A three-phase heterostructure composite CF/Co0.2Fe2.8O4/PANI with a layer by layer (LBL) structure was designed and synthesized for achieving improvement in electromagnetic (EM) wave attenuation of carbon fiber (CF). The structure and morphology analyses demonstrated the LBL structure of the absorber. The electromagnetic parameters of the absorber and wax composite were measured at 2–18 GHz to evaluate its EM wave attenuation performance. The three-phase heterostructures absorber CF/Co0.2Fe2.8O4/PANI demonstrated the highest attenuation effectiveness value of −38.2 dB (>99.9% attenuation) at 12.7 GHz with a thickness of 4.1 mm. Moreover, for CF/Co0.2Fe2.8O4/PANI, with an absorber thickness of 3.1–4.1 mm, the minimum RL values are all lower than −20 dB in Ku band. The excellent EM wave absorbency in the Ku band for CF/Co0.2Fe2.8O4/PANI results from the combined effect of magnetic loss and dielectric loss by introducing more phase onto CF. Considering the EM wave absorption performance and the effortless fabrication process, it is believable that by introducing more specially designed phases, the EM wave attenuation performance of CF can be significantly improved.
High-performance electromagnetic (EM) wave absorption property could be achieved by architecture design of nanomaterials . Herein, two layer hybrid Co 0.2 Fe 2.8 O 4 /carbon nanofibers with porous three-dimensional (3D) hierarchical structure were synthesized successfully through facile electrospinning, carbonization and mild chemical treatment. The Co 0.2 Fe 2.8 O 4 particles grew along the carbon nanofibers , forming the enhanced heterogeneous interfaces and high specific areas. As expected, the EM wave absorbent showed an excellent absorbing capability. The composites achieved a maximum reflection loss (RL) of −43.45 dB at 11.1 GHz with thickness of 3.0 mm. More importantly, the effective bandwidth (RL ≤ −10dB) was 5.85 GHz, covering 30% of the entire measured bandwidth. The absorption intensity and bandwidth were superior to other typical CoFe-based composites. The intrinsic mechanism of the absorption revealed that the polarization losses, magnetic losses, magnetic natural resonance and exchanged resonance losses contributed to the high-performance microwave absorption. Moreover, good impedance matching and complex transmission paths that generated from unique porous network also played an important role. This study is expected to guide future exploration on designing and synthesizing high performance EM wave absorbents.
A nanocomposite consisting of nanoparticles decorated by multi-wall carbon nanotubes (MWCNTs/Ag/Co0.2Fe2.8O4) was designed and synthesized to meet requirements for a wider, thinner, and stronger electromagnetic (EM) wave absorber. The structure and morphology analysis revealed the structure of the nanocomposite absorber. The introduction of Ag nanoparticles can increase the interface by bringing stronger coupling into the heterogeneous nanocomposite, whereas Co0.2Fe2.8O4 can introduce dipoles and magnetic loss as well as additional interfaces into the absorber. The electromagnetic parameters of absorber and wax composite with different absorber contents were measured in the range of 2–18 GHz to evaluate its EM wave attenuation performance. With an absorber loading of 20%, at a low thickness of 1.8 mm, the highest attenuation effectiveness value of −52.4 dB can be achieved at 10.2 GHz. Moreover, with absorber thicknesses from 1.1 to 3.7 mm, RL values below −20 dB can be achieved over a wide frequency range from 4.0 to 18 GHz covering the C band, the X band and the Ku band. Consequently, the nanocomposite absorber has an excellent EM wave attenuation ability with the characteristics of a wide absorption band (4–18 GHz), strong absorption (−52.4 dB) and low absorber thicknesses (1.1–3.7 mm). The excellent EM wave absorbency can be attributed to strong interfacial and dipole polarization, dielectric loss caused by Debye dipolar relaxation and the combination of dielectric loss and magnetic loss. Such a nanocomposite could serve as an attractive candidate for EM wave attenuation applications in the future.
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