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Procédés mécaniques d'élaboration à sec de particules composites à propriétés d'usage contrôlées. Caractérisation et stabilité d'un gel de silice

Abstract : Dry particle coating to change the surface properties and/or functionality of powders appears as a very important for many industries.
In this study the dry coating experiments were performed with three different devices, the Hybridizer (high-speed-dry impact blending coater), the Cyclomix (high shear mixer) and the Turbula mixer. To compare these techniques, a particulate model of powders with very different properties was then chosen. A hydrophilic silica gel powder (SG, 55 μm) was treated with different mass ratio of fine particles of a hydrophobic magnesium stearate (MgSt, 5 μ m).
The surface morphology of the coated silica gel particles were observed by environmental scanning electron microscopy (ESEM). In addition, the phase contrast in tapping mode atomic force microscopy (AFM) analysis revealed how this coating process allows obtaining a discrete dispersion of the MgSt particles onto the surface of silica gel particles. The adhesion forces between the StMg attached to the AFM probe and the different powders were measured in contact mode. The effect of mechanical dry coating on the affinity between the silica gel and water was evaluated by the Sessile drop method and DVS measurements. The flowability modification of silica gel after mechanical treatment was analysed by the Volumeter.
The study of the stability of the coated silica gel particles showed the effect of relative humidity on the aging of the coating. This phenomenon was accompanied by a diminution in the specific pore volume of silica gel. A diffusion mechanism of MgSt from the surface of SG particles into the pores was proposed
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Submitted on : Tuesday, April 29, 2008 - 3:42:18 PM
Last modification on : Wednesday, June 24, 2020 - 4:19:21 PM
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  • HAL Id : tel-00276411, version 1

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Yamina Ouabbas. Procédés mécaniques d'élaboration à sec de particules composites à propriétés d'usage contrôlées. Caractérisation et stabilité d'un gel de silice. Sciences de l'ingénieur [physics]. Ecole Nationale Supérieure des Mines de Saint-Etienne, 2008. Français. ⟨tel-00276411⟩

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