étude expérimentale des mécanismes moléculaires de la friction fluides simples/solide: rôle des interactions et de la rugosité à l'échelle nanométrique

Abstract : In this work, we present results related to the slippage of simple liquids sheared against a solid boundary and analyze how it depends on the interactions between the liquid and the solid as well as on a controlled nanometric surface roughness. The experimental technique we have used to determine the slip velocity relies on measuring the mean velocity of the fluid close to the solid wall using Near Field Laser Velocimetry (NFLV). Past experiments have shown that a simple liquid such as hexadecane could slip at the wall on totally and partially wetted surfaces. We adapted the existing NFLV technique to study another simple liquid, squalane, with similar physical and chemical properties but different geometrical shapes. Our results show that squalane as well as hexadecane slips on different smooth solid surfaces. The slip length is found to be much greater than the fluid's molecular size. This slip is always smaller on wetted surfaces rather than non-wetted surfaces. Squalane slips always less than hexadecane on the same surface, showing that the shape of the molecule is crucial in determining the magnitude of the slip length. Hexadecane has indeed on average a cigar shape whereas squalane is more spherical. The systematic effect of a nanometric roughness on slippage was studied using hexadecane. A well controlled nanometric roughness was achieved by grafting hyperbranched polymer nanoparticules on a dense monolayer of SiH terminated oligomeres, varying the size and the surface density of the nanoparticules. Importance of the respectives roles of height and lateral lengths of the surface roughness on the decrease of the slip at the wall is qualitatively discussed.
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Contributor : Tatiana Schmatko <>
Submitted on : Wednesday, February 11, 2004 - 1:40:36 PM
Last modification on : Thursday, February 7, 2019 - 1:33:42 AM
Document(s) archivé(s) le : Tuesday, September 7, 2010 - 4:57:26 PM

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  • HAL Id : tel-00004617, version 1

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Tatiana Schmatko. étude expérimentale des mécanismes moléculaires de la friction fluides simples/solide: rôle des interactions et de la rugosité à l'échelle nanométrique. Dynamique des Fluides [physics.flu-dyn]. Université Pierre et Marie Curie - Paris VI, 2003. Français. ⟨tel-00004617⟩

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