Low-Temperature Oxidation of Silicon Nitride by Water in Supercritical Condition

摘要

Oxidation tests carried out in supercritical water (400-500℃) revealed a noticeable corrosion attack on the silicon nitride surface in spite of the low temperatures. Increasing water pressure generally caused an increase in the oxidation phenomena. Oxidation scale evolution depended strictly on the silicon nitride sintering process, sintering aids, porosity and impurities, which influenced oxidation kinetics and surface morphology. In such test conditions the solubility of silica in water seemed to have a great influence on the stability of the oxidation scale, mainly in reaction-bonded silicon nitride samples.