviet Union (FSU) have recently declared quantities of weapons materials, including weapons-grade (WG) plutonium, excess to strategic requirements. One of the leading candidates for the disposition of excess WG plutonium is irradiation in light water reactors (LWRs) as mixed uranium-plutonium oxide (MOX) fuel. A description of the MOX fuel fabrication techniques in worldwide use is presented. A comprehensive examination of the domestic MOX experience in US reactors obtained during the 1960s, 1970s, and early 1980s is also presented. This experience is described by manufacturer and is also categorized by the reactor facility that irradiated the MOX fuel. A limited summary of the international experience with MOX fuels is also presented. A review of MOX fuel and its performance is conducted in view of the special considerations associated with the disposition of WG plutonium. Based on the available information, it appears that adoption of foreign commercial MOX technology from one of the successful MOX fuel vendors will minimize the technical risks to the overall mission. The conclusion is made that the existing MOX fuel experience base suggests that disposition of excess weapons plutonium through irradiation in LWRs is a technically attractive option

  7. International safeguards for a modern MOX [mixed-oxide] fuel fabrication facility

    International Nuclear Information System (INIS)

    Pillay, K.K.S.; Stirpe, D.; Picard, R.R.

    1987-03-01

    Bulk-handling facilities that process plutonium for commercial fuel cycles offer considerable challenges to nuclear materials safeguards. Modern fuel fabrication facilities that handle mixed oxides of plutonium and uranium (MOX) often have large inventories of special nuclear materials in their process lines and in storage areas for feed and product materials. In addition, the remote automated processing prevalent at new MOX facilities, which is necessary to minimize radiation exposures to personnel, tends to limit access for measurements and inspections. The facility design considered in this study incorporates all these features as well as state-of-the-art measurement technologies for materials accounting. Key elements of International Atomic Energy Agency (IAEA) safeguards for such a fuel-cycle facility have been identified in this report, and several issues of primary importance to materials accountancy and IAEA verifications have been examined. We have calculated detection sensitivities for abrupt and protracted diversions of plutonium assuming a single materials balance area for all processing areas. To help achieve optimal use of limited IAEA inspection resources, we have calculated sampling plans for attributes/variables verification. In addition, we have demonstrated the usefulness of calculating σ/sub (MUF-D)/ and detection probabilities corresponding to specified material-loss scenarios and resource allocations. The data developed and the analyses performed during this study can assist both the facility operator and the IAEA in formulating necessary safeguards approaches and verification procedures to implement international safeguards for special nuclear materials

  8. Analysis of mixed oxide fuel loaded cores in the heavy water reactor FUGEN

    International Nuclear Information System (INIS)

    Ohtani, Tsukasa; Iijima, Takashi; Shiratori, Yoshitake

    2003-01-01

    Uranium-plutonium mixed oxide (MOX) fuel cores in the heavy reactor, FUGEN, were analyzed using the Advanced Thermal Reactor (ATR) type core design code system WIMS-ATR/POLESTAR and the accuracy of this code system also has been evaluated by means of operational data through the 34 burnup cycles and on-site γ-scanning data. The root mean square errors of calculated thermal neutron flux distributions were less than 5% compared with the power calibration monitor traverse data. The root mean square error of calculated power distributions was less than 4% compared with the γ-scanning data. The root mean square error of calculated burnup distributions was less than 3% compared with the γ-scanning data. The averaged effective multiplication factor was 1.000 and its standard deviation was 0.002. The calculation accuracy of void reactivity coefficient was ±3x10 -5 Δk/k% void for the equilibrium cores. The calculation accuracy of power coefficient was ±1.5 x 10 -5 Δk/k/%power. The accuracy of ATR type core design code system was enough for the core management in the Fugen Nuclear Power Station. (author)

  9. Calculational assessment of critical experiments with mixed oxide fuel pin arrays moderated by organic solution

    International Nuclear Information System (INIS)

    Smolen, G.R.

    1987-01-01

    Critical experiments have been conducted with organic-moderated mixed oxide (MOX) fuel pin assemblies at the Pacific Northwest Laboratory (PNL) Critical Mass Laboratory (CML). These experiments are part of a joint exchange program between the United States Department of Energy (USDOE) and the Power Reactor and Nuclear Fuel Development Corporation (PNC) of Japan in the area of criticality data development. The purpose of these experiments is to benchmark computer codes and cross-section libraries and to assess the reactivity difference between systems moderated by water and those moderated by an organic solution. Past studies have indicated that some organic mixtures may be better moderators than water. This topic is of particular importance to the criticality safety of fuel processing plants where fissile material is dissolved in organic solutions during the solvent extraction process. In the past, it has been assumed that the codes and libraries benchmarked with water-moderated experiments were adequate when performing design and licensing studies of organic-moderated systems. Calculations presented in this paper indicated that the SCALE code system and the 27-energy-group cross-section accurately compute k-effectives for organic moderated MOX fuel-pin assemblies. Furthermore, the reactivity of an organic solution with a 32-vol-% TBP/68-vol-% NPH mixture in a heterogeneous configuration is the same, for practical purposes, as water. 5 refs

  10. Co2 Effect on the Catalytic Behavior of Alumina Supported Mixed Oxides

    International Nuclear Information System (INIS)

    Aouissi, A.; Aldhayan, D.; Mahdjoubi, H.A.

    2005-01-01

    The industrial catalysts for the reforming reactions suffer from coke which accelerates their deactivation. One of the remedy is to adjust the partial pressure of hydrogen. This work is focused on the work of CO2 on the total conversion of n-heptane and on its cyclization reaction into cyclohexane. The tests were carried out over a series of bifunctional catalysts constituted of mixed oxides supported on alumina. The catalysts, which are prepared by co-precipitation method, were characterized by means of atomic absorption spectroscopy and Fourier-transformed infrared spectroscopy (FTIR). Catalytic tests were carried out with and without carbon dioxide under atmospheric pressure. Results indicate that carbon dioxide influences the total activity of the catalysts and selectivity to form cyclohexane. So that, at 250C, the total conversion was high but the cyclohexane selectivity was low. In the range 250C-450C, results indicate an increase of both conversion and selectivity due to temperature increase, but fast deactivation was observed due to coke formation which can be removed by CO2 at higher temperatures. (author)

  11. Advanced oxidation and reduction processes: Closed-loop applications for mixed waste

    International Nuclear Information System (INIS)

    Coogan, J.J.; Tennant, R.A.; Rosocha, L.A.; Wantuck, P.J.

    1993-01-01

    At Los Alamos we are engaged in applying innovative oxidation and reduction technologies to the destruction of hazardous organics. Non thermal plasmas and relativistic electron-beams both involve the generation of free radicals and are applicable to a wide variety of mixed waste as closed-loop designs can be easily engineered. Silent discharge plasmas (SDP), long used for the generation of ozone, have been demonstrated in the laboratory to be effective in destroying hazardous organic compounds and offer an altemative to existing post-incineration and off-gas treatments. SDP generates very energetic electrons which efficiently create reactive free radicals, without adding the enthalpy associated with very high gas temperatures. A SDP cell has been used as a second stage to a LANL designed, packed-bed reactor (PBR) and has demonstrated DREs as high as 99.9999% for a variety of combustible liquid and gas-based waste streams containing scintillation fluids, nitrates, PCB surrogates, and both chlorinated and fluorinated solvents. Radiolytic treatment of waste using electron-beams and/or bremsstrahlung can be applied to a wide range of waste media (liquids, sludges, and solids). The efficacy and economy of these systems has been demonstrated for aqueous waste through both laboratory and pilot scale studies. We win present recent experimental and theoretical results for systems using stand alone SDP, combined PBR/SDP, and electron-beam treatment methods

  12. Survey of Worldwide Light Water Reactor Experience with Mixed Uranium-Plutonium Oxide Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Cowell, B.S.; Fisher, S.E.

    1999-02-01

    The US and the Former Soviet Union (FSU) have recently declared quantities of weapons materials, including weapons-grade (WG) plutonium, excess to strategic requirements. One of the leading candidates for the disposition of excess WG plutonium is irradiation in light water reactors (LWRs) as mixed uranium-plutonium oxide (MOX) fuel. A description of the MOX fuel fabrication techniques in worldwide use is presented. A comprehensive examination of the domestic MOX experience in US reactors obtained during the 1960s, 1970s, and early 1980s is also presented. This experience is described by manufacturer and is also categorized by the reactor facility that irradiated the MOX fuel. A limited summary of the international experience with MOX fuels is also presented. A review of MOX fuel and its performance is conducted in view of the special considerations associated with the disposition of WG plutonium. Based on the available information, it appears that adoption of foreign commercial MOX technology from one of the successful MOX fuel vendors will minimize the technical risks to the overall mission. The conclusion is made that the existing MOX fuel experience base suggests that disposition of excess weapons plutonium through irradiation in LWRs is a technically attractive option.

  13. Structural Investigation of (U0.7Pu0.3)O2-x Mixed Oxides.

    Science.gov (United States)

    Vigier, Jean-François; Martin, Philippe M; Martel, Laura; Prieur, Damien; Scheinost, Andreas C; Somers, Joseph

    2015-06-01

    Uranium-plutonium mixed oxide containing 30% of plutonium is a candidate fuel for several fast neutron and accelerator driven reactor systems. In this work, a detailed structural investigation on sol-gel synthesized stoichiometric U0.7Pu0.3O2.00 and substoichiometric U0.7Pu0.3O2-x, using X-ray diffraction (XRD), oxygen 17 magic angle spinning nuclear magnetic resonance ((17)O MAS NMR) and X-ray absorption spectroscopy is described. As observed by XRD, the stoichiometric U0.7Pu0.3O2.00 is monophasic with a lattice parameter in good agreement with Vegard's law, while the substoichiometric U0.7Pu0.3O2-x material is biphasic. Solid solution ideality in terms of a random distribution of metal atoms is proven for U0.7Pu0.3O2.00 with (17)O MAS NMR. X-ray absorption near-edge structure (XANES) spectroscopy shows the presence of plutonium(III) in U0.7Pu0.3O2-x. Extended X-ray absorption fine-structure (EXAFS) spectroscopy indicates a similar local structure around both cations, and comparison with XRD indicates a close similarity between uranium and plutonium local structures and the long-range ordering.

  14. Synthesis and Characterization of K-Ta Mixed Oxides for Hydrogen Generation in Photocatalysis

    Directory of Open Access Journals (Sweden)

    Beata Zielińska

    2012-01-01

    Full Text Available K-Ta mixed oxides photocatalysts have been prepared by impregnation followed by calcination. The influence of the reaction temperature (450°C–900°C on the phase formation, crystal morphology, and photocatalytic activity in hydrogen generation of the produced materials was investigated. The detailed analysis has revealed that all products exhibit high crystallinity and irregular structure. Moreover, two different crystal structures of potassium tantalates such as KTaO3 and K2Ta4O11 were obtained. It was also found that the sample composed of KTaO3 and traces of unreacted Ta2O5 (annealed at 600°C exhibits the highest activity in the reaction of photocatalytic hydrogen generation. The crystallographic phases, optical and vibronic properties were examined by X-ray diffraction (XRD and diffuse reflectance (DR UV-vis and resonance Raman spectroscopic methods, respectively. Morphology and chemical composition of the produced samples were studied using a high-resolution transmission electron microscope (HR-TEM and an energy dispersive X-ray spectrometer (EDX as its mode.

  15. Integrated demonstration of molten salt oxidation with salt recycle for mixed waste treatment

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, P.C.

    1997-11-01

    Molten Salt Oxidation (MSO) is a thermal, nonflame process that has the inherent capability of completely destroying organic constituents of mixed wastes, hazardous wastes, and energetic materials while retaining inorganic and radioactive constituents in the salt. For this reason, MSO is considered a promising alternative to incineration for the treatment of a variety of organic wastes. Lawrence Livermore National Laboratory (LLNL) has prepared a facility and constructed an integrated pilot-scale MSO treatment system in which tests and demonstrations are performed under carefully controlled (experimental) conditions. The system consists of a MSO processor with dedicated off-gas treatment, a salt recycle system, feed preparation equipment, and equipment for preparing ceramic final waste forms. This integrated system was designed and engineered based on laboratory experience with a smaller engineering-scale reactor unit and extensive laboratory development on salt recycle and final forms preparation. In this paper we present design and engineering details of the system and discuss its capabilities as well as preliminary process demonstration data. A primary purpose of these demonstrations is identification of the most suitable waste streams and waste types for MSO treatment.

  16. Integrated demonstration of molten salt oxidation with salt recycle for mixed waste treatment

    International Nuclear Information System (INIS)

    Hsu, P.C.

    1997-01-01

    Molten Salt Oxidation (MSO) is a thermal, nonflame process that has the inherent capability of completely destroying organic constituents of mixed wastes, hazardous wastes, and energetic materials while retaining inorganic and radioactive constituents in the salt. For this reason, MSO is considered a promising alternative to incineration for the treatment of a variety of organic wastes. Lawrence Livermore National Laboratory (LLNL) has prepared a facility and constructed an integrated pilot-scale MSO treatment system in which tests and demonstrations are performed under carefully controlled (experimental) conditions. The system consists of a MSO processor with dedicated off-gas treatment, a salt recycle system, feed preparation equipment, and equipment for preparing ceramic final waste forms. This integrated system was designed and engineered based on laboratory experience with a smaller engineering-scale reactor unit and extensive laboratory development on salt recycle and final forms preparation. In this paper we present design and engineering details of the system and discuss its capabilities as well as preliminary process demonstration data. A primary purpose of these demonstrations is identification of the most suitable waste streams and waste types for MSO treatment

  17. Safety issues in fabricating mixed oxide fuel using surplus weapons plutonium

    International Nuclear Information System (INIS)

    Buksa, J.; Badwan, F.; Barr, M.; Motley, F.

    1998-07-01

    This paper presents an assessment of the safety issues and implications of fabricating mixed oxide (MOX) fuel using surplus weapons plutonium. The basis for this assessment is the research done at Los Alamos National Laboratory (LANL) in identifying and resolving the technical issues surrounding the production of PuO 2 feed, removal of gallium from the PuO 2 feed, the fabrication of test fuel, and the work done at the LANL plutonium processing facility. The use of plutonium in MOX fuel has been successfully demonstrated in Europe, where the experience has been almost exclusively with plutonium separated from commercial spent nuclear fuel. This experience in safely operating MOX fuel fabrication facilities directly applies to the fabrication and irradiation of MOX fuel made from surplus weapons plutonium. Consequently, this paper focuses on the technical difference between plutonium from surplus weapons, and light-water reactor recycled plutonium. Preliminary assessments and research lead to the conclusion that no new process or product safety concerns will arise from using surplus weapons plutonium in MOX fuel

  18. Performance of IN-706 and PE-16 cladding in mixed-oxide fuel pins

    International Nuclear Information System (INIS)

    Makenas, B.J.; Lawrence, L.A.; Jensen, B.W.

    1982-05-01

    Iron-nickel base, precipitation-strengthened alloys, IN-706 and PE-16, advanced alloy cladding considered for breeder reactor applications, were irradiated in mixed-oxide fuel pins in the HEDL-P-60 subassembly in EBR-II. Initial selection of candidate advanced alloys was done using only nonfueled materials test results. However, to establish the performance characteristics of the candidate cladding alloys, i.e., dimensional stability and structural integrity under conditions of high neutron flux, elevated temperature, and applied stress, it was necessary to irradiate fuel pins under typical operating conditions. Fuel pins were clad with solution treated IN-706 and PE-16 and irradiated to peak fluences of 6.1 x 10 22 n/cm 2 (E > .1 MeV) and 8.8 x 10 22 n/cm 2 (E > .1 MeV) respectively. Fabrication and operating parameters for the fuel pins with the advanced cladding alloy candidates are summarized. Irradiation of HEDL-P-60 was interrupted with the breach of a pin with IN-706 cladding at 5.1 at % and the test was terminated with cladding breach in a pin with PE-16 cladding at 7.6 at %

  19. Synthesis and characterization of Tin / Titanium mixed oxide nanoparticles doped with lanthanide for biomarking

    International Nuclear Information System (INIS)

    Paganini, Paula Pinheiro

    2012-01-01

    This work presents the synthesis, characterization and photo luminescent study of tin and titanium mixed oxide nanoparticles doped with europium, terbium and neodymium to be used with luminescent markers on biological systems. The syntheses were done by co-precipitation, protein sol-gel and Pechini methods and the nanoparticles were characterized by infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, X-ray diffraction and X-ray absorption spectroscopy. The photo luminescent properties studies were conducted for luminophores doped with europium, terbium and neodymium synthesized by coprecipitation method. For luminophore doped with europium it was possible to calculate the intensity parameters and quantum yield and it showed satisfactory results. In the case of biological system marking it was necessary the functionalization of these particles to allow them to bind to the biological part to be studied. So the nanoparticles were functionalized by microwave and Stöber methods and characterized by infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction obtaining qualitative response of functionalization efficacy. The ninhydrin spectroscopic method was used for quantification of luminophores functionalization. The photo luminescent studies of functionalized particles demonstrate the potential applying of these luminophores as luminescent markers. (author)

  20. Characterization of aerosols from industrial fabrication of mixed-oxide nuclear reactor fuels

    International Nuclear Information System (INIS)

    Hoover, M.D.; Newton, G.J.; Yeh, H.C.; Edison, A.F.

    1983-01-01

    Information on the characteristics of aerosols in three industrial facilities during fabrication of uranium and plutonium mixed-oxide reactor fuels is summarized. Aerosol characterization included measurements of air concentrations particle size distributions, particle morphology, aerosol electrostatic charge characteristics and in vitro dissolution. These were the physicochemical properties considered most relevant to evaluating the consequences of potential accidents wherein aerosols might be released from their normal containment and inhaled by workers. Alpha radioactivity concentrations in air ranged about 1-15,000 nCi/l, depending on the fabrication step and facility. Particle size distributions were approximately log-normal, and activity median aerodynamic diameter (AMAD) ranged 1.6-3.5 μm, with a geometric standard deviation of about 1.6. Electron microscopy indicated that particles were irregularly shaped agglomerates. In vitro dissolution half-times were on the order of years, with some dependence on aerosol size, temperature history and fabrication step. No unique potential exposure conditions were found in any step of the fabrication processes

  1. Development of probabilistic safety assessment method for mixed oxide fuel fabrication facilities

    International Nuclear Information System (INIS)

    Tamaki, Hitoshi; Yoshida, Kazuo; Watanabe, Norio; Muramatsu, Ken

    2006-01-01

    A Probabilistic Safety Assessment (PSA) procedure for Mixed Oxide (MOX) fuel fabrication facilities was developed. The procedure is a 'two-part five-step' approach which takes characteristics of MOX fuel fabrication facilities into consideration. In the first part, so-called preliminary PSA, the hazard analysis approach was applied, which consists of two analysis steps: Functional Failure Modes and Effects Analysis (FFMEA) and Risk Matrix Analysis. The FFMEA analyzes a variety of functions of equipment composing the facility to identify potential abnormal events exhaustively. In the Risk Matrix Analysis, these potential events are screened to select abnormal events as candidates to be analyzed in the second part, using two-dimensional matrix based on the likelihood evaluated by probabilistic index method and maximum unmitigated radioactive release calculated by the Five-Factor Formula. For the selected abnormal events, in the second part, so-called detailed PSA, accident sequences, their occurrence frequencies and consequences are analyzed. These three analysis steps correspond to PSA procedure for nuclear power plant. The applicability of the PSA procedure was demonstrated through the trial application to model plant of MOX fuel fabrication facility. (author)

  2. Mesoporous mixed metal oxides derived from P123-templated Mg-Al layered double hydroxides

    International Nuclear Information System (INIS)

    Wang Jun; Zhou Jideng; Li Zhanshuang; He Yang; Lin Shuangshuang; Liu Qi; Zhang Milin; Jiang Zhaohua

    2010-01-01

    We report the preparation of mesoporous mixed metal oxides (MMOs) through a soft template method. Different amounts of P123 were used as structure directing agent to synthesize P123-templated Mg-Al layered double hydroxides (LDHs). After calcination of as-synthesized LDHs at 500 o C, the ordered mesopores were obtained by removal of P123. The mesoporous Mg-Al MMOs fabricated by using 2 wt% P123 exhibited a high specific surface area of 108.1 m 2 /g, and wide distribution of pore size (2-18 nm). An investigation of the 'memory effect' of the mesoporous MMOs revealed that they were successfully reconstructed to ibuprofen intercalated LDHs having different gallery heights, which indicated different intercalation capacities. Due to their mesoporosity these unique MMOs have particular potential as drug or catalyst carriers. - Graphical abstract: Ordered mesoporous Mg-Al MMOs can be obtained through the calcination of P123-templated Mg-Al-CO 3 LDHs. The pore diameter is 2.2 nm. At the presence of ibuprofen, the Mg-Al MMOs can recover to Mg-Al-IBU LDHs, based on its 'remember effect'. Display Omitted

  3. Whole-body fat oxidation determined by graded exercise and indirect calorimetry: a role for muscle oxidative capacity?

    DEFF Research Database (Denmark)

    Nordby, P; Saltin, B; Helge, J W

    2006-01-01

    During whole-body exercise, peak fat oxidation occurs at a moderate intensity. This study investigated whole-body peak fat oxidation in untrained and trained subjects, and the presence of a relation between skeletal muscle oxidative enzyme activity and whole-body peak fat oxidation. Healthy male...... subjects were recruited and categorized into an untrained (N=8, VO(2max) 3.5+/-0.1 L/min) and a trained (N=8, VO(2max) 4.6+/-0.2 L/min) group. Subjects performed a graded exercise test commencing at 60 W for 8 min followed by 35 W increments every 3 min. On a separate day, muscle biopsies were obtained...... oxidation was determined. The body composition was determined by DEXA. Whole-body peak fat oxidation (250+/-25 and 462+/-33 mg/min) was higher (Ptrained compared with untrained subjects, respectively. Muscle...

  4. Ambient-temperature NO oxidation over amorphous CrOx-ZrO2 mixed oxide catalysts: Significant promoting effect of ZrO2

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Aiyong; Guo, Yanglong; Gao, Feng; Peden, Charles H. F.

    2017-03-01

    Three series of Cr-based mixed oxides (Cr-Co, Cr-Fe, and Cr-Ni oxides) with high specific surface areas and amorphous textures are synthesized using a novel sol-gel method. These mixed oxides, in comparison to their pure metal oxide (CrOx, Co3O4, FeOx and NiO) counterparts, display enhanced performance for catalytic oxidation of low-concentration NO at room temperature. Over best performing catalysts, 100% NO conversion can be maintained up to 30 h of operation at a high space velocity of 45,000 ml g-1 h-1. The amorphous structure is found to be critical for these catalysts to maintain high activity and durability. Cr/M (M=Co, Fe and Ni) molar ratio, nitrate precursor decomposition temperature and catalyst calcination temperature are important criteria for the synthesis of the highly active catalysts. This work was supported by National Basic Research Program of China (2013CB933200), National Natural Science Foundation of China (21577035, 21577034), Commission of Science and Technology of Shanghai Municipality (15DZ1205305) and 111 Project (B08021). Aiyong Wang gratefully acknowledges the China Scholarship Council for the Joint-Training Scholarship Program with the Pacific Northwest National Laboratory (PNNL). PNNL is operated for the U.S. Department of Energy (DOE) by Battelle. FG and CHFP are supported by the U.S. DOE/Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Office.

  5. Roles of Bulk and Surface Chemistry in the Oxygen Exchange Kinetics and Related Properties of Mixed Conducting Perovskite Oxide Electrodes

    Directory of Open Access Journals (Sweden)

    Nicola H. Perry

    2016-10-01

    Full Text Available Mixed conducting perovskite oxides and related structures serving as electrodes for electrochemical oxygen incorporation and evolution in solid oxide fuel and electrolysis cells, respectively, play a significant role in determining the cell efficiency and lifetime. Desired improvements in catalytic activity for rapid surface oxygen exchange, fast bulk transport (electronic and ionic, and thermo-chemo-mechanical stability of oxygen electrodes will require increased understanding of the impact of both bulk and surface chemistry on these properties. This review highlights selected work at the International Institute for Carbon-Neutral Energy Research (I2CNER, Kyushu University, set in the context of work in the broader community, aiming to characterize and understand relationships between bulk and surface composition and oxygen electrode performance. Insights into aspects of bulk point defect chemistry, electronic structure, crystal structure, and cation choice that impact carrier concentrations and mobilities, surface exchange kinetics, and chemical expansion coefficients are emerging. At the same time, an understanding of the relationship between bulk and surface chemistry is being developed that may assist design of electrodes with more robust surface chemistries, e.g., impurity tolerance or limited surface segregation. Ion scattering techniques (e.g., secondary ion mass spectrometry, SIMS, or low energy ion scattering spectroscopy, LEIS with high surface sensitivity and increasing lateral resolution are proving useful for measuring surface exchange kinetics, diffusivity, and corresponding outer monolayer chemistry of electrodes exposed to typical operating conditions. Beyond consideration of chemical composition, the use of strain and/or a high density of active interfaces also show promise for enhancing performance.

  6. METHODS FOR DETERMINING AGITATOR MIXING REQUIREMENTS FOR A MIXING & SAMPLING FACILITY TO FEED WTP (WASTE TREATMENT PLANT)

    Energy Technology Data Exchange (ETDEWEB)

    GRIFFIN PW

    2009-08-27

    The following report is a summary of work conducted to evaluate the ability of existing correlative techniques and alternative methods to accurately estimate impeller speed and power requirements for mechanical mixers proposed for use in a mixing and sampling facility (MSF). The proposed facility would accept high level waste sludges from Hanford double-shell tanks and feed uniformly mixed high level waste to the Waste Treatment Plant. Numerous methods are evaluated and discussed, and resulting recommendations provided.

  7. METHODS FOR DETERMINING AGITATOR MIXING REQUIREMENTS FOR A MIXING and SAMPLING FACILITY TO FEED WTP (WASTE TREATMENT PLANT)

    International Nuclear Information System (INIS)

    Griffin, P.W.

    2009-01-01

    The following report is a summary of work conducted to evaluate the ability of existing correlative techniques and alternative methods to accurately estimate impeller speed and power requirements for mechanical mixers proposed for use in a mixing and sampling facility (MSF). The proposed facility would accept high level waste sludges from Hanford double-shell tanks and feed uniformly mixed high level waste to the Waste Treatment Plant. Numerous methods are evaluated and discussed, and resulting recommendations provided.

  8. Synthesis of Mixed Cu/Ce Oxide Nanoparticles by the Oil-in-Water Microemulsion Reaction Method

    Directory of Open Access Journals (Sweden)

    Kelly Pemartin-Biernath

    2016-06-01

    Full Text Available Cerium oxide and mixed Cu/Ce oxide nanoparticles were prepared by the oil-in-water (O/W microemulsion reaction method in mild conditions. The Cu/Ce molar ratio was varied between 0/100 and 50/50. According to X-ray diffraction (XRD, below 30/70 Cu/Ce molar ratio, the materials presented a single phase consistent with cubic fluorite CeO2. However, above Cu/Ce molar ratio 30/70, an excess monoclinic CuO phase in coexistence with the predominant Cu/Ce mixed oxide was detected by XRD and High-Resolution Transmission Electron Microscopy (HRTEM. Raman spectroscopy showed that oxygen vacancies increased significantly as the Cu content was increased. Band gap (Eg was investigated as a function of the Cu/Ce molar ratio, resulting in values from 2.91 eV for CeO2 to 2.32 eV for the mixed oxide with 30/70 Cu/Ce molar ratio. These results indicate that below 30/70 Cu/Ce molar ratio, Cu2+ is at least partially incorporated into the ceria lattice and very well dispersed in general. In addition, the photodegradation of Indigo Carmine dye under visible light irradiation was explored for selected samples; it was shown that these materials can remove such contaminants, either by adsorption and/or photodegradation. The results obtained will encourage investigation into the optical and photocatalytic properties of these mixed oxides, for widening their potential applications.

  9. Oxidative stabilization of mixed mayonnaises made with linseed oil and saturated medium-chain triglyceride oil

    NARCIS (Netherlands)

    Raudsepp, P.; Brüggemann, D.A.; Lenferink, Aufrid T.M.; Otto, Cornelis; Andersen, M.L.

    2014-01-01

    Mayonnaises, made with either saturated medium chain triglyceride (MCT) oil or unsaturated purified linseed oil (LSO), were mixed. Raman confocal microspectrometry demonstrated that lipid droplets in mixed mayonnaise remained intact containing either MCT oil or LSO. Peroxide formation during storage

  10. Standard test methods for chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade mixed oxides ((U, Pu)O2)

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 These test methods cover procedures for the chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade mixed oxides, (U, Pu)O2, powders and pellets to determine compliance with specifications. 1.2 The analytical procedures appear in the following order: Sections Uranium in the Presence of Pu by Potentiometric Titration Plutonium by Controlled-Potential Coulometry Plutonium by Amperometric Titration with Iron (II) Nitrogen by Distillation Spectrophotometry Using Nessler Reagent 7 to 14 Carbon (Total) by Direct Combustion-Thermal Conductivity 15 to 26 Total Chlorine and Fluorine by Pyrohydrolysis 27 to 34 Sulfur by Distillation-Spectrophotometry 35 to 43 Moisture by the Coulometric, Electrolytic Moisture Analyzer 44 to 51 Isotopic Composition by Mass Spectrometry Rare Earths by Copper Spark Spectroscopy 52 to 59 Trace Impurities by Carrier Distillation Spectroscopy 60 to 69 Impurities by Spark-Source Mass Spectrography 70 to 76 Total Gas in Reactor-Grade Mixed Dioxide P...

