A Hamraoui | PubMed Health

PubMed2002

Films driven by surface tension gradients.

Fingering instabilities are often observed at the contact line of drops of surfactant solutions spreading spontaneously on solid surfaces. It has been recognised recently that a usual linear stability analysis predicts stable behaviour in contrast to the observed instability. It now seems the instability arises from short-time transients, where the thickness of the film ahead of the main drop is a crucial parameter for amplification. We reconsidered previous experiments and performed new ones along these lines. The strengths and weaknesses of the available models were analysed.

Journal Article↗

PubMed1998

Impact of Bulk Phase Transitions and Wetting Transitions on Adsorption Isotherms in Binary Systems in Contact with Solid.

This paper presents several studies essentially on the solid/liquid interface. The studied system is the liquid binary mixture water-2,5dimethylpyridine (2,5DMP) in contact with an amorphous silica (Aerosil type). The study of wetting along the two-liquid bulk phases coexistence in contact with silica allows the determination of a wetting transition temperature, which is an important parameter for the adsorption behavior at coexistence. The adsorption isotherms in a diluted phase and in a concentrated phase present some very significant features. In diluted solutions the isotherms show a succession of plateaus; these transitions of layers persist in concentrated phases presenting a sequence of maxima and minima of relative adsorption (Gibbs adsorption) of 2,5DMP with respect to water. In concentrated solutions, they interfere with the prewetting that gives an original shape to the isotherms in concentrated solutions. These adsorption measurements were completed by activity measurements which allow one to obtain the chemical potential of mixtures and linked information. The whole study shows the behavior of colloidal suspensions close to bulk phase changes. Copyright 1998 Academic Press.

Journal Article↗