Mechanical Engineering Commons^™

High-Yield Bioinspired Atmospheric Water Capture Through Hydrogels, Yiwei Gao

UNLV Theses, Dissertations, Professional Papers, and Capstones

Water scarcity is a global issue affecting billions of people, and atmospheric water harvesting (AWH) technology has been identified as a potential solution. However, existing single-material AWH approaches have limited water harvesting yields due to alternated water capture, storage, and release stages, and only function within a high relative humidity range. In my doctoral research project, we developed a bio-inspired, hydrogel-based multi-layer AWH approach that allows for segregated capture, storage, and release stages, and is envisioned to have higher daily water harvesting efficiency even in low-humidity areas. My research began with understanding the relations between hydrogel mechanical stiffness, hydraulic permeability, …

Metastability And Degradation In Cu(In,Ga)Se2 Thin-Film Solar Cells, Mohsen Jahandardoost

UNLV Theses, Dissertations, Professional Papers, and Capstones

Cu(In,Ga)(S,Se)2 or CIGS is a thin-film semiconductor that has shown a device efficiency of 23.35% and 24.2% for single-junction and perovskite/CIGS tandem solar cells, respectively. CIGS offers promising properties such as tunable bandgap and ease of processing making them great candidates for thin-film tandem devices. However, knowledge of the effect of material defects, buffer materials, and post-deposition treatment (PDT) on degradation and metastability behavior in these devices is not well understood.In this dissertation, metastability and long-term degradation of CIGS thin-film solar cells have been investigated under combinatorial stress factors of heat, light, and voltage bias to systematically understand the effect …

Comparative Analysis On Low Cost Continuous Carbon Fiber Polypropylene Composite Using Compression Molding And Automated Tape Placement, Benjamin U. Schwartz

Masters Theses

Carbon fiber reinforced plastics (CFRP) are widely used throughout the aerospace industry where a weight reduction remains the highest priority with less emphasis on cost. Textile grade carbon fiber (TCF) and other low cost carbon fiber (LCCF) alternatives have recently emerged for use in the automotive market where emissions regulations have pushed automotive manufacturers and research institutions to look for cost effective light weight materials. Fiber reinforced thermoplastics provide an effective solution that align with automotive design including low cost, high processing rates, high impact toughness, unlimited shelf life, and recyclability.

TCF and Zoltek_PX35 fibers are two LCCF aimed at …

Super P-Sulfur Cathodes For Quasi-Solid-State Lithium-Sulfur-Batteries., Milinda Bharatha Kalutara Koralalage

Electronic Theses and Dissertations

Lithium-Sulfur (Li-S) batteries have become a promising candidate to meet the current energy storage demand, with its natural abundance of materials, high theoretical capacity of 1672 mAhg-1, high energy density of 2600 Whkg-1, low cost and lower environmental impact. Sulfide based solid state electrolytes (SSEs) have received greater attention due to their higher ionic conductivity, compatible interface with sulfur-based cathodes, and lower grain boundary resistance. However, the interface between SSEs and cathodes has become a challenge in all solid-state Li-S batteries due to the rigidity of the participating surfaces. A hybrid electrolyte containing SSE coupled with a small amount of …

Classification Of Electrical Current Used In Electroplastic Forming, Tyler Grimm

All Dissertations

Electrically assisted manufacturing (EAM) is the direct application of an electric current to a workpiece during manufacturing. This advanced manufacturing process has been shown to produce anomalous effects which extend beyond the current state of modeling of thermal influences. These purported non-thermal effects have collectively been termed electroplastic effects (EPEs).

While there is a distinct difference in results between steady-state (ideal DC) testing and pulsed current testing, the very definition of these two EAM methods has not been well established. A "long" pulse may be considered DC current; a "short" pulse may produce electroplastic effects; and even "steady-state" current shapes …

Mesoscale Modeling And Machine Learning Studies Of Grain Boundary Segregation In Metallic Alloys, Malek Alkayyali

All Dissertations

Nearly all structural and functional materials are polycrystalline alloys; they are composed of differently oriented crystalline grains that are joined at internal interfaces termed grain boundaries (GBs). It is well accepted that GB dynamics play a critical role in many phenomena during materials processing or under operating environments. Of particular interest are GB migration and grain growth processes, as they influence many crystal-size dependent properties, such as mechanical strength and electrical conductivity.

