石墨填充PMIA材料摩擦学性能研究

用MM—200型试验机在于摩擦条件下考察了石墨填充聚间苯二甲酰间苯二胺(PMIA)材料的摩擦学特性。结果表明,填充适量石墨能有效地改善PMIA的摩擦磨损性能,而填充2%的石墨可使PMIA材料的摩擦系数从0.38升高到0.42。电子探针微区分析和X光电子能量色散谱分析表明,在PMIA中填充适量石墨时对偶面上形成的连续的、富含碳元素的转移膜是提高摩擦磨损性能的主要原因;当PMIA中石墨含量较少时,不但没有上述效果,反而影响PMIA自身的转移,使材料的摩擦系数增大。     

Friction and wear behaviour of liquid paraffin containing an S-P type additive and amine

Sulphurised olefin (SO) and dibutyl phosphite (DBP) are two popular antiwear and extreme-pressure additives for gear oils. Investigation of the effects of the weight ratio of SO to DBP in liquid paraffin, and the effects of dodecyl amine, on the friction and antiwear properties of oil, were conducted with a four-ball wear tester. The chemical composition of the film, formed was examined using X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and reflecting infrared spectro-scopic (IR) microscopy. The four-ball test results indicate that the weight ratio of SO to DBP affects the friction and wear behaviour of the oil and, with a weight ratio of SO to DBP of 20:1, a stable friction coefficient, and the smallest wear scar, were observed. Wear tests also showed that dodecyl amine improves or reduces the antiwear ability of the oil at certain concentrations. AES profile analyses demonstrate a thick boundary film formed on the rubbed surface with the weight ratio of SO to DBP at 20:1. Both AES and IR results indicate that the addition of dodecyl amine to an S-P type oil results in competitive adsorption, and hinders the reaction of SO and DBP with the steel surfaces.     

On the effects of friction on free volume holes in PTFE

Since the macroscopic properties of materials are relevant to their micro structure, the detection of microscopic defects or their changes in size and concentration is an interesting topic in materials science. The positron annihilation lifetime (PAL) method used here is established as a unique technique that can provide information about the size and concentration of free volume holes directly without significantly intervening in the bulk properties of the specimens. To our knowledge, this is the first time that PAL techniques have been used to study the wear mechanism of macromolecular tribomaterials. Here we present the results of a study in which the correlation between the fretting wear behaviour of polytetrafluorethylene (PTFE) and the changes in its free volume size and concentration in amorphous-crystal interface regions was found to be δω =A.δτ₃, where δω is the wear loss of PTFE under fretting wear conditions, A is a constant, and δτ₃ represents the relative change in the third lifetime components after the friction test. The results indicate that fretting mainly influences the characteristics of atomic-scale free volume holes in the amorphous-crystal region in PTFE, and under high-load fretting wear conditions the ductile polymer PTFE possesses a self-curing function for its defect-free micro volume holes.     

The correlation of wear behaviors and microstructures of graphite-PTFE composites studied by positron annihilation

The correlation between the wear behaviors of graphite-polytetrafluoroethylene (PTFE) composites and their macro-and microscopic structural changes was studied in a wide graphite volume content range of 0 to 50%. It was found that the macroscopic structure of graphite-PTFE composites changes from the state of PTFE-wrap-graphite to the state of detachment between PTFE and graphite powder along with an increase of graphite volume content. The sudden change occurred at the point of graphite volume content of about 40%. In this article the positron annihilation lifetime spectrum was used to detect the properties of microscopic imperfections. The results indicated that the changes of microimperfects of graphite-PTFE composites in size and in concentration are also related to the increase of graphite volume content while the crystallinity of PTFE shows a tendency to increase. The wear behaviors of graphite-PTFE composites corresponded to the physical properties of imperfects in a macro- and microscopic sense and were reflected fairly well by the interfacial properties between crystal and amorphous regions in PTFE. The positron annihilation technique is a useful tool for the study of tribological behaviors of polymers. © 1996 John Wiley & Sons, Inc.     

