Engineering Commons^™

Reconfiguration-Driven Assembly Of Inorganic Nanomembranes, Divya Jyoti Prakash

Chemical and Biological Engineering ETDs

This thesis focuses on the guided self-assembly of metastable nanomembranes (NMs) that are either amorphous or polycrystalline. Guided self-assembly of NMs is a robust and scalable method to obtain a variety of three-dimensional structures such as helices, rolled-up tubes, and networks of interconnected channels. These 3D structures have important applications as on-chip actuators, sensors, inductors, transformers, waveguides, and antennas. Furthermore, a large amount of strain and strain gradient can be imparted in NMs by bending them to a nanoscale and microscale radius of curvature, making guided self-assembly on NMs a viable route to extreme strain engineering of amorphous and polycrystalline …

Modeling And Performance Analysis Of Deb Based Hydrogen Getters, John A. Matteson

Chemical and Biological Engineering ETDs

Hydrogen getter materials are used to irreversibly absorb hydrogen gas in sealed environments. The DEB based getter system, despite finding widespread use in this application, still posses challenges with respect to experimental performance analysis and fundamental understanding of reaction mechanism. The second chapter of this report addresses the experimental challenges of this getter system by demonstrating the utility and experimental strengths of a custom magnetic suspension balance (MSB) based gravimetric sorption system. This apparatus enables performance evaluation in process relevant conditions including dilute mixed gas environments which our results indicate is necessary for accurate performance evaluation of getter systems. Chapter …

Prediction Of Self-Diffusion Constants In Model And Real Systems Using Machine Learning, Joshua P. Allers

Chemical and Biological Engineering ETDs

Understanding diffusion of chemical compounds is important for the design and optimization of many chemical engineering and energy processes. Recent modifications to the Darken equation allow for accurate prediction of Maxwell-Stefan (MS) diffusion in mixtures. Still, there are few practical applications due to the requirement of individual self-diffusion constants. A reliable predictive model for self-diffusion constants would be highly valuable when used in conjunction with the modified Darken equation. Here, we show that Machine Learning (ML) can be used to develop generalized models for self-diffusion in Lennard Jones (LJ) systems and real systems of pure solutions. The use of Artificial …

Copper Electrodeposition In Full Wafer Thickness Through-Silicon Vias, Rebecca P. Schmitt

Chemical and Biological Engineering ETDs

Through-silicon vias (TSVs) are a key interconnect technology for advanced packaging of microelectronic devices, and full wafer thickness TSVs are required for certain microelectromechanical systems (MEMS) applications. In this work, electrolytes containing copper sulfate, an acid, chloride, and Tetronic 701 suppressor were implemented for Cu filling of high aspect ratio (10:1), full wafer thickness TSVs. For each electrolyte system, rotating disk electrode voltammetry was used to identify a voltage range for bottom-up Cu filling in the TSVs. Die level feature filling was performed using voltage ramping, which moved active deposition through the vias to yield void-free Cu features. During voltage-controlled …

Coulombic And Non-Coulombic Effects Of Single And Overlapping Electric Double Layers With Surface Charge Regulation, Raviteja Vangara

Chemical and Biological Engineering ETDs

The physical origin of charged interfaces involving electrolyte solutions is in the thermodynamic equilibrium between the surface reactive groups and certain dissolved ionic species in the bulk. This equilibrium is very strongly dependent on the precise local density of these species, also known as potential determining ions in the solution. The latter, however, is determined by the overall solution structure, which is dominated by the large number of solvent molecules relative to all solutes. Hence, the solvent contribution to the molecular structure is a crucial factor that determines the properties of electric double layers. Models that explicitly account for the …

An Investigation Of The Chemistry, Thermodynamics And Catalytic Activity Of Molybdenum Carbides, Shanti Kiran Nayak

Chemical and Biological Engineering ETDs

These studies investigate the chemistry and stability of molybdenum carbides as an electrocatalyst. Due to their unique electronic properties, molybdenum carbides are purposed as electrocatalysts for reaction systems such as hydrogen evolution reaction, bifunctional water splitting and CO oxidation.

In this study, various synthesis processes were utilized to produce different types of molybdenum carbide with varying properties of particle size, surface area and excess carbon. The samples characterized by XRD accompanied by Whole Profile Fitting, Electron Microscopy, Gas Adsorption (surface area) and XPS.

These synthesis processes were refined using fundamental thermodynamic analyses. These analyses highlight regions of stability of different …

Symmetry And Dopant Diffusion In Inverted Nanopyramid Arrays For Thin Crystalline Silicon Solar Cells, Seok Jun Han

Chemical and Biological Engineering ETDs

In this dissertation, we enhance the efficiency of thin flexible monocrystalline silicon solar cells by breaking symmetry in light trapping nanostructures and improving homogeneity in dopant concentration profile. These thin cells are potentially less expensive than conventional thick silicon cells by using less silicon material and making the cells more convenient to be handled when supported on polymer films. Moreover, these cells are widely applicable due to their flexibility and lightweight. However, for high efficiencies, these cells require effective light trapping and charge collection. We achieve these in cells based on 14-mm-thick free-standing silicon films with light-trapping arrays of nanopyramidal …

