Preparation Of Mxene-based Structural Composites And Study On Microwave Absorption Property

The vigorous development of portable electronic and communication equipment is accompanied by a series of potential electromagnetic pollution risks,which will not only affect the normal work of electronic equipment,but also adversely affect human health.Therefore,it is urgent to explore microwave absorbing materials with "wide,light,thin and strong"characteristics to solve the problem of electromagnetic pollution.As a newly emerging twodimensional(2D)transition metal carbide and nitride material,Ti3C2Tx MXene has attracted widespread attention due to its large specific surface area,unique layered structure and excellent metal conductivity.However,due to the limited loss mechanism and the poor impedance mismatch caused by the inherent high conductivity,it limits its practical application in the field of microwave absorption.In this project,Ti3C2Tx MXene was selected as the matrix and metalorganic framework derivatives(MOF)and silicon carbide nanowires(SiCNWs)were introduced from ceramic materials.By regulating its dielectric and magnetic properties,and optimizing impedance matching,MXene-based microwave absorbing materials with a variety of morphological structures were prepared.The main research contents are as follows:(1)High-quality few-layer or single-layer MXene nanosheets were successfully prepared by HCI etching method,and the few-layer MXene nanosheets had typical layered structures.0D/1D/2D CoPC/CNTs@MXene hybrid systems supported by porous carbon,one-dimensional carbon nanotubes and two-dimensional MXene nanosheets were studied.Mixed-dimensional CoPC/CNTs@MXene(CCM)absorbers were successfully prepared by carbonizing bimetallic Zn-Co MOFs at 800℃,initially generating 0D/1D layered CoPC/CNTs samples,and then interlayering between MXene matrices by electrostatic self-assembly.The impedance matching performance is optimized by varying the content of CoPC/CNTs,and the complex structure of 0D/1D/2D structure favors multiple reflection and scattering of EM W.Finally,the CCM absorber exhibits an optimal reflection loss of-54.2 dB at 5.56 GHz,achieving an effective bandwidth of 5.6 GHz(12.4-18 GHz)at an ultra-thin matching thickness(1.8 mm).This excellent microwave absorption performance is attributed to the synergy of its special structure,interface polarization,and dielectric/magnetic loss.This structural microwave absorbing material has broad application prospects in the field of aviation and intelligent packaging.(2)Bird nest-like MXene@SiCNWs@Co/C composites were successfully prepared by insitu growth,carbonization process and electrostatic self-assembly.ZIF-67 was grown in situ on the surface of SiCNWs,carbonized at high temperature to obtain SiCNWs@Co/C material,and selfassembled with MXene electrostatic to obtain a bird’s nest-like MXene@SiCNWs@Co/C composite.By changing the ratio of MXene to SiCNWs@Co/C,the microwave absorption performance of the composite can be effectively adjusted and optimized.The prepared bird’s nestlike MXene@SiCNWs@Co/C hybrid absorber showed excellent impedance matching,complementary dissipation mechanism and rich heterogeneous interface,not only that,but also synergistic with MXene surface intrinsic defects and functional groups to achieve excellent dielectric/magnetic loss capacity.The resulting composite absorber has an optimal reflection loss of-76.5 dB at a thickness of 3.9 mm and a frequency of 6.36 GHz,and a maximum effective absorption bandwidth of 6.2 GHz(11.8-18.0 GHz),with a thickness of only 2.0 mm,covering the entire Ku-band.This special structure,highly absorbent MXene matrix composite,provides new insights in precision instrumentation and wearable electronics.