Ultra-High-Purity Synthesis Improves Nanotube Materials Published Nov. 17, 2009 By Maria Callier Office of Scientific Research ARLINGTON, Virginia -- Scientists and engineers from Air Force Research Laboratory, Fisk University and Riehl Engineering, Ltd., have achieved a significant advancement in the field of carbon nanotechnology. Using an innovative process for achieving ultra-high-purity synthesis, the combined research and development effort successfully and economically produced the world's only known carbon nanotube material with 99.99% purity. Carbon nanotube material is critical to the production of special coatings for military aircraft, advanced lithium batteries, bio-batteries, biofuel/fuel cells, ultracapacitors, and chemical and biological sensor platforms. Ultra-high-purity synthesis allows nanotube materials to be used without postproduction purification, which is necessary in the production of conventional, chemical-vapor-deposition-grown materials. The increased use of electronics in the battle environment places an increased demand on battery systems. In an effort to increase the capacity and life cycle of aircraft and spacecraft power packs, AFRL collaborated with Fisk University (Nashville, Tennessee) to develop a thermal, noncatalytic, high-purity carbon nanotube synthesis process to produce a material suitable for these applications. The unique three-dimensional structure of the newly produced materials provides more space between the atoms for lithium insertion, lower electrode internal resistance and more electrochemically active sites than traditional carbon materials. Eliminating cleaning techniques used to prepare the nanotube material for applications reduces time and cost. The AFRL research team began working with Riehl Engineering (Kettering, Ohio) to investigate the feasibility of using this process on other silicon carbide materials. Wafers of SiC used in the electronics industry can be very expensive. In contrast, SiC powders, foams, and fibers--which can be as low cost as cents per pound of raw material--were found to transform under the same processing conditions. Using this AFRL batch production methodology, Riehl demonstrated proof-of-concept and production viability, successfully scaling up the process to make carbon nanoclusters. The company now sells the nanotubes it produces using this new process. The electrochemical work completed by AFRL and Riehl Engineering, built from the collaboration with Fisk University, has effectively demonstrated that the new carbon nanotube materials can be used without fear of electrochemical contamination from residual metal catalysts. Further, the effort has shown that the electrochemical performance of the carbon nanoclusters meets or exceeds that of carbon nanotubes without the background current or transient nature of commercially produced carbon nanotubes.