The sintering kinetics and properties of sintered glass-ceramics from coal fly ash of different particle size

Abstract

Coal fly ash, a solid waste from powder plant, was fully used to produce sintered glass-ceramics by direct sintering in air after dry pressing at 10 MPa. The influence of particle size on the sinterability and properties of sintered glass-ceramics had been systematically discussed. Compared with CFA (d50 = 12.6 μm), sintered glass-ceramics issued from 20CFA (d50 = 7.5 μm) and 40CFA (d50 = 4.9 μm) had higher bulk density, higher linear shrinkage and lower porosity. The sintering activation energy of the sintered glass-ceramics obtained from the three sizes of coal fly ash (CFA, 20CFA and 40CFA) were estimated by bulk density and linear shrinkage, which were 127, 102, 81 kJ/mol and 124, 106, 83 kJ/mol respectively, meaning the smaller the particle size, the easier the sintering. According to the XRD analysis, anorthite was formed by the reaction of portion dissolved quartz with the amorphous metastable glassy phase in coal fly ash. The smaller the particle size of coal fly ash is, the easier the formation of anorthite. Moreover, the properties (water absorption, flexural strength and chemical resistance) of the sintered glass-ceramics were enhanced with the decrease of the particle size and reached the standards of architectural decoration materials.