在原子力/摩擦力显微镜（AFM/FFM）实验中，通常只能得到摩擦力信号的相对值，为了比较各种样品表面的微观摩擦性能，常选用新鲜解理的云母作为摩擦力测量的参考样品。由于新鲜解理云母表面摩擦性能的不稳定性，使得不同条件下在云母表面上测得的摩擦力信号有较大的变化。为此，需要通过对云母表面摩擦性能的系统研究，建立一个以云母为AFM/FFM摩擦力测试参考样品实验规范。实验结果表明，云母样品的摩擦特性受其解理时间的长短湿度以及测试针尖的变化等多种因素的影响。不同针尖在云母表面的摩擦力信号大约在±15%的范围内波动；新针尖在云母表面作摩擦实验时，摩擦力信号随磨损次数的增加逐渐增大，然后趋于稳定。对于新鲜解理的云母表面，其摩擦力信号随解理时间的增长而逐渐增大并逐步趋于稳定。由于云母表面的亲水性，其摩擦力信号随湿度的增大而逐渐减小。

With a nano-indenter and a microhardness testing machine, nano-indentation hardness and microhardness are measured in a wide load range (0.1-19600mN) for five materials. Even fused silica and silicon almost have constant hardness during the load range, the nanoindentation hardness of copper, stainless steel and nickel titanium alloy shows obvious indentation size effect, namely that the hardness decreases with the increase of depth. For the measured materials, the nano-indentation hardness is about 10-30% in magnitude larger than the microhardness. The main reasons can be explained as the analysis of the nano-indentation hardness using the projected contact area at peak load Ac instead of the residual projected area Ar, as well as the purely elastic contact assumption describing the elastic/plastic indentation process. The analysis based on a simple model indicates that Ac is always smaller than Ar, and the more heavily the indent piles up (or sinksin), the larger the difference between the nano-indentation hardness and microhardness.

The fretting behavior of superelastic nickel titanium (NiTi) shape memory alloy was studied at various displacement amplitudes on a serve-hydraulic dynamic test machine. The results showed that the superelastic properties of the material played a key role in the observed excellent fretting behavior of NiTi alloy. Due to the low phase transition stress (only 1/4 the value of its plastic ield stress) and the large recoverable phase transition strain (5%) of NiTi, the friction force of NiTi/GCr15 stainless steel pair is smaller than the value of GCr15/GCr15 pair and at the same time the Rabinowicz wear coefficient of NiTi plate is about 1/9 the value of GCr15 plate under the same fretting conditions. For NiTi/GCr15 pair, even NiTi has a much lower hardness than GCr15, the superelastic NiTi alloy exhibits superior fretting wear property than GCr15 steel. It was found that the weak ploughing was the main wear mechanism of NiTi alloy in the partial slip regime. While in the mixed regime and gross slip regime, the wear of NiTi was mainly caused by the abrasive wear of the GCr15 debris in the three-body wear mode.

In this paper, we present our experimental results on the process of the in situ chemical modification of the silicon nitride atomic force microscopy/frictional force microscopy tip by n-octadecyltrimethoxysilane (OTE)/mica, OTE/SiO2, and SiO2. The modified tips have different friction and adhesion properties against mica reference samples compared to those before modification. The resultant tip modification depends not only on OTE self-assembled monolayer (SAM) but also on the substrates the OTE SAM is prepared on. In the case of OTE/mica, the friction of the modified tip against mica reference is greatly reduced; in the case of OTE/SiO2, the friction of the modified tip against mica reference is greatly increased. It is surprising that bare SiO2 can also chemically modify the Si3N4 tip to increase the friction against mica reference. In the case of OTE modification, it was found that the tips could be cleaned by repetitive friction scans on mica. However, a tip modified by SiO2 cannot be mechanically cleaned. Moreover, it was found that humidity and load could also affect the tip chemical modification. Ourresults are important for interpreting tribological data since the actual contact chemistry was often overlooked in the atomic force microscopy experiments in the past.

Pure organic molecules exhibiting a suitable concave rigid shape are expected to give porous glasses in the solid state. Such a feature opens new opportunities to avoid crystallization and to improve molecular solubility in relation to the high internal energy of these solid phases. To quantitatively explore the latter strategy, a series of rigid tetrahedral conjugated molecules nC and the corresponding models nR have been synthesized. Related to the present purpose, several properties have been investigated using UV absorption, steady-state fluorescence emission, differential scanning calorimetry, 1H NMR translational self-diffusion, magic angle spinning 13C NMR, and multiple-beam interferometry experiments. The present tetrahedral crosses are up to 8 orders of magnitude more soluble than the corresponding model compounds after normalization to the same molecular length. In addition, they give concentrated monomeric solutions that can be used to cover surfaces with homogeneous films whose thickness goes down to the nanometer range. Such attractive features make cross-like molecular architectures promising for many applications.