The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform

Petra E De Jongh - One of the best experts on this subject based on the ideXlab platform.

  • carbon supported lithium hydride nanoparticles impact of preparation conditions on particle size and hydrogen sorption
    International Journal of Hydrogen Energy, 2017
    Co-Authors: Peter L Bramwell, Peter Ngene, Petra E De Jongh
    Abstract:

    Abstract Nanosizing of Light Metal hydrides has yielded significant improvements to their hydrogen storage properties. We explored for the first time a procedure for preparing supported LiH nanoparticles. Impregnation of a carbon framework with a butyllithium solution, followed by reaction with gaseous hydrogen yielded LiH particles ranging in size from 2 nm to the micrometer scale. Reducing the reaction temperature from 300 °C to 100 °C, as well as the use of a t-butyllithium precursor instead of an n-butyllithium precursor, gave significant improvements on the degree of confinement of the LiH particles. The particle size of the LiH has a significant impact on the hydrogen release profile, 11 nm crystallites begin to release hydrogen as low as 100 °C under argon flow, a reduction of roughly 400 °C on the macrocrystalline system. The hydrogen release is reversible, with hydrogen uptake after desorption as high as 7.0 wt% w.r.t. LiH (0.8 wt% w.r.t the sample) under 0.1 bar of hydrogen at 200 °C and full uptake takes place within 5 min at 26 bar. This new preparation procedure for supported Light Metal hydrides is particularly relevant for the field of hydrogen storage.

  • nanoconfined Light Metal hydrides for reversible hydrogen storage
    Mrs Bulletin, 2013
    Co-Authors: Petra E De Jongh, Mark D Allendorf, John J Vajo, Claudia Zlotea
    Abstract:

    Nano-sizing and scaffolding have emerged in the past decade as important strategies to control the kinetics, reversibility, and equilibrium pressure for hydrogen storage in Light Metal hydride systems. Reducing the size of Metal hydrides to the nanometer range allows fast kinetics for both hydrogen release and subsequent uptake. Reversibility of the hydrogen release is impressively facilitated by nanoconfining the materials in a carbon or Metal–organic framework scaffold, in particular for reactions involving multiple solid phases, such as the decomposition of LiBH4, NaBH4, and NaAlH4. More complex is the impact of nanoconfinement on phase equilibria. It is clear that equilibrium pressures, and even decomposition pathways, are changed. However, further experimental and computational studies are essential to understand the exact origins of these effects and to unravel the role of particle size, physical confinement, and interfaces. Nevertheless, it has become clear that nanoconfinement is a strong tool to change physicochemical properties of Metal hydrides, which might not only be of relevance for hydrogen storage, but also for other applications such as rechargeable batteries.

  • the impact of carbon materials on the hydrogen storage properties of Light Metal hydrides
    Journal of Materials Chemistry, 2011
    Co-Authors: Philipp Adelhelm, Petra E De Jongh
    Abstract:

    The safe and efficient storage of hydrogen is still one of the remaining challenges towards fuel cell powered cars. Metal hydrides are a promising class of materials as they allow the storage of large amounts of hydrogen in a small volume at room temperature and low pressures. However, usually the kinetics of hydrogen release and uptake and the thermodynamic properties do not satisfy the requirements for practical applications. Therefore current research focuses on catalysis and the thermodynamic tailoring of Metal hydride systems. Surprisingly, carbon materials used as additive or support are very effective to improve the hydrogen storage properties of Metal hydrides allowing fast kinetics and even a change in the thermodynamic properties. Even though the underlying mechanisms are not always well understood, the beneficial effect is probably related to the peculiar structure of the carbon materials. This feature article gives an introduction to the different carbon materials, an overview of the preparation strategies to synthesize carbon/hydride nanocomposites, and highLights the beneficial effect of carbon by discussing two important hydrides: MgH2 and NaAlH4.

Rainer Gadow - One of the best experts on this subject based on the ideXlab platform.

  • modeling of thermally sprayed coatings on Light Metal substrates layer growth and residual stress formation
    Surface & Coatings Technology, 2004
    Co-Authors: Martin Wenzelburger, Maria Escribano, Rainer Gadow
    Abstract:

    Automotive Lightweight engineering is indispensable for fuel saving and reduction of emissions. The substitution of cast iron engine blocks by Light Metal components yields significant weight savings. Thereby, protective coatings, which can be applied by thermal spraying, are essential for cylinder liner surfaces to resist mechanical and tribological load during operation of the internal combustion engine. Aluminum alloys and ceramic coating materials show a principal mismatch in their thermophysical and mechanical properties. Due to the fast and dynamic heat and mass transfer processes during thermal spraying this leads to the formation of residual stresses in the layer composite. Hence, residual stress analysis and understanding their generation mechanisms are essential for the optimization of the manufacturing process and for the operational reliability of the component. Numerical finite element analysis (FEA) provides the facility to examine stress formation in real-time depending on temporary heat distribution in the component during the manufacturing process. A cylinder liner tube is modeled and an inside coating process with continuous material deposition is simulated. To analyze the influence of heat transfer manipulation during manufacturing, different simultaneous cooling techniques are adopted to the model. Finally, FEA results are verified (or supplemented) by measurements with the microhole drilling and milling method. Combined, this yields a deeper understanding of residual stress formation and a tool for an effective optimization of thermal spray processes.