  11. The effect of oxidant and the non-oxidant alteration of cellular thiol concentration on the formation of protein mixed-disulfides in HEK 293 cells.

    Directory of Open Access Journals (Sweden)

    Jasen Lee Gilge

    Full Text Available Cellular molecules possess various mechanisms in responding to oxidant stress. In terms of protein responses, protein S-glutathionylation is a unique post-translational modification of protein reactive cysteines forming disulfides with glutathione molecules. This modification has been proposed to play roles in antioxidant, regulatory and signaling in cells under oxidant stress. Recently, the increased level of protein S-glutathionylation has been linked with the development of diseases. In this report, specific S-glutathionylated proteins were demonstrated in human embryonic kidney 293 cells treated with two different oxidative reagents: diamide and hydrogen peroxide. Diamide is a chemical oxidizing agent whereas hydrogen peroxide is a physiological oxidant. Under the experimental conditions, these two oxidants decreased glutathione concentration without toxicity. S-glutathionylated proteins were detected by immunoblotting and glutathione concentrations were determined by high performance liquid chromatography. We further show the effect of alteration of the cellular thiol pool on the amount of protein S-glutathionylation in oxidant-treated cells. Cellular thiol concentrations were altered either by a specific way using buthionine sulfoximine, a specific inhibitor of glutathione biosynthesis or by a non-specific way, incubating cells in cystine-methionine deficient media. Cells only treated with either buthionine sulfoximine or cystine-methionine deficient media did not induce protein S-glutathionylation, even though both conditions decreased 65% of cellular glutathione. Moreover, the amount of protein S-glutathionylation under both conditions in the presence of oxidants was not altered when compared to the amount observed in regular media with oxidants present. Protein S-glutathionylation is a dynamic reaction which depends on the rate of adding and removing glutathione. Phenylarsine oxide, which specifically forms a covalent adduct with

  12. Urogenital Chlamydia trachomatis infections among ethnic groups in Paramaribo, Suriname; determinants and ethnic sexual mixing patterns.

    Directory of Open Access Journals (Sweden)

    Jannie J van der Helm

    Full Text Available BACKGROUND: Little is known about the epidemiology of urogenital Chlamydia trachomatis infection (chlamydia in Suriname. Suriname is a society composed of many ethnic groups, such as Creoles, Maroons, Hindustani, Javanese, Chinese, Caucasians, and indigenous Amerindians. We estimated determinants for chlamydia, including the role of ethnicity, and identified transmission patterns and ethnic sexual networks among clients of two clinics in Paramaribo, Suriname. METHODS: Participants were recruited at two sites a sexually transmitted infections (STI clinic and a family planning (FP clinic in Paramaribo. Urine samples from men and nurse-collected vaginal swabs were obtained for nucleic acid amplification testing. Logistic regression analysis was used to identify determinants of chlamydia. Multilocus sequence typing (MLST was performed to genotype C. trachomatis. To identify transmission patterns and sexual networks, a minimum spanning tree was created, using full MLST profiles. Clusters in the minimum spanning tree were compared for ethnic composition. RESULTS: Between March 2008 and July 2010, 415 men and 274 women were included at the STI clinic and 819 women at the FP clinic. Overall chlamydia prevalence was 15% (224/1508. Age, ethnicity, and recruitment site were significantly associated with chlamydia in multivariable analysis. Participants of Creole and Javanese ethnicity were more frequently infected with urogenital chlamydia. Although sexual mixing with other ethnic groups did differ significantly per ethnicity, this mixing was not independently significantly associated with chlamydia. We typed 170 C. trachomatis-positive samples (76% and identified three large C. trachomatis clusters. Although the proportion from various ethnic groups differed significantly between the clusters (P = 0.003, all five major ethnic groups were represented in all three clusters. CONCLUSION: Chlamydia prevalence in Suriname is high and targeted prevention

  13. Development of ORIGEN libraries for mixed oxide (MOX) fuel assembly designs

    Energy Technology Data Exchange (ETDEWEB)

    Mertyurek, Ugur, E-mail: mertyureku@ornl.gov; Gauld, Ian C., E-mail: gauldi@ornl.gov

    2016-02-15

    Highlights: • ORIGEN MOX library generation process is described. • SCALE burnup calculations are validated against measured MOX fuel samples from the MALIBU program. • ORIGEN MOX libraries are verified using the OECD Phase IV-B benchmark. • There is good agreement for calculated-to-measured isotopic distributions. - Abstract: ORIGEN cross section libraries for reactor-grade mixed oxide (MOX) fuel assembly designs have been developed to provide fast and accurate depletion calculations to predict nuclide inventories, radiation sources and thermal decay heat information needed in safety evaluations and safeguards verification measurements of spent nuclear fuel. These ORIGEN libraries are generated using two-dimensional lattice physics assembly models that include enrichment zoning and cross section data based on ENDF/B-VII.0 evaluations. Using the SCALE depletion sequence, burnup-dependent cross sections are created for selected commercial reactor assembly designs and a representative range of reactor operating conditions, fuel enrichments, and fuel burnup. The burnup dependent cross sections are then interpolated to provide problem-dependent cross sections for ORIGEN, avoiding the need for time-consuming lattice physics calculations. The ORIGEN libraries for MOX assembly designs are validated against destructive radiochemical assay measurements of MOX fuel from the MALIBU international experimental program. This program included measurements of MOX fuel from a 15 × 15 pressurized water reactor assembly and a 9 × 9 boiling water reactor assembly. The ORIGEN MOX libraries are also compared against detailed assembly calculations from the Phase IV-B numerical MOX fuel burnup credit benchmark coordinated by the Nuclear Energy Agency within the Organization for Economic Cooperation and Development. The nuclide compositions calculated by ORIGEN using the MOX libraries are shown to be in good agreement with other physics codes and with experimental data.

  14. Performance of fast reactor mixed-oxide fuels pins during extended overpower transients

    International Nuclear Information System (INIS)

    Tsai, H.; Neimark, L.A.; Asaga, T.; Shikakura, S.

    1991-02-01

    The Operational Reliability Testing (ORT) program, a collaborative effort between the US Department of Energy and the Power Reactor and Nuclear Fuel Development Corp. (PNC) of Japan, was initiated in 1982 to investigate the behavior of mixed-oxide fuel pin under various slow-ramp transient and duty-cycle conditions. In the first phase of the program, a series of four extended overpower transient tests, with severity sufficient to challenge the pin cladding integrity, was conducted. The objectives of the designated TOPI-1A through -1D tests were to establish the cladding breaching threshold and mechanisms, and investigate the thermal and mechanical effects of the transient on pin behavior. The tests were conducted in EBR-2, a normally steady-state reactor. The modes of transient operation in EBR-2 were described in a previous paper. Two ramp rates, 0.1%/s and 10%/s, were selected to provide a comparison of ramp-rate effects on fuel behavior. The test pins chosen for the series covered a range of design and pre-test irradiation parameters. In the first test (1A), all pins maintained their cladding integrity during the 0.1%/s ramp to 60% peak overpower. Fuel pins with aggressive designs, i.e., high fuel- smear density and/or thin cladding, were, therefore, included in the follow-up 1B and 1C tests to enhance the likelihood of achieving cladding breaching. In the meantime, a higher pin overpower capability, to greater than 100%, was established by increasing the reactor power limit from 62.5 to 75 MWt. In this paper, the significant results of the 1B and 1C tests are presented. 4 refs., 5 figs., 1 tab

  15. Lithium Storage in Microstructures of Amorphous Mixed-Valence Vanadium Oxide as Anode Materials.

    Science.gov (United States)

    Zhao, Di; Zheng, Lirong; Xiao, Ying; Wang, Xia; Cao, Minhua

    2015-07-08

    Constructing three-dimensional (3 D) nanostructures with excellent structural stability is an important approach for realizing high-rate capability and a high capacity of the electrode materials in lithium-ion batteries (LIBs). Herein, we report the synthesis of hydrangea-like amorphous mixed-valence VOx microspheres (a-VOx MSs) through a facile solvothermal method followed by controlled calcination. The resultant hydrangea-like a-VOx MSs are composed of intercrossed nanosheets and, thus, construct a 3 D network structure. Upon evaluation as an anode material for LIBs, the a-VOx MSs show excellent lithium-storage performance in terms of high capacity, good rate capability, and long-term stability upon extended cycling. Specifically, they exhibit very stable cycling behavior with a highly reversible capacity of 1050 mA h g(-1) at a rate of 0.1 A g(-1) after 140 cycles. They also show excellent rate capability, with a capacity of 390 mA h g(-1) at a rate as high as 10 A g(-1) . Detailed investigations on the morphological and structural changes of the a-VOx MSs upon cycling demonstrated that the a-VOx MSs went through modification of the local VO coordinations accompanied with the formation of a higher oxidation state of V, but still with an amorphous state throughout the whole discharge/charge process. Moreover, the a-VOx MSs can buffer huge volumetric changes during the insertion/extraction process, and at the same time they remain intact even after 200 cycles of the charge/discharge process. Thus, these microspheres may be a promising anode material for LIBs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Preparation and characterization of vanadia-titania mixed oxide for immobilization of Serratia rubidaea CCT 5732 and Klebsiella marcescens bacteria

    International Nuclear Information System (INIS)

    Saragiotto Colpini, Leda Maria; Correia Goncalves, Regina A.; Goncalves, Jose Eduardo; Maieru Macedo Costa, Creusa

    2008-01-01

    Vanadia-titania mixed oxide was synthesized by sol-gel method and characterized by several techniques. Texturally, it is formed by mesopores and presents high-specific surface area and controlled porosity. Scanning electron microscopy revealed that vanadium is homogeneously distributed in the material. Structurally, it was possible to identify characteristic V=O stretching bands by IR. The analysis of X-ray diffraction showed that the material, particularly vanadium, is highly dispersed. Application experiments were carried out through the immobilization of Serratia rubidae CCT 5732 and Klebsiella marcescens bacteria by adsorption on the surface of mixed oxide. The micrographies revealed that the bacteria were adsorbed on the entire support, with average surface densities of 8.55 x 10 11 cells/m 2 (Serratia rubidae CCT 5732) and 3.40 x 10 11 cells/m 2 (K. marcescens)

  17. Calibration Tools for Measurement of Highly Enriched Uranium in Oxide and Mixed Uranium-Plutonium Oxide with a Passive-Active Neutron Drum Shuffler

    International Nuclear Information System (INIS)

    Mount, M; O'Connell, W; Cochran, C; Rinard, P

    2003-01-01

    Lawrence Livermore National Laboratory (LLNL) has completed an extensive effort to calibrate the LLNL passive-active neutron drum (PAN) shuffler (Canberra Model JCC-92) for accountability measurement of highly enriched uranium (HEU) oxide and HEU in mixed uranium-plutonium (U-Pu) oxide. Earlier papers described the PAN shuffler calibration over a range of item properties by standards measurements and an extensive series of detailed simulation calculations. With a single normalization factor, the simulations agree with the HEU oxide standards measurements to within ±1.2% at one standard deviation. Measurement errors on mixed U-Pu oxide samples are in the ±2% to ±10% range, or ±20 g for the smaller items. The purpose of this paper is to facilitate transfer of the LLNL procedure and calibration algorithms to external users who possess an identical, or equivalent, PAN shuffler. Steps include (1) measurement of HEU standards or working reference materials (WRMs); (2) MCNP simulation calculations for the standards or WRMs and a range of possible masses in the same containers; (3) a normalization of the calibration algorithms using the standard or WRM measurements to account for differences in the 252 Cf source strength, the delayed-neutron nuclear data, effects of the irradiation protocol, and detector efficiency; and (4) a verification of the simulation series trends against like LLNL results. Tools include EXCEL/Visual Basic programs which pre- and post-process the simulations, control the normalization, and embody the calibration algorithms

  18. Electrochemical properties of mixed conducting (La,M)(CoFe) oxide perovskites (M=3DSr, Ca, and Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Stevenson, J.W.; Armstrong, T.R.; Bates, J.L. [and others

    1996-04-01

    Electrical properties and oxygen permeation properties of solid mixed-conducting electrolytes (La,M)(CoFe) oxide perovskites (M=3DSr, Ca, and Ba) have been characterized. These materials are potentially useful as passive membranes to separate high purity oxygen from air and as the cathode in a fuel cell. Dilatometric linear expansion measurements were performed as a function of temperature and oxygen partial pressure to evaluate the stability.

  19. Intrinsic Halide Segregation at Nanometer Scale Determines the High Efficiency of Mixed Cation/Mixed Halide Perovskite Solar Cells.

    Science.gov (United States)

    Gratia, Paul; Grancini, Giulia; Audinot, Jean-Nicolas; Jeanbourquin, Xavier; Mosconi, Edoardo; Zimmermann, Iwan; Dowsett, David; Lee, Yonghui; Grätzel, Michael; De Angelis, Filippo; Sivula, Kevin; Wirtz, Tom; Nazeeruddin, Mohammad Khaja

    2016-12-14

    Compositional engineering of a mixed cation/mixed halide perovskite in the form of (FAPbI 3 ) 0.85 (MAPbBr 3 ) 0.15 is one of the most effective strategies to obtain record-efficiency perovskite solar cells. However, the perovskite self-organization upon crystallization and the final elemental distribution, which are paramount for device optimization, are still poorly understood. Here we map the nanoscale charge carrier and elemental distribution of mixed perovskite films yielding 20% efficient devices. Combining a novel in-house-developed high-resolution helium ion microscope coupled with a secondary ion mass spectrometer (HIM-SIMS) with Kelvin probe force microscopy (KPFM), we demonstrate that part of the mixed perovskite film intrinsically segregates into iodide-rich perovskite nanodomains on a length scale of up to a few hundred nanometers. Thus, the homogeneity of the film is disrupted, leading to a variation in the optical properties at the micrometer scale. Our results provide unprecedented understanding of the nanoscale perovskite composition.

  20. X-ray diffraction and microsampling techniques applied to the determination of the O/M ratio of irradiated oxides

    International Nuclear Information System (INIS)

    Trotabas, Maria.

    1980-05-01

    In order to understand the behavior of a mixed irradiated oxide in a fast neutron reactor, it is necessary to know the evolution of one of its principle parameters which is the O/M ratio. A method has been developed based on a double determination of reticular parameters; one after irradiation and the other after an oxidation-reduction heat treatment which brings the O/M ratio down to 2.00. A description is given of the X ray diffraction apparatus that was specially adapted for the examination of irradiated fuels and of the micro-sampling technique that enables spot determinations to be made according to the radius the sample [fr

  1. Using Aspen simulation package to determine solubility of mixed salts in TRU waste evaporator bottoms

    Energy Technology Data Exchange (ETDEWEB)

    Hatchell, J.L.

    1998-03-01

    Nitric acid from plutonium process waste is a candidate for waste minimization by recycling. Process simulation software packages, such as Aspen, are valuable tools to estimate how effective recovery processes can be, however, constants in equations of state for many ionic components are not in their data libraries. One option is to combine single salt solubility`s in the Aspen model for mixed salt system. Single salt solubilities were regressed in Aspen within 0.82 weight percent of literature values. These were combined into a single Aspen model and used in the mixed salt studies. A simulated nitric acid waste containing mixed aluminum, calcium, iron, magnesium and sodium nitrate was tested to determine points of solubility between 25 and 100 C. Only four of the modeled experimental conditions, at 50 C and 75 C, produced a saturated solution. While experimental results indicate that sodium nitrate is the first salt to crystallize out, the Aspen computer model shows that the most insoluble salt, magnesium nitrate, the first salt to crystallize. Possible double salt formation is actually taking place under experimental conditions, which is not captured by the Aspen model.

  2. DETERMINATION OF DIETARY FIBRE – THE INFLUENCE OF MILLING FRACTION AND MIXING PROCESS

    Directory of Open Access Journals (Sweden)

    Blaž FERJANČIČ

    2018-04-01

    Full Text Available Dietary fibre is an important constituent of a healthy diet, composed of non-digestible carbohydrates and lignin. Over the last decades dietary fibre has gained importance for human nutrition, due to its beneficial effects on health. In addition to classical enzyme-gravimetric methods, new methods for the determination of total, insoluble and soluble dietary fibres in foods have recently been developed, but have not yet been fully implemented for use. For the purpose of creating food composition databases and for food labelling, the classical AOAC 985.29 and 991.43 methods are still widely used. The methods are enzyme-gravimetric and therefore sensitive to enzyme kinetics. The aim of the study was to investigate the effect of milling fraction and mixing of the sample on dietary fibre content determined with the AOAC method 991.43. The results showed that milling fraction significantly influences the content of dietary fibre, especially in unprocessed or slightly processed cereals, the mixing acts synergistically with milling. According to the results it is proposed to mill the sample between 200 and 500 μm. For accurate determination of dietary fibre content, it is necessary to prepare the sample correctly, since the AOAC 991.43 method is, despite its robustness, sensitive during the sample preparation step.

  3. Storage and characterization of the hydrogen in mixed oxides on base of cerium-nickel and zirconium or the aluminium

    International Nuclear Information System (INIS)

    Debeusscher, S.

    2008-12-01

    The mixed oxides based on cerium-nickel and zirconium or aluminium are able to store large quantities of hydrogen, To determine nature, reactivity and properties of hydrogen species (spill-over, direct desorption), the solid were studied by different physicochemical techniques in the dried, calcined and partially reduced states: XRD, porosity, TGA, TPR, TPA, TPD, chemical titration and inelastic neutron scattering (INS). Solids are mainly meso-porous with a common pore size at 4 nm, They are constituted of CeO 2 phase, Ce-Ni or Ce-Ni-Zr solid solution and of Ni(OH) 2 in the dried state and NiO in the calcined state. The Ni species are in various environments and the strong interactions between the cations in solid solution and at different particles interface influence their reducibility and the creation of anionic vacancies. Activation in H 2 in temperature is determining for hydrogen storage in the solid while calcination step is not necessary. INS Analyses evidence that the hydrogen species inserted during treatment in H 2 are H + (OH - ), hydride H - and H * (metallic nickel) species, present in various chemical environments, in particular for hydride species. All kinds of hydrogen species participate to the reaction during the chemical titration in agreement with the proposed hydrogenation mechanism. The study of the adsorption of hydrogen shows that this step is fast and in quantity of the same order as that measured by chemical titration. The direct desorption of H 2 is very low, linked to the presence of hydrogen in interaction with metallic nickel (H *- .). Desorption of water is also observed, in parallel, corresponding to the elimination of groups. The hydride species are not desorbed. These various observations allow connecting hydrogen species properties with their localization in the structure and to model active sites. (author)

  4. Detection of liquid petroleum gas using mixed nanosized tungsten oxide-based thick-film semiconductor sensor.

    Science.gov (United States)

    Chaudhari, G N; Bende, A M; Bodade, A B; Patil, S S; Manorama, S V

    2006-03-15

    The thick-film semiconductor sensor for liquid petroleum gas (LPG) detection was fabricated using a mixed WO(3)-based sensor. We present the characterization of both their structural properties by means of XRD measurements and the electrical characteristics by using gas-sensing properties. The sensing characteristics such as sensitivity, working range, cross-sensitivity and response time were studied by using nanosized WO(3)-based mixed with different metal oxides (SnO(2), TiO(2) and In(2)O(3)) and doped with noble metals (Au, Pd and Pt). The WO(3)-based mixed with 5 wt.% In(2)O(3) and 0.5 wt.% Pd showed the higher sensing characteristic at low concentration of LPG sensor at an operating temperature 225 degrees C.

  5. Evaluation Parameter to Determine the Sharing of Electricity Production Mix in Malaysia

    International Nuclear Information System (INIS)

    Syirrazie Che Soh; Mohd Ashhar Khalid

    2011-01-01

    As Malaysia have various possible energy sources based on the fossil fuels and renewable energies, the optimization for the usage of the energy sources to produce electricity should be managed as good as possible. It should be managed based on the desired demand for electricity on distributed location and its activities. In Malaysia, the location is divided with the two categories of Off-grid System and On-Grid System. Thus, this paper discuss on the parameters that could be used to determine the sharing of electricity production mix to meet the electricity demand for a location in Malaysia with for both two types the grid system categories. (author)

  6. [A method for the determination of tartrazine in candies and pudding mixes (author's transl)].

    Science.gov (United States)

    Wisker, E; König, R; Feldheim, W

    1980-04-01

    The use of food additives is viewed increasingly from a critical point of view. In some countries, stronger regulations with limitations for the use of synthetic coal-tar dyes are planned or exist already. For that reason, a quantitative method for the determination of tartrazine (E 102) is needed for supervision of food quality. A method is described using as its steps extraction of the dyestuffs from the samples, chromatography on silicagel plates and automatically recorded densitometry. In candies amounts of up to 285 mg tartrazine/kg and in pudding mixes up to 1223 mg tartrazine/kg were found.

  7. A precise determination of the elektroweak mixing angle from semi-leptonic neutrino scattering

    International Nuclear Information System (INIS)

    Allaby, J.V.; Amaldi, U.; Barbiellini, G.; Baubillier, M.; Bergsma, F.; Capone, A.; Flegel, W.; Grancagnolo, F.; Lanceri, L.; Metcalf, M.; Nieuwenhuis, C.; Pain, R.; Panman, J.; Plunkett, R.; Winter, K.; Abt, I.; Aspiazu, J.; Bungener, A.; Buesser, F.W.; Gall, P.D.; Hebbeker, T.; Niebergall, F.; Schuett, P.; Staehelin, P.; Baroncelli, A.; Barone, L.; Borgia, B.; Bosio, C.; Diemoz, M.; Dionisi, C.; Dore, U.; Ferroni, F.; Longo, E.; Loverre, P.; Luminari, L.; Monacelli, P.; Morganti, S.; De Notaristefani, F.; Santoni, C.; Tortora, L.; Valente, V.

    1986-01-01

    The cross section ratio of neutral-current and charged-current semi-leptonic interactions of muon-neutrinos on isoscalar nuclei has been measured with the result: R v =0.3093±0.0031 for hadronic energy larger than 4 GeV. From this ratio, the electroweak mixing angle is determined to be sin 2 θ w =0.236+0.012(m c -1.5)±0.005 (exp.)±0.003 (theor.), where m c is the charm-quark mass in GeV/c 2 . (orig.)

  8. Total Oxidation of Ethanol over Layered Double Hydroxide-Related Mixed Oxide Catalysts: Effect of Cation Composition.

    Czech Academy of Sciences Publication Activity Database

    Jirátová, Květa; Kovanda, F.; Ludvíková, Jana; Balabánová, Jana; Klempa, Jan

    2016-01-01

    Roč. 277, NOV 15 (2016), s. 61-67 ISSN 0920-5861. [Czech-Italian- Spanish Conference on Molecular Sieves and Catalysis /16./. Amantea, 14.06.2015-17.06.2015] R&D Projects: GA ČR GA14-13750S Institutional support: RVO:67985858 Keywords : layered double hydroxides * transition metal oxides * vox oxidation Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 4.636, year: 2016

  9. Total Oxidation of Ethanol over Layered Double Hydroxide-Related Mixed Oxide Catalysts: Effect of Cation Composition.

    Czech Academy of Sciences Publication Activity Database

    Jirátová, Květa; Kovanda, F.; Ludvíková, Jana; Balabánová, Jana; Klempa, Jan

    2016-01-01

    Roč. 277, NOV 15 (2016), s. 61-67 ISSN 0920-5861. [Czech-Italian-Spanish Conference on Molecular Sieves and Catalysis /16./. Amantea, 14.06.2015-17.06.2015] R&D Projects: GA ČR GA14-13750S Institutional support: RVO:67985858 Keywords : layered double hydroxides * transition metal oxides * vox oxidation Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 4.636, year: 2016

  10. Synthesis and Photocatalytic Activity of One-dimensional ZnO-Zn2SnO4 Mixed Oxide Nanowires

    Science.gov (United States)

    Bai, Xue-lian; Pan, Nan; Wang, Xiao-ping; Wang, Hai-qian

    2008-02-01

    Mixed oxide photocatalysts, ZnO-Zn2SnO4 (ZnO-ZTO) nanowires with different sizes were prepared by a simple thermal evaporation method. The ZnO-ZTO nanowires were characterized with a scanning electron microscope, X-ray diffraction, high-resolution transmission electron microscopy, energy-dispersive spectrometer, and X-ray photoelectron spectra. The photocatalytic activity of the ZnO-ZTO mixed nanowires were studied by observing the photodegradation behaviors of methyl orange aqueous solution. The results suggest that the ZnO-ZTO mixed oxide nanowires have a higher photocatalytic activity than pure ZnO and Zn2SnO4 nanowires. The photocatalyst concentration in the solution distinctly affects the degradation rate, and our results show that higher photodegradation efficiency can be achieved with a smaller amount of ZnO-ZTO nanowire catalyst, as compared to the pure ZnO and ZTO nanowires. Moreover, the photocatalytic activity can also be enhanced by reducing the average diameter of the nanowires. The activity of pure ZnO and ZTO nanowires are also enhanced by physically mixing them. These results can be explained by the synergism between the two semiconductors.

  11. Actinide Oxidation State and O/M Ratio in Hypostoichiometric Uranium-Plutonium-Americium U0.750Pu0.246Am0.004O2-x Mixed Oxides.

    Science.gov (United States)

    Vauchy, Romain; Belin, Renaud C; Robisson, Anne-Charlotte; Lebreton, Florent; Aufore, Laurence; Scheinost, Andreas C; Martin, Philippe M

    2016-03-07

    Innovative americium-bearing uranium-plutonium mixed oxides U1-yPuyO2-x are envisioned as nuclear fuel for sodium-cooled fast neutron reactors (SFRs). The oxygen-to-metal (O/M) ratio, directly related to the oxidation state of cations, affects many of the fuel properties. Thus, a thorough knowledge of its variation with the sintering conditions is essential. The aim of this work is to follow the oxidation state of uranium, plutonium, and americium, and so the O/M ratio, in U0.750Pu0.246Am0.004O2-x samples sintered for 4 h at 2023 K in various Ar + 5% H2 + z vpm H2O (z = ∼ 15, ∼ 90, and ∼ 200) gas mixtures. The O/M ratios were determined by gravimetry, XAS, and XRD and evidenced a partial oxidation of the samples at room temperature. Finally, by comparing XANES and EXAFS results to that of a previous study, we demonstrate that the presence of uranium does not influence the interactions between americium and plutonium and that the differences in the O/M ratio between the investigated conditions is controlled by the reduction of plutonium. We also discuss the role of the homogeneity of cation distribution, as determined by EPMA, on the mechanisms involved in the reduction process.

  12. Effects of Calcination Temperature and Acid-Base Properties on Mixed Potential Ammonia Sensors Modified by Metal Oxides

    Science.gov (United States)

    Satsuma, Atsushi; Katagiri, Makoto; Kakimoto, Shiro; Sugaya, Satoshi; Shimizu, Kenichi

    2011-01-01

    Mixed potential sensors were fabriated using yttria-stabilized zirconia (YSZ) as a solid electrolyte and a mixture of Au and various metal oxides as a sensing electrode. The effects of calcination temperature ranging from 600 to 1,000 °C and acid-base properties of the metal oxides on the sensing properties were examined. The selective sensing of ammonia was achieved by modification of the sensing electrode using MoO3, Bi2O3 and V2O5, while the use of WO3, Nb2O5 and MgO was not effective. The melting points of the former group were below 820 °C, while those of the latter group were higher than 1,000 °C. Among the former group, the selective sensing of ammonia was strongly dependent on the calcination temperature, which was optimum around melting point of the corresponding metal oxides. The good spreading of the metal oxides on the electrode is suggested to be one of the important factors. In the former group, the relative response of ammonia to propene was in the order of MoO3 > Bi2O3 > V2O5, which agreed well with the acidity of the metal oxides. The importance of the acidic properties of metal oxides for ammonia sensing was clarified. PMID:22319402

  13. Effects of Calcination Temperature and Acid-Base Properties on Mixed Potential Ammonia Sensors Modified by Metal Oxides

    Directory of Open Access Journals (Sweden)

    Kenichi Shimizu

    2011-02-01

    Full Text Available Mixed potential sensors were fabriated using yttria-stabilized zirconia (YSZ as a solid electrolyte and a mixture of Au and various metal oxides as a sensing electrode. The effects of calcination temperature ranging from 600 to 1,000 °C and acid-base properties of the metal oxides on the sensing properties were examined. The selective sensing of ammonia was achieved by modification of the sensing electrode using MoO3, Bi2O3 and V2O5, while the use of WO3, Nb2O5 and MgO was not effective. The melting points of the former group were below 820 °C, while those of the latter group were higher than 1,000 °C. Among the former group, the selective sensing of ammonia was strongly dependent on the calcination temperature, which was optimum around melting point of the corresponding metal oxides. The good spreading of the metal oxides on the electrode is suggested to be one of the important factors. In the former group, the relative response of ammonia to propene was in the order of MoO3 > Bi2O3 > V2O5, which agreed well with the acidity of the metal oxides. The importance of the acidic properties of metal oxides for ammonia sensing was clarified.

  14. A high-throughput reactor system for optimization of Mo–V–Nb mixed oxide catalyst composition in ethane ODH

    KAUST Repository

    Zhu, Haibo

    2015-01-01

    75 Mo-V-Nb mixed oxide catalysts with a broad range of compositions were prepared by a simple evaporation method, and were screened for the ethane oxidative dehydrogenation (ODH) reaction. The compositions of these 75 catalysts were systematically changed by varying the Nb loading, and the Mo/V molar ratio. Characterization by XRD, XPS, H2-TPR and SEM revealed that an intimate structure is formed among the 3 components. The strong interaction among different components leads to the formation of a new phase or an "intimate structure". The dependency of conversion and selectivity on the catalyst composition was clearly demonstrated from the results of high-throughput testing. The optimized Mo-V-Nb molar composition was confirmed to be composed of a Nb content of 4-8%, a Mo content of 70-83%, and a V content of 12-25%. The enhanced catalytic performance of the mixed oxides is obviously due to the synergistic effects of the different components. The optimized compositions for ethane ODH revealed in our high-throughput tests and the structural information provided by our characterization studies can serve as the starting point for future efforts to improve the catalytic performance of Mo-V-Nb oxides. This journal is © The Royal Society of Chemistry.

