Carbon nanotubes vaporization/condensation

Are carbynes produced in laboratory carbon and C IC Ar vapors designed to simulate the properties carbon dust in astrophysical environments Field-emission scanning electron microscope (FESEM) and HRTEM studies of vapor-condensed carbon smokes showed a wide range of carbon morphologies that were free of metal impurities (at EDS detection limits), viz. 1. Ceo and higher fullerenes that agglomerated into amorphous soot grains, 2. fullerenic nanotubes and onions, 3. amorphous carbon sheets,... 

Single shell carbon nanotubes were produced in over 70 percent yields by condensation of a laser-vaporized carbon-nickel-cobalt mixture at 1200°C [12] [81]. No multishell nanotubes were detected in the VLS process. X-ray diffraction and electron microscopy showed that the single shell nanotubes have uniform diameters and self-organize into metallic ropes (mats or arrays) of 100-500 nanotubes having a single-rope resistivity of <10 ohm-cm at 300 K. The particulate mixed-metal Ni-Co catalyst exists at the live end of the growing nanotube and leaves the end by evaporation. 

Table 9.2 is a sununaiy of the main findings for the syntheses of carbon nanotubes and fullerenes by using the route of carbon vaporization/condensation. SWNT has never been found without the use of a catalyst. Fe, Co, and Ni are the main catalysts used in forming SWNTs. 

Carbon nanotubes have attracted huge attention ever since they were discovered because of their unique structures. The studies are mainly focused on the mechanical, electrical, and thermal properties of carbon nanotubes and the applications of their novel properties. Fluid behavior inside carbon nanotubes and fluid transport through carbon nanotubes have been investigated only recently and novel fluidic phenomena, such as abnormally low flow resistance, have been observed. Carbon nanotubes are usually synthesized by arc-discharge, laser ablation, and Chemical Vapor Deposition (CVD) [4]. The arc-discharge and laser ablation methods involve the condensation of carbon... 

Chemical vapor deposition (CVD), which requires vapor condensation on a solid surface in a vacuum chamber or inside of a tube furnace at relatively high temperatures. Nowadays, this technique is used for coating metal and optical components,. Also, CVD is used for producing carbon nanotubes of a few nanometers in diameter on a variety of substrates at relatively low temperatures, but their alignment and direction on a substrate apparently ate difficult to achieve. This may be attributable to the graphite sheet size and morphology. 

In 1993, lijima and Ichibashi [91] prepared single wall nanotubes (SWNT) by creating a carbon arc discharge in 1.33 kPa methane, 40 torr argon and iron filings. The iron is melted, vaporized and finally condensed as iron carbide above the cathode. The nanotubes formed as bundles, from which individual SWNTs could be isolated. Bethune et al [92] used a different method to produce single wall nanotubes with daimeter of 1.2 nm. Methods... 

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