Processing and applications of carbon-based electrical conductors




Khanbolouki, Pouria

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The next generation of power-dense and efficient machines used in the aerospace, marine, transportation, energy, electronics, and electrical power industries will require superior electrical conductors. To this end, this dissertation investigates i) new post-processing (purification and intercalation) approaches for advanced carbon-based conductors and ii) numerical modeling of advanced conductors for practical applications. Most synthesis approaches leave impurities, catalyst particles and reaction by-products, in carbon nanotubes (CNT) that are not easy to remove. This dissertation investigates a fast and energy-efficient post-processing method for the purification and annealing of CNT yarns. The approach utilizes joule heating under high vacuum for the incandescent annealing process (IAP) of CNT yarns. Electrical properties of CNT yarns, spun directly from a floating catalyst chemical vapor deposition reactor, are correlated with the morphological changes of their structure resulting from the IAP. The correlations between the yarns’ chemical composition, structure, and electrical conductivity provide new insight into doping mechanisms and the stability of CNT conductors. Next, the effect of IAP is extended to other types of CNT yarns fabricated via dry spinning from vertically aligned CNT yarns and wet spinning from super-acid CNT solutions. A potential advantage of advanced electrical conductors is their relatively low density, thermal coefficient of resistance, and high thermal conductivity. This dissertation investigates the elevated temperature performance of advanced electrical conductors by developing, verifying, and validating a one-dimensional ampacity prediction model. Copper (as the reference) is subsequently compared with carbon-based conductors and copper nanocomposites on the basis of equivalent volume and equivalent weight. The performance of advanced carbon-based conductors improves drastically with nano-additives, however, they don’t readily integrate with carbonaceous materials. This dissertation explores gas-phase metal-halide intercalation of carbon-based conductors. Specifically, copper chloride is used as an intercalant with different CNT yarns and carbon fibers as host materials. A chemical vapor transport reactor was designed and constructed for intercalation studies. Dynamic of the process and chemical composition/structure of the intercalated compounds in different carbon hosts are correlated with physical properties of resulting advanced conductors. Advanced carbon-based conductors can survive the harsh space environment. This work investigates the electron irradiation and IAP damage recovery of CNT yarns.


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