OXIDATION BEHAVIOR OF A HOT ISOSTATICALLY PRESSED SILICON-NITRIDE MATERIAL

The oxidation behaviour of a dense silicon nitride material containing the minimum amount of additives was studied. A silicon nitride powder was hot isostatically pressed in the presence of 0.5 wt% Y2O3 and 0.0 25 Wt% Al2O3. The dense material obtained was oxidized for 24 hours, i n an oxygen atmosphere within the temperature range 1475-1650-degrees- C. The high oxidation resistance of this material may be related to th e low amount of sintering aid initially introduced and consequently to the composition of the grain boundary phase. According to the tempera ture, the apparent activation energies for the oxidation processes, ra nged from 355 to 680 kJ/mole.