Synthesis and Characterization of Carbon Nanotube, Threads, Yarns, and Sheets

The purpose of this dissertation is to bring the excellent properties of carbon nanotubes (CNT) to macroscale materials, specifically, yarns and sheets. Methods to synthesize high quality aligned CNT arrays, produce yarn and sheets from these arrays, apply different treatment techniques to enhance their properties, and incorporate the materials into technological applications are discussed. We use chemical vapor deposition (CVD) to synthesize CNT arrays with an average height <1mm on silicon substrates coated with an iron-cobalt alloy. This method produced the highest quality, spinnable CNT yarns. Conventional spinning techniques were modified to enhance the CNT yarn properties. In addition, various treatments were introduced both during the spinning process and post yarn fabrication. During spinning, the yarn was immersed in a dimethyl sulfoxide solution followed by polymer infiltration using either polyvinyl alcohol, polyimide, or epoxy as the polymer. Polyimide infiltration resulted in yarn with the highest tensile strength and electrical conductivity (884MPa and 746S/cm). In contrast to polymer infiltration during spinning, we also post treated as spun yarn by reiterative spinning and thermal or electrical annealing. Reiterative spinning increased tensile strength and electrical conductivity while decreasing cross sectional area. Thermal annealing at 2500° C in an inert environment resulted in a modest improvement. Applying a voltage bias across the yarns increased the electrical conductivity by ∼17% compared to the as-spun yarn. In addition to producing CNT based yarn, a new processing method was developed to make CNT sheets. We demonstrated production rates of about 20 to 30 meters per minute. These multilayer CNT sheet are more electrically conducting than carbon tape, flexible, light weight, and have high load carrying capacity.;Finally, two real world applications of these materials were realized: a CNT based incandescent light bulb and a CNT scaffold for neural axonal growth. We demonstrated that CNT yarn filaments for household light bulbs emit more light at lower power compared to tungsten filaments. Also the excellent CNT macro-materials show promise in nervous tissue repair. Towards understanding how CNT materials support nervous tissue regeneration, we examined the in vitro interactions between CNT materials and neural stem cell-containing neurospheres prepared from newborn mouse cortices. The results indicate that CNT yarns appeared to be a promising scaffold for neuronal regeneration. In conclusion, the extremely broad scope of potential applications for CNT based materials leaves open many possibilities for future work.