Beschreibung:
The hydrogen-absorbing alloys currently used in industry form residual hydrogen that reduces the alloy’s reversible hydrogen capacity, decreasing its useful life. RNi3 intermetallic compounds, which have a PuNi3 -type crystal structure composed of MgZn2-type and CaCu5-type cells that exhibit structural change in relation to their hydrogenation properties, have been the focus of much research, but only a few of those reports focus on the interplay between residual hydrogen and alloy structure. Thus, this study seeks to clarify the residual hydrogen occupation mechanisms in MgZn2-type and CaCu5-type cells during the hydrogen absorption-desorption process. The structural changes and deuterium occupation in NdNi3Dx were investigated using X-ray diffraction (XRD) and neutron powder diffraction (NPD). Rietveld refinement was performed for NdNi3, NdNi3D2.6, NdNi3D3.2, NdNi3D4.0, and NdNi3D4.8, during the deuterium absorption-desorption process. The deuterium capacity reached 0.9 D/M at the first absorption process and 0.7 D/M of residual deuterium was formed after the first desorption at 248 K. For NdNi3D2.6 (phase II), the residual deuterium contents of MgZn2-type and CaCu5-type cells were determined to be 1.0 D/M and 0.4 D/M, respectively. The residual deuterium preferred the deuterium site in the MgZn2-type cell