Preventing ageing on Al2O3 casting slips dispersed with polyelectrolytes

Slip casting process needs a highly stabilized and well-characterized suspe nsion, which involves not only the traditional rheological measurements, bu t an estimation of the colloidal stability in terms of interaction potentia ls between particles. For electrosterically stabilized ceramic suspensions the calculation of the steric contribution is not well described in the ava ilable theories because they are developed for ideal conditions where many variables affecting the stability of concentrated suspensions are neglected . In this work, alumina suspensions were prepared at 75 wt% solids and char acterized considering the potential energy curves and the rheological behav iour. The main objective is to select the proper dispersing conditions in o rder to prevent ageing of the slips, which is an important problem in any m anufacturing cycle. For the polyacrylate dispersant used it was shown that a concentration of 0.8 wt% provided the lowest viscosity, allowed ageing pr evention and resulted in higher green and sintered densities. (C) 2000 Kluw er Academic Publishers.