| Summary: | Abstract Background High alumina refractory batches were prepared from Egyptian clay and imported China calcined bauxite. Three concentrations of phosphoric acid 3, 5, and 7%, were added to study their effects on some of their technological properties. Designed batches tend to form a composition of 76% alumina and ~ 17% silica in addition to the other fluxing and alkali oxides. Chemical and mineralogical composition as well as density and plasticity of both clay and calcined bauxite was performed. Results Three batches of different phosphoric acid concentrations were fired at 1350 °C for 1 h. Densification parameters of the fired batches as well as the cold crushing strength and thermal shock resistance were carried out. The mineral composition and microstructure of the selected batch were done using XRD as well as SEM and EDAX. It is concluded that by increasing phosphoric acid percentages, the porosities slightly increase and the cold crushing strengths drastically decrease; however, densities and shrinkages exhibit no remarked effects. Conclusions The mineral composition of the selected fired batch exhibits mullite as a main phase with subordinate amount of corundum, while berlinite, quartz, and cristobalite are in less frequent contents. Microstructure of the selected batch ensures that mullite and corundum are the main mineral phases, in addition to minor phases of phosphate minerals. The fluxing and alkali oxides together with some alumina and silica form a liquid phase, which is responsible for the densification of the batch, while mullite and corundum are the essential formed minerals.
|
|---|
