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Etude de l'energie superficielle de charges minerales industrielles, en l'occurrence des melanges de talc et de chlorites. Nous les avons caracterises par calorimetrie d'immersion. Cette experience est une mesure de... more
Etude de l'energie superficielle de charges minerales industrielles, en l'occurrence des melanges de talc et de chlorites. Nous les avons caracterises par calorimetrie d'immersion. Cette experience est une mesure de l'enthalpie de creation d'une interface solide-liquide a partir d'un solide parfaitement degaze. A l'aide d'un formalisme thermodynamique rigoureux, un lien peut etre etabli entre l'enthalpie d'immersion et les angles de contact. Des lors il devient possible de relier les modeles de determination de la tension superficielle des solides, utilises pour traiter les angles de contact, a nos resultats experimentaux. L'analyse des enthalpies d'immersion, pour divers couples solide/liquides, montre qu'elles resultent de differentes contributions energetiques, chacune etant associee a un type d'interaction (apolaire et polaire) entre le solide et le liquide a l'interfacens. Il apparait que les solides etudies sont relat...
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ABSTRACT Three polymorphic phases of Xaliproden are evidenced through thermal analysis: Form II has an orthorhombic symmetry while Forms I and III have monoclinic unit cells. Structural characterizations of Xaliproden are carried out by... more
ABSTRACT Three polymorphic phases of Xaliproden are evidenced through thermal analysis: Form II has an orthorhombic symmetry while Forms I and III have monoclinic unit cells. Structural characterizations of Xaliproden are carried out by means of single-crystal and synchrotron powder X-ray diffraction (XRD), as well as high-resolution solid-state 13C cross-polarization at magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectroscopy. Diffraction crystallography indicates that the structures of two of the polymorphs are highly similar despite different thermal events observed by thermal analysis. Further X-13C (X = 1H or 19F) CPMAS NMR spectra, recorded under either 1H or double-resonance 1H/19F decoupling, provide evidence for the occurrence of 19F self-decoupling in Form III, indicating that the structural disorder observed in the X-ray diagram is dynamic, with rotation of the CF3 group around the C-C single bond. The results show that polymorphism between Xaliproden Forms I and III mostly deals with the degree of freedom of the CF3 group, higher in Forms III than in Form I and clarifies the status of Form III that can therefore be assigned to a well-defined polymorph of Xaliproden.
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The surface energies of talc and chlorite is computed using a simple model, which uses the calculation of the electrostatic energy of the crystal. It is necessary to calculate the atomic charges. We have chosen to follow... more
The surface energies of talc and chlorite is computed using a simple model, which uses the calculation of the electrostatic energy of the crystal. It is necessary to calculate the atomic charges. We have chosen to follow Henry's model of determination of partial charges using scales of electronegativity and hardness. The results are in correct agreement with a determination of the surface energy obtained from an analysis of the heat of immersion data. Both results indicate that the surface energy of talc is lower than the surface energy of chlorite, in agreement with observed behavior of wettability. The influence of Al and Fe on this phenomenon is discussed. Surface energy of this type of solids seems to depend more strongly on the geometry of the crystal than on the type of atoms pointing out of the surface; i.e., the surface energy depends more on the physics of the system than on its chemistry.
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The surface energies of talc and chlorite is computed using a simple model, which uses the calculation of the electrostatic energy of the crystal. It is necessary to calculate the atomic charges. We have chosen to follow... more
The surface energies of talc and chlorite is computed using a simple model, which uses the calculation of the electrostatic energy of the crystal. It is necessary to calculate the atomic charges. We have chosen to follow Henry's model of determination of partial charges using scales of electronegativity and hardness. The results are in correct agreement with a determination of the surface energy obtained from an analysis of the heat of immersion data. Both results indicate that the surface energy of talc is lower than the surface energy of chlorite, in agreement with observed behavior of wettability. The influence of Al and Fe on this phenomenon is discussed. Surface energy of this type of solids seems to depend more strongly on the geometry of the crystal than on the type of atoms pointing out of the surface; i.e., the surface energy depends more on the physics of the system than on its chemistry.