Materials Science and Engineering Commons^™

Properties Of 25cr7ni Stainless Steel Fabricated Through Laser-Powder Bed Fusion., Arulselvan Arumugham Akilan

Electronic Theses and Dissertations

Stainless steel is a low carbon high alloyed system with higher concentrations of Cr& Ni, which impart high corrosion resistance to them. Alloys with approximately 25% Cr & 7% Ni in their chemical composition are commercially referred to as ‘Super Duplex Stainless Steel’. They have a unique phase composition of approximately 50% ferrite & 50% austenite, yielding a robust combination of high mechanical strength & corrosion resistance. They find extensive interest & application in the fields which demand a longer service life under intense mechanical / corrosive environment such as offshore oil rigs & pipelines in nuclear power plants. Traditional …

Structural, Charge Transport, Gas Sensing, Magnetic, Pseudocapacitive, And Electrocatalytic Properties Of Perovskite Oxides., Surendra Bahadur Karki

Electronic Theses and Dissertations

Perovskites are functional materials with the general formula ABO₃ (A = alkali, alkaline earth or lanthanoid cations and B = transition metal or main group cations). These materials are marked by a variety of crystal structures and interesting properties such as colossal magnetoresistance, ferroelectricity, multiferroicity, superconductivity, pseudocapacitance, gas sensing, charge transport, and electrocatalytic properties. The formula of perovskite can be written as AA’BB’O₆, when there is ordering between two cations over A and B-sites. Such compounds are called double perovskite oxides. Some amount of oxygen could be lost from crystal structure without decomposition of the phase. Such …

Effects Of Sizing Agents On Mechanical Properties Of Carbon Fiber–Polymer Composites Via Fused Filament Fabrication Additive Manufacturing., Benjamin D. Mitchell

Electronic Theses and Dissertations

This study demonstrated the effects of changing the sizing agent parameter during the preparation of carbon fibers on the mechanical properties of composite made with acrylonitrile butadiene styrene (ABS) as the matrix material and carbon fibers as the fiber material. Three types of sizing agents produced by Allnex were used to coat three different batches of carbon fibers that were mixed with a torque rheometer and extruded with a barrel-style melt extruder into continuous spools of 1.75 mm filament for use with commercial 3D printers. Tensile tests were conducted on the filaments and tensile bars printed from the materials. Results …

Development Of Porous Solid Acid Catalysts For Lignocellulose And Plastic Upcycling., Mohammad Shahinur Rahaman

Electronic Theses and Dissertations

My goal is to develop chemical processes for transforming waste to solve environmental problems and enhance sustainability. Environmental problems such as pollution and massive amounts of waste are the main drivers that stimulate my research ideas. I focused on creating novel, efficient catalytic processes for converting polymeric waste "feedstocks" into high-value chemicals by integrating my expertise in catalysis, materials science, and synthetic chemistry to develop porous solid catalytic materials. During my Ph.D., I focused on two polymeric feedstocks, lignocellulose, and discarded plastic.

Early in my Ph.D. journey, I focused on catalytic upcycling of lignocellulose. Lignocellulosic biomass is cost-effective, abundant, and …

Monitoring Of State Transitions In Extreme Environment Application Materials Using Fiber Bragg Grating Sensors, Sabuj Khadka

Electronic Theses and Dissertations

By embedding both a single fiber Bragg grating (FBG) sensor and a thermocouple (TC) during the manufacturing for extreme environment applications of certain classes of materials such as metals and polymers, a novel in-situ approach was developed to precisely monitor their entire manufacturing processes. This novel monitoring technique was able to identify many characteristic points during the curing of room and high-temperature epoxies and the solidification processes of metal alloys composed of tin and bismuth which were selected in this research purely for verification purposes. Some of the characteristic points identified for the epoxies were: (i) the gel point, (ii) …

Nanomechanical Characterization And Comparison Of Additively Manufactured Grcop-42 Alloy, Trupti Suresh Mali

Electronic Theses and Dissertations

In an aggressive thermomechanical environment, the superior mechanical as well as thermal properties of materials play an essential role. GRCop which is a copper-based alloy developed by NASA has the potential to fulfill the requirements necessary for hightemperature applications such as the combustion chamber of liquid rocket engines. The first alloy of this family, GRCop-84 (Cu-8 wt.% Cr-4 wt.% Nb) was discovered followed with the development of GRCop-42 (Cu-4 wt.% Cr, 2 wt.% Nb). The reduction in alloying element percentage enhanced thermal conductivity with less built time while maintaining the strength of the material. The conventional fabrication is replaced with …

