Effect ofcatalystpreparationontheyieldofcarbonnanotubegrowth

ESCOBAR, MARIANO; RUBIOLO, GERARDO; CANDAL, ROBERTO; GOYANES, SILVIA

PHYSICA B - CONDENSED MATTER

ELSEVIER SCIENCE BV

Año: 2009 vol. 404 p. 2795 - 2798

0921-4526

Multiwallcarbonnanotubes(MWCNTs)weresynthesizedbycatalyticchemicalvapordeposition(CVD) on catalyticironnanoparticlesdispersedinasilicamatrix,preparedbysolgelmethod. In this contribution,variationofgelationconditiononcatalyststructureanditsinfluenceontheyieldof carbonnanotubesgrowth was studied.Theprecursor utilized were tetraethyl-orthosilicate and iron nitrate. The sols were dried at two different temperatures in air(25or80 1C) and thentreated at 450 1C for 10h.The xerogels were introduced into the chamber and reduced in ahydrogen/nitrogen(10%v/v) atmosphereat600 1C. MWCNTs were formed by deposition of carbon atoms from decomposition of acetylene at700 1C. The system gelled at RT shows a yield of 100% respect to initial catalyst mass whereas the yield of that gelled at 80 1C was lower than10%. Different crystalline phases are observed for both catalysts in each step of the process. Moreover,TPR analysis shows that iron oxide can be efficiently reduced to metallic iron only in the system gelled at room temperature.Carbon nanotubes display a diameter of about25–40nm and several micron lengths. The growth mechanism of MWCNTs is base growth mode for both catalysts. .