Graphene Based Materials For Electrical And Thermal Conductive Intercontect

With increasing miniaturization of systems and circuit density, the operational lifetime and reliability of the electronics are more and more relay on the solution of the problems of conductive connection and heat dissipation. Graphene is the best material of electrical conductivity and thermal conductivity at present. So it is with great significant for the research on the graphene based materials for electrical and thermal conductivity in electrical packing field.The chemically derived graphene sheets are often decorated by abundant intrinsic active sites, such as functional groups（mainly-OH,-COOH,-C=O,-C-O-C-）, lattice defect（atom vacancy, distortion, dangling bonds） on the lateral surface and edge. The active sites could be further modified by surface reaction with atoms such as nitrogen, boron, and phosphorus, so as to tune the acid/base property and electronic structure of graphene. Or introduce the active materials to form graphene based composite as materials for energy storage and conservation. These specific advantages provided potential application of graphene for advanced energy conversion and storage. This work has been carried out on the graphene based materials for electrical and thermal conductivity. Concentrate on the electrical and thermal conductivity of graphene film, and the electrical electrode for energy storage materials of three-dimensional graphene based materials. The main results of the thesis are as follows:（1） Graphene nanosheets are prepared by electrochemical exfoliated of graphite in sodium lauryl sulfate（SDS） electrolytes. Through the characterization of AFM, TEM and SEM, we know the morphology and size of the exfoliated graphene; XRD and Raman indicated the quality of graphene. The graphene films exhibit low sheet resistance and excellent heat conductivity, the sheet resistance is 85Ω/sq and the thermal conductivity is 674.3 Wm-1K-1.（2） SnO₂-graphene composite are prepared by electrochemical exfoliated of graphite in sodium stannate（Na₂SnO₃）. Morphology and structure analysis confirmed the presence of few layer graphene sheets in as-exfoliated products. Exfoliated in the electrolyte can be observed that the size of the graphene layers from nano-to-micrometer, yield is relative high, low oxidation degree and high quality. Moreover, high conductivity（electrical conductivity ¹9980 S m-1） and excellent flexibility of graphene paper was obtained via vacuum filtration. The graphene paper exhibits high in-plane thermal conductivity of 535.3 W m-1K-1, this obtained results are important for thermal management in lithium ion and other high-power-density batteries. And the lithium storage properties based on such exfoliated binder-free flexible freestanding graphene paper electrode demonstrates a high special capacity of about 698.8 m Ah g-1 at the current density of 200 m A g-1 after 100 cycles and excellent rate capacity.（3） Hollow spherical SnO₂-Fe₂O₃ mesoporous spheres（h-SnO₂-Fe₂O₃） are fabricated using Si O2 spheres as template. Three-dimensional（3D） reduced graphene oxide（RGO） frameworks confined hollow spherical SnO₂-Fe₂O₃@RGO（3D h-SnO₂-Fe₂O₃@RGO） are successfully obtained by hydrothermal reduction of h-SnO₂-Fe₂O₃@GO in graphene oxide（GO） suspension. As anode materials for lithium-ion batteries（LIBs）, the 3D h-SnO₂-Fe₂O₃@RGO hieratical architectures display great improvement in revisable capacity（⁸30 m Ah g-1 after 100 cycles at 200 m A g-1）, cycling performance and rate capability（⁵50 m Ah g-1 at 1000 m A g-1）, which is much better than those of hollow SnO₂ spheres（h-SnO₂）, h-SnO₂-Fe₂O₃, and 3D RGO frameworks wrapped hollow spherical SnO₂@RGO nano-shells（3D h-SnO₂@RGO）.