Department: Chemical Engineering ![[clear]](close-x.png "Remove this limiter")
44 matches in the database.
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1.
Al-Juhni, Abdulhadi A.
INCORPORATION OF LESS TOXIC ANTIFOULING COMPOUNDS INTO SILICONE COATINGS TO STUDY THEIR RELEASE BEHAVIORS.
Degree: Doctor of Philosophy, Chemical Engineering, 2006, University of Akron
► Biofouling has always caused serious problems, including increased fuel consumption and maintenance…
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▼ Biofouling has always caused serious problems, including increased fuel consumption and maintenance costs for vessels, to the naval industry. The use of toxic antifouling compounds to combat the organisms attached and accumulated on the surface of submerged structures has been common. However, the current ban on the application of conventional tin-based antifouling compounds has accelerated the research to seek for less toxic alternatives. In this study, four much less-toxic antifouling compounds (sodium benzoate, benzoic acid, capsaicin, and tannic acid), as compared to tin-based antifoulants, were incorporated into two types of silicone coatings (Sylgard® 184 and RTV11) by applying a solvent-blending technique. These compounds were proven to be effective against some bacterial growth and attachments; however, a systematic study on the miscibility and the release of these compounds from the coatings is lacking. Therefore, the focus of the current study is to correlate the miscibility of the compounds in the coatings and their release rates in water, for the purpose of controlling the release of the compounds. It was found that benzoic acid and capsaicin formed large crystals inside the coating; whereas sodium benzoate and tannic acid were able to form small aggregates inside the coatings. The magnitude of the leaching of the four compounds was in the order of: benzoic acid > capsaicin > sodium benzoate > tannic acid. The solvent-assisted blending technique was adequate for the cases of sodium benzoate and tannic acid whereas it was not suitable for benzoic acid and capsaicin. Sodium benzoate/Sylgard® 184 coating was then selected as the model system to obtain the miscibility-release relationship. The preparation conditions were found to have important effects on the morphological structure and final distribution of sodium benzoate in silicone, hence the leaching. The minimum average aggregate size obtained was ~ 3 ìm, which had resulted in the lowest value for the steady leaching rate of ~ 0.1 ìg/cm2/day. Empirical correlations were obtained between the aggregate size as well as the matrix loading of sodium benzoate and the leaching rate. It was found that increasing the aggregate size had a sharp effect on the increase of the leaching rate, whereas increasing the matrix loading (up to 5 wt. %) had a mild effect on the leaching rate. The current study did show that the solvent-assisted blending technique can be an efficient approach for constructing the miscibility-release correlations. Both thermodynamic analysis and experimental observations showed that sodium benzoate has limited solubility in the Sylgard® 184 coating. This, combined with the mass transfer analysis of the leaching, led us to confirm that the release mechanism of the monolithic sodium benzoate/silicone coatings generated via the solvent-assisted blending technique is mainly by the diffusion of the compound through water-filled pores and constricted channels within the matrix, not through the continuum of the polymer phase.
Advisors/Committee Members: Newby, Bi-Min Zhang.
Subjects: Engineering, Chemical
Keywords: less-toxic antifouling compounds; controlling the release; miscibility-release correlations; release mechanism
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2.
Baskaya, Fadime Suhan.
Phase equilibrium at supercritical (SC) conditions: solubility analysis of curcumin in supercritical carbon dioxide and co-solvent mixtures, and phase equilibrium analysis of cis-1,4-(poly)isoprene in propane and co-solvent mixtures.
Degree: Master of Science, Chemical Engineering, 2005, University of Akron
► Although the existence of supercritical fluids has been known for over a…
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▼ Although the existence of supercritical fluids has been known for over a century, relatively little attention was given to them until recently. After the significant rise of energy costs, and increased governmental regulations due to environmental concerns, their application has attracted more attention. In this thesis, the study of high-pressure phase behavior was extended to a highly polar component, and a polymeric substance in the binary and ternary systems of curcumin-supercritical CO2, curcumin-supercritical CO2/acetone, cis-1,4-(poly)isoprene-propane, and cis-1,4-(poly)isoprene-propane/supercritical CO2. The equipment used in the study had a view cell, for accurate visual observation of the high-pressure phase behavior, and syringe pumps to supply necessary fluids to the system. Supercritical CO2 and propane were used as solvents to investigate the curcumin. Curcumin has been known for a very long time, and used in Ayurvedic and Chinese medicine for centuries. Recently curcumin attracted researchers’ attention due to its effect on Alzheimer, AIDS, cancer, and various diseases. Natural rubber, present in Russian dandelion and guayule plants, has the potential to be a valuable chemical commodity produced by sustainable biotechnology. Cis-1,4-(poly)isoprene is the main compound in natural rubber. The Elliott-Suresh-Donohue (ESD) and Peng Robinson (PR) equation of states were used to correlate the experimental data in the literature. The ESD equation of state is a semi empirical equation of state that was developed especially for associated and non-spherical mixtures. The model is cubic for non-associating molecules, and has only three real roots for associating fluids. For the systems involved with self-associating fluids, hydrogen bonding between similar molecules, model needs a single interaction parameter (kij) for each component pairs. The ESD equation of state was also used to correlate experimental data obtained from phase equilibrium analyzer. In an effort to place the thermodynamic modeling on a firmer theoretica basis, the Step Potential Equilibrium and Dynamics (SPEAD) model was studied. The model was extended to new chemical families in the study. Furthermore, its application to variable polymer structure was demonstrated by evaluating the asymptotic trend of the perturbation terms to the infinite chain limit and showing the similarities and differences to n-alkane (polyethylene) chains. This research will enlighten the understanding of phase behavior of highly polar material in supercritical conditions, and cis-1,4-(poly)isoprene in supercritical conditions. It will also guide further possible applications, such as producing fine particles using supercritical antisolvent method, or cis-1,4-(poly)isoprene extraction from a plant origin.
Advisors/Committee Members: Elliott, J. Richard.
Subjects: Engineering, Chemical
Keywords: Supercritical fluids; High pressure behavior; ESD equation of state; SPEAD Model
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3.
Chen, Fan.
Metabolism of Pseudomonas Aeruginosa Under Simultaneous Aerobic Respiration and Denitrification.
Degree: Doctor of Philosophy, Chemical Engineering, 2005, University of Akron
► Pseudomonas aeruginosa is ubiquitous in the nature and is one of the…
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▼ Pseudomonas aeruginosa is ubiquitous in the nature and is one of the most commonly found microorganisms in petroleum-contaminated environments. With versatile metabolic activities, it can be used to produce various industrial and pharmaceutical products. P. aeruginosa is also a clinically important, opportunistic pathogen that causes a variety of infections, particularly in patients with severe burns, cancer, AIDS and cystic fibrosis. An important metabolic trait that supports the efficient adaptation of P. aeruginosa to this wide range of environments is its ability of active denitrification. The bacterium’s properties and respiratory behaviors under different growth rates and dissolved oxygen concentrations (DO) were therefore systematically studied in this research. Continuous cultures of P. aeruginosa (ATCC 9027) were maintained at different DO (0-4.8 mg/L) and dilution rates (D, 0.01, 0.026, 0.06, and 0.13 h-1). Aerobic denitrification was found to function as an electron-accepting mechanism supplementary, instead of competitive, to aerobic respiration. The experimental results suggested that the zero-DO conditions were more favorable for survival of the bacterium. A closer examination revealed that increasing DO enhanced O2 respiration only at extremely low DO (< 0.05 mg/L), beyond which the increasing DO only slightly increased its weak inhibition on denitrification. While O2 was the preferred electron acceptor, the fraction of electrons accepted (and the ATP generated) via denitrification increased with increasing D. Unlike glucose, when hexadecane was used as the sole carbon source, there was a critical DO (0.4 mg/L in this study), below which the system could not reach the steady state. Phosphate concentration appeared to be also very important to the behaviors of culture growing on the hexadecane-based media. Furthermore, intriguing metabolic fluctuations were observed during the transition from non-aerated batch culture to aerated continuously-fed culture. The phenomenon suggested the complex nature of the microaerobic metabolism by P. aeruginosa as well as the inter-regulation between the two respiratory mechanisms. DO appeared to have a more pronounced effect on nitrite reduction during the transition period than at the chemostat (steady state) eventually reached after the culture adapted to the microaerobic condition. In the transition period, the autoinducer PAI1 or its homologue was found to trigger the inhibition to cell growth and nitrite reduction. The effect of autoinducer PAI2 on rhamnolipid (RL) production by Pseudomonas aeruginosa was also evaluated by a model developed to describe the production kinetics regulated by the rhl quorum-sensing system. The best-fit model parameters obtained also provided important insights. To complex half of the intracellular RhlR proteins would require 1.61 µM of PAI2, about half of the PAI2 concentration obtained in the stationary-phase culture of wild-type PAO1. On the other hand, to activate the synthesis of rhamnosyltransferase at half of its maximum rate would require the binding of 39% of RhlR with PAI2. The maximum RL production rate of the culture was found 0.042 g/L-h and the fully induced culture would require at least 1.61 h to synthesize the enzyme to the level for producing RL at half of the maximum rate.
Advisors/Committee Members: Ju, Lu-Kwang.
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4.
Choi, Sung-Hwan.
