Phase composition and microstructure evolution of bauxite-based homogenized grogs during heating
Bauxite-based homogenized grogs with 85 mass％Al2O3 were prepared through wet co-grinding homogenization and high-temperature heat treatment,and utilizing D-K type bauxite as the raw material.The evolution of the phase composition,microstructure,and properties of the bauxite-based homogenized grogs during the heating process(800-1 630 ℃)was systematically studied using thermodynamic soft-ware FactSage,XRD and SEM.The results show that the main crystal phases of the sample are corundum and mullite;as the heat treatment temperature increases,the corundum content decreases gradually while the mullite content increases gradually;(2)within 800-1 550 ℃,as the heat treatment temperature increa-ses,the apparent porosity and water absorption of the sample rapidly decrease,while the linear shrinkage,bulk density,and the cold compressive strength significantly increase;within 1 550-1 630 ℃,the properties of the sample tend to stabilize,with the apparent porosity less than 3.4％,the water absorption rate less than 1.00％,the linear shrinkage rate of about 16％,the bulk density higher than 3.27 g·cm-3,and the cold compressive strength higher than 460 MPa;the sample is basically densified;(3)after heat treatment at temperatures of 1 400 ℃ or below,the corundum crystals in the sample are small and porous,while the mullite crystals are microcrystalline and not fully developed;the pores are mainly open or through;after the heat treatment at 1 600 ℃ or above,the sample exhibits a typical network structure of alternating corundum and mullite phases;the glass phases are few and isolatedly distributed in the network structure of the co-rundum grains or mullite grains;the pores are mainly closed;(4)thermodynamic calculations show that the liquid phase is generated in the samples at 1 150 ℃,and the amount of the liquid phase gradually increa-ses with the increasing temperature;while the viscosity of the hot liquid phase significantly decreases.
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