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Interdisciplinary integration and industrial upgrading have put forward new requirements for the development of electromagnetic functional materials. The design of electromagnetic stealth antennas with excellent electromagnetic wave absorption ability and good signal transmission performance has attracted much attention, and the construction of micro-morphology engineering and heterogeneous structures is expected to be the key to solving the problem.
Recently, Professor Yu Meijie's team at Shandong University published a research result entitled "The Design of Ternary Nanofibers with Core-shell Structure for Electromagnetic Stealthy Antenna" in Advanced Fiber Materials. This work achieved excellent electromagnetic wave absorption performance by coordinating a variety of different components to construct a microstructure, with a minimum reflection loss value of -60.1 dB and an effective absorption bandwidth of 7.6 GHz. In addition, when used as a dielectric substrate in the design of patch antennas, the prepared ternary composite Electrospun Nanofbers showed great application potential, providing new ideas for the design of future electromagnetic stealth antennas.
In this work, a ternary composite nanofiber absorber with a core-shell structure was prepared by electrospinning and high-temperature carbonization. The preparation process is shown in Figure 1(a). The phase analysis results of Figure 1(b-g) show that elemental nickel (Ni) has good conductivity and magnetism, which can give the material strong conductivity loss and magnetic loss; as a common low-dielectric material, the introduction of zirconium oxide (ZrO2) is expected to tune the electromagnetic parameters, thereby optimizing the impedance matching performance of the material. The three-dimensional network structure composed of carbon nanofibers not only helps to promote the dispersion of Ni and ZrO2, increase the contact area between the incident wave and the material, but also promotes the multiple scattering of the incident wave inside the material.
The microscopic morphology analysis of Figure 2 shows that Ni is uniformly dispersed in the entire carbon fiber in the form of small particles, and ZrO2 forms a "shell" with uniform thickness on the fiber surface. This unique one-dimensional core-shell structure significantly increases the contact area between different components in the material. Charges are easy to gather at these heterogeneous interfaces and reciprocate with the change of the alternating electric field phase, consuming the energy of electromagnetic waves. In addition, various defects inside the material are also an important component of polarization relaxation loss.
Figure 3 shows the electromagnetic parameters and impedance matching performance of the material. From the simulation results of electromagnetic parameters and spatial electric field distribution, it is found that the excellent microwave attenuation ability of the composite material is derived from the synergy of multiple loss mechanisms, including conductivity loss, magnetic loss and polarization relaxation. However, to give full play to the high loss capacity of the material, the key is that microwaves can enter the interior of the material without being reflected. Therefore, the presence of low-dielectric ZrO2 effectively alleviates the antagonistic relationship between the high conductivity and impedance matching of the material, thereby ensuring that more microwaves can enter the interior of the material and then effectively lose.
As shown in Figure 4, Ni/C@ZrO2 achieves a minimum reflection loss of -60.1 dB at 11.0 GHz, and the effective absorption bandwidth of the material reaches 7.6 GHz. At different matching thicknesses, its effective absorption bandwidth exceeds 5.0 GHz, proving that Ni/C@ZrO2 is an efficient and broadband absorber. In addition, at all observation angles, the radar reflection cross section of the material is less than -20 dBm2, indicating that the material has excellent far-field electromagnetic wave absorption ability and shows great application potential.
In order to achieve efficient information transmission, a new type of patch antenna is designed, whose dielectric substrate is made of Ni/C@ZrO2 ternary nanofibers. As shown in Figure 5, it can be seen that in a wide test frequency range, the reflection coefficient of the antenna is less than -10 dB, which means that more than 90% of the incident power is transmitted. In addition, under different dielectric thicknesses, the patch antenna has a stable minimum reflection coefficient in the X-band, ensuring the wide applicability of the antenna. At the same time, the antenna has good directivity, which provides a basis for its application in wearable wireless devices and can effectively protect the human body from radiation damage.
In summary, this work prepared a ternary composite nanofiber absorber with a core-shell structure by electrospinning and high-temperature carbonization. The synergistic combination of elemental metals, transition metal oxides and carbonaceous materials gives Ni/C@ZrO2 excellent electromagnetic wave absorption performance, making it a strong competitor for the candidate material of the future patch antenna dielectric substrate, and also provides a new strategy for the development of fiber-based functional materials.
Electrospinning Nanofibers Article Source:
https://link.springer.com/article/10.1007/s42765-024-00492-8
