Materials Science and Engineering Commons^™

Experiments And Modeling Of The Chemo-Mechanically Coupled Behavior Of Polymeric Gels, Nikola Bosnjak

Dissertations

Polymeric materials consist of mutually entangled or chemically crosslinked long njitmolecular chains which form a polymer network. Due to their molecular structure, the njitpolymeric materials are known to undergo large deformation in response to various njitenvironmental stimuli, such as temperature, chemical potential and light.

When a polymer network is exposed to a suitable chemical solvent, the solvent molecules are able to diffuse inside the network, causing it to undergo a large volumetric deformation, known as swelling. In addition to volumetric deformation, this process involves the chemical mixing of the polymer network and solvent molecules, and is typically environmentally responsive. A …

Practical Adhesion Measurements In Organic Coatings; Advancing Understanding And Mechanical Methods Development, Diana Gottschalk

Dissertations

“Adhesion” can be considered either a mechanical or chemical phenomenon. The mechanical interpretation describes the difficulty of separating surfaces and is useful for quantifying performance within applications that depend on bulk and interfacial properties. Chemical adhesion describes interfacial resistance to chemical attack and does not depend on bulk properties. Predicting chemical failure through mechanical measurement is confounded by the influence of bulk properties. However, the prospect is attractive because of the robust tolerance for sample geometries, allowing experiments to resemble an end-use system. The present work's primary goal was to elevate mechanical methods to provide a detailed interfacial characterization of …

Development Of Functional Materials And Devices On Flexible Platforms Using Additive Print Manufacturing Processes For Biomedical And Environmental Applications, Dinesh Maddipatla

Dissertations

In recent years, considerable research has been vested into the development of printed electronics (PE) to explore the best ways of fabricating electronic devices on flexible platforms using additive print manufacturing processes. PE produces flexible devices that are compatible with complex geometries, foldable applications and conformal to curved surfaces, with a promising potential for large‐area device fabrication at relatively lower manufacturing costs. This dissertation focuses majorly on the design and fabrication of novel flexible functional materials and devices for biomedical and environmental applications using additive printing processes.

Initially, a simple paper-based low cost and rapid prototypable platform with oxygen sensors …

Graphene Based Barrier Membrane For Gas Separation Processes, Cheng Peng

Dissertations

Novel graphene oxide (GO) flake-based composite lamellar membrane structure is being developed as a potential component of a garment for protection against chemical warfare agents (CWAs) represented here by simulants, dimethyl methyl phosphonate (DMMP) (a sarin-simulant) and 2-chloroethyl ethyl sulfide (2-CEES) (a simulant for sulfur mustard), yet allowing a high moisture transmission rate. GO flakes of dimensions 300-800 nm, 0.7-1.2 nm thickness and dispersed in an aqueous suspension are formed into a membrane by vacuum filtration on a porous polyethersulfone (PES) or poly (ether-ether-ketone) (PEEK) support membrane for noncovalent π-π interactions with GO flakes. After physical compression of such a …

Numerical And Analytical Methods To Predict Behavior Of Reinforced Ductile Concrete Composites, Mandeep Pokhrel

Dissertations

Structural components constructed with ductile concrete composites, such as high-performance fiber-reinforced cementitious composites (HPFRCC), are known to perform exceptionally well under extreme mechanical and environmental loading conditions compared to traditional concrete. HPFRCC flexural components exhibit enhanced performance in terms of displacement ductility, energy dissipation capacity, and damage tolerance capacity. However, recent research suggests that the flexural behavior of reinforced HPFRCCs in terms of crack progression, reinforcement plasticity, and failure mechanism is significantly different than conventional reinforced concrete. Specifically, the failure mode of flexural members is found to be predominantly through the fracture of longitudinal reinforcement rather than compression crushing of …

The Impact Of Conversion On The Durability Of Calcium Aluminate Cement Concrete Systems, Marwa Mohsen Korayem

Dissertations

The deterioration of infrastructure in North America has resulted in a significant need for concrete repair materials that can be used to maintain service life of these structures. Hydraulic cement based rapid repair materials can be used to repair pavement and bridge deterioration with minimal impact on economic activities such as freight handling or public transportation. While there are many options for use in repair situations, calcium aluminate cements have become more popular recently, particularly in situations where repairs must be completed rapidly.

