▼ Thermophotovoltaic, a technology that utilizes the photovoltaic effect to convert infrared radiation emitted from a hot source into electricity, is an attractive technology that can be used in applications in industrial waste heat recovery, space applications, hybrid cars, powering remote off-grid areas and many others. Emitters used in TPV systems must meet functional requirements imposed by the PV cell and structural requirements imposed by the high temperature used to achieve high density radiation. Most of the functional and structural requirements of the emitter can be realized by using a selective emitter in the fibrous form. In this research, selective emitter media made from electrospun ceramic nanofibers doped with rare-earth oxides is presented. The materials of choice are aluminum oxide for the fibers and erbium oxide as the emitting material. It is found that the fabricated emitters emit IR-radiation selectively in a range that can be effectively coupled with GaSb and InGaAs PV cells. A mathematical model is also developed based on the general equation of radiative transfer to calculate the net radiation obtained from the fabricated emitters. The model is coupled with experimentally measured optical properties to calculate the emissivity. A very satisfactory agreement is found between the theoretically calculated and the experimentally measured values of emissivity Advisors/Committee Members: Evans, Edward A.

▼ 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.

▼ Pure air/gas is very critical to many industrial applications. Gas streams contain impurities in the form of solid and liquid aerosols in micron and submicron sizes. It is very important to remove these aerosols for protecting our health and environment, improving the reliability of industrial processes and equipments. Among different filters being used, fibrous filters are very effective in removing aerosols in micron-submicron sizes. Important applications include compressed gas cleaning, CCV, HVAC, refineries, breathing apparatus etc. To remove liquid droplets from a gas stream, fibrous filters act as a coalescing medium where smaller droplets merge to form bigger droplets which eventually drain out of the filter with clean gas going to the downstream process. The performance of a coalescing filter medium depends on many factors like droplet and fiber size, face velocity, gas and liquid properties, liquid accumulation etc. The current work aims at developing a model to determine the liquid accumulation which is otherwise referred as the saturation. Higher the saturation at steady state, higher is the pressure drop which will increase the operating cost. This dissertation work is divided in to three categories. In the first category, the multiphase equations are solved at steady state with various saturation profiles and determine the filtration performance. The main goal of this part is to check is the saturation is really an important parameter for coalescing filtration. In the second category, the saturation profile is determined using layered filter medium. Several layers of glass fiber filters are arranged in series and challenged with liquid aerosols. The saturation is measured using the weight of the liquid accumulated on each layer. In the third category, the multiphase equation is solved at unsteady state to predict the saturation theoretically. The unsteady state model takes in to account the dominant mechanisms for drop capture, growth and break-up on the media. The proposed mechanisms are droplets on fibers, droplets on drops, sweep and break-up mechanisms. The model evaluates each mechanism on a step-by-step process and updates the number of drops of each size with respect to time and position. Total volume of drops at each position is then calculated to determine saturation with time. The sensitivity of few important parameters towards the final filtration performance is also determined using this model. The model results can be used to determine optimum parameter values to achieve higher efficiency with much less pressure drop. Advisors/Committee Members: Chase, George.