In metallic alloys, GBs offer a plethora of preferential atomic sites for alloying elements to occupy. Indeed, recent experimental studies employing in-situ microscopy revealed strong GB solute segregation …

Molecular Dynamics Simulation On Molybdenum Disulfide: Thermal-Mechanical Properties And Phase Transitions Under External Loading, Mahabubur Rahman

All Dissertations

Due to their remarkable properties, transition metal dichalcogenides (TMDs) have received much scientific interest throughout the past decade. Two layers of chalcogen atoms (S, Se, Te) sandwich a layer of transition metal atoms (Mo, W, Ta) to form the three-atom thick unit cell in TMDs. The interaction between TMD "single layers" is mediated by neighboring chalcogen planes and bonded by Van der Waals forces. Due to this weak out-of-plane interaction, bulk samples can be thinned down to a single layer by exfoliation. Among the TMDs, Molybdenum Disulfide (MoS₂) shows promise in the field of electronics, optics, and sensing …

Engineered Material Systems For Mimicking Tissue And Disease, Margrethe Ruding

McKelvey School of Engineering Theses & Dissertations

This thesis comprises two studies involving design and application of soft material systems. The goal of the first study was to design, fabricate, and characterize hydrogel lattice structures with consistent, controllable, anisotropic mechanical properties. Lattices, based on four types of unit cells (cubic, diamond, vintile, and Weaire-Phelan), were printed using stereolithography (SLA) of polyethylene glycol diacrylate (PEGDA). In order to create structural anisotropy in the lattices, unit cell design files were scaled in one direction by a factor of two in each layer and then printed. The mechanical properties of the scaled lattices were measured in shear and compression and …

Correlating Large-Format Additive Manufacturing Processing Parameters To Fiber Length And The Mechanical Performance Of Reinforced Polymer Composites, Andrew Phillip Rhodes

Masters Theses

The Big Area Additive Manufacturing (BAAM) system at Oak Ridge National Laboratory has been used to produce carbon fiber reinforced structures for several years, including vehicles, building constituents, composite tooling, etc. While the development of a large-format polymer additive manufacturing (AM) system has moved quickly, the impact of the BAAM’s extruder on the length of carbon fiber feedstock has not been systematically studied. Numerous studies in processing fiber reinforced thermoplastics in plasticizing and injection molding systems have shown that fibers are subjected to significant shear as they are processed, which can cause a drastic reduction in fiber length which negatively …

Shape Memory Polymer-Based Multifunctional Syntactic Foams, Siavash Sarrafan

LSU Doctoral Dissertations

With the increase in popularity of shape memory polymers (SMPs), especially in applications such as aerospace, textile, biomedical engineering, and even structures, the weight of the material and the devices made with it has always been a crucial factor. Using the shape memory polymer as a matrix to make a syntactic foam is one of the best and most affordable approaches to creating a lighter material that still has the shape memory effect. The addition of particles of different stiffness, strength, and size, with variable fractions, creates a composite that enables engineering the mechanical, as well as other physical and …

Mechanical Characterization Of Additively Manufactured Alloys Compared To Their Wrought Counterparts, Laith A. Alqawasmi

Mechanical Engineering ETDs

Additive manufacturing is a method of manufacturing based on building parts layer by layer, allowing for more control over shape of the product, therefore reducing machining costs, reducing material waste, faster production times and the ability to build complex engineering design that other manufacturing technologies won’t be able to produce. This research is on the tensile and indentation testing (following ASME standards) of 3D printed Ti-6Al-4V and Inconel 718 built by powder-based direct energy deposition technology. Ti-6Al-4V is an attractive material for the aerospace and aviation industry, and Inconel 718, a nickel-chromium based superalloy, is an attractive material for usage …

Controlling Mechanical Properties Of Well-Defined Polymer Networks, Ipek Sacligil

Doctoral Dissertations

Polymer networks are one of the most versatile and highly studied material class that revolutionized many aspects of life. Connecting the final network properties to the molecular parameters of its building blocks remains a major research thrust. Recent advances in network synthesis techniques allowed for accurate predictions of elastic modulus in model networks. Tew Group has developed highly efficient, thiol-norbornene networks with controllable mechanical properties. Chapter 2 focuses on modifying the gel fracture energy predicted by Lake-Thomas theory by accounting for loop defects. This study allowed for a priori estimates of gel fracture energy by combining theory, experiments, and simulations. …

