Engineering Commons^™

Multiscale Modeling Of Electrolytes For Energy Storage And Conversion, Fatemeh Sepehr

Doctoral Dissertations

Fuel cells, redox flow batteries, and secondary ion batteries are under active investigation to fulfill the requirements of efficient and sustainable energy storage and conversion technologies. The discovery of high-performance stable electrolytes that are relatively cheap and versatile is crucial to the commercialization of these electrochemical devices and necessitates a comprehensive understanding of the materials (i.e., from the atomistic to continuum levels). This dissertation is on multiscale modeling and simulations of several electrolytes under consideration in vanadium redox flow batteries (VRFBs), alkaline fuel cells (AFCs), or secondary magnesium batteries.

The hydrated structure and associated solvation Gibbs energies were determined for …

Innovative Electrode Nanocomposites For Energy Storage And Conversion Systems, Yiran Wang

Doctoral Dissertations

Nanocomposites emerged as suitable alternatives for electrode materials, are defined as “two or more materials with different properties remain separate and distinct on a macroscopic level within one unity and with any dimension in any phase less than 100 nm”. Recently, polymer/carbon based nanocomposites have attracted significant research interests for energy applications due to their multi-functionalities, improved structure stability and ease of production. This dissertation work focusing on the development of innovative electrode nanocomposites for proton exchange membrane fuel cell, supercapacitor and electrochromic applications.

Chapter 1 is an introduction. Chapter 2 & 3 focus on the synthesis of Pd-based nanocatalysts …

Large Scale Brownian Dynamics Simulation Of Dilute And Semidilute Polymeric Solutions, Amir Saadat

Doctoral Dissertations

Excluded Volume (EV) and Hydrodynamic Interactions (HI) play a central role in static and dynamic properties of macromolecules in solution under equilibrium and nonequilibrium settings. The computational cost of incorporating HI in mesoscale Brownian dynamics (BD) simulations, particularly in the semidilute regime has motivated significant research aimed at development of high-fidelity and efficient techniques.

In this study, I have developed several algorithms for the mesoscale bead-spring representation of a macromolecular solution in dilute and semidilute regimes. The Krylov subspace method enables fast calculation of single chain dynamics with simulation time scaling of O(N_b²) [order N …

Impedance-Resolved Performance And Durability In Redox Flow Batteries, Alan Michael Pezeshki

Doctoral Dissertations

The realization of redox flow batteries (RFBs) as a grid-scale energy solution depends on improving the performance and lifetime of the technology to decrease the high capital costs. The electrodes are a key component in the RFB; performance enhancement is often achieved through chemical or thermal treatments of commercially available porous carbon materials.

This dissertation uses impedance spectroscopy-based methods to gain insight into performance and durability in RFBs, enabling intelligent cell design. Initial work focused on understanding the impact of improved electrode and membrane properties on system performance. An accelerated stress test was then developed that can be used to …

Elucidating The Effects Of Metabolic State On Nanoparticle Distribution In Mice And In Vitro Uptake, Kevin James Quigley

Doctoral Dissertations

Since almost 70% of the U.S. population over 20 years old is overweight and 30% is obese, with much of the western world following suit, many patients that will potentially be administered circulating nanoparticles designed to localize to tumors and avoid non-target areas will have significant amounts of white adipose tissue (WAT), enlarged livers, and additional metabolic complications such as type 2 diabetes. However, studies on nanoparticle biodistribution and efficacy take place almost without exception in lean rodents with healthy metabolic states. In this work, I determined the biodistribution of model nanoparticles – neutral filomicelles and polystyrene spheres both carrying …

Thermodynamic And Dynamic Models For Directed Assembly Of Small Ensembles Of Colloidal Particles, Raghuram Thyagarajan

Doctoral Dissertations

Self and directed assembly of finite clusters (10 to 1000) of colloidal particles into crystalline objects is an emerging area of scientific interest that finds applica- tions in manufacturing of photonic crystals and other meta-materials. Such assembly problems are also of fundamental scientific interest because they involve thermodynamically small systems, with a number of particles that is far below the bulk limit. Robust methods for assembling defect-free target structures will ultimately require reduced-dimension process models that link the particle-level dynamics of the colloids to the actuator states. We have developed a three-part strategy for developing such process models. First, we …

Biopolymer Electrospun Nanofiber Mats To Inactivate And Remove Bacteria, Katrina Ann Rieger