▼ The migration of compounding ingredients to the surface of cured or uncured rubber tends to be one of the contributing factors towards the properties imparted on a rubber article such as the making of a multi-ply article like belts or tires. The effect from the migration of the compounding ingredients may or may not be detrimental to the performance of the rubber article. For instance, there are specific situations where the migration of compounding ingredients like antioxidants or waxes to the surface of a rubber compound may be beneficial to act in protecting the rubber from ozone aging. However, there are other instances where the migration of compounding ingredients harmful to the properties of the rubber compound. One of such compounding ingredients is sulfur, which can act to decrease the tackiness of rubber and hinder the formation of multi-ply articles like a tire. Therefore, there is a need to prevent the migration and formation of excess compounding ingredients like sulfur on the surface of rubber. Microencapsulation of compounding ingredients may be used as one of the methods to prevent the migration of compounds like sulfur which was the primary area of focus. Microencapsulation of sulfur by using primarily alginate, served as the mechanism used to prevent the migration of sulfur to the surface of rubber. The microencapsulated sulfur beads produced had a number frequency distribution with 87% having a bead size less than 150 µm and the lower percentage accounting for larger bead sizes. In the 87% of the bead distribution, 44.3% accounted for bead sizes with a size range from 50 to 100 µm while 24.7% and 18.0% accounted for bead sizes with a size range from 0 to 50 µm and 100 to 150 µm respectively. The bulk of the lower percentage was in the size range from 150 to 200 µm with a value of 9.3%. Beads produced had a high percentage (> 80%) of sulfur encapsulated. These microencapsulated sulfur beads were compared with ordinary rubbermaker’s sulfur and insoluble sulfur to distinguish their effects in the compounding formulation during rubber testing. The rubber testing involved tensile study and a sulfur blooming study. The results from the sulfur blooming study suggested that microencapsulated soluble sulfur functioned better than ordinary rubbermaker’s sulfur to prevent sulfur blooming at the tested temperatures (100ËšC and 120ËšC). The results from the study also suggested that microencapsulated soluble sulfur performed relatively better than insoluble sulfur at the 120ËšC temperature; however, a relatively better result was obtained for insoluble sulfur in comparison with microencapsulated soluble sulfur at the 100ËšC temperature. The tensile study on the other hand, indicated that both ordinary rubbermaker’s sulfur and insoluble sulfur achieved better results than microencapsulated soluble sulfur. The lower result obtained for microencapsulated sulfur was attributed to the microencapsulated soluble sulfur bead characteristics (size, shape, etc.) and the interaction of the beads in the rubber matrix. These properties might have been influential in the lower results achieved for microencapsulated soluble sulfur in addition to the crosslink density of the cured rubber compound. The results obtained from the research were useful to guide the future developments on the microencapsulation of soluble sulfur. Advisors/Committee Members: Ju, Lu-Kwang.

▼ Ceramic matrix composites (CMC) constitute a category of composite materials widely used in the aerospace industry as they satisfy the thermal, chemical and mechanical requirements of a good composite material with the drawback being in the high processing costs. Chemical vapor deposition is a process long known for its importance in aerospace and structural applications. Chemical vapor deposition can be used to develop thin interfacial coatings on fibers, which are reinforced in to a matrix according to the application. The interfacial layers are useful for preventing reactions between the fibers and the matrix material at high temperatures. Interfacial coatings can also deflect crack propagation once the composite is put into service. This work focuses on developing a suitable gas phase and surface kinetics model for obtaining the deposition profiles in the chemical vapor deposition of pyrocarbon on silicon carbide fibers at the given conditions of temperature, pressure and feed rate. The model uses an existing gas phase mechanism (National Institute for Standards and Technology and Gas Research Institute). There are combinations of species in the gas phase, but all of them do not lead to the deposition of pyrocarbon. This raises a question as to which of them would affect the rate of deposition and why. For the given conditions of temperature, pressure and flow rate and from the information available in different literature sources acetylene is assumed to be the major depositing specie of pyrocarbon. Also, the gas phase mechanism was modified to simplify and suit the needs of the given conditions. The importance behind modeling the surface kinetics is that it could help understand the actual process in the formation of pyrolytic carbon. The mechanism of the pyrocarbon deposition could be important in knowing the type of carbon being deposited, which is of utmost importance in its applications. The modeling data is validated by means of using data obtained from experiments. Advisors/Committee Members: Evans, Edward.

▼ 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.

