Production of Single-Wall Carbon Nanotubes at High Pressure

Using a graphite rod with a hole filled with the powder of a mixture of Y−Ni alloy and graphite as anode, single-wall carbon nanotubes (SWCNTs) with 50%−70% purity were produced in quantity of tens of grams a day under the arc conditions of 40−60 A d.c. and helium pressure of 2 atm. If calcium−nickel was used as catalyst instead of yttrium−nickel, high yields of SWCNTs can also be produced in large quantities, although the yield was slightly less than that of yttrium−nickel. The samples were characterized by SEM, HREM, and Raman spectroscopy. The results showed that the SWCNTs produced with yttrium−nickel as catalyst had the same structures as those obtained from laser-ablation with Co−Ni as catalyst. SWCNTs with smaller diameters were found when calcium−nickel was used as catalyst, proving that the diameter of SWCNTs is dependent on the properties of the metal catalysts. Furthermore, high helium pressure can lead to a high yield of SWCNTs. Our results suggested a formation mechanism of SWCNTs and the roles played by nickel and yttrium or calcium element.