Interaction of Water Vapour with Germanium Real Surface

Kawasaki, Koji; Kanou, Kyoichi; Sekita, Yoshiyasu

doi:10.1143/jpsj.14.233

Cited by 5 publications

(1 citation statement)

References 2 publications

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“…This results in increased rates of molecular relaxation behind the front, leading to the acceleration of water sorption [eq. (2)] and the observed Fickian-like behavior in which Fickian diffusion and polymer relaxation contributions are superim-posed upon each other. While the relaxation contribution becomes more important due to increasing water concentration as sorption proceeds further, the Fickian contribution decreases as a result of decreasing concentration gradient.…”

Section: Water Sorption Mechanismmentioning

confidence: 99%

Bending‐beam study of water sorption by thin poly(methyl methacrylate) films

Tong

Saenger

1989

J of Applied Polymer Sci

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SynopsisA bending-beam technique has been employed to study the effects of film thickness (7-55 pm) and rate of cooling during film preparation ( -6"C/h to a dry ice quench) on sorption characteristics of water by poly(methy1 methacrylate) films coated on thin fused quartz beams ( -84 pm thick). In each experiment, the curvature of a polymer coated beam exposed to liquid water was monitored as a function of time by a low power laser pointer. With the use of a transport model which considers the sorption process as the linear superposition of contributions from Fickian diffusion and a first-order polymer molecular relaxation process, the beam curvature data were analyzed to determine the governing transport kinetics and associated transport parameters such as water diffusion coefficient and relaxation rate constant. From curvature analysis for thin films (7-13 pm in thickness), it was found that water diffusion proceeds at early times in a Fickian-like manner with a diffusion constant of 2-4 X cm2/s. At later times, significant relaxation contributions lead to non-Fickian diffusion behavior, an effect that is more pronounced as the film thickness or sample cooling rate decreases. In addition, sorption of water was found to reduce the film stress (initially tensile a t -10* dyn/cm2) a t a rate that increases with sample cooling rate.The high initial film stress not present in free-standing films may account for the relatively higher diffusion coefficient ( -2 X lo-' cm2/s) found here for very thick (55 pm) PMMA coatings.Because the bending-beam technique uses coated samples, it is especially well suited for studying penetrant transport into polymer coatings.

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Section: Water Sorption Mechanismmentioning

confidence: 99%