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Stabilization of Ethanol‐Based Alumina Suspensions
Author(s) -
Me Mohan,
Decourcelle Sophie,
Ramousse Severine,
Larsen Peter Halvor
Publication year - 2006
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2005.00744.x
Subject(s) - dlvo theory , isoelectric point , citric acid , tetramethylammonium hydroxide , dispersant , chemistry , suspension (topology) , chemical engineering , agglomerate , particle (ecology) , particle size , viscosity , chromatography , inorganic chemistry , materials science , colloid , dispersion (optics) , organic chemistry , composite material , physics , oceanography , mathematics , homotopy , geology , pure mathematics , optics , enzyme , engineering
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).