Vapor Adsorption Studies on Low-Energy Solids
In cases where the three-phase angle of contact between vapor, liquid, and solid is finite the adsorbed phase is not the conventional multilayer. In prior work it has been demonstrated that an acceptable model for the adsorbed phase is the post two-dimensional critical temperature form of the Hill — de Boer equation. Two-dimensional van der Waals constants and energetic parameters associated with vertical interactions can be obtained by computer curve-fit techniques making it possible to utilize gravimetric adsorption data in spite of Kelvin condensation which would normally obscure the mass change relevant to adsorption for particulate samples.
Hydrocarbons adsorbed on Teflon and both hydrocarbons and water vapor adsorbed on carbon surfaces are examples of adsorbed phases of interest in relating energetic data obtained by immersion heat techniques to contact angles. Adsorption data have been obtained for these systems using a McBain — Bakr gravimetric adsorption system in which the rather limited accuracy of the technique has been extended. Specially designed quartz springs opaqued by a gold deposit are photographed using Nikkon motordriven cameras. The distance from the spring to the reference point can be obtained from the film either by traveling microscope or less laboriously, from a Gerber digital readout for direct computational input.
This paper describes the adsorption system and the theory and practice of resolving the submonolayer adsorption relevant to wetting parameters for the above-mentioned systems.
KeywordsEntropy Quartz Graphite Manifold Hexane
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