▼ Experimental observations show fiber orientation and layer orientation in filter media effect the permeability and the separation efficiency of coalescing filters. The effects of fiber orientation have been studied by various industries including polymer, paper and textiles, to enhance their product lines. This has also been proven beneficial to the filtration industry because orientation of fibers can lead to lower pressure drop. The main objective of this work is to study the effects of layer orientations and test its performance. This technique is an alternative to using electric field for making oriented fiber media. It incorporates stacking micro fiber sheets at different angles (0,30,45,60 and 90). For capture of liquid droplets, the decrease in pressure drop obtained is offset by the decrease in capture efficiency, resulting in nearly constant quality factor regardless of fiber orientation. However, in coalescing filter media this method shows improvement in liquid drainage from the filter and can improve the quality factor from 20 to 60%. In coalescing filter media the fiber orientation can have an added benefit of reducing the liquid saturation in the filter media, which leads to an improved quality factor for the filter media and can be very useful in making self-cleaning filters. The stacking sheets can be extended to a pleated structure, which is relatively easier to construct from an industrial point of view. However, it is challenging to control the angle of the pleats during the construction of the media. Therefore varying the angle of the pleated structure with respect to the flow can surmount this problem. Another filter design is proposed which can mimic the angled pleated design by keeping the pleating angle constant (at zero degree) and changing the angle of the filter holder. Both designs have higher performance compared to a regular pleated media. Multiphase continuum equations are used to model the flow through the media to calculate the velocity and pressure profile through a pleated media to compare with the experimental results. Advisors/Committee Members: Chase, George.

▼ This dissertation describes the development of simple and non-photolithographic techniques for patterning proteins. Protein patterns have relied mainly on conventional photolithography and photolithography-based soft lithography, which require sophisticated instruments and clean room facilities and therefore are expensive. As simple and cost-effective alternatives, the four techniques developed in this study allow protein patterning to be performed at bench top in any common laboratories. The first technique utilizes the dewetting of a polystyrene (PS) thin film on a proteinresistant poly(ethylene glycol) (PEG)-modified substrate. The dewetted PS droplets allow the selective adsorption of proteins while the exposed PEG-modified substrate act as the non-fouling background. Micro- and nanoscale droplet patterns can easily be achieved by tuning the thickness of PS thin films. The second technique is based on stepwisely contact printing octadecyltrichlorosilane (OTS) gradients by using a hemispherical poly(dimethylsiloxane) (PDMS) stamp. The stepwise OTS gradient is further backfilled by PEG-silane, resulting in an OTS-PEG mixed monolayer gradient. The amount of adsorbed proteins and cell density on the stepwise gradient decrease with the increasing surface coverage of PEG, which increases with the increasing contact printing time for each step. The third and fourth techniques focus on using non-photolithographic approaches to fabricate masters for creating PDMS stamps. The masters in the third technique are porous PS films fabricated by using the ordered arrays of water droplets as templates, which result from Marangoni flow. The arrangement, size, and inter-pore distance of the porous films can be tuned. For the fourth technique, parallel PDMS strips are fabricated by peeling a PDMS sheet bonded onto a SiOx substrate. The periodicity and the coverage of the PDMS strips can be controlled by varying the bending strain applied during peeling and UV/Ozone oxidation time prior to bonding. By using the porous films and PDMS strips as masters, PDMS stamps with arrays of posts structures and strips can be fabricated respectively for contact printing OTS patterns, which are subsequently used for protein patterns. Advisors/Committee Members: Bi-min, Zhang Newby.

