Growth mechanisms of spinel crystals in vanadium slag under different heat treatment conditions

This paper investigated the growth of spinel crystals in vanadium slag under different heat treatment conditions. The growth mechanism was clarified by SEM + EDS and statistical analyses based on the CSD theory. The results showed that all CSDs follow lognormal distributions. Long holding time and low holding temperature below 1300 °C benefit the growth of spinel crystals. We proposed that the growth mechanisms of the spinel crystals consist of two regimes: in the first regime, nucleation control with a decaying rate within the temperature range of 1400 to 1250 °C; in the second regime, surface control when the temperature is below 1250 °C. The mean crystal diameter changes from 16.6 to 26.2 μm with an increase in holding time at 1250 °C. The relationship between the mean diameter of the spinel crystals and the holding time in the present study can be best described by the equation D = 16.32t^0.11.