  • Ceramic matrix- and layer-composites in advanced automobile technology
    Ceramic transactions, 2002
    Co-Authors: Michael Buchmann, Dietmar Scherer, Rainer Gadow, Marcus Speicher
    Abstract:

    Bulk ceramic materials for structural and functional applications have been in the center of interest in R&D and product development of various industries since many years. Even if the technical requirements could be achieved the cost/performance ratio was unsatisfying in many cases. Recent product development in Light weight design and engineering offers a lot of interesting manufacturing and operation features if cost effective composite solutions including ceramic components can be realized. Advanced Light Metal engineering and ceramics must not be competitors or contrary but in an appropriate combination they can excel in production cost, functionality, performance and energy consumption. Ceramic matrix composites with carbon fiber reinforcement can fulfill these requirements for high temperature, structural and friction applications and the same is true if Light Metal substrates can be combined with performing ceramic, cermet, Metallurgical or polymer based surface layers for various machine elements and system components. Protective and functional coatings on Light Metal surfaces can be individually designed. The paper describes manufacturing technologies as well as materials and components characterization results, e. g. high temperature resistant friction materials made from SiC based CMC as well as coating technologies for the deposition of ceramic, Metallurgical and preceramic polymer coatings on various Light Metal substrates. The specific characteristics and advantages of these composites are presented for advanced disk brake technology and full Light Metal motor engineering with a focus on ceramic coated crankcases and cylinder surfaces of combustion engines. In addition, tribologically optimized combined coatings on Light Metal components are introduced. Their tailored surface properties can compete with bulk ceramics and feature with additional characteristics like antiadhesive and dry lubricant ability.

Sean Fudger - One of the best experts on this subject based on the ideXlab platform.

  • residual stress induced mechanical property enhancement in steel encapsulated Light Metal matrix composites
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017
    Co-Authors: Sean Fudger, D Sediako, Prashant Karandikar
    Abstract:

    Abstract Macro hybridized systems consisting of steel encapsulated Metal matrix composites (MMCs) were produced with the goal of creating a low cost/Light weight system with enhanced mechanical properties. The systems exhibit the high strength and modulus commonly expected from steels and high specific stiffness and low density observed in MMCs. The material combination also works to alleviate the high density of steels and the poor ductility of the MMCs. Furthermore, a coefficient of thermal expansion (CTE) mismatch induced residual compressive stress method is utilized to improve the ductility of the MMCs. Systems consisting of an A36 or 304 stainless steel shell with an Al-SiC or Al-Al 2 O 3 shell are evaluated via neutron diffraction to quantify bulk residual stresses. The analysis shows variation in the measured strain due to steel thickness, difference in CTE between materials, and position within the composite. Improvements in ductility and yield stress are a result of these strains.

Kazuyuki Hokamoto - One of the best experts on this subject based on the ideXlab platform.

  • Initiation of Nitromethane Deflagration Promoted by the Oxidation Reaction of Vaporized Metal Wire
    Applications in Energy and Combustion Science, 2020
    Co-Authors: Shigeru Tanaka, Ivan Bataev, Daisuke Inao, Kazuyuki Hokamoto
    Abstract:

    Abstract The rapid construction of rescue routes following natural disasters is of global interest. Nitromethane (NM) is among the proposed means of creating such routes via controlled explosions. However, the use of NM typically requires a highly energetic input when tungsten is employed to initiate deflagration. In this study, a high-current pulse passing through a thin Metal wire was used to initiate the deflagration and heating of NM. We found that Light-Metal elements vaporized by the electrical explosion of a wire chemically reacted with the oxygen in NM, and when the energy density applied to the Light Metal wire increased, NM began the deflagration process via heating within several microseconds. If the Metal wire was partially vaporized, the deflagration reaction began at the point where this occurred because of selective heating. Heating NM with solid or liquid tungsten failed to achieve an instantaneous NM deflagration reaction. The oxidation reaction of vaporized Metal elements was found to accelerate the deflagration of NM. We demonstrated that Al and Mg could successfully replace tungsten in electric-discharge impulse crushing systems, as they have lower energy-input requirements for initiating the deflagration reaction. The heat of the oxidation reaction that initiates NM deflagration can be controlled by varying the diameter of the Light-Metal wire.

Prashant Karandikar - One of the best experts on this subject based on the ideXlab platform.

  • residual stress induced mechanical property enhancement in steel encapsulated Light Metal matrix composites
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017
    Co-Authors: Sean Fudger, D Sediako, Prashant Karandikar
    Abstract:

    Abstract Macro hybridized systems consisting of steel encapsulated Metal matrix composites (MMCs) were produced with the goal of creating a low cost/Light weight system with enhanced mechanical properties. The systems exhibit the high strength and modulus commonly expected from steels and high specific stiffness and low density observed in MMCs. The material combination also works to alleviate the high density of steels and the poor ductility of the MMCs. Furthermore, a coefficient of thermal expansion (CTE) mismatch induced residual compressive stress method is utilized to improve the ductility of the MMCs. Systems consisting of an A36 or 304 stainless steel shell with an Al-SiC or Al-Al 2 O 3 shell are evaluated via neutron diffraction to quantify bulk residual stresses. The analysis shows variation in the measured strain due to steel thickness, difference in CTE between materials, and position within the composite. Improvements in ductility and yield stress are a result of these strains.