Title of Paper:A Comparative Study of Different Amorphous and Paracrystalline Silica by NMR and SEM/EDS

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Date of Publication:2015-10-01

Journal:JOURNAL OF WUHAN UNIVERSITY OF TECHNOLOGY-MATERIALS SCIENCE EDITION

Included Journals:SCIE、EI、ISTIC、Scopus

Volume:30

Issue:5

Page Number:900-907

ISSN No.:1000-2413

Key Words:amorphous and paracrystalline silica; the structure models; NMR; Al-substituted

Abstract:This work aimed to research the structure models of amorphous materials. Five amorphous and paracrystalline samples (natural or artificial) were investigated via Si-29/Al-27 nuclear magnetic resonance (NMR) and field emission scanning electron microscopy/energy dispersive spectroscopy (FE-SEM/EDS). The results of NMR showed the resonances of different specimens: -93.2 ppm, -101.8 ppm, -111.8 ppm for natural pozzolana opal shale (POS). These peaks were assigned to the Q(2)(2OH), Q(3)(OH)/Q(4)(1Al) and Q(4) respectively. The results of Al-27 MAS NMR indicated that Al substituted for Si site in tetrahedral existing in the POS, while the Al/Si atomic ratio in opal was low (around 0.04). For the alkali-silicate-hydrate gel, there were at least three resolved signals assigned to Q(0) and Q(1), respectively. For the fused silica glass powder, there were the primary signals centered about at the range from -107 to -137 ppm, which were assigned to Q(4) units. In addition, the peaks at around -98 and -108 ppm were corresponding to Q(3)(1OH) and Q(4) units existing in aerogel silica structure.