Materials Science and Engineering Commons^™

Crystalline Phase Change In Steel Alloys Due To High Speed Impact, Muna Slewa

UNLV Theses, Dissertations, Professional Papers, and Capstones

The effect of hypervelocity projectile impact on the crystalline grain structure near the target impact location of A36 steel has been studied. A36 steel is a mostly single phase body centered cubic material (BCC). Impact velocities ranged from 3.54 to 6.70 km/sec. Target materials were studied before and after impact to determine if these impact conditions result in a phase change of the A36. Scanning electron microscopy, electron back-scatter diffraction, and x-ray diffraction methods were used to investigate deformation, lattice defects, twinning, and phase transformation. A limited number of impacted targets made from 304L and HY100 steels were also examined. …

Synthesis And Characterization Of Oleophobic Fluorinated Polyester Films, Tugba Demir

All Dissertations

The study presented in this dissertation is dedicated to the synthesis and characterization of oleophobic fluorinated polyester films. Specifically, the blending of oleophilic polyethylene terephthalate (PET) with low surface energy materials such as fluorinated polyesters has been used in order to fabricate oleophobic PET films. First, fluorinated polyesters (P(PF-oate-R)) possessing different end-groups (-COOH, -OH and -CF3) are synthesized via polycondensation reaction of isophthaloyl chloride with perfluoro ether alcohols. Then, they are solvent-blended with PET at various concentrations to obtain oleophobic polyester films of different compositions. In addition, the films are annealed to investigate the effect of annealing on surface properties …

Microstructure Alone Induced Wetting Transition From Hydrophilic To Hydrophobic On Silicon And Graphene, Henry L. Ems

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

In the present work, transition from hydrophilic to hydrophobic wetting states for an intrinsically hydrophilic surface (contact angle less than 45 degrees) using only surface microstructuring is presented. The surface microstructures are re-entrant microcavities (inverted trapezoidal microstructures) which promote air entrapment below the water droplet causing a Cassie wetting state as opposed to a Wenzel state where the surface is completely wetted. The microstructures were fabricated on a Silicon-On-Insulator (SOI) wafer through steps of deposition, photolithography, etching, and bonding. Contact angle measurements demonstrated the ability of the microfabricated surfaces to sustain large contact angles above 100°, in comparison to a …

Experimental Investigation And Thermal Modeling On Electro Discharge Drilling Of Pcd, Farnaz Nourbakhsh

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

This study presents an experimental investigation and finite element simulation of Electro Discharge Drilling (ED-Drilling) of Polycrystalline Diamond (PCD). PCD has many outstanding properties including uniformly high hardness, high wear resistance and strong corrosion which are the main causes of widely using PCD. While PCD has many advantages and an important role in industrial applications, its high level of hardness and wear resistance cause this material to be difficult to form and machine by using traditional machining methods. EDM as a nontraditional machining process is an effective method among other non-traditional methods for PCDs due to its low cost and …

Effect Of Nano-Oxide Particle Size On Radiation Resistance Of Ironechromium Alloys, Weizong Xu, Lulu Li, James A. Valdez, Mostafa Saber, Yuntian Zhu, Carl C. Koch, Ronald O. Scattergood

Mechanical and Materials Engineering Faculty Publications and Presentations

Radiation resistance of Fe-14Cr alloys under 200 keV He irradiation at 500 ­*C was systematically investigated with varying sizes of nano oxide Zr, Hf and Cr particles. It is found that these nano oxide particles acted as effective sites for He bubble formation. By statistically analyzing 700-1500 He bubbles at the depth of about 150-700 nm from a series of HRTEM images for each sample, we established the variation of average He bubble size, He bubble density, and swelling percentage along the depth, and found them to be consistent with the He concentration profile calculated from the SIRM program. Oxide …

Imaging Thermal Conductivity With Nanoscale Resolution Using A Scanning Spin Probe, Abdelghani Laraoui, Halley Aycock-Rizzo, Yang Gao, Xi Lu, Elisa Riedo, Carlos A. Meriles

Advanced Science Research Center

The ability to probe nanoscale heat flow in a material is often limited by lack of spatial resolution. Here, we use a diamond-nanocrystal-hosted nitrogen-vacancy centre attached to the apex of a silicon thermal tip as a local temperature sensor. We apply an electrical current to heat up the tip and rely on the nitrogen vacancy to monitor the thermal changes the tip experiences as it is brought into contact with surfaces of varying thermal conductivity. By combining atomic force and confocal microscopy, we image phantom microstructures with nanoscale resolution, and attain excellent agreement between the thermal conductivity and topographic maps. …

