Ball milling induced reduction of SrSO4 by Al

The reduction of celestite concentrate to SrS using Al has been shown to be induced by mechanical activation. A thermodynamic appraisal showed that the reaction between SrSO4 and Al is highly exothermic and should be self-sustaining. XRD analyses showed that reaction started only after milling for an induction time of 30–35 min, after induction only product peaks were present. Increasing milling time up to 60 min had no significant effect other than refining the crystallite size. The aluminium product was not Al2O3 as expected but mixed phases such as Sr3Al32O51, SrAl4O7 and SrAl2O4 which were thought to be formed by an adventitious oxidation process.