Characterization of microstructural changes of mechanically activated ilmenite

Structural changes of mechanically-activated ilmenite during milling by a planetary mill are monitored and determined as a function of the milling time. The maximum specific BET surface area of ۱۰.۷۶ m۲/g is obtained after ۱۵۰ min of milling. The results obtained indicate that agglomeration of the particles occurs after ۴۵ min of milling. The maximum X-ray amorphization degree of ca. ۹۵% has been calculated after ۱۵۰ min of milling. Estimation of the stored energy reveals that the X-ray amorphization degree has a dominant contribution to the excess enthalpy of the activated materials. The surface-weighted crystallite size in the ground ilmenite reaches ۴.۴۵ nm, which corresponds to the volume-weighted crystallite size of ۸ nm and ۱۱.۱۸ nm obtained by the Williamson-Hall and Rietveld methods, respectively. After ۱۵۰ min of mechanical activation, the root mean square strain, , increases to ۰.۷۸%, which corresponds to the strains of ۱.۴۳% and ۱.۰۴% obtained from the Williamson-Hall and Rietveld methods, respectively. Reduction in the crystallite size leads to the contraction of the ilmenite unit cell after ۱۵۰ min. The reaction rate constant of the ilmenite dissolution increases by over ۵۸ times after ۱۵۰ min of milling. Activation energy of the dissolution reaction decreases from ۵۷.۴۵ kJ/mol to ۴۱.۰۹ kJ/mol after ۱۵۰ min of milling.

کلیدواژه ها:

Ilmenite ، Mechanical Activation ، Structural changes ، XRD line profile analysis ، Reactivity