Study On The Synthesis Of Ti₃C₂MXene And Its Microwave Absorbing Properties

With the ever faster development of electronic industry,the demand for high performance and broadband microwave absorbers is greatly urgent and progressively becoming the hot spot of materials science.After with the rise of graphene,two dimentional materials are widely studied as lightweight and high performance microwave absorbing materials,owning to their laminated structures,good thermal stability and unique mechanical properties,as well as abundant chemical and physical properties different from that of body materials.In this work,we present a rapid and controllable method for synthesizing the newly rised 2D material-MXene.The microwave absorption performance of MXene is studied and the dielectric properties and microwave absorption mechanism are intensively discussed.Furthermore,the microwave absorption performance of MXene can be greatly enhanced through Ni-modification and functional composition of MXene.Besides,a broadband and tunable high performance microwave absorbing material derived from MXene is well demonstrated.Main points of this study are summarized as following:Firstly,we demonstrate the ultrasonic assisted etching and delaminating of MXene.The caviation effect and mechanical effect of ultrasonic could effectively accelerate the kinetic process of chemical reaction between HF and Ti3AlC2.Etching process is greatly shortened from 24 h to 4 h,and the combination of etching and delaminating process resultfully promote the exfoliation of MXene flakes.Exfoliation rate as high as 46 wt%is achieved through this method.Secondly,MXene enabled MXene/paraffin microwave absorber exhibits excellent microwave absorbing ability within frequency range of C-band(4-8 GHz),X-band(8-12 GHz)and Ku-band(12-18 GHz),respectively.When the thickness of microwave absorber is fixed only at 2 mm,the Reflection loss is all below-10 dB over frequency range of whole Ku-band.Besides,dielectric and microwave absorbing properties of MXene are intensively discussed through Cole-Cole diagram.MXene is a typical dielectric loss type microwave absorption material,the excellent microwave absorbing ability is mainly ascribed to the polarization process between and inside MXene particles,as well as the multi-reflection and multi-scattering between MXene layers.Furthermore,the dielectric resonse of MXene exhibits double-peaked effects,and we have presented a modified Lorentz-Debye mode to better simulate the dielectric properties of MXene.Thirdly,we have achieved the adjustion and regulation of acid-base property of surface terminations(-OH)of MXene,and Ni-modification of MXene is successfully conducted through the self-assembly chemical reaction between Ni2+ and alkalized MXene.Ni-modification makes MXene possible to attenuate microwave energy through magnetic loss as well as a strong dielectric loss.Effective absorption bandwidth is greatly broadened,especially in lower frequency of 2-8 GHz.The synergistic effect of dielectric loss and magnetic loss is believed to be the main reason behind the broadening of the effective microwave absorbing bandwidth.This cation modification also provides a way to improve other properties of MXene.Lastly,a novel laminated and magnetic composite derived from MXene is designed and successfully synthesized via facile hydrothermal oxidization of nickel ion intercalated MXene.Highly disordered carbon sheets are obtained by low temperature hydrothermal oxidization,and the in-situ produced TiO2 and NiO nanoparticles embedded closely between them.This layered hybrid exhibits excellent microwave absorbing performance with an effective absorbing bandwidth as high as 11.1 GHz(6.9-18 GHz)and 9 GHz(9-18 GHz)when the thickness is 3 mm and 2 mm,respectively.Besides the high dielectric loss,magnetic loss and ohmic loss of the composite,the amorphous nature of obtained carbon sheets and multi-reflections and multi-scatterings between them are believed to play a decisive role in achieving such superior microwave absorbing performance.Our work provides theoretical foundation and realistic possibilities to apply MXene as high performance microwave absorption materials,and also paves the way to the improvement of properties of MXene and MXene derived composites.