Role of hot-pressing temperature on densification and microstructure of ZrB₂–SiC ultrahigh temperature ceramics

This examination is aimed to study the various densification mechanisms in the ZrB₂-SiC system at different sintering temperatures. For such an objective, hot-pressing process was implemented to fabricate three ceramics at sintering temperatures of 1650, 1850, and 2050 °C under 10 MPa for 1 h. According to the results, particle rearrangement and fragmentation were the predominant densification mechanisms at the lowest sintering temperature. Additionally, it was found that the activation of the liquid phase sintering mechanism was advantageous in the particle rearrangement at low temperatures. However, rising the sintering temperature to 1850 °C changed the dominant mechanism to the plastic deformation. Such a phenomenon was accompanied by the creation of many dislocations in both ZrB₂ and SiC grains. Implementing a higher sintering temperature (2050 °C) activated another consolidation mechanism called diffusion. This occurrence, together with the evaporation of the majority of the liquid phase at elevated temperatures, resulted in emerging transgranular fracture mode in the sample.