Al2O3／TiB2／SiCW陶瓷刀具加工镍基合金时的磨损机理研究

研究了Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣＷ陶瓷刀具加工Ｉｎｃｏｎｅｌ７１８镍基合金时的切削性能和磨损机理。结果表明；在低速切削条件下，Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣＷ和硬质合金刀具的抗后刀面磨损的能力相差不大；而在高速切削条件下，前者的抗后刀面磨能力远高于后者。     

超高密度磁记录的课题与展望

介绍了超高密度记录的研究开发状况 ,论述了垂直磁记录技术的课题以及采用TMR磁头的、记录密度为Subterabit in2 的记录 读出特性。作为高密度记录所必需的头 盘界面技术 ,提出了接触记录技术的课题 ,还就STM (Scanningtunnelingmicroscopy)存储器论述了未来超高密度技术     

An analysis method for atomistic abrasion simulations featuring rough surfaces and multiple abrasive particles

We present a molecular dynamics (MD) model system to quantitatively study nanoscopic wear of rough surfaces under two-body and three-body contact conditions with multiple abrasive particles. We describe how to generate a surface with a pseudo-random Gaussian topography which is periodically replicable, and we discuss the constraints on the abrasive particles that lead to certain wear conditions. We propose a post-processing scheme which, based on advection velocity, dynamically identifies the atoms in the simulation as either part of a wear particle, the substrate, or the sheared zone in-between. This scheme is then justified from a crystallographic order point of view. We apply a distance-based contact zone identification scheme and outline a clustering algorithm which can associate each contact atom with the abrasive particle causing the respective contact zone. Finally, we show how the knowledge of each atom’s zone affiliation and a time-resolved evaluation of the substrate topography leads to a break-down of the asperity volume reduction into its components: the pit fill-up volume, the individual wear particles, the shear zone, and the sub-surface substrate compression. As an example, we analyze the time and pressure dependence of the wear volume contributions for two-body and three-body wear processes of a rough iron surface with rigid spherical and cubic abrasive particles.     

耐磨抗冲击氧化铝陶瓷异型件的研制

主要研究了高铝快速磨罐、弧形衬板、球磨机磨口、研钵等异型件的配方及注浆成型工艺。试验配制了高铝泥浆用复合稀释荆及复合添加剂，使制品的显微结构均匀，密度得到了显著提高。     

几种工程塑料摩擦磨损性能的分析与比较

对聚甲醛，尼龙1010和聚四氟乙烯三种工程塑料的摩擦磨损性能进行了测试，分析和比较了它们不同截荷及不同对磨时间的摩擦磨损性能。     

Mechanisms of hydrocarbon conversion reactions on heterogeneous catalysts: analogies with organometallic chemistry

Catalysis is central to most industrial processes for chemical manufacturing. As catalytic processes have become more complex and more demanding, selectivity has become the central issue in their design. Selectivity is defined by the relative rates of competing reaction pathways available to crucial intermediates, and can be controlled by subtle changes in the nature of the catalyst, the reactants, and/or the reaction conditions. In order to be able to do this in a systematic manner, a good understanding of the catalytic reaction mechanisms is needed. Here a connection is drawn between the key elementary steps comprising hydrocarbon conversion reactions on surfaces and those known to occur on discrete organometallic complexes. This way, the hydrogenation, dehydrogenation, hydrogenolysis, chain growth, and isomerization reactions typical in heterogeneous catalysis are redefined in terms of hydride elimination, oxidative addition, reductive elimination, migratory insertion, and 1, 2-shift elementary steps, among others. It is suggested that the knowledge already available from organometallic chemistry can be used to further advance the understanding of the surface science involved in heterogeneous catalysis. Thanks to the commonality of the chemistry involved, a better synergy could also be established between homogeneous and heterogeneous catalytic development. These ideas are discussed in this article in a critical and personal way.*Invited contribution to the special volume entitled The Interface between Heterogeneous and Homogeneous Catalysis, stemming from contributions at the recent International Symposium on Relations between Heterogeneous and Homogeneous Catalysis, and dedicated to the memory of Robert L. Burwell.     

