Study On Microstructure Controlling And Microwave Absorption Of Ti₃C₂T_x/rGO Composite Foam

With the development of electronic countermeasures,it is very important to study and explore radar electromagnetic wave absorbers to improve the controllability of military warfare.Traditional absorbers such as ferrite and conductive polymer,are still suffering from high density and narrow effective absorption frequency bandwidth,which can hardly meet the requirements of practical military applications.To meet the four requirements named "thin,light,wide and strong" of microwave absorbers,Ti₃C₂T_x MXene,a new 2D nanomaterial with excellent electrical properties,was prepared.Oriented 3D Ti₃C₂T_x MXene and MXene/graphene composite foams were prepared by directional freeze-casting process,wherein 2D nanosheets are assembled in directional configuration.Herein,oriented foam’s anisotropic property,and its application prospect in the field of microwave absorption were studied.In this paper,an improved Li F-HCl reaction system was used to etch and intercalate the MAX phase precursor Ti3 Al C2,and the aqueous dispersion of single-layer Ti₃C₂T_x MXene was obtained.The Ti₃C₂T_x MXene nanosheets were then prepared by freeze-drying the dispersion.The Ti₃C₂T_x MXene monolayer has the width of 5 μm,which is larger and more suitable for 3D assembly than the one from original Li F-HCl system.Ti₃C₂T_x MXene nanosheet has good electromagnetic wave absorption performance,the maximum reflection loss（RL）reaches-14.89 d B at 13.46 GHz and the effective bandwidth is 3.10 GHz when the sample thickness is 2 mm,indicates that Ti₃C₂T_x MXene has excellent potential in the field of wave absorption.To solve the agglomeration problem of Ti₃C₂T_x MXene nanosheets under van der Waals force,the Ti₃C₂T_x MXene foam with 3D directional structure was obtained by directional freezing casting of single-layer Ti₃C₂T_x MXene dispersion,which regulated microstructure successfully.Ti₃C₂T_x MXene foam has good microwave absorption property,in the vertical direction of the structure,the maximum reflection loss reaches-19.18 d B at 2.26 GHz when the sample thickness is 5 mm,and the 4 mm thickness sample has the maximum effective bandwidth of 0.38 GHz;in the parallel direction of the structure,the sample with 2 mm thickness reaches the maximum reflection loss of-15.89 d B at 17.19 GHz and has the maximum effective bandwidth of 3.89 GHz.In order to solve the problems of weak adhesion among nanosheets and poor foam forming in pure Ti₃C₂T_x MXene foam,as well as further optimize the absorption effect,based on the above work,the gal-strong GO was introduced to assist the construction of 3D assembly,followed by directional freeze-casting and hydrazine hydrate chemical reduction.Combined with the excellent electrical properties of graphene,the resultant MXene/graphene foam exhibit great microwave absorption performance.When the mass ratio of MXene and GO is 1:1,after chemical reduction,the MXene/graphene composite foam has the best absorption property,in the vertical direction of the structure,the maximum reflection loss reaches-26.79 d B at 4.39 GHz when the sample thickness is 5 mm,and the 2 mm thickness sample has the maximum effective bandwidth of 4.46 GHz;The sample with 4 mm thickness in the direction of parallel orientation structure reaches the maximum reflection loss of-26.03 d B at 8.62 GHz,the 3 mm thickness sample has the maximum effective bandwidth of 8.34 GHz.