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Carbon tubes were obtained by chemical vapor deposition at 700 and 800°C using Ni phthalocyanine as a starting material. The tubes grew perpendicularly on a quartz glass substrate, and then bent and often coiled as their diameter decreased. Transmission electron microscopy images revealed that the outer and inner diameters of the thin part of the tube were 20∼40 nm and about 10 nm, respectively...
Adsorption methods, mercury porosimetry, electron and tunneling microscopy, and diffraction techniques were used to study filamentous carbon produced by methane decomposition on coprecipitated Ni/alumina and Ni-Cu/alumina catalysts. The porous structure of carbons was generally classified as follows: 1) micropores on the filament surface; 2) mesopores produced by filament surface roughness; 3) meso-...
Ethane, ethylene, acetylene, propane and neopentane have been pyrolyzed at 1173 K, and methane at 1372 K in a flow system, and the volatile pyrolysis products analyzed. Eleven aromatic hydrocarbons, containing 14 or fewer carbon atoms, accounted for 98 + % of the liquid products recovered in each case. Benzene was the main product, followed by naphthalene. No compounds with branched chains or multiple...
A carbonaceous thin film was made by CVD of 2,5-dimethyl-p-benzoquinone at temperatures between 500 and 1000°C and its structural and electronic properties have been studied. The carbonaceous thin film made at 500°C has a energy bandgap of 0.25-0.3 eV and a positive Hall coefficient of 5 10 -5 m 3 C -1 belong to a p-type semiconductor. A photovoltaic cell with...
Pyrocarbon deposition from ethylene, acetylene and 1,3-butadiene was studied with a vertical hot-wall reactor at ambient pressure and 1000°C; initial partial pressures of the hydrocarbons and residence time were varied. Steady-state pyrocarbon deposition rates and corresponding compositions of the gas-phase were determined. Reaction models describing homogeneous gas-phase and heterogeneous pyrocarbon...
Pyrocarbon deposition from propylene and benzene was studied at ambient pressure and 1000°C using a vertical hot-wall reactor. Initial partial pressures of the hydrocarbons and residence time were varied; the influence of hydrogen in the feed gas was additionally studied. Gaseous and liquid reaction products were analyzed by on-line gas chromatography. The results are discussed in terms of homogeneous...
Pyrocarbon deposition from methane was studied at ambient pressure and a temperature of 1100°C using a vertical hot-wall reactor with a honeycomb structure as substrate. Compared to the deposition tube used in previous studies this substrate exhibits a 15-fold increase in surface area. The methane initial partial pressure was varied up to 75 kPa, and the residence time up to 1 second. The results...
Pyrocarbon deposition from methane was studied at ambient pressure and 1100°C using a vertical hot-wall deposition reactor; the methane initial partial pressure was varied up to 75 kPa and the residence time up to 1 second. The influence of hydrogen partial pressure was studied at constant methane partial pressure. Steady-state pyrocarbon deposition rates and corresponding compositions of the gas-phase...
Hydrogenated amorphous carbon films (a-C:H) grown on unheated Si with and without microrelief morphology substrates (MRS, FS) by chemical vapor deposition were investigated using scanning electron microscopy, Auger electron spectroscopy analysis and reflection electron diffraction methods. A difference in the Auger spectra was found in the dependence on the surface morphology of the substrate, the...
Amorphous CN x thin films with x up to 1.1 were obtained by ArF excimer laser chemical vapor deposition (CVD) from NH3 CCl4 or cyanogen azide NCN 3 as precursors in the substrate temperature range of 200–650 °C. The films are optically transparent and electrically insulating. Depending on the preparation conditions their Tauc gap varies between 1.4 and 3.1 eV. The X-ray photon spectroscopy...
Thin filamentous boron-substituted carbon, BC x , has been synthesized by chemical vapor deposition using a nickel catalyst at 800°-1100°C from benzene, boron trichloride and hydrogen. The C/B ratios of the deposited products increased from 4 to 58 with increase in the deposition temperature from 800° to 1100°C. BC x samples also contained oxygen and hydrogen, the amount of which...
Chemical vapor infiltration of pyrocarbon with methane as the carbon source was studied at a total pressure of 20 kPa, a temperature of 1100°C and methane partial pressures from 2.5 to 20 kPa. A cylindrically-shaped porous alumina ceramic, 20 mm in height and 16 mm in diameter, was used as the substrate. The pore entrance diameters of the porous ceramic range from 1 to 36 μm; the total porosity...
Silicon infiltration pretreatment has been used to improve the high-temperature oxidation resistance of CVD-SiC coated C/C composites. C/C composites were infiltrated with silicon in an Ar atmosphere and then coated with CVD-SiC coating to a thickness of ca 50 μm. Isothermal and cyclic oxidation tests at 1500 on the CVD-SiC coated C/C composites with and without silicon infiltration pretreatment...
Chemical vapor infiltration of pyrocarbon was studied at 1100 o C and methane pressures ranging from 5 to 100kPa. A cylindrically shaped porous alumina ceramic, 20mm in height and 16mm in diameter, was used as the substrate. The pore diameters of the porous ceramic range from 1 to 36μm and the total porosity amounts to 23%. Theoretical considerations based on the Weisz modulus and the pore...
Several amorphous carbonitride films have been elaborated by plasma enhanced chemical vapor deposition. A radio frequency discharge has been used under standard conditions with different graphitic nitrogenated compounds. It is shown that the influence of molecular precursor is important concerning in particular the magnetic properties. The films issued from pyrrole and cyanuric chloride exhibit a...
Using Grafoil® (Union Carbide) as a substrate, we compare the effect of two catalyst precursors, namely Fe(NO 3 ) 3 .9H 2 O and Fe 3 (CO) 12 on the elaboration of carbon fibres. For each precursor, the mass of deposited carbon, of carbon fibres, and especially the fibre length was found to be strongly dependent on the concentration of catalyst precursor over...
A boron carbide crystallite encapsulated in multiwalled graphitic carbon clusters has been synthesized by the laser-induced vapor-phase reaction of C 6 H 6 +BCl 3 . The composite particles were characterized by analytical electron microscopy. The size of the capsules ranged from 30 to 80 nm and the number of graphitic carbon layers surrounding a core particle ranged from 20...
We have deposited nanotube films on silicon via a chemical vapor deposition (CVD) growth process known from the deposition of diamond. We used a metallic catalyst which was deposited onto the silicon surface prior to the CVD deposition. The films are very pure, adhere well and are very well suited for electron field emission. We measured emission at 2.6 V/μm (for 1 nA emission current) and an emission...
A study is presented on minority carrier transport parameters, in particular mobility-lifetime products, in natural and CVD diamond materials with different morphology. μτ products are obtained by photocurrent versus field measurements and their values range between 10 -8 -10 -5 cm 2 V -1 depending on grain size and orientation. Observed variations are...
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