Solid state formation process of carbon nanotubes

31 March 2007

Carbon nanotubes are formed by milling graphite sample for long duration in a steel mill followed by immediate annealing at 1400 degree Celsius for a fixed duration. For single wall carbon nanotube formation, the graphite is milled in a steel-rotating mill for 150 hours and thereafter it is immediately annealed at 1400 degree Celsius for six hours under inert atmosphere of nitrogen gas. The iron might have acted as catalysts, however the yield of carbon nanotubes was very less. The outer diameter of the carbon nanotube was below 30 nanometer and size was approximately 1.5 nanometer.

In a similar way multiwall carbon nanotube (MWNTS) were formed. The graphite was milled for long duration of 150-200 hours in a steel-rotating mill. The graphite was annealed at 1400 degree Celsius under inert atmosphere. Scientists carried out the TEM analysis after different batches so produced and found large sample clusters. The MWNTS so formed were having outer diameters in the range of 4 nanometer to 10 nanometer and the inner diameter around 1.8 to 2 nanometer. The length of such carbon nanotubes was above 100 nanometers.

In a similar way a bamboo type carbon nanotubes were formed. The graphite sample was milled for 165 hours in a steel rotating mill and thereafter it was annealed at 1300 degree Celsius for 4 hours under inert atmosphere. The TEM analysis showed a bamboo like structure of carbon nanotubes containing an iron particle at the tip of the structure. Graphite layers have covered the iron particles during annealing process and thus this particle acts as a catalyst and initiated growth of the bamboo type carbon nanotubes.

Related Posts: