Time-resolved X-ray microscopy of nanoparticle aggregates under oscillatory shear.

Of all the current detection techniques with nanometre resolution, only X-ray microscopy allows imaging of nanoparticles in suspension. Can it also be used to investigate structural dynamics? When studying the response to mechanical stimuli, the challenge lies in its application with a precision comparable with the spatial resolution. In the first shear experiments performed in an X-ray microscope, this has been accomplished by inserting a piezo actuator driven shear cell into the focal plane of a scanning transmission X-ray microscope.

Viscoelasticity of suspensions of magnetic particles in a polymer: effect of confinement and external field.

We study the suspensions of magnetic particles, the precursor state of magnetic gels and elastomers. We use magnetic particles with a permanent magnetization which is high enough to overcome thermal energy and low enough to guarantee a long live time of the sample. These particles form a space-filling structure at very low volume fractions (approximately 0.

Oscillatory instabilities in phase separation of binary mixtures: fixing the thermodynamic driving.

Binary liquid mixtures can show pronounced oscillations in the differential scanning calorimeter signal for the specific heat and in the turbidity when phase separation is induced by continuously ramping the temperature. For a fixed ramp rate, i.e.

Shear-induced instabilities in layered liquids.

Motivated by the experimentally observed shear-induced destabilization and reorientation of smectic-A-like systems, we consider an extended formulation of smectic-A hydrodynamics. We include both, the smectic layering (via the layer displacement u and the layer normal p(circ)) and the director n(circ) of the underlying nematic order in our macroscopic hydrodynamic description and allow both directions to differ in nonequilibrium situations. In an homeotropically aligned sample the nematic director does couple to an applied simple shear, whereas the smectic layering stays unchanged.