Volatile Condensible Material Deposition In Leo Simulated Environment, Jinya Pu

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Room Temperature Vulcanized (RTV) silicone and compounds are widely used in outer-space for bonding or potting spacecraft components. In geosynchronous equatorial orbit (GEO), the silicone may outgas species which can condense on optically sensitive surfaces and degrade their performance, therefore shortening the lifetime of spacecraft. In low-earth-orbit (LEO), the silicone rubber is subject to an energetic and corrosive environment. Atomic oxygen (AO) and ultraviolet radiation can cause abrasion and degradation of the silicone rubber, cause changes in existing condensed VCM films and affect the properties of VCM films condensing in this atmosphere. Experiments were performed to simulate GEO conditions. In …

In Vacuo Fabrication And Electronic Structure Characterization Of Atomic Layer Deposition Thin Films, Michael Schaefer

USF Tampa Graduate Theses and Dissertations

Improvement of novel electronic devices is possible by tailor-designing the electronic structure at device interfaces. Common problems observed at interfaces are related to unwanted band alignment caused by the chemical diversity of interface partners, influencing device performance negatively. One way to address this problem is by introducing ultra-thin interfacial dipole layers, steering the band alignment in a desired direction. The requirements are strict in terms of thickness, conformity and low density of defects, making sophisticated deposition techniques necessary. Atomic layer deposition (ALD) with its Ångstrom-precise thickness control can fulfill those requirements.

The work presented here encompasses the implementation of an …

Investigation Of Low Thermal Conductivity Materials With Potential For Thermoelectric Applications, Kaya Wei

USF Tampa Graduate Theses and Dissertations

Thermoelectric devices make it possible for direct energy conversion between heat and electricity. In order to achieve a high energy conversion efficiency, materials with a high thermoelectric figure of merit (ZT = S²σT/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the thermal conductivity) are in great demand. The standard approach is to optimize charge carrier transport while at the same time scatter the heat transport, a task that is easier said than done. Improving the electrical properties in order to increase ZT is limited since electrons …

Near-Field Microwave Microscopy For Surface And Subsurface Characterization Of Materials, Maria Fernanda Cordoba Erazo

USF Tampa Graduate Theses and Dissertations

This dissertation presents an investigation on the capabilities of Near-Field Microwave Microscopy (NFMM) for the characterization of surface and subsurface materials. Subsurface characterization refers to the detection, differentiation and imaging of dielectric, and metallic features that are coated with an insulating layer. The design, simulation and modeling, and testing of a dielectric resonator (DR)-based NFMM and a coaxial transmission line resonator-based NFMM are discussed in detail in this work. Additionally, materials differentiation and imaging capabilities of each microscope are examined using several bulk samples, liquids, GaAs MMIC circuits, and gold/glass testing patterns.

The 5.7 GHz DR-based NFMM uses a microwave …

Structure And Corrosion Behavior Of Sputter Deposited Cerium Oxide Based Coatings With Various Thickness On Al 2024-T3 Alloy Substrates, Yuanyuan Liu, Jiamu Huang, James B. Claypool, Carlos E. Castano, Matthew J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

Cerium oxide-based coatings from ∼100 to ∼1400 nm in thickness were deposited onto Al 2024-T3 alloy substrates by magnetron sputtering of a 99.99% pure CeO₂ target. The crystallite size of CeO₂ coatings increased from 15 nm to 46 nm as the coating thickness increased from ∼100 nm to ∼1400 nm. The inhomogeneous lattice strain increased from 0.36% to 0.91% for the ∼100 nm to ∼900 nm thick coatings and slightly decreased to 0.89% for the ∼1400 nm thick coating. The highest adhesion strength to Al alloy substrates was for the ∼210 nm thick coating, due to a continuous …

Augmented Finite Element Method For Virtual Testing Of High Temperature Cmcs, Qingda Yang, Jaedal Jung, Bao-Chan Do

Composites at Lake Louise (CALL 2015)

Ceramic matrix composites (CMCs) have been increasingly used in high heat flux applications due to their ultra-high temperature resisting capabilities. However, CMCs are prone to processing-induced or in-serve cracking due to the large thermal stresses. Thermally-induced cracking are dangerous because they provide pathways for further damaging processes such as oxidation and vapor-assisted corrosion, which may lead to catastrophic failure [1]. High-fidelity thermal-mechanical analyses to CMCs with consideration of arbitrary cracking are very challenging because the heterogeneous nature makes it impossible to know the cracking locations a priori. Yet correct and efficient treatment of crack coalescence and bifurcation is critical …

