Theses and Dissertations - Department of Chemical & Biological Engineering

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Matilda: a mass filtered nanocluster source
(University of Alabama Libraries, 2009) Kwon, GiHan; Klein, Tonya M.; University of Alabama Tuscaloosa
Cluster science provides a good model system for the study of the size dependence of electronic properties, chemical reactivity, as well as magnetic properties of materials. One of the main interests in cluster science is the nanoscale understanding of chemical reactions and selectivity in catalysis. Therefore, a new cluster system was constructed to study catalysts for applications in renewable energy. Matilda, a nanocluster source, consists of a cluster source and a Retarding Field Analyzer (RFA). A moveable AJA A310 Series 1"-diameter magnetron sputtering gun enclosed in a water cooled aggregation tube served as the cluster source. A silver coin was used for the sputtering target. The sputtering pressure in the aggregation tube was controlled, ranging from 0.07 to 1torr, using a mass flow controller. The mean cluster size was found to be a function of relative partial pressure (He/Ar), sputtering power, and aggregation length. The kinetic energy distribution of ionized clusters was measured with the RFA. The maximum ion energy distribution was 2.9 eV/atom at a zero pressure ratio. At high Ar flow rates, the mean cluster size was 20 ~ 80nm, and at a 9.5 partial pressure ratio, the mean cluster size was reduced to 1.6nm. Our results showed that the He gas pressure can be optimized to reduce the cluster size variations. Results from SIMION, which is an electron optics simulation package, supported the basic function of an RFA, a three-element lens and the magnetic sector mass filter. These simulated results agreed with experimental data. For the size selection experiment, the channeltron electron multiplier collected ionized cluster signal at different positions during Ag deposition on a TEM grid for four and half hours. The cluster signal was high at the position for neutral clusters, which was not bent by a magnetic field, and the signal decreased rapidly far away from the neutral cluster region. For cluster separation according to mass to charge ratio in a magnetic sector mass filter, the ion energy of the cluster and its distribution must be precisely controlled by acceleration or deceleration. To verify the size separation, a high resolution microscope was required. Matilda provided narrow particle sized distribution from atomic scale to 4nm in size with different pressure ratio without additional mass filter. It is very economical way to produce relatively narrow particle size distribution.
The localization and behavior of fluorescently tagged magnetic nanoparticles in biological systems
(University of Alabama Libraries, 2009) Sewell, Mary Kathryn; Brazel, Christopher S.; University of Alabama Tuscaloosa
A novel combination cancer therapy platform incorporating chemotherapy and hyperthermia is proposed. Magnetic nanoparticles are included as a way to achieve the hyperthermia treatment, as well as for use as a platform for targeting, imaging, or other therapeutic moieties. Cobalt ferrite (CoFe₂O₄) magnetic nanoparticles (MNPs) were synthesized and tagged with the fluorescent dye rhodamine for tracking in biological systems. The MNP solutions were characterized to determine average diameters of the nanoparticles. Results indicate that sample age, solvent, and concentration can affect the diameters of MNP agglomerates as measured by dynamic light scattering. Older and more concentrated samples, which also tend to be less stable, showed larger MNP sizes than newer and less concentrated samples. Rhodamine-tagged MNPs showed smaller diameters than untagged MNPs at the same concentrations. For MNP in HeLa cell localization studies, the rhodamine-tagged MNPs showed uptake and localization in the cytoplasm of the cells. Partition coefficients, or the ratios of MNP concentrations inside the cells to the extracellular concentration, were shown to increase during the first 6 h of incubation time, with values reaching as high as 3.805, indicating favorable uptake of the MNPs. After 24 h, a smaller ratio of internalized MNPs was seen due to cytotoxic properties of the high concentration of MNPs used in those experiments. Toxicity studies showed that at concentrations below approximately 0.025 mg/mL, both rhodamine-tagged and untagged CoFe₂O₄ MNPs have little effect on cell viability. MNP localization and toxicity studies were also carried out on a model organism, C. elegans worms, with an indication that rhodamine-tagged CoFe₂O₄ MNPs were non-toxic to worms over a period of 12 days. Localization of the MNPs within the worms was inconclusive due to indistinguishable autofluorescence of the C. elegans and the rhodamine fluorescence of tagged MNPs. Further work is needed to characterize the CoFe₂O₄ MNPs for use in the cancer treatment platform.
