Oxidation Behaviors of ZrB₂–SiC Ceramics with Different Porosity

ZrB₂–SiC ceramics have great application potential in thermal protection system of hypersonic aircraft, due to their excellent oxidation resistance and mechanical properties. Porosity is one of the main factors which will obviously affect the oxidation behaviors of ZrB₂–SiC ceramics. Herein, ZrB₂–SiC ceramics with three different porosity are sintered by spark plasma sintering at different temperatures. Then, a series of oxidation tests of the ceramics with different porosity are carried out at different temperatures and with different time. Morphologies and microstructures of the oxidation surface and cross section, as well as the oxide layer thickness and weight change are discussed in detail. Results show that the porosity of ZrB₂–SiC ceramics has great influence on the oxidation behaviors of ceramics. The oxide layer thickness and weight change gradually increase with the increase of oxidation temperature and oxidation time for ZrB₂–SiC ceramics with different porosity. As the porosity of ZrB₂–SiC ceramics decreases, the oxide layer thickness and weight change generally decrease, which shows that the ceramics with lower porosity have stronger oxidation resistance. This work provides a relative systematic analysis of the effects of porosity on the oxidation behaviors of ZrB₂–SiC ceramics.