Preparation,Structure And Properties Research Of Multifunctional MXene-based Electromagnetic Shielding And Thermal Camouflage Film

With the rapid development of communication technology and the widespread application of electronic equipment,the electromagnetic pollution has become an environmental pollution problem that cannot be ignored in the industrial,commercial and military fields.These electromagnetic radiation interferences will not only affect the normal use of precision electronic instruments and systems,but pollute the environment and jeopardize human health.Therefore,effective measures are needed to control or reduce electromagnetic pollution.Electromagnetic shielding materials are a key factor in realizing high-efficiency electromagnetic shielding.Conventional electromagnetic shielding materials are mainly metals and polymer composites,which is difficult to meet the requirements of fast-developing wearable electronic devices.Meanwhile,the increasingly complex and diversified use environment of electronic devices puts forward higher requirements on the functional characteristics of electromagnetic shielding materials,such as thermal camouflage,fire protection,anisotropic thermal conductive,high strength and toughness,etc.Therefore,the design and construction of a new type of multifunctional and high-performance electromagnetic shielding composite material is of great significance and value in solving electromagnetic wave pollution.In order to the above problems,the high-performance MXene-based electromagnetic shielding composite film were prepared by simple vacuum-assisted filtration method and introducing other two-dimensional nanomaterials(nano-montmorillonite and graphene oxide),and their thermal camouflage performance,fire-proof,anisotropic thermal conductive and mechanical properties were investigated.The main research contents and results are as follows:(1)A series of high-temperature thermal camouflage MXene electromagnetic shielding films with different thicknesses were prepared by the vacuum-assisted filtration method.The middle IR emissivity of Ti₃C₂T_x MXene is as low as 0.19,which is almost comparable to metals and far below other two-dimensional materials such as graphene.The MXene film exhibited the excellent high-temperature thermal camouflage performance,which can reduce the indoor/outdoor radiation temperature of high-temperature objects(>500?)by around 300?.And the superior high-temperature thermal camouflage performance of the as-obtained ultrathin MXene films can be maintained well after working for several hours continuously or after being burned.Meanwhile,the ultrathin MXene films also exhibited superior thermal camouflage ability for objects with extremely low temperature(<-10?).Moreover,the MXene film exhibited excellent disguised electrical heating performance.The MXene films exhibited high electromagnetic interference shielding efficiency(EMI SE).The conductivity and EMI SE of 13-?m-thick-MXene film was 1105 S/cm and 59d B,respectively.And the specific EMI SE accounting for the thickness contribution(SSE_t)of 13-?m-thick-MXene film was 22210 d B cm²/g.(2)A series of high anisotropic thermal conductive and fire-proof MXene/MMT electromagnetic shielding composite film with nacre-like structure were prepared by the vacuum-assisted filtration method and introducing nano-montmorillonite.The introduced MMT can form strong hydrogen bond interaction with MXene,which induced the orderly orientation of MXene nanosheets along the plane direction.The MXene/MMT composite film exhibited excellent electromagnetic shielding performance.The electrical conductivity and EMI SE of the MXene/MMT composite film was 566 S/cm and 67 d B when the content of MMT was 10 wt%.The EMI SE was maintained over 55 d B even after burning and heating.Meanwhile,MXene/MMT composite film also showed excellent thermal camouflage performance,which can reduce the indoor/outdoor radiation temperature of high-temperature objects(?400?)by around 240?.Moreover,the impressive thermal conductive performance:high in-plane thermal conductivity(28.8 W/m K)and low cross-plane thermal conductivity(0.27 W/m K).(3)The MXene@GO films with alternating multilayer structure were prepared by the vacuum-assisted filtration method and introducing graphene oxide,and electromagnetic shielding,thermal camouflage,mechanical properties and anisotropic thermal conductive were investigated.The MXene@GO alternating multilayer film exhibited excellent electromagnetic shielding performance.The electrical conductivity and EMI SE of the 7-layer MXene@GO alternating multilayer composite film was3326 S/cm and 57 d B,respectively,and the SSE_t was 35955 d B cm²/g.Meanwhile,MXene@GO alternating multilayer composite film also showed excellent thermal camouflage performance,which can reduce the indoor radiation temperature of high-temperature objects(?400?)by around 260?.By controling the number of layers of MXene@GO alternating multilayer composite film,the performance of the MXene@GO film can be adjusted.The tensile strength and toughness were 163.7 MPa and 4.27 MJ/m³ when the number of layers of the alternating multilayer film was 7.Moreover,the impressive thermal conductive performance:high in-plane thermal conductivity(22.8 W/m K)and low cross-plane thermal conductivity(0.25 W/m K).