In-situ investigation and mitigation of carbon support corrosion of cathode catalyst in PEM fuel cells
(University of Alabama Libraries, 2010) Li, Wei; Lane, Alan M.; University of Alabama Tuscaloosa
Carbon support corrosion (CSC) is one of the key factors causing cathode electrocatalyst (Pt/C) degradation in proton exchange membrane fuel cells (PEMFC). It is electrochemical oxidation and thus needs to be investigated in-situ with potential imposed. CSC was characterized in-situ and correlated to the Pt redox reactions and Pt-catalyzed oxygen reduction reaction (ORR) by the differential electrochemical mass spectrometry (DEMS) spectra of cathode exhaust gases, CO₂, H₂ and O₂, from a PEMFC fed with humidified H₂ and He to the anode and cathode respectively. Furthermore, the catalytic effects on CSC from different oxidation states of Pt were indicated. To determine the oxygen sources and pathways of CSC, oxygen was isotopically labeled by replacing regular water with oxygen-18 (¹⁸O) enriched water (H₂¹⁸O, 98%) in DEMS, denoted as ¹⁸O-DEMS. 18O-DEMS spectra of the cathode exhaust gases O₂, O¹⁸O, ¹⁸O₂, CO₂, CO¹⁸O and C¹⁸O₂ during cyclic voltammetry and chronoamperometry were analyzed to verify that water is the main direct oxygen source for CSC. Moreover, water reacts with carbon to produce at least three types of carbon surface oxides, which are further electrochemically oxidized with water to produce CO₂ in different potential ranges. After accelerated testing of cathode catalyst degradation in PEMFC using potential cycling between 100-1400 mV at the rate of 400 mV/s, the changes of mass spectra of CO₂, H₂ and O₂ over time showed that the CSC decreases as Pt electrochemically active surface area (ECSA) decreases, i.e. catalyst activity decreases, but the membrane does not degrade significantly in gas permeability. A hypothesis is proposed here that Au nanoparticles (NPs) added to a carbon-supported Pt (Pt/C) catalyst can mitigate the Pt catalytic effects on CSC by suppressing the Pt oxidation. Several methods were tried to synthesize Pt/C (20 wt% Pt) and bimetallic AuPt/C (20 wt% Pt, 5 wt% Au) catalysts including deposition-precipitation, two phase liquid-liquid colloidal, polyol, microwave-assisted polyol, and surface redox methods. TEM pictures showed that the EG method (polyol method using ethylene glycol), microwave-assisted EG method, and colloidal method produced Pt/C catalysts with high dispersion and narrow particle size distribution of Pt NPs uniformly loaded on the carbon support. Au NPs with high dispersion and narrow particle size distribution can be made only by the colloidal method. AuPt/C catalysts were synthesized by two methods: physically by mixing Au NPs prepared by the colloidal method on Pt/C prepared by the EG method, and chemically by surface redox reactions of a Au precursor on Pt NPs prepared by the EG method and then loaded on the carbon support (denoted as AuPtC-EG-SR). The existence of Au on Pt/C was confirmed by EDX and by a larger ring current from ORR experiment using a rotating ring-disk electrode. Three membrane electrode assemblies (MEA) with commercial Etek Pt/C and those two types of AuPt/C catalysts as cathode catalyst respectively were fabricated for CSC comparison. Larger ECSA but less CO₂ intensity of the MEA with a AuPtC-EG-SR cathode than those of the MEA with Etek Pt/C gives preliminary confirmation of the hypothesis.
Hafnium alkylamides and alkoxide adsorption and reaction on hydrogen terminated silicon surfaces in a flow reactor
(University of Alabama Libraries, 2010) Li, Kejing; Klein, Tonya M.; University of Alabama Tuscaloosa
This work is a study of the gas phase and surface chemistry of three metalorganic Hf (IVB) precursors - tetrakis(dimethylamido)hafnium (TDMAH), tetrakis(ethylmethylamido)hafnium (TEMAH), and hafnium tert-butoxide (HTB) adsorption and reaction onto hydrogen terminated Si(100), Si(111) and Ge surfaces during low pressure chemical vapor deposition (CVD) in a temperature range of 25 ºC to 300 ºC in a flow reactor. The main methods used include in-situ attenuated total reflectance Fourier transforms infrared spectroscopy (ATR-FTIR), transmission IR, quadrupole mass spectrometer (Q-MS), ab inito density functional theory (DFT), photoelectron spectroscopy (XPS), finite element analysis (FEA), computational fluid dynamics (CFD), and atomic force microscopy (AFM). Possible gas phase decomposition and surface adsorption reactions were surveyed. Reaction energies, vibrational spectra and transition states were calculated for the three precursors and especially the two alkylamido hafnium precursors to support experimental observations. Interfacial bonding and surface catalyzed reaction processes initiated by the adsorption of precursors were detected. For TDMAH and TEMAH, β-hydride elimination and insertion reactions were calculated to be not favorable thermodynamically at these low experimental temperatures. Interfacial bonding during adsorption between the Si was through N-Si and/or C-Si. Decomposition products containing Hf-H species were observed on the surface at room temperature and 100 ºC and the peak assignment was confirmed by deuterated water experiments. The gas phase by-products were mostly dimethylamine (DMA) and a small amount of methylmethleneimine (MMI) or ethylmethylamine (EMA) and methylethyleneimine (MEI). A surface three-member cyclo species was tentatively identified. For HTB, interfacial bonding was Si-O or Ge-O. Another β-hydride elimination generated Hf-OH on the surface and t-butene in the gas phase. A monodentate and bidentate model was proposed for chemisorption of HTB with different concentration on two Si surface orientations at temperatures below 150 ºC. Carbonate was found to form in the film at higher temperatures. The effect of HTB buoyancy driven flow in the ATR flow through cell on thin film topography was observed using AFM of thin films deposited from HTB at 250 ºC. The images showed a wavy surface at the downstream end of the substrate due to roll-type flow predicted by CFD calculations.
