Preparation And Properties Of Functional Graphene Composite Paper

With excellent electrical and thermal conductivity,as well as being flexible,lightweight and bendable,graphene paper has great potential for applications in flexible electronics,energy storage,electromagnetic shielding and biomedical applications.However,the preparation process of high-performance pure graphene film materials is complex and the mechanical properties of the materials are poor,making it difficult to achieve rapid scale preparation.In recent years,the traditional wet papermaking process has attracted attention in the simple and rapid preparation of two-dimensional macroscopic graphene-based functional materials.With the help of the interaction between paper fibres and graphene,nano-sized graphene can be immobilised on the fibres,thus realising the rapid scale preparation of graphene paper,which is of great significance for the preparation of new graphene-based functional materials and the transformation of the traditional paper industry.This thesis is oriented towards the development needs of high-performance graphene paper-based functional materials,based on the wet papermaking process,and investigates the copying and performance changes of functional graphene composite paper by regulating the interaction between graphene,functional additives and fibres,the main research contents and related conclusions are as follows:（1）Graphene oxide（GO）was prepared from natural flake graphite by a modified Hummers method,then GO was blended with pulped fibres and dispersed uniformly,cationic polyacrylamide（CPAM）was used to induce self-assembly of GO on the fibre surface,and GO/cellulose composite paper was prepared by a conventional wet papermaking process.The effects of pulping degree on the structure of cellulose fibres and the interwoven network of graphene nanosheets were investigated;the synergistic effects of pulping degree and GO content on the mechanical and barrier properties of the composite paper were analysed;furthermore,the reduced graphene oxide（RGO）/cellulose composite paper was obtained by green reduction of ascorbic acid,and the effects of pulping degree and GO content on the over-permeability threshold and electrical conductivity of the composite paper were investigated.The composite paper has good electrical conductivity and mechanical strength,and can be used as a paper-based electrode in supercapacitors with a mass specific capacitance of 106 F g^-1.（2）Cellulose fibres and polypropylene（PP）fibres were used as the substrate for the composite paper,the effects of different size ranges of graphene oxide and mechanically exfoliated graphene slurry on the fibre network structure were investigated,and PP fibre/cellulose/graphene composite paper with high graphene loading was prepared by a wet papermaking process.In the composite paper,graphene was loaded onto the cellulose fibre surface by electrostatic action up to a maximum loading of 70 wt%,thus the composite paper obtained excellent electrical conductivity(21000.2 S m^-1),thermal conductivity(57.899 W m^-1K^-1),and gas barrier(0.037μm Pa^-1 s^-1).The PP fibres act as the three-dimensional backbone of the laminated paper,effectively inhibiting the water absorption and swelling of the cellulose fibres.The composite paper exhibits a certain degree of water resistance,and the shape of the composite paper remains intact after stirring for 24 h in water.The PP fibre/cellulose/graphene composite paper has good thermal conductivity,is water resistant and washable,and is highly airtight,and is expected to be used as a total heat exchange paper in total heat ventilation systems.（3）The conductive composite paper with flexibility and water resistance was prepared by a wet papermaking process using polypropylene（PP）fibres as the substrate and graphene as the filler.During the preparation of the composite paper,a polar surface was constructed on the surface of PP fibres through the dissolution and regeneration of chitosan,which improved the water dispersibility of PP fibres while also promoting the bonding of graphene with PP fibres;chitosan and graphene could form a copolymer by physical adsorption,which improved the retention rate of graphene on PP fibres and obtained a conductive composite paper with a high graphene loading.When the graphene content is 50 wt%,the electrical conductivity of the composite paper can reach 11995 S m^-1,the electromagnetic shielding effectiveness is 31.1 d B and the thermal conductivity can reach 10.17 W m^-1 K^-1.It also shows good water resistance and stability,which enhances the stability of the composite paper in wet environment,and has good application potential and broad development prospects in electromagnetic shielding and thermal interface materials.