Tailoring Microwave Absorption Performance Using Tunable Core–Shell CoNi Alloy Nanospheres

Abstract

In contemporary research endeavors, we have successfully synthesized a composite material endowed with extraordinary microwave absorption properties through a meticulously designed process involving the encapsulation of transition metal nanoparticles with a phenolic resin layer. This innovative material, centered around a core–shell architecture, boasts the incorporation of transition metals Co and Ni, presenting a systematic exploration of their compositional influence on the material’s wave absorption characteristics. Our investigation unravels a sophisticated interplay between alloy composition and microwave absorption performance. Noteworthy observations reveal a non-linear correlation between nickel content and absorption efficiency, where an initial decline precedes a subsequent augmentation. Intriguingly, this dynamic behavior is accompanied by a gradual shift in the absorption peak towards lower frequencies, elucidating the tunable nature of the material’s performance. Crucially, the pinnacle of absorption efficiency is attained at a precisely tuned Co:Ni ratio of 2:1, underscoring the significance of alloy composition in tailoring the material’s electromagnetic response. At an absorber thickness of 2.1 mm, our engineered material achieves a remarkable minimum reflection loss (RL) of −46.1 dB at a frequency of 13.5 GHz. This achievement is coupled with an impressive effective absorption bandwidth spanning 5.5 GHz, indicative of the material’s versatility and applicability across a wide frequency range. The results not only highlight the efficacy of the core–shell CoNi alloy composites but also emphasize the importance of meticulous composition control in achieving optimal microwave absorption performance. The work reported here presents a notable advancement in the synthesis of tunable microwave-absorbing materials, showcasing the potential for tailored electromagnetic responses. The intricate relationship between alloy composition and absorption characteristics elucidated in this study opens avenues for the development of radar-absorbing materials that meet the evolving demands of reduced thickness, light weight, and enhanced absorption performance across diverse frequency ranges.