ULTRA HIGH TEMPERATURE CERAMICS FOR HYPERSONIC VEHICLE

Abstract

Ultra High Temperature Ceramics (UHTCs) are advanced ceramic materials capable of withstanding extremely high temperatures and severe thermal environments encountered in hypersonic vehicle applications. This project focuses on the development and analysis of Hafnium Diboride (HfB₂) and Zirconium Diboride (ZrB₂) based ceramic composites reinforced with Silicon Carbide (SiC) for thermal protection systems used in hypersonic and reentry vehicles. Conventional thermal protection materials fail under temperatures exceeding 2000°C, whereas UHTCs possess very high melting points above 3200°C, excellent oxidation resistance, high thermal conductivity, and superior mechanical strength. The project investigates the processing, microstructure, thermal properties, oxidation behavior, and mechanical performance of HfB₂-SiC and ZrB₂-SiC composites prepared using hot pressing techniques at 2000°C and 5000 psi. Different compositions containing 0% to 20% SiC were fabricated and analyzed using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), thermal diffusivity testing, and flexural strength measurements. The experimental results showed that the addition of SiC improved densification, oxidation resistance, and thermal stability of the ceramics. The developed UHTCs achieved high fracture toughness values, excellent thermal conductivity, and flexural strengths up to 500 MPa at elevated temperatures. Thermal diffusivity decreased with increasing temperature and porosity, while SiC additions enhanced oxidation protection through borosilicate layer formation. The project successfully demonstrates that HfB₂-SiC and ZrB₂-SiC composites are promising materials for advanced aerospace thermal protection systems and hypersonic vehicle applications due to their outstanding thermal and mechanical properties.