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Ghods, MasoudEffect of Convection Associated with Cross-section Change during Directional Solidification of Binary Alloys on Dendritic Array Morphology and Macrosegregation
Doctor of Engineering, Cleveland State University, 2017, Washkewicz College of Engineering
This dissertation explores the role of different types of convection on macrosegregation and on dendritic array morphology of two aluminum alloys directionally solidified through cylindrical graphite molds having both cross-section decrease and increase. Al- 19 wt. % Cu and Al-7 wt. % Si alloys were directionally solidified at two growth speed of 10 and 29.1 µm s-1 and examined for longitudinal and radial macrosegregation, and for primary dendrite spacing and dendrite trunk diameter. Directional solidification of these alloys through constant cross-section showed clustering of primary dendrites and parabolic-shaped radial macrosegregation profile, indicative of “steepling convection” in the mushy-zone. The degree of radial macrosegregation increased with decreased growth speed. The Al- 19 wt. % Cu samples, grown under similar conditions as Al-7 wt. % Si, showed more radial macrosegregation because of more intense “stepling convection” caused by their one order of magnitude larger coefficient of solutal expansion. Positive macrosegregation right before, followed by negative macrosegregation right after an abrupt cross-section decrease (from 9.5 mm diameter to 3.2 mm diameter), were observed in both alloys; this is because of the combined effect of thermosolutal convection and area-change-driven shrinkage flow in the contraction region. The degree of macrosegregation was found to be higher in the Al- 19 wt. % Cu samples. Strong area-change-driven shrinkage flow changes the parabolic-shape radial macrosegregation in the larger diameter section before contraction to “S-shaped” profile. But in the smaller diameter section after the contraction very low degree of radial macrosegregation was found. The samples solidified through an abrupt cross-section increase (from 3.2 mm diameter to 9.5 mm diameter) showed negative macrosegregation right after the cross-section increase on the expansion platform. During the transition to steady-state after the expansion, radial macrosegregation profile in locations close to the expansion was found to be “S-shaped”. This is attributed to the redistribution of solute-rich liquid ahead of the mushy-zone as it transitions from the narrow portion below into the large diameter portion above. Solutal remelting and fragmentation of dendrite branches, and floating of these fragmented pieces appear to be responsible for spurious grains formation in Al- 19 wt. % Cu samples after the cross-section expansion. New grain formation was not observed in Al-7 wt. % Si in similar locations; it is believed that this is due to the sinking of the fragmented dendrite branches in this alloy. Experimentally observed radial and axial macrosegregations agree well with the results obtained from the numerical simulations carried out by Dr. Mark Lauer and Prof. David R. Poirier at the University of Arizona. Trunk Diameter (TD) of dendritic array appears to respond more readily to the changing growth conditions as compared to the Nearest Neighbor Spacing (NNS) of primary dendrites.

Committee:

Surendra Tewari, Ph.D. (Advisor); Jorge Gatica, Ph.D. (Committee Member); Orhan Talu, Ph.D. (Committee Member); Rolf Lustig, Ph.D. (Committee Member); Kiril Streletzky, Ph.D. (Committee Member)

Subjects:

Aerospace Materials; Automotive Materials; Chemical Engineering; Condensed Matter Physics; Engineering; Fluid Dynamics; High Temperature Physics; Materials Science; Metallurgy

Keywords:

Directional Solidification; Natural Convection; Fluid Flow; Binary Alloys; Macrosegregation; Dendritic Array; Dendrite Morphology; Solutal Remelting; Thermosolutal Convection; Aluminum Alloy; Cross section Change

Loman, Abdullah AlEnzyme Based Processing of Soybean Meal: Production of Enriched Protein Product and Utilization of Carbohydrate as Fermentation Feedstock for Arabitol Production
Doctor of Philosophy, University of Akron, 2016, Chemical Engineering
Soy protein is one of the major components of the diet of food producing animals and is increasingly important in the human diet as well. However, soy protein cannot be used as an ideal protein supplement in foods, because of the presence of high amount of indigestible carbohydrates in the soybean meal. Adverse nutritional and digestion effects have been reported in many animals and fish following the consumption of soybean meal and soybean meal derived products. To enhance the nutritional value of soybean meal in human food and animal feed, it is necessary to improve the protein content and remove the indigestible carbohydrates from the soybean meal during the processing of soy protein diets. This project aims to develop economically feasible technologies and processes for separating, enriching and upgrading soy proteins and carbohydrates from soybean meal. The objective is to separate proteins from carbohydrates (and other minor components) in soybean meal, facilitated by enzymatic hydrolysis of poly- and oligo-meric carbohydrates and other non-protein materials. The enriched proteins obtained are valuable for high-quality feed, food and industrial uses. The hydrolyzed carbohydrates could also be converted via fermentation into bio-fuel related products and other value added chemicals.

Committee:

Lu-Kwang Ju, Dr. (Advisor); George Chase, Dr. (Committee Member); Nic Leipzig, Dr. (Committee Member); Stephen Duirk, Dr. (Committee Member); Thomas Leeper, Dr. (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Enzyme hydrolysis, soy carbohydrate, arabitol, fermentation feedstock

Liu, ZhouyangHeterogeneous Catalytic Elemental Mercury Oxidation in Coal Combustion Flue Gas
PhD, University of Cincinnati, 2017, Engineering and Applied Science: Chemical Engineering
The new Mercury and Air Toxics Standards issued by US EPA require the reduction of mercury emissions from coal-fired power plants by 90% starting from 2016. Oxidizing elemental mercury using the HCl that exists in the flue gas or additional halogen and catalysts, followed by oxidized mercury capture in the wet Flue Gas Desulfurizer (FGD), is a viable option for mercury removal in coal-fired power plants. The aim of this study is to develop effective and reliable mercury oxidation catalysts, advance the mechanistic understandings of heterogeneous mercury oxidation, and obtain information on heterogeneous mercury oxidation kinetics. CuCl2 supported on ?-Al2O3 showed excellent Hg(0) oxidation performance and SO2 resistance at 140 °C. After extensive characterizations of the CuCl2/?-Al2O3 catalyst, the existence of multiple copper species was identified. It was found that CuCl2 forms inert copper aluminate on the surface of ?-Al2O3 at lower loadings. At higher loadings, CuCl2 exists in a highly dispersed amorphous form that is active for Hg(0) oxidation by working as a redox catalyst. The CuCl2/?-Al2O3 catalyst with high loadings has the potential to be used as a low temperature Hg(0) oxidation catalyst. RuO2 catalyst was found to be an excellent Hg(0) oxidation catalyst. When rutile TiO2 was used as the catalyst support, RuO2 formed well dispersed nano-layers due to the very similar crystal structures of RuO2 and rutile TiO2, giving higher Hg(0) oxidation activity over anatase TiO2 support. The RuO2/rutile TiO2 catalyst showed good Hg(0) oxidation performance under sub-bituminous and lignite coal simulated flue gas conditions with low concentration of HCl or HBr gas. It also showed excellent resistance to SO2. The RuO2/rutile TiO2 catalyst can be used at the tail end section of the SCR unit for Hg(0) oxidation. Linear combination fitting of the X-ray Absorption Near Edge Spectroscopy (XANES) was used to quantify oxidized mercury species over RuO2/TiO2 and SCR catalysts under different simulated flue gas conditions. In the absence of halogen gas, elemental mercury can react with sulfur that is contained in both the RuO2/TiO2 and SCR catalysts to form HgS and HgSO4. In the presence of HCl or HBr gas, HgCl2 or HgBr2 is the main oxidized mercury species. When both HCl and HBr gases are present, HgBr2 is the preferred oxidation product and no HgCl2 can be found. Other simulated flue gas components such as NO, NH3, SO2 and CO2 do not have significant effect on oxidized mercury speciation when halogen gas is present. Mechanistic and kinetic studies of the heterogeneous oxidation of Hg(0) by HCl gas over a RuO2/rutile TiO2 catalyst were conducted. The experimental evidence of HCl adsorption was obtained using in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). Based on this result, a steady-state kinetic study was conducted to determine an intrinsic reaction kinetic expression for Hg(0) oxidation over the catalyst under HCl, NH3 and SO2 gases for the first time. The kinetic expression obtained could reasonably predict the Hg(0) oxidation performance under the competitive adsorption of NH3 and SO2 gases.