▼ Rhamnolipids causes severe foaming during its production by conventional aerobic fermentation of Pseudomonas aeruginosa. This problem necessitates the reduction of aeration, which in turn limits the cell concentration employable and productivity achievable in the process. As a continual work to the previous study conducted by Chayabutra and Ju [162], a mixed-mode operation of aerobic and anaerobic fermentation was examined for its potential to minimize foaming and for its related problems when implemented rhamnolipid production. The key factors investigated in this study included: [1] the method for nitrate delivery that would minimize the inhibitory or toxic effects of high nitrate concentration on cell metabolism; [2] the phosphorous supplementation to maintain specific rhamnolipid productivity while cells were still growing; and [3] the effects of quorum sensing systems, a nature population control mechanism, on cell growth and rhamnolipid production. It was found that in the micro-aerobic process, amixed solution of sodium nitrate and nitric acid could be used to meet cell respiration needs and support cell growth to a relatively high concentration (> 10 g/L). A 5-fold increase in cell concentration was achieved in this study when compared to the typical aerobic fermentation. According to the results from the phosphorous-limiting continuous cultureconducted in the study, high specific rhamnolipid productivity could be maintained when the specific cell growth rate was lower than 0.08 (h-1). It was also observed that, an early onset of stationary phase took place in the P. aeruginosa culture when there was no apparent nutrient limitation. The phenomenon was attributed to the effect of quorum-sensing systems of the bacterium. The rhl quorum-sensing system (involving rhlR and rhlI genes) was known to regulate cell growth and rhamnolipid production. The degradation and synthesis kinetics of the rhlI gene-derived product, an autoinducer, were therefore evaluated in this study. The autoinducer was found to be unstable in the fermentation broth and its degradation could be empirically described with a first-order decay kinetics. To maintain the maximal rhamnolipid productivity, at least 13% of the peak autoinducer concentration (v/v) needs to be added in the fermentation broth in the beginning. The micro-aerobic rhamnolipid fermentation overcomes foaming problem, that retards the productivity achievable and market applicables. The autoinducer degradation and synthesis kinetics could have a medicinal application through the development of a stable autoinducer analogue to control the population of P. aeruginosa that could cause death rate in the hospitals. Advisors/Committee Members: Ju, Lu-Kwang.

▼ 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.

