The Experts below are selected from a list of 165 Experts worldwide ranked by ideXlab platform
L A Collins - One of the best experts on this subject based on the ideXlab platform.
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transport properties of Lithium Hydride from quantum molecular dynamics and orbital free molecular dynamics
Physical Review B, 2009Co-Authors: D A Horner, J D Kress, Flavien Lambert, L A CollinsAbstract:We have performed a systematic study of Lithium Hydride in the warm-dense-matter regime for a density range from one to four times ambient solid and for temperatures from 2 to 6 eV using both finite-temperature density-functional theory quantum molecular dynamics (QMD) and orbital-free molecular dynamics (OFMD) with a focus on dynamical properties such as diffusion and viscosity. The validity of various mixing rules, especially those utilizing pressure, were checked for composite properties determined from QMD/OFMD simulations of the pure species against calculations on the fully interacting mixture. These rules produce pressures within about 10% of the full-mixture values but mutual-diffusion coefficients as different as 50%. We found very good agreement overall between the QMD, employing a three-electron pseudopotential, and the OFMD in the local-density approximation, especially at the higher temperatures and densities.
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quantum molecular dynamics simulations of warm dense Lithium Hydride examination of mixing rules
Physical Review B, 2008Co-Authors: D A Horner, J D Kress, L A CollinsAbstract:We have performed a systematic study of Lithium Hydride (LiH) in a density range from half to twice solid for temperatures from 0.5 to 3.0 eV using quantum molecular dynamics (QMD) methods and have tested density and pressure mixing rules for obtaining equations of state and optical properties such as frequency-dependent absorption coefficients and Rosseland mean opacities. The QMD simulations for the full LiH fluid served as a benchmark against which to assess the rules. In general, the mixing rule based on the pressure matching produces superior equations of state and mean opacities for the mixture except at the very lowest temperatures and densities. However, the frequency-dependent absorption coefficients displayed considerable differences in some frequency ranges except at the highest temperatures and densities.
D A Horner - One of the best experts on this subject based on the ideXlab platform.
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transport properties of Lithium Hydride from quantum molecular dynamics and orbital free molecular dynamics
Physical Review B, 2009Co-Authors: D A Horner, J D Kress, Flavien Lambert, L A CollinsAbstract:We have performed a systematic study of Lithium Hydride in the warm-dense-matter regime for a density range from one to four times ambient solid and for temperatures from 2 to 6 eV using both finite-temperature density-functional theory quantum molecular dynamics (QMD) and orbital-free molecular dynamics (OFMD) with a focus on dynamical properties such as diffusion and viscosity. The validity of various mixing rules, especially those utilizing pressure, were checked for composite properties determined from QMD/OFMD simulations of the pure species against calculations on the fully interacting mixture. These rules produce pressures within about 10% of the full-mixture values but mutual-diffusion coefficients as different as 50%. We found very good agreement overall between the QMD, employing a three-electron pseudopotential, and the OFMD in the local-density approximation, especially at the higher temperatures and densities.
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quantum molecular dynamics simulations of warm dense Lithium Hydride examination of mixing rules
Physical Review B, 2008Co-Authors: D A Horner, J D Kress, L A CollinsAbstract:We have performed a systematic study of Lithium Hydride (LiH) in a density range from half to twice solid for temperatures from 0.5 to 3.0 eV using quantum molecular dynamics (QMD) methods and have tested density and pressure mixing rules for obtaining equations of state and optical properties such as frequency-dependent absorption coefficients and Rosseland mean opacities. The QMD simulations for the full LiH fluid served as a benchmark against which to assess the rules. In general, the mixing rule based on the pressure matching produces superior equations of state and mean opacities for the mixture except at the very lowest temperatures and densities. However, the frequency-dependent absorption coefficients displayed considerable differences in some frequency ranges except at the highest temperatures and densities.
Steven Dubowsky - One of the best experts on this subject based on the ideXlab platform.
