Synthesis and sintering of TiB2 and TiB2–TiC composite under high pressure

TiB2 and TiB2–TiC composite compacts with 98–99% density are prepared by high-pressure sintering (HPS) of premixed powders and by high-pressure self-combustion synthesis (HPCS) from the elemental constituents. The sintering and synthesis experiments are carried out at 3 GPa in the temperature and time ranges 2250–2750 K and 5–300 s, respectively. A high sintering temperature (2750 K) is required to obtain dense monolithic TiB2 compacts (98% density) by HPS. Compacts with a similar density are obtained at lower sintering temperature (2250 K) when 15 mol% TiC is added to TiB2. The composite compacts have marginally better fracture toughness than that of monolithic compacts. TiB2 and TiB2–TiC compacts (99% density) are also prepared by HPCS from elemental constituents. A minimum ignition temperature of 2250 K is required to make the reaction self-sustaining. The compacts prepared by HPCS have superior fracture toughness to those prepared by HPS. The microstructures and the properties of the compacts prepared by HPS and HPCS are compared. A possible sequence of reaction during the HPCS of TiB2–TiC is proposed.