Development of hydroxypropyl cellulose-filled poly(2-hydroxyethyl methacrylate) semi-interpenetrating networks for drug delivery
(University of Alabama Libraries, 2010) Melnyczuk, John Michael; Brazel, Christopher S.; University of Alabama Tuscaloosa
Cancer is the second leading cause of death in the United States of America and the National Cancer Institute has released a paper stating that the ideal cancer therapy should have an imaging, targeting, reporting, and therapeutic part. The overall project goal is to be able to create a delivery system that can be triggered externally to the body and can release an anticancer agent in a controlled manner. The current project deals specifically with using hydroxypropyl cellulose (HPC) filled poly(2-hydroxyethyl methacrylate) (PHEMA) (HFPG) hydrogel to cause a release of theophylline when the hydrogel is placed at a temperature above the lower critical solution temperature (LCST) of HPC (57 ºC) and to have no release at normal body temperature, 37 ºC. In a series of polymerization reactions, various compositions of hydroxypropyl cellulose (HPC) filled crosslinked PHEMA gels were synthesized by free radical polymerization. The LCST for different average molecular weights, M̅_n, of HPC were found to be 44.8 ºC ± 0.8, 48.7 ºC ± 0.3, and 46.2 ºC ± 0.7 for 80,000, 100,000, and 370,000 M̅_n HPC respectively. A change in concentration of HPC with a M̅_n 80,000 from 0.01 to 0.05 g/mL showed an increase in the LCST from 44.8 ºC ± 0.8 to 46.6 ºC ± 1.0. Changing the media from water to 0.65M sodium chloride change LCST from 46.6 ºC ± 1.0 to 35.4 ºC ± 2.3. The swelling study showed the mesh size was unaffected by synthesis temperature, analytical temperature, and HEMA to HPC ratio, indicating that HPC was pore-filling. Mechanical testing confirmed the results of the swelling study, in that there was no net change in the calculated mesh size with a change in analytical or synthesis temperature by either method. This study showed that HPC did change the mesh size with a change in the HEMA:HPC ratio. Dissolution testing for the release of theophylline from the HFPG hydrogel showed an increased release rate with an increase in analytical temperature was possible. The increase in synthesis temperature increased the release rate. It is shown that an increase in the HEMA:HPC ratio with a decrease in the diffusion coefficient. The HPC collapsed and evolved out of the HFPG and this effect could produce a higher diffusion. Further investigations should be conducted to test the effects of different initiators and crosslinking ratio's on the release of HFPG hydrogels.
Wet chemical synthesis strategies to develop aluminum manganese nanoparticles for high density magnetic recording
(University of Alabama Libraries, 2010) Ivie, Michael Allen; Wiest, John M.; University of Alabama Tuscaloosa
As the technology era grows rapidly, there is always a need for quick access to stored data. Magnetic tape is one type of recording media used of information storage. Its main use in computer applications is for archival storage and mass storage systems. Magnetic tape is a multi-component material consisting of a base film with a top layer of magnetic particles. Particles that are used for magnetic recording devices must exhibit good magnetic properties including large coercivity and saturation magnetization. As the need for tape performance and storage capacity increases, new types of particulate media are needed to meet these demands. One candidate of particles for future magnetic tape is ferromagnetic AlMn nanoparticles. AlMn has a ferromagnetic tetragonal L10 phase which is exhibited by a class of transition metal alloy systems such as FePt, CoPt, FePd, MnPt, etc. This phase in the AlMn binary system is labeled as the τ phase and has a large anisotropy value of approximately 107 ergs/cc which translates to good magnetic properties suitable for use in magnetic tape. The advantages of producing AlMn nanoparticles for magnetic recording are the low cost and abundance of precursor materials. This dissertation investigated strategies of a solution phase chemical synthesis to produce AlMn nanoparticles. Metal nanoparticle systems are synthesized primarily by the reduction of metal salt precursors with a reducing agent in the presence of stabilizing agents in an organic solvent. Systems of metal nanoparticles with the tetragonal L10 phase characterized by high anisotropy values such as FePt and MnPt are produced via this route, and these techniques are considered as a foundation to make AlMn nanoparticles. Cyclic voltammetry experiments give the reduction potentials of Al and Mn precursors to determine suitable reducing agents. The results of the AlMn nanoparticle synthesis attempts are chronicled by the reducing agent that was used in the reaction. Different combinations of precursors, surfactants, and solvents are used in coordination with the following reducing agents: superhydride (C6H16BLi), potassium (K), hydrogen (H2), lithium aluminum hydride (LiAlH4), and sodium (Na). Also, synthesis attempts of AlMn(X) tertiary nanoparticles and core-shell AlMn nanoparticles are presented.
Chemical vapor deposition of thin film materials for electronic and magnetic applications
(University of Alabama Libraries, 2011) Li, Ning; Klein, Tonya M.; University of Alabama Tuscaloosa
Chemical vapor deposition (CVD) has been employed to pursue high quality thin film growth for four different materials with excellent electronic or magnetic properties for certain device applications. The relationship between CVD processing conditions and various thin film properties has been systematically studied. Plasma enhanced atomic layer deposition (PEALD) is a special type of CVD technique and can be used for the deposition of very thin (few nanometers) and highly conformal thin films. PEALD of hafnium nitride (HfN) thin film is studied by using tetrakis (dimethylamido) hafnium (IV) (TDMAH) and hydrogen plasma. Prior to thin film deposition, TDMAH adsorption and reaction on hydrogenated Si(100) surface has been investigated by in-situ ATR-FTIR. It has been found that between 100˚C and 150˚C surface adsorbed TDMAH molecules start to decompose based on the ß-hydride elimination mechanism. The decomposition species on the surface has been found hard to desorb at 150˚C, which can contaminate the thin film if the purging/pumping time is insufficient. Uniform and moderately conductive HfNxCy films are deposited on hydrogen terminated Si(100) and thermally grown SiO2 (on Si) substrates by PEALD process. The dependence of thin film resistivity on plasma power is found to be related to the change of surface chemical composition. In vacuo XPS depth profile analysis showed the existence of hafnium carbide phase, which to a certain degree can improve the film conductivity. Direct liquid injection chemical vapor deposition (DLI-CVD) has been utilized for epitaxial growth of nickel ferrite (NiFe2O4), lithium ferrite (LiFe5O8) and barium titanate (BaTiO3) films on various lattice match substrates. For the deposition of nickel ferrite, anhydrous Ni(acac)2 and Fe(acac)3 (acac = acetylacetonate) are used as precursor sources dissolved in N,N-dimethyl formamide (DMF) for the DLI vaporizer system. Epitaxial nickel ferrite films of stoichiometric composition are obtained in the temperature range of 500-800 ºC on both MgO(100) and MgAl2O4(100). Film morphology is found to be dependent on the deposition temperature with atomically smooth films being obtained for deposition temperature of 600 and 700 ºC. Magnetic measurements reveal an increase in the saturation magnetization for the films with increasing growth temperature, which correlates well with the trend for improved epitaxial growth. Nickel ferrite films deposited on MgAl2O4 (100) at 800ºC exhibit saturation magnetization very close to the bulk value of 300 emu/cm3. Out-of-plane FMR measurement shows the narrowest FMR line width of ~160 Oe for films deposited at 600˚C. For lithium ferrite deposition, anhydrous Li(acac) and Fe(acac)3 are dissolved in DMF in a molar ratio of 1:5. Epitaxial growth of lithium ferrite films on MgO(100) are observed in the temperature range of 500˚C to 800˚C. The as grown films show increasing saturation magnetization with increasing deposition temperature due to the improved degree of crystal texture. For barium titanate thin film deposition, Ba(hfa)2*tetraglyme and Ti(thd)2(OPri)2 are dissolved in toluene in a molar ratio of 1:1. Epitaxial growth of barium titanate on MgO(100) has been found at the temperature of 750˚C. Film with a thickness of ~500 nm has a relatively large roughness of ~20 nm. Small amount of F elements, which exists in Ba-F bonds, has been detected in the thin film by XPS.