金属组分对负载型Pd/Al2O3催化剂性能的影响

研究了金属助组分对以Pd为活性组分的Pd/Al2O3催化剂催化性能的影响.结果表明,添加第二金属组分对金属Pd催化剂的性能有明显的改进作用.通过对PdMo/Al2O3催化剂进行裂解馏分油选择性加氢评价分析,证明了金属Mo与Pd发生了电子相互作用,改变了Pd的电子状态,从而改善了裂解馏分油选择性加氢的活性和选择性.     

聚甲醛／聚四氟乙烯共混物的摩擦学性能研究

采用冷压－热烧结工艺研制了一系列不同含量ＰＴＦＥ的ＰＯＭ／ＰＴＦＥ共混物，在往复摩擦磨损试验机上评价了共混物的摩擦磨损性能，并利用ＳＥＭ、ＸＰＳ和ＡＥＳ对其磨损机理进行了研究。结果表明，在共混物中ＰＴＦＥ的成分增加，不仅可以降低ＰＯＭ／ＰＴＦＥ共混物的摩擦系数，还可以增强ＰＯＭ的耐磨性，主要原因是共混物中ＰＯＭ和ＰＴＦＥ皆向对偶转移，形成了富集ＰＴＦＥ的转移膜。同时发现填加１０％～２０％ＰＴＴＥ的共混物具有较好的摩擦磨损性能。     

A study of 2-(n-alkyldithio)-benzoxazoles as novel additives

The syntheses of 2-(n-alkyldithio)-benzoxazoles are described. Their wear and friction performances are examined in liquid paraffin using a four-ball machine. The synthesized products have been found to exhibit appreciable antiwear capability. The effect of additive chain length on wear scar diameter and friction coefficient is investigated under different test conditions. The film formed by the additive during the sliding process was investigated by using X-ray photoelectron spectroscopy. This revised version was published online in August 2006 with corrections to the Cover Date.     

铝热反应的活化增强机制的研究

针对ＳＨＳ铝热还原合成中氧化铝膜可造成反应的活化障碍，研究了氯盐对其活化增强的效果以及作用机理，研究表明，ＮａＣｌ、ＬｉＣｌ、ＭｇＣｌ２、ＣａＣｌ２、ＢａＣｌ２在一加入的条件下，均有不同程度提高铝热基ＳＨＳ反应速度的作用，其增强效果取决于氯化物的热稳定怀，百作用机一为加碳卤化反应导致的化铝膜汽化。     

Preparation and performance of a novel multifunctional plasma electrolytic oxidation composite coating formed on magnesium alloy

Plasma electrolytic oxidation (PEO) in an alkaline phosphate electrolyte was used to produce a novel multifunctional polytetrafluoroethylene (PTFE)-containing oxide composite coatings on AM60B magnesium alloys. The composition and microstructure of the PTFE-containing PEO coatings were analyzed by X-ray photoelectron spectroscope (XPS), X-ray diffraction (XRD), and scanning electron microscope (SEM). The electrochemical corrosion behavior, tribological properties, and wetting properties of the PTFE-containing PEO composite coatings were evaluated using potentiodynamic polarization measurements, a reciprocating ball-on-disk tribometer, and a contact angle meter, respectively. Results show that the PTFE-containing PEO composite coatings exhibited superior corrosion resistance, excellent self-lubricating property, and better hydrophobic property when compared with pure PEO coatings, and will be the attractive advanced materials for a wide range of functional applications.     

The effect of LaF3 nanocluster modified with succinimide on the lubricating performance of liquid paraffin for steel-on-steel system

LaF₃ nanocluster modified with succinimide was prepared. The effect of the modified LaF₃ nanocluster on the lubricating performance of liquid paraffin for steel-on-steel sliding system was investigated on a four-ball machine. The morphology of LaF₃ and its lubricating mechanisms as additive in liquid paraffin were studied by means of transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). It was found that LaF₃ nanocluster modified with succinimide as an additive in liquid paraffin increased the load-carrying capacity and had good antiwear and friction-reduction behaviour. The XPS analysis of the worn steel surfaces indicated that a boundary lubricating film consisting of physically adsorbing film (succinimide) and tribochemically reacting film (lanthanum oxide and ferrous fluoride) was generated during the friction process. This contributed to improving the lubricating performance of liquid paraffin.