Characterization of ceramic PVD thin films on AZ31 magnesium alloys

Ceramic thin films have been widely used to protect the metal substrate as coatings in the past years. In order to improve the poor corrosion resistance of AZ31 magnesium alloy, the study in this paper used the electron beam evaporation method to prepare ceramic PVD films on its surface with TiO₂ and Al₂O₃ as donors, respectively. Atomic force microscopy (AFM), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS), Auger electron spectroscopy (AES) and X-ray diffraction (XRD) were used to investigate the surface morphology, composition and microstructure of the thin films. Both films deposited on AZ31 took on compact top surface morphologies and grew as amorphous structures on substrate. AES test not only showed that films compositions deviated the standard stoichiometric ratios, but also found that element Mg diffused into films and existed as magnesium oxide in the TiO_x film as well as the AlO_x film. In the electrochemical corrosion test, the AlO_x coating on AZ31 exhibited the largest electrochemical impedance in a 3.5% NaCl solution. But it did not show better corrosion resistance than others for the poorer adhesion. Even if its thickness was small, the TiO_x coating on AZ31 exhibited the best corrosion resistance in this study. According to the observation and analysis, the damage of these films on AZ31 in aggressive solutions was mainly due to the existence of pores, microcracks, vacancies and poor adhesion between coating and substrate.     

低电阻测量设计实验中电位差计指针不稳的解决方法

本文分析了J33Q型电位差计在实验中指针不稳的原因,并提出了解决的办法。     

替代法测量微安表内阻的不确定度分析

在测量微安表内阻的众多方法中,替代法是最简单的方法。本文全面分析了影响测量结果不确定度的因素,求出了实验测量的最佳条件,计算了普通仪器组合下测量结果的相对不确定度。     

离心泵快速启动过程外部特性的试验研究

介绍离心泵快速启动试验装置和试验方法,对一台出口直径为80 mm的小型管道离心泵进行试验研究,分别测试了试验泵的稳态性能和各项瞬态性能,比较分析了两者的区别。结果显示,启动过程中,离心泵的扬程紧跟转速到达最大值,转速稳定后的瞬态性能与稳态假设对应,流量和扬程的上升历程与管路阻力特性直接相关,而转速与其基本无关; 在启动初始阶段,无量纲扬程呈现很大值,继而迅速减小到低于稳态假设值,表现出明显的瞬态效应。     

电桥线路功率灵敏度的研究

从电桥线路功率的角度出发,讨论了电桥线路的灵敏度,得出了电桥功率灵敏度的表达式,该式比电流灵敏度公式简单,并能够反映电桥电路的实际情况。     

接地电阻对放电击中点的影响

采用对比性试验,研究了接地电阻对火花放电击中点的影响.试验结果和观测均表明,接地电阻能抑制从接地端产生的迎面放电的发展速度和通道强度,从而使其被击中概率下降,负极性比正极性下接地电阻对火花放电击中点的影响要显著得多.     

High temperature superconducting thin films for microwave filters

YBa₂Cu₃O_7-δ and Tl₂Ba₂CaCu₂O₈ thin films for microwave filters were synthesized by pulsed laser deposition and the two-step thalliation process. Substrate quality requirements and the relation of thin film morphology, microstructure with microwave surface resistance were discussed.     

战国时期农家思想的考察

战国时代，农家的产生是时代孕育的结晶，战国时代的农家可分为农业政治经济思想学家和农业技术专家两大学派，这两派农家对于战国时期的政治经济思想都有较大的贡献，对于此期的传统农业生产技术的总结尤为重要。     

湿地松对松针褐斑病的抗性测定

从松针褐斑病（Ｌｅｃａｎｏｓｔｉｃｔａ ａｃｉｃｏｌａ）重病林分中选出３６个湿地松（Ｐｉｎｕｓ ｅｌｌｉｏｔｔｉｉ）抗病表现型优树无性系，用人工喷洒病菌孢子液接种法对其进行抗病测定，结果表明，有２２个是高度抗病的。与用松针褐斑病产生的毒素粗提液处理上述无性系的离体针叶进行抗病性测定的结果基本一致，相关系数为０．８０。     

新型薄壁柴油机缸体铸件的研制与应用

采用低合金化、合锑多元复合孕育剂、扫描电镜、200h台架试验、以及l000h耐久试验等方法对新型薄壁柴油机缸体铸件进行了研制与应用试验．试验结果表明：碳当量控制在3．9％--4．1％时(与菲亚特缸体的碳当量大体相当)，采用低合金化及合锑复合孕育剂，可稳定获得高强度铸件，抗拉强度σb＞270MPa，硬度HB＞210，白口倾向小，硬度差小于35HB，其性能均达到菲亚特缸体的性能要求．对无缸套缸体的缸壁表面进行激光处理，比传统缸套的耐磨性提高一倍以上．由于采用了无缸套缸体生产技术，简化了柴油机的结构，降低了柴油机的生产成本，提高了柴油机使用性能和技术含量．