1070-4272/05/7802-0339 + 2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 2, 2005, p. 339. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005,
Original Russian Text Copyright + 2005 by Pashchenko.
Mechanochemical Changes in the Structure of Layered Silicates
Si NMR Data
E. A. Pashchenko
Kiev National University of Technology and Design, Kiev, Ukraine
Received July 20, 2004
Abstract-Mechanochemical structural changes in layered silicates were studied by
Layered silicates and, in particular, pyrophyllite
and montmorillonite, are widely used in manufacture
of radio- and electroceramics  and as sorbents and
various fillers . Their use in some fields involves
preliminary dispersion .
In this study,
Si NMR spectroscopy was
used to examine changes in the coordination state of
aluminum and silicon ions in pyrophyllite and mont-
morillonite upon a mechanical activation.
As objects of study served natural zeolites: mor-
denite and clinoptilolite. Air-dry samples were acti-
vated by dispersion in a mechanical agate mortar for
203120 min. The
Si NMR spectra were
obtained on a Bruker CXP-200 spectrometer with
sample rotation at a magic angle to the external field
at a frequency of ~3 kHz. The chemical shifts were
measured relative to the Al(H
ion and tetra-
methylsilane as external standards.
It was found that the mechanochemical activation
of pyrophyllite causes a strong distortion of alumi-
num- and silicon-oxygen polyhedra, which leads to
broadening of signals at d 1 ppm (octahedral oxygen
configuration) and 94 ppm (tetrahedral oxygen config-
uration), respectively, in
Si NMR spectra.
However, the positions of the peaks in the spectra do
not change noticeably even upon a mechanochemical
treatment of a sample for 1 h. This means that the ex-
isting Si3O3Al bonds are for the most part preserved
in the deformed structure of pyrophyllite.
The study demonstrated that the structure of mont-
morillonite more readily undergoes profound changes
in the course of mechanical treatment, compared with
that of pyrophyllite. For example, it was found that
changes in the
Si NMR spectra are similar to those
for pyrophyllite, but occur upon a more prolonged
treatment. However, changes in the
Al NMR spec-
tra have a different nature. For example, similarly to
the spectra of the initial sample, spectra of activated
montmorillonite show two signals with d close to
the initial values. The intensity of the signal at d =
50 ppm in these spectra markedly increases upon ac-
tivation, which points to a considerable transforma-
tion of the octahedral layer, accompanied by a de-
crease in the coordination of Al
ions to a tetrahedral
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