High-quality double-walled carbon nanotube super bundles grown in a hydrogen-free atmosphere

High-quality double-walled carbon nanotube (DWNT) super bundles were selectively grown above a bowl-like cathode by arc discharge in a hydrogen-free atmosphere. These DWNTs can resist high-temperature (up to 720 degreesC) oxidation in air without additional annealing even after acid treatment, which is due to an in-situ defect-healing effect of the bowl-like cathode and the absence of reactive gases during arc discharge. Selective formation of DWNTs is ascribed to the increased presence of carbon clusters in the enlarged hot plasma region inside the cathode and optimized composition of the catalysts.