Hamaker constants for talc minerals using spectral ellipsometric data
(English)Manuscript (preprint) (Other academic)
Measurements of refractive indices over a large wavelength span for talc minerals using spectral ellipsometry allow more accurate determinations of Hamaker constants than previously reported, or otherwise calculated from literature data. We report that for the birefringent talc minerals different Hamaker constants are obtained for samples cut in different crystallographic orientations. In water, very small differences, from 1.710-20 to 1.910-20 J is obtained for nanocrystalline talc samples cut in different directions, whereas a microcrystalline sample from another source give considerably higher value of the Hamaker constant, 4.210-20J. The difference is explained by a significant difference in the refractive index. Implications for interactions relevant in connection to the use of talc as a pitch control agent, in the action of wetting and dispersing additives used as processing aids, and in combinations of talc with cellulose, calcite and polystyrene are indicated.
Talc, Hamaker constant, van der Waals force, spectroscopic ellipsometry, dielectric properties, refractive index
IdentifiersURN: urn:nbn:se:kth:diva-24103OAI: oai:DiVA.org:kth-24103DiVA: diva2:343426
QC 201008132010-08-132010-08-132014-09-22Bibliographically approved