Hydrogenation reaction characteristics and properties of its hydrides for magnetic regenerative material HoCu₂

Abstract

The hydrogenation reaction characteristics and the properties of its hydrides for the magnetic regenerative material HoCu₂ (CeCu₂-type) of a cryocooler were investigated. The XRD testing reveals that the hydrides of HoCu₂ were a mixture of Cu, unknown hydride I, and unknown hydride II. Based on the PCT (pressure−concentration−temperature) curves under different reaction temperatures, the relationships among reaction temperature, equilibrium pressure, and maximum hydrogen absorption capacity were analyzed and discussed. The enthalpy change ΔH and entropy change ΔS as a result of the whole hydrogenation process were also calculated from the PCT curves. The magnetization and volumetric specific heat capacity of the hydride were also measured by SQUID magnetometer and PPMS, respectively.

Keywords

hydrogenation reaction / magnetic regenerative material / X-ray diffraction analysis / magnetization / volumetric specific heat

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