Materials Science and Engineering Commons^™

Computational And Experimental Study Of Structure-Property Relationships In Nial Precipitate-Strengthened Ferritic Superalloys, Shenyan Huang

Doctoral Dissertations

Ferritic superalloys strengthened by coherent ordered NiAl B2-type precipitates are promising candidates for ultra-supercritical steam-turbine applications, due to their superior resistance to creep, coarsening, oxidation, and steam corrosion as compared to Cr ferritic steels at high temperatures. Combined computational and experimental tools have been employed to investigate the interrelationships among the composition, microstructure, and mechanical behavior, and provide insight into deformation micromechanisms at elevated temperatures.

Self and impurity diffusivities in a body-centered-cubic (bcc) iron are calculated using first-principles methods. Calculated self and impurity diffusivities compare favorably with experimental measurements in both ferromagnetic and paramagnetic states of bcc Fe. The calculated …

Effects Of Grain Boundary Character On Dynamic Recrystallization Using A Modified Monte Carlo Method, Michael B. Morse

Boise State University Theses and Dissertations

Dynamic recrystallization (DRX) is the recrystallization that occurs during high temperature deformation of metals and alloys. While DRX has been observed experimentally, the parameters that affect the microstructure are still being explored. For example, the effects of temperature, strain rate, and initial grain size have already been studied, yet the effect of initial special boundary fraction is still unknown. Special boundaries are high-angle, low-energy grain boundaries. It is believed that higher initial fractions of special boundaries will lead to a delay in the onset of recrystallization and a higher peak stress.

Experimentation has shown that triple junctions are preferred nucleation …

Modeling Of A Novel Solar Down Beam Test Facility Utilizing Newtonian Optics, Ryan J. Hoffmann

UNLV Theses, Dissertations, Professional Papers, and Capstones

As advances in concentrated solar energy progress there will inevitably be an increase in the demand of resources for testing new conceptions. Currently, there are limited facilities available for taking concentrated solar energy concepts from the laboratory bench scale to the engineering test scale. A proposed solution is a scientific and developmental facility that provides highly concentrated solar energy at ground level. The design presented is a solar down beam test facility utilizing a Newtonian optics approach with a flat rectangular down beam mirror to reflect and concentrate the sun's rays at ground level.

Literature review suggests a hyperbolic reflector …

Distributed Spacing Stochastic Feature Selection And Its Application To Textile Classification, Jeffrey D. Clark

Theses and Dissertations

Many situations require the need to quickly and accurately locate dismounted individuals in a variety of environments. In conjunction with other dismount detection techniques, being able to detect and classify clothing (textiles) provides a more comprehensive and complete dismount characterization capability. Because textile classification depends on distinguishing between different material types, hyperspectral data, which consists of several hundred spectral channels sampled from a continuous electromagnetic spectrum, is used as a data source. However, a hyperspectral image generates vast amounts of information and can be computationally intractable to analyze. A primary means to reduce the computational complexity is to use feature …

On Developing Novel Energy-Relates Nanostructured Materials By Atomic Layer Deposition, Xiangbo Meng

Electronic Thesis and Dissertation Repository

ABSTRACT

This thesis presents the fabrication of a series of novel nanostructured materials using atomic layer deposition (ALD). In contrast to traditional methods including chemical vapor deposition (CVD), physical vapor deposition (PVD), and solution-based processes, ALD benefits the synthesis processes of nanostructures with many unrivalled advantages such as atomic-scale control, low temperature, excellent uniformity and conformality. Depending on the employed precursors, substrates, and temperatures, the ALD processes exhibited different characteristics. In particular, ALD has capabilities in fine-tuning compositions and structural phases. In return, the synthesis and the resultant nanostructured materials show many novelties.

This thesis covers ALD processes of four …

Study Of Mechanical Behaviors And Structures Of Bulk Metallic Glasses With High-Energy Synchrotron X-Ray Diffraction, Feng Jiang

Doctoral Dissertations

This dissertation addresses two critical issues in the mechanical behaviors and structures of bulk-metallic glasses (BMGs): (1) the effect of composition, fabrication method, and pretreatment of plastic deformation on mechanical properties and structures of BMGs; (2) the mechanical response and structural evolution of BMGs in the elastic and plastic region.