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a passive Lithium Hydride based hydrogen generator for low power fuel cells for long duration sensor networks
International Journal of Hydrogen Energy, 2014Co-Authors: Daniel Strawser, Jekanthan Thangavelautham, Steven DubowskyAbstract:This paper focuses on developing an efficient fuel storage and release method for hydrogen using Lithium Hydride hydrolysis for use in PEM fuel cells for low power sensor network modules over long durations. Lithium Hydride has high hydrogen storage density and achieves up to 95e100% yield. It is shown to extract water vapor freely from the air to generate hydrogen and has a theoretical fuel specific energy of up to 4900 Wh/kg. A critical challenge is how to package Lithium Hydride to achieve reaction completion. Experiments here show that thick layers of Lithium Hydride nearly chokes the reaction due to buildup of Lithium hydroxide impeding water transport and preventing reaction completion. A model has been developed that describes this Lithium Hydride hydrolysis behavior. The model accurately predicts the performance of an experimental system than ran for 1400 h and consists of a passive Lithium Hydride hydrogen generator and PEM fuel cells. These results offer important design guidelines to enable reaction completion and build long-duration
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Lithium Hydride powered pem fuel cells for long duration small mobile robotic missions
International Conference on Robotics and Automation, 2012Co-Authors: Jekanthan Thangavelautham, Daniel Strawser, Mei Yi Cheung, Steven DubowskyAbstract:This paper reports on a study to develop power supplies for small mobile robots performing long duration missions. It investigates the use of fuel cells to achieve this objective, and in particular Proton Exchange Membrane (PEM) fuel cells. It is shown through a representative case study that, in theory, fuel cell based power supplies will provide much longer range than the best current rechargeable battery technology. It also briefly discusses an important limitation that prevents fuel cells from achieving their ideal performance, namely a practical method to store their fuel (hydrogen) in a form that is compatible with small mobile field robots. A very efficient fuel storage concept based on water activated Lithium Hydride (LiH) is proposed that releases hydrogen on demand. This concept is very attractive because water vapor from the air is passively extracted or waste water from the fuel cell is recycled and transferred to the Lithium Hydride where the hydrogen is “stripped” from water and is returned to the fuel cell to form more water. This results in higher hydrogen storage efficiencies than conventional storage methods. Experimental results are presented that demonstrate the effectiveness of the approach.
J D Kress - One of the best experts on this subject based on the ideXlab platform.
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transport properties of Lithium Hydride from quantum molecular dynamics and orbital free molecular dynamics
Physical Review B, 2009Co-Authors: D A Horner, J D Kress, Flavien Lambert, L A CollinsAbstract:We have performed a systematic study of Lithium Hydride in the warm-dense-matter regime for a density range from one to four times ambient solid and for temperatures from 2 to 6 eV using both finite-temperature density-functional theory quantum molecular dynamics (QMD) and orbital-free molecular dynamics (OFMD) with a focus on dynamical properties such as diffusion and viscosity. The validity of various mixing rules, especially those utilizing pressure, were checked for composite properties determined from QMD/OFMD simulations of the pure species against calculations on the fully interacting mixture. These rules produce pressures within about 10% of the full-mixture values but mutual-diffusion coefficients as different as 50%. We found very good agreement overall between the QMD, employing a three-electron pseudopotential, and the OFMD in the local-density approximation, especially at the higher temperatures and densities.
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quantum molecular dynamics simulations of warm dense Lithium Hydride examination of mixing rules
Physical Review B, 2008Co-Authors: D A Horner, J D Kress, L A CollinsAbstract:We have performed a systematic study of Lithium Hydride (LiH) in a density range from half to twice solid for temperatures from 0.5 to 3.0 eV using quantum molecular dynamics (QMD) methods and have tested density and pressure mixing rules for obtaining equations of state and optical properties such as frequency-dependent absorption coefficients and Rosseland mean opacities. The QMD simulations for the full LiH fluid served as a benchmark against which to assess the rules. In general, the mixing rule based on the pressure matching produces superior equations of state and mean opacities for the mixture except at the very lowest temperatures and densities. However, the frequency-dependent absorption coefficients displayed considerable differences in some frequency ranges except at the highest temperatures and densities.
