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Forces between Alumina Surfaces in Salt Solutions: Non‐DLVO Forces and the Implications for Colloidal Processing
Author(s) -
Ducker William A.,
Xu Z.,
Clarke David R.,
Israelachvili Jacob N.
Publication year - 1994
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.1151-2916.1994.tb07012.x
Subject(s) - dlvo theory , surface force , colloid , chemistry , range (aeronautics) , chemical physics , slurry , work (physics) , mineralogy , materials science , thermodynamics , classical mechanics , composite material , physics
Direct measurements of the forces between basal (0001) surfaces of sapphire in salt solutions are presented. The measurements reveal the presence of forces in addition to those described by classical DLVO theory. At pH 7.2 in 0.01 M NaBr solution, we find an additional short‐range oscillatory force with periodicity approximately equal to twice the diameter of a water molecule. At pH 3 we find an additional strong, short‐range, monotonic, repulsive force and a long‐range attractive force over a range of NaBr concentrations from 0.001 M to 0.1 M . Both monotonic forces are approximately exponential, with decay lengths of 0.55 and 12 nm, respectively. The short‐range force is analogous to hydration forces previously measured on negatively charged surfaces. This force would provide plasticity to alumina slurries and is suggested to be the force responsible for the anomalous viscosity and consolidation behavior of alumina slurries at high salt concentrations.