A COLLOIDAL METHOD FOR MANGANESE OXIDE ADDITION TO ALUMINA POWDER ANDINVESTIGATION OF PROPERTIES

Various methods can be applied to introduce additives to ceramic mater ials. Of these methods, mechanical mixing may not always be suitable t o obtain a uniform distribution of the small quantities of additive wi thin the structure, requiring colloidal methods to be applied for the purpose. The addition of manganese oxide to alumina powder has been st udied using a colloidal method. The effect of the manganese addition o n alumina microstructure and the later stages of the densification beh aviour was investigated, together with the hardness and mechanical str ength. No evidence of secondary phase formation was detected between t he manganese cation and alumina powder for up to 0.5 wt % manganese ad dition, suggesting that manganese is in solid solution with alumina. T he microstructural evidence presented suggests that small quantities o f a manganese addition to alumina enhance the densification process th rough the formation of fast diffusion paths within the crystalline str ucture, similar to the effect of TiO2 addition.