부산대학교 도서관

为优化导电织物对电磁波的阻抗匹配性,减少电磁波的二次污染,在棉织物中引入磁损耗材料中空Fe3O4纳米球,并通过层层组装的方法将其与过渡金属碳化物/氮化物(MXene)结合制备中空磁性Fe3O4 纳米球/MXene复合棉织物,探究中空磁性Fe3O4 纳米球对复合棉织物电磁屏蔽性能的影响规律和作用机制.借助超景深显微镜、扫描电子显微镜和矢量网络分析仪对中空磁性Fe3O4 纳米球/MXene复合棉织物的形貌结构和电磁屏蔽性能进行表征与分析.结果表明:通过水热合成制备的Fe3O4 具有中空球状形貌和尖晶石晶体结构,颗粒尺寸较为均匀,为(271.9±4.6)nm;随着Fe3O4/MXene负载循环次数的增加,复合棉织物的方阻逐渐减小,最低为(10.5±1.7)Ω/□,并展现出较好的透气性;复合棉织物的电磁屏蔽性能也逐渐增强,最高电磁屏蔽效能可达(29.03±0.3)dB,且织物的屏蔽机制由吸收为主逐渐向反射为主转变,其优异的电磁屏蔽性能主要归因于MXene纳米片和中空磁性Fe3O4 纳米球的协同作用.
Objective Lightweight,flexible,air permeable and high-performance electromagnetic interference(EMI)shielding materials are urgently required to solve the increasingly serious electromagnetic radiation pollution.Transition metal carbides/nitrides(MXenes)have attracted much attention in the area of EMI shielding because of their high metallic electrical conductivity.However,the MXene modified fabrics usually exhibited reflection-dominant EMI shielding mechanism because of the impedance mismatch.Therefore,it is still a critical challenge to fabricate high-performance MXene-based EMI shielding fabrics with tunable EMI shielding performance and mechanism. Method Constructing multilayer heterogeneous structure of hollow magnetic Fe3O4 nanospheres(HFOs)/MXene is an efficient approach to improve and tune the EMI shielding performance of the composite fabrics,because the HFOs and MXene can absorb the electromagnetic waves by means of the magnetic loss and conductive loss,respectively.More importantly,the electromagnetic waves will be attenuated in the multilayer heterogeneous structure due to the multiple reflections.However,the paper proposed relatively few studies devote to studying the EMI shielding performance of HFOs/MXene modified fabrics.Herein,the paper proposed a layer-by-layer assembly strategy to construct multilayer heterogeneous structure of hollow magnetic Fe3O4 nanospheres/MXene on the cotton woven fabrics to fabricate high-performance EMI shielding fabrics. Results HFOs were prepared by hydrothermal method,which exhibited the hollow morphology(with a diameter of(271.9±4.6)nm)with the inverse spinel structure(Fig.2).Fe3O4/MXene modified fabrics were fabricated by the layer-by-layer assembly.The cotton fabrics were firstly deposited with MXene nanosheets by the spray-coating method.The HFOs were positively charged by using the cetyltrimethylammonium bromide(CTAB),which were deposited on the MXene modified fabrics by the electrostatic attraction to fabricate the HFOs/MXene composite fabrics.The layer-by-layer assembly was repeated for 11 cycles to increase the loading of active materials.The HFOs and MXene were uniformly deposited on the fabrics and exhibited MXene-dominant structure(Fig.4 and Fig.5),which facilitated constructing complete electrically conductive networks in the composite fabrics.The sheet resistance of the composite fabric was decreased from(5 800±85)Ω/□ to(10.5±1.7)Ω/□ when the assembling cycle increased from 1 to 11(Fig.8),which was attributed to the increased MXene loading and the corresponding completed electrically conductive networks.In addition,the composite fabric demonstrated good air permeability(Fig.9).The HFOs/MXene composite cotton fabrics also demonstrated good EMI shielding performances.The EMI shielding performance of the fabric was improved with the assembling cycles,and the maximum EMI shielding effectiveness was up to(29.03±0.3)dB(Fig.10 and Fig.11).The absorption EMI shielding effectiveness was higher than reflection EMI shielding effectiveness for all the composite fabrics.More importantly,the EMI shielding mechanism was tunable for the composite fabrics,and the EMI shielding mechanism changed from absorption-dominant to reflection-dominant when the HFOs/MXene assembling cycles was more than 5(Fig.12).The tunable EMI shielding mechanism of the HFOs/MXene composite cotton fabrics may be attributed to the transition from the impedance match to impedance mismatch. Conclusion The good EMI shielding performance of the HFOs/MXene composite fabric is attributed to the synergistic effects between hollow magnetic Fe3O4 nanospheres and MXene,and the multilayer heterogeneous structure,including the conductive loss from MXene nanosheets,magnetic loss of HFOs and inner multiple reflection from the multilayer heterogeneous structure.The high electrical conductivity and good EMI shielding performance of HFOs/MXene composite cotton fabric makes is attractive in the application of flexible electromagnetic protection,wearable heater,and sensors.