Single-walled carbon nanotubes (SWNTs) offer the prospect of both new fundamental science and useful (nano)technological applications 1 . High yields (70-90%) of SWNTs close-packed in bundles can be produced by laser ablation of carbon targets 2 . The electric-arc technique used to generate fullerenes and multiwalled nanotubes is cheaper and easier to implement, but previously has led to only low yields of SWNTs 3,4 . Here we show that this technique can generate large quantities of SWNTs with similar characteristics to those obtained by laser ablation. This suggests that the (still unknown) growth mechanism for SWNTs must be independent of the details of the technique used to make them. The ready availability of large amounts of SWNTs, meanwhile, should make them much more accessible for further study.In our electric arc-discharge apparatus 5 , the arc is generated between two electrodes in a reactor under a helium atmosphere (660 mbar). The cathode was a graphite rod (16 mm diameter, 40 mm long) and the anode was also a graphite rod (6 mm diameter, 100 mm long) in which a hole (3.5 mm diameter, 40 mm deep) had been drilled and filled with a mixture of a metallic catalyst and graphite powder. The arc discharge was created by a current of 100 A; a voltage drop of 30 V between the electrodes was maintained by continuously translating the anode to keep a constant distance (ϳ3 mm) between it and the cathode. Typical synthesis times were ϳ2 min. As the catalyst we used mixtures such as Ni-Co, Co-Y or Ni-Y in various atomic percentages; these are known to yield a series of interesting carbon nanostructures 6 . The mixture used by Guo et al. 7 during their laser ablation process (Co and Ni, both at 0.6 at.%) did not produce a good yield of nanotubes in our case. However, we found that a mixture of 1 at.% Y and 4.2 at.% Ni gave the best results. In this case we observed (in a total carbon mass of 2 g): (1) large quantities of rubbery soot condensed on the chamber walls; (2) web-like structures between the cathode and the reactor walls (no webs when either Y or Ni were absent); (3) a cylindrical deposit at the cathode's end; and (4) a small 'collar' (ϳ20% of the total mass) around the cathode deposit, as a black, very light and porous but free-standing material.Within all these products it was possible to observe by scanning electron microscopy (SEM; using a JEOL JSM 6300F instrument) filament-like structures that are more or less dense, depending on where in the reactor they were deposited. The 'collar' deposit was densest; the soot was the least dense. A characteristic SEM image of the collar deposit (Fig. 1) shows large amounts of entangled carbon filaments, homogeneously distributed over large areas (here at least a few square millimetres) and with diameters ranging from 10 to 20 nm. The average length between two entanglement points is several micrometres; we could not identify any filament ends. From several SEM images we estimate the yield of these filaments (with respect to the total volume of the solid material...

A simple method was used to assemble single-walled carbon nanotubes into indefinitely long ribbons and fibers. The processing consists of dispersing the nanotubes in surfactant solutions, recondensing the nanotubes in the flow of a polymer solution to form a nanotube mesh, and then collating this mesh to a nanotube fiber. Flow-induced alignment may lead to a preferential orientation of the nanotubes in the mesh that has the form of a ribbon. Unlike classical carbon fibers, the nanotube fibers can be strongly bent without breaking. Their obtained elastic modulus is 10 times higher than the modulus of high-quality bucky paper.

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Composite sheets and nanotubes of different morphologies containing carbon, boron, and nitrogen were grown in the electric arc discharge between graphite cathodes and amorphous boron-filled graphite anodes in a nitrogen atmosphere. Concentration profiles derived from electron energy-loss line spectra show that boron and nitrogen are correlated in a one-to-one ratio; core energy-loss fine structures reveal small differences compared to pure hexagonal boron nitride. Boron and carbon are anticorrelated, suggesting the substitution of boron and nitrogen into the carbon network. Results indicate that singlephaase CyBxNx as well as separated domains (nanosize) of boron nitride in carbon networks may exist.