Spark plasma sinterability and thermal diffusivity of TiN ceramics with graphene additive

The effects of adding graphene nano-platelets (6 wt%) on the microstructure and thermal diffusivity and conductivity of TiN-based ceramics were investigated. Two samples, a monolithic TiN, and a graphene-added TiN ceramics were fabricated using spark plasma sintering technique at 1900 °C for 7 min under 40 MPa. The microstructure of the polished and fractured surfaces of both samples was analyzed by scanning electron microscopy. Adding graphene resulted in a 2% reduction in the relative density, but led to obtaining a fine-grained microstructure. The consumption of graphene nano-additive during the sintering, through the reduction of surface oxide layers of TiN matrix (TiO₂), and consequently, the formation of titanium carbonitride (TiN_0·8C_0.2) were disclosed by X-ray diffraction analysis. The measurement of the thermal diffusivity was done using the laser flash technique. The TiN–6 wt% graphene sample obtained lower thermal conductivity compared to the monolithic TiN, which can be attributed to the smaller grain size of the graphene-added sample.