Calcium aluminate cement (CAC) is a cement characterized by its rapid strength gain, even at low temperatures …

Modeling Single Microtubules As A Colloidal System To Measure The Harmonic Interactions Between Tubulin Dimers In Bovine Brain Derived Versus Cancer Cell Derived Microtubules, Arooj Aslam

Dissertations

The local properties of tubulin dimers dictate the properties of the larger microtubule assembly. In order to elucidate this connection, tubulin-tubulin interactions are be modeled as harmonic interactions to map the stiffness matrix along the length of the microtubule. The strength of the interactions are measured by imaging and tracking the movement of segments along the microtubule over time, and then performing a fourier transform to extract the natural vibrational frequencies. Using this method the first ever reported experimental phonon spectrum of the microtubule is reported. This method can also be applied to other biological materials, and opens new doors …

Schwann Cells In Combination With Gag-Mimetic Scaffolds For Spinal Cord Repair, Sharareh Hashemi

Dissertations

Spinal cord injury (SCI) being a devastating neurological dysfunction can cause extensive irreversible neuronal loss and axonal damage. Fifty-four cases of spinal cord injury per million people occur annually in the United States. Due to the loss of glial cells and demyelination of axons, the neuronal function of surviving neurons is disrupted leading to permanent loss of sensory and motor functions. The glial scar formed by astrogliosis at the chronic stage protects undamaged tissues, but it is known to be a major barrier for axonal regeneration. The limited regeneration capacity of spinal cord makes it challenging to successfully treat the …

Bulk Properties Correlated To The Hydrogen Bond Organization In Dendrimers, Hyperbranched Polymers, And Linear Polymers, Beibei Chen

Dissertations

Although a lot of research was conducted on dendritic polymers, our understanding of their structure-property is still limited. Our previous study, which focused on a family of dendritic polymers based on 2,2-bis(hydroxymethyl) propionic acid (bis-MPA) as a monomer, discovered unique hydrogen bond organizations contributed by their dendritic structures. However, the influence of the H-bond organization on bulk properties has yet to be understood. The goal of this dissertation is to elucidate the correlation between the H-bond organization with the dielectric and volumetric properties of bis-MPA based dendritic polymers, with an emphasis on developing a fundamental understanding of to what extent …

Towards Completely Automated Glycan Synthesis, Matteo Panza

Dissertations

Carbohydrates are ubiquitous both in nature as biologically active compounds and in medicine as pharmaceuticals. Although there has been continued interest in the synthesis of carbohydrates, chemical methods require specialized knowledge and hence remain cumbersome. The need for development of rapid, efficient and operationally simple procedures has come to the fore. This dissertation focuses on the development of a fully automated platform that will enable both experts and non-specialists to perform the synthesis of glycans. Existing automated methods for the synthesis of oligosaccharides are highly sophisticated, operationally complex, and require significant user know-how. By contrast, high performance liquid chromatography (HPLC) …

Improving Boron For Combustion Applications, Kerri-Lee Annique Chintersingh

Dissertations

Boron has received much attention as a potential additive to explosives and propellants due to its high theoretical gravimetric and volumetric heating values. The challenge, however, is that boron particles tend to agglomerate, have lengthy ignition delays and very low combustion rates. Prior research indicates that boron’s long ignition delays are due to its inhibiting naturally occurring oxide layer, impeding the diffusion of reactants for oxidation. For combustion, current studies report that boron particles have two consecutive stages, but the actual reaction mechanism is poorly understood. Despite many years of relevant research, quantitative combustion data on micron-sized boron particles are …

Supercapacitors With Gate Electrodes, Tazima Selim Chowdhury

Dissertations

A new approach to improve the capacitance of supercapacitors (SC) is proposed in this study. A typical SC is composed of an anode and a cathode; a separator in between them assures an unintentional discharge of the capacitor. The study focuses on a family of structured separators, either electronically active or passive which are called gates. An active structured separator layer has been fabricated and analyzed. The structured separator has characteristics of electrical diode and is fabricated out of functionalized carbon nanotubes (CNT). Improvement of the overall capacitance of SC, equipped with either active or passive structured separators demonstrated a …

Epitaxial Growth Of Iii-Nitride Nanostructures And Their Optoelectronic Applications, Moab Rajan Philip

