Search Results (1 - 25 of 949 Results)

Sort By  
Sort Dir
 
Results per page  

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

Kang, SooYeonHIGH-THROUGHPUT METABOLISM-INDUCED TOXICITY ASSAYS ON A 384-PILLAR PLATE
Master of Science in Chemical Engineering, Cleveland State University, 2018, Washkewicz College of Engineering
The U.S Environmental Protection Agency (EPA) launched the Transform Tox Testing Challenge in 2016 with the goal of developing practical methods that can be integrated into conventional high-throughput screening (HTS) assays to better predict the toxicity of parent compounds and their metabolites in vivo. In response to this need and to retrofit existing HTS assays for assessing metabolism-induced toxicity of compounds, we have developed a 384-pillar plate that is complementary to traditional 384-well plates and ideally suited for culturing human cells in three dimensions (3D) at a microscale. Briefly, human embryonic kidney (HEK) 293 cells in a mixture of alginate and Matrigel were printed on the 384-pillar plates using a microarray spotter. These cells were then coupled with 384-well plates containing nine model compounds provided by the EPA, five representative Phase I and II drug metabolizing enzymes (DMEs), and one no enzyme control. Membrane integrity and viability of HEK 293 cells were measured with the calcein AM and CellTiter-Glo® kit, respectively, to determine the IC50 values of the nine parent compounds and DME generated metabolites. Out of the nine compounds tested, six compounds showed augmented toxicity with DMEs and one compound showed detoxification with a Phase II DME. This result indicates that the 384-pillar plate platform can be used to measure metabolism-induced toxicity of compounds with high predictivity. In addition, the Z’ factors and the coefficient of variation (CV) measured were above 0.6 and below 14%, respectively, indicating that the assays established on the 384-pillar plate are robust and reproducible.

Committee:

Moo-Yeal Lee (Advisor); Chandrasekhar R. Kothapalli (Committee Member); Geyou Ao (Committee Member)

Subjects:

Biomedical Engineering; Chemical Engineering

Celik, GokhanSwellable Organically Modified Silica as a Novel Catalyst Scaffold for Catalytic Treatment of Water Contaminated with Trichloroethylene
Doctor of Philosophy, The Ohio State University, 2018, Chemical Engineering
Groundwater contamination by chlorinated compounds is a serious environmental concern because of its potential impact on groundwater and surface water that serves as a major source of public drinking water. Among chlorinated compounds, trichloroethylene (TCE) is one of the most abundantly detected groundwater contaminants with high level of toxicity. The toxicity and the carcinogenic effects of TCE pose a serious threat to human health and the environment. Hydrodechlorination (HDC) is an efficient elimination-based remediation technique to clean groundwater contaminated by chlorinated compounds. In HDC, chlorinated compounds react with hydrogen and are catalytically converted to chloride-free hydrocarbons and hydrogen chloride. Active research on HDC of chlorinated compounds has resulted in promising conversions and catalytic activities over state-of-the-art palladium-based catalysts. However, the existing HDC catalysts reported in the literature suffer from the following shortcomings: (i) catalyst poisoning due to anionic species present in real groundwater such as sulfur-containing species (SO42-, HS-), chloride species (Cl-), etc., (ii) inhibition by the unavoidable reaction product HCl, (iii) formation of carbonaceous species on active sites, and (iv) active metal leaching during operation. The above-mentioned challenges impede the commercialization and widespread utilization of HDC. For industrial organizations to adapt catalytic HDC as a remediation technique, these deactivation issues need to be addressed. Our research has therefore focused on developing a novel catalytic water treatment system in which the deactivation-resistance is improved. The focus of this dissertation is the use of a newly-discovered material, namely swellable organically-modified silicate (SOMS) as a catalyst scaffold for HDC of TCE. SOMS is a highly animated material with unique properties. It is adsorptive, extremely hydrophobic and swellable when contacted with organics. The SOMS structure consists of a cross-linked network of organosilica particles that provide flexibility to the structure of the material. The catalytic system developed in this dissertation has addressed the above-mentioned challenges by utilizing the unique characteristics of SOMS in the following ways: (i) The swelling capability of SOMS allows the active metals dissolved in organic solvents, to be deposited inside the swollen matrix of SOMS. Hence, an effective protection of the active sites is achieved since they are not situated on the exterior surface. (ii) The hydrophobicity of SOMS guides the organics towards the active sites and repels anionic poisons and HCl. Thus, the catalyst deactivation problems are alleviated. (iii) The surface of SOMS does not contain substantial amounts of surface hydroxyls. This was attributed to decreasing the formation of carbonaceous deposits. An experimental approach has been undertaken to demonstrate that the catalytic system developed within this work can meet the above-mentioned challenges. The work performed in this dissertation includes building experimental set-ups where intrinsic kinetic measurements can be performed, developing experimental protocols to synthesize metal-impregnated SOMS, performing aqueous-phase hydrodechlorination activity experiments, performing accelerated-poisoning experiments to investigate the deactivation-resistance characteristics, and carrying out ex-situ and in-situ characterization studies over pristine and poisoned catalysts. These experimental studies were repeated for the commercially-used water treatment catalyst, Pd/Al2O3 in order to have a basis for comparison. In this dissertation, SOMS has been presented as a promising catalyst scaffold due to its unique properties and animated nature. It has the potential to meet the challenges associated with catalytic treatment of water. Based on the studies conducted as a part of this dissertation, it can be concluded that Pd-incorporated SOMS catalysts are catalytically active and more resistant to inhibition and deactivation than the commercially employed counterparts.

