Modification Of Graphene And Its Fabrication And Properties Of Composites

Graphene, a flat monolayer of carbon atoms tightly packed into a two-dimensional honeycomb lattice, has attracted enormous attentions since it was discovered in 2004, due to its potential applications in electronics and electrical appliance, energy chemical industry, biomedical engineering and many other areas.In order to utilize the unique structure and excellent properties of graphene, graphene was first modified and then added into other materials to prepare the graphene composites with good properties. The main contents and results of this dissertation are summarized as follows:1) PNIPA/graphene oxide?PNIPA/GO? hydrogel composite was synthesized through in-situ polymerization. And then it was reduced to PNIPA/graphene composite with hydrazine hydrate. The research results show that with the addition of graphene, porous structure of hydrogel increases, which provides more water-releasing channel. Therefore, compared with pure PNIPA hydrogel, PNIPA/graphene hydrogels exhibit higher equilibrium swelling ratio, faster deswelling rate and better temperature sensitivity. With the increasing content of graphene, PNIPA/graphene hydrogels show better smart properties.2) 1- pyrene methanol was used to modify graphene, based on the ?-? interaction between 1- pyrene methanol and graphene, the unique structure and excellent properties could be preserved. Then the modified graphene was added into poly?vinylidene fluoride? and the graphene/PVDF composites was obtained by solution-casting and layer-by-layer hot-pressing. The experiment results show that 1- pyrene methanol could be firmly attached on the surface of graphene. This modified graphene can be well dispersed in N,N-dimethyl formamide? DMF? and PVDF matrix. The dielectric constant of the Gr-P/PVDF composites improves with the increase of Gr-P content. When the Gr-P content was 5wt%, the dielectric constant of the composites reaches up to 47.6, which is 10.6 times than pure PVDF.3) The reduced graphene and Li₂ S was mixed thoroughly to prepare the Gr/Li₂ S composites. The composites' structure and morphology, along with the electrochemical properties were characterized. The experiment results show that the Gr/Li₂ S composites exhibit super electrochemical properties. It remains the capacity of 528 mA h g^-1 after 50 cycles at the current density of 0.1 A g^-1, which changes little compared with the capacity after 10 cycles(529 mA h g^-1). The Coulombic efficiency of the composite was 50.9% at the first time, however, it reaches up to 97.6% after 50 cycles.