Effects of α- And β-Si3N4 as precursors on combustion synthesis of (α + β)-SiAlON composites

Abstract

Preparation of (α + β)-SiAlON composites from the powder compacts of Si, Si3N4, SiO2, Al, and AlN was investigated by self-propagating high-temperature synthesis (SHS) in nitrogen of 2.17 MPa. Test samples adopted not only pure α- and β-Si 3N4, but also a mixture of (α + β)-Si 3N4. The combustion temperature and flame-front propagation velocity decreased with increasing ratio of Si/Si3N 4, but they increased with proportion of α/β-Si 3N4. For the sample containing pure α-Si 3N4, the synthesis reaction yielded only α-SiAlON with various morphologies including equiaxed crystals, elongated grains, and fine whiskers. As a mixture of (α + β)-Si3N4 was employed, the resulting products were (α + β)-SiAlON composites, within which the content of β-SiAlON increased with increasing β-Si3N4. For the sample adopting 100% β-Si 3N4, comparable amounts of α- and β-SiAlON were produced. Additionally, the morphology of (α + β)-SiAlON composites was dominated by elongated grains with a high aspect ratio. © 2011 Elsevier B.V. All rights reserved.