ARC-DISCHARGE -- 2 rods of graphite (anode+cathode) are electrified, the carbon gas produces the nanotubes. This process produces more pure (usually multi-walled) tubes with very few defects, but it doesn’t produce very many tubes. Many other ‘shapes’ of tubes are also produced which are hard to separate.
CHEMICAL VAPOR DEPOSITION (CVD) –– start with carbon-based gas and ‘grow’ tubes from metal catalysts. The solution is heated to anywhere from 300 - 1150 degrees Celsius. Can produce long tubes, but with impurities and vague structure. Can easily alter diameter of tube by altering the catalyst, as well as the length of the tube by altering the period which heat is applied. This process easily allows for the introduction of other ‘additives’ like boron or nitrogen.
LASER ABLATION –- Process uses a laser to vaporize the carbon from graphite rods. Single-wall tubes are produced.
ELECTROLYSIS – Process similar to CVD, but the graphite is immersed in molten ionic salts. Only multi-walled (10-15) tubes are produced which are inevitably bundled (generally a weak organization).
Source: Women in Nano with nano2hybrids and Vega Science Trust
Single Wall CNTs are produced at 50 grams per hour through a process developed by Idaho Space Materials, which is currently the highest production rate. For a list of USA CNT suppliers follow the link to the right.
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