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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 138 (Mar. 2008), p. 63-70 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Hydrogen is suggested as a promising fuel of the near future for the utilization inautomotive and mobile applications. Therefore, safe and effective hydrogen storage systems need tobe developed. One of the possibilities, suitable especially for mobile applications, is the storage ofhydrogen in the form of light-metal hydrides. In this work we studied microstructure and hydrogenabsorption and desorption kinetics in selected Mg-Ni alloys. Hydrogen saturation was carried out bythe cathodic polarization in alkaline water-based solution. It was confirmed that hydrogen could bestored in the Mg2Ni intermetallic phase forming Mg2NiH0.3 phase using this technology. MgH2hydride is also formed when the temperature of 90 °C is applied. The total content of hydrogen inthe material after saturation is approx. 0.7 wt. % according to the thermogravimetry analysis. Thislow value is caused probably by the surface oxidation, blocking further hydrogen diffusion. Thermalhydrogen desorption tests showed that the Mg2NiH0.3 phase is able to release hydrogen even attemperatures lower than 100 °C
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 138 (Mar. 2008), p. 145-152 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Aluminium-chromium based alloys are promising candidates for manufacture of lightcomponents exposed to elevated temperatures. The work describes properties of Al-6.0wt.%Cr-2.1wt.%Fe-0.5wt.%Ti alloy. The rapidly solidified powder was prepared by the pressure nitrogenmelt atomization. The powder was then subject to heat treatment in order to investigate solid statephase transformations. Compaction of the powder was carried out by hot extrusion after preheatingat 450 °C. Microstructure, phase composition and structural transformations on heat treatment wereinvestigated in the as-atomized powder, as well as in the as-extruded alloy. It is found thatmetastable state of the rapidly solidified powder is characterized by presence of quasi-crystallinephases and supersaturated solid solution. Heating before and during the hot extrusion inducesdecomposition of the supersaturated solid solution and quasicrystalline to crystalline phasetransformations. The hot extruded alloy has a refined recrystallized structure that remains verystable aven after long-term annealing at 400 °C. Mechanical properties of the extruded alloy arediscussed in terms of strengthening mechanisms
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 567-568 (Dec. 2007), p. 217-220 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Hydrogen is the promising pollutant-free fuel of the near future. For various hydrogenapplications, suitable storage systems have to be developed. One of the safe ways is the reversiblestorage of hydrogen in the form of light metal (lithium or magnesium) hydrides. MgH2 magnesiumhydride shows very high storage capacity (approx. 7 wt. %), but its problem is high thermodynamicstability. Therefore, high temperature (over 400°C) is necessary for MgH2 to decompose producinghydrogen. The solution of this problem can be the utilization of the complex magnesium hydridescontaining nickel, copper or other transition metals.In this work, the microstructure and hydrogen storage properties of the various magnesium alloys(Mg-Ni, Mg-Zn, Mg-Cu and Mg-Cu-Al) are described. The aim was to find suitable hydrogenstorage system with good storage capacity and sufficient rate of formation and decomposition ofhydrides. Microstructure, chemical and phase composition of the alloys were determined by thelight and scanning electron microscopy, EDS and XRD. Hydrogen saturation was carried out bycathodic polarization in the alkaline solution. Hydrogen content in the material was estimated byXRD from the shift of the diffraction lines of present phases
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 519-521 (July 2006), p. 389-394 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Rapidly solidified (RS) Al-TM (TM = transition metal) alloys are perspectivematerials from scientific, as well as technological point of view. Generally, they are producedby the melt atomization or by the melt spinning. Subsequent compaction is commonlyperformed by the hot extrusion. Since transition metals, such as Cr, Fe, Ni, Zr, Ti, Mn andothers, have low diffusion coefficients in solid aluminium (lower by several orders ofmagnitude than those of common alloying elements like Cu, Si, Mg, Zn etc.) the RS Al-TMalloys are characterized by a high thermal stability. In this paper, several RS Al-TM(TM = Cr, Fe, Ti, Mn, Ni) alloys prepared by the melt spinning and melt atomization arecompared to commercially available 2xxx, 6xxx and 7xxx wrought alloys. The mainstructural features of both RS and wrought alloys are described. The RS alloys arecharacterized by the presence of micro and nano-scale crystalline and/or quasi-crystallinephases and supersaturated solid solutions. The elevated-temperature behaviour is comparedfor both groups of materials. The thermal stability of the investigated materials is determinedby room temperature hardness measurements after various annealing regimes and a highthermal stability of the RS alloys is demonstrated. The microstructural changes and phasetransformations occurring in the investigated materials upon heating are described. In theAl-TM alloys, very slow decomposition of the supersaturated solid solutions, precipitationand decomposition of the metastable quasi-crystalline phases occur
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 567-568 (Dec. 2007), p. 197-200 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In the presented paper, properties of Al-Cr-Fe-Ti alloy produced by powder metallurgy(PM) are described. Rapidly solidified powder alloy was prepared by the pressure nitrogen meltatomization. The granulometric powder fraction of less than 45 μm was then hot-extruded.Microstructure of the as-extruded material comprised recrystallized α-Al grains and spheroids ofintermetallic phases. Tensile strength of the investigated material was similar to that of aconventional casting Al-Si alloy commonly used in elevated temperature applications. Excellentthermal stability of the PM Al-Cr based material, which much exceeded the elevated temperaturecasting alloy, was proved by room temperature tensile tests after long-term annealing at elevatedtemperature. Reasons for the observed thermal stability of the investigated PM alloy are discussed
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 482 (Apr. 2005), p. 243-246 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The paper describes a positive influence of silicon on the high-temperature oxidationresistance of titanium. Since silicon additions can be realized both by bulk and by surface alloying, the surface siliconizing techniques, as well as structure of the Si-rich layers, are illustrated. Furthermore, the high-temperature cyclic oxidation resistance of the surface siliconized titanium and of the TiSi2 alloy are compared to that of pure Ti and TiAl6V4 alloy, and the oxidation mechanism is discussed
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 482 (Apr. 2005), p. 219-222 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The paper reports on a detailed investigation of microstructure and phase composition of rapidly solidified and annealed AlNi18.5 and AlNi17Zr1.8 ribbons. The ribbons were prepared by the melt spinning (planar flow casting) technique. The microstructure and phase composition have been studied by TEM and XRD. The specimens were annealed and subsequently subjected to microstructure investigations to asses their thermal stability. Rapidly solidified alloys are composedof a-Al and Al3Ni phase grains. No significant difference in the shape between Al and Al3Ni grains was found. The Al9Ni2 metastable phase was identified in the rapidly solidified AlNi17Zr1.8 alloy and the Al3Zr phase precipitates from the a-Al solid solution in the AlNi17Zr1.8 alloy after the high temperature annealing
    Type of Medium: Electronic Resource
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