Ceramics Based on Reaction-Bonded Boron Carbide for Heat Protection Coatings of Space Aircraft

The method for activated sintering of reaction-bonded boron carbide by diffusion doping of boron carbide powder particles with amorphous boron was developed. On the basis of X-ray phase analysis, it is shown that under the conditions of activated sintering in the presence of boron the formation of the B12 (B, C, Si)3 phase occurred. According to the results of microstructural studies of the material, it is proved that on the surface of polycrystals there is a diffusion layer saturated with boron and silicon, which surrounds each particle. It is found that the structure of obtained ceramics based on boron carbide by doping with boron and silicon, represents the boron carbide grains penetrated by needle crystals of secondary silicon carbide. It has been experimentally proved that this nature of the structure leads to an increase in the fracture toughness of the material in 2–3 times compared to the existing sintered reaction-bonded boron carbide. This allows us to use the material for creating heat-proof coatings for hypersonic spacecraft.