Synthesis and characterization of mullitea€“zirconia composites by reaction sintering of zircon flour and sillimanite beach sand

摘要

Mullitea€“zirconia composites containing 10a€“30 wt% zirconia were prepared by reaction sintering of zircon flour, sillimanite beach sand and calcined alumina. Raw materials were attrition milled, shaped into pellets and bars and sintered in the temperature range of 1450a€“1600?°C with 2 h soaking at peak temperature. Sintered products were analysed in terms of various physical, mechanical and thermo-mechanical properties. The analyses of phases developed and microstructural analyses were carried out by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. It was observed that the addition of ZrO₂ up to 20 wt% significantly improves flexural strength and fracture toughness. The transformation of t $ ightarrow$ m zirconia was found to be the dominant mechanism for enhancement in mechanical properties. ZrO₂ occupies both the intergranular as well as intragranular positions. However, intragranular zirconias are much smaller compared to intergranular zirconias.