Oxidation behavior of Si3N4 fibers derived from polycarbosilane

Abstract Si 3 N 4 fibers prepared from polycarbosliane are exposed in dry and wet air respectively from 800 to 1300 °C for up to 1 h. After dry air oxidation, an uniform SiO 2 coating doped with nitrogen is formed on fiber surface. However, the coating obtained in wet air is much thicker with more complex microstructure containing sub-layers of N-doped SiO 2 , near stoichiometric Si 3 N 4 and graphite-like nanoribbons. Activation energy for oxidation in wet and dry air is determined as 108 and 152 kJ mol −1 , respectively. Both of the values are lower than the known Si 3 N 4 materials with E a of 259–485 kJ mol −1 .