ABSTRACT
A method for preparation of nano ZrOz in liquid medium and for simultaneous mixing of the resultant nano Zr02 with powder of polytetrafluoroethylene (PTFE) was established. The tribological behavior of nano Zr02-PTFE composites was investigated under dry friction. It was found that at lower filler content, the optimal filler content for minimum wear rate of nano Zr02-PTFE changed with the particle size. The larger the filler size, the higher the optimal filler content. However, at higher filler content, the critical filler content was almost a constant and had no relation with the particle size. Combined the tribological behavior with the microstructural characteristics of the composites, a percolation model was proposed to explain the experimental results. It was concluded primarily that the wear behavior of the composites could be mathematically treated as a special percolation phenomenon. The critical content of the nano particles with different size in matrix for the lowest wear rate could be correlated with the composite system's percolation threshold, where the critical matrix ligament thickness was about 1 1.64 nm, and the critical volume fraction at percolation threshold 0.2 1.
