ISSN 0004-881X

Effect of MgO on Phase Formation and Mullite Morphology of Different Egyptian Clays

by W.M.N. Nour and H.M. Awad

Dept. of Refractories, Ceramics, and Building Materials, National Research Center, Dokki, Egypt

Abstract

In the present study, three Egyptian clays from different localities with different Al/Si ratios were investigated to characterize their chemical and mineralogical compositions, thermal decomposition and particle size distribution in order to investigate the effect of up to 4 wt % MgO addition on the phase formation, morphology of the developed mullite as well as physical and mechanical properties of these clays when sintered in the range 1200-1400oC. XRD results revealed that mullite, quartz, and cristobalite were the main phases in the sintered clays; however, cordierite was formed at the expense of the other phases in compositions containing 4 wt % MgO. SEM revealed the role of MgO in mullite grain growth and the formation of pseudohexagonal cordierite. The physical and the mechanical properties of the sintered clays were discussed in terms of their phase constitutions and microstructures.

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