Materials Science and Engineering Commons^™

Shape Memory Alloy Capsule Micropump For Drug Delivery Applications, Youssef Mohamed Kotb

Theses and Dissertations

Implantable drug delivery devices have many benefits over traditional drug administration techniques and have attracted a lot of attention in recent years. By delivering the medication directly to the tissue, they enable the use of larger localized concentrations, enhancing the efficacy of the treatment. Passive-release drug delivery systems, one of the various ways to provide medication, are great inventions. However, they cannot dispense the medication on demand since they are nonprogrammable. Therefore, active actuators are more advantageous in delivery applications. Smart material actuators, however, have greatly increased in popularity for manufacturing wearable and implantable micropumps due to their high energy …

Combinatorial Studies Of Noble Metal Catalysts For Carbon Utilization, Natalie Leong Page

Theses and Dissertations

Electrocatalysts demonstrate significant promise for sustainable processes like carbon capture and generating recycled carbon fuels which are needed to achieve net zero carbon emissions. However, the commercialization of these processes is limited by several factors, one of which is the high cost of catalysts. The discovery and development of cheaper alternatives has been difficult due to constraints in experimental methodologies, scalability limitations, and a lack of understanding of reaction mechanisms. Within this dissertation is the development of a novel scanning electrochemical system and its implementation for high-throughput data generation from combinatorially sputtered material libraries. Combinatorial Pd-Au alloys were investigated for …

The Effect Of Extended Saltwater Absorption And Uv Cure On The Compressive Properties Of Msla 3d-Printed Photopolymer Resin Samples With Printing Variations, Suzanne Dixon

Theses and Dissertations

Liquid Crystal Display (LCD) 3D printers, also known as Masked Stereolithography Apparatus (MSLA), is a type of vat polymerization printing technique that cures liquid resin into a solid object. This technique is relatively new. Consequently, there is a shortage of detailed research on the impact of long-term environmental exposure on the MSLA-printed materials. The research within this document informs engineers and scientists of resin compressive properties after extended exposure to saltwater and ultraviolet (UV) light. Saltwater absorption of the material was analyzed at atmospheric pressure, 30-psi, 60-psi, and 90-psi; the samples reached saturation in saltwater after 56 days. The variation …

Thermal Conductivity Of Thin Porous Ceramic Coatings: An Analytical And Experimental Study, Lei Zhao

Theses and Dissertations

An analytical model of the thermal conductivity of the porous yttrium-stabilized zirconia (YSZ) layer used in the thermal barrier coatings (TBCs) is presented. Such high-temperature resistant coatings are essential to protect the metallic components of gas turbine engines. The model calculates the conductivity based on the coating's porosity, pore size distribution, and pore morphology, including the individual pore cross-section area, aspect ratio, and orientation, which are extracted from the scanning electron microscopy images. The model was verified through comparisons with numerical simulation results from a multiphysics software tool. A laser temperature gradient test was performed to validate the analytical model …

Towards A Practical Method For Monitoring Kinetic Processes In Polymers With Low-Frequency Raman Spectroscopy, Robert Vito Chimenti

Theses and Dissertations

Unlike liquids and crystalline solids, glassy materials exist in a constant state of structural nonequilibrium. Therefore, a comprehensive understanding of material kinetics is critical for understanding the structure-property-processing relationships of polymeric materials. Amorphous materials universally display low-frequency Raman features related to the phonon density of states resulting in a broad disorder band for Raman shifts below 100 cm-1, which is related to the conformational entropy and the modulus. This disorder band is dominated by the Boson peak, a feature due to phonon scattering because of disorder and can be related to the transverse sound velocity of the material, and a …

Mechanical Characterization Of Hemp, Jute, And Flax Based Natural Fibre Composites For Non-Structural Applications In Aircraft And Automobiles, Ravi Kumar B

Theses and Dissertations

Demand for reducing energy consumption and detrimental environmental impacts after the effective lifetime of an engineering material are the major driving factors for the development of natural fibre reinforced composites (NFRCs) in various sectors. Compared to synthetic fibre like carbon-fibres or Kevlar, natural fibres provide several benefits including light weight, inexpensive, recyclability, superior specific strength, biodegradable, non-toxic during handling, and less energy intensive during manufacturing. This doctoral work presents observations from mechanical tests and interpretations on the suitability of natural fibre reinforced composites for less heavily loaded engineering applications areas.

