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We have demonstrated a nonlinear behavior for the bandgap opening of doped graphene by controlling the concentration of B and N co-dopants. X-ray absorption and emission spectra reveal that the bandgap increases from 0 to 0.6 eV as the concentration of BN dopants is increased from 0 to 6%, while the bandgap closes when the doping concentration becomes 56%. This nonlinear behavior of bandgap opening...
Adsorption isotherms and isosteric heats have been studied experimentally and by computer simulation for the krypton-graphitic hexagonal pore and krypton–graphite planar surface systems in the 60–109K temperature range. The existence of a 2D transition in the sub-monolayer film on the basal plane of graphite that is observed experimentally is confirmed by the computer simulation results, but this...
Large amount of vertically aligned carbon nanotube (CNT) arrays were grown among the layers of vermiculite in a fluidized bed reactor. The vermiculite, which was 100–300μm in diameter and merely 50–100μm thick, served as catalyst carrier. The Fe/Mo active phase was randomly distributed among the layers of vermiculite. The catalyst shows good fluidization characteristics, and can easily be fluidized...
Fluffy carbon nanotubes (CNTs), which are cotton-like macroscopic structures, are obtained by simple high-speed shearing of vertically aligned CNT (VACNT) arrays. The fluffy CNTs are composed of CNT bundles with a diameter of several micrometers, and have an extremely low apparent density of 3–10g/L. A requisite for their formation is the alignment of CNTs in the initial array. The shear between the...
Vertically aligned carbon nanotube (VACNT) arrays grown on ceramic spheres are obtained from ethylene using a floating catalysis process. The exhaust gas mainly contains light gaseous hydrocarbons, which decreases the contamination at the outlet of the reactor. Linear synchronous growth of the VACNT arrays is demonstrated and the morphology evolution of VACNT array grown on spheres is shown. The VACNT...
N 2 adsorption isotherms at 77 K of single-wall carbon nanotubes (SWNTs), multi-wall carbon nanotubes (MWNTs), and mixtures of these carbon nanotubes (CNTs) were analyzed for differences in their pore size distributions (PSDs). The PSDs, calculated in the microporous region by the Horvath-Kawazoe method and in the mesoporous region by the BJH method, are in agreement with the structures of...
CNT agglomerates, prepared by catalytic chemical vapor deposition in a nano-agglomerate fluidized-bed reactor are separated and dispersed. The effects of shearing, ball milling, and ultrasonic and chemical treatments on the dispersing of the carbon nanotubes were studied using SEM, TEM/HRTEM and a Malvern particle size analyser. The resulting microstructures of the agglomerates and the efficiency...
Ultrahigh purity multi-walled carbon nanotubes (MWNTs) were obtained, which were produced by a catalytic chemical vapor deposition method and subsequently annealed at vacuum pressures between 10 -3 and 10 Pa and temperatures between 1500 and 2150 o C. Acid treatments were made for comparison. Scanning electron microscopy, transmission electron microscopy and energy dispersive...
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