Mechanical Property Evaluation Of Additively Manufactured Materials Across A Wide Temperature Range, Sanket Vinayak Hirve

Electronic Theses and Dissertations

Additive manufacturing (also called 3d printing) has transitioned from a prototyping-only technology to a technology that is able to create usable parts with complex geometries. 3D printed parts are beginning to be used across all areas of engineering, such as biomedical, aerospace, automobile and many more. Typically, the term “3D printing” refers to layer by layer deposition of polymer materials, while the term “additive manufacturing” refers to layer by layer metal deposition. Conventional manufacturing, or substrative manufacturing, has several main problems that additive manufacturing can help overcome, such as high cost for low volume production, inability to create very complex …

An Investigation Into Energy-Material Properties Interaction In Additive Manufacturing Of Polymers., Pu Han

Electronic Theses and Dissertations

Additive manufacturing (AM), known as three-dimensional (3D) printing, is a fabrication process to build 3D objects layer by layer based on computer aided design (CAD) model or digital 3D model. Fused filament fabrication (FFF) has become a preferred method for additive manufacturing due to its cost-effectiveness and flexibility. However, the parts built using FFF process suffer from lower mechanical strength compared to that fabricated using traditional method and rough surface finish. With this motivation, this dissertation aims to develop and implement a novel in-process laser assisted technique on FFF to heal the microstructure of FFF built objects by enhancing reptation …

Synthesis, Crystal Structure And Ionic Conductivity Of Ruddlesden-Popper Oxide Materials: Effects Of Ionic Radii And Defects On Lithium-Ionic Conductivity., Selorm Joy Fanah

Electronic Theses and Dissertations

Layered perovskite oxides of the Ruddlesden-Popper (RP) type structure can be good lithium-ion conductors for solid electrolyte applications in all-solid-state batteries, due to the large gap separating octahedral layers which can be useful pathways for Li-ion conduction. However, little work has been done on their lithium-ion transport properties in these materials despite their interesting structural properties. This work highlights the synthesis and study of the ionic conductivities in a series of n = 2 and 3 Ruddlesden-Popper oxides, as part of an ongoing investigation in search of alternative solid electrolyte materials. Several different strategies were employed for the enhancement of …

Mixed Metal Oxide Nanowires Via Solid State Alloying., Veerendra Atla

Electronic Theses and Dissertations

Mixed metal oxide materials with composition control find applications in energy conversion and storage processes such as heterogenous catalysis, photoelectrochemical catalysis, electrocatalysis, thermal catalysis, and lithium-ion batteries. Mixed metal oxides and/or complex oxides with composition control and in one-dimensional form as nanowires could be interesting to various catalysis applications due to control on single crystal surfaces, active sites, acidity versus basicity site density, and oxygen vacancies. The major challenge is to synthesize mixed metal oxide nanowires beyond binary oxides with composition control. In this dissertation, solid state alloying of binary oxide nanowires with solid and liquid precursors is studied to …

Rapid Annealing Of Perovskite Solar Cell Thin Film Materials Through Intense Pulse Light., Amir Hossein Ghahremani

Electronic Theses and Dissertations

Perovskite solar cells (PSCs) have garnered a great attention due to their rapid efficiency improvement using cheap and solution processable materials that can be adapted for scalable high-speed automated manufacturing. Thin film perovskite photovoltaics (PVs) are typically fabricated in an inert environment, such as nitrogen glovebox, through a set of deposition and annealing steps, each playing a significant role on the power conversion efficiency (PCE), reproducibility, and stability of devices. However, atmospheric processing of PSCs would achieve lucrative commercialization. Therefore, it is necessary to utilize materials and methods that enable successful fabrication of efficient PSCs in the ambient environment. The …

Observation Of New Particle Formation In The Northern Hemisphere At Altitude From 4 To 20 Km, Mohamed Saad

Electronic Theses and Dissertations

New particle formation (NPF) is investigated using measurements of aerosol size distributions and meteorological variables made in two continents, including USA and Europe. Despite the considerably different aerosol particle abundances among the sites, a common relationship was found between the characteristics of NPF events and the air mass convective and/or advective transport. CO and O3 act as tracers of tropospheric and stratospheric air, respectively, their statistical relationship can be used to quantify air mass characteristics and origins. The mixing ratio values of CO increased within the upper troposphere layer before/during NPF events, which may serve as an indicator of occurring …

