title: Phase diagram of polydisperse Na-fluorohectorite-water suspensions: a synchrotron small-angle x-ray scattering study.
abstract: 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.
authors.affiliation: Department of Physics, Norwegian University of Science and Technology (NTNU), Trondheim, Norway. fonseca@ntnu.no
authors.forename: D M
authors.initials: DM
authors.lastname: Fonseca
authors.forename: Y
authors.initials: Y
authors.lastname: Méheust
authors.forename: J O
authors.initials: JO
authors.lastname: Fossum
authors.forename: K D
authors.initials: KD
authors.lastname: Knudsen
authors.forename: K P S
authors.initials: KP
authors.lastname: Parmar