Sub-millisecond time-resolved small-angle neutron scattering measurements at NIST

Abstract

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.

Controlling the rotation modes of hematite nanospindles by dynamic magnetic fields

“…31 Small-angle scattering probes nanoscale inhomogeneities with suitable spatial resolution to address the orientation distribution of a nanoparticle ensemble, 25,32,33 whereas timeresolved approaches give versatile opportunities to study in-situ nanoparticle ensemble dynamics. [34][35][36] Stroboscopic SAXS provides the necessary time resolution to monitor changes in the orientation distribution near the characteristic frequencies. We therefore performed time-resolved SAXS at the microfocus beamline ID13 (ESRF) to monitor the dynamic fielddependent orientation of hematite spindles driven by a custom-made set of Helmholtz coils.…”

Using small-angle scattering to guide functional magnetic nanoparticle design

“…228 From an analysis of the frequency-dependent phase delay of the scattering amplitude to the oscillating magnetic eld, one can extract the rotational diffusion coefficient of opaque, dense magnetic particle dispersions. 229 The structure-directing inuence of static and dynamic magnetic elds 179,230,231 can induce self-assembly of nanocrystals with translational and orientation order that exhibit strongly anisotropic properties that can be used for optical lters, and nanometer-scale viscoelasticity sensors. 232 Furthermore, doping ferronematic liquid crystals with elongated MNPs such as the hematite spindles is a promising approach to improve their performance, and thus understanding the relaxation dynamics of these composites is crucial for potential applications, e.g., in at panel displays.…”

Using small-angle scattering to guide functional magnetic nanoparticle design

“…228 From an analysis of the frequency-dependent phase delay of the scattering amplitude to the oscillating magnetic field, one can obtain information on the rotational diffusion coefficient of opaque, dense magnetic particle dispersions. 229 The structure-directing influence of static and dynamic magnetic fields 179,230,231 can induce self-assembly of nanocrystals with translational and orientation order that exhibit strongly anisotropic properties that can be used for optical filters, and nanometer-scale viscoelasticity sensors 232 . Furthermore, doping ferronematic liquid crystals with elongated MNPs such as the hematite spindles is a promising approach to improve their performance, and thus understanding the relaxation dynamics of these composites is crucial for potential applications, e.g., in flat panel displays.…”