Hollow and Threadlike Nanostructures of Boron Carbide

An original low-temperature method is proposed for the synthesis of boron carbide from simple materials. It made it possible to obtain a powdered product in the form of hollow and threadlike nanostructures. The boron carbide nanotubes are shorter than bundles of nanotubes. The boron carbide nanostructures are grown from vapor-phase reagents at a high-temperature nanocenter, the enhanced reactivity of which is maintained as a result of the exothermic effect of the reaction.     

Short test procedures for R-2R D/A converters by electrical modeling and application of the ambiguity algorithm

A reduced physical model of the integral non-linearity error in high resolution R-2R D/A converters is obtained by circuit analysis and application of the ambiguity algorithm. Its relationships with the well establisheda priori model based on Rademacher functions is discussed. Experiments, carried out on a sample of commercial 12 bit converters, demonstrate that functional test programs based on this model achieve shorter test times and lower prediction errors than those based on larger models obtained by straight QR factorization.     

Nano-deformation of a Ni-P coating surface after nanoparticle impacts

Chemical mechanical polishing (CMP) has become a primary planarization technique required for the manufacture of a computer hard disk substrate. In CMP, erosive wear, which is regarded as one of the wear mechanisms underlying the interaction between the abrasive particles and polished surfaces, can occur when materials are removed by the surface collision of particles which are carried by a fluid medium. A fundamental understanding of the process in which nanoparticles impact on the surface of the nickel-phosphorous (Ni-P) coating plated on the computer hard disk substrate is important to the control and preventing of surface defects during CMP. In this study, a cylindrical liquid jet containing de-ionized water and SiO₂ nanoparticles impacts obliquely on the surface of Ni-P coating at a speed of 10 m/s. Microscopic examinations of the impacted surface are performed using a high resolution transmission electron microscope, an atomic force microscope, etc. Experimental results indicate that craters and scratches in the surface have taken place after nanoparticle impacts, and crystal grains in nano-scale and an element phosphorus concentration can be found in the sub-surface layer of the impacted surface.     

Improvement of polyacrylate coating by filling modified nano-TiO2

Nano-TiO₂ is modified by a method, by which nano-TiO₂ first reacts with silane coupling agent WD-70 with double bond group which subsequently copolymerizes with methyl methacrylate and butyl acrylate to produce a thin polymer shell on the nanoparticles. The modified nanoparticles have stable organophilicity. They are applied to polyacrylate coating and performances of the coating are measured by different methods. The modification of nano-TiO₂ particles can improve their dispersibility in coating, enhance hardness of coating and reduce water absorption and permeability of polyacrylate coating. The mechanism has been analyzed in this paper.     

Deep SiC etching with RIE

SiC is currently an important topic in power devices. This new technology leads to lower power losses, faster switching, and higher working temperature. The design of SiC power devices requires the integration of edge termination techniques to obtain a high blocking voltage. The mesa structure approach is one well-established method. It could be used alone or in combination with a Junction Termination Extension (JTE). The mesa consists of a structure that removes material around the pn-junction. Due to the strong Si–C bonds, conventional chemical–wet etching solutions are inefficient on SiC, so plasma methods are required to etch SiC.The presented work is based on the use of an RIE reactor with an SF₆/ O₂ plasma. Its geometry structure and parameters were optimized. An etch rate of 0.35 μm/min was obtained without any trenching phenomenon. Trenches deeper than 10 μm deep were realized with a nickel etching mask that shows a high selectivity. AFM analysis revealed an etched surface as smooth as the initial one.     

涂层界面结合强度检测研究(Ⅱ)：涂层结合界面应力检测系统

利用X射线衍射技术(XRD)测试了涂层及其基体材料的应力及其变化规律，建立了一种涂层结合界面应力检测系统，进行界面结合状态的检测研究.利用涂层从基体脱粘前后的界面应力变化量，结合涂层材料的物性参数和涂层-基体系统温度场参数，用涂层残余应力衍射峰来表征涂层与基体的结合强度，创立一种研究检测涂层结合强度理论的实验新方法，适用于各种热障涂层的界面结合强度测量. 关键词： X射线衍射法(XRD) 界面结合强度 涂层 残余应力     

Commercial SiC device processing: Status and requirements with respect to SiC based power devices

SiC power devices have been commercially available since 2001. In the meantime the standard wafer diameter increased from 2″ to 3″ and a lot of processes which are needed for SiC device technology and which have not been standard in Si device fabrication (e.g. rapid thermal annealing of metal layers, stepper lithography for 3″ etc.) have now found a place in the list of common processes. On the other hand there are still processing issues or process steps that are not yet solved satisfactorily or not yet fulfilling the standards set in the production of Si devices. After a short introduction about the application and market of SiC power devices the paper will present a brief status of today’s productive SiC device processing. This part will mainly focus on Schottky diode manufacturing which is currently the only SiC power device produced in significant amounts. In a second part the paper will focus on remaining issues like wafering, availability of defect density monitoring, ohmic contact formation, high quality substrates and epi, oxidation, and post implantation annealing. All topics will be related to the needs resulting from an industrial point of view concerning process stability, influence on device costs, quality and on commercialization. The paper concludes that the major tasks to be attacked are the quality and price of substrates and epitaxial layers. Other technical issues are ranked behind those.     

Synthesis of Fe-based amorphous composite coatings with low purity materials by laser cladding

Amorphous composite coatings Fe₃₈Ni_30−XSi₁₆B₁₄V₂M_X (X = 0, 1, 2) (M contains Al, Ti, Mo, and C) were prepared with low purity of raw materials by laser cladding. X-ray diffraction and transmission electron microscopy results show that the coating have an amorphous structure with a few crystalline phase on it. The amorphous phase is the primary phase. The glass forming ability as well as the microhardness of the Fe-based alloy made from low purity raw materials can be much enhanced by adding small amount of multi-components. However, the elements addition has its optimal quantity. When X is equal to 1, the microstructure of the coating contains 97.93% amorphous phase and 2.07% crystalline phase on it. As a result, the microhardness of the coating reaches maximum. With further increasing of the additions, the amorphous phase in the coating lessens instead of augment and the crystalline phase begins to accumulate, which result in the decrease of the microhardness.     

机床疲劳载荷的统计分析和概率设计

本文对复杂的机床传动系统的动力特性和疲劳载荷进行统计分析，对传动件的疲劳寿命也视为概率分布状态，在探讨载荷与疲劳寿命的分布规律基础上，提出了机床传动件概率设计的理论公式，用这种新的设计方法可以预测传动件的可靠度或疲劳寿命。