With the rapid development of radio communication and electronic information technology, the problem of electromagnetic radiation pollution has become increasingly prominent, posing a serious threat to the stability of electronic equipment and human health. Electromagnetic wave absorbing materials provide an effective way to solve the above problems by converting electromagnetic energy into other forms of energy, so they have attracted extensive attention from researchers at home and abroad. Among them, the rational design of the microstructure and defects of composite materials can increase the degree of freedom of control of loss mechanism and impedance matching, which is considered to be the key measure to optimize the absorption performance of electromagnetic waves.
In this context, the team of Su Xiaogang/Liu Yaqing from North University of China, Professor Xu Hexiu from Air Force Engineering University and Professor Wu Hongjing from Northwestern Polytechnical University designed a heteroatom sulfur-doped carbon nanofiber/hollow cobalt sulfide hybrid aerogel through a controlled atom migration method, and innovatively proposed a strategy to control the electromagnetic wave absorption performance by the preferential reaction of defect-hollow structure. Specifically, bacterial cellulose and cobalt salts were used as raw materials to obtain hybrid aerogels through selective oxidation, physical cross-linking, directional freeze-drying, high-temperature treatment and vulcanization. Among them, the sulfidation process involves the Kirkendall effect and doping reaction, and changing the sulfur vapor concentration can precisely adjust the hollow structure and doping degree. It is found that the low concentration of sulfur vapor is mainly used for structural control, while the high concentration of sulfur vapor can achieve the joint regulation of structure and defects, which is mainly due to the thermodynamic difference between the two reactions. Combined with experimental and theoretical methods, the coupling relationship between the priority effect and the absorption performance of electromagnetic waves is deeply studied. The final hybrid aerogel showed excellent performance, with a maximum reflection loss of -52.82 dB and an effective absorption bandwidth of 8.82 GHz. In addition, its excellent thermal insulation and superhydrophobicity make it a potential application value in infrared stealth and self-cleaning. The research results have been published online in the internationally renowned journal Advanced Functional Materials under the title of "Controllable atomic migration in microstructures and defects for electromagnetic wave absorption enhancement".
Illustrated reading
Figure 1. Preparation process and microscopic characterization of CSC aerogels
Figure 2. Basic characterization of CSC aerogels
Figure 3. Analysis of electromagnetic wave absorption characteristics of CSC aerogel
Figure 4: Verification of electromagnetic wave absorption and development of multifunctional features
brief summary
Based on the Kirkendall effect and heteroatom sulfur-doped carbon, a strategy for precise structure and defect construction by controlling the migration of sulfur atoms is proposed and verified experimentally. The mechanism of the formation of sulfur vapor concentration and hollow structure and defects is revealed, and the correlation between the preferential reaction between them and electromagnetic parameters and wave-absorbing performance is found. Finally, the aerogel achieves good impedance matching, interfacial polarization, defect polarization and conductance loss, with a maximum reflection loss of -52.82 dB and an effective absorption bandwidth of 8.82 GHz. This work provides a new idea for the design of high-performance electromagnetic absorbing materials.
Source: Frontiers of Polymer Science