Physical characterization and arcjet oxidation of hafnium-based ultra high temperature ceramics fabricated by hot pressing and field-assisted sintering

For this study, HfB2-based ultra high temperature ceramic (UHTC) samples were prepared by hot pressing and field-assisted sintering (FAS) with 10-20 vol.% SiC (baseline), 5 vol.% TaSi2, and 5 vol % indium Dense billets were tested for hardness and mechanical strength When compared, the FAS method consistently yielded materials with a grain size 1 5-2 times finer than samples processed via hot pressing In general, room temperature flexural strengths of these materials were found to be lower (similar to 400 MPa) than similar fully dense HfB2-SiC materials, with strengths between 500 and 700 MPa. Oxidation resistance testing of flat-face models was conducted in a simulated re-entry environment, at Q(Cold Wall) similar to 250 W/cm(2) for 5 mm. Samples processed by FAS had reduced oxide thickness and SIC depletion zones compared to the baseline HfB2-20SiC material. In all cases oxide thickness was reduced by similar to 3x and SiC depletion zone thickness was reduced similar to 3x over the baseline. Published by Elsevier Ltd.