Additive Manufacturing For Phase Change Thermal Energy Storage And Management, Thomas B. Freeman

Doctoral Dissertations and Master's Theses

Phase change materials can enhance the performance of energy systems by time shifting or reducing peak thermal loads. Certain electronic devices such as batteries, laser systems, or electric vehicle power electronics are highly transient and require pulse heat dissipation. Heat sinks, or thermal management devices made of a phase change material can absorb large heat spikes while maintaining a constant temperature. Additive manufacturing techniques hold tremendous potential to enable co-optimization of material properties and device geometry, while potentially reducing material waste and manufacturing time. Recently, a few efforts have emerged that employ additive manufacturing techniques to integrate a phase change …

Development Of Novel Turbomachinery Manufacturing Methods, Timothy P. Winkler

Theses and Dissertations

Compact turbine engines are of increasing interest as a means of propulsion for small, lightweight, low cost, unmanned aerial systems. This study looks to leverage advancements in novel manufacturing technology to produce turbomachinery components while simultaneously reducing costs and manufacturing time. To determine the feasibility of drop-in replacements for stock components this study focused on several research areas. This included materials research on both polymer-reinforced and ceramic materials, specimen tensile testing to determine temperature-dependent material properties, finite element analysis of multiple candidate materials, design and fabrication of a spin test rig, and physical spin testing of manufactured components to predict …

Accurate Evaluation Of The Direction-Dependent Mechanical Properties Of Ideal Single Crystals: A Comparative Ab Initio Study, Jaylan Ali Elhalawani

Theses and Dissertations

The mechanical properties of a single crystal or a grain in a polycrystalline material are highly dependent on the direction of the applied load. Key properties of interest are the Young’s modulus and the Poisson ratio in the small strain limit, and the ideal tensile strength in the large strain regime. Prior atomistic computations of these properties interchangeably used two approaches. In one approach the stress-strain response is explicitly calculated via a numerical tensile test experiment. In the second approach the second order single crystal elastic constants are computed via small deformations and then used in analytical equations to derive …

Mechanical Design Of A Microwave Imaging Device For Breast Cancer Detection In Mri Scanners, Grace M. Player

Dartmouth College Master’s Theses

This project seeks to develop an updated version of a microwave imaging device for use in conjunction with breast MRI, improving upon existing technology and developing novel concepts for the device. It posits three primary redesign targets for updating the previous system: resizing the system height, making the device more iteration- friendly, and improving the overall manufacturability of the device by replacing custom components with commercially available alternatives. All three of these redesign targets are met in the new design, V2.0. The height is reduced by reducing antenna travel and height, embedding some components, and shortening the tank wall, resulting …

Modified Reactive Sputter Deposition Of Titanium Nitride Thin Films Via Hipims With Kick-Pulse And Improvement Of The Structure-Zone Model, Andrew Miceli

UNF Graduate Theses and Dissertations

Direct current (DC) and radio frequency (RF) sputtering methods have been commonplace in industry for several decades and widely studied in literature. Hard films of nitrides, such as titanium nitride (TiN), have been deposited using reactive DC sputtering onto cutting tools and medical devices extensively as well. For these applications, the films require excellent adhesion, high density, and high hardness. High-Power Impulse Magnetron Sputtering (HIPIMS) has emerged over the last several years as a method to produce films with increased density and mechanical properties. Process-structure-property relationships for reactive HIPIMS are not yet well developed. Additionally, conventional HIPIMS suffers from relatively …

Mechanical Behavior Of Metallic Core-Shell Nanoparticles Under Compressive Loading, Phillip Tomich

Graduate Research Theses & Dissertations

Core/shell metallic nanoparticles have been shown to be a promising material type for additive manufacturing in the aerospace and automotive fields. Within additive manufacturing they will be used to accurately make an array of nanoparticles within the grains of metal matrix composites. This in turn will help to strengthen the material while remaining ductility and light weight. In this study, copper/aluminum core/shell nanoparticles are compressed under [100], [110], [111], and [112] directions to showcase their anisotropic material properties. Models of their individual counterparts were also investigated. There are no previous works showing the deformation mechanisms of copper/aluminum core/shell nanoparticles. Molecular …

