Engineering Commons^™

Modeling Of Quad-Station Module Cluster Tools Using Petri Nets, Aung Nay

Theses

The semiconductor industry is highly competitive, and with the recent chip shortage, the throughput of wafers has become more important than ever. One of the tools that the industry has deployed is to use of quad-station modules instead of the traditional single-station modules that allow for higher throughput and better wafer consistency by processing multiple wafers at the same time and distributing work. The industry trend is to use multiple transfer chamber robots to stack the quad-station modules in a series, particularly for etch products. In this work, the quad-station cluster tool wafer movement is modeled by using Petri net …

Energy Dissipation In A Sand Damper Under Cyclic Loading, Ehab Sabi

Civil and Environmental Engineering Theses and Dissertations

Various seismic and wind engineering designs and retrofit strategies have been in development to meet structures' proper and safe operation during earthquake and wind excitation. One such method is the addition of fluid and particle dampers, such as sand dampers, in an effort to reduce excessive and dangerous displacements of structures. The present study implements the discrete element method (DEM) to assess the performance of a pressurized sand damper (PSD) and characterize the dissipated energy under cyclic loading. The idea of a PSD is to exploit the increase in shearing resistance of sand under external pressure and the associated ability …

Sulfonated Styrene Grafted Sebs/Abs Made By Additive Manufacturing For Ion Exchange Applications, Avianna Elaine Gallegos

Open Access Theses & Dissertations

An interpenetrating polymer network (IPN) for cation exchange applications was synthesized from a blend of styrene-ethylene/butylene-styrene (SEBS) and acrylonitrile butadiene styrene (ABS), which was 3D printed, grafted with crosslinked polystyrene (PS), and sulfonated. A method for styrene grafting was applied to reduce the damage to polymer phases caused by the sulfonation reaction. Styrene and divinylbenzene monomers were introduced to the IPN and induced with heat treatment to polymerize in situ. The graft copolymerization reaction was enhanced with varying quantities of benzoyl peroxide as a chemical initiator. The samples were subsequently sulfonated with chlorosulfonic acid in dichloroethane and functionalized for ion …

Fabrication, Thermophysical, And Mechanical Properties Of Cermet And Cercer Fuel Composites For Nuclear Thermal Propulsion, Neal D. Gaffin

Doctoral Dissertations

Nuclear thermal propulsion (NTP) utilizes nuclear fission to double the efficiency of
in-space propulsion systems compared with traditional combustion rocket systems.
NTP systems are limited primarily by the fuel material choice, due to the extreme
conditions they will need to endure, including temperatures up to 3000 K, multiple
thermal cycles with rapid heating and cooling, exposure to hot flowing hydrogen,
large thermal gradients, and high neutron flux. Particle based fuels, namely ceramic-
metallic (cermet) and ceramic-ceramic (cercer) composites are both promising fuel
element material candidates for NTP. Given the high temperature nature, these
materials are difficult to fabricate and very …

Nano-Engineered Soft Magnets: Potential Application In Water Treatment, Hyperthermia And Molecular (Organic) Magnets, Yohannes Weldemariam Getahun

Open Access Theses & Dissertations

Scrutinizing the remarkable and tunable properties of magnetic materials at a nanoscale size "There's Plenty of Room at the Bottom..." Richard Feynman, this study attempts to find sustainable solutions to some of the deteriorating environmental, health, and energy problems the world is encountering. Due to their simple preparation, surface adaptability, and tunable magnetic and optical properties, magnetic nanoparticles have been extensively investigated in water treatment, cancer therapy, data storage, and more. However, relying on non-reusable and chemical-based treatment agents in water, complex and costly cancer treatment procedures and molecular magnets that operate far below room temperature limited those attempts from …

The Qualification Of Sealability And Creep Relaxation Of Additively Manufactured Zytel Gaskets For Pem Fuel Cells, Robert Lazarin

Open Access Theses & Dissertations

The purpose of this thesis is to study the feasibility of low-cost additive manufacturing of gaskets for proton exchange membrane fuel cells exposed to extreme temperature conditions ranging from -55°C to 100°C. With the growing popularity and decreasing costs of additive manufacturing technologies, specifically Material Extrusion (ME), research is being conducted to determine the feasibility of ME components. Thermally cycled PEMFCs may exhibit accelerated gasket deterioration, therefore, the mechanical stability of material extruded gaskets following a harsh thermal cycle must be assessed. The feasibility of the material extruded gaskets will be proven by manufacturing optimization and mechanical testing. The target …

