Vibrogrinding and washing commercial alumina

Conclusions The temperature of precalcination of commercial alumina for manufacturing corundum ceramics should not exceed 1550°C. In this case fine grinding of calcined alumina can be successfully done in a short period in a vibromill by the dry method.The advantage of the dry method of vibrogrinding is the substantial reduction, compared with the wet method, of iron pickup, and consequently the abrasion of the balls and the linings, and also the consumption of hydrochloric acid.Calcined commercial alumina ground dry is effectively washed to get rid of impurities compared with ground material using the wet method; in the washed dry ground alumina the content of Na₂O is less by a factor of 4–7 than in the wet ground, and the content of Al₂O₃ is higher by 0.15%.From commercial alumina type G-00 according to GOST 6912-54 it is possible to obtain finely ground calcined alumina containing more than 99.9% Al₂O₃ and 0.020% Na₂O. Together with this the use for the preparation of densely sintered corundum ceramics of dry ground vibromilled alumina is more effective than for wet milled [16].