N–O mix optimisation in low energy dense DC glow surface Ti conditioning

Samples of pure titanium have been treated by means a plasma immersed ion implantation (PIII) process in a DC glow discharge in pure oxygen and in different nitrogen-oxygen mixtures. In contrast with conventional voltage supply based glow PIII, the present study has been conducted with a novel specifically designed high current supply which allows a high electron density to be kept constant, regardless of gas pressure variations, within the operational ranks. Thus, the acquired sample characteristics can be more clearly ascribed to the chemical composition of the mixture. One stratified TiO₂ (rutile) and TiN_0.26 layer was identified from XRD and Raman spectroscopy, both of these compounds reputedly being highly biocompatible. The superficial hardness of the samples was improved up to more than five times that of the untreated reference sample, namely, ∼1600 Vickers microhardness (10 g load) thanks to a 2–6 μm deep implanted layer. These optimal results have been obtained from an 80% nitrogen 20% oxygen mixture at 1×10^-2 torr. Furthermore, with this gas proportion, the best roughness finishing of the sample set was accomplished, which can be relevant for biocompatible applications.     

超高分子量聚乙烯—SiC陶瓷摩擦副生物摩擦学特性的研究

用Ｆａｌｅｘ摩擦磨损试验机测定了３７℃下超分子量聚乙烯与ＳｉＣ陶瓷摩擦副分别在干摩擦，水润滑和血浆润滑下的摩擦学性能，且用扫描电镜观察了摩擦副表面形貌。结果表明：滑动初期的摩擦系数以干摩擦下的量大，血浆润滑下的最小，而滑动２ｋｍ后的摩擦数仍以干摩擦下的最大，但以水润滑下的最小；摩损率以水润滑下的最大，血浆润滑下的最小。采用表面轮廓仪对摩擦磨损前后的ＳｉＣ陶瓷表面进行了测试，发现ＳｉＣ陶瓷的磨损甚微     

Effect of adhesive and cohesive strength on the tribological behaviour of non‐reactively sputtered TiC thin films

Titanium carbide (TiC) thin films were deposited on D9 steel substrates at room temperature (RT), 200 °C and 400 °C. A compound TiC target was sputtered to deposit films in a non‐reactive argon atmosphere. As‐deposited films were characterised for structural, chemical and mechanical properties. Nanoindentation and scratch tests were performed to evaluate the cohesive and adhesive strength of the films, respectively. Tribological properties of the films were investigated using a tribometer. An increase in nano‐hardness from 7.2 to 10.5 GPa was observed as deposition temperature was increased. The films deposited at RT and 200 °C showed poor adhesion leading to the inferior tribological performance. In contrast, films deposited at 400 °C showed better adhesion which improved the wear resistance. Tribological behaviour of TiC thin films was correlated with contact deformation modes of coatings. These modes revealed significant role of adhesive and cohesive strength associated with the coatings. Copyright © 2009 John Wiley & Sons, Ltd.     

The effect of the addition of talc on tribological properties of aramid fiber‐reinforced polyimide composites under high vacuum,ultraviolet or atomic oxygen environment

The aramid fibers‐reinforced polyimide composites filled with talc were fabricated by means of a hot press molding technique, and mechanical and tribological behaviors were comparatively investigated. Experimental results showed that the elastic modulus of the composites increased with an increase of the talc, but the impact intensity and loss factor decreased. Besides, the coefficient of friction decreased with the increase of the talc content. To contrast the effects of the ultrahigh vacuum (VC), ultraviolet (UV) or atomic oxygen (AO) on the composites, experiments without irradiation or after UV or AO irradiation were conducted. Scanning electron microscopy and X‐ray photoelectron spectroscopy (XPS) analysis showed that UV or AO irradiation can change the surface structure and chemical composition of the polymer because of the photooxidation and chemical erosion. Copyright © 2012 John Wiley & Sons, Ltd.     

Fe基非晶纳米晶电弧喷涂层的摩擦学性能

采用自动化高速电弧喷涂技术在AZ91镁合金基体上制备了FeCrBSiMnNbW非晶纳米晶涂层.研究了涂层材料在干摩擦条件下的摩擦学性能.采用配备有能谱分析仪（EDAX）的扫描电子显微镜（SEM）和X射线衍射仪（XRD）对涂层的微观组织结构进行了表征.采用显微硬度计和纳米压痕仪对涂层的力学性能进行了分析,摩擦磨损试验在UMT-2型摩擦磨损试验机上进行,并采用三维白光干涉表面形貌仪（Phase Shift MicroWAM-3D）测定磨损量.结果表明：涂层组织均匀、结构致密、氧化物含量低,涂层主要由非晶相和纳米晶相组成;涂层具有较高的硬度和弹性模量;在相同的试验条件下,非晶纳米晶合金涂层的相对耐磨性是传统3Cr13涂层的3倍;磨损机制主要为典型的脆性剥落.     

Influence of the Interfacial Characteristics on the Tribological Behaviour of TiN-Base Films on Iron

The dry sliding behaviour of TiN-base films deposited onto a tool steel by two different physical vapour deposition techniques is discussed on the basis of the characteristics of both coatings and interfacial regions. It is shown that film adhesion is determining for the wear resistance. Other important factors are the film hardness and the intensity of the stress state at the film-substrate interface.     

Hysteresis and elastic interactions of microasperities in dry friction

Velocity independent dry friction of a slider upon a base is due to an hysteretic response of relative displacement to a tangential driving force F. We show that the purely elastic model for multistability considered in a previous publication is in no way essential: multistability arises just as well from adhesion. We emphasize the physical consequences of multistability for dynamic/static, a.c./d.c. friction. When the slider is moved from rest by an amount the transition from the zero force static configuration to dynamic behaviour is progressive, spreading on a range equal to the width of the hysteresis cycle. When is small, an elastic restoring force ensues, in agreement with observations. The competition of that elastic pinning with bulk elasticity generates a screening length which we believe is the natural size of Burridge Knopoff blocks. We then study the effect of elastic interactions between asperities: it is weak for dilute asperities, but its long range makes it important. In lowest order the interaction mediated displacement of a given asperity has logarithmically divergent fluctuations: they become comparable to the asperity radius when the slider size reaches another characteristic “Larkin length”, which for dilute micronic asperities is exponentially large. We give arguments suggesting that individually monostable asperities display collective multistability on scales larger than . For individually multistable sites we show that elastic interactions give rise to cascade processes in which the spinodal jump of a given asperity triggers the jump of others. We estimate the size of these cascades that should show up in the noise spectrum. Received: 3 February 1998 / Accepted: 19 March 1998     

纳米复相陶瓷及其摩擦学研究进展

介绍了纳米复相陶瓷的结构和分类、制备方法和力学性能以及纳米复相陶瓷的强韧化机理,评述了纳米复相陶瓷的摩擦学研究进展,分析了影响纳米复相陶瓷摩擦磨损性能的主要因素,指出当前纳米复相陶瓷摩擦学研究领域存在的问题及有待于研究的课题.     

溶胶—凝胶法陶瓷超薄膜的制备及其摩擦学研究进展

介绍了溶胶—凝胶陶瓷超薄膜制备技术，评述了陶瓷超薄膜性能检测方法以及溶胶—凝胶陶瓷薄膜的摩擦学研究和应用进展．