The magnetic response of spindle-shaped hematite (α-Fe2O3) nanoparticles was investigated by simultaneous small-angle and wide-angle X-ray scattering (SAXS/WAXS) experiments.
Instrumentation for time-resolved small-angle neutron scattering measurements with sub-millisecond time resolution, based on Gä hler's TISANE (timeinvolved small-angle neutron experiments) concept, is in operation at NIST's Center for Neutron Research. This implementation of the technique includes novel electronics for synchronizing the neutron pulses from high-speed counterrotating choppers with a periodic stimulus applied to a sample. Instrumentation details are described along with measurements demonstrating the utility of the technique for elucidating the reorientation dynamics of anisometric magnetic particles.
Accurate characterization of the
nanocrystal shape with high statistical
relevance is essential for exploiting the strongly shape-dependent
properties of cuboidal nanoparticles toward applications. This work
presents the development of a new small-angle scattering form factor
based on the superball geometry. The superball quantifies the characteristic
rounding of corners and edges of cuboidal nanoparticles with a single
parameter. Applied to small-angle scattering data of sufficiently
monodisperse nanoparticles, the superball form factor enables differentiation
between the effects of extended particle size distribution and irregular
particle shape. The quantitative application of the superball form
factor is validated against microscopy data for a series of monodisperse
nanoparticles and implemented into the user-friendly, open-source
software Sasview.
A magnetorheological sample environment is presented that allows for in situ magnetic field and shear flow during small-angle neutron scattering (SANS) measurements and is now available at the Institut Laue-Langevin (ILL). The setup allows performing simultaneous magnetorheological measurements together with the investigation of structural and magnetic changes on the nanometer length scale underlying the rheological response of ferrofluids. We describe the setup consisting of a commercial rheometer and a custom-made set of Helmholtz coils and show exemplarily data on the field and shear flow alignment of a dispersion of hematite nanospindles in water.
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