Doctoral Dissertations

The persistence of antibiotic resistance in bacterial pathogens remains a primary concern for immunocompromised and critically-ill hospital patients. Hospital associated infections can be deadly and reduce the successes of medical advancements, such as, cancer therapies and medical implants. Thus, it is imperative to develop materials that can (i) deliver new antibiotics with accuracy, as well as (ii) uptake pathogenic microbes. In this work, we will demonstrate that electrospun nanofiber mats offer a promising platform for both of these objectives because of their high surface-to-volume ratio, interconnected high porosity, gas permeability, and ability to contour to virtually any surface. To provide …

Label-Free And Aptamer-Based Surface Enhanced Raman Spectroscopy For Detection Of Food Contaminants, Shintaro Pang

Doctoral Dissertations

The development of analytical methods to detect food contaminants is a critical step for improving food safety. Surface enhanced Raman spectroscopy (SERS) is an emerging detection technology that has the potential to rapidly, accurately and sensitively detect a wide variety of food contaminants. However, SERS detection becomes a challenge in real complex matrix, such as food, since non-specific matrix signals have the potential to drown out target associated Raman peaks. In this dissertation, we focused on the development and application of label-free, aptamer-based SERS in order to improve the accuracy and specificity of target contaminant detection in food. To accomplish …

Study Of The Self-Assembly Process Of Microporous Materials Using Molecular Modeling, Mohammad Navaid Khan

Doctoral Dissertations

Zeolites are an important class of materials in modern technology with applications in catalysis, separations, biosensing and microelectronics. There are over 200 different zeolite frameworks reported in literature, but only a handful have been used commercially. Understanding their self-assembly process would assist in the fabrication of new zeolites through the control of their pore size/shape, and surface area for advanced applications. With our research we aim to elucidate aspects of zeolite formation using molecular simulations. We have extended the lattice model of silica tetrahedra developed by Jin et al. [L. Jin, S. M. Auerbach and P. A. Monson J. Chem. …

Kinetics And Dynamics Of Electrophoretic Translocation Of Polyelectrolytes Through Nanopores, Harshwardhan Katkar

Doctoral Dissertations

The idea of sequencing a DNA based on single-file translocation of the DNA through nanopores under the action of an electric field has received much attention over the past two decades due to the societal need for low cost and high-throughput sequencing. However, due to the high speed of translocation, interrogating individual bases with an acceptable signal to noise ratio as they traverse the pore has been a major problem. Experimental facts on this phenomenon are rich and the associated phenomenology is yet to be fully understood. This thesis focuses on understanding the underlying principles of polymer translocation, with an …

Polymer And Small Molecule Designs For Anion Conducting Membranes: Connected Ion-Channel Morphologies And Highly Alkaline Stable Ammonium Cations, Sedef P. Ertem

Doctoral Dissertations

Fuel cells are one of the oldest sustainable energy generation devices, converting chemical energy into electrical energy via reverse-electrolysis reactions. With the rapid development of polymer science, solid polymer electrolyte (SPE) membranes replaced the conventional liquid ion transport media, rendering low-temperature fuel cells more accessible for applications in portable electronics and transportation. However, SPE fuel cells are still far from commercialization due to high operation cost, and insufficient lifetime and performance limitations. Anion exchange membrane fuel cells (AEMFCs) are inexpensive alternatives to current proton exchange membrane fuel cell (PEMFC) technology, which relies on utilizing expensive noble-metal catalysts and perfluorinated SPE …

Extracellular Matrix Control Of Breast Cancer Metastasis And Dormancy, Lauren Barney

Doctoral Dissertations

To metastasize, a cell must travel through circulation to a secondary tissue, and this process causes 90% of all cancer deaths. Although inefficient, metastasis is not random, and only capable seeds in hospitable soils are capable of outgrowing into detectable metastases. The overall hypothesis in this work is that the secondary tissue microenvironment, particularly the extracellular matrix (ECM), mediates metastasis. We posit that the ability of metastatic cells to survive dormancy, exit quiescence, and colonize a tissue depends upon the ability of the soil to sustain survival, and subsequently trigger outgrowth. We created a simple biomaterial platform with systematic control …

Mass And Charge Transport In Hydrated Polymeric Membranes, Marshall T. Mcdonnell

Doctoral Dissertations

Mass and charge transport through hydrated polymer membranes has significant importance for many areas of engineering and industry. Multi-scale modeling and simulation techniques were used to study transport in relation to two specific membrane applications: (1) food packaging and (2) additives for polymer electrolytes.

