Chemical Engineering Commons^™

Rate-Determining Step And Active Sites Probing For Platinum-Group-Metal Free Cathode Catalyst In Fuel Cell, Yechuan Chen

Chemical and Biological Engineering ETDs

With the increasing demand on renewable energy, the fuel cell has attracted more and more interests because of its large power density and controllable size. However, the insufficiency of element abundance and unstable expensive price of conventional platinum-based electrocatalysts used in anode and cathode makes it essential to find their substitutes. As one of the most promising candidates to be used in cathode for oxygen reduction reaction (ORR), iron-nitrogen-carbon (Fe-N-C) catalysts have been widely investigated and get commercialized recently, but still lacks comprehensive understanding on the kinetic mechanism.

This dissertation has been divided into three parts with a discussion on …

An Investigation Of The Effects Of The Second Pyrolysis On The Chemistry, Morphology, And Performance Of Iron-Nicarbazin Catalysts, Elizabeth B. Weiler

Chemical and Biological Engineering ETDs

Proton exchange membrane fuel cells offer a cost-effective, environmentally friendly, and sustainable alternative to petroleum-based power sources to the transportation sector. However, slow electrochemical reactions at the cathode of these fuel cell prevent the technology from being competitive. Iron-nitrogen-carbon based catalysts have emerged as a viable answer to this problem, yet further progress is needed to improve their performance beyond that of current state-of-the-art platinum-based catalysts, which are economically and geopolitically impractical to be a final solution. Currently, a two-step high temperature pyrolysis method has proven a promising way to synthesize iron-nitrogen-carbon catalysts for optimized performance, but there is a …

Anodic Catalysts For Anion Exchange Membrane Fuel Cells, Aaron Joseph Roy

Chemical and Biological Engineering ETDs

With a limited availability of energy resources from petroleum and other fossil fuels, as well as growing concerns relating to the environmental implications of fossil fuel emissions, non-carbon fuels which can be utilized in proton and anion exchange membrane fuel cells (PEMFC’s/AEMFC’s), such as hydrogen and hydrazine hydrate (HH), are becoming more attractive as alternative fuels. Historically, platinum and platinum group metal catalysts (PGM) have been used as cathode and anode catalyst materials for both PEMFC’s and AEMFC’s. Although these catalysts are the highest performing catalysts available for the conversion of hydrogen energy in fuel cells, the limited availability and …

Microbial Desalination Cells With Efficient Platinum Group Metal-Free Cathode Catalysts, Morteza Rezaei Talarposhti

Chemical and Biological Engineering ETDs

Iron-nitrogen-carbon based catalyst was used at the cathode of a microbial desalination cell (MDC) and compared with platinum (Pt) and activated carbon (AC) cathode. Fe-N-C catalyst was prepared using nicarbazin (NCB) as organic precursor by sacrificial support method (SSM). Rotating ring disk electrode (RRDE) experiments shows that Fe-NCB had higher electrocatalytic activity compared to AC and Pt. The utilization of Fe-NCB into the cathode improved substantially the performance output with initial maximum power density of 49±2 μWcm^-2 in contrast to Pt and AC catalysts which have shown lower values of 34±1 μWcm^-2 and 23.5±1.5 μWcm^-2, respectively. …

Designing Nanocomposite Materials For Catalyzing Electrochemical Reactions In Anion Exchange Membrane Fuel Cells, Sadia Afrin Kabir

Chemical and Biological Engineering ETDs

Fuel cells are considered to be one the most promising sustainable energy technologies for energy conversion and electric power generation. With the development of stable, conductive and high performance anion exchange membranes and ionomers, there has been an increased interest towards studying various electrochemical reactions in Anion Exchange Membrane Fuel Cells (AEMFC). This increased attention has been attributed to the comparatively facile reaction kinetics, minimized corrosion effects and reduced fuel crossover in alkaline media. However, the oxygen reduction reactions (ORR) taking place in the cathode compartment of fuel cells plays a crucial role in optimizing the electrochemical energy conversion efficiency, …

Microdischarges Utilized In Portable Gas Sensing And Their Atmospheric Contaminants, Colin H. Sillerud

Chemical and Biological Engineering ETDs

Portable applications of microdischarges such as the chemical detection, remediation of gaseous wastes, or the destruction of volatile organic compounds will mandate operation in the presence of contaminant species. This work examines the temporal evolution of microdischarge optical and ultraviolet emissions during pulsed operation by experimental methods. By varying the pulse length of a microdischarge initiated in a 4-hole silicon microcavity array operating in a 655 Torr ambient primarily composed of Ne, we were able to measure the emission growth rates for different contaminant species native to the discharge environment as a function of pulse length. It was found that …

