ИСТИНА

Cu-H samples are synthesized by exposing platelets of metal copper 0.3–1 mm thick to gaseous hydrogen at a temperature of 600ºC and pressures 5–7 GPa followed by quenching down to room or liquid nitrogen temperature. The quenched samples are recovered to ambient pressure and studied by inelastic neutron scattering (INS), small angle neutron scattering (SANS) and X-ray diffraction, and their hydrogen content is determined by hot extraction. The INS spectra of the samples quenched to room temperature exhibit peaks characteristic of rotational transitions in molecular hydrogen. This points to the presence of H2 molecules trapped in micro-pores of the host metal. The SANS and ultra-SANS investigations indicate that the size of these pores is larger than 10 μm. The INS spectrum of the sample quenched to the liquid nitrogen temperature and never warmed above this temperature before the INS experiment exhibits a hydrogen vibration band with the principal peak at 100 meV. Such a band is typical of the optical vibrations of hydrogen occupying octahedral interstitial sites in transition metals with close packed fcc and hcp structures. This new band disappears after warming the sample to room temperature. The hot extraction shows that the hydrogen content of most samples quenched to the liquid N2 temperature reaches 2–3 at.% and decreases to 1–1.5 at.% after warming to room temperature. The X-ray examination of the quenched Cu-H samples at 85 K detects no hydride phase and reveals an increase in the parameter of the fcc copper lattice to a ≈ 3.606–3.609 Å compared to a0 = 3.604 Å of the virgin Cu metal and Cu-H samples warmed to room temperature. This suggests that the peak at 100 meV in the INS spectrum of the quenched Cu-H sample should be ascribed to optical H vibrations in the diluted Cu-H solutions.