▼ Introduction: Adhesions following surgery represent a significant problem often resulting in pain, disability, and additional surgeries. Compounds are available for the prevention of postoperative adhesions, but effectiveness is difficult to assess; current models of adhesion comparison are limited to qualitative methods with much potential bias. Objectives: The objectives of the research performed were to create a quantitative model of adhesion strength assessment, to successfully encapsulate ketorolac tromethamine (KT) into poly(lactic-co-glycolic acid) microspheres, and to characterize of the microspheres for use in preventing adhesion formation. Quantitative Model Methods: The primary focus of this research was the creation of an adhesion complex that was suitable to quantitative testing using the Material Testing System (MTS™ System Corp, Eden Prairie, MN) machine platform. Following a midline infraumbilical laparotomy, bowel packing and retraction, and adequate exposure of the uterine horns and adjacent pelvic sidewall, a salpingostomy is made using electrocautery 1cm caudal the uterus-fallopian tube junction. A 7cm 8fr. latex urinary catheter, reinforced with a coaxial internal semi-rigid 5fr. polypropylene catheter, is inserted until it lies entirely within the lumen of the uterus. A 10cm segment of 6.35mm ID latex rubber drain tubing is secured to the dorsal aspect of the broad ligament medial the uterine horn; this is placed to prevent sidewall-broad ligament adhesion avoiding interference with the sidewall-uterus adhesion. The uterus and latex rubber drain are attached to the sidewall of the pelvis. The peritoneum lateral to the attached uterus is coagulated along the full length of the catheter insert at a setting of 6/10 (17W output) using a shielded electrocautery tip; cauterized area corresponds to the uterine horn lie and is limited to the peritoneum only. This injury is mirrored on the cannulated uterus to desiccate the superficial layer, and repeated on the contralateral side. Upon completion of the injury, antibiotic rinse is administered, excess fluid is removed via suction, packing and retractors are removed and abdomen is closed. Following a 2-week survival, a midline laparotomy is again performed; the surgeon visual assesses the pelvic uterine horn adhesion. Euthanasia is achieved and the entire complex of cannulated uterine horn, sutures, adherent pelvic sidewall and muscle is removed en bloc. The sample is marked cranial and caudally for reference; muscle, broad ligament, and latex rubber drain are cautiously dissected away. The remaining uterine horn and pelvic sidewall is cut at 1.5cm and 4.5cm from the cranial suture. The catheters are replaced by a 0.64cm OD by 8cm stainless steel rod. The length of uterus being tested is measured and recorded. Rubber O-rings, 0.95cm OD and 1.28cm OD, are placed to prevent lateral movement and stabilize the specimen during testing. The peritoneal sidewall is tightly secured within a jig clamp and the complex is loaded on the MTS machine platform. The hydraulically controlled ram moves the stainless steel rod a total of 40mm at 1.6mm/sec; force and displacement measurements are recorded during the pull. Histological assessment adjacent to the testing site is completed. To establish the statistical significance of this study SigmaStat® (Systat Software, Inc., Ashburn, VA) was employed. Pearson and Spearman analyses were performed to identify correlations among variables, and an analysis of variance (ANOVA), blocking on the animal was performed using a post hoc Tukey standardized range test to evaluate the main effects. Also, each grading method was tested with paired t-test to establish statistical differences while blocking on the animal. Significance was accept at p<0.05. Ketorlac Tromethamine Encapsulated Microspheres Methods: Ketorolac tromethamine was utilized as a water soluble adjuvant. In order to encapsulate it within PLGA microspheres, a standard water-in-oil-in-water emulsion technique was utilized. Two stabilizers PVA and PVP were examined at concentrations of 1%, 2%, and 5%. Theoretical loadings of 0.1 and 0.2 were studied; all six solutions were used to produce microspheres at both theoretical loadings. The samples were analyzed for drug loading efficiency, yield, microsphere surface morphology determination, particle size analysis, release profiles, and differential scanning calorimetry studies. To establish statistical significance in this section, SigmaStat® (Systat Software, Inc., Ashburn, VA) was employed. Whenever possible, Student's t-tests were used; when normality or variance did not allow for this method, Mann-Whitney Rank Sum Tests were utilized. Analysis of variance (ANOVA) was employed when more than two variables were compared. Significance was accepted at p<0.05. Results and Discussion: The MTS measures force by displacement which can be quantitatively analyzed and interpreted, while the histology provided a comprehensive description, including vascularity, density, collagen content, and organization of the adhesion being quantified. Blocking on the swine, the cranial and caudal histology scores were shown to have a positive correlation (p < 0.002, r2 = 0.46) and were not significantly different from one another. Furthermore, the visual score showed no correlative relationship with either histological score or with any MTS force parameters. This model is unique and advantageous in its ability to quantitatively assess the strength of the adhesion complex, minimizing the potential for bias. The significant advantage of this method is that the adhesions are created in a manner appropriate for quantitative assessment using the MTS system. The ultimate utility of this technique lies not with the testing of adhesions themselves, but in testing and comparing of adhesion prevention techniques. The encapsulation studies showed that ketorolac tromethamine was successful encapsulated in all six solutions. The data collected regarding to the criteria of yield, and drug loading efficiency failed to produce a ‘most efficient’ solution for encapsulation ability. The microspheres showed a smooth surface morphology and appeared to consist of three distinct size ranges. This observation was corroborated by particle size analysis. In the release studies, it was observed that there were discrepancies between the different solutions although the yield and encapsulation efficiencies were similar. There are several possible explanations for the variable release rates. When examined in conjunction with the size analysis data it would seem that the most plausible is that the initial burst and transition regions are directly affected by the particle sizes. Differential scanning calorimetry verified encapsulation and showed a relationship between encapsulated ketorolac tromethamine and Tg. The results presented and discussed in this thesis represent the initial steps toward the creation of a pharmaceutical adjuvant for the prevention of pelvic adhesions. The analysis shows that KT can be successfully encapsulated into PLGA. While the release time seen above was longer than the originally sought release of 14 days, the desired initial burst effect was large and this could be potentially advantageous. Future work: The next important step to take in developing KT microspheres for pharmaceutical drug delivery is to determine the effect of sterilization on the microsphere structure, size, and duration of drug release under in vitro conditions. Once microsphere sterilization has been characterized and if there are no significant issues, in vitro and in vivo testing can be pursued. In order to determine the optimum single size or combination of sizes, it is necessary to determine an optimum therapeutic concentration for adhesion growth prevention. To achieve this, a co-culture of mouse fibroblast cells and macrophage cells would be useful. From this in-vitro study, an optimum, minimum, and toxicity level for KT can be determined. Provided this information, the efficacy, size, and release rate of the produced microspheres can be reevaluated and a single or combination of sizes can be isolated via filtration. Without in-vitro studies, it is impossible to move forward. From the studies, the synthesis technique can be refined to produce microspheres with the most desirable properties following sterilization. Once this is completed, animal studies and eventual implementation as a pharmaceutical adjuvant for the prevention of pelvic adhesions can commence. Advisors/Committee Members: Newby, Dr. Bi-min.

