沉积压力对非平衡磁控溅射沉积MoS2-Ti复合薄膜的结构与性能影响研究

采用非平衡磁控溅射沉积技术制备MoS2-Ti复合薄膜,研究了沉积压力对薄膜的结构和性能的影响.利用XRF、轮廓仪和XRD分析测试薄膜的成分、厚度和晶相结构,用CSEM薄膜综合性能测试仪测试薄膜的硬度和与基底间的附着力,用球-盘摩擦试验机和真空环模系统评价薄膜的真空摩擦磨损性能.结果表明:降低沉积压力使溅射粒子的平均自由程变大,薄膜沉积过程中再溅射作用加强,对薄膜的结构和性能产生较大的影响.沉积压力升高,薄膜中S和Mo原子比和Ti质量分数随之增大,变化范围分别为1.50～1.77和5.8%～8.1%,薄膜沉积厚度先增大后减小,薄膜晶相结构从明显的(002)基面优势取向向准晶态转变;薄膜的硬度、与基底间的附着力都随沉积压力的升高而降低,薄膜硬度变化范围是5.7～3.5 GPa,薄膜与基底间附着力变化范围是100～75 mN;薄膜在真空环境中的减摩性能不受工作压力变化影响,摩擦因数平均值为0.02,波动范围为0.01～0.04,薄膜耐磨寿命随沉积压力升高依次为9 000,21 500,28 000,18 000 m ,工作压力低时再溅射作用破坏了MoS2分子层间的滑移能力从而使其耐磨寿命降低.     

The Effect of Surface Roughness on Contact Fatigue Behavior Using Mesoscopic Approach

The effect of surface roughness on the contact fatigue was investigated in this study. To accomplish this goal, contact analysis based on the influence functions and the rectangular patch solutions was performed to obtain the subsurface stress. Mesoscopic multiaxial fatigue criterion is then applied to predict fatigue damage. Rainbow counting method and damage rule were used to evaluate the fatigue life under random loadings caused by the rough surface contact. As a result of the fatigue analysis, the relationship among the fatigue life, the crack initiation depth, and the surface roughness were revealed. It is observed that the fatigue life has hardly changed and a crack is initiated at subsurface for the surface with the surface roughness below a critical value. However, if the surface roughness exceeds the critical value, fatigue life is remarkably reduced and the site of crack initiation moves to the near surface.     

带桩帽桩网加固路堤的模型试验及分析比较

采用三维模型试验,考虑路堤高度、桩帽宽度、桩净间距、工后固结沉降、桩间土压缩模量、水平加筋体等影响因素,对桩网结构加固路堤的沉降变形和荷载传递规律进行系统的研究,得到一些有益的结论,并且将试验的部分结果与理论解析解进行比较,结果发现:对于三维空间土拱,BS 8006法、改进的太沙基法、Hewlett和Randolph法所计算的结果与试验结果较为吻合,并且随着桩帽尺寸的增加,它们之间的吻合程度越来越好。而改进的Guido法和Carlsson法计算的结果与试验结果差异较大。该研究成果可为桩网结构加固路堤设计提供有益的参考。     

Thermal Conductivity of Monazite-Type REPO4 (RE=La, Ce, Nd, Sm, Eu, Gd)

Low-thermal conductivity ceramics in monazite-type REPO₄ (RE=La, Ce, Nd, Sm, Eu, Gd) ceramics are expected to have potential in structural (refractories, thermal insulator) and nuclear applications. To this end, the present study determines their thermal conductivities and examines how differences of the rare earth ions change their thermal conductivity at different temperatures. The results show that their conductivities are remarkably low from 25° to 1000°C. In addition, different conductivity variation mechanisms exist that change gradually upon altering from LaPO₄ to GdPO₄ at low and high temperatures. At relatively lower temperatures (≤400°C), the thermal conductivities of all the REPO₄ ceramics decrease nearly at first, reach a minimum value, and then rise with gradual altering from LaPO₄ to GdPO₄. It may be due to the combined effects of the increase of both the anharmonicities in lattice vibrations and the bond strength. As the temperature increases, the conductivity trends become obscure, and the conductivities of the monazite-type REPO₄ approach their minimum thermal conductivities when the temperature is above 800°C.     

