A study on the preparation of CMAS glass–ceramics by in situ crystallization

Natural minerals and industrial slag are used as the starting materials for the preparation of glass–ceramics. Based on the glass system of CaO–MgO–Al2O3–SiO2 (CMAS), the CaO/MgO ratio, the kind and content of nucleating agent, the processing schedule for nucleation and crystallization on the microstructure and properties of the glass–ceramics were investigated. Results show that a dense and homogeneous glass–ceramics with a crystal size of about 50–200 nm was prepared using natural minerals only. The main phases of the glass–ceramics are wollastonite (β-CaSiO3) and diopside (CaMg(SiO3)2). With the decrease of CaO/MgO ratio, the crystallizing temperature of the glass becomes higher, and the content of diopside increases. When CaF2 was used as nucleating agent, it results in a large number of nucleus by the phase separation in the glass and benefits the fine-grained microstructure of the glass–ceramics. The best mechanical properties of the glass–ceramics were obtained under the processing schedules of nucleation at 840 °C and crystallization at 960 °C.