Electromagnetic wave absorber better, and thinner, than ever
Electromagnetic wave absorber better, and thinner, than ever lead image
The air is filled with pollution — and not only the well-known chemical and particulate kinds. Electromagnetic waves (EMW) from radio, television, microwave technology, and radar devices clog up the airways, causing signal interference and potentially endangering human and animal health.
Different functional materials absorb EMW, but their performance is compromised by various limitations. Cobalt-nickel alloy is a magnetic loss absorber but only absorbs within a narrow range of frequencies. Reduced graphene oxide is a dielectric loss absorber but has difficulties with impedance matching.
For peak performance, Yu et al. combined these two materials to develop reduced graphene oxide hollow microspheres loaded with cobalt-nickel alloy nanoparticles (Air@RGO/CoNi).
“The enhanced EMW absorption performance of Air@RGO/CoNi microspheres mainly stems from a combination of dielectric and magnetic loss,” said author Qi Yu. “The dielectric loss originates from the interfacial polarization and dipole polarization, likely due to an abundant CoNi alloy-graphene heterogeneous interface, crystal defects, and surface functional groups. The magnetic loss is caused by natural resonance and exchange resonance, largely depending on the size and geometry of CoNi nanocrystals, magneto-crystalline anisotropy, and the dipole interaction between the magnetic CoNi domains.”
Microspheres are key for improved absorption in low-density materials because the hollow microsphere acts like a resonator, scattering the incident EMW, converting it to thermal energy. In turn, thermal energy further improves the material’s absorption capacity.
As a result of these improvements, Air@RGO/CoNi is a thin and highly effective absorber, with a large effective bandwidth. It can protect the body or appliances from radiation and could be applied in anti-radar reconnaissance.
Source: “Facile synthesis and excellent electromagnetic wave absorption properties of Air@RGO/CoNi hollow microspheres,” by Qi Yu, Yanan Xue, Weicheng Nie, Yiming Tang, Yunlong Wang, and Chenglong Du, Journal of Applied Physics (2023). The article can be accessed at https://doi.org/10.1063/5.0147860 .
This paper is part of the Multi-Principal Element Materials: Structure, Property, and Processing Collection, learn more here .
