Carbon nanotubes grown from a surface typically have poor bonding strength at the interface. A process has been developed for adding a metal coat to the surface of carbon nanotubes (CNTs) through a “wicking” process, which could lead to an enhanced bonding strength at the interface. This process involves merging CNTs with indium as a bump-bonding enhancement.

Classical capillary theory would not normally allow materials that do not “wet” carbon or graphite to be drawn into the spacings by capillary action because the contact angle is greater than 90°. However, capillary action can be induced through JPL’s ability to fabricate oriented CNT bundles to desired spacings, and through the use of deposition techniques and temperature to control the size and mobility of the liquid metal streams and associated reservoirs. A reflow and plasma cleaning process has also been developed and demonstrated to remove indium oxide, and to obtain smooth coatings on the CNT bundles.

This work was done by James L. Lamb, Matthew R. Dickie, Robert S. Kowalczyk, and Anna Liao of Caltech; and Michael J. Bronikowski of Atomate Corporation for NASA’s Jet Propulsion Laboratory. NPO-46594

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Carbon Nanotube Bonding Strength Enhancement Using Metal “Wicking” Process

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This article first appeared in the March, 2012 issue of NASA Tech Briefs Magazine.

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