Pressure cells for in situ neutron total scattering: time and real-space resolution during deuterium absorption

Abstract

In situ gas-loading sample holders for two-dimensionally arranged detectors in time-of-flight neutron total scattering experiments have been developed to investigate atomic arrangements during deuterium absorption using time and real-space resolution. A single-crystal sapphire container was developed that allows conditions of 473 K and 10 MPa hydrogen gas pressure. High-resolution transient measurements detected deuterium absorption by palladium that proceeded within a few seconds. A double-layered container with thick- and thin-walled vanadium allowed conditions of 423 K and 10 MPa hydrogen gas pressure. The deuterium occupation sites of a lanthanum–nickel–aluminium alloy are discussed in detail on the basis of real-space high-resolution data obtained from in situ neutron scattering measurements and reverse Monte Carlo structural modeling.

Hydrogen Absorption Reactions of Hydrogen Storage Alloy LaNi5 under High Pressure

“…Thus, the high-pressure experiments on LaNi 5 suggest that its maximum hydrogen storage capacity of LaNi 5 could be 2.07 mass% at 6 GPa, indicating that 33% of the available interstitial sites in LaNi 5 remain unoccupied under practical operating conditions. Although hydrogen atoms in LaNi 5 occupy octahedral sites coordinated by two La and four Ni atoms and tetrahedral sites coordinated by two La and two Ni atoms (see Figure 1 ), a small number of hydrogen atoms in LaNi 5 with Al (LaNi 4.5 Al 0.5 ) occupied other tetrahedral sites, coordinated by one La and three Ni atoms and by four Ni atoms, as reported by atomic pair distribution function analysis [ 30 ]. Therefore, it can be speculated that the hydrogen storage capacities might improve if more hydrogen atoms could occupy the respective tetrahedral sites coordinated by one La, three Ni atoms, and four Ni atoms.…”

“…Among hydrogen storage materials, LaNi 5 -based alloys of the AB 5 alloy type (A and B are typically lanthanides with high hydrogen affinities and transition metals with low hydrogen affinities, respectively) are well-known as practical hydrogen storage materials because of their ability to undergo reversible hydrogen absorption and desorption reactions at room temperature and below 1 MPa of hydrogen gas pressure. Therefore, many studies have investigated the hydrogen storage properties of LaNi 5 -based alloys, including the hydrogen absorption and desorption reaction cycles, crystal structures, microstructures, and morphologies [ 5 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. The crystal structures of LaNi 5 before and after hydrogen absorption are shown in Figure 1 [ 18 , 21 ].…”

Vacancies Introduced during the Crystallization Process of the Glass-Ceramics Superionic Conductor, Na3PS4, Investigated by Neutron Total Scattering and Reverse Monte Carlo Method

“…These trends are consistent with the TEM observation results. 9 In contrast, g(r) is capable of extracting accurate information in the short-range region 52 and can discuss the intrinsic local structure regarding Na and vacancy surroundings. Therefore, RMC structural modeling of a 20 × 20 × 20 superlattice was performed based on the composition determined by PDF refinement to investigate the detailed local structure of the crystalline phase precipitated during the heating process.…”