DEWETTING OF POLYSTYRENE THIN FILMS ON ORGANOSILANE MODIFIED SURFACES.
Degree: Doctor of Philosophy, Chemical Engineering, 2006, University of Akron
► The importance of polymer thin films (< 100 nm) in microelectronics, coatings/paints,…
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▼ The importance of polymer thin films (< 100 nm) in microelectronics, coatings/paints, adhesives, nanofabrication, or biodevices has promoted extensive studies on the dewetting phenomenon of these thin films. Most of the studies have been focused on the effects of polymer properties on the dewetting and the associated kinetics while the effects of substrates on the dewetting behaviors, which could be crucial in some cases, have rarely been reported. For the few experimental studies that utilized modified substrates, none has systematically varied substrate surface energy (gS) to examine its effects on the dewetting. Therefore, in this study, the effects of gS on the dewetting process of supported polystyrene (PS, Mn of 63k and 9.3k) thin films were studied. The substrates were modified using various organosilanes under different preparation conditions to systematically vary gS, ranging from 13 to 63 mJ/m2. In particular, the preparation methods included (1) contact printing of octadecyltrichlorosilane on oxidized silicon wafers for different contact times, (2) vapor phase deposition of mixed CF3- and CH3-terminated organosilanes with different ratios, and (3) solution deposition of polar organosilanes with functional groups of -COOH, -CH2Cl, -NH2, or -SH. On these substrates, the kinetics of dewetting was first investigated as a function ofgS. Empirical relationships between the rate of hole growth (dewetting velocity, VR) and gS, VR ≈ 530 exp(-0.13gS) and 310 exp(-0.10gS), were obtained from the dewetting of PS-63k thin films on the -CH3 and -CF3/-CH3 covered surfaces, respectively. For PS-9.3k on the OTS surfaces, VR ≈ 1.1 x 104 exp(-0.13gS) was obtained. In analogous to a desorption process, the exponential relationship between VR and gS was hypothesized to be originated from the energy required to overcome the free energy of adhesion in the dewetting process, which is proportional to gS1/2. Second, an origin of the instability of the rim, formed around the dewetting hole, was elucidated in relation to gS. The rim instability, in terms of undulations of the rim, became more pronounced as gS decreased. A narrower and higher rim was also observed as gS decreased. A simple material balance of the rim formation verified that gS determined the rim profile through the variation of dynamic contact angle. The predicted rim profiles were used in combination with the analysis of the Rayleigh instability of a cylindrical fluid to interpret the rim instability. The model captures the basic trend of the rim instability dependence on gS. Third, the possible mechanism of the enhancement of the PS thin film stability on substrates modified using an NH2-terminated organosilane, aminopropyltriethoxysilane (APTES), was proposed and evaluated. Dewetting suppression was only observed for PS/APTES that was thermally treated at ~ 80 or 120C prior to annealing the thin film at higher temperatures, and much stronger suppression was observed for PS having a molecular weight higher than Me (entanglement molecular weight). For PS thin films deposited onto non-cured or precured APTES networks, no dewetting suppression was resulted. These results suggested that the penetration of the entangled PS chains into the APTES layer and the thermal crosslinking of the APTES molecules over the penetrated PS chains were responsible for the dewetting suppression. This study has indicated the importance of S in the dewetting kinetics or rim morphology of the dewetting holes and the capability of dewetting suppression by simply modifying the substrate. However, it can be suggested that for the dewetting kinetics, the assumption of the “thermally-activated” dewetting process in our hypothesis could be verified by temperature-dependent studies of VR with a fixed gS; and for the dewetting suppression of the PS/APTES systems, the interface of PS/APTES could be investigated using X-ray or neutron reflectometry to probe any interdiffusion across the interface. Furthermore, other factors affecting the dewetting behaviors, e.g. film thickness of PS or molecular weights of PS, could also be systematically varied for a fixed gS, providing a possibility of multidimensional combinatorial analysis of the dewetting.
Advisors/Committee Members: Zhang Newby, Bi-min.
Subjects: Engineering, Chemical
Keywords: Polymer thin film; Dewetting; Surface Modification; Surface Energy; Organosilane; Dewetting kinetics; Dewetting suppression; Rim instability; Dynamic contact angle; Aminopropyltriethoxysilane
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5.
Dawar, Saru.
MICROSCALE STUDY OF DROP MIGRATION ON FIBERS IN COALESCING FILTERS.
Degree: Doctor of Philosophy, Chemical Engineering, 2007, University of Akron
► The micro scale study of drop motion on fibers is significant to…
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▼ The micro scale study of drop motion on fibers is significant to many industrial applications such as drop coalescence and drainage in fibrous filter media. Removal of the liquid droplets from the exhaust streams of many chemical, automotive, aeronautics, textile and health and safety industries is of vital importance. These droplets can lead to clogging of the fibrous filters during the cleaning operation. It is significant to design a self cleaning filter, whereby the liquid droplets collect on the filter and drain down onto some collecting device. This reduces the operational and cleaning cost of the filter. The underlying need for all these applications is estimation of the velocity of a drop along the fiber axis. This can be done by defining and determining the drag coefficient correlation. In this work, the drag coefficient is correlated to Reynolds and capillary numbers from experiments and models with the axial and transverse air flow conditions. The experiments are conducted for different types of fibers and using acoustic fields. Correlations to predict the probability of the motion of the drops on fibers are also developed considering the effect of acoustic fields. These correlations are unique approach to determine the velocities of the liquid drops on fibers for different fiber orientations. Very little has been published on the development of such correlations to predict drop migration on fibers which makes this work unique.
Advisors/Committee Members: Chase, George G.
Subjects: Engineering, Chemical
Keywords: Coalescence; Fibers; Drops; Motion; Drag Correlations; Fiber orientations; Acoustic fields
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6.
Dharmanolla, Sailaja.
A Computer Program for Filter Media Design Optimization.
Degree: Master of Science, Chemical Engineering, 2007, University of Akron
► In depth filtration, mixtures of nanofibers and microfibers provide efficient and effective…
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▼ In depth filtration, mixtures of nanofibers and microfibers provide efficient and effective filters for capture of micron and submicron sized particles. Experimental approaches are time consuming and expensive to design filters. There is a need for reliable computational models to analyze and evaluate the filter performance. The objective of this research is to present a computational approach for designing mixed fiber filter media for depth filtration. The goal is to find an optimum solution, given specified ranges for a set of design parameters: thickness of the media, diameter of microfiber, diameter of nanofiber, surface area ratio of nanofiber to microfiber, and mass of microfiber. The idea is to develop with a software tool that may reduce the number of experiments.This program applies a Genetic Algorithm to search for an optimum filter media design based on Quality Factor which quantifies the filter performance. A user friendly computer program is developed that provides inputs, outputs and controls to design a filter media. This program provides a starting point for design of filter media for particular applications.Experiments were performed to validate the modeling and experimental data for comparison. The results show about 25% error in quality factor between computer model and experiments. More experiments are needed in future work for model validation.
Advisors/Committee Members: Chase, George.
Subjects: Engineering, Chemical
Keywords: Filter Design Optimization
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7.
Drews, Aaron M.
Control of Thermal Expansion Coefficient of a Metal Powder Composite via Ceramic Nanofiber Reinforcement.
Degree: Master of Science, Chemical Engineering, 2009, University of Akron
► Solder is used in nearly all electronic packages to provide mechanical, electrical…
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▼ Solder is used in nearly all electronic packages to provide mechanical, electrical and thermal contact between various components. The mismatch between the components‟ coefficient of thermal expansion results in thermal stresses which can damage components or connections and render the circuit board useless. In order to reduce this mismatch, a novel fabrication method was developed to produce composites of solder and ceramic reinforcement are presented. Composites were prepared by uniaxial compression of 63Sn/37Pb solder powder and various morphologies of titania reinforcement. A solution of poly(vinyl pyrrolidone), ethanol and tetraisopropyl titanate was used to produce beaded nanofibers; acetic acid was added to the solution in order to lower the dielectric constant of the solution and produce smooth nanofibers. Ultrasonication was used to cut the calcined, electrospun nanofibers to consistent lengths of about 6μm. Optical microscopy, electron microscopy and x-ray diffraction were used to characterize the size, shape and crystalline phase of the filler. Analysis of the different fillers revealed three distinct categories of shape and size, including spherical titania powder (6.5μm diameter), smooth cylindrical titania nanofibers (150nm diameter) and a mixture of 80wt% spherical beaded titania (3.5μm diameter) with 20wt% cylindrical nanofibers (400nm diameter). A 25% reduction in the coefficient of thermal expansion of the composite was achieved regardless of the shape, size or quantity of reinforcement. The melting and freezing points of the composite samples were not statistically different from that of pure solder but the specific gravity was lowered by about 1.5%. During reflow it was observed that the majority of the filler was expelled from the molten solder core. The differences in density between the filler and solder provide a buoyant force that tends to expel the less dense titania from the more dense molten solder. A force balance on a rigid cylinder floating at a liquid-gas interface revealed that the filler is dominated by surface tension forces; once the filler reaches the surface of the molten solder its equilibrium position is located primarily in the surrounding gas. Therefore a novel recommendation is presented to investigate neutrally buoyant filler in order to prevent filler expulsion during reflow.
