Corrosion behavior of silicon oxycarbide-based ceramic nanocomposites under hydrothermal conditions

Abstract

Abstract Silicon oxycarbide-based ceramic nanocomposites (SiOC, SiZrOC and SiHfOC) were prepared by means of hot pressing techniques and their behavior upon hydrothermal corrosion at moderate temperatures (up to 250°C) was investigated. The results indicated linear corrosion behavior for all samples. The corrosion rates of the SiOC ceramic materials were found to be remarkably lower than those of silicon carbide and comparable to values reported for silicon nitride. Furthermore, SiZrOC and SiHfOC were found to show improved resistance with respect to the non-modified SiOC, due to a unique synergistic effect: whereas zirconia/hafnia act as “reinforcing” phases with respect to hydrothermal corrosion (due to their extremely low solubility in water under the testing conditions), the silicon oxycarbide matrix protects the MO2 phase from a corrosion-induced t-MO2 → m-MO2 phase transformation. Consequently, the prepared silicon oxycarbide-based materials exhibit high potential for applications which require high resistance in corrosive media at moderate temperatures.