Material removal and surface damage in EDM of Ti3SiC2 ceramic

Material removal and surface damage of Ti₃SiC₂ ceramic during electrical discharge machining (EDM) were investigated. Melting and decomposition were found to be the main material removal mechanisms during the machining process. Material removal rate was enhanced acceleratively with increasing discharge current, i_e, working voltage, u_i, but increased deceleratively with pulse duration, t_e. Microcracks in the surface and loose grains in the subsurface resulted from thermal shock were confirmed, and the surface damage in Ti₃SiC₂ ceramic led to a degradation of both strength and reliability.     

Optimization of anodic oxidation and Cu–Cr oxide catalyst preparation on structured aluminum plates processed by electro discharge machining

This paper describes the optimization of three processes applied in fabrication of a microstructured reactor for complete oxidation of volatile organic compounds. The first process involves the optimization of the electro discharge machining (EDM) method to produce a set of microchannels with a high length to diameter ratio of 100, with a standard deviation from the average diameter below 0.2%, and with a surface roughness not higher than 2.0 μm. To satisfy these criteria, fabrication of microchannels must be carried out with two machining passes in the Al51st alloy. Then, the effect of several parameters on the anodization current efficiency with respect to oxide formation was studied. The best process conditions to get a 30 μm porous alumina layer in a 0.4 M oxalic acid electrolyte, were found to be a temperature of 1 °C, an anodic current density of 5 mA/cm², and 23 h oxidation time. At last, the resulting coatings were impregnated with an aqueous solution of copper dichromate followed by drying and calcination at 450 °C to produce active catalysts. The effect of a copper dichromate concentration, number of impregnation cycles (1 or 2), and different after-treatments on catalytic activity and stability in complete oxidation of n-butane were studied. The catalytic activity of the obtained coatings is superior to that of alumina supported pelletized catalysts even at much lower loadings of active metals.     

Synthesis of polyurethane resins and its improvement on dimensional stability and finishing performances of medium‐ and small‐diameter softwoods

This study analyzed the effects of polyurethane (PU) resin treatments on surface homogeneity, dimensional stability, and finishing performances of medium‐ and small‐diameter softwoods produced in Taiwan. Two‐pack PU resins were prepared by combing short castor oil‐modified alkyd resin serving as a polyol with polymeric 4,4′‐diphenymethane diisocyanate (PMDI) serving as a hardener, by the molar ratio of NCO/OH+COOH of 1.2. Four types of short oil‐modified alkyd resins with different polyhydric alcohols (glycerin and pentaerythritol) and polybasic acids (phthalic anhydride and isophthalic acid) were synthesized. Three kinds of medium‐ and small‐diameter softwoods, including China fir, Taiwanina, and Japanese fir with a diameter of 10–15 cm were obtained from Hui‐Sun Forest Station, Taiwan. The wood coating of nitrocellulose (NC) lacquer including sanding sealer and top clear was used. Results show that the surface hardness, homogeneity, moisture excluding efficiency, and antiswelling efficiency of woods were enhanced by PU resin treatments. Among all the PU resins, the isophthalic acid and pentaerythritol‐containing PU resin (IPA‐P‐MDI) achieved the best improved efficiency on dimensional stability of woods. Results of two types of finishing procedure, i.e. NC lacquer sanding sealer plus top clear and top clear only, applied onto the PU‐treated woods revealed that the hardness, adhesion, and durability of NC lacquer films on the PU‐treated wood were superior to those of untreated one, especially for top clear finishing alone. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

橡胶Mooney—Rivlin模型材料系数对轴向刚度影响分析

在橡胶小变形范围内，采用理论推断的方法，得到在相同硬度下橡胶Mooney—Rivlin模型材料系数由C2／C1决定的关系式。并采用ABAQUS有限元软件分析的方法，结合橡胶轴向刚度常规解，分析了C2／C1不同值对橡胶轴向刚度的影响进行，结果显示其影响呈现一定规律性。     

国内中小皮化企业如何适应激烈的市场竞争

总结了目前国内中、小皮化企业中存在的主要问题 :自主开发能力差 ,造成产品品种单一、配套性差 ;新产品市场推广能力也较差 ,造成即使有好的产品 ,也无法打开市场 ;而普遍存在的制革厂欠款 ,皮化企业自身体制陈旧及国外皮化公司的进一步本土化策略 ,使国内皮化企业面临更严峻的挑战。根据自身多年经营皮化材料的经验 ,提出了切实可行的应对措施     

二次电池电极基板用复合多孔金属材料的研究

介绍了一种复合金属多孔体的制备及其方法，首先以泡沫塑料为芯膜，经过导电化处理使其具有导电性，其次进行电沉积金属铁，再进行电沉积金属镍，经过热处理后可制备出复合金属多孔体。该复合金属多孔体用铁取代金属镍，其抗拉性能优于单质泡沫镍，同时可以降低制造成本，主要用于载体如电池电极。     

中小型液压缸防漏结构工艺

气弹簧后端省去封头，而用缸体直接封口，杜绝了漏气，强化了结构。文章着重介绍了实现这一结构的径向进给封口工具及工艺。     

日产1000t水泥熟料生产线的提产措施

通过对五级旋风筒下料管、回转窑转速、配料方案、物料稳定等四方面进行改进,达到提产目的。     

Hydrogen production from methane in a dielectric barrier discharge using oxide zinc and chromium as catalyst

The hydrogen fuel cell is a promising option as a future energy resource; however, the nature of the gas is such that the conversion process of other fuels to hydrogen on board is necessary. Among the raw fuel resources, methane could be the best candidate as it is plentiful. In this experiment, the possibility of producing hydrogen with less carbon formation from methane by a dielectric barrier discharge (DBD) was investigated. Without the addition of a catalyst, the formation of hydrogen reached between 30% and 35% at methane residence time of 0.22 min and supplied powers in the range of 60-130 W. The hydrogen selectivity increased at higher supplied power, but the process efficiency, defined as a ratio of the produced hydrogen to the supplied power, decreased slightly. In order to boost the hydrogen production with less carbon formation, a mixed oxide catalyst of zinc and chromium was added to the reactor. It was shown that the production of hydrogen was ca. 40% higher than the non-catalytic plasma process.     

小容量机组保护监控一体化

以数字信号处理器(DSP)和复杂可编程逻辑器件(CPLD)为硬件平台,研制了新一代面向中、小型水电站的综合自动化模块.充分发挥MB40智能可编程逻辑控制器(iPLC)及MB100系列保护测控系统的技术优势,将小型水电站的保护装置做成模块插件,融入监控系统,降低了小型水电站自动化设备的成本,为推出真正意义上的面向小型水电站的"五合一"产品打下坚实的基础.