In this paper, the use of solid-state reactions for the storing of thermal energy at high\ntemperature is proposed. The candidate reactions are eutectoid- and peritectoid-type transitions\nwhere all the components (reactants and reaction products) are in the solid state. To the best of our\nknowledge, these classes of reactions have not been considered so far for application in thermal\nenergy storage. This study includes the theoretical investigation, based on the Calphad method, of\nbinary metals and salts systems that allowed to determine the thermodynamic properties of interest\nsuch as the enthalpy, the free energy, the temperature of transition, the volume expansion and the\nheat capacity, giving guidelines for the selection of the most promising materials in view of their\nuse for thermal energy storage applications. The theoretical investigation carried out allowed the\nselection of several promising candidates, in a wide range of temperatures (300â??800 Degree Celsius). Moreover,\nthe preliminary experimental study and results of the binary Mn-Ni metallic system are reported. This\nsystem showed a complex reacting behavior with several discrepancies between the theoretical phase\ndiagram and the experimental results regarding the type of reaction, the transition temperatures and\nenthalpies and the final products. The discrepancies observed could be due both to the synthesis\nmethod applied and to the high sensitivity of the material leading to partial or total oxidation upon\nheating even if in presence of small amount of oxygen (at the ppm level)
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