US Patent 7767186 - Microwave purification of CNTs

http://ip.com/patent/US7767186

Fabrication methods of single walled carbon nanotubes often result in a 1/3 portion of the nanotubes having metallic rather than semiconducting characteristics. This patent covers a technique developed by Honda Motors in 2003 using microwaves to increase the semiconducting portion. Claim 1 reads:

1. A method for processing carbon nanotubes comprising:

receiving a carbon nanotube sample consisting essentially of metallic-type and semiconducting-type carbon nanotubes;

positioning said carbon nanotube sample in a microwave cavity at a location corresponding to a maximum in the electric field of a stationary wave having a first microwave frequency and a first power; and

exposing said carbon nanotube sample to the stationary wave.