Effect of solids concentration on particle size distribution of deagglomerated barium titanate in stirred media mills

The effect of solids concentration on particle size distribution of a suspension of barium titanate in toluene/ethanol solvent, deagglomerated in a re-circulating stirred media mill, has been examined by experimentation. The effect on the particle size distribution curves was recorded for solids concentrations ranging from 10% to 85% by weight and for impeller tip velocities of 4 m/s, 6 m/s and 8 m/s. Lower D50 (median) particle sizes were found at both low and high concentrations. Additionally the span of the distribution curves was found to be widest at both the lower and higher concentrations. At low concentrations high specific energies per pass of product through the grinding chamber were measured and this was as a result of high calculated stress numbers indicating high numbers of successful contact between particles and media. At high concentrations, high specific energies per pass were also measured and this was due to the increased density and viscosity of the suspension which had the effect of increasing residence time, reducing the number of passes. Thus an optimum range for solids concentration was determined which gave the narrowest spans of the particle size distribution curve, an important characteristic for deagglomeration of barium titanate for MLCC manufacture. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.