Verification of universal surface scaling behavior in critical binary liquid mixtures with neutron and x-ray reflectometry

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Show simple item record Brown, Matthew D. 2007-05-09T14:06:50Z 2007-05-09T14:06:50Z 2007-05-09T14:06:50Z
dc.description.abstract We have studied two critical binary liquid mixtures in the mixed phase regime with x-ray and neutron reflectometry to verify universal critical scaling at a non-critical interface. We compared our results with previous results obtained with ellipsometry. At a solid-liquid or liquid-vapor interface of an AB binary liquid mixture the component with the lower surface tension will dominate that interface. If the surface tension differential between the components of the mixture is large enough the composition of the surface layer will loose its dependence on. This case is referred to as strong adsorption. We study the case of strong adsorption for a binary liquid mixture at the critical composition with respect to the demixing phase transition. Sufficiently close to the critical temperature Tc the influence of bulk critical behavior is expected to dominate the way the surface adsorption layer decays with depth z from the surface composition to the bulk composition. The length scale of the decay profile is expected to be proportional to the composition correlation length, and is expected to scale with a universal composition scaling function. In a neutron reflectometry study of a critical mixture of D2O and 3-methylpyridine against a quartz substrate we verify universal critical scaling using a scaling function previously used to describe ellipsometry data. In an x-ray reflectometry study of the liquid-vapor interface of a critical mixture of n-dodecane and 1,1,2,2 tetrabromoethane, which had previously been studied with ellipsometry, we find that we are able to describe all data by using the same scaling function provided that we account for non-critical, system dependent surface structure as well. We are also able to simulate ellipsometry with our mathematical profile model and compare the simulation to the previous ellipsometry data. en
dc.description.sponsorship Department of Energy National Science Foundation en
dc.language.iso en_US en
dc.publisher Kansas State University en
dc.subject reflectometry en
dc.subject ellipsometry en
dc.subject critical en
dc.subject binary en
dc.subject neutron en
dc.subject scaling en
dc.title Verification of universal surface scaling behavior in critical binary liquid mixtures with neutron and x-ray reflectometry en
dc.type Dissertation en Doctor of Philosophy en
dc.description.level Doctoral en
dc.description.department Department of Physics en
dc.description.advisor Bruce M. Law en
dc.subject.umi Physics, Condensed Matter (0611) en 2007 en May en

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