SAXS reveals the magnetic alignment pathway of the goethite columnar liquid crystal phase.

The alignment of board-like colloidal goethite particles in the dense rectangular centred columnar liquid crystal phase in an external magnetic field is studied using small angle X-ray scattering (SAXS). Transient SAXS-patterns show broadening of the columnar reflections in specific directions. While the reflections along the field stay at a constant Q-value, the other reflections do not.

Liquid crystal phase behavior of sterically-stabilized goethite.

The liquid crystalline phase behavior of sterically-stabilized goethite particles in toluene was studied using small-angle X-ray scattering. The results were compared with those from charged particles in water, with and without magnetic field: similarly rich phase behavior was found. Furthermore, the special magnetic properties were retained after coating the particles with amino-functionalized polyisobutylene chains.

Simple rectangular columnar phase of goethite nanorods and its martensitic transition to the centered rectangular columnar phase.

Using high-resolution small-angle X-ray scattering, we observed a new type of the columnar phase with a simple rectangular (R(S)) structure in colloidal goethite dispersions. Furthermore, it displays a martensitic transition into the usual centered rectangular (R(C)) structure in an external magnetic field. The findings are rationalized in terms of entropic effects within a simple cell model.

Size fractionation in a phase-separated colloidal fluid.

Phase separation of a polydisperse colloidal dispersion implies size fractionation. An application of this effect is given by size-selective purification procedures associated with the colloidal synthesis of so-called monodisperse nanoparticles. We used electron microscopy to determine detailed particle size distributions of coexisting colloidal fluid phases containing highly polydisperse iron oxide nanoparticles with a log-normal distribution (sigma = 0.