Browsing by Author "Kazimierska, Ewa"

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    Effect of Applied Pressure on the Electrical Resistance of Carbon Nanotube Fibers
    (MDPI, 2021) Barnett, Chris J.; McGettrick, James D.; Gangoli, Varun Shenoy; Kazimierska, Ewa; Orbaek White, Alvin; Barron, Andrew R.
    Carbon nanotubes (CNTs) can be spun into fibers as potential lightweight replacements for copper in electrical current transmission since lightweight CNT fibers weigh <1/6th that of an equivalently dimensioned copper wire. Experimentally, it has been shown that the electrical resistance of CNT fibers increases with longitudinal strain; however, although fibers may be under radial strain when they are compressed during crimping at contacts for use in electrical current transport, there has been no study of this relationship. Herein, we apply radial stress at the contact to a CNT fiber on both the nano- and macro-scale and measure the changes in fiber and contact resistance. We observed an increase in resistance with increasing pressure on the nanoscale as well as initially on the macro scale, which we attribute to the decreasing of axial CNT…CNT contacts. On the macro scale, the resistance then decreases with increased pressure, which we attribute to improved radial contact due to the closing of voids within the fiber bundle. X-ray photoelectron spectroscopy (XPS) and UV photoelectron spectroscopy (UPS) show that applied pressure on the fiber can damage the π–π bonding, which could also contribute to the increased resistance. As such, care must be taken when applying radial strain on CNT fibers in applications, including crimping for electrical contacts, lest they operate in an unfavorable regime with worse electrical performance.
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    Investigation into the Re-Arrangement of Copper Foams Pre- and Post-CO2 Electrocatalysis
    (MDPI, 2021) Rudd, Jennifer A.; Hernandez-Aldave, Sandra; Kazimierska, Ewa; Hamdy, Louise B.; Bain, Odin J.E.; Barron, Andrew R.; Andreoli, Enrico
    The utilization of carbon dioxide is a major incentive for the growing field of carbon capture. Carbon dioxide could be an abundant building block to generate higher-value chemical products. Herein, we fabricated a porous copper electrode capable of catalyzing the reduction of carbon dioxide into higher-value products, such as ethylene, ethanol and propanol. We investigated the formation of the foams under different conditions, not only analyzing their morphological and crystal structure, but also documenting their performance as a catalyst. In particular, we studied the response of the foams to CO2 electrolysis, including the effect of urea as a potential additive to enhance CO2 catalysis. Before electrolysis, the pristine and urea-modified foam copper electrodes consisted of a mixture of cuboctahedra and dendrites. After 35 min of electrolysis, the cuboctahedra and dendrites underwent structural rearrangement affecting catalysis performance. We found that alterations in the morphology, crystallinity and surface composition of the catalyst were conducive to the deactivation of the copper foams.
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    Understanding the effect of carbon nanotube functionalization on copper electrodeposition
    (Springer, 2019) Kazimierska, Ewa; Andreoli, Enrico; Barron, Andrew R.
    The dynamics of electrochemical deposition and dissolution of copper in the presence of functionalized multiwalled carbon nanotubes in solution has been studied in detail using an electrochemical quartz crystal microbalance. Results demonstrate the central role of carbon nanotube functionalization on the values of mass and current densities of copper deposition. Amine functionalization increases competitive hydrogen evolution without significantly affecting the total amount of deposited copper, whereas carboxylic functionalization clearly enhances the deposition of larger amounts of smoother copper deposits. Molar mass analysis of deposited species reveals interactions of carbon nanotubes with the electrode surface dependent on the type of functionalization. The effect of carbon nanotube functionalization should be closely considered in the development of electrochemical strategies for the integration of carbon nanotubes in metallic copper.