Conducting polymers-NiFe₂O₄ coated on reduced graphene oxide sheets as electromagnetic (EM) wave absorption materials

In this work, conducting polymers (polyaniline, polypyrrole and poly (3,4-ethylenedioxythiophene)) and NiFe₂O₄ coated on Reduced Graphene Oxide Sheets were successfully fabricated by a two-step method. The structure and morphology were characterized by several analytical techniques, including XRD, XPS, Raman, TEM and VSM. The microwave-absorbing properties of the composites were measured by a vector network analyzer. TEM photographs reveal that many NiFe₂O₄ nanoparticles with the sizes in the range of 5–20 nm firmly attached on the surface of RGO-CPs. The ternary composites have superparamagnetic character due to the presence of NiFe₂O₄ nanoparticles. The electromagnetic data demonstrates that the combination of graphene with conducting polymers and NiFe₂O₄ nanoparticles can improve the impedance matching, the 2D-structure RGO with large specific surface area improve the dielectric loss, the presence of CPs coating layer enhances the Debye dipole and dipole polarization enhances the dielectric loss. The maximum reflection loss of RGO-PANI-NiFe₂O₄, RGO-PPy-NiFe₂O₄ and RGO-PEDOT-NiFe₂O₄ are −49.7 dB, −44.8 dB and −45.4 dB, the absorption bandwidths with the reflection losses below −10 dB are 5.3 GHz, 5.3 GHz and 3.7 GHz with a thickness of 2.4 mm, 1.7 mm and 2.0 mm, respectively. Such excellent microwave absorption composites could be used as a new kind of candidate for the new types of microwave absorbing materials.