| Graphene, with its unique two-dimensional structure and excellent electrical, mechanical and thermal properties, has a bright future in the application of composite materials. In this study, graphene oxide (GO) was prepared by chemical method, and the effects of the size of the graphite particles and the oxidation process had been invesitaged in terms of the morphorlogy, structure and oxygen content. Based on the solution mixing method, two-dimensional graphene oxide/ poly(vinyl alcohol) (GO/PVA) nanocomposites were prepared. Detailed studies on the composition, microstructure and mechanical properties had been carried out. Furthermore, three-dimensional GO/PVA foam and its reduced GO/PVA foam (r-GO/PVA) nanocomposites were successfully fabricated using a freeze-drying method followed by thermal treatment. The microstructure, mechanical stability and electrical properties of the 3D foams were investigated, and its application in lithium lion-battery has been tentatively discussed as well.For GO, the morphorlogy of its flakes were directly influenced by the size of the original graphite and the oxidation process. With the oxidation processed, the graphite experienced exfoliating, crushing and turned into small pieces from large ones. Also, the interlayer distance and the oxygen content increased with the oxidation time.For two-dimensional GO/PVA nanocomposite, GO and PVA were combined by hydrogen bondings with a good dispersion. The results of tensile tests and nanoindentation showed that GO (<1 wt%) additive can significantly improve the mechanical properties of the PVA matrix. The water content in the GO/PVA films can significantly influence the mechanical properties, that the water molecules can form the weak hydrogen bonds between water-GO, water-PVA and water-water by breaking the primary strong hydrogen bond between GO and PVA. Tensile tests indicated that the strength and modulus of the nanocomposite increased by dehydration, while the fracture changed into a brittle mode from a ductile one.For three-dimensional GO/PVA and r-GO/PVA foam, they had excellent structure stability. With control of ratio of GO and PVA, the pore size properties can be well tuned, and a good combination of mechanical property and electrical conductivity can be obtained. It is the first time to try it in application of the cathode of lithium ion battery, and the results showed that the first discharge capacity was up to 776mAh/g, higher than the theory reversible capacity of graphite, and the capacity was about I30mAh/g after 100 cycles. |
PDF Full Text Request