A Synthetic Na-Rich Mica: Synthesis and Characterization by 27Al and 29Si Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy

Sridhar Komarneni1, Rajyalakshmi Pidugu1, W. Hoffbauer2 and Hartmut Schneider3
1 Department of Agronomy and Materials Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
2 Institute of Inorganic Chemistry, University of Bonn, D-53121 Bonn, Germany
3 Ceramic Department, Institute of Materials Research, German Aerospace Research Establishment-DLR, D-51170, Koln, Germany

Abstract: A swelling mica, Na2Mg3(Al2Si2)O10F2·xH2O, (hereafter “Na-4 mica”) was synthesized from metakaolinite + MgO and Mg aluminosilicate gels at different temperatures and durations using NaF flux. The various samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and 27Al and 29Si magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The results showed that phase-pure Na-4 mica was obtained from metakaolinite which serves as a cost-effective aluminosilicate source. 27Al MAS NMR spectra showed that all or nearly all Al is in tetrahedral coordination whereas 29Si MAS NMR spectra showed that the nearest neighbor environment of Si is mainly Si(3Al), as expected based on the Si:Al ratio.

Key Words: KGa-1 • MAS NMR Spectroscopy • Metakaolinite • Mica • Na Mica • Synthetic Clay Mineral

Clays and Clay Minerals; August 1999 v. 47; no. 4; p. 410-416; DOI: 10.1346/CCMN.1999.0470403
© 1999, The Clay Minerals Society
Clay Minerals Society (www.clays.org)