Papers by Keyword: Carbon Spheres

Abstract: The nitrogen-doped mesoporous carbon spheres have been synthesized via soft-template and hydrothermal synthetic strategies using phenol/formaldehyde resins as carbon sources and melamine as a nitrogen source. The obtained carbon spheres exhibit a spherical morphology with a size range of 3-5 μm, which possess the narrow microporosity (ca. 1.2 nm) and mesoporosity (ca. 4 nm), large surface area (560-1200 m² g^-1) and high nitrogen contents (up to 15.7 wt%). Due to the well-developed porous structure and high nitrogen content, the carbon spheres show high performance for hydrogen storage, and the hydrogen adsorption capacities are in the range of 140-185 cm³ g^-1, which is better than that of most activated carbons. The incorporation of nitrogen into carbons is favored for hydrogen uptake in low pressure.

Abstract: Carbon nanospheres of uniform diameter around 40 nm have been achieved in the absence of catalyst by microwave pyrolysis chemical vapor deposition. The products have been characterized by field emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, Raman spectroscopy and thermogravimetric analysis. The results show that the nanospheres with high purity, which are solid by their cross-sections, consisting of concentric incompletely closed graphitic layers. Their thermal stability in dynamic air atmosphere is also discussed.

Abstract: The reactions were carried out by decomposing acetylene at 700 °C in a two-stage furnace system under different conditions. In the two furnaces, an AAO template with the average diameter about 50 nm was placed respectivly, whose temperature was designed to be 700 °C. The samples were characterized by scanning electron microscopy and high resolution transmission electron microscopy. The results show that when the reaction was carried out in C2H2-Ar atmosphere, dense and entangled CNTs with diameter, ca. 50 nm were obtained on the top surface of the AAO template in the first furnace and dense and entangled CNTs with morphology of rope were obtained on the top surface of the AAO template in the second furnace. When the reaction was carried out in C2H2- H2-Ar atmosphere, dense and entangled CNTs with diameter, ca. 50 nm were obtained on the top surface of the AAO template in the first furnace, however only a few CNTs were obtained in the second furnace. When the reaction was carried out in C2H2- H2 atmosphere, CNTs were both observed stood on the top of AAO template in the two furnaces

Abstract: Carbon spheres were synthesized by chemical vapor deposition using iron catalyst supported on aluminum hydroxide, in the presence of acetylene as the carbon source. The effects of catalyst on the diameters of carbon spheres were investigated in detail. The products were characterized by field-emission scanning electron microscopy, element analysis, high resolution transmission electron microscope. The results show that the carbon spheres, to some degree, can be controlled by the catalyst

Abstract: In this paper, carbon spheres were synthesized by CVD method. These carbon spheres exhibit diameters of about 200 nm. Thermal gravimetric analysis indicated the good stability in high temperature of the carbon spheres. The products were treated by microwave plasma and high temperature vacuum heat treatments respectively. The products were characterized by X-ray diffraction, Raman spectroscopy and Field Emission Scanning Electron Microscope. The study indicated that the original products, with perfect morphology and low graphitization degree, were converted to crystal. The different techniques were considered for the influence on the graphitization degree.

Abstract: The reactions were carried out by decomposing acetylene at 1000 °C in a two-stage furnace system for 10 min. In the first furnace no catalyst was placed and an AAO template with the average diameter about 50 nm was placed in the second furnace whose temperature was designed to be 500 °C, 600 °C and 700 °C. The samples were characterized by scanning electron microscopy and high resolution transmission electron microscopy. The results show that carbon spheres with average diameter about 50 nm on the AAO template surface were obtained when the temperature of the second furnace was designed to be 700 °C. These carbon spheres are composed of unclosed graphene layers with an interlayer distance of 0.33–0.35 nm between the layers.

Abstract: The present work used hydrothermal synthesis method utilizing glucose as carbon source to obtain homogeneous nano-sized carbon spheres. The holding time and the concentration of glucose have a remarkable effect on the microstructure of nanometer carbon spheres. When synthesized at a constant temperature and kept the same in the productivity, the lower concentration of glucose or the shorter holding time, the easier to acquired homogeneous and tiny nanometer carbon spheres

Abstract: Carbon spheres were synthesized by chemical vapor deposition. The products deposited at different zones were separately collected. Furthermore, an anodic aluminum oxide template was used to control the size of carbon spheres. The products were characterized by field-emission scanning electron microscopy, high resolution transmission electron microscopy and X-ray diffraction. The results show that carbon spheres with controllable size distribution were obtained and the size distribution of these carbon spheres can be controlled to some degree by deposition zone and anodic aluminum oxide template.

Abstract: The reactions were carried out by decomposing acetylene at 1000 °C in a two-stage furnace system for 10 min. In the first furnace no catalyst was placed and an AAO template with average diameter about 50 nm was placed in the second furnace whose temperature was designed to be 700 °C. The samples were characterized by scanning electron microscopy and high resolution transmission electron microscopy. The results show that carbon spheres with average diameter about 50 nm on the AAO template surface were obtained and these carbon spheres are composed of unclosed graphene layers with an interlayer distance of 0.33–0.35 nm between the layers.

Abstract: Carbon nanotubes, carbon spheres and slices of vertically aligned multiwalled carbon nanotubes (MWNTs) were synthesized simultaneously by chemical vapour deposition (CVD). Electron microscopy image showed carbon nanotubes were multiwalled carbon nanotubes, several micrometers in length. Carbon spheres were of uniform diameter (about 1 μm). Slices of vertically aligned multiwalled carbon nanotubes were about 5 mm in length, 3 mm in width and 8 μm in thickness. The interior of the slice was composed of densely packed, vertical aligned MWNTs, and faceted carbon beads. They were stable and easily separated from each other. The formation mechanism of slice was also discussed.