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Materials 2014, 7(8), 5982-5991; doi:10.3390/ma7085982

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

School of Materials Science and Engineering, Pusan National University, Pusan 609-735, Korea
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Received: 13 June 2014 / Revised: 11 August 2014 / Accepted: 12 August 2014 / Published: 19 August 2014
(This article belongs to the Special Issue Recycled Materials)
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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. View Full-Text
Keywords: coal fly ash; mullite/alumina; camphene; freeze casting; pore channels; compressive strength coal fly ash; mullite/alumina; camphene; freeze casting; pore channels; compressive strength
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MDPI and ACS Style

Kim, K.H.; Yoon, S.Y.; Park, H.C. Recycling of Coal Fly Ash for the Fabrication of Porous Mullite/Alumina Composites. Materials 2014, 7, 5982-5991.

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