Functionalized membranes for membrane chromatography
(University of Alabama Libraries, 2011) Shethji, Jayraj Kiritbhai; Ritchie, Stephen M. C.; University of Alabama Tuscaloosa
The focus of this thesis is synthesis and quantification of homopolymer and block copolymer grafts and understanding controlled polymer growth. The homopolymer and block copolymer grafts were synthesized through sequential cationic polymerization of styrene and substituted styrene monomers chloromethylstyrene (CMS) and 4-ethoxystyrene (ES) in the pores of microfiltration polyethersulfone (PES) membrane. Polymer growth aspects like kinetics of reaction, amount of monomer reacted, ion-exchange capacity (IEC), and graft length were studied with respect to initiator contact time and monomer feed concentration. Functionalization of the microfiltration membrane was achieved by a two step procedure. The first step was to introduce sulfonic acid initiator sites by mild sulfonation with 0.5N H2SO4. This was followed by cycling through each type of monomer solution (styrene and substituted styrenes). Successful introduction of homopolymer and block copolymer grafts was confirmed by material balances on the monomer/toluene permeate solutions. Analytical techniques used for quantification of polymer grafting include UV-Visible spectroscopy, gas chromatography and atomic absorption. The functionalized membrane showed a steep decrease in membrane permeability compared to the raw membrane indicating the presence of polymeric chains in the membrane flow path. Functionalized membranes prepared by this method have as many as 125 repeat units per chain. Given the initiator concentration, this equates to an IEC of 4.9 meq/g, indicating high dynamic and equilibrium binding capacity. Pseudo-first-order kinetic expression correlated well with the experimental data for each monomer reacted. At lower initiator surface density, graft length and IEC were impacted by both monomer feed concentration and initiator contact time. However, for higher initiator surface density, monomer feed concentration parameter dominates. Block copolymer formation is the first step to synthesizing an analog of the phenylalanine/tyrosine dipeptide structure in protein A, which is shown in literature for selective adsorption of immunoglobulin G (IgG). This work will lead to further development of functionalized membranes as membrane adsorbers for high throughput production of monoclonal antibodies for new cancer therapies. In addition, it will lead to discoveries in sequential polymerization to generate customized structures and design of synthetic affinity ligands.
Enhanced biogas production through the optimization of the anaerobic digestion of sewage sludge
(University of Alabama Libraries, 2011) Beam, Ryan Grant; Ritchie, Stephen M. C.; Clark, Peter E.; University of Alabama Tuscaloosa
The anaerobic digestion of sewage sludge has long been used for solids reduction by wastewater treatment facilities, but has gained recognition as a form of energy production. Biogas is formed as a byproduct of anaerobic digestion and is composed mostly of methane and carbon dioxide with other trace elements. The focus of this thesis is the enhancement of biogas production through the optimization of the anaerobic digestion of sewage sludge. Batch experiments showed that digest pH is indicative of the current stage of digestion. This will provide wastewater treatment facilities with a way to monitor digester activity, as each stage of digestion was identified through constant pH monitoring. The digestion process was optimized through various parametric studies designed to determine the effect of each parameter and find an optimal range for operation. The optimum range for pH was 7.0-7.5. Testing of temperature showed that the mesophilic range (30-40°C) provided the highest, most constant gas production. Alkalinity adjustment with magnesium hydroxide increased both pH and alkalinity. Biogas production was highest in samples with alkalinity ranging from 2,000-2,500 mg/L as CaCO_3 . Volatile fatty acid (VFA) adjustment with sodium propionate increased both alkalinity and VFA content within the digest. High levels of VFA caused digestion to struggle while small adjustments showed an increase in production. Pressure measurement showed that an increase in pressure during digestion improved both the quality and quantity of produced biogas. Semi-continuous experimentation showed consistent biogas production. However, high VFA content resulted in poor gas quality. Digester energy balances completed at the Hilliard-Fletcher Wastewater Treatment Plant showed that 1,705 m^3/day biogas are required for daily operation (basis: 60:40 ratio CH_4 :CO_2 ). Parametric tests showed the ability to provide up to 1,944 m^3/day at a methane content of 80%. Increasing the methane content from 60 to 80% increases the heating value of the gas by one-third, requiring less gas for daily operation. This allows for better energy efficiency. All gas volumes are reported at atmospheric pressure and a temperature of 35°C. Future work will focus on the effect of pressure to identify the extent with which it affects digestion.