Committee:

Joo Youp Lee, Ph.D. (Committee Chair); Anastasios Angelopoulos, Ph.D. (Committee Member); William Connick, Ph.D. (Committee Member); Peter Panagiotis Smirniotis, Ph.D. (Committee Member)

Subjects:

Chemical Engineering

Keywords:

heterogeneous catalysis;mercury removal;kinetic;mechanism;characterization;ruthenium oxide

Miranda, Michael AngeloBio Based Active Barrier Materials and Package Development
Doctor of Philosophy, University of Toledo, 2016, Chemical Engineering
The food and packaging industries are interested in approaches to reduce the permeability of oxygen in polyethylene terephthalate (PET) to extend the shelf-life of product. This has led to considerable research in barrier improvement including the use of active scavenger that permanently bind oxygen. The purpose of this work is to investigate the use of renewably sourced unsaturated fatty acids as scavengers to reduce the O¬2 permeability in PET. Specifically fatty acids were characterized and incorporated within PET using both blended and reactive extrusion to analyze the impact on thermal-mechanical and oxygen transport properties. Oleic, linoleic and linolenic acid are renewably resourced unsaturated fatty acids that are being investigated as active scavenger. Utilization of scavenger capacity and kinetics of oxidation are two key parameters that must be considered while selecting a scavenger. The O¬2 uptake capacities and the utilization of scavenger sites analysis were used to determine the most appropriate scavenger used to make a copolymer with PET. Linoleic acid was chosen due to its higher utilization capacity and relatively fast kinetics the cost was also taken into account. Thus linoleic acid was used in preparation of PET/Scavenger system. The effect of addition of unsaturated fatty acid on the thermal, mechanical properties and morphology of PET, were analyzed by preparing blends of PET/linoleic acid of loading of (0.25-2 weight %). The presence of the scavenger were analyzed using end group analysis where an increase in carboxyl end group was determined and NMR to obtain the peaks for the fatty acid. The appropriate method to determine molecular weight was also established. Effects of permeation through amorphous and biaxial oriented films with and without linoleic acid were investigated. The bottles were produced in two different ways (i) reactive extruded bottle and (ii) blended bottles (0.5% weight loading of Linoleic acid). The mechanical properties and density of the bottles were similar. The oxygen permeability of these bottles side wall was lower than that of PET. NMR on sample that has been exposed to oxygen was conducted to confirm the reactivity of linoleic acid with oxygen.

Committee:

Maria Coleman (Committee Chair); Saleh. A. Jabarin (Committee Co-Chair); Sridhar Vimajala (Committee Member); Yakov Lapitsky (Committee Member); Young- Wah Kim (Committee Member)

Subjects:

Chemical Engineering; Gases; Packaging; Polymers

Mamtani, KuldeepCarbon-based Materials for Oxygen Reduction Reaction (ORR) and Oxygen Evolution Reaction (OER) in Acidic Media
Doctor of Philosophy, The Ohio State University, 2017, Chemical Engineering
Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are electrochemical reactions of paramount importance considering the global energy scenario. One of the challenges here is posed by the slow kinetics of these reactions necessitating Pt-based and Ir-based catalysts respectively. The fact that both Pt and Ir are expensive and rare has raised significant interest in the scientific community towards developing low-cost, active and stable ORR and OER catalysts. The present study demonstrates the promise of two carbon-based catalyst materials namely iron-nitrogen-carbon (FeNC) and nitrogen-doped carbon nanostructures (CNx) in this regard. A combination of catalyst synthesis, electrochemical testing and characterization experiments has been used to study ORR and OER on FeNC and CNx catalysts. Valuable insights on the nature of active sites in these catalysts will be instrumental in understanding the detailed ORR mechanisms and designing these catalysts with high active site density. A brief introduction and pertinent literature review on the subject is provided in chapter 1. The principles of electrochemical testing and characterization tools extensively used in this work are discussed in chapter 2. Chapter 3 provides our results on using CO as a probe to investigate the nature of ORR active sites in FeNC catalyst materials. Significant decrease was observed in the ORR activity upon CO exposure demonstrating that Fe is an essential part of ORR active site for FeNC catalyst materials. We attribute this loss in activity to strong binding of CO to FeNC catalyst surface. These results on FeNC catalysts were in sharp contrast to those obtained previously by our group on CNx catalysts where no change in ORR activity was noted after CO exposure. Chapters 4 and 5 present our strategies to identify the actual active sites in FeNC and CNx catalysts. Planar FeN4 (Fe2+, LS) with Fe (II) ion coordinated to four pyrrolic nitrogen atoms and attached to the carbon support was identified as the ORR active site in FeNC catalysts by combining Mossbauer spectroscopy and electrochemical measurements. On the other hand, phosphate ion poisoning was used as a probe for CNx catalysts. Pyridinic-N species on edges of carbon planes were found to be important in imparting ORR activity to CNx. Chapters 6 and 7 demonstrate that FeNC and CNx catalysts are promising bifucntional materials for ORR and OER. They exhibit significantly lower combined overpotential than those by state of the art catalysts namely Pt/C (for ORR) and Ir/C (for OER). The ORR activity, OER activity as well as bifunctionality were found to increase with pyridinic-N content for CNx catalysts. CNx catalysts were resistant to chloride ion poisoning and were extremely stable in HCl electrolyte. This demonstrates their promise as cathode catalysts for oxygen depolarized cathode (ODC)-based HCl electrolysis to manufacture chlorine. Results are described in chapter 8. Chapter 9 points out key conclusions and future research directions.

Committee:

Umit Ozkan (Advisor); Anne Co (Committee Member); Aravind Asthagiri (Committee Member); Sheryl Szeinbach (Committee Member)

Subjects:

Chemical Engineering; Engineering

Seeley, Marisa AInteractions of Additives on Surfaces via Temperature Programmed Desorption
Master of Science in Engineering, University of Akron, 2017, Chemical Engineering
Motion under load between any two surfaces that are in contact with each other most likely will develop damage. Lubricants are used between two surfaces in contact to reduce the amount of damage which occurs. Within these lubricants, additives are included to further enhance the beneficial properties such as anti-wear. The overall goal of this project is to build reaction mechanisms and achieve activation energies for the surface reactions that take place. The analogs di-tert-octyl polysulfide (DTOPS) was used for the sulfur class, triphenyl phosphate (TPP) was used for the phosphorous class, and zinc dialkyldithiophosphate (ZDDP) was used for the SP class. Additionally, mineral oil (MO) and fully formulated (FF) oil provided additional information within the scope of this research. Temperature programmed desorption (TPD) was used to identify the reaction species as they desorb from the surface. These surfaces were then analyzed by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis, Fourier transfer infrared (FTIR) spectroscopy, and Raman spectroscopy. Tribological tests such as high frequency reciprocating rig (HFRR) testing studied the wear between two surfaces. The HFRR testing was performed with neat additives, which resulted in the sulfur class to perform the worst, the phosphorous class next, and the SP class performed the best. The HFRR data are used to calculate activation energies in the tribological contact based on the time and temperature that the wear regime begins. The TPD data are used to calculate the activation energies in the bulk desorption inside of a vacuum chamber. The activation energies are compared to see how they change from tribological contact to the bulk desorption. Suggested reaction mechanisms that follow the results are presented.

Committee:

Gary Doll, Dr. (Committee Chair); Paul Shiller, Dr. (Committee Member); Edward Evans, Dr. (Committee Member)

Subjects:

Chemical Engineering; Engineering

Keywords:

Temperature Programmed Desorption; TPD; lubrication; tribology; friction; wear; desorption; kinetics; reaction mechanisms;

Zhan, XunCrystallization Micro-mechanism of Amorphous Ni-P
Doctor of Philosophy, Case Western Reserve University, 2017, Materials Science and Engineering
The crystallization of near-eutectic amorphous Ni–P can be significantly retarded by alloying a small fraction of tungsten. Complimentary characterization techniques are applied to understand this phenomenon. DSC (differential scanning calorimetry) reveals the isochronal and isothermal crystallization kinetics. XPS (X-ray photoelectron spectroscopy) provides core-level electronic signatures of Ni, phosohorus and tungsten, which reflect SRO (short-range order) evolution during crystallization. FEM (fluctuation electron microscopy) provides the MRO (medium-range order) evolution during crystallization. TEM (transmission electron microscopy) provides high-spatial-resolution information on phase nucleation and spatial distribution of atom species. Physical theory has been developed by combining results of these techniques to explain the role of tungsten: Macroscopic aspect (energetics and kinetics), the presence of tungsten reduces the driving force and increases the activation energy for crystallization. Microscopic aspect (micro-mechanistics), the presence of tungsten probably reduces the free volume (hypothesis) due to large atomic radius ratios of rW/rNi and rW/rP; introduces tungsten atoms diffusion to segregate due to chemical potential difference of tungsten in different crystalline phases; involves the breaking of all of W–P bonds with high bond energy. Moreover, theoretical criteria of an effective metal X alloying to improve the thermal stability of M–ML (metal–metalloid) amorphous systems has been proposed. The criteria are: (1) Large negative heat of mixing among X, M and ML. (2) Minimum amorphous free volume by appropriate combination of rX, rM and rML. (3) Large chemical potential difference of X in minor than in major crystalline phase. (4) Large X–ML and X–M bond energy. The criteria conclude on what other potential alloying elements will do, which has implications for fundamental science and technologies. In addition, magnetization curves of as-plated and tempered Ni80P20 and Ni76W4P20 were measured by VSM (vibrating sample magnetometer). Alloying tungsten does not change the paramagnetism of amorphous Ni80P20, but decreases the saturation magnetization of Ni80P20 after crystallization.

