| With the advancement of science and technology and the arrival of 5G era,the radiation and pollution of electromagnetic waves(EMWs)are becoming increasingly serious,which seriously threatens human health and the normal operation of electronic instruments and equipment.Therefore,it is necessary to develop high-performance electromagnetic interference(EMI)shielding materials.The EMI shielding materials with textile substrates not only have excellent EMI shielding characteristics,but also maintain softness,breathability,easy cutting and wearability,and will play an important role in the labor protection of industrial production,improve the performance of microwave devices,and electronic countermeasures in military operations.Therefore,this subject aims to design and develop a flexible high-performance EMI shielding composite fabric to meet the current development needs of "thin,light,wide and strong".It also provides experimental ideas and theoretical basis for the development of a new generation of EMI shielding materials.In view of the difficulty of constructing multiple reflective interfaces of current EMI shielding composite fabrics and the difficulty of integrating textile properties with EMI shielding design,this project intends to carry out structural design and performance research of EMI shielding composite fabrics based on layer-by-layer(L-b-L)assembly technology.First,the new two-dimensional conductive transition metal carbon/nitride(MXenes)and polyaniline(PANI)are used as shielding agents,and carbon fiber fabric is used as the substrate.Successively through solution impregnation and in-situ polymerization,a PANI/MXene/carbon fiber EMI shielding composite fabric with the L-b-L coating structure was successfully designed and prepared.Then,the microstructure and properties were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction phase(XRD)and energy spectrum(EDS)analysis;and the electrical conductivity,EMI shielding performance and various application properties were also tested.Finally,the composite fabric can reach the electrical conductivity of 24.5 S/m and the EMI shielding effectiveness of 26.0 d B after 5 times of assembly,basically meeting the daily protection needs.In this process design,the construction of multiple effective interfaces on the fiber surface was achieved by adjusting the bonding mode and the number of assembly.Finally,the simple,fast and efficient preparation was also achieved on the basis of better maintaining the properties of carbon fiber fabrics.Secondly,in order to achieve the higher performance and multi-functional requirements of EMI shielding fabrics,we carried out structural design and improvement on the basis of previous experiments.Mainly by using vacuum-assisted suction filtration,one-dimensional(1D)polyaniline nanowires and two-dimensional(2D)sheet-like MXene were sequentially loaded on carbon fibers to form a denser conductive network.Afterwards,it was hydrophobically finished with polydimethylsiloxane(PDMS),and the resulting composite fabric achieved a significant improvement in various properties.Through performance tests including EMI shielding performance and microstructure characterization,it is found that the thickness of composite fabric is only 0.36 mm after 50 times of assembly.Its electrical conductivity and EMI shielding effectiveness can reach 325 S/m and 35.3 d B,respectively.At the same time,its contact angle with water can reach 135.2°,indicating good hydrophobicity and self-cleaning ability.In addition,the Joule heating property can be realized under the low voltage drive of 3 V,and the surface temperature of the fabric can be stabilized at about 53.3 ?,which further expands the application field of the material.In addition,unlike other composite fabrics,the improved material better maintains the original characteristics of the fabric advantages,namely excellent air permeability(346 mm/s),flexibility and tailability,is a new type of EMI shielding material with great development potential. |
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