| Abstract | O'-sialon (x = 0.19) (Si1.81Al0.19O1.19N1.81) powder, prepared by silicothermal reduction and nitridation of clay, has been pressureless sintered to full density at 1700-1720°C without the use of sintering aids. Samples were sintered in a silica rich powder bed to minimise surface depletion of silicon and oxygen during sintering. The effects of powder bed composition, sintering temperature and sintering time are investigated. The bend strength (445 MPa) and Weibull modulus (19) of fully dense O'-sialon discs, sintered without additives, were determined using the ball on ring method. These results indicate a single population of fracture determining flaws. Hardness (HV10 = 1700), Poissons ratio (0.19), elastic modulus (221 GPa) and mean thermal expansion (3.3 × 10-6°C-1, 25-1000°C) were also measured. |