Committee:

Frank Ernst, Dr. (Advisor); John Lewandowski, Dr. (Committee Member); Matthew Willard, Dr. (Committee Member); Rohan Akolkar, Dr. (Committee Member)

Subjects:

Chemical Engineering; Materials Science

Amaya, Andrew JFreezing Supercooled Water Nanodroplets near ~225 K through Homogeneous and Heterogeneous Ice Nucleation
Doctor of Philosophy, The Ohio State University, 2017, Chemical Engineering

This work studies the freezing of supercooled water droplets, <r> ~10 nm, both in the pure liquid state and as mixtures with n-pentanol. The supercooled droplets are formed via homogeneous vapor-liquid nucleation of H2O vapor in a supersonic nozzle. Using an aerosol method for droplet formation is advantageous because the high particle number density, ~1018 kg-1, generated ensures that the droplets are unlikely to contain any contaminants. Avoiding contaminants is important for our study because pure supercooled water freezes through homogeneous liquid-solid nucleation and the presence of contaminants can change the mechanism of freezing to heterogeneous nucleation. The primary goals of our study are to use Wide Angle X-ray Scattering (WAXS) to gain insight into the structure of the frozen droplets during and after freezing has completed. In addition, we seek to explore the ice nucleation rates of droplets at temperatures close to but still colder than the homogeneous freezing limit, TH ~235 K, which marks the boundary of water’s "no man’s land".

Our WAXS experiments were conducted on the Coherent X-ray Imaging (CXI) beamline at the Linac Coherent Light Source (LCLS) user facility of the SLAC National Laboratory. We successful observed scattering from frozen droplets as distinct concentric rings indicating crystalline particles. Although the diffraction pattern resembles that of pure cubic ice I, Ic, analysis is more consistent with stacking-disordered ice, Isd, which is a crystal structure composed of layers of both Ic, and hexagonal ice, Ih. By comparing the experimental results to theoretically predicted scattering spectra for particles with specific cubicities and sizes, we found that ~80% of the crystal layers are Ic making our crystals some of the purest experimentally produced cubic ice.

To complement the WAXS experiments, we determined the ice nucleation rates of these droplets using a combination of pressure trace measurements (PTM), Fourier Transform Infrared Spectroscopy (FTIR), and Small Angle X-ray Scattering (SAXS). We confirmed that the onset of droplet freezing is at ~225 K. Within in the temperature range of 217 K to 225 K, we find that the ice nucleation rate varies from ~1021 cm-3 s-1 to ~1022 cm-3 s-1. These results fill a gap along the ice nucleation vs temperature curve that had been unexplored and represent a sharp corner for ice nucleation rates of small droplets. This sharp transition in nucleation rates is difficult to replicate with theory.

Finally, we explored the changes to freezing of supercooled water droplets, <r> ~7 nm, in the presence of a n-pentanol monolayer. The amount n-pentanol was varied from 3 to 6 mol% of the condensable and distinct differences were observed in the FTIR spectra when pure water droplets froze compared to when water/n-pentanol droplets froze. Quantifying these changes and relating them to the freezing mechanism is the subject of future work.

Committee:

Barbara Wyslouzil (Advisor); Isamu Kusaka (Committee Member); David Tomasko (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Homogeneous and Heterogeneous Ice Nucleation; freezing of supercooled water droplets

Stapleton, Jacob DSYNTHESIS OF UPPER CRITICAL SOLUTION TEMPERATURE POLYMER FOR APPLICATIONS IN BIOTECHNOLOGY
Master of Science, Miami University, 2017, Chemical, Paper & Biomedical Engineering
There has been significant interest in the conjugation of proteins with lower critical solution temperature (LCTS) polymers such as poly(N-isopropylacrylamide). These protein-polymer conjugates, which become insoluble with an increase of temperature, have been studied as a means to increase protein stability, modify enzyme activity, and for applications such as biocatalysis, bioseparations, and drug delivery. There are very few examples of protein-polymer conjugates with upper critical solution temperature (UCST) polymers. In this case, proteins conjugated with UCST polymers would become insoluble by lowering the temperature below the UCST temperature. This type of protein-polymer conjugate could be especially useful for recovery and recycling of temperature sensitive proteins. In this study, RAFT polymerization was used to create a family of UCST polymers composed of a random copolymer of acrylamide and acrylonitrile (p(AAm-co-AN) and of the zwitterionic polymer poly(N,N’-dimethyl(methacryloylethyl)ammonium propane sulfonate) (pDMAPS). The resulting polymers were studied to determine the impact of polymer chain length, polymer composition, solution pH and salt concentration on the cloud point temperature. Different approaches to synthesize protein-polymer conjugates with UCST polymer were explored.

Committee:

Jason Berberich (Advisor); Justin Saul (Committee Member); Jessica Sparks (Committee Member)

Subjects:

Chemical Engineering; Chemistry; Polymer Chemistry; Polymers

Blickensderfer, Jacob KElectroless Deposition of Amorphous Iron-Alloy Coatings
Doctor of Philosophy, Case Western Reserve University, 2018, Chemical Engineering
Electroless Deposition of Amorphous Iron-Alloy Coatings Abstract by Jacob K. Blickensderfer Amorphous iron alloys are a potentially benign alternative for replacing nickel-phosphorus films commonly used in electronics and surface finishing applications. In addition to being environmentally friendly, the amorphous iron alloys provide excellent corrosion resistance, solderability and micro hardness. In this work, electroless deposition of two such iron alloys, i.e., iron boron (FeB) and iron phosphorus (FeP), is investigated. A process for electroless deposition of FeB without the use of substrate activation is developed. Mixed potential behavior and polarization behavior of individual half-reactions occurring during electroless FeB deposition are characterized, and then used to elucidate the process conditions necessary for activation-free electroless FeB deposition. Corrosion resistance of amorphous FeB films deposited using this newly developed process is tested and the corrosion current is determined to be 31.1 µA/cm2, which is an order of magnitude lower than that typical of crystalline Fe deposits. Unlike FeB deposition, electroless FeP plating critically needs substrate activation by palladium (Pd). The role of substrate (Cu) activation by Pd in enabling electroless FeP deposition is studied in depth. Specifically, it is demonstrated that a critical Pd surface coverage of 10.6% is essential for spontaneous electroless FeP deposition to commence. Below this critical Pd coverage, the surface is catalytically inactive for FeP deposition. A mechanistic model that incorporates surface heterogeneity due to partial Pd coverage of Cu and the effect of this heterogeneity on electrocatalysis of the reductant oxidation reaction during electroless deposition is presented. Model predictions are compared to experimental observations of the electroless surface mixed potential to gain insights into the mechanism by which Pd catalyzes electroless FeP deposition. Implications of these findings to the optimization of pretreatment and activation processes commonly used in electroless deposition systems is discussed.

Committee:

Rohan Akolkar (Advisor); Uziel Landau (Committee Member); Heidi Martin (Committee Member); Mark De Guire (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Electroless; Corrosion Resistant Coatings; Iron Alloys; Iron Phosphorus; Iron Boron

Najfach, Aaron JacobEFFECT OF MANGANESE AND ZEOLITE COMPOSITION ON ZEOLITE-SUPPORTED NICKEL CATALYSTS FOR DRY REFORMING OF METHANE
Master of Science, Miami University, 2017, Chemical, Paper & Biomedical Engineering
Dry reforming of methane (DRM) is a reaction of interest for utilizing two greenhouse gases, carbon dioxide and methane, for syngas production. Catalysts are used to facilitate DRM as high temperatures are required. Noble metals are chosen for their effectiveness; however, these metals are expensive. Nickel as a substitute for DRM catalysts has interest for its low relative cost while still exhibiting effectiveness. Carbon deposition from side reactions is a concern as it causes catalysts fouling. To address this, addition of a second metal has shown success at facilitating the consumption of built-up carbon. Manganese has shown promise as an inexpensive second metal for this purpose. This study examines the effect of manganese loading on nickel catalysts and the effect different zeolites have on DRM. Samples were characterized with BET analysis, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Thermogravimetric Analysis (TGA). Catalysts were tested for activity and carbon deposition. It was found that the addition of manganese has a beneficial effect on reducing catalyst fouling. It was also found, over 24 hours, zeolite type had some effect on catalyst activity and may influence carbon formation. The role of manganese and sodium on zeolite destruction is also discussed.