Chitosan/chitin films were studied due to their use as a sustainable, biodegradable food packaging film. The effects of hydration on the solvation, diffusivity, solubility, and permeability of oxygen molecules in these films were studied via molecular dynamics and confined random walk simulations. With increasing hydration, the membrane was observed to have a more homogeneous water distribution …

The Impacts Of Biopolymer-Ionic Liquid Interactions On The Utilization Of Lignocellulosic Biomass, Jing Wang

Doctoral Dissertations

In the bioenergy field, the recalcitrance of lignocellulosic biomass has been mainly attributed to lignin. Many ionic liquid (IL) pretreatments were performed to maximize the removal of lignin. However, those methods seriously degraded lignin and hemicellulose, and could generate lignin or hemicellulose for developing an integrated biorefinery that utilizes efficiently the whole biomass. To fulfill the requirements of the integrated biorefineries, this dissertation explored the interactions between biopolymers and IL for a better utilization of lignocellulosic biomass as feedstock. By removing a large portion of hemicellulose, through an autohydrolysis, this physical and chemical barrier for IL diffusion was dismantled and …

Synthesis And Characterization Of Polymeric Anion Exchange Membranes, Wenxu Zhang

Doctoral Dissertations

As alkaline anion exchange membrane fuel cells (AAEMFC) are regarded as promising and important energy devices, the development of high performance anion exchange membranes are in urgent need, as well as fundamental investigation on the structure-property relationship, which are the motivation of this dissertation. Three different polymer systems are presented and focused on polymer synthesis, material morphology, and ion transport phenomena. Crosslinked membranes are promising as practical materials, however, the understanding and further improvement of its performance is hindered by the lack of an ordered morphology or well-defined chemical structure. In Chapter 2, a series of crosslinked membranes were design …

Bioengineered Platforms To Study Carcinoma Cell Response To Drug Treatment, Thuy V. Nguyen

Doctoral Dissertations

The tumor extracellular matrix (ECM) plays an important role in facilitating tumor growth and mediating tumor cells' resistance to drugs. However, during drug development, potential chemotherapeutics are screened in plastic plates, which lack relevant ECM physicochemical cues. In order to improve drug development process, this dissertation includes the development of relevant 2D and 3D biomaterial systems that can be used to study carcinoma cell response to drug treatment. A novel poly(ethylene glycol)-phosphorylcholine (PEG-PC) high-throughput biomaterial platform was developed to study how the ECM mechanochemical properties affect cancer cells' response to drug. The PEG-PC biomaterial is optically transparent, has a mechanical …

Structure And Dynamics Of Charged Colloidal Disks In Colloid-Polymer Mixtures, Suhasini Kishore

Doctoral Dissertations

Complex fluid mixtures of colloids and polymers are extensively used in several conventional and emerging technological applications. Particles self-assemble under different conditions to form colloidal glasses and gels and it often leads to the development of unusual viscoelastic features. In the case of aspherical particles, shape anisotropy and physical aging effects add to the existing complexities so the implementation of a strategic formulation method to improve performance and stability remains a critical challenge. This thesis presents a comprehensive analysis of particle interactions in mixtures of charged disk-shaped colloids and weakly-adsorbing polymers like poly(ethylene oxide) (PEO). Here, we discuss the behavior …

Analysis Of External-Field-Driven Surface Stabilization And Patterning, Dwaipayan Dasgupta

Doctoral Dissertations

The ability to form, manipulate, and stabilize fine-scale materials features by controlling macroscopic forces is essential to advancing microelectronics and nanotechnology. For example, externally applied electric fields and thermal gradients drive atomic motion through the mass transport phenomena of electromigration or thermomigration, respectively, that have been considered for several decades as major sources of materials reliability problems in microelectronics. However, when tuned optimally, the same "destructive" forces can provide paradigm shifts in surface engineering and nanofabrication. Toward this end, developing a fundamental understanding and multi-physics, multi-scale mathematical models capable of predicting external-field-driven surface morphological evolution constitutes the main focus of …

In Silico Driven Metabolic Engineering Towards Enhancing Biofuel And Biochemical Production, Richard Adam Thompson

Doctoral Dissertations

The development of a secure and sustainable energy economy is likely to require the production of fuels and commodity chemicals in a renewable manner. There has been renewed interest in biological commodity chemical production recently, in particular focusing on non-edible feedstocks. The fields of metabolic engineering and synthetic biology have arisen in the past 20 years to address the challenge of chemical production from biological feedstocks. Metabolic modeling is a powerful tool for studying the metabolism of an organism and predicting the effects of metabolic engineering strategies. Various techniques have been developed for modeling cellular metabolism, with the underlying principle …

