Structure Evolution and Crystallization Behavior of CaO–SiO2-Based Slags with Varying Carbon

Abstract

The effect of carbon on the structure and crystallization behavior of CaO–SiO2-based slags was investigated through Raman and single hot thermocouple technique. Raman analysis showed that with increasing carbon, Q3, Q2 increased, Q1, Q0 decreased (Qn, n is the number of bridge oxygen in a [SiO4]-tetrahedral unit), and then the degree of polymerization (i.e., the complexity of silicate slag network structure) increased. The time–temperature-transformation result showed that the incubation time first prolonged and then shortened with adding carbon, which was related to the form of carbon in slags. When carbon dissolved in slags, it reacted with O2−, increased viscosity, and then inhibited the crystallization property. When carbons existed in the particles form, it enhanced the heterogeneous nucleation and then the crystallization behavior. The crystallization kinetics research indicated that with the addition of carbon, the limiting factor of crystallization could be converted from interface reaction controlled to diffusion controlled and then to interface reaction controlled again. Concurrently, the activation energy of crystallization first increased from 370.36 to 446.61 kJ/mol and then reduced to 313.37 kJ/mol.