Recycling Of Fiber Polymer Matrix Composites In Cementitious Materials, Edward Patton Clark

Electronic Theses and Dissertations

Recycling options for fiber polymer matrix composite waste materials are limited because they typically cannot be reused, reprocessed for down-cycling, and are generally environmentally unfriendly. The utility industry, specifically electrical distribution, has been increasingly using hybrid carbon, glass fiber, and epoxy resin composite rods for high-voltage (HV) conductor transmission lines. The high-voltage conductor core (HVCC) used in the transmission line can have an optimal in-service-life of roughly several decades, in which the material is then retired to a waste landfill. Currently, there is limited research and recycling methodology for these hybrid composite rods. In this research, powder carbon fiber, glass …

Material Analysis Of 3d Welded 5356 Aluminum Alloy, Ryan Fouts

Electronic Theses and Dissertations

Metal 3D printing has been reserved for aerospace and high-end automotive industries because of its cost. A gas metal arc welder (GMAW) on a rugged 3D printer frame could make metal additive manufacturing an option for more industries and consumers. 3D welded aluminum has not been examined in depth as an option for additive manufacturing (AM). Extensive tests are necessary to determine the correct settings to use a metal inert gas (MIG) welder for AM. Porosity within the welded material must be evaluated to better understand the additive process. The material properties of 3D welded aluminum will be tested and …

Monitoring Of Overhead Polymer Core Composite Conductors Under Excessive Mechanical Loads Using Fiber Bragg Grating Sensors, Daniel H. Waters

Electronic Theses and Dissertations

This combined experimental and numerical study addresses mechanical effects associated with static and dynamic loading of novel High Temperature Low Sag (HTLS) transmission line polymer core composite conductors. The developed methodology was successfully applied to ACCC® to explain the complex failure mechanisms associated with combined bending and tension loading. Furthermore, the use of Fiber Bragg Grating (FBG) sensors was investigated for the first time to monitor the ACCC® design during installation and in-service.

Transverse low-velocity impacts to the ACCC® conductor having either free or constrained end conditions and large axial tensile loads were performed. It was identified that the most …

Biomechanical Investigation Of Plant Vascular Tissue For Bio-Inspired Design And Flexible Composites, Mukesh Roy

Electronic Theses and Dissertations

Since the inception of evolution, nature has continuously optimized all the natural materials. These optimizations are so efficient that scientists and engineers have started taking inspiration from nature. Such inspiration-based solutions provide sustainable development of new materials with enhanced structural properties and functionalities (such as stiffness, stability, toughness, self-healing etc.). This variety of properties and functionalities is mainly due to the hierarchical organization of such components. Abstraction of the hidden cues of the hierarchical organization, principles and underlying structure-function relations are some of the critical approaches of bioinspired materials design. Inspiration from animals and plants has helped develop the design …

Development Of A High Strength Composite Material Using Large Scale 3d Printing Applications Using Waste Plastic And Steel, Naga Sri Madhavareddy

Electronic Theses and Dissertations

This project focuses on developing a high strength composite material for largescale 3D printing applications using recycled materials like High-Density Polyethylene (HDPE) and Steel 430. This material has applications for in-space manufacturing (the Moon or Mars) as well as large-scale manufacturing on earth. In addition to creating a strong useful material, materials that are easily recycled, but are often not recycled, are used. Recycling plastic and metal reduces pollution, saves resources, reduces waste going to landfills, and prevents the destruction of habitats from the polymerization of new plastic and similarly mining new ore. The percentage of HDPE generated from recycled …

Effect Of Composition And Print Orientation On Thermal Conductivity Of 3d Printed Composites, Cory Jacques

Electronic Theses and Dissertations

Additive manufacturing (AM) technologies have become widely used for rapid prototyping and are beginning to be used for end-use applications. Fused Deposition Modeling (FDM) is a type of 3D printing where molten thermoplastic is extruded layer by layer to create parts. There is an increasing need for improvement and diversification of material properties to further extend the use of AM parts. AM parts have not been commonly used in heat transfer applications due to the limited availability of information on thermal conductivity of materials and the effects of printing orientation. A special apparatus was designed and built to experimentally test …