Development and characterization of high-performance functionalized membranes for antibody adsorption
(University of Alabama Libraries, 2012) Shethji, Jayraj Kiritbhai; Ritchie, Stephen M. C.; University of Alabama Tuscaloosa
Capacity and selectivity are the major bottlenecks for the development of affinity membrane adsorbers for protein and antibody purification. The focus of this doctoral research is to develop polyethersulfone (PES) microfiltration (MF) membranes containing multiple highly selective poly(styrene-co-hydroxystyrene) grafts mimicking the key dipeptide Phe-132/Tyr-133 motif of ligand protein A to selectively adsorb immunoglobulin G (IgG) under convective flow conditions. This research work consists of two phases. In phase 1, homopolymer and block copolymer grafts were synthesized and characterized in the membrane pores using monomers styrene, ethoxystyrene, and chloromethylstyrene. 1H NMR characterization showed successful incorporation of the sequential stages of graft chemistry, including: polystyrene, poly(chloromethylstyrene), poly(ethoxystyrene), poly(styrene-b-ethoxystyrene), and poly(styrene-b-chloromethylstyrene). A study of monomer reactivity showed that chloromethylstyrene reacted approximately 1.3 times slower than styrene and ethoxystyrene during formation of homopolymers and block copolymers. The ion-exchange capacity of sulfonated functionalized membranes was 4.9 meq/g with as many as 125 repeat units per chain. In phase 2, PES MF membranes tailored with two different graft chemistries including poly(styrene-co-hydroxystyrene) and glycine functionalized poly((styrene-co-hydroxystyrene)-b-chloromethylstyrene) grafts were developed and tested for selective IgG adsorption. 1H NMR characterization confirmed membrane pore functionalization by poly(styrene-co-hydroxystyrene), chloromethylstyrene block addition, and subsequent glycine functionalization of the chloromethyl block. The dynamic binding capacity (DBC) for IgG was as high as 95 mg/ml, more than 9 times as compared to Sartobind® and Ultrabind® membranes and twice as compared to affinity resin. The DBC was independent of flow rate and there was no significant loss (<5%) in capacity at higher linear velocities (230 cm/h) indicating that the transport of IgG to the adsorptive sites is predominantly by convection. Bind and elute experiments showed that there was no significant loss of DBC over a period of five cycles and the average recovery of antibody was >94%. Competitive sorption using membranes containing negatively charged spacer arms showed that the membrane was ~11 times more selective for IgG than BSA. Additionally, the DBC was 22% higher (115 mg/ml) than without spacer arms indicating that the negatively charged spacer arms moved the grafted chains apart and improved the accessibility of IgG to the binding sites.
Enhanced oil recovery simulation study for Citronelle field, Alabama
(University of Alabama Libraries, 2012) Cox, William Brannon; Carlson, Eric S.; University of Alabama Tuscaloosa
The world is on the verge of an energy crisis due to rising demand for fossil fuel to meet both domestic and industrial energy requirements. In order to meet this rising fossil fuel need, it is important that enhanced oil recovery (EOR) schemes, which are more efficient hydrocarbon recovery techniques than primary and secondary recovery methods, are used to recover conventional oil reserves from already discovered fields. Continuous CO2 and the Water Alternating Gas (WAG) injection schemes are two basic EOR techniques for gasflooding reservoirs. The primary objective of this research project focuses on enhancing oil recovery from a very small pilot area of Citronelle oil field using CO2 miscible flooding. The miscible flood performance of carefully targeted CO2 injection was modeled using a fine-scale open source compositional simulator nSpyres. The simulation runs were performed using regular grids with a total of 8.2 million cells. The CO2 injection pilot did not result in any new recovery. However, it helped identify many crucial characteristics for consideration in a comprehensive CO2 project for entire Citronelle field, such as non-workability of WAG scheme due to loss of injectivity after converting back to water injection, presence of natural and induced fractures that affects flood performance, as well as operational issues - down-hole pumps, well integrity, and difficulties with data collection due to the mixing of "power oil" with produced oil - which will need thorough consideration.
Magnetic heating of Fe3O4 nanoparticles and magnetic micelles for a magnetothermally-triggered drug delivery system for cancer therapy
(University of Alabama Libraries, 2012) Bennett, James Brandon; Brazel, Christopher S.; University of Alabama Tuscaloosa
Magnetic nanoparticles, MNPs, combined with stimuli-responsive polymers show potential to enhance the efficacy of cancer therapy in multifunctional nanoscale drug delivery systems. This project investigates the use of iron oxide nanoparticles (magnetite) to generate heat, via an applied magnetic field, to stimulate drug release of doxorubicin from an RGD-peptide targeted thermo-sensitive poly (ethylene glycol)-b-poly (caprolactone) micelle. Fe_3 O_4; nanoparticles custom synthesized at UA show the ability to heat to temperatures adequate for melting a semi-crystalline poly (caprolactone) micelle core. Investigations into parameters effecting magnetic heating of Fe_3 O_4 included studying the effects of magnetic field strength, H, and frequency, f. The results showed magnetic heating of the MNPs could induce hyperthermic temperatures. Specific absorption rates (SAR) for the MNPs were in the range of previously reported magnetite SARs, and followed the relationship with magnetic field strength predicted by the Rosensweig equation. The internal energy change in magnetic micelles was larger than that observed for MNPs in hexane when heated by an AC magnetic field. Drug release studies using triamterene- and doxorubicin- loaded micelles show a temperature-dependent acceleration of drug release at temperatures above 42 °C, the melting point of poly (caprolactone), as well as the possibility of magnetic induction hyperthermia-activated release.
