ROLE OF THE CLOGGING EFFECT IN THE SLIP CASTING PROCESS

Particle segregation phenomena occurring during consolidation of the g reen bodies lead to non-homogeneous microstructures and poor reliabili ty of the ceramic components. The two driving forces responsible for p article segregation in the slip casting process are the gravity force and the capillary suction of the plaster moulds. Both segregation mech anisms depend on other factors such as particle density, particle size distribution, particle interaction forces, and solid loading. The rel ative importance of each segregation mechanism was investigated by? us ing two commercial silicon carbide powders having different particle s ize distributions, as well as different colours. The effects of the in terparticle forces, solid loading and the driving force of the slip ca sting process Ir cre studied. The results obtained showed that for mod erately concentrated suspensions and a driving force given by the capi llary suction of the plaster moulds, the clogging effect plays the mai n role in particle segregation, whilst sedimentation predominates for low driving forces. Inadequacy of the existing models to explain the c logging effect is discussed and a new model is proposed. (C) 1998 Else vier Science Limited. All rights reserved.