Fabrication of the single-wall carbon nanotube compound polymer film electrode and the simultaneous electrochemical behavior of aminophenol isomers

We describe a simple, rapid and selective voltammetry for simultaneous determination of electroactive isomers using nanometer composite electrode. The electrode was constructed by electropolymerization of 4-aminopyridine at single-wall carbon nanotubes modified glassy carbon electrode (SWNTs/POAPE). The configuration and electrochemical properties of SWNTs/POAPE were characterized by scanning electronic micrographs (SEM) and voltammetry. The SWNTs/POAPE showed an excellent electrocatalytic activity to the oxidation of aminophenol isomers and capability of determining three aminophenol isomers simultaneously. The oxidation peak potential difference between m-aminophenol and o-aminophenol was 416 mV, o-aminophenol and p-aminophenol 119 mV, indicating that the o-, m- and p-aminophenol could be identified entirely at the SWNTs/POAPE. The proposed electrode has been applied to the simultaneous voltammetric determination of aminophenol isomers in mixture without previous chemical or physical separations.     

Optimization of the activity of CaO/Al2O3 catalyst for biodiesel production using response surface methodology

In this work the response surface methodology (RSM) in conjunction with the central composite design (CCD) were used to optimize the activity of CaO/Al₂O₃ solid catalysts for the production of biodiesel. In order to measure the catalyst activity, we used palm oil as a representative raw material for the conversion to biodiesel. The biodiesel production was carried out in a batch laboratory scale reactor. The results showed that both the calcination temperature and the amount of calcium oxide loaded on the support had significant positive effects on the biodiesel yield. The maximum basicity and biodiesel yield obtained were about 194 μmol/g and 94%, respectively. Overall, the catalyst showed high performance at moderate operating conditions and its activity was maintained after two cycles.     

光固化聚氨酯型阴极电泳清漆的研究

以甲基异丁基酮作为起始溶剂,用聚丙二醇扩链IPDI得到聚氨酯预聚体.将三乙醇胺引入聚氨酯预聚体中使其阳离子化,利用含羟基的内烯酸酯类封端为树脂提供光敏基团,合成出漆膜性能优异的光固化聚氨酯型阴极电泳清漆.通过检测电泳漆膜的性能,确定了光固化阳离子聚氨酯树脂中聚醚的相对分子质量、封闭剂的种类和用量、稳定剂的加入、溶剂体系.该电泳清漆可以应用在各种小五金涂装领域,具有环保,固化快速的特点.     

基于滑模控制的 IEEE1588 时钟同步算法研究

针对IEEE1588时钟同步过程中存在时钟频率漂移问题,提出了一种基于滑模控制的新型时钟同步算法。首先根据主从时钟偏差与漂移的递推关系,建立系统状态空间模型;然后运用滑模控制缩小时钟偏差与时钟漂移;最后结合滑动平均滤波对实验过程中的频率抖动和随机误差进行优化。结果表明,基于滑模控制的时钟同步算法可有效抑制时钟漂移引起的时钟偏差线性增长,将时钟偏差控制在1μs以下,从而实现亚微秒级网络对时。相比传统IEEE1588协议同步方法,所提方法提供了更高的同步精度。     

基于VMM的可重用FPGA验证平台

针对FPGA设计中如何高效、充分验证功能的问题,本文介绍了集众多优势一体的VMM验证方法,并通过GFP封装与解封装项目的具体应用,讲解了平台的搭建,并重点分析了其重用性策略。验证结果表明,这种验证方法采用层次化的平台结构,具有随机约束、覆盖率驱动、自动化、可重用性和可维护性等优点,能最大限度的提高验证效率和覆盖率,有效的减少验证工作量和缩短验证时间。