Influence of acidity on the stability and rheological properties of ionically stabilized alumina suspensions in ethanol

The ionic stability of alumina particles in moderately concentrated ethanol suspensions is studied. Surface chemistry and interparticle forces are man ipulated by controlling the acidity of the suspensions without dispersants. The acidity of ethanol solution is determined using ion transfer functions , wherein the relationships between acidity, alumina particle surface charg e, zeta-potential, stability, and suspension rheological behavior are estab lished. Positive isoelectric point (IEP) shift is observed for alumina in e thanol on increasing the solids concentration. However, dilute and concentr ated aqueous suspensions of alumina give the same IEP. The viscosity and fl ow curves for alumina/ethanol suspensions are acidity dependent. The flow c urves of the suspensions follow the Casson model, and the Casson yield valu e is used to evaluate suspension stability.