Role of Transition Metal Catalysts in Single-Walled Carbon Nanotube Growth in Chemical Vapor Deposition

Abstract

We characterize the iron and cobalt catalysts for carbon nanotube growth in chemical vapor deposition (CVD) by using electron microscopy. Nanoparticles of iron and cobalt exhibit a melting point drop in the methane ambient. Nanoparticles after nanotube growth are identified as Fe 3 C and Co 3 C for iron and cobalt, respectively. Those results indicate that a eutectic compound of metal and carbon is formed in the methane ambient, resulting in the phase separation into graphite (nanotubes) and metal carbide as the carbon uptake in the catalyst melt increases. This supports the vapor-liquid-solid mechanism for nanotube growth by CVD. Iron or cobalt silicide formation causes the poisoning of the catalysts. However, the coexistence of oxygen due to native oxide on the silicon surface or the metal surface causes formation of a SiO 2 base, which can prevent silicidation of iron particles.

Reagent control over the composition of mixed metal oxide nanoparticles

“…We have used Mn, Pd and Cu-doped Fe-O NPs as catalysts for the growth of single-walled carbon nanotubes (SWNTs). Since the composition of the catalyst can have a significant effect on the diameter and chirality of the SWNTs grown, [2][3][4][5] the more uniform a catalyst the more narrow the distribution of SWNT that will be grown. Our second application is for down-hole sensors for the oil and gas industry, in which the temperature-dependant low-field magnetic susceptibility is used as an identification tool.…”

“…This is particularly true in the area of catalysis where small changes in composition can have large effects on the catalytic activity. [2][3][4][5][6][7] Recently, we have gained interest in the potential use of superparamagnetic NPs as traces in geological formations. The idea being that variation in the Curie temperature can be used as a method for differentiating one tracer from another and from naturally occurring background materials.…”

Cobalt Nano Particle Size Dependence of Noise Modulations in Relation to Nonlinearity

“…They can work as catalysts for CNT growth with methane for the forms of SWCNT or their bundles depending on the growth conditions [12]. Carbon complexes of iron or cobalt catalyst during CNT growth have also been studied with electron microscopy to observe the detailed growth mechanism [13,14]. We can also use thin film or nano * This paper was presented at 10th International Conference on Atomically Controlled Surfaces, Interfaces and Nanostructures (ACSIN-10), Granada Conference Centre, Spain, 21-25 September, 2009.…”

Resonance R aman Spectroscopy

“…As for SWNT growth by ACCVD process (Figure 3-4), the oxidized catalyst particles were reduced prior to SWNT growth by Ar containing 3% of H 2 (Ar/H 2 ) with a flow rate of 300 sccm and pressure of approximately 40 kPa during heating of the CVD reaction chamber. The Ar/H 2 mixture was employed to reduce the oxidized catalysts, because they are generally catalytically inactive [34]. After reaching the growth temperature, the Ar/H 2 mixture was stopped and the ethanol vapor (99.5% dehydrated ethanol) was introduced to initiate SWNT growth.…”