Carbon nanostructures and methods of preparation

A method for forming tubular carbon nanostructures comprises the steps of heating a non-graphitizable carbon precursor in the presence of a gas at a temperature and pressure sufficient to form the tubular carbon nanostructures from the carbon precursor and including a dopant in the non-graphitizable carbon precursor in an amount sufficient to form the tubular carbon nanostructures, wherein the dopant is amorphous boron which is present in an amount sufficient to increase the length of the tubular carbon nanostructures to greater than 0.5 microns.

A method of forming tubular carbon nanostructures which comprises discharging a direct current arc between an anode and a cathode, the anode comprising a conducting electrode containing a carbon precursor, the discharging in the presence of a gas at a temperature and pressure such that the carbon precursor is maintained in a solid phase and for a period of time sufficient to form the tubular carbon nanostructures on the anode from the carbon precursor.

An arc furnace for forming tubular carbon nanostructures comprising a cathode, an anode opposite the cathode, sources of voltage and current in amounts sufficient to create charged particles and produce an arc between the anode and cathode, a source of a gas to surround the arc, and a source of carbon precursor positioned adjacent the anode and within the arc, wherein the arc has a sufficiently high temperature and is maintained at a pressure for a time sufficient to heat the carbon precursor to form carbon nanotube on the anode.