Tribology of SiC/SiC Ceramic Matrix Composites in Liquid Oxygen in Relation to the Design of Hydrostatic Bearings

This paper reports on the characterisation of ceramic matrix composites (CMCs) for bearing applications in liquid oxygen (LOX). Compatibility tests were performed to determine the safety and feasibility of subsequent research operations. Tribological tests were then made on a pin‐on‐disc apparatus using LOX as the working environment. The measurement of friction and wear allowed a comparison between different kinds of CMCs and 440C steel materials. As a logical progression a real geometry test rig is now being built. The design of a hybrid journal bearing has been finished and the manufacturing of the rig components started.     

Vacuum insulation of the high energy negative ion source for fusion application

Vacuum insulation on a large size negative ion accelerator with multiple extraction apertures and acceleration grids for fusion application was experimentally examined and designed. In the experiment, vacuum insulation characteristics were investigated in the JT-60 negative ion source with >1000 apertures on the grid with the surface area of ～2 m(2). The sustainable voltages varied with a square root of the gap lengths between the grids, and decreased with number of the apertures and with the surface area of the grids. Based on the obtained results, the JT-60SA (super advanced) negative ion source is designed to produce 22 A, 500 keV D(-) ion beams for 100 s.     

Diagnostics for ion beam driven high energy density physics experiments

Intense beams of heavy ions are capable of heating volumetric samples of matter to high energy density. Experiments are performed on the resulting warm dense matter (WDM) at the NDCX-I ion beam accelerator. The 0.3 MeV, 30 mA K(+) beam from NDCX-I heats foil targets by combined longitudinal and transverse neutralized drift compression of the ion beam. Both the compressed and uncompressed parts of the NDCX-I beam heat targets. The exotic state of matter (WDM) in these experiments requires specialized diagnostic techniques. We have developed a target chamber and fielded target diagnostics including a fast multichannel optical pyrometer, optical streak camera, laser Doppler-shift interferometer (Velocity Interferometer System for Any Reflector), beam transmission diagnostics, and high-speed gated cameras. We also present plans and opportunities for diagnostic development and a new target chamber for NDCX-II.     

Micro- and macro-tribological properties of SiC ceramics in sliding contact

Surface properties of single-crystalline and polycrystalline silicon carbide (SiC) specimens were measured using atomic force/friction force microscopy, Auger electron spectroscopy and nano-indentation techniques. Running-in behavior during sliding tests in vacuum was studied on self-mated SiC pairs as a function of surface quality produced by machining. Tribological mechanisms were analyzed in short-time tests using a high-resolution micro-tribometer and then were related to results obtained from macro-tribological tests in humid air and in the presence of distilled water. Information on the structure, chemical composition and properties of SiC surfaces resulting from measurements on the nanoscale can be very useful for explaining tribological performance under far different operating conditions such as in vacuum or air, with contact areas ranging from diameters of a few nanometers to one millimeter and initial applied contact pressure from about 1 MPa to 3 GPa. Friction and wear mechanisms are discussed as functions of surface composition and roughness, vacuum and humidity of air.     

Effect of microstructure on erosive wear behavior of SiC ceramics

Grit blasting wear tests (gas-blast method) have been performed on three SiC structural ceramics by silicon carbide particles using different impingement angles and blasting velocities at room temperature. The three SiC ceramics were sintered with different technologies of pressureless sintering, hot pressing and hot isostatic pressing respectively. The damage to the surfaces that has been observed to occur in the wear of test ceramics is described in detail. The major part of the paper concentrates on the different surface microstructure of test ceramics and the effect of the microstructure on wear.     

