Ultrahigh temperature ceramic HfB2-SiC coating by liquid phase sintering method to protect carbon materials from oxidation

Abstract To investigate the anti-oxidation modification behaviors and mechanisms of the pure HfB 2 phase in dynamic aerobic environment, HfB 2 -SiC coating was prepared through liquid phase sintering method. The average particle size of the synthetic pure phase HfB 2 powders is about 335 nm. The TG curve of pure HfB 2 powders exhibits excellent anti-oxidation modification ability for Si-based coating. After the modification of HfB 2 phase, the anti-oxidation ability of SiC coating achieved prominent improvement. The initiative mass loss temperature of SiC coating lagged by 41.8%, while the percentage of mass loss and rate in fastest mass-loss zone of the SiC coating lagged by 57.6% and 33.3%, respectively. The generated B 2 O 3 is responsible for the obviously improved oxidation resistance below 1200 °C. It compensates the oxidation protection weaknesses of the Si-based ceramic coating in this temperature region. With the fluid of the SiO 2 glass layer, the dispersed Hf-oxides were inlaid in it to form the compound Hf- O -Si glass layer. The Hf-oxides heterogeneous phases with ultra-high melting temperature are able to improve the stability of the SiO 2 glass layer at ultra-high temperature. It improves the ability of microcracks restriction and reduces the erosion of oxygen to the carbon matrix.