Polymer-Derived Nano-Sized SiC-Containing ZrB<sub>2</sub> Composites: Densification, Microstructure and Flexural Strength

Abstract

Silicon carbide (SiC)-containing zirconium diboride (ZrB2) composites have become an important class of ultra-high temperature ceramic materials for the thermal protection systems of re-entry hypersonic vehicles with sharp leading edge profiles. Previous studies in ZrB2-SiC composites showed that nano-sized SiC particles-containing ZrB2 composites had a greater strength and a better oxidation resistance compared to ZrB2-beased composites with micron-sized SiC particles. However, it is difficult for obtaining a homogenous microstructural ZrB2-based composite with nano-sized SiC particles because of agglomerates of the SiC particles. In this study, homogenously dispersed nano-sized SiC particles-containing ZrB2 composites were prepared using polymer-derived SiC-dispersed ZrB2 composite powders followed by hot pressing at different temperatures between 1750°C and 1900°C. The microstructure of the resulting composites was characterized by field emission scanning electron microscopy. Four-point flexural strength of the obtained composites was measured at room temperature. The effects of the sintering temperatures and SiC content on the microstructure and the flexural strength of the composites were discussed.