  15. Reduced Cu–Co–Al Mixed Metal Oxides for the Ring-Opening of Furfuryl Alcohol to Produce Renewable Diols

    Energy Technology Data Exchange (ETDEWEB)

    Sulmonetti, Taylor P. [School; amp, Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive NW, Atlanta, Georgia 30332, United States; Hu, Bo [School; amp, Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive NW, Atlanta, Georgia 30332, United States; Lee, Sungsik [Advanced; Agrawal, Pradeep K. [School; amp, Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive NW, Atlanta, Georgia 30332, United States; Jones, Christopher W. [School; amp, Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive NW, Atlanta, Georgia 30332, United States

    2017-08-29

    The ring-opening of furfuryl alcohol to diol products, including 1,2-pentanediol and 1,5- pentanediol, is investigated over reduced Cu-Co-Al mixed metal oxides in a liquid phase batch reactor under H2 pressure. These catalysts are synthesized through the calcination of layered double hydroxides (LDH) to yield well-dispersed, porous mixed metal oxides, which upon reduction displayed activity towards diols, mainly the valuable monomer 1,5-pentanediol. The addition of Cu facilitated the reduction of Co oxide species at lower temperatures, and under optimized conditions a yield towards 1,5-pentanediol of 44% (total diol yield of 62%) was achieved. Various characterization techniques including TPR, XPS, and XAS are employed to elucidate the structure of the catalysts, suggesting the formation of both metallic (Co and Cu) and oxide (CoO) species after reduction and passivation. Ultimately, this study demonstrates the promising characteristics that non-precious multi-metal catalysts have for the conversion of biomass derived platform molecules to plastic precursors

  16. Development of Impregnated Agglomerate Pelletization (IAP) process for fabrication of (Th,U)O 2 mixed oxide pellets

    Science.gov (United States)

    Khot, P. M.; Nehete, Y. G.; Fulzele, A. K.; Baghra, Chetan; Mishra, A. K.; Afzal, Mohd.; Panakkal, J. P.; Kamath, H. S.

    2012-01-01

    Impregnated Agglomerate Pelletization (IAP) technique has been developed at Advanced Fuel Fabrication Facility (AFFF), BARC, Tarapur, for manufacturing (Th, 233U)O 2 mixed oxide fuel pellets, which are remotely fabricated in hot cell or shielded glove box facilities to reduce man-rem problem associated with 232U daughter radionuclides. This technique is being investigated to fabricate the fuel for Indian Advanced Heavy Water Reactor (AHWR). In the IAP process, ThO 2 is converted to free flowing spheroids by powder extrusion route in an unshielded facility which are then coated with uranyl nitrate solution in a shielded facility. The dried coated agglomerate is finally compacted and then sintered in oxidizing/reducing atmosphere to obtain high density (Th,U)O 2 pellets. In this study, fabrication of (Th,U)O 2 mixed oxide pellets containing 3-5 wt.% UO 2 was carried out by IAP process. The pellets obtained were characterized using optical microscopy, XRD and alpha autoradiography. The results obtained were compared with the results for the pellets fabricated by other routes such as Coated Agglomerate Pelletization (CAP) and Powder Oxide Pelletization (POP) route.

  17. Investigation of TiO2 based Mixed-metal Oxide Catalysts for the Production of Hydrogen

    Science.gov (United States)

    Luo, Si

    Abstract of the Dissertation. Investigation of TiO2 based Mixed-metal Oxide Catalysts for the Production of Hydrogen. by. Si Luo. Doctor of Philosophy. in. Chemistry. Stony Brook University. 2017. The environmental impacts of fossil fuel consumption and the resulting global warming have attracted increasing attention to technologies and fuels that are both sustainable and renewable in the 21st century. To date, hydrogen has been proposed as an encouraging candidate of the next generation of chemical fuels, which meets all demands for carbon free and efficient chemistries that could be produced from a variety of sources. However, despite tremendous efforts, there is a clear need to develop new catalysts for the production of hydrogen through catalytic processes that are sustainable, such as in the photocatalytic splitting of water (PCS: H2O → H2 + 0.5O2) and the water-gas shift process (WGS: CO + H2O → H2 + CO2). This thesis is primarily motivated by this challenge and has focused on the photochemical and thermal production of H2 by the employment of novel TiO2 based catalysts. TiO2 is one of the most widely studied photocatalysts in all history, due to its relatively high activity, robust stability, safety and low cost. In this thesis, several TiO2-based mixed metal oxide nano catalysts (CeOx-TiO2, Ru-TiO2, Ga-TiO2) have been synthesized with carefully controlled morphology/structure and with inclusion of co-catalysts (Pt). These novel materials were comprehensively characterized to better understand their morphology, crystal structure, and electronic properties in an attempt to unravel phenomena responsible for high catalytic performance for the production of H2 from H2O. We have discovered the importance of low-dimensional metal oxide and interfacial stabilized nano-scaled mixed metal oxides for H2 production, while learning how best to tune such structure to optimize both thermal and photochemical conversion. Optimized structure and/or composition have been

  18. Chemical and Radiochemical Composition of Thermally Stabilized Plutonium Oxide from the Plutonium Finishing Plant Considered as Alternate Feedstock for the Mixed Oxide Fuel Fabrication Facility

    International Nuclear Information System (INIS)

    Tingey, Joel M.; Jones, Susan A.

    2005-01-01

    Eighteen plutonium oxide samples originating from the Plutonium Finishing Plant (PFP) on the Hanford Site were analyzed to provide additional data on the suitability of PFP thermally stabilized plutonium oxides and Rocky Flats oxides as alternate feedstock to the Mixed Oxide Fuel Fabrication Facility (MFFF). Radiochemical and chemical analyses were performed on fusions, acid leaches, and water leaches of these 18 samples. The results from these destructive analyses were compared with nondestructive analyses (NDA) performed at PFP and the acceptance criteria for the alternate feedstock. The plutonium oxide materials considered as alternate feedstock at Hanford originated from several different sources including Rocky Flats oxide, scrap from the Remote Mechanical C-Line (RMC) and the Plutonium Reclamation Facility (PRF), and materials from other plutonium conversion processes at Hanford. These materials were received at PFP as metals, oxides, and solutions. All of the material considered as alternate feedstock was converted to PuO2 and thermally stabilized by heating the PuO2 powder at 950 C in an oxidizing environment. The two samples from solutions were converted to PuO2 by precipitation with Mg(OH)2. The 18 plutonium oxide samples were grouped into four categories based on their origin. The Rocky Flats oxide was divided into two categories, low- and high-chloride Rocky Flats oxides. The other two categories were PRF/RMC scrap oxides, which included scrap from both process lines and oxides produced from solutions. The two solution samples came from samples that were being tested at Pacific Northwest National Laboratory because all of the plutonium oxide from solutions at PFP had already been processed and placed in 3013 containers. These samples originated at the PFP and are from plutonium nitrate product and double-pass filtrate solutions after they had been thermally stabilized. The other 16 samples originated from thermal stabilization batches before canning at

  19. Spectrophotometric determination of the formation constant of triiodide ions in aqueous-organic solvent or polymer mixed media both in absence and presence of a surfactant

    Science.gov (United States)

    Naorem, Homendra; Devi, Seram Dushila

    2013-01-01

    The formation constant of triiodide ions from iodine-iodide equilibrium in aqueous-organic solvent or polymer mixed media have been determined spectrophotometrically at three different temperatures 20, 30 and 40 °C. The organic solvents chosen for the study are ethylene glycol, 2-methoxy ethanol, and 2-ethoxy ethanol while the polymers include polyethylene glycol (PEG), hydroxypropyl cellulose (HPC) or polyethylene oxide (PEO). Effect of a surfactant on the formation of triiodide ions in the mixed media has also been investigated. Though presence of the organic solvents led to an increase in the triiodide formation except for 2-ethoxy ethanol mixed media at low percentage, the increase in presence of PEG or the other polymer mixed media even at very low percentage was much higher as compared to those in ethylene glycol or its homologues. The increase in the formation constant has been discussed in terms of changes in its solvation properties and the hydrophobic character of the mixed media besides the solvent dielectric effects. The sharp increase in triiodide formation in presence of the polymer under study suggests the possibility of iodine being present as triiodide or other higher polyiodides in the inclusion complexes of iodine with other polymers like starch or PVA. The decrease in the triiodide formation in presence of surfactant micelles may, however, be attributed to solubilization of iodine by the micelles. Iodine was found to be better solubilized in TX-100 micelles as compared to SDS micelles.

  20. To study the flow property of seven commercially available zinc oxide eugenol impression material at various time intervals after mixing.

    Science.gov (United States)

    Katna, Vishal; Suresh, S; Vivek, Sharma; Meenakshi, Khandelwal; Ankita, Gaur

    2014-12-01

    Aims and objective of the study was to evaluate the flow property of seven commercially available zinc oxide eugenol impression materials at various time intervals, after mixing 49 samples (seven groups) were fabricated for flow property of the material. The sample were fabricated as equal length of base and accelerator paste of the test materials was taken on the glass slab and mixed with a rigid stainless steel spatula as per manufacturers recommendation till the homogenous mix was obtained. The mix material was loaded in glass syringe and 0.5 ml material was injected on a cellophane sheet placed on marked glass plate. A cellophane sheet and glass plate 70 and 500 g weight was carefully placed on freshly dispensed zinc oxide eugenol impression paste sequentially. The diameter of the mix was noted after 30 s and 1 min of load application and also after the final set of material. The diameter gives the flow of material. The samples were stored at the room temperature. The data of the flow property was analyzed with analysis of variance, Post hoc test and t test. The flow of the zinc oxide eugenol impression paste after 30 s, 1 min and final set of load application for Group A to Group G was noted. Maximum flow was seen for Group G zinc oxide eugenol impression material followed by Group F, D, E, B, C and A in descending order respectively after 30 s, where as the flow property changed after 1 min in the sequence of maximum for Group G followed by Group E, D, B, A, C, and F. Lastly after final set of the impression material the flow maximum for Group G followed by Group E, D, C, F, A and B in descending order. Based on statistical analysis of the results and within in the limitations of this in-vitro study, the following conclusions were drawn that; the flow of zinc oxide eugenol impression material after 30 s, 1 min and that after the final set was maximum for P.S.P. (Group G) and the flow for PYREX (Group A) was minimum.

  1. Evaluation of Chemical Structure and Resistance Switching Characteristics of Undoped Titanium Oxide and Titanium-Yttrium Mixed Oxide

    Science.gov (United States)

    Ohta, Akio; Goto, Yuta; Wei, Guobin; Murakami, Hideki; Higashi, Seiichiro; Miyazaki, Seiichi

    2011-10-01

    We have studied the chemical bonding features in the region near the TiO2/Pt interface after resistance change to gain a better understanding of the mechanism of resistance switching in TiO2-based resistance random access memory (ReRAM). For the Pt/TiO2/Pt structure after resistance switching, oxidation of the Pt electrode at the Pt/TiO2 interface in switching from a high resistance state (HRS) to a low resistance state (LRS) and reduction of this Pt-oxide in switching from the LRS to the HRS were observed by hard X-ray photoelectron spectroscopy. The result suggests that the generation of oxygen vacancies in the Ti-oxide matrix is responsible for the formation of the conductive pass resulting in the LRS and that repeatable redox reaction at the Pt/TiO2 interface plays an important role in resistance switching behavior. To modify the oxide network, which leads to the change in the conduction pass formation, trivalent Y ions were added to the oxide matrix of quadrivalent Ti ions. Raman scattering and X-ray diffraction measurements show that the crystallization of TiO2 by thermal annealing was suppressed by the Y2O3 addition. In Au/TiYxOy/Pt structures, it has been demonstrated that the variations in resistance switching voltages are markedly suppressed by the Y2O3 addition to TiO2.

  2. Rhizospheric methane oxidation determined via the methyl fluoride inhibition technique

    Science.gov (United States)

    Epp, Michelle A.; Chanton, Jeffrey P.

    1993-10-01

    Methane oxidation rates in the rhizosphere of aquatic macrophytes were quantified by development of a technique employing a recently described inhibitor of methane oxidation, methyl fluoride. Unlike other inhibitors, methyl fluoride appears to be nontoxic to the plants, allowing them to act as natural conduits, transporting the inhibitor from the headspace to the rhizosphere. Increases in methane emissions were recorded after closed chamber methyl fluoride incubations, primarily in greenhouse (Pontederia cordata and Sagittaria landfolia) experiments with some preliminary outdoor and field (Oryza sativa and Typha latifolia) data. Comparison of emissions before and after incubation indicated oxidation of 23 to 90% of the methane produced (defined as CH4 emission in the absence of oxidation) in greenhouse studies and 10 to 47% in field and outdoor studies. A comparison of 1.5 and 3.0% methyl fluoride chamber headspace incubations as well as initial dose response data indicated that the lower concentration was sufficient to obtain inhibition of methane oxidation in the greenhouse studies without significantly affecting methanogenesis. Inhibition was possible with one 16- to 18-hour incubation period. Methyl fluoride within the rhizosphere disappeared after approximately 1 week due to plant ventilation and possible bacterial uptake.

  3. Catalytic transformations of biomass substrates using mixed metal oxides derived from substituted hydrotalcites

    Science.gov (United States)

    Macala, Gerald Stephen, II

    Fueled by seemingly endless reserves of cheap and easily accessible fossil energy, the industrial age has brought to the developed world tremendous advances in human health and well being. Unfortunately the burning of fossil fuels has also been implicated in increasing atmospheric CO2 concentrations and global climate change. Concerns about short-term and long-term supply further build a case for the need for alternative energy sources. Biomass derived materials are a tantalizing source of fuels and fine chemicals. Unlike petroleum derived hydrocarbons, biomass can be both renewable and carbon neutral. Crops can be regenerated annually or even more often in tropical climates, and since the captured carbon originates as atmospheric CO2, the overall cycle has the potential to be nearly carbon neutral regardless of the final fate of the carbon. In contrast to petroleum derived hydrocarbons, which can often be made more valuable by adding functionality, biomass derived materials are already highly functionalized and can usually be made more valuable by selective removal of functionality. The development of robust catalysts capable of selective defuntionalization of biomass derived substrates remains an important challenge with potentially enormous economic and societal impact. In addition to being robust and selective, catalysts should preferably be heterogeneous to allow for easier removal and regeneration after the reaction is complete. New materials consisting of Mg-Al hydrotalcite-like structures, with a limiting percentage of Mg or Al substituted with other M2+ or M3+ cations, were synthesized by a co-precipitation process in basic aqueous solution with carbonate as counterion. Calcination of these materials at 460 °C resulted in evolution of CO2 and water and yielded high surface area mixed metal oxides with enhanced reactivity. Materials were characterized by ICP for elemental analysis, XRD for structural information, XPS for surface elemental analysis and TEM

  4. Synthesis, characterization and magnetic behavior of Mg–Fe–Al mixed oxides based on layered double hydroxide

    Energy Technology Data Exchange (ETDEWEB)

    Heredia, Angélica C., E-mail: angelicacheredia@gmail.com [Universidad Tecnológica Nacional, Facultad Regional Córdoba-CITeQ, Maestro López esq. Cruz Roja Argentina, Ciudad Universitaria, 5016 Córdoba (Argentina); Oliva, Marcos I. [IFEG, Universidad Nacional de Córdoba, Córdoba (Argentina); CONICET (Argentina); Agú, Ulises [Universidad Tecnológica Nacional, Facultad Regional Córdoba-CITeQ, Maestro López esq. Cruz Roja Argentina, Ciudad Universitaria, 5016 Córdoba (Argentina); CONICET (Argentina); Zandalazini, Carlos I. [CONICET (Argentina); INFIQC, FCQ Universidad Nacional de Córdoba, Córdoba (Argentina); Marchetti, Sergio G. [CINDECA, UNLP, Buenos Aires (Argentina); Herrero, Eduardo R.; Crivello, Mónica E. [Universidad Tecnológica Nacional, Facultad Regional Córdoba-CITeQ, Maestro López esq. Cruz Roja Argentina, Ciudad Universitaria, 5016 Córdoba (Argentina)

    2013-09-15

    In the present work, Mg–Al–Fe layered double hydroxides were prepared by coprecipitation reaction with hydrothermal treatment. The characterization of precursors and their corresponding calcinated products (mixed oxides) were carried out by X ray diffraction, X-ray photoelectron spectroscopy (XPS), termogravimetric analysis and differential scanning calorimetry, diffuse reflectance UV–vis spectroscopy, specific surface area, Mössbauaer and magnetic properties. The Fe{sup 3+} species were observed in tetrahedrally and octahedrally coordination in brucite layered. The XPS analysis shows that the Fe{sup 3+} ions can be found in two coordination environments (tetrahedral and octahedral) as mixed oxides, and as spinel-structure. Oxides show a decrease in the specific surface areas when the iron loading is increased. The magnetic and Mössbauaer response show that MgAlFe mixed oxides are different behaviours such as different population ratios of ferromagnetic, weak-ferromagnetic, paramagnetic and superparamagnetic phases. The better crystallization of spinel structure with increased temperature, is correlated with the improved magnetic properties. - Highlights: • Mg–Al–Fe were successfully prepared by coprecipitation with hydrothermal treatment. • MgO, α-Fe{sub 2}O{sub 3,} MgFe{sub 2}O{sub 4} were detected by XRD in the calcined samples. • The Fe{sup 3+} is in tetrahedral and octahedral coordination in the brucite layered. • The specific surface area is directly related with the iron content. • The magnetic properties and MgFe{sub 2}O{sub 4} improve with increasing calcination temperature.

  5. Fabrication of Nb2O5/SiO2 mixed oxides by reactive magnetron co-sputtering

    International Nuclear Information System (INIS)

    Juškevičius, Kęstutis; Audronis, Martynas; Subačius, Andrius; Kičas, Simonas; Tolenis, Tomas; Buzelis, Rytis; Drazdys, Ramutis; Gaspariūnas, Mindaugas; Kovalevskij, Vitalij; Matthews, Allan; Leyland, Adrian

    2015-01-01

    This paper investigates niobia/silica mixed oxide thin films deposited by reactive pulse-DC/RF magnetron co-sputtering of Nb and Si metal targets at room temperature. The reactive gas flow during the sputtering processes was either controlled by direct mass flow rate (i.e. constant reactive gas flow) or by an active feedback process control system. 61% and 137% higher deposition rates of Nb 2 O 5 and SiO 2 layers, respectively, were obtained using the latter technique as compared to constant reactive gas flow. Films exhibited bulk or near-bulk density. All mixture films produced in this study had an amorphous structure. A volume law of mixtures was used to determine the coating composition. It is shown that the fraction of SiO 2 or/and Nb 2 O 5 has a linear dependency on sputter target power density. On this basis, rugate filter coating designs can be easily deposited, where refractive index gradually varies between that of pure Nb 2 O 5 and pure SiO 2 . Substantially less inhomogeneity of coating mixtures was found in films produced using a reactive sputtering process with feedback-control. - Highlights: • 61% and 137% increase in deposition rates of Nb 2 O 5 and SiO 2 • Rugate coating designs can be readily deposited. • Nb 2 O 5 /SiO 2 mixture films exhibited bulk or near-bulk density. • Optimized process leads to stoichiometric and homogenous mixtures. • Films are amorphous and suitable for low loss optical coatings

  6. Performance of Platinum and Gold Catalysts Supported on Ceria-Zirconia Mixed Oxide in the Oxidation of Chlorobenzene

    Czech Academy of Sciences Publication Activity Database

    Topka, Pavel; Delaigle, R.; Kaluža, Luděk; Gaigneaux, E.M.

    2015-01-01

    Roč. 253, SEP 15 (2015), s. 172-177 ISSN 0920-5861 R&D Projects: GA ČR GP13-24186P Institutional support: RVO:67985858 Keywords : oxidation * chlorobenzene * zirconia Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 4.312, year: 2015

  7. Turbidimetric determination of polyacrylamide in aqueous solutions with the use of oxidizing agents

    International Nuclear Information System (INIS)

    Karpyuk, A.D.; Kolyada, N.S.; Pshenichnikova, E.Yu.

    1992-01-01

    Polyacrylamide is widely used in industry. For example, one of the methods for obtaining microspheres of metal oxides, particularly a mixed nuclear fuel, is based on a process involving the ammoniacal precipitation of hydroxides from aqueous solutions of metal nitrates in the presence of polyacrylamide (PAA), which promotes the formation of spheres in the initial stages of the process. Monitoring the industrial process, the course of the treatment of the production waste products, and the composition of the waste water calls for determination of the content of PAA in industrial solutions. The existing methods for determining PAA are based on its chemical properties, which are specified by the presence of amide groupings in its molecule. The use of the classical methods of analysis, which are based on the reactions of PAA with formaldehyde, sulfuric acid, etc. and the hydrolysis of PAA, do not provide reliable results, since PAA is partially or completely hydrolyzed in industrial solutions. In addition, industrial solutions contain various modifiers, including urea and urotropin, and the method of determining PAA from the amount of ammonia evolved is consequently unacceptable. Turbidimetric methods of analysis, in which the content of PAA is evaluated from the turbidity caused by the formation of suspension during hydrolysis or upon the introduction of NaClO 4 or diisotubylphenoxyethoxyethyldimethylbenzyl chloride, are known. The purpose of the present work was to develop a simple quick method for determining polymers in solutions, including solutions from the production and treatment of nuclear fuel. The following reagents were proposed for the turbidimetric determination of PAA: cerium(IV) sulfate, potassium dichromate, and potassium permanganate. 5 refs., 3 figs., 1 tab

  8. Determination of the oxidation states of metals and metalloids: An analytical review

    Science.gov (United States)

    Vodyanitskii, Yu. N.

    2013-12-01

    The hazard of many heavy metals/metalloids in the soil depends on their oxidation state. The problem of determining the oxidation state has been solved due to the use of synchrotron radiation methods with the analysis of the X-ray absorption near-edge structure (XANES). The determination of the oxidation state is of special importance for some hazardous heavy elements (arsenic, antimony, selenium, chromium, uranium, and vanadium). The mobility and hazard of each of these elements depend on its oxidation state. The mobilities are higher at lower oxidation states of As, Cr, V, and Se and at higher oxidation states of Sb and U. The determination of the oxidation state of arsenic has allowed revealing its fixation features in the rhizosphere of hydrophytes. The known oxidation states of chromium and uranium are used for the retention of these elements on geochemical barriers. Different oxidation states have been established for vanadium displacing iron in goethite. The determination of the oxidation state of manganese in the rhizosphere and the photosynthetic apparatus of plants is of special importance for agricultural chemists.

  9. Destruction of hazardous and mixed wastes using mediated electrochemical oxidation in a Ag(II)HNO3 bench scale system

    International Nuclear Information System (INIS)

    Balazs, B.; Chiba, Z.; Hsu, P.; Lewis, P.; Murguia, L.; Adamson, M.

    1997-01-01

    Mediated Electrochemical Oxidation (MEO) is a promising technology for the destruction of organic containing wastes and the remediation of mixed wastes containing transuranic components. The combination of a powerful oxidant and an acid solution allows the conversion of nearly all organics, whether present in hazardous or in mixed waste, to carbon dioxide. Insoluble transuranics are dissolved in this process and may be recovered by separation and precipitation.The MEO technique offers several advantages which are inherent in the system. First, the oxidation/dissolution processes are accomplished at near ambient pressures and temperatures (30-70 degrees C). Second, all waste stream components and oxidation products (with the exception of evolved gases) are contained in an aqueous environment. This electrolyte acts as an accumulator for inorganics which were present in the original waste stream, and the large volume of electrolyte provides a thermal buffer for the energy released during oxidation of the organics. Third, the generation of secondary waste is minimal, as the process needs no additional reagents. Finally, the entire process can be shut down by simply turning off the power, affording a level of control unavailable in some other techniques.Numerous groups, both in the United States and Europe, have made substantial progress in the last decade towards understanding the mechanistic pathways, kinetics, and engineering aspects of the process. At Lawrence Livermore National Laboratory, substantial contributions have been made to this knowledge base in these areas and others. Conceptual design and engineering development have been completed for a pilot plant-scale MEO system, and numerous data have been gathered on the efficacy of the process for a wide variety of anticipated waste components. This presentation will review the data collected at LLNL for a bench scale system based primarily on the use of a Ag(II) mediator in a nitric acid electrolyte; results

  10. Aerosol synthesis and electrochemical analysis of niobium mixed-metal oxides for the ethanol oxidation reaction in acid and alkaline electrolyte

    Science.gov (United States)

    Konopka, Daniel A.

    Direct ethanol fuel cells are especially important among emerging electrochemical power systems with the potential to offset a great deal of the energy demand currently met through the use of fossil fuels. Ethanol can be refined from petroleum sources or attained from renewable biomass, and is more easily and safely stored and transported than hydrogen, methanol or gasoline. The full energy potential of ethanol in fuel cells can only be realized if the reaction follows a total oxidation pathway to produce CO2. This must be achieved by the development of advanced catalysts that are electrically conductive, stable in corrosive environments, contain a high surface area on which the reaction can occur, and exhibit a bi-functional effect for the ethanol oxidation reaction (EOR). The latter criterion is achievable in mixed-metal systems. Platinum is an effective metal for catalyzing surface reactions of many adsorbates and is usually implemented in the form of Pt nanoparticles supported on inexpensive carbon. This carbon is believed to be neutral in the catalysis of Pt. Instead, carbon can be replaced with carefully designed metals and metal oxides as co-catalysis or support structures that favorably alter the electronic structure of Pt slightly through a strong metal support interaction, while also acting as an oxygen source near adsorbates to facilitate the total oxidation pathway. Niobium mixed-metal-oxides were explored in this study as bi-functional catalyst supports to Pt nanoparticles. We developed a thermal aerosol synthesis process by which mesoporous powders of mixed-metal-oxides decorated with Pt nanoparticles could be obtained from liquid precursors within ˜5 seconds or less, followed by carefully refined chemical and thermal post-treatments. Exceptionally high surface areas of 170--180m2/g were achieved via a surfactant-templated 3D wormhole-type porosity, comparable on a per volume basis to commercial carbon blacks and high surface area silica supports

  11. Ca-Sr-Ga-Nb mixed oxide system for high temperature superconductor substrate applications

    Energy Technology Data Exchange (ETDEWEB)

    Erdei, S.; Cross, L.E.; Ainger, F.W.; Bhalla, A. (Materials Research Lab., The Pennsylvania State Univ., Univ. Park, Pennsylvania (United States))

    1994-05-01

    Twin-free crystals with relatively low melting temperatures are desirable as substrates for high temperature superconductor (HTSC) oxide substrate materials. In the selection of new oxide substrate compositions, special requirements (e.g. suitable dielectric properties for microwave application and perovskite structure with good lattice matching with YBa[sub 2]Cu[sub 3]O[sub 7-[delta

  12. Method for Determining the Time Constants Characterizing the Intensity of Steel Mixing in Continuous Casting Tundish

    Directory of Open Access Journals (Sweden)

    Pieprzyca J.

    2015-04-01

    Full Text Available A common method used in identification of hydrodynamics phenomena occurring in Continuous Casting (CC device's tundish is to determine the RTD curves of time. These curves allows to determine the way of the liquid steel flowing and mixing in the tundish. These can be identified either as the result of numerical simulation or by the experiments - as the result of researching the physical models. Special problem is to objectify it while conducting physical research. It is necessary to precisely determine the time constants which characterize researched phenomena basing on the data acquired in the measured change of the concentration of the tracer in model liquid's volume. The mathematical description of determined curves is based on the approximate differential equations formulated in the theory of fluid mechanics. Solving these equations to calculate the time constants requires a special software and it is very time-consuming. To improve the process a method was created to calculate the time constants with use of automation elements. It allows to solve problems using algebraic method, which improves interpretation of the research results of physical modeling.

  13. Sorption behaviour of uranium and thorium on hydrous tin oxide from aqueous and mixed-solvent HNO3 media

    International Nuclear Information System (INIS)

    Misak, N.Z.; Salama, H.N.; El-Naggar, I.M.

    1983-01-01

    In aqueous nitric acid, uranyl and thorium ions seem to be sorbed on hydrous tin oxide mainly by a cation exchange mechanism. In 10 - 3 M aqueous solutions, the hydrous oxide prefers thorium to uranium at the relative low pH values, while the reverse is true at the higher pH values. The exchange of uranium is particle diffusion controlled while that of thorium is chemically controlled, and the isotherms point to the presence of different-energy sites in the hydrous oxide. Except for the solutions containing 80% of methanol, ethanol, or acetone, cation exchange is probably still the main mechanism of sorption of uranium. Anionic sorption of thorium seems to occur in all the mixed-solvent solutions and is perhaps the main mechanism in 80% ethanol. The equilibrium distribution coefficient K sub (d) increases almost in all cases with organic solvent content, probably due to dehydration of sorbed ions and to increasing superposition on anionic sorption. Unlike the aqueous medium, large U/Th separation factors are achieved in many of the mixed-solvent solutions and separation schemes are suggested. (Authors)

  14. Support effect on the structure and CO oxidation activity of Cu-Cr mixed oxides over Al2O3 and SiO2

    International Nuclear Information System (INIS)

    Pantaleo, G.; Liotta, L.F.; Venezia, A.M.; Deganello, G.; Ezzo, E.M.; El Kherbawi, M.A.; Atia, H.

