Thermodynamic model of hydride formation and dissolution in spherical particles

摘要

A model of hydride formation and dissolution has been proposed for a single spherical particle and for a collection of such particles with a given size distribution. The phase transformation strain gives rise to an elastic barrier to the transformation, which scales with thevolume of the particle and produces a hysteresis effect known experimentally. Experimentally observed finite slopes of hydrogen pressurevs. chemical composition plots (instead of expected plateaus) are explained by the model for both the hydrogenization and dehydrog-enization processes. These finite slopes and the amount of the pressure hysteresis depend on elastic properties of the hydride and metal phases, the transformation strain, and on the particle-size distribution in the powder.