Alkali borosilicate glass by fly ash from a coal-fired power plant

The possibility of using coal fly ash as a silica source for alkali borosilicate glass was investigated. Alkali borosilicate glasses were prepared from the coal fly ash mixed with 30 wt.% reagents composed of Na₂O and B₂O₃ by susceptor-induction heating. Their densities ranged from 2.24 to 2.55 g cm^-3 and decreased as the amount of B₂O₃ addition increased. However, the Vickers microhardness showed a different tendency with the density since the glass network connectivity improved by boron anomaly, which was identified by a nuclear magnetic resonance analysis. The Vickers microhardness of the glass product, with the addition of 15 wt.% B₂O₃ and 15 wt.% Na₂O, was about 4030 MPa. Furthermore, the changes in microstructure were consistent with those in the chemical stability by the toxicity characteristic leaching procedure (TCLP).