Etude du transport incohérent de lumière en milieu anisotrope : application à l'étude des fluides complexes

Abstract : To build the link between the structural organization between concentrated dispersions and their mechanical properties, you have to be able to identify their microscopic structure. In particular, for anisotropic particles (fibbers for example) or deformable particles (emulsions, red blood cells...), the knowledge of the particle size, the concentration, the deformation or the orientation of particles (partial or global) are very important. Most of concentrated dispersions are generally opaque to visible light (biological fluids as blood, clays...). An optical diffusing method based on multiple diffusion light has been developed in the laboratory to study this kind of materials. In this thesis, we are interested in the general problem of characterizing concentrated dispersions with anisotropic objects. Under shear rate, a preferential orientation or a global deformation of particles has been observed. The objective of this thesis is to study the mechanisms which involve deformation and/or orientation of anisotropic particles. An experimental device based on the incoherent light transport has been developed at the laboratory in order to determine the orientation or the deformation. The experimental device is composed of a focused laser diode and a CCD camera to acquire the backscattered images. A data base of Monte Carlo simulation has been created in order to get the form factor or the orientation of particles by analyse of anisotropic backscattered images. By comparing the numerical data with the experimental data, we are able to determine the average rate of orientated particles. Thanks to this optical diffusing method, the deformation of red blood cells in physiological concentration (40 to 50% volume fraction) and the orientation of fibbers dispersion has been study.
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Nadjim Moumini. Etude du transport incohérent de lumière en milieu anisotrope : application à l'étude des fluides complexes. Autre [cond-mat.other]. Université Henri Poincaré - Nancy 1, 2010. Français. ⟨NNT : 2010NAN10035⟩. ⟨tel-01748216⟩

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