Real-time observation of hydrogen absorption by LaNi5 with quasi-dynamic neutron tomography

The uptake of hydrogen by lanthanum pentanickel (LaNi5) to form lanthanum nickel hydride (LaNi5H6) is followed with three-dimensional imaging by neutron tomography. The hydrogen absorption process is slower than the time needed for acquiring a single radiograph, about 10 s, but fast relative to the time to acquire a fully-sampled tomographic data set, about 6000 s. A novel data acquisition scheme is used with angles based upon the Greek Golden ratio, a scheme which allows considerable flexibility in post-acquisition tomography reconstruction. Even with tomographic undersampling, the granular structure for the conversion of LaNi5 particles to LaNi5H6 particles is observed and visually tracked in 3D. Over the course of five sequential hydrogen uptake runs with various initial hydrogen pressures, some grains are repeatedly observed.