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Materials (Basel). 2014 Aug 19;7(8):5982-5991. doi: 10.3390/ma7085982.

Recycling of Coal Fly Ash for the Fabrication of Porous Mullite/Alumina Composites.

Author information

1
School of Materials Science and Engineering, Pusan National University, Pusan 609-735, Korea. kgh31202@gmail.com.
2
School of Materials Science and Engineering, Pusan National University, Pusan 609-735, Korea. syy3@pusan.ac.kr.
3
School of Materials Science and Engineering, Pusan National University, Pusan 609-735, Korea. hcpark1@pusan.ac.kr.

Abstract

Coal fly ash with the addition of Al₂O₃ was recycled to produce mullite/alumina composites and the camphene-based freeze casting technique was processed to develop a controlled porous structure with improved mechanical strength. Many rod-shaped mullite crystals, formed by the mullitization of coal fly ash in the presence of enough silicate, melt. After sintering at 1300-1500 °C with the initial solid loadings of 30-50 wt.%, interconnected macro-sized pore channels with nearly circular-shaped cross-sections developed along the macroscopic solidification direction of camphene solvent used in freeze casting and a few micron-sized pores formed in the walls of the pore channels. The macro-pore size of the mullite/alumina composites was in the range 20-25 μm, 18-20 μm and 15-17 μm with reverse dependence on the sintering temperature at 30, 40 and 50 wt.% solid loading, respectively. By increasing initial solid loading and the sintering temperature, the sintered porosity was reduced from 79.8% to 31.2%, resulting in an increase in the compressive strength from 8.2 to 80.4 MPa.

KEYWORDS:

camphene; coal fly ash; compressive strength; freeze casting; mullite/alumina; pore channels

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