基体稀释或基体匹配石墨炉原子吸收光谱法测定土壤样品中铅和镉

用石墨炉原子吸收光谱法测定土壤样品中Pb和Cd时,有时候直接按照方法标准GB/T 17141—1997操作,测定结果不能满足质控要求。研究结果表明,目标元素系列标准溶液中,分别含和不含土壤基体元素Na、Mg、Al、Si、Fe、Ca等元素混合成分时,校准曲线斜率明显不同。为减小基体效应的影响,基于文献调研和实验结果,对上述方法标准实验步骤进行了下列改进:(1)取相同体积实际样品消解液混合后,定量加入到用于建立校准曲线的系列标准溶液中,用于基体匹配;(2)对消解液进行适度稀释,仍采用标准溶液建立校准曲线。用4个土壤标样和土壤样品加标测定结果对改进后的方法进行了验证,结果表明,基体稀释法测定Pb的回收率范围分别为90.4%~114%;测定低含量Cd时,回收率范围为84.1%~125%。基体匹配法测定Pb和Cd的回收率范围分别为93.0%~105%和102%~119%,基本满足土壤样品中重金属回收率为80%~120%的质控要求。样品中痕量镉在测定下限附近时,应严格控制稀释倍数,或采用基体匹配法测定。改进后的操作步骤适合日常检测工作中大批量土壤样品中Pb和Cd的准确测定。     

Enhancement of energy storage density in antiferroelectric PbZrO3 films via the incorporation of gold nanoparticles

In this work, antiferroelectric Au–PbZrO₃ (Au–PZO) nanocomposite thin films were prepared by chemical solution deposition (CSD), and the effects of Au concentration on the antiferroelectric properties and the recoverable energy density were investigated. The results showed that the optimal Au concentration in the Au–PZO nanocomposite thin films was about 1 mol% for structural and electric properties. In the Au–PZO nanocomposite thin films with 1 mol% Au, Au nanoparticles (NPs) were distributed uniformly in the perovskite PZO matrix. Moreover, the recoverable energy density was 10.8 J/cm³ at 600 kV/cm, which is 42% higher than that of the pure PZO films. The results demonstrate that adding an appropriate amount of noble metal NPs in antiferroelectric thin films is an effective method to improve the energy storage properties.     

Enhancing the hydrogen generation of TiO2 nanoparticles by decorating its surface with BiI3 and PbI2 quantum dots

This work reports the performance of TiO₂/BiI₃ and TiO₂/PbI₂ nanocomposites for hydrogen generation. BiI₃ and PbI₂ quantum dots (QDs) were grown on TiO₂ (P25 Degussa) using a fast injection method. According to the analysis by X-ray diffraction, the nanocomposites have a mixture of anatase, rutile and cubic phases from TiO₂, BiI₃ and PbI₂. The images obtained from transmission electron microscopy revealed that the TiO₂ support have sizes in the range of 70–220 nm while the QDs of BiI₃ and PbI₂ (co-catalysts) grown on TiO₂ have sizes in the range of 12–17 nm. The presence of these iodides on TiO₂ created oxygen vacancies defects (confirmed by photoluminescence measurements) that extended the light absorption of TiO₂ from the UV to the VIS range. According to the results from the photocatalytic experiments for hydrogen generation (achieved using pure water and UV-VIS light), the hydrogen generation rates produced by the TiO₂/BiI₃ and TiO₂/PbI₂ nanocomposites were 437–580 times, 81–108 times and 21–30 times, higher than these for pure TiO₂, PbI₂ and BiI₃, respectively. The maximum hydrogen generation rates of the TiO₂/BiI₃ and TiO₂/PbI₂ nanocomposites were 290.7 and 219.2 μmol h^?1 g^?1, respectively. In addition, the TiO₂/BiI₃ and TiO₂/PbI₂ nanocomposites contained defects that acted as electron trapping centers, which in turn, delayed the electron-hole recombination and this favored the photocatalytic generation of H₂. Moreover, the heterojunction formed between the TiO₂ and the iodides allowed the transfer of electrons from the conduction band of TiO₂ toward the conduction band of the iodides, creating a “sink” for the electrons which delayed the electron hole recombination. The results presented here demonstrated that the deposition of iodide co-catalyst on TiO₂ is a feasible option to enhance the hydrogen generation.     

