Materials Science and Engineering Commons^™

Reclamation Of Fused Silica From Investment Shells Used For Casting Steel, Samuel L. Holt

College of Graduate Studies: Theses & Dissertations

Fused silica is widely used for investment casting shell molds. Fused silica shells are discarded after being used for casting one time. This is due to the transformation of fused silica to beta cristobalite above 1652℉ (900℃). To reduce cost and waste of investment casting foundries, this study is exploring a method to inhibit transformation of fused silica and reclaim it from high temperature investment casting shells. This research has employed firing to minimalize fused silica transformation to cristobalite. The phase transformation is minimalized due to sintering and coarsening of the particles during firing. Coarsening reduces surface area to volume …

Mechanical Properties Of Nanomodified Hybrid Gfrp Composite Materials, Micah Rop Kimutai

College of Graduate Studies: Theses & Dissertations

The mechanical behavior of the nanomodified hybrid epoxy matrix was investigated in glass fiber reinforced plastics (GFRP). In this study, five nanocomposites enriched with as received halloysite, nanomer I.28E, HNT-APTES, and the hybrid combinations of the two HNTs with the nanomer I.28E were successfully fabricated. To evaluate the effects and morphological characteristics of the individual fillers and the hybrid configurations on the epoxy resin matrix, TGA, DSC, and DMA were analyzed. To understand the effect of the five configurations on the neat GFRP laminate, mode I interlaminar fracture toughness, tensile, and vibration properties were investigated. Electron microscopy testing techniques were …

Microstructure Evolution And Mechanical Property Response Of Tc11 Titanium Alloy Under Electroshock Treatment, Chang Liu, Lechun Xie, Dongsheng Qian, Lin Hua, Liqiang Wang, Lai-Chang Zhang

Research outputs 2014 to 2021

© 2020 The Authors This work investigated the effects of electroshock treatment (EST) on the microstructure variation and mechanical properties of TC11 alloy. The average hardness of the specimens decreased from 358 HV to 328 HV after EST of 0.04 s, then increased to 396 HV after EST of 0.06 s. After EST, the yield strength of specimen declined from 959 MPa to 797 MPa after EST of 0.04 s, and then increased to 1265 MPa after EST of 0.06 s, but the fracture strain decreased continuously. The variation in mechanical properties was closely related to the phase transition from …

The Effect Of Tin-, Ticn-, Tialn-, And Tisin Coated Tools On The Surface Defects And Geometric Tolerances Of Holes In Multi-Spindle Drilling Of Al2024 Alloy, Muhammad Aamir, Adrian Davis, William Keeble, Ugur Koklu, Khaled Giasin, Ana Vafadar, Majid Tolouei Rad

Research outputs 2014 to 2021

The integrity of machined holes depends on many parameters, some of which are related to the cutting tool (geometry, coating, material). Other influential parameters are related to the machining process variables (spindle speed, feed rate, workpiece material), all of which can affect the quality of the hole and drilling induced damage on its surface. This study investigates the effect of uncoated tools and four types of tool coatings (TiN-, TiCN-, TiAlN-, and TiSiN) on the hole quality and its microstructure. The study analyzed several hole geometrical metrics, namely hole size, circularity, cylindricity, and perpendicularity of an Al2024 aluminum alloy using …

Dry Reforming Of Methane Using Microwave Irradiated Metal Oxide/Coal Char Catalysts, Anthony Carter

Graduate Theses, Dissertations, and Problem Reports (ETD)

This research focuses on the synthesis of both shaped and amorphous powder materials, the combination of these materials with dried Powder River Basin (PRB) coal char, and their reactionary properties with methane and carbon dioxide gasses with conventional and microwave (MW) heating. The first goal of this project was to synthesize shaped micro and nano sized particles with ideal dielectric properties for converting electromagnetic energy into heat and proven capabilities of activating methane. These particles were synthesized via solvothermal, hydrothermal, and co-preceptory treatments alone and onto the surface of dried PRB coal char. PRB is a sub-bituminous, low-ranking coal (LRC) …

Metal Supported Solid Oxide Fuel Cell Using Proton Conducting Electrolyte For Direct Ammonia Utilization, Edwin Vega Hiraldo

