Shape Anisotropic Chain‐Like CoNi/Polydimethylsiloxane Composite Films with Excellent Low‐Frequency Microwave Absorption and High Thermal Conductivity

Abstract

The demand for low‐frequency microwave absorption materials is becoming more and more urgent. Novel shape anisotropy chain‐like CoNi is fabricated using polyvinylpyrrolidone as a shape‐directing agent via solvothermal method, which is then mixed with polydimethylsiloxane (PDMS) to prepare corresponding multifunctional chain‐like CoNi/PDMS composite films. Shape anisotropy and strong magnetic coupling effect of chain‐like CoNi enhance natural resonance and magnetic loss capability. The minimum reflection loss (RLmin) is −50.5 dB and low‐frequency effective absorption bandwidth (EAB) is 1.04 GHz (2.64–3.68 GHz) at 3.9 mm for chain‐like CoNi. The corresponding 18 vol% chain‐like CoNi/PDMS composite films present optimal low‐frequency microwave absorption performance with RLmin of −56.7 dB and low‐frequency EAB of 1.04 GHz (2.96–4.00 GHz) at 4.1 mm, which is far superior to 18 vol% spherical CoNi/PDMS composite films with RLmin of −9.5 dB. Meantime, the in‐plane and inter‐plane thermal conductivity coefficients of 18 vol% chain‐like CoNi/PDMS composite films are 2.05 and 0.61 W m−1 K−1, about 1.5 times higher than 18 vol% spherical CoNi/PDMS composite films (1.36 and 0.42 W m−1 K−1), also 220% and 190% higher than pure PDMS (0.64 and 0.21 W m−1 K−1). This composite films with low‐frequency microwave absorption and thermal conductivity can broaden applications in 5G communications and flexible electronics.

Embedded 3D printing of RGO frameworks with mechanical strength, and electrical and electromagnetic interference shielding properties

“…Conductive polymer composites have been widely used in the field of electromagnetic protection due to their advantages of lightweight, chemical stability, and easy processing. 55 Compared with magnetic conductive fillers (CoNi, 56 Fe 3 O 4 , 57,58 Fe 3 O 4 @MWCNTs/Ni, 59 Fe 3 O 4 @MWCNTs, 60 etc. ), the RGO framework has rich conductive networks and designed macrostructure to enhance shielding performance.…”

Metamaterial Absorbers with Archimedean Tiling Structures: Toward Response and Absorption of Multiband Electromagnetic Waves

“…Based on the moth-eye bionic hexagonal structure with antireflective properties, , Archimedean tiling structures, as shown in Figure , are utilized to introduce primitive structures of different sizes while maintaining the original main hexagonal structure. Therefore, (3.6.3.6), (3.4.6.4), and (4.6.12) structures of Archimedean tiled structures are discussed in this paper, and smaller or larger size primitives are introduced into the original moth-eye bionic hexagonal structure for simulation and experimentation, respectively, to validate the feasibility of the introduction of multisize primitives into the multiband electromagnetic wave-response mechanism.…”

“…Due to the high-speed development of modern electromagnetic wave application technology such as microwave communication, electromagnetic radiation and interference existing in the environment have gradually become non-negligible problems. − Electromagnetic radiation will not only cause thermal and nonthermal damage to the human body, − but the information transmitted by electromagnetic waves can also be easily captured and cause the exposure of people or weapons and equipment, which will greatly reduce the combat effectiveness of the military and seriously threaten national defense security. , Therefore, in order to cope with the threat of the increasingly mature detection technology with “omni-directional, large depth, all-weather, multilevel” and other significant features, , in-depth research and development of multifrequency band response of electromagnetic wave-absorbing materials and how to make the electromagnetic absorber have good absorption performance in multiple frequency bands, improve the broadband absorption efficiency, and realize the application requirements of “light mass, thin thickness, broadband, and strong absorption” has become a hot issue for the design of absorbers nowadays. − At present, for the above problems such as multiband response, if we solely rely on the characteristics of the raw material itself, it will have certain limitations and impacts on the wave-absorbing performance. − Therefore, the design and development of wave absorbers based on the design concept of metamaterials is a more effective solution. − …”

Adhesion Energy-Assisted Low Contact Thermal Resistance Epoxy Resin-Based Composite

“…Epoxy resins have been widely used in electrical packaging, circuit boards, etc., due to their excellent mechanical properties and good processability. − However, with the development of electronic components toward integration, miniaturization, and intelligence, − their increasing heat dissipation requirements pose a big challenge to epoxy resins, which possess low thermal conductivity in the range from 0.1 to 0.5 W/(m·K). The addition of thermal conductive fillers, such as hexagonal boron nitride (h-BN), , boron nitride nanotube, Al 2 O 3 , and carbon materials (carbon nanotube, graphene), has been widely utilized to enhance the thermal conductivity of epoxy resins.…”