    2009-01-01

    Cu-Cr based catalysts supported on silica and alumina with 5 wt% total loading of (CuO + Cr 2 O 3 ), in different molar ratios, were prepared by wet impregnation. The samples were studied by nitrogen adsorption isotherms (BET), temperature-programmed reduction (TPR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Their catalytic activity was tested in the CO oxidation reaction. Different structures were obtained in dependence of the support, the atomic ratio and the calcination temperature. In particular, whereas on Al 2 O 3 there was no experimental evidence for interaction between Cu and Cr, over the silica supported systems formation of new phases CuCr 2 O 4 and CuCrO 2 occurred. Moreover, due to the different metal support interaction the increasing calcination temperature affected differently the surface segregation process of the two oxides. Indeed, at variance with the alumina case, Cu and Cr were found to segregate at the surface of the silica systems. The catalytic tests in CO oxidation indicated a synergetic effect between copper and chromium in the mixed oxides supported on silica and calcined at 500 deg. C. An increased calcination temperature affected negatively the activity due to surface sintering and formation of less active phases

  15. Advanced Mixing of Fuel/Oxidant System in High Speed Gaseous Flows Stage 1

    National Research Council Canada - National Science Library

    Bityurin, Valentin

    2000-01-01

    ...) pulse electrical discharge, and (2) by MHD interaction. The task of this activity is to develop an integrated model including all significant mechanisms of in-flow mixing and controlling means...

  16. Experimental determination of tritium oxidation speed in atmosphere

    International Nuclear Information System (INIS)

    Clerc, H.; Calando, J.P.; Paillard, P.; Gros, R.; Hircq, B.

    1988-01-01

    In the framework of fusion reactor safety studies it is necessary to know the kinetics of gaseous tritium oxidation. Literature differences have conducted the European Communities to realize a research program in case of tritium release for a rapid accidental release and for a slow routine release. This report gives the experimental conditions and the results of rapid accidental release. Experiments have been done at Bruyeres-le-Chatel (FR) with a 40 meters chimney [fr

  17. DETERMINATION OF THE LOADING OF CONTAINERS IN MIXED TRAINS WHEN TRANSPORTING BY TRAIN FERRIES

    Directory of Open Access Journals (Sweden)

    A. O. Lovska

    2017-12-01

    Full Text Available Purpose. The study is aimed at determination of the loading of containers in mixed trains when transporting by train ferries. Methodology. In order to achieve the objective the author studied accelerations (as components of the dynamic load influencing the bearing structure of a 1CC standard container located on a flat car during transportation by train ferry. In order to determine accelerations influencing the bearing structure of a container, a mathematical model of the container’s movements under train ferry oscillations was made. The model considered angular displacements of a train ferry relative to the longitudinal axis (bank as being the maximum load on the bearing structure, as well as changes in the container stability relative to the flat car frame. While working out the motion equations three diagrams of interrelation between the container and the flat car located on the train ferry deck were considered: 1 absence of displacements of the flat car and containers relative to the initial place under the train ferry oscillations; 2 with displacements of the flat car under the train ferry oscillations when containers are immovable relative to the flat car frame; 3 with displacements of the flat car relative to the deck and relative to the flat car frame. The differential equations of motion were solved in Mathсad taking into account their reduction to a normal Cauchy problemwith a subsequent integration by the Runge–Kutta method. Findings. Refined values of accelerations influencing the bearing structure of containers located on the flat car while transporting by train ferry were obtained. Originality. The mathematical models of displacements of container bearing structures located on a flat car while transporting by train ferry were proposed. Practical value. The results of investigations can be applied for designing bearing structures of new generation containers, besides they may improve the efficiency of mixed transportation along

  18. Determination of a scale-up factor from mixing time studies in orbitally shaken bioreactors

    OpenAIRE

    Tissot Stéphanie

    2010-01-01

    Efficient mixing in bioreactors is essential in order to avoid concentration gradients which can be harmful for mammalian cells. To study mixing and its scalability in orbitally shaken cylindrical bioreactors we measured mixing times in containers with nominal volumes from 2 to 1500 L with a colorimetric method using two pH indicators. Four operating parameters were tested: the liquid height the shaking diameter the agitation rate and the inner diameter of the container. The mixing time decre...

  19. A precise determination of the electroweak mixing angle from semileptonic neutrino scattering

    International Nuclear Information System (INIS)

    Allaby, J.V.; Amaldi, U.; Barbiellini, G.; Baubillier, M.; Bergsma, F.; Capone, A.; Flegel, W.; Grancagnolo, F.; Lanceri, L.; Metcalf, M.; Nieuwenhuis, C.; Pain, R.; Panman, J.; Plunckett, R.; Winter, K.; Abt, I.; Aspiazu, J.; Bungener, A.; Buesser, F.W.; Gall, P.D.; Hebbeker, T.; Niebergall, F.; Schuett, P.; Staehelin, P.; Baroncelli, A.; Bosio, C.; Tortora, L.; Barone, L.; Borgia, B.; Diemoz, M.; Dionisi, C.; Dore, U.; Ferroni, F.; Longo, E.; Loverre, P.F.; Luminari, L.; Monacelli, P.; Morganti, S.; De Notaristefani, F.; Santoni, C.; Valente, V.

    1987-01-01

    The cross-section ratio of neutral-current and charged-current semileptonic interactions of muon-neutrinos on isoscalar nuclei has been measured with the result: R ν = 0.3093±0.0031 for hadronic energy larger than 4 GeV. From this ratio we determined the electroweak mixing angle sin 2 θ W = 0.236+0.012 (m c -1.5)±0.005(exp.)±0.003(theor.), where m c is the charm-quark mass in GeV/c 2 . Comparison with direct measurements of m W and m Z determines the radiative shift of the intermediate boson mass Δr=0.077±0.025(exp.)±0.038(syst.), in agreement with the prediction. Assuming the validity of the electroweak standard theory we determined ρ = 0.990-0.013(m c -1.5)±0.009(exp.)±0.003(theor.). (orig.)

  20. Characterization of the Fe-Doped Mixed-Valent Tunnel Structure 2 Manganese Oxide KOMS-2

    Energy Technology Data Exchange (ETDEWEB)

    Hanson J. C.; Shen X.; Morey A.M.; Liu J.; Ding Y.; Cai J.; Durand J.; Wang Q.; Wen W.; Hines W.A.; Bai J.; Frenkel A.I.; Reiff W.; Aindow M.; Suib S.L.

    2011-11-10

    A sol-gel-assisted combustion method was used to prepare Fe-doped manganese oxide octahedral molecular sieve (Fe-KOMS-2) materials with the cryptomelane structure. Characterization of the nanopowder samples over a wide range of Fe-doping levels (0 {le} Fe/Mn {le} 1/2) was carried out using a variety of experimental techniques. For each sample, Cu K{alpha} XRD and ICP-AES were used to index the cryptomelane structure and determine the elemental composition, respectively. A combination of SEM and TEM images revealed that the morphology changes from nanoneedle to nanorod after Fe doping. Furthermore, TGA scans indicated that the thermal stability is also enhanced with the doping. Anomalous XRD demonstrated that the Fe ions replace the Mn ions in the cryptomelane structure, particularly in the (211) planes, and results in a lattice expansion along the c axis, parallel to the tunnels. Reasonable fits to EXAFS data were obtained using a model based on the cryptomelane structure. Moessbauer spectra for selected Fe-KOMS-2 samples indicated that the Fe is present as Fe{sup 3+} in an octahedral environment similar to Mn in the MnO{sub 6} building blocks of KOMS-2. Magnetization measurements detected a small amount of {gamma}-Fe{sub 2}O{sub 3} second phase (e.g., 0.6 wt % for the Fe/Mn = 1/10 sample), the vast majority of the Fe being in the structure as Fe{sup 3+} in the high-spin state.

  1. Make or mix to order: Determining the type of intermediate products in a flour mill

    DEFF Research Database (Denmark)

    Akkerman, Renzo; van der Meer, Dirk; van Donk, Dirk Pieter

    2008-01-01

    In contrast to discrete manufacturers, food-processing companies can sometimes produce the same end products in different ways: either mix early and process or process first and mix later. Moreover, a product can be mixed from different raw materials or intermediates. That implies that choices can...

  2. Solar energy as an alternate energy source to mixed oxide fuels in light-water cooled reactors

    International Nuclear Information System (INIS)

    Bertini, H.W.

    1977-01-01

    Supplemental information pertaining to the generic environmental impact statement on the Pu recycling process for mixed oxide light-water cooled reactors (GESMO) was requested from several sources. In particular, the role of alternate sources of energy was to be explored and the implications of these alternate sources to the question of Pu recycle in LWRs were to be investigated. In this vein, solar energy as an alternate source is the main subject of this report, along with other information related to solar energy. The general conclusion is that solar energy should have little effect on the decisions concerning GESMO

  3. Electronic structure of mixed caesium actinide oxides Cs2AnO4 (An = U, Np, Pu, Am)

    Science.gov (United States)

    Kovács, Attila

    2018-01-01

    Relativistic multireference CASSCF/CASPT2 calculations have been performed on the mixed caesium actinide oxide molecules Cs2AnO4 with An = U, Np, Pu and Am. Probing the lowest-energy spin multiplicities the spin-orbit-free (SF) ground and low-energy excited states have been evaluated and characterised. After optimizing the molecular geometries of the SF ground states further calculations have been performed taking into account spin-orbit (SO) coupling. The SO ground and vertical low-lying excited states have been characterised.

  4. Mixed Oxide Supported MoO3 Catalyst: Preparation, Characterization and Activities in Nitration of o-xylene

    OpenAIRE

    S.M. Kemdeo; V.S. Sapkal; G.N. Chaudhari

    2010-01-01

    TiO2-ZrO2 mixed oxide support was prepared and impregnated with 12 wt % MoO3 and calcined at various temperatures. The resultant catalyst systems were characterized by XRD, FT-IR, BET, SEM, NH3-TPD and pyridine adsorbed FT-IR methods to know the physico-chemical changes occurred in course of thermal treatment. Activities of these catalysts were tested by employing them in the nitration of o-xylene. Mostly, 500 oC calcined catalyst sample was found to be most active for nitration reactio...

  5. Mixed Oxide Supported MoO3 Catalyst: Preparation, Characterization and Activities in Nitration of o-xylene

    OpenAIRE

    S.M. Kemdeo; G.N. Chaudhari; V.S. Sapkal

    2010-01-01

    TiO2-ZrO2 mixed oxide support was prepared and impregnated with 12 wt % MoO3 and calcined at various temperatures. The resultant catalyst systems were characterized by XRD, FT-IR, BET, SEM, NH3-TPD and pyridine adsorbed FT-IR methods to know the physico-chemical changes occurred in course of thermal treatment. Activities of these catalysts were tested by employing them in the nitration of o-xylene. Mostly, 500 oC calcined catalyst sample was found to be most active for nitration reaction. Cat...

  6. Note: Application of CR-39 plastic nuclear track detectors for quality assurance of mixed oxide fuel pellets

    Science.gov (United States)

    Kodaira, S.; Kurano, M.; Hosogane, T.; Ishikawa, F.; Kageyama, T.; Sato, M.; Kayano, M.; Yasuda, N.

    2015-05-01

    A CR-39 plastic nuclear track detector was used for quality assurance of mixed oxide fuel pellets for next-generation nuclear power plants. Plutonium (Pu) spot sizes and concentrations in the pellets are significant parameters for safe use in the plants. We developed an automatic Pu detection system based on dense α-radiation tracks in the CR-39 detectors. This system would greatly improve image processing time and measurement accuracy, and will be a powerful tool for rapid pellet quality assurance screening.

  7. Structure and electronic properties of MoVO type mixed-metal oxides - a combined view by experiment and theory.

    Science.gov (United States)

    Chiu, Cheng-Chau; Vogt, Thomas; Zhao, Lili; Genest, Alexander; Rösch, Notker

    2015-08-21

    In this review we address recent efforts from experimental and theoretical side to study MoVO-type mixed metal oxides (MMOs) and their properties. We illustrate how structures of MMOs have been evaluated using a large variety of experimental techniques, such as electron microscopy, neutron diffraction, and X-ray diffraction. Furthermore, we discuss the current view on structure-catalysis correlations, derived from recent experiments. In a second part, we examine useful tools of theoretical chemistry for exploring MoVO-type systems. We discuss the need for using hybrid DFT methods and we analyze how, in the context of MMOs studies, semi-local DFT approximations can encounter problems due to a notable self-interaction error when describing oxidic species and reactions on them. In addition, we discuss various aspects of the model that are important when attempting to map complex MMO systems.

  8. MLS/Aura L2 Nitrous Oxide (N2O) Mixing Ratio V003

    Data.gov (United States)

    National Aeronautics and Space Administration — ML2N2O is the EOS Aura Microwave Limb Sounder (MLS) standard product for nitrous oxide derived from radiances measured primarily by the 640 GHz radiometer (Band 12)...

  9. MLS/Aura Level 2 Nitrous Oxide (N2O) Mixing Ratio V004

    Data.gov (United States)

    National Aeronautics and Space Administration — ML2N2O is the EOS Aura Microwave Limb Sounder (MLS) standard product for nitrous oxide derived from radiances measured primarily by the 640 GHz radiometer (Band 12)...

  10. Hydroxylation of benzene to phenol over magnetic recyclable nanostructured CuFe mixed-oxide catalyst

    CSIR Research Space (South Africa)

    Makgwane, PR

    2015-03-01

    Full Text Available A highly active and magnetically recyclable nanostructured copper–iron oxide (CuFe) catalyst has been synthesized for hydroxylation of benzene to phenol under mild reaction conditions. The obtained catalytic results were correlated with the catalyst...

  11. MLS/Aura L2 Nitrous Oxide (N2O) Mixing Ratio V002

    Data.gov (United States)

    National Aeronautics and Space Administration — ML2N2O is the EOS Aura Microwave Limb Sounder (MLS) standard product for nitrous oxide derived from radiances measured primarily by the 640 GHz radiometer (Band 12)...

  12. Nanostructured Metal Oxides And Mixed Metal Oxides, Methods Of Making These Nanoparticles, And Methods Of Their Use

    KAUST Repository

    Polshettiwar, Vivek

    2013-04-11

    Embodiments of the present disclosure provide for nanoparticles, methods of making nanoparticles, methods of using the nanoparticles, and the like. Nanoparticles of the present disclosure can have a variety of morphologies, which may lead to their use in a variety of technologies and processes. Nanoparticles of the present may be used in sensors, optics, mechanics, circuits, and the like. In addition, nanoparticles of the present disclosure may be used in catalytic reactions, for CO oxidation, as super-capacitors, in hydrogen storage, and the like.

  13. Study of the dissolution of (U,P)O2 mixed oxides with a high plutonium content

    International Nuclear Information System (INIS)

    Fournier, S.

    2001-01-01

    Plutonium from nuclear reactors is partially integrated in the fuel cycle as Mixed OXide (U,Pu)O 2 (MOX). Their dissolution in nitric acid is needed to reprocess them in present reprocessing plants. The main difficulty of this study is that dissolution is a phenomenon depending on solution characteristics as well as the structural properties of the pellets, which depend themselves on the material fabrication process. After showing kinetic and thermodynamic dissolution data of mixed oxides in nitric media, an inventory of the parameters which affect the dissolution process has been made. A separable variable concept was introduced in order to describe the process by studying separately the role of chemical parameters of the solution and geometric parameters of the material. The first part of the study estimates the effect of nitric solution chemical parameters (concentrations, acidity, temperature) on the dissolution and underlines the role of the oxide surface protonation step. The second part of this work deals with the study of surface area evolution for materials with controlled plutonium rich heterogeneities. Experimental results show that the pellet surface undergoes erosion and is progressively weakened by the formation of fault lines in the bulk of the material followed by the dispersion of sub-millimeter fragments in the solution. An heterogeneous kinetic model derived from study of solid-gas interface systems has been applied to fuel pellets dissolution, allowing a mechanism to be proposed, based on surface dissolution of the oxide as well as fault creation in the volume. The dissolution kinetics are therefore dependant on the microstructure and mechanical strength and cohesion of the pellets. (author)

  14. DRIFT study of CuO-CeO₂-TiO₂ mixed oxides for NOx reduction with NH₃ at low temperatures.

    Science.gov (United States)

    Chen, Lei; Si, Zhichun; Wu, Xiaodong; Weng, Duan

    2014-06-11

    A CuO-CeO2-TiO2 catalyst for selective catalytic reduction of NOx with NH3 (NH3-SCR) at low temperatures was prepared by a sol-gel method and characterized by X-ray diffraction, Brunner-Emmett-Teller surface area, ultraviolet-visible spectroscopy, H2 temperature-programmed reduction, scanning electron microscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). The CuO-CeO2-TiO2 ternary oxide catalyst shows excellent NH3-SCR activity in a low-temperature range of 150-250 °C. Lewis acid sites generated from Cu(2+) are the main active sites for ammonia activation at low temperature, which is crucial for low temperature NH3-SCR activity. The introduction of ceria results in increased reducibility of CuO species and strong interactions between CuO particles with the matrix. The interactions between copper, cerium and titanium oxides lead to high dispersion of metal oxides with increased active oxygen and enhanced catalyst acidity. Homogeneously mixed metal oxides facilitate the "fast SCR" reaction among Cu(2+)-NO, nitrate (coordinated on cerium sites) and ammonia (on titanium sites) on the CuO-CeO2-TiO2 catalyst at low temperatures.

  15. Deterioration of yttria-stabilized zirconia by boron carbide alone or mixed with metallic or oxidized Fe, Cr, Zr mixtures

    Science.gov (United States)

    De Bremaecker, A.; Ayrault, L.; Clément, B.

    2014-08-01

    In the frame of severe accident conditions (PHEBUS FPT3 test), different experiments were carried out on the interactions of 20% yttria-stabilized zirconia (YSZ) and 20% ceria-stab zirconia with boron carbide or its oxidation products (B2O3): either tests under steam between 1230° and 1700 °C with B4C alone or B4C mixed with metals, either tests under Ar with boron oxide present in a mixture of iron and chromium oxides. In all cases an interaction was observed with formation of intergranular yttrium borate. At 1700 °C boron oxide is able to “pump out” the Y stabiliser from the YSZ grains but also some trace elements (Ca and Al) and to form a eutectic containing YBO3 and yttrium calcium oxy-borate (YCOB). At the same time a substantial swelling (“bloating”) of the zirconia happens, qualitatively similar to the foaming of irradiated fuel in contact with a Zr-melt. In all samples the lowering of the Y (or Ce)-content in the YSZ grains is so sharp that in the interaction layers zirconia is no longer stabilized. This is important when YSZ is envisaged as simulant of UO2 or as inert matrix for Am-transmutation.

  16. Intraspecies diversity of Lactobacillus sakei response to oxidative stress and variability of strain performance in mixed strains challenges.

    Science.gov (United States)

    Guilbaud, Morgan; Zagorec, Monique; Chaillou, Stéphane; Champomier-Vergès, Marie-Christine

    2012-04-01

    Lactobacillus sakei is a meat-borne lactic acid bacterium species exhibiting a wide genomic diversity. We have investigated the diversity of response to various oxidative compounds, between L. sakei strains, among a collection representing the genomic diversity. We observed various responses to the different compounds as well as a diversity of response depending on the aeration conditions used for cell growth. A principal component analysis revealed two main phenotypic groups, partially correlating with previously described genomic clusters. We designed strains mixes composed of three different strains, in order to examine the behavior of each strain, when cultured alone or in the presence of other strains. The strains composing the mixtures were chosen as diverse as possible, i.e. exhibiting diverse responses to oxidative stress and belonging to different genomic clusters. Growth and survival rates of each strain were monitored under various aeration conditions, with or without heme supplementation. The results obtained suggest that some strains may act as "helper" or "burden" strains depending on the oxidative conditions encountered during incubation. This study confirms that resistance to oxidative stress is extremely variable within the L. sakei species and that this property should be considered when investigating starter performance in the complex meat bacterial ecosystems. Copyright © 2011 Elsevier Ltd. All rights reserved.

  17. Using dissolved oxygen concentrations to determine mixed layer depths in the Bellingshausen Sea

    Directory of Open Access Journals (Sweden)

    K. Castro-Morales

    2012-01-01

    Full Text Available Concentrations of oxygen (O2 and other dissolved gases in the oceanic mixed layer are often used to calculate air-sea gas exchange fluxes. The mixed layer depth (zmix may be defined using criteria based on temperature or density differences to a reference depth near the ocean surface. However, temperature criteria fail in regions with strong haloclines such as the Southern Ocean where heat, freshwater and momentum fluxes interact to establish mixed layers. Moreover, the time scales of air-sea exchange differ for gases and heat, so that zmix defined using oxygen may be different than zmix defined using temperature or density. Here, we propose to define an O2-based mixed layer depth, zmix(O2, as the depth where the relative difference between the O2 concentration and a reference value at a depth equivalent to 10 dbar equals 0.5 %. This definition was established by analysis of O2 profiles from the Bellingshausen Sea (west of the Antarctic Peninsula and corroborated by visual inspection. Comparisons of zmix(O2 with zmix based on potential temperature differences, i.e., zmix(0.2 °C and zmix(0.5 °C, and potential density differences, i.e., zmix(0.03 kg m−3 and zmix(0.125 kg m−3, showed that zmix(O2 closely follows zmix(0.03 kg m−3. Further comparisons with published zmix climatologies and zmix derived from World Ocean Atlas 2005 data were also performed. To establish zmix for use with biological production estimates in the absence of O2 profiles, we suggest using zmix(0.03 kg m−3, which is also the basis for the climatology by

  18. Analysis of plutonium isotope ratios including238Pu/239Pu in individual U-Pu mixed oxide particles by means of a combination of alpha spectrometry and ICP-MS.

    Science.gov (United States)

    Esaka, Fumitaka; Yasuda, Kenichiro; Suzuki, Daisuke; Miyamoto, Yutaka; Magara, Masaaki

    2017-04-01

    Isotope ratio analysis of individual uranium-plutonium (U-Pu) mixed oxide particles contained within environmental samples taken from nuclear facilities is proving to be increasingly important in the field of nuclear safeguards. However, isobaric interferences, such as 238 U with 238 Pu and 241 Am with 241 Pu, make it difficult to determine plutonium isotope ratios in mass spectrometric measurements. In the present study, the isotope ratios of 238 Pu/ 239 Pu, 240 Pu/ 239 Pu, 241 Pu/ 239 Pu, and 242 Pu/ 239 Pu were measured for individual Pu and U-Pu mixed oxide particles by a combination of alpha spectrometry and inductively coupled plasma mass spectrometry (ICP-MS). As a consequence, we were able to determine the 240 Pu/ 239 Pu, 241 Pu/ 239 Pu, and 242 Pu/ 239 Pu isotope ratios with ICP-MS after particle dissolution and chemical separation of plutonium with UTEVA resins. Furthermore, 238 Pu/ 239 Pu isotope ratios were able to be calculated by using both the 238 Pu/( 239 Pu+ 240 Pu) activity ratios that had been measured through alpha spectrometry and the 240 Pu/ 239 Pu isotope ratios determined through ICP-MS. Therefore, the combined use of alpha spectrometry and ICP-MS is useful in determining plutonium isotope ratios, including 238 Pu/ 239 Pu, in individual U-Pu mixed oxide particles. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Oxygen Storage Capacity and Oxygen Mobility of Co-Mn-Mg-Al Mixed Oxides and Their Relation in the VOC Oxidation Reaction

    Directory of Open Access Journals (Sweden)

    María Haidy Castaño

    2015-05-01

    Full Text Available Co-Mn-Mg-Al oxides were synthesized using auto-combustion and co-precipitation techniques. Constant ratios were maintained with (Co + Mn + Mg/Al equal to 3.0, (Co + Mn/Mg equal to 1.0 and Co/Mn equal to 0.5. The chemical and structural composition, redox properties, oxygen storage capacity and oxygen mobility were analyzed using X-ray fluorescence (XRF, X-ray diffraction (XRD, Raman spectroscopy, scanning electron microscopy (SEM, temperature-programmed reduction of hydrogen (H2-TPR, oxygen storage capacity (OSC, oxygen storage complete capacity (OSCC and isotopic exchange, respectively. The catalytic behavior of the oxides was evaluated in the total oxidation of a mixture of 250 ppm toluene and 250 ppm 2-propanol. The synthesis methodology affected the crystallite size, redox properties, OSC and oxide oxygen mobility, which determined the catalytic behavior. The co-precipitation method got the most active oxide in the oxidation of the volatile organic compound (VOC mixture because of the improved mobility of oxygen and ability to favor redox processes in the material structure.

  20. Redox properties and VOC oxidation activity of Cu catalysts supported on Ce{sub 1−x}Sm{sub x}O{sub δ} mixed oxides

    Energy Technology Data Exchange (ETDEWEB)

    Konsolakis, Michalis, E-mail: mkonsol@science.tuc.gr [Laboratory of Physical Chemistry and Chemical Processes, Department of Sciences, Technical University of Crete, University Campus, 73100 Chania (Greece); Carabineiro, Sónia A.C., E-mail: scarabin@fe.up.pt [Laboratório de Catálise e Materiais (LCM), Laboratório Associado LSRE/LCM, Faculdade de Engenharia, Universidade do Porto, 4200-465 Porto (Portugal); Tavares, Pedro B. [CQVR, Centro de Química – Vila Real, Departamento de Química, Universidade de Trás-os-Montes e Alto Douro, 5001-911 Vila Real (Portugal); Figueiredo, José L. [Laboratório de Catálise e Materiais (LCM), Laboratório Associado LSRE/LCM, Faculdade de Engenharia, Universidade do Porto, 4200-465 Porto (Portugal)

    2013-10-15

    Highlights: • Complete elimination of ethyl acetate is achieved at 260 °C with Cu/CeO{sub 2} catalysts. • Samarium has a detrimental impact on VOC oxidation, proportional to its content. • Incorporation of Sm in ceria has a detrimental effect on textural characteristics and reducibility. • Increase of Sm/Ce ratio results in a more reduced Cu species, inactive for VOC oxidation. • A correlation between VOC activity and catalysts redox properties is established. -- Abstract: A series of Cu catalysts supported on Ce{sub 1−x}Sm{sub x}O{sub δ} mixed oxides with different molar contents (x = 0, 0.25, 0.5, 0.75 and 1), was prepared by wet impregnation and evaluated for volatile organic compounds (VOC) abatement, employing ethyl acetate as model molecule. An extensive characterization study was undertaken in order to correlate the morphological, structural and surface properties of catalysts with their oxidation activity. The optimum performance was obtained with Cu/CeO{sub 2} catalyst, which offers complete conversion of ethyl acetate into CO{sub 2} at temperatures as low as 260 °C. The catalytic performance of Cu/Ce{sub 1−x}Sm{sub x}O{sub δ} was interpreted on the basis of characterization studies, showing that incorporation of samarium in ceria has a detrimental effect on the textural characteristics and reducibility of catalysts. Moreover, high Sm/Ce atomic ratios (from 1 to 3) resulted in a more reduced copper species, compared to CeO{sub 2}-rich supports, suggesting the inability of these species to take part in the redox mechanism of VOC abatement. Sm/Ce surface atomic ratios are always much higher than the nominal ratios indicating an impoverishment of catalyst surface in cerium oxide, which is detrimental for VOC activity.

  1. Mechanism of mechanochemical synthesis of complex oxides and the peculiarities of their nano-structurization determining sintering

    Directory of Open Access Journals (Sweden)

    Zyryanov V.V.

    2005-01-01

    Full Text Available A mechanism of superfast mechanosynthesis reaction for oxide systems is proposed on the base of a dynamics study. The threshold effect and linear dependence of the chemical response on the effective temperature of the reaction zone are established. Major factors are determined: molecular mass of reagents, enthalpy and difference of reagents in Mohs’s hardness, which also influence the composition of the primary product. Primary acts are characterized by a superfast roller mechanism of mass transfer with the formation of a transient dynamic state (D*. Secondary acts slowly approximate the composition of the product to the composition of the starting mixture by diffusion mass transfer in a deformation mixing regime with a contribution of a rotation (roller mechanism. The list of structure types for complex oxides derived by mechanosynthesis includes perovskites, fluorites, pyrochlors, sheelites, and some other ones. Powders of crystal products display multilevel structurization. In all studied complex oxides strong disordering of the “anti-glass” type was observed. The mechanism of sintering was studied in BaTiO3 powders of different origin and in metastable complex oxides derived by mechanosynthesis. The major contribution in shrinkage belongs to rearrangements of crystalline particles as a whole. Structure transformations accompany, as a rule, sintering of inhomogeneous powders derived by mechanosynthesis.

  2. Shelf sea tidal currents and mixing fronts determined from ocean glider observations

    Science.gov (United States)

    Sheehan, Peter M. F.; Berx, Barbara; Gallego, Alejandro; Hall, Rob A.; Heywood, Karen J.; Hughes, Sarah L.; Queste, Bastien Y.