Graduate Theses, Dissertations, and Problem Reports (ETD)

Transportation represents about 27% of global warming greenhouse gas emissions nowadays. To reduce these emissions, fuel cell electric vehicles have been poised to be a new trend to provide zero-emission transportation. Among them, solid oxide fuel cells (SOFCs) offer efficient, clean energy, especially when powered by carbon-free fuel, such as ammonia. To enable onboard ammonia-fed SOFCs, a metal-supported, proton-conducting SOFC is investigated in this study. The metal support would provide physical robustness for thermal shock during vehicles’ quick start-up and shutdown, reduce internal temperature gradients due to the greater thermal conductivity of the metal, and enable conventional metal joining for …

Recovery Of Phosphorus From Florida Phosphatic Waste Clay, Amir Eskanlou

Graduate Theses, Dissertations, and Problem Reports (ETD)

This MS thesis examines the recovery of phosphorus (P) from Florida waste clay (WC). A comprehensive literature review revealed that: (i)-The most important values being lost to WC are P and rare earth elements (REEs). For the recovery of these values from WC, two crucial attempts are the removal of extremely fine-sized clays, followed by the recovery of phosphate content, which can pave the path for the recovery of REEs; (ii)-Any scientific/ technological solution should, at the same time, be economically and environmentally attractive to the industry. As such, moving from mostly chemical separation processes to the primarily physical/ physicochemical …

Generation Of Excited Species In A Streamer Discharge, Shirshak K. Dhali

Electrical & Computer Engineering Faculty Publications

At or near atmospheric pressure, most transient discharges, particularly in molecular gases or gas mixture containing molecular gases, result in a space charge dominated transport called a streamer discharge. The excited species generation in such discharges forms the basis for plasma chemistry in most technological applications. In this paper, we simulate the propagation of streamers in atmospheric pressure N₂ to understand the energy partitioning in the formation of various excited species and compare the results to a uniform Townsend discharge. The model is fully two-dimensional with azimuthal symmetry. The results show a significantly larger fraction of the energy goes …

Thermophysical Properties Of Nominally Phase Pure Boride Ceramics, Austin D. Stanfield

Doctoral Dissertations

"This research focusses on the thermophysical properties of nominally phase pure boride ceramics. As interest in ultra high temperature ceramics increases due to a renewed interest in hypersonic flight vehicles and with the expanding materials design space accompanying interest in high entropy materials, it is imperative to understand the intrinsic properties of boride ceramics. By reducing Hf content in ZrB₂ from the natural abundance, ~1.75 at% in this case, to ~100 ppm, thermal conductivity increased from 88 W/m·K to 141 W/m·K. Removal of Hf allowed the thermal conductivity of ZrB₂ with small transition metal solute additions to be …

Investigation Of The Tribological Behavior Of Mineral Lubricant Using Copper Oxide Nano Additives, Ahmed A. Abdel-Rehim, Sayed Akl, Sherif Elsoudy

Mechanical Engineering

In this study, tribological properties of custom formulated and stabilized nano lubricant are investigated. Spherical CuO nanoparticles are suspended in 20W-50 mineral base lubricant using Oleic Acid (OA) as a surfactant. Three different nano lubricant concentrations with 0.2, 0.5, and 1 wt.% were analyzed through ASTM G-99 pin-on-disc tribometer standardized test under boundary/mixed lubrication regimes. The generated friction and wear analyses confirm a consolidation of tribological properties with a reduction in friction coefficient in the range of 14.59–42.92%, compared with the base lubricant. Analysis of worn surfaces (SEM/EDX) as well as (AFM) was conducted. Combined hypotheses were proposed from the …

Potential Advantages Of Basalt Frp Bars Compared To Carbon Frp Bars & Conventional Steel, Yosra El Maghraby, Mohamed Nagib Abou-Zeid Prof., Ezzeldeen Yazeed El Sayed Ahmed Prof

Civil Engineering

No abstract provided.

The Effects Of Rigid Polyurethane Foam As A Confinement Material On Breaching Charge Detonations, Nathan Franz Paerschke-O'Brien

Masters Theses

"The effects of a rigid polyurethane foam used as a confinement material on four types of breaching explosives were tested, focusing on the changes in shockwave peak pressures, detonation load compression forces, and brisance cratering abilities. The Plate Dent testing procedure was modified to incorporate a load cell force sensor, and two air overpressure sensors were included adjacent to the blast to quantify each test result. The testing variables focused on the polyurethane foam cure times and thickness volumes around the breaching explosives to determine the breaching charges' optimal energy output capabilities when confined by the foam material. The rigid …

Relating Detonation Parameters To The Detonation Synthesis Of Nanomaterials, Martin Langenderfer

Doctoral Dissertations

“This research investigates the physical and chemical processes that contribute to the detonation synthesis of silicon carbide nanoparticles. Bulk production of SiC nanoparticles through detonation is possible due to pressures achieved over 20 GPa and temperatures over 2000 K as well as quenching rates in excess of 13 billion K/second. These conditions catalyze reaction and bottom-up molecular growth while retaining particles < 100 nm in diameter. In this work, detonation synthesis of SiC was demonstrated by incorporation of polycarbosilane, an SiC precursor material, into an RDX/TNT explosive matrix prior to detonation. Detonation Synthesis of SiC was also accomplished by reacting elemental silicon with carbon liberated by the detonation of negatively oxygen balanced TNT. Hydrodynamic simulation of a 60:40 mass ratio RDX/TNT detonation created conditions thermodynamically suitable to produce cubic silicon carbide within the first 500 nanoseconds after the passage of the detonation wave while carbon remains chemically reactive for molecular formation. Simulations and experimental tests indicated that loading configuration and impedance mismatch of the precursor additives used in detonation synthesis results in conditions in the additives that exceed the accepted detonation pressure of the explosive by greater than three times. Finally, a full factorial experimental design showed increasing silicon concentration, reducing silicon size, and reducing oxygen balance by adjusting the ratio of RDX to TNT decreased the explosives detonation pressure by 20% and increased the soot yield and concentration of SiC observed in the detonation products by 82% and 442% respectively”--Abstract, page iv.

Experimental And Numerical Studies Of Novel Thermal Energy Storage Materials For Applications In Concrete And Energy Storage Systems, Wenyu Liao

Doctoral Dissertations

In this work, several types of novel thermal energy storage (TES) materials and composites are explored, and a series of numerical simulation models and experimental protocols are developed to evaluate the potentials of these materials to be applied in concrete, pavement, and thermal energy storage systems.

The first two types of novel TES materials/composites are at the micro-scale, which use micro diatomite (DE) and cenosphere (Ceno) as carriers of phase change material (PCM), respectively. The third type of novel TES material is at the macro-scale, utilizing lightweight sand (LWS) and lightweight coarse aggregate as carriers to load PCM. The last …

Effects Of Corrosion On The Sers Activity And Optical Response Of Silver Nanorods, Christopher J. Mealer

UNF Graduate Theses and Dissertations

The nanoscience and nanotechnology community have a common goal in better understanding the surfaced enhanced Raman scattering (SERS) that occurs due to laser plasmon resonance in conjunction with metal enhanced substrates. Metallic nanostructures, such as silver (Ag) nanorods, are widely used in biological and chemical sensing applications that rely on the measurement of subtle changes in the optical response of the nanostructures in the presence of a target agent. The optical response of Ag nanorods and most other metallic nanostructures is highly sensitive to morphology and surface chemical termination. In pristine condition, the optical properties of Ag nanorods and other …

The Investigation Of The Underlying Microstructure Associated With Fracture Features In 6061 Cold Sprayed Aluminum, Justin White

UNF Graduate Theses and Dissertations

Cold gas dynamic spraying commonly known as cold spray is a process currently used for restoration, re-tolerancing, and application of coatings. With additional resources allocated towards the development of a through process model aimed at predicting the properties of bulk material produced via the Cold Spray process, more lab testing and investigation must be done to capture the effects of the varying microstructure in CS materials. The properties of ultra-fine-grained materials are derived from data collected from coarse grained materials and processes that do not accurately capture the effects as elevated strain rates and ultra-fine-grained materials. The lack of property …

New Horizons For Processing And Utilizing Red Mud, M. Archambo

Dissertations, Master's Theses and Master's Reports

Red mud is an industrial slurry waste that is produced as a byproduct of the Bayer process for alumina. The waste is generated in large quantities, up to a ratio of 2:1 against the valued product alumina. Red mud exhibits many chemical and physical properties that categorize it as a hazardous material. Due to the addition of sodium hydroxide in processing, the pH is typically at values close to 13. Small particle size discourages separation from water for disposal, so drying red mud happens over many years.

