| In recent years,carbon materials have attracted extensive attention due to their excellent properties,such as light weight,high strength and environmental friendliness.Graphene,as a two-dimensional carbon material with excellent mechanical,thermal and electrical properties,has been widely used in many fields.However,due to the irreversible stacking is prone to occur,which seriously inhibits the mechanical strength of a single graphene sheet,and affects the service performance.Thus,graphene can be assembled into three-dimensional graphene aerogels,which can remain the excellent properties of graphene while effectively avoiding interlaminar slip.Carbon Nanotube(CNT)as another kind of carbon material with excellent performance,also have great mechanical strength and stability.So when they are composite with other materials,they can keep their morphology and shape from being destroyed.Thus,CNT can enhance the graphene matrix by compositing with graphene aerogel,just like the vein of a leaf,forming a composite structure jointly constructed by one and two-dimensional carbon materials,and endowing it with high mechanical properties and other excellent properties.Therefore,CNT/graphene composite aerogel with sandwich structure was prepared based on the bionic structure of leaf venation by taking advantage of the unique amphiphilicity of GO molecule and interacting with CNT through electrostatic adsorption and van der Waals force,which realized the preparation of special structure and the improvement of compression performance.In order to explore the influence of different contents of carbon nanotubes on the compression performance of composite aerogels,the compressing behavior of the sandwich structure was simulated by molecular dynamics using the coarse-grained model.In this paper,carbon nanotubes and graphene oxide were used as raw materials to prepare a composite aerogel with reinforced structure by ultrasonic dispersion,freezedrying and high temperature reduction.SEM analysis shows that the composite aerogel has a transverse honeycomb and longitudinal channel anisotropic structure,and the channels are evenly distributed.Furthermore,the aerogel microstructure was affected by GO concentration and CNT content.When the GO concentration is 1 mg/m L,the composite aerogel has large pore size and loose structure.When the concentration of GO was 6 mg/m L and the content of CNT was 10%-12.5%,the reinforcement structure was the most obvious in aerogel,and a lots of carbon nanotubes were distributed on the graphene sheets.When the concentration of GO was 6 mg/m L and 7mg/ m L and the content of CNT was 50%,CNT agglomerated in aerogel and the structure formability was poor.At the same time,we tested the compressive mechanical properties of the prepared aerogels,and it was found that the compressive stiffness of the composite aerogels presented nonlinear changes with the increase of the content of carbon nanotubes.When the concentration of GO is 6 mg/m L and the mass fraction of CNTs is 11.1%,the compressive stiffness of composite aerogels can reach 675.78 N/m,which is 1.7 times of that of pure graphene aerogels,indicating that the compressive mechanical properties of aerogels are improved after the addition of CNTs.It was found that the composite aerogel had excellent resilience and compression stability through compression cycle tests.The compressive stress only decreased by 8% under 50% strain after 100 compression cycles.What′s more,the coarse-grained model is used to further reveal the compression mechanism of the sandwich structure.It was found that during the compression process,the flat graphene sheets gradually curled up and eventually formed an arch.The CNT randomly distributed in the flat graphene sheets gradually moved towards one end of the compression direction with the movement of the graphene sheets.Moreover,with the increase of the number of carbon nanotubes,the structural pressure also presents a nonlinear change law. |
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