VSE knjižnice (vzajemna bibliografsko-kataložna baza podatkov COBIB.SI)
  • Local environment of iron in the mesoporous hexagonal aluminophosphate catalyst
    Novak Tušar, Nataša ...
    Iron-containing hexagonal mesoporous aluminophosphate (FeHMA) was synthesised hydrothermally in a microwave oven in the presence of cetyltrimethylammonium chloride (CTACl) as a template. The local ... environment of aluminium and phosphorus forming the aluminophosphate walls was studied by MAS NMR. The local environment of iron incorporated in HMA was investigated by X-ray absorption spectroscopy (XAS). X-ray absorption near edge structure (XANES) studies showed that iron in the as-synthesised and template-free FeHMA was present predominantly in the form of octahedrally coordinated Fe3+ ions. X-rayabsorption fine structure (EXAFS) analyses confirmed that iron cations inthe as-synthesised and template-free FeHMA were in octahedral coordination with the Fe-O distances of 1.97 . Mössbauer spectroscopy revealed the presenceof octahedrally coordinated Fe3+ and also tetrahedrally coordinated Fe2+ in the template-free FeHMA in the ratio of 4Č1, which could not be detected by XANES. After the thermal treatment of template-free FeHMA at 427 °C in vacuum the Mössbauer spectra showed that almost half of the iron cationspresent in the sample were tetrahedrally coordinated. The framework positions of tetrahedrally coordinated Fe2+ and octahedrally coordinated Fe3+ are suggested.
    Vrsta gradiva - članek, sestavni del
    Leto - 2005
    Jezik - angleški
    COBISS.SI-ID - 3363866