Spark plasma sinterability of TaC-based composites co-doped with SiC, TiC and graphene

TaC–TiC–SiC composites were successfully fabricated via spark plasma sintering (SPS) method under the conditions of 2000 °C temperature, 8 min dwell time and 35 MPa pressure. The influences of graphene on the microstructure, densification and hardness were studied and the results were compared with those of a graphene-free sample. X-ray diffractometry (XRD) and field emission scanning electron microscopy (FESEM) were employed to investigate the phase evolution and microstructure, respectively. The XRD analysis detected TaC, TiC and SiC as the main phases, related to the initial raw materials, and some new phases such as Ta₄C₃, TaC_0.47, Ti₅Si₃, Ti₃SiC₂, Ti₆C_3.75, TiSi₂ as well as (Ta,Ti,Si)C solid solution. The presence of such phases implied that many chemical reactions happened during the sintering. Thermodynamic calculations were conducted for each reaction and discussed in details. It was revealed that graphene can promote the densification (~3 %) and hardness (~1.2 GPa) and prevent the grain growth of TiC. Also, the solid solution formation may be facilitated in the presence of graphene.