Experimental studies on the relationships between the electron work function (EWF), adhesion and friction for 3d transition metals were reported. EWF was measured using a scanning Kelvin probe. Adhesion and friction under light loads between a silicon nitride tip and sample surfaces were evaluated employing an atomic force microscope (AFM) that may also function as a lateral force microscope (LFM). Friction of the samples under a sharp tip at higher load levels was also measured using a microtribometer. It was demonstrated that there was strong correlation between the EWF, adhesion and friction. Higher EWF corresponded to lower adhesive force and thus to lower friction when measured under light loads using the AFM/LFM. Such a correlation stems from the fact that the measured adhesion and friction are largely attributed to the intrinsic interaction between the sample and AFM/LFM tip, which is governed by the electronic behavior reflected by the EWF. However, such a correlation became weaker when the friction was evaluated under a sharp tip at higher load levels. In this case, the friction behavior of a target metal was mainly determined by its mechanical behavior.

Properties of a crystal are generally anisotropic, which makes different crystallographic planes behave differently. By choosing a suitable crystallographic plane or textured polycrystalline surface, one may obtain optimum mechanical and tribological properties, e.g., the maximum strength and desired friction coefficient. Up to date, we have had sufficient knowledge about the relationship between mechanical properties and the crystallographic orientation for different crystal systems. However, when the contact force is decreased to nano/micro-Newton level, will the crystallographic faces of a crystal keep their order in strength and other properties? This article reports our recent studies on this issue using copper as a sample material and demonstrates that there are transitions in hardness and friction coefficient between different crystallographic planes of Cu. It has been demonstrated that the closely packed plane (111) is harder and has a smaller friction coefficient than the (001) plane; however, the situation is reversed when the load is reduced to nano/micro-Newton level that only results in distortion of a few atomic layers. Such changes are of particular importance to the application of crystalline materials in nanomachines or nanodevices.

Alloying yttrium to Co-based alloys has been proven to considerably improve their oxide scales that play an important role in resisting wear at elevated temperatures. In addition to the formation of Y 2 O 3 phase in the oxide scale, the yttrium addition may also change the oxidation mechanism, which could be responsible for many benefits of yttrium to the wear resistance of this alloy at elevated temperatures. In this study, the effect of yttrium on the oxidation behavior of Stellite 21 alloy was investigated and correlated to the changes in microstructure and improvement in properties of the oxide scale formed at 600°C which in turn improved high-temperature wear behavior.

It was recently noticed that in vitro motility assays, driven by random distributed dynein c, microtubules could form self-organized circular patterns, which could be of importance to the design of nanobiomechanical machines. In order to determine key parameters that control the self-organized movement of microtubules, a phenomenological modeling study taking account of the microtubule joining probability distribution and microtubule bias was conducted to investigate the self-organization of microtubules driven by dynein motors.

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