A Characterization Study On Catalyst Layers In Proton Exchange Membrane Fuel Cells, Luyue Li

Doctoral Dissertations

This thesis describes the work for the catalyst layer (CL) characterization study of proton exchange membranes (PEM) for fuel cells. In particular, both the structure and performance of catalyst layers with alternative ionomers were studied. Structure wise, the morphology, surface area and pore size distribution studies were accomplished with scanning electron microscopy (SEM), transmission electron microscope (TEM) and nitrogen adsorption processed through Brunauer–Emmett–Teller (BET) and Barrett-Joyner-Halenda (BJH) theory. Water uptake isotherms of the CLs have been developed under well controlled relative humidity (RH) levels. The performance characterization focuses on polarization study, catalyst layer proton conductivity measurement and estimation of the …

Tandem Laser Ablation Synthesis In Solution-Galvanic Replacement Reaction (Lasis-Grr): A Facile Route For The Synthesis Of Complex Intermetallic Nanomaterials With Engineered Functionalities, Sheng Hu

Doctoral Dissertations

Tailoring the heteronanostructures of nanoscale materials to tune their structure-property relations for desirable interfacial energetics is imperative for their catalytic, optoelectronic and electrochemical applications. Current PhD thesis develops a facile, yet “green” synthesis route that uses laser ablation synthesis in solution in tandem with galvanic replacement reaction (tandem LASiS-GRR) as a one-pot, one-step technique for manufacturing diverse and complex heteronanostructures of metal oxides, hydroxides, nanocomposites (NCs), and nanoalloys (NAs). The scientific concept here is that the non-equilibrium thermodynamics and kinetics of high-energy LASiS-GRR can be tuned by laser parameters and solvent chemistry to form complex NCs/NAs of tailored sizes/shapes, metastable …

Immobilization Of Cellulase For Large Scale Reactors To Reduce Cellulosic Ethanol Cost, Dezhi Zhang

Doctoral Dissertations

Cellulosic ethanol is an alternative renewable energy source. Cellulase used in the production of cellulosic ethanol is very expensive. The difficulty in separating cellulase from the cellulose solution after the hydrolysis process limits the reusability of the cellulase, which highly precludes the scales of this application because of the high cost of the enzyme. Immobilization of cellulase provides a promising approach to allow the enzyme to be recycled, thus reducing the production cost. This research focused on immobilizing cellulase for reuse to reduce the cellulosic ethanol cost.

Four immobilization techniques were explored for the immobilization of cellulase on four different …

Manufacturing Polyacrylonitrile Nanowires And Nanofibers For Sensing And Energy Storage Applications, Juan Chen

Doctoral Dissertations

A novel flow guided assembly approach is presented to well align and accurately position nanowire arrays in pre-defined locations with high throughput and large scale manufacturing capability. In this approach, polyacrylonitrile (PAN)/N, N-dimethylformamide (DMF) solution is first filled in an array of microfluidic channels. Then a gas flow is introduced to blow out most solutions while pushing a little leftover against the channel wall to assemble into polymer nanowires. In this way, highly-ordered nanowires are conveniently aligned in the flow direction and patterned along both sides of the microchannels. In this study, we demonstrated this flow-guided assembly process by producing …

(I) Polymer Nanocomposites: Rheology And Processing For Mesoporous Materials And (Ii) Nanopatterning Of Metal Oxides Using Soft Lithography, Rohit Kothari

Doctoral Dissertations

The research in this dissertation is categorized into two parts. The first part is focused on investigation of order-to-disorder transitions (ODT) in nanocomposites of an amphiphilic block copolymer containing various hydrogen-bonded additives, and fabrication of novel mesoporous silica based materials by utilizing such nanocomposites as templates. Disordered Pluronic®, poly(ethylene oxide) (PEO)−poly(propylene oxide) (PPO)−PEO triblock copolymer upon blending with small molecule additives containing hydrogen-bond-donating functional groups (carboxyl or hydroxyl) result into ordered nanoscale morphologies by preferentially interacting with the hydrophilic PEO chains in the Pluronic®. The dependence of ODT-temperature in these novel Pluronic®/small-molecule-additive complexes on composition, number and type of functional …

