Study of the microstructure of dolomite doped alumina

Abstract

In this work, the microstructure, density and phases produced by adding dolomite to Alumina were determined. Variable concentrations of dolomite such as 1, 2, 3 and 5mol% of dolomite were used as an additive in the reactive sintering of Alumina. The Calcined powders were mixed according to the batch calculations and were pressed to form pellets. The pellets were then sintered at different temperatures. The characterization and the determination of phases were done by XRD analysis. Scanning Electron Microscope helped to describe the grain morphology and pores distribution. The Dilatometer tests gave an idea about the shrinkage. As the concentration of dolomite was increased the formation of spinel (MgAl2O4) and Calcium Hexaluminate (CaAl12O19) became significant. The formation of more spinel (MgAl2O4) and Calcium Hexaluminate (CaAl12O19) began segregating the pores to the grain boundaries. However, the Bulk Density began decreasing on increasing the amount of dolomite due to the evolution of large amount of Carbon Dioxide (CO2) which enhanced the pore formation. The shrinkage began at lower temperatures upon increasing the dolomite concentrations.