The pH of red mud can be reduced with inexpensive reagents. Carbon dioxide …

The Effects Of Molybdenum, Chromium, And Niobium On Gray Iron For Brake Rotor Applications, Matthew Hasbrouck

Dissertations, Master's Theses and Master's Reports

Brake rotor composition and microstructure must be optimized for thermal and mechanical performance to avoid thermal-mechanical cracking, excessive wear, and to reduce noise. Niobium is an element that increases the strength and wear resistance of gray iron; however, the interaction of niobium with other common alloying elements (chromium and molybdenum) is not well understood. Thirteen gray cast iron alloys were produced with varying levels of carbon equivalent (CE), Cr, Mo, and Nb. Bars with four different diameters (8, 14, 22, and 30 mm) were cast from each alloy and microstructural and physical properties such as graphite flake morphology, pearlite spacing, …

Role Of Eta Phase Evolution On Creep Properties Of Nickel Base Superalloys Used In Advanced Electric Power Generation Plants, Ninad Mohale

Dissertations, Master's Theses and Master's Reports

Advanced fossil energy power generation plants require materials that withstand high temperatures and corrosive environments. One such material that is used in steam turbines is Nimonic 263. It is a nickel-base superalloy that is principally strengthened by gamma primephase (Ni₃(Ti, Al)) and has an L1₂structure. At extended times and at turbine operating temperatures however, eta (Ni₃Ti) phase is known to form at the expense of gamma prime. Eta has a complex DO₂₄structure and is the stable phase between 750°C and 900°C, but with slow kinetics of formation. Little is understood about eta …

Analyzing Variation In Dispersoid Formation In Aluminum Alloys By Minor Changes In Homogenization Temperature, Brendan Treanore

Dissertations, Master's Theses and Master's Reports

The homogenization of billets in the aluminum extrusion industry is a critical step that removes chemical segregation from casting, dissolves low melting point phases, forms nanoscale dispersoid phases, and promotes the beta to alpha transformation of iron particles in the matrix. With ever increasing use of aluminum extrusion in the automotive industry there is a constant need for increased efficiency and consistency in processing of extruded aluminum. The work in this thesis explores the effects of 10°C differences in the homogenization temperature on the formation of dispersoids in 6082 alloys used in the automotive industry. The role of dispersoids is …

Anaerobic Reductive Bioleaching Of Manganese Ores, Neha Sharma

Dissertations, Master's Theses and Master's Reports

The increasing demand of manganese in the industries and various hindrances in its production from low grade ores by conventional method has made it imperative for researchers around the world to develop a method of manganese extraction from low grade ores that is both environment friendly and economical. Bioleaching has shown significant potential in manganese extraction and efficiencies of extraction have been found to be 70-98% with the help of various bacteria and fungi.

This study focuses on extraction of manganese with the help of mixed bacterial strains that have been collected from their natural anaerobic environment. The extraction of …

Studying The Effects Of Initial Crack Angle On The Crack Propagation In Graphene Nano-Ribbon Through Molecular Dynamics Simulations, Vijay Kumar Pathak

Dissertations, Master's Theses and Master's Reports

In this research, we have worked on the brittle fracture of graphene nano-ribbon to explore the behavior of crack propagation at different crack angles. We have performed classical Molecular Dynamics simulations using LAMMPS at ten different crack angles between 0 degrees and 45 degrees, in an increment of 5 degrees to observe the parameters that dominate the crack path. The graphene nanoribbon is loaded in the zigzag direction by pulling it in the armchair direction with a pre-existing crack in the center. We have used OVITO for the visualization of the simulation. AIREBO potential is employed in this work because …

Viability Of A Proposed Transparent Fluid Model For Analog Metal Casting Filling Process, Andres Segura Irazoqui

Dissertations and Theses @ UNI

This research work was conducted to develop a proposed transparent fluid model to mimic dross formation and dispersion in metal castings during the mold filling process. The major cause for dross formation includes the air entrainment, surface turbulence, and bubbles, which create oxide films inside the molten metal. The oxide films are trapped inside the casting after solidification causing detrimental effects on the mechanical properties of the casting.