(Cu₅₀Zr₅₀)₉₄Al₆ and (Cu₅₀Zr₅₀)₉₂Al₈ amorphous alloys were used to study the effect of composition on mechanical properties and structures of BMGs. The (Cu₅₀Zr₅₀)₉₄Al₆ alloy exhibits lower yield stress and Young’s …

Discovery And Development Of Rare Earth Activated Binary Metal Halide Scintillators For Next Generation Radiation Detectors, Kan Yang

Doctoral Dissertations

This work focuses on discovery and development of novel binary halide scintillation materials for radiation detection applications. A complete laboratory for raw materials handling, ampoule preparation, material rapid synthesis screening, single crystal growth, sample cutting, polishing and packaging of hygroscopic halide scintillation materials has been established. Ce³⁺ and Eu²⁺ activated scintillators in three binary systems: Alkali Halide – Rare Earth Halide (AX–REX₃), Alkali Halide – Alkaline Earth Halide (AX–AEX₂) and Alkalin Earth Halide – Rare Earth Halide (AEX₂–REX₃) were systematically studied. Candidates for new scintillation materials in the three systems …

Acoustic Emission And X-Ray Diffraction Techniques For The In Situ Study Of Electrochemical Energy Storage Materials, Kevin James Rhodes

Doctoral Dissertations

Current demands on lithium ion battery (LIB) technology include high capacity retention over a life time of many charge and discharge cycles. Maximizing battery longevity is still a major challenge partly due to electrode degradation as a function of repeated cycling. The intercalation of lithium ions into an active material causes the development of stress and strain in active electrode materials which can result in fracture and shifting that can in turn lead to capacity fade and eventual cell failure. The processes leading to active material degradation in cycling LIBs has been studied using a combination of acoustic emission (AE) …

Design, Fabrication, And Characterization Of A Thin-Film Nickel-Titanium Shape Memory Alloy Diaphragm For Use In Micro-Electro-Mechanical Systems, Brian Joel Alvarez

Master's Theses

Previous work done at Cal Poly has shown that thin-film nickel-titanium (NiTi) can be easily sputtered onto silicon wafers and annealed to create a crystallized shape memory alloy (SMA) film. Initial work on creating devices yielded cantilevers that were highly warped due to thin-film stress created during the sputtering process. The objective of this work was to create a thin-film NiTi SMA device that could be better characterized. A membrane was selected due to the simplicity of fabrication and testing which would also oppose the thin-film stress due to the increase in attachment points to the substrate.

Silicon wafers were …

Flexi-Focus Lens: Pdms Variable Focal Length Lens, Patrick Angulo, Alex Doyle, Dylan Mcdaniel, Michael Olivarez

Industrial and Manufacturing Engineering

The design of a variable focal length, or flexi-focus, polydimethylsiloxane (PDMS) lens incorporating a light emitting diode (LED) source is intended for future use on board commercial aircraft. Specifically, the design is intended for the Boeing 787 Dreamliner aircraft, serving as a personal reading light for the passengers seated in the cabin. Most current reading lights on board aircraft are rigid, incandescent, and have very limited freedom in terms of adjusting the emitted light. Incandescent lamps are also inefficient with respect to energy consumption and light output as well as a high heat output. In an economy of increasing demand …

Understanding The Effects Of Temperature Extremes On The Tensile And Short Beam Shear Strength Of Epoxy-Based, Glass-Fiber Reinforced Composites, Jonathan Blake Patterson

Materials Engineering

Aptera (Oceanside, CA) has developed two epoxy-based, silica fiber-reinforced composites to be used on their three-wheeled all-electric vehicle called the 2e. Aptera’s composites were studied at temperature extremes using a dynamic mechanical analysis (DMA) system and by tensile and short beam shear (SBS) testing using an Instron testing system. These tests were conducted to simulate the loading of the composite in the 2e vehicle. Tensile and short beam shear samples were machined to 150 mm x 25 mm x 2 mm and 40 mm x 13 mm x 6 mm, respectively. DMA samples were machined to 30 mm x 5 …

Artificial Muscle Project: Process Development Of Polydimethyl Siloxane Thin Films For Use In Dielectric Electroactive Polymer Artificial Muscle Actuators, Vincent J. Gayotin, Richard W. Morrison, Paul A. Preisser

Materials Engineering

An artificial muscle design was created founded on the principles of a dielectric electroactive polymer (DEAP), which is fundamentally similar to a capacitor. A polydimethyl siloxane (PDMS)-based elastomer, Sylgard 184 from Dow Corning, was chosen for the design and spun coat onto polystyrene (PS) Petri dishes at varying speeds to create a thin film, using speeds of 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, and 6000 rpm. The film thicknesses were measured optically through use of a microscope with coupled computer imaging software to generate a characteristic curve of film thickness to spin speed, achieving a minimum film thickness …

