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Microstructural and Swelling Properties of Ca and Na Montmorillonite: (In Situ) Observations with Cryo-TEM and SAXS

Segad, Mo LU ; Hanski, S.; Olsson, Ulf LU ; Ruokolainen, J.; Åkesson, Torbjörn LU and Jönsson, Bo LU (2012) In Journal of Physical Chemistry C 116(13). p.7596-7601
Abstract
Aqueous dispersions of pure sodium and calcium smectite clays with platelet sizes on the order of a few hundred nanometers were characterized using a combination of cryo-transmission electron microscopy (cryo-TEM) and small-angle X-ray scattering (SAXS). With monovalent sodium counterions the clay is dispersed as individual platelets, as seen by cryo-TEM, that order into a nematic phase. From SAXS a one-dimensional swelling of the day in water is observed with the characteristic spacing h(s) = delta/phi(c), where h(s) is the separation between the platelets, delta = 1 nm is the effective platelet thickness, and phi(c) is the clay volume fraction in the sample. In calcium montmorillonite, on the other hand, cryo-TEM images dearly show the... (More)
Aqueous dispersions of pure sodium and calcium smectite clays with platelet sizes on the order of a few hundred nanometers were characterized using a combination of cryo-transmission electron microscopy (cryo-TEM) and small-angle X-ray scattering (SAXS). With monovalent sodium counterions the clay is dispersed as individual platelets, as seen by cryo-TEM, that order into a nematic phase. From SAXS a one-dimensional swelling of the day in water is observed with the characteristic spacing h(s) = delta/phi(c), where h(s) is the separation between the platelets, delta = 1 nm is the effective platelet thickness, and phi(c) is the clay volume fraction in the sample. In calcium montmorillonite, on the other hand, cryo-TEM images dearly show the presence of tactoids, where the platelets have aggregated into stacks with a periodic spacing of 2 nm. From imaging a large number of tactoids the distribution function f(N) far the number of platelets per tactoid was estimated, and the average number (N) approximate to 10. The characteristic 2 nm spacing as well as the small number of platelets per tactoid was also confirmed by SAXS. The present study demonstrates that cryo-TEM, with carefully prepared specimen, is a very useful technique to characterize clay dispersions, particularly in aggregated systems. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Physical Chemistry C
volume
116
issue
13
pages
7596 - 7601
publisher
The American Chemical Society
external identifiers
  • wos:000302336700046
  • scopus:84859576029
ISSN
1932-7447
DOI
10.1021/jp300531y
language
English
LU publication?
yes
id
93e58ec2-3224-43cd-be66-9f0961bd67d4 (old id 2587529)
date added to LUP
2012-05-30 16:33:02
date last changed
2017-09-24 03:25:32
@article{93e58ec2-3224-43cd-be66-9f0961bd67d4,
  abstract     = {Aqueous dispersions of pure sodium and calcium smectite clays with platelet sizes on the order of a few hundred nanometers were characterized using a combination of cryo-transmission electron microscopy (cryo-TEM) and small-angle X-ray scattering (SAXS). With monovalent sodium counterions the clay is dispersed as individual platelets, as seen by cryo-TEM, that order into a nematic phase. From SAXS a one-dimensional swelling of the day in water is observed with the characteristic spacing h(s) = delta/phi(c), where h(s) is the separation between the platelets, delta = 1 nm is the effective platelet thickness, and phi(c) is the clay volume fraction in the sample. In calcium montmorillonite, on the other hand, cryo-TEM images dearly show the presence of tactoids, where the platelets have aggregated into stacks with a periodic spacing of 2 nm. From imaging a large number of tactoids the distribution function f(N) far the number of platelets per tactoid was estimated, and the average number (N) approximate to 10. The characteristic 2 nm spacing as well as the small number of platelets per tactoid was also confirmed by SAXS. The present study demonstrates that cryo-TEM, with carefully prepared specimen, is a very useful technique to characterize clay dispersions, particularly in aggregated systems.},
  author       = {Segad, Mo and Hanski, S. and Olsson, Ulf and Ruokolainen, J. and Åkesson, Torbjörn and Jönsson, Bo},
  issn         = {1932-7447},
  language     = {eng},
  number       = {13},
  pages        = {7596--7601},
  publisher    = {The American Chemical Society},
  series       = {Journal of Physical Chemistry C},
  title        = {Microstructural and Swelling Properties of Ca and Na Montmorillonite: (In Situ) Observations with Cryo-TEM and SAXS},
  url          = {http://dx.doi.org/10.1021/jp300531y},
  volume       = {116},
  year         = {2012},
}