Activity Of Pgm-Free Electrocatalysts For Oxygen Reduction Reaction: Ph And Co-Catalysis Effects, Mario Santiago Rojas Carbonell 8148369

Chemical and Biological Engineering ETDs

Fuel cells offer a source to the current and always increasing demand for electric power. But as any new technology, there are challenges that need to be addressed to render it feasible for the market place. One of this challenges is finding the appropriate materials to catalyze the oxygen reduction reaction (ORR) that occurs in the cathode. Oxygen is used as an oxidant in a significant portion of the fuel cells due to its readily availability and high reduction potential. Now, one the bottlenecks that stops the large-scale adoption is the expensive and rare metals that have been used as …

Electrochemical Oxidation Of Antibiotic, Antihistamine, Analgesic And Cns Stimulant Pharmaceuticals, Md Mosaddek Hossen

Chemical and Biological Engineering ETDs

Electrochemical oxidation is a common method for the degradation of chemicals by applying potential at a definite value. In this research, ‘cyclic voltammetry’ experiments were conducted to find out the oxidation potential for 8 different pharmaceuticals. Mainly, 3 different pH solutions (pH 6.0, 7.5, 9.0) and 9 different concentrations (1, 2, 5, 10, 20, 50, 100, 200, 500 µM) were studied for each of the pharmaceuticals in this experiments. Acetaminophen, Ibuprofen, Naproxen Sodium, Caffeine showed oxidation peak at 0.34-0.79V, 1.37- 1.39V, 0.94-1.01V, 1.44-1.55V respectively at different pH and concentrations. Antibiotic and antihistamine pharmaceuticals i.e. Erythromycin Hydrate, Triclosan, Sulfanilamide, Diphenhydramine Hydrochloride …

Development Of Metal Matrix Composite Gridlines For Space Photovoltaics, Omar K. Abudayyeh

Chemical and Biological Engineering ETDs

Space vehicles today are primarily powered by multi-junction photovoltaic cells due to their high efficiency and high radiation hardness in the space environment. While multi-junction solar cells provide high efficiency, microcracks develop in the crystalline semiconductor due to a variety of reasons, including: growth defects, film stress due to lattice constant mismatch, and external mechanical stresses introduced during shipping, installation, and operation. These microcracks have the tendency to propagate through the different layers of the semiconductor reaching the metal gridlines of the cell, resulting in electrically isolated areas from the busbar region, ultimately lowering the power output of the cell …

Electrochemical Fabrication Of Energetic Thin Films, Jonathan J. Coleman

Chemical and Biological Engineering ETDs

Current thermal battery heat sources suffer from slow reaction propagation rates and require extreme care when handling to protect from inadvertent ignition sources. Nanostructured intermetallic heat sources are strong candidates for improved heat sources as they have high enthalpy of reaction, are highly conductive before and after firing and are completely gasless reactions. Current fabrication methods of these heat sources rely on a PVD multistep layering process that is time and capital intensive, and cost prohibiting to their use. The composition and nanostructuring these films require can be provided with electrochemical codeposition, where the two components (aluminum and nickel) are …

Dielectric Characterization Of Mylar And The Effects Of Doping Processes, Cami B. Belcher

Chemical and Biological Engineering ETDs

Mylar® polymer is a bi-axially oriented polyethylene terephthalate (PET) polymer film used widely as a dielectric, specifically in capacitors. The dielectric characteristics of Mylar have been well studied and documented over the years; however, many of the mechanisms responsible for dielectric breakdown and failure are not understood for modified versions of the material. Previous studies on Mylar confirm that factors such as temperature, humidity, and voltage ramp rates can also have a significant effect on the dielectric properties and measurement of the dielectric properties. This study seeks to determine how dielectric properties, including permittivity, dielectric loss, and breakdown strength, are …

Controlling The Structure And Dynamics Of Magnetoresponsive Particle Suspensions For Enhanced Transport Phenomena, Kyle J. Solis

Chemical and Biological Engineering ETDs

The work contained herein describes the use of various magnetic fields to control the structure and dynamics of magnetic particle suspensions, with the practical aim of enhancing momentum, heat, and mass transport. The magnetic fields are often multiaxial and can consist of up to three orthogonal components that may be either static (dc), time-dependent (ac), or some combination thereof. The magnetic particles are composed of a ferromagnetic material—such as iron, nickel, cobalt, or Permalloy—and can exist in a variety of shapes, including spheres, platelets, and rods. The shape of the particles is particularly important, as this can determine the type …

