Heterogeneous interface engineering of spindle shaped Fe/C through optimizing impedance response for enhanced microwave absorption and thermal conductivity

Abstract

Heterogeneous interface design is pivotal in creating lightweight, broadband, and high-efficiency electromagnetic wave (EMW) absorption materials. These materials enhance wave absorption by adaptively matching impedance. In this study, spindle-shaped Fe/C nanocomposites with heterogeneous interfaces and diverse surface microtopographies were synthesized by calcining iron-supported metal-organic frameworks (MOFs). During controlled pyrolysis, Fe3+ was reduced by carbon and conversely induced the graphitization of carbon, which is essential for the distribution and appearance of Fe and graphitized carbon as well as for modulating impedance matching. The porous structure of the Fe/C composites and the polarization loss and ferromagnetic resonance from the defective carbon and Fe magnetic particles synergistically enhance the wave absorption performance. The Fe/C-700 nanocomposite achieves a reflection loss (RL) of −55.9 dB at 12.48 GHz with an effective absorption bandwidth (EAB, RL ≤ −10 dB) of 3.9 GHz at 1.8 mm. The Fe/C-900 nanocomposite demonstrates a significant RL of −63.5 dB at 15.8 GHz with an EAB of 4.4 GHz between 13.6 GHz and 18 GHz at 1.5 mm, and an EAB of 5.5 GHz at 1.63 mm. These improvements are attributed to the impedance matching facilitated by the introduction of Fe magnetic particles and graphitized carbon. Additionally, the thermal conduction pathway formed among the Fe/C nanocomposites significantly enhances the thermal conductivity to 0.502 W m−1 K−1. Thus, this work offers a novel approach to the design of advanced wave-absorbing and thermal conductive materials by optimizing impedance through heterogeneous interfaces.