Study Of Nanocomposite Materials Using Molecular Dynamics, Prashik Sunil Gaikwad

Dissertations, Master's Theses and Master's Reports

There is an increase in demand for new lightweight structural materials in the aerospace industry for more efficient and affordable human space travel. Polymer matrix composites (PMCs) with reinforcement material as carbon nanotubes (CNTs) have shown exceptional increase in the mechanical properties. Flattened carbon nanotubes (flCNTs) are a primary component of many carbon nanotube (CNT) yarn and sheet materials, which are promising reinforcements for the next generation of ultra-strong composites for aerospace applications. These flCNT/polymer materials are subjected to extreme pressure and temperature during curing process. Therefore there is a need to investigate the evolution of properties during the curing …

Development Of Corn Kernel-Based Biocomposite Films For Food Packaging Applications, Swastika Bera

Electronic Theses and Dissertations

Most of the current and active food packaging resources and methods are nonbiodegradable and nonrenewable therefore harmful to the environment. Due to this, alternate sources of food packaging materials are in high demand. In this study, a bio-composite film has been developed, with Corn kernel powder as fiber reinforcement which is mixed with gelatin, and lignin two biopolymers as the matrix. The effect of Corn Kernel (CK) reinforcement on the Gelatin/Lignin (G/L) matrix on mechanical and barrier properties has been studied. CK has shown great potential as reinforcement to natural polymer, gelatin, and lignin (G/L) for food packaging applications as …

System Analysis Of An Internal Combustion Engine (Ice) – Solid Oxide Fuel Cell (Sofc) Hybrid Cycle, Jose Javier Colon Rodriguez

Graduate Theses, Dissertations, and Problem Reports

Due to the intermittent nature of renewable energy and the rigid operation of existing coal plants, the need for flexible power generation technology is eminent. Hybrid energy systems have shown potential for flexible, grid following dynamics while maintaining higher efficiencies. The work below focuses on the performance analysis of a proposed 100 kW pressurized Internal Combustion Engine (ICE) and Solid Oxide Fuel Cell (SOFC) hybrid system. The un-utilized fuel from the SOFC stack provided the chemical energy to operate the engine. A turbocharger was used to deliver the necessary air flow for both the stack and engine. An external reformer …

Molecular Dynamics Modeling Of Polymers For Aerospace Composites, Swapnil Sambhaji Bamane

Dissertations, Master's Theses and Master's Reports

Polymer matrix composite materials are widely used as structural materials in aerospace and aeronautical vehicles. Resin/reinforcement wetting and the effect of polymerization on the thermo-mechanical properties of the resin are key parameters in the manufacturing of aerospace composite materials. Determining the contact angle between combinations of liquid resin and reinforcement surfaces is a common method for quantifying wettability. It is challenging to determine contact angle values experimentally of high-performance resins on CNT materials such as CNT, graphene, bundles or yarns, and BNNT surfaces. It is also experimentally difficult to determine the effect of polymerization reaction on material properties of a …

Advanced Microstructural Characterization Of Functionally Graded Dental Ceramic Material For Materials-Informed Finishing, Angani Vigneswaran

Theses and Dissertations--Manufacturing Systems Engineering

Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) has gained popularity as the choice of material for dental prosthetics. Ivoclar Vivadent’s IPS e.max ZirCAD Prime dental ceramic incorporates a unique gradient technology that varies the yttria content over the thickness of the material. The top layer is composed of 5Y-TZP which is desired for its optical properties while the bottom layer is composed of a much stronger 3Y-TZP. In between the two layers, 5Y-TZP and 3Y-TZP are mixed to form a transition layer. Varying the amount of yttria allows for more esthetically pleasing translucency in the visible areas of the restoration without compromising …

Investigation Of Oxidation And Corrosion Resistance Of Ni-Based Alloys And Stainless Steels Under Co2 Environments At Elevated Temperatures, Spencer Roy Fultineer

Graduate Theses, Dissertations, and Problem Reports

High mechanical strength integrity, high robustness towards oxidation, and high resistance to carburization under CO2 environments at elevated temperatures are usually required for metallic systems that are employed for power generation. INCONEL 625 is a nickel-based superalloy that started development in the 1950s. This material was designed with the distinct purpose of use in high-temperature and high-pressure systems. While various materials possess the physical properties to handle these conditions, the creation of IN625 addresses the need for a material to withstand the highly corrosive properties of these kinds of environments. In order to evaluate the oxidation and corrosion resistance of …

Multimaterial, Core-Shell Direct Ink Writing Of Flexible Strain Sensors For Pneumatically-Actuated Soft Robotic Hinge Joints, John Michael Burke