Microbial Biofilm Development And Electron Transfer In Electrochemical Systems, Jose Cornejo

Chemical and Biological Engineering ETDs

Energy harvesting from microorganisms has created vibrant research efforts for the past 20 years that has lead to the development of emerging topics such as microbial electrochemistry, biofilm formation in electrochemical systems and alternative energy technologies applied in environmental processes. In this study we present procedures that aim for further understanding of bacterial physiological conditions in electrochemical systems and interactions between biofilms and solid surfaces, particularly, for the facultative anaerobe Shewanella oneidensis MR-1. These systems consist of microbial fuel cells (MFCs) whose anode component will be evaluated with regards to performance, electrical current generation, and microbial coverage and biofilm development. …

Composition And Manufacturing Effects On Electrical Properties Of Li/Fes2 Thermal Battery Cathodes, Emilee Lolita Reinholz

Chemical and Biological Engineering ETDs

Li/FeS2 thermal batteries provide a stable, robust, and reliable power source capable of long-term electrical energy storage without performance degradation. These systems rely on a eutectic salt that melts at elevated temperature, activating the cell. When the electrolyte melts, the cathode becomes a suspension, with cathode particles suspended in a molten salt. The suspension experiences mechanical deformation, or slumping.' This slump changes the mechanical compression of the cell, as well as the tortuosity and electronic and ionic conductivity of the cell as the cathode mesostructure is reordered in response to the external compressive stress. The combined effect of deformation, component …

The Electroreduction Of Carbon Dioxide On Porous Copper Nanoparticles, Monica Alisa Padilla

Chemical and Biological Engineering ETDs

Copper nanoparticles of porous, controlled structure were synthesized using the sacrificial support method (SSM). The precursor weight percent (wt%) of copper (Cu) and fumed silica (EH-5) was varied to determine the optimum ratio for this material. The precursors were reduced at i) 350°C in a 7% H2 atmosphere and ii) at 250°C in a 100% H2 atmosphere. The specific surface areas of the nanoparticles was measured by Brunauer-Emmett-Teller N2 absorption. The morphologies and widths of the nanoparticles were confirmed by imaging the nanoparticles by scanning electron microscopy (SEM). The bulk composition of the nanoparticles was determined by X-ray diffraction (XRD). …

The Nucleation And Growth Of Nanoparticles For Heterogeneous Catalysis, Angelica Benavidez

Chemical and Biological Engineering ETDs

These studies investigate the nucleation and growth of nanoparticles and how their interaction with a support affects their reactivity as a heterogeneous catalyst. As capabilities in both synthesis methods and characterization methods advance, the use of nanoparticles and sub-nanometer species are more commonly used. These small particles introduce new factors that can cause differences in reactivity. Various catalyst synthesis methods are employed to deposit mono-dispersed particles on different oxide and carbon supports. Electron microscopy is used to study nanoparticle sintering and the careful tracking of individual particles gives insight into growth mechanisms. X-ray absorption spectroscopy measurements are used to characterize …

Spatial Stochastic Modeling Of The Erbb Receptor Family, Meghan Pryor

Chemical and Biological Engineering ETDs

ErbB transmembrane receptors are a family of 4 receptor tyrosine kinases that interact with one another through homo and heterodimer interactions. When these dimers form, the kinase domains on the receptor tails interact with one another, transphosphorylating one another, initiating a signal cascade. The signaling pathways these receptors participate in are responsible for many different cell functions including apoptosis, growth, and proliferation. The overexpression of these receptors has been linked to various forms of cancer, emphasizing the importance of understanding how these receptors interact with one another to trigger these cascades. Single Particle Tracking experiments have provided more precise and …

Nanoparticle Cerium Oxide And Mixed Cerium Oxides For Improved Fuel Cell Lifetime, Stephen Stewart

Chemical and Biological Engineering ETDs

While there is a rich body of literature concerning of properties of bulk cerium oxide and cerium cations in solution, the discussion has been inappropriately applied to nanoscale cerium oxide resulting in many unexpected or unexplained results. In particular, there is very limited understanding about the properties of cerium oxide and its potential use as a radical scavenger, and how the catalytic properties of cerium oxide change as the particle size approaches the nanoscale. For example, the involvement of Ce+4 and Ce+3 cations in reactions such as hydrogen peroxide decomposition have been investigated for both cerium cations and bulk cerium …

