Preparation of porous CoNi/N-doped carbon microspheres based on magnetoelectric coupling strategy: A new choice against electromagnetic pollution

Abstract

Magnetoelectric coupling is a key strategy to obtain high-performance microwave absorption materials. Especially for carbon matrix composites, the absorbing capacity can be optimized via the tuning of the graphitization degree and the content ratio of the magnetic and dielectric components. Based on this theory, a simple strategy, consisting of the solvothermal method and annealing in an inert atmosphere, is adopted in this study to combine CoNi magnetic alloys with graphitized carbon into micron-scale composite spherical particles. Additionally, special attention is paid to the correlation among the graphitization degree of carbon matrix, component proportion, and dielectric response ability, so as to achieve a flexible micromorphology design and a tunable microwave absorption performance. When the pyrolysis temperature is offset to the best of 700 ℃, a broadband absorption of 6.61 GHz (reflection loss < − 10 dB) is achieved at an ultrathin matching thickness of 1.9 mm. Adjusting the carbon content can further optimize the impedance matching and realize a high-intensity absorption with a reflection loss of − 72.7 dB. Our work proposes a useful strategy to realize the effective combination of the magnetic and dielectric loss mechanisms and boost the microwave absorption capacity toward achieving the desired broadband and a high-efficiency absorption performance.