Modeling And Analysis For Unit Cell Size, Material Anisotropy And Material Imperfection Effects Of Cellular Structures Fabricated By Powder Bed Fusion Additive Manufacturing., Yan Wu

Electronic Theses and Dissertations

Cellular structures are networks of interconnected struts or walls with porosities and are widely found in many natural load-bearing structures such as plants and bones. Cellular structures offer unique functional characteristics such as high stiffness to weight ratio, tailorable heat transfer coefficient, and enhanced mechanical energy absorption, which makes them highly attractive in various engineering disciplines such as biomedical implants, electrodes, heat exchangers, and lightweight structures. There exists an abundance of literatures that have investigated various mechanical properties of various cellular structures such as Poisson’s ratio, elastic modulus, ultimate strength, yield strength, and failure characteristics. Based on the classic cellular …

Aqueous Redox Flow Batteries With Boron Doped Diamond As An Electrode., Alex M. Bates

Electronic Theses and Dissertations

As the interest and implementation of renewable energy accelerates, so does that of grid energy storage. It is widely believed that a cost-effective energy storage technology will bring about the proliferation of renewable energy. Redox flow battery (RFB) technology represents a promising solution to cost-effective grid energy storage. Compared to other technologies, RFBs have a long lifetime, high efficiency, are non-flammable, significantly reduce cost, and separately scale power and energy. The separation of power and energy enables increased energy capacity by simply adding electrolyte volume. Of the challenges facing RFB technology, one readily apparent is the cost of the active …

Materials-Processing Relationships For Metal Fused Filament Fabrication Of Ti-6al-4v Alloy., Paramjot Singh

Electronic Theses and Dissertations

Additive manufacturing (AM) is at the mainstream to cater the needs for rapid tooling and small-scale part production. The metal AM of complex geometries is widely accepted and promoted in the industry. While several metal AM technologies exist and are matured to a level where expectation in terms of design and properties are possible to realize. But the metal AM suffers from the heavy expense to acquire equipment, isotropic property challenges, and potential hazards to work with loose reactive metal powder. With this motivation, the dissertation aims to develop the fundamental aspects to print metal parts with bound Ti-6Al-4V powder …

Selective Laser Melting 17-4 Ph Stainless Steel And The Effect Of Varied Thermal Treatments On Fatigue Behavior., Sean Daniel Dobson

Electronic Theses and Dissertations

Fatigue failure is the leading source of loss in industry. In order for new means of manufacturing to move towards mainstream use a complete understanding of material and mechanical behavior must be gained. This endeavor seeks to aide in that task by observing the fatigue behavior of selective laser melting (SLM) additive manufacturing (AM) specimens and the effect of differing thermal treatment conditions for an optimized AM process. Stainless steel 17-4 PH specimens were fabricated using SLM AM and thermally treated to three conditions: as-built, solutionized and hardened, and direct hardened. These specimens were characterized for material (powder quality, density, …

Graphene/Oxide Interactions With Polymer Networks Modeled Using Molecular Dynamics, Matthew Alan Reil

Electronic Theses and Dissertations

Due to its unique physical properties, graphene has shown great promise as an additive to Polymer Matrix Composites (PMCs) for material property enhancement. Achieving homogeneous dispersion of the graphene platelets within a polymeric network is critical to realizing these enhancements. Research has shown that achieving homogeneous dispersion of graphene platelets within PMCs is challenging as graphene is immiscible with most polymeric networks. This work used Molecular Dynamics (MD) simulations to demonstrate dispersion of graphene platelets within PMCs is inhibited by molecular surface charge potentials. Further simulations were conducted to demonstrate functionalized forms of graphene, specifically graphene oxide, have altered surface …

Thermally Driven Spin Transport In Ferromagnetic Metals, Wafa Saud Aljuaid

Electronic Theses and Dissertations

Since the discovery in 2008, the spin Seebeck effect has become one of the most active topics in the spin caloritronics research field. It opened a new way to create spin current by a combination of magnetic fields and heat. A temperature gradient in ferromagnetic (FM) metals generates a ow of spin current due to split of spin chemical potential between spin up and spin down electrons. This thermal spin current has been detected using an attached nonmagnetic heavy metal with large spin Hall angle via the inverse spin hall effect (ISHE). A voltage signal is generated since the nonmagnetic …

