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Electron paramagnetic resonance (EPR) study of air-physisorbed defective carbon nano-onions evidences in favor of microwave assisted formation of weakly-bound paramagnetic complexes comprising negatively-charged O2− ions and edge carbon atoms carrying π-electronic spins. These complexes being located on the graphene edges are stable at low temperatures but irreversibly dissociate at temperatures above...
π-Electronic edge-localized spin magnetism in defective carbon nano-onions (DCNOs) derived from detonation nanodiamonds was investigated in terms of molecular oxygen adsorption and microwave (MW) irradiation effect. At low MW power (P MW ⩽200μW) electron paramagnetic resonance (EPR) spectra of air-contained DCNO samples show progressive broadening of the g=2.0014(2) edge-spin signal on temperature...
Compositional changes of the residual iron compounds in isothermally treated catalytic chemical vapor deposition derived multi-walled carbon nanotubes have been monitored using 57 Fe transmission Mössbauer spectroscopy and X-ray fluorescence. The iron phases entrapped in the as-synthesized carbon nanotubes consist of γ-iron, α-iron, Fe 3 C and Fe 1−x S. The Fe 1−x S...
Systematic isothermal annealing has been carried out on catalytic chemical vapor deposition-derived highly disordered multi-walled carbon nanotubes in order to understand the structural evolution of carbon nanotubes kinetically. After specified isothermal time the crystallographic parameters strongly depend on annealing temperature, and can be divided into three stages. Rapid structural enhancement...
The time evolution of graphitization was analyzed based on the structural and magnetic properties of nanodiamond samples annealed at 1600°C for various time intervals. High resolution TEM and XRD show that the nanodiamond particles are converted to spherical onions for short annealing time intervals, and then they are completely transformed to polyhedral nanographite through the annealing for 120min...
Here we describe synthesis of very unusual multi-walled carbon nanotubes through a catalytic chemical vapor deposition method using a floating reactant method and subsequent thermal treatment up to 2600°C in a large quantity. Main characteristics of these nanotubes are (1) relatively wide distribution of diameters ranging from 20 to 70nm and linear, long macro-morphology (aspect ratio >100), (2)...
Systematic studies of structural changes in stacked cup carbon nanofibers by heat treatment from 1800 to 3000 o C are carried out. The most prominent feature upon heat treatment of these nanofibers is the formation of energetically stable loops between adjacent active end planes both on the inner and outer surfaces. The appearance of the jagged outer and inner surfaces at 3000 o C...
A morphological characterization of activated AR-resin was carried out. The time and temperature effect of the EDLC (electric double layer capacitor) properties of AR-resin were investigated. In order to clarify the relation between the electric double layer capacitance and the ion mobility in the organic solvent, a computer simulation was used to calculate the possible solvation size of Et 4...
Carbon nanofibers with diameters of 80-100 nm were obtained by the pyrolytic method when a benzene solution containing ferrocene was used as a feedstock. A higher flow rate of carrier gas induced variations in the macro-morphology and also in the microstructure. The characteristics of these fibers were bundle formation, such as a macro-fibril, with a different tip morphology as compared with that...
The topological change of the surface of vapor-grown carbon fibers (VGCFs) as a function of heat treatment temperature was observed using FE-SEM, STM and AFM. The morphological change at the micrometre scale from a smooth surface, to a rope-like structure, and to a grain-like structure was closely related with the volume change, especially due to the annular fiber form. The extent to which the micro-domain...
Submicron vapor grown carbon fibers (VGCFs) obtained by a floating growth method were evaluated in terms of their microstructural development with heat treatment temperature (HTT), physical properties of a single fiber and of the bulk state, and additional effects, such as the filler in the electrode of a lead-acid battery and a Li-ion battery system. Its desirable properties, such as relatively high...
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