Synthesis of Single-Wall Carbon Nanotubes by Atmospheric Thermal CVD

At the growth temperature at and above 700degC as well as C
₂
H
₄
flow rate of 20 seem,, carbon nanotubes (CNTs) were synthesized on the SiO
₂
substrates dip-coated with Co acetate only. The fine dispersion of Co particles was caused by a strong interaction between metal acetate and SiO
₂
support. Due to the high process (atmospheric) pressure, the reduced catalytic activity of Co could not assist CNT growth for the Co-Mo bimetallic catalysts on oxide surface. CNTs could not be synthesized with the addition of nitrogen to the carrier gas, either. It was inferred that the carrier gas of pure hydrogen is essential to inhibit the formation of cobalt oxides due to the trace oxygen in the atmospheric furnace and thus sustain the activity of Co particles. With the catalyst of 0.02 wt% Co acetate, highly selective growth of high-purity SWNTs was attained at the growth temperature at and above 800degC by atmospheric thermal CVD. The SWNT diameter measured by AFM confirmed the value determined from the RBM of Raman spectrum and Bandow's relationship.