Microraman Study of Single Wall Carbn Nanotubes Obtained by Arc Method Using Metal and Oxide Catalysts

Single wall carbon nanotubes (CNTs) were synthesised by the arc method (He atmosphere) using Pt/WO_3, Ni/Co and Ni/Co/Fe, Ni/Y₂O₃ and NiO/Y₂O₃ as catalysts. The samples were collected in two regions of reactor: the collar and the wall zones. The presence of oxygen in the catalyst decreased the carbon impurities (amorphous carbon and graphite). Raman scattering and TEM were used as characterisation tools. Different CNT yields were found for the different catalysts: almost zero or a very poor yield for the Pt/ WO₃ and ternary Ni/Co/Fe metal catalysts, better and promising results for the Ni/Co catalyst, especially after treatment with nitric acid, and for metal - oxide and oxide - oxide catalysts based on Ni/Y₂O₃ and NiO/Y₂O₃.