    2018-03-01

    Tides and tidal mixing fronts are of fundamental importance to understanding shelf sea dynamics and ecosystems. Ocean gliders enable the observation of fronts and tide-dominated flows at high resolution. We use dive-average currents from a 2-month (12 October-2 December 2013) glider deployment along a zonal hydrographic section in the north-western North Sea to accurately determine M2 and S2 tidal velocities. The results of the glider-based method agree well with tidal velocities measured by current meters and with velocities extracted from the TPXO tide model. The method enhances the utility of gliders as an ocean-observing platform, particularly in regions where tide models are known to be limited. We then use the glider-derived tidal velocities to investigate tidal controls on the location of a front repeatedly observed by the glider. The front moves offshore at a rate of 0.51 km day-1. During the first part of the deployment (from mid-October until mid-November), results of a one-dimensional model suggest that the balance between surface heat fluxes and tidal stirring is the primary control on frontal location: as heat is lost to the atmosphere, full-depth mixing is able to occur in progressively deeper water. In the latter half of the deployment (mid-November to early December), a front controlled solely by heat fluxes and tidal stirring is not predicted to exist, yet a front persists in the observations. We analyse hydrographic observations collected by the glider to attribute the persistence of the front to the boundary between different water masses, in particular to the presence of cold, saline, Atlantic-origin water in the deeper portion of the section. We combine these results to propose that the front is a hybrid front: one controlled in summer by the local balance between heat fluxes and mixing and which in winter exists as the boundary between water masses advected to the north-western North Sea from diverse source regions. The glider observations

  3. Shelf sea tidal currents and mixing fronts determined from ocean glider observations

    Directory of Open Access Journals (Sweden)

    P. M. F. Sheehan

    2018-03-01

    Full Text Available Tides and tidal mixing fronts are of fundamental importance to understanding shelf sea dynamics and ecosystems. Ocean gliders enable the observation of fronts and tide-dominated flows at high resolution. We use dive-average currents from a 2-month (12 October–2 December 2013 glider deployment along a zonal hydrographic section in the north-western North Sea to accurately determine M2 and S2 tidal velocities. The results of the glider-based method agree well with tidal velocities measured by current meters and with velocities extracted from the TPXO tide model. The method enhances the utility of gliders as an ocean-observing platform, particularly in regions where tide models are known to be limited. We then use the glider-derived tidal velocities to investigate tidal controls on the location of a front repeatedly observed by the glider. The front moves offshore at a rate of 0.51 km day−1. During the first part of the deployment (from mid-October until mid-November, results of a one-dimensional model suggest that the balance between surface heat fluxes and tidal stirring is the primary control on frontal location: as heat is lost to the atmosphere, full-depth mixing is able to occur in progressively deeper water. In the latter half of the deployment (mid-November to early December, a front controlled solely by heat fluxes and tidal stirring is not predicted to exist, yet a front persists in the observations. We analyse hydrographic observations collected by the glider to attribute the persistence of the front to the boundary between different water masses, in particular to the presence of cold, saline, Atlantic-origin water in the deeper portion of the section. We combine these results to propose that the front is a hybrid front: one controlled in summer by the local balance between heat fluxes and mixing and which in winter exists as the boundary between water masses advected to the north-western North Sea from diverse source

  4. On the methods for determining the transverse dispersion coefficient in river mixing

    Science.gov (United States)

    Baek, Kyong Oh; Seo, Il Won

    2016-04-01

    In this study, the strengths and weaknesses of existing methods for determining the dispersion coefficient in the two-dimensional river mixing model were assessed based on hydraulic and tracer data sets acquired from experiments conducted on either laboratory channels or natural rivers. From the results of this study, it can be concluded that, when the longitudinal dispersion coefficient as well as the transverse dispersion coefficients must be determined in the transient concentration situation, the two-dimensional routing procedures, 2D RP and 2D STRP, can be employed to calculate dispersion coefficients among the observation methods. For the steady concentration situation, the STRP can be applied to calculate the transverse dispersion coefficient. When the tracer data are not available, either theoretical or empirical equations by the estimation method can be used to calculate the dispersion coefficient using the geometric and hydraulic data sets. Application of the theoretical and empirical equations to the laboratory channel showed that equations by Baek and Seo [[3], 2011] predicted reasonable values while equations by Fischer [23] and Boxwall and Guymer (2003) overestimated by factors of ten to one hundred. Among existing empirical equations, those by Jeon et al. [28] and Baek and Seo [6] gave the agreeable values of the transverse dispersion coefficient for most cases of natural rivers. Further, the theoretical equation by Baek and Seo [5] has the potential to be broadly applied to both laboratory and natural channels.

  5. The Determination of Total Nitrogen Oxides in Stack Gases. Phenoldisulfonic Acid Method.

    Science.gov (United States)

    Thorpe, Charles J. D.

    The well known Saltzman method for oxides of nitrogen is intended for the determination of these constituents in the ambient atmosphere in the range of a few parts per billion to about 5ppm. However, when sulfur dioxide is present in the gas to be sampled and/or the concentration range of the oxides of nitrogen is from five to several thousand…

  6. Determination and characterization by numerical simulations of flow mixing due to electrokinetic instabilities in cross-shaped microchannels

    Science.gov (United States)

    Guerrero, Esteban; Chen, Daming; Hageman, Logan; Guzman, Amador

    2017-11-01

    This article describes a computational study of flow mixing in microchannels due to electrokinetic instabilities that are compared to experimental results obtained in a cross- microchannel with an ionic solution of potassium chloride with two different ionic concentrations, with the purpose of determining the parameter combinations to produce the onset of flow mixing and its characteristics. For the numerical simulation process carried out using a finite element method-based commercial code, we applied a typical zeta potential used in other articles as a boundary condition for the microchannel walls. For the experiments, we used a commercial silicon glass (Caliper NS95) microchannel. For determining a flow mixing regime, we use the concept of ``mixing index'' established by (Fu et al., 2005) for an electrical conductivity ratio range of 18 to 52 with an electric field range of 1100 to 1900 V/cm. From our numerical simulation results we have found a threshold for the electrical Rayleigh number for starting a flow mixing regime, and a minimum microchannel characteristic length for achieving a 90% of flow mixing that will allow us to significantly reduce the mixing time. Vicerrectoria de Investigacion y Departamento de Ingeniera Mecánica y Metalúrgica Pontificia Universidad Catolica de Chile.

  7. A new method for the determination of the mixing ratio hydrogen to helium in the giant planets.

    Science.gov (United States)

    Gautier, D.; Grossman, K.

    1972-01-01

    By using a numerical iterative method, it is demonstrated that the mixing ratio H2/He on the giant planets can be inferred from spectral measurements of the intensity emitted by these planets in the far infrared range. The method is successfully applied to synthetic spectra of Saturn computed from atmospheric thermal models. The effect of random and systematic measurement errors on the determination of the mixing ratio is also studied.

  8. Analysis of homogeneity of mixed oxide (MOX) fuel surface by laser induced break down spectroscopy (LIBS)

    International Nuclear Information System (INIS)

    Detalle, V.; Lacour, J.L.; Mauchien, P.; Wagner, J.F.

    2000-01-01

    In the nuclear fuel cycle, plutonium is recycled to produce MOX fuel for use in PWR reactors. Surface inspections of mixed PuO 2 /UO 2 pellets is very important in the process. The performance of Laser Induced Breakdown Spectroscopy (LIBS) or Laser Ablation Optical Emission Spectroscopy (LA-OES) was therefore assessed for surface analysis of simulated MOX pellets containing a mixture of UO 2 and CeO 2 , and compared with results obtained with the standard Castaing microprobe analyzer technique. In LIBS, a material is ablated by focussing a laser beam, and the emission from neutral and ionized atoms can be used to determine the composition. An original experimental set up was developed to obtain a LIBS microprobe system for microanalysis of the sample surface. The instrument has three main components : a laser (quadrupled Nd YAG), an ablation head (using a microscope lens) and a detection unit (spectrometer combined with an ICCD Intensified Charge Coupled Device camera). The LIBS technique has well-known advantages particularly for nuclear applications: (1) it requires no sample preparation ; (2) only a small amount of material (craters 7 or 3 μm wide and 1 to 3 μm deep) is needed for the analysis; (3) analysis can be performed remotely via optical fiber, allowing measurements in a hostile environment and at atmospheric pressure. The experimental set-up developed demonstrated that the LIBS microprobe system can be used for surface analysis of UO 2 /CeO 2 pellets. Figure 1 shows the calibration curve obtained, with the Ce/U ratio versus Ce/U concentration. Good linearity was found and a relative standard deviation of 5 % was determined for 100 single shots. A qualitative comparison of the LIBS microanalysis set up and the Castaing microprobe analyzer is shown in Figure 2, which reveals the same features. Thus, both analytical techniques can identify the surface non-homogeneity of the pellet. While LIBS is destructive, it requires no sample preparation, is faster (2

  9. Synthesis and CO Oxidation Activity of 1D Mixed Binary Oxide CeO2-LaO x Supported Gold Catalysts

    Science.gov (United States)

    Yu, Huanhuan; Zhong, Siyuan; Zhu, Baolin; Huang, Weiping; Zhang, Shoumin

    2017-11-01

    One-dimensional (1D) Ce-La nanorods with different La contents (Ce and La in the molar ratio of 1:0, 3:1, 1:1, 1:3, and 0:1) were synthesized by hydrothermal process. Au/Ce-La nanorod catalysts were obtained by a modified deposition-precipitation method. The samples were characterized by N2 adsorption-desorption (BET), ICP, X-ray diffraction (XRD), SEM, TEM, EDX, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), and temperature-programmed reduction (H2-TPR). It revealed that La existed as LaO x in the 1D nanorods. The catalysis results demonstrated that the mixed binary Ce-La nanorod oxides could be a good support for gold catalysts. The contents of La had an important influence on the catalytic performance of Au/Ce-La nanorod catalysts. Among the catalysts, when the Ce/La molar ratio was 3:1, the 1.0%Au/Ce0.75-La0.25 nanorods pretreated at 300 °C showed the best activity among the catalysts for CO oxidation, which could convert CO completely at 30 °C. The catalysts also performed high temperature resistance and good stability for CO oxidation at the reaction temperatures of 40, 70, and 200 °C.

  10. Synthesis and CO Oxidation Activity of 1D Mixed Binary Oxide CeO2-LaOxSupported Gold Catalysts.

    Science.gov (United States)

    Yu, Huanhuan; Zhong, Siyuan; Zhu, Baolin; Huang, Weiping; Zhang, Shoumin

    2017-11-02

    One-dimensional (1D) Ce-La nanorods with different La contents (Ce and La in the molar ratio of 1:0, 3:1, 1:1, 1:3, and 0:1) were synthesized by hydrothermal process. Au/Ce-La nanorod catalysts were obtained by a modified deposition-precipitation method. The samples were characterized by N 2 adsorption-desorption (BET), ICP, X-ray diffraction (XRD), SEM, TEM, EDX, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), and temperature-programmed reduction (H 2 -TPR). It revealed that La existed as LaO x in the 1D nanorods. The catalysis results demonstrated that the mixed binary Ce-La nanorod oxides could be a good support for gold catalysts. The contents of La had an important influence on the catalytic performance of Au/Ce-La nanorod catalysts. Among the catalysts, when the Ce/La molar ratio was 3:1, the 1.0%Au/Ce 0.75 -La 0.25 nanorods pretreated at 300 °C showed the best activity among the catalysts for CO oxidation, which could convert CO completely at 30 °C. The catalysts also performed high temperature resistance and good stability for CO oxidation at the reaction temperatures of 40, 70, and 200 °C.

  11. Thermodynamics of alkali ion exchange from methanolic solutions on hydrous stannic oxide: Excess thermodynamic functions of mixing

    International Nuclear Information System (INIS)

    Misak, N.Z.; Mikhail, E.M.; Ghoneimy, H.F.

    1996-01-01

    Hydrous oxides are important adsorbents and ion exchangers whose use is particularly important in the nuclear fuel cycle and in isotope separation. One of their major advantages is their stability at relatively high radiation doses and temperatures. The thermodynamics of Li/Na and Li/Cs exchange on hydrous stannic oxide (α-stannic acid) was studied in aqueous and methanolic solutions. With respect to ΔG degree, the results in the aqueous medium are qualitatively similar to those for a β-stannic acid sample. For ΔH degree and ΔS degree, contrary results are obtained, possible reasons for which are discussed. The addition of methanol generally leads to a decrease in ΔG degree due to the changed entropy term. When comparison could be made (consistent standard states), the data of transfer thermodynamics showed that the effect of this addition on ion-solvent interactions is the major effect. However, the excess thermodynamic functions of mixing, calculated at different loadings, showed that upon the addition of methanol, the excess enthalpy and entropy of mixing decrease considerably at relatively low loadings and increase at high loadings. As these functions express the departure of the exchange reaction from ideality due to interactions (ion-fixed site and ion-solvent) in the solid phase, it was concluded that alcohol addition affects these interactions. This was not revealed in the transfer data where the whole-exchanger composition range was considered

  12. Ceramic processing of uranium-plutonium mixed oxide fuels (U1-yPuy)O2 with high plutonium content

    International Nuclear Information System (INIS)

    Vauchy, Romain; Robisson, Anne-Charlotte; Audubert, Fabienne; Hodaj, Fiqiri

    2014-01-01

    The ternary thermodynamic U-Pu-O system has been studied for decades for MOX fuel applications but the phase diagram is still not precisely described mostly in the UO 2 -PuO 2 -Pu 2 O 3 sub-system. Furthermore, uranium-plutonium mixed oxides containing high amounts of plutonium are now being considered within the scope of future nuclear reactors. Within this framework, obtaining homogeneous mixed oxides by powder metallurgy is paramount. The studied process is based on UO 2 and PuO 2 co-milling and applied to compounds with high Pu content. The objective of this study is obtaining microstructures free of local heterogeneities in the U-Pu distribution which are not suitable for research studies. Furthermore, in case of prospective irradiation application, local high Pu concentrations lead to 'hot spots' in the material influencing the fission gas release behaviour such as the thermal conductivity which may raise a number of safety issues. This study describes the effect of some fabrication parameters on the powder morphology and/or, on the final microstructure (e.g. U-Pu distribution). The co-milling, sieving and sintering steps were investigated within this scope and the resulting powders and pellets were characterised by X-ray diffraction (XRD) and optical microscopy observations, respectively. (authors)

  13. Improvement of power generation of microbial fuel cell by integrating tungsten oxide electrocatalyst with pure or mixed culture biocatalysts

    International Nuclear Information System (INIS)

    Varanasi, Jhansi L.; Nayak, Arpan K.; Sohn, Youngku; Pradhan, Debabrata; Das, Debabrata

    2016-01-01

    Highlights: • WO 3 as an efficient electrocatalyst for microbial fuel cell. • Effect of nanocatalyst depends on the type of biocatalyst used. • Significant improvement in biocatalysis with WO 3 modified electrodes. • Amendment of WO 3 improves capacitive properties of anodes. • Pt/WO 3 composites provide maximum power densities. - Abstract: The anode of microbial fuel cell was impregnated with tungsten oxide (WO 3 ) and platinum-tungsten oxide (Pt/WO 3 ) nanocomposites to improve its power generation. The amended anodes were tested against pure and mixed culture type of biocatalysts. Improved performance was exhibited by the modified electrodes as compared to the uncatalyzed electrodes using both biocatalysts. However, pure culture showed higher power outputs as compared to the enriched mixed consortia. The maximum power density up to 0.15 mW cm −2 (1.46 W m −2 ) was obtained using pure culture which was almost 45% higher as compared to uncatalyzed electrodes. The anode modification also helped in lowering the charge transfer resistance and improving the coulombic efficiencies of the MFCs. High capacitance with nanostructure catalysts implied their role in holding an electric charge while SEM and epifluorescent images revealed enhanced bacterial adhesion. The high electrode conductivity, stability, and biocompatibility of the modified anodes make them more attractive for practical microbial fuel cell applications.

  14. The surface behaviour and catalytic properties of Nd2-XSrXCoO4±Λ mixed oxides

    Directory of Open Access Journals (Sweden)

    Laitao Luo

    2006-12-01

    Full Text Available The mixed oxides, Nd2-xSrxCoO4±λ (0.4 ≤ x ≤ 1.2, ( = non-stochiometric oxygen with the K2NiF4 structure were prepared by the polyglycol gel method and used as catalysts for NO reduction. The samples were investigated by IR, TPD, TPR, and XRD methods and iodometry and the effects of the coefficient x on the structure and catalytic activity of the samples were studied. The results show that the Nd2-xSrxCoO4±λ mixed oxides have the K2NiF4 structure; other phases are found when x 1.2. The amount of Co3+ and the lattice oxygen in Nd2-xSrxCoO4±λ increase with increasing x. The catalytic activity of Nd2-xSrxCoO4±λfor NO reduction is closely correlated with the concentration of oxygen vacancies and the amount of Co3+.

  15. Electrocatalytic Oxidation and Determination of Cysteine at Oxovanadium(IV Salen Coated Electrodes

    Directory of Open Access Journals (Sweden)

    Piyush Kumar Sonkar

    2014-01-01

    Full Text Available A transition metal complex, oxovanadium(IV salen (where salen represents N,N′-bis(salicylideneethylenediamine is immobilized on glassy carbon (GC electrodes and utilized for electrocatalytic oxidation of cysteine. In presence of oxovanadium(IV salen, increased oxidation current is observed due to the effective oxidation of cysteine by the electrogenerated oxovanadium(V salen species. The oxidation current linearly varies with the concentration of cysteine from 0.1 to 1.0 mM. The modified electrode has good sensitivity and low limit of detection. These properties make the oxovanadium(IV salen as an effective electrocatalyst for the determination of cysteine.

  16. Techniques for determining total body water using deuterium oxide

    Science.gov (United States)

    Bishop, Phillip A.

    1990-01-01

    The measurement of total body water (TBW) is fundamental to the study of body fluid changes consequent to microgravity exposure or treatment with microgravity countermeasures. Often, the use of radioactive isotopes is prohibited for safety or other reasons. It was selected and implemented for use by some Johnson Space Center (JCS) laboratories, which permitted serial measurements over a 14 day period which was accurate enough to serve as a criterion method for validating new techniques. These requirements resulted in the selection of deuterium oxide dilution as the method of choice for TBW measurement. The development of this technique at JSC is reviewed. The recommended dosage, body fluid sampling techniques, and deuterium assay options are described.

  17. Reactivity of oxygen ions in mixed oxides in dehydrogenation of propane

    NARCIS (Netherlands)

    Crapanzano, S.D.

    2010-01-01

    Propane pulse experiments are used as a method to select suitable oxides as oxygen supplier for operation of catalytic dense membrane reactor (CDMR) in oxidative dehydrogenation of propane. Ba0.5Sr0.5Co0.8Fe0.2O3-d (BSCF), La2NiO4+d (LN), La2Ni0.9V0.1O4.15+d (LNV-10) and PrBaCo2O5+d (PBC) powders

  18. Determinants of the acetate recovery factor: implications for estimation of 13C substrate oxidation.

    NARCIS (Netherlands)

    P. Schrauwen; E.E. Blaak; A.J.M. Wagenmakers; dr. Lars B. Borghouts; D.P.C. van Aggel-Leijssen

    2000-01-01

    The data of this study indicate that the acetate recovery factor, used in stable isotope research, needs to be deteremined in every subject, under similar conditions as used for the tracer-derived determination of substrate oxidation.

  19. A CFD model for determining mixing and mass transfer in a high power agitated bioreactor

    OpenAIRE

    Bach, Christian; Albæk, Mads O.; Stocks, Stuart M.; Krühne, Ulrich; Gernaey, Krist V.

    2016-01-01

    Prediction of mixing and mass transfer in agitated systems is a vital tool for process development and scale up in industrial biotechnology. In particular key process parameters such as mixing time and kLa are essential for bioprocess development [1]. In this work the mixing and mass transfer performance of a high power agitated pilot scale bioreactor has been characterized using a novel combination of computational fluid dynamics (CFD) and experimental investigations. The effect of turbulenc...

  20. Indirect spectrophotometric determination of piroxicam and tenoxicam through oxidation with potassium permanganate

    OpenAIRE

    A.S. Amin; H.A. Dessouki; K.M. Khalil

    2010-01-01

    Three rapid, simple, accurate and selective validated spectrophtometric methods (A, B and C) for the determination of piroxicam (PX) and tenoxicam (TX) in bulk sample and in dosage forms are described. The methods are based on the oxidation of the studied drugs by a known excess of potassium permanganate in sulfuric acid medium and subsequent determination of unreacted oxidant by reacting it with Methylene Blue (Basic Blue 9) dye (method A), Acid Red 27 (Amaranth) dye (method B) and Acid Oran...

  1. Determination of plutonium oxidation states at trace levels pertinent to nuclear waste disposal

    International Nuclear Information System (INIS)

    Nitsche, H.; Lee, S.C.; Gatti, R.C.

    1987-04-01

    A scheme was developed for the determination of oxidation states of plutonium in environmental samples. The method involves a combination of solvent extractions and coprecipitation. It was tested on solutions with both high-level and trace-level concentrations. The scheme was used to determine Pu oxidation states in solutions from solubility experiments in groundwater from a potential nuclear waste disposal site. At steady-state conditions, Pu was found to be soluble predominantly as Pu(V) and Pu(VI)

  2. Synthesis of coral-like tantalum oxide films via anodization in mixed organic-inorganic electrolytes.

    Directory of Open Access Journals (Sweden)

    Hongbin Yu

    Full Text Available We report a simple method to fabricate nano-porous tantalum oxide films via anodization with Ta foils as the anode at room temperature. A mixture of ethylene glycol, phosphoric acid, NH4F and H2O was used as the electrolyte where the nano-porous tantalum oxide could be synthesized by anodizing a tantalum foil for 1 h at 20 V in a two-electrode configuration. The as-prepared porous film exhibited a continuous, uniform and coral-like morphology. The diameters of pores ranged from 30 nm to 50 nm. The pores interlaced each other and the depth was about 150 nm. After calcination, the as-synthesized amorphous tantalum oxide could be crystallized to the orthorhombic crystal system. As observed in photocatalytic experiments, the coral-like tantalum oxide exhibited a higher photocatalytic activity for the degradation of phenol than that with a compact surface morphology, and the elimination rate of phenol increased by 66.7%.

  3. Mixed Oxidant Process for Control of Biological Growth in Cooling Towers

    Science.gov (United States)

    2010-02-01

    Generation Process • Electrolysis of salt to generate chlorine biocides • Small-scale electrolytic cell generates biocide on site, on demand from a...Laboratory US Army Corps of Engineers Engineer Research & Development Center Construction Engineering Research Laboratory Brine and Oxidant Tanks

  4. Physical Properties of Mixed Conductor Solid Oxide Fuel Cell Anodes of Doped CeO2

    DEFF Research Database (Denmark)

    Mogensen, Mogens Bjerg; Lindegaard, Thomas; Hansen, Uffe Rud

    1994-01-01

    conductivity vs. oxygen partial pressure. For both typesof conductivity a dependence on dopant valency was observed. The electronic conductivity was independent of dopantradius in contrast to the ionic which was highly dependent. These measured physical properties are compared with the idealrequirements...... for solid oxide fuel cell anodes. Not all requirements are fulfilled. Measures to compensate for this arediscussed....

  5. Effect of Promoters in Co-Mn-Al Mixed Oxide Catalyst on N2O Decomposition

    Czech Academy of Sciences Publication Activity Database

    Karásková, K.; Obalová, L.; Jirátová, Květa; Kovanda, F.

    2010-01-01

    Roč. 160, č. 2 (2010), s. 480-487 ISSN 1385-8947 R&D Projects: GA ČR GA106/09/1664 Institutional research plan: CEZ:AV0Z40720504 Keywords : nitrous oxide * catalytic decomposition * promoter effect Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 3.074, year: 2010

  6. Degradation of organophosphorus pesticide parathion methyl on nanostructured titania-iron mixed oxides

    Czech Academy of Sciences Publication Activity Database

    Henych, Jiří; Štengl, Václav; Slušná, Michaela; Matys Grygar, Tomáš; Janoš, P.; Kuráň, P.; Šťastný, M.

    2015-01-01

    Roč. 344, JUL (2015), s. 9-16 ISSN 0169-4332 R&D Projects: GA ČR(CZ) GAP106/12/1116 Institutional support: RVO:61388980 Keywords : Titania-iron oxides * Homogeneous hydrolysis * Degradation of organophosphates * Parathion methyl Subject RIV: CA - Inorganic Chemistry Impact factor: 3.150, year: 2015

  7. Testing of wet scrap recovery equipment for mixed oxide scrap reprocessing

    International Nuclear Information System (INIS)

    Demiter, J.A.; Klem, M.J.; Owen, T.J.

    1984-08-01

    The Wet Scrap Recovery (WSR) program was initiated at the Hanford Engineering Development Laboratory (HEDL) by Westinghouse Hanford Company in Richland, Washington to demonstrate fuel fabrication scrap recovery and reconversion to fuel grade oxide powder using the continuous coprecipitation-calcination (COPRECAL) conversion process. Advancements in process control equipment and instrumentation were also developed and demonstrated

  8. Thermal expansion and thermal conductivity of (Th,U)O{sub 2} mixed oxides: A molecular dynamics and experimental study

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, P.S., E-mail: psghosh@barc.gov.in [Materials Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Somayajulu, P.S. [Radiometallurgy Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Krishnan, K. [Fuel Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Pathak, N. [Radio Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Arya, A.; Dey, G.K. [Materials Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

    2015-11-25

    Thermal expansion and thermal conductivity of ThO{sub 2} and (Th,U)O{sub 2} mixed oxides (MOX) have been investigated by using molecular dynamics (MD) simulation and experimental study. MD simulation have been performed to determine lattice thermal expansion of Th{sub 1−x}U{sub x}O{sub 2} (x = 0 to 0.3125) solid-solutions in the temperature range of 300–3000 K using a combination of Coulomb-Buckingham-Morse and many-body potential model with partial ionic charges. Special quasi-random structures were employed to establish solid-solution configurations. Experimental verification of the lattice thermal expansion behavior is carried out on polycrystalline sample of ThO{sub 2} -x wt.% UO{sub 2} (x = 0, 6, 13, 25 and 30) MOX from room temperature to 1273 K in vacuum using high temperature X-ray diffraction (HT-XRD). Our combined MD simulations and HT-XRD measurements indicate that incorporation of UO{sub 2} in ThO{sub 2} systematically increases coefficient of thermal expansion but the rate of increase is higher in low UO{sub 2} composition range (≤13 wt.%). A comparative evaluation of the thermal properties of ThO{sub 2}-6wt.% UO{sub 2} pellets prepared by coated agglomerate pelletization (CAP) process and powder metallurgy routes (sintered in Ar-8%H{sub 2} atmosphere) have been performed with respect to micro-inhomogeneity, porosity, O/M and trace impurities. The thermal conductivity of ThO{sub 2} and ThO{sub 2}-6 wt.% UO{sub 2} calculated under equilibrium condition by Green–Kubo formalism show good agreement with our experimental measurements. - Highlights: • Thermal expansions of ThO{sub 2} and ThO{sub 2}-6,13,25 and 30 wt.% UO{sub 2} are measured by HT-XRD. • MD calculated lattice thermal expansion of Th{sub 1−x}U{sub x}O{sub 2} (0 ≤ x ≤ 0.3125) between 300 and 3000 K. • Comparative evaluation of thermal properties of ThO{sub 2}-6wt.% UO{sub 2} (CAP and POP pellets). • Evaluation of micro-inhomogeneity, porosity, O/M and trace impurities of

  9. Precision determination of uranium in uranium oxide by constant-current coulometry

    International Nuclear Information System (INIS)

    Xu Laili; Wang Chunhuan.

    1990-01-01

    A method of constant-current coulometric titration for determination of uranium in uranium oxide is described. This method involves preliminary reduction of U (VI) in H 2 SO 4 -H 3 PO 4 medium by Cr (II) as a reductant, followed by air oxidation of excess of Cr (II), addition of solid K 2 Cr 2 O 7 in quantity slightly more than that of the required for quantitative oxidation of U (IV) and final titration of excess of K 2 Cr 2 O 7 with the electrogenerated Fe (II). The endpoint is determined amperometrically. The effect of various factors on the sample treatment and reduction-oxidation processes has been examined. The precision of the method as indicated by the standard deviation of an individual observation is less than 0.01% for l gram uranium oxide

  10. Rapid and Sensitive Determination of Lipid Oxidation Using the Reagent Kit Based on Spectrophotometry (FOODLABfat System

    Directory of Open Access Journals (Sweden)

    Chang Woo Kwon

    2016-01-01

    Full Text Available The reliability and availability of FOODLABfat system for determining acid value (AV and peroxide value (POV were assessed during the hydrolytic rancidification and lipid oxidation of edible oils. This reagent kit based on spectrophotometry was compared to the official methods (ISO 660 and 3960 protocols based on manual titration employing the standard mixture for the simulated oxidation models and edible oils during the thermally induced oxidation at 180°C. The linear regression line of standard mixture and the significant difference of thermally oxidized time course study determined between them showed high correlations (R2=0.998 and p<0.05 in both AVs and POVs. Considering ISO protocols with a probability of human error in manual titration, the rapidness and simplicity of the reagent kit based on spectrophotometry make it a promising alternative to monitor the lipid oxidation of edible oils and lipid-containing foods.

  11. Advanced methods for the fabrication of mixed uranium plutonium oxide, monocarbide and mononitride fuels for fast breeder reactors

    International Nuclear Information System (INIS)

    Ganguly, C.

