Tribocatalytic oxidation of ethylene in the rubbing of palladium against aluminum oxide

Friction experiments of palladium rubbed against aluminum oxide in ethylene/oxygen mixed atmosphere have been carried out. The complete oxidation of ethylene to carbon dioxide and water at room temperature was demonstrated. The evolution of carbon dioxide was initiated just after the start of friction; momentarily the pressure reached its equilibrium whereas water was produced gradually. On the other hand, by heating the palladium wire in the same partial pressure of both gases, carbon monoxide and hydrogen were generated at 600 K and above. By increasing oxygen partial pressure, carbon dioxide and water were produced. These results indicate that the ethylene oxidation activity on palladium catalyst is enhanced by the friction of catalyst. Two kinds of reactions, fast and slow, are attributed to near-contact and out-of-contact activities of friction surfaces. The near-contact reaction is governed by tribo-electron emission, whereas the out-of-contact activity is due to the generated nascent surface.     

Tribological Behaviors of 52100 Steel in Carbon Dioxide Atmosphere

The tribological behavior of 52100 steel in a carbon dioxide (CO₂) atmosphere was investigated using a reciprocating ball-on-disk tribometer. X-ray photoelectron spectroscopy (XPS) was used to identify the adsorbed surface layers and tribochemical products. We found that CO₂can substantially reduce friction and wear of the steel. Adsorbed and reacted surface layers containing iron carbonate and/or bicarbonate play an important role in reducing friction. A disk, exposed once to CO₂atmosphere, also shows a low friction for a long time even in a vacuum environment. An optimum CO₂pressure exists for effectively reducing friction and wear. A low-pressure CO₂atmosphere is insufficient to produce iron carbonate. In contrast, high pressure engenders serious chemical wear.     

库仑法测定催化裂化催化剂中的微量碳

采用库仑法全自动碳氢元素分析仪,建立了一种催化裂化催化剂中微量碳含量的分析方法。样品经高温燃烧,碳生成二氧化碳,二氧化碳再与氢氧化锂反应生成相应的水,将水送入涂有五氧化二磷的电解池电解,测量电解所消耗的电量,依照法拉第电解定律计算出样品中的碳含量。实验证明,该分析方法重复性好,准确度高,检测限低,能够满足催化装置上的催化剂分析需要,对实际生产具有指导意义。     

The Tribological Properties of Low-friction Hydrogenated Diamond-like Carbon Measured in Ultrahigh Vacuum

In this paper, we investigate the sliding friction and wear behavior of a hydrogenated diamond-like carbon (DLC) film in ultrahigh vacuum (UHV) and under partial pressures of water vapor, oxygen, nitrogen and hydrogen. The initial friction coefficient of the film in UHV was ~0.15, but decreased steadily to values as low as 0.03 after about 30 sliding passes. During longer duration tests, the friction coefficient increased again to values as high as ~0.15 and such an increase in friction coincided with hydrogen desorption from the contacting surfaces (as detected by a mass spectrometer). Heating DLC to temperatures higher than 360 K also caused desorption of hydrogen and a resulting marked increase in friction. The presence of molecular nitrogen, oxygen and hydrogen in the test chamber did not have any noticeable effect on friction, but the presence of thermally dissociated or ionized hydrogen within the close proximity of sliding surfaces had a beneficial effect by restoring the low friction behavior of the DLC films. The introduction of water vapor into test chamber had an adverse effect on friction. The results of this study confirm that hydrogen is key to low friction behavior of hydrogenated DLC films and that the presence of water molecules has an adverse effect on their friction behavior.     

采用富集方法提高气敏元件对甲醛的响应

用纳米SnO_2制作了旁热式甲醛气敏元件,测试了气敏元件对甲醛的响应,为了提高气敏元件对低浓度甲醛的响应,组装了一套富集装置.甲醛气体通过测试腔之前,先通过富集腔对其浓缩富集一段时间,然后加热活性炭使甲醛解吸出来,送入测试腔进行测试.测试了活性炭的最佳解吸温度为160 ℃.比较了富集前后气敏元件对甲醛的响应,富集前后气敏元件对20 ppm(1 ppm=10-6)甲醛的响应为分别为1.2和13.6.结果表明:富集后气敏元件对甲醛的响应明显提高.     

