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Structure d'interface de fluides complexes

Abstract : The structure of liquid-vapour interfaces is investigated in this thesis. Different kinds of surfaces have been examined in order to determine the influence of each component of molecular interactions on the physical properties of these surfaces. The height-height fluctuation spectrum of different bare liquid-vapour surfaces has been determined by x ray diffuse scattering. These measurements show that the capillary-wave model fails at small length scales (wave-vector > 108 m-1). The problem of the small scale structure can be addressed by considering corrections to the surface energy through an effective momentum-dependent surface energy. We show that the momentum-dependent surface energy first decreases from its macroscopic value and then increases with increasing wave vector. The agreement with a theory proposed by K. Mecke and S. Dietrich is excellent. We then turned to fatty acid films at the water-air interface: a bending energy is sufficient to describe the whole momentum-dependent surface energy. It has been measured for films in various phases. The particular case of a polymerized monolayer has been in particular investigated, and a coupling between height fluctuations and in-plane phonons have been evidenced. Surfaces of ionic solutions have also been investigated: height fluctuations spectrum has been measured. In addition, x ray grazing incidence fluorescence and ellipsometry experiment have been performed in order to measure the adsorption of ions. Knowing this excess is essential to understand the origins of surface tension's variation when salts are added, and to explain ion specificity and the Hofmeister effect.
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Submitted on : Monday, November 24, 2003 - 3:08:47 PM
Last modification on : Monday, February 10, 2020 - 6:12:21 PM
Long-term archiving on: : Friday, April 2, 2010 - 7:12:04 PM

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  • HAL Id : tel-00003830, version 1

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Serge Mora. Structure d'interface de fluides complexes. Dynamique des Fluides [physics.flu-dyn]. Université Paris Sud - Paris XI, 2003. Français. ⟨tel-00003830⟩

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