The objective of the investigation was to explore the feasibility using phenolic urethane as a transparent fluid material to investigate air entrainment mechanism. The experimentation consists of the following materials: the phenolic …

Phase Formation And Thermal Conductivity Of Zirconium Carbide, Yue Zhou

Doctoral Dissertations

“This research focused on the synthesis and phase formation of zirconium carbide with different carbon contents, and lattice thermal conductivity of zirconium carbide with different carbon vacancy, hafnium, and oxygen contents.

Nominally pure phase ZrC_x was synthesized by solid-state reaction of zirconium hydride (ZrHs) and carbon black at a temperature as low as 1300°C. The powder synthesized at 1300C was carbon deficient ZrC_x . Carbon stoichiometry of the as- synthesized powders increased as the synthesis temperature increased. As the synthesis temperature increase, the oxygen content of ZrC_x decreased due to the increasing C site occupancy. Low stoichiometry …

Semi-Empirical Modeling Of Liquid Carbon's Containerless Solidification, Philip C. Chrostoski

Doctoral Dissertations

“Elemental carbon has important structural diversity, ranging from nanotubes through graphite to diamond. Previous studies of micron-size core/rim carbon spheres extracted from primitive meteorites suggest they formed around such stars via the solidification of condensed carbon-vapor droplets, followed by gas-to-solid carbon coating to form the graphite rims. Similar core/rim particles result from the slow cooling of carbon vapor in the lab. The long-range carbon bond-order potential was used to computationally study liquid-like carbon in (1.8 g/cm³) periodic boundary (tiled-cube supercell) and containerless (isolated cluster) settings. Relaxations via conjugate-gradient and simulated-annealing nucleation and growth simulations using molecular dynamics were …

Thermal And Mechanical Properties Of Novel Carbide Materials, Evan Charles Schwind

Doctoral Dissertations

"This research focuses on studying the thermal and mechanical properties of novel carbide materials at room and elevated temperatures. The novel carbide materials investigated include zeta phase tantalum carbide (ζ-Ta₄C_3-x) and a high entropy (Ta,Hf,Nb,Zr)C carbide. The electrical resistivity and thermal conductivity of zeta phase tantalum carbide (~96 wt.%) were measured as 160 ± 4.2 μΩ-cm and 9.6 W/m•K. These are higher and lower (respectively) than for cubic tantalum carbide, most likely due to planes of carbon vacancies present in the ζ-Ta₄C_3-x crystal structure. The thermal conductivity of (Ta,Hf,Nb,Zr)C was lower than any …

Studying The Effects Of New Additive Materials For The Improvement Of The Capacity And Cycle Life Performance Of The Lead-Acid Battery, Julian Kosacki

Doctoral Dissertations

"Lead-acid batteries are an established technology with nearly 99% recyclability; however, lead-acid batteries produce only 40% of their theoretical capacity due to poor active mass utilization and PbSO4 pore blockage, and the longevity of the batteries is hampered by secondary reactions during the cycle life such as corrosion and gassing.

Lead-acid batteries were investigated and improved through several different approaches: an alternative electrolyte to mitigate secondary reactions, graphite additives to improve positive active mass (PAM) utilization, and dispersant additives to help the industrial pasting process.

