Ultrasmall superparamagnetic Ni nanoparticles embedded in polyaniline as a lightweight and thin microwave absorber

Abstract

In this work, we have reported the preparation and lightweight and thin microwave absorbent application of ultrasmall Ni nanoparticles embedded in polyaniline (PANI). Ni nanoparticles have the average diameter of 2.1 nm, and are in the form of single crystals and possess a single magnetic domain structure. The blocking temperature of the Ni@PANI nanocomposite is established to be 52 K. The Ni@PANI nanocomposite is in a superparamagnetic state at 300 K. The optimal reflection loss value of a paraffin-bonded composite with 25 wt% of Ni@PANI nanocomposite reaches −22.98 dB at 17.8 GHz for a thickness of 1.0 mm. Compared with the represented Ni-based nanocomposites, Ni@PANI nanocomposites possess favorable properties at lower density and thinner thickness, resulting from the combined effect of magnetic loss and dielectric loss by introducing ultrasmall superparamagnetic Ni nanoparticles into the PANI matrix.