Study of mechanical property, oxidation property and mechanism of Si3N4/O'-SiAlON composites fabricated by adding different sizes of SiO2

Si3N4/O'-SiAlON composites were developed by adding different sizes of SiO2 particles. The effects of SiO2 particle sizes on microstructure evolution, mechanical property, oxidation resistance property and mechanism of Si3N4/O'-SiAlON composites were studied. The results showed that the bulk density and bending strength firstly increased and then decreased throughout, whereas the oxidation weight gain initially fell and subsequently enhanced, with an increase in SiO2 size. Among these samples, the sample with 2 mu m SiO2 obtained the highest bulk density of 2.86 g/cm(3), the optimum bending strength of 305.38 MPa and the lowest oxidation weight gain of 0.025 mg/cm(2). The weight gain of the sample with 2 mu m SiO2 varied from 0.025 mg/cm(2) to 0.765 mg/cm(2) when the oxidation temperature ranged from 1100 degrees C to 1500 degrees C. The oxidation resistance mechanism of Si3N4/O'-SiAlON composites was associated with the distribution of O'-SiAlON grains.