New Method To Prepare Graphene And Its Application In Thermal Conductive Silicone Rubber

Graphene, the two-dimensional sp2-hybridized carbon, is a single-atom-thick material. Since its discovery in 2004, it has attracted lots of researchers due to its excellent properties of electricity, thermal conductivity and mechanical strength etc.. However, the preparations of Graphene are still limited in Oxidation-Reduction method, Liquid-phase Exfoliation or others. These preparations have their respective pros and cons. For example, Oxidation-Reduction method has the high yield but the product structure is badly destroyed while Liquid-phase Exfoliation could preserve its property but the yield is quite low. Moreover, Graphene has no reactive functional-groups and could not be dispersed in common solvents, which restrict its application in many fields. In the past years, methods to modify Graphene Oxide have been constantly reported. But the decoration of high-quality Graphene is rarely concerned. In this dissertation, we focus on the synthesis and modification of Graphene, employing the Stage-1 Intercalation-Exfoliation combined with the Sonication to prepare high-quality Graphene. Then we modify high-quality Graphene by edge-sulfonation and gain the Graphene-base Composite by Anionic Polymerization. In the last chapter, we do a systematic research on the application of Graphene in Thermal Conductive Silicone rubber. Specific work is as follow:1) Based on Micromechanical and Liquid-Phase Exfoliation, we design a route to peel Graphite from inside out and prepare high-quality Graphene. Stage-1 Graphite Intercalation Compound is taken as precursor and expanded in Na BH4 solution. After Sonication and drying, we gain the Graphene powder with the layers from 1 to 5. By characterization of TEM, SEM, XRD, Raman etc., We found that our product has low structural defect(ID/IG=0.12), high electrical property(2.6×10^5 S/m) and could be controlled in two-dimensional size by the size of nature flake graphite.2) Recent modification of Graphene is mainly focus on its surface and edge. Although derivation on Graphene surface could well improve its dispersibility, the sp2 lattice structure is badly damaged. In this dissertation, we report the methods to modify high-quality Graphene and disperse it by edge-sulfonation or anionic polymerization coating. With the characterization of FT-IR, TG, Raman, SEM etc., it shows that the structure of Sulfonated Graphene is less destroyed(ID/IG=0.17) and its sulfonation is about 1%wt while Coated Graphene by anionic polymerization preserves lattice structure well(ID/IG=0.12). All these methods result in the well dispersion of Graphene in common solvents.3) We apply high-quality Graphene in Addition-Cure Silicone Rubber to study its effect on the thermal conductivity, viscosity, hardness and other properties of Silicone Rubber. Our research found that by adding 3 parts of Graphene, the hardness of Silicone Rubber is reduced 24% and the thermal conductivity is reach to 0.35W/m.K, representing a 120% increase compared with the blank(0.16W/m.K). But the addition of Graphene would seriously increase the viscosity of Silicone Rubber even result in thixotropy. When Graphene and Alumina filler are combined to apply in Silicone Rubber, by synergistic analysis of thermal conductivity, we found that 1-3 parts of Graphene has synergistic effect for 50-100 copies of Alumina. But there has no synergistic phenomenon when the amount of Alumina filler is more than 250 copies.