Study on mechanical and tribological behaviors of GQDs @ Si3N4 composite ceramics

Aiming to improve the mechanical and tribological performance of silicon nitride ceramic, one biomass material - nanoscale lignin as precursor was added into silicon nitride matrix. Through pyrolysis and hot pressing sintering, an overlayer (composed of the derivatives of nanoscale lignin - graphene quantum dots) was formed around the silicon nitride grains with a doping amount of 2 wt. %. The special core-shell microstructure refined the ceramic grains, and improved the mechanical properties of the composite by hindering the crack propagation and absorbing the fracture energy. When the composite with doping amount of 2 wt. % lignin slid against GH4169 in air, a lower friction coefficient of 0.22 and a lower pin wear rate of 1.74 x 10(-6) mm(3)/(N center dot m) were fulfilled, which was attributed to the formation of surface layer containing GQDs and tribochemical products SiO2. In this study, a high performance green ceramic composite was prepared, and the composite possessed a very good application potential in industry such as cutting tools.