Factors Affecting the Formation of Quasi-Crystals of Montmorillonite1
- R. S. B. Greene,
- A. M. Posner and
- J. P. Quirk2
Light scattering techniques and the development of flow birefringence by suspensions have been used to follow the rearrangement of elementary silicate sheets of Ca-montmorillonite to form quasi-crystals.
Shaking transforms Ca-montmorillonite particles in a 0.25M CaCl2 suspension from loose, fluffy floccs into stable, compact particles >2.0µ in lateral extent and as much as 20 to 30 layers thick, known as quasi-crystals. Quasi-crystals of similar lateral extent but only four layers thick took longer to form at low electrolyte levels, <10-3M CaCl2, in which more extensive double layers are present. Dialysis of Ca-montmorillonite suspensions also produced quasi-crystals, which are intermediate in thickness between those formed by the above two preparations.
The stability of quasi-crystals was demonstrated by the fact that high energy ultrasonic radiation was required to disrupt their structure.
Sodium montmorillonite suspensions subjected to similar conditions of mechanical agitation and dialysis failed to form quasi-crystals, the only form of aggregation being into unstable floccs.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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