Iron removal from ultra-fine silicon carbide powders with ultrasound-assisted and its kinetics

In the present work, the occurrence form of iron impurities of SiC crystals were analyzed using the field emission scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), and the leaching kinetics of iron from the ultra-fine SiC powders in the acid system with ultrasound-assisted was also examined. The effects of the different parameters such as the types of acid, acid concentration, leaching temperature, reaction time, stirring speed, ultrasound frequency and power affecting on the iron removal efficiency were comprehensively studied to obtain an optimum condition. The results indicated that iron impurities are determined to exist in the form of FexSiy and Fex-Siy-Tiz phases in SiC crystals. Under the optimized conditions with ultrasound, the removal rate of iron can reach more than 92%. The leaching kinetics fit a homogeneous control model with the second order model as the rate-controlling step, and the activation energy of the ultrasound-assisted leaching process is determined to be 53.6 kJ/mol. The presence of the ultrasound can accelerate the leaching process and improve the iron removal efficiency, compared to conventional stirring. [Display omitted] •The effect of main parameters on the iron removal rate is evaluated.•The removal rate of iron can reach more than 92% with ultrasound-assisted.•The ultrasound-assisted can greatly improve 2.4%–6.8% of the iron removal rate.•The leaching kinetics obeys a homogeneous control model with the second order model as the rate-controlling step.