The thermodynamics and chemical reactions of a commercial electrolyte replacement called Tydrolyte^TM were investigated …

ผลของความหยาบผิวของโลหะผสม Ti-6al-4v ที่ขึ้นรูปด้วยวิธีการพิมพ์สามมิติต่อลักษณะทางสัณฐานวิทยาของท่อนาโนไทเทเนียมไดออกไซด์และความต้านทานการกัดกร่อน, ปาณิสรา พุทธสุวรรณ

Chulalongkorn University Theses and Dissertations (Chula ETD)

นอกจากวัสดุไทเทเนียมจะนิยมนำมาใช้เป็นวัสดุทดแทนกระดูกหรือข้อต่อที่เสียหายเนื่องจากมีสมบัติที่ดีในเรื่องของความแข็งแรงสูง มีความต้านทานการกัดกร่อนสูงและมีความเข้ากันได้ทางชีวภาพแล้ว การสร้างท่อนาโนไทเทเนียมไดออกไซด์ก็ใช้กันอย่างแพร่หลายในการปรับสภาพผิววัสดุเช่นกัน เนื่องจากช่วยส่งเสริมการยึดเกาะของเซลล์และให้การตอบสนองของเซลล์ได้ดีกว่าพื้นผิวโลหะเอง แม้มีการศึกษาหลายชิ้นได้รายงานความสัมพันธ์ระหว่างท่อนาโนไทเทเนียมไดออกไซด์กับอัตราการเชื่อมประสานของเซลล์ แต่อย่างไรก็ตามอัตราการกัดกร่อนของชั้นท่อนาโนไทเทเนียมไดออกไซด์ภายใต้สภาวะการใช้งานนั้น ๆก็มีความจำเป็นที่ต้องศึกษาเช่นกัน ในงานนี้เราได้ศึกษาผลจากการปรับสภาพผิวที่ถูกเตรียมด้วยเงื่อนไขต่าง ๆ ต่อพฤติกรรมการกัดกร่อนของวัสดุ Ti-6Al-4V และลักษณะทางสัณฐานวิทยาของชั้นท่อนาโนไทเทเนียมไดออกไซด์ซึ่งการศึกษาจะแบ่งเป็น 2 กลุ่มคือกลุ่มที่ทำการปรับสภาพผิวด้วยการขัดและกลุ่มที่ทำการปรับสภาพผิวด้วยการขัดต่อด้วยการแอโนไดซ์ โดยจะทำการวัดความหยาบพื้นผิวที่เตรียมได้ก่อนการแอโนไดซ์โดยเครื่องวัดความหยาบผิวและศึกษาลักษณะพื้นผิวหลังแอโนไดซ์ด้วยกล้องจุลทรรศน์อิเล็กตรอนแบบส่องกราดและศึกษาพฤติกรรมการกัดกร่อนในสารละลายฟอตเฟสบัฟเฟอร์ซาลีนโดยเทคนิคโพเท็นชิโอไดนามิกโพลาไรเซชัน ผลการวิจัยชี้ให้เห็นว่าก่อนการแอโนไดซ์ความหยาบผิวที่เตรียมได้ไม่มีความสัมพันธ์กับอัตราการกัดกร่อนโดยตรง แต่อย่างไรก็ตามหลังจากแอโนไดซ์พบว่าความหยาบผิวตั้งต้นจากการเตรียมผิวก่อนแอโนไดซ์มีผลต่อลักษณะการเกิดท่อนาโนไทเทเนียมไดออกไซด์ รวมถึงอัตราการกัดกร่อนมีความสัมพันธ์กับขนาดเส้นผ่านศูนย์กลาง ค่าส่วนเบี่ยงเบนมาตรฐานของขนาดเส้นผ่านศูนย์กลางท่อและลักษณะการเรียงตัวของท่อที่เกิดขึ้น

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

Dissertations

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

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

Cooling Under Applied Stress Rejuvenates Amorphous Alloys And Enhances Their Ductility, Nikolai Priezjev

Mechanical and Materials Engineering Faculty Publications

The effect of tensile stress applied during cooling of binary glasses on the potential energy states and mechanical properties is investigated using molecular dynamics simulations. We study the three-dimensional binary mixture that was first annealed near the glass transition temperature and then rapidly cooled under tension into the glass phase. It is found that at larger values of applied stress, the liquid glass former freezes under higher strain and its potential energy is enhanced. For a fixed cooling rate, the maximum tensile stress that can be applied during cooling is reduced upon increasing initial temperature above the glass transition point. …