Fabrication Of Flexible Graphene-based Paper And Its Performance Optimization

Graphene is a two-dimensional crystal material with only one carbon atom thickness.It has excellent electrical,thermal,optical and mechanical properties.Since its discovery,it has drawn a lot of interest in many fields.Graphene's high electrical conductivity and thermal conductivity make it a great potential for applications in heat-dissipating materials and electromagnetic shielding materials.Among graphene-based materials,flexible graphene-based paper has attracted the attention of many researchers in recent years due to its excellent electrical and thermal conductivities.Graphene flakes with large size are usually known as the key factor for improved paper performance.However,in the fabrication of graphene-based paper,voids and space between the flakes are inevitable,resulting in the reduction of electrical and thermal conductivities.Therefore,it is important to make the paper structure more compact,based on the advantages of large-size graphene flakes,and thus to prepare the graphene-based paper with excellent performance.In this work,high-quality graphene has been successfully prepared by supercritical CO₂ exfoliation method,the characterization results show that the number of layers is generally less than 10 layers and the crystal structure is well preserved.In this experiment,mixed acid treatment and ultrasonic treatment are used to make graphene dispersion.By adjusting the sonication time,graphene samples with different size distributions are obtained.The flexible paper was fabricated by mixing large-size graphene?LSG?and small-size graphene?SSG?through multi-filtration,in which the orientation of flakes is high.The physical properties of the as-prepared graphene paper with contents of small-size graphene varying from 0 wt%to 100 wt%have been investigated.It is found that the electrical and thermal conductivities of the paper with25 wt%small-size graphene are both around 140%higher than that of pure large-size graphene paper,implying the significant synergistic effect.Large-size graphene flakes play the role of a backbone structure,whereas small-size graphene flakes fill the voids in the paper without disturbing the high orientation.Our results indicate that the lightweight and flexible graphene-based paper has great potential for lateral heat dissipation applications requiring heat movement in a particular direction.