Influence of Graphite on Tribological Properties of Hexagonal Boron Nitride Hybrid/Polyimide Composites in Wide Temperature Range

Tribological and mechanical properties of aramid fiber (AF), graphite (Gr), and hexagonal boron nitride (h-BN) hybrid polyimide composites were investigated under room and high temperature. Results show that, Gr in composite reinforced with AF and h-BN can reduce coefficient of friction (COF) and improve antiwear property of composites under room temperature. Gr can accelerate the formation of transfer film under high temperature without sacrificing the wear resistant of composites. Transfer film of composites reinforced with Gr and h-BN simultaneously present more smooth and uniform compared with that of composites reinforced with only AF and h-BN. However, under higher temperature, composite reinforced with pure Gr present higher COFs and wear rates (WRs) compared with composites filled with h-BN and Gr simultaneously. Comprehensively, composite filled with 10% AF, 3% h-BN, and 4% Gr is the optimum composition.

Tribological studies on chemically modified rapeseed oil with CuO and CeO2 nanoparticles

The environmental problems that are being caused by the mineral-based lubricants has prompted for exploring the possibility of using vegetable-based oil as a lubricant and this has become a worldwide trend. In the present study, the tribological behavior of the chemically modified rapeseed oil has been studied by using a four-ball tester. The CuO and CeO2 nanoparticles of size less than 50 nm were added to the chemically modified rapeseed oil ranging from 0.1 to 1 wt%. And the friction and antiwear properties were analyzed as per the ASTM standard D4172. The size of the nanoparticles was calculated qualitatively by using Scherrer equation with the help of X-ray diffraction analysis. Tribological results showed that the chemically modified rapeseed oil has good antiwear and friction-reducing properties than the raw rapeseed oil. The addition of oxide nanoparticles at an optimum concentration in the chemically modified rapeseed oil showed the good friction-reducing property nonetheless not good antiwear property. The surface topography of the worn ball surfaces was also studied by using a scanning electron microscope.