The assessment of microscopic charging effects induced by focused electron and ion beam irradiation of dielectrics

Energetic beams of electrons and ions are widely used to probe the microscopic properties of materials. Irradiation with charged beams in scanning electron microscopes (SEM) and focused ion beam (FIB) systems may result in the trapping of charge at irradiation induced or pre-existing defects within the implanted microvolume of the dielectric material. The significant perturbing influence on dielectric materials of both electron and (Ga(+)) ion beam irradiation is assessed using scanning probe microscopy (SPM) techniques. Kelvin Probe Microscopy (KPM) is an advanced SPM technique in which long-range Coulomb forces between a conductive atomic force probe and the silicon dioxide specimen enable the potential at the specimen surface to be characterized with high spatial resolution. KPM reveals characteristic significant localized potentials in both electron and ion implanted dielectrics. The potentials are observed despite charge mitigation strategies including prior coating of the dielectric specimen with a layer of thin grounded conductive material. Both electron- and ion-induced charging effects are influenced by a delicate balance of a number of different dynamic processes including charge-trapping and secondary electron emission. In the case of ion beam induced charging, the additional influence of ion implantation and nonstoichiometric sputtering from compounds is also important. The presence of a localized potential will result in the electromigration of mobile charged defect species within the irradiated volume of the dielectric specimen. This electromigration may result in local modification of the chemical composition of the irradiated dielectric. The implications of charging induced effects must be considered during the microanalysis and processing of dielectric materials using electron and ion beam techniques.     

热等静压氮化硅陶瓷、钴铬15及钼50钢摩擦学研究

介绍了国内外陶瓷材料研究现状及发展趋势。作为耐高温、耐腐蚀等复合摩擦副材料，介绍了热等静压烧结的氮化硅陶瓷、钴铬15及钼50高速合金钢的摩擦学性能。对陶瓷材料的润滑及摩擦化学反应对陶瓷材料摩擦学特性的影响进行了初步探讨。     

Tribology and the liquid-crystalline state

The results of study of the efficiency of nematic-type liquid crystals as additives to lubricants are discussed. Liquid crystals are shown to provide high tribological characteristics of lubricants due to the ordered layers formed on friction surfaces. This results in increased loading capacity, decreased coefficient of friction and wear of the joint, as well as decreased energy losses. Usage of nematic liquid crystals as additives to oils is a new trend in tribology. In 1998 a group of scientists from Belyi Metal-Polymer Research Institute of the Belarus National Academy of Science received a certificate for the discovery of “Property of the Synovial Environment to Provide High Antifriction Behavior of Cartilage by Realization of Mesomorphic Nematic State of Lubricant in the Friction Zone.”     

Measurement of the high energy component of the x-ray spectra in the VENUS electron cyclotron resonance ion source

High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (Versatile ECR for NUclear Science), produce large amounts of x-rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet, adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental setup to measure bremsstrahlung spectra from ECR ion sources is somewhat different from that for the traditional nuclear physics measurements these detectors are generally used for. In particular, the collimation and background shielding can be problematic. In this paper, we will discuss the experimental setup for such a measurement, the energy calibration and background reduction, the shielding of the detector, and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates depending on various ion source parameters, such as confinement fields, minimum B-field, rf power, and heating frequency.     

SiC二极管在高频大功率电流型逆变器中的应用

针对电流型逆变器桥臂并联扩容时开关损耗较大的问题,对SiC肖特基二极管和Si快恢复二极管的正反向恢复特性、MOSFET并联均流特性以及容性状态下电流型逆变器工作过程进行了研究。提出了在电流型逆变器中用SiC肖特基二极管代替Si快恢复二极管以实现保持逆变器良好并联均流效果的同时降低逆变器损耗。分别搭建了基于Si快恢复二极管和SiC肖特基二极管的电流型逆变器实验平台以对比验证SiC肖特基二极管在系统扩容应用中实际效果。研究结果表明,在电流型逆变器中使用SiC肖特基二极管可以极大地降低逆变器损耗同时保持逆变器良好的均流效果,提高逆变器效率。     

离子色谱在能源领域中的应用

离子色谱作为近20年来发展最快的分析技术之一,其应用已经渗透到众多领域。该文简要综述离子色谱在能源生产及研究中的应用,主要包括石油化工、核能和电力、可再生能源研究方面的应用。     

摩擦学研究及发展趋势

简要评述了摩擦学研究的进展.指出极端条件下的摩擦、磨损与润滑性能,分子水平上的摩擦磨损本质,环境友好润滑材料,摩擦学失效问题及摩擦学设计是摩擦学研究的主要方向.     

