Carbon Nanotube Ink Technology

SouthWest NanoTechnologies Inc. (SWeNT), a leading manufacturer of single-wall and speciality multi-wall carbon nanotubes (CNT) was created in 2001 to spin off nanotube research developed at the University of Oklahoma.  Recently they have announced a partnership with Chasm Technologies Inc to provide a method for printing carbon nanotubes using commercial, high-volume printing methods and equipment, including flexographic, gravure and screen printing.  The method uses the V2V ink technology (from Chasm Technologies) as a vehicle for the CNT.  Full details can be read on their press release.

I was particularly interested in the patents around the carbon nanotubes and it turns out that most of the intellectual property for the CNT manufacture is held by the University of Oklahoma and relates to the CoMoCAT ® process.  Some of the earliest single walled CNT patents are held by IBM and NEC and it appears that SWeNT have license agreements with these companies but they have also developed the process to make it more controllable  so that specific diameter CNTs can be made.

For example, their most recent patent US 7,357,907 B2 describes a method of preferentially forming single walled carbon nanotubes having a diameter between about 0.7 nm to about 0.9 nm.  This is done by using a catalyst comprising Co and Mo on a Si support material wherein the majority of the Mo occurs as dispersed Mo oxide clusters and the majority of the Co occurs as CoMoO4 with the Co primarily in an octahedral configuration.   The ratio of Co:Mo is ideally less than 3:4.  The catalyst is exposed in a reactor to carbon monoxide gas at a temperature between about 700°C and 800°C (during which the CO disproportionates to C and CO2) and maintaining a CO2 concentration in the reactor below a threshold CO2 concentration, typically 0.9% or less, above which the conversion of ionic Co to metallic Co is inhibited.   The diameter of the carbon nanotubes thus formed can be increased by increasing the temperature range of the reaction vessel, e.g. by using a range of 800-900°C the diameter will be between about 0.9 nm to about 1.2 nm.  Some details around the mechanism of this process are provided on the SWeNT website.

The patents for the V2V ink technology are pending and so are not yet available in the public domain.

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