Probing the flow- and magnetic-field-induced orientation of cellulose nanocrystals and magnetic nanoparticles via wide-angle X-ray scattering

We investigated the flow- and magnetic-field-induced orientation of cellulose nanocrystals (CNC) suspensions, pure and loaded with magnetite (Fe3O4) nanoparticles, using a custom-built flow cell placed in the D1 beamline of the Cornell High Energy Synchrotron Source. 2D wide-angle X-ray scattering (2D-WAXS) was used to quantify the direction and degree of orientation of the CNC suspensions under Poiseuille flow. We observed that the pure CNC suspensions and those with 1wt% Fe3O4 nanoparticles (NPs) exhibited very strong orientation along the flow direction. The CNC suspensions doped with higher concentrations of Fe3O4 NPs, 3wt%, showed different director-orientation patterns: isotropic, along the direction of flow, and bimodal. For these suspensions, the alignment along the flow direction occurs only at the highest values of apparent shear rates (60 s-1 and 100 s-1) in the absence of magnetic field. Conversely, under the action of the magnetic field, the induced alignment along the flow occurs at low apparent shear rates, as low as 10 s-1. We anticipate that these responsive effects, to flow and to magnetic fields, may offer new approaches to tailor and understand the behavior of composite materials with magnetic anisotropic responses. It is also hoped that further development of our exploratory work will translate these findings into new processing methods for the manufacturing of magnetically responsive composite materials.