The structure of n -alkane binary mixtures adsorbed on graphite
Date
2005
Authors
Espeau, Philippe
White, John
Papoular, Robert
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Publisher
Elsevier
Abstract
The thermodynamics and structure of the surface adsorbed phase in binary C15-C16 and C15-C17 n-alkane mixtures confined in graphite pores have been studied by differential scanning calorimetry and small-angle X-ray scattering. The previously observed selective adsorption of the longer alkane for chain length differences greater than five carbon atoms is verified but reduced for chain length differences less than or equal to two. With a difference in chain length of one carbon atom, Vegard's law is followed for the melting points of the adsorbed mixture and the (0 2) d-spacing is a continuous function of the mole fraction x. With a two-carbon atom difference, samples aged for 1 week have a lamellar structure for which the entities A1-xBx try to be commensurate with the substrate. The same samples aged for 1 month show a continuous parabolic x-dependence for both the melting points and the d-spacings. An explanation in terms of selective probability of adsorption is proposed based on crystallographic considerations.
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Keywords: Adsorption; Binary mixtures; Crystallography; Differential scanning calorimetry; Functions; Melting; Paraffins; X ray diffraction; X ray scattering; Adsorbed phases; Alkane mixtures; Lamellar structure; Mole fraction; Graphite Adsorbed phase; Alkanes; Binary mixtures; DSC; Graphite; X-ray diffraction
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Source
Applied Surface Science
Type
Journal article
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2037-12-31
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