Phase diagram of polydisperse Na-fluorohectorite­water suspensions: A synchrotron small-angle x-ray scattering study

D.M. Fonseca (1) , Yves Méheust (1, 2) , Jon Fossum (1) , Kenneth Knudsen (3) , K.P.S. Parmar (1)

1 Physics NTNU - Department of Physics [Trondheim]
2 GR - Géosciences Rennes
3 Institute for Energy Technology

Systems of platelet-shaped nanostacks of the synthetic clay Na-fluorohectorite, suspended in saline solutions of various salt concentrations, exhibit a rich phase behavior with up to four phases coexisting in a single sample tube. They are studied here using small-angle x-ray scattering: the anisotropy of the obtained images is quantified, and, together with x-ray absorption measurements, this provides a precise determination of the phase boundaries, as well as a measure of the orientational ordering of the clay colloids in the various gel phases. The coexistence of different phases results from a sedimentation-induced vertical gradient in particle fraction. Quantitative relation of the vertical coordinate to the clay particle fraction in these samples allows determination of a phase diagram for these Na-fluorohectorite systems, as a function of the particle fraction and salt concentration.

Domaines: Géochimie

D.M. Fonseca, Yves Méheust, Jon Fossum, Kenneth Knudsen, K.P.S. Parmar. Phase diagram of polydisperse Na-fluorohectorite­water suspensions: A synchrotron small-angle x-ray scattering study. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, 2009, 79 (2), pp.art n°021402. ⟨10.1103/PhysRevE.79.021402⟩. ⟨insu-00381694⟩