ENERGY-SIZE REDUCTION LAWS FOR ULTRASONIC FRAGMENTATION

The energy requirement is a key criterion for the selection and use of a grinding process. Ultrasonic dispersion is extensively used to disp erse submicron agglomerated powders in liquid suspensions. Suspensions of silica agglomerates were ground with solids concentration up to 50 % by weight. The fragmentation or grinding rate is inversely proportio nal to suspension volume. Starting from a semiempirical expression tha t relates fragmentation rate to particle size, suspension volume and u ltrasonic power, energy consumption laws for both eroding and non-erod ing powders are developed. Experimental results supporting the energy consumption laws are given. Lower power input for ultrasonication favo rs efficient energy use. For eroding powders (e.g. silica, zirconia) t he energy expenditure per unit powder mass (specific energy) by ultras onic grinding is lower than that of conventional grinding techniques. In contrast, it is slightly higher than ball milling for non-eroding p owders (e.g. titania).