Other Materials Science and Engineering Commons^™

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 …

Surface Corrosion Response Of Al Alloys A383 And Aural 2 With Ce Additions In Aqueous Nacl And Salt-Fog Environments, Michael James Thompson

Masters Theses

Copper is commonly used in aluminum alloys to increase its strength by solid solution and precipitation strengthening, however, the corrosion resistance is inversely related to the amount of copper in the alloy. Over 70 percent of material used to produce aluminum alloys in the US come from recycled (secondary) alloys, many of which have a copper content of more than one percent by weight. Alloys with tightly controlled tolerances, where copper is seen as an impurity, are unable to utilize many of the recycling feedstock without adding newly processed (primary) aluminum to dilute impurities to within specifications. Primary aluminum is …

Cell Contraction, De-Adhesion, And Shape Effects Investigated By Cohesive Model With Finite Element Simulations, Margarita Vladimirovna Semenova Petrova

Masters Theses

Cell adhesion is a complex mechanism, and different factors control this process including surface morphology, chemical, and mechanical interactions. These aspects are usually combined to achieve robust adhesion between surfaces. The later stage in bio-adhesion process involves the formation of molecular bonds through diffusion or interpenetration of molecules at the interface. In order to create contact, cells sense their physical environment by applying mechanical forces or responding to them via traction force. The force is transmitted through cell skeleton. However, how this force is transmitted is mostly unknown. Also, there are still many open questions about fracture mechanism in bio-adhesive …

Integrated Solar Technologies With Outdoor Pedestrian Bridge Superstructure Decking, Richard K. Racz

Masters Theses

Solar technology has been a major topic in sustainable design for many years. In the last five years, however, the solar technology industry has seen a rapid growth in installations and technological advances in cell design. Combined with a rapidly declining overall system cost, the idea of introducing solar technology into a wider range of applications is becoming a focus for engineers and scientists around the world. So many variables which alter solar energy production, such as the sun and surrounding environment, determine whether a solar design is beneficial. This thesis presents a bridge deck surface integrated with solar cells …

Kinetic And Thermodynamic Modeling Of Long Term Phase Stability In Alloy 800h Subjected To Lwr Core Conditions, Wayne Ethan Pratt

Masters Theses

An in depth literature review of Incoloy Alloy 800H was conducted and presented to summarize the current understanding of microstructural evolution under irradiation and secondary phase precipitate stability. Due to a lack of radiation induced segregation (RIS) data for Alloy 800H, Isopleth sections varying Cr, Ni, Ti, and Si were generated from a computational thermodynamics approach using ThermoCalc and analyzed to compensate for knowledge related to radiation induced precipitates (RIP’s). These isopleths were analyzed for a composition range based off previous knowledge of RIS tendencies in austenitic stainless steels. Analysis of four major binary phase diagrams and complex phase diagrams …

Mixing Metals For Magic Materials: Analysis Of Binary Eutectic Alloys For Metamaterial Applications, Ethan Elder Fox

Masters Theses

Uses of metamaterials, also known as negative index materials (NIMs), are wide ranging and include lenses that have a resolution beyond the diffraction limit, incredibly small antenna, and cloaking devices for optical, infrared, and microwave wavelengths.

The unique properties of metamaterials are not found in any naturally occurring material. By having simultaneously negative values for ε [electrical permittivity] and μ [magnetic permeability], a metamaterial can have a negative index of refraction over a certain frequency band. The unique properties of negative index materials emerge chiefly from their highly ordered structure.

Binary eutectic alloys have the potential to be used as …

A High Pressure Cell For Spark Plasma Sintering, Justin Robert Carmichael

Masters Theses

Many nanostructured materials have been shown to have performance gains strongly dependent on the grain size in the material. Nanostructured thermoelectric materials for instance have found great performance increases through reduction of the grain sizes, due mostly to the scattering of phonons while retaining a good electrical conductivity. Other such examples abound where the grain size plays an important role in the performance of the material, including magnetic materials, proton fuel cell membranes, or simply improving the mechanical properties of a system through the Hall-Petch relationship.

