Steps toward Hydrogen Alloys

Abstract

Efforts to synthesize and characterize metal-hydrogen alloys over wide ranges of composition, temperature and hydrogen pressure are described, taking examples mostly from our own experiments. General trends in the phase diagram of M-H systems include (a) drastic melting-point reduction, (b) transition to close-packed structures (hcp, dhcp and fcc) with dissolution of hydrogen, and (c) appearance of an eutectic liquid phase at high H concentrations. Thus, possibilities of synthesizing H-rich alloys at high hydrogen pressures are envisaged. A brief recollection of collaborative work with Professor Akimoto on the Fe-H₂O reaction and its implication for the Earth’s core formation is also made.