Synthesis of Multi Wall Carbon Nanotube (WCNT) over thin films of SiO₂-Fe₂O₃ deposited by Combustion Chemical Vapor Deposition

M.D.Lima, M.J. de Andrade, C.P. Bergmann

Federal University of Rio Grande do Sul, Dept. of Materials Engineering,

 Osvaldo Aranha Av. 99, room 705-c, 90035190, Porto Alegre, RS, Brazil

 

Carbon nanotubes (CNT) constitute a new class of materials discovered in 1991 by Sumio Iijima that present unusual mechanical, electrical and thermal properties. CNT synthesis directly over metallic or ceramic substrates is of great interest in the electronic industry for the development of circuits or displays. Many ceramic catalysts have been reported for CNT growth, and a great part of them is based on the formation of a solid solution between transition metallic oxides (Fe, Ni, Co) and ceramic oxides. In this report homogeneous mixtures of Fe₂O₃ and amorphous SiO₂ were prepared through their co-deposition by Combustion Chemical Vapour Deposition (CCVD). This technique allows the deposition of thin films using low cost equipment and precursors. After that, they were kept in an atmosphere of H₂/CH₄ to promote the CNT growth. The temperatures of synthesis were varied from 950 to 1100 °C. The efficiency of the synthesis process was evaluated according to its thermal analysis, mass variation during the synthesis,  purification, scanning and transmission electron micrographies. Multiwall Carbon Nanotubes were obtained with diameters of less than 15 nm.