A considerable amount of effort has been applied into reducing the grain size of …

Transparent Superhydrophobic Polycarbonate Coating, Gimgun Loi

Masters Theses

Superhydrophobicity is a property commonly seen in nature such as the lotus leaf. This unique property allows the surface of a material to exhibit water repellency and self-cleaning abilities. This effect is contributed by two important components: the rough surface topography and low surface free energy. Since the discovery of this unique property, several methods and various materials have been used to produce this effect and used in a wide variety of applications. However, the use of this type of effect on transparent surfaces is still being researched. I have proposed a method to develop a transparent superhydrophobic coating using …

Fabrication And Characterization Of Cu-Co Alloy Nanoparticles Via Pulsed Laser Dewetting, Shaofang Fu

Masters Theses

The fabrication and characterization of Cu[Copper]-Co[Cobalt] alloy nanoparticles are addressed in this thesis. First, Cu-Co alloy thin films with total thickness of ~10 nm [nanometer] were deposited on both 100 nm SiO₂ [silicon dioxide] coated silicon wafers and quartz substrates using RF magnetron sputtering system. Three structures were studied in this work: (1) ~10 nm co-sputtered Cu-Co alloy thin film. (2) ~5 nm (at center) Cu thin film covered by ~5 nm (at center) Co thin film. (3) ~5 nm (at center) Co thin film covered by ~5 nm (at center) Cu thin film. In addition, ~10 nm pure …

Low Temperature Thermally Activated Cvd Of Silicon On Molybdenum For Oxidation Protection, Brian C. Jolly

Masters Theses

The United States Global Threat Reeducation Initiative (GTRI) is promoting the production of molybdenum-99 without the use of uranium-235. One possible route, called neutron capture technology, is through the activation of molybdenum-98 via irradiation. GE-Hitachi has identified a location within their boiling water reactors for molybdenum-98 irradiation, but the elevated temperatures present risk oxidizing the molybdenum. This work explored using a silicon coating to protect the molybdenum from oxidation. With silane gas as the precursor, chemical vapor deposition was employed to produce the silicon coating. Characterization was performed and showed a discrete silicon layer was deposited with little to no …

Structural Analysis Of The Tablerock Thrust Sheet, Grandfather Mountain Window, Northwestern North Carolina: Emplacement Kinematics Of A Large Horse In A Major Thrust System, Ann Elizabeth Walker

Masters Theses

The Tablerock thrust sheet is exposed along the southwestern margin of Grandfather Mountain window in northwestern North Carolina, where it separates basement and cover rocks inside the window from basement thrust sheets of the overriding Blue Ridge-Piedmont megathrust sheet. It is a complex of footwall-derived horses of rifted-margin metasedimentary rocks, including Neoproterozoic to Early Cambrian Chilhowee Group quartzite and phyllite, and Shady Dolomite. Penetrative deformation throughout the Tablerock thrust sheet is defined by an extensively transposed foliation, and strong colinearity between well developed transport lineations and SE/NW-trending tight, isoclinal, and sheath folds. Centimeter- to meter-scale sheath folds are common throughout …

Spectroscopic, Thermal, And Physical Analysis Of The Raw Materials In Europium Doped Cesium Strontium Iodide Scintillator, Bonnie Dell Blalock

Masters Theses

Scintillators are widely used in homeland security applications that utilize gamma-ray spectroscopy. An ideal scintillator for this purpose should possess a high effective atomic number, high light yield, and good energy resolution. The scintillator CsSrI₃: Eu [cesium strontium iodide: europium], recently developed at the Scintillation Materials Research Center, has excellent properties. Recent efforts have been made to evaluate the basic thermal properties and IR spectra of the compound’s raw materials as part of a project to improve the quality of grown crystals. Fourier transform infrared spectroscopy of high purity anhydrous CsI [cesium iodide], SrI₂ [strontium iodide], and …

Evaluation Of The Transient Thermal Performance Of A Graphite Foam/Phase Change Material Composite, Michael Paul Trammell

Masters Theses

The thermal transient response of graphite foam infiltrated with paraffin wax as a thermal protection composite was investigated. Graphite foam is a rigid open-celled porous carbon material that exhibits high thermal conductivity along the ligaments. To increase the ability of graphite foam to store heat energy, it was infiltrated with a phase change material, paraffin wax. Filling the foam with a phase change material (PCM) creates a composite that transfers heat through an interconnected network of ligaments to a large surface area of PCM for absorption. Foams were made at various pressures to understand the effect of porosity, which also …