Committee:

Umit Ozkan (Advisor); Andre Palmer (Committee Member); Chalmers Jeffrey (Committee Member); Rebecca Kim (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Swellable Organically Modified Silica; SOMS; Hydrodechlorination; Trichloroethylene; Organosilicate; Swelling; Smart Catalytic Materials; Stimuli-Induced Materials; Palladium; Pd-Al2O3; Deactivation; Hydrophobicity; Groundwater remediation

Jiang, PengfeiSustained Release of Anti-VEGF from Injectable Devices for Treating Wet Age-Related Macular Degeneration
Master of Science, The Ohio State University, 2018, Chemical Engineering
Age-related macular degeneration (AMD) is the fourth most common cause of blindness in the world. There are more than 11 million people diagnosed with AMD in the United States. It is estimated that this number will double in 2050. Accordingly, much work has been done understanding disease pathogenesis and developing therapeutic methods. It is widely noted that overexpression of vascular endothelial growth factor (VEGF) along with aging stimulates neovascularization in the choroid, which leads to irreversible damages to the retina during bleeding and scarring of newly formed blood vessels. The current gold standard treatment for wet AMD is a monthly intravitreal injection of anti-VEGF such as bevacizumab or ranibizumab to inhibit VEGF and to prevent angiogenesis. However, frequent injections often lead to infection, elevated intraocular pressure and rhegmatogenous retinal detachment, as well as issues with patient compliance. Therefore, there is a need for an improved therapeutic approach for the treatment of wet AMD. To address the problems associated with the current clinical treatment, we have developed several novel devices made from two polymeric materials to extend the period of drug release and to avoid the side effects associated with the monthly anti-VEGF injection. Our novel devices are in two different forms, microparticle and capsule. The preliminary results demonstrate that the devices enable the longer-term local drug administration as compared to previously reported devices. This study provides an alternative method to raise the therapeutic efficacy and further improve the quality of life for people diagnosed with wet AMD.

