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Chemical vapor infiltration was used for the production of carbon/carbon composites based on exfoliated graphite and pyrolytic carbon. Two different exfoliated graphites compacted to densities of 0.05–0.4g/cm 3 were used as a preform. The influence of the synthesis conditions (temperature, pressure, time etc.) on the degree of infiltration, the pyrolytic carbon morphology and the C/C composite...
Expandable graphite of two types was synthesized by (1) hydrolysis of graphite nitrate of II stage and (2) anodic polarization of graphite in 60% HNO 3 . Exfoliated graphite samples were produced by thermal shock of expandable graphite samples in air at 900°C. A comparative study of microstructural distinctions of both expandable and exfoliated graphite samples was carried out using X-ray...
The interaction between evaporated gold and pristine or oxygen plasma treated multi-walled carbon nanotubes (MWCNTs) is investigated. Experimental and theoretical results indicate that gold nucleation occurs at defect sites, whether initially present or introduced by oxygen plasma treatment. Uniform gold cluster dispersion is observed on plasma treated carbon nanotubes (CNTs) and associated with the...
Expanded graphite decorated with nickel oxide particles (EG NiO ) has been synthesized through electrochemical oxidation of natural graphite in an aqueous nickel nitrate solution followed by a heat treatment. EG NiO was used to prepare nickel/carbon composites using two techniques: (a) hydrogen reduction of nickel oxide particles loaded on the expanded graphite surface and (b) pyrolysis...
Exfoliated graphite samples (EG) with different bulk densities were prepared by the exfoliation of expandable graphite under a thermal shock regime. As a conductive filler, EG has been incorporated successfully into the coal tar pitch matrix by mechanical mixing. The conducting behavior of the composite was interpreted based on the percolation theory. The percolation threshold of the EG/pitch conducting...
Multi-wall carbon nanotubes (MWCNTs) were exposed to a CF 4 rf-plasma. X-ray photoelectron spectroscopy analysis shows that the treatment effectively grafts fluorine atoms onto the MWCNTs. The fluorine atomic concentration and the nature of the C–F bond (semi-ionic or covalent) can be tuned by varying the exposure time. Ultraviolet photoelectron spectroscopy analysis confirms that the valence...
The vibratory mill is used to decrease the single-wall carbon nanotubes (SWNTs) length and to increase their specific surface area. Electron microscopy, Raman spectroscopy, X-ray diffraction and BET measurements indicated that the optimum time of treatment seems to be 2 h. After that, the SWNTs quality decreases, with a complete disruption of the tubular structure leading to multi-layered polyaromatic...
Several TEM techniques are used to characterise the local structure of low dimensional forms of carbon. HREM is particularly useful to describe the defect structure of thin films of diamond or fullerenes and C 60 –C 70 nanoclusters. A columnar form of graphite is analysed, mainly by electron diffraction which allowed us to propose a growth mechanism. Diffraction contrast dark field...
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