The Effect of SiO₂ Additives on Sintering Ca-α-SiAlON Powder Prepared by Combustion Synthesis

Abstract

Composite of Ca-α-SiAlON and β-SiAlON was obtained by hot pressing of mixture of commercially available Ca-α-SiAlON and SiO₂ powders under 40 MPa at 1800°C for 2hours. The Ca-α-SiAlON powder used in this study was manufactured with combustion synthesis technique. Effect of SiO₂ additive on the mechanical properties of the SiAlON composite was investigated by changing the amount of the additives; 1, 3, 5 and 7 wt%. The highest strength, 736 MPa for the 4 points bending strength, was obtained in the SiAlON composite sintered with the addition of 5 wt% SiO₂ powder. From the results of XRD, SEM, and EPMA analysis, we found the formation of columnar β-SiAlON grains facilitated by the addition of SiO₂ powder led to the high strength.