Crystal-size control and characterization of Na-4-mica prepared from kaolinite

T. Kodama, Y. Harada, M. Ueda, K. I. Shimizu, K. Shuto, S. Komarneni, W. Hoffbauer, H. Schneider

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Abstract

A simple and economical method for the synthesis of high-charge-density Na-4-mica (ideal chemical composition of Na4Mg6Al4Si4O20 F4·χH2O) from kaolinite was investigated. Synthesis conditions were varied to control crystal size. This novel swelling Na-4-mica was synthesized from a mixture of kaolinite, magnesium nitrate (or ultrafine MgO) and NaF at 850°C, and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size analysis by laser diffraction and 27Al and 29Si magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. Decreasing the mass of NaF flux during the crystallization of Na-4-mica reduced the crystallite size from 2 to 0.2 μm. As the crystallite size decreased, the average particle size of the mica decreased from 5 to 2 μm. 27Al MAS-NMR spectra showed that all or nearly all Al is in tetrahedral coordination whereas 29Si MAS-NMR spectra showed that the nearest neighbour environment of Si is mainly in Si(3Al), as expected based on the Si:Al ratio.

Original languageEnglish (US)
Pages (from-to)1222-1227
Number of pages6
JournalJournal of Materials Chemistry
Volume11
Issue number4
DOIs
StatePublished - May 1 2001

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Chemistry

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