Influence of phenylalanine dispersant on colloidal processing of alumina particles

This paper reports the adsorption behavior of phenylalanine (PHA) onto alumina surfaces in a wide pH range of 3.6-9.5, rheology and packing densities of concentrated alumina suspensions with PHA, and mechanical properties of consolidated alumina compacts with and without PHA. A small amount of PHA was adsorbed on both the positively and negatively charged alumina surfaces and enhanced zeta potential of alumina particles in acidic and basic suspensions. However, the adsorbed and free PHA provided little influence on the dispersibility of primary particles. In the neutral and basic suspensions, the apparent viscosity decreased with addition of PHA because of the formation of weakly coagulated particle clusters, leading to the increase in the packing density for neutral alumina suspensions. During drying of wet alumina compacts, PHA remaining in the alumina compacts relaxed the applied compressive stress. However, added PHA provided no influence on Young's moduli and compressive strengths of alumina compacts after calcination. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.