Price and lead time differentiation,capacity strategy and market competition

We study a duopoly market in which customers are heterogeneous, and can be segmented as price or time sensitive. Each firm tailors (differentiates) its products/services for the two customer classes solely based on guaranteed lead time and the corresponding price. Our objective is to understand how competition affects price and lead time differentiation of the firms in the presence of different operations strategy (shared versus dedicated capacity), product substitution and asymmetry between the competing firms. Our results suggest that when firms use dedicated resources to serve the two market segments, pure price competition always tends to decrease individual prices as well as price differentiation, irrespective of the market behaviour. Further, the effect of competition is more pronounced when customers are allowed to self-select, thereby introducing substitutability between the two product options. On the other hand, when firms compete in time, in addition to price, the effect of competition on product differentiation depends crucially on the behaviour of the market. Our results further suggest that the firm with a larger market base should always maintain a larger price and lead time differentiation between the two market segments. Similarly, the firm with a capacity cost advantage should also maintain a larger lead time differentiation.     

Computer Simulation Study of Transient Diffusion of Cesium through Granite with Unsteady-State Diffusion Model

A steady-state diffusion model has been used widely to determine the diffusivities of radionuclides in rocks. Buffer container at the source solution side is used to keep the concentration constant. It is suitable for non-sorptive species, but not for sorptive species. Some researchers proposed a unsteady-state diffusion model recently. It is possible to use simple experimental apparatus without buffer container to measure the diffusivity with this model. To obtain the diffusional information more easily according to the sorption properties of radionuclides, through- diffusion experiments were performed in granites. Methods of determining of diffusivities are discussed according to sorption properties of species. For the non-sorptive species, the steady- state diffusion model was effective to determine the diffusivity. For the sorptive species, the analytical solution of the unsteady-state diffusion model found to be more appropriate to determine the diffusivity. Surface diffusion of sorbed species on rock did important role in diffusive transport.     

Rapid and efficient deoxygenation of sulfoxides to sulfides with tantalum(V) chloride/sodium iodide system

TaCl₅/NaI system converts a wide range of sulfoxides to the corresponding sulfides in high yields with short reaction times, under mild conditions. It is worth mentioning that this protocol is chemoselective and tolerates various functional groups (such as –Br, –Cl, –OCH₃, –CHO, and –NO₂) and double bond.     

Removal of Liquid and Solid Impurities from Uranyl Nitrate Hexahydrate Crystalline Particles in Crystal Purification Process

The purification behavior of uranyl nitrate hexahydrate (UNH) was investigated to evaluate the decontamination performance of liquid and solid impurities using a dissolver solution of mixed oxide (MOX) fuel in batch experiments. The UNH crystal recovered from the MOX fuel dissolver solution containing simulated fission products (FPs) was purified by a sweating and melt filtration process. Although the decontamination factors (DFs) of Pu, Cs, and Ba did not change in the sweating process, that of Eu increased with increases in temperature and time. These results indicate that liquid impurities such as Eu were effectively removed by the sweating method, but solid impurities such as Pu, Cs, and Ba were minimally affected in the batch experiments. On the other hand, the DF of Ba increased with 0.45 and 5.0 μ filters in the melt filtration process. Since Pu and Cs formed as Cs₂Pu(NO₃)₆ in the course of U crystallization and was accompanied with the UNH crystal, these behaviors were similar to each other. Although the DFs of Pu and Cs did not change with the 5.0 μ filter, it increased approximately twofold with the 0.45 μ filter. The particle size of Cs₂Pu(NO₃)₆ is relatively small and might pass through the 5.0 μ filter in the melt filtration process. The liquid impurities as Eu remained in the molten UNH crystal with some filters.     

活性炭吸附原子吸收光度法测定铅锑精矿中金的含量

通过在铅锑精矿焙烧时加入一定量的氧化锌或氧化钙，使铅锑精矿在灼烧过程中的单质硫、有机质、硫化物、碳充分焙烧，然后采用王水分解矿样，活性炭动态吸附富集金，灰化除碳，王水溶解，原子吸收光度法测定铅锑精矿中金含量，方法快速、准确，同时适用于含碳、硫较高焙烧时易结块的精矿样品。