Synthesis of Carbon nanotubes by CVD: Effect of acetylene pressure on nanotubes characteristics

MARIANO ESCOBAR; SERGIO MORENO; ROBERTO J. CANDAL; M. CLAUDIA. MARCHI; ALVARO CASO; PABLO POLOSECKI; GERARDO H. RUBIOLO; SILVIA GOYANES

APPLIED SURFACE SCIENCE

Elsevier

Año: 2007 vol. 254 p. 251 - 256

0169-4332

The effect of acetylene partial pressure on the structural and morphological properties of multi-walled carbon nanotubes (MWCNTs)synthesized by CVD on iron nanoparticles dispersed in a SiO2 matrix as catalyst was investigated. The general growing conditions were: 110 cm3/min flow rate, 690 8C synthesis temperature, 180 Torr over pressure and two gas compositions: 2.5% and 10% C2H2/N2. The catalyst and nanotubeswere characterized by HR-TEM, SEM and DRX. TGA and DTAwere also carried out to study degradation stages of synthesized CNTs. MWCNTssynthesized with low acetylene concentration are more regular and with a lower amount of amorphous carbon than those synthesized with a highconcentration. During the synthesis of CNTs, amorphous carbon nanoparticles nucleate on the external wall of the nanotubes. At high acetyleneconcentration carbon nanoparticles grow, covering all CNTs’ surface, forming a compact coating. The combination of CNTs with this coating ofamorphous carbon nanoparticles lead to a material with high decomposition temperature.