Investigation of hydrogen interaction with magnetic materials of Nd–Fe–B type by calorimetry method

Abstract

The interaction of hydrogen with the Nd–Fe–B system is studied via calorimetry with use of a Tian–Calvet differential calorimeter and reconstruction of the pressure–composition isotherms (P–C–T, where Р is the equilibrium pressure of hydrogen, С = H/Nd₂Fe₁₄B, and T is the reaction temperature). No hybrid phase coexistence is found on the P–C hydrogen sorption/desorption isotherms or on plots of the dependence of the enthalpy on the hydrogen concentration in the metallic matrix. Nevertheless, several segments with constant enthalpy values can be distinguished in the reaction enthalpy on the hydrogen content plot.