Committee:

Katelyn Swindle-Reilly (Advisor); Eduardo ReƔtegui (Committee Member)

Subjects:

Chemical Engineering

Shah, Vedant RavindraAttrition Behavior of Oxygen Carrier Particles and Pressure Fluctuations in Chemical Looping Systems
Master of Science, The Ohio State University, 2018, Chemical Engineering
Chemical looping process deals with conversion of fossil fuels into desired products by making use of oxygen carrier particles. These particles transfer their oxygen to the fuel in reducer reactor and themselves get reduced. The reduced particles are sent to the combustor reactor where they are re-oxidized using air. Thus, the oxygen carrier particles are subjected to multiple redox cycles. Oxygen carrier particles are subjected to high stress, which originates from harsh operating conditions like elevated temperatures, high pressure and chemical reactions. After multiple cycles, the particles tend to lose their strength and become more susceptible to breaking. This phenomenon is known as attrition. Apart from operating conditions and chemical reactions, process conditions such as presence of cyclones, gas jets in combustor reactor, etc. also contribute to attrition of oxygen carrier particles. This work deals with study of attrition behavior of oxygen carrier particles developed by OSU which presented excellent resistance towards attrition. To characterize the tendency of particle to undergo attrition, jet cup test rig was used to quantify attrition. Jet cup studies were used to compare the attrition behavior of oxygen carrier particles before and after chemical reactions. Various parameters affecting jet cup attrition like jet velocity, particle loading in the jet cup, dimeter of particles were studied. Also, jet cup was used to analyze the attrition behavior of particles that were sampled from different locations along the moving bed reducer reactor. This helped to analyze the strength of particles as they went under different extents of IV reduction in the moving bed reducer reactor. As combustor reactor forms an essential part of chemical looping processes, this work also focused on understanding the effect of various parameters on pressure fluctuations that occurred in the combustor reactor. Effect of different parameters like aspect ratio of fluidized bed, column diameter, gas velocity, etc. on pressure fluctuation amplitude and frequency was studied. This study helped to understand the role of aspect ratios on various regimes of fluidization. Aspect ratio, which is defined as the ratio of height of particle bed at minimum fluidization to column diameter significantly affects the performance of combustor reactor as well as the economics associated with it. Experiments were done to understand pressure fluctuations that are associated with different regimes of fluidization. It was found out that the frequency of fluctuations increased with increase in superficial gas velocity. Also, fluctuation frequency was found to be dependent on aspect ratio of the fluidization column. All these observations were consistent with data reported in literature. Conclusions were drawn based on the findings and mechanistic approach was used to propose suitable reasoning. Future work regarding these experiments would include use of Electrical capacitance volumetric tomography (ECVT) to correlate the pressure fluctuation data with capacitance data to image the fluidized bed.

Committee:

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

Subjects:

Chemical Engineering

Keywords:

Chemical Looping, attrition, jet cup, pressure fluctuations

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

Zhang, MingzhenMultiscale Molecular Simulations of Cross-sequence Interactions between Amyloid Peptides
Doctor of Philosophy, University of Akron, 2017, Chemical Engineering
Amyloid aggregation have been implicated in the pathology of many neurodegenerative diseases, including prion disease, Alzheimer's disease (AD), type II diabetes (T2D), and Parkinson disease. Amyloid peptides undergo the nucleation-polymerization aggregation process, during which amyloid peptides experience structural conversions from unstructured monomers to critical nucleus, and eventually to amyloid fibrils containing dominant ß-sheet structures. Such common misfolding and aggregation characteristics, in some cases, drive cross-seeding interactions between amyloid peptides, which play a major role in the progression and transmission between the neurodegenerative diseases. In the experiments, the cross-seeding interactions between amyloid peptides including ß-amyloid (Aß)-islet amyloid peptides (IAPP), Aß-tau, Aß-prion, human IAPP-rat IAPP, and tau-synuclein amyloids have been extensively implicated. However, high-resolution evidence is still unavailable and little is known about how these two peptides interact with each other. In our research, we perform the multiscale molecular simulations to sysmetically study the cross-seeding interactions between different amyloid peptides at the atomic resolution, with the particular focus on the prediction of the atomic structures, the dynamic behavious in bulk and membrane enviroment, and the interface properties of the hIAPP-rIAPP and Aß-hIAPP cross-seeding assemblies. In Chapter I and II, we model and simulate different heteroassemblies formed by the amyloidogenic hIAPP and the nonamyloidogenic rIAPP peptides. The U-shaped hIAPP monomers and oligomers can interact with conformationally similar rIAPP to form stable complexes and to co-assemble into heterogeneous structures via the interfacial hydrogen bonds and hydrophobic contacts at ß-sheet regions. This work demonstrates the existence of cross-interactions between the two different IAPP peptides at the atomic level, providing an improved fundamental understanding of the cross-seeding of different amyloid sequences towards amyloid aggregation and toxicity mechanisms. In Chapter III, IV and V, we investigate the cross-seeding interactions between Aß and hIAPP using a combination of coarse-grained (CG) replica-exchange molecular dynamics (REMD), all-atom molecular dynamics (MD) simulations and Markov Chain Monte Carlo (MCMC) simulations. We for the first time obtain the full free energy landscape for Aß-hIAPP cross-seeding interactions, by which the atomic structure of Aß-hIAPP cross-seeding assembly is determined. Computational mutagenesis studies reveal that disruption of interfacial salt bridges largely disfavor the ß-sheet-to-ß-sheet association, highlighting the importance of salt bridges in the formation of cross-seeding assemblies. We also probe the behaviors of Aß-hIAPP cross-seeding assemblies on zwitterionic POPC and anionic POPC/POPG membranes, determining the specific orientations and demonstrating that electrostatic interactions are the major forces governing peptide-lipid interactions. This work confirms the cross-seeding interactions between Aß and hIAPP, explaining the potential pathological link between AD and T2D. The atomic insights into the cross-seeding intearctions between amyloid peptides obtained from this work are expected to improve the understanding of the amyloid peptides and inspire the peptide inhibitor design towards the neurodegenerative diseases.

Committee:

Jie Zheng (Advisor); Zhenmeng Peng (Committee Member); Ernian Pan (Committee Member); Lingyun Liu (Committee Member); Tsige Mesfin (Committee Member)

Subjects:

Chemical Engineering

Keywords:

Amyloid, Cross-Seeding, Multiscale Molecular Simulation, Cross-Sequence

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

Miozzi, JackelynColumn-free Purification Method for Recombinant Proteins Using a Self-Cleaving Aggregating tag
Master of Science, The Ohio State University, 2018, Chemical Engineering
Conventional column-based chromatography processes for the purification of recombinant proteins result in high production costs and slow volumetric throughput at both laboratory and large scale. Non-chromatographic purifications based on selective aggregating tags have the potential to reduce costs with acceptable protein yields. A significant drawback, however, is that current proteolytic approaches for tag removal after the purification are expensive and non-scalable. To address this problem, we have developed a non-chromatographic purification strategy that uses the ¿-roll tag (BRT17) in combination with an engineered split intein for tag removal. The use of the split intein eliminates premature cleavage during expression, which occurs when using a full-length intein such as ¿I-CM, and provides controlled cleavage under mild conditions after purification. The full-length intein aggregating tag was used to effectively purify ¿-lactamase (¿-lac) and resulted in low protein yield due to pre-cleavage. The split intein aggregating tag was used to efficiently purify ¿-lactamase (¿-lac), super-folder green fluorescent protein (sfGFP), streptokinase (SK) and maltose binding protein (MBP), resulting in increased yields compared to previous BRT17-based purifications.

