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Etude de la limite de solubilité de la chromine (Cr2O3) dans les liquides sodo-silicatés : Détermination de grandeurs thermodynamiques et physicochimiques

Abstract : In the field of "corrosion and thermodynamics of systems at high temperature", the objective of this study is to increase the knowledge of corrosion by glass melts with carrying a particular interest to define the factors determining the chromia dissolution. The precise goal of this work was to determine the total solubility of chromia in the soda-silicate and soda-lime systems, as a function of temperature, oxygen fugacity and melt composition. After a detailed bibliographic introduction, the first part of this work describes the experimental device developed and validated for this study. This reactor allows controlling independently different experimental parameters. Therefore, the kinetic study shows clearly, at first, that the achievement of the equilibrium is limited by the dissolved oxygen diffusion in the matrix. Subsequently, the kinetic study allows the construction of two isothermal sections of the pseudo-ternary system Na2O-SiO2-Cr2O3 pointing the stability domain of each solid phase (Na2CrO4, Cr2O3, NaCrSi2O6 and SiO2) in the melt. The total chromium oxide (Cr2O3) solubility was then measured in Na2O-xSiO2 melts considering the effect of each experimental parameter. The presence of CrII, CrIII and CrVI species was evidenced and their respective contributions in the total Cr content dissolved in the melt were determined. The experimental results were described using a model of chromium chemistry in silicate melts involving dissolution, redox and oxo complex reactions. A mathematical treatment, using the obtained results, allows the correlation between the proposed model and thermodynamic properties of the system. The free enthalpies and entropies associated to the different reactions. Finally, the same processes could be extended to the Na2O-CaO-SiO2 system.
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Hichem Khedim. Etude de la limite de solubilité de la chromine (Cr2O3) dans les liquides sodo-silicatés : Détermination de grandeurs thermodynamiques et physicochimiques. Autre. Université Henri Poincaré - Nancy 1, 2008. Français. ⟨NNT : 2008NAN10134⟩. ⟨tel-01748524⟩

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