Advisors/Committee Members: Evans, Edward.
Subjects: Chemical engineering; Mechanical engineering
Keywords: solder; composite; coefficient of thermal expansion; nanofiber; titania
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8.
El-Zahab, Bilal Mohamad Issam.
Multi-Enzyme Biocatalysis Using Nano-Structured Materials for Bioprocessing Applications.
Degree: Doctor of Philosophy, Chemical Engineering, 2009, University of Akron
► With the increasing awareness of environmental safety and the need for renewable…
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▼ With the increasing awareness of environmental safety and the need for renewable fuels, enzyme-catalyzed reactions provide convenient substitutes for future industries relative to most catalysis used today. To our date, multienzyme systems involving cofactors have not been fully explored. In this work, novel cofactor-dependent multienzyme biocatalysts were developed for bioprocessing applications. Areas investigated ranging from proof-of-concept to specific applications were: 1) The separation of enzymes from bacteria: to mimic microbes, multienzyme extracts from trichloroethylene degrading bacteria were separated and in vitro degradation was achieved. 2) Immobilization of a multi-enzyme system in nanoporous glass: successful enzyme-cofactor interaction was possible on the same surface if concave structures were used while smaller pores and longer spacers provided remarkable enhancement. 3) Attachment to nanoparticles: efficient cofactor regeneration and reuse for the novel sequential enzyme-catalyzed synthesis of methanol and L-lactate from CO2. Theoretical and experimental approaches to optimize the synthesis involved studying the flexibility of the polymeric spacer-arm over a range of solubility conditions. In summary, a green multi-enzyme system able to catalyze complex redox reactions was demonstrated while using a cofactor regeneration mechanism rendering it cost-effective. Such system suggests a wealth of potential in catalysis, remediation, and sensing applications.
Advisors/Committee Members: Wang, Ping.
Subjects: Chemical engineering
Keywords: Biocatalysis; nanoparticles; multi-enzyme; cofactor regeneration; immobilization
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9.
Emami, Fatemesadat.
Prediction of Thermodynamic Properties by Structure-Based Group Contribution Approaches.
Degree: Master of Science, Chemical Engineering, 2008, University of Akron
► This research suggests two new group contribution methods to facilitate phase behavior…
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▼ This research suggests two new group contribution methods to facilitate phase behavior calculation when reliable experimental data are lacking. The first method pertains to the implementation of an updated version of the Elliott and Natarajan method to the Statistical Associating Fluid Theory (SAFT) and Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equations of state. Shape factor parameters have been correlated for 878 compounds including different variety of families and the parameters from Elliott and Natarajan have been updated to improve accuracy for alcohols. Thereafter, thermodynamic properties such as boiling temperatures and vapor pressures have been predicted. We obtain 36%, 65%, and 32% AAD% in pressures for the ESD, SAFT, and PC-SAFT equations of state. Additionally, we have compared our GC-PC-SAFT to the one by Tihic et al., applying their suggested First-Order and Second-Order groups for 650 non-associating compounds. We observed higher accuracy for our method relative to the Tihic et al. The resulting P AAD% were 53% for Tihic FOG and 42% for Tihic SOG. The second method suggests a new group contribution model for Tb at 760mmHg and Tb at 10 mmHg. These correlations recognize a finite limit in boiling temperature as infinite molecular weight is approached. The availability of two vapor pressures enables straightforward application of the Clausius-Clapeyron equation to estimate boiling temperatures at other points. In the presented approach, there are 3 parameters and 72 functional groups for each temperature which are regressed through a database consisting of 336 hydrocarbons and 642 non-hydrocarbons. The average absolute percent deviations (AAD%) between the correlated and experimental temperatures are calculated in comparison with Joback-Reid and Gani approaches. We obtain 3.5, 4.7, and 4.1 AAD% in temperature for the present work, Joback, and Gani methods, respectively. Additionally, the accuracy of the present work is evaluated by calculating the vapor pressures from the DIPPR correlation at the predicted temperatures of each model. We obtained 33.2, 104.3 and 48.1 AAD% in pressure for the present work, Joback, and Gani methods. Finally, the accuracy of the presented correlations are tested against Asher and Pankow model, UNIFAC-PL°, for 66 volatile compounds in the temperature range of 290 ⦥uro;“ 320 K. For the vapor pressure at the 10mmHg boiling temperature, we obtain 36.9 AAD% for the present work and 94.5 AAD% for the Asher method. Overall, these group contribution methods establish a standard for comparison of more fundamental methods like molecular simulations with transferable potentials. Transferable potentials generally provide accuracy of 10-30AAD% in pressure, but have only been developed for relatively small databases over narrow temperature ranges.
Advisors/Committee Members: Elliott, J. Richard.
Subjects: Chemical engineering
Keywords: Group contribution; Asymptotic limit; Boiling temperature; Vapor pressure; equation of state; UNIFAC; ESD; SAFT; PC-SAFT
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10.
Fisher, James C II.
A Novel Fuel Cell Anode Catalyst, Perovskite LSCF: Compared in a Fuel Cell Anode and Tubular Reactor.
Degree: Master of Science, Chemical Engineering, 2006, University of Akron
► The development of solid oxide fuel cells (SOFCs) has attracted research interest…
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▼ The development of solid oxide fuel cells (SOFCs) has attracted research interest the recently due to an increasing concern on the depletion of available crude oil reserves and environmental issues such as global warming and emission of pollution. SOFCs have received special attention because of their higher energy efficiency, rapid electrode kinetics without using expensive electro-catalysts such as platinum, relative resistance to impurities in the fuel and the ability to use hydrocarbons as fuel. Research efforts have resulted in the development of traditional SOFC materials such as zirconia electrolytes stabilized with various metals, lanthanum doped strontium (LSM) cathodes and Ni-YSZ cermet anodes. Nickel has disadvantages when applied as an anode catalyst and operated with hydrocarbon fuels. The most significant problems are deactivation through coking, long term sintering and sulfur poisoning. The perovskite lanthanum strontium cobalt iron oxide (LSCF) was used as a fuel cell anode; LSCF is a common cathode material. LSCF has been shown by previous research to be resistant to coking, resistant to sulfur poisoning and structurally stable at high temperatures. Perovskites are electronically conductive, like nickel, and are also conductive of oxygen ions. This is allows an extension on the three phase boundary, where the fuel, electron and ions meet and the reaction occurs. Due to the complexity of fabricating and producing a functioning SOFC, traditionally minimal research was done on the catalyst in the fuel cell. A large amount of catalysis research has been done a various catalyst in a tubular reactor that emulates a fuel cell anode, but there is no research to test the validity of this data and its usefulness in relation to a SOFC. A comparison of LSCF as the fuel cell anode and in a tubular reactor was done to further understand the advantages and disadvantages of tubular reactors that emulate SOFC conditions. This study involves developing a functional SOFC that yields respectable results using LSCF as the anode. The results of this study demonstrate the possibility of using the same material on both the cathode and anode reducing complexity of the SOFC and potentially reducing manufacturing costs. This can eliminate the need for cleaning sulfur from fuel and other contaminates from the fuel as shown by utilizing industrial propane as fuel. The tubular reactor study has shown that some results in the SOFC maybe simulated in simple and quick testing system; reducing the time to test a catalyst from 1 month in a tradition SOFC to 1 day in a tubular reactor. Future studies should include testing other perovskite catalyst on the anode or adding promoters to the LSCF. Coking was observed in the SOFC, studies on how to prevent this and the damage done by coking should be considered. More catalysts need to be tested in the tubular reactor and related to its performance in a SOFC anode to make a substantial conclusion that a catalyst’s behavior in a SOFC can be accurately emulated. Future studies should also focus on the effects of electron and/or ion charge that occurs in the SOFC, how it effects the electro-catalytic properties of the catalyst and if it can be emulated in the tubular reactor should be evaluated.
Advisors/Committee Members: Chuang, Steven.
Subjects: Engineering, Chemical
Keywords: LSCF, SOFC, double cathode, perovskite anode, LSCF anode
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11.
Fisher, James C. II.
The Reduction of CO2 Emissions Via CO2 Capture and Solid Oxide Fuel Cells.