    1988-01-01

    Mixed uranium plutonium monocarbide (MC) and mononitride (MN) are considered as advanced LMFBR fuels. 'Powder-pellet (POP) is the conventional method for production of MOX, MC and MN fuel pellets starting from UO 2 and PuO 2 powders. The POP route involves generation and handling of plutonium bearing fine powder or dust particles which has the problem of radiotoxic dust hazard. Further, fine powders have poor flowability which makes automation and remote fabrication difficult. The combination of ammonium uranyl plutonyl carbonate (AUPuC) process and low temperature oxidative sintering (LTS) minimises the radiotoxic dust hazard and the fabrication cost of MOX fuel and is considered as advanced POP route. Vibro-sol (or sphere-pac) and sol-gel microsphere pelletisation (SGMP) are advanced methods for fabrication of MOX, MC and MN fuels. Here, dust-free and free-flowing gel microspheres of the oxide or oxide-carbon are prepared from heavy metal nitrate feed solutions by 'internal' or 'external' gelation processes. The gel microspheres are subjected to controlled calcination for MOX or carbothermic reduction for MC and MN. Thereafter, the microspheres are either vibropacked in fuel pins or directly pelletised and sintered. These processes minimise radiotoxic dust hazard, facilitate automation and remote processing and ensure excellent microhomogeneity. The present paper summarises the state-of-art of the POP, vibrosol and SGMP processes for the fabrication of MOX, MC and MN fuels, highlighting the author's experience in SGMP process. (author). 21 refs., 11 figs

  12. Determination of Protein Content by NIR Spectroscopy in Protein Powder Mix Products.

    Science.gov (United States)

    Ingle, Prashant D; Christian, Roney; Purohit, Piyush; Zarraga, Veronica; Handley, Erica; Freel, Keith; Abdo, Saleem

    2016-01-01

    Protein is a principal component in commonly used dietary supplements and health food products. The analysis of these products, within the consumer package form, is of critical importance for the purpose of ensuring quality and supporting label claims. A rapid test method was developed using near-infrared (NIR) spectroscopy as a compliment to current protein determination by the Dumas combustion method. The NIR method was found to be a rapid, low-cost, and green (no use of chemicals and reagents) complimentary technique. The protein powder samples analyzed in this study were in the range of 22-90% protein. The samples were prepared as mixtures of soy protein, whey protein, and silicon dioxide ingredients, which are common in commercially sold protein powder drink-mix products in the market. A NIR regression model was developed with 17 samples within the constituent range and was validated with 20 independent samples of known protein levels (85-88%). The results show that the NIR method is capable of predicting the protein content with a bias of ±2% and a maximum bias of 3% between NIR and the external Dumas method.

  13. Determining the optimal product-mix using integer programming: An application in audio speaker production

    Science.gov (United States)

    Khan, Sahubar Ali Bin Mohamed Nadhar; Ahmarofi, Ahmad Afif Bin

    2014-12-01

    In manufacturing sector, production planning or scheduling is the most important managerial task in order to achieve profit maximization and cost minimization. With limited resources, the management has to satisfy customer demand and at the same time fulfill company's objective, which is to maximize profit or minimize cost. Hence, planning becomes a significant task for production site in order to determine optimal number of units for each product to be produced. In this study, integer programming technique is used to develop an appropriate product-mix planning to obtain the optimal number of audio speaker products that should be produced in order to maximize profit. Branch-and-bound method is applied to obtain exact integer solutions when non-integer solutions occurred. Three major resource constraints are considered in this problem: raw materials constraint, demand constraint and standard production time constraint. It is found that, the developed integer programming model gives significant increase in profit compared to the existing method used by the company. At the end of the study, sensitivity analysis was performed to evaluate the effects of changes in objective function coefficient and available resources on the developed model. This will enable the management to foresee the effects on the results when some changes happen to the profit of its products or available resources.

  14. On-line determination of ammonia at low pptv mixing ratios in the CLOUD chamber

    CERN Document Server

    Bianchi, F; Mathot, S; Baltensperger, U

    2012-01-01

    A new instrument for the on-line determination of ammonia was developed. Since ammonia is a rather sticky compound, sampling losses were minimised with a new sam- pling device where the ammonia was transferred to the liq- uid phase only 5 mm after the inlet tip. The liquid phase was then analyzed by long pathlength absorption spectrophotom- etry using the Berthelot reaction with phenol and hypochlo- rite as reagents. The measurements were made during the CLOUD3 campaign at CERN where the influence of ammo- nia on the nucleation rate was studied. At stable conditions the detection limit reached with this instrument was 35 pptv (air flow rate of 2 l min − 1 , liquid flow rate of 0.3 ml min − 1 ), although occasionally the instrument was affected by back- ground problems. The range of mixing ratios during this campaign was varied from the background contamination ( < 35 pptv) up to around 2 ppbv. The measured ammonia concentration was correlated with the rate of ammonia in- jected into the chamber, but wi...

  15. Motivating medical students to do research: a mixed methods study using Self-Determination Theory.

    Science.gov (United States)

    Rosenkranz, Sara K; Wang, Shaoyu; Hu, Wendy

    2015-06-02

    It is widely accepted that all medical graduates should understand the uses and methods of rigorous research, with a need to promote research to graduates who will pursue an academic career. This study aimed to explore, identify and explain what motivates and demotivates medical students to do research. A convergent parallel mixed methods study was conducted. Cross-sectional quantitative survey data (n = 579) and qualitative semi-structured interview findings (n = 23) data were separately collected and analysed. Informed by Self-Determination Theory (SDT), quantitative and qualitative findings were integrated to develop a model for the factors associated with medical students' expressed motivation to do research, and related to clinical and research learning activities at different stages in an undergraduate medical program. Only 7.5% of students had research experience prior to entering the program. Survey results revealed that students who had experienced exposure to the uncertainties of clinical practice through clerkships (Pre-Clinical (48%) vs Clinical Years (64%), p motivation to do research is associated with increasing internalization of intrinsic motivators; in particular those associated with competence (Confidence) and relatedness (Clinical Relevance, Research as a Social Activity). SDT is useful for understanding the motivation of individuals and how curriculum can be designed to optimise motivation. Study findings suggest that well supported compulsory research activities that incorporate group learning and elements of choice may promote motivation to do research, and potentially, careers in research, even in a research naive student body.

  16. Electric field strength determination in filamentary DBDs by CARS-based four-wave mixing

    Science.gov (United States)

    Boehm, Patrick; Kettlitz, Manfred; Brandenburg, Ronny; Hoeft, Hans; Czarnetzki, Uwe

    2016-09-01

    The electric field strength is a basic parameter of non-thermal plasmas. Therefore, a profound knowledge of the electric field distribution is crucial. In this contribution a four wave mixing technique based on Coherent Anti-Stokes Raman spectroscopy (CARS) is used to measure electric field strengths in filamentary dielectric barrier discharges (DBDs). The discharges are operated with a pulsed voltage in nitrogen at atmospheric pressure. Small amounts hydrogen (10 vol%) are admixed as tracer gas to evaluate the electric field strength in the 1 mm discharge gap. Absolute values of the electric field strength are determined by calibration of the CARS setup with high voltage amplitudes below the ignition threshold of the arrangement. Alteration of the electric field strength has been observed during the internal polarity reversal and the breakdown process. In this case the major advantage over emission based methods is that this technique can be used independently from emission, e.g. in the pre-phase and in between two consecutive, opposite discharge pulses where no emission occurs at all. This work was supported by the Deutsche Forschungsgemeinschaft, Forschergruppe FOR 1123 and Sonderforschungsbereich TRR 24 ``Fundamentals of complex plasmas''.

  17. Purity of graphene oxide determines its antibacterial activity

    Science.gov (United States)

    Barbolina, I.; Woods, C. R.; Lozano, N.; Kostarelos, K.; Novoselov, K. S.; Roberts, I. S.

    2016-06-01

    Nanomaterials based on two-dimensional (2D) atomic crystals are considered to be very promising for various life-science and medical applications, from drug delivery to tissue modification. One of the most suitable materials for these purposes is graphene oxide (GO), thanks to a well-developed methods of production and water solubility. At the same time, its biological effect is still debated. Here we demonstrate that highly purified and thoroughly washed GO neither inhibited nor stimulated the growth of E.coli, ATCC25922; E.coli NCIMB11943 and S.aureus ATCC25923 at concentrations of up to 1 mg ml-1. Moreover, transmission electron microscopy (TEM) of GO exposed bacteria did not reveal any differences between GO exposed and not exposed populations. In contrast, a suspension of insufficiently purified GO behaved as an antibacterial material due to the presence of soluble acidic impurities, that could be removed by extended purification or neutralisation by alkaline substrates. A standardised protocol is proposed for the generation of clean GO, so it becomes suitable for biological experiments. Our findings emphasise the importance of GO purification status when dealing with biological systems as the true effect of material can be masked by the impact of impurities.

  18. Quantitative determination of tritium in metals and oxides

    International Nuclear Information System (INIS)

    Vance, D.E.; Smith, M.E.; Waterbury, G.R.

    1979-04-01

    Metallic samples are analyzed for tritium by heating the sample at 1225 K in a moist oxygen stream. The volatile products are trapped and the tritium is quantitatively determined by scintillation spectroscopy. The method is used to determine less than 1 ppb of tritium in 100-mg samples of lithium, iron, nickel, cerium, plutonium, and plutonium dioxide. Analysis of 18 cuts of a tritium-zirconium, copper foil standard over a 3-yr period showed a tritium content of 45 ppM and a standard deviation of 6 ppM

  19. The determinants of traditional medicine use in Northern Tanzania: a mixed-methods study.

    Directory of Open Access Journals (Sweden)

    John W Stanifer

    Full Text Available Traditional medicines are an important part of healthcare in sub-Saharan Africa, and building successful disease treatment programs that are sensitive to traditional medicine practices will require an understanding of their current use and roles, including from a biomedical perspective. Therefore, we conducted a mixed-method study in Northern Tanzania in order to characterize the extent of and reasons for the use of traditional medicines among the general population so that we can better inform public health efforts in the region.Between December 2013 and June 2014 in Kilimanjaro, Tanzania, we conducted 5 focus group discussions and 27 in-depth interviews of key informants. The data from these sessions were analyzed using an inductive framework method with cultural insider-outsider coding. From these results, we developed a structured survey designed to test different aspects of traditional medicine use and administered it to a random sample of 655 adults from the community. The results were triangulated to explore converging and diverging themes.Most structured survey participants (68% reported knowing someone who frequently used traditional medicines, and the majority (56% reported using them themselves in the previous year. The most common uses were for symptomatic ailments (42%, chronic diseases (15%, reproductive problems (11%, and malaria/febrile illnesses (11%. We identified five major determinants for traditional medicine use in Northern Tanzania: biomedical healthcare delivery, credibility of traditional practices, strong cultural identities, individual health status, and disease understanding.In order to better formulate effective local disease management programs that are sensitive to TM practices, we described the determinants of TM use. Additionally, we found TM use to be high in Northern Tanzania and that its use is not limited to lower-income areas or rural settings. After symptomatic ailments, chronic diseases were reported as

  20. Electrochemical determination of oxygen stoichiometry and entropy in oxides

    DEFF Research Database (Denmark)

    Zachau-Christiansen, Birgit; Jacobsen, Torben; Skaarup, Steen

    1996-01-01

    in the temperature range 800-1000 degrees C. With scan rates of 2 mu V/s potential sweeps on CeO2 are reversible. The change in entropy is determined by either subtraction of e.m.f. curves obtained by potential sweeps of different temperatures or by measuring the e.m.f. during a temperature scan. The latter method...

  1. Determination of contaminators in high purity lead oxide

    International Nuclear Information System (INIS)

    Bellavigna, H.J.; Farias de Funes, S.; Garavaglia, R.N.

    1990-01-01

    Litharge (PbO) is one of the raw materials used in glass fabrication for shielding and cathodic ray tubes employed in measurement instruments; some elements such as silver, chromium, arsenic, bismuth, etc. may confer to the mentioned glasses different unwanted tones which cause image distortion. Emission spectroscopy with photographic detection gives a quick, effective and economical alternative to determine these impurities. (Author) [es

  2. Research on identification and determination of mixed pesticides in apples using surface enhanced Raman spectroscopy

    Science.gov (United States)

    Zhai, Chen; Li, Yongyu; Peng, Yankun; Xu, Tianfeng; Dhakal, Sagar; Chao, Kuanglin; Qin, Jianwei

    2015-05-01

    Residual pesticides in fruits and vegetables have become one of the major food safety concerns around the world. At present, routine analytical methods used for the determination of pesticide residue on the surface of fruits and vegetables are destructive, complex, time-consuming, high cost and not environmentally friendly. In this study, a novel Surface Enhanced Raman Spectroscopy (SERS) method with silver colloid was developed for fast and sensitive nondestructive detection of residual pesticides in fruits and vegetables by using a self-developed Raman system. SERS technology is a combination of Raman spectroscopy and nanotechnology. SERS can greatly enhance the Raman signal intensity, achieve single-molecule detection, and has a simple sample pre-treatment characteristic of high sensitivity and no damage; in recent years it has begun to be used in food safety testing research. In this study a rapid and sensitive method was developed to identify and analyze mixed pesticides of chlorpyrifos, deltamethrin and acetamiprid in apple samples by SERS. Silver colloid was used for SERS measurement by hydroxylamine hydrochloride reduced. The advantages of this method are seen in its fast preparation at room temperature, good reproducibility and immediate applicability. Raman spectrum is highly interfered by noise signals and fluorescence background, which make it too complex to get good result. In this study the noise signals and fluorescence background were removed by Savitzky-Golay filter and min-max signal adaptive zooming method. Under optimal conditions, pesticide residues in apple samples can be detected by SERS at 0.005 μg/cm2 and 0.002 μg/cm2 for individual acetamiprid and thiram, respectively. When mixing the two pesticides at low concentrations, their characteristic peaks can still be identified from the SERS spectrum of the mixture. Based on the synthesized material and its application in SERS operation, the method represents an ultrasensitive SERS performance

  3. Final Report: Fiscal Year 1997 demonstration of omnivorous non-thermal mixed waste treatment: Direct chemical oxidation of organic solids and liquids using peroxydisulfate

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, J.F.

    1998-01-01

    Direct Chemical Oxidation (DCO) is a non-thermal, ambient pressure, aqueous-based technology for the oxidative destruction of the organic components of hazardous or mixed waste streams. The process has been developed for applications in waste treatment, chemical demilitarization and decontamination at LLNL since 1992. The process uses solutions of the peroxydisulfate ion (typically sodium or ammonium salts) to completely mineralize the organics to carbon dioxide and water. The expended oxidant may be electrolytically regenerated to minimize secondary waste. The paper briefly describes: free radical and secondary oxidant formation; electrochemical regeneration; offgas stream; and throughput.

  4. Final Report: Fiscal Year 1997 demonstration of omnivorous non-thermal mixed waste treatment: Direct chemical oxidation of organic solids and liquids using peroxydisulfate

    International Nuclear Information System (INIS)

    Cooper, J.F.; Ballazs G.B.

    1998-01-01

    Direct Chemical Oxidation (DCO) is a non-thermal, ambient pressure, aqueous-based technology for the oxidative destruction of the organic components of hazardous or mixed waste streams. The process has been developed for applications in waste treatment, chemical demilitarization and decontamination at LLNL since 1992. The process uses solutions of the peroxydisulfate ion (typically sodium or ammonium salts) to completely mineralize the organics to carbon dioxide and water. The expended oxidant may be electrolytically regenerated to minimize secondary waste. The paper briefly describes: free radical and secondary oxidant formation; electrochemical regeneration; offgas stream; and throughput

  5. The use of the average plutonium-content for criticality evaluation of boiling water reactor mixed oxide-fuel transport and storage packages

    International Nuclear Information System (INIS)

    Mattera, C.

    2003-01-01

    Currently in France, criticality studies in transport configurations for Boiling Water Reactor Mixed Oxide fuel assemblies are based on conservative hypothesis assuming that all rods (Mixed Oxide (Uranium and Plutonium), Uranium Oxide, Uranium and (Gadolinium Oxide rods) are Mixed Oxide rods with the same Plutonium-content, corresponding to the maximum value. In that way, the real heterogeneous mapping of the assembly is masked and covered by an homogenous Plutonium-content assembly, enriched at the maximum value. As this calculation hypothesis is extremely conservative, Cogema Logistics (formerly Transnucleaire) has studied a new calculation method based on the use of the average Plutonium-content in the criticality studies. The use of the average Plutonium-content instead of the real Plutonium-content profiles provides a highest reactivity value that makes it globally conservative. This method can be applied for all Boiling Water Reactor Mixed Oxide complete fuel assemblies of type 8 x 8, 9 x 9 and 10 x 10 which Plutonium-content in mass weight does not exceed 15%; it provides advantages which are discussed in the paper. (author)

  6. A novel electronic current-blocked stable mixed ionic conductor for solid oxide fuel cells

    NARCIS (Netherlands)

    Sun, Wenping; Jiang, Yinzhu; Wang, Yanfei; Fang, S.; Zhu, Zhiwen; Liu, Wei

    2011-01-01

    A novel ionic conductor, BaCe0.8Sm0.2O3¿¿¿Ce0.8Sm0.2O2¿¿ (BCS¿SDC, weight ratio 1:1), is reported as an electrolyte material for solid oxide fuel cells (SOFCs). Homogeneous BCS¿SDC composite powders are synthesized via a one-step gel combustion method. The BCS and SDC crystalline grains play a role

  7. A novel electronic current-blocked stable mixed ionic conductor for solid oxide fuel cells

    NARCIS (Netherlands)

    Sun, Wenping; Jiang, Yinzhu; Wang, Yanfei; Fang, S.; Zhu, Zhiwen; Liu, Wei

    2011-01-01

    A novel ionic conductor, BaCe0.8Sm0.2O3−δ–Ce0.8Sm0.2O2−δ (BCS–SDC, weight ratio 1:1), is reported as an electrolyte material for solid oxide fuel cells (SOFCs). Homogeneous BCS–SDC composite powders are synthesized via a one-step gel combustion method. The BCS and SDC crystalline grains play a role

  8. In-situ investigation of the calcination process of mixed oxide xerogels with Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Panitz, J.C. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    The controlled calcination of materials derived by sol-gel reactions is important for the evolution of the final structure. Raman spectroscopy is an ideal tool for the identification of surface species under in-situ conditions, as demonstrated in the following for the example of a molybdenum oxide-silica xerogel. Raman spectra of this particular sample were recorded at temperatures as high as 1173 K, and compared with those of a reference material.(author) 3 figs., 4 refs.

  9. Supported Co-Mn-Al Mixed Oxides as Catalysts for N2O Decomposition.

    Czech Academy of Sciences Publication Activity Database

    Pacultová, K.; Karásková, C.; Strakošová, J.; Jirátová, Květa; Obalová, L.

    2015-01-01

    Roč. 18, č. 20 (2015), s. 1114-1122 ISSN 1631-0748. [AWPAC2014 - International Symposium on Air & Water Pollution Abatement Catalysis. Krakow, 01.09.2014-05.09.2014] R&D Projects: GA ČR GA14-13750S Institutional support: RVO:67985858 Keywords : supported catalysts * heterogeneous catalysis * spinel phase * nitrogen oxides Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.798, year: 2015

  10. Mixed valence transition metal 2D-oxides: Comparison between delafossite and crednerite compounds

    Science.gov (United States)

    Martin, Christine; Poienar, Maria

    2017-08-01

    Transition metal oxides offer large opportunities to study relationships between structures and properties. Indeed these compounds crystallize in numerous frameworks corresponding to different dimensionalities and, accordingly, show a huge variety of properties (as high Tc superconductivity, colossal magnetoresistivity, multiferroicity..). The control of the oxidation state of the transition metal, via the monitoring of the oxygen content, is of prime importance to understand and optimize the properties, due to the strong coupling that exists between the lattice and the charges and spins of the transition metals. In this large playground for chemists, we reinvestigated several 2D-compounds derived from delafossite structure. Considering this paper as a very short review, we report here the results obtained on CuMO2 compounds (with M = Cr, Mn or Mn+Cu) by using a combination of techniques, as X-ray, neutrons and/or electrons diffraction on poly-crystals for structural characterisations that are correlated with electrical and/or magnetic properties. The complementarity of studies is also addressed by the synthesis and characterization of single crystals in addition to poly-crystals. Moreover the comparison of the structures of similar Cr and Mn based oxides highlights the crucial role of the Jahn-Teller effect of trivalent manganese to lift the degeneracy, which is responsible of the magnetic frustration in CuCrO2.

  11. In-situ fabrication of cobalt oxide / sulphide mixed phase nanoparticles in Polyphenylenesulphide matrix

    Directory of Open Access Journals (Sweden)

    Narendra Rumale

    2013-03-01

    Full Text Available A novel approach for the in-situ fabrication of combined cobalt oxide / sulphide nanoparticles in sulphur containing polymer polyphenylenesulphide (PPS by polymer inorganic solid-solid reaction technique is reported here. At present, there is considerable interest in polymer-metal chalcogenides / oxides based nano-composites on account of their optical, magnetic, electronic and catalytic properties. We have demonstrated the suitability of solid-solid reaction methodology by reacting commonly available cobalt precursors with engineering thermoplastic PPS. The cobalt precursor was reacted with PPS in 1:1, 1:5, 1:10, and 1:15 molar ratios, respectively, by heating the mixture at the melting temperature of the polymer (285 ºC for six hours. The resultant products were characterized by X-ray diffractometry (XRD, Field-emission scanning electron microscopy (FESEM, Thermogravimetric analysis (TGA, Differential scanning calorimetry (DSC, Diffuse reflectance spectroscopy (DRS techniques and High resolution transmission electron microscope (HRTEM. The shift in melting temperature of PPS was observed. Increase in absorption peak is observed in the range of 320 to 370 nm with the increase in PPS concentration. Resultant nanoparticles of cobalt sulphide and cobalt oxide embedded in the PPS matrix showed spherical and distorted rod like morphology.

  12. Matrix-Matched Iron-Oxide Laser Ablation ICP-MS U–Pb Geochronology Using Mixed Solution Standards

    Directory of Open Access Journals (Sweden)

    Liam Courtney-Davies

    2016-08-01

    Full Text Available U–Pb dating of the common iron-oxide hematite (α-Fe2O3, using laser-ablation inductively-coupled-plasma mass-spectrometry (LA-ICP-MS, provides unparalleled insight into the timing and processes of mineral deposit formation. Until now, the full potential of this method has been negatively impacted by the lack of suitable matrix-matched standards. To achieve matrix-matching, we report an approach in which a U–Pb solution and ablated material from 99.99% synthetic hematite are simultaneously mixed in a nebulizer chamber and introduced to the ICP-MS. The standard solution contains fixed U- and Pb-isotope ratios, calibrated independently, and aspiration of the isotopically homogeneous solution negates the need for a matrix-matched, isotopically homogenous natural iron-oxide standard. An additional advantage of using the solution is that the individual U–Pb concentrations and isotope ratios can be adjusted to approximate that in the unknown, making the method efficient for dating hematite containing low (~10 ppm to high (>1 wt % U concentrations. The above-mentioned advantage to this solution method results in reliable datasets, with arguably-better accuracy in measuring U–Pb ratios than using GJ-1 Zircon as the primary standard, which cannot be employed for such low U concentrations. Statistical overlaps between 207Pb/206Pb weighted average ages (using GJ-1 Zircon and U–Pb upper intercept ages (using the U–Pb mixed solution method of two samples from iron-oxide copper-gold (IOCG deposits in South Australia demonstrate that, although fractionation associated with a non-matrix matched standard does occur when using GJ-1 Zircon as the primary standard, it does not impact the 207Pb/206Pb or upper intercept age. Thus, GJ-1 Zircon can be considered reliable for dating hematite using LA-ICP-MS. Downhole fractionation of 206Pb/238U is observed to occur in spot analyses of hematite. The use of rasters in future studies will hopefully minimize

  13. Iron Oxide Nanoparticles: Tunable Size Synthesis and Analysis in Terms of the Core-Shell Structure and Mixed Coercive Model

    Science.gov (United States)

    Phong, P. T.; Oanh, V. T. K.; Lam, T. D.; Phuc, N. X.; Tung, L. D.; Thanh, Nguyen T. K.; Manh, D. H.

    2017-04-01

    Iron oxide nanoparticles (NPs) are currently a very active research field. To date, a comprehensive study of iron oxide NPs is still lacking not only on the size dependence of structural phases but also in the use of an appropriate model. Herein, we report on a systematic study of the structural and magnetic properties of iron oxide NPs prepared by a co-precipitation method followed by hydrothermal treatment. X-ray diffraction and transmission electron microscopy reveal that the NPs have an inverse spinel structure of iron oxide phase (Fe3O4) with average crystallite sizes ( D XRD) of 6-19 nm, while grain sizes ( D TEM) are of 7-23 nm. In addition, the larger the particle size, the closer the experimental lattice constant value is to that of the magnetite structure. Magnetic field-dependent magnetization data and analysis show that the effective anisotropy constants of the Fe3O4 NPs are about five times larger than that of their bulk counterpart. Particle size ( D) dependence of the magnetization and the non-saturating behavior observed in applied fields up to 50 kOe are discussed using the core-shell structure model. We find that with decreasing D, while the calculated thickness of the shell of disordered spins ( t ˜ 0.3 nm) remains almost unchanged, the specific surface areas S a increases significantly, thus reducing the magnetization of the NPs. We also probe the coercivity of the NPs by using the mixed coercive Kneller and Luborsky model. The calculated results indicate that the coercivity rises monotonously with the particle size, and are well matched with the experimental ones.

  14. Thermal stability and oxidizing properties of mixed alkaline earth-alkali molten carbonates: A focus on the lithium-sodium carbonate eutectic system with magnesium additions

    International Nuclear Information System (INIS)

    Frangini, Stefano; Scaccia, Silvera

    2013-01-01

    Highlights: • TG/DSC analysis was conducted on magnesium-containing eutectic Li/Na eutectic carbonates. • Magnesium influence on the oxygen solubility properties of carbonate was also experimentally determined at 600 °C and 650 °C. • A reproducible partial decarbonation process in premelting region caused formation of magnesium oxycarbonate-like phases. • The acidobase buffering action of magnesium oxycarbonate species could explain the high basic/oxidizing properties of such carbonate melts. • A general correlation between thermal instability in premelting region and basic/oxidizing melt properties was established. - Abstract: A comparative study on thermal behavior and oxygen solubility properties of eutectic 52/48 lithium/sodium carbonate salt containing minor additions of magnesium up to 10 mol% has been made in order to determine whether a general correlation between these two properties can be found or not. Consecutive TG/DSC heating/cooling thermal cycles carried out under alternating CO 2 and N 2 gas flows allowed to assign thermal events observed in the premelting region to a partial decarbonation process of the magnesium-alkali mixed carbonates. The observed decarbonation process at 460 °C is believed to come from initial stage of thermal decomposition of magnesium carbonate resulting in the metastable formation of magnesium oxycarbonate-like phases MgO·2MgCO 3 , in a similar manner as previously reported for lanthanum. Reversible formation and decomposition of the magnesium carbonate phase has been observed under a CO 2 gas atmosphere. The intensity of the decomposition process shows a maximum for a 3 mol% MgO addition that gives also the highest oxygen solubility, suggesting therefore that instability thermal analysis in the premelting region can be considered as providing an effective measure of the basicity/oxidizing properties of alkali carbonate melts with magnesium or, in more general terms, with cations that are strong modifiers of

  15. Mixed metal oxide nanoparticles inhibit growth of Mycobacterium tuberculosis into THP-1 cells

    Directory of Open Access Journals (Sweden)

    A R Jafari

    2016-01-01

    Conclusion: Although Ag NPs exhibited low cytotoxicity, they were unable to inhibit Mtb growth in vitro. ZnO NPs exhibited strong anti-Mtb activity and inhibited bacterial growth, but exhibited high cytotoxicity to human macrophage cells. By mixing Ag and ZnO NPs at a ratio of 8ZnO/2Ag, we acquired a mixture that exhibited potent antibacterial activity against Mtb and no cytotoxic effects on THP-1 cells, resulting in inhibition of both in vitro and ex vivo Mtb growth [Figure 1],[Figure 2],[Figure 3], [Table 1],[Table 2],[Table 3].{Figure 1}{Figure 2}{Figure 3} {Table 1}{Table 2}{Table 3}

  16. Motivational Determinants of Exergame Participation for Older People in Assisted Living Facilities: Mixed-Methods Study.

    Science.gov (United States)

    Meekes, Wytske; Stanmore, Emma Kate

    2017-07-06

    Exergames (exercise-based videogames) for delivering strength and balance exercise for older people are growing in popularity with the emergence of new Kinect-based technologies; however, little is known about the factors affecting their uptake and usage by older people. The aim of this study was to determine the factors that may influence the motivation of older people to use exergames to improve their physical function and reduce fall risk. Mixed methods were employed in which 14 semistructured interviews were conducted with older people (n=12, aged 59-91 years) from 2 assisted living facilities in the North West of the United Kingdom. The older people participated in a 6-week trial of exergames along with one manager and one physiotherapist; 81 h of observation and Technology Acceptance Model questionnaires were conducted. The findings suggest that the participants were intrinsically motivated to participate in the exergames because of the enjoyment experienced when playing the exergames and perceived improvements in their physical and mental health and social confidence. The social interaction provided in this study was an important extrinsic motivator that increased the intrinsic motivation to adhere to the exergame program. The findings of this study suggest that exergames may be a promising tool for delivering falls prevention exercises and increasing adherence to exercise in older people. Understanding the motivation of older people to use exergames may assist in the process of implementation. ©Wytske Meekes, Emma Kate Stanmore. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 06.07.2017.

