2005 年 12 巻 315 号 p. 131-137
Increasing accumulation of coal ash have been becoming a serious social problem in view of environmental loading, and its reuse or recycling of coal ash as raw materials of ceramics products is urgently required. Since the glass-ceramics of the CaO-Al2O3-SiO2 system have been promising as construction materials, we have investigated the preparation technique of the glass-ceramics of this system using coal ash by the bulk crystallization method. The glass-ceramics were investigated by means of scanning electron microscope (SEM), powder X-ray diffraction (XRD), and so on.
Batches were prepared by mixing the starting materials in the various mass ratios of MIR : SiO2 : CaCO3 : FeS : Na2SO4 : C =150 : 0-18 : 30-60 : 0-4.5 : 0-6 : 0-1.5. Glass samples were produced by melting the batches at 1450°C. By those batch compositions, the glasses were homogeneously produced. They were reheated at 850°C for 1 hr to induce nucleation in the glasses. Further, the glasses were reheated at 1100°C for 2 hr, to make them to transform into glass-ceramics. The results of SEM photographs and powder XRD patterns of the obtained glass-ceramics showed that the homogeneous precipitations of the prismatic crystals (about 1×5μm) of anorthite (CaO·Al2O3·2SiO2) have occurred in the glasses by the bulk crystallization, accompanied by the precipitations of gehelenite (2CaO·Al2O3·SiO2) and/or nepheline (NaO2·Al2O3·25iO2).