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Vertical graphene (VG) films can be fabricated on the surface of nickel foil from fullerene soot (FS) under microwave plasma irradiation (MPI) in a mixture gas of H2 and Ar at 1200 W for 15 min. The resulting FS-derived VG films mostly consist of few-layer graphene sheets with large domain graphene sizes, high graphitization order, and high purity, as characterized by scanning and transmission electron microscopies, Raman spectroscopy, and X-ray photoelectron spectroscopy. Combined the present and previous results, MPI technique is an effective and versatile approach to synthesize vertically oriented graphene sheets from any carbon-containing sources.

The composites consisting of graphene oxides (GOs) and carbon spheres (CSs), which were hydrothermally derived from the aqueous solution of glucose with average diameter of 200 nm, were mechanically mixed, and the GOs/CSs (GCSs) were thermally treated at high temperatures in the range of 700–900 °C. In the GCS composites, the CSs as spacers located between the GO sheets prevent the aggregation and restacking of graphene sheets. The GCS composites (GO/CS = 1) treated at 800 °C (GCS@800) have the high specific capacitances of 272.8 and 197.5 F g−1 in a three-electrode cell at the current density of 0.2 and 10 A g−1, respectively, in 6 M KOH aqueous solution, and demonstrated high rate capability and good cycling stability. The excellent electrochemical performance of the GCS@800 electrode is attributed to its structure with hierarchical porous structures including overwhelming micropores and a few of macropores. This work provides an effective and simple technique by integrating CSs and graphene sheets into composite structures for high-performance energy storage devices.

Nitrogen-doped porous carbon monoliths (NDP-CMs) have long been pursued as the desirable supercapacitor electrode materials. However, the currently effective template methods and Lewis acid/base activation strategy suffer from the drawbacks of either high costs or tedious steps. We report on a simple and practicable novel method to the production of CNTs constructed NDP-CMs. Polyacrylonitrile (PAN) contained carbon nanotubes (CNTs), being dispersed into tubular level of dispersions (mono-dispersions), were used as the starting material and NDP-CMs were obtained through a direct carbonization process. First, PAN/CNT based mesostructured polymeric monoliths with interconnected networks were formed using a template-free temperature-induced phase separation (TTPS) method and the mono-dispersed CNTs networks act as the backbones of PAN molecules. Then, NDP-CMs with a surface area of 840 m2/g and a pore diameter 2.48 nm were obtained through heat treatment. Thus, the NDP-CMs based supercapacitor demonstrated a reversible specific capacitance of 246 F/g. Furthermore, pyridinic nitrogen and quaternary nitrogen species contribute significantly to the advantageous electrochemical activities of NDP-CMs.

Graphitization of carbon materials plays an important role their microstructures and conductivity, and then influences their applications. However, the graphitization of hydrothermal carbon spheres (CSs) has not systemically investigated heretofore. The CSs with 60–250 nm in diameter were prepared from aqueous glucose solution by hydrothermal carbonization, and were treated at the high temperatures of 900–2900 °C in Ar atmosphere. The heat-treated CSs have demonstrated that their surface structure, microstructure, porosity, and polygonization strongly depend on the treatment temperatures. These results are supported by scanning and transmission electron microscopes, energy dispersive x-ray spectrometry, Raman, X-ray diffraction, and BET surface area analyses. We also investigated the electrical properties of the heat-treated CSs under compression, and found that the resistivity of the carbon particles is very dependent on their surface, microstructure, density, and polygonization. Therefore, high temperature treatment is an effective method to tailor the structure, morphology, and property of the hydrothermal CSs.

Recently, graphene and carbon nanotube (CNT) composites have attracted great interest of scientists and exhibited fascinating properties even better than they could on their own. Here, we have synthesized the graphenated CNTs (g-CNTs), one of graphene–CNT composites, from waste rice husk (RH) by one-step microwave plasma irradiation (MPI) process. The RH-derived g-CNTs were composed of graphene standing on the sidewalls of CNTs, in which the graphene sheets possessed a large amount of sharp edges, which mainly consisted of 2–6 layers, and the CNTs had several tens of micrometers in length and 50–200 in diameter. They offer great promise in the application of electrochemical electrodes due to their special features including high surface area and specific capacitance. The successful MPI technique can be spread to other waste biomass, in which their components are made of cellulose, hemicellulose, and lignin similar to RHs, to fabricate high-added-value nanocarbons including graphene, CNTs, and g-CNTs, which were dependent of experimental pressure.

Helical graphite whiskers (GWs) have been synthesized from fullerene waste soot, which is a byproduct in fullerene production by arc discharge technique, at 2600 °C for 1 h with Ar gas flow at 760 Torr. The as-synthesized GWs consisting of graphite layers with some disclination possess various kinds of morphological structures with loop-like brims and arch-shaped protrusion on their surfaces, as observed by scanning and transmission electron microscopy. The GWs show strong intensity of 2D peak in Raman spectra, which could be attributed to disclination in the whiskers.

