Water lubricated ceramics exhibited excellent tribological properties such as super lubricity and good thermal stability. However, long running-in period and low load-carrying capacity limited the application of water lubricated ceramics. Silica nanoparticles have been shown to be highly effective additives for oil lubrication. And because of their economic efficiency, eco-friendliness and excellent tribological properties, silica nanoparticles are considered to be great potential additives for water-based lubricant, especially for ceramic lubrication. Here, we present an exploratory study on silica nanoparticles as water-based lubricant additives for ceramic lubrication. Different silica nanoparticles were synthesized, characterized and added into water as additives. The tribological properties of silica nanoparticles as water based lubricant additives were tested. The tribological mechanism of silica nanoparticles was analyzed. It was found that silica nanoparticles dispersed well and kept stable in water. Both the running-in period and the stable period were influenced by silica nanoparticles. With the optimal 5 wt. % amino modified silica nanoparticles added into the water lubricant, the running-in time dropped by 97.0% and the average friction coefficient by 86.6% compared with the pure water.

The traditional contact devices measure material's surface roughness by scratching its surface, which may cause surface damage and sampling error. In order to avoid these troubles, an optical measurement system is used in this paper. Considering the anisotropic and inhomogeneous surface structure of Cf/SiC composite, a multi-scale measure system must be established. Fiber bundle is the first scale to be studied, whose appropriate measurement parameters are studied here. When sampling area is 150μm×150μm and sampling step is from 0.1μm to 0.5μm, the values of 3D surface parameters Sa, Sq, Ssk and Sku are steady and their relative changes are small. 2D surface roughness Ra is adopted to select the proper sampling length. The results show that as long as the sampling length is more than 112μm, the mean value of 2D surface roughness Ra are relatively stable. The critical sampling length is about 1/7 of the standard minimum sampling length in ISO 468-1982. According to the results obtained, the research provides a useful guideline for determination on the appropriate sampling conditions of Cf/SiC composite fiber bundle surface measurement.