Constructing 3D hierarchical CNTs/VO2 composite microspheres with superior electromagnetic absorption performance

Herein, an efficient one-dimensional (1D) N-doped Co/C nanotube absorber was designed by a cobalt source and solvent ratio comodulation strategy. First, we explored the influences of different cobalt sources (CoCl 2 , Co(OAc) 2 , Co-(NO 3 ) 2 , and CoSO 4 ) on the morphology and microwave absorption (MA) property, which showed that CoCl 2 facilitated the formation of nanotubes with a relatively uniform diameter and length. Notably, the Co/C nanotubes displayed an ultrawide effective absorption bandwidth (EAB) of 6.885 GHz at 2.2 mm when the filling ratio was only 8 wt %. Then, by adjusting the solvent ratio of isopropanol (IPA) and water, Co/C showed a strong absorption of −44.51 dB with an EAB of 5.44 GHz at 2.35 mm. The outstanding MA performance is ascribed to the synergistic effect of dielectric and magnetic components, which is conducive to optimizing the impedance matching, thus broadening the EAB. In addition, the 1D nanostructure is good for constructing three-dimensional (3D) conductive networks and enhancing conductive loss. Since Co nanoparticles are wrapped in carbon nanotubes (CNTs), the confinement effect can effectively prevent the agglomeration of ferromagnetic nanoparticles, adjusting the MA performance. It is worth mentioning that the maximum Radar cross section (RCS) value of Co/C can be reduced by 28.8 dB m 2 . Furthermore, the RCS values are all lower than −10 dB m 2 from −90 to 90°and the minimum RCS value can reach −46.8 dB m 2 . This work provides a strategy for designing lightweight MA absorbers with strong RL and ultrawide EAB.

Section: Resultsmentioning

confidence: 99%

Co Nanoparticles Embedded in N-Doped Carbon Nanotubes for Broadband Microwave Absorption

Xu,

Liao,

Zhu

et al. 2024

“…The weakened portion is a sum equivalent to the reflection losses at the two interfaces. Absorption loss refers to the loss of electromagnetic energy caused by the propagation and heating of EMWs in the shield. , When the EMWs reach the shield surface, they reflect the incident wave owing to the discontinuous impedance at the interface between the material and the air. The energy that is not reflected from the surface and enters the shield is weakened by the shielding materials when it propagates through the shield, which is called absorption.…”

Section: Electromagnetic Shieldingmentioning

confidence: 99%

Electrospun Composite Nanofiber Membranes for Electromagnetic Protection

Yan,

2024

With the rapid development of electronic information technology, the impact of electromagnetic waves (EMWs) on human health, information security, and precision electronic equipment cannot be ignored. Therefore, how to prepare lightweight, flexible and multifunctional materials to shield EMWs is an urgent problem to be solved. Electrospun nanofiber membranes (NFMs) have many merits, such as being lightweight and porous and having a high specific surface area, for electromagnetic interference (EMI) shielding. In this review, the mechanism of EMI shielding as well as the principle and development of electrospinning are first introduced. Then, the commonly used materials in electrospun NFMs for EMI shielding are summarized, and the factors affecting their EMI shielding performance are discussed. Afterward, the modification methods to enhance the EMI shielding performance of NFMs are investigated. Finally, the enhancement effects of different structures of NFMs on their EMI shielding performance are analyzed. This review can provide a more comprehensive understanding of electrospun NFMs used for EMI shielding and play a guiding role in preparing electrospun NFMs with excellent EMI shielding performance in the future.

Section: Dielectric Oxides and Compositesmentioning

confidence: 99%

“…Mao et al were able to synthesize three-dimensional graduated CNTs/VO 2 composite microspheres by an ultrasound nebulization method . The VO 2 microspheres were derived by the total reduction of V 2 O 5 from oxalic acid (Figure c1), and the three-dimensional wormlike spherical heterostructures were established from the introduction of CNTs with tubular structure (Figure c2).…”

Section: Dielectric Oxides and Compositesmentioning

confidence: 99%

“…And the splitting energy level spacing occurs just in the microwave energy range so that some materials originally without microwave absorption properties after sizing down to the nanometer scale have excellent microwave absorption properties. Dielectric-type nanomaterials are generally composite materials consisting of various hybrid nanostructures of highly conductive carbonaceous nanoparticles, dielectric ceramic nanoparticles, and metal–semiconductor oxides. − They mostly count on electron polarization or interfacial effects to attenuate electromagnetic waves, including loss mechanisms such as interfacial polarization, dipole polarization, and conduction loss. Polarization relaxation loss is caused by electromagnetic energy conversion during polarization relaxation, which mainly includes electron polarization, ion polarization, dipole polarization, and interface polarization.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Review of Dielectric Carbide, Oxide, and Sulfide Nanostructures for Electromagnetic Wave Absorption

Lu,

Zhang,

Liu

et al. 2023

Following the growth of infotech and electronic industries, electromagnetic-wave-absorbing materials play an essential role in the traction of the need for high-precision weaponry and intelligent electronic equipment. The exploitation of high-performance electromagnetic-wave-absorbing materials has emerged as a strategic challenge to be solved in the upgrading of military equipment and civil electromagnetic security. The more maturely studied absorbing materials (carbon, ferrite, etc.) have a single loss mechanism and poor resistance matching, which are already not enough to cover the basic needs. To explore absorbing materials that satisfy both impedance matching and attenuation balance, dielectric nanomaterials have come to the fore. They can realize light weight, thin layer, broad band, and multiband, which have great application prospects. In this review, we start with a summary of typical dielectric loss mechanisms (interfacial polarization, dipole polarization, and conduction loss). Next, diverse carbides, oxides, sulfides, and their composites with dielectric or magnetic materials are described, and the nanostructure advantages and wave-absorbing performance advantages are investigated. Then, the applications of wave-absorbing materials are depicted. Lastly, the challenges faced by dielectric-type materials are outlined, and future development trends are foreseen. Overall, this review offers an overview of the advances in the study of dielectric nanoabsorbing materials.