HDDR Process and Hydrogen-Absorption Properties of Didymium–Aluminum–Iron–Boron (Dd12.3Al1.2Fe79.4B6) Alloy

Abstract

We investigate the interaction of hydrogen with the alloy of the Dd–Al–Fe–B system containing (in wt. %) 28.6% Dd, up to 0.5% Al, 1.1% B, and the rest Fe. At an initial hydrogen pressure of 1.0 MPa, hydride with a hydrogen content of 0.5 wt. % is formed. Hydrogen adsorption is accompanied by an increase in the lattice constants (a grows by 1.4% and c does by 1.1%) under a total volume increase of 4.1%. According to the kinetics of hydrogen adsorption, the duration of a full saturation by hydrogen is 3–5 h at an initial gas pressure of 0.1–0.2 MPa. Under heating in the hydrogen medium, the alloy disproportionates at a temperature of 1003 K. X-ray diffraction data indicate that the ferromagnetic phase disproportionates into didymium hydride DdHx [a = 0.5443(2) nm, α-Fe (a = 0.2865(1) nm) and a = 0.5112(8) nm, c = 0.423(2) nm] and iron boride Fe2B. Heating of the products of disproportionation in vacuum to a temperature of 1123 K results in the recombination of the initial ferromagnetic phase.