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Magnetic and Dielectric Properties of Composites Consisting of Oriented, Iron Flake Filler within a Thermoplastic Host: Part I. Material Fabrication and Electromagnetic Characterization

Center for Composite Materials, University of Delaware Newark, DE 19716, USA, Department of Materials Science and Engineering University of Delaware, Newark, DE 19716, USA

S. Yarlagadda

Center for Composite Materials, University of Delaware Newark, DE 19716, USA

J.W. Gillespie, jr

Center for Composite Materials, University of Delaware Newark, DE 19716, USA, gillespie{at}udel.edu, Department of Materials Science and Engineering University of Delaware, Newark, DE 19716, USA, Department of Civil and Environmental Engineering University of Delaware, Newark, DE 19716, USA

Materials that contain both electric permittivity and magnetic permeability greater than unity (magneto-dielectrics) are currently being investigated for microwave applications. An experimental procedure for fabricating magneto-dielectric composite materials based upon flake-like iron inclusions was developed. Samples consisting of iron flakes oriented within a low loss thermoplastic host were produced by extrusion film forming, to minimize loss and maximize permeability. The electrical and magnetic properties of the magneto-dielectric samples were measured as a function of the filler’s aspect ratio, surface characteristics and volume fraction. It was found that forming iron powder into flakes increases the permeability by reducing the demagnetization factor of the shape of the particle. The change to higher aspect ratio filler also increased the dielectric constant and the dielectric loss due to greater instances of inter-particle conduction. Insulating the flakes with a low dielectric greatly significantly mitigated this effect.

Key Words: magneto-dielectric • composite • high-aspect ratio filler • ferromagnetic flakes.

This version was published on November 1, 2009

Journal of Thermoplastic Composite Materials, Vol. 22, No. 6, 551-567 (2009)
DOI: 10.1177/0892705709099695


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