▼ Mechanics and performance of solid oxide fuel cells (SOFCs) have been investigated with methane and solid carbon as fuels. The work with methane fuels investigated methane reactions on Ni/YSZ and deactivation of Ni/YSZ. The Cu-Ni/YSZ anode was developed to resist the coking and sustain the durability of Ni/YSZ anodes. The results of Ni/YSZ deactivation showed that the coking caused by methane was fast (i.e., less than 5 min) and irreversible. A combined in situ infrared (IR) and mass spectroscopy (MS) complemented the deactivation studies in open circuit and suggested that CH4 reactions on Ni/YSZ followed (i) dissociation of C-H bond, (ii) initial oxidation of adsorbed carbon to CO2 and CO followed by depletion of lattice oxygen, and (iii) accumulation of carbon on the anode surface. The Cu-Ni/YSZ anode was made by electroless plating copper on Ni/YSZ anodes. Addition of copper slowed down the C-H dissociation and carbon accumulation from CH4 by formation of Cu-Ni alloy, which was tolerant to coking and sulfur. The X-ray fluorescence (XRF) and X-ray diffraction (XRD) confirmed the successful copper deposition on Ni/YSZ anodes. The maximum power density of 125 mW cm-2 was achieved using the Cu-Ni/YSZ anode in CH4 (100 ml min-1) at 750 °C. A preparation protocol of copper plating on the anode of SOFCs was established for the applications of coking resistant methane- and carbon-based SOFCs. The work with solid carbon fuels tested the feasibility of direct use of solid carbon on SOFCs for power generation and investigated the chemical reactions involved. Two types of solid carbon: biomass-derived coconut coke and bituminous Ohio #5 coke, were used on carbon-based SOFCs (C-SOFCs). The results showed that biomass-based coconut coke exhibited a higher oxidation and gasification reactivity than bituminous Ohio # 5 coke due to higher content of functional groups and alkali metals. The power generation from coconut coke produced a power density of 140 mW cm-2 continuously over 15 h and an electrical efficiency of 51.82 % based on CO2 production at 800 °C. Transient techniques consisting of pulse injection and step switch showed that both Boudouard reaction (C+CO2→2CO) and CO electrochemical oxidation contributed to power generation of carbon fuel cells. The carrier gas flow rates also affected these gaseous reactions on C-SOFCs by changing the residence time of gas species and their concentration. The results showed that low carrier gas flow rates increased residence time of CO, thereby increasing its contribution to current generation. The contribution of CO oxidation to current generation was estimated to 66 % at the carrier gas flow rate of 50 ml min-1. The pulse transient studies confirmed the effect of flow rates on cell performance and also revealed that CO and CO2 can displace adsorbed hydrogen on carbon fuels. The results demonstrated the successful utilization of solid carbon on Ni/YSZ anode supported SOFCs for power generation and provided the insight of reaction mechanisms for development of carbon-based fuel cells. Advisors/Committee Members: Chuang, Steven S. C.

▼ 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 (γS) to examine its effects on the dewetting. Therefore, in this study, the effects of γS 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 γS, 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 of γS. Empirical relationships between the rate of hole growth (dewetting velocity, VR) and γS, VR ≈ 530 exp(-0.13γS) and 310 exp(-0.10γS), 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(-0.13γS) was obtained. In analogous to a desorption process, the exponential relationship between VR and γS was hypothesized to be originated from the energy required to overcome the free energy of adhesion in the dewetting process, which is proportional to γS1/2. Second, an origin of the instability of the rim, formed around the dewetting hole, was elucidated in relation to γS. The rim instability, in terms of undulations of the rim, became more pronounced as γS decreased. A narrower and higher rim was also observed as γS decreased. A simple material balance of the rim formation verified that γS 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 γS. 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 120 °C 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 γS 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 γS; 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 γS, providing a possibility of multidimensional combinatorial analysis of the dewetting. Advisors/Committee Members: Zhang Newby, Bi-min.