Dissertations

Light-emitting diodes (LEDs) using III-nitride nanowire heterostructures have been intensively studied as promising candidates for future phosphor-free solid-state lighting and full-color displays. Compared to conventional GaN-based planar LEDs, III-nitride nanowire LEDs exhibit numerous advantages including greatly reduced dislocation densities, polarization fields, and quantum-confined Stark effect due to the effective lateral stress relaxation, promising high efficiency full-color LEDs. Beside these advantages, however, several factors have been identified as the limiting factors for further enhancing the nanowire LED quantum efficiency and light output power. Some of the most probable causes have been identified as due to the lack of carrier confinement in …

N8- Polynitrogen Stabilized On Carbon-Based Supports As Metal-Free Electrocatalyst For Oxygen Reduction Reaction In Fuel Cells, Zhenhua Yao

Dissertations

The sluggish oxygen reduction reaction (ORR) kinetics at the cathode is one of the key factors limiting the performance of polymer electrolyte membrane fuel cell (PEMFC). Platinum-based materials are the most widely studied catalysts for this ORR reaction while their large-scale practical application in fuel cells is hindered due to their scarcity and low stability. Therefore, highly active, low cost and robust non-Pt catalysts are being developed to overcome the drawbacks. Recently, a novel polynitrogen N8- (PN) stabilized on multiwall carbon nanotube (MWNT) was synthesized under ambient condition for the first time by our group and demonstrated high ORR activities. …

Surface-Enhanced Raman Detection Of Glucose On Several Novel Substrates For Biosensing Applications, Laila Saad Alqarni

Dissertations

The small normal Raman cross-section of glucose is considered to be a major challenge for its detection by Surface Enhanced Raman Spectroscopy (SERS) for medical applications. These applications include blood glucose level monitoring of diabetic patients and evaluation of patients with other medical conditions, since glucose is a marker for many human diseases. This dissertation focuses on Surface-Enhanced Raman Scattering primarily for the detection of glucose. Some experiments also are carried out for the detection of the corresponding enzyme glucose oxidase that is used in electrochemical glucose sensors and in biofuel cells. This project explores the possibility of utilizing Surface …

“Polysoaps” Via Raft Copolymerization To Form Well-Defined Micelles For Water Remediation And Targeted Drug Delivery Applications, Phillip Pickett

Dissertations

Amphiphilic copolymers have become increasingly important for environmental and biological applications due to their behavioral characteristics in aqueous solution. For example, structurally-tailored statistical amphiphilic copolymers or “polysoaps” can self-assemble into micelles or other architectures in water at various concentrations. Polysoaps may be differentiated from small molecule surfactant micelles in their capability to self-assemble into unimolecular associates (unimolecular micelles) with no dependence on concentration. Such micelles offer enormous potential for dispersion of hydrophobic species in water at high dilution. Importantly, each polymer chain forms its own micelle and upon dilution, these micelles remain intact and capable of dispersing hydrocarbon material in …

Engineering Multifunctional And Morphologically Diverse Polymer Brush Surfaces, Cassandra M. Reese

Dissertations

The combination of surface-initiated polymerization (SIP) and post-polymerization (PPM) serves as a powerful approach to fabricate complex, multifunctional polymer films, which can be precisely tuned for desired surface engineering applications. Careful manipulation of PPM parameters such as reaction conditions, the tethered brush parameters, and the physical properties of the unbound post-modifier greatly influence the depth of penetration of the post-modifier and the polymer brush compositional heterogeneity. This dissertation focuses on engineering polymer brush surfaces with multifunctional chemistries and tunable morphologies by investigating the PPM parameters that dictate the distribution of post-modifiers on grafted polymer brush surfaces.

The first chapter of …

Magnetic Field Assisted Milli-Scale Robotic Assembly Machine: An Approach To Massively Parallel Swarm Robotic Automation Systems, Yan Liu

Dissertations

The vision of highly parallel, automated manufacturing systems that can build macroscopic products by heterogeneous assembly of many small devices will have a major impact in manufacturing. In this study, a novel milli-scale robotic assembly machine with parallel capabilities, assisted with programmable magnetic field, is developed. The machine prototype consists of a 16x16 array of electromagnets. The dimensions of the electromagnets are 5mm high with an inner diameter of 1.1mm and outer diameter of 2.5mm. All the electromagnets are driven by a 16x16 array of H-Bridges, and an Arduino microcontroller is used to control and program the arrays.