Magnetic Structures Of Sawtooth Olivines Mn2six 4 (X = S, Se) Determined Through Neutron Powder Diffraction, Melaku Sisay Tafere

Open Access Theses & Dissertations

In olivine chalcogenide Mn2SiX 4 (X = S, Se) compounds, the Mn lattice produces a sawtooth, which is of critical significance in magnetism due to the potential for manifesting at bands in the magnon spectrum, a crucial component in magnonics. The compounds Mn2SiS4 and Mn2SiSe4 in Mn2SiX 4 family undergo antiferromagnetic phase transitions at T â?? 85 K and â?? 66 K, respectively, as determined from the specific heat, Cp(T). The average and local crystal structuresare determined using synchrotron X-ray, neutron diffraction, and X-ray total scattering data followed by Rietveld and pair distribution function (PDF) analysis. It is found from …

Fabrication, Microstructure And Mechanical Characterization Of Crvnbtaw High Entropy Alloy Coatings Using Magnetron Sputtering, Jorge Quezada

Open Access Theses & Dissertations

In this project a CrVNbTaW high entropy alloy was evaluated. The samples were made using radio frequency magnetron sputtering and were made under similar conditions. The deposition parameters were explored to find the ideal deposition process. The process included a pressure from 0.1-2mTorr, 600C, 1 hour duration, at 100W power to guns, and constant argon flow. The samples were fabricated under similar parameters using silicon steel and sapphire substrates. The samples were analyzed and characterized using X-ray diffraction, scanning electron microscopy, atomic force microscopy, nanoindentation and corrosion testing. Based on these results we were able to get a better understanding …

A Comparative Evaluation Of Oxidation And Combustion Phenomena In Ti-6al-4v Exposed To Earth Re-Entry And Arc-Jet Test Environments, Arlene Smith

Open Access Theses & Dissertations

The Ti-6Al-4V alloy is widely used in aerospace applications for its beneficial combination of properties. However, this alloy has high solubility for oxygen and thus a high reactivity. Recovered data contained within the Columbia artifacts suggests that this alloy underwent an accelerated degradation and combustion reaction when exposed to the high enthalpy, low-pressure surroundings experienced during reentry into Earth's atmosphere. Arc-jet testing has provided a simulated aerothermodynamic heating environment to mimic what the spacecraft endured. When the effect of thermal alteration on this alpha-beta phase alloy was investigated during previous studies, optical metallography and microhardness tests revealed inconsistencies between samples …

Novel Interlaminar Reinforcement To Enhance The Impact Damage Resistance Of Carbon Fiber-Reinforced Polymer Matrix Composites, Daisy Haidee Mariscal

Open Access Theses & Dissertations

Aerospace, aircraft, marine, and automobile applications are increasingly using composite materials for lighter, higher stiffness, and strength properties. Despite these advantages, composite materials have one major disadvantage. The through-thickness properties are extremely weak when subjected to impact damage. When a composite material is subjected to a low-velocity impact, there is hardly any visible damage on the surface compromising the composite material internally without any external notice. Internal damage may be delamination, which is the most common, matrix cracking, and fiber breakage. A composite material is made up of layers of fiber. The interlaminar region is located in between these layers. …

Laser Powder Bed Fusion Process, Structure, And Properties: Holistic Approach To Establishing Metallurgical Quality, Hunter Taylor

Open Access Theses & Dissertations

The advent of metal additive manufacturing (AM) was posed as a disruption to casting, forging, machining, and forming with the notion "complexity is free". However, since invention in the late 1990's the marketed potential has not been realized. Metal based AM is best viewed from the process-structure-properties-performance (PSPP) paradigm taught in material science and engineering, which links the process history to the part performance. Understanding the complex and localized process control made available by AM creates a significant challenge in defining the materials structure, properties, and performance. The lack of holistic understating of inputs and corresponding results has been identified …

Experimental Tests And Numerical Study Of Trajectories Of Different Types Of Dropped Objects, Yi Li

University of New Orleans Theses and Dissertations

In marine and offshore engineering, dropped objects, such as drill pipes, anchor chains, containers and some small parts, can accidentally fall into the water from ships or offshore platforms, causing casualties on deck or damage to underwater equipment. Damaged equipment can further harm the environment, such as oil spills from damaged wellheads. Therefore, for safe engineering and environmental protection reasons, we need to develop methods and tools that can predict the trajectory of dropped objects.