Degree: Doctor of Philosophy, Chemical Engineering, 2009, University of Akron
► The increase in CO2 emissions over past decades are the result of…
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▼ The increase in CO2 emissions over past decades are the result of a growing dependence on fossil fuels. Examination of CO2 emission sources revealed that more than 33% of global CO2 emissions result from coal-fired power plants, which represent the largest stationary source of CO2. Two proposed approaches for reduction of CO2 emissions: (i) a short term (i.e. 7-10 years) capture of CO2 from coal-fired power plants and (ii) a long term (i.e. 10-15 years) approach is the replacement of coal-fired power plants by coal-based fuel cells. These approaches purify CO2 for sequestration. Carbon capture from existing power plants could be accomplished by passing the flue gas through a sorbent. The sorbent captures the CO2 from the flue gas then regenerated producing purified CO2. Direct coal fuel cells directly convert coal to electricity through the electrochemical oxidation of carbon. The mixing of air and coal does not occur in the fuel cell, leading to highly concentrated CO2 effluent for sequestration. CO2 capture was investigated by transient flow, bed temperature measurement, and temperature programmed CO2 desorption coupled with IR effluent measurement of seventeen sorbents, which had SiO2, carbon, or beta zeolite as a support. The heat released during the exothermic adsorption of CO2 onto amine resulted in a bed temperature rise. The heat generated could be dissipated with a smaller particle size and greater thermal conductivity. The heat released was used to verify the capture capacity using a thermal camera and high throughput adsorber that screened thirteen sorbents simultaneously. The carbon initially investigated produced an ammonia odor and had a low capture capacity. The ammonia odor was the result of acid-base interaction between the support and amine groups. The use of a neutral carbon increased the capture capacity to 2.8 mmol CO2/g-sorbent. Beta zeolite, which captures 1.8 mmol CO2/g-sorbent, was found to contain acid sites that lowered the capture capacity. Molecular probing with benzene indicated a reduction of acidic sites with basic NH3 treatment and the reduction of surface –OH groups with basic NH4OH treatment. Beat zeolite treatment with NH3 and NH4OH resulted in a capture capacity of 2.0 and 2.2 mmol CO2/g-sorbent, respectively. Further DRIFTS IR investigation showed the amine interacted with the –OH groups of beta zeolite. Adsorption of CO2 formed carbonates, which may utilized the O atom from the interaction of the amine and support. The carbonate formation profile was parallel to H-bonding indicating adsorbed CO2 had a dual-interaction where a carbonate and H-bond was formed. This dual interaction may have inhibited gas and adsorbed phase CO2 exchange observed on metal surfaces. LSCF was investigated as an anode material for a direct CH4 solid oxide fuel cell (SOFC) through unsteady state response coupled with mass spectrometer analysis. Comparison of a Ni anode and LSCF/Ni anode was done to determine if LSCF promoted the electrochemical oxidation of carbon. The introduction of 50% CH4 into the LSCF/Ni anode SOFC produced a greater amount of CO than the Ni anode, indicating the LSCF increased the initial intrinsic rate of carbon oxidation. The H2 and CO profile produced by the LSCF/Ni anode lacked a parallel structure indicating different reaction pathways. Current-voltage measurement over LSCF/Ni during 50% CH4 led to a higher formation of CO than that of the Ni anode, confirming a high intrinsic rate of formation. Removal of CH4 from the Ni anode resulted in a rapid drop in current; removal of CH4 from the LSCF/Ni anode resulted in a slow decrease in current and the formation of CO and CO2. The formation of CO2 on the LSCF/Ni anode suggests the presences H2 and CH4 inhibit the electrochemical oxidation of carbon to CO2. The formation of CO2 over the LSCF/Ni anode indicates LSCF ability to completely electrochemically oxidize carbon, which was not observed on the Ni anode. Structural degradation led to failure the Ni anode cell after 0.5 hours of pure CH4 operation and after 2 hours on the LSCF/Ni anode. These results suggest LSCF promotes the electrochemical oxidation of carbon resulting in a lower intrinsic rate of formation of coke in the Ni/LSCF SOFC.
Advisors/Committee Members: Chuang, Steven S.C.
Subjects: Chemical engineering; Energy; Environmental engineering
Keywords: TEPA; solid sorbent; LSCF; SOFC; solid oxide fuel cell; CO2 capture; carbon capture
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12.
Gazawi, Ayman.
EVALUATING COSMO-RS FOR VAPOR LIQUID EQUILIBRIUM AND TURBOMOLE FOR IDEAL GAS PROPERTIES.
Degree: Master of Science, Chemical Engineering, 2007, University of Akron
► The focus of this study is to evaluate the COSMO-RS approach as…
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▼ The focus of this study is to evaluate the COSMO-RS approach as a mainstream engineering property methodology. Particular emphasis was placed on the VLE and vapor pressure predictions. We used Turbomole software package version 5.8 with DFT/TZVP ab initio method for; sigma profile, ideal gas heat capacity and ideal gas absolute entropy computation of 71 pure compounds. We used Cosmotherm program version 2.1 for VLE calculation of 104 binary systems based on COSMORS-E and COSMORS-gamma approach. Also, the Cosmotherm program was used for vapor pressure computation of 71 pure compounds. For the VLE predictions; the %AADbp for COSMORS-E results were in the 29 to 55% range with an overall average of 35%, while the %AADbp for COSMORS-gamma results were in the 4 to 16% range with an overall average of 8.8%. The % AADP for COSMO-RS vapor pressure results; were in the 3 to 142% range with an overall average of 35%. The %CpERROR; was in the 0 to 21% range with an overall average of 7%. The %SabsERROR; was in the range of 0 to 13 % with an overall average of 4 %. The average deviation in Hf was 138 kcal/mole, and included errors in sign.
Advisors/Committee Members: Elliott, Richard Jr.
Keywords: COSMO-RS, VLE, Ideal Gas: Heat Capacity, Absolute Entropy and Enthalpy of Formation, Sigma Profile, Binary Interaction Parameters
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13.
Gerek, Zeynep Nevin.
Semi-Empirical Correlation of Transport Properties Based on the Step Potential Equilibria and Dynamics (SPEAD) Model.
Degree: Doctor of Philosophy, Chemical Engineering, 2006, University of Akron
► Our purpose is to extend Step Potential Equilibria and Dynamics (SPEAD) method…
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▼ Our purpose is to extend Step Potential Equilibria and Dynamics (SPEAD) method to predict transport properties like diffusivity, viscosity, and thermal conductivity. The SPEAD method is basically the combination of chemical process simulation with molecular modeling method that is based on Discontinuous Molecular Dynamics (DMD) with Thermodynamic Perturbation Theory (TPT). The method has already been successful in the calculation of the equilibrium and coexistence properties of alkanes, aromatic compounds, alcohols, ketons, fluro and chloro compounds The transport coefficients are evaluated as the long term-limit of the slope of the mean-squared displacement corresponding to the transport property. Having established the methodology of transport property calculations for hard spheres and tangent hard sphere chains, the more realistic molecular models of the SPEAD method are also applied. Predictions of self diffusivities, viscosities, and thermal conductivities are compared with the experimental data and we observe that disperse attractions appear to play a major role in diffusivities at longer chains and higher densities. We developed new correlation form based on purely repulsive simulation results and semi-empirical perturbation approach for attractive forces to predict transport properties.
Advisors/Committee Members: Elliott, J. Richard.
Subjects: Engineering, Chemical
Keywords: Molecular Dynamics, Diffusivity, Viscosity, Thermal Conductivity, Physical Propert Prediction
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14.
Guzman Montanez, Felipe.
SAMARIUM-BASED INTERMEDIATE TEMPERATURE SOLID OXIDE FUEL CELLS.
Degree: Master of Science, Chemical Engineering, 2005, University of Akron
► The development of electrochemical converters (i.e. fuel cells) has attracted research interest…
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▼ The development of electrochemical converters (i.e. fuel cells) has attracted research interest during the last decades due to an increasing concern on the depletion of available fossil fuel reserves and environmental issues such as global warming and emission of pollutant gases. Solid oxide fuel cells have received special attention because of their higher energy efficiency, rapid electrode kinetics without using expensive electrocatalysts such as Pt, relative resistance to impurities in the fuel and the possibility of processing CO, CH4 and other Carbon based fuels. Extensive research efforts have resulted in the development of solid oxide fuel cell materials such as Yttria stabilized Zirconia (YSZ) electrolytes, Lanthanum or Calcium doped Strontium Manganite (LSM) cathodes and Ni-YSZ cermet anodes. YSZ electrolytes require high operation temperatures (~ 1000 °C) in order to achieve sufficient ionic conductivity, placing large restrictions to candidate electrode, interconnect and housing materials. As a result, the cost of solid oxide fuel cell systems has become an important factor preventing their commercialization. Recent research efforts have shown that a variety of samarium doped oxides can be used as electrolyte and electrode materials in order to develop solid oxide fuel cells operating in intermediate temperatures. Samarium doped Ceria (SDC) has been shown to possess sufficient ionic conductivity at intermediate temperatures (600-800 °C). iv Similarly, Strontium doped Samarium Cobaltite (SSC) has been shown to act as an active electrode material. During this study we developed a synthesis procedure in order to fabricate a samarium doped ceria electrolyte and a samarium strontium cobaltite electrode material. Different fabrication conditions were tested in order to elucidate a procedure to manufacture an intermediate temperature fuel cell using an SDC electrolyte and two SSC electrodes. The impact of several fabrication variables on the resulting fuel cell performance was evaluated. Results from this study concluded that SDC electrolyte materials can be successfully synthesized according to the pechini method. Similarly, SSC electrodes can be synthesized using a solid state reaction starting with respective oxide species. Fabrication of electrolyte supported fuel cells using an SDC electrolyte and two SSC were also developed according to a cold pressing technique. The effect of the solid electrolyte fabrication procedure on the fuel cell performance was also evaluated.
Advisors/Committee Members: Chuang, Steven.
Subjects: Engineering, Chemical
Keywords: INTERMEDIATE TEMPERATURE FUEL CELL, SDC, SSC, RAMAN, XRD, SEM, CATALYSIS, SSC ELCTRODES.
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15.
Hancock, James.
Organic Phase Entrapment of Glucose Oxidase In Polymeric Nanoparticles.
