Catalytic Chemical Vapor Deposition of Single-Wall Carbon Nanotubes at Low Temperatures (original) (raw)
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Advances in Natural Sciences: Nanoscience and Nanotechnology, 2011
Single-walled carbon nanotubes (SWCNTs) have been successfully synthesized by chemical vapor deposition (CVD) using acetylene (C 2 H 2 ) gas as a carbon source and a mixture of Fe/Mo/Co on an Al 2 O 3 support as a catalyst. The effects of the weight percentage (wt%) of metals in the Fe/Mo/Co/Al 2 O 3 catalysts, growth time, gas flow rate and growth temperature on SWCNT growth were studied in detail. The optimum growth conditions were found to be a growth time of 60 min, a growth temperature of 750 • C, Ar/H 2 /C 2 H 2 flow rates of 420/100/14 sccm and a catalyst composition of Fe/Mo/Co/Al 2 O 3 = 5/3/1/80 (wt%). The morphologies and structures of the grown SWCNTs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy techniques.
Journal of Nanoscience and Nanotechnology, 2009
We report the growth of isolated single walled carbon nanotubes (SWCNTs) on a silicon surface by chemical vapor deposition, in the temperature range from 800 to 950 C using two different iron catalyst precursors, Fe(NO 3) 3 • 9H 2 O and Fe(CO) 5. The results show that while for the first catalyst precursor temperature is the key factor in determining nanotube length, for the second it is the density of catalyst precursor on the surface. Solutions of Fe(CO) 5 adsorbed on silicon oxide result in a suitable catalyst precursor to obtain SWCNTs of controllable diameter and with clean surfaces.
Formation of Single-Walled Carbon Nanotubes via Reduced-Pressure Thermal Chemical Vapor Deposition
Journal of Physical Chemistry B, 2003
We report the growth of carbon nanotubes (CNTs) via reduced-pressure chemical vapor deposition (CVD), using a gas mixture of methane/hydrogen and iron/molybdenum catalyst supported by alumina nanoparticles. The CNTs are either single-walled or double-walled as characterized by transmission electron microscopy. Investigation of various growth parameters indicates that CNT growth is limited by the gas supply when CVD is performed in the temperature range of 750-900°C, whereas the limiting factor for growth at 700°C is the rate of carbon diffusion through the catalyst particles. The density of CNTs changes with CVD pressure as well as gas flow rates when growth is limited by gas supply. We also use a single-step lithographic approach to form catalyst islands on top of patterned electrodes and to selectively grow CNTs bridging neighboring electrodes. The process yields both semiconducting and metallic CNTs as characterized by current-voltage measurements.
Nanotechnology, 2004
The effect of organic additives, including citric acid, PEG (2000) and PEG (200), on the yield and quality of single-wall carbon nanotubes (SWNTs) synthesized by a Fe-Mo catalyst dispersed on an alumina matrix prepared by the sol-gel process in assisted chemical vapour deposition (CVD) has been investigated by transmission electron microscopy (TEM), thermo-gravimetric analysis (TGA) and Raman spectroscopy. Different morphologies of catalyst including big flakes, spherical particles and porous supporting materials were obtained using citric acid, PEG (2000) and PEG (200) as dispersant, respectively. SWNT yields of 10 wt%, 16 wt% and 33 wt% were obtained using citric acid, PEG (2000) and PEG (200) as the dispersants, respectively, which implies that the PEG (200) is the most effective at improving the yield of SWNTs due to the effect of additives on the specific surface area of the catalyst. The as-grown SWNTs are mostly in large bundles with diameters of 0.5-2 nm, but in some cases, isolated tubes with much larger diameters can also be found. Finally a preliminary explanation for the increased SWNT yield using PEG (200) is presented.
Growth of Single-Walled Carbon Nanotubes by the Rapid Heating of a Supported Catalyst
Chem Mater, 2004
Single-walled carbon nanotubes (SWNTs) have been synthesized by the rapid injection of a nickel formate/silica gel catalyst/support into a hot fluidized-bed reactor. The initial rapid heating of the catalyst in the hydrocarbon feedstock was found to be essential for the nucleation of SWNTs since only amorphous or graphitic carbon particles were formed without it. These results suggest that the rapid heating of the catalyst precursor enables the formation of the small metal particles required for SWNT growth, probably due to the accelerated thermal decomposition of the catalyst precursor and enhanced nucleation rate. The growth of the SWNTs was investigated by the adoption of different methods for introducing the catalyst, and by varying the synthesis parameters including the catalyst loading, hydrocarbon gas flow rate, and concentration. The results found that SWNTs formed only under certain reaction conditions. The nanotubes produced were characterized by electron microscopy and Raman spectroscopy.
Chemical vapor deposition of methane for single-walled carbon nanotubes
. Ž . We report the synthesis of high-quality single-walled carbon nanotubes SWNT by chemical vapor deposition CVD of methane at 10008C on supported Fe O catalysts. The type of catalyst support is found to control the formation of individual 2 3 or bundled SWNTs. Catalysts supported on crystalline alumina nanoparticles produce abundant individual SWNTs and small bundles. Catalysts supported by amorphous silica particles produce only SWNT bundles. Studies of the ends of SWNTs lead to an understanding of their growth mechanism. Also, we present the results of methane CVD on supported NiO, CoO and NiOrCoO catalysts. q