An Investigation into the Thermal Boundary Resistance Associated with the Twin Boundary in Bismuth Telluride

The thermal boundary resistances (TBRs) of twin boundaries occurring at three different atomic layers (Te1, Bi, and Te2) of bismuth telluride (Bi₂Te₃) are investigated in use of the non-equilibrium molecular dynamics (NEMD) simulation method. The simulation results show that among all, the Te1-twin boundaries bring about a lowest interfacial energy corresponding to a most stable system, which explains why this type of twin boundaries is mostly often observed in the laboratory; the Te2-twin boundaries on the other hand possess a largest interfacial energy, resulting in a least stable system. The order in magnitude of the TBRs associated with these three types of twin boundaries is Te2-twin > Bi-twin > Te1-twin. Moreover, the TBR associated with a pair of twin boundaries separated by a distance of 4 unit cell (UC) is found to be about twice as large as that of a single twin boundary of the same type. It implies that the mutual coupling, which causes an increase in TBRs, may be ignored and the effect of twin boundaries may be counted individually as long as the separation distance is larger than 4 UC.     

湿法消化-氢化物原子荧光法测定植物提取物中镉的含量

探讨了应用原子荧光光法测定植物提取物中镉含量的方法。样品用硝酸+高氯酸混合液消化,在盐酸介质中,试样中的镉在镉专用2号试剂存在下,镉1号专用还原剂将二价镉还原成镉的挥发性组分,用AFS-8230原子荧光光度计测定。该法线性范围为0~60μg/L,相关系数r=0.9998,检出限为0.0024μg/L,相对标准偏差为1.36%,回收率为92.8%~96.1%。     

Coupling of electrodialysis and leaching processes for removing of cadmium from phosphate ore

Phosphate rock is a valuable material that is used for the production of large phosphorus chemicals. However, this natural material usually contains some toxic elements such as cadmium (Cd). Cd is a non-nutritive metal regarded as harmful to both humans and the environment. The main toxic effects of Cd on human health are the kidney and renal cortex diseases. Other effects were observed on pulmonary, cardiovascular, and musculoskeletal systems, in addition to including Cd as a human carcinogen. In order to reduce the cadmium content in the phosphate ore, an original method was studied and consists of coupling both leaching and electrodialysis. The effects of process parameters, such as reaction time, nature, and concentration of the extracting agent, liquid/phosphate ore ratio, pH, temperature, and current density, were investigated. The obtained results show that the cadmium extraction from phosphate ore using simple batch leaching does not reduce the cadmium content to the required level. However, the application of leaching- electrodialysis coupled method at optimum current density of 10 mA cm^?2 increases the cadmium extraction efficiency up to 84.3%. This synergetic process could be applied to the treatment of phosphate ore containing cadmium.     

Synthesis,characterisation of ternary layered double hydroxides (LDH) for sorption kinetics and thermodynamics of Cd2+

Kinetic and thermodynamic studies were carried out on the sorption of Cd²⁺ on three synthesised and characterised layered double hydroxides, namely: Ni-Co-Ti, Ni-Co-La and Mn-Ni-Al-CO₃. Sorption kinetics were investigated through time-dependent studies. Thermodynamics were determined by the effect of temperature on adsorption. Kinetic modelling of the adsorption of Cd(II) ions on the LDHs was determined using the first-order, pseudo-first order, pseudo-second order and Elovich kinetic models, as well as additional diffusion models. The results showed that the pseudo-second-order model best correlated the adsorption data with R² values of 1.000, 0.998 and 1.000 for NiCoTi, NiCoLa and MnNiAl-LDH respectively. Diffusion of the adsorbate was best correlated by the Weber-Morris intraparticle diffusion model with R² values of 0.9753, 0.8472 and 0.9412 for NiCoTi, NiCoLa and MnNiAl-LDH respectively. Thermodynamic studies showed that the adsorption was spontaneous and exothermic with a high probability of sticking.     

乙内酰脲体系无氰电镀镉工艺

目的开发一种新型的无氰镀镉工艺,替代传统的氰化镀镉。方法以海因和柠檬酸为主、辅络合剂,通过选用光亮剂和表面活性剂获得无氰镀镉工艺配方,优化pH值、电流密度和温度等工艺参数。按规定的方法测试镀液的分散能力、深镀能力。利用SEM、三维显微镜观察镀层的微观形貌,通过极化曲线和循环伏安曲线讨论镀液的极化度和成膜机理,利用塔尔菲尔曲线和点滴实验测试其耐蚀性。结果镉电沉积是通过"成核/生长"机理进行的,乙内酰脲体系无氰镀镉双络合剂协同作用明显,镀液极化能力强。与氰化镀镉相比,该工艺电流效率提高20%,沉积速率提高30%,分散能力可达89%以上,镀液深镀能力和镀层结合力检验合格,镀层表面光亮细致,钝化膜彩虹色明显。无氰镀镉层耐蚀性优于氰化镀镉层,与氰化镀镉钝化层相比,钝化封闭后,自腐蚀电流密度降低至之前的1/15,耐蚀性显著提高。结论该配方及工艺条件为:硫酸镉30～50 g/L,硫酸钠60～100 g/L,乙内酰脲60～70 g/L,柠檬酸20～40 g/L,光亮剂1～3 g/L,表面活性剂1～3g/L,pH=5～6,温度15～35℃。镀液镀层各项性能优越,完全可以替代氰化镀镉工艺用于我国飞机和航空发动机钢结构的防护。     

高镉锌真空蒸馏镉

论述了高镉锌真空蒸馏提镉的基本原理及内热式真空蒸馏炉的结构特点和材质,讨论了影响锌镉分离的重要因素(真空度、温度、合金含镉百分数、进料速度、蒸馏级数等),列出了试验取得的技术经济指标和提镉真空蒸馏的实例。扩大试验用含Cd29.11％、Zn68.72％的高镉锌,经20级空真蒸馏后,可产出精镉和粗锌。     

废弃印刷线路板Pb,Cd和Cr的测定

研究用原子吸收分光光度计测定废弃印刷线路板中重金属元素Pb，Cd和Cr的含量。结果表明，方法灵敏、快速、准确、操作方便，实用性强。Pb，Cd和Cr的回收率在98．9％～103．6％之间，相对标准偏差RSD〈1．45％。