Investigation of Parameters Affecting Formation of Mullite from Kaolin

Abstract

This study aims to improve the understanding of formation of mullite from kaolin at low process temperature using different sintering regimes. The optimum parameters affecting mullite formation from kaolin such as sintering temperature (from 1000 to 1500 °C), heating rate (3 and 20 °C min -1 ) and dwell time (3 min, 1 and 5 h) were investigated. There was a marked increase in bulk density values with increasing sintering temperature up to ~1300 °C, resulting in a significant decline at the apparent porosity values. The lower heating rate and the longest dwell time appeared to be more effective to obtain a maximum density value at 1300 °C. Microstructural features were examined using SEM, and the nature of crystalline phases present was confirmed by XRD analysis. It was observed that formation of mullite grains started at ~1100 °C. Although there was a significant amount of mullite grains at 1200 °C, completely elongated mullite crystals were formed at 1300 °C.