Novel Anti-Decay Self-Setting Paste Of Hydroxyapatite/Collagen Nanocomposite Utilizing Gptms, Masanori Kikuchi, Taira Sato, Mamoru Aizawa, Yuki Shirosaki

Composites at Lake Louise (CALL 2015)

Bone is a typical inorganic/ortganic nanocomposite mainly composed of hydroxyapatite (HAp) nanocrystals and collagen molecules. The composition and nanostructure is closely related to bone’s biomechanical and biochemical properties. One of the most important things for bone is a bone remodeling process that maintains mechanical strength of bone to allow walking and running as well as homeostasis of calcium in our body. In fact, sintered HAp composed of HAp crystals approximately 1 µm in particle size is considered as non-bioresorbable; however HAp nanocrystals easily resorbed by osteoclasts. A hydroxyapatite/collagen bone-like nanocomposite (HAp/Col) was successfully synthesized by the authors via self-organizing process. …

Physical Aging And Glass Transition Of Single Component Nanocomposites, Hilmar Koerner

Composites at Lake Louise (CALL 2015)

Matrix free assemblies of polymer-grafted, “hairy” nanoparticles (HNP) exhibit novel morphology, dielectric and mechanical properties, as well as providing means to overcome dispersion challenges ubiquitous to conventional polymer-inorganic blended nanocomposites. Physical aging of the amorphous polymer glass between the close-packed nanoparticles (NPs) will dominate long-term stability. However, the energetics of cooperative relaxation of tethered chains confined within the interstitial spaces in single component nanocomposites is unknown. Herein, we compare glass transition temperature (Tg) and physical aging behavior of matrix free assemblies of HNPs (aHNPs) to conventional NP-polymer blends, across different nano-silica loadings (0-50 v/v%) and brush architecture of grafted polystyrene …

Printed And Structurally Integrated Electronics For Air Force Applications, Daniel Berrigan, Benjamin Leever, Michael Durstock

Composites at Lake Louise (CALL 2015)

Both printed and flexible electronic systems promise to integrate functional devices into new form factors (e.g., structures or clothing) and environments. Of particular interest are the mechanically harsh environmental conditions to which military systems are sometimes exposed, which can be quite severe (i.e., upward of 100,000 G peak acceleration within 0.1 ms), and commercial off-the-shelf components are not designed to maintain functionality under such rugged conditions. The overarching aim of this project is to leverage the unique ability of additive manufacturing to digitally control materials properties in three dimensions to create multifunctional systems whose structure is ruggedized for mechanically these …

Ice Formation In Iron Containing Hydrogel Films, Hyun-Joong Chung

Composites at Lake Louise (CALL 2015)

The states of water in polymers, including ice formation, is of increasing interest for a broad range of science and engineering, including the application and the longevity of water-bourne polymeric coatings, cryogenic preservation of cells and organs, ice mediated porous structure formation, freeze-drying process in food preservation, low temperature operation of batteries and supercapacitors, and the tailing pond sedimentation in oil sands production. The freezing point of water is heavily influenced by the polymer-water interaction and the concentration of ionic species in the water and in the polymer backbones. Various species of salt ions are abundant in the operating conditions …

Simultaneously Strong And Tough Continuous Nanofibers For Next Generation Structural Supernanocomposites, Yuris Dzenis

Composites at Lake Louise (CALL 2015)

Modern advanced composites and fibers are strong but brittle. Optimization of damage progression in composites has led only to moderate toughening. The advent of novel nanomaterials such as CNT and graphene has raised hopes for the development of strong and tough structural materials. However, problems with dispersion, alignment, achieving high volume fraction of discontinuous nanoreinforcement, and interfacial stress transfer proved to be more difficult than was initially thought. Recently, a different class of nanomaterials, i.e. continuous nanofibers, has been shown to possess unusual mechanical properties. This presentation will review recent breakthroughs on ultra-high-performance continuous nanofibers and their composites. Controlled nanofiber …

Biopolymer Composites From High-Cellulose Pulps And/Or Nanocellulose, Fabiola Vilaseca

Composites at Lake Louise (CALL 2015)

Increasingly our society seeks an economy based on renewable resources (bio-based economy) with the goal of providing materials of high value and from renewable resources. One popular renewable resource is cellulose, or forest products in general. In this study, cellulose derivatives will be combined together with bio-plastics to produce granules of thermoplastic nano-biocomposites by melt processing. The intention is to get bio-based materials with highly advanced properties that can be shaped into complex geometries using widely used industrial melt-processes such as extrusion or injection molding.

