Molecular mixed crystals: another REALM of alloys

Thermodynamic approach to molecular alloys, in spite of their specificities, is essentially the same as the approach to metallic alloys. The examples of binary phase diagrams that are given make clear that the term alloy is to be preferred over solid solution and mixed crystal. The joint approach of thermodynamics and crystallography has given rise to significant new insights into the relation between pure component properties and thermodynamic mixing properties, as well as to the particular temperature dependence of the latter. In addition it has let to an updating of the concept of isomorphism. To end with, some of the applications of molecular alloys are given

New insights on the crystalline forms in binary systems of n-alkanes: Characterization of the solid ordered phases in the phase diagram tricosane + pentacosane

X-ray diffraction analyses of the pure components n-tricosane and n-pentacosane and of their binary mixed samples have enabled us to characterize the crystalline phases observed at low temperature. On the contrary to what was announced in literature on the structural behavior of mixed samples in odd-odd binary systems with D n = 2, the three domains are not all orthorhombic. This work has enabled us to show that two of the domains are, in fact, monoclinic, (Aa, Z = 4) and the other one is orthorhombic (Pca21, Z = 4). The conclusions drawn in this work can be easily transposed to other binary systems of n-alkanes

Binary Phase Diagram with Non Isomorphous n-Alkanes:C12H26-C15H32. Implication of the Rotator Phase R-I in the Melting Behaviour of Odd-Even and Even-Odd Phase Diagrams

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Interdiffusion between sodium chloride and potassium chloride

L'interdiffusion dans le système NaCl-KCl a été étudiée entre monocristaux et/ou polycristaux, dans la gamme de température 485-640 °C. Les courbes de pénétration ont été obtenues par analyse à la microsonde électronique. Les variations des coefficients d'interdiffusion [MAHT] en fonction de la concentration sont données pour T variant de 600 à 640 °C. Par ailleurs, il apparaît que l'interdiffusion permet la formation de phases métastables dans le cas de non-miscibilité totale. Le phénomène d'effet Kirkendall a été mis en évidence et évalué.Interdiffusion has been investigated in the NaCl-KCl system, over the temperature range 485-640 °C. Experiments have been carried out on single crystals and/or polycrystalline samples. Penetration profiles have been determined by the electron microprobe technique. The values of the interdiffusion coefficient [MATH] versus concentration and temperature (600-640 °C) are given. When studied in the temperature range of the demixtion phenomenon (T < 500 °C), the interdiffusion leads to a miscibility gap slightly smaller than those observed by the equilibrium methods. The existence of a Kirkendall effect in this system has been proved and studied

From concept to application. A new phase change material for thermal protection at-11 degrees C

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