Synthesis and characterization of platinum decorated iron oxide nanoparticles for biomedical applications
(University of Alabama Libraries, 2012) Palchoudhury, Soubantika; Bao, Yuping; University of Alabama Tuscaloosa
This dissertation focuses on the development of a bifunctional nanoparticle system that can potentially offer simultaneous imaging and therapy in the future. Recently, small platinum (Pt) nanoparticles (< 5 nm) have shown great potential in therapeutic applications, such as DNA dissociation, radiation therapy, and oxidative stress treatment. Therefore, the small Pt nanoparticles of size comparable to DNA grooves are chosen as potential therapeutic components in this research. However, such small sized Pt nanoparticles tends to aggregate, and are difficult to target. Therefore, this research reports the synthesis, characterization, and DNA interaction of small Pt decorated iron oxide nanoparticles. The iron oxide carriers provide stability to the small Pt nanoparticles, and can potentially serve as MRI contrast agents. The hypothesis of this research is that the Pt nanoparticles supported on iron oxide nanoparticle surfaces can effectively interact with DNA molecules similar to the free Pt nanoparticles. A reproducible synthetic technique was first developed to prepare iron oxide nanoparticles with excellent size control and narrow size distribution. Subsequently, two different approaches were utilized to produce multiple small Pt nanoparticle attached iron oxide nanoparticles. The first route involved attachment of Pt nanoparticles onto iron oxide seeds of various shapes in an organic solvent, followed by an aqueous phase transfer. Here, the shape of the nanoparticles was controlled to facilitate heterogeneous nucleation of Pt nanoparticles. The protective biocompatible polymer coating (polyacrylic acid) in this method could prevent interaction of the Pt nanoparticles with undesirable biomolecules. Several non-spherical iron oxide nanoparticles were explored, including whiskers, worms, plates, and flowers. In the second method, an aqueous phase ligand exchange process was performed first, prior to the deposition of multiple Pt nanoparticles. This facile method provided more accessibility of the Pt nanoparticles for DNA interactions. The DNA interaction of these nanoparticles was investigated using gel electrophoresis, electron microscopy, dynamic light scattering, and atomic absorption spectroscopy. By comparing with control DNA, we suggested that two possible interactions between DNA and Pt-iron oxide nanoparticles were present: (1) DNA molecules directly linked to the Pt-iron oxide nanoparticles, and (2) DNA molecules de-attached the Pt nanoparticles from the iron oxide support. This reported nanodrug system could potentially open up new possibilities in the design of therapeutic agents using multifunctional nanoparticles. Future efforts are to investigate the in vivo characteristics of this integrated nanostructure.
Computer simulation of geologic sequestration of CO_2
(University of Alabama Libraries, 2012) Islam, Akand W.; Carlson, Eric S.; University of Alabama Tuscaloosa
The research conducted here is an attempt to develop a simulation framework of CO2 sequestration in geologic formations. One of the very important parts of this framework is centered on phase equilibrium computations between CO2 and Brines for a wide range of temperature and pressure. Besides accuracy of the models, time efficiency is extremely important to save computational expenses. Therefore, thorough investigations have been carried out to model the phase equilibrium of CO2 and Brines system over the temperature range 20 - 300 °C, and pressure range 1 - 600 bar from different perspectives, like, vapor state Equation of State (EoS), liquid state EoS, and Statistical Associating Fluid Theory (SAFT), in time efficient manner. First, a non intuitive scheme and a new EoS for CO2 has been proposed which gives more than 1000 times speed up after integrating with the simulator compared with other EoS's. To model the phase equilibrium for super critical CO2, currently available liquid state models such as UNIQUAC, LSG, NRTL, and GEM-RS have been modified which reproduce literature data within fair deviation. SAFT, which is a theoretically sound model, has also been modified to apply in the simulator. A comprehensive study is carried out to model the viscosity of CO2 and Brines applicable for the geologic environment. While modeling the viscosity, the effect of CO2 dissolution is taken into consideration. Double diffusive natural convection of CO2 in brine saturated porous media is investigated to show how CO2 dissolves over the time after injection.
Evaluation of fluid dynamic effect on thin film growth in a horizontal type meso-scale chemical vapor deposition reactor using computational fluid dynamics
(University of Alabama Libraries, 2013) Tabatabaei Sadeghi, Sahar; Klein, Tonya M.; University of Alabama Tuscaloosa
To design and analyze chemical vapor deposition (CVD) reactors, computer models are regularly utilized. The foremost aim of this thesis research is to understand how thin film uniformity can be controlled in a CVD reactor. A complete understanding of chemical reactions that take place both in gas phase and at the deposition surface is required to predict thin film properties such as growth rate and composition precisely, however, deposition rates and surface topography can be determined by the arrival flux of reactants in a mass-transfer limited regime. In order to understand experimental thickness and roughness uniformity, a predictive model has been developed to study the fluid dynamic effect on thin film growth in a horizontal type reactor using velocity, temperature, pressure and viscosity as tunable parameters upon which velocity profiles within a CVD reactor have been evaluated using computational fluid dynamic (CFD) calculations. Through this predictive model, it is shown that fluid velocity is the major variable contributing to transverse roll cell formation compared to temperature and pressure gradients present during thin film deposition in a meso-scale CVD reactor. These results provide a physical insight regarding improved reactor operation conditions that influence uniformity.
