共查询到20条相似文献,搜索用时 15 毫秒
1.
N. M. Porotnikova A. V. Khodimchuk M. V. Ananyev V. A. Eremin E. S. Tropin A. S. Farlenkov E. Yu. Pikalova A. V. Fetisov 《Journal of Solid State Electrochemistry》2018,22(7):2115-2126
Oxygen surface exchange kinetics and diffusion were studied in Pr2NiO4?+?δ (PNO) by the isotope exchange method with gas phase equilibration in the temperature range of 600–800 °C and oxygen pressure range of 0.33–1.62 kPa. The oxygen heterogeneous exchange rate (rH), oxygen diffusion coefficient (D), rates of oxygen dissociative adsorption (ra), and oxygen incorporation (ri) were calculated along with the apparent activation energies of oxygen surface exchange and diffusion processes. The temperature dependence of rH was found to benon-linear in Arrhenius coordinates. The apparent activation energy changed from 1.4?±?0.2 eV at T?>?700 °C to 2.0?±?0.1 eV. This might be attributed to the change in the rate-determining stage of oxygen exchange for Pr2NiO4?+?δ at T ~?700 °C, because of a shift in the ratio between ra and ri caused by the difference in their activation energies. Possible reasons for the observed changes in the rate-determining stage are discussed. 相似文献
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Starting with an accurate mathematical model a theoretical study for the analysis of the separation of uranium isotopes by
chemical exchange has been presented. The experimental data used in this study were obtained by reverse breakthrough technique
and the numerical algorithm developed for simulation in previous studies was adapted and found to be suitable for this kind
of processes. The model parameters were identified from experimental data and simulations were carried out for different experimental
conditions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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A. V. Podoplelov Sen Chel Su R. Z. Sagdeev M. S. Shtein V. M. Moralev V. I. Gol'danskii Yu. N. Molin 《Russian Chemical Bulletin》1985,34(10):2041-2044
Conclusions Magnetic isotope effects from tin are not observed during the isotope analysis of the products from reactions involving trimethylstannyl radicals. One of the possible reasons for this is the demonstrated presence of degenerate exchange processes between the initial compounds and the products during the reaction.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2207–2211, October, 1985. 相似文献
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Some water-soluble organic iodine compounds (aqueous solution) can be analyzed for iodine by isotopically exchanging with labelled elementary iodine (organic solution). The method is applicable to exchange systems in which the rate of the exchange is rather small but measurable, before the exchange equilibrium is attained. The iodine content of iodoaromatic amino acids such as 5-iodouracil and 3,5-diiodotyrosine can be determined within an error of ±4%. 相似文献
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N. M. Porotnikova M. V. Ananyev V. A. Eremin D. A. Medvedev A. S. Farlenkov A. A. Pankratov S. V. Plaksin E. Kh. Kurumchin 《Russian Journal of Electrochemistry》2014,50(7):680-689
The stability of the properties of the composite 40 vol % La0.6Sr0.4MnO3 ? δ-60 vol % Zr0.83Y0.17O1.92 (LSM-YSZ) held for 1000 h at a temperature of 800°C and an oxygen pressure of 1.01 kPa and changes in its microstructure were studied by isotope exchange and gas-phase analysis. The oxygen exchange was found to occur by the dissociative adsorption mechanism involving the adsorption forms of oxygen on the triple-phase LSM-YSZ-O2 boundary. The rate-determining step of the oxygen exchange of the composite did not change with time. The rate of oxygen exchange decreased by 22%, which is comparable to the decrease in the length of the LSM-YSZ-O2 triple-phase boundary (~20%), on which oxygen exchange is dominant. The conductivity of the LSM-YSZ composite increased due to the connectivity of the material. 相似文献
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Dong Won Kim Young Shin Jeon Young Kyu Jeong Moo Yul Suh Kih Soo Joe 《Journal of Radioanalytical and Nuclear Chemistry》1995,189(2):219-227
The chromatographic separation of lithium isotopes was investigated by chemical exchange with the recently synthesized polymer-bound dibenzo pyridino diamide azacrown (DBPDA) and reduced dibenzo pyridino diamide azacrown (RDBPDA). Column chromatography was employed for the determination of the effect of solvents and ligand conformation on the separation coefficients. The maximum separation coefficients, , for the DBPDA and RDBPDA at 20.0±0.02°C with acetonitrile as eluent, were found to be 0.034±0.002 and 0.035±0.002, respectively. The isotope separation coefficient and adsorption capability of the lithium ion on the DBPDA and RDBPDA were only slightly dependent on ligand structure, but strongly dependent on the solvent. DBPDA and RDBPDA appeared to have almost the same value for the isotope separation coefficient of lithium. 相似文献
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The present paper is concerned with the isotope exchange between185W and tungsten, and32P and phosphorus respectively, in uranium(IV) trivacant Keggin and Dawson polyoxotungstophosphate complexes, in water. These