Graduate Theses, Dissertations, and Problem Reports

Direct ink writing (DIW) provides for an expansive material library and the ability to print multiple materials with tailored functionalities in a controllable and single-step process. Particularly beneficial is the net shape printing under ambient conditions of a wide range of materials normally incompatible with one another. Coaxial DIW is a 3D printing technique that allows for two dissimilar inks to be extruded simultaneously in a co-flow manner. In this work, custom-designed coaxial nozzles were 3D-printed using a stereolithography printer. Composite inks comprised of thermoplastic polyurethane and silver were developed and studied. The coaxial nozzles were then used to co-extrude …

Material Characterization Of Thermoplastic Polyurethane (Tpu) And Thermoplastic Elastomers (Tpe) For Development Of 3d-Printed Surrogate Organs For Medical Training, Anastasia Elizabeth Lucci

Graduate Theses, Dissertations, and Problem Reports

Cadaveric specimens are a necessary, albeit limited, resource for training medical students on basic surgical skills. The availability of surrogate 3D-printed organs would readily allow access to resources that could reduce or potentially eliminate the need for cadaveric specimens or, at a minimum, provide students the opportunity to practice with 3D-printed surrogates before transitioning to those specimens. This research focuses on determining which thermoplastic material most closely mimics mechanical properties such as hardness and stiffness of human organs and allows 3D printing surrogate organs to be used as safe, educational tools. Relatively “soft” materials such as thermoplastic polyurethanes (TPU) and …

Dome Tester, Clark Bates, Nikolas M. Kulin

Williams Honors College, Honors Research Projects

We are reconfiguring and modifying the previously built dome tester to be more user friendly and mechanically applicable. This has a long-term goal of being a usable teaching tool for manufacturing education within the college of engineering and polymer sciences. The dome tester pushes a metal dome into a clamped sheet of metal to test its forming limits and where necking occurs. We have implemented a better method of viewing the sheet sample as it is being deformed, and improved measuring methods for the distance a sample is deformed. By introducing these changes in conjunction with improved documentation of the …

Development Of Inconel 718f And Inconel 718e Powders For Parts Manufacturing Utilizing Binder Jet Three-Dimensional Printing And Compressed Pellet Methods, Duncan Eric Manor Ii

Graduate Theses, Dissertations, and Problem Reports

Alloy Inconel 718 is a Ni based superalloy used for high temperature applications including turbine blades, turbocharger rotors and nuclear reactors. Inconel 718 is a popular commercial atomized powder that has limitations in performance for use in additive manufacturing applications due to poor part quality and efficiency of current fabrication methods. Developing new compositions and additive manufacturing (AM) methodologies of IN718 is critical to improve the quality and the efficiency of IN718 parts manufacturing. Developing new additive manufacturing methodology that produces higher quality parts made of IN718 as compared to current methods has the potential to greatly impact industry, academia, …

Investigation Of Microstructurally Dependent Mechanical Properties Of Cold Sprayed Copper Using Correlative Microscopy, Quintin Otto

UNF Graduate Theses and Dissertations

This project employs multi-instrument materials characterization to analyze material made with the “Cold Spray” additive manufacturing process. Cold spray is an emerging additive manufacturing technique with unique benefits resulting from its low temperature adhesion process induced by plastic deformation. Metallic powder collides at high speeds creating three dimensional materials and coatings without the need for melting. Copper cold sprayed specimens were analyzed using a series of imaging techniques to characterize the microstructure at varying levels of detail and magnification. Scanning electron microscopy and electron back scattered diffraction were paired with microhardness testing to generate a correlative comparison between microstructure and …

Stability Of Ruddlesden-Popper Phase Lanthanum Nickelate As Air Electrode For Reversible Solid Oxide Cells, Daniel De Lorenzo Moreira

Graduate Theses, Dissertations, and Problem Reports

This thesis studied the long-term stability of Ruddlesden-Popper phase Lanthanum Nickelate under operating conditions as the air electrode for Reversible Solid Oxide Cells (R-SOC). Renewable energies have gone through increase in popularity throughout the last decades, mainly due to the consequences of the rapid population growth in the world. These new energies have been pointed as the rightful successor of fossil fuel energies in order to decrease the environmental impact of our day-to-day life. Solid Oxide Fuel Cells as well as Solid Oxide Electrolysis Cells are believed to be the key to stabilizing the energy supply when environmental conditions are …