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Research Progress on Carbon-based Electromagnetic Wave Absorbing Materials and Their Mechanisms
Abstract
With the increasing demand for electromagnetic interference (EMI) shielding in various fields, carbon-based electromagnetic wave absorbing materials have attracted significant attention for their excellent EMI shielding properties, lightweight, and low cost. This review summarizes recent advances in carbon-based materials for electromagnetic wave absorption, including carbon nanotubes, graphene, and carbonaceous materials, such as activated carbon and carbon fiber. The characterization of the materials and the mechanisms of electromagnetic wave absorption are also discussed. Finally, the future prospects and challenges in the development of carbon-based electromagnetic wave absorbing materials are presented.
Introduction
Electromagnetic radiation is becoming increasingly ubiquitous in modern society, leading to the problem of electromagnetic interference (EMI) and electromagnetic compatibility (EMC) in electronic devices and communication systems. EMI can cause signal distortion, errors, and even damage to the equipment, resulting in significant economic losses. Therefore, it is essential to develop effective EMI shielding and electromagnetic wave absorbing materials.
Traditional metallic materials, such as copper, aluminum, and stainless steel, have been widely used as EMI shields and electromagnetic wave absorbing materials due to their high electrical conductivity. However, these metals are heavy, bulky, and expensive, making them unsuitable for some applications. Therefore, carbon-based materials, including carbon nanotubes, graphene, and carbonaceous materials, have gained significant attention for their excellent EMI shielding properties, lightweight, and low cost.
Carbon-based materials for electromagnetic wave absorption
Carbon nanotubes (CNTs) are hollow tubular structures composed of rolled-up graphene sheets. CNTs possess excellent mechanical, thermal, and electrical properties and have been demonstrated to exhibit significant EMI shielding effectiveness (SE). CNTs can absorb microwaves and millimeter waves by inducing charge movements and polarization in the nanotubes. The conductivity of CNTs can be controlled by doping, which can further optimize the electromagnetic wave absorption performance.
Graphene is a two-dimensional sheet of sp2-bonded carbon atoms arranged in a honeycomb lattice. Graphene has excellent electrical conductivity, high mechanical strength, and a large surface area, making it an ideal material for EMI shielding and electromagnetic wave absorption. The excellent electrical conductivity of graphene can effectively dissipate the electromagnetic energy, while the large surface area can increase the interaction between the electromagnetic waves and the graphene sheets. Graphene-based composites have been developed by combining graphene with other materials, such as polymers, metals, and ceramics, to improve the electromagnetic wave absorption performance.
Activated carbon is a highly porous carbonaceous material with a large surface area and a high adsorption capacity. Activated carbon has been shown to effectively absorb electromagnetic waves due to the microwave absorption properties of the carbon matrix and the large surface area, which can enhance the interactions between the electromagnetic waves and the activated carbon. Various activated carbon-based materials have been developed, including activated carbon fibers, activated carbon foam, and activated carbon nanotubes.
Carbon fiber is a high-strength and lightweight material that can effectively absorb electromagnetic waves by inducing charge movements and magnetic loss. Carbon fiber composites have been developed, such as carbon fiber reinforced polymer (CFRP) composites and carbon fiber paper, which have excellent electromagnetic wave absorption performance.
Characterization and mechanisms of electromagnetic wave absorption
The characterization of carbon-based electromagnetic wave absorbing materials includes the measurement of the EMI SE, specific surface area, electrical conductivity, and complex permittivity and permeability. The EMI SE is a crucial parameter to evaluate the effectiveness of the materials for EMI shielding and electromagnetic wave absorption. The specific surface area determines the adsorption of electromagnetic waves on the materials, while the electrical conductivity reflects the dissipative ability of the materials. The complex permittivity and permeability describe the electromagnetic wave absorption mechanisms, including dielectric loss, magnetic loss, and conductive loss.
The mechanisms of electromagnetic wave absorption for carbon-based materials include multiple losses, such as dielectric loss, magnetic loss, and conductive loss. Dielectric loss occurs when a material is subjected to an electric field, leading to the polarization and relaxation of the electrical dipoles in the material. Magnetic loss arises from the magnetic resonance of the electromagnetic waves and the ferromagnetic behavior of the materials. Conductive loss occurs when the electrical conductivity of the materials dissipates the electromagnetic energy.
Future prospects and challenges
Carbon-based electromagnetic wave absorbing materials have shown great potential in EMI shielding and electromagnetic wave absorption. However, challenges remain in the development of these materials, including the low-temperature performance, the stability under harsh environments, and the scalability of the production. Further research is required to address these challenges and optimize the electromagnetic wave absorption performance of carbon-based materials. The development of novel carbon-based composites and the exploration of new mechanisms for electromagnetic wave absorption are also promising directions for future research.
Conclusion
In conclusion, carbon-based materials, including CNTs, graphene, activated carbon, and carbon fiber, have shown excellent electromagnetic wave absorption properties and have become a focus of research in EMI shielding and electromagnetic wave absorption. The characterization and mechanisms of electromagnetic wave absorption for carbon-based materials have been explored, and future prospects and challenges have been discussed. The development of carbon-based electromagnetic wave absorbing materials will continue to play a significant role in various applications, such as aerospace, telecommunications, and electronic devices.