Integrated reservoir characterization and modeling for enhanced hydrocarbons recovery from mature gas-condensate reservoirs: a case study of Big Escambia Creek field, Escambia County, Alabama, USA
(University of Alabama Libraries, 2013) Dumkwu, Francis A.; Carlson, Eric S.; University of Alabama Tuscaloosa
The world is on the verge of energy crisis due to rising demand for fossil fuel to meet domestic and industrial energy requirements. In order to meet the rising fossil fuel need, the development of a framework for enhanced hydrocarbons recovery from mature reservoirs should be given a high priority given the fact that 70% of world oil production comes from mature reservoirs. The objective of this research project is to develop a framework for enhanced hydrocarbons recovery from mature reservoirs using Big Escambia Creek (BEC) field as a case study. This developed framework is hinged on accurate characterization of reservoir rock and fluid properties, successful modeling of variation of average reservoir pressures with time, and presentation of existing well models and how to appropriately represent them in numerical simulators to ensure performance of successful reservoir simulation studies. In order to ensure successful development of a framework, the Smackover reservoir portion of BEC field was comprehensively characterized to delineate the porosity and permeability profiles of the field using laboratory measured porosity and permeability data, as well as well log porosity data. In addition, the average reservoir pressure, which is required to estimate initial hydrocarbon in place, estimate hydrocarbon reserves, and monitor reservoir performance, was modeled with a decaying exponential function using static bottom-hole pressures available for some wells on the field. Furthermore, accurate modeling of reservoir fluid using available commercial fluid simulators, such as PVTi, was impossible due to high concentration of acid gas. Therefore, least square optimization technique was used to accurately model the fluid. The reservoir fluid PVT properties obtained through this technique were used successfully to estimate initial hydrocarbon in place and determine aquifer influence on BEC field using material balance calculations. The original hydrocarbon in place of 1.502 Tcf of gas obtained was in perfect agreement with earlier estimates made using pressure decline data and volumetric calculations. On the basis of this developed framework, simulation studies for enhanced hydrocarbons recovery could be performed on BEC field and other fields with similar rock and fluid properties in USA and around the world.
Multifunctional iron oxide nanoparticles for biomedical applications
(University of Alabama Libraries, 2014) Xu, Yaolin; Bao, Yuping; University of Alabama Tuscaloosa
This dissertation focuses on the preparation of multifunctional nanoparticles through the integration of iron oxide nanoparticles with other desired moieties. Iron oxide nanoparticles have been widely explored in localized therapy, targeted delivery, and magnetic resonance imaging. However, inaccessible MRI instruments for most research labs and lack of targeting ligands limits the further exploration of iron oxide nanoparticles in routine tumor diagnosis and efficient therapy. Therefore, the preparation of dual-imaging or targeted nanoparticles is highly desirable. In our studies, fluorescent gold nanoclusters or anti&ndashdisialoganglioside&ndashGD2 monoclonal antibodies are integrated onto iron oxide nanoparticle surfaces. The gold nanoclusters provide additional fluorescent imaging capability, which can be easily accessed in common research labs. The conjugation of cancer cell&ndashtargeting antibodies allows for specific localization of nanoparticles. Indeed, these are the two central themes of this dissertation. To prepare multifunctional nanoparticles, high&ndashquality iron oxide nanoparticles were first synthesized in organic solvents following a modified &ldquoheat&ndashup&rdquo method. During synthesis, a modification was made by introducing a co&ndashsurfactant (trioctylphosphine oxide&ndashTOPO). TOPO facilitated the subsequent ligand exchange process because it weakly bound to nanoparticle surfaces and prevented the formation of densely&ndashpacked surfactant coatings. As a result, hydrophilic molecules (such as polyacrylic acid, polyethylenimine, glutathione and dopamine) were capable of replacing the original ligands, yielding water&ndashsoluble iron oxide nanoparticles. In addition to water solubility, dopamine coatings offered nanoparticles additional conjugation capability upon surface oxidization. These surface&ndashoxidized nanoparticles can directly conjugate with amine and/or thiol group&ndashcontained molecules through Michael addition and/or Schiff base formation. Using this conjugation strategy, dual&ndashimaging nanoparticles were prepared by integrating dopamine&ndashcoated nanoparticles with protein (such as bovine serum albumin, trypsin and lysozyme) &ndash encapsulated fluorescent gold nanoclusters. All integrated nanoparticles maintained their functionalities and structural integrity in biological environments. Furthermore, effects of protein characteristics on the photo&ndashchemical properties of gold nanoclusters and integrated nanoparticles were systematically examined. Similarly, cancer cell&ndashtargeting molecules (e.g. anti&ndashGD2 monoclonal antibodies) were conjugated onto dopamine&ndashcoated nanoparticles. After conjugation, antibodies retained their high targeting specificity, suggested by our cellular targeting studies. More promisingly, conjugated nanoparticles were capable of transporting into cytosols, which opens up new possibilities in cancer&ndashcuring drug loading and targeted therapy. Besides these already&ndashpublished works, we have studied the biological responses of human monocytes to different surface&ndashcharged iron oxide nanoparticles (manuscript in preparation). For dual&ndashimaging nanoparticles, their stability and bio&ndashimaging potential will be evaluated in phorbol myristate acetate (PMA)&ndashtreated monocytes using differential interference contrast (DIC) and confocal microscopy.