▼ 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.

▼ 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.

▼ 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.

▼ 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.

▼ 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 – 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.

▼  Periodic nano- or microstructures play an essential role in many fundamental researches and technological applications. This study reports the experimental details in creating periodic parallel silicone strips by simply peel an oxidized silicone sheet from its bonded substrate. This spontaneous formation of strips is initiated by a mixed-mode of separation along the peeling direction and subsequent channeling of initiated cracks. This study also provides experimental evidence on the fracture formation of ordered strips using glassy polymer thin films. For fracture induced strips formation over a large area following the method developed by Yangjun Cai, both the oxidization extent of the Poly(dimethylsiloxane) (PDMS) sheet using UV/Ozone and the effect of oxidization extent on the strip spacing were examined. The effects of various experimental parameters, including elastic modulus of silica-like layer, pre-crack, and pre-wrinkling of the silicone surface bonded to the substrate, and glassy silica-like layer on the edge were examined. The results showed that these parameters were possible to change the initiation of the cracks during fracture or the spacing between cracks. The effect of other factors including the peeling angle, peeling force, elastic modulus and the thickness of the PDMS sheet were also explored. Those conditions proved to have little to no effect on the spacing or initiation of the cracks. Fracture-induced structuring (FIS) of glassy polymer thin films developed by Chai et al, was also followed. Similar results on the dependency of strip spacing on film thickness were observed. Advisors/Committee Members: Newby, Bi-min Zhang.

▼ 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.

▼ 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.

▼ 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.

▼ 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.

▼ 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.

▼ Development of novel technologies for the conversion and storage of energy has been actively investigated in recent years. The use of a combined approach consisting of direct electrochemical and photocatalytic oxidation reactions could allow the efficient utilization of energy resources. Direct electrochemical oxidation in a fuel cell could offer significant advantages over conventional combustion technologies, in light of their increased energy efficiency, reduction in emission of toxic pollutants, and overall process simplicity. The majority of fuel cell research has focused on the use of hydrogen, an environmentally friendly fuel characterized by high energy density and production of H2O byproduct. Despite these advantages, commercialization of hydrogen powered fuel cells is currently limited by difficulties in hydrogen production and storage. The high operation temperature of the solid oxide fuel cell (700-1000 °C) facilitates the direct use of hydrocarbon and carbon fuels, avoiding the complex and expensive reforming processes for the generation of concentrated H2 fuel. Exposure of gaseous hydrocarbons to the fuel cell at these high temperatures provides a thermodynamically favorable pathway for formation of carbon deposits (i.e., coking) which can lead to rapid and irreversible anode electrode degradation. This dissertation presents a study of the use of a novel Cu/Ni-YSZ anode electrode that reduces the formation of coke deposits and allows the energy efficient operation of the solid oxide fuel cell in hydrocarbon and carbon fuels. The microstructure of the Cu/Ni-YSZ anode electrode is extensively characterized by scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The performance of the Cu/Ni-YSZ anode and the energy efficiency during the operation on carbon (i.e., coke, a devolatized form of coal) is experimentally measured with the aid of in situ electrochemical analysis and, mass spectrometry (MS) and gas chromatograph (GC), demonstrating higher energy efficiencies compared with combustion technologies. Photocatalytic reactions over semiconductor catalysts such as TiO2 have received significant attention due to their potential applications for conversion and storage of solar energy to chemicals and the degradation of harmful pollutants present in air streams and wastewaters. Excitation of photocatalysts by exposure to light of appropriate energy causes promotion of electrons from the valence band to the conduction band, resulting in the generation of electron/ hole pairs that can initiate redox reactions with species adsorbed on the surface of the photocatalyst. Hydrogen can be produced by the photocatalytic reduction of water (i.e. splitting reaction). Addition of alcohol molecules have been shown to improve the photocatalytic evolution of H2 from H2O due to hole scavenging oxidation reactions that limit electron/hole recombination. Detail knowledge of the mechanisms governing the photocatalytic oxidation of alcohols could facilitate the development of highly efficient photocatalysts for water splitting and degradation of volatile organic compounds (VOC). The photocatalytic evolution of H2 from aqueous solutions containing methanol (CH3OH) hole scavenging reagents was studied by tracing the reaction of D2O over a Cu/S-TiO2 catalyst under UV illumination. Use of D2O/CH3OH produced higher formation rates of HD and D2 than that of H2. The low H2 formation rates indicate that the direct reaction of CH3OH with photogenerated holes does not proceed to an appreciable extent in the presence of high concentrations of D2O. The role of CH3OH in accelerating hydrogen formation can be attributed to its ability to produce an electron donor, injecting its electrons to the conduction band. The photocatalytic oxidation of alcohols was further studied at 30 °C and 1 atm by in situ infrared methods, using ethanol as a model compound. Results from these studies have shown ethanol adsorbs on TiO2 in the presence of high contents of water as molecularly adsorbed ethanol (CH3CH2OHad), which exhibit a lower initial C-H scission and CO2 formation rate than ethoxy CH3CH2Oad produced from ethanol adsorbed low water content TiO2 catalysts. CH3CH2OHad photooxidation produced formic acid (HCOOHad) and formate (HCOO-ad) species, whereas CH3CH2Oad reactions proceed via formation of acetaldehyde (CH3CHOad) and acetate (CH3COO-ad). CH3CHOad was found to react on TiO2 via hydrogen abstraction of the -Carbon producing CH3COO-ad which can be further oxidized to HCOO-ad and CO2. The rate of ethanol photooxidation was found to decrease due to the accumulation of CH3COO-ad species on the TiO2 surface. In the presence of excess H2O, weakly adsorbed species (i.e., acetic acid CH3COOHad) can be redistributed in the surface and dissociated producing acetate. Advisors/Committee Members: Chuang, Steven S.