Takayuki Ichikawa - One of the best experts on this subject based on the ideXlab platform.
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kinetic modification on hydrogen desorption of Lithium Hydride and magnesium amide system
Materials, 2015Co-Authors: Hiroki Miyaoka, Takayuki Ichikawa, Shigehito Isobe, Satoshi Hino, Yongming Wang, Kazuhiko Tokoyoda, Yoshitsugu KojimaAbstract:Various synthesis and rehydrogenation processes of Lithium Hydride (LiH) and magnesium amide (Mg(NH2)2) system with 8:3 molar ratio are investigated to understand the kinetic factors and effectively utilize the essential hydrogen desorption properties. For the hydrogen desorption with a solid-solid reaction, it is expected that the kinetic properties become worse by the sintering and phase separation. In fact, it is experimentally found that the low crystalline size and the close contact of LiH and Mg(NH2)2 lead to the fast hydrogen desorption. To preserve the potential hydrogen desorption properties, thermochemical and mechanochemical rehydrogenation processes are investigated. Although the only thermochemical process results in slowing the reaction rate due to the crystallization, the ball-milling can recover the original hydrogen desorption properties. Furthermore, the mechanochemical process at 150 °C is useful as the rehydrogenation technique to preserve the suitable crystalline size and mixing state of the reactants. As a result, it is demonstrated that the 8LiH and 3Mg(NH2)2 system is recognized as the potential hydrogen storage material to desorb more than 5.5 mass% of H2 at 150 °C.
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improvement of reaction kinetics by metal chloride on ammonia and Lithium Hydride system
International Journal of Hydrogen Energy, 2012Co-Authors: Hiroki Miyaoka, Takayuki Ichikawa, H Fujii, Hikaru Yamamoto, Satoshi Hino, Haruyuki Nakanishi, Yoshitsugu KojimaAbstract:Abstract Ammonia NH3 and Lithium Hydride LiH system releases hydrogen even at room temperature to form Lithium amide LiNH2. LiNH2 is recycled back to NH3 and LiH below 300 °C under hydrogen H2 flow condition. However, the reaction rate of the system is slow for a practical application. In this work, various kinds of transition metal chlorides were examined as a potential catalyst to improve the kinetics. For hydrogen desorption reaction, the reaction kinetics of titanium chloride TiCl3 dispersing LiH was about 8 times faster than the raw LiH, suggesting that TiCl3 possessed an excellent catalytic effect. In the case of the regeneration reaction, the reaction kinetics was also improved by the addition of TiCl3. It was mainly caused by physical effects in contrast to the hydrogen desorption process, in other words, the small crystallite and/or particle were formed by the milling with the additive.
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rechargeable hydrogen storage in nanostructured mixtures of hydrogenated carbon and Lithium Hydride
Applied Physics Letters, 2005Co-Authors: Takayuki Ichikawa, H Fujii, Shigehito Isobe, Koji NabetaAbstract:A hydrogen storage ability caused by the interaction between nanostructured carbon (CnanoHx) and Lithium Hydride (LiH) is demonstrated, which should be recognized as Li-C-H system in the H-storage materials. Especially, the 2:1 mixture of CnanoHx and LiH exhibited promising hydrogen storage properties with a rechargeable hydrogen capacity of more than 4 mass% below 350 °C, preserving the nanostructural feature in the mixture even after hydrogen release. On the other hand, the 1:2 and 1:1 mixtures exhibited the crystal growth of Li2C2 after hydrogen desorption, leading to poorer hydrogen rechargeability.