Synthesis And Microwave Absorption Performance Of Carbon Nanotube-based Nanocomposites

The rapid development of radio communication and electronic equipment has brought higher microwave transmission efficiency to human.It has also brought serious electromagnetic wave pollution problems at the same time.In addition,the anti-stealth technology of microwave radar and the microwave stealth of existing weapons and equipment have become important issues related to national security.Therefore,the demand for absorbing materials with broadband compatibility,high absorption efficiency,light weight and thin thickness has become increasingly urgent.At present,the development of absorbing materials is changing from single to composite due to the multiple requirements of the industry.Carbon materials have become one of the most popular absorbing materials due to their high conductivity and low density.In addition to the common characteristics of nano-carbon materials,carbon nanotubes have a higher Young's modulus and better thermal stability.However,the performance of carbon nanotubes is not ideal.Too high conductivity will cause the electromagnetic matching to be unbalanced.Then the electromagnetic wave is likely to be highly reflected on the surface resulting in a low electromagnetic wave absorption rate.Compounding with other materials to prepare carbon nanotube-based composites is an effective method to improve impedance matching and microwave absorption performance.On this basis,three carbon nanotube-based composite materials are prepared in this paper,and the absorbing performance and absorbing mechanism of 2-18 GHz were discussed.The influence of the composite material's microwave absorbing properties is studied.XRD,XPS,TGA,SEM,TEM,VSM and VNA are used to evaluate and explore the phase composition,chemical state,composition ratio,morphology,magnetic and electromagnetic parameters of composites.The specific research results obtained are as follows:First,the carbon nanotube/zinc oxide(CNT/ZnO)composite is prepared under normal temperature and pressure.The influence of the preparation parameters on the morphology and performance of the composite absorbor is studied.By adjusting the type of reaction solvent,composites with flake-shaped and“gypsophila”-shaped ZnO are prepared.In addition,the influence of CNT content on the microwave absorbing properties of composites is explored.Due to the special nanostructure and enhanced dielectric loss caused by the morphology and composition variables,the CNT/ZnO composite exhibits an excellent microwave absorption performance of-55.42 d B.Secondly,the carbon nanotube/zinc ferrite(CNT/Zn Fe₂O₄)composite is prepared by the hydrothermal method introducing magnetic Fe particles.The dielectric loss and magnetic loss work together to attenuate electromagnetic waves.And the relationship among the preparation conditions,composition,morphology,and loss mechanism is studied.Using hydrothermal reaction time and component content as variables,the effect on the microwave absorbing properties of composite is explored.When the hydrothermal reaction time is 8 h and the content of Zn Fe₂O₄is 4 mmol,the maximum reflection loss is-41.8 d B.Finally,the microstructure of the composite is designed.A three-phase composite carbon nanotube@zinc ferrite@zinc oxide(CNT@Zn Fe₂O₄@ZnO)with a coated structure is constructed to form a morphology of ZnO nanoparticles partially coated on the surface of CNT and Zn Fe₂O₄microspheres.The cladding structure can form a large number of heterogeneous interfaces,which is conducive to the enhancement of interface polarization and dipole polarization,thereby enhancing the attenuation loss of the composite.In addition,the influence of the content of Zn Fe₂O₄in the composite on its microwave absorbing performance is explored.When the content of Zn Fe₂O₄is 1 mmol,the maximum reflection loss of is-33.5dB.