Preparation And Property Regulation Of The Graphene Conductive Composite Structure

Graphene has attracted worldwide attention due to its unique two-dimensional structure and excellent physical properties since its discovery in 2004.As a new type of conductive filler,graphene has a wide application prospect in the field of functional composites.However,graphene is prone to be agglomerated owing to its two-dimensional structure,which results in problems such as hard to well disperse,high filling content,and less improvement in electrical and thermal transmission performance in the polymer-based composite.For functional graphene composites,the core issue is the efficient stretching of the graphene network.In this paper,the preparation of edge modified graphene and coating graphene on the surface of fibers and microspheres were studied in order to obtain the conducting network with excellent electronic transmission performance and high-efficient stretching structure,so as to promote the application of graphene in the field of functional composites.This paper is oriented by the application of graphene in the field of conductive composites and focuses on the preparation and performance regulation of graphene conductive composite structure.The main contents are as follows:(1)Chemical modification of graphene while maintaining its structural integrity is the key to the preparation of high performance graphene nanocomposites.In this paper,the difference in reactivity between the carbon atoms at graphene edge and in the lattice was used to synthesis the edge-modified graphene from large-sized multi-layer graphene by combining physical smashing and chemical oxidation.A series of characterization methods were used to analyze the micro structure and chemical composition of the modified graphene,and the effects of different preparation conditions on the structure or properties of the modified graphene were also compared.The edge oxidation of graphene can significantly improve the water solubility of graphene while maintaining its conductivity.When the Zeta potential of the modified graphene dispersion reaches-32.8 mV,its volume conductivity is 320.3 S/cm,which still accounts for more than 40%of the graphene raw material,which is attributed to the highly oxidized edge and perfect internal structure of the edge-modified graphene.(2)Coating two-dimensional graphene on the surface of fibrous template is an effective method to construct long-range conductive pathway of graphene.In this paper,continuous graphene conductive coating was prepared on the surface of glass fiber through sol-gel and dip-coating technique.Landau-Levich equation and Plateau-Rayleigh instability were used to analyze the effects of different preparation processes on the morphology,thickness and uniformity of the graphene coatings.The graphene coating changes the wettability of the fiber,which contact angle against water gradxually increased from 230°to 105°.On the other hand,graphene endows the fibers with fine conductivity,which conductivity could reach to 24.9 S/cm.Further analysis shows that the graphene coating has gradient structure,which compactness and reduction degree is closely related to the dip coating process.(3)Construction of the outstretched graphene network is the precondition of preparing high performance conductive composites.In this paper,a new method of coating graphene on the surface of microspheres was proposed.By bounding graphene and a single bead of hollow glass microsphere inside the dispersed droplets of emulsion simultaneously,the graphene coated hollow glass microspheres were obtained a:fter evaporation of the emulsion?in which graphene accounts for 3%of the mass fraction in the composite microspheres.The fiunctions of each related factor in the preparation process were analyzed emphatically.Then the graphene coated microspheres were added into silicone rubber as conductive filler to prepare composites.When the content of graphene is 1.2 wt%,the resistivity of the composites is 3.16×105?·cm,which is 6 orders of magnitude lower than that of the composites filled with graphene and hollow glass beads respectively.The reason is that graphene can maintain good stretching state in polymer matrix supported by rigid template,which is beneficial to the establishment of graphene conductive network in composites and effectively reduces the percolation threshold of the composites.