Thomas Ekiert

High frequency properties of polymer composites consisting of aligned Fe flakes

We have successfully fabricated composites consisting of aligned Fe flakes embedded in a polymer matrix. Similarly high values of permeability and permittivity have been achieved, resulting in potentially significant improvements in device miniaturization, impedance matching, and bandwidth. Various effective medium theory models fail to give accurate values of permeability and permittivity of flake/polymer composites, indicating that modifications are needed for flake shape inclusions.

Structure and magnetic properties of chemically prepared mixtures of crystalline and amorphous Fe(B) nanoparticles

A fine dispersion of crystalline and amorphous Fe(B) nanoparticles has been chemically prepared and its structural and magnetic properties compared to those of the corresponding single phase nanoparticles. The coercivity of the as-prepared dispersion was intermediate between that of the single phase crystalline and amorphous nanoparticles but less than expected from a simple rule of mixtures. Moreover, after annealing at temperatures below the crystallization temperature of the amorphous phase, the coercivity of the dispersion was reduced significantly below that of the single phase amorphous nanoparticles suggesting a modified interparticle interaction arising from the characteristic nanostructure of the dispersion.

High Frequency Properties of Magnetodielectric Composites Consisting of Oriented Febased Flakes Embedded in a Polymeric Matrix

Magnetodielectric composites offer the potential for combining a large index of refraction, favorable impedance matching and bandwidth characteristics, and low power losses in a single material. These properties are determined by the effective permeability (mueff) and effective permittivity (epsiveff) of the composite and can be controlled by the choice and shape of the magnetic and dielectric constituents of the composite. The sample have been prepared, characterized, and studied the electrodynamic properties of a series of oriented Fe-based flakes embedded within an insulating polymeric matrix. The ferromagnetic constituents of the magnetodielectric composite were prepared by mechanically deforming commercially available spherical Fe particles. Low magnification SEM images for the sample were analysed. These images clearly indicate the degree to which the Fe-based flakes have been aligned by an applied field prior to the polymerization of the matrix. The effects of this alignment were also seen in the hysteresis loops and X-ray diffraction patterns of these samples.