| With the rapid development of science and technology,a large number of applications of Internet communication technology and related electronic products have further improved information transmission,and people’s life has become more convenient and efficient.Meanwhile,the electromagnetic radiation generated by the overuse of electronic equipment has brought great harm to the environment and human health,which has aroused people’s concern.Electromagnetic shielding technology,as an effective means of shielding electromagnetic wave and electromagnetic compatibility,has been widely developed and applied in electromagnetic application field.Traditional metal materials have high electromagnetic shielding efficiency,but their response to electromagnetic wave is mainly reflected,which causes secondary electromagnetic wave pollution,and because of its high density,difficult to process and other characteristics,limits its application,so more attention should be paid to the study of flexible electromagnetic shielding materials based on absorption.In real life,the use of household appliances makes people in the electromagnetic wave environment,so it is of practical significance to develop flexible shielding materials which can be used in chassis.Graphene,with its light weight,high strength and excellent electrical properties,is often used as an electromagnetic shielding material.Combined with metals,the electromagnetic shielding efficiency of the material can be further improved.However,graphene is easy to agglomerate and difficult to disperse,and as a conductive filler,it often requires a higher filling amount to get a better conductivity,so it cannot give consideration to flexibility.In this paper,three-dimensional porous graphene structures were constructed on the surface of arylon non-woven fabric by laser direct writing technology and copper nanoparticles were deposited by electroless plating process to obtain a shielding fabric with good shielding performance.On this basis,a sandwich composite fabric with both thermal conductivity and electromagnetic shielding properties is constructed,which provides a new idea for the preparation of flexible shielding composites.The main contents of this paper are as follows:(1)Aiming at the problem of electromagnetic wave secondary reflection easily caused by the use of single metal materials,based on the loose structure of aramid non-woven fabric,three-dimensional porous laser-induced graphene(LIG)was generated in-situ on the fabric surface by laser direct writing technology to prepare LIG/aramid fabric(GAF).By adjusting the laser parameters,the electrical conductivity of LIG was optimized to explore the optimal laser parameters.At the same time,the porous structure and functional groups(hydroxyl and carboxyl groups,etc.)induced by laser effectively increase the specific surface area of the fabric and improve its hydrophilicity,which is conducive to the subsequent loading of metal nanoparticles and the improvement of binding force.Then,a low cost electroless plating process was used to deposit copper nanoparticles on its surface and the influence of electroless plating time on electromagnetic shielding efficiency was discussed.Finally,after 60 min electroless plating,the average electromagnetic shielding efficiency of Cu GAF-60 in X band(8.2-12.4 GHz)is 34.3 d B,in which the SE_A accounts for 81.8%.This is mainly due to the fact that the porous structure of GAF substrate provides a rich interface for the incident electromagnetic wave,so that the electromagnetic wave can be reflected for many times and then absorbed.(2)Aiming at the problem that Cu GAF is brittle and not suitable for direct use,and in order to meet the heat dissipation requirements of chassis,aramid electromagnetic shielding composites with good thermal conductivity and service performance are prepared.Different resins(silica gel,epoxy resin and polyurethane)mixed with carbon nanotubes(CNTs,0.5 wt.%-2.0 wt.%)were combined with Cu AF-60 by means of the mold.The thermal conductivity and electromagnetic shielding performance of the composite were improved by changing the resin type and the concentration of carbon nanotubes.When the content of carbon nanotubes is 2.0wt.%,the thermal conductivity of the composite is 0.1817 W/(m·K),and the average shielding efficiency in the X-band is about 35.8d B,the shielding efficiency is 99.9%,and the absorption ratio is 94.4%,which is 12.6%higher than that of Cuaf-60.In addition,the insulating electromagnetic shielding composite material has certain water resistance and flexibility,which plays a protective role on electronic devices and can be conformal with the processed devices in the process of machining.It is expected to be applied to the electromagnetic shielding material in the case of damp environment. |
PDF Full Text Request