Committee:

Catherine Almquist (Advisor); Andrew Paluch (Committee Member); Douglas Coffin (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Catalysis, Dry reforming, methane, carbon dioxide, syngas, nickel, manganese, zeolites

venoor, varun Investigation of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/Natural Rubber blends and Polystyrene/Polybutadiene Silica Nano-Composites
Master of Science, The Ohio State University, 2017, Chemical Engineering
Increased use of bio-based polymers and rubbers could help decrease our dependency on fossil fuel feedstocks. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a semicrystalline polymer. PHBV gets its importace from being biocompatible and biodegradable. Virgin PHBV is a brittle thermoplastic with high water and oxygen transmission rates. Also, PHBV has poor thermal properties above 160ºC, thus limiting its packaging application. It has been previously demonstrated that improved bioplastic properties (increased softness and flexibility) can be achieved by blending natural high viscosity rubber (gel) extracted from natural rubber, with PHBV. These blended materials proved suitable for making TV trays and blown films. However, commercial sources of high viscosity natural rubber were found to no longer exist. The preliminary objective of this work was to manufacture peroxide cured high viscosity natural rubber matched to that of natural rubber gel so that the bioplastic-rubber blend could be scaled up to commercially meaningful volumes. A new organic peroxide cure system was sourced, which is completely consumed during an initial heating step and so can be used to induce controlled and complete crosslinking. Hence, organic peroxide cured matched viscosity natural rubber (MVNR) was developed to achieve properties comparable to that of high viscosity rubber (Hevea gel). Different lodgings of peroxide such as 0.5, 1, 1.5, 2 phr (parts per hundred rubber) were considered. Rheological and mechanical testing’s were conducted on each of the peroxide cured natural rubber samples. 2phr peroxide (Luperox101XL45) cured natural rubber (SMR-L) at 180oC was found to have higher complex viscosity than Hevea gel. This matched viscosity natural rubber is referred as MVNR. Our next step was to incorporate this MVNR into a PHBV matrix. Dynamic vulcanization effectively dispersed and vulcanized the elastomeric (MVNR) phase within the thermoplastic (PHBV) matrix. Such systems are called thermoplastic vulcanizates (TPV) or thermoplastic elastomers (TPE). A two-stage process was employed to produce these TPVs. Firstly, 2, 5, 10, 15, 20 and 25 percent weight loadings of natural rubber (SMR-L) were melt blended with PHBV in a twin-screw extruder. These blends were then dynamically vulcanized with required the quantity of peroxide (2phr on weight loading of rubber) to produce TPVs. These TPVs were characterized for thermal properties and rheological properties. FTIR spectroscopic analysis was conducted to investigate the interfacial interaction between the cross-linked elastomer and PHBV matrix. In the recent years, the need for reduction in rolling resistance (low hysteresis tire tread) and increased traction of tires has taken center stage. Fillers such as silica (silane modified and unmodified) and carbon black have been extensively used in the tire industry improve properties of virgin polymers. The presence of nanoparticle fillers within the polymer matrix is known to alter molecular mobility, relaxation behavior, free volume, crystallization and glass transition temperature (Tg) of the resulting composites. Desorption and re-adsorption of polymer chains near nanoparticles is an important mechanism determining hysteresis. In-depth understanding of polymer-filler interaction is still needed. To understand the physics of polymer-filler interaction, simple filled polymeric systems were investigated. Virgin polybutadiene (PBD) and polystyrene (PS) was reinforced with unfunctionalized and silane functionalized silica. Reinforcement of filler was carried out using melt blending in a DACA micro-compounder and solvent casting. The rheological analysis was carried on pure and silica filled PBD and PS systems. Viscoelastic properties of unfunctionalized silica/polymer (PBD and PS) and functionalized silica/polymer (PBD and PS) were measured: the loss and storage modulus of both the system increased with loading. The increase in storage modulus is attributed to increased polymer-filler interaction, rendering it to be elastic sold in nature. In future, the dielectric spectroscopic analysis will be carried out to understand polymer relaxation behavior within the unfunctionalized silica/polymer and silane functionalized silica/polymer system.

Committee:

Koelling Kurt , PhD (Advisor); Cornish Katrina, PhD (Committee Member); Vodovotz Yael, PhD (Committee Member)

Subjects:

Chemical Engineering; Packaging; Plastics; Polymer Chemistry; Polymers

Keywords:

PHBV, Natural Rubber, Peroxide, Dynamic Vulcanization, Polystyrene, Polybutadiene, Silica

Sriram, VishnuStudy of Reaction Kinetics for Elemental Mercury Vapor Oxidation for Mercury Emission Control
MS, University of Cincinnati, 2017, Engineering and Applied Science: Chemical Engineering
Elemental mercury (Hg(0)) is a persistent, toxic metal that is released during the combustion of coal in power plants. Its toxicity, and bioaccumulation is of concern for public health and the environment. The need to control and capture mercury is of importance and relevant in today’s world since coal still plays a significant role as it is one of the major energy sources in the United States. While elemental mercury is difficult to capture, oxidized mercury (Hg(2+)) is captured easily due to its high solubility in water and its ability to easily adsorb onto sorbents such as powdered activated carbon (PAC). Previously in our lab, CuCl2-based substrates have been tested and has shown good potential to play a role in oxidizing Hg(0). Mechanistic studies have been performed on CuCl2-based substrates and a fundamental understanding of the adsorption of Hg(2+) onto activated carbon (AC) has been investigated in the past. In order to understand the oxidation kinetics of CuCl2 and the role it plays in oxidizing Hg(0) oxidation using CuCl2-based substrate, experiments and kinetic simulations were performed to obtain the activation energy for this reaction. It was found that CuCl2 played an important role in lowering the activation energy for this reaction compared to other reported values of Hg(0) oxidation catalysts under HCl and O2 conditions. This work is discussed in Chapter 2. In addition, we wanted to study the various factors that can impact the adsorption of Hg(2+) in the ductwork and fabric filter by raw AC injection in coal combustion flue gas. Factors such as internal, external mass transfer, inlet HgCl2 concentration, sorbent loading, and particle size were studied and its impact on the performance was investigated. In-flight Hg(2+) removal was found to be negligible while comparatively, the removal of Hg(2+) in the fabric filter was better but it was negligible nevertheless. For the removal of Hg(2+) in fabric filter, the effect of particle size was significant. A novel discontinuous injection mode was used and resulted in higher sorbent utilization. However at the end of the cleaning cycle, most of the sorbent capacity was < 0.2%. This work is discussed in Chapter 3.

Committee:

Joo-Youp Lee, Ph.D. (Committee Chair); Anastasios Angelopoulos, Ph.D. (Committee Member); Peter Panagiotis Smirniotis, Ph.D. (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Reaction kinetics;heterogeneous elemental mercury oxidation reaction;cupric chloride;mercury emissions control;grain model

pottimurthy, yaswanthIron-Based Coal Direct Chemical Looping Process: Operation of Sub Pilot Scale Unit with Ohio #6 Bituminous Coal
Master of Science, The Ohio State University, 2017, Chemical Engineering
The coal direct chemical looping process is an advanced oxy-combustion process where the oxygen required for fuel combustion is provided by iron based oxygen carrier rather than the conventional air separation unit. The integrated 25 kWth sub-pilot unit designed and developed at Ohio State University is the first chemical looping demonstration system that consists of a countercurrent moving bed for coal conversion. To date, the sub pilot unit has been successfully operated for more than 1000 hours with various fuels such as metallurgical coke, sub-bituminous coal, lignite coal and biomass, with a 200 hours continuous operation that demonstrated the ability of the process to achieve high conversions along with low oxygen demand and high carbon capture efficiency. However, the process was not operated with Ohio-based bituminous coals, which have a high caking propensity. The moving bed design poses a challenge to the smooth injection of bituminous coals. The lack of agitation in the moving bed reactor combined with caking tendencies of bituminous coals causes unstable stable solid circulation which affects reaction conversion, flow hydrodynamics and overall system performance. Thus, decaking of bituminous coals to allow smooth injection is highly desired to operate CDCL system successfully. To achieve this goal, this work focuses on utilizing low temperature partial oxidation of bituminous coals in a fluidized bed as a method to reduce the caking tendency of bituminous coals. Subsequently, the smooth flowability of various partially oxidized bituminous coals prepared is validated by testing those coal samples on a bench scale moving bed reducer, which is a scaled down version of sub-pilot CDCL moving bed reducer. Finally, this work discusses the operational experience of integrated sub pilot unit with 50/50 mixture by mass of sub-bituminous coal (PRB) and partially oxidized bituminous coal as a feedstock that was proven successful from bench scale moving bed tests. Sub-pilot operation achieved high coal conversion with high purity of carbondioxide in the reducer. The combustor gas analysis also confirms trace amounts of carbonaceous species indicating minimal carryover of char from reducer.