  17. Accurate determination of the oxidative phosphorylation affinity for ADP in isolated mitochondria.

    Directory of Open Access Journals (Sweden)

    Gilles Gouspillou

    Full Text Available BACKGROUND: Mitochondrial dysfunctions appear strongly implicated in a wide range of pathologies. Therefore, there is a growing need in the determination of the normal and pathological integrated response of oxidative phosphorylation to cellular ATP demand. The present study intends to address this issue by providing a method to investigate mitochondrial oxidative phosphorylation affinity for ADP in isolated mitochondria. METHODOLOGY/PRINCIPAL FINDINGS: The proposed method is based on the simultaneous monitoring of substrate oxidation (determined polarographically and phosphorylation (determined using the glucose-hexokinase glucose-6-phosphate dehydrogenase-NADP(+ enzymatic system rates, coupled to the determination of actual ADP and ATP concentrations by bioluminescent assay. This enzymatic system allows the study of oxidative phosphorylation during true steady states in a wide range of ADP concentrations. We demonstrate how the application of this method allows an accurate determination of mitochondrial affinity for ADP from both oxidation (K(mVox and phosphorylation (K(mVp rates. We also demonstrate that determination of K(mVox leads to an important overestimation of the mitochondrial affinity for ADP, indicating that mitochondrial affinity for ADP should be determined using phosphorylation rate. Finally, we show how this method allows the direct and precise determination of the mitochondrial coupling efficiency. Data obtained from rat skeletal muscle and liver mitochondria illustrate the discriminating capabilities of this method. CONCLUSIONS/SIGNIFICANCE: Because the proposed method allows the accurate determination of mitochondrial oxidative phosphorylation affinity for ADP in isolated mitochondria, it also opens the route to a better understanding of functional consequences of mitochondrial adaptations/dysfunctions arising in various physiological/pathophysiological conditions.

  18. Emission computer tomography on a Dodewaard mixed oxide fuel pin. Comparative PIE work with non-destructive and destructive techniques

    Energy Technology Data Exchange (ETDEWEB)

    Buurveld, H.A.; Dassel, G.

    1993-12-01

    A nondestructive technique as well as a destructive PIE technique have been used to verify the results obtained with a newly 8-e computer tomography (GECT) system. Multi isotope Scanning (MIS), electron probe micro analysis (EPMA) and GECT were used on a mixed oxide (MOX) fuel rod from the Dodewaard reactor with an average burnup of 24 MWd/kg fuel. GECT shows migration of Cs to the periphery of fuel pellets and to radial cracks and pores in the fuel, whereas MIS shows Cs migration to pellet interfaces. The EPMA technique appeared not to be useful to show migration of Cs but, it shows the distribution of fission products from Pu. EPMA clearly shows the distribution of fission products from Pu, but did not reveal the Cs-migration. (orig./HP)

  19. Evaluation of existing United States' facilities for use as a mixed-oxide (MOX) fuel fabrication facility for plutonium disposition

    International Nuclear Information System (INIS)

    Beard, C.A.; Buksa, J.J.; Chidester, K.; Eaton, S.L.; Motley, F.E.; Siebe, D.A.

    1995-01-01

    A number of existing US facilities were evaluated for use as a mixed-oxide fuel fabrication facility for plutonium disposition. These facilities include the Fuels Material Examination Facility (FMEF) at Hanford, the Washington Power Supply Unit 1 (WNP-1) facility at Hanford, the Barnwell Nuclear Fuel Plant (BNFP) at Barnwell, SC, the Fuel Processing Facility (FPF) at Idaho National Engineering Laboratory (INEL), the Device Assembly Facility (DAF) at the Nevada Test Site (NTS), and the P-reactor at the Savannah River Site (SRS). The study consisted of evaluating each facility in terms of available process space, available building support systems (i.e., HVAC, security systems, existing process equipment, etc.), available regional infrastructure (i.e., emergency response teams, protective force teams, available transportation routes, etc.), and ability to integrate the MOX fabrication process into the facility in an operationally-sound manner that requires a minimum amount of structural modifications

  20. Licensing issues associated with the use of mixed-oxide fuel in U.S. commercial nuclear reactors

    International Nuclear Information System (INIS)

    Williams, D.L. Jr.

    1997-04-01

    On January 14, 1997, the Department of Energy, as part of its Record of Decision on the storage and disposition of surplus nuclear weapons materials, committed to pursue the use of excess weapons-usable plutonium in the fabrication of mixed-oxide (MOX) fuel for consumption in existing commercial nuclear power plants. Domestic use of MOX fuel has been deferred since the late 1970s, principally due to nuclear proliferation concerns. This report documents a review of past and present literature (i.e., correspondence, reports, etc.) on the domestic use of MOX fuel and provides discussion on the technical and regulatory issues that must be addressed by DOE (and the utility/consortia selected by DOE to effect the MOX fuel consumption strategy) in obtaining approval from the Nuclear Regulatory Commission to use MOX fuel in one or a group of existing commercial nuclear power plants

  1. Alumina supported/unsupported mixed oxides of Ca and Mg as heterogeneous catalysts for transesterification of Nannochloropsis sp. microalga’s oil

    International Nuclear Information System (INIS)

    Teo, Siow Hwa; Taufiq-Yap, Y.H.; Ng, F.L.

    2014-01-01

    Highlights: • Biodiesel made from oleaginous microalgae through transesterification process. • Effects of methanol/oil molar ratio, catalyst amount, reaction temperature and reaction time were optimized. • High biodiesel yields (75% and 85%) achieved at 60 °C. • The supported catalyst was very sustainable in high water content feedstocks. • The catalysts were characterized using TGA, XRD, FTIR, TPD-CO 2 and SEM. - Abstract: In this study, calcium magnesium (CaMgO) and alumina (Al 2 O 3 ) supported CaMgO mixed oxide catalysts were prepared via pH-controlled co-precipitation (Na 2 CO 3 and NaOH as a precipitant) for transesterification of crude Nannochloropsis oculata (N. oculata) oil with methanol. The catalysts were characterized by means of Thermogravimetric analyses (TGA), X-ray diffraction (XRD), Fourier transform-infrared (FTIR), Temperature programmed desorption of CO 2 (CO 2 -TPD), Inductively coupled plasma–atomic emission spectrometer (ICP–AES) and Scanning electron microscopy (SEM) analysis. At optimization condition, CaMgO mixed oxide catalyst showed 75.2% of fatty acid methyl ester (FAME) yield with catalyst loading of 20 wt.% at 3 h. Meanwhile, the supported CaMgO mixed oxide catalyst gave a higher FAME yield of 85.3% with catalyst loading of 10 wt.% at same conditions. Besides, the reusability study of catalyst was performed to investigate the stability and durability of supported/unsupported catalysts. The high content of Ca 2+ and Mg 2+ precipitated on Al 2 O 3 supported CaMgO mixed oxide catalyst tend to increase the total basicity and provide more active sites for transesterification reaction. Moreover, better moisture resistant on the Al 2 O 3 supported CaMgO mixed oxide catalyst compared with CaMgO mixed oxide catalyst, which is favourable for transesterification reaction on high water content microalgae oil

  2. Spectrophotometric determination of uranium with 2-thenoyltrifluoroacetone and trioctylphosphine oxide in aqueous solution containing nonionic surfactant

    International Nuclear Information System (INIS)

    Taketatsu, Tomitsugu; Aihara, Makoto; Kimoto, Yuuko.

    1981-01-01

    The uranium (VI)-2-thenoyltrifluoroacetone (TTA)-trioctylphosphine oxide (TOPO) mixed complexes are easily solubilized in an aqueous solution containing nona oxyethylene dodecyl ether (BL-9EX). The solubilized complexes give an absorption maximum at 376 nm which can be applied to the spectrophotometric determination of uranium. The adopted procedure is as follows: Transfer a dilute acidic solution containing less than about 400 μg of uranyl ions to a beaker. Add 5 ml of 1 x 10 -2 M TTA/2 x 10 -3 M TOPO/2.5% (w/v) BL-9EX aqueous solution and 2 ml of acetate buffer solution (pH 3.7) to the beaker. Adjust the pH to (3.5 -- 4.0) with dilute hydrochloric acid or sodium hydroxide solution. Then, transfer the solution to a 25-ml volumetric flask and dilute to the mark with distilled water. Measure the absorbance of the solution in a 1-cm quartz cell at 376 nm against a reagent blank. Beer's law was obeyed in the range of 0 -- 16 μg ml -1 of uranyl ion. The presence of 100-fold amount of sulfate and nitrate ions and 10-fold amount of magnesium and calcium ions did not interfere. Ten-fold amount of zinc, cadmium, lead ions and equi-amount of cobalt, nickel, copper, aluminum, iron (III), chromium (III), thorium and zirconium ions caused serious interference. But reasonable values were obtained by addition of EDTA as a masking agent. The molar absorption coefficient was 2.1 x 10 4 cm -1 mol -1 dm 3 . The combined ratio of the solubilized complex was UO 2 2+ :TTA:TOPO = 1:2:1. (author)

  3. Generalised two-dimensional correlation analysis of the Co, Ce, and Pd mixed oxide catalytic systems for methane combustion using in situ infrared spectroscopy

    Science.gov (United States)

    Chlebda, Damian K.; Jodłowski, Przemysław J.; Jędrzejczyk, Roman J.; Łojewska, Joanna

    2018-03-01

    The process of methane combustion over the surface of a catalyst is still not fully understood. The identification of the reaction path and the intermediates created during catalysis is crucial for understanding the transformation of methane molecules. Two-dimensional (2D) correlation spectroscopy was engaged as a tool for the quantitative analysis of a series of temperature-dependent infrared spectra registered in situ during methane combustion. The prepared samples of catalysts were based on a Co, Pd and Ce mixed oxide adsorbed on an aluminium oxide layer deposited on kanthal steel. The registered spectra were transformed into 2D synchronous and asynchronous contour maps. The sequential order of spectral intensity changes was determined, and the resolution enhancement of overlapping IR bands by 2D correlation was demonstrated. The changes in the bands' intensity and information about band position can be correlated with a specific bond, and thus, the possible process intermediates can be identified. The 2DCoS analysis proved to be a powerful tool for band enhancement and revealed the changes occurring within the analysed catalyst systems as responses to increased temperature.

  4. Electrical characteristics of mixed Zr-Si oxide thin films prepared by ion beam induced chemical vapor deposition at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Ferrer, F.J., E-mail: fjferrer@us.e [Centro Nacional de Aceleradores (CSIC - U. Sevilla), Av. Thomas A. Edison 7, E-41092 Sevilla (Spain); Frutos, F. [E.T.S. de Ingenieria Informatica, Avda. Reina Mercedes s/n, E-41012 Sevilla (Spain); Garcia-Lopez, J. [Centro Nacional de Aceleradores (CSIC - U. Sevilla), Av. Thomas A. Edison 7, E-41092 Sevilla (Spain); Jimenez, C. [Laboratoire de Materiaux et de Genie Physique, BP 257 - INPGrenoble Minatec - 3 parvis Louis Neel - 38016 Grenoble (France); Yubero, F. [Instituto de Ciencia de Materiales de Sevilla (CSIC - U. Sevilla), c/ Americo Vespucio 49, E-41092 Sevilla (Spain)

    2009-07-31

    Mixed Zr-Si oxide thin films have been prepared at room temperature by ion beam decomposition of organometallic volatile precursors. The films were flat and amorphous. They did not present phase segregation of the pure single oxides. A significant amount of impurities (-C-, -CH{sub x}, -OH, and other radicals coming from partially decomposed precursors) remained incorporated in the films after the deposition process. This effect is minimized if the Ar content in the O{sub 2}/Ar bombarding gas is maximized. Static permittivity and breakdown electrical field of the films were determined by capacitance-voltage and current-voltage electrical measurements. It is found that the static permittivity increases non-linearly from {approx} 4 for pure SiO{sub 2} to {approx} 15 for pure ZrO{sub 2}. Most of the dielectric failures in the films were due to extrinsic breakdown failures. The maximum breakdown electrical field decreases from {approx} 10.5 MV/cm for pure SiO{sub 2} to {approx} 45 MV/cm for pure ZrO{sub 2}. These characteristics are justified by high impurity content of the thin films. In addition, the analysis of the conduction mechanisms in the formed dielectrics is consistent to Schottky and Poole-Frenkel emission for low and high electric fields applied, respectively.

  5. Rational Design of Mixed-Metal Oxides for Chemical Looping Combustion of Coal via Coupled Computational-Experimental Studies

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, Amit; Li, Fanxing; Santiso, Erik

    2017-09-18

    Energy and global climate change are two grand challenges to the modern society. An urgent need exists for development of clean and efficient energy conversion processes. The chemical looping strategy, which utilizes regenerable oxygen carriers (OCs) to indirectly convert carbonaceous fuels via redox reactions, is considered to be one of the more promising approaches for CO2 capture by the U.S. Department of Energy (USDOE). To date, most long-term chemical looping operations were conducted using gaseous fuels, even though direct conversion of coal is more desirable from both economics and CO2 capture viewpoints. The main challenges for direct coal conversion reside in the stringent requirements on oxygen carrier performances. In addition, coal char and volatile compounds are more challenging to convert than gaseous fuels. A promising approach for direct conversion of coal is the so called chemical looping with oxygen uncoupling (CLOU) technique. In the CLOU process, a metal oxide that decomposes at the looping temperature, and releases oxygen to the gas phase is used as the OC. The overarching objective of this project was to discover the fundamental principles for rational design and optimization of oxygen carriers (OC) in coal chemical looping combustion (CLC) processes. It directly addresses Topic Area B of the funding opportunity announcement (FOA) in terms of “predictive description of the phase behavior and mechanical properties” of “mixed metal oxide” based OCs and rational development of new OC materials with superior functionality. This was achieved through studies exploring i) iron-containing mixed-oxide composites as oxygen carriers for CLOU, ii) Ca1-xAxMnO3-δ (A = Sr and Ba) as oxygen carriers for CLOU, iii) CaMn1-xBxO3-δ (B=Al, V, Fe, Co, and Ni) as oxygen carrier for CLOU and iv) vacancy creation energy in Mn-containing perovskites as an indicator chemical looping with oxygen uncoupling.

  6. Fundamental Study of Facile and Stable Hydrogen Evolution Reaction at Electrospun Ir and Ru Mixed Oxide Nanofibers.

    Science.gov (United States)

    Cho, Yun-Bin; Yu, Areum; Lee, Chongmok; Kim, Myung Hwa; Lee, Youngmi

    2018-01-10

    Electrochemical hydrogen evolution reaction (HER) has been an interesting research topic in terms of the increasing need of renewable and alternative energy conversion devices. In this article, Ir x Ru 1-x O y (y = 0 or 2) nanofibers with diverse compositions of Ir/IrO 2 and RuO 2 are synthesized by electrospinning and calcination procedures. Their HER activities are measured in 1.0 M NaOH. Interestingly, the HER activities of Ir x Ru 1-x O y nanofibers improve gradually during repetitive cathodic potential scans for HER, and then eventually reach the steady-state consistencies. This cathodic activation is attributed to the transformation of the nanofiber surface oxides to the metallic alloy. Among a series of Ir x Ru 1-x O y nanofibers, the cathodically activated Ir 0.80 Ru 0.20 O y shows the best HER activity and stability even compared with IrO y and RuO y , commercial Pt and commercial Ir (20 wt % each metal loading on Vulcan carbon), where a superior stability is possibly ascribed to the instant generation of active Ir and Ru metals on the catalyst surface upon HER. Density functional theory calculation results for hydrogen adsorption show that the energy and adsorbate-catalyst distance at metallic Ir 0.80 Ru 0.20 are close to those at Pt. This suggests that mixed metallic Ir and Ru are significant contributors to the improved HER activity of Ir 0.80 Ru 0.20 O y after the cathodic activation. The present findings clearly demonstrate that the mixed oxide of Ir and Ru is a very effective electrocatalytic system for HER.

  7. Mixed Oxide Supported MoO3 Catalyst: Preparation, Characterization and Activities in Nitration of o-xylene

    Directory of Open Access Journals (Sweden)

    S.M. Kemdeo

    2010-10-01

    Full Text Available TiO2-ZrO2 mixed oxide support was prepared and impregnated with 12 wt % MoO3 and calcined at various temperatures. The resultant catalyst systems were characterized by XRD, FT-IR, BET, SEM, NH3-TPD and pyridine adsorbed FT-IR methods to know the physico-chemical changes occurred in course of thermal treatment. Activities of these catalysts were tested by employing them in the nitration of o-xylene. Mostly, 500 oC calcined catalyst sample was found to be most active for nitration reaction. Catalyst calcined at higher temperatures showed the negative influence on o-xylene conversion and 4-nitro-o-xylene selectivity. Conversion can be correlated with the presence of strong Brönsted acid sites over the catalyst surface whereas change in selectivity was found attributed to the pore diameter of the catalyst. These catalysts also performed satisfactorily, when used for nitration of other aromatics. No use of corrosive sulfuric acid and efficient reusability of the catalyst make the process environmentally friendly and economic. ©2010 BCREC UNDIP. All rights reserved(Received: 9th February 2010, Revised: 5th March 2010; Accepted: 18th March 2010[How to Cite: S.M. Kemdeo, V.S. Sapkal, G.N. Chaudhari. (2010. Mixed Oxide Supported MoO3 Catalyst: Preparation, Characterization and Activities in Nitration of o-xylene. Bulletin of Chemical Reaction Engineering and Catalysis, 5(1: 39-49. doi:10.9767/bcrec.5.1.7126.39-49][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.5.1.7126.39-49 || or local:  http://ejournal.undip.ac.id/index.php/bcrec/article/view/7126 ]Cited by in: Taylor Francis |

  8. Development and sintering of alumina based mixed oxide ceramic products for sensor applications in petroleum industries

    Energy Technology Data Exchange (ETDEWEB)

    Yadava, Y.P.; Muniz, L.B.; Aguiar, L.A.R.; Sanguinetti Ferreira, R.A. [Departamento de Engenharia Mecanica, Universidade Federal de Pernambuco, CEP 50741-530, Recife-PE (Brazil); Albino Aguiar, J. [Departamento de Fisica, Universidade Federal de Pernambuco, CEP 50670-901 Recife-PE (Brazil)

    2005-07-01

    In petroleum production, different types of sensors are required to monitor temperature, pressure, leakage of inflammable gases, etc. These sensors work in very hostile environmental conditions and frequently suffer from abrasion and corrosion problems. Presently perovskite oxide based ceramic materials are increasingly being used for such purposes, due to their highly inert behavior in hostile environment. In the present work, we have developed and characterized alumina based complex perovskite oxide ceramics, Ba{sub 2}AlSnO{sub 5.5}. These ceramics were prepared by solid state reaction process and produced in the form of circular discs by uniaxial pressure compaction technique. Green ceramic bodies were sintered at different sintering temperatures (1200 to 1500 deg. C) in air atmosphere. Structural and microstructural characteristics of sintered Ba{sub 2}AlMO{sub 5.5} were studied by XRD and SEM techniques. Mechanical properties were tested by Vickers microhardness tests. Ceramics sintered in the temperature range 1300 deg. C 1400 deg. C presented best results in terms of microstructural characteristics and mechanical performance. (authors)

  9. Mixed Pro- and Anti-Oxidative Effects of Pomegranate Polyphenols in Cultured Cells

    Science.gov (United States)

    Danesi, Francesca; Kroon, Paul A.; Saha, Shikha; de Biase, Dario; D’Antuono, Luigi Filippo; Bordoni, Alessandra

    2014-01-01

    In recent years, the number of scientific papers concerning pomegranate (Punica granatum L.) and its health properties has increased greatly, and there is great potential for the use of bioactive-rich pomegranate extracts as ingredients in functional foods and nutraceuticals. To translate this potential into effective strategies it is essential to further elucidate the mechanisms of the reported bioactivity. In this study HepG2 cells were supplemented with a pomegranate fruit extract or with the corresponding amount of pure punicalagin, and then subjected to an exogenous oxidative stress. Overall, upon the oxidative stress the gene expression and activity of the main antioxidant enzymes appeared reduced in supplemented cells, which were more prone to the detrimental effects than unsupplemented ones. No differences were detected between cells supplemented with the pomegranate juice or the pure punicalagin. Although further studies are needed due to the gaps existing between in vitro and in vivo studies, our results suggest caution in the administration of high concentrations of nutraceutical molecules, particularly when they are administered in concentrated form. PMID:25350111

  10. Late effects following inhalation of mixed oxide (U,PuO2) mox aerosol in the rat

    International Nuclear Information System (INIS)

    Griffiths, N.; Van Der Meeren, A.; Fritsch, P.; Maximilien, R.

    2008-01-01

    Exposure to alpha-emitting particles is a potential long-term health risk to workers in nuclear fuel fabrication plants. Mixed Oxide (MOX: U,PuO 2 ) fuels containing low percentages of plutonium obtained from spent nuclear fuels are increasingly employed and in the case of accidental contamination by inhalation or wounds may result in the development of late-occurring pathologies such as lung cancer. However the long term risks particularly with regard to lung cancer are to date unclear. In the case of MOX the risk may indeed be different from that assigned to the individual components, plutonium and uranium. Several factors are influential (i) the dissolution of Pu depends on the physico-chemical properties, for example risk of lung cancer is increased 10 fold after Pu(NO 3 ) 2 as compared with PuO 2 . (ii) The solubility of Pu is variable whether delivered as PuO 2 or contained within MOX. (iii) The risk of cancer appears to increase with spatial homogeneity of the lung alpha dose. The objective of this study was to investigate the long term effects in rat lungs following MOX aerosol inhalation of similar particle size containing 2.5 or 7.1% Pu. Conscious rats were exposed to MOX aerosols using a 'nose-only' system and kept for their entire life (2-3 years). Different Initial Lung Deposits (ILDs) were obtained using different concentrations of the MOX suspension. Lung total alpha activity was determined in vivo at intervals over the study period by external counting as well as at autopsy in order to estimate the total lung dose. Anatomo-pathological and immunohistochemical analyses were performed on fixed lung tissue after euthanasia. The frequencies of lung pathologies and tumours were determined on lung sections at several different levels. In addition, autoradiography of lung sections was performed in order to assess the spatial localisation of a activity. Inhalation of MOX at ILD ranging from 1-20 kBq resulted in lung pathologies (90% of exposed rats

  11. Fluorine and chlorine determination in oxides and metals by ion chromatography

    International Nuclear Information System (INIS)

    Evseeva, T.I.; Poletaeva, I.L.; Zemlyanukhina, N.A.; Pavlova, I.V.; Rybin, A.M.; Malykh, M.Yu.; Fedorova, L.A.

    1989-01-01

    Method for simultaneous determination of fluorine and chlorine microquantitie in tantalum, uranium and plutonium oxides, based on combined methods of pyrohydrolysis (1000-1100 deg C) and two-column ion chromatography with conductometric detection is suggested. The relative root-mean-square deviation of determination error is 0.2, the fluorine and chlorine content being 5·10 -4 mass%

  12. A general method to determine sampling windows for nonlinear mixed effects models with an application to population pharmacokinetic studies.

    Science.gov (United States)

    Foo, Lee Kien; McGree, James; Duffull, Stephen

    2012-01-01

    Optimal design methods have been proposed to determine the best sampling times when sparse blood sampling is required in clinical pharmacokinetic studies. However, the optimal blood sampling time points may not be feasible in clinical practice. Sampling windows, a time interval for blood sample collection, have been proposed to provide flexibility in blood sampling times while preserving efficient parameter estimation. Because of the complexity of the population pharmacokinetic models, which are generally nonlinear mixed effects models, there is no analytical solution available to determine sampling windows. We propose a method for determination of sampling windows based on MCMC sampling techniques. The proposed method attains a stationary distribution rapidly and provides time-sensitive windows around the optimal design points. The proposed method is applicable to determine sampling windows for any nonlinear mixed effects model although our work focuses on an application to population pharmacokinetic models. Copyright © 2012 John Wiley & Sons, Ltd.

  13. Determination of mixing characteristics of the river Kabul and the river Indus using physico-chemical and stable isotope parameters

    International Nuclear Information System (INIS)

    Qureshi, R.M.; Hussain, Q.M.; Sajjad, M.I.; Hussain, S.D.; Latif, Z.

    1990-11-01

    This report presents a comparative study on the usefulness of stable isotope parameters (hydrogen and oxygen) versus the physico-chemical parameters (electrical conductivity, temperature, pH value) of water to determine the extent of mixing of the river Kabul with the river Indus near Attock. In view of the sampling techniques employed in the present investigations, electrical conductivity and temperature are found to be the best field parameters for a quick estimate of mixing path length. However, the stable isotopes of the water molecule, due to their greater sensitivity and measuring accuracy, provide a better scenario of mixing characteristics as compared to the physico-chemical parameters. It appears that under normal flow condition, it takes about 5 km channel distance for complete mixing of the Kabul river water in the Indus river channel. A computer code MIXABC is developed to determine the percentage contribution of one river water along a mixing channel in the other river. Details of the source programs are presented. The code can be used on any IBM-compatible microsystem. (author)

  14. Evaluation of oxide-chemical mechanical polishing characteristics using ceria-mixed abrasive slurry

    Science.gov (United States)

    Lee, Youngkyun; Seo, Yong-Jin; Jeong, Haedo

    2012-10-01

    Chemical-mechanical polishing (CMP) characteristics of mixed abrasive slurry (MAS) were studied which was retreated by adding of Ceria (CeO2) abrasives within 1:10 diluted silica slurry (DSS). The slurry was designed for optimal performance which produces reasonable removal rate, acceptable polishing selectivity with respect to underlying layer, low surface defects after polishing, and good slurry stability. The modified abrasives in MAS are evaluated with respect to their particle size distribution, surface morphology, and CMP performances such as removal rate and non-uniformity. As an experimental result, we could obtain successful slurry characteristics compared with traditional silica slurry in the viewpoint of removal rate and non-uniformity.

  15. Experimental Methodology for Determining Optimum Process Parameters for Production of Hydrous Metal Oxides by Internal Gelation

    Energy Technology Data Exchange (ETDEWEB)

    Collins, J.L.

    2005-10-28

    The objective of this report is to describe a simple but very useful experimental methodology that was used to determine optimum process parameters for preparing several hydrous metal-oxide gel spheres by the internal gelation process. The method is inexpensive and very effective in collection of key gel-forming data that are needed to prepare the hydrous metal-oxide microspheres of the best quality for a number of elements.

  16. Constrained Mixed-Effect Models with Ensemble Learning for Prediction of Nitrogen Oxides Concentrations at High Spatiotemporal Resolution.

    Science.gov (United States)

    Li, Lianfa; Lurmann, Fred; Habre, Rima; Urman, Robert; Rappaport, Edward; Ritz, Beate; Chen, Jiu-Chiuan; Gilliland, Frank D; Wu, Jun

    2017-09-05

    Spatiotemporal models to estimate ambient exposures at high spatiotemporal resolutions are crucial in large-scale air pollution epidemiological studies that follow participants over extended periods. Previous models typically rely on central-site monitoring data and/or covered short periods, limiting their applications to long-term cohort studies. Here we developed a spatiotemporal model that can reliably predict nitrogen oxide concentrations with a high spatiotemporal resolution over a long time span (>20 years). Leveraging the spatially extensive highly clustered exposure data from short-term measurement campaigns across 1-2 years and long-term central site monitoring in 1992-2013, we developed an integrated mixed-effect model with uncertainty estimates. Our statistical model incorporated nonlinear and spatial effects to reduce bias. Identified important predictors included temporal basis predictors, traffic indicators, population density, and subcounty-level mean pollutant concentrations. Substantial spatial autocorrelation (11-13%) was observed between neighboring communities. Ensemble learning and constrained optimization were used to enhance reliability of estimation over a large metropolitan area and a long period. The ensemble predictions of biweekly concentrations resulted in an R 2 of 0.85 (RMSE: 4.7 ppb) for NO 2 and 0.86 (RMSE: 13.4 ppb) for NO x . Ensemble learning and constrained optimization generated stable time series, which notably improved the results compared with those from initial mixed-effects models.

  17. Determination of oxygen nonstoichiometry and diffusivity in mixed conducting oxides by oxygen Coulometric titration

    NARCIS (Netherlands)

    Lankhorst, M.H.R.; Lankhorst, Martijn H.R.; Bouwmeester, Henricus J.M.

    1997-01-01

    Oxygen coulometric titration has been applied to measure chemical diffusion in La0.8Sr0.2CoO3-δ between 700 and 1000°C. The transient current response to a potentiostatic step has been transformed from the time domain to the frequency domain. The equivalent circuit used to fit the resulting

  18. Determination of renewable energy yield from mixed waste material from the use of novel image analysis methods.

    Science.gov (United States)

    Wagland, S T; Dudley, R; Naftaly, M; Longhurst, P J

    2013-11-01

    Two novel techniques are presented in this study which together aim to provide a system able to determine the renewable energy potential of mixed waste materials. An image analysis tool was applied to two waste samples prepared using known quantities of source-segregated recyclable materials. The technique was used to determine the composition of the wastes, where through the use of waste component properties the biogenic content of the samples was calculated. The percentage renewable energy determined by image analysis for each sample was accurate to within 5% of the actual values calculated. Microwave-based multiple-point imaging (AutoHarvest) was used to demonstrate the ability of such a technique to determine the moisture content of mixed samples. This proof-of-concept experiment was shown to produce moisture measurement accurate to within 10%. Overall, the image analysis tool was able to determine the renewable energy potential of the mixed samples, and the AutoHarvest should enable the net calorific value calculations through the provision of moisture content measurements. The proposed system is suitable for combustion facilities, and enables the operator to understand the renewable energy potential of the waste prior to combustion. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. Quantitative determination of carbonaceous particle mixing state in Paris using single-particle mass spectrometer and aerosol mass spectrometer measurements

    Directory of Open Access Journals (Sweden)

    R. M. Healy

    2013-09-01

    Full Text Available Single-particle mixing state information can be a powerful tool for assessing the relative impact of local and regional sources of ambient particulate matter in urban environments. However, quantitative mixing state data are challenging to obtain using single-particle mass spectrometers. In this study, the quantitative chemical composition of carbonaceous single particles has been determined using an aerosol time-of-flight mass spectrometer (ATOFMS as part of the MEGAPOLI 2010 winter campaign in Paris, France. Relative peak areas of marker ions for elemental carbon (EC, organic aerosol (OA, ammonium, nitrate, sulfate and potassium were compared with concurrent measurements from an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS, a thermal–optical OCEC analyser and a particle into liquid sampler coupled with ion chromatography (PILS-IC. ATOFMS-derived estimated mass concentrations reproduced the variability of these species well (R2 = 0.67–0.78, and 10 discrete mixing states for carbonaceous particles were identified and quantified. The chemical mixing state of HR-ToF-AMS organic aerosol factors, resolved using positive matrix factorisation, was also investigated through comparison with the ATOFMS dataset. The results indicate that hydrocarbon-like OA (HOA detected in Paris is associated with two EC-rich mixing states which differ in their relative sulfate content, while fresh biomass burning OA (BBOA is associated with two mixing states which differ significantly in their OA / EC ratios. Aged biomass burning OA (OOA2-BBOA was found to be significantly internally mixed with nitrate, while secondary, oxidised OA (OOA was associated with five particle mixing states, each exhibiting different relative secondary inorganic ion content. Externally mixed secondary organic aerosol was not observed. These findings demonstrate the range of primary and secondary organic aerosol mixing states in Paris. Examination of the

  20. Mixed conductivity studies in silver oxide based barium vanado-tellurite glasses

    International Nuclear Information System (INIS)

    Pant, Meenakshi; Kanchan, D.K.; Sharma, Poonam; Jayswal, Manish S.

