Synthesis And Electromagnetic Wave Absorption Properties Of Carbon Nanotube-Based Conductive Polymer Composites

With the widespread applications of electromagnetic instruments in the commercial,industrial and military fields,electromagnetic pollution has become increasingly prominent.Therefore,the development of efficient,cheap and lightweight electromagnetic wave absorbing materials has been extensively delved.Carbon nanotube(CNT)has potential applications in the field of electromagnetic wave absorption due to its unique morphology and structure.However,CNT has disadvantages such as poor impedance matching and single loss mechanism.Conductive polymers(CPs)are regarded as excellent electromagnetic wave absorbing materials.In them,polypyrrole(PPy)and polyaniline(PANi)as typical CPs not only have the advantages of low density and are easy for large-scale industrial production,but also have adjustable electrical conductivity,which are beneficial to their practical applications.However,they are difficult to meet the requirements of strong absorption characteristics and wide absorption bandwidth,which seriously restrict their practical application in the field of electromagnetic wave absorption.Structures have a crucial effect on the absorbing properties of composite materials.Constructing a feasible core-shell structure is generally considered as an effective method to improve electromagnetic wave absorption performance.In this dissertation,a simple in-situ chemical oxidation polymerization method is used.By controlling the reaction conditions,the thicknesses of the PPy shell and the length of the spiked shell of PANi can be accurately controlled.Through the structural characterization tests of composite materials,it was found that when the amount of Pyrrole added in the reaction is 0.1 m L,the CNT@PPy has the best morphology.At the same time,when the amount of Aniline added in the reaction is 0.3 m L.the CNT@PANi has the best morphology.The electromagnetic wave absorption characteristics of CNT@PPy and CNT@PANi composite materials are analyzed by the vector network analyzer,and the reflection loss(R_L)values with different thicknesses are calculated at the frequency of 2.0-18.0 GHz.The results indicate that when the thicknesses of the CNT@PPy-2 are in the range of 1.3-1.9 mm,the R_Lvalues are all lower than-30 d B.When the thickness is 1.9 mm and the frequency is 12.4GHz,the effective absorption bandwith(EAB)can reach 4.2 GHz and the minimum R_L(R_L,min)value can reach-51.2 d B;when the thickness is 2.0 mm and the frequency is 11.8GHz,its R_L,min value can reach-51.4 d B and the corresponding EAB is 3.7 GHz.In addition,by testing the impedance matching,complex dielectric constant,dielectric loss tangent values,and attenuation coefficient,the absorption principle and loss mechanism of composite materials were analyzed.The analysis results show that the core-shell structure can cause enhanced dielectric loss and impedance matching,thereby improving the ability of the composite material to absorb and attenuate electromagnetic waves.