The Effects Of Cure Schedule On Properties Of Glass-Fiber Reinforced Epoxy Matrix Composites, Trevor J. Lee

Materials Engineering

Two different two-component resin systems were cured, via Differential Scanning Calorimetry, for the times recommended by their respective manufacturers. The resin cure schedules were designed to simulate typical and attainable processing conditions; they were cured at 120°F, 140°F, and 160°F, and in-mold post-cured at 200°F, 230°F, and 260°F. The resulting scans were then compared to a baseline cure for each resin system, consisting of two heating-cooling cycles at a constant rate of temperature change. These baseline cures were then used to determine the percent cure of each sample and the shift in glass transition temperature between the baseline cure and …

Investigating The Mechanical Properties Of Compression Molded Carbon Fiber Reinforced Sheet Molding Compound, Bradley A. Jones

Materials Engineering

Callaway Golf receives a proprietary blend of prepreg material from Quantum Composites. Callaway processes the prepreg in-house and supplied 254mm x 254mm x 1.3mm panels of carbon fiber sheet molding compound (CFSMC) for characterizing. Tensile strength was analyzed by conducting tensile tests per ASTM D3039. Tensile coupons were cut to 254mm long by 25.4mm wide. Tabs were constructed from 1.6mm thick GFRP printed circuit board material. A commercial grade two part epoxy was used to bond the tabs to the CFSMC. Tensile results were inconclusive due to consistent fractures occurring outside the gauge lengths of the specimens.

Flexure strength was …

Oxidation Kinetics Of Silver Thin Films For Antimicrobial Applications In The Health Care Industry, Sean D. Morham

Materials Engineering

To determine if varying city water qualities from around the United States can support a developing “oxidation corrosion of silver thin films” method of creating aqueous ionic silver solutions for the anti-microbial treatment of healthcare linens, a test was devised holding all variables constant with the exception of water quality parameters. This corrosion style test was done in order to assess a pass/fail criteria of 25 ppb ionic silver concentration in the aqueous solutions which resulted from the corrosion of silver thin film coated substrates. Above 25 ppb being a pass, below 25 ppb being a fail. While varying the …

The Effects Of Heat Treatment On Area Percent Porosity And Corrosion Behavior Of High-Nickel Thermal Spray Coatings, Travis Crowe, Alec Guraydin

Materials Engineering

Samples of two Thermal Spray Coating (TSC) alloys on a low carbon steel substrate were obtained: alloy C276 and Nicko-Shield 200. Specimens of each alloy were subjected to heat treatments at temperatures at 1100° for 60 minutes and 1200° for 10 minutes, with some specimens left in the as-sprayed condition. Three replicates were prepared for each condition. Thin 1” strips were cut using a diamond wafering blade for porosity measurements and 2” x 1” specimens were cut for corrosion testing using a SiC abrasive saw. The porosity specimens were mounted in acrylic resin, polished, and examined using SEM. From these …

Characterization Of The Oxidation Kinetics Of Fecral Ferritic Stainless Steels At 900°C For Catalytic Converter Applications, Stacy Stamm

Materials Engineering

This study characterized the oxidation kinetics of two types of ferritic stainless steel foils used as substrates for catalytic converters. Catalytic converters rely on an alumina layer on the surface of the foils, which allows the catalyst to attach to the substrate. Because the alumina layer is so important, this study characterized the weight gain, thickness, and composition of the alumina as it grew at 900°C for up to 400 hours. The two foils characterized were an MK foil, used for gasoline engines, and an EMS foil, used for diesel engines. The MK foil showed a percent weight gain of …

Memristive Properties Of Thin Film Cuprous Oxide, Brett C. Castle

Theses and Dissertations

Memristive properties of thin film copper oxides with different grain sizes were characterized using tunneling atomic force microscopy (TUNA) and optical reflection measurements. The thin films containing copper ions of different chemical states were prepared by thermal oxidation of metallic copper thin films, deposited via magnetron sputtering onto silicon wafer substrates at an elevated temperature for various lengths of time. The TUNA measurements showed a memristive hysteresis in the I-V curves under an applied bias profile with an initial bias of -3.5V, a ramp up to 3.5V, and subsequent return to -3.5V. Histogram analysis of the barrier height distribution for …