Influence of metakaolin from Mayouom, Cameroon, on the properties of high grade calcined bauxite sintered at 1500 °C

Abstract

Processing of high calcined grade bauxite and metakaolin-based ceramic by unidirectional humid pressing using five formulation approaches have been studied. They include bauxite with high content of alumina Al2O3 > 86 wt% and metakaolin with silica content SiO2 > 56 wt%; the ceramic products obtained at 1500 °C present 65.9 to 26.8 MPa biaxial bending four points strength, respectively, for 0 wt% and 20 wt% of substitution of bauxite by metakaolin. The increase of metakaolin in bauxite favored the formation of cumulative pore volume from 63 to 145 ml/g for 0 wt% and 20 wt%, respectively. The decrease of linear shrinkage has been observed for 21.9 to 13.3%, respectively, for 0 wt% and 20 wt% of metakaolin. The SEM and EDS investigations show round grains of corundum and 3:2 mullite particles of about 10 μm; with 20 wt% of metakaolin in bauxite, grain of corundum and 3:2 mullite are corroded by the impurities like Ti, Fe, and K. The ceramic product obtained for 0 wt% has properties for high rigidity materials for structural application and the substituted one up to 20 wt% by metakaolin is favored for microfiltration.