采用光干涉法相对光强原理对点接触中心区进行了润滑膜厚度测量，该方法在垂直方向的分辨率可达O.5nm，水平方向可达1μm，讨论了膜厚与压力，速度和润滑油粘度之刘的关系，观察和分析了流体润滑膜的失效现象。实验结果表明如果接触压力足够小或者润滑油粘度足够高，即使在一个很低的速度下也能清晰地观察到流体动压润滑效应。当压力增至某一定值，在膜厚-速度曲线上可观察到一个转辑点，当速度降到此点以下时，润滑膜厚度将很快减小到几个分子层厚，此时，润滑膜不再具有流体润滑特征，即流体润滑膜失效，失效点会出现在不同的速度和压力下。要使接触区在较高的压力下形成流体膜就必须加更高的速度或使用更大粘魔的润滑油。最后建立了失效点的压力、速度和润滑油粘度之间的关系。

Using friction force microscopy (FFM) under controlled environments, we have systematically investigated the humidity effect on the frictional properties of two important classes of self-assembled monolayers (SAMs), i.e., N-octadecyltrimethoxysilane (OTE,CH3(CH2)17Si(OCH3)3) on SiO2 (OTE/SiO2); and N-alkanethiols on Au (111), together with their respective substrates. Experimental results show that both OTE and alkylthiol SAMs can decrease the friction force between a Si3N4 atomic force microscope (AFM) tip and substrates. The nearly humidity-independent friction of the two kinds of SAMs indicates that these SAMs are ideal lubricants in applications of micro-electro-mechanical systems (MEMS) under different environments. The humidity dependence-as the humidity increases, the friction first increases and then decreases-of the two substrates, SiO2 and Au (111), can be explained by the adsorption of water. The decrease in the friction at high humidity is attributed to the low viscosity in the multilayers of water, while the increase in the friction at low humidity can be explained by the high viscosity between the water monolayer and the surfaces (AFM tip and sample), possibly due to the confinement effects. The effect of modification of the AFM tip with alkanethiol molecules on the humidity dependence of Au (111) friction has also been investigated.

We have studied the behavior of microwear and hardness of a superelastic nickel-titanium alloy using a triboindenter at various temperatures. Wear resistance was found to anomalously decrease with an increase in hardness. The observations are analyzed based on simple contact theory which suggests that the increase of hardness with the temperature is mainly due to an increase in phase transition stress, while the decrease of wear resistance with the temperature is due to an increase of the austenite elastic modulus and a decrease of the amount of phase transition that can be recovered.

A cationic polyelectrolyte was adsorbed on mica from highly concentrated solutions. The friction and surface force behaviors of the adsorbed layers in aqueous media were studied using a new homemade surface force apparatus (SFA). The long-range repulsions produced by the pure cationic polymer at low salt concentration indicate that the chains are in an extended conformation. The addition of anionic surfactant or of salt condenses the cationic polymer chains as evidenced by the much shorter range of the repulsions. These forces are, for both conformations, a combination of steric and double-layer forces. During sliding, the friction forces produced by the adsorbed layers increase monotonically with the load. A strong dependence of these forces on the sliding speed is noticeable for the extended conformations, while the dependence vanishes in the coiled conformations. This study shows the important role of the conformational state of adsorbed polymer chains on their tribological properties.

Friction forces measurements between smooth surfaces across two layers of linear alkanes over five decades of speeds are presented. A maximum friction dissipation is observed at a characteristic speed. This behaviour is described by a new approach: the formation and destruction of molecular bridges between confined alkane layers. These bridges which interdigitate between the layers exhibit a thermally activated resistance to shear. An analytical model involving activation barriers accounts for the overall behaviour of the speed dependence of the forces over four decades. This first simple semi-quantitative description sheds new light on the subtle mechanisms of friction at the nanoscale level and shows how the molecular length influences the tribological properties of the liquid.