In this dissertation, we first study containers dropped from ships. More and more containers are falling into the sea due to bad weather. Containers lost …

Hierarchical Structure And Material Integration For Electrocatalytic Co2 Reduction, Hamed Mehrabi

Graduate Theses and Dissertations

CO2 released by the combustion of fossil fuels is driving significant changes to the earth’sclimate. The natural cycle for removing CO2 from the atmosphere, namely photosynthesis, cannot keep up with the rate at which it is being added. Developing engineering approaches to remove CO2 from the atmosphere is becoming essential to reduce these effects. Removal leads to further issues of carbon sequestration and favorable CO2 reuse strategies, including the electrochemical transformation of recovered CO2 to useful products such as fuels and materials. Copper is an important electrocatalyst for the CO2 reduction reaction (CO2RR) because of its unique capability for producing …

An Application Of Optimized Bistable Laminates As A Low Velocity, Low Impact Mechanical Deterrent, Graham Lancaster

All Theses

This research considers the problem of using bistable laminates as a mechanical deterrent to the impending impact of a particle. The structure will be controlled through an algorithm that will utilize piezoelectric devices to activate them in unison with the bistable laminate to successfully deter. A novel experimental setup will be constructed to ensure that the bistable laminate stays fixed when acting as a mechanical deterrent. Piezoelectricity is the main driving force of the bistable laminate to morph and this study will use a Macro Fiber Composite (MFC) actuator that contains piezoelectric ceramic rods in a patch to transfer electrical …

Towards The Electronic Response Of Carbon-Based Van Der Waals Heterostructures In A Diamond Anvil Cell, George Thomas Foskaris

UNLV Theses, Dissertations, Professional Papers, and Capstones

The nanoscale regime of materials has been at the forefront of research and interest in condensed matter physics for many years. In a merger of the fields of two-dimensional (2D) materials and high pressure physics, we present an investigation of the electronic response of carbon-based, van der Waals (vdW) heterostructures in a diamond anvil cell (DAC). Combining these fields presents us with the ability to study the characteristics of such systems both optically, and through electrical transport. Properties such as conductance, band structure, and layer number are considered. The samples in this study are assembled using exfoliation and stacking techniques …

Using Ultrasonication For The Improvement Of Grade And Recovery In Molybdenum Sulfide Flotation, Wayne Alexander Campbell

Open Access Theses & Dissertations

Experimentation was performed on molybdenite slurry by using ultrasonication to elucidate the effects of ultrasonic-induced bubble cavitation on the grade, recovery, and gangue reduction during small-scale flotation tests and was followed by a topographical analysis of quartz particles using SEM. Ultrasonic waves at 20-80 kHz that propagate through a liquid medium cause microbubbles to form, grow, and implode. The cavitation bubble's implosion causes brief extreme local conditions where temperatures can reach 5,000 K and pressures of 1,000 bar. The resulting microjets create mechanical and chemical changes to the system and were directed at improving flotation dynamics in these experiments. Through …

Near-Ir Laser Ablation Of Simulated Radiologically Contaminated Oxides On Carbon Steel Feeder Pipes, Thao Viet Do

Electronic Thesis and Dissertation Repository

As nuclear power plants age and retire from service, many countries face significant challenges concerning the safe long-term storage and disposal of large volumes of low and intermediate level radioactive wastes (L&ILW). The volumes of metallic waste are of particular concern, as when metal corrodes it produces hydrogen that could lead to pressure build-up in interim storage and disposal. In Canada, a significant fraction of the metallic wastes for Canada Deuterium Uranium (CANDU) nuclear reactors are out-of-core reactor components, such as carbon steel (CS) feeder pipes. The radioactive contamination is expected to be largely confined to the surface oxide layers …

Designing And Cnc Machine Valve Sub-Plates And Quick Mounts For Hydraulic Power Training Systems, Connor Maxam

Morehead State Theses and Dissertations

A thesis presented to the faculty of the College of Business and Technology at Morehead State University in partial fulfillment of the requirements for the Degree of Master of Science by Connor Maxam on November 22, 2022.

