Tailoring Industrial Scale CNT Production to Specialty Markets
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Tailoring Industrial Scale CNT Production to Specialty Markets Mark W. Schauer, Meghann A. White Nanocomp Technologies, Merrimack, NH Abstract: The vast majority of industrial scale Carbon Nanotube (CNT) production involves short nanotubes (< 100 microns) that appear as a powder. These products are typically utilized as minor components (usually less than 2%) in polymers where they may or may not impart marginal improvements in composite properties. At Nanocomp Technologies we produce large-format CNT material by floating catalyst chemical vapor deposition. This technique produces very long CNTs (> 1 mm) in the gas phase, where entanglement produces large format material of exceptional strength and electrical conductivity. By manipulating the physics and chemistry of the process, the format and properties of the material can be controlled. Post-production processing further enhances the desired material properties. In this way applications such as Armor, Wiring and Cables for aerospace, and Integrated Energy Storage can be realized. Introduction: While bulk materials made with carbon nanotubes (CNTs) have still not attained the properties seen in individual nanotubes1, the macroscopic sheets, yarns and tapes produced by floating catalyst chemical vapor deposition (FC-CVD) have the strength and electrical conductivity necessary for many applications. The FC-CVD technique involves injecting a catalyst precursor (i.e. ferrocene), carbon source (i.e. ethanol), and a catalyst activator such as thiophene, together with hydrogen, into a high temperature furnace (> 1200C). The catalyst particles are formed in the furnace, and the nanotubes grow on the unsupported activated, metallic nanoparticles. The nanotubes exit the furnace with the gas flow. The CNT material from an FC-CVD furnace can be collected on a rotating and translating drum to produce a large-format (~ 1.3 m x 2.4 m) sheet of material that can be integrated into a variety of products. CNT sheets made by direct collection from FCCVD are much stronger and more electrically conductive than analogous material made from CNT powders using paper-making technology (“buckypaper”)2. CNT sheets from FC-CVD can be infiltrated with resins such as polyurethanes, epoxies, bis-maleimides, polystyrene, and others, resulting in composites with higher levels of CNT loading than is possible using the standard approach of integrating powdered CNTs into polymer manufacturing processes. Different polymers can be used for specific applications, such as a component in body armor vests3, or electromagnetic shielding for the aerospace industry4. The CNT sheet material can also be coated with silicon to form the anode for a lithium ion battery5, or infiltrated with various chemical species to form the cathode in a battery6. CNT yarns can be made by direct spinning of FC-CVD material7. Instead of collecting the CNT material on a drum to form a sheet, the material can be directly collected into a roving or tow. This roving can be spun into a yarn and then plied, braided or woven into a fina
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