Preparation of porous mullite ceramic-based aggregates from low-voltage electroceramic wastes and sec-ondary aluminum dross
This work aims at finding an effective and low-cost new process for the preparation of porous ag-gregates,while alleviating the pressure of industrial solid wastes.Porous mullite ceramic-based aggregates were developed through low-temperature sintering using low-voltage electroceramic wastes and secondary aluminum dross as the main raw materials,and activated carbon powder as the pore-forming agent.The in-fluence of the secondary aluminum dross addition(5 mass％to 40 mass％)on the properties of the sam-ples was studied.The results show that:(1)with the increasing addition of secondary aluminum dross,the bulk density of the samples gradually decreases,while the apparent porosity gradually increases,and final-ly both tend to be stable;the linear shrinkage ratio first slightly increases and then decreases,and the cold compressive strength gradually decreases;(2)the addition of secondary aluminum dross promotes the for-mation of mullite crystalline nuclei,reduces the viscosity of the alumina-silica liquid phase,making it easier for internal gases to diffuse through the liquid phase to the material surface,forming large pores;moreover,the increase in the linear growth rate of mullite crystals accompanied by volume expansion further inhibits the sintering shrinkage of the liquid phase;the decrease in the cold compressive strength of the samples is related to the decrease in the liquid phase viscosity;after cooling to room temperature,a coating of alumina-silica glass phases forms on the surface of the aggregates,reducing the number of micropores and in-creasing the number of macropores,leading to increased stress concentration around the pores;(3)when the secondary aluminum dross addition is 25 mass％,the comprehensive performance of the sample is optimal.
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