Surface And Structure Engineering For Next Generation Lithium Metal Batteries, Ke Chen

Electronic Theses and Dissertations

Lithium (Li) metal has been considered as one of the most promising anode materials to replace conventional graphite for Li-ion battery due to its high theoretical capacity (3860 mAh g-1) and low electrochemical potential (-3.04 V vs standard hydrogen electrode). However, it still faces some problems such as unstable solid electrolyte interphase (SEI), uncontrolled Li dendrites growth, and infinite volume change during battery charging/discharging. To develop a stable and low-cost Li metal anode for next-generation Li metal battery, in this dissertation, we have made efforts to understand and solve these problems in two aspects, by introducing an artificial SEI and …

Characterization Of Directed Energy Deposition Additively Manufactured Grcop-42 Alloy, Scott Landes

Electronic Theses and Dissertations

GRCop is an alloy family constructed of copper, chromium, and niobium and was developed by NASA for high heat flux applications. The first of its kind, GRCop-84, was specifically designed for the environments seen by channel cooled main combustion chamber liners. To further increase thermal conductivity while maintaining material strength characteristics, the percentage of alloying elements were cut in half and GRCop- 42 was developed. In recent years, NASA has successfully additively manufactured GRCop with comparable material characteristics to wrought GRCop using a Laser Powder Bed Fusion (L-PBF) process. Benefits of this process include fabrication of intricate cooling channels as …

Two-Dimensional Nanomaterials And Their Composites For Electrochemical Detection Of Toxic Mercury Ions In Water, Md Tawabur Rahman

Electronic Theses and Dissertations

The presence of trace amounts of mercury ion (Hg²⁺) in drinking water has a detrimental effect on human health. The development of an electrochemical sensor for Hg²⁺ detection is still challenging to obtain ultra-trace sensitivity, excellent selectivity, wide Linear Detection Ranges (LDRs), and ultra-low detection limit. This work presents an electrochemical sensor based on two-dimensional nanomaterials and their composites for the enhanced sensing of Hg²⁺ in water. Graphene oxide (GO)-silver nanowires (AgNWs) composite and metallic 1T phase tungsten disulfide (WS2) microflowers were utilized for the fabrication of electrochemical sensors using drop-casting. Under the optimized experimental conditions, …

Ultrasonic-Based Condition Assessment Of Wooden Utility Poles, Yishi Lee

Electronic Theses and Dissertations

More than 300 million utility poles shoulder the utility grid in the United States. However, the ineffectiveness of the current inspection process causes roughly a third of utility poles removed from the service deemed suitable for reuse. Due to the utterly essential role of the power infrastructure, budget shrinkage, and the structural degradation of the modern distribution grid, this Ph.D. dissertation addresses the challenges by proposing a physics-based signal analysis method with a jointly developed ultrasonic UB1000 system c to enhance the objectivity in ultrasonic-based nondestructive evaluation (NDE). The proposed methodology has been deployed commercially in the field and featured …

Triple-Junction Solar Cells : In Parallel., Levi C Mays

Electronic Theses and Dissertations

This paper looks into the current inefficiency of solar cells and attempts a few alternative solar cell structures in order to provide a more effective source of renewable energy. Currently, multi-junction solar cells are being developed to capture the sun’s light more efficiently. One of the ideas in this paper is to add a window to see if the addition of such a layer into a junction will increase the voltage while maintaining nearly the same current output. Central to this paper is the rearranging of the conducting layers of the multi-junction cell so that the junctions can be connected …

Fundamental Core Effects In Co-Cr-Fe-Ni Based High Entropy Alloys, Abhishek Mehta

Electronic Theses and Dissertations

High entropy alloys (HEAs) are near equiatomic multi-principal-element-alloys (MPEAs) which are different from traditional solvent-based multicomponent alloys. Based on initial work by Yeh and Co-workers, they were proposed to exhibit four "core" effects: high entropy, sluggish diffusion, lattice distortion, and cocktail effect. Present work investigates two of the four "core" effects, i.e. high entropy and sluggish diffusion effects, in Co-Cr-Fe-Ni based transition metal high entropy alloys. Solid-to-solid diffusion couple approach was adopted to investigate, these core effects. Experimental results contradicts the "high entropy" effect based on thermodynamics analysis: that the HEAs with low entropy of mixing may be thermodynamically more …