Optimization of Flame Synthesis for Carbon Nanotubes Using Supported Catalyst

Abstract

A series of rich premixed flames are used to realize a post-flame gas mixture for optimum carbon nanotube (CNT) growth using inexpensive hydrocarbon fuels. The mixture of CO, CO 2 , H 2 , and H 2 O is varied through use of hydrocarbon fuels with different H/C ratio in flames with different fuel/air ratios. Both SEM and HRTEM imaging are used to correlate the nanotube morphology and internal structure to the reaction gas composition. The variations observed are understood in light of the gas composition and the interaction of the reactive components with both the deposited Co catalyst particles and supporting metal substrate. Further comparisons between flames producing the same CO or H 2 concentrations identify the roles of these gases in CNT synthesis. Optimal flame synthesis conditions, defined upon a H 2 and CO concentration map, are gauged on the basis of CNT length, relative surface density, and level of graphitic structure.

Large Scale Synthesis of Carbon Nanofibres on Sodium Chloride Support

“…CNFs are usually obtained by the chemical vapour deposition [7] (CVD) method from the decomposition of gaseous hydrocarbon over metal catalyst particles. Other methods such as flame synthesis [8], arc discharge [9] and laser ablation [10] have also been used to synthesize CNFs and CNTs, but they are energy intensive, expensive and yield less when compared to CVD. The catalytic growth of CNFs mechanism is well established and contains several steps as follows: (i) a carbon source is decomposed on the surface of transition metal nanoparticles, (ii) liquidised metal carbide is formed by diffusion of carbon atoms into the nanoparticles, (iii) after over saturation or due to cooling down of the particles, the carbon precipitates to form polyaromatic layers (graphenes).…”

Carbon nanotubes synthesis using diffusion and premixed flame methods: a review

“…Premixed flame synthesis methods have certain advantages over the diffusion flame method, including the availability of a broad range of fuels, continuous and multistaged processing, scalability of stoichiometry of reagent gases, flame temperature (can be reduced by using chimneys), reactive gas profile, and equivalent ratio [72].…”

“…In other studies, substrate-supported catalyst methods were used [72,81,84]. The substrate can also interact physically or chemically with the catalyst particles and may control their catalytic activity.…”

Production of Carbon Nanotubes by Different Routes-A Review

“…This method is based o controlled flame environment, that produces the temperature, forms the carbon atoms from the inexpensive hydrocarbon fuels and forms small aerosol metal catalyst islands [22,23]. SWNT are grown on these metal islands in the same manner as in laser ablation and arc discharge.…”

“…These metal catalyst islands can be made in three ways. The metal catalyst (cobalt) can either be coated on a mesh [22], on which metal islands resembling droplets were formed by physical vapor deposition. These small islands become aerosol after exposure to a flame.…”