Effects of heat treatment process on the microstructure and properties of BOF slag based glass ceramics

Using BOF slag as raw materials, glass ceramics with the basicity (w(CaO)/w(SiO₂) of 0.5, 0.6, and 0.7 were produced by sintering. Their structure and properties were studied under different heat treatment conditions by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), sample shrinkage and mechanical strength testing. Experimental results show that the mechanical strength of the glass ceramics is mainly dependent on the sintering property of parent glass and internal crystal structure. At a higher sintering shrinkage rate, internal crystals in the glass ceramics exhibit a cylindrical intertwined form and the mechanical strength of the glass ceramics performs better. Main crystal phases in the glass ceramics are melilite and pyroxene, and high-temperature conditions are in favor of melilite growth and pyroxene.to-melilite ratio decrease. The maximum shrinkage rate belongs to the glass-ceramic with the basicity of 0.6, in which melilite performs columnar interwoven constituting a crystal skeleton that forms the microstructure of high mechanical strength with residual glass phase. Thereby this glass ceramic has excellent mechanical properties.