期刊名称：International Journal of Environmental Science and Development
印刷版ISSN：2010-0264
出版年度：2013
卷号：4
期号：6
页码：633-636
DOI：10.7763/IJESD.2013.V4.428
摘要：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.
关键词：Clay mineral; positronium; nanosheet; local molecular structure; open spaces