Committee:

Liang-Shih Fan, PhD (Advisor); Andre Palmer, PhD (Committee Member)

Subjects:

Chemical Engineering

Keywords:

coal, coal direct chemical looping, moving bed, fluidization

Lacdao, ClaudineInfluence Of Cross-Section Change During Directional Solidification On Dendrite Morphology, Macrosegregation And Defect Formation In Pb-6 wt Sb Alloy
Master of Science in Chemical Engineering, Cleveland State University, 2017, Washkewicz College of Engineering
The purpose of this research is to examine the dendrite array morphology, macrosegregation, and defect formation caused by the fluid flow at the abrupt cross-section changes during directional solidification of Pb-6% Sb alloy. Four 24-cm long cylindrical alloy samples were directionally solidified in graphite crucibles: two having a constant diameter (9-mm) grown at 10.4 and 63.1 μm s-1 , one having an abrupt cross-section decrease (from 12.7 to 6.35 mm) and one having an abrupt increase (from 6.35 to 12.7 mm) by pulling down the alloy containing cylindrical graphite crucibles from the upper hot-zone of a stationary vertical furnace into its cold-zone below. Microstructures were examined on transverse slices cut along the length of the directionally solidified samples. Dendrite spacing and distribution were characterized on these transverse sections. The Pb-6% Sb alloy was selected as a low melting point analog for commercially used multicomponent nickel-base superalloys, because its thermophysical properties are well characterized. Also, a density inversion occurs in the inter-dendritic melt in the “mushy-zone” during directional solidification of this alloy, because the density of the melt decreases as Sb content increases from the array tips at the top of the mushy zone to the eutectic at their bottom. In constant cross-section crucibles, the formation of dendrite-trees in the mushy zone will be subject only to this “plume type” convection as solidification proceeds from the bottom end of the crucible to its top. Whereas in crucibles with abrupt cross-section change, the solidifying mushy-zone will be subject to additional “cross-section change induced” solidification shrinkage flow, when the speed of the liquid flowing downwards to feed the solidification shrinkage occurring below, will either suddenly accelerate or decelerate, because of the abrupt area change. This sudden change in the incoming fluid speed may break slender side-branches of dendrite trees. These broken dendrite fragments may rotate, sink, and grow further to develop into misaligned “spurious” grains. The “plume type of flow” is different than the “steepling convection flow” which was recently examined during directional solidification of Al-19% Cu and Al-7% Si alloys by Dr. Masoud Ghods in our laboratory.

Committee:

Surendra Tewari, Ph.D. (Committee Chair); Orhan Talu, Ph.D. (Committee Member); Christopher Wirth, Ph.D. (Committee Member); Nolan Holland, Ph.D. (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Cross-Section Change; Directional Solidification; Dendrite Morphology; Macrosegregation And Defect Formation In Pb-6 wt Sb Alloy; Density Inversion; Dendrite Trunk Diameter; Nearest Neighbor Spacings; Lead Antimony Alloy; Binary Alloy

Richardson, Kristopher EmilOxygenation Potential of Tense and Relaxed State Polymerized Hemoglobin Mixtures: A Potential Therapeutic to Accelerate Chronic Wound Healing
Doctor of Philosophy, The Ohio State University, 2017, Chemical Engineering
In the United States, millions of people are affected by chronic wounds every year. Chronic wounds are characterized by low levels of oxygen (O2) and high levels of pro-inflammatory macrophages that fail to transition to the anti-inflammatory, pro-healing macrophages. There is a need for a therapeutic that simultaneously targets multiple deficiencies of chronic wounds in order to promote healing and avoid devastating outcomes. The main goal of this dissertation is to engineer the oxygen affinity of pure tense state (T-state) and relaxed state (R-state) polymerized hemoglobin (Hb) (PolyHb) mixtures. These mixtures could be topically administered to a chronic wound in order to accelerate the wound healing process by increasing the oxygen flux and exerting additional therapeutic effects by attracting and promoting pro-healing, anti-inflammatory macrophages. To our knowledge, none of the Hb wound healing therapeutics currently in existence use PolyHb mixtures. The partial pressure of oxygen (pO2) of a chronic wound can range from 2-20 mm Hg. By controlling the oxygen affinity (P50 ) of the PolyHb mixture, it is possible to control the pO2 range where the majority of oxygen delivery occurs at the wound site. Therefore, engineering PolyHb mixtures possessing a P50 range of 2-30 mmHg should elucidate the role P50 plays in accelerating wound healing and increasing wound pO2. This dissertation focuses on the development, characterization, and oxygenation potential of human and bovine PolyHb mixtures consisting of pure R-state and T-state PolyHb. This work presents analysis of the biophysical properties of R-state and T-state mixtures for both human and bovine polymerized Hb (PolyhHb and PolybHb) (Chapter 2). In addition, presented is the oxygenation potential of PolyHb mixtures using Comsol Multiphysics to simulate O2 transport in a hepatic hollow fiber bioreactor (Chapter 3). We produced PolyHb by polymerizing Hb using the chemical crosslinker glutaraldehyde, thereby creating pure 35:1 T-state PolyHbs and pure 20:1 R-state PolyHbs. PolyHb mixtures were formulated by combining pure T- and R-state PolyHb solutions at different mole fractions. We created PolyHb mixtures possessing a large P50 range: 1.5-31 mm Hg for PolyhHb mixtures and 2-37 mm Hg for PolybHb mixtures. We observed that increasing the T-state mole fraction in the mixture linearly increased the P50 for both PolyhHb and PolybHb mixtures. Our simulations revealed that T-state PolyHbs have better oxygenation potential under in vivo O2 tensions, while R-state PolyHbs may be better suited to oxygenate hypoxic tissue. Liver zonation and O2 delivery can be controlled by adjusting the mole fraction of T-state PolyHb in the mixture. Therefore, to replicate in vivo O2 tensions, it is recommended that mixtures of PolybHb contain a mole fraction of no less than 0.25 T-state PolybHb and PolyhHb mixtures contain no less than 0.40 T-state PolyhHb. The results of this dissertation will be used to guide the future work using of PolyHb mixtures in wound healing studies. In addition, this work also helps to advance the state of the next generation of hemoglobin based O2 carriers for use in tissue engineering, transfusion medicine, and wound healing applications.

Committee:

Andre Palmer, Dr. (Advisor); David Wood, Dr. (Committee Member); Jeffery Chalmers, Dr. (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Chronic Wound Healing;Polymerized Hemoglobin;oxygen transport;hemoglobin-based oxygen carrier; HBOC

Colahan, Martin L.Formation of Black Powder Components by Dewing and Hygroscopic Corrosion Processes
Master of Science (MS), Ohio University, 2017, Chemical Engineering (Engineering and Technology)
The presence of black powder in natural gas pipelines can lead to equipment erosion, valve failure, instrumentation malfunction, and increased pressure drop. However, despite its impact on downstream and midstream operations, black powder production is poorly understood. In the present work, black powder formation as a result of corrosion was investigated by simulating sales gas conditions in a glass cell. Steel specimens were systematically exposed to a range of CO2, H2S, and O2 partial pressures at differing water condensation rates. The potential for hygroscopic material assisting black powder formation was also investigated. Friable corrosion products found in dewing conditions consisted of siderite, mackinawite, and hematite. Buckle-driven delamination was identified as a leading cause of black powder production from FeS. The presence of hygroscopic NaCl crystals facilitated corrosion at relative humidities as low as 33%, but flakey corrosion products were only found if deliquescence occurred.

