Effect of some transition metal oxide additives on the fired properties of tri- axial ceramics

Abstract

A tri-axial ceramic or Porcelain can be defined as a glazed or unglazed vitreous ceramic body made by porcelain process, and used for technical purposes when they are vitreous. Porcelain is distinguished from other whitewares because of the lack of open pores. Porcelain possess properties such as high strength, toughness, low permeability, translucency etc. which makes porcelain useful in various fields of applications such as electrical, mechanical, chemical, structural fields. All these properties possessed by porcelain comes mainly from the mullite and the glassy phase present in the system. Earlier studies showed that by the addition of mineralizing agents or additives, the reaction rates and the phase formations can be varied. Also most of the transition metal oxide additives showed a higher affinity towards the mullite incorporation and enhancing reaction rates. To the best of our knowledge, there was not much literatures available on the effect of transition metal oxides such as Cr2O3, CoO and NiO incorporation in tri-axial systems. Hence the effect of these oxides on the physical and mechanical properties together with phase formation was studied by preparing porcelain batches containing different additive percentages and fired at temperatures 1100oC, 1200oC and 1300oC. It was observed that Cr2O3 because of its refractory nature does not help during the reaction stages and hence deterioration of properties was observed, whereas CoO, and NiO enhances the reactions by regulating the viscosity of the melt at certain conditions. These reactions lead to increased secondary mullitization and hence advances in properties such as bulk density, porosity and also mechanical properties obtained. Hence transition metal oxides like CoO and NiO can be used further for applications in different fields requiring higher strength and densities.