Time Resolved Polarised Grazing Incidence Neutron Scattering from Composite Materials

Abstract

Neutron scattering experiments are a unique tool in material science due to their sensitivity to light elements and magnetic induction. However, for kinetic studies the low brilliance at existing sources poses challenges. In the case of periodic excitations these challenges can be overcome by binning the scattering signal according to the excitation state of the sample. To advance into this direction we have performed polarised and time resolved grazing incidence neutron scattering measurements on an aqueous solution of the polymer F127 mixed with magnetic nano-particles. Magnetic nano-composites like this provide magnetically tuneable properties of the polymer crystal as well as magnetic meta-crystals. Even though the grazing incidence small angle scattering and polarised signals are too weak to be evaluated at this stage we demonstrate that such experiments are feasible. Moreover, we show that the intensity of the 111 Bragg peak of the fcc micellar crystal depends on the actual shear rate, with the signal being maximised when the shear rate is lowest (and vice-versa).

Small-Angle Scattering from Fractals: Differentiating between Various Types of Structures

“…With the recent advances of its derivative techniques, i.e., grazing-incidence [3], anomalous [4], scanning [5] or magnetic [6] SAS, the range of applications has been greatly extended. This includes now a much larger class of hierarchical materials, i.e., materials in which the structural elements themselves have a structure, such as biological macromolecules [1,[7][8][9], polymers [10][11][12][13], composites [14][15][16][17] or cellular solids [18][19][20].…”

Self-Assembly of Magnetic Nanoparticles in Ferrofluids on Different Templates Investigated by Neutron Reflectometry

“…This article has provided detailed examples of different types of physical interactions among magnetic nanoparticles and their interactions with the surface, some practical aspects of performing neutron reflectivity experiments, and the resultant characteristics revealed for NP self-assemblies prepared under different conditions. The representative selection of the early NR studies reviewed here demonstrated the tendency of magnetic NPs in FFs to order into close-packed layers on nearby surfaces [53,[59][60][61][62][63][64][65][66][67]. The three studies that are described in more detail [49,50,52] further highlight the utility of PNR for in-depth insights into the complex nanoscaled structures formed by the interactions of different NPs in different concentrations and with different surfaces.…”

“…They reported that small quantities of magnetic micelles can facilitate the crystallization of Pluronic F127 micelles solvated in water into single crystalline structures via a micro-shear effect under applied magnetic field. Later, Wolff et al [65] combined polarized and time-resolved GISANS measurements on similar samples mixed with magnetic NPs. They showed that NR, off-specular scattering and GISANS are, in principle, able to track the self-assembly process on time scales below one second and to also provide information on the magnetic induction in the sample.…”

Using small-angle scattering to guide functional magnetic nanoparticle design

“…242 Polarized GISANS, on the other hand, is an emerging technique that will enhance our understanding of lateral interparticle coupling. 243 The strong potential of reectometry and grazing incidence scattering techniques towards depth-and laterally resolved nanostructures nds wide application in the structural and magnetic characterization of MNP assemblies in different dimensions: ranging from nanoparticle monolayers 244 through multilayers 245 to highly ordered 3D superstructures such as mesocrystals. 246,247 The following subsections will give an overview of recent achievements using reectometry (4.1) and grazing incidence scattering (4.2), emphasizing also timeresolved studies of in situ self-organization phenomena.…”

“…Schlage et al 275 combined the structural analysis of in situ grown magnetic antidot arrays using GISAXS with magnetic characterization using nuclear resonance X-ray scattering, revealing the magnetization of the growing iron nanostructure and the impact of an iron oxide capping layer. GISANS in combination with polarized neutrons will be a suitable tool to investigate interparticle interactions, such as short-range coupling between nanoparticles in layered assemblies as demonstrated for Co nanoparticles by Theis-Bröhl et al 276,277 Wolff et al 243 applied a magnetic eld to induce a microshearing effect on small quantities of magnetic polymer nanocomposites that improved the crystallization behavior of nonmagnetic surfactant micelles in water. The authors suggest a time-resolved and polarized GISANS experiment to elucidate the shear-induced magnetic structure formation and lateral interparticle coupling.…”