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971.
《Analytical letters》2012,45(4):347-354
Abstract A method for the determination of impurities in 233UO2 has been developed and applied to the analysis of a product stream of ceramic grade 233UO2 powder. The analytical method has combined isotope dilution and internal standard methods to permit the determination of impurities at concentrations between 0.1 and 500 ppm in a single sample. 相似文献
972.
《Analytical letters》2012,45(5):523-533
Abstract The present work deals with the determination of vanadium in high grade carbons by the thermal neutron activation using a Van de Graaff Accelerator. In this study, gadolinium oxide is used as the internal standard material, and the detection limit of this method is c. a. 1 ppm. 相似文献
973.
《Analytical letters》2012,45(15):2761-2762
Abstract The present note deals with the optimization of the combustion of organic materials to CO2 in Pyrex and quartz tubes. The influence of temperature and oxidant on the combustion yield was investigated. Different physical forms of CuO and a CuO/MnO2-mixture were used as oxidants. Possible isotopic effects during combustion were tested by gas isotope ratio mass spectrometry (GIRMS) of the CO2. Excellent results were obtained for combustion in Pyrex at 530 °C using CuO rods mixed with 20% MnO2 as oxidant. The stable isotope results for CO2 prepared with this method were accurate and showed a very good precision of 0.030 %. Applications for which quantitative combustion is a necessity, we suggest the use of CuO powder (< 100 μm) as oxidant and a combustion temperature of 850 °C. 相似文献
974.
Fe2O3/Al2O3氧载体制备方法的研究 总被引:1,自引:0,他引:1
采用溶胶-凝胶法、共沉淀法、水热合成法、低热固相合成法、机械混合法、燃烧合成法和冷冻成粒法制备铁基氧载体Fe2O3/Al2O3,并通过物理和化学表征手段来筛选和优化制备方法和制备工艺。对煅烧后的氧载体进行硬度测试,结果表明,溶胶-凝胶法、共沉淀法、机械混合法、燃烧合成法和冷冻成粒法制备的氧载体硬度较高;载体的X射线衍射(XRD)谱图表明,各种制备方法均能制得物相组成为Fe2O3/Al2O3的氧载体,且随着煅烧温度的提高、煅烧时间的延长,氧载体的结晶度、晶体粒径逐渐增大,煅烧温度1 200℃的氧载体的机械性能、晶体结构、晶相组成更稳定。借助化学吸附仪的程序升温还原(TPR)实验表征氧载体的反应活性,并计算氧载体活性度。综合物理和化学表征实验结果表明,最优制备方法为溶胶-凝胶法和冷冻成粒法。 相似文献
975.
《Analytical letters》2012,45(1-2):47-64
Abstract A research program was initiated to evaluate the stability of selected organic compounds collected on porous polymer sorbents during combustion source sampling. This type of study is necessary to determine if destruction and removal of hazardous materials waste has occurred during incineration and not as a result of the sampling and analytical approach used. Two compounds, hexachlorobenzene and toluene diisocyanate, were selected for study. Due to difficulties encountered in preliminary work, studies on toluene diisocyanate were discontinued. Hexachlorobenzene sorbed onto XAD-2 resin at the 1 μg level was exposed to the following conditions intended to simulate hazardous waste incineration stack samplin: moist air, moist air in combination with HCl (two concentrations), and warm air. Recoveries following exposure were determined for each of three trials. The results indicate that hexachlorobenzene sorbed onto XAD-2 is stable with respect to the conditions routinely encountered during incineration stack sampling. 相似文献
976.
《Analytical letters》2012,45(1):25-33
Abstract A multiple internal reflectance method and a chemical method for the quantitative determination of poly(vinyl acetate) binder on non-woven polyester battings are described. The band assignments, poly (vinyl acetate) concentration, and standard battings preparation are discussed. 相似文献
977.
978.
The ignition solutions for the scalar nonconvex Chapman-Jouguet (CJ) combustion model are studied as the ignited perturbation vanishes. We let the perturbation vanish in the result of the interactions of the combustion waves and noncombustion waves, thereby obtaining that the unburnt gas is unstable when the binding energy is larger than a critical value. Furthermore, in the vanishing process, the transitions between deflagration and detonation waves are observed. 相似文献
979.
A theoretical model is established to investigate the intragranular particle residual stress in A1203-SiC nanocom-posites. Using this model, we calculate the average compressive stress on the A1203 grain boundary (GB) and the average tensile stress within A1203 grains caused by SiC nanoparticles. The normal compressive stress strengthens the GB, and the average tensile stress weakens the grains. The model gives a reasonable interpretation of the strength changes of A1203-SiC nanocomposites with the number of SiC particles. 相似文献
980.
建立了一个考虑热阻、热漏和内不可逆性且热源和工质之间满足牛顿传热规律的不可逆Braysson热机模型。导出了该模型下输出功率、效率和生态学目标函数的表达式。计算了最大输出功率、最大效率和最大生态学目标函数及它们对应的参数值并通过图来反映它们的变化情况。讨论了热漏、内不可逆性对该热机各种性能参数的影响同时给出了一些重要参数的优化范围。所得结果对实际Braysson热机的优化设计提供了理论依据。 相似文献