This item is available under a Creative Commons License for non-commercial use only
Materials engineering, Ceramics
Abstract. Each manufacturing stage in the production of zinc oxide varistors from powder preparation to the final encapsulated device is important not only for the formation of the varistor component with optimum microstructure and thus electrical characteristics but also for avoiding the introduction of flaws and reduced yield. In this paper the authors describe and discuss the effect of multi-elemental oxide additives having been milled for different durations using a vibratory mill with cylindrical zirconia media on the powder characteristics of the subsequent processing stages. A commercial ZnO varistor formulation was used. The subsequent processing stages that are given particular attention include first spray drying and second milling. The characteristics include agglomerate size, powder density and elemental uniformity of the first spraydried powders, and particle size, specific surface area, zirconium concentration and pore size of the second milled powders. They were evaluated using laser diffraction, scanning electron microscopic, mercury porosimetry, Brunauer, Emmett and Teller (BET) and inductively coupled plasma (ICP) analysis. Some interesting correlations are observed between the powder properties and vibratory milling durations of the mixed metal oxide additives (MMOA).
Kelleher, M.C., Hashmi, M.S.J., Effect on the processing characteristics of ZnO varistors produced using vibratory milling, AIP Conference Proceedings Volume 1315, 2010, Pages 253-258 International Conference on Advances in Materials and Processing Technologies, AMPT2010; Paris; France; 24 October 2010 through 27 October 2010