The effect of wet and dry milling on the surface properties of silicon nitride powders

• The effects of dry milling in air and wet miling in isopropanol, on the surface properties of silicon nitride powders have been investigated. The ground powders have been analyzed with resoect to oxygen and carbon content, electrokinetic behviour, wetting characteristics and adsorption of acidic and basic probe molecules. The results show that dry milling in air leeds to a higher degree of surface oxidation which is correlated to substantially lower isoelectric points for dry milled vs. wet milled powders. The wet milled powders were contaminated by an adsorbed layer of isopropanol which resulted in an initially hydrophobic behaviour and low levels of adsorption of most probe molecules. This coating can be removed by heat treatment at elevated tempratures.

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