Formation kinetics and transition mechanism of CaO·SiO₂ in low-calcium system during high-temperature sintering

Abstract

The crystal structure, formation kinetics and micro-morphology of CaO·SiO₂ during high-temperature sintering process were studied in low-calcium system by XRD, FT-IR, Raman and SEM-EDS methods. When the molar ratio of CaCO₃ to SiO₂ is 1.0, β-2CaO·SiO₂ forms firstly during the heating process, and then CaO·SiO₂ is generated by the transformation reaction of pre-formed 2CaO·SiO₂ with SiO₂. 3CaO·SiO₂ and 3CaO·2SiO₂ do not form either in the heating or sintering process. Rising the sintering temperature and prolonging the holding time promote the phase transition of 2CaO·SiO₂ to CaO·SiO₂, resulting in the sintered products a small blue shift and broadening in Raman spectra. The content of CS can reach 97.4% when sintered at 1400 °C for 1 h. The formation kinetics of CaO·SiO₂ follows the second-order chemical reaction model, and the corresponding apparent activation energy and pre-exponential factor are 505.82 kJ/mol and 2.16×10¹⁴ s⁻¹ respectively.

Keywords

calcium silicate compounds / formation kinetics / crystal structure / microstructure / sinter process

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