Surface Observation of LaNi₅ under Deuterium Atmosphere Using Small-Angle Neutron Scattering

Abstract

We developed a new sample holder for small-angle neutron scattering (SANS) experiments under controlled atmospheres. Using this new sample holder, SANS profiles of conventional hydrogen-absorbing alloy LaNi₅ under a deuterium atmosphere were measured. Changes in the SANS profile of LaNi₅ were clearly observed during absorption and desorption. It was found that there is reversibility in the surface morphology of LaNi₅; it changed from being markedly rough (fractal dimension of particle surface D_S = 2.8, before deuteration) to smoother (D_S = 2.5 at 1.05 D/M, i.e., LaNi₅D_6.3) during absorption (up to 1 MPa), and then reverted to being rough (D_S = 2.8) during desorption (under vacuum <5 Pa), where D/M is the deuterium-to-metal ratio.