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Stabilization of Ethanol‐Based Alumina Suspensions

2005; Wiley; Volume: 89; Issue: 2 Linguagem: Inglês

10.1111/j.1551-2916.2005.00744.x

1551-2916

Mohan Menon, Sophie Decourcelle, Séverine Ramousse, Peter Larsen,

Ferroelectric and Piezoelectric Materials

Al 2 O 3 powders have been successfully dispersed in ethanol by varying the suspension acidity. An operational pH (O.pH) was defined to measure the acidity of these ethanol‐based suspensions. The isoelectric point of Al 2 O 3 in ethanol was at an O.pH of 8. According to Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, suspensions between an O.pH of 3.5–10.5 possessed only attractive inter‐particle potential. Suspensions below 3.5 had high ζ potential, fine particle size, and were Newtonian. However, suspensions at high pH were shear thinning and consisted of agglomerates, despite their high ζ potential. The use of citric acid as a dispersant has also been investigated. At an O.pH of 3, optimum additions of citric acid between 0.6 and 1.0 wt% decreased the particle size, resulted in repulsive inter‐particle potentials and increased the solid loading capacity to 15 vol% from 2 vol% while maintaining Newtonian behavior and similar viscosity to suspensions at O.pH 2. Addition of citric acid created agglomerated suspensions that were negatively charged at O.pH 10.5 (obtained by adding NH 4 OH), but positively charged suspensions at O.pH 13.6 (obtained by adding tetramethylammonium hydroxide).