Interface Structures Design And Wave Absorbing Property Regulation Of Sn-based/rGo Composites

The invention of a novel absorbing material with strong absorption in X-band is important for the development of electromagnetic wave absorption field.Herein,the nanoscale SnO2 is designed in microstructure to construct Sn-based/rGO composites with different heterogeneous interfacial properties.The interactions between microstructure and dielectric parameters,wave absorption properties are systematically and thoroughly studied,and the related microwave loss mechanism is revealed and elaborated by combining with first-principles calculations.The effect of SnO2 and Snmicrostructure design on the electronic structure and dielectric properties of Sn-based/graphene is investigated by using first-principles calculations,which are used to guide the subsequent experimental work.It was found that the interfacial bonding modes,the oxygen vacancies and the In and Cu elements doping have certain effects on the electrical conductivity and the dielectric parameters of Sn-based/graphene.With a lower content of oxygen vacancies/In and Cu doping,Sn-based/graphene has high dielectric properties,and theoretically possesses excellent wave absorption performance.The nanoscale SnO2 was synthesized by sol-gel method,and the SnO2?Sn/rGO composites were prepared by hydrothermal-heat treatment process.Controlling the heat-treated temperature and stoichiometry ratio allows SnO2?Sn/rGO to have different heterogeneous interface,which optimizes the impedance matching characteristics and microwave attenuation capability of the system.With a stoichiometric ratio of 1:20,Sn/rGO composites show excellent wave absorption performance with an RLmin value of-39.54 d B,corresponding thickness and frequency of 3.0 mm and 9.60 GHz,respectively.Its main absorption frequency band is in the X band and the effective absorption bandwidth is 2.96 GHz.In addition,the contribution of polarization relaxation loss is dominant in the microwave loss mechanism.The increase in heat-treated temperature and rGO content enhances the electron transport capacity and space charge polarization contribution in the system,which improves the dielectric parameters of the composites and contributes to its excellent wave absorption properties.In order to optimize the wave-absorbing properties of SnO2/rGO and Sn/rGO composites,point defects were constructed in the nanoscale SnO2 by aluminum thermal reduction and In doping.When the stoichiometric ratio is 1:30,the RLmin value of SnO2/rGO composite(Al-0.1)is-47.37 d B,the corresponding absorption frequency is 10.08 GHz,and the effective absorption bandwidth is 5.04 GHz.The RLmin value of In-Sn/rGO composite(In-1.0)is-51.16 d B,the corresponding absorption frequency is 8.72 GHz,the effective absorption bandwidth is 3.60 GHz.The key to optimize the absorbing performance is that the introduction of oxygen vacancies and In 4d new energy levels change the nanoscale SnO2 electronic structure,prompting enhanced conductivity loss and interfacial polarization loss in the SnO2?Sn/rGO system,which is beneficial to its strong microwave absorption.The Cu-coated SnO2-Sn/rGO composites were prepared by chemical deposition and heat-treated processes,and the dielectric parameters and microwave loss contribution of the composite system were adjusted by designing Schottky junctions and metal-dielectric structures to optimize the absorbing properties of the composites.The Cu@Sn/rGO composite exhibit strong absorption with RLmin of-50.40 d B(3 mm)and-50.10 d B(2 mm)for a stoichiometric ratio of 1:20 and a filling of 5 wt.%,and effective absorption bandwidths of 3.60 GHz and 3.92 GHz,respectively.The formation of an intermediate dielectric layer between Cu and Snwith lower barrier facilitates electron transport.In addition,based on the synergistic effect of Schottky junction and plasmon resonance effect,the interfacial effect and electromagnetic wave attenuation ability of the material can be effectively enhanced to show strong absorption properties.