EAPSI: Improving the Connections Between Carbon Nanotubes (CNT) and the Surfaces They are Grown On

Westover Andrew S, Nashville TN

Investigators

Abstract

Carbon nanotubes (CNT) are one of the most exciting novel materials discovered in the last few decades. This is in part due to their immense mechanical strength 100 times greater than steel, their high electrical and thermal conductivity, and high surface area. Because of these fantastic properties CNT have been suggested for a wide range of applications. Unfortunately these applications for the most part have not been realized. One major reason for this is that although CNT are incredibly strong, the connection between the CNT and the surfaces they are grown on is in general very weak. CNT are grown by heating a carbon based gas up to extremely high temperatures, breaking the gas into its most basic elemental components. The carbon from this gas then deposits on a specially prepared surface. As more and more carbon deposits it will grow into a carbon nanotube. It is this connection that is the weak link in CNT based applications. This research aims to explore the effect of different surfaces and of different surface treatments on the strength of the connections between the growth surfaces and the CNT. The goal is twofold, (i) to understand what causes these connections to be so weak, and (ii) to develop CNT with stronger connections to the surfaces they are grown on. This research will be conducted in collaboration with Dr. Shigeo Maruyama of the University of Tokyo in Japan, one of the leading experts in CNT growth. Despite the importance of the mechanical strength of the CNT/growth substrate interface there has been very little research into how to improve the strength of these interfaces. One of the few studies that has explored the mechanical strength of these interfaces found that CNT grown on copper substrates had interfaces with about 3X more mechanical strength than those grown on silicon. In light of this study, the first step in this research is to grow CNT on a variety of different substrates, and with various different surface treatments. The second step will be to perform mechanical measurements of the interfacial strength via a micromanipulator attached to a scanning electron microscope (SEM). Using a SEM to observe the failure of CNT films in-situ will allow for greater insight into the fundamental mechanisms that are limiting the strength of these interfaces. This project if successful, will aid in the development of mechanically strong CNT film/substrate interfaces, which has the potential to have a huge impact on the ability to apply CNT forests to devices ranging across a whole range of fields including flexible electronics, CNT based solar cells, and CNT energy storage devices. This NSF EAPSI award is funded in collaboration with the Japan Society for the Promotion of Science.