Selective controlled precipitation mechanism of canasite and xonotlite in glass-ceramics from silica slag

In this paper, Na2O-CaO-SiO2-X(NCSX) glass-ceramics was prepared to use industrial silicon slag as the main raw material. We employed XRD, FTIR and NMR to analyze the influence of Na2O/SiO2 on the composition of microstructure units Qn in the glass-ceramics. It revealed the precipitation mechanism of xonotlite and canasite. Spectroscopy study indicated that sodium atoms could selectively destroy the glass network to form Q(3) units while silicon atoms could rebuild the network to form Q(4) units. Q(3) units can combine with calcium atoms to form Si-O-Ca bonds that generated the precipitation of xonotlite phase. However, Si-O-Si bond wrapped the Si-O-Ca bond to form an interlayer structure in canasite crystal. And the effective method for controlling the formation of canasite crystal was adopted cautiously. That is, synergistic regulation of Na2O/SiO2 and heat treatment to precipitate the canasite phase exclusively.