ICP—MS法测定高纯碳化硅粉表面的痕量杂质

本文采用ICP-MS法对高纯碳化硅粉表面的Na、Al、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Cd 12种痕量杂质进行测定,用氢氟酸溶液浸提试样表面杂质,用钆做内标补偿基体效应和仪器的漂移,用碰撞反应技术消除多原子离子干扰,通过实验确定最佳优化测定条件。方法检出限为0.005-0.036μg/L;加标回收率为80.0%-120.3%之间;RSD为1.78%-8.95%。方法操作简便、快速、准确。     

Novel Resonant Accelerometer with Micro Leverage Fabricated by MEMS Technology

For the purpose of improving the precision of the inertial guidance system,it is necessary to enhance the accuracy of the accelerometer.Combining the micro-fabrication processes with resonant sensor technology,a high-resolution inertial-grade novel micro resonant accelerometer is studied.Based on the detecting theory of the resonant sensors,the accelerometer is designed,fabricated,and tested.The accelerometer consists of one proofmass,two micro leverages and two double-ended-tuning-fork (DETF) resonators.The sensing principle of this accelerometer is based on that the natural frequency of the DETF resonator shifts with its axial load which is caused by inertial force.The push-pull configuration of the DETF is for temperature compensation.The two-stage micro leverage mechanisms are employed to amplify the force and increase the sensitivity of the accelerometer.The micro leverage and the resonator are modeled for static analysis and nonlinear modal analysis via theory method and finite element method (FEM),respectively.The geometrical parameters of them are optimized.The amplification factor of the leverage is 102,and the sensitivity of the resonator on theory is about 62 Hz/g.The samples of the accelerometer are fabricated with deep reactive ion etching (DRIE) technology which can get a high-aspect ratio structure for contributing a greater sensing-capacitance.The measuring results of the samples by scanning electron microscopy (SEM) show that the process is feasible,because of the complete structure,the sound combs and micro leverages,and the acceptable errors.The frequency of the resonator and the sensitivity of the accelerometer are tested via printed circuit board (PCB),respectively.The result of the test shows that the frequency of the push-resonator is about 54 530 Hz and the sensitivity of the accelerometer is about 55 Hz/g.The amplification factor of the leverage is calculated more accurately because the coupling of the two stages leverage is considered during derivation of the analysis formula.In addition,the novel differential structure of the accelerometer can greatly improve the sensitivity of the accelerometers.     

多层压电陶瓷降压变压器的环境测试研究

电压增益、输出功率、效率是表征压电变压器(MPT)工作性能的3个重要参数。使用为华公司提供的径向振动型多层压电陶瓷降压变压器,测量其基本电学性能;温度对导纳圆等阻抗特性的影响;温度对其基本电学性能的影响等。综合研究降压变压器的环境温度稳定性。结果表明:压电变压器环境稳定性良好,但长时间剧烈的环境变化会对其使用性能产生一定影响,高温环境对其影响比较大。     

Effect of polyaniline on hydrogen absorption–desorption properties and discharge capacity of AB3 alloy

A series of AB₃/PANI composites were prepared by adding polyaniline (PANI) into La_0.7Mg_0.25Ti_0.05Ni_2.975Co_0.525 (AB₃) hydrogen storage alloy, which was prepared by magnetic levitation melting, and the composites were investigated by XRD and SEM. The effects of PANI concentration on the hydrogen absorption–desorption properties and discharge capacities of AB₃ alloy were systematically studied by P–C–T isotherms and LAND battery test system, respectively. The results indicated that the addition of PANI did not change the hydrogen absorption capacity of AB₃ alloy distinctly, while the hydrogen desorption plateau pressure of AB₃ alloy decreased firstly, and then increased with the increase in the PANI concentration, the minimum plateau pressures of 0.022, 0.1, 0.321 and 0.55 MPa were obtained with PANI concentration of 2 wt% at 25, 50, 80 and 100 °C, respectively. It was theoretically verified by the changes in enthalpy and entropy of AB₃/PANI hydrides dehydrogenation which were calculated by Van’t Hoff equation. In the present paper, the phenomenon that PANI improved the hydrogen absorption kinetics of AB₃ alloy was found; the influence of PANI concentration on hydrogen absorption kinetics of AB₃ alloy was more apparent at higher temperature. The activation energies of dissolved hydrogen in AB₃/PANI hydrides were calculated from hydrogen absorption kinetics and the Arrhenius equation. LAND experiments demonstrated that, the AB₃/PANI electrodes composites possessed higher cycling discharge capacity retention rates than AB₃ electrode alloy.     

