Mechanochemical Changes in the Structure of Layered Silicates according to 27Al and 29Si NMR Data

Mechanochemical Changes in the Structure of Layered Silicates according to 27Al and 29Si NMR Data Russian Journal of Applied Chemistry, Vol. 78, No. 2, 2005, p. 339. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005, p. 344. Original Russian Text Copyright 2005 by Pashchenko. BRIEF COMMUNICATIONS Mechanochemical Changes in the Structure of Layered Silicates 27 29 according to Al and Si NMR Data E. A. Pashchenko Kiev National University of Technology and Design, Kiev, Ukraine Received July 20, 2004 27 29 Abstract Mechanochemical structural changes in layered silicates were studied by Al and Si NMR spectroscopy. Layered silicates and, in particular, pyrophyllite isting Si O Al bonds are for the most part preserved in the deformed structure of pyrophyllite. and montmorillonite, are widely used in manufacture of radio- and electroceramics [1] and as sorbents and The study demonstrated that the structure of mont- various fillers [2]. Their use in some fields involves morillonite more readily undergoes profound changes preliminary dispersion [3]. in the course of mechanical treatment, compared with 27 29 that of pyrophyllite. For example, it was found that In this study, Al and Si NMR spectroscopy was changes in the Si NMR spectra are similar to those used to examine changes in the coordination state of for pyrophyllite, but occur upon a more prolonged aluminum and silicon ions in pyrophyllite and mont- treatment. However, changes in the Al NMR spec- morillonite upon a mechanical activation. tra have a different nature. For example, similarly to As objects of study served natural zeolites: mor- the spectra of the initial sample, spectra of activated denite and clinoptilolite. Air-dry samples were acti- montmorillonite show two signals with close to vated by dispersion in a mechanical agate mortar for the initial values. The intensity of the signal at = 27 29 20 120 min. The Al and Si NMR spectra were 50 ppm in these spectra markedly increases upon ac- obtained on a Bruker CXP-200 spectrometer with tivation, which points to a considerable transforma- sample rotation at a magic angle to the external field tion of the octahedral layer, accompanied by a de- 3+ at a frequency of 3 kHz. The chemical shifts were crease in the coordination of Al ions to a tetrahedral 3+ measured relative to the Al(H O) ion and tetra- coordination. 2 6 methylsilane as external standards. REFERENCES It was found that the mechanochemical activation of pyrophyllite causes a strong distortion of alumi- 1. Myagii, M.Ya., Samoson, A.V., Tarmak, M.Kh., et al., num- and silicon-oxygen polyhedra, which leads to Dokl. Akad. Nauk SSSR, 1981, vol. 261, no. 5, broadening of signals at 1 ppm (octahedral oxygen pp. 1169 1173. configuration) and 94 ppm (tetrahedral oxygen config- 2. Stepanov, V.G., Shubin, A.A., Ione, K.G., et al., Kinet. 27 29 uration), respectively, in Al and Si NMR spectra. Kataliz, 1984, vol. 25, no. 5, pp. 1225 1227. However, the positions of the peaks in the spectra do 3. Goncharuk, V.V., Kornilovich, B.Yu., Pavlenko, B.M., not change noticeably even upon a mechanochemical et al., Khim. Tekhnol. Vody, 2001, vol. 23, no. 4, treatment of a sample for 1 h. This means that the ex- pp. 410 415. 1070-4272/05/7802-0339 2005 Pleiades Publishing, Inc. Russian Journal of Applied Chemistry Springer Journals

Mechanochemical Changes in the Structure of Layered Silicates according to 27Al and 29Si NMR Data

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Copyright © 2005 by MAIK “Nauka/Interperiodica”
Chemistry; Chemistry/Food Science, general; Industrial Chemistry/Chemical Engineering
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