Current Search: Division of Undergraduate Studies (x) » Psychology (x) » The Synthesis of Controlled Carbon Nanotube Spun Aerogels By Floating Catalyst Chemical Vapor Deposition For High-Performance Materials (x)
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Title
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The Synthesis of Controlled Carbon Nanotube Spun Aerogels By Floating Catalyst Chemical Vapor Deposition For High-Performance Materials.
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Creator
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Leonhardt, Branden Erich
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Abstract/Description
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The customary vertical-growth chemical vapor deposition (CVD) method to synthesize carbon nanotubes (CNTs) requires an expensive substrate with limited surface area thus leading to low production rate, contrary to the continuous floating catalyst chemical vapor deposition (FCCVD) process. A reliable FCCVD reactor is required for repeatable CNT production with specific properties such as length, diameter and wall count. These tailored CNT structures may be used for next-generation ultra-strong...
Show moreThe customary vertical-growth chemical vapor deposition (CVD) method to synthesize carbon nanotubes (CNTs) requires an expensive substrate with limited surface area thus leading to low production rate, contrary to the continuous floating catalyst chemical vapor deposition (FCCVD) process. A reliable FCCVD reactor is required for repeatable CNT production with specific properties such as length, diameter and wall count. These tailored CNT structures may be used for next-generation ultra-strong and ultra-stiff carbon nanomaterials in structural and electronic applications. In the reactive region, CNTs grow in mid-air off floating catalyst nanoparticles and entangle to form an aerogel intended to be spun into various threaded structures (i.e. fibers, sheets, & composites). In this work, a fully operational FCCVD reactor capable of producing high quality and continuous CNTs was constructed based on materials science and chemical engineering principles. The reactor utilizes an original, in-house automated catalyst and carrier gas injection system with feedback control loops for maintaining temporal homogeneity. On the other end, a motorized spindle simultaneously collects the resulting aerogels into CNT sheets. The chemical process is mostly autonomous, producing product without the significant need of an operator. At an optimal carrier gas ratio of 3.75 H2:Ar, our work showed that multiple catalyst molar concentrations (on the range of 0 to 5 S:Fe) are capable of producing different CNT products in this reactor. It was found that as the sulphur concentration increased, the Raman IG:ID ratio decreased from ~5 to ~2, as well as the catalyst residue weight percentage from ~44% to ~19%. Moreover, the parameters plateaued, suggesting a saturation point for sulphur at the given Fe concentration. The possible catalyst nanoparticle mechanisms are discussed. Multiple techniques of characterization were employed such as scanning electron microscopy (SEM) to study surface morphology, transmission electron microscopy (TEM) for studying single nanotube surfaces and catalyst nanoparticles, Raman spectroscopy for probing the extent of tube disorder (i.e. G:D peak ratio), and thermogravimetric analysis for clues towards chemical composition. By using this particular FCCVD system, CNTs can be synthesized indefinitely given an unlimited source of catalyst solution. Therefore, the scalability of this system is only limited to the amount of catalyst solution available, indicating the potential for mass production.
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Date Issued
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2018-04-19
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Identifier
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FSU_libsubv1_scholarship_submission_1524653934_41e77801
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Format
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Thesis
