K. Numata and K. Sato
Abstract—The rheological mechanism of long-term
self-assembly caused by H2O molecules is highlighted for
layered saponite nanoparticles based on the results of
positronium (Ps) annihilation spectroscopy and
thermogravimetry and differential thermal analysis (TG-DTA).
A-type zeolite powder of typical cage material is also
investigated to compare with the layered material. Prior to
self-assembly, saponite nanoparticles exhibit two kinds of local
molecular structures, where one and two nanosheets are
inserted into interlayer spaces forming open spaces with their
sizes of ~ 3 Å and ~ 9 Å, respectively. The angstrom-scale open
spaces for the saponite vary in the time scale of ~ 100 h much
longer than that of TG-DTA of ~ 8 h. The long-term molecular
dynamics probed by Ps annihilation spectroscopy originates
from the self-assembly of saponite nanoparticles. It is found that
the self-assembly of layered saponite nanoparticles is
accelerated with increasing the humidity from 35 % to 70 %
owing to the formation of two-layer hydration. The present
results demonstrate that the long-term self assembly originates
from the layered structures together with H2O molecules on the
layer surfaces.
Index Terms—Clay mineral, positronium, nanosheet, local
molecular structure, open spaces.
The authors are with Department of Environmental Sciences, Tokyo
Gakugei University, 4-1-1 Koganei, Tokyo 184-8501, Japan (e-mail:
m121817m@st.u-gakugei.ac.jp; sato-k@u-gakugei.ac.jp).
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Cite:K. Numata and K. Sato, "Self- Assembly of Saponite Nanoparticles Influenced by Interlayer H2O Molecules," International Journal of Environmental Science and Development vol. 4, no. 6, pp. 633-636, 2013.