Poly(N-Isopropyl Acrylamide)-Coated Surfaces: Investigation Of Cytotoxicity With Mammalian Cells And The Mechanism Of Cell Detachment, Marta Cooperstein

Chemical and Biological Engineering ETDs

With the increase in life expectancy and with growing numbers of an aging population, there is a rising need worldwide for replacement tissues and organs. One way to address this growing need is through engineered tissues, such as those generated from stimulus-responsive polymers. Stimulus-responsive polymers undergo a physical or chemical change when a stimulus is applied. One such material is poly(N-isopropyl acrylamide), (pNIPAM), which undergoes a conformation change in a physiologically relevant temperature range to release intact mammalian cell monolayers capable of being used to engineer tissues. Two factors currently limit the use of cell sheets for this purpose: 1) …

Modeling Of Kinetically Limited Growth Rate For Solution-Synthesized Germanium Nanocrystals, Nicholas Shoop

Chemical and Biological Engineering ETDs

Solution synthesis is a common method of generating semiconductor nanocrystals. For solution synthesis, many studies have assumed that the growth rate is diffusion-limited with an unphysically low diffusion constant. In this thesis, a model is developed that considers both diffusion and surface kinetics. The diffusion coefficient of Ge monomers through the solvent, octadecene, at elevated synthesis temperatures is estimated to be on the order of 10-5 to 10-4 cm2/sec, while the mass transfer boundary layer thickness is estimated to be on the order of a few nanometers, similar to the nanocrystal size. These two realistic conditions strongly suggest that the …

Model Systems For The Study Of Active Phase Evolution In Complex Bimetallic Catalysts (Pdzn), Jonathan Paiz

Chemical and Biological Engineering ETDs

This study used PdZn as a model system to investigate phase transformations and its influence on reactivity. Aerosol synthesis was used to study the oxide precursors of the PdZn system, spin coating was used to synthesize model PdZn nanoparticles for phase transformations studies and preliminary work with CO oxidation coupled with methanol steam reforming (MSR) was used to gain insight into in-situ surface reactivity of PdZn for MSR. Multiple characterization techniques including XRD, Raman Spectroscopy, XPS, EDX along with TEM and STEM were used to gain valuable insight into the nature of the samples used in these studies. Investigations into …

Facile Synthesis Of High Surface Area Molybdenum Carbide And Nitride: An Application In Support Materials For Oxygen Reduction Reaction, Aaron Roy

Chemical and Biological Engineering ETDs

A method to synthesize high surface area α-MoC(1-x) without the temperature programmed reduction (TPR) of MoO3 is described. This method was then used, in conjunction with a novel in situ method to obtain highly dispersed PtMoz supported on α- MoC(1-x), to explore the suitability of such materials as catalysts for oxygen reduction reaction (ORR) in a proton exchange membrane fuel cell (PEMFC). Mg2(Mo3O8) and Zn2(Mo3O8), alternative tetravalent Mo intermediates to MoO2, were obtained through the thermal decomposition of Mg(MoO4) and Zn(MoO4) in mixtures of CO and H2. A novel sacrificial support method was developed where MgO and ZnO were investigated …

Multinode Acoustic Systems For High Throughput Cellular Analysis, Pearlson Prashanth Austin Suthanthiraraj

Chemical and Biological Engineering ETDs

For decades, flow cytometry is used as the gold standard for cellular analyses as it measures multiple properties of single cells. Traditional flow cytometry uses the hydrodynamic focusing technique where the sheath fluid focuses cells in the sample into a narrow stream. Although such precise focusing provides accurate optical measurements, high sheath fluid pressure and high linear velocities limit analysis rate to 50,000 particles/s. Such rates are too low for detecting rare events where one cell may have to be detected in a population of about a billion cells. Therefore, it is necessary to eliminate the sheath fluid and improve …

Adatom Emission From Nanoparticles: Implications For Ostwald Ripening, Tyne Johns

Chemical and Biological Engineering ETDs

To achieve clean air in our cities, all modern means of ground transportation make use of catalytic converters. Precious metal-based catalysts such as Pt and Pd are currently used in catalytic converters. To achieve higher fuel efficiency, combustion can be carried out in excess air resulting in a reduction of greenhouse gas (GHG) emissions. Reduction of these emissions has emerged as a major challenge. Most of the pollutants are emitted within the first 30 seconds after starting an engine because the catalyst is cold. The development of catalysts which achieve high activity at low temperatures will improve fuel efficiency and …

Numerical Analysis Of Co-Flowing Immiscible Liquids In Co-Axial Microtubes, In-Hwan Yang

Chemical and Biological Engineering ETDs

This research developed dimensionless correlations, based on the numerical simulations, for the boundaries between the dripping, transition and jetting regimes. Additional correlations are also developed for the radius and formation frequency of disperse droplet in the dripping regime and the transition regime, when the total volume of the satellite droplets is less than 1% of the disperse primary droplets.