Committee:

David Wood, Dr. (Advisor); Jeffrey Chalmers, Dr. (Committee Member)

Subjects:

Chemical Engineering

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

Shallman, Julie MGalvanic and Pitting Corrosion of a Fastener Assembly
Master of Science, University of Akron, 2018, Applied Mathematics
This research focuses on coupled galvanic/pitting corrosion of AA7075 when combined with stainless steel in a fastener assembly. A one-dimensional mathematical model of a well-mixed electrolyte is developed to predict the damage profile of the AA7075 surface when its protective coating is damaged. The damage exposes the galvanic couple. A time dependent system of partial differential equations for potential, chloride concentration, aluminum ion concentration, and damage is developed and solved numerically. Four approaches to calculate the current density within aluminum pits are discussed. The first is a current balance of the system. This reflects the local chemistry that drives pit growth early on. The second approach uses the potential calculated at the bottom of each initiated pit with a polarization curve relevant to the pit chemistry. The third approach assumes the entire aluminum surface is active and thus uses the bulk polarization curves to determine the current density. The last approach is a combination of the above three approaches to simulate the different mechanisms during the corrosion of the aluminum surface. This approach reflects the growth of pits during the formation of oxide that leads to repassivation. Hence, the model developed describes high local pit current densities and damage done to the AA7075 surface over time.

Committee:

Curtis Clemons, Dr. (Advisor); Kevin Kreider, Dr. (Committee Member); Gerald Young, Dr. (Committee Member)

Subjects:

Applied Mathematics; Chemical Engineering; Civil Engineering; Engineering

Keywords:

Galvanic corrosion; pitting corrosion; AA7075 and steel; pit current density; mathematical model

Zhang, XuFabrication, Characterization, and Application of Elastic Hydrophobic Electrospun Fiber Mats
Doctor of Philosophy, University of Akron, Chemical Engineering
Electrospinning is a simple, effective, and versatile method to produce polymeric micro- and nanofibers. The electrospun fibers and fabrics are extensively used in a variety of fields such as filtration, biomedical engineering, energy storage, and catalysis. Specifically, electrospun nowoven fibrous media used as various types of filters function efficiently in filtration, separation, and purification applications. This dissertation studies the novel research of using elastic electrospun fiber mats as filter media for filtration and separation applications, which has not been discussed in literatures. In this work, submicron elastic acrylonitrile-butadiene copolymer fibers were fabricated via electrospinning. Fiber morphologies and diameters were investigated. The surface wettability of the fiber mats were characterized by water contact angle, and the surfaces showed hydrophobicity. Fiber mats and yarns rolled from the mats were conducted uniaxial tensile tests to study their mechanical behaviors and it turned out different stress-strain performance, which was essentially due to the difference in fiber slippage and rearrangement mechanisms. Air permeabilities of the stretched elastic fiber mats were evaluated when subject to air flow. As the fiber mats stretched, fibers shifted apart relative to each other such that the pores enlarged. The permeability/mat thickness values increased initially and then reached constant as a result of the pore structure change during stretch. Poly (vinyl pyrrolidone) (PVP) electrospun fiber mats were measured for bubble point and mean flow pore diameters to determine their dependence on fiber diameter and fiber mat basis weight. Generally, pore sizes were smaller for a fiber mat of higher basis weight and for those composed of fibers of smaller diameters. More interestingly, the two characteristic pore diameters decreased initially and then reached minimum plateau as the basis weight increased. The elastic fiber mats were built into different types of filter media to capture solid nanoparticles from air as well as remove dispersed water droplets from diesel fuel to inspect the filter performance in terms of penetration, separation efficiency, pressure drop, and overall Filtration Index. For the solid aerosol separation, particle penetration increased and pressure drop decreased when the elastic fiber mats stretched to give larger pores. For the water-in-diesel emulsion separation, better separation efficiencies were achieved by using filter media containing electrospun fiber mats of higher basis weight under lower emulsion face velocities.

Committee:

George Chase (Advisor); Judit Puskas (Committee Member); Chelsea Monty (Committee Member); Shivakumar Sastry (Committee Member); Kevin Kreider (Committee Member)

Subjects:

Chemical Engineering

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

Next Page