Committee:

David Young (Advisor); Marc Singer (Committee Member); Srdjan Nesic (Committee Member); Rebecca Barlag (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Black Powder; Corrosion; Natural Gas; Dewing Corrosion; Hygroscopic Corrosion

Lalsare, Amoolya DattatrayaHigh Pressure Steam Reactivation of Calcium Oxide Sorbents For Carbon Dioxide Capture Using Calcium Looping Process
Master of Science, The Ohio State University, 2016, Chemical Engineering
Calcium looping is a sorbent based chemical looping process that uses calcium oxide or similar calcium sorbent precursors for pre-/post-combustion carbon dioxide capture. Extensive study of this process at the Ohio State University has led to the development of two variants of this process: Carbonation-calcination reaction (CCR) process for post-combustion carbon capture in electricity generation and calcium looping process (CLP) for pre-combustion carbon capture in hydrogen production and electricity generation. CCR is a cyclic post-combustion carbon capture process, demonstrated at a 120 KWth scale at OSU. This demonstration achieved more than 90% carbon dioxide removal and over 99% sulfur dioxide (SO2) removal. It has been shown through process simulations that CCR process induces less energy penalty than the conventional amine/oxy-combustion based carbon dioxide capture technologies. This process involves carbonation-calcination-steam hydration of calcium sorbents. Steam hydration is a reactivation step which mitigates the effect of sintering of sorbents during calcination, regenerates the sorbent surface, and retains carbon capture capacity over a large number of cycles. High pressure steam reactivation of calcium sorbents was investigated and the dependence of hydration rate on steam pressure is obtained. Higher steam partial pressure allows for higher temperatures (500-550oC) to get higher hydration conversions. The reaction being highly exothermic (-109 kJ/mol), high temperature gives high quality heat which can be used elsewhere in the process. Reaction kinetics of steam hydration for four different limestone based sorbents was studied using high pressure thermogravimetric analysis. Elevated pressures (1-3.5 atm) and high temperature (500-530oC) were used in this study. Steam hydration of PG Graymont limestone sorbent experimentally showed second order w.r.t steam pressure driving force (PH2O – P*H2O). Rate constants for each operating conditions were calculated and activation energy of the reaction was computed from these calculations. The activation energy obtained from this study is 5.18 KJ/mol. Nitrogen physisorption studies were performed for characterization of the sorbents and their reactivity was compared via the steam hydration studies in the TGA at 500oC and PH2O 1.5 atm. CaO sorbent derived after hydration shows the highest surface area and pore volume, which is more than 6-10 times that of the sorbent derived by calcination of CaCO3. This study is a strong indication that hydration with water/steam regenerates the sorbent morphology, in process reactivating the sorbents with high porosity. It is believed, however, that initial particle size has little or no bearing on the reactivation process or sorbent reactivity in the multi-cyclic studies as hydration causes particle breakage. This study is significant in regard to the post-combustion and pre-combustion carbon capture calcium looping processes developed at OSU as the hydration temperature would be comparable to the carbonator temperature as it is expected to make the processes economically viable. There exists a trade-off however for the steam pressure to be used for hydration. Very high steam pressure would incur high compression costs and affect the energy penalty of the process. This could deter the compensating effect of heat recovered from the hydrator and in turn make the process more energy intensive. This study is limits the pressure to 4-5 times the atmospheric pressure and still obtain higher conversions.

Committee:

Liang-Shih Fan, Distinguished University Professor (Advisor); Andre Palmer, Professor (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Calcium Looping Process, Carbon Dioxide Capture, Steam Hydration Reactivation of Calcium Sorbents, Activation Energy

HE, ZHUOHUI JOEEffects of digestate, magnesium sulfate, and dipotassium hydrogen phosphate/potassium dihydrogen phosphate on microalga, Scenedesmus dimorphus
Master of Science in Chemical Engineering, Cleveland State University, 2016, Washkewicz College of Engineering
Digestate (D), the remaining substance after anaerobic digestion of a biodegradable feedstock, is rich in inorganic contents, which makes it a good candidate for growing algae for biofuel production. Previous studies showed digestate at around 1.25% to 1.75% (v/v) dilution is suitable for algae growth. In this study, magnesium sulfate (MgSO4) and dipotassium hydrogen phosphate/potassium dihydrogen phosphate (K-P) were added to diluted digestate growth media. Two sets of experiments were conducted in batch reactor mode to identify the digestate (D), magnesium sulfate (MgSO4) and dipotassium hydrogen phosphate/potassium dihydrogen phosphate (K-P) concentrations that would optimize the algae growth. Algae growth parameters, such as maximum growth rate (r) and maximum algae concentration (Xmax) were estimated by using non-linear regression with a four-parameter logistic equation. Average biomass productivity (Pa), instantaneous biomass productivity (Pi), and specific growth rate (ug) were also calculated. This study used a central composite design. A surface response regression equation was generated for each of these algae growth parameters; the equation contained linear terms, quadratic terms, and the first order interaction terms of the three factors (D, MgSO4, and K-P). The resulting regression models showed both the maximum growth rate and the maximum algae concentrations were mainly dependent on digestate. The highest maximum growth rate was obtained at around 1% (v/v) digestate dilution. Within the tested digestate dilutions (0.184 to 1.817% (v/v)), maximum algae concentration increases with digestate concentration. In addition, the data and analysis showed that digestate concentration of 1.4% (v/v) dilution and low K-P and MgSO4 concentrations would be expected to result in high average biomass productivity and instantaneous biomass productivity. The digestate concentrations does not alter the effects of K-P and MgSO4 on algae growth, but an interaction was seen between K-P and MgSO4. At low concentrations of these two factors (MgSO4 < 0.61 mmol/L and K-P < 2.81 mmol/L), both experiments 1 and 2 showed that lower the K-P and MgSO4 concentrations would yield higher maximum growth rate. The cause might be that the additional K-P and MgSO4 might promote larger cell production rather than cell replication, or the replicated cells may stay attached, which would lead to slower perceived growth rate but higher maximum algae concentration at the end of the batch growth.

Committee:

Joanne Belovich, Ph.D. (Advisor); Jorge Gatica, Ph.D. (Committee Member); Moo-Yeal Lee, Ph.D. (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Digestate; Scenedesmus dimorphus; magnesium sulfate; dipotassium hydrogen phosphate;potassium dihydrogen phosphate; algae;

Yang, DongqingMechanism and Mitigation of Biocorrosion by Nitrate Reducing Pseudomonas aeruginosa against Stainless Steel
Master of Science (MS), Ohio University, 2016, Biomedical Engineering (Engineering and Technology)
Biocorrosion, also known as microbiologically influenced corrosion (MIC), is the deterioration of metals and other materials due to the metabolic activity of microorganisms. MIC is a major problem in the oil and gas field and many other industries. It is caused by microbes in biofilms. In addition, biofilms have been recognized to be the cause of infections. It also occurs in medical devices and implants in the human body. Biocatalytic cathodic sulfate reduction (BCSR) theory illustrates the mechanism of MIC caused by sulfate reducing bacteria (SRB) from a bioenergetics perspective. BCSR can be adapted to explain MIC caused by other types of microbes such as nitrate reducing bacteria (NRB) in the form of biocatalytic cathodic nitrate reduction (BCNR). Pseudomonas aeruginosa is known as an opportunistic pathogen, which can grow as NRB using denitrification under anaerobic condition. In this work, the BCNR theory was supported by the starvation test using the wild-type P. aeruginosa (PAO1) in an anaerobic environment. The results suggested that NRB switched to elemental iron (Fe0) as an electron donor when there was a shortage of carbon sources under anaerobic condition. Compared to the control test, the highest weight loss (58% increase) and pit depth (more than twice deeper) were achieved under no carbon source condition. Extracellular electron transfer (EET) explains how electrons transfer from steel surface to sessile cells and cause MIC pitting corrosion of NRB. Two common electron mediators, riboflavin and flavin adenine dinucleotide (FAD), were tested to accelerate the electron transfer and enhance MIC in lab tests. The results showed that the maximum pit depth increased about 40% by adding either 10 ppm (w/w) FAD or 10 ppm riboflavin. Biocorrosion can occur in various fields and affect a variety of metal materials. Primarily due to their corrosion resistance, stainless steels have been widely used in the biomedical field. However, stainless steel is not antimicrobial and it may suffer MIC attack. The experimental data in this work showed that MIC pitting corrosion occurred in 304 type stainless steel caused by anaerobic PAO1 culture. A maximum pit depth of 3.91 µm was obtained after the 7-day culture. For the 14-day culture, more pits and larger pit diameters were observed. The maximum pit depth was 7.4 µm. D-amino acids have been investigated as antimicrobial enhancers to trigger biofilm disassembly under an antimicrobial stress. In order to inhibit and kill P. aeruginosa, a cocktail of D-tyrosine (D-tyr) and ciprofloxacin (CIP) was investigated in both the biofilm prevention test and the biofilm removal test using anaerobic PAO1 biofilms grown on carbon steel. The combined effect showed less weight loss and lower pit depth in the prevention test and achieved lower sessile cell counts in both the biofilm prevention test and the biofilm removal test. Compared to 30 ppm CIP alone treatment, there were one extra log reduction in the sessile cell count, an extra 24% reduction in the weight loss, an extra 17% decrease in the average maximum pit depth by using the cocktail of 30 ppm CIP + 2 ppm D-tyr in the biofilm prevention test.