The challenges in this study deal with production technologies for the realization of nanocomposites for …

Chemical Heterogeneity In Electroceramics: The Good, The Bad, And The Difficult To Characterize, Michaela Kuzara, Narit Triamnak, Harlan Brown-Shaklee, David Cann, Geoff Brennecka

Composites at Lake Louise (CALL 2015)

As characterization techniques continue to advance, the materials community is reminded again and again that our samples are not as perfect as we generally describe them to be. This presentation will focus on Bi(Zn_0.5Ti_0.5)O₃–BaTiO₃-based ceramics in which subtle mesoscale cation gradients have been identified as a key factor in the phenomenal temperature- and field-stable permittivity of these unusual dielectrics as well as their remarkably high resistivity values and associated activation energies.[1,2] Earlier work has shown that the single perovskite phase that results after calcination of mixed oxides and carbonates is formed through …

Iron Oxide Thin Film Photoelectrodes For Water Splitting, Avner Rothschild

Composites at Lake Louise (CALL 2015)

Reliable utilization of solar power on a large scale requires affordable energy storage technology, cheaper than batteries, in order to synchronize the variable power production with the changing demand. Likewise, there is a need for renewable fuels to replace fossil fuels. These challenges can be achieved, potentially, by splitting water into hydrogen and oxygen, H₂O à H₂ + ½O₂, using solar power to drive this endergonic reaction uphill. The hydrogen can be stored and converted to electricity and heat on demand. Alternatively, it may serve as feedstock for the production of liquid fuels for transportation …

Nature’S Tough Composites: A Look Into Biological Fibrous Architectures, Christopher Salinas

Composites at Lake Louise (CALL 2015)

Over a period of hundreds of millions of years, numerous examples of biological organisms have evolved light-weight, strong, and tough composite materials in order to adapt to ecological pressures and thrive in their specific niches. These composite structures consist of fiber-reinforced materials with different architectures including lamellar, cellular and helicoidal motifs. This lamellar motif is a common design utilized by a variety of distantly related organisms from mollusks to plants (e.g., queen conch and bamboo). The strength of the structures are dependent on the orientation of the reinforcing fibers. The fiber-matrix interface increases the toughness of the composite through crack …

Increasing Dispersion, Performance, And Pot-Life In Cellulose Nanocrystal/Waterborne Epoxy Composites, Meisha Shofner

Composites at Lake Louise (CALL 2015)

Recent emphasis on the pilot scale production of cellulosic nanomaterials, cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs), has increased interest in the effective use of these materials as reinforcements for polymer composites. These studies have been motivated in part by the combination of attractive specific mechanical properties of cellulosic nanomaterials as well as their renewable and possibly sustainable manufacturing routes. The objective of this research complements these efforts and is concerned with more fully understanding the materials design space available for CNC reinforced polymer composites, specifically CNC/waterborne epoxy composites. These composites were processed using different protocols and the structure and …

Radiation Resistance Of Vanadium-Graphene Nanolayered Composites, Seung Min Han

Composites at Lake Louise (CALL 2015)

Metal nanolyered composites are regarded as promising nuclear structural material due to not only the high strength, but due to the ability to absorb the crystalline defects that are introduced from irradiation environment. In this work, vanadium-graphene nanolayered composite is explored for radiation resistance using He ion irradiation tests. Metal-graphene nanolayered composite was previously reported to be ultra high strength due to the effectiveness of graphene in constraining the dislocation motion. Our experimental and MD simulations indicate that the crystalline defects that are produced from He ion irradiations can also absorbed at the metal-graphene interfaces that results in significantly reduced …

Probing Micro- And Nano-Scale Elastic Modulus Variation In Organic-Rich Shale—A Naturally Occurring Composite, Corinne Packard, Taylor Wilkinson, Saeed Zargari, Manika Prasard

Composites at Lake Louise (CALL 2015)

Organic-rich shales are heterogeneous, naturally occurring composites that act as source rocks for oil and gas, which can be extracted through the process of hydraulic fracturing. Shales are composed of clays, minerals, and evolving organic matter and developed through long periods of sedimentation and compression. An elastic modulus mapping technique based on spatially continuous dynamic nanoindentation is applied to map microscale variations in a fine-grained, organic-rich shale consisting of inorganic minerals with an inter-

penetrating network of microscale pores filled with organic matter. A sample of Bakken shale from the Williston Basin was chosen for analysis, in which the organic …

