Low temperature synthesis of pure phase TaB2 powders and its oxidation protection modification behaviors for Si-based ceramic coating in dynamic oxidation environments

Abstract To reveal the generation mechanisms of the Ta-Si-O glass ceramics layer in dynamic oxidation environments, a 40 wt% TaB 2 -SiC coating was prepared by liquid phase sintering method. To obtain pure phase TaB 2 powders at lower temperature (1500 °C), excessive B 2 O 3 powders were added in raw materials to eliminate the TaC byproduct phase. The hexagonal pure phase TaB 2 powders own average particle size of about 386 nm. During the TGA dynamic oxidation tests, after the modification of 40 wt% TaB 2 , the initial weight loss temperature of the sample delayed by about 48%, while the weight loss percentage and rate in fastest weight loss zone decreased by about 61% and 53%, respectively. During oxidation, the generated Ta-oxides were peeled and carried away by the formed fluid SiO 2 glass layer to form “Ta-oxides halation” at first, which results the dissolution of Ta-oxides in the SiO 2 glass, thus forming the Ta-Si-O glass ceramics with dendritic structure. With the spread of the SiO 2 glass layer and growth of the Ta-Si-O dendrite, the Ta-Si-O glass ceramics gradually cover on the surface of the SiO 2 glass layer, forming the structure of Ta-Si-O/SiO 2 double glass layer that is capable of sealing and arresting of microcracks.