Effect of ultrasonic vibration treatment on solid-state reactions between Fe2O3 and CaO

In the present study, ultrasonic vibration was applied to the solid-state reaction between Fe2O3 and CaO. The effect of the ultrasonic vibration treatment on the formation of CaFe2O4 (CF) from the solid-state reaction was investigated by X-ray diffraction (XRD) and the Rietveld structure refinement method. The results indicated that the solid-state reaction between Fe2O3 and CaO was accelerated by ultrasonic treatment (UT), which efficiently lowered the formation temperature of the solid-state CF and increased the quantity formed by enhancing the mass transfer process of the reactions. Without the UT, CF and Ca2Fe2O5 (C2F) were produced at 750 °C and the mass fractions of CF and C2F increased with the experiment temperature, with approximately 47.76% CF and 40.66% C2F produced at 850 °C. With the UT, mass fractions of 5.67% CF and 18.20% C2F were formed at 700 °C, and increasing the experiment temperature enhanced the formation of CF and C2F. Moreover, a significantly greater amount of CF than C2F was formed when the temperature exceeded 700 °C. A CF mass fraction of approximately 98.73% was obtained by UT at 850 °C, much higher than the 47.76% obtained without UT. In addition, increasing the ultrasonic power influenced the formation of the CF phase. The CF content increased from 19% to 77.34% with increasing ultrasonic power from 0 to 89% × 2 kW. Furthermore, a prolonged UT time also promoted the formation of solid phase CF. The mass fraction of CF ranged from 19% to 77.34% when the UT time was varied from 0 to 150 min.