Wednesday, December 28, 2011

US Patent 8084011 - Method of increasing thickness of carbon nanotube arrays

Most of the techniques used to mass produce carbon nanotube arrays involve chemical vapor deposition (CVD). However, there is a limit to the thickness of the nanotubes which can be grown due to the effect of reaction byproduct gas and an excess raw material gas during CVD growth. This patent from the Denso Corporation of Japan teaches a growth method to deal with this problem and grow nanotubes with a greater thickness to improve the efficiency of mass production. Claim 1 reads:

1. A method of manufacturing a vertically aligned carbon nanotube by using a chemical vapor deposition method, comprising the steps in the order named of:

providing a substrate and a catalyst to be fixed on the substrate, in a reaction chamber;

heating the catalyst fixed on the substrate in the reaction chamber;

filling-up the reaction chamber with a raw material gas serving as a carbon source, thereby synthesizing vertically aligned carbon nanotubes in the reaction chamber;

after a film thickness of vertically aligned carbon nanotubes synthesized on the substrate has increased by at least a measurable amount, exhausting a reaction byproduct gas from the reaction chamber; and

repeating the filling-up step and the exhausting step until a film of vertically aligned carbon nanotubes having a desired film thickness is manufactured.