Production of carbon nanostructured materials by CVD method using supported catalysts: Study of two different carbon precursor gases

Chemical Vapor Deposition (CVD) has been reported as a good method to synthesize carbon nanostructured materials.1 The growth of carbon nanostructures by thermal CVD employs a carbon precursor molecule and a transition metal as a catalyst.2 In the present study we examine the possibility to synthesize carbon nanostructured using supported catalysts. The catalysts consist of iron oxides doped with copper (MagSilCu2,5) or nickel (MagSilNi2,5) supported on amorphous silica and presented a good dispersion of metals.3 Two carbon precursors were tested: acetylene and methane. CVD was carried out at atmospheric pressure, in a horizontal fixed-bed reactor at a temperature of 700 °C. The reactor consists of a quartz tube placed inside a horizontal high temperature furnace. Before the reaction, the active metal components were reduced by heating at 800 °C for 1 h in 1:1 H2/N2 at a flow rate of 40 mL min-1. The carbonaceous materials obtained were characterized by thermogravimetric analysis (TGA) and Raman spectroscopy. TGA (Fig. 01) shows that samples synthesized with methane gas presented no significant amount of carbonaceous material after synthesis. However, a good thermal stability of structured carbonaceous materials was observed with acetylene gas. The Raman spectra (Fig. 02) showed that the products of the reaction with acetylene gas have the CNTs characteristic bands (D, G and G'), comparing them to the commercial CNTs and the literature. ID/IG ratio indicated that the carbon nanostructured for both samples presented lower degree of ordering and probably more defects than the commercial CNTs.