Manufacturing And Testing Of Lightweight, Liner-Less All-Composite Tanks For Storage And Transportation Of Cng, Ranji Vaidyanathan

Composites at Lake Louise (CALL 2015)

Compressed natural gas is one viable fuel source to replace gasoline or diesel in cars, trucks and other passenger vehicles. There are 5 types of tanks that can be used for storage and transportation of CNG. Out of these 5 types, 3 types of tanks have some form of composite structure introduced into the tank construction. Additionally, the type V tank is an all-composite construction, which has not been introduced into the NGV market in a significant manner. In this presentation, we will describe the manufacturing and testing of type V all-composite tanks by the team formed between a small …

In Situ Study Of Phase Transformations And Phase Equilibria In The Tantala And Hafnia Binary System, Waltraud Kriven

Composites at Lake Louise (CALL 2015)

Tantala (Ta₂O₅) has useful dielectric, optical, catalytic and chemical properties while hafnia (HfO₂) has found applications as a high temperature structural ceramic. Tantala and hafnia ceramics have yet to be studied in detailed. During this study, the Ta₂O₅-HfO₂ binary system was investigated using high temperature x-ray diffraction from room temperature to 1650˚C in air using synchrotron radiation. The crystal structures of Ta₂O₅, HfO₂ and Hf₆Ta₂O₁₇ were examined with their corresponding phase transformations and 3-D thermal expansions.

Preparation Of Chitosan-Siloxane Porous Hybrids With Hydroxyapatite For Repair Of Skull Defect, Yuki Shirosaki

Composites at Lake Louise (CALL 2015)

A craniotomy is performed for various neurological diseases, injuries, or conditions such as brain tumors, hematomas, aneurysms, and skull fractures. First, the small-sized holes, called “burr holes” were made to insert some surgical tools such as a shunt, a drain, an intracranial pressure monitor, and endoscope, etc. or be the starting point of removing large skull fracture. After surgery, the holes should be closed by the calcium phosphate cements or the titanium plates, because the skull defects are not spontaneously regenerated.

Calcium phosphate cements (CPCs) have attracted great interest as bone substitute material. However, the cements easily flow into the …

Exploration Of The Materials Paradigm With Respect To Bioinspiration, John Nychka

Composites at Lake Louise (CALL 2015)

From the perspective of materials science and engineering the materials paradigm has traditionally been made of four grouped, and interrelated, fundamental aspects of materials: structure, properties, processing/synthesis, and performance. In order to make connections between these aspects we often rely on characterization techniques. When considering the field of bioinspiration, does the materials paradigm adequately cover what nature has to offer? Our way of approaching the issue of bioinspiration has largely been based in applying the materials paradigm, however, is there anything missing in our approach? Can we map nature to the materials paradigm? How can we? What can the paradigms …

Enhancing Grain Boundary Ionic Conductivity In Mixed Ionic Electronic Conductors, Kyle Brinkman, Ye Lin, Shumin Fang, Frank Chen, Dong Su

Composites at Lake Louise (CALL 2015)

The emergent properties arising from the interactions of phases including interfacial contributions and phase evolution at the mesoscale present new opportunities, as well as challenges, for materials performance and functionality. Mixed ionic-electronic conductors are widely used in devices for energy conversion and storage. Grain boundaries in these materials have nanoscale spatial dimensions, which can generate substantial resistance to ionic transport due to dopant segregation. Here, we report a concept of targeted phase formation in a Ce_0.8Gd_0.2O_2-δ-CoFe₂O₄ (CGO-CFO) composite that serves to enhance the grain boundary ionic conductivity. Using spatially resolved electron …

Characterizing The Functionality Of Transmembrane Ion Channels Using Planar Bilayer Membranes Device And Stopped Flow Spectrometer, Andrew Jo, Hiofan Hoi, C. Montemagno

Composites at Lake Louise (CALL 2015)

Transmembrane ion channels can be used in biomaterials as a way to selectively allow only certain molecules to pass through a given membrane. To produce these types of membranes predictably and reliably for commercial activity, its characterization is crucial. We have characterized the conductivity and ion selectivity of NaChBac, a voltage-gated sodium channel from Bacillus haloduran, using a planar bilayer membrane device. Furthermore, we have devised a dye-free flux assay to measure the channel function using stopped flow spectrometer.. Planar bilayer membrane is a common technique for ion channels function characterization. We first incorporated purified NaChBac protein into lipid vesicle. …