Pea-like Fe/Fe₃C Nanoparticles Embedded in Nitrogen-Doped Carbon Nanotubes with Tunable Dielectric/Magnetic Loss and Efficient Electromagnetic Absorption

One-dimensional microstructure has been regarded as one of the most desirable configurations for magnetic carbon-based microwave absorbing materials (MAMs). Herein, pea-like Fe/Fe₃C nanoparticles embedded in nitrogen-doped carbon nanotubes (Fe/Fe₃C@NCNTs) are successfully prepared through a direct pyrolysis of the mixture of FeCl₃·6H₂O and melamine under inert atmosphere. The chemical composition and microstructural feature of these Fe/Fe₃C@NCNTs composites are highly dependent on the pyrolysis temperature. As a result, their electromagnetic properties can be also manipulated, where dielectric loss gradually decreases with the increasing pyrolysis temperature and magnetic loss presents a reverse variation trend. When the pyrolysis temperature reaches 600 °C, the as-obtained composite, Fe/Fe₃C@NCNTs-600 can perform a maximum reflection loss of −46.0 dB at 3.6 GHz with a thickness of 4.97 mm and a qualified bandwidth of 14.8 GHz with the integrated thickness from 1.00 to 5.00 mm. It is very interesting that the microwave absorption performance of this new kind of composites is not so susceptible to the pyrolysis temperature as those common magnetic carbon-based MAMs because there is an effective balance between dielectric loss and magnetic loss, which accounts for a very stable attenuation ability when the pyrolysis temperature range changes from 600 to 700 °C. These favorable characteristics, including low-cost raw materials, easy preparation, and stable performance, may render Fe/Fe₃C@NCNTs composites as a novel kind of MAMs in the future.