Phase reactions in a hot pressed TiC/Si powder mixture

This work investigated the possibility of producing dense Ti₃SiC₂ by hot pressing TiC/Si powders. A hot press with graphite heating elements was used for densification and the phase reactions of some hot pressed samples were further evaluated by pressureless heating in a dilatometer. The density and phase composition of the heat treated samples were evaluated using Archimedes principle and by X-ray diffractometry, respectively. Hot pressing resulted in a low Ti₃SiC₂ yield; the main phases were TiC and TiSi₂ regardless of starting powder composition, temperature, holding time or pressure. A second heating without pressure resulted in Ti₃SiC₂ formation, but only in samples initially hot pressed at 1300 °C or lower. At higher hot pressing temperatures, thin oxide layers on particle surfaces were locked into the structure. Acting as diffusion barriers, they prevented the Ti₃SiC₂ forming reaction. In hot pressed samples the density was significantly higher than in samples sintered without pressure.