▼ 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.

▼ Over the past 50 years the use of fossil fuels has lead to a 22% increase in the CO2 concentration levels in the atmosphere. It has also been recognized that the energy producing sector, coal-fired power plants in particular, contribute approximately 33% of the total global emissions. It is of immediate concern that a technology be developed that can be retrofit to the power plants in order to capture CO2 from the flue gas, eliminating a significant source of CO2 emissions. Current commercialized technologies such as liquid amine scrubbing using monoethanolamine (MEA) and chilled ammonia capturing processes have demonstrated successful capture of CO2 gas but involve using highly toxic and corrosive compounds with high heats of regeneration. Development of a solid immobilized amine sorbent that exhibits high CO2 capture and cyclical stability may prove to be a more sensible solution due to its low heat of regeneration, toxicity, and corrosive properties. In this study, fumed silica was chosen as the solid support because of its high commercial availability and high surface area. In this thesis, silica based sorbents were developed through impregnation of tetraethylenepentamine (TEPA) at various weight percent ratios and further modified with the addition of polyethylene glycol (PEG) to aid in dispersing TEPA and cyclical stability of the sorbent. Although the development of sorbents using the same compounds have been reported on in literature, there has been no work done using infrared (IR) characterization to determine the way the compounds interact with each other and with the surface. This thesis has been constructed in order to develop an understanding of these surface interactions and use it to fabricate the best possible sorbent. The IR results concluded that the co-impregnation of PEG and TEPA with corresponding TEPA/PEG/SiO2 weight ratios of 24/36/40 yielded the highest CO2 capture capacity (2.53 mmolCO2/gramSorbent) and best cyclical stability (3% degradation). A gram scale process was also developed for the adsorption and regeneration of CO2 gas from a feed stream of 15% CO2. The process was designed mirroring industrial conditions and resulted in good initial CO2 regeneration concentrations. Advisors/Committee Members: Chuang, Steven.

▼ 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.

▼ 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.

▼ 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.