Study On Preparation And Performance Enhancement Of Graphene Aerogel Based On Dopamine Reduction Induced Assembly

With the rapid development and widespread use of electronic systems and electronic equipment,electromagnetic pollution has become a major concern.Driven by environmental issues and a wide range of applications,the search for efficient materials to mitigate electromagnetic interference?EMI?pollution has become a major area of materials research today.With the development of current electromagnetic shielding materials,the currently studied electromagnetic shielding materials are developing in the direction of light weight,small thickness,high shielding frequency bandwidth and high absorption performance.As one of the more popular two-dimensional materials,graphene has attracted extensive attention in the field of electromagnetic shielding due to its excellent physical properties.Two-dimensional graphene can form three-dimensional graphene aerogel?Graphene Aerogel,GA?by overlapping between graphene sheets.The unique three-dimensional structure and physical properties of graphene can have potential applications in electromagnetic shielding and supercapacitors.However,the weak cohesion between the graphite sheets in GA's three-dimensional structure limits its application in many ways.Therefore,enhancing the mechanical properties of GA has become a more focused issue in current research.Generally GA can be prepared by CVD method,self-assembly method and chemical cross-linking method.Among these three methods,aerogel with better mechanical properties can be prepared by chemical cross-linking method,but the use of cross-linking agent will reduce the overall material electrical performance.Inspired by marine mussels,this thesis is based on the self-assembly of modified graphene oxide?GO?into GA by micromolecule dopamine?DA?reduction.DA self-polymerizes to form the"adhesion"of polydopmine?PDA?to the graphite sheet inside the aerogel,which realizes the functional modification of the PDA deposition layer to the reduced graphene oxide sheet.Based on the versatility of PDA,on the one hand,the introduced iron ions can form chelate compounds with it,and the Fe-Nx coordination crosslinking can still be retained after high temperature heat treatment.The generated Fe₃O₄ has a special structure like a cluster of flowers.Therefore,the introduction of iron ions can achieve the double enhancement of the mechanical properties and electromagnetic shielding properties of the three-dimensional graphene structure.The main content and research results are as follows:?1?Adjust the concentration ratio of DA and GO from the experiment,prepare the PDA modified graphene aerogel?PA?through the optimal concentration ratio,and further heat-treat the aerogel to improve the overall conductivity.When DA:GO=1:1,the best aerogel?6.84 KPa?was prepared.XPS and XRD results verified that PDA exists in DA-modified GA.Through the mechanical properties verification after heat treatment at different temperatures,800?was the best heat treatment temperature.At this time,the volume conductivity can reach?1.83±0.25?*10^-2S/m,and it can still reach 5.5 KPa after 800?heat treatment.The electromagnetic shielding efficiency of GA induced by DA induction reduction at 12-18 GHz can reach more than 20 d B.?2?In order to enhance the performance of graphene aerogels,the combination of magnetic materials and carbon-based materials expands the overall electromagnetic shielding effectiveness and frequency band.Here we adopt the method of co-precipitation and vacuum impregnation to grow Fe₃O₄ in-situ inside the aerogel,and use the framework support of Fe₃O₄ and the chelation of PDA and iron ion to improve the overall aerogel mechanical properties.The microscopic morphology observed that Fe₃O₄ was evenly distributed on the surface of the graphite sheet.XPS and XRD verified the successful introduction of Fe₃O₄,and the introduction of Fe₃O₄ did not affect the overall material conductivity.The dynamic mechanics of hydrogels verified the effect of Fe₃O₄ on the storage modulus of the material.In terms of mechanical properties,compared with the original aerogel HPA-800 after heat treatment at 800?and the aerogel containing three different magnetic particle loadings HFA-2-800/HFA-4-800/HFA-6-800,which HFA-4-800 shows more excellent performance.HFA-4-800 can show an average electromagnetic shielding efficiency of 35 d B at 2-18 GHz with 2 mm simple thickness,and an average electromagnetic shielding efficiency of 41 d B when the thickness increases to 3 mm.