Using the …

Development Of Flexible Nickel-Zinc And Nickel-Iron Batteries, Xianyang Meng

Dissertations

The fabrication of flexible nickel-zinc batteries using a facile mixing of electroactive components for electrode preparation is presented. Polytetrafluoroethylene (PTFE) is found to be an effective binder by reducing concentration polarization, providing chemical/physical stability and enhancing flexibility. The zinc electrode containing PTFE maintains its original porous morphology even after hundreds of cycles while polymers such as PEO show morphology change. Each component, as well as the assembled flexible cells show desired flexibility and stability even under bending conditions.

The fabrication of flexible nickel-iron batteries using printable composite electrodes embedded with multiwalled carbon nanotubes (CNT) is also presented. All the metal …

Polyhedral Oligomeric Silsesquioxane-Phosphate Glass Matrix Nanocomposites With Additional Chapter On Phosphate Glass-Poly(Ethylene Terephthalate) Matrix Composites, Kyoungtae Kim

Dissertations

Preparation and characterization of tin fluorophosphate glass (Pglass) matrix nanocomposites incorporating polyhedral oligomeric silsesquioxane (POSS) were investigated on the structural, thermal, morphological, mechanical, and rheological properties. Various processes including synthesis, extrusion and sintering processes were applied to prepare the nanocomposite samples. Another application of POSS with hydrophobic functional groups on the well-structured nanoscale silicate cage with three silanol groups was investigated to present the feasibility to use POSS molecule as a coating material on the surface of the hydrophilic inorganic glass. In addition, Poly(ethylene terephthalate) polymer matrix composites incorporating Pglass was studied to present the benefits of the Pglass with …

Hydrogen Bond Mediated Water Structuring, Diffusion, And Elastic Properties In Acrylamide Copolymer Glycohydrogels, April Levu Fogel

Dissertations

Glycohydrogels have recently gained considerable interest as biocompatible and high water content hydrogels that have similar physicochemical nature to the cell membrane, making them ideal materials for targeted biomedical and personal care applications (e.g., drug delivery systems, biosensors, and contact lenses). Regardless of the specific application, water-polymer and water-water hydrogen bonding interactions have been shown to dictate hydration stability and diffusional properties in traditional hydrogel architectures (e.g., crosslinked HEMA). However, due to the development of glycohydrogel materials within the past two decades, most literature focuses on synthetic techniques and general hydration characteristics. Furthermore, scant literature examines the effect of hydrophobically …

Cellulose-Derived Glycosaminoglycan Mimetic For Use In Cartilage Tissue Engineering Strategies, Roseline Dominic Menezes

Dissertations

Articular cartilage has limited healing and self-repair capability due to the absence of vasculature, lymphatic vessels, and nerves. Damage to articular cartilage becomes irreversible leading to formation of osteoarthritis that could severely degrade a person's quality of life. Approximately, 5-10% of cartilage tissue is made up of glycosaminoglycans (GAG), which sequester growth factors as well as provide structural integrity to the native cartilage tissue. Transforming growth factor-beta3 (TGF-β3) is an important growth factor for inducing chondrogenesis in mesenchymal stem cells (MSCs). Bioavailability of TGF-β3 plays a critical role in cartilage repair both in vitro and in vivo. This study evaluates …

Silicon Based Uncooled Microbolometer, Asahel Banobre

Dissertations

During the last decade, uncooled microbolometer infrared detectors have attracted the attention of military and civilian infrared detection and imaging industry due to their significant advantages. In actuality, infrared imaging systems play a critical role in sectors such as thermography (predictive maintenance and building inspection), commercial and civilian applications (vision automotive, surveillance, navigation and fire-fighting), and defense industry (thermal weapon sight, soldier vision and vehicle vision enhancer). Compared with the cryogenically cooled infrared photon detectors, uncooled infrared imaging technology offers advantages such as operation at room temperature, light weight and size, reduced power consumption, easy integration with read-out electronics and …

Structural Studies To Determine The Mechanisms Supporting Multiferroic And Ferroelectric Properties Of Complex Oxides, Han Zhang

Dissertations

Multiferroics are a class of materials which possess both magnetic and electrical polarization with possible coupling between them. They show promise to enable new sensors and data storage devices with novel features, such as the possibility of writing polarization bits with magnetic fields at low power. The coexisting magnetic and ferroelectric order parameters are usually weakly coupled, preventing practical use. The development and study of new classes of materials with large magnetoelectric couplings is of high importance. Understanding the structure of these materials is key to this effort.