Development Of Surface Based Platforms For Biomolecular Recognition And Protease Assays, Jose Cornejo

Chemical and Biological Engineering ETDs

The discovery of analytical tools for biomolecular recognition in the area of diagnostics is a research trend rich in innovative methods. Some of the main drivers found in this area are the constant need for low cost devices and biosensors, simplicity in design and operation, and time efficiency. In this thesis we present novel approaches for the development of protease activity assays. Our focus of study is the protease assay development process on two types of characterized platforms: microspheres and self-assembled monolayers (SAMs) on flat surfaces. The surface preparation and conjugation process with biological components of interest is presented along …

Experimental Characterization And Modeling Of Aspect-Rario-Dependent Diffusion Of Nanocrystals In Nanochannels, Louis Tribby

Chemical and Biological Engineering ETDs

The investigation of aspect-ratio-dependent diffusion and equilibrium partitioning of semiconductor nanocrystals in rectangular nanochannels has been undertaken. The nanocrystals are terminated with hydrocarbon ligands and suspended in toluene, considered an aprotic solvent. Time-dependent concentration profiles are measured as a function of distance from the channel entrance by the calibrated fluorescence intensity of the nanocrystals. Both the forward diffusion of the nanocrystals and their reverse diffusion are characterized. Nanocrystals are first allowed to diffuse forward from a reservoir into the nanochannels over a long period (\u2265 3 days) until the inlet concentration reaches a steady state. Subsequently, these nanocrystals are allowed …

Impact Of Carbon Support Chemistry, Morphology, And Structure On Platinum Catalyst Durability For Pemfc Applications, Anant Patel

Chemical and Biological Engineering ETDs

Polymer electrolyte membrane fuel cells are a promising alternative energy source, capable of being deployed as successful replacements in many stationary and mobile applications. These devices, however, lack durability, and this has become one of the limiting factors for commercialization. Many projects have focused on finding ways to improve their lifetimes, but few have tried to examine the underlying causes behind their corrosion. The goal of this project was to identify which parameters have a significant impact, both positive and negative, on PEMFC durability. To do this, three series of samples were analyzed using microscopic, spectroscopic, and electrochemical methods. Electron …

Flow In Thin Regions Bounded By Structured And Porous Surfaces : Applications To Load Bearings, Abishek Venkatakrishnan

Chemical and Biological Engineering ETDs

The effect of surface roughness on the load capacity and friction force of hydrodynamic bearings has received considerable interest from scientists and engineers. Surfaces of most engineered materials are textured at some level either deliberately to achieve some desired effect or produced by wear and friction of surfaces. This thesis analyses the effect of surface roughness and porosity on the load capacity of hydrodynamic bearings. The surface roughness is characterized by a single sinusoidal wave function. The implementation of sinusoidal roughness model is verified using a verification problem. Reynolds lubrication theory, derived from thin-region approximations of the Navier-Stokes equations, is …

In Vitro Cytotoxicity And Skin Irritation Testing Of Antimicrobial Conjugated Electrolytes : Interactions With Mammalian Cells, Kristin N. Wilde

Chemical and Biological Engineering ETDs

An estimated 19,000 deaths and $3-4 billion in health care costs per year in the U.S. are attributed to methicillin-resistant Staphylococcus aureus (MRSA) infections. Certain cationic phenylene ethynylene (CPE)-based polymers (PPEs) and oligomers (OPEs) have been demonstrated to exhibit dark and light-activated antimicrobial activity. Envisioned applications of these CPEs include the fabrication of antimicrobial surfaces to reduce or prevent the spread of potentially untreatable strains of bacteria. Until recently, it was unknown if the polymers or oligomers would exhibit similar biocidal activity toward mammalian cells. This work examines the toxicity of CPEs to mammalian cells at three levels: cytoxicity testing …