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Title

Evolution of phases and Al-Si distribution during Na-4-mica synthesis

AuthorsAlba, María D. ; Castro Arroyo, Miguel Ángel ; Naranjo, Moisés; Orta, M. Mar ; Pavón, Esperanza ; Pazos, M. Carolina
Issue Date2011
PublisherAmerican Chemical Society
CitationJournal of Physical Chemistry C 115: 20084- 20090 (2011)
AbstractNa-4-mica, a highly charged fluorophlogopite, has recently attracted much attention because of its unique combination of high charge (four charges per unit cell) and its swelling and cation-exchange properties. The ability to improve the properties of this mica depends on gaining knowledge about its phase evolution during the calcination process. For the synthesis, the stoichiometric powder mixture (4SiO2/2Al2O3/6MgF 2/8NaCl) was heated to 900 °C for 0-600 h. The obtained solids were characterized by X-ray fluorescence (XRF); X-ray diffraction (XRD); scanning electron microscopy/energy-dispersive X-ray (SEM/EDX) analysis; 29Si, 27Al, and 23Na magic-angle-spinning MAS NMR spectroscopy; and thermogravimetric/differential thermal analysis (TG/DTA). The results showed that the precursors are rapidly (t < 3 h) transformed into sodalite, Al6Na8(SiO4)6Cl 2, and a 2:1 phyllosilicate. For t = 7.5 h, the amount of 2:1 phyllosilicate increased as a result of the decomposition of sodalite, with a progressive incorporation of aluminum in the 2:1 phyllosilicate being observed. For t = 7.5 h, synthesis of Na-4-mica was considered to be complete, as the material remained essentially unaltered for the next 15 h. For t = 30 h, the mica started to decompose, and for very long reaction times (t ≥ 300 h), only forsterite and a carnegierite phase were present. © 2011 American Chemical Society.
URIhttp://hdl.handle.net/10261/62628
DOI10.1021/jp207408h
Identifiersdoi: 10.1021/jp207408h
issn: 1932-7447
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