Fluid Transport In Porous Media For Engineering Applications, Eric M. Benner

Chemical and Biological Engineering ETDs

This doctoral dissertation presents three topics in modeling fluid transport through porous media used in engineering applications. The results provide insights into the design of fuel cell components, catalyst and drug delivery particles, and aluminum- based materials. Analytical and computational methods are utilized for the modeling of the systems of interest. Theoretical analysis of capillary-driven transport in porous media show that both geometric and evaporation effects significantly change the time dependent behavior of liquid imbibition and give a steady state flux into the medium. The evaporation–capillary number is significant in determining the time-dependent behavior of capillary flows in porous media. …

Cellular Modification And Artificial Cell Construction, Jimin Guo

Chemical and Biological Engineering ETDs

With all its complexities and different biofunctionalities, a cell is the basic structural and functional unit of all living organisms with the exception of viruses. In this dissertation, I demonstrated gain of function strategies of modifying mammalian cells using silicification and modular nanoparticle (NP) exoskeletons. In addition, I used a modular design concept to build a multifunctional artificial RBC system which can mimic the unique characteristics (e.g. shape, flexibility, the ability to carry oxygen, and long circulation times) of the native RBCs. Together, these cell modification or artificial cell construction strategies are expected to generate new mammalian cell-like structures with …

Metabolon-Inspired Design Of Multi-Modal Catalytic Cascade, Madelaine Seow Chavez

Chemical and Biological Engineering ETDs

Developing hybrid catalytic systems has been researched for the past decade in an effort to efficiently incorporate catalysts of different modalities in catalytic cascades. It has become imperative to design a cascade system where the catalysts are spatially organized to control the delivery of precursors, intermediates, and products. In this work, we have shown that a molecular catalyst, biocatalyst, and metallic catalyst can be co-localized using a carbonaceous support to create a hybrid catalytic system and complete the oxidation of oxalic acid to create a microchemical reactor. The molecular, pyrene-TEMPO catalyst oxidizes glyoxalic acid to oxalic acid. The enzyme oxalate …

Reaction Of Titanium Subhydride With Multiple Passivating Gasses, Erik C. Strobert Jr

Chemical and Biological Engineering ETDs

Sandia National Laboratories has used substoichiometric titanium hydride as a pyrotechnic fuel for decades. Production of titanium subhydride requires partial dehydriding of titanium hydride powder and subsequent chemical passivation to render the resultant bare titanium surface nonreactive and the powder non-pyrophoric. Novel passivation techniques, using a gas other than air, have been suggested in the past but have never been investigated. This work examines the reaction kinetics of titanium subhydride with three passivating agents, nitrogen, oxygen, and propane. These passivation experiments took place under isothermal conditions (420 ˚C) with varied dehydriding and passivation time periods. It was found that the …

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 …

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. …

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). …

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 …

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 …

Methods Of Cellular Integration And Techniques For Improving Encapsulated Cell Viability For The Purpose Of Developing Living Materials And Cell Based Bio-Sensing Materials, Travis J. Savage

Chemical and Biological Engineering ETDs

Living materials offer the potential for detection-reporter systems based on living cells that are genetically tailored to sense target analytes with high levels of specificity and accuracy. A biotic or living material would allow the development of simple, hand held devices that could be utilized for many applications including industrial process monitoring, environmental remediation, military and defense applications and drug delivery. Many living materials have been developed and characterized but they still lack heightened and prolonged encapsulated cell viability necessary to make the material a candidate for widespread use. One particular material offers several advantages to increase yeast cell viability …

Development Of Novel Bio/Nano Interfaces For Materials Science And Biomedical Applications, Carlee Ashley

Chemical and Biological Engineering ETDs

Virus-like particles (VLPs) of MS2 bacteriophage possess a variety of characteristics that enable their use in biomedical and materials science applications. MS2 VLPs are perfectly monodisperse and possess a highly regular periodic structure. Their protein capsids can be modified in precise locations via chemical conjugation or genetic display of peptides, and their interior volumes can be readily loaded with a variety of non-genomic materials by taking advantage of their ability to self-assemble in the presence of RNA and RNA-modified cargos. Using peptides identified by filamentous phage display, I have demonstrated the utility of MS2 VLPs as targeted nanocarriers capable of …

Reactivity Study Of Platinum Nanoparticles And Nanowires Inside The Channels Of Mesoporous Silica, Marcus R. Smith

Chemical and Biological Engineering ETDs

Pt metal nanowires and nanoparticles were prepared using mesoporous silica as the template. Mesoporous silica with straight 1-dimensional, tortuous 1-dimensional and 3-dimensional channels was used. The experimental techniques included CO oxidation, Chemisorption, XRD, and STEM. CO oxidation and chemisorption provided the data to calculate the intrinsic reactivity, known as turn over frequency (TOF). Powder XRD was used to measure line broadening. The FWHM of the XRD line broadening was used with the Scherrer formula to determine Pt metal crystallite size. STEM images permitted for the measurement of the particle diameters, and the determination of morphology.

Two commercially available reference samples …

Activation Of Precipitated Iron Fischer-Tropsch Catalysts, Mehul D. Shroff

Chemical and Biological Engineering ETDs

The Fischer-Tropsch Synthesis (FTS) is an important step in the manufacture of synthetic fuels from coal. The use of iron catalysts for FTS, though desirable from the standpoint of process economy, is hampered by problems relating to catalyst attrition and carbon buildup. In addition, from a research perspective, there has been a long-standing controversy in the literature with regard to the nature of the active phase.

The effect of activation and reaction treatments on the resulting phase transformations in a commercial, precipitated and spray-dried, Fe₂O₃ - CuO - K₂O Fischer-Tropsch catalyst have been studied. Different …