In the first stage, jute, flax, and hemp fibres were …

Detection Of Endocrine-Disrupting Chemicals In Personal Care Products Using A Polyhedral Oligomeric Silsesquioxane-Based Hybrid Material, Aarthi K

Theses and Dissertations

Personal care products (cosmetics) are a diverse group of goods, that includes all the essential routines including the personal hygiene products used in our day-to-day life. It contains a variety of ingredients in its formulation, including preservatives, flavor, UV filters, and other additives. Few of the chemicals utilized are found to impair human health and have serious environmental impacts. The major chemicals include parabens, triclosan, oxybenzone, phthalates, heavy metals, fragrances, etc, Though the Scientific Committee on Consumer Safety (SCCS) has set the usage limits for the chemicals used, exposure to these chemicals from multiple products may exceed the exposure limit. …

Characterization Of An Omega Type Bi-Anisotropic Material, Moriel Gindi

Theses and Dissertations

A theory is presented for the extraction of the complete set of material parameters for a bi-anisotropic sample consisting of conductive omega-type particles governed by the mm21′ point-group symmetry. A rectangular-to-square wave-guide can be used to obtain the required measurements by allowing three distinct orientations of the material. The focus of this work is to develop the appropriate theory detailing the derivation of how the material parameters are extracted from the measurements in an analytical methodology that is similar in manner to the well-known Nicolson-Ross-Weir (NRW) algorithm.

Spectroscopic Characterization Of Trivalent Holmium In Liyf4 And Bay2F8 Crystals, Vivian R. Hedberg

Theses and Dissertations

Yttrium-fluoride crystals doped with trivalent holmium are promising laser gain media for mid-infrared laser systems. To accurately model laser systems, a complete optical characterization of the laser gain medium is required. The key modeling parameters were obtained by a spectroscopic investigation of Ho³⁺ in LiYF₄ and BaY₂F₈ crystal hosts. Several important mid-infrared laser transitions were characterized at nominal Ho³⁺ ion concentrations of 10-30 at.%. Polarized emission cross-sections were determined from the fluorescence spectra using the Füchtbauer-Ladenburg method. Polarized absorption cross-sections were obtained using the Integral Reciprocity method. The upper-state lifetimes were measured at room …

Influence Of Environmental Barrier Coatings On The Overall Effectiveness Of A Film Cooled Ceramic Matrix Composite Plate, Shane P. Lindsay

Theses and Dissertations

Silicon carbide ceramic matrix composites, a promising new potential upgrade over the conventional metals currently used for jet engine turbine blades, have a propensity to oxidize in a combustion environment. Engine manufacturers often apply environmental barrier coatings to prevent the composites from oxidizing. What is unclear, however, is how environmental barrier coatings effect underlying composite temperatures. This research examined the coatings’ effects by first characterizing the influence of environmental barrier coatings on the underlying temperature of a protected ceramic, then evaluating the significance of lateral conduction for cooling a coated ceramic, and finally comparing cooling results for coated and uncoated …

Applicability Of Using Bio-Receptive Concrete For Building Facades In Egypt, Gina Roupheil

Theses and Dissertations

The significant increase in carbon dioxide emissions caused by the construction industry is detrimental to our planet. This is rapidly increasing with the urbanization of cities that is gradually taking its toll on the available green spaces, which help in balancing such emissions. Recently, researchers have been trying to make use of bio-receptivity to create biomaterial systems that could be spread on building envelopes and support the growth of small plant species and microorganisms to establish on. Out of those materials, comes the concrete as a promising material for bio-colonization.

Within this context, this study aims at investigating the applicability …

Thermal Insulation And Fire Protection Plaster For Frp System Incorporating Aerogel Nanoparticles And Phyllosilicates, Athnasious Ghaly

Theses and Dissertations

For more than two decades, new innovative materials have been introduced to the market such as nano materials that can be utilized for their high performance in different aspects of the construction industry. Structural repair and strengthening is one of the most demanding fields in the construction industry for innovative and high-performance materials due to its specialty. Time, quality, economy, and sustainability are the main factors that control this field, and for that, new systems keep being introduced to the market to reduce the time of repair and enhance its efficiency. Fiber Reinforced Polymers (FRP) Systems are the most advanced …

Assessing Adoption Barriers Of Sustainable Packaging In Egypt, Carol Ramses Morgan

