Bifunctional organic/inorganic nanocomposites for energy harvesting, actuation and magnetic sensing applications

•Polyurethane based composites were prepared using iron carbide nanofilaments.•Iron carbide acts as a semiconducting and ferromagnetic material.•A new bifunctionality has been created in this kind of organic/inorganic composites. The fabrication of a single material being a competitive actuator as well as an electric current generator is no longer a challenge. This article presents novel nanocomposites based on a polyurethane (PU) matrix containing (0–5wt.%) iron carbide-based nanofillers (Fe3C@C) fabricated by electrospinning. Such materials have both electrostrictive and magnetoelectric properties. The introduction of conductive fillers in PU, which is a good candidate for actuating applications, improved the electro-mechanical coupling due to an increase in the composite permittivity. A significant increase of the dielectric permittivity and an almost 7 fold gain for the deflection strain under 17V/μm were measured on a diaphragm-type actuator for the PU-2.5wt.% Fe3C@C nanocomposite. It was shown that a higher loading led to reduced actuation properties, probably due to the presence of Fe3C aggregates in the composite as shown by Focused Ion Beam characterization. The magnetoelectric (ME) properties of the nanocomposites still showed an increase for contents over 2.5wt.%. The current generated by the nanocomposite, when subjected to a magnetic field, was comparable or higher than several ceramic materials and at least 100 times higher than polymer-based systems studied for their ME behavior.