    2008-01-01

    The dc conductivity and frequency dependent ac conductivity of the quaternary glass system x(BaO:1.5 Ag 2 O)-(95 - x)V 2 O 5 -5TeO 2 , are reported in the frequency range 1 Hz to 32 MHz in the temperature range from room temperature to 433 K. The dc conductivity measured in high temperature range increased with transition metal oxide content while the activation range decreased. The conductivity arises mainly from polaron hopping between V 4+ and V 5+ ions. High temperature conductivity data satisfy Mott's small polaron hopping model. It is found that a mechanism of non-adiabatic hopping is the most appropriate conduction model for these glasses. A power law behavior σ(ω) = σ dc + Aω n (with 0 < n < 1) is well exhibited by the ac conductivity data of the glasses. The activation energy calculated from both the relaxation time and dc conductivity is found to be nearly same in both the cases. A scaling of the conductivity spectra with respect to temperature and composition is attempted and it is observed that the relaxation dynamics of charge carriers in the present glasses is independent of temperature and composition

  1. Synthesis, characterization and trivalent arsenic sorption potential of Ce-Al nanostructured mixed oxide

    Science.gov (United States)

    Bhattacharya, S.; Gupta, K.; Ghosh, U. C.

    2017-04-01

    Arsenic contamination in the ground water has serious health consequences in many parts of the world. The surface sorption method for arsenic mitigation has been widely investigated due to its simple method, inexpensive operation, highly efficient and low content of by-products. In the present study, nanostructured hydrated cerium aluminum oxide (NHCAO) was synthesized and characterized and its arsenic (III) sorption behavior from the aqueous solution was studied. The material was characterized in SEM, FE-SEM, TEM, AFM, XRD, and FT-IR. Batch method was used for the kinetics of As (III) sorption on nanoparticles at 303 (± 1.6) K and at pH 7.0 (± 0.2). The experiments on isotherm subject were performed individually at 288K, 303K, 318K temperatures at pH 7.0 (± 0.2) using the batch sorption method. In the kinetics study of arsenic (III) sorption, the sorption percentage was observed to remain nearly unchanged up to pH 9.0, thereafter only slight reduction in sorption percentage. The equilibrium sorption results were tested using the models of Langmuir and the Freundlich isotherm. The Langmuir model is the most fitted model for the sorption reaction. NHCAO was highly efficient in As(III) removal out of the water in the extensive range of pH and could be used for arsenic removal from contaminated water.

  2. Textural, structural, and morphological characterizations and catalytic activity of nanosized CeO(2)-MO(x) (M=Mg(2+), Al(3+), Si(4+)) mixed oxides for CO oxidation.

    Science.gov (United States)

    Yu, Qiang; Wu, Xiaoxia; Tang, Changjin; Qi, Lei; Liu, Bin; Gao, Fei; Sun, Keqin; Dong, Lin; Chen, Yi

    2011-02-01

    The present work focuses on the combination of ceria with another oxide of different ionic valences from period 3 (Mg(2+), Al(3+), and Si(4+)) using coprecipitation method, followed by calcination at 450 and 750°C, respectively. The textural, structural, morphological and redox properties of nanosized ceria-magnesia, ceria-alumina and ceria-silica mixed oxides have been investigated by means of N(2) physisorption, XRD, Raman, HRTEM, DRS, FT-IR, and H(2)-TPR technologies. XRD results of these mixed oxides reveal that only nanocrystalline ceria (ca. 3-6nm for the 450°C calcined samples) could be observed. The grain size of ceria increases with the increasing calcination temperature from 450 to 750°C due to sintering effect. The highest specific surface area is obtained at CeO(2)-Al(2)O(3) mixed oxides when calcination temperature reaches 750°C. Raman spectra display the cubic fluorite structure of ceria and the existence of oxygen vacancies, and displacement of oxygen ions from their normal lattice positions in the ceria-based mixed oxides. DRS measurements confirm that the smaller the grain size of the ceria, the higher indirect band gap energy. H(2)-TPR results suggest that the reductions of surface and bulk oxygen of ceria were predominant at low and high calcination temperature, respectively. Finally, CO oxidation were performed over these ceria-based mixed oxides, and the combination of CeO(2)-Al(2)O(3) exhibited highest activity irrespective of calcination temperature, which may due to excellent textural/structural properties, good homogeneity, and redox abilities. Copyright © 2010 Elsevier Inc. All rights reserved.

  3. Determination of the oxidative stability by DSC of vegetable oils from the Amazonian area.

    Science.gov (United States)

    Pardauil, Juliana J R; Souza, Luiz K C; Molfetta, Fábio A; Zamian, José R; Rocha Filho, Geraldo N; da Costa, C E F

    2011-05-01

    Differential scanning calorimetry (DSC) and a Rancimat method apparatus were applied to evaluate the oxidative stability of buriti pulp oil (Mauritia flexuosa Mart), rubber seed oil (Hevea brasiliensis), and passion fruit oil (Passiflora edulis). The Rancimat measurements taken for the oxidative induction times were performed under isothermal conditions at 100°C and in an air atmosphere. The DSC technique involved the oxidation of oil samples in an oxygen-flow DSC cell. The DSC cell temperature was set at five different isothermal temperatures: 100, 110, 120, 130 and 140°C. During the oxidation reaction, an increase in heat was observed as a sharp exothermic curve. The value T(0) represents the oxidative induction time, which is determined from the downward extrapolated DSC oxidative curve verses the time axis. These curves indicate a good correlation between the DSC T(0) and oxidative stability index (OSI) values. The DSC method is useful because it consumes less time and less sample. Copyright © 2011 Elsevier Ltd. All rights reserved.

  4. Determinants of oxidative stress related to gender: relevance of age and smoking habit.

    Science.gov (United States)

    Vassalle, Cristina; Novembrino, Cristina; Maffei, Silvia; Sciarrino, Rosalia; De Giuseppe, Rachele; Vigna, Luisella; de Liso, Federica; Mercuri, Antonella; Bamonti, Fabrizia

    2011-09-01

    Magnitude and major causes of oxidative stress may be different between sexes, although limitedly addressed in clinical studies with controversial results. The present study aimed to determine whether any gender-related difference exists concerning oxidative stress in a population of 332 subjects of both sexes, in a wide age range, with and without cigarette smoking habit. The Oxidative-INDEX was calculated after evaluation of serum hydroperoxides (ROMs) and total antioxidant capacity (OXY) by means of commercial kits (d-ROMs and Oxy-adsorbent Tests, Diacron, Italy) subtracting the OXY standardized variable from the ROMs standardized variable. The Oxidative-INDEX resulted higher in women with respect to men (phigh blood pressure, and smoking habit as factors independently associated with the Oxidative-INDEX in men, whereas cigarette smoking and age represented the independent risk factors for an elevated oxidative stress status in women. Gender-based differences in oxidative stress levels may provide a biochemical basis for the epidemiologic differences in the disease susceptibility between sexes, and suggest different strategies for risk assessment, diagnosis, and treatment specifically targeted to men and women.

  5. Determination of the oxidizing property: proposal of an alternative method based on differential scanning calorimetry

    International Nuclear Information System (INIS)

    Gigante, L.; Dellavedova, M.; Pasturenzi, C.; Lunghi, A.; Mattarella, M.; Cardillo, P.

    2008-01-01

    Determination of chemical-physical and hazardous properties of substances is a very important matter in the chemical industry, considering the growing attention of public opinion regarding safety and eco-compatibility aspects of products. In the present work, attention was focused on characterization of oxidizing properties. In case of solid compounds, the current method (Dir 84/449/CEE 6) compares the maximum combustion rate of the examined substance to the maximum combustion rate of a reference mixture. This method shows a lot of disvantages and does not provide a quantitative result. In the following work an alternative method, based on DSC measurements, is proposed for the determination of oxidizing properties. [it

  6. Determining maximum stand density index in mixed species stands for strategic-scale stocking assessments

    Science.gov (United States)

    Chris W. Woodall; Patrick D. Miles; John S. Vissage

    2005-01-01

    Stand density index (SDI), although developed for use in even-aged monocultures, has been used for assessing stand density in large-scale forest inventories containing diverse tree species and size distributions. To improve application of SDI in unevenaged, mixed species stands present in large-scale forest inventories, trends in maximum SDI across diameter classes...

  7. Theranostic Application of Mixed Gold and Superparamagnetic Iron Oxide Nanoparticle Micelles in Glioblastoma Multiforme.

    Science.gov (United States)

    Sun, Lova; Joh, Daniel Y; Al-Zaki, Ajlan; Stangl, Melissa; Murty, Surya; Davis, James J; Baumann, Brian C; Alonso-Basanta, Michelle; Kaol, Gary D; Tsourkas, Andrew; Dorsey, Jay F

    2016-02-01

    The treatment of glioblastoma multiforme, the most prevalent and lethal form of brain cancer in humans, has been limited in part by poor delivery of drugs through the blood-brain barrier and by unclear delineation of the extent of infiltrating tumor margins. Nanoparticles, which selectively accumulate in tumor tissue due to their leaky vasculature and the enhanced permeability and retention effect, have shown promise as both therapeutic and diagnostic agents for brain tumors. In particular, superparamagnetic iron oxide nanoparticles (SPIONs) have been leveraged as T2-weighted MRI contrast agents for tumor detection and imaging; and gold nanoparticles (AuNP) have been demonstrated as radiosensitizers capable of propagating electron and free radical-induced radiation damage to tumor cells. In this study, we investigated the potential applications of novel gold and SPION-loaded micelles (GSMs) coated by polyethylene glycol-polycaprolactone (PEG-PCL) polymer. By quantifying gh2ax DNA damage foci in glioblastoma cell lines, we tested the radiosensitizing efficacy of these GSMs, and found that GSM administration in conjunction with radiation therapy (RT) led to ~2-fold increase in density of double-stranded DNA breaks. For imaging, we used GSMs as a contrast agent for both computed tomography (CT) and magnetic resonance imaging (MRI) studies of stereotactically implanted GBM tumors in a mouse model, and found that MRI but not CT was sufficiently sensitive to detect and delineate tumor borders after administration and accumulation of GSMs. These results suggest that with further development and testing, GSMs may potentially be integrated into both imaging and treatment of brain tumors, serving a theranostic purpose as both an MRI-based contrast agent and a radiosensitizer.

  8. Fabrication of uranium-americium mixed oxide fuels: thermodynamical modeling and materials properties

    International Nuclear Information System (INIS)

    Prieur, D.

    2011-01-01

    Fuel irradiation in pressurized water reactors lead to the formation of fission products and minor actinides (Np, Am, Cm) which can be transmuted in fast neutrons reactors. In this context, the aim of this work was to study the fabrication conditions of the U 1-y Am y O 2+x fuels which exhibit particular thermodynamical properties requiring an accurate monitoring of the oxygen potential during the sintering step. For this reason, a thermodynamical model was developed to assess the optimum sintering conditions for these materials. From these calculations, U 1-y Am y O 2+x (y=0.10; 0.15; 0.20; 0.30) were sintered in two range of atmosphere. In hyper-stoichiometric conditions at low temperature, porous and multiphasic compounds are obtained whereas in reducing conditions at high temperature materials are dense and monophasic. XAFS analyses were performed in order to obtain additional experimental data for the thermodynamical modeling refinement. These characterizations also showed the reduction of Am(+IV) to Am(+III) and the partial oxidation of U(+IV) to U(+V) due to a charge compensation mechanism occurring during the sintering. Finally, taking into account the high - activity of Am, self-irradiation effects were studied for two types of microstructures and two Am contents (10 and 15%). For each composition, a lattice parameter increase was observed without structural change coupled with a macroscopic swelling of the pellet diameter up to 1.2% for the dense compounds and 0.6% for the tailored porosity materials. (author) [fr

  9. Molybdenum-based additives to mixed-metal oxides for use in hot gas cleanup sorbents for the catalytic decomposition of ammonia in coal gases

    Science.gov (United States)

    Ayala, Raul E.

    1993-01-01

    This invention relates to additives to mixed-metal oxides that act simultaneously as sorbents and catalysts in cleanup systems for hot coal gases. Such additives of this type, generally, act as a sorbent to remove sulfur from the coal gases while substantially simultaneously, catalytically decomposing appreciable amounts of ammonia from the coal gases.

  10. Tuning the acidity of niobia: Characterization and catalytic activity of Nb{sub 2}O{sub 5}–MeO{sub 2} (Me = Ti, Zr, Ce) mesoporous mixed oxides

    Energy Technology Data Exchange (ETDEWEB)

    Stošić, Dušan; Bennici, Simona [Université Lyon 1, CNRS, UMR 5256, IRCELYON, Institut de recherches sur la catalyse et l' environnement de Lyon, 2 avenue Albert Einstein, F-69626 Villeurbanne (France); Pavlović, Vladimir; Rakić, Vesna [Faculty of Agriculture, Department of Chemistry, University of Belgrade, Nemanjina 6, 11080 Zemun (Serbia); Auroux, Aline, E-mail: aline.auroux@ircelyon.univ-lyon1.fr [Université Lyon 1, CNRS, UMR 5256, IRCELYON, Institut de recherches sur la catalyse et l' environnement de Lyon, 2 avenue Albert Einstein, F-69626 Villeurbanne (France)

    2014-08-01

    Mesoporous Nb{sub 2}O{sub 5}–MeO{sub 2} (Me = Ti, Zr, Ce) mixed oxides were successfully prepared using evaporation-induced self-assembly (EISA) method. The structural and textural properties of these materials have been fully characterized using appropriate techniques (low-temperature adsorption–desorption of nitrogen, thermogravimetric analysis, X-ray diffraction analysis (XRD) transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Raman spectroscopy). Acid–base properties were estimated by adsorption microcalorimetry of NH{sub 3} and SO{sub 2} molecules in order to determine the population, strength and strength distribution of acidic or basic sites. Formation of mesoporous structure was confirmed by the results of XRD, TEM and BET techniques. Results of adsorption microcalorimetry technique showed that the type of transition metal oxide added to niobia has a decisive role for acidic-basic character of investigated mixed oxides. Among the investigated mixed oxide formulations only Nb{sub 2}O{sub 5}–CeO{sub 2} was amphoteric, while the other samples showed prominent acidic character. All the investigated materials are catalytically active in fructose dehydration; conversion of fructose and selectivity to 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA) are proved to be dependant on the number of acidic sites on the surface of catalysts. Furthermore, presence of the basic sites on the surface of the catalyst decreases the activity in the fructose dehydration reaction, as in the case of Nb{sub 2}O{sub 5}–CeO{sub 2} sample. - Highlights: • Mesoporous Nb{sub 2}O{sub 5}–MeO{sub 2} mixed oxides were successfully prepared by EISA method. • Acidic–basic properties depend on the nature of the oxide that was mixed with niobia. • Catalytic activity was tested in fructose dehydration in aqueous phase. • Selectivity and conversion in reaction are correlated to the number of acid sites.

  11. Synthesis and Characterization of Mixed-Conducting Corrosion Resistant Oxide Supports

    Energy Technology Data Exchange (ETDEWEB)

    Ramani, Vijay K. [Washington Univ., St. Louis, MO (United States)

    2015-01-31

    An extensive search and evaluation of electrochemically stable catalyst supports (including metal oxides like RuO2-SiO2, RuO2-TiO2, and ITO was perfomed during the 4 years of the project. The suports were also catalyzed by deposition of Pt and tested for its performance and electrochemical stability in RDE and fuel cell experiments. For testing the electrochemical stability and fuel cell performance of the catalysts and supports, we have employed the protocols in use at the Department of Energy and Nissan Technological Center North America (NTCNA). The use of such procedures allows a precise and reproducible estimation of the performance and stability of the materials and permits comparisons among laboratories and DOE funded projects. RuO2-SiO2 catalyst supports showed no loss in surface area during start-stop stability tests that were performed by cycling the electrode potential between 0 V to 1.8 V for 1000 cycles. Catalyzed support (40% Pt/RuO2-SiO2; 1:1 mole ratio) were tested in a PEFC, resulting in a current density of 750 mA/cm2 at 0.6 Volts, and a maximum power density of 570 mW/cm2. Measurements were conducted at 80 ºC with 75% relative humidity of the inlet gases (H2/O2); Pt loadings were 0.4 mg/cm2 at the cathode and 0.2 mg/cm2 at the anode. Start-stop stability tests for support and catalyzed support performed in RDE and PEFC set-ups have confirmed RuO2-TiO2 support stability. The beginning of life performance was exactly equal to end of life performance (in an MEA that has been subjected to severe start-stop cycling for 10,000 start/stop cycles between 1 V to 1.5 V). This result was in sharp contrast to baseline Pt/C catalyst that showed significant performance deterioration after accelerated stability tests. The Pt/TRO showed minimal loss in performance upon exposure to start-stop cycles. The loss in cell voltage at 1 A/cm2 at 100% RH was almost 700 mV for Pt/C whereas it was only ca. 15 mV for Pt/TRO. 40% RH data (of inlet gases) revealed a similar

  12. Electrochemical determination of activation energies for methanol oxidation on polycrystalline platinum in acidic and alkaline electrolytes.

    Science.gov (United States)

    Cohen, Jamie L; Volpe, David J; Abruña, Héctor D

    2007-01-07

    The oxidation pathways of methanol (MeOH) have been the subject of intense research due to its possible application as a liquid fuel in polyelectrolyte membrane (PEM) fuel cells. The design of improved catalysts for MeOH oxidation requires a deep understanding of these complex oxidation pathways. This paper will provide a discussion of the literature concerning the extensive research carried out in acidic and alkaline electrolytes. It will highlight techniques that have proven useful in the determination of product ratios, analysis of surface poisoning, anion adsorption, and oxide formation processes, in addition to the effects of temperature on the MeOH oxidation pathways at bulk polycrystalline platinum (Pt(poly)) electrodes. This discussion will provide a framework with which to begin the analysis of activation energy (E(a)) values. This kinetic parameter may prove useful in characterizing the rate-limiting step of the MeOH oxidation at an electrode surface. This paper will present a procedure for the determination of E(a) values for MeOH oxidation at a Pt(poly) electrode in acidic and alkaline media. Values from 24-76 kJ mol(-1) in acidic media and from 36-86 kJ mol(-1) in alkaline media were calculated and found to be a function of applied potential and direction of the potential sweep in a voltammetric experiment. Factors that influence the magnitude of the calculated E(a) include surface poisoning from MeOH oxidation intermediates, anion adsorption from the electrolyte, pH effects, and oxide formation processes. These factors are all potential, and temperature, dependent and must clearly be addressed when citing E(a) values in the literature. Comparison of E(a) values must be between systems of comparable electrochemical environment and at the same potential. E(a) values obtained on bulk Pt(poly), compared with other catalysts, may give insight into the superiority of other Pt-based catalysts for MeOH oxidation and lead to the development of new catalysts

  13. Role of elastic deformation in determining the mixed alkaline earth effect of hardness in silicate glasses

    DEFF Research Database (Denmark)

    Kjeldsen, Jonas; Smedskjær, Morten Mattrup; Potuzak, M.

    2015-01-01

    show that the mixed alkaline earth effect manifests itself as deviations from linearity in shear modulus, Poisson’s ratio, glass transition temperature, liquid fragility index, hardness, volume of densification, and volume of plastic flow. We find no correlation between the elastic part......Glasses deform permanently as a result of indentation and the total resistance to deformation consists of three individual resistances, i.e., those to elastic deformation, densification, and plastic flow. The link between Vickers hardness and the resistances to densification and plastic flow has...... been investigated previously, but the link between the resistance to elastic deformation and hardness has not yet been studied. In this work, we investigate the link between elastic deformation during indentation and Vickers hardness in a series of mixed magnesium-barium boroaluminosilicate glasses. We...

  14. Determination of DB10B values of single and mixed cultures of ...

    African Journals Online (AJOL)

    The survi-ving fraction of isolates decreased with increased irradiation doses. DB10B values of E. coli, S. aureus and S. parat-hyphi B were respectively 0.27, 0.33 and 0.44 kGy when inoculated as single cultures, and 0.24, 0.28 and 0.32 kGy respectively when inoculated as mixed cultures. DB10B values were lower for ...

  15. Development of a rapid test method for asphalt concrete content determination in hot-mix paving mixtures

    Science.gov (United States)

    Chavez, J. J. M.

    1984-01-01

    A rapid test method was developed for the determination of asphalt cement content in hot-mix bituminous paving mixtures. It is based on the extraction of asphalt cement from mixtures with trichloroethylene and subsequent measurement of the transmittance of light through the extracted solution. A good correlation was found between the results obtained using the rapid test and those obtained using the standard test (ASTM D-2172, Method E1) for samples tested in the field at asphalt mix plants. The test uses a portable spectrophotometer and a metal can for extraction. The asphalt content can be determined in less than ten minutes. The possibility of using the rapid test on materials containing emulsified asphalt, slag aggregate, unusually high amounts of fine material and recycled material was also studied.

  16. Determination of sediment provenance by unmixing the mineralogy of source-area sediments: The "SedUnMix" program

    Science.gov (United States)

    Andrews, John T.; Eberl, D.D.

    2012-01-01

    Along the margins of areas such as Greenland and Baffin Bay, sediment composition reflects a complex mixture of sources associated with the transport of sediment in sea ice, icebergs, melt-water and turbidite plumes. Similar situations arise in many contexts associated with sediment transport and with the mixing of sediments from different source areas. The question is: can contributions from discrete sediment (bedrock) sources be distinguished in a mixed sediment by using mineralogy, and, if so, how accurately? To solve this problem, four end-member source sediments were mixed in various proportions to form eleven artificial mixtures. Two of the end-member sediments are felsic, and the other two have more mafic compositions. End member and mixed sediment mineralogies were measured for the Excel macro program named SedUnMix, and the results were evaluated to determine the robustness of the algorithm. The program permits the unmixing of up to six end members, each of which can be represented by up to 5 alternative compositions, so as to better simulate variability within each source region. The results indicate that we can track the relative percentages of the four end members in the mixtures. We recommend, prior to applying the technique to down-core or to other provenance problems, that a suite of known, artificial mixtures of sediments from probable source areas be prepared, scanned, analyzed for quantitative mineralogy, and then analyzed by SedUnMix to check the sensitivity of the method for each specific unmixing problem. ?? 2011 Elsevier B.V..

  17. Yttrium aluminum garnet (YAG) obtained by rare-earth mixed oxide (RE{sub 2}O{sub 3})

    Energy Technology Data Exchange (ETDEWEB)

    Castro, D.F.; Daguano, J.K.M.F.; Rodrigues Junior, D., E-mail: claudinei@demar.eel.usp.b [Universidade de Sao Paulo (EEL/USP), Lorena, SP (Brazil). Escola de Engenharia; Santos, C. [Centro Universitario de Volta Redonda (MEMAT/UNIFOA), RJ (Brazil); Suzuki, P.A. [Laboratorio Nacional de Luz Sincrotron (LNLS), Campinas, SP (Brazil); Silva, O.M.M. [Centro Tecnico Aeroespacial (CTA-IAE), Sao Jose dos Campos, SP (Brazil). Inst. de Atividades Espaciais. Div. de Materiais

    2010-07-01

    In this work, the substitution of commercial Y{sub 2}O{sub 3} by a rare earth mixed oxide, RE{sub 2}O{sub 3}, to form Yttrium aluminum Garnet-Y{sub 3}Al{sub 5}O{sub 12}, was investigated. Al{sub 2}O{sub 3}:Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3}:RE{sub 2}O{sub 3} powder-mixtures, in a molar ratio of 60:40, were milled and subsequently cold uniaxially-pressed. Compacts were sintered at 1000, 1400 or 1600 deg C, for 120 minutes. RE{sub 2}O{sub 3} oxide was characterized by high-resolution synchrotron X-ray diffraction (HRXRD) and compared to Y{sub 2}O{sub 3}. X-ray diffraction pattern of the RE{sub 2}O{sub 3} indicates a true solid solution formation. Rietveld refinement of the sintered YAG and (RE)AG reveled a similar crystal structure to the YAGs obtained by the use of Al{sub 2}O{sub 3}-Y{sub 2}O{sub 3} or Al{sub 2}O{sub 3}-RE{sub 2}O{sub 3} respectively. Microstructural analysis of both, YAG or (RE)AG, revealed similar grain sizes of about 2.5 {mu}m besides mechanical properties, with hardness of 400HV and fracture toughness of 3.8MPa.m1/2. It could be, thus, demonstrated that pure Y{sub 2}O{sub 3} can be substituted by the rare-earth solid solution, RE{sub 2}O{sub 3}, in the formation YAGs, presenting similar microstructural and mechanical properties. (author)

  18. Electrochemical characterization of mixed matrix heterogeneous cation exchange membranes modified by simultaneous using ilmenite-co-iron oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hosseini, Sayed Mohsen; Hamidi, Alireza; Moghadassi, Abdolreza [Faculty of Engineering, Arak University, Arak (Iran, Islamic Republic of); Madaeni, Sayed Siavash [Razi University, Kermanshah (Iran, Islamic Republic of)

    2015-03-15

    Mixed matrix heterogeneous cation exchange membranes were prepared by solution casting technique. Ilmenite-co-iron oxide nanoparticle was also employed as inorganic filler additive in membrane fabrication. The effect of the used additives on membrane electrochemical properties was studied. Membrane ion exchange capacity, membrane potential, transport number and selectivity all were improved by use of FeTiO{sub 3}/Fe{sub 3}O{sub 4} nanoparticles in membrane matrix. Utilizing FeTiO{sub 3}-co-Fe{sub 3}O{sub 4} nanoparticles in the casting solution also led to increase in ionic flux obviously. The modified membranes containing FeTiO{sub 3}-co-Fe{sub 3}O{sub 4} nanoparticles showed higher transport number, selectivity and ionic flux compared to modified membrane containing ilmenite. Electrodialysis experiment in laboratory scale also showed higher cation removal for modified membrane containing FeTiO{sub 3}-co-Fe{sub 3}O{sub 4} nanoparticles compared to other modified membranes and pristine ones. Results showed that membrane areal electrical resistance declined sharply by use of FeTiO{sub 3}-co-Fe{sub 3}O{sub 4} nanoparticles in membrane matrix. Moreover, modified membrane containing ilmenite showed lower electrical resistance compared to others. Results showed that oxidative stability of membranes was decreased slightly by use of FeTiO{sub 3}/Fe{sub 3}O{sub 4} nanoparticles in membrane matrix. The results revealed that modified membranes in this study are comparable with that of other commercial ones.

  19. Electrochemical Oxidation and Determination of Oxalic Acid at an Exfoliated Graphite-Polystyrene Composite Electrode

    NARCIS (Netherlands)

    Schoonman, J.; Manea, F.; Radovan, C.; Corb, I.; Pop, A.; Burtica, G.; Malchev, P.G.; Picken, S.J.

    2007-01-01

    An exfoliated graphite-polystyrene composite electrode was evaluated as analternative electrode in the oxidation and the determination of oxalic acid in 0.1 M Na2SO4supporting electrolyte. Using CV, LSV, CA procedures, linear dependences I vs. C wereobtained in the concentrations range of oxalic

  20. [Determination of the carboxyl content of oxidized starch by fourier transform infrared (FTIR) spectroscopy].

    Science.gov (United States)

    Ding, Long-Long; Zhang, Yan-Hua; Gu, Ji-You; Tan, Hai-Yan; Zhu, Li-Bin

    2014-02-01

    In the present study, the carboxyl content of oxidized starch was determined by FTIR spectroscopy. Standard curve was drawn in which the ordinate was carboxyl content determined by national standard method with the ratio of carbonyl absorbance to the key of C-H absorbance in FTIR spectroscopy as the abscissa. The ratio of absorbance of unknown oxidized starch tested by FTIR spectroscopy was obtained, The carboxyl content was calculated by standard curve, and then compared with the carboxyl content determined by national standard method, and the deviation is between 2% and 4%. In order to improve the accuracy of the experiment, standard sample was selected to draw standard curve to better ensure that the carboxyl content of the unknown oxidized starch is in the range of standard curve calculation limit, and deviates from the limit of standard curve. Compared with the carboxyl content determined by national standard method, testing with FTIR spectroscopy is simple, easy to operate, and of high efficiency and better accuracy. So, it is significant to forecast the carboxyl content of oxidized starch by FTIR spectroscopy.