Influence of particle size and particle size distribution on drying-shrinkage behaviour of alumina slip cast bodies

Abstract

This paper focuses on the possibility of characterising slip cast bodies microstructures through their behaviour during drying, by using the Bigot’s curves. The Bigot’s curves are normally used as routine control in traditional clay-based ceramic production (tiles, sanitary wares, earthenware, etc.) for testing the sensitivity of clays and pastes to drying. In order to test the validity and usefulness of the Bigot’s curves to characterise wet porous structures as that obtained by slip casting, “tailored” alumina slip cast bodies, prepared from suspensions having different mean particle sizes (PSs) and particle size distributions (PSDs), were used. The results showed that a decrease of the mean PS leads to an increase of the shear-thinning behaviour in the low shear rate range due to the predominance of the surface forces, relative to the hydrodynamic forces. In the slip cast bodies, a diminution of the mean PS leads to an overall decrease of green density and to an increase of both Critical Moisture Content (CMC) and total shrinkage in the first stage of the drying process. Regarding the effect of the PSD shape, alumina CT530 characterised by a bimodal PSD, gave slips with lower viscosity and denser slip cast bodies, compared with the other aluminas characterised by a continuous PSD. Accordingly, the Bigot’s curves showed a decreasing trend of CMC and total shrinkage. Overall, this work demonstrates that the use of Bigot’s curves can be extended to the advanced ceramic field, as an important tool for characterisation of slip cast bodies, including the wet state, giving complementary information in respect of Hg porosimetry or density.