Degree: Master of Science, Chemical Engineering, 2008, University of Akron
► Immobilizing enzymes using polymeric particles is an excellent means to increase the…
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▼ Immobilizing enzymes using polymeric particles is an excellent means to increase the reusability of a biocatalyst. Recovering active enzyme free in solution is difficult. However, the immobilized enzyme-particle system can be easily removed using methods such as filtration or centrifugation. One interesting immobilization technique is to entrap enzymes within the polymer matrix. To achieve this, polystyrene particles of varied size (100 to 750 nm) and degree of cross-linking (monomer: cross-linker molar ratios ranging from 1: 1 to systems with no cross-linker) were treated with glucose oxidase in toluene solution. In toluene, the polymer expands, allowing enzyme to diffuse into the matrix. Then, the particles are treated with hexane, a worse solvent, which forces the polymer to shrink, entrapping the enzyme. The enzyme-polymer particle complexes were tested using a standard enzyme activity assay to quantify the various systems of varied size and cross-linking. The effect of cross-linking appears to be that there is a minimum level at about 0.1 moles/mole required to support reaction, which had an observed reaction rate of about 65 micro moles per min per mg solid. Kinetic studies at varied polymer particle size indicate that smaller particles result in higher reaction rates. Kinetic studies at varied polymer particle size indicate that smaller particles result in higher reaction rates; for the case of 250 nm particles, the observed rate was close to 30 micro moles per min per mg solid.
Advisors/Committee Members: Wang, Ping.
Subjects: Biochemistry; Chemical engineering; Engineering; Particle physics; Polymers
Keywords: nanoparticle; nanotechnology; enzyme immobilization; enzyme entrapment; enzyme kinetics; polymer swelling
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16.
Kanjickal, Deenu George.
Perivascular Drug Delivery Systems for the Inhibition of Intimal Hyperplasia.
Degree: Doctor of Philosophy, Chemical Engineering, 2005, University of Akron
► The long-term clinical success of autologous vein and synthetic vascular grafts is…
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▼ The long-term clinical success of autologous vein and synthetic vascular grafts is limited due to the development of anastomotic intimal hyperplasia (IH). Previously published data suggests that cyclosporine (CyA) (an immunosuppressive drug) may reduce the development of IH in a canine model [1]. However, systemic administration of CyA could create serious adverse effects. Therefore, it is our long-term goal to test the hypothesis that the controlled local release of cyclosporine from a polymeric vascular wrap will prevent the development of IH. In order to test this hypothesis, we developed three controlled release polymeric devices that could be placed around vascular graft anastomotic sites to deliver therapeutic drugs locally. The first device is a poly(ethylene glycol) (PEG) hydrogel sheet. The second device is a composite device consisting of poly(DL-lactide-co-glycolide) (PLGA) microspheres dispersed in the PEG hydrogel sheet. The third device is in the form of a ring (referred to as PolyRing from here on) that can be slipped around the anastomotic sites. PolyRing is a composite polymeric device consisting of PLGA microspheres embedded in a PEG hydrogel. In-vitro studies were conducted on the three devices to evaluate the effects of different sterilization procedures on the properties of the device. It was determined that gamma sterilization was the preferred sterilization method of choice. In-vivo studies were conducted on a swine model to evaluate the biocompatibility, drug optimization and efficacy of PolyRing. The biocompatibility study utilized four (4) domestic swine with non-drug loaded PolyRings harvested at two (2) and four (4) week time points. PolyRings (ID 3-5 mm; OD 7-8 mm; Length 5 mm) were implanted in subcutaneous and muscular tissues and around jugular veins and carotid arteries. The histological findings of gamma sterilized PolyRing implants at two and four weeks demonstrated the biocompatibility of this device. A minimal foreign body reaction with macrophages and foreign body giant cells was identified at the tissue/material surfaces at both two and four week implantation periods. This is a normal and expected finding for biocompatible materials. The drug optimization study utilized three (3) domestic swine with CyA-loaded PolyRings harvested at one (1) week. The drug loaded PolyRings were implanted around jugular veins and carotid arteries. The drug optimization studies revealed a proportional increase in the concentration of CyA in tissue with the concentrations of the drug loaded within PolyRing. The systemic circulation showed concentrations less than the sensitivity of the assay (25 ng/ml). Hence, we were able to achieve truly local concentrations of the drug using the device PolyRing.
Advisors/Committee Members: Lopina, Stephanie.
Keywords: perivascular drug delivery device; intimal hyperplasia; controlled drug delivery; poly(ethylene glycol) (PEG) hydrogel; poly(lactide-co-glycolide) (PLGA) microspheres; biocompatibility; tissue culture; cyclosporine (CyA); PolyRing
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17.
Katta, Prathyusha.
Development, Characterization and Testing of Titanium Dioxide Nanofibers Enhanced Ceramic Fibrous Filter Medium for Filtration Applications.
Degree: Doctor of Philosophy, Chemical Engineering, 2006, University of Akron
► Microfibrous filters are extensively used for the capture of fine particles. However,…
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▼ Microfibrous filters are extensively used for the capture of fine particles. However, not much research has been conducted on development of high temperature durable fibrous filters. Environmental Protection Agency regulations starting at the model year 2007, demands for 97% reduction in the diesel engine particulates. Development of fibrous filters for capturing particulates from hot exit gases evolving out of tail pipes of automobiles, chimneys of industries etc is essential. Broad range of particulates in the flue hot gases suggests that the microfibers filter performance would improve by the addition of nanofibers. In this work, nanofiber enhanced ceramic filter medium is developed. TiO2 nanofibers, which can withstand temperature ~ 1200C, are synthesized using electrospinning process and are incorporated into the microfibers filter. The ratio of the surface area of nanofibers to microfibers in filters is varied and the filters are tested for aerosol filtration. Analytical models are developed to study the performance of filters at different uniform temperatures. Modeling and experimental results showed that the quality factor of fibrous filters is enhanced by the incorporation of nanofibers. However, after reaching a maximum quality factor, the quality factors of fibrous filters recedes, because of the increase in pressure drop to intolerable extent.
Advisors/Committee Members: Chase, George G.
Subjects: Engineering, Chemical
Keywords: Nanofibers; High temperature; Filtration.
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18.
Keskin, Sevgul.
PHASE BEHAVIOR IN POLY ETHYLENE CO-VINYL ALCOHOL BLENDS WITH SOLVATING POLYMERS.
Degree: Master of Science, Chemical Engineering, 2006, University of Akron
► The main objective of this study is to show the effects of…
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▼ The main objective of this study is to show the effects of hydrogen bonding on the phase behavior of Poly-ethylene-co-vinyl alcohol (pEVOH), para-Poly-vinyl-pyridine (pVPy), Poly-nbutyl-methacrylate (pBMA) ternary polymer blends by using Fourier Transform Infrared Spectroscopy - Attenuated Total Reflectance (FTIR/ATR). FTIR/ATR provides rapid and accurate IR capability through the averaging process made possible by Fourier Transform scanning.
Advisors/Committee Members: Elliott, Richard.
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19.
Komurcu, Ramazan.
TRYPTAMINE TERMINATED 1st GENERATION POLYAMIDE DENDRIMER:SYNTHESIS AND DRUG RELEASE.
Degree: Master of Science, Chemical Engineering, 2007, University of Akron
► Polymer-based drug delivery is used to overcome poor drug water solubility and…
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▼ Polymer-based drug delivery is used to overcome poor drug water solubility and to deliver drugs more effectively and efficiently. It is also used to reduce the amount of the needed drug, to increase the half-life of drug, and to keep the drug level in a desirable range. One interesting polymer-based drug delivery method uses dendrimers as carriers, continuously releasing drugs into the human body. In this study, first generation of carboxylic acid–terminated four-directional Z-cascade: methane [4]: (3-oxo-6-oxa-2-azapentylidyne): propanoic acid and tryptamine were used as a dendrimer and a model drug, respectively. It is the first time this dendrimer and model drug were used in advanced drug delivery. Before coupling tryptamine to the dendrimer, the coupling strategy was examined with an aliphatic acid, heptanoic acid, and the dendrimer building block, tetra acid. The synthesis and characterization of the products were completed successfully and the yields for tryptamine conjugated heptanoic acid, tetra acid, and polyamide dendrimer were observed as 70%, 67%, and 53%, respectively. Then, in vitro enzymatic release study of tryptamine conjugated polyamide dendrimer was studied. Half of the drug was released within nine hours, demonstrating the concept of using this dendrimer for extended release.
Advisors/Committee Members: Lopina, Stephanie.
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20.
Lo, Chi-Ming.
Cellulase Production by Trichoderma Reesei Rut-C30.
