PREPARATION OF GLASS-CERAMICS USING FLY ASH AS A RAW MATERIAL

The possibility of effective utilization of fly ash originated from a coal burning thermal power plant was investigated as one of the starting materials to synthesize wollastonite-based glass-ceramics. About 35% of fly ash was introduced into a batch as a raw material, and bubble-free and dark green glasses were obtained. The glass free from CaF2 or spodumene showed surface crystallization; however, glass containing CaF2 and/or spodumene exhibited bulk crystallization. The crystalline phases were wollastonite for glass with CaF2, and wollastonite and spodumene for glass with CaF2 and spodumene. The percent crystallinity was about 50%. The fracture strength of the glass-ceramics was about 220 MPa, which was two times higher than that of the original glass, and the surface hardness might be high, resulting in a scratch-free surface. However, thermal expansion coefficient did not change with crystallization, and hence the thermal shock resistance was presumed to be 2 times higher than that of original glass. Thus, fly ash supplied from a coal burning thermal power plant could be used for glass-ceramics as a raw material.

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