Graphene-sheet fiber, a novel structure of graphitic carbon, grew from coffee grounds under the condition of microwave plasma irradiation. The resulting fiber consisted of only few-layer graphene without a hollow structure inside while possessing a large amount of graphene edges and high conductivity. Due to these advantages, graphene-sheet fibers may find applications in electrochemical energy conversion and storage.

Vertically-aligned carbon nanosheets (CNSs), which were fabricated by microwave plasma-enhanced chemical vapor deposition in Ar and CH 4 system, have been annealed at high temperatures in the range of 1200–3000 °C. The morphologies and microstructures of the treated CNSs were analyzed by scanning and transmission electron microscopes, and Raman spectroscopy. High temperature treatment process efficiently removed the amorphous carbon and some defects and improved the graphitization of the CNSs. The graphitized grains increase and the interlayer spacing decreases with increasing heat temperatures. Heat treatment of the CNSs at temperatures from 1500 to 2000 °C was found to achieve the edges consisting of many single-layer graphene sheets. Annealing at temperatures above 2100 °C, the edges of nanosheets consist of 2–5 layer graphene with many zigzag junctions. The mechanism of reconstruction for the edges in the CNSs ascribes possibly to the carbon atom vaporization at high temperatures.

We report the synthesis of high purity double-wall carbon nanotubes encapsulating GdCl 3 nanowires (GdCl 3 @DWCNTs). The obtained GdCl 3 @DWCNTs were characterized by transmission electron microscopy (TEM), Raman spectroscopy, UV–Vis-NIR spectroscopy, and fluorescence spectroscopy. TEM measurements show that GdCl 3 impurities were absent on the exterior of the tubes and bundles. Furthermore, significant changes of the optical properties of the inner tubes were not triggered by being filled with GdCl 3 nanowires, which suggests that significant charge transfer does not occur between the encapsulated GdCl 3 and the inner tubes. Our results indicate that GdCl 3 @DWCNTs could be useful for various applications using the expected magnetic properties of GdCl 3 and almost unchanged optical properties of DWCNTs. [TANSO 2013 (No. 260) 279–83.]

A limited use of hydrogen peroxide in supercritical water has produced graphitic carbons from hydrocarbons at the low temperature of 400 °C. The choice of precursor hydrocarbons leads to morphological and microstructural variations. The use of n-hexane has provided chain-like interlinked nanoparticles comprised of graphitic layers, while benzene has been converted to a fine spherical shape of colloidal carbons with sub-micron size. The microstructure of the colloidal carbons is comprised of smaller aromatic clusters than the hexane-derived graphitic layers. Furthermore, the graphitization of the colloidal carbons at 2300 °C has induced not closed shell-like graphitic layers with concentric arrangement but ribbon-like graphitic layers growing in no particular direction. The arbitrary direction of the graphitization demonstrates the smallness of the aromatic clusters allowing for their flexible rearrangement.

Article, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS. 69(10): 2481-2486 (2008)

A simple construction of sol–gel sheaths onto the surface of multi-walled carbon nanotubes (MWCNTs) has been carried out in water by a hydrophobicity-induced covering with the assistance of ultrasound. The ultrasound assistance prevents in water an unregulated agglomeration induced by the hydrophobicity of MWCNTs and phenyl-containing sols, leading to a selective construction of sol–gel sheaths on the nanotube surface. The phenyl groups of the resulting sol–gel sheaths were successfully removed by air-oxidation to provide the MWCNTs covered with amorphous SiO 2 sheaths. The effect of the SiO 2 sheaths on the electrical and thermal properties of the SiO 2 -MWCNT nanocomposites was evaluated from the electrical resistivities of the nanocomposites with two different SiO 2 concentrations and the thermal conductivities of their phenol-resin composites. The results indicate that the small increase of the SiO 2 concentration remarkably increases the electrical resistivity of the SiO 2 -MWCNT nanocomposites. Furthermore, the SiO 2 sheaths have more directly influenced the thermal property of the polymer composites than the inside nanotubes.

A high dispersion of carbon-supported Pt–Ru alloy nanoparticles have been prepared in an alkaline aqueous solution by using glyoxylate as a reducing agent. The glyoxylate monoanion is converted to oxalate dianion with the reduction of metal precursor ions. The surface-potential analysis of unsupported Pt–Ru black in the presence of all the anion species coexistent in the preparation system suggests a possibility of oxalate dianion as the most effective particle stabilizer. In the glyoxylate-reduction system, a precursor–support interaction is significantly promoted to affect the formation and stabilization of nanoparticles. The glyoxylate reduction at 20-wt% metal loading has provided a higher Pt(0)/Ru concentration ratio in the near-surface region than that of 60-wt% catalyst. The structural and morphological features and advantageous surface composition of the 20-wt% catalyst contribute to the high mass activity for methanol oxidation in the anode overpotential range of typical direct methanol fuel cells.