Multi-Robot Symbolic Task And Motion Planning Leveraging Human Trust Models: Theory And Applications, Huanfei Zheng

All Dissertations

Multi-robot systems (MRS) can accomplish more complex tasks with two or more robots and have produced a broad set of applications. The presence of a human operator in an MRS can guarantee the safety of the task performing, but the human operators can be subject to heavier stress and cognitive workload in collaboration with the MRS than the single robot. It is significant for the MRS to have the provable correct task and motion planning solution for a complex task. That can reduce the human workload during supervising the task and improve the reliability of human-MRS collaboration. This dissertation relies …

Frontiers In The Self-Assembly Of Charged Macromolecules, Khatcher O. Margossian

Doctoral Dissertations

The self-assembly of charged macromolecules forms the basis of all life on earth. From the synthesis and replication of nucleic acids, to the association of DNA to chromatin, to the targeting of RNA to various cellular compartments, to the astonishingly consistent folding of proteins, all life depends on the physics of the organization and dynamics of charged polymers. In this dissertation, I address several of the newest challenges in the assembly of these types of materials. First, I describe the exciting new physics of the complexation between polyzwitterions and polyelectrolytes. These materials open new questions and possibilities within the context …

Plasmonic Nanomaterials-Based Point-Of-Care Biosensors, Rohit Gupta

McKelvey School of Engineering Theses & Dissertations

Point-of-care (POC) biosensors, although rapid and easy-to-use, are orders magnitude less sensitive than laboratory-based tests. Further they are plagued by poor stability of recognition element thus limiting its widespread applicability in resource-limited settings. Therefore, there is a critical need for realizing stable POC biosensors with sensitivity comparable to gold-standard laboratory-based tests. This challenge constitutes the fundamental basis of this dissertation work– to expand access to quality and accurate biodiagnostic tools. At the heart of these solutions lies plasmonic nanoparticles which exhibit unique optical properties which are attractive for label-free and labelled biosensors.Firstly, we improve the stability and applicability of label-free …

Synthesis And Consolidation Of Metal Oxide Nanocrystals Via Nonthermal Plasma, Austin Cendejas

McKelvey School of Engineering Theses & Dissertations

Nonthermal plasmas offer a unique nonequilibrium environment that has been leveraged in a wide variety of applications in the fields of material processing, lighting, and waste management to name a few. In all of these cases, the plasma serves as a source of high energy electrons, ions, reactive gas species, and radicals that interact in several ways with surfaces brought into contact with the plasma. Specifically, nonthermal plasmas have been shown to be very successful in achieving continuous, high-throughput, monodisperse nanocrystals of a wide variety of materials. The crystallinity of nanoparticles synthesized in nonthermal plasmas can be attributed to the …

Soft Electronics And Sensors For Wearable Healthcare Applications, Li-Wei Lo

McKelvey School of Engineering Theses & Dissertations

Wearable electronics are becoming increasingly essential to personalized medicine by collecting and analyzing massive amounts of biological signals from internal organs, muscles, and blood vessels. Conventional rigid electronics may lead to motion artifacts and errors in collected data due to the mismatches in mechanical properties between human skin. Instead, soft wearable electronics provide a better platform and interface that can form intimate contact and conformably adapt to human skin. In this respect, this thesis focuses on new materials formulation, fabrication, characterization of low-cost, high sensitivity and reliable sensors for wearable health monitoring applications.

More specifically, we have studied the silver …

Characterization Of 3d Stereolithography (Sla) Printed Polymer For Autonomous-Flow Microfluidic Devices, Michelle Gamboa

Open Access Theses & Dissertations

3D Stereolithography (SLA) printing is a high-throughput, precise and reproducible manufacturing platform which makes it a desirable technique to develop microfluidic devices for bioanalytical applications. However, limited information exists regarding the physical, chemical, and biological properties of the polymer resins used in 3D SLA printing. This project demonstrates the characterization of a commercially available 3D SLA printed resin polymer used to develop an autonomous-flow (self-driven) microfluidic device. In this investigation, time-dependent materials characterization was done on the Formlabs clear V4 resin to observe changes in mechanical and surface properties. The clear, printed polymer was analyzed with attenuated total reflectance (ATR), …

