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L'inversion de phase des émulsions est un processus employé dans de nombreux procédés industriels, pour obtenir des émulsions très fines. Le suivi de l'inversion et la compréhension des phénomènes physico-chimiques mis en jeu constituent donc des enjeux majeurs pour maîtriser la formation et la stabilité des émulsions. Notre travail a porté sur l'étude de l'inversion de phase induite par le changement de température de systèmes de type CiEj / n-alcane / Eau (+NaCl). En premier lieu, nous avons mis au point une méthode de détection de l'inversion par mesure du signal de rétrodiffusion de lumière. D'autre part, nous avons étudié des diagrammes de phase afin de les corréler avec la carte formulation-composition, en s'appuyant sur un système simple. La rétrodiffusion de lumière permet de caractériser des systèmes SEH même exempts d'électrolytes. De plus, elle fournit un signal lorsque la phase continue est huileuse contrairement à d'autres techniques comme la conductimétrie. Elle apporte également une information sur la taille des gouttes, qualitative certes, mais plus significative que la mesure de viscosité. La construction et l'analyse physicochimique et géométrique détaillée des différents diagrammes de phase formant le prisme SEH - Température d'un système défini (C10E4 / n-octane / NaCl 10-2M) a permis de mettre en évidence certaines zones de diagrammes non explorées et de présenter des interprétations novatrices des diagrammes de phases. La confrontation des résultats obtenus par les processus d'inversion standard et dynamique souligne la relation étroite existant entre les diagrammes de phases et les cartes formulation - composition obtenues après émulsification. / The phase inversion of emulsions is used in many industrial processes to obtain very fine emulsions. The tracking of inversion and the understanding of the implied physico-chemical phenomena are thus major issues to control the formation and stability of emulsions. We have been studying the phase inversion induced by a temperature change in CiEj/n-alkane/Water(+NaCl) systems. ln the first place, a method to detect the phase inversion by measuring the backscatterîng signal has been developed. On the other hand, we have studied phase diagrams in order to correlate them with the formulation-composition map, by using a simple system. Light backscattering allows characterizing SOW systems, even free from electrolytes. Moreover, ît gives a signal when the continuous phase is oily, contrarily to other techniques like conductimetry. It also gives some information about the droplet size, although qualitatively, but more significantly than viscosity does. The construction and the physico-chemical and geometrical analyses of the different phase diagrams forming the SOW - Temperature prism for a defined system (C10E4 / n-octane / NaCI 10-2M) has put forward some unexplored zones of the diagrams and allowed to present novel interpretations of the phase diagrams. The comparison of the results obtained with the standard and dynamic inversion processes underlines the tight relation existing between the phase diagrams and the fommlation-composition maps obtained after emulsification.

A study of the subsolidus region of the BaO-La2O3-V 2O5 phase diagram has been carried out. Four ternary phases can be prepared, one of which has not been previously identified. The four ternary phases are a palmierite solid solution Ba3-3xLa2x V2O8, Ba2LaV3O11, BaLa10V4O26 (new phase) and Ba3La 40V12O93. Addition of BaLa10V 4O26 and the previously omitted phase La1.42V 0.58)3.58 to the ternary system has resulted n a re-determination of the complete phase diagram. A comprehensive study of the Ba3-3xLa 2xV2O8 solid solution has been carried out, employing a number of techniques including x-ray diffraction, infra-red spectroscopy, thermogravemetric analysis, impedance spectroscopy, electron paramagenetic resonance spectroscopy, inductively coupled plasma mass spectroscopy and x-ray absorption near edge structure spectroscopy. Conductivity measurements show the end-member Ba3V2O8 to be an oxide ion conductor, with the conduction mechanism being facilitated by the ease of transformation of the BaO3 layers to BaO2 and vice versa. The La-doped members show an increase in conductivity, with electrons becoming the dominant conducting species. The crystal structure of Ba2LaV 3O11 was confirmed to be isostructural with Ba2BiV 3O11. A full refinement of the structural parameters has been performed. The unit cell is primitive monoclinic, a = 12.44510(3)A, b = 7.78854(12)A, c = 11.26245(21)A and beta = 103.134(4)°, space group P21/c. Preliminary structural studies have begun on the new phase BaLa10V4O26. The x-ray powder pattern has been fully indexed and a possible monoclinic unit cell of a = 20.2939A, b = 5.886A, c = 12.6234A and beta = 118.05° is proposed. The serendipitous synthesis of a barium-deficient celsian phase, Ba0.8A11.6 Si2.4O8, is reported; the structure was solved using Patterson methods. The phase has a monoclinic unit cell with, a = 8.6090(8)A, b = 13.0858(12)A, c = 7.2047(7)A and beta = 115.418(2)°, space group C2/m.