Theses and Dissertations

Sustainable packaging has become an essential part of business decisions and corporate directions. With the rise of environmental damages due to improper waste management and unsustainable practices, businesses have a major responsibility to analyze their products’ life cycles and redesign them with sustainability in mind. Applying sustainable packaging could save companies large amounts of resources, therefore cutting costs, while also achieving the legal and social duty as a corporation towards society and the environment. Many developing countries, with specific focus on Egypt, have recently focused on legislative and corporate decisions in order to encourage more sustainable practices. Egypt’s new Waste …

Degradation Of The Mechanical Properties And Hydrogen Generation In Cement Under Gamma Irradiation Assessed By Atomistic Simulation, Omar Al Najjar

Theses and Dissertations

Although understanding the effect of the gamma-ray on cement-based materials is essential for many applications, such as the concrete contaminate of nuclear reactors or the storage of radioactive waste in cement-based waste forms, such understanding is still not fully developed. The importance of having such an understanding is becoming of utmost importance, especially with calls to extend the lifetime of nuclear power plants, and also due to some recent incidents of failures of the concrete structure in the nuclear fields. In this work, the details of preparing three molecular models as a representative structure of the main binding phase of …

A 3d Imaging-Based Critique Of Wire Arc Additive Manufacturing (Waam) Simulations, Omar Oraby

Theses and Dissertations

Residual stresses play a critical role in the mechanical behavior and structural integrity of engineered components. Understanding and quantifying these stresses are essential for ensuring the reliable performance and durability of materials and structures. Traditionally destructive methods are used that involve sample sectioning and material removal. However, non-destructive methods have gained popularity due to their advantages in preserving the specimen's integrity for further testing and material waste reduction. Among these techniques, Digital Image Correlation (DIC) stands out as a powerful non-contact and full-field measurement approach. DIC captures displacements and strain distributions by analyzing the deformation of speckle patterns on the …

The Effect Of Mechanical Strain On The Electronic Conductivity Of Α- Fe2o3: A Density Functional Theory Study, Sheriff Naziru Abdulmutalib

Theses and Dissertations

Hydrogen has emerged as a promising future energy carrier due to its ability to produce zero carbon dioxide (CO2) emissions when burned. However, the limited natural abundance of hydrogen necessitates the development of cost-effective and environmentally friendly methods for large-scale hydrogen production. Among the different hydrogen production approaches, photoelectrochemical water splitting, which employs a photoanode material in a cell using solar energy to split water into hydrogen and oxygen, is the focus of this work. α-Fe2O3 (hematite) is a photoanode material that shows a promising future for hydrogen generation in a photoelectrochemical cells due to its cheapness, availability, and its …

Mechanical And Electromagnetic Properties Of Incorporating Graphene Oxide In Cementitious Mixtures, Cherif Khalil

Theses and Dissertations

This multidisciplinary study aimed at investigating the impact of incorporating graphene oxide (GO) on the mechanical properties and electromagnetic (EM) shielding effectiveness of cementitious mixtures, as well as critically examining the mechanism with which GO affects their microstructure properties. Analysis of the literature review showed that there are discrepancies in reporting the impact of GO on the mortar mix. Consequently, this study focuses on exploring the cause for such discrepancies and identifies three main factors which are thoroughly investigated. The factors were the different sonication energies applied to the GO (Shear Mixing, 1.5 kJ/ml, 3 kJ/ml and 6 kJ/ml), the …

Nano-Patterned Si Structures For Optical Filters And Electro-Mechanical Relays: Fabrication, Characterization, Prospects, And Limitations, Md Ataul Mamun

Theses and Dissertations

Nanofabrication technology, especially nanopatterning, is a rapidly advancing field that has already resulted in creating novel devices and holds promise for producing even more with unmatched performance. These techniques also allow us to gain insight into physical phenomena at the micro- and nanoscale. The ultimate performance of nanofabricated devices and their compatibility with existing Si-based CMOS technology hinge upon the careful selection of materials and precise design, coordinated with meticulous pattern transfer. In this work, we applied nanopatterning techniques on silicon to create optical filters for the shortwave infrared (SWIR) region and nanoelectromechanical system (NEMS) relay-based logic gates. Additionally, these …

Insights Into The Characterization And Degradation Of Electrospun Polycaprolactone Scaffolds For Tissue Engineering Applications, Caleb B. Wells

Theses and Dissertations

Electrospun polymeric biodegradable scaffolds are essential in tissue engineering, particularly for Engineered Tissue Vascular Grafts (ETVGs), which promise advancements in treating coronary artery disease, peripheral arterial disease, congenital cardiovascular defects, and renal disease. These scaffolds present a solution to issues with autologous graft availability and durability. While large-diameter grafts in low-pressure environments have seen success, small-diameter grafts in high-flow scenarios remain challenging. Understanding polymeric scaffold degradation and behavior during incubation, especially under dynamic mechanical loading, is vital for clinical translation of small-caliber ETVGs.

