Ni-MH电池稀土AB_2型贮氢合金负极材料的研究

本文主要对稀土AB_2型贮氢合金用于Ni-MH电池负极材料的电化学性能进行了研究。结果表明，（一）通过优化合金组分，发现多相结构的 LaNi_(2-x)Al_x合金(0.15 ≤ x ≤ 0.25)显示突出的放电性能和长的循环寿命；（二）非化学计量比贮氢合金呈现更高的放电容量和满意的活化性能；（三）原材料的纯度对合金的电极性能影响甚微；（四）退火使合金的结构重整，但对合金电极的电化学性能不利；（五）长时间球磨可以促进活化，但导致电化学容量迅速衰减；短时间球磨大大增加放电容量和提高倍率放电性能；（六）合金电极高能辐照可以激活合金电极的表面活性，促进活化，有效的控制自放电；（七）随着在热碱液中浸泡时间的增加，合金电极的充放电性能得到明显的改善；（八）以镍粉为导电剂的合金电极比以铜粉为导电剂的合金电极有较好的综合电化学性能；（九）温度对合金的电极性能有很大影响。在30 ℃和40 ℃ 测试温度下所得的放电容量几乎相同，但在60 ℃和70 ℃放电容量开始减少。随着温度增加，电极的活化过程加速，高倍率放电能力略有所增加。合金电极呈现不理想的低温放电性能；（十）循环后合金电极的 XPS、XRD、ICP、SEM的图谱分析表明，LaNi_2基合金的腐蚀是造成容量衰减的主要原因，合金的本征衰退也可能是造成容量衰减的原因之一。

A Radial Stub Test Circuit for Microwave Power Devices

With the principles of microwave circuits and semiconductor device physics, two microwave power device test circuits combined with a test fixture are designed and simulated, whose properties are evaluated by a parameter network analyzer within the frequency range from 3 to 8GHz. The simulation and experimental results verify that the test circuit with a radial stub is better than that without. As an example, a C-band AlGaN/GaN HEMT microwave power device is tested with the designed circuit and fixture. With a 5.4GHz microwave input signal, the maximum gain is 8.75dB, and the maximum output power is 33.2dBm.

Low-Microwave Loss Coplanar Waveguides Fabricated on High-Resistivity Silicon Substrate

Three kinds of coplanar waveguides （CPWs） are designed and fabricated on different silicon substrates---common low-resistivity silicon substrate （LRS）, LRS with a 3μm-thick silicon oxide interlayer, and high-resistivity silicon （HRS） substrate. The results show that the microwave loss of a CPW on LRS is too high to be used, but it can be greatly reduced by adding a thick interlayer of silicon oxide between the CPW transmission lines and the LRS.A CPW directly on HRS shows a loss lower than 2dB/cm in the range of 0-26GHz and the process is simple,so HRS is a more suitable CPW substrate.

Frequency limitation in calibrating microwave test fixtures

The problem of frequency limitation arising in calibration of the test fixtures is investigated in this paper. It is found that at some frequencies periodically, the accuracy of the methods becomes very low, and. the denominators of the expressions of the required S-parameters approach zero. This conclusion can be drawn whether-the test fixtures, are symmetric or not. A good agreement between theory and experiment is obtained.