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Publisher: Basel : MDPI × Subject: Transmission electron microscopy ×

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Now showing 1 - 2 of 2
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    New Insight on the Hydrogen Absorption Evolution of the Mg–Fe–H System under Equilibrium Conditions
    (Basel : MDPI, 2018-11-19) Puszkiel, Julián; Castro Riglos, M. Victoria; Ramallo-López, José; Mizrahi, Martin; Gemming, Thomas; Pistidda, Claudio; Arneodo Larochette, Pierre; Bellosta von Colbe, José; Klassen, Thomas; Dornheim, Martin; Gennari, Fabiana
    Mg2FeH6 is regarded as potential hydrogen and thermochemical storage medium due to its high volumetric hydrogen (150 kg/m3) and energy (0.49 kWh/L) densities. In this work, the mechanism of formation of Mg2FeH6 under equilibrium conditions is thoroughly investigated applying volumetric measurements, X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), and the combination of scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectroscopy (EDS) and high-resolution transmission electron microscopy (HR-TEM). Starting from a 2Mg:Fe stoichiometric powder ratio, thorough characterizations of samples taken at different states upon hydrogenation under equilibrium conditions confirm that the formation mechanism of Mg2FeH6 occurs from elemental Mg and Fe by columnar nucleation of the complex hydride at boundaries of the Fe seeds. The formation of MgH2 is enhanced by the presence of Fe. However, MgH2 does not take part as intermediate for the formation of Mg2FeH6 and acts as solid-solid diffusion barrier which hinders the complete formation of Mg2FeH6. This work provides novel insight about the formation mechanism of Mg2FeH6.
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    Process induced skin-core morphology in injection molded polyamide 66
    (Basel : MDPI, 2020) Spoerer, Yvonne; Androsch, René; Jehnichen, Dieter; Kuehnert, Ines
    Polyamide 66 (PA 66) was injection-molded to obtain samples with a structure gradient between skin and core, as it was revealed by analysis of the semi-crystalline morphology using polarized-light optical microscopy (POM). Wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) were employed to characterize thin sections with a thickness in the order of magnitude of 50 µm, allowing detection of crystals of different perfection, as a function of the distance from the surface. It was found that the transparent and non-spherulitic skin layer contains rather imperfect α-crystals while the perfection of α-crystals continuously increases with extending distance from the surface. Since variation of the molding conditions allows tailoring the skin-core morphology, the present study was performed to suggest a reliable route to map the presence of specific semi-crystalline morphologies in such samples