Effect of Ti2AlC on Sintering of Ultrahigh-Temperature Ceramics Based on HfB2–HfO2–SiC System

The effectiveness of the application of 15 vol % Ti2AlC MAX phase in reducing the consolidation temperature of ultrahigh–temperature ceramics of the HfB2–HfO2–SiC composition was demonstrated through the utilization of both hot pressing and spark plasma sintering techniques. It was observed that the introduction of Ti2AlC enabled an increase in the relative density of the ceramic material from 74 to ~92% at a hot pressing temperature of 1850°C. This resulted in enhanced oxidation resistance when heated in an air current up to a temperature of 1200°C, with a more than 35-fold reduction in mass gain compared to the unmodified sample. It was observed that the density of the ceramic composites increased with the sintering temperature. It was determined that the materials obtained at the lowest temperatures did not contain the Ti2AlC phase, which was introduced into the initial powder mixture as a result of its thermal destruction and interaction with other components of the system. At temperatures exceeding 1400°C, the formation of a solid solution (Hf,Ti)B2 and a cubic HfB/HfC phase occurs, accompanied by the dissolution of titanium as a consequence of the interaction between HfB2 and the Ti2AlC MAX phase.