studies were carried out at different concentrations and temperature. The isotope exchange rate increases with the temperature
and the reagents' concentration. The experimental results show that the complexes are labile kinetically. 相似文献
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Pszonicki L 《Talanta》1966,13(3):403-408
A procedure has been developed for the very precise determination of uranium in high-purity uranium compounds. Uranium(VI) is reduced in a strong hydrochloric acid solution with aluminium in the presence of cadmium ions to uranium(III). It is oxidised to uranium(IV) in the presence of excess orthophosphoric acid and then quantitatively oxidised to uranium(VI) with potassium dichromate using a potentiometric end-point detection. The coefficient of variation based on 20 analyses is -/+ 0.003%. 相似文献
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E. Kemnitz A. A. Galkin T. Olesch S. Scheurell A. P. Mozhaev G. N. Mazo 《Journal of Thermal Analysis and Calorimetry》1997,48(5):997-1010
The oxygen diffusion and exchange behaviour of NdBa2Cu3O7–x is investigated by means of isothermal and dynamic-thermal analytical techniques. From the results it is concluded that oxygen anions move along vacancies in the CuO2-layers of the perovskite-like structure. In temperature regions where the diffusion rate is low (665 K<T<773 K) heterogeneous oxygen exchange reactions take place on the phase boundary. The higher the exchange rate the more the partially heterogeneous exchange is favoured in comparison to the completely heterogeneous isotope exchange. Depending on the oxygen deficiency of NdBa2Cu3O7–x the out-diffusion of oxygen becomes dominating at higher temperatures. 相似文献
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核事故状态下的应急处理,要求对环境介质中的放射性核素进行快速分析。尿样中铀同位素测量作为内照射剂量评价的主要手段,其分析效率越高,则对核事故中涉铀人员的安全救治越及时、有效。而尿样中其它无机离子是铀含量的106倍,导致ICP-MS测量过程中尿盐堵塞进样毛细管。为降低样品的含盐量并获得较好的检测结果,本文对样品预处理过程进行优化。采用先加热氧化去除有机物,再进行1~10倍稀释后测试样品的铀同位素丰度及浓度。结果表明:将25 mL样品稀释至100 mL后效果最佳,分析方法不确定度为5.4 %,回收率95 %~105 %。 相似文献
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Malinowski J 《Talanta》1967,14(2):263-265
A procedure is described for very precise determination of uranium in high-purity uranium and uranium compounds. Uranium(VI) is reduced in a concentrated hydrochloric acid solution by metallic aluminium in the presence of cadmium ions to uranium(III). This is oxidized to uranium(IV) by protons on addition of an excess of orthophosphoric acid, and then oxidized to uranium(VI) by adding a weighed quantity of potassium dichromate in small excess. The excess of potassium dichromate is determined by constant-current coulometry. The coefficient of variation does not exceed 0.003%. 相似文献
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《Journal of Inorganic and Nuclear Chemistry》1981,43(4):807-813
Experiments have shown that the sorption of uranium from acidic sulphate solutions onto strong base anion exchange resins is particle diffusion controlled in the uranium concentration range 0.0001–0.004M. A simplified diffusion model, based on Fick's Law, fits the kinetic data at each concentration. The rate of sorption falls significantly at lowered solution concentration. This corresponds with a lowered equilibrium loading of uranium and can be predicted with the Nernst-Planck equations using the measured self diffusion coefficient of uranium (1.65 × 10−8 cm2/s) and sulphate ions. The importance of this lowering of uranium sorption on the design of ion exchange equipment is stressed. 相似文献
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The kinetic parameters of the tritium exchange between*H2O(*D2O) and (CH3)2PH in the gas phase and between*H2O(*D2O) and (C6H5)2PH in liquid were measured. Both reactions appeared to be heterogeneous ones. The*HH/*DD kinetic isotope effects were estimated and compared with the results of exchange between methanol and phosphines. The differences
in isotope effects are explained by the change of the symmetry of the four center cyclic transition complex resulting from
the various type of solvation of this complex. 相似文献
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L. Lešetický S. Smrček P. Jelen 《Journal of Radioanalytical and Nuclear Chemistry》1998,227(1-2):161-162
The catalysed isotope exchange method was studied with the aim to elaborate the optimal procedure for labeling of amitriptyline
with iodine125I. Besides the catalysts published, cuprous salts and ammonium sulphate, a series of transition metal complexes as catalysts
were tested at different reaction conditions. The best result (91% radiochemical yield) was achieved with trans-chlorocarbonylbis-(triphenylphosphine)
iridium complex (Vaska catalyst) and sonification. 相似文献
20.
A radiometric method for the determination of cadmium based on two-phase isotope exchange has been developed. The sample containing cadmium is shaken in the presence of tartrate with a standard cadmium-115m diethyldithiocarbamate solution in chloroform. From the distribution of the activity between the aqueous and organic phases 0.05–7 g of cadmium in 5–20 ml sample can be determined.Dedicated to Prof. V. D. Nefedov on the occasion of his 70th birthday 相似文献