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-N i alloy and graphite as anode; single-wall carbon nanotubes (SWCNTs) with 5 0%-70% purity were produced in quantity of tens of grams a day under the ar e conditions of 40-60 A d.c. and helium pressure of 2 arm. If calcium-nicke l 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 yt trium-nickel as catalyst had the same structures as those obtained from las er-ablation with Co-Ni as catalyst. SWCNTs with smaller diameters were foun d when calcium-nickel was used as catalyst, proving that the diameter of SW CNTs is dependent on the properties of the metal catalysts. Furthermore, hi gh helium pressure can lead to a high yield of SWCNTs. Our results suggeste d a formation mechanism of SWCNTs and the roles played by nickel and yttriu m or calcium element.