Search

To meet the requirements of the energy storage materials for high energy density and high power density, porous silicon carbide/derived carbon-spherical natural graphite (SiC-CDCs@NG) composites were prepared. The composites were composed of tailored porous carbide-derived carbon and graphitized carbon with excellent conductivity and a high energy storage capacity. The composition, structure, morphology, pore structure, and specific surface area of the composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and N2 adsorption/ desorption analysis. The composites exhibited a high and adjustable specific surface area and micro-pore volume, with a micro-pore size of between 0.5 and 0.7 nm. Varying the molar ratio of NG and Si allowed optimization of the micro-pore volume, pore size distribution, specific surface area, and composition and content of the CDCs shell and NG core.

Partially reduced graphene oxide/titanium dioxide (RGO/TiO 2 ) composite was synthesized using tetrabutyl titanate and graphite oxide by a hydrothermal method. Photocatalytic activity of the material was evaluated by the degradation of methylene blue solution under visible light and UV light. The results suggest that the crystal phase and dispersion of titanium oxide in the composite can be controlled by varying the reaction temperature and amount of graphite oxide. Graphene oxide was partially reduced in the hydrothermal reaction process. Photocatalytic activities of partially reduced graphene oxide/titanium dioxide composites under both visible and UV light irradiation were higher than those of pure TiO 2 . Partially reduced graphene oxide may act as a support and electron acceptor, and can also extend and enhance the band edge absorption of TiO 2 into the visible light region, hence effectively enhancing the adsorbability and photocatalytic activity of TiO 2 .

Using a naphthalene derived mesophase pitch as starting material, high oriented ribbon-shaped carbon fibers with smooth and flat surface were prepared by melt-spinning, oxidation stabilization as well as further carbonization and graphitization processes. The composition, morphologies and microstructure of the ribbon-shaped carbon fibers treated at various conditions were characterized by elemental analyses, IR spectroscopy, XRD, Raman spectroscope, scanning electron microscope and polarized-light microscope. The results show that the carboxyl, carbonyl and ether functional groups formed during the oxidizing stabilization process are removed by subsequent carbonization treatment. The width and thickness of the ribbon-shaped fibers at the transverse section decrease from 1.6mm and 18μm of pitch fiber to 1.2mm and 9μm of graphitized carbon fibers, respectively. The relative intensity of the diffraction peak at about 2θ = 26° corresponding to (002) crystal plane of hexagonal graphite increases with the heat-treatment temperature increasing. This indicates that the crystal size of graphite in this carbon fibers also increases in this process. In comparison with the carbonized fibers, the carbon fibers after graphitization treatment display more perfect crystal orientation along the main surface of ribbon-shaped carbon fibers.

Using mesophase pitch as the raw material, with the rectangular-section spinnerets at different aspect ratios (length divided by width), ribbon-shaped mesophase pitch-based carbon fibers with various cross-section sizes and crystal orientations were prepared by adjusting the spinning rate. Effects of the heat-treatment temperature and aspect ratio of spinnerets on structure and properties of the ribbon-shaped carbon fibers were investigated. The results show that the aspect ratio of spinneret and the spinning rate of pitch fibers have a significant influence on the crystal orientation of carbon fibers. Within the specified spinning rate of pitch fibers, the crystal orientation of carbon fibers varies from a parallel-fold structure to a vertical-radial structure with the decrease of the aspect ratio of the spinnerets. The electrical conductivity and the mechanical property of ribbon-shaped carbon fibers significantly increase with the increase of heat-treatment temperature. With increase in spinning rate, there is no obvious change in the room-temperature axial electrical resistivity along the longitudinal direction of fiber, whereas obvious changes in the mechanical property are observed. At 30:1 of the aspect ratio of the spinneret and 75 m/min of spinning rate, the tensile strength and young’s modulus of the graphite fibers heat-treated at 2500°C are up to 2.53 GPa and 234.77 GPa, respectively. 第 11期 熊小庆, 等: 不同晶体取向中间相沥青基带状炭纤维的制备与表征 1187