类富勒烯碳薄膜的结构演变及摩擦学性能研究

通过等离子体增强化学气相沉积技术,以不同沉积时间在硅表面上制备类富勒烯碳薄膜,探究类富勒烯碳薄膜结构演变和摩擦学性能随沉积时间变化规律。利用拉曼光谱和透射电子显微镜,考察类富勒烯碳薄膜微结构和表面形貌随沉积时间的变化。结果表明:碳薄膜内类富勒烯结构含量随沉积时间先增加后保持不变;采用沉积时间为3 h的类富勒烯碳薄膜组成摩擦配伍对,当载荷从8 N增加到14 N时,摩擦因数从0.013降至0.006,即随载荷的增加实现了由低摩擦向超滑的转变。这是因为摩擦诱使类富勒烯碳薄膜发生结构转变,并形成有利于减少摩擦的类球状或外部石墨壳层闭合的纳米颗粒。     

Effect of lubricant bonding fraction at the head–disk interface

Tribochemical studies of the effect of lubricant bonding on the tribology of the head–disk interface (HDI) were conducted using hydrogenated (CHx) carbon disk samples coated with perfluoropolyether ZDOL lubricant. The studies involved drag tests with uncoated and carbon-coated Al₂O₃–TiC sliders and also thermal desorption experiments in an ultrahigh vacuum (UHV) tribochamber. The friction and catalytic decomposition mechanisms as well as the thermal behavior of ZDOL are described. We observed that a larger mobile lubricant portion significantly enhances the wear durability of the HDI by providing a reservoir to constantly replenish the lubricant displaced in the wear track during drag tests. In the thermal desorption tests we observed two distinct temperatures of desorption. The mobile ZDOL layer is desorbed at the lower thermal desorption temperature and the residual bonded ZDOL layer is desorbed at the higher thermal desorption temperature.     

Tribological Properties of PTFE and PTFE Composites at Different Temperatures

The friction and wear properties of polytetrafluoroethylene (PTFE) and its composites with fillers such as bronze, glass fiber, carbon fiber, carbon, graphite, and polymer were studied at ambient temperature and high temperature. The wear resistance and hardness were enhanced by the fillers. Results showed that the wear resistance of all composites was much higher than that of pure PTFE. Pure PTFE has the lowest friction coefficient at ambient temperature (temperature: 23 ± 2°C, humidity: 50 ± 10%) but highest friction coefficient at high temperature (above 100°C). The PTFE composite filled with bronze showed the best wear resistance at ambient temperature but the poorest wear resistance at high temperature. The carbon-graphite- or polymer-filled PTFE composite showed a lower friction coefficient and moderate wear resistance at both ambient and high temperature.     

以超临界二氧化碳为介质的径向箔片轴承静特性分析

以超临界二氧化碳(S-CO2)布雷顿循环所用压缩机中的径向箔片气体轴承为研究对象,考虑S-CO2在近临界区的实际物性,运用有限差分法数值求解变密度变黏度湍流雷诺方程,耦合弹性箔片变形方程,计算以S-CO2为润滑介质的径向气体轴承的气膜压力分布规律,并分析近临界区S-CO2物性变化对轴承承载力、摩擦力矩的影响.计算结果表...     

碳纤维含量对摩擦材料性能的影响

用D-MS摩擦试验机研究了摩擦材料中碳纤维含量对其摩擦磨损性能的影响。结果表明，碳纤维含量对摩擦材料的摩擦磨损性能影响显著，其摩擦系数和磨损率都随碳纤维含量的增加而减小，推荐碳纤维的含量≤5％。SEM分析表明，其摩擦磨损机理亦与碳纤维含量密切相关。     

A study on mechanical and tribological properties of silicone rubber reinforced with white carbon black

This paper analysed the effect of different white carbon black (fumed silica and precipitated silica) on the mechanics and friction property of silicone rubber. The tensile strength, tearing strength, elongation rate and shore hardness of silicone rubber reinforced with different kinds or dosages of white carbon black were investigated in detail. The wear morphology, worn surface analysis and chemical compositions of the rubber sample after the friction test were analysed by means of scanning electron microscopy, three-dimensional profile metre and energy dispersive spectrometer, respectively. Results showed that the mechanics properties of silicone rubber were obviously enhanced with the increase in white carbon black content. Moreover, after the friction test, the vulcanised rubber reinforced with fumed silica has less wear surface protrusions and grinding than that of precipitated silica. The wear rubber filled with fumed silica surface is quite smooth and shows few furrows and grooves, which well corresponds to good anti-wear ability of the reinforcing fillers. In the course of practical application, it is necessary to take into account of the mechanical properties, wear resistance of rubber and the adding amount of filler to achieve the optimum coordination for the best mechanical and friction properties of silicone rubber.     

