Fabrication and mechanical properties of C/C-HfC-SiC composites

Many researchers study on reusable spacecraft/hypersonic aircraft for purpose of new aerospace transportation system. These transport aircraft flies at a speed of more than Mach 5. So researchers are considering the use of scramjet engine. Because this engine uses air as an oxidant and liquid hydrogen as a fuel, the combustion gas temperature is more than 2500°C. So the combustor is required lightweight material and super-heat-resistant material. SiC-based ceramics is used as heat-resistant material in the aerospace field. This material maintain the mechanical properties at high temperatures and has a high oxidation resistance. However, heat resistance temperature of this material is about 1600°C. Therefore, SiC-based ceramics can not be used in an environment of scramjet engine combustor. There are measures with a metal structure that is forcibly cooled by the refrigerant of fuel. Because this structure is very heavy and a complex system, it is difficult to a apply. This study uses the hafnium-based super heat-resistant ceramics that is having a melting point more than 2000°C. Purpose is to develop a new technique for forming the ceramics mainly composed from Hafnium Carbide by melt impregnation to inside C/C composite. Hafnium carbide is very high melting point (3950°C) and has oxidation resistance. In addition, material that has been created evaluate by the tissue changes due to cross-sectional observation and the strength test by three-point bending.