Microstructure and properties of HfC and TaC-based ceramics obtained by ultrafine powder

HfC and TaC-based ceramics were hot pressed at 1900°C for 5-20 min starting from synthesized ultrafine powders. The addition of 5 vol.% of MoSi2 improved the densification, which increased from around 85-90% for the pure matrices to 95% for the composites. The flexural strength was measured at room temperature and at 1500°C under protective atmosphere. The added value of this work consists in the utilization of cheap synthesized powders for the realization of the composites with properties comparable to those obtained using more expensive commercial powders. The effect of the nanometric size of the starting powder showed to have the potential to improve the densification behavior and the mechanical properties, however it is necessary a further optimization of the synthesis condition in order to avoid the formation of agglomerates of unreacted powder