Study On Preparation And Properties Of Flexible Mxene-Based Electromagnetic Interference Shielding Composite Films

With the widespread popularity of electronic products,electromagnetic interference（EMI）has become more and more serious.It not only hinders the normal operation of equipment,but also threatens human health as an invisible killer.The research on EMI shielding materials is the key to solving this problem.Two-dimensional metal carbides or nitrides（MXene）has the advantages of high electrical conductivity,light weight,and easy processing,but due to the weak interaction between MXene nanosheets,resulting in poor mechanical properties of films,which cannot meet potential application requirements.The mechanical properties of MXene films are usually improved by composite methods,but it is difficult to improve the strength and toughness at the same time,and the introduction of electrically insulating fillers destroys the conductive paths between the MXene sheets,seriously weakening the electromagnetic shielding properties of the MXene films.In response to the above problems,this paper constructs a three-component system of MXene/graphene oxide（GO）/cellulose nanofibers（CNF）,and prepares MXene-based composite films with high strength,high toughness and excellent electromagnetic shielding properties.The specific research contents are as follows.（1）In order to solve the problem that it is difficult to improve the strength and toughness of MXene-based composite films at the same time,large-scale MXene nanosheets are prepared by optimizing the etching method of MAX,high-strength two-dimensional sheet GO and high-toughness one-dimensional fiber CNF are introduced as interfaces.The surface of the three components is rich in oxygen-containing functional groups that can be bonded to each other.Among them,GO can optimize the orientation degree of MXene sheets,and CNF can form an interlocking structure between different components,which can synergistically improve the mechanical strength and fracture toughness of MXene.The experimental results show that when CNF content is 10 wt%,the fracture strength and toughness of MGF-10%composite films reach 559.3±81.2 MPa and 7.6±1.6 MJ m^-3.（2）In order to solve the problem that the mechanical properties and electromagnetic shielding properties of MXene-based composite films cannot be balanced,hydroiodic acid（HI）solution is used to remove the remaining functional groups,restore the electron transport path,improve the conductivity and electromagnetic shielding properties of the film while ensuring its mechanical properties.The experimental results show that the r MGF-10%films in different wavelength bands have tunable electromagnetic shielding effectiveness（EMI SE）,which increases with the increase of film thickness.The EMI SE of r MGF-10%films with thickness of 10μm can reach 53 d B.At the same time,the mechanical properties of the films are preserved,and the fracture strength and toughness can reach 541.5±35.8 MPa and 11.1±3.2 MJ m^-3.In addition,the r MGF-10%films exhibit fast thermal response under low voltage（1 V）driving,and the temperature-time curves are still highly coincident after 40 cycles of heating/cooling.When irradiated by an infrared lamp,the surface temperature of r MGF-10%films rises rapidly,showing excellent photothermal conversion performance.The r MGF-10%films are hydrophobic and have a contact angle of 112.9°,which can exist stably in different liquid environments for more than 5 h,showing excellent structural stability.