Abstract
Different Al2O3/SiO2 glass-ceramics were prepared from blast furnace slag by traditional sintering method. The structure and properties of glasses or glass-ceramics were investigated by DSC, XRD, SEM, FTIR, 27Al MAS NMR. The DSC results showed that with the increase of Al2O3/SiO2, the glass transition temperature (Tg) first increased and then decreased, reached the minimum when Al2O3/SiO2 was 0.34. The volume density, bending strength and microhardness of glass-ceramics also showed the same variation rule. The FTIR and 27Al MAS NMR spectra results revealed this phenomenon. When Al2O3/SiO2 was 0.19, a large amount of Si4+ was added to the glass network to make the structure dense. With Al2O3/SiO2 increased from 0.24 to 0.34, the amount of [AlO6] in the glass increased while [AlO4] decreased, and the degree of network polymerization of the glass decreased; as Al2O3/SiO2 further increased from 0.34 to 0.39, [AlO4] increased and [AlO6] decreased in the glass, and the degree of network polymerization of the glass increased. The XRD results showed that the crystal phase of the glass-ceramics was composed of gehlenite, diopside and hyalophane. Moreover, with the increase of Al2O3/SiO2, the gehlenite content in the glass-ceramics increased, while the content of diopside and hyalophane decreased.
Transparent glass-ceramics for thermal management application: achievement of optical transparency and high thermal conductivity
