The oxidation kinetics of β-sialon ceramics

摘要: Abstract The oxidation behaviour of β-sialons (Si6 − zAlzOzN8 z) with the composition z = 0·5 and 3·8, prepared without an addition 3 6 wt% yttria, has been investigated isothermally during 20 h in a TG unit at temperatures between 1200 1450 C. A comparison is also given from two Si3N4 powders different amounts impurities; finally single-phase 1,2·5 3·8 compared that Si3N4. Only few obtained curves followed parabolic rate law entire experiment. Most could, however, be interpreted modified law. ( δw 0 )=a arctan(bt) 1 2 +c(t) +d either exhaustively or combination constants activation energies for process could determined were found to increase increasing amount intergranular phase impurities. lower yttria than ‘pure’ Si3N4, but energy was about same. kinetics materials not conclusively determined, evolution microstructure oxide scale showed its crystallization had important influence on rate.