Multiscale simulation of boron-doped nanocarbons in electrochemical applications
(University of Alabama Libraries, 2014) Zhang, Zhongtao; Turner, C. Heath; University of Alabama Tuscaloosa
The stability, properties, and dispersion of novel organometallic/doped nanocarbon complexes for electrochemical application are investigated in this work with density functional theory (DFT) and molecular dynamics (MD) simulations. We suggest that electrochemical active centers like cyclopentadiene (Cp) transition metal (TM) complexes can be stabilized on boron-doped nanocarbons to create stable and high-performance support materials. We present a systematic study of the geometries, energetics, and electronic properties of CpTM (where TM=Fe, Ni, Co, Cr, Cu) complexes adsorbed on both pristine and boron-doped carbon nanotubes (CNTs) and graphene supports using DFT calculations. Significant stabilization of CpTM on boron-doped CNTs (B-CNTs) and graphenes are found, which surpasses the binding energies (BEs) of the isolated TM atoms by about 2 eV. To evaluate the redox activity (CpFe) on B-doped nanocarbon supports, we calculate the redox potentials of CpFe/B-doped, N-doped and pristine graphene complexes with different doping patterns and concentrations with DFT calculations, combined with a conductor-like polarizable continuum model (CPCM) solvation model. The CpFe/B-doped graphene complexes show potential to be a ferrocene substitute for ferrocene-mediated electrochemical process, such as bio-sensing and dye-sensitized solar cells. The dispersion of B-doped nanocarbons is also investigated in our work. Molecular dynamics (MD) simulations, parameterized by DFT-calculated partial charges are used to investigate the water-induced interactions, the hydration, and the debundling behavior of B-CNTs with varying diameters and B-doping patterns within aqueous solutions. By evaluating the potential of mean force (PMF) of one, two, and three solvated B-CNTs, we demonstrate that the water-induced interactions between B-CNTs extend over prolonged distances, and the B-CNTs are shown to be more reagglomeration resistant. In addition, the hydration behavior of the B-CNTs can be understood by evaluating the water density profiles and hydrogen bonds during the solvation. These results provide guidelines for separating and dispersing B-doped nanocarbons in aqueous environments. Overall, our simulations predict that the CpTM/B-doped nanocarbon complexes are potential candidates for multiple electrochemical applications with significant stability, comparable redox performance to ferrocene, and enhanced dispersibility.
Novel imidazole and ionic liquid-based platforms as media for co2 capture applications
(University of Alabama Libraries, 2014) Shannon, Matthew Samuel; Bara, J. E.; University of Alabama Tuscaloosa
The objective of this extensive research project was to investigate imidazoles as potential solvents for acid gas removal applications. Imidazoles are integral starting materials and neutral analogs for the synthesis and production of imidazolium-based ionic liquids (ILs) and virtually have not been explored as candidates for novel, CO₂ capture media. N-functionalized imidazoles also provide a similar platform as seen in ILs as tunable structures that govern physical and chemical properties leading towards lower volatilities, lower viscosities, higher CO₂uptake, etc. Physical properties (including density, viscosity, and gas solubilities) of N-functionalized imidazoles were recorded providing an initial database for comparisons to commercially-available organic solvents and imidazolium-based ILs. These results show that some novel N-functionalized imidazoles contend with common organic solvents for CO₂ separations in terms of dynamic processing properties (i.e. viscosity and CO₂ uptake). Imidazoles and ILs also provide a non-volatile media in which fugitive emissions and evaporative losses during solvent regeneration are reduced significantly. Chemical simulations and calculations via COSMOtherm software were also employed to rapidly predict thermophysical properties of these imidazoles and ILs, providing a means of screening of such novel solvents to be optimized for CO₂ separation processes. In the concluding chapters of this dissertation, continued research with the N-functionalized imidazole platform are noted, including areas of hybrid solvents, multiply-substituted, isomeric compounds, and imidazole-based polymeric media for acid scavenging (CO₂, SO₂, etc).
P22 virus templated synthesis of plasmonic photocatalytic nanostructures
(University of Alabama Libraries, 2015) Zhou, Ziyou; Gupta, Arunava; University of Alabama Tuscaloosa
The objective of the work presented in this dissertation is to examine the fabrication of novel viral-templated gold-cadmium sulfide (Au-CdS) plasmonic photocatalytic nanostructures and to investigate their photocatalytic behavior via photodegradation of methylene blue. Bacteriophage P22 shells, assembled from 420 copies of coat protein, have been demonstrated to act as selective biotemplates for the growth of ordered gold nanostructures in two different routes: 1) the incubation of gold precursor with P22 biotemplates before the addition of reducing agent; 2) and the direct reduction of gold precursor in the solution of P22 biotemplates with a pre-existing reducing agent. In both routes, gold nanocrystals could find their selective binding sites to form an ordered nanostructure over P22 shells. However, in our current study, the incubation of inorganic precursor with biotemplates, which is a common practice in the biotemplated synthesis of inorganic nanoparticles, did not produce better outcome compared to direct reduction without protein/gold precursor interaction. Genetically engineered scaffolding proteins evenly positioned inside P22 virus-like particles (VLP) can act as selective biotemplates for the constrained growth of CdS nanocrystals. The formation of CdS confined inside the VLP involves initial uniform nucleation and growth at the genetically engineered sites of the scaffolding proteins, followed by a more stochastic growth for longer reaction periods. The presence of the biotemplates does not affect the reaction order for the formation of CdS, but significantly influences the rate constant for the hydrolysis of thioacetamide (TA) and subsequent reaction of released S ions with Cd2+. Combining the coat protein templated synthesis of gold and the scaffolding protein templated synthesis of CdS, we have been able to utilize genetically engineered P22 VLP as a robust nanoplatform for fabricating gold/CdS plasmonic photocatalytic nanostructures. The controlled formation of gold nanoparticles on the outer shell of VLP-CdS dramatically enhances the photoactivity of CdS confined inside the VLP. However, the gold nanoparticles by themselves exhibit no significant effect on the photodegradation of MB. These findings are relevant for the synthesis of a wide range of alternative plasmonic photocatalytic materials with desired components, architectures, and performance.

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