As one class of these systems, the RX3(BO₃)₄ has …

A Biodegradable Piezoelectric Composite Scaffold Containing Zinc Oxide For Cartilage Repair Applications, Ateka Mohd Arabi Khader

Dissertations

Osteoarthritis (OA) affects 27 million adults in the United States. OA causes degeneration of articular cartilage and subchondral bone. Articular cartilage has limited ability to regenerate and repair. Bone and cartilage tissues have known piezoelectric properties, which means they can generate electrical activity in response to mechanical deformation. Using a biomimetic approach, zinc oxide (ZnO), which has known piezoelectric properties, is fabricated into a flexible three-dimensional fibrous scaffold by embedding ZnO nanoparticles into slow degrading polycaprolactone (PCL). Zinc ions can be released from the fibrous scaffold over time, which also may be beneficial for cell function since zinc has well-known …

Polymer Nanocomposites Containing High Aspect Ratio Particulates: Innovation In Co-Extruded Multilayer Barrier Films, Kevin Meyers

Dissertations

Delaminated montmorillonite (MMT) clay/ maleic anhydride grafted LLDPE nanocomposite multilayer films with alternating layers of LDPE were produced through multilayer co-extrusion. The MMT concentration within the nanocomposite layers was increased through annealing the films in the melt due to a mismatch in interdiffusion rates of the polymer layers. Analysis of the nanocomposite layers upon annealing revealed that the platelets impinged upon one another resulting in significant improvement in oxygen barrier in the multilayer system, exceeding the results of bulk nanocomposites.

Model analysis demonstrated that increasing the nanoplatelet aspect ratio or initial concentration in the filled layers would lead to even …

Antimicrobial Materials Via Thiol-Ene Chemistry, Dahlia Amato

Dissertations

With the increasing prevalence of antimicrobial resistance, the escalation of opportunistic/pathogenic infections is a looming global crisis. To avoid the pitfalls of conventional antibiotics, this dissertation focuses on developing macromolecular solutions to develop novel antimicrobial materials based on essential oils (thymol, carvacrol, and aldehydes). It is well established that essential oil derivatives exhibit high potency towards a wide range of pathogenic microbes. The rapid photopolymerization kinetics, limited by-products, and homogeneous network formation afforded by thiol-ene photopolymerization are utilized to either encapsulate essential oil derivatives or convert them into monomers which can subsequently be incorporated into new antimicrobial materials with new …

Functionalized Nanoporous Carbon Scaffolds For Hydrogen Storage Applications, Christopher Carr

Dissertations

Recent efforts have demonstrated confinement in porous scaffolds at the nanoscale can alter the hydrogen sorption properties of metal hydrides, though not to an extent feasible for use in onboard hydrogen storage applications, proposing the need for a method allowing further modifications. The work presented here explores how the functionalization of nanoporous carbon scaffold surfaces with heteroatoms can modify the hydrogen sorption properties of confined metal hydrides in relation to non-functionalized scaffolds (FS). Investigations of nanoconfined LiBH₄and NaAlH₄indicate functionalizing the carbon scaffold surface with nitrogen can shift the activation energy of hydrogen desorption in excess of …

Black Silicon – Optical Properties And Applications, Sita Rajyalaxmi Marthi

Dissertations

Crystalline Silicon (c-Si) is one of the most abundant and widely used semiconductors. Si is a semiconductor with indirect bandgap. The average reflectance of Si is about 30% in the visible range of wavelengths. Standard Si solar cells are not entirely useful in the infrared spectrum region. In order to make Si useful in a wide spectral range, the surface of Si is modified to reduce the reflectance of Si. The silicon thus modified is called Black Silicon (BSi).

This dissertation describes the model based on effective medium approximation to determine the effective optical constants, refractive index and extinction coefficient …

Preparation Of Benzoxazine Monomers And Prepolymers From Continuous Reactor: Effects Of Molecular Architecture On Properties, Andrew S. Frazee

Dissertations

Despite the modularity in molecular design and high-performance properties of benzoxazine thermoset chemistries, there are two primary shortcomings of benzoxazine marketability. Firstly, multifunctional benzoxazines are unfavorable for processing as they are glassy solids at ambient temperature. Secondly, benzoxazine chemistries are commercially synthesized using batch reactors, which are energy intensive and require the use of environmentally unfavorable solvents.

The purpose of the work herein is to address these shortcomings, which include:

1.) interrelationships between molecular architectures of synthesized monofunctional benzoxazine monomers and their ambient temperature physical states (i.e. liquid or solid) using molecular dynamics simulations and experimental comparisons,

2.) continuous high-shear …