Pressure-Induced Phase Transition And Electronic Structure Changes In Equiatomic Fev, Homero Reyes Pulido

Open Access Theses & Dissertations

Classical molecular dynamics methods can accurately describe a broad set of many-atomssystems. Although more economical, the results given by this framework lack the precision capable of density functional theory (DFT). Therefore, the structural stability of the B2 phase of a body-centered-cubic iron-vanadium (FeV) alloy using DFT on the electronic structure level is analyzed to verify and further explain classical results obtained by our group in this same alloy. Using Quantum Espresso and Phonopy for the computational simulations, the plotted band structure, electronic density of states (eDOS), phonon dispersions, charge density, and Fermi surfaces for various compressed unit cells are presented. …

Reflectance Spectral Characterization And Taxonomy Applications Of Spacecraft Materials To Aid Space Situational Awareness, Jacqueline Andrea Reyes

Open Access Theses & Dissertations

The increasing number of space missions involving successfully deployed spacecraft have resulted in an augmented density of artificial objects positioned in orbital domains near Earth. With this steady accumulation of objects in space, it has become increasingly imperative to characterize spacecraft materials, which may ultimately be contributors to the orbital debris population. In an effort to identify unique material-specific spectroscopic markers, a variety of spacecraft materials frequently utilized in the aerospace industry to construct typical spacecraft were analyzed using reflectance spectroscopy as a characterization technique for assessment on material type according to optical features. This is significant in providing information …

Crack Control And Bond Performance Of Alternative Coated Reinforcements In Concrete, Sachin Sreedhara

All Dissertations

Concrete cracking in structures is a ubiquitous problem which can lead to the deterioration of the structure. Other than affecting the strength aspect of a structure, cracking impacts the serviceability criteria as well. Although cracking phenomenon in any structure is highly inevitable, it has to be minimized in order to maintain a structure’s life effectively. Cracking in reinforced concrete structures is related to the bond strength developed between the bar and the concrete. It also depends on an ability of the bar to resist the stresses due to shrinkage to minimize the crack. Another important aspect is the resistance offered …

Study Of Thermoelectric And Lattice Dynamics Properties Of 2d Layered Mx (M = Sn, Pb; X = S, Se, Te) And Zrs2 Compounds Using First-Principles Approach, Abhiyan Pandit

Graduate Theses and Dissertations

The aim of this dissertation is the investigation of thermoelectric and lattice dynamics properties of two-dimensional (2D) MX (M = Sn, Pb; X = S, Se, Te) and ZrS2 compounds based on the first-principles density functional theory. The dimensionality reduction (e.g., using 2D structure) of bulk materials is found to have enhanced thermoelectric efficiency. This enhancement is attributed to the increase of the Seebeck coefficient as a result of higher electronic density of states near the Fermi level in low-dimensional materials. In addition, lowering the dimensionality increases phonon scattering near interfaces and surfaces in 2D materials, which leads to a …

Etching Process Development For Sic Cmos, Weston Reed Renfrow

Graduate Theses and Dissertations

Silicon Carbide (SiC) is an exciting material that is growing in popularity for having qualities that make it a helpful semiconductor in extreme environments where silicon devices fail. The development of a SiC CMOS is in its infancy. There are many improvements that need to be made to develop this technology further. Photolithography is the most significant bottleneck in the etching process; it was studied and improved upon. Etching SiC can be a challenge with its reinforced crystal structure. Chlorine-based inductively coupled plasma (ICP) etching of intrinsic SiC and doped SiC, SiO2, and Silicon has been studied. A baseline chlorine …

Additive Manufacturing Of Aluminum Alloy By Metal Fused Filament Fabrication (Mf3)., Luke J. Malone

Electronic Theses and Dissertations

This research studies metal-fused filament fabrication (MF3) for manufacturing aluminum alloy parts. An aluminum alloy powder-based feedstock with a polymer-binder system was extruded via capillary rheometry to form a filament. The filament was used to print green parts that were involved in a two-step debinding process combining solvent and thermal extraction of the polymer binder, then sintered in a partial vacuum. Resulting grain structure, sintered density, and mechanical properties will be characterized and compared to metal injection molded (MIM) specimens. The main objective is to gain an understanding of the MF3 process characteristics and the ensuing material properties and microstructure …