Electromagnetic Wave Absorption Of Three-Dimensional Nitrogen-Doped Carbon Nanotube Composites

The development of high-performance electromagnetic wave absorption materials is one of the most feasible strategies to solve electromagnetic radiation pollution.The traditional ferrite absorption materials have the disadvantages of poor stability,low yield,single loss mechanism,and high density,which seriously hinder the application of electromagnetic wave absorption materials.Multifunctionalization is the future development direction of electromagnetic wave absorption materials.The preparation of multifunctional electromagnetic wave absorption materials can not only reduce the manufacturing space but also reduce the production costs.However,effectively integrating multiple functions into one material is still a huge challenge.Due to the high specific surface area,low density,and good mechanical stability,one-dimensional(1D)carbon nanotubes(CNTs)have potential applications in the field of electromagnetic wave absorption materials.1D CNTs can combine with other dielectric/magnetic materials to form a three-dimensional(3D)interconnected network structure,which can not only overcome the shortcomings of poor impedance matching of single CNTs absorption materials but also adjust other properties of the material,further realizing the multi-functionalization of the electromagnetic wave absorption material.However,the investigations about electromagnetic wave absorption properties and other auxiliary functional properties of 3D CNTs composites have not been documented well.In this work,several 3D nitrogen-doped carbon nanotube(NCNTs)composites have been successfully prepared by an in-situ growth strategy.Electromagnetic wave absorption properties and other functional properties of 3D NCNTs were investigated.The main research contents are as follows:(1)Using melamine as the carbon and nitrogen source for the growth of NCNTs,and magnetic particles as the catalyst,NCNTs arrays can grow on ultrathin r GO by an in-situ growth strategy(3D NCNTs/r GO).Due to the unique 3D interconnected network structure,high specific surface area,and abundant defects,3D NCNTs/r GO composites exhibit excellent electromagnetic wave absorption properties.At the same time,the dielectric loss of the material can be modulated by the metal composition and the material morphology,leading to the controllable electromagnetic wave absorption properties of 3D NCNTs/r GO.The synthesis of 3D NCNTs/r GO composites only involves vacuum freeze-drying and subsequent high-temperature carbonization processes,affording the possibility of large-scale production.Under laboratory conditions,the yield of each batch of 3D NCNTs/r GO can exceed 9 g.(2)The electromagnetic energy conversion properties of 3D NCNTs/r GO composites were studied.The theoretical values of electromagnetic energy storage and conversion of the3 D NCNTs/r GO composite can reach 75% and 34.2%,respectively,indicating that the composite can efficiently store and convert the absorbed electromagnetic energy.The electromagnetic energy conversion device model is designed to realize the rational utilization and conversion of the absorbed electromagnetic energy,which can achieve the purpose of controlling electromagnetic pollution and rational utilization of electromagnetic energy.(3)Commercial,inexpensive,and readily available cotton fibers were used as the growth substrate of NCNTs arrays,and NCNTs arrays embedded with metallic Co nanoparticles were constructed on the surface of cotton fibers(3D Co@NCNTs/CFs).The unique 3D double-layer conductive network structure,large specific surface area,and abundant N doping endow 3D Co@NCNTs/CFs with excellent electromagnetic wave absorption performances,strong hydrophobicity,and good electro-thermal performance.The successful preparation of multifunctional composite materials has greatly expanded the application of electromagnetic wave absorption materials in other fields.In this work,3D NCNTs composites were controllably prepared.The large-scale production of 3D NCNTs composites shows enhancement of electromagnetic wave absorption performances and multifunctional properties.At the same time,the loss mechanism of electromagnetic energy of 3D NCNTs composites was analyzed in detail,providing theoretical basis for the construction of efficient electromagnetic wave absorption materials.