Effect of magnesia additions on the properties of zirconia–mullite composites derived from sillimanite beach sand

Abstract

Zirconia–mullite composites with 4–8 mol% magnesium oxide have been prepared from Indian coastal sillimanite beach sand, zirconia and alumina. The X-ray diffraction study reveals all raw materials are crystalline in nature. In zirconia, monoclinic is the major phase detected. Alumina is having α-Al 2 O 3 as main constituent. X-R-D of magnesia shows periclase is major phase. Milling of the mixtures of all raw materials has been carried out in an attritor mill for 9 h. After drying and pressing the samples were sintered between 1500 °C and 1600 °C with 2 h of soaking. The physical properties of the sintered materials namely bulk density and linear shrinkage have been evaluated. The infra-red spectrums of sillimanite sand and sintered samples have been described. The thermo-mechanical and mechanical properties namely hot modulus of rupture, hardness and fracture toughness of sintered materials have also been evaluated. Microstructural characterization of the sintered samples through scanning electron microscope have shown mullite and zirconia are the two main phases.