Degree: Doctor of Philosophy, Chemical Engineering, 2008, University of Akron
► As the price of oil continues to increase and the concern over…
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▼ As the price of oil continues to increase and the concern over global warming heightens, finding alternative renewable sources of energy becomes more and more imperative. Considering the abundance of lignocellulosic biomass, the potential significance of its conversion to fuel such as ethanol has long been recognized. Ethanol production from lignocellulosic biomass requires the breakdown of the solid material to simple sugars that can be consumed by microorganisms. The breakdown of lignocelluloses includes the important step of hydrolyzing cellulose, which are β-1, 4 linked polymers of glucose, by a group of enzymes collectively termed cellulase. The cost of cellulase production profoundly influences the economics of the entire ethanol production process. Trichoderma reesei Rut C-30 is the most commonly used fungal strain for industrial cellulase production. With an overall goal of decreasing the cellulase production cost, this thesis work was focused on two topics: (1) investigation of the performance of different cellulase-inducing substrates in T. reesei Rut C-30 fermentation and (2) development of a more advanced model to describe the culture behaviors of T. reesei Rut C-30 grown on lactose-based media. The cellulase-inducing substrates investigated in this work included the acid-treated hydrolysate, lactose, and the sophorolipids produced by the yeast Candida bombicola. In addition to the above focused topics, the effects of culture conditions on cellulase production were also investigated. The acid-treated hardwood hydrolysates used in the study were prepared by a two-stage process, with different durations of boiling and acid concentrations. The results indicated that the inducing ability of the hydrolysates decreased with increasing boiling time (less oligomers). The observation was attributed to the lower amounts of inducing oligomers remaining after the longer boiling in acid. When compared with cultures growing on mixed carbon substrates of cellulose and glucose, the culture growing on hydrolysates showed a longer lag phase of about 24 hours (before the active cell growth began), but produced adequately comparable final cellulase activity. The study with lactose as an inducing substrate was conducted in both batch and continuous culture systems with lactose and other relevant substrates (glycerol, glucose and galactose) as the carbon source. Instead of direct ingestion, lactose is believed to be hydrolyzed by extracellular enzymes to glucose and galactose, which are then taken up by the cells. The study results indicated that glucose strongly represses the galactose metabolism: Cells started to consume galactose only after the glucose had been depleted. A mathematical model incorporating all important metabolic activities was developed to describe the culture behaviors. All of the experimental results obtained were used in model fitting to generate a set of best-fit model parameters. The study provided significant conceptual and quantitative insights to the lactose metabolism and cellulase production by T. reesei Rut C-30. This study was also the first to hypothesize and demonstrate the use of sophorolipids as the inducing substrate for cellulase production. A unique process for cellulase production using a mixed culture of T. reesei Rut C30 and Candida Bombicola growing on glycerol-based media was investigated. Hypothetically, the sophorolipids produced by C. bombicola were hydrolyzed to form sophorose, which then served as the inducer for cellulase production by T. reesei. Further study to optimize the sophorolipid-induced cellulase production process is recommended.
Advisors/Committee Members: Ju, Lu-Kwang.
Subjects: Chemical engineering
Keywords: "Trichoderma; cellulase; fermentation; hydrolysate"
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21.
Lotus, Adria Farhana.
Synthesis of Semiconducting Ceramic Nanofibers, Development of P-N Junctions, and Bandgap Engineering by Electrospinning.
Degree: Doctor of Philosophy, Chemical Engineering, 2009, University of Akron
► Nanostructured semiconducting metal oxides, such as nanotube, nanowires, nanoribbons and nanofibers are…
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▼ Nanostructured semiconducting metal oxides, such as nanotube, nanowires, nanoribbons and nanofibers are of considerable interest for solar energy conversion, sensors and in various electronic applications. Nanoscale structures especially, nanofibers have unusually high aspect ratio and hence, very high surface area per volume ratio. The characteristic high surface area per unit mass of nanofibers provides detecting sensitivity of part per million and even below, and decrease the response time remarkably in comparison with thin film materials. In this work, several semiconducting metal oxide nanofibers are synthesized by sol-gel processing followed by electrospinning. Fibers are made of ZnO, TiO2, Al2O3, NiO, CuO, SnO2, TiO2/Al2O3, TiO2/ZnO, Al doped ZnO, and In doped ZnO materials. The diameters of these electrospun ceramic nanofibers range 50-300 nm. Different analytical techniques are used to characterize ceramic nanofibers which include scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), Fourier transform infra red spectroscopy (FTIR), UV-Vis spectroscopy, electrical property (I-V, conductivity) measurements. Fibers are made as randomly oriented fiber mat as well as axially oriented nanofibers in yarns. Making the nanofibers into a twisted nanofiber yarn provides the macroscopic handling capability of the nanofibers while retaining some of the nanoscale properties of materials. Ceramic nanofiber p-n junctions are developed using twisted nanofiber yarns of ZnO and NiO which clearly showed rectifying I-V properties at dark (non-illuminated) condition. Bandgap energy of ZnO nanofibers are engineered by co-electrospinning of ZnO precursor with dopants (Al or In) in the precursor solution. Doping of ZnO nanofiber matrix with Al or In materials brings about significant structural, electrical, and optical property modification. The optical bandgap energy increases with the addition of Al dopants in the ZnO nanofiber matrix while the bandgap energy of In doped ZnO nanofibers decreases with the increasing concentration of In dopants in the ZnO matrix. Electrospinning proved to be a simple, low cost, and reliable technique for dopant incorporation to attain modified structural, electrical, and optical properties of these semiconducting nanofibers.
Advisors/Committee Members: Chase, George.
Subjects: Chemical engineering; Materials science
Keywords: Electrospinning; Ceramic nanofiber; Nanofiber yarn; Nanofiber p-n junction; Doping of ZnO nanofiber
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22.
Meduri, Praveen.
CHARACTERIZATION OF UNCOATED AND SPUTTER COATED NANOFIBERS.
Degree: Master of Science, Chemical Engineering, 2005, University of Akron
► Synthesis and characterization of nanofibers is receiving a great deal of attention…
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▼ Synthesis and characterization of nanofibers is receiving a great deal of attention because of their potential as materials for nano-electronics. Surface energy plays an important role in understanding the wetting, adhesion and cohesion properties of materials. Synthesizing and effectively controlling the surface energy of nanomaterials, could highly improve their efficiency in different applications. This thesis is primarily focused on the surface energy characterization of uncoated and sputter coated nanofibers. The objectives include the extension of a proposed method in literature for calculating the surface energy of nanoparticles and preparation of optimal surface energy thin films of boron nitride (BN) on nanofibers.
Advisors/Committee Members: Evans, Edward A.
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23.
Miller, Duane D.
IN SITU INFRARED SPECTROSCOPY STUDY OF GOLD OXIDATION CATALYSIS.
Degree: Master of Science, Chemical Engineering, 2006, University of Akron
► Infrared spectroscopy has been extensively applied in catalysis and the structural determination…
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▼ Infrared spectroscopy has been extensively applied in catalysis and the structural determination of adsorbed molecules. Its application to surface chemistry has provided one of the most direct means of observing the interactions that occur at the surface during chemisorption as well as helping in elucidation of reaction mechanisms. Among infrared spectroscopy extensive use, the catalytic oxidation of CO with O2 has been investigated most extensively and intensively in heterogeneous catalysis because of the simplicity of the CO/O2 oxidation reaction resulting in CO2 being a gaseous product. CO is a hazardous gas which is a concern in environmental protection. Pollutants in automobile exhaust gases, indoor air quality control, and the selective removal of trace CO concentrations in hydrogen fuel demonstrates the importance of the CO oxidation reaction finding many applications today. CO oxidation at low temperatures from room temperature to 160 oC has become a subject of study of great importance. Gold catalysts prepared by coprecipitation, deposition-precipitation, and homogeneous deposition-precipitation (HDP) have been prepared for CO oxidation at room temperature. Gold catalyst activity is very sensitive to preparation method; ideal preparation methods should provide a well dispersed particle diameters below 5 nm. The result of this study demonstrates HDP method was the best preparation method for high catalytic activity in the CO oxidation reaction. Understanding the reaction mechanism and kinetics under transient conditions can lead to approach for preparation of highly active catalyst. This study used a transient pulse technique which introduced the reactants into inert gas to determine the reactivity of adsorbed oxygen in CO and CH3CH2OH oxidation reaction. Use of this technique and infrared spectroscopy of CO and CH3CH2OH found H2O2 promotes total oxidation. The result of this study demonstrated hydrogen peroxide promotes both CO and CH3CH2OH oxidation. One hypothesis investigated reduced gold, Au0, is thought to be the catalytic active site for CO oxidation. This study used a transient technique to step switch CO and nitric oxide to investigate the active site for CO oxidation. The result of this study determined linearly adsorbed CO at 2013 and 2056 cm-1 is the active intermediate for CO oxidation. In situ infrared spectroscopy technique demonstrated nitric oxide coordinates the Au sites preventing room temperature CO oxidation. At higher temperatures, nitrite and nitrate species desorbed providing more Au0 sites for CO oxidation showing Au0 is the active site for CO oxidation reaction. The result of this study demonstrates Au+1 and Au+3 were not active for CO oxidation and Au0 is active for CO oxidation. One of the biggest problems with gold catalysts is the sintering of the small Au particles into larger particles. Bulk gold melting temperature is 1336 K but as the gold particles gets smaller the melting temperature lowers to 537 K. Au particle mobility is a major problem thus future study should be directed towards locking in the particle size while reducing particle mobility to prevent sintering while maintaining high catalytic activity.
Advisors/Committee Members: Chuang, Steven S.C.
Subjects: Engineering, Chemical
Keywords: gold titania; Au/TiO2; gold catalysis; CO oxidation
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24.
