Influence of dispersing agents on microstructure-related properties of slip cast cordierite ceramics

Abstract

Abstract This study aims to reveal the effects of the concentrations of solids and dispersing agents on the rheological properties of the suspensions prepared from multicomponent cordierite precursor powder system and on the final properties of the cordierite bodies consolidated by slip casting. For this purpose, the suspensions having solid loadings of 40, 45, and 50 wt% were prepared. In these suspensions, Darvan 821A and Dolapix CE-64 were used as dispersants. The dispersant-induced changes in the properties of both casting suspensions and their slip-cast bodies were characterised. The results indicate that Dolapix CE-64 had less impact on reducing the shear stress values compared to the Darvan series, and thus Darvan 821A rendered suspensions with lower shear stress values than observed with Dolapix CE-64. Both dispersants also caused distinct effects on the crystallinity, secondary phase formation, and porosity, as well as on the physico-mechanical properties. Dolapix CE-64 provided good physico-mechanical properties, which may be attributed to the formation of clustered and interlocked mullite crystals within the cordierite glass matrix. Furthermore, the results revealed that Darvan 821A confers higher thermal conductivities to the cordierite ceramics, while Dolapix CE-64 favours the sintered density and enhances the dielectric constant and dielectric loss tangent values. Consequently, it was found that the slip-cast bodies prepared from the suspensions dispersed with the different type of dispersants exhibit different microstructure-related properties.