This research focuses on characterizing the mechanical and microstructural properties of electrospun polycaprolactone (PCL) scaffolds and their …

Photoluminescence Of Beryllium-Related Defects In Gallium Nitride, Mykhailo Vorobiov, Mykhailo Vorobiov

Theses and Dissertations

This study explores the potential of beryllium (Be) as an alternative dopant to magnesium (Mg) for achieving higher hole concentrations in gallium nitride (GaN). Despite Mg prominence as an acceptor in optoelectronic and high-power devices, its deep acceptor level at 0.22 eV above the valence band limits its effectiveness. By examining Be, this research aims to pave the way to overcoming these limitations and extend the findings to aluminum nitride and aluminum gallium nitride (AlGaN) alloy. Key contributions of this work include. i)Identification of three Be-related luminescence bands in GaN through photoluminescence spectroscopy, improving the understanding needed for further material …

A Precision-Controlled Investigation Into The Fundamentals Which Drive The Incredible Superhydrophobic Properties Of Soot, Ashton Bressler

Theses and Dissertations

A PRECISION-CONTROLLED INVESTIGATION INTO THE FUNDAMENTALS WHICH DRIVE THE INCREDIBLE SUPERHYDROPHOBIC PROPERTIES OF SOOT

By Ashton Bressler

A thesis submitted as a partial fulfilment of the Virginia Commonwealth University requirements for a Masters of Science at Virginia Commonwealth University.

Virginia Commonwealth University, 2024.

This thesis investigates a precision controlled superhydrophobic soot surface, composed of semi-rigid linked chains of spheres, with a radii of roughly 14um. These spheres have exceptionally useful hydrophobic properties due to; their large surface area, their large triple phase line length, their low area fraction of solid-liquid interface, their ability to deform, and their strength from both …

Extrusion-Based Additive Manufacturing Of Magnetic Heat Exchange Structures For Caloric Applications, Vaibhav Sharma

Theses and Dissertations

Currently, the commercial building sector accounts for 18% of total U.S. end-use energy consumption, of which almost a third was from on-site combustion of fossil fuels for space and water heating. Magnetic heat pumping (MHP) technology is an energy-efficient, sustainable, environmentally-friendly alternative to conventional vapor-compression cooling technology. Several MHP designs today are predicted to be highly energy efficient, on condition that suitable working materials can be developed. This materials challenge has proven to be daunting due to issues associated with intricate synthesis/post-processing protocols and complications related to shaping the mostly brittle magnetocaloric alloys into thin-walled channeled regenerator structures to facilitate …

Advanced Synthesis And Rational Design Of Support Structures For Nobel Metal Heterogeneous Catalysis: Towards Enhanced Activity And Continuous Processes, Brian R. Clark

Theses and Dissertations

The field of catalysis has a wide-ranging impact. Our group has identified the constant need for improved catalytic activity in high-impact applications such as hydrosilylation and cross-coupling reactions. For these reactions, precious metal catalysts often exhibit markedly better performance than their counterparts, but they can be a significant process cost that decreases overall economic efficiencies. To address this challenge, we explored support structures that can enhance catalytic activity at low metal loadings and improve precious metal recovery through simple filtration. We found that a platinum on graphene nanoplatelet catalyst (PtGNP) synthesized via strong electrostatic adsorption with microwave irradiation (SEA-MW) exhibits …

Effect Of Annealing On Photoluminescence From Defects In Gan, Oleksandr Andrieiev

Theses and Dissertations

Annealing is a critical process in modern GaN technology, essential for achieving p-type conductivity by activating the Mg_Ga acceptor, as first demonstrated by Shuji Nakamura in the early 1990s. Despite the omnipresence of hydrogen as an impurity in GaN crystals, the precise mechanisms governing hydrogen diffusion and acceptor passivation remain only partially understood. The presented research investigates the effects of annealing-induced activation and hydrogen passivation on C and Be acceptors in GaN grown by MOCVD, HVPE, and MBE methods. We explored these effects by using several annealing techniques, gas compositions, and thermal regimes. A transient behavior between the C …

Advancing Polymer Sustainability Through Custom Interpenetrating Polymer Network Synthesis, Processing, And Design, Alexandra Maria Lehman-Chong

