Research On The Performance Of Aqueous Graphene&Carbon Black Based Conductive Paste

Conductive carbon paste is a kind of special functional ink which is made of carbon conductive filler dispersed in the binder,and it's the key material of printed electronics.At present,the widely used conductive carbon paste exists serious problem of volatile organic compounds emissions,thus it is imperative to develop an environmentally friendly water-based system.In addition,the resistivity of traditional conductive carbon paste is high.It is necessary to improve the conductivity of conductive carbon paste by adding new materials.The appearance of graphene,a twodimensional nanomaterial with excellent electric conductivity,thermal conductivity and mechanical properties,provides an opportunity to improve the performance of conventional conductive carbon pastes.Now,countries around the world are increasing water-based functional paste research efforts to make it to the water-based,functional,inorganic direction.In view of the surface tension and volatile properties of water-based solvents,the solvent system was studied firstly.In order to research the influence of cosolvent hydroxyl group number on properties of water-based conductive carbon paste,a series of water-based conductive carbon pastes were prepared using isopropyl alcohol,propylene glycol,and glycerin as cosolvent,respectively.The influence of cosolvent hydroxyl group number was studied by considering the rheological properties,drying characteristics of the conductive carbon pastes and the surface morphologies and conductivities of the printed patterns.By adjusting the surface tension of the composite solvent,the "coffee ring" effect in the curing process was inhibited,and the interface between the solvent / filler interface and the paste / printed substrate was effectively controlled,and the conductive coating with controlled surface morphology was obtained.Results showed that the viscosity of the paste increased with the increase of hydroxyl group abundance,and the number of hydroxyl group affected the thixotropy of the paste also.Besides,with the increasing of hydroxyl group number,the boiling point and surface tension of cosolvent increased,which impacted the hydrodynamic flow within the paste.Thus the surface morphologies and microstructures of the printed patterns were affected by cosolvent and result in various conductivities.The conductive carbon paste with propylene glycol as cosolvent was the best for screen printing due to the weakness of coffee-ring effect and appropriate rheological properties which result in a smooth surface of the coating and uniform deposition of the fillers.The resistivity of the pattern printed by paste PG(with propylene glycol as cosolvent)reached to 0.44 ?·cm with the closest accumulation of conductive carbon black particles in it.In this paper,conductive graphene-carbon black pastes with different ratios were prepared.The rheological properties of the conductive carbon pastes and the surface morphologies,microstructures and resistivities of the printed coatings were systematically studied.It was proved that the synergistic effect of graphene and carbon black and the flexible two-dimensional layered structure of graphene played an important role in the construction of conductive network,which highlights the structural characteristics of graphene.The conductive graphene & carbon black paste with a weight ratio of 1:9 was best for screen printing and storage.The conductive fillers in the printed coating dispersed well and formed a good conductive network.The surface morphology of the printed coating is smooth.The electrical conductivity of the printed coating is the best and as low as 0.241?·cm.Considering the properties of the reduced graphene oxide prepared at different reduction temperatures were not the same,this paper compared the properties of aqueous conductive graphene & carbon black paste prepared by graphene with different degrees of reduction.It was found that the number of oxygen-containing functional groups on the surface of graphene had an effect on the viscosity,yield stress,stability and thixotropy of the conductive carbon paste and the conductivity of the printed coating.The less the oxygen-containing functional groups on the surface of graphene,the lower viscosity,elastic storage modulus and yield stress of the prepared conductive carbon paste,and the better the conductivity of the printed coating.