Committee:

Tingyue Gu (Advisor); Douglas Goetz (Committee Member); Monica Burdick (Committee Member); Xiaozhuo Chen (Committee Member)

Subjects:

Biomedical Engineering; Chemical Engineering

Keywords:

microbiologically influenced corrosion; nitrate reducing bacteria; Pseudomonas aeruginosa; mitigation; stainless steel

Batmanghelich, FarhadEffect of mixed denitrifying and sulfate reducing bacterial biofilms on corrosion behavior of cast iron
Master of Science, University of Toledo, 2015, Chemical Engineering
The impact of biofilm and bacterial solutions of desulfovibrio vulgaris and pseudomonas aeruginosa on corrosion of cast iron was assessed and compared in this study. No matter how stringent mitigation techniques are in the drinking water systems, corrosion is inevitable as the water leaves the plant and enters the – mostly metallic – distribution system; this has drastically adverse effects on water quality. Corrosion also jeopardizes structural integrity of municipal and hospital sewage systems. Since aforementioned environments are highly hydrated, biological activity is inevitable. Corrosion induced by biofilms is the result of synergistic interactions of different species of environmental microbes that coexist in a mixed consortium. Biofilms have an inexorable effect on interfacial behavior of metals in electrolytes. Biofilms might impose a decrement or an increment in corrosion of metallic infrastructure in water distribution systems where biofilm EPS and microbial species play crucial roles in the corrosion of iron alloys. In this study, biofilms of Pseudomonas aeruginosa as a model for denitrifying bacteria and Desulfovibrio vulgaris as a model for sulfate reducing bacteria were selected to study the effect of mixed species biofilms and their extracellular polymeric substances on corrosion behavior of cast iron coupons. The protection level offered by these biofilms in a standard aggressive electrolyte (3.5 % NaCl, pH = 4) was also studied. All the P. aeruginosa and D. vulgaris strains were cultured in 1249 Modified Baar’s medium under anaerobic condition in a glovebox containing N2 – 5% H2. Electrochemical interactions at the metal/biofilm interface were monitored via Tafel polarization and electrochemical impedance spectroscopy (EIS) as a function of immersion time. Standard weight loss experiments were conducted on cast iron coupons with same chemical composition. To grasp an idea about the morphology evolution of corrosion products and the extent of corrosion, atomic force microscopy (AFM) technique was implemented. Bacterial attachment was studied using fluorescence microscopy. From the electrochemical impedance, Tafel polarization, weight loss, AFM, and bacterial attachment results, it was found that although SRB solution is more corrosive compared to mixed and PAO1 respectively; these biofilms protect the surface against the attack of an aggressive standard electrolyte The underlying reason for protective behavior of SRB biofilms compared to PAO1 and mixed was attributed to the higher surface coverage and a more massive biofilm covering the surface. Furthermore, compared to SRB monocultures; a decrement in the extent of corrosion was observed in the presence of mixed species of PAO1 and SRB which can be attributed to toxic effects of anaerobic denitrification process towards SRB activities.

Committee:

Youngwoo Seo, PhD (Advisor); Dong-Shik Kim, PhD (Committee Member); Mohammad Elahinia, PhD (Committee Member)

Subjects:

Chemical Engineering

Keywords:

biofilm; corrosion; electrochemistry; sulfate reducing bacteria; denitrifying bacteria;

Sohn, HyuntaeApplied and Fundamental Heterogeneous Catalysis Studies on Hydrodechlorination of Trichloroethylene and Steam Reforming of Ethanol
Doctor of Philosophy, The Ohio State University, 2016, Chemical Engineering

The dissertation herein reports heterogeneous catalysis studies conducted on two different projects, (1) Hydrodechlorination of trichloroethylene and (2) Ethanol steam reforming. The former is associated with the process for trichloroethylene waste treatment and groundwater remediation technology whereas the latter pertains to hydrogen production. The presented work involves not only investigations on the catalytic activity, but also fundamental studies to understand how and why a catalyst works for a particular reaction. This dissertation is composed of two major parts. (1) Part I (Chapter 1-4): Trichloroethylene (TCE) is a chlorinated hydrocarbon solvent which has been widely used as a vapor degreaser for metal cleaning. TCE contains high level of toxicity, also known as a carcinogen. Recently, contamination of groundwater due to untreated TCE is a rapidly rising environmental issue, affecting the drinking water quality. The current waste treatment process for removal of TCE are mostly based on adsorption and extraction techniques. However, these processes do not provide a complete destruction of the TCE chemical structure; hence, it requires an additional incinerator to convert TCE into non harmful products. Hydrodechlorination (HDC) of TCE is a catalytic chemical reaction where TCE is converted to ethane and hydrochloric acid using hydrogen as a reducing agent. The treatment is a single step process, also can be performed in situ in groundwater. The most extensively used catalysts for this reaction are based on Pd metal. The main purpose of this study is to investigate the catalytic activity and stability of Pd supported on swellable organically modified silica (SOMS) for HDC of TCE. SOMS is a highly hydrophobic and adsorptive material. The material was recently developed and was reported in the literature. An interesting characteristic of SOMS is “swelling”, i.e., the volume of SOMS expands while adsorbing organics. The expansion of SOMS leads to generation of new pores thereby increasing its pore volume and surface area. When SOMS is treated with heat, contraction of SOMS occurs resulting a decrease in volume to its original size. Another important characteristic is its high hydrophobicity. It was deduced that Pd/SOMS showed promising catalytic activity compared to commercial Pd/Al2O3 in liquid phase HDC of TCE. This was attributed to the adsorptive and swelling properties of Pd/SOMS and its hydrophobicity, which helped to concentrate the TCE reactants in the vicinity of the active Pd sites. The increase in concentration near the active sites resulted in better kinetics for HDC reaction obtaining high TCE conversion. Furthermore, the strong hydrophobicity of SOMS helped to secure the Pd sites from ionic poisons such as sulfur and chlorine containing groups without losing its catalytic activity, e.g., when Pd/SOMS and Pd/Al2O3 was treated with 1 M HCl, Pd/SOMS retained its catalytic performance whereas Pd/Al2O3 was completely degraded because of Pd leaching under HDC of TCE conditions. On the other hand, better catalytic activity was observed over Pd/Al2O3 compared to Pd/SOMS for gas phase HDC of TCE. It was found that the swelling of SOMS in gas phase, in other words, the expansion of the catalyst due to TCE vapors was not enough so that most of the embedded Pd sites were not accessible to the TCE reactants. To resolve this issue, Pd was impregnated on a pre-calcined SOMS which was treated under inert condition at high temperatures (H-SOMS). With respect to Pd/H-SOMS, the Pd accessibility in gas phase to the TCE molecules were improved drastically. A significant increase in Pd dispersion as well as decreased in Pd particle size was observed. When tested for HDC of TCE activities, higher TCE conversions were obtained over Pd/H-SOMS catalyst compared to Pd/SOMS. (1) Part II (Chapter 5-10): Hydrogen has been considered as the next alternative and renewable energy carrier that can be utilized for many industrial applications. The production of energy from hydrogen is typically conducted through a fuel cell, which only generates water as a product. Among many other hydrogen production processes, ethanol steam reforming (ESR), a catalytic chemical reaction, has gained a lot of attention since it provides a closed carbon loop cycle when ethanol is derived from environmentally friendly sources such as bio-mass. With respect to catalysts, noble metals such as Pt, Pd, Rh and Ru have been tested under ESR conditions and have shown excellent catalytic activities obtaining high hydrogen yield and ethanol conversion. However, noble metals are expensive thereby increase the overall operating cost. In this dissertation, the catalytic performance and stability of non-noble metals such as Co supported on CeO2 (cerium oxide) was investigated. According to the results obtained in our laboratory during the past decade, Co/CeO2 with 10 wt % cobalt loading, had significant activity for ESR at relatively lower temperatures, around 350 to 600 °C. Some of the findings include 1) high oxygen mobility of CeO2 reduces carbon deposition, 2) transition of Co3O4 to CoO and metallic Co was observed during steam reforming, 3) reducibility of Co and surface activity, morphology and particle size of CeO2 significantly influence the catalytic activity of Co/CeO2 for ESR. Herein, a detailed kinetic analysis to acquire activation energies of reduction and re-oxidation processes of cobalt was conducted. Moreover, reducibility of CeO2 was studied in two different particle sizes where nano-sized CeO2 contained more Ce3+ reduced sites compared to micro-sized CeO2 both in bulk and surface of the catalyst under ESR conditions. The difference in extent of reduction of CeO2 led to a more basic surface for nano-sized CeO2 resulting better catalytic activity for ESR. When cobalt was present on the catalyst surface (Co/CeO2), the oxidation state of Ce was lower in comparison to a bare CeO2 support under same reaction conditions. This was attributed to the reduction of cobalt taking precedence over the reduction of CeO2. Lastly, the effect of microgravity on synthesis of CeO2 was studied. It was found that CeO2 prepared in microgravity consists lower surface area and pore volume compared to the CeO2 prepared in normal-gravity. A significant difference in particle shape was observed where microgravity-CeO2 was more like rods whereas normal-gravity-CeO2 contained polyhedral particles.