Theses and Dissertations

The need for improving polymer sustainability is as ubiquitous as the role of polymers in modern society. Interpenetrating polymer network (IPN) design flexibility offers opportunities for improved polymer sustainability while balancing desired polymer properties for various applications. This work investigates the structure-property-processing relationships of IPNs judiciously designed under the framework of the polymer life cycle. Sustainable polymer design was largely considered at the feedstock and manufacturing stages while considering overall polymer performance. Chemicals from bio-based feedstocks were used to design a full simultaneous polybenzoxazine-epoxy IPN, focusing on the effects of monomer and polymer structure on polymer properties. Processing-property relationships were …

Fabrication & Characterization Of Hybrid Piezoelectric/Triboelectric Nanocomposite Nanogenerators Via Fusion Deposition Modeling, Khaled El Toukhy

Theses and Dissertations

This thesis aims to discuss the potential of using piezoelectric and triboelectric nanogenerators (PTENGs) for energy harvesting, particularly in the sportswear industry. PTENG's main advantage is that it offers good flexibility making it suitable for high-strain applications. The piezoelectric effect is induced by embedding piezoelectric nanofillers into one of the two triboelectric layers. PTENGs can generate both piezoelectric and triboelectric signals when strained resulting in an enhanced output compared to regular piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs). TPU was adopted as the matrix for PTENGs advantageous due to their flexibility, low electrical resistivity, and compatibility with additive manufacturing techniques. …

Fabrication And Characterization Of Flexible Microelectrode Arrays On Kapton Polyimide For Implantable Spinal Cord Stimulation Applications, Nabil Jamhour

Theses and Dissertations

Recent advances in spinal cord stimulation (SCS) technology have made a significant impact in the treatment of chronic pain which is a prevalent issue amongst 20% of the population in developed nations. A few medical device manufactures have developed SCS devices that have been studied in clinical environments and reported to be effective and safe for commercial use. However, the current SCS devices available are bulky, rigid, and still present infection, fibrosis, discomfort, pulse delivery challenges and other concerns for patients. In this study, flexible electrodes processed on Kapton® polyimide films by physical vapor and inkjet deposition are fabricated and …

Mechanical Characterization Of Functionally Graded M300 Maraging Steel Cellular Structures, Bradley Jay Sampson

Theses and Dissertations

Traditional methods for increasing the energy absorption of a structure involve using a stronger material or increasing the volume of the structure, resulting in a higher cost or additional weight. Additive manufacturing (AM) can be used to maximize the energy absorption of materials with the ability to create complex geometries such as cellular structures. Previous work has shown that the energy absorption of additively manufactured parts can be improved through functionally graded cellular structures; however, this strategy has not been applied to ultra-high strength steel materials. This work characterizes the effect of multiple functional-grading strategies (e.g. uniform, rod-graded, size-graded) on …

Moisture Effects On Visible Near-Infrared And Mid-Infrared Soil Spectra And Strategies To Mitigate The Impact For Predictive Modeling, Francis Hettige Chamika Anuradha Silva

Theses and Dissertations

Instrumental disparities and soil moisture are two of the key limitations in implementing spectroscopic techniques in the field. This study sought to address these challenges through two objectives. The first objective was to assess Visible-near infrared (VisNIR) and mid-infrared (MIR) spectroscopic approaches and explore the feasibility of transferring calibration models between laboratory and portable spectrometers. The second objective addressed the challenge of soil moisture and its impact on spectra. The portable spectrometers demonstrated comparable performance to their laboratory-based counterparts in both regions. Spiking with extra-weight, was the most effective calibration transfer method eliminating disparities between instruments. The samples were rewetted …

Analyzing The Effects Of Ultrafast Laser Processing On Mechanical Properties Of 3d-Printed Pla Parts, Darshan Pramodbhai Yadav

Theses and Dissertations

Recent advances in additive manufacturing technologies have already led to wide-scale adoption of 3D-printed parts in various industries. The expansion in choice of materials that can be processed, particularly using Fused Deposition Modeling (FDM), and the steady advancements in dimensional accuracy control have extended the range of applications far beyond rapid prototyping. However, additive manufacturing still has considerable limitations compared to traditional and subtractive manufacturing processes. This work addresses limitations associated with the as-deposited surface roughness of 3D-printed parts. The effects of roughness-induced stress concentrations were studied on ultimate tensile strength and fatigue life. The samples were manufactured using a …