Scientists have made progress in regulating microwave absorption properties

Recently, Wang Hui and Sheng Zhigao, researchers of the Strong Magnetic Field Science Center of the Hefei Institute of Physical Sciences, Chinese Academy of Sciences, used solvothermal methods assisted by different magnetic fields to synthesize polyvinylpyrrolidone-coated nickel nanowires (PNNWs), inducing a variety of electromagnetic loss mechanisms to attenuate electromagnetic waves (EW), in which dielectric loss dominates, magnetic loss, current loss and resonance effect only play an auxiliary role. The research was published in Advanced Materials Interfaces.

In recent years, electromagnetic waves have been widely used in various electronic, radar and wireless equipment, which not only bring convenience to human life, but also cause harm to environmental pollution and human health. Among the many microwave absorbers that have been studied, one-dimensional magnetic nanowire materials have attracted much attention because of their excellent mechanical properties, large aspect ratio and excellent electron transport properties. At present, nickel nanowires have outstanding characteristics such as strong corrosion resistance, large anisotropic field, high saturation magnetization strength, and high Snoek limit above gigahertz, and have become one of the ideal materials for electromagnetic wave absorption. However, the smooth surface and insufficient magnetic properties of nickel nanowires synthesized by conventional methods inhibit the process of EW passing through the absorber and dissipating as heat. Therefore, it is urgent to find a preparation method that can increase the surface roughness and magnetic properties of nickel nanowires to enhance the microwave absorption performance.

The researchers synthesized polyvinylpyrrolidone-coated nickel nanowires by applied magnetic field-induced solvothermal method, and the morphology and properties of PNNWs showed a magnetic field strength dependent relationship. The 9T-PNNW synthesized under the 9T magnetic field has a high aspect ratio, large specific surface area and good magnetic properties, thereby giving it excellent microwave absorption performance. When the thickness is 4.5 mm, the minimum reflection loss (29.82 dB) at 4.08 GHz is achieved; At a thickness of 1.5 mm, the effective absorption bandwidth can exceed 3.6 GHz at 14.4 GHz to 18.0 GHz. The material induces a variety of electromagnetic loss mechanisms to attenuate electromagnetic waves, among which dielectric loss dominates, and magnetic loss, current loss and resonance effect only play an auxiliary role. This work opens up a new way for the rational design and preparation of nickel nanowires, and more importantly, the magnetic field has reference significance for the regulation of absorbent properties.

Schematic diagram of EW attenuation mechanism of 9T-PNNW sample: a, EW incidence, b, interface polarization, c, magnetic loss, d, conduction loss and dipole polarization.

The research work is supported by the National Key Research and Development Program, the National Natural Science Foundation of China, the President Fund of Hefei Research Institute, the Anhui Provincial High Magnetic Field Laboratory Direction Fund and the Hefei Natural Science Foundation. (Source: Hefei Institute of Physical Sciences, Chinese Academy of Sciences)

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