Microwave irradiation effects on reversible hydrogen desorption in sodium aluminum hydrides (NaAlH4)

Rahul Krishnan, Dinesh Agrawal, Tabbetha Dobbins

    Research output: Contribution to journalArticle

    10 Citations (Scopus)

    Abstract

    The effect of microwave irradiation on the reversible desorption reaction in sodium aluminum hydride (NaAlH4) is explored. NaAlH4 is doped with 2 mol% TiCl2 and pre-activated by high energy ball milling and aging to show the presence of metallic aluminum phase. As a catalyst, Ti2+ has been used to improve desorption kinetics in sodium alanate. X-ray diffraction was performed on the samples exposed to microwave irradiation for 10, 20, 30, 40 and 50 min. Results show that when the powders show the presence of aluminum, a steady increase in the formation of the hexahydride (Na3AlH6) phase and Al occurs during microwave irradiation; and is accompanied by a steady reduction in the NaAlH4 phase XRD peak (h k l) intensities. This data suggests that microwave irradiation drives the reversible H2 desorption reaction in NaAlH4. NaAlH4 doped with 2 mol% TiCl2 which does not show the presence of Al phase, undergoes a reduction in NaAlH4 peak intensities with increasing microwave exposure (and no reversible product phases are detected in this case). Dielectric studies on NaAlH4 indicate that microwave penetration is low. Therefore, it is proposed that microwave irradiation heating of the Al particulate phase is responsible for the hydrogen desorption reaction pathway which is similar to that of conventional heating.

    Original languageEnglish (US)
    Pages (from-to)250-255
    Number of pages6
    JournalJournal of Alloys and Compounds
    Volume470
    Issue number1-2
    DOIs
    StatePublished - Feb 20 2009

    Fingerprint

    Microwave irradiation
    Hydrides
    Hydrogen
    Desorption
    Sodium
    Aluminum
    Microwaves
    Heating
    Ball milling
    Aging of materials
    sodium aluminum hydride
    Powders
    X ray diffraction
    Catalysts
    Kinetics

    All Science Journal Classification (ASJC) codes

    • Mechanics of Materials
    • Mechanical Engineering
    • Metals and Alloys
    • Materials Chemistry

    Cite this

    Krishnan, Rahul ; Agrawal, Dinesh ; Dobbins, Tabbetha. / Microwave irradiation effects on reversible hydrogen desorption in sodium aluminum hydrides (NaAlH4). In: Journal of Alloys and Compounds. 2009 ; Vol. 470, No. 1-2. pp. 250-255.
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    abstract = "The effect of microwave irradiation on the reversible desorption reaction in sodium aluminum hydride (NaAlH4) is explored. NaAlH4 is doped with 2 mol{\%} TiCl2 and pre-activated by high energy ball milling and aging to show the presence of metallic aluminum phase. As a catalyst, Ti2+ has been used to improve desorption kinetics in sodium alanate. X-ray diffraction was performed on the samples exposed to microwave irradiation for 10, 20, 30, 40 and 50 min. Results show that when the powders show the presence of aluminum, a steady increase in the formation of the hexahydride (Na3AlH6) phase and Al occurs during microwave irradiation; and is accompanied by a steady reduction in the NaAlH4 phase XRD peak (h k l) intensities. This data suggests that microwave irradiation drives the reversible H2 desorption reaction in NaAlH4. NaAlH4 doped with 2 mol{\%} TiCl2 which does not show the presence of Al phase, undergoes a reduction in NaAlH4 peak intensities with increasing microwave exposure (and no reversible product phases are detected in this case). Dielectric studies on NaAlH4 indicate that microwave penetration is low. Therefore, it is proposed that microwave irradiation heating of the Al particulate phase is responsible for the hydrogen desorption reaction pathway which is similar to that of conventional heating.",
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    Microwave irradiation effects on reversible hydrogen desorption in sodium aluminum hydrides (NaAlH4). / Krishnan, Rahul; Agrawal, Dinesh; Dobbins, Tabbetha.

    In: Journal of Alloys and Compounds, Vol. 470, No. 1-2, 20.02.2009, p. 250-255.

    Research output: Contribution to journalArticle

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