A rapid test to measure performance,emission and wear of a diesel engine fueled with palm oil diesel

Results of performance, emission and tribological evaluations of palm oil methyl ester and its blends with conventional diesel in an automobile diesel engine test bed are presented. Polymerization and carbon deposits on the fuel injector were monitored. CO, CO₂, O₂, combustion efficiency and temperature of exhaust gases were also measured. Palm oil methyl ester and its blends have great potential as alternative diesel fuel. Performance and exhaust gas emission for palm oil methyl ester and its blends with conventional diesel are comparable with those of conventional diesel fuel. Palm oil methyl ester does not pose a severe environmental problem and will not deteriorate engine and bearing components.     

Durability of Adhesion Between Metals and Polymers

Adequate adhesion between metals and polymers is primarily the result of chemical bonds in the boundary layer. This region, however, is subject to degradation by moisture. Three modes of deterioration are observed. The first is a largely reversible weakening effect in the polymer layer near the metal oxide surface. The structure of this layer differs from that of the bulk and is influenced by the chemical and physical properties of the surface. The second is a slow transformation of the oxide by hydration and a diffusion of oxide constituents into the polymer. This process is irreversible and is influenced by the state of the surface and chemical properties of the polymer. The third is a fast deterioration of the oxide by primary corrosion usually initiating at an unprotected edge but occasionally arising within the body of a joint.     

Mechanistic aspects of the water–gas shift reaction on alumina-supported noble metal catalysts: In situ DRIFTS and SSITKA-mass spectrometry studies

Steady-state isotopic transient kinetic analysis (SSITKA) experiments coupled with mass spectrometry were performed for the first time to study essential mechanistic aspects of the water–gas shift (WGS) reaction over alumina-supported Pt, Pd, and Rh catalysts. In particular, the concentrations (μmol g⁻¹) of active intermediate species found in the carbon-path from CO to the CO₂ product gas (use of ¹³CO), and in the hydrogen-path from H₂O to the H₂ product gas (use of D₂O) of the reaction mechanism were determined. It was found that by increasing the reaction temperature from 350 to 500 °C the concentration of active species in both the carbon-path and hydrogen-path increased significantly. Based on the large concentration of active species present in the hydrogen-path (OH/H located on the alumina support), the latter being larger than six equivalent monolayers based on the exposed noble metal surface area (θ > 6.0), the small concentration of OH groups along the periphery of metal-support interface, and the significantly smaller concentration (μmol g⁻¹) of active species present in the carbon-path (adsorbed CO on the noble metal and COOH species on the alumina support and/or the metal-support interface), it might be suggested that diffusion of OH/H species on the alumina support towards catalytic sites present in the hydrogen-path of reaction mechanism might be considered as a slow reaction step. The formation of labile OH/H species is the result of dissociative chemisorption of water on the alumina support, where the role of noble metal is to activate the CO chemisorption and likely to promote formate decomposition into CO₂ and H₂ products. It was found that there is a good correlation between the surface concentration and binding energy of CO on the noble metal (Pt, Pd or Rh) with the activity of alumina-supported noble metal towards the WGS reaction.     

Duration of slip-resistant shoe usage and the rate of slipping in limited-service restaurants: results from a prospective and crossover study

Several studies have indicated that slip-resistant shoes may have a positive effect on reducing the risk of slips and falls, a leading cause of injury at work. Few studies, however, have examined how duration of shoe usage affects their slip-resistance properties. This study examined the association between the duration of slip-resistant shoes usage and the self-reported rate of slipping in limited-service restaurant workers. A total of 475 workers from 36 limited-service restaurants in the USA were recruited to participate in a 12-week prospective study of workplace slipping. Of the 475 participants, 83 reported changing to a new pair of shoes at least once during the 12-week follow-up. The results show that slip-resistant shoes worn for less than six months were moderately more effective than those worn for more than six months. Changing to a new pair of shoes among those wearing slip-resistant shoes at baseline was associated with a 55% reduction in the rate of slipping (RR = 0.45, 95% CI = 0.23–0.89). Further research is needed to develop criteria for the replacement of slip-resistant shoes.

Practitioner Summary: The duration of usage impacts the slip-resistance properties of slip-resistant shoes. Slip-resistant shoes worn for less than six months were moderately more effective in reducing slips than slip-resistant shoes worn for more than six months. Shoe use policies should not only encourage or require their use but also include guidance on replacing slip-resistant shoes at regular intervals.