Recycling of Coal Fly Ash for the Fabrication of Porous Mullite/Alumina Composites |
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Authors: | Kyu H Kim Seog Y Yoon Hong C Park |
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Institution: | School of Materials Science and Engineering, Pusan National University, Pusan 609-735, Korea; E-Mails: (K.H.K.); (S.Y.Y.) |
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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. |
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Keywords: | coal fly ash mullite/alumina camphene freeze casting pore channels compressive strength |
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