Voltage Driven Translocation Of Polyelectrolytes Through Nanopores, Byoung-Jin Jeon

Doctoral Dissertations

Recently, translocations of polyelectrolyte molecules through membrane channel protein pores or solid-state nanopores have been actively studied. Although the polymer translocation researches emerged mainly due to technological demands in terms of genome sequencing, the detailed physics of the single molecule transport through a narrow channel remains fully understood. To obtain further understanding of common features of the translocation process, this thesis focuses on the effects of salt concentration, pore-polymer electrostatic interactions, and externally applied electric field on the voltage-driven polymer translocations. The study is carried out by performing a series of systematically designed experiments using alpha-hemolysin (αHL) protein pore to …

Rational Development Of Carbon-Based Materials For Adsorption-Enhanced Conversion Of Cellulose To Value-Added Chemicals, Paul J. Dornath

Doctoral Dissertations

The increasing demands for transportation fuels and commodity chemicals as well as concerns over diminishing fossil fuel resources have driven research efforts towards the efficient utilization of renewable feedstocks, such as naturally abundant lignocellulosic biomass. Co-impregnation of microcrystalline cellulose with dilute sulfuric acid and glucose catalyzed the formation of a(1→6) branches onto b(1→4) glucan prior to ball-milling and reduce the time needed for ball-milling 4-fold compared to impregnation with acid alone. A three dimensionally ordered mesoporous (3DOm) carbon-based catalyst was developed that rapidly hydrolyzed the water-soluble glucan oligomers to 91.2% glucose yield faster than conventional approaches. A structure-property relationship was …

An Integrated Computational And Experimental Approach To Study And Scale-Up Vacuum Drying Of Pharmaceutical Products, Aditya G. Dodda

Doctoral Dissertations

Drying of Active Pharmaceutical Ingredients (APIs) is an energy intensive process that is often a manufacturing bottleneck due to its relatively long processing times. A key objective is the ability to determine the drying end point, the time at which all solvent has been evaporated from the solid cake. A novel method for determining the end point of pharmaceutical dryers, based on on-line mass spectrometry is developed and tested. The proposed method offers several advantages over existing spectrometric methods, including the ability to detect when the cake is dry from vapor phase measurements and a very simple implementation that does …

Model Systems For Characterizing The Intrinsic Properties Of Polymer Semiconductors: Oligomers And Single Crystals, Nicholas S. Colella

Doctoral Dissertations

Polymer semiconductors hold great promise for the realization of inexpensive, flexible electronic devices. One of the greatest strengths of these materials, their low-cost processability from solution, results in a wide range of solid-state structures. The crystallinity and morphology of these materials strongly impacts their performance as charge carriers. Furthermore, the nature of polymerization inherently leads to the production of materials which are disperse in their molecular character, with regard to both coupling and molecular weight. Thus, it is difficult to deconvolute the intrinsic properties of polymer semiconductors from their synthetic and processing conditions. Polythiophenes are particularly susceptible to performance variations …

Rational Development Of Solid Lewis Acid Catalysts For Biomass Conversion, Chun-Chih Chang

Doctoral Dissertations

The need for sustainable production of everyday materials in addition to declining reserves of petroleum-based feedstocks has motivated research into the production of renewable aromatic chemicals from biomass. We have proposed a multistep pathway to produce renewable p-xylene from lignocellulosic biomass using heterogeneous catalysts. The pathway includes formation of glucose by saccharification of cellulose, isomerization of glucose into fructose, dehydration/hydrogenolysis for production of 2,5-dimethylfuran (DMF), and final step for producing p-xylene from reacting DMF with ethylene. Lewis acid zeolite catalysts (e.g. Sn-BEA, a tin containing molecular sieve with zeolite BEA structure) exhibited critical roles in the pathway because …

Modeling Gas Inflow For Extremely Low Permeability Shale Using Cfd, Chatetha Chumkratoke

Doctoral Dissertations

"Computational fluid dynamics (CFD) has been used to model 2-D well inflow over a range of permeabilities to study the impact of various well completion strategies (Augustine, 2011). Augustine's 2-D model was subsequently extended for 3-D flow by Thepporprapakorn (2013), for gas flow in the permeability range of tight gas (0.01 mD).

This work presents a 3-D CFD model of gas inflow valid for extremely low ranges of permeability (0.00001 mD). In extremely low permeability, gas flow is complex and includes flow from fractures, flow through porous media, and diffusive gas transport. Diffusive gas transport is important when strong density …