Miller, Duane D.
In Situ Infrared Study of G-S/L-S Adsorption and Photocatalytic Processes.
Degree: Doctor of Philosophy, Chemical Engineering, 2009, University of Akron
► Coal fired power plants release large quantities of CO2 and trace amounts…
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▼ Coal fired power plants release large quantities of CO2 and trace amounts of SO2 into the atmosphere, affecting global warming and worldwide climate change. CO2 is a concern as a greenhouse gas in relation to global temperature raise. SO2 is a concern in environmental protection as a precursor for acid rain. The impact of CO2, SO2, and H2S on the environment demonstrate the removal process is a subject of study of great importance. Removal of these gases has been focused on the development of amine based sorbents for sequestration by the adsorption and desorption process. Fourier Transform Infrared spectroscopy (FTIR) is a powerful tool for investigating the adsorption/desorption process and structure of adsorbing molecules. The application of FTIR, coupled with ab initio quantum chemistry, can provide a direct means for understanding the interactions that occur during chemisorption. The removal of CO2 and H2S by an amine based sorbent has been studied. The hypothesis for this study is to investigate the use of polyethylene glycol (PEG) to promote tetraethylenepentamine (TEPA) CO2 and H2S removal capacity. It is thought that the use of PEG may improve the catalytic adsorption capacity through hydrogen bonding. This study used in situ FTIR and ab initio quantum chemistry to investigate the adsorption and desorption processes during CO2 and H2S capture at the molecular level. The FTIR results determine that PEG interacts with the primary amine functional groups of TEPA dispersing the adsorption sites leading to improved adsorption capacity for CO2 and H2S. Ab initio quantum chemistry determined that PEG lowers the binding energy of CO2 and H2S leading to a lower desorption temperature. Removal of the nauseous gas SO2 by an amine based sorbent is studied. The hypothesis investigated the use of 1,3-phenylenediamine low basic property for creating a reusable solid amine based sorbent for SO2 removal. It is thought that the low basic property of the aromatic amine will allow the effective SO2 adsorption and desorption at low temperature. This study used in situ FTIR spectroscopy to investigate the adsorption and desorption processes during SO2 capture. The result of this study determined that 1,3-phenylenediamine basic property allowed SO2 adsorption and desorption at 373 K, however, sorbent deactivation occurs. The in situ UV-Visible spectroscopic technique provided insight that deactivation is the result of agglomeration of 1,3-phenylenediamine. Addition of PEG prevented the agglomeration and improved the adsorption capacity of 1,3-phenylenediamine through hydrogen bonding with the primary amine functional group. Amine based sorbents have been proven as an effective and economic process for the removal of CO2 and the hazardous gases H2S and SO2. Advancing knowledge in the area of amine based sorbents will improve our ability for hazardous waste management. Hazardous waste management may also be achieved by the oxidation and reduction (redox) of toxic materials. TiO2 based catalysts have the ability to oxidize a number of hazardous materials to nontoxic products where TiO2 has become the benchmark semiconductor in photo-detoxification of contaminated water. This work also investigates the photocatalytic dehydrogenation process over TiO2 based catalysts. The hypothesis investigated the relationship of the photogenerated electrons and adsorbed species during the photocatalytic dehydrogenation of 2-propanol. It is thought that the interaction of the photogenerated electrons and adsorb species may be elucidated from the reaction mechanism during the photocatalytic dehydrogenation of 2-propanol. 2-propanol is used as a model compound because it provides a simple and standard way to measure the photo-catalytic activity during the gas/liquid phase reactions. This study suggest that in the presence of adsorbed H2O, the dehydrogenation process proceeded by a hydroxyl radical species while in the absence of adsorbed H2O the active species is an adsorbed ion. Au/TiO2 unique ability to generate adsorbed oxygen ions resulted in higher catalytic activity in the absence of adsorbed H2O under UV-irradiation. The reaction pathway for the photocatalytic dehydrogenation of 2-propanol is strongly dependent on the coverage of surface H2O.
Advisors/Committee Members: Chuang, Steven.
Subjects: Chemical engineering
Keywords: CO2; H2S; SO2; sequestration; NOx removal; Pohotcatalytic oxidation
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25.
Moorthy, Kavitha.
EFFECT OF SURFACE ENERGY OF FIBERS ON COALESCENCE FILTRATION.
Degree: Master of Science, Chemical Engineering, 2007, University of Akron
► Water - oil emulsion separations are of importance to petrochemical industries. Water…
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▼ Water - oil emulsion separations are of importance to petrochemical industries. Water molecules of less than 100µ diameter are present as secondary emulsions. The presence of water reduces the efficiency of the fuel combustion, the water droplets can plug or interfere with performance of small orifices, and the water can dissolve polar compounds from the fuel and form corrosive materials such as sulfuric acid which can damage engine parts. Thus, fuel filtration extends the life of engine. Coalescence filters are efficient and effectual for the removal of secondary emulsions. The surface functionalization of fibers used to make coalescence filters can potentially provide cleaner air, and cleaner fuel with reduced water concentration. The solid surface energy of the fiber is a crucial factor in coalescence phenomena. The aim of this work is to eliminate these water molecules by development of filters made of glass with modified surface energy using coupling agents like silanes. Three coupling agents used in this work are 3-aminopropyltriethoxysilane (APTS), (2-(carboxymethylthio) ethyltrimethylsilane) (CES), and ((heptadecafluoro-1, 1, 2, 2-tetra-hydrodecyl) trichlorosilane) (FTS). The APTS functionalized surface having an intermediate surface energy of 65mJ/m2 was found to be the most effective fiber for water-in-oil coalescence. Functionalized and unfunctionalized fiber filters were also tested for gas-liquid coalescence filtration. The experimental results showed an improvement in the performance of FTS coated glass filters compared to the untreated glass fiber filter. Intermediate wettability is commonly accepted to provide the best coalescing filter performance, but direct experimental evidence is scarce. This work experimentally confirms that intermediate wettability provides the best performance.
Advisors/Committee Members: Chase, George.
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26.
Park, Soo-Jin.
Catalytic Decomposition of Nitric Oxide and Carbon Monoxide Gases Using Nanofiber Based Filter Media.
Degree: Doctor of Philosophy, Chemical Engineering, 2008, University of Akron
► The main sources of NOx are diesel engines, automotives, electric utilities, other…
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▼ The main sources of NOx are diesel engines, automotives, electric utilities, other industrial, commercial, and residential sources that burn fuels at high temperature. The control and abatement of NOx emissions are important because of their harmful effects on the human body and the environment. The strict regulations of NOx emissions and the growing demand for power compel new design of catalytic materials for pollution removal. The most common method for car exhaust NOx treatment involves wet impregnation of noble metals on ceramic substrates. In this work, catalytic nanoparticles doped on nanofiber enhanced ceramic fibrous filter medium structure are developed as an alternative method. The noble metals, palladium, platinum and rhodium doped ceramic nanofibers, are synthesized using electrospinning and are incorporated into the micro-fibrous filter. We have discovered ceramic nanofiber containing noble metals also work in liquid phase catalysis by converting styrene to ethylbenzene at room temperature and atmospheric pressure. The reaction temperature is varied and the filters are tested for decomposition of nitric oxide and carbon monoxide using nanofiber based fibrous filter. Carbon dioxide, nitrogen and nitrous oxide gases were produced. Produced nitrous oxide gas was consumed by reacting with carbon monoxide. The efficiency of the catalytic fibrous filter was similar to commercial catalytic converter by adding of smaller amount of catalyst doped on alumina microfibers. As the amount of catalyst in the fibrous filter media increases the temperature at which all NO disappears decreases. As the inlet concentration of NO gas decreases, all NO disappears from the outlet at a lower temperature. As the face velocity through the fibrous filter media increases, efficiency becomes lower as the residence time of gases through the media decreases. We also tested a catalytic fibrous filter media containing Pd, Pt and Rh, and the performance is similar to that of catalytic convertor. Analytical models are developed to study the performance of filters for isothermal nitric oxide and carbon monoxide gas reaction. The kinetic parameters for the model were determined using the Genetic Algorithm (GA) computer program to determine species concentrations as a function of position. Model and experimental results showed that the decomposition temperature of nitric oxide gas decreases by lowering the inlet gas concentration and increasing of catalyst concentration in the nanofibers. Also a non-isothermal model was developed for direct nitric oxide decomposition to predict temperature and concentration profiles along the filter length.
Advisors/Committee Members: Chase, George G.
Subjects: Chemical engineering; Environmental engineering
Keywords: Catalytic Decomposition; Nanofiber Based Filter Media; Nitric Oxide; Carbon Monoxide
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27.
Pinzon-Gamez, Neissa M.
HETEROCYSTOUS N2-FIXING CYANOBACTERIA: MODELING OF CULTURE PROFILES, EFFECT OF RED LIGHT, AND CELL FLOCCULATION STUDY.