Convective Drying of Sludge Cake

This paper presented an experimental study on convective drying of waste water sludge collected from Beijing GaoBeiDian Sewage Treatment Plant, particularly on the correlation between the observed shrinkage dynamics of sludge cake and the drying curve. During the initial stage of drying the process resembles to that of a particulate bed, in which moisture diffuses and evaporates at the upper surface. Conventional drying theory assuming a diffusion-evaporating front interprets this period of drying. Consequently, owing to the very large shrinkage ratio of the dried cake, cracks emerges and propagates on and within the cake body, whence inducing evaporating channel that facilitates the water removal. This occurrence compensates the reduction of surface area for evaporation, whence extending the constant-rate period during the test. Afterwards, the cracks meet with each other and form isolated cake piles, while the subsequent drying occur mainly within these piles and the conventional theory fails. The tran     

Polycrystalline silicon solar cells on low cost foreign substrates

The use of polycrystalline silicon layers on low-cost substrates is a promising approach for the fabrication of low-cost solar cells. Using low-carbon steel and graphite as substrates, solar cell structures have been deposited by the thermal decomposition of silane and appropriate dopants.Steel was selected as a substrate on the sole basis of its low cost. However, steel and silicon are not compatible in their properties, and an interlayer of a diffusion barrier, such as borosilicate, must be used to minimize the diffusion of iron from the substrate into the deposit. The deposited silicon on borosilicate/steel substrates is polycrystalline with a grain size of 1–5 μm, depending on deposition conditions. P-n junction solar cells were found to have low open-circuit voltages and poor current-voltage characteristics, and Schottky-barrier solar cells were found to show negligible photovoltages.Graphite is more compatible with silicon in properties than steel, and silicon deposited on graphite substrates shows considerably better microstructures. A number of solar cells, 2·5×2·5 cm in area, have been fabricated from n⁺-silicon/p-silicon/p⁺-silicon/graphite structures. The best cell to date had a V_oc of 0·35 V and an AMO efficiency of 1·5% (no antireflection coating). This type of solar cell is very promising because of the simplicity in fabrication.     

连杆形状优化设计的灵敏度分析

首先讨论了结构形状灵敏度分析的边界元摄动法，然后对柴油机连杆进行了灵敏度分析，得到了一些重要结论，为改进连杆设计提供了依据。     

氢发动机性能的改进

本文论述了氢发动机的最新研究成果，着重描述了氢的储存和混合气形成及点火等技术问题，并提出了相应的措施。试验表明，采用氢的高压喷射、火花点火，并调整最佳点火正时，就能获得良好的经济和动力性能     

柴油-甲醇乳化燃料乳化剂的最佳HLB值及水含量的影响

柴油机中掺烧醇的最大难点之一在于难以获得价廉、稳定的柴油-甲醇乳化燃料。作者研究了柴油-甲醇乳化燃料乳化剂的最佳HLB值以及不同含水量对最佳HLB值的影响。研究结果表明：柴油-甲醇乳化燃料乳化剂的最佳HLB值在3．5左右，当柴油甲醇乳化燃料中含水形成了甲醇-水-柴油三元乳化燃料时，其最佳HLB值与柴油-水的最佳HLB值相同，且三元乳化燃料乳化剂的最佳HLB值不随含水量的增加而变化，但随着含水量增加，乳化燃料分层时间会产生变化；在柴油-甲醇-水乳化液中，当水在甲醇-水混合液中的比例为40％左右时，甲醇-水-柴油三元乳化燃料(柴油：甲醇 水=8：1)的分层时问最长，即在柴油-甲醇乳化燃料中加水有利于提高乳化燃料的稳定性。     

青铜峡3~#机组水轮机转轮室的更新改造

本文就水轮机转轮室的更新改造工作,从准备、旧件拆除、新件组装调整、试运等方面进行了较为详细的介绍,并且从中总结出经验和教训.