Lignin Yield Maximization Of Lignocellulosic Biomass By Taguchi Robust Product Design Using Organosolv Fractionation, Anton Friedrich Astner

Masters Theses

Lignin, a byproduct of the organosolv pretreatment process using lignocellulosic biomass from switchgrass (Panicum virgatum) and tulip poplar (Liriodendron tulipifera) is currently being explored for its potential use in the production of value-added chemicals and biobased polymers. Pretreatment is one of the most expensive processing steps in cellulosic biomass conversion. Optimization of the process is one of the major goals of the biomass-toethanol conversion process. Taguchi Robust Product Design (TRPD) provides an effective engineering experimental design method for optimizing a system and designing products that are robust to process variations. Given the results of several preliminary …

Pretreatment And Pyrolysis Of Rayon-Based Precursor For Carbon Fibers, Kokouvi Akato

Masters Theses

In this work, two rayon fibers were investigated as carbon fiber precursors. A detailed consideration has been applied to a domestically produced cellulose fiber to carbon fiber (CF) transition. This transition of precursor to carbon fiber can be subdivided into two stages: pyrolysis (thermal decomposition) of cellulose in air and high temperature treatment in an inert atmosphere. The specific objectives were to investigate the stabilization stage of the produced rayon with respect to changes taking place during thermal decomposition, and to evaluate the effects on the properties of the carbonized fiber. Changes taking place during the conversion process of the …

Compatibility Evaluation Of Glass/Epoxy Insulation For Use In Iter’S Central Solenoid Superconducting Electromagnets, Carolyn Grace Kidwell

Masters Theses

A variety of glass fiber types are being considered for use as insulation material in the central solenoid superconducting electromagnets for the International Thermonuclear Experimental Reactor (ITER). Before these materials can be used, a compatibility of these glass products with an epoxy matrix has to be characterized. In this study, three candidate glass types (1581, 7781, and 38050) were considered and their compatibility with a DGEBF epoxy matrix was determined via three-point flexure tests at room temperature (295K) and liquid nitrogen temperature (77K) and constant load flexure creep tests at room temperature. The material variables among these glass products were …

Effect Of Moisture Absorption On The Sinter Quality Of Central Solenoid (Cs) Coil Pack, Zeshaan Sher Mohammed

Masters Theses

Fusion energy has been said to be the solution to all the world’s energy problems. The International Thermonuclear Experimental Reactor (ITER) is the flagship project to demonstrate the feasibility of fusion energy. The Central Solenoid (CS), an important component of the reactor, is needed to induce plasma current, initiate, ramp-up, ramp-down, and sustain plasma in a very controlled manner. In order to achieve this, the CS coil packs must be manufactured under controlled conditions. The CS conductor is an advanced cable-in-conduit Nb3Sn superconductor. The CS cable will be made in long continuous sections but with thousands of meter of cable …

Elastic And Magnetic Properties Of Tb6fe(Sb,Bi)2 Using Resonant Ultrasound Spectroscopy., David Michael Mccarthy

Masters Theses

Tb6FeSb2 and Tb6FeBi2 are novel rare earth compounds with little prior research. These compounds show high and variable curie temperatures for rare-earth compounds. This has lead to a literature review which includes the discussion of: elasticity, resonance, and magnetism. This review is used to discuss the theory and methodology which can relate these various properties to each other. Furthermore, synthesis, x-ray analysis, and RUS sample preparation of Tb6FeSb2 and Tb6FeBi2 were completed.

Resonant Ultrasound Spectroscopy (RUS) elastic studies were taken for Tb6FeSb2 and Tb6FeBi2 as a function temperature from 5-300K, in various magnetic fields ranging from 0-9T. Tb6FeSb2’s and Tb6FeBi2’s …

Development Of Knowledge Base Of Concrete Bridge Maintenance System, Bahre Karam

Masters Theses

Bridges are the key elements of any transportation system of a country. Bridges are expensive structures and therefore, it's essential to maintain and repair them on regular basis. Almost one third of the bridges in United States are reported to be in some what deteriorated conditions. This Research presents the development of knowledge base for decision support system for concrete bridges.

During this research various concrete bridge problems are investigated including COlTosion, delamination, cracks, spalling and scour etc. The inspection tools and techniques are addressed in order to identify these problems both for above and below water surface. The various …