Kun Wang

Friction and Wear of Hybrid PTFE/Kevlar Fabric Composite Filled with ZnO Nanoparticles Sliding against Steel, Copper, and Aluminum

ZnO nanoparticles were incorporated into phenolic resin and the effect of the ZnO content on tribological properties of hybrid polytetrafluoroethylene (PTFE)/Kevlar fabric/phenolic composite was investigated. Fabric composite filled with 5 wt.% ZnO nanoparticles sliding against steel, copper, or aluminum was investigated in detail. Friction and wear tests showed that fabric composite/steel exhibited lower friction coefficient and wear rate with varied loads and speeds. It is believed that the coherent transfer film and tribochemical reactions involved in fabric composite/steel contributed to the reduced friction coefficient and wear rate of the fabric composite.

Preparation of PTFE Nanosphere with the Assistant of Modified Multi-Walled Carbon Nanotubes

PTFE nanospheres have been obtained with the assistant of different multi-walled carbon nanotubes (MWNTs) by means of a simple preparation method. The results show that the PTFE nanospheres possess the best dispersion stability using the fluorocarbon-modified MWNTs as the assistant. The products are characterized by field-emission scanning electron microscopy and X-ray photoelectron spectroscopy, respectively.

Mechanical Behavior and Microstructure Characteristics of Directionally Solidified TWIP Steel

The mechanical behavior and microstructure characteristics of three high Mn austenitic steels prepared by directional solidification at withdrawal rates of 60, 120, and 240xa0μmxa0s−1 were investigated and compared with common TWIP steel with equiaxed grains. For each steel, the Hollomon analysis, differential C–J analysis, and modified C–J analysis as an alternative method to describe the work-hardening behavior were studied. The directionally solidified samples (DS samples) exhibited higher mechanical properties along the axis, five stages (A, B, C, D, and E) divided on the plot of stain hardening rate vs true strain, and a more stable and uniform deformation feature with larger strain-hardening coefficients when the true strain is over 0.25, in comparison with the common TWIP steel. The modified C–J analysis was found to be the best one for revealing the strain-hardening behavior characterized by several different stages with a definite work-hardening exponent n. In the case of DS samples, the dendrite spacings increase but the morphology becomes simple when decreasing the withdrawal rate. The larger volume fraction of twins and prevalent activation of twin systems, together with the fragmentations of the original grains in a sample solidified at a withdrawal rate of 120xa0μmxa0s−1, lead to the best mechanical behavior in a medium-to-large strain range.