Formation of Oxide Films on ZrB2-15 vol% SiC Composites During Oxidation: Evolution with Time and Temperature

The evolution of convection cells features that form in oxide films on ZrB2-SiC composites are quantified by the number population, size, and distribution in oxide films on ZrB2-15 vol% SiC oxidized at temperatures between 1500 degrees and 1600 degrees C for various oxidation times. The number of convection cells per unit area increases after short exposure times of the oxidation at 1550 degrees C, but then decreases slowly with increasing time. The results indicate that these convection cells are transient, they form and transport boria-silica-zirconia liquid to the surface but with increasing exposure time the increasing amount of flowing viscous SiO2-rich liquid submerges them and they become extinct.