Composites: Processing and Fabrication Methodologies of Nonoxide Ceramic Composites. Processing HfB2 Composites for Use in Extreme Environments

HfB2 and ZrB2 composites containing SiC are known to have good thermal shock and configurational stability at elevated temperatures. These are promising ultra-high temperature ceramics (UHTCs) for use on the sharp leading edges of next generation space vehicles. Sharp leading edges on these vehicles will need to: withstand repeated exposures to temperatures > 2200 C in oxidizing environments; have good thermal shock and ablation resistance; and withstand the mechanical stress of launch and reentry. The HfB2/SiC composite is currently undergoing processing improvements in an effort to better the performance of a material that has been studied for approx. 35 years. The potential for HfB2/SiC composites to meet the requirements of hypersonic flight depends on controlling processing techniques. This presentation will focus on understanding processing steps now being undertaken to optimize the material properties of HfB2/SiC composites at NASA Ames Research Center. Correlation between processing techniques and microstructure will be shown. Preliminary oxidation studies will also be discussed.