Preparation And Printability With Screen Printing Of Water-based Graphene Electrically Conductive Ink

Water-based electrically conductive ink is a novel type of functional ink with both water-based ink and electrically conductive properties.Addingthe conductive materials in water-based ink can have an electrical conductive function.The water-based conductive ink is widely used in membrane switch,heating element,solar cell,and integrated circuit.Graphene is a two-dismensional honeycomb crystal by sp~2 hybridized carbon atoms,each carbon atom connects with 3 adjacent carbon atoms,form?bonds,that endow graphene with superior mechanical properties.Each carbon atom provides an unpaired electron,which can freely move on the surface of graphene crystal and endow graphene with a good electrical conductivity.Its electron mobility is2×10~5cm~2/(V·S)and electron velocity can reach 1/300 of light velocity,which is much faster than that of general conductors.Also,besides excellent conductivity and low resistivity,graphene has a stable lattice structure.Using graphene as an excellent conductive material and adding it into ink can become an excellent graphene conductive ink.In this dissertation,the preparation,properties and printability with screen printing process of a water-based electrically conductive ink prepared with polyurethane resin as binder,water-based graphene dispersion as solvent,graphite and conductive carbon black as conductive filler,were investigated.In Chapter 1,graphene and its preparation and characterization methods were summarized.Also,the definition,composition,classification,conductive mechanism,printing process and recent development of conductive ink were introduced.The objectives and contents of this dissertation were given.In Chapter 2,a graphene powder was preparedby an ultrasonic peeling method.The graphene powder was prepared into a graphene aqueous dispersion with a polymer dispersant in a high-energy stirred bead mill.The graphene powder and water-based dispersion were examined and characterized.The experimental results show that the thickness of graphene is approximately 3nm,which belongs to multilayer graphene(MLG)with less than 10 layers,and its powder resistivity is 1.13 m?·cm.The water-based graphene dispersion has a good dispersibility.The dry film resistivity is 2m?·cm,and the viscosity is 145.3cP,thus leading to a good fluidity.In Chapter 3,the effects of pigment/binder ratio,the content of conductive fillers,the mixing ratio of graphite and carbon black and the quantity of dispersant on the resistivity and adhesion of conductive ink were investigated via an orthogonal experiment.The experimental results show that the conductive ink has a superior performance(i.e.,resistivity and adhesion)when the pigment/binder ratio is 3:1,the content of conductive fillers is 35%,the mixing ratio of graphite and carbon black is 3:1 and the amount of dispersant is 16%.In Chapter 4,the effects of ink viscosity,shore hardness and angle of squeegee,mesh number of the screen printing plate on the printability of conductive ink were investigated by an orthogonal experiment.The experimental results show that the optimum printability can be obtained when the viscosity of ink is 30Pa·s,the shore hardness of squeegee is 75,the angle of squeegee is 75°,and the screen printing plate is120 mesh.Finally,the main conclusions obtained and some future promising outlooks are given.