Office of Research and Development (ORD), US Environmental Protection Agency (USEPA),
Keywords: sustainable materials, CNT composites, blast energy dissipation, infrastructure protection
Summary:This presentation describes the synthesis of Carbon Nanotubes (CNT) using the floating catalyst chemical vapor deposition (FC-CVD) method with ferrocene as the catalyst and with a focus on controlling entanglements in CNT forests. The focus of the research was to study the effect of carbon source and temperature on the CNT structure and nano-coiling and entanglement behavior of the CNT forests. We have used substituted benzenes as the carbon source. Our results show that the carbon precursors with more substitutions on benzene influence CNT forests with more entanglements. We obtained stress-strain diagrams for the CNT forests and after 12 cycles of compressing the CNT forests to 0.25 strain, the absorbed energy was nearly equal for m-xylene and toluene but much smaller for benzene. The stress vs. strain measurements indicated that the structure of the aligned forest of CNTs is more “spring-like” or coiled for m-xylene as it has a high restitution and energy dissipation. The restitution was much higher for the nanotubes fabricated with m-xylene and decreased for toluene, further decreasing for benzene. The CNT forests synthesized using benzene are the least coiled, as evidenced by the SEM images and the high buckling factor indicated by the low restitution. The overall scope of the presentation encompasses the study of microstructural systems and macroscale material behavior under dynamic and static loadings. For example, interlaminar strength can be increased by reinforcing multilayer composites with CNTs, thus limiting the growth of a crack and failure. The presentation will also include developing specific applications for the coiled, or entangled CNT forests to act like nano springs. Various metals, including silver, iron, and indium, were deposited on the top and bottom of these CNT forests by paste, sputtering, and thermal evaporation, respectively. Stacks of one, two, and three metalized CNTs were arranged and compressed to explore their mechanical properties. These were then compared to non-metalized CNTs stacks. Composite structures incorporating nano-coiled CNTs will have applications in developing other multifunctional composite materials. I request an opportunity for an Oral Presentation.