Microstructure and properties of mullite-based porous ceramics produced from coal fly ash with added Al_2O_3

摘要

Using coal fly ash slurry samples supplemented with different amounts of Al_2O_3,we fabricated mullite-based porous ceramics via a dipping-polymer-replica approach,which is a popular method suitable for industrial application.The microstructure,phase composition,and compressive strength of the sintered samples were investigated.Mullite was identified in all of the prepared materials by X-ray diffraction analysis.The microstructure and compressive strength were strongly influenced by the content of Al_2O_3.As the Al/Si mole ratio in the starting materials was increased from 0.84 to 2.40,the amount of amorphous phases in the sintered microstructure decreased and the compressive strength of the sintered samples increased.A further increase in the Al_2O_3 content resulted in a decrease in the compressive strength of the sintered samples.The mullite-based porous ceramic with an Al/Si molar ratio of 2.40 exhibited the highest compressive strength and the greatest shrinkage among the investigated samples prepared using coal fly ash as the main starting material.