Degree: Master of Science, Chemical Engineering, 2006, University of Akron
► The concern about the exhaustion of fossil fuels and the harmful effects…
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▼ The concern about the exhaustion of fossil fuels and the harmful effects of their emissions to the environment is guiding efforts to find new energy alternatives. One of the most promising energy resources is hydrogen (H2). Cyanobacteria are among the most important candidates for photobiological H2 production. Some filamentous cyanobacteria have evolved to differentiate specialized cells called heterocysts where nitrogen fixation and H2 production take place. The complete understanding of the process of heterocyst differentiation is of great importance for photobiological H2 production. Prior to this study, there were no quantitative culture-level models that describe the effects of cellular activities and cultivation conditions on the heterocyst differentiation. Such a model was developed in this thesis, incorporating photosynthetic growth, heterocyst differentiation, self-shading effect on light penetration, and nitrogen fixation. This first-generation model was found to describe well the experimental results and it was able to predict different culture properties. Since the productivity and economics of all photosynthesis-related processes are influenced by the light utilization efficiency, the effect of red vs. white light, and their intensities, on cell growth and heterocyst differentiation was also investigated. Red light was found not only to stimulate the growth of the studied microorganisms but also to give higher heterocyst frequencies. Gas vesicles were another interesting structure of some cyanobacteria studied in this thesis. Gas vesicles provide cyanobacteria with a mechanism of buoyancy regulation. Purified gas vesicle suspensions had been shown to improve oxygenation in oxygen limited systems. In order to improve the cell-collection efficacy of cyanobacteria with gas vesicles, three different flocculants were tested and compared, i.e. polyethyleneimine (PEI), chitosan and MPE-50 (a commercial product from Ondeo Nalco Center, exact formulation unknown). Even though, they showed similar flocculation efficacy at low cell concentrations, chitosan flocculation ability was greatly increased when the pH of the cell suspension was adjusted to lower values. Chitosan was proved to be useful for cyanobacterial cell collection using a concentration of 50 mg/L and adjusting pH of the cell sample to 5-7. The sensitivity of chitosan to changes in pH may be useful also in the later step of recovery and purification of gas vesicles after cell lysis.
Advisors/Committee Members: Ju, Lu-Kwang.
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28.
Qiu, Shuyan.
NANOFIBER AS FLOCCULANT OR MODIFIER IN MEMBRABE BIOREACTORS FOR WASTEWATER TREATMENT.
Degree: Master of Science, Chemical Engineering, 2005, University of Akron
► The more stringent regulations for wastewater discharge present new technology challenges to…
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▼ The more stringent regulations for wastewater discharge present new technology challenges to wastewater treatment (WWT) plants. There is a particular pressing need for improving the hygienic quality of the treated water. Membrane bioreactors (MBRs) represent one of the most innovative approaches to restrain the release of pathogens from WWT plants. Using membranes with a pore-size of 0.1~0.5 mm or less, not only bacteria but also viruses are virtually completely retained. However, membrane fouling is a very serious problem faced by MBRs. Cake layer formation generates largest resistance for membrane filtrations. It was well known that adding flocculants could flocculate small sludge flocs and soluble EPS (Extracellular Polymeric Substances) into large flocs. Flocculated sludge flocs can form a more porous cake, which would enable a higher permeate flux. A procedure was developed to prepare glutaraldehyde-crosslinked chitosan nanofibers as a flocculant that is insoluble but well dispersible in water. Polyacrylonitrile (PAN) nanofiber serves as the reference for evaluating the nanofiber structure contribution to membrane filtration, because of its poor flocculation ability. Another commercial soluble flocculant MPE50 (Nalco Company, Naperville, Illinois) was also compared. The toxicity/inhibition test, turbidity reduction test, and short-time filtration test were conducted to evaluate the flocculant performance. There was no obvious inhibition to the growth of microorganisms by addition of 50~100 mg/L of any of the tested flocculants. It was also demonstrated that adding dissolved chitosan and MPE50 could help reduce the turbidity of the supernatant up by 80% and 55% respectively after allowing the sludge to settle for 45 minutes. Chitosan was effective in the pH range of 5-8, while MPE50 was effective in the wider range of 4-9. PAN nanofiber and crosslinked chitosan nanofiber showed low turbidity reduction ability at concentrations higher than 25 and 50 mg/L, respectively, after adjusting for the turbidity of nanofibers themselves. Total filtration resistance Rt and membrane fouling rate were calculated from the short-term filtration tests. Both dissolved chitosan and MPE50 could improve the filtration performance with lower transmembrane pressure (TMP) and higher permeate flux. However, the performance of PAN and crosslinked chitosan nanofibers was not very consistent from replicate experiments. It is demonstrated that adding nanofiber would not harm the filtration system but the crosslinked chitosan did not improve the filtration process as expected. The possible reasons are discussed for future improvements.
Advisors/Committee Members: Ju, Lu-Kwang.
Subjects: Engineering, Environmental
Keywords: flocculation, fouling, membrane bioreactor, wastewater treatment
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29.
Sans, Amanda Dzintra.
TRANSFERABLE STEP-POTENTIALS FOR HALOGENATED HYDROCARBONS AND MIXTURE PREDICTIONS FROM SPEADMD.
Degree: Master of Science, Chemical Engineering, 2006, University of Akron
► Molecular simulation is a powerful tool used to find thermodynamic properties of…
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▼ Molecular simulation is a powerful tool used to find thermodynamic properties of fluids. In this research, the molecular simulation program called Step-Potentials for Equilibria and Molecular Dynamics, SPEADMD, was advanced by developing the potentials for halogenated hydrocarbons and by examining mixtures. Previous to this work, mixture behavior could not be extensively examined because of the absence of halogenated hydrocarbons. The step-potentials for halogenated hydrocarbons were found by regressing the simulation results to match experimental data for vapor pressure and liquid density resulting in roughly 3% absolute average deviation in vapor pressure for most compounds. The potential for the perfluorinated hydrocarbons showed a unique softness that could not be explained by the traditional step-potential, thus a “soft-shoulder” potential was needed to explain the slope of the vapor pressure curve and coincidentally explain the mixture behavior of perfluoroalkanes + alkanes. The mixing rules developed for SPEADMD were tested using a standard vapor-liquid equilibrium database, which includes a variety of non-ideal and ideal mixtures. A new approach called the SPEADMDã method was implemented in order to separate the SPEADMD vapor pressure error from the mixture bubble pressure error. The SPEADMDã was competitive with other mixture models while SPEADMD was not because of the high vapor pressure error from simulation results.
Advisors/Committee Members: Elliott, Jarrell Richard.
Subjects: Engineering, Chemical
Keywords: Molecular simulation, SPEADMD, vapor pressure, vapor-liquid equilibria, perfluoroalkanes, halogenated hydrocarbons
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30.
Sarkar, Debanjan.
DEVELOPMENT AND CHARACTERIZATION OF L-TYROSINE BASED POLYURETHANES FOR TISSUE ENGINEERING APPLICATIONS.
Degree: Doctor of Philosophy, Chemical Engineering, 2007, University of Akron
► Natural amino acid based synthetic polymers have limited applicability as biomaterial due…
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▼ Natural amino acid based synthetic polymers have limited applicability as biomaterial due to several unfavorable material and engineering properties. This has led to the development of a new class of polymers known as ‘pseudo poly(amino acid)s’. Several L-tyrosine based pseudo poly(amino acid)s have been developed and characterized extensively for biomaterial applications. Desaminotyrosine tyrosyl hexyl ester (DTH), a diphenolic dipeptide molecule developed from L-tyrosine and its metabolite, is used to synthesize amino acid based pseudo polymers with improved physical and chemical properties. Polyurethanes are extensively used as biomaterials due to excellent biocompatibility and the ability to tune the structure for a wide range of properties. The uses of polyurethanes are mainly focused on biostable implants and biomedical devices. But polyurethanes have shown their susceptibility to degradation under the conditions of their performance. The use of polyurethanes for tissue engineering applications emerged mainly due to the degradability of the polyurethanes. Biodegradable polyurethanes with degradable linkages are developed by altering their structure and composition. The aim of the research presented in this dissertation is focused on developing L-tyrosine based polyurethanes for biomaterial applications including tissue engineering. L-tyrosine based polyurethanes can be developed by using DTH as the chain extender with different polyols and diisocyantes. The use of amino acid based component will improve the biocompatibility and biodegradability of the polymers for tissue engineering application. In addition, by using the different components, the structure and composition of the polyurethanes can be altered to achieve a range of properties that are pertinent to biomaterial applications. This research describes the design, synthesis and characterization of L-tyrosine based polyurethanes with DTH as the chain extender. The polyurethanes are extensively characterized for different bioengineering properties, including surface characteristics, water absorption, degradation characteristics, and controlled release along with other important chemical, physical, thermal and mechanical characterizations. The structure-property relationships of the polyurethanes were investigated by developing a library of polyurethanes with different polyol and diisocyante. This library provides an important tool to design polyurethanes with relevant properties for biomaterial application. The effect of structure and composition of these polyurethanes in determining the material properties were studied in detail. In addition, blends of the polyurethanes were studied as an alternative to adjust different properties according to the requirements. The results show that L-tyrosine based polyurethanes are potential candidates for biomaterial applications including tissue engineering. The material characteristics are strongly dependent on the polyurethane structure and composition, and therefore a wide range of properties can be achieved by altering the structure and composition.
Advisors/Committee Members: Lopina, Stephanie T.
Subjects: Engineering, Chemical
Keywords: L-tyrosine, Polyurethane, structure, property, tissue engineering, biomaterial
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