| In recent years, with the rapid development of communication products, computers, portable electronics and household appliances, electromagnetic interference has brought growing electromagnetic pollution to modern society. On one hand, an increase in outward radiated electromagnetic energy brought more electromagnetic pollution to the environment; On the other hand, due to digitization of electronic devices and small signal quantification, electronics are highly vulnerable to external electromagnetic interference, seriously affecting daily work and life. Reducing electromagnetic interference (EMI) has become an urgent need to solve the problem. Developing useful absorbing material is an effective way to solve this problem. Recently, considerable attentions have been paid to the development of high-efficient microwave absorbers with light weight, thin thickness, wide absorption frequency range, strong absorption characteristics, and anti-oxidation.As a kind of important nanomaterial, ferrite nanoparticles (Fe3O4), with a small size, the surface effects,unique magnetic properties, a low cost and high design flexibility, has been studied by other researchers. However, Fe3O4 has some shortcomings, such as high density, relatively narrow absorbing band, low Curie temperature and poor high-temperature stability. These drawbacks limit its application. This paper focuses on the multi-component, multi-level structure of Fe3O4@mSiO2 with a super paramagnetic Fe3O4 core and a SiO2 shell. Systematic study of the dielectric constant, complex permeability, complex permittivity and microwave absorbing properties inthe 2-18 GHz bands has been done. A sample preparation method for testing the electromagnetic parameters of vector network equipment has been proposed. The method has been used to measure the electromagnetic parameters of flower-like CoNi alloys. The corresponding analysis of its absorbing characteristics and mechanism has also been conducted. |
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