摩擦学的进展和未来

在过去的20年内,随着纳米技术的飞速发展和人们社会需求的日益增加,摩擦学迅速发展,并随之产生了几个新的领域,比如纳米摩擦、生物摩擦、超滑、表面织构摩擦学、极端工况摩擦学、微动摩擦学等等。在未来的10年,这些领域和其他新出现的概念,比如:绿色摩擦、纳米制造摩擦学、新型超滑材料和新能源领域摩擦学等等,将在摩擦学研究工作中发挥重要的作用。纳米摩擦学包括纳米尺度下的薄膜润滑、纳米摩擦、纳米磨损、表面黏附等等。绿色摩擦学包括环境友好润滑剂、摩擦噪声的减小、没有环境污染的磨损。生物摩擦学包括人类器官中的摩擦学和仿生摩擦学。超滑包含不同类型的润滑剂,比如类金刚石膜、水基润滑剂、一些生物润滑剂,其具有极低的摩擦因数(0.001量级)。纳米制造摩擦学包括纳米结构制造中的摩擦学、纳米精度制造中的摩擦学和跨尺度(微观、中观和宏观)制造中的摩擦学。这些领域需要不同的理论和技术,以适应不同的制造对象和尺度。极端工况摩擦学包括在重载下、在高/低温度下、在高/低速度下和强腐蚀或氧化环境条件下的摩擦学问题。与表面织构相关的摩擦学理论和技术也是当今发展较快的领域。这些领域的新进展和未来10年的新需求将在下文中具体介绍。     

Measurement of ion energy distributions using a combined energy and mass analyzer

A method is described for measuring ion energy distributions using a commercially available, combined energy analyzer/mass spectrometer. The distributions were measured at an electrode located adjacent to pulsed, electron beam-generated plasmas produced in argon. The method uses energy-dependent tuning and was tested for various plasma conditions. The results indicate an improved collection efficiency of low-energy ions when compared to conventional approaches in measuring ion energy distributions.     

浅析止推轴承的摩擦学

从潜油电泵止推轴承的摩擦原理出发,分析了润滑、表面粗糙度、材料选择及表面处理工艺等因素,对止推轴承的影响和失效原因,提出了相应的解决办法.     

Ion mixing at 20 keV: a comparison of the effects of Ga+, Ar+ and CF4+ ion irradiation

Medium-energy (some tens of keV) ion irradiation is frequently used in various technologies. It is well known that during this irradiation serious alterations are introduced to the material, changing its structure, composition, etc. While there are studies on the amorphization, no results have been reported on the medium-energy ion beam-induced mixing, however. In this work, we present Auger electron spectroscopy (AES) depth profiling measurements of Si/Cr multilayer samples, which were irradiated by various ions (Ga+, Ar+, CF4+) of 20 keV applying angles of incidence of 5 degrees (Ga+), 65 degrees (Ga+) and 75 degrees (Ar+, CF4+). The ion beam-induced mixing at the Si/Cr interface (the broadening of the interface) was measured as a function of the removed layer thickness. The weakest and strongest ion mixing (for a given removed layer thickness) were found for CF4+ and Ga+ 5 degrees irradiations, respectively. In the case of Ga+ irradiation, the larger the angle of incidence the weaker the ion mixing. The extent of mixing does not correlate with the corresponding projected range. Comparison of the experimentally measured ion mixed profiles with those given by dynamic TRIM simulations gave poor agreement for Ar+ and fails for Ga+ irradiations, respectively.     

齿轮摩擦学的研究现状与展望

介绍了中国齿轮摩擦学技术的发展概况,论述了齿轮摩擦学的理论研究、润滑剂开发及其应用技术。并对发展我国齿轮摩擦学技术提出几点建议。