Preparation Of Graphene Porous Composites And Their Electromagnetic Shielding And Absorbing Properties

With the rapid development of information technology,especially the arrival of the 5G era,there are more and more applications of high-power electronic equipment such as satellite communications,radar broadband,and wireless networks.The resulting electromagnetic waves are harmful to human health,information security,and national defense.Security poses a serious threat.Electromagnetic pollution caused by a large amount of electromagnetic radiation has become the fifth largest pollution source after the four major pollutions including air pollution.Although metal materials(Such as copper,silver and so on)have excellent electromagnetic shielding performance,they are gradually replaced by Conductive Polymer Composites(CPCs)due to their high density,easy corrosion,and strong reflection.However,conventional CPCs usually require a higher filler content to meet commercial electromagnetic interference performance,which causes problems such as processing difficulties,high costs,and deterioration of mechanical properties.The development of lightweight CPCs with porous structures is considered an effective strategy.For this reason,this paper conducts research on the porous structure design and electromagnetic interference performance of CPCs.The main contents are as follows:(1)Using the melamine foam(MF)skeleton as a template,the MF three-dimensional conductive network skeleton(GNSs@MF)coated with graphene nanosheets(GNSs)was prepared by ultrasonic-assisted treatment,and then use thermoplastic polyurethane(TPU)for packaging to obtain TPU-GNSs@MF composite material with excellent mechanical properties and electromagnetic shielding effectiveness.SEM,electrical conductivity,electromagnetic shielding performance and other test results show that the unique three-dimensional conductive network structure endows TPU-GNSs@MF composite with good electrical conductivity and electromagnetic shielding effectiveness.When the content of GNSs is 2.01 vol%,the TPU-GNSs@MF composite material with a thickness of only 2 mm shows a conductivity of 45.2 S/m and a 35.3 dB electromagnetic shielding effectiveness(EMI)in the X-band SE.More importantly,the inherent elasticity of MF and the protective effect of the TPU layer enable the prepared composite material to still have excellent EMI SE even after undergoing severe physical and chemical damage and long-term compression cycles.(2)A graphene nanosheet/carbon nanotube/polyvinylidene fluoride(GNS/CNT/PVDF)composite material with a hierarchical porous network structure was successfully prepared by solution mixing and phase inversion methods.Through SEM observation and analysis,there are a large number of holes and interconnections on the upper surface of the composite material,which is conducive to the incidence of electromagnetic waves and multiple reflections and scattering inside the material.When the thickness of the GNS/CNT/PVDF composite material is 3.5 mm,the minimum reflection loss value(RLmin)at 11.50 GHz frequency reaches-32.7 dB.When the thickness is 4mm,it has an ultra-wide effective absorption band(reflection loss is less than-10 dB)(the entire x-band).