Committee:

Umit S. Ozkan, Ph.D. (Advisor); Andre Palmer, Ph.D. (Committee Member); Lisa Hall, Ph.D. (Committee Member); T.V. (Babu) RajanBabu, Ph.D. (Committee Member)

Subjects:

Chemical Engineering

Keywords:

hydrodechlorination; trichloroethylene; groundwater remediation; modified silica; SOMS; palladium; alumina; poison resistant; hydrophobicity; ethanol steam reforming; hydrogen production; cobalt; ceria; particle size; microgravity; synthesis of ceria

Chede, Sneha AFouling Control Using Temperature Responsive Membranes composed of N-isopropylacrylamide (NIPAAm) and Iron Oxide Nanoparticles
Doctor of Philosophy, University of Toledo, 2015, Chemical Engineering
Membrane fouling occurs when there is reversible or irreversible accumulation of macrosolutes present in the water on the membrane surface. Membrane cleaning and eventual replacement due to fouling can add to the operating costs of membrane systems. Reversible fouling can be minimized by crossflow operation and/or backflushing. On the other hand, irreversible fouling cannot be minimized during operation, often requires chemical cleaning, and may result in permanent flux decline. Among irreversible foulants, natural organic matter (NOM) is considered to be a major contributor. NOM is composed of a wide range of hydrophilic and hydrophobic components; hence, any stagnant hydrophobic or hydrophilic membrane has the potential to become fouled. Therefore, a dynamic membrane able to alternate between being more or less hydrophilic would be expected to decrease fouling. The purpose of this study was to cast stimuli responsive membranes to control fouling made of cellulose acetate (CA) and N-isopropylacrylamide (NIPAAm). NIPAAm is a stimuli-responsive polymer, which offers the potential to reversibly collapse or expand the membrane as a function of changes in temperature. Membranes were cast using phase inversion, were characterized chemically and morphologically, and were used in filtration experiments using bovine serum albumin (BSA), lipase and humic acid solutions. Flux studies were conducted at alternating cold and hot temperature cycles. CA-NIPAAm membranes displayed on average higher fluxes during operation, along with lower protein and humic accumulation on the membrane surface as compared to regular CA membranes. CA-NIPAAm membranes also showed higher flux recoveries as compared to CA membranes. Temperature activation of temperature-responsive membranes can be energy extensive since it requires heating entire housing and feed streams. Furthermore, heat transfer resistances within the housing can hinder the temperature response time of the membranes. To address these, heating was localized within the membrane matrix by embedding superparamagnetic iron oxide (SPIO) nanoparticles within the temperature-responsive NIPAAm polymer film. Nanoparticles were chemically attached to polyNIPAAm, and the resultant product was added to the dope solution. Membranes were fabricated and tested for their response to the RF heating. An alternating current (AC) electromagnetic field was used to activate the temperature responsive membrane via electromagnetic heating caused by nanoparticles. Membranes with nanoparticles were studied with and without RF heating, and the results suggested that during RF heating, CA-NIPAAm membranes with nanoparticles became less hydrophilic as compared to without RF heating. CA-NIPAAm membranes with and without SPIO nanoparticles were subjected to RF heating to investigate the effect of the presence of nanoparticles on water infiltration. Higher temperatures were recorded near the membranes with nanoparticles as compared to the membranes without nanoparticles suggesting that an oscillating magnetic field has the potential to be used for temperature activation. Finally, the performance of the membranes fabricated at the laboratory-scale and at production scale was evaluated. Since laboratory-scale doctor's blade method could become challenging during the scale up of the membranes, a well-developed pre-metered method, slot die extrusion, was used for continuous casting of liquid films. The feasibility of processing cellulose acetate membranes using a doctor’s blade versus a slot die extrusion was examined. The effects of processing methods, conditions, and substrate on the morphology and on the flux of CA membranes were studied. Membranes were tested for their performance under the same process conditions. Overall, membranes fabricated at the laboratory-scale and scale up were similar.

Committee:

Isabel Escobar (Committee Chair); Maria Coleman (Committee Member); Yakov Lapitsky (Committee Member); Saleh Jabarin (Committee Member); Geoffrey Bothun (Committee Member)

Subjects:

Chemical Engineering

Bootsma, Katherine JeanThe Development of 3D Printable Materials
Master of Science, Miami University, 2016, Chemical, Paper & Biomedical Engineering
An interpenetrating polymer network (IPN) is a material that possesses unique physical and mechanical properties. These unique properties give rise to the use of IPNs in a variety of applications including drug delivery, tissue engineering scaffolds, and as actuators in soft robotics. This thesis reports two separate applications of IPNs where 3D printing could prove useful. The first study focuses on the use of an alginate-polyacrylamide IPN hydrogel as a potential material for use in a medical simulator. The chemistry of a previously reported biomimetic IPN was altered so that 3D printing could be achieved. The elastic and viscoelastic behaviors of the 3D printed IPNs were quantified and found to be on the range of various biological tissues. The second study focuses on the development of a PVDF-poly(glycidyl methacrylate-co-methyl methacrylate) IPN as a separator membrane in a flexible lithium ion battery. A second polymer network was added to a preexisting separator formulation to create a semi-IPN. This separator membrane was characterized with dissolution tests, tensile mechanical tests, and rheology.

Committee:

Jessica Sparks (Advisor); Jason Berberich (Advisor); Dominik Konkolewicz (Committee Member)

Subjects:

Biomedical Engineering; Chemical Engineering

Keywords:

3D printing; hydrogel; IPN; medical simulation

Giammanco, Giuseppe E.Photochemistry of Fe(III)-carboxylates in polysaccharide-based materials with tunable mechanical properties
Doctor of Philosophy (Ph.D.), Bowling Green State University, 2016, Photochemical Sciences
We present the formulation and study of light-responsive materials based on carboxylate-containing polysaccharides. The functional groups in these natural polymers allow for strong interactions with transition metal ions such as Fe(III). The known photochemistry of hydroxycarboxylic acids in natural waters inspired us in exploring the visible light induced photochemistry of the carboxylates in these polysaccharides when coordinated to Fe(III) ions. Described in this dissertation are the design and characterization of the Fe(III)-polysaccharide materials, specifically the mechanistic aspects of the photochemistry and the effects that these reactions have on the structure of the polymer materials. We present a study of the quantitative photochemistry of different polysaccharide systems, where the presence of uronic acids was important for the photoreaction to take place. Alginate (Alg), pectate (Pec), hyaluronic acid (Hya), xanthan gum (Xan), and a polysaccharide extracted from the Noni fruit (NoniPs), were among the natural uronic acid-containing polysaccharide (UCPS) systems we analyzed. Potato starch, lacking of uronate groups, did not present any photochemistry in the presence of Fe(III); however, we were able to induce a photochemical response in this polysaccharide upon chemical manipulation of its functional groups. Important structure-function relationships were drawn from this study. The uronate moiety present in these polysaccharides is then envisioned as a tool to induce response to light in a variety of materials. Following this approach, we report the formulation of materials for controlled drug release, able to encapsulate and release different drug models only upon illumination with visible light. Furthermore, hybrid hydrogels were prepared from UPCS and non-responsive polymers. Different properties of these materials could be tuned by controlling the irradiation time, intensity and location. These hybrid gels were evaluated as scaffolds for tissue engineering showing great promise, as changes in the behavior of the growing cells were observed as a result of the photochemical treatment of the material. We present these natural and readily available, polysaccharide-based, metal-coordination materials as convenient building blocks in the formulation of new stimuli responsive materials. The photochemical methods developed here can be used as convenient tools for creating advanced materials with tailored patterns and gradients of mechanical properties.

Committee:

Alexis Ostrowski, Ph.D. (Advisor); Michael Geusz, Ph.D. (Committee Member); George Bullerjahn, Ph.D. (Committee Member); R. Marshall Wilson, Ph.D. (Committee Member)

Subjects:

Chemical Engineering; Chemistry; Materials Science; Polymer Chemistry; Polymers

Keywords:

photochemistry; polymers; polysaccharides; hydrogels; stimuli-responsive materials; iron; coordination chemistry; biomimetic materials; drug delivery; tissue engineering; cartilage; biomaterials; nanotechnology; photopatterning; green chemistry

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