Engineering Commons^™

Pyrene Oligomers: Their Isolation, Molecular Characterization, And Phase Behavior, David Esguerra Taborda

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Carbonaceous pitches can serve as attractive precursors for advanced carbon materials such as high thermal conductivity fibers or carbon-carbon composites. Yet the effects of composition and molecular structure on the bulk properties (e.g., mesophase content and melting point) of these precursors remain only partly known, mainly because of the difficulties associated with the isolation, identification, and quantification of the large (i.e., molecular weight (mol wt) > 350-400 Da) polycyclic aromatic hydrocarbon (PAH) oligomers comprising these pitches. In this study, oligomeric fractions were isolated via supercritical extraction (SCE) from two representative pitches: a petroleum pitch (M-50) produced by the thermal polymerization of …

Effect Of Graphitic Carbon Nanomodifiers On The Electromagnetic Shielding Effectiveness Of Linear Low Density Polyethylene Nanocomposites, Byron Villacorta Hernandez

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Conductive polymer composites have become alternative materials for providing electromagnetic and electrostatic shielding where metals are not suitable. In this study, the effect of crystallinity, morphology, concentration and orientation of carbon nanomodifiers on shielding provided by their polyethylene-based composites has been investigated relative to their transport properties.

First, the electrical properties and EM SE of composites consisting of heat-treated carbon nanofibers (Pyrograf^® -III PR-19 CNF) in a linear low density polyethylene (LLDPE) matrix were assessed. Heat treatment (HT) of CNF at 2500°C significantly improved their graphitic crystallinity and intrinsic transport properties, thereby increasing the EM SE of the nanocomposites. …

Sulfonated Perfluorocyclobutyl (Pfcb) Aryl Ether Polymers: Synthesis, Reactivity, And Characterization For Polymer Electrolyte Applications, Jiyoung Park

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Perfluorocyclobutyl (PFCB) aryl ether copolymers are excellent candidates for proton exchange membrane (PEM) component in PEM fuel cells. Sulfonated PFCB copolymer membranes exhibit not only high chemical/thermal/mechanical stability but also high proton conductivity. In this regard, PFCB aryl ether copolymers were synthesized via thermal step-growth [2 + 2] cyclopolymerization from aryl bis-(trifluorovinyl ether) (TFVE) monomers and oligomers. Experimental and computational studies confirmed that copolymerization of relatively electron-rich and electron-poor TFVE monomers gave selective-segmented copolymers in an one-pot polymerization. After sulfonation, the PFCB copolymers comprising hydrophilic and hydrophobic segments gave membranes with high proton conductivity. Cross-linked membranes of the sulfonated PFCB …

Uv-Assisted Stabilization Of Polyacrylonitrile-Based Carbon Fiber Precursors, Marlon Salvador Morales Sandoval

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Due to their high strength and stiffness coupled with low density, carbon fibers are the preferred reinforcing fibers used in high-performance polymer matrix composites. Consequently, the demand for carbon fibers is expected to grow from 40,000 metric tons to about 150,000 metric tons over the next decade. A large fraction of the increase is anticipated in the industrial sector that is cost-sensitive. Therefore, there is a need for the development of novel processes and precursors to reduce the carbon fiber production cost and expand the use of carbon fibers. This research focuses on the development of an alternative, rapid stabilization …

A Computational Approach For The Rational Design Of Bimetallic Clusters For Ethanol Formation From Syn-Gas, Ming He

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There is currently a growing interest in the catalytic synthesis of ethanol from syn-gas (2CO + 4H2 --> C2H5OH + H2O). A major challenge associated with this direct route is an inability to find a low-cost catalyst that promotes the proper combination of CO dissociation and CO insertion steps, so as to yield ethanol as the primary reaction product. Bimetallic catalysts, in which one metal promotes hydrocarbon production and the other oxygenate production, may exhibit a synergistic effect that can facilitate the formation of ethanol. Given the complexity of this reaction system, a simple trial-and-error approach to catalyst design is …

A Localized Controlled Delivery System Utilizing A Block Copolymer To Improve The Current Paradigm Of Chemotherapy, Jason Olbrich

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The goal of the field of Bioengineering has always been to bring about a better standard of care for patients. As a field encompassing a broad array of researchers and talents, such improvements often are brought about through the integration of different fields. This work advances the integration of controlled delivery and chemotherapy. The use of cytotoxic chemotherapy has become and will continue to be a powerful tool for the treatment of solid malignancies. Conventional dose scheduling of cytotoxic agents and newer biological response modifiers are investigated under a clinical paradigm initially designed to identify a drug dose that elicits …

Perfluorocyclobutyl Polymer Thin-Film Composite Membrane Fabrication, Plasticization And Physical Aging, Jinxiang Zhou

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Membrane technologies have been used widely in industrial practices such as waste water treatment, sea water desalination, gas separations, pharmaceutical separations, and food and beverage processing to name a few. Among the features that make them attractive are that they are cost effective, highly efficient, scalable, and environmentally benign. The focus of this dissertation is to contribute to the understanding and use of polymeric membranes for carbon dioxide separations.
Currently, the largest carbon capture demand lies in the natural gas industry. However, since global warming has become a severe concern for human existence, flue gas cleaning is potentially another very …

Advanced Biomaterials From Renewable Resources: An Investigation On Cellulose Nanocrystal Composites And Co2 Extraction Of Rendered Materials, Jose Orellana

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The annual global consumption of petroleum-based plastics is approximately 280 million tons and is impacting the sustainability of our planet and prosperity of future generations. One solution is the development of bio-based polymer materials with advanced properties for commercial applications. Therefore, the ultimate goal of this dissertation is to investigate the properties of new bio-based materials for broader applications. This dissertation includes two research areas: cellulose nanocomposites, and CO₂ extractions of rendered fat. In the first half, cellulose nanocrystals (CNCs), which exhibit excellent mechanical and optical properties, were investigated for the reinforcement of a biodegradable polymer. The properties of …

Novel Ceria-Zirconia-Yttria Mesostructures: Synthesis, Characterization, Diffusional Studies And The Effects Of Morphology On Their Properties, Alma Cordova Morales

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Ceria-zirconia-yttria (CZY) mixed oxides are used as catalyst supports for three-way catalysts for automotive exhaust emission control and in solid oxide fuel cells. By improving the morphology of CZY mesopores it is possible to reduce the sintering of supported noble metals and enhance overall catalyst lifetime and performance. However, limited studies have been published on the synthetic control of the morphology of CZY materials and the effects that CZY pore geometry has on catalyst operation.
To create optimized CZY catalyst supports, novel mesoporous CZY oxides were synthesized via classical sol-gel and evaporation induced self-assembly (EISA) methods, obtaining mesostructures that exhibited …

Aqueous Suspensions Of Polymer Coated Magnetite Nanoparticles: Colloidal Stability, Specific Absorption Rate, And Transverse Relaxivity, Steven Saville

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The design, functionalization, characterization, and applications of magnetic nanoparticles have garnered significant interest over the past several decades. While this area has garnered increasing attention, several questions remain unanswered about the stability of these systems and it's influence on their biomedical applications. To help answer these questions about the stability of these, a novel tri(nitroDOPA) terminated polymer based ligand has been developed for the stabilization of magnetite nanoparticles. The synthesis involves a process in which ethylene oxide is polymerized using a trivinyl initiator, modified with carboxylic acid using a free radical addition of mercaptoundecanoic acid, and then functionalized with nitroDOPA …