以高压CO2为介质的推力箔片轴承静特性分析

针对超临界二氧化碳布雷顿循环用压缩机中的推力箔片轴承开展了数值研究,通过MATLAB编程数值计算求解变密度、变黏度湍流雷诺方程和耦合弹性箔片变形方程,得到楔形间隙内气膜压力分布及推力箔片轴承承载力和摩擦功耗,并与空气润滑介质对比;进一步分析推力箔片轴承节距比、瓦张角、楔形高度及最小气膜厚度对轴承承载力和摩擦功耗的影响。计算结果表明:高压CO₂下弹性箔片变形比常压空气时更大,轴承承载力远高于常压空气轴承;瓦张角为45°和节距比为0.5的推力箔片轴承具有较高的承载力和较低的摩擦功耗;楔形高度设计过大会降低承载力,增大摩擦功耗,使载荷集中在水平区域;增大最小气膜厚度设计值虽能减小摩擦功耗,但却引起承载力的显著降低。     

含碳量对车轮材料磨损影响的试验研究

为研究车轮剥离失效的影响因素，为车轮的选材提供依据，通过选择儿种不同含碳量的钢材，研究了含碳量对磨损及剥离的影响。研究结果表明：含碳量的改变，对材料的摩擦因数基本没有影响，但可以改变材料的磨损机制；材料的抗磨损能力随含碳量增加而迅速增大。     

Friction and Wear of Metals in Gases Up to 600 C

Apparatus is described for measuring friction and wear in controlled atmospheres. A comparison is made of the room temperature behavior of copper, mild steel and brass, rubbed against a hardened tool steel, in four environments—vacuum (10^?3 mm Hg), dry helium, dry carbon dioxide, and dry air. The effect of varying the water vapor content in air is also discussed.

The initial selection of rubbing pairs for service at elevated temperatures is gaseous environments under unlubricated conditions, is based on their long-term resistance to corrosion and their ability to give low wear rates. In general, therefore, the materials must be hard. Several alloys having chromium contents of between 1% and 30%, and hardness values in the range 200–1000 vpn have been investigated. These included two low-chromium nitrided steels, a tungsten-chromium tool steel and a series of four Co-Cr-W alloys. Specific wear rates and friction coefficients varied markedly with temperature, and values in the ranges 10^?13–10^?8 cm³/cm kg and 0.1–0.8, respectively, were obtained in both dry carbon dioxide and dry helium. Lowest wear rates were observed with the nitrided steels. The diverse characteristics observed are discussed on the basis of current theories of adhesive wear.     

水润滑硅基非氧化陶瓷摩擦学性能及其表面改性研究进展

综述了水润滑条件下硅基非氧化物陶瓷(Si3N4和SiC)摩擦学性能的研究状况,包括水润滑条件下其摩擦磨损特性以及其表面改性技术对其摩擦学性能的影响.硅基非氧化物陶瓷在水中显示出较低的摩擦因数以及良好的抗磨损能力;表面改性技术能有效地改善硅基非氧化陶瓷的水润滑摩擦磨损性能,离子注入技术是表面改性技术的一个重要发展趋势.     

石墨干膜润滑剂在碳钢表面摩擦磨损性能试验研究*

传统油或脂润滑剂在极端工况环境下无法满足碳钢类零件的减摩要求,采用干膜润滑剂是提高极端工况环境下碳钢表面摩擦磨损性能的可行性方法。采用超声波分散方法制备以石墨粉末为基体的干膜润滑剂,使用压力喷涂技术使其沉积在碳钢试件表面,在端面摩擦试验仪中开展干摩擦和石墨干膜润滑剂润滑下摩擦磨损性能对比性试验研究。试验结果表明：石墨干膜润滑剂在碳钢表面的沉积效果较好,沉积的石墨干膜润滑剂具有较好的润滑性能,可以有效地保护碳钢表面不被过度磨损;喷涂石墨干膜润滑剂的碳钢试件的工作寿命随着压力载荷和主轴转速的增大而缩短,负载和滑动速度的联合作用会加速涂层向稳定方向的过渡;磨损过程中形成的微观润滑剂颗粒会形成颗粒流润滑,适当添加石墨颗粒粉末可能会延长润滑剂正常发挥减摩作用的时间。制备的石墨干膜润滑剂为碳钢在极端工况环境下的减摩提供了支持。     

