Diamond paste-based electrodes for determination of Cr(III) in pharmaceutical compounds

A new class of monocrystalline diamond paste-based electrodes is proposed for the determination of chromium(III) at trace levels in vitamins. Three types of monocrystalline diamond—natural diamond 1 (natural diamond), synthetic diamond 50 (synthetic-1), and synthetic diamond 1 (synthetic-2)—were used for electrode construction. The linear concentration ranges are between 10^–10 and 10^–8; 10^–9 and 10^–7, and 10^–10 to 10^–8 mol L^–1, with limits of detection of 10^–12, 10^–12, and 10^–11 mol L^–1, when natural diamond, synthetic-1, and synthetic-2, respectively, are used as electrode materials. For electrodes based on natural diamond and synthetic-1 it was found that Cr(III) yields a peak at about +0.275±0.015 V (vs. Ag/AgCl) within a predetermined positive potential range situated between +0.4 and +0.2 V, while for the electrode based on synthetic-2 the peaks are found at +0.300±0.015 V (vs. Ag/AgCl). The proposed method is reliable for the determination of chromium(III) at trace levels in two vitamin tablets (RSD<0.2%).     

太阳能电池制绒设备研究的几点心得

着重对太阳能电池制绒工艺的研究进行了阐述,并以研究所得的工艺数据为基础,对制绒设备的关键部件——工艺槽体的设计进行了详细说明,保证所研发的最终设备满足了大规模生产线对制绒设备的需要。     

Discharge cutting technology for specific crystallographic planes of monocrystalline silicon

Crystallographic planes were detected with X-ray crystal orientation instrument to study wire-cut electrical discharge machining (WEDM) technology for specific crystallographic planes of monocrystalline silicon. The unidirectional conductivity of monocrystalline silicon was analyzed. The contact potential barrier was decreased by preparing Ohmic contact to the surface discharging of the input terminal. Finally, the high-precision discharge cutting of the specific crystallographic planes of monocrystalline silicon was validated. Finished silicon products with specific crystallographic planes were prepared by WEDM, and the cutting efficiency, surface quality, crystal orientation precision, and qualified rate were determined. With cutting thickness of 200 mm, the cutting efficiency reached 100 mm²/min, and the precision of crystal orientation reached 3′ or less.     

Electrochemical polishing of monocrystalline silicon with specific crystallographic planes

In this study, an electrolytic polishing experimental system was developed to obtain a uniform, flat-surfaced monocrystalline silicon with specific crystallographic planes. Several key factors reflecting specific electrolytic polishing on monocrystalline silicon with specific crystallographic planes were summarized. These factors, including electrolyte, conduction mode, Schottky barrier, semiconductor body resistance, and unidirectional conductivity, were analyzed comprehensively through energy spectrum analysis, theoretical modeling, and potential simulation. The effects of electrolytic polishing process were obtained, and corresponding solutions were proposed. Finally, the electrolytic polishing experiment for monocrystalline silicon with specific crystallographic planes was conducted. A uniform, flat-surfaced monocrystalline silicon with no metamorphic layer was then obtained. The flatness error of the center area was less than 0.201 µm. Furthermore, the crystallographic planes of monocrystalline silicon wafers showed no change.     

THE GROWTH OF MONOCRYSTALLINE SILICON THIN FILM ON INSULATOR (SOI) BY SCANNING ELECTRON BEAM

An experiment for preparation of SOI films by using the scanning electron beam to modify the polycrystalline silicon on SiO2 is presented. This method takes on the epitaxial lateral growth of liquid phase with the crystallon to form monocrystalline silicon films. The effects of the beam power density, scanning velocity, temperature of the substrates and the construction of samples on the quality of the monocrystalline silicon films were discussed. A good experimental result has been obtained, the monocrystalline silicon zone is nearly 200×25μm2.     

The onset of spherulitic growth in crystallization of calcium carbonate

Batch and semi-batch crystallization experiments were performed in aqueous solutions for the three anhydrous polymorphs of calcium carbonate vaterite, aragonite and calcite to investigate the effect of crystallization parameters on the onset of spherulitic growth and particle morphology.     

国产炉拉制Φ＞76.2mm无位错FZ硅单晶的两种工艺热场分析

对国产设备试制及生产Φ＞７６．２ｍｍ无位错ＦＺ硅单晶的两种最为稳定的工艺热场作了较全面的分析总结。     

Diamond paste based electrodes for the determination of Pb(II) at trace concentration levels

Three types of monocrystalline diamond: natural diamond 1 μm, synthetic diamond 50 μm (synthetic-1), and synthetic diamond 1 μm (synthetic-2) were used for electrodes’ construction. The linear concentration ranges recorded for Pb(II), when natural diamond, synthetic-1 and synthetic-2 based electrodes were used were between 10⁻⁹ and 10⁻⁶; 10⁻¹⁰ and 10⁻⁷; and between 10⁻¹⁰ and 10⁻⁸ mol l⁻¹, respectively. Low detection limits which lie between 10 and 100 pmol l⁻¹ proves the sensitivity of the electrodes. It was found that Pb(II) yielded a peak at about +0.3±0.02 V (versus Ag/AgCl) for all the electrodes. Lead was determine with high reliability from water and tea samples at trace concentration levels using the proposed diamond paste based electrodes.     

点缺陷对单晶硅力学性能影响的分子动力学研究

本文采用分子动力学方法模拟了含有不同大小点缺陷的单晶硅在恒定应变率作用下的破坏过程,以及点缺陷对单晶硅屈服强度的影响,结果表明:点缺陷能显著减小单晶硅的屈服强度,且屈服强度的变化趋势和点缺陷的大小服从指数函数关系,经过分析发现是点缺陷诱发的应力集中效应降低了屈服强度.通过利用已有的四类强度理论进行校核,发现米塞斯强度理论最适合描述单晶硅的屈服强度,且单晶硅晶体的破坏过程可以由米塞斯应力的演化和聚集效应来说明.最后,在可视化分析破坏后的结构时,发现破坏过程产生的微结构沿着解理面分布,其微观构造类似于二维网格.本文研究结果为评估点缺陷对单晶硅屈服强度的影响机理提供了参考.