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SYNTHESIS OF CARBON NANOTUBES BY CHEMICAL VAPOR DEPOSITION OF CH4/H2 MIXTURES: EXPERIMENTAL STUDY AND COMPUTER MODELING

Evgeniya Skichko, E.M. Koltsova, Anna Shaneva

Abstract

The aim of this work is to experimentally study the synthesis of carbon nanotubes and nanofibers by catalytic pyrolysis of methane-hydrogen mixtures, as well as to develope a kinetic scheme that takes into account the accelerating and suppressing effect of hydrogen on pyrolysis. Carbon nanotubes were synthesized in a laboratory kinetic setup with a vertical quartz reactor at a temperature of 700?. The oxide system (Fe0.45Co0.15Al0.40)2O3 obtained by combustion method was taken as a catalyst. The hydrogen concentration in the initial gas mixture was 0, 20, 40, and 60% vol. Electron microscopy of the obtained carbon material was performed on a LEO 912AB Omega transmission electron microscope at an accelerating voltage of 100 kV. As a result of synthesis, carbon nanotubes were obtained with a small admixture of bamboo-type carbon nanofibers with an outer diameter of 10-20 nm. At a hydrogen concentration of 40%, the maximum carbon yield is reached, which is approximately 3 times higher than with the pyrolysis of undiluted methane. A kinetic scheme of pyrolysis was developed, which made it possible to describe the accelerating and suppressing effect of hydrogen and provide a good agreement between the experimental and calculated data.

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