Effect of polar groups in lubricants on sliding speed dependent friction coefficients of DLC coatings

The speed dependent friction coefficients of two types of DLC coatings, a-C:H and ta-C, were evaluated when lubricated with 1-hexadecene, which did not contain any functional group, and with oleic acid and oleyl alcohol that did. The friction coefficient measured for ta-C at a low sliding speed of 0·01 mm s^?1 with the 1-hexadecene lubricant that did not contain any functional group was 0·22, which was higher than the value of 0·11 seen for a-C:H. The friction coefficients measured for a-C:H and ta-C at a high sliding speed of 50 mm s^?1 with 1-hexadecene were 0·10 and 0·06 respectively. The friction coefficients measured with oleic acid and oleyl alcohol were 0·02 for a-C:H and less than 0·001 for ta-C. The results showed that the friction coefficient of ta-C was more strongly influenced by the functional group in the lubricants than that of a-C:H. It is assumed that this difference between the two coatings can be attributed to a difference in the capability to form a tribochemical reacted film under boundary lubrication. Under mixed lubrication, differences in lubricity also affected this friction coefficient difference, in addition to the properties of the tribochemical reacted film.     

Effect of Water Adsorption on Microtribological Properties of Hydrogenated Diamond-Like Carbon Films

Microtribological properties of diamond-like carbon (DLC) films in the presence of water molecule have been studied. The amount of water adsorbed on DLC films was measured by the quartz crystal microbalance (QCM), while microtribological properties of the film were evaluated by an environment-controlled microtribometer. The hydrogenated-DLC showed an advancing water contact angle of 97°, indicating a relatively hydrophobic surface. No hysteresis in adsorption and desorption isotherms were observed. This suggests an absence of micropores at the DLC surface. The greatest adhesion and friction forces between a W-tip and DLC films deposited onto QCM were observed at a water coverage of 2-3 monolayers, which corresponds to a relative humidity of 70-80%. This abrupt increase in adhesion was explained by the generation of a meniscus from the condensed water between tip and DLC surface. The atomically flat DLC surface showed maximum adhesion and friction forces at lower humidity than those of DLC on OCM, implying the importance of surface texturing, which reduces the effect of water condensation.     

Comparative studies of perfluorinated lubricants adsorbed on hydrogenated amorphous carbon and amorphous carbon nitride

Temperature-programmed desorption and scanning force microscopy have been used to probe the interaction of a perfluorinated lubricant (Fomblin ZDOL) with hydrogenated amorphous carbon (a:C-H _x ) and amorphous carbon nitride (a:C-N _x ) substrates, two materials used as hard coatings in disk drive products. Temperature-programmed desorption measurements indicate that the nitride surfaces are more reactive toward this perfluorinated lubricant and, as a result, the thin lubricant film is more tightly bound to this substrate. Frictional force microscopy has been used to measure the coefficient of friction of the lubricated surfaces, 0.18 ± 0.02 for both substrate materials, and finds that frictional properties of these interfaces in the low load regime are influenced more by the presence of the lubricant rather than the adsorbed state of the film. Likewise, similar disjoining pressures were measured for the lubricant adsorbed on the different coating materials and suggest that the ultrathin nature of the adsorbed lubricant film dominates this property rather than adsorption states.     

碳纤维含量对铜-石墨电刷摩擦因数的影响

为进一步改善铜-石墨复合材料电刷的导电和耐磨性,提高其使用寿命,研究了在通电条件下,碳纤维含量对铜-石墨电刷摩擦因数的影响。结果表明,随碳纤维含量的增加,电刷摩擦因数降低,但碳纤维含量超过5%以后,摩擦因数呈增大趋势;即摩擦因数随碳纤维含量的增加存在极小值。