Water Rinsing and Ultrasonication Result in Longer Carbon Nanotubes

In U.S. Patent Application 20100092369, Brother International Corporation Senior Principal Engineer Farzad Parsapour (Bartlett, TN) discloses a method for fabricating carbon nanotube structures with enhanced length. Generally, the diameter and length of the carbon nanotubes will depend, in part, on the process parameters (e.g., temperature, time, ratio of gases, etc.) and gases used in growing the nanotubes. In addition, some nanotube formation techniques grow single-walled nanotubes and others techniques grow multi-walled nanotubes.

The patent pending method developed by Parsapour includes an ultrasonication and exposure to water step which involves (1) immersing the catalyst deposited on the substrate in a bath containing a liquid, such as, for example, an aqueous solution or a non-aqueous solution, (2) subjecting the catalyst/bath system to acoustic waves generated from an ultrasonic apparatus (e.g., sonicator), and (3) exposing the catalyst to water (e.g., via rinsing). Following the ultrasonication and exposure to water step, the CNTs are grown utilizing CVD.

The specific enhancement manifests itself as a substantial increase in the length of the CNTs under identical catalytic growth via chemical vapor deposition (CVD). Comparison of CNTs grown with the ultrasonication and exposure to water step, and CNTs grown in an identical manner but without the ultrasonication and exposure to water step, reveals a significant increase in the length of the CNTs when the ultrasonication and exposure to water step is included. The range of applications for CNTs with increased length covers gas diffusion layers for fuel cells to thin conductive film

FIG. 3B is an image of  nanotubes grown in the conventional manner.

FIG. 4A   is an  image of nanotubes grown in accordance with Parsapour’s method.