Preparation And Microwave Absorption Properties Of Carbon Nanotubes / Metal Oxide Composites

Metal oxides and multi-walled carbon nanotubes?MWCNTs?as important materials have been widely used in the field of electromagnetic wave absorption.MWCNTs are conductive materials,when combined with dielectric metal oxides?MnO₂/ZrO₂/TiO₂?compounds,can enhance the electromagnetic wave absorption performance.The morphology,composition and structure of the material have an important influence on the absorbing property.MWCNTs@?–MnO₂,MWCNTs/ZrO₂ and MWCNTs/TiO₂ binary compound materials were prepared in this work.XRD,XPS,TEM,SEM and other characterization methods were used to analyze the composition and morphology of the composite.The vector network analyzer is used to test the electromagnetic parameters of the material in the frequency range of 2-18 GHz.According to the transmission line theoretical formula,the reflection loss?RL?of the materials are simulated and calculated.The specific analysis and characterization results are as follows:?1?The porous flower MWCNTs@?–MnO₂ composite was prepared by one-step water bath heating with acidified MWCNTs and KMnO₄ as raw materials,ethyl acetate?CH₃COOCH₂CH₃?as reducing agent and water as solvent.The growth mechanism and electromagnetic wave loss mechanisms were studied.The results showed that the interface reaction between KMnO₄ and ethyl acetate occurred and the flake?–MnO₂ was formed.It is concluded from the analysis of electromagnetic parameters that the impedance matching of MWCNTs@?–MnO₂ is well,and the electromagnetic wave attenuation is mainly caused by dielectric loss and structural wave absorbing.When the matching thickness of composite material is 1.4mm,the optimal reflection loss value?RL?is-50.6 dB,and the maximum effective absorption bandwidth below-10 dB is 4.2 GHz.?2?MWCNTs/ZrO₂ complex was prepared by hydrothermal reaction at a certain temperature for a certain time by acidizing MWCNTs and Zr?NO₃?₄?5H₂O as raw materials,NH₃?H₂O as reducing agent,and adding these into the Teflon-lined stainless steel autoclave.The morphology,formation procedure mechanism and electromagnetic absorbing properties of the composites were studied.And the results indicated that the synthesized ZrO₂ nanoparticles with a diameter of 5¹0 nm and attached to the surface of MWCNTs.Electromagnetic losses caused by MWCNTs/ZrO₂ composites are mainly caused by dielectric losses.When the coating thickness of MWCNTs/ZrO₂ composite is only 1.5 mm,the effective absorption bandwidth with the RL values less than-10 dB reaches 3.4 GHz?11.3-14.7 GHz?.When the coating thickness is only 2 mm,the maximum reflection loss value can reach-39.7 dB.?3?MWCNTs/TiO₂ composite was synthesized by acidified MWCNTs and n-butyl titanate in a simple one-step hydrothermal process.The crystal structure,morphology,electromagnetic absorption and mechanism of the composite were studied.The results show that the carbon tubes are entwined with each other and TiO₂nanoparticles of about 7¹0 nm are attached on the surfaces.Electromagnetic wave attenuation is mainly caused by dielectric loss and polarization.The optimal reflection loss value?RL?of-35.2 dB can be reached at the coating thickness of 2 mm.A maximum reflection loss of-40 dB can be achieved at 4 mm.The maximum effective bandwidth reaches 3.6 GHz at a thickness of 1.5 mm.Figures[27]Tables[6]References[107]...