Thermomechanical behavior of a zircon-mullite composite

A zircon-mullite composite was made by reaction sintering from a mixture of mullite and zircon powders. The thermomechanical characterization (strength and toughness) revealed an intermediate behavior between mullite and zircon. The composite presents a high cooling thermal shock resistance for temperatures between the ambient and 1000 °C. Bending creep tests were made at temperatures between 1100 and 1300 °C using stresses from 10 up to 90 MPa. The stress exponent value is between 2 and 3 while the activation energy varies from 280 up to 900 kJ mol−1 between 1000 and 1300 °C. Microscopic observations suggest an intergranular creep mechanism. The grain interface forces between mullite and zircon are more important than those of zircon-zircon grains. The incorporation of mullite particles in a zircon matrix produces a composite that has both the good mullite behavior toward creep and the high thermal shock resistance of zircon.