Fabrication of arrayed needle-like Fe-particle composite films under an applied magnetic field, and their angularly dependent transmittances

Abstract

Needle-like Fe particles were synthesized by heat-treatment of needle-like α-FeOOH particles in an H2 atmosphere. The obtained needle-like particles and a UV-curable liquid urethane resin were mixed with 0.05 vol% of Fe particles, and the resulting slurry was formed into a film with a thickness of 150 μm. The needle-like Fe particles were arrayed normally to the film surface under a 10 mT magnetic field; subsequently, the urethane resin was cured by UV irradiation. The transmittance of the film was changed from 55.7% to 38.3% by adjusting the light irradiation angle from 0° to 60°. Next, a composite film containing needle-like Fe particles tilted at 30° from the film surface normal was prepared by rearranging the applied magnetic field. The angular dependence of the resulting film was much larger than that of the composite film with the needle-like particles arrayed normal to the film surface.