Showing papers by "Naoyuki Hashimoto published in 2016"
TL;DR: Experimental and theoretical evidence reveals the catalytic mechanism of Li2TiO3 in LiAlH4, and first principles calculations show the improvement of H- and Li+ mobility by doping Li2 TiO3, where calculations indicate that the physical origin of the catalytical effect is due to two factors: charge transfer and minor surface relaxation.
Abstract: High efficiency catalysts are needed to improve the kinetics of complex hydrides for practical applications. In this study, lithium metatitanate (Li2TiO3) is introduced in lithium alanate (LiAlH4), and the catalytic effect for notable complex/metal hydrides, such as LiAlH4, is investigated. Experiment results indicate that Li2TiO3 improves the kinetics of LiAlH4. In particular, Li2TiO3 dramatically improves the onset temperature of LiAlH4, which decreases to 75 °C and is within the temperature range for use in proton exchange membrane fuel cells. Transmission electron microscopy (TEM) observations help understand the catalytic effect of Li2TiO3 in the nanoscale. First principles calculations also show the improvement of H− and Li+ mobility by doping Li2TiO3, where calculations indicate that the physical origin of the catalytic effect is due to two factors: charge transfer and minor surface relaxation. Thus, experimental and theoretical evidence reveals the catalytic mechanism of Li2TiO3 in LiAlH4.
17 citations
TL;DR: In this article, the effects of metal-based additives in a wide range of elements doping into ammonia borane (AB) were systematically investigated, and a strong correlation between H2 desorption temperature and the Pauling electronegativity of metal (χp) was observed.
Abstract: The effects of metal-based additives in a wide range of elements doping into ammonia borane (AB) were systematically investigated. Pure transition metals in period 4 and total of 17 metal chlorides were selected as additives and ball-milled with AB. Metal chloride additives were effective to decrease H2 desorption temperature and the amounts of byproduct gas emissions of AB, whereas pure transition metals did not show any ability because they did not work as Lewis acids. The strong correlation between H2 desorption temperature and the Pauling electronegativity of metal (χp) was observed. Mn+ of MCln would work as Lewis acid to initiate the AB dehydrocoupling reaction. The amount of NH3 emission was correlated with the ionic radius of M, suggesting MCln·mNH3 complexes be formed in this system. AB–CuCl2 and AB–AgCl mixtures showed the similar H2 desorption processes. The Cl-containing intermediate phase would destabilize AB during reaction.
16 citations
TL;DR: In this article, the authors performed in situ observation of one-dimensional (1D) migration of self-interstitial atom (SIA) clusters in iron under electron irradiation at 110-300 k using highvoltage electron microscopy.
Abstract: We performed in situ observation of one-dimensional (1D) migration of self-interstitial atom (SIA) clusters in iron under electron irradiation at 110–300 K using high-voltage electron microscopy. Most 1D migration was stepwise positional changes of SIA clusters at irregular time intervals at all temperatures. The frequency of 1D migration did not depend on the irradiation temperature. It was directly proportional to the damage rate, suggesting that 1D migration was induced by electron irradiation. In contrast, the 1D migration distance depended on the temperature: distribution of the distance ranged over 100 nm above 250 K, decreased steeply between 250 and 150 K and was less than 20 nm below 150 K. The distance was independent of the damage rate at all temperatures. Next, we examined fluctuation in the interaction energy between an SIA cluster and vacancies of random distribution at concentrations 10−4–10−2, using molecular statics simulations. The fluctuation was found to trap SIA clusters of 4 ...
12 citations
TL;DR: A window type of the environmental cell system for a high-voltage electron microscope was developed and applied to in situ observation of a palladium (Pd) thin film, and the lattice fringes were clearly distinguished and the dislocation behavior during Pd hydrogenation was easily recognized according to the corresponding inverse fast fourier transform images.
Abstract: A window type of the environmental cell system for a high-voltage electron microscope was developed and applied to in situ observation of a palladium (Pd) thin film For in situ hydrogenation of Pd thin films, the distances of the lattice fringes were 020 and 023 nm, which correspond to the lattice d spacings of β-phase (200) and (111) planes Expansion of the Pd lattice happened as a result of phase transformation from the α phase to the β phase In particular, the lattice fringes were clearly distinguished, and the dislocation behavior during Pd hydrogenation was easily recognized according to the corresponding inverse fast fourier transform images Furthermore, significant growth in the number of dislocations was observed at the grain boundary during increasing hydrogen pressure in the cell
11 citations