Significantly enhanced wear resistance of PEEK by simply filling with modified graphitic carbon nitride

Graphitic carbon nitride (g-C3N4) was synthesized and the tribological behaviors of g-C3N4 reinforced polyether-ether-ketone (PEEK) were investigated. It was demonstrated that the addition of as-synthesized g-C3N4 (AS-CN) enhanced dramatically the wear resistance of PEEK, and meanwhile the friction coefficient was increased. Moreover, interlayer hydrogen bonds (H-bonds) of g-C3N4 played an important role in the tribological characteristics of PEEK composites. In comparison to AS-CN, thermal-etched g-C3N4 led to a lower friction coefficient owing to destruction of the H-bonds. On the contrary, hydroxylated g-C3N4 (h-CN) possessed strengthened interlayer H-bonds and a denser stacking structure, and hence further enhanced the wear resistance. Compared to carbon fibers, conventionally employed for developing anti-wear polymer composites, h-CN was identified to be significantly more effective for improving the wear resistance of PEEK, i.e. a very low specific wear rate of 4.0 x10(-7) mm(3)/Nm was achieved by simply filling with 10 vol% h-CN. Characterizations of tribofilms' nanostructures manifested that significant fraction of g-C3N4 transferred onto the counterface and led to generation of a load-carrying tribofilm. It is expected that the output of the present work will pave a route for developing binary and eco-friendly anti-wear materials.