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

Using coal fly ash slurry samples supplemented with different amounts of Al2O3, 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 Al2O3. 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 Al2O3content 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. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Preparation and characterization of the porous ceramics from fly ash

Porous ceramics was made from coal fly ash, and the microstructure and other properties were characterized as a function of the amount of the pore-forming agent and firing temperature. The results indicated that the proper sintering temperature for the useful ceramic materials is 1 250℃, and a liquid-phase was involved in the densification process.

Effect of Starch Addition on Properties of Corundum-mullite Porous Ceramics

Corundum-mullite porous ceramics(CMPCs)were fabricated using fly ash and aluminum ash as the raw materials,adding different amounts of starch(0,10%,20%,and 30%,by mass)as the pore-forming agent,molding and firing at 1200℃ for 1 h.The apparent porosity,the bulk density,the cold compressive strength,the thermal shock resistance and the thermal conductivity of the CMPCs were tested.The phase composition and the microstructure of the CMPCs were characterized by XRD and SEM.The effect of the starch addition on the properties of the CMPCs was studied.The results show that:(1)the CMPCs with high porosity can be successfully prepared by adding starch as the pore-forming agent and firing at 1200℃ for 1 h;(2)with the starch addition increasing,the porosity increases;the cold compressive strength and the number of the quenching cycles of the CMPCs decrease,but they remain at high levels;meanwhile,the thermal conductivity decreases;(3)generally,when adding 20 mass%starch,the CMPC has the apparent porosity of 48.6%,the cold compressive strength of 52.1 MPa,the quenching cycles of 5 and the thermal conductivity of 1.63 W·m-1·K-1 and 1.52 W·m-1·K-1,respectively,at 25℃ and 500℃,showing good performance.

Study on Preparation of Ceramic Material and Its Properties

This paper introduces the classification, properties and application of porous ceramic materials, reviewed preparation of porous ceramics. Taking fly ash and red mud as the main raw material to generate porous ceramics, the paper study the influence of different proportions of raw materials, sintering temperature, porosity of porous ceramic sample rate, bending strength, and microstructure. The results show that, fly ash and red mud proportioning and sintering temperature are the main factors that influence the structure and properties of samples. The4#sample is a kind of high porosity and high strength quality of porous ceramics.