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Articles 1 - 30 of 77
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Optimizing Production Methods For Artifical Silk Proteins Through Bioreactor And Purification Studies Of Recombinant Proteins Expressed From Pichia Pastoris, Aaron Ramey
All Theses
Advancements in the field of biomaterials are being made to produce an artificial silk fiber. A gene was constructed which utilized components from both the dragline silk of Nephila clavipes and nematode collagen. For this engineered protein, the yeast strain Pichia pastoris was chosen to be the host organism. Previous research has shown P. pastoris to have comparatively low amounts of specific protein productivity. Therefore, this problem must be compensated for by obtaining extremely high cell densities. The main focus of this study was to optimize the fermentation parameters of transgenic yeast cultures within a bioreactor in order to increase …
Influence Of Temperature And Polymer/ Mold Surface Interactions On Micro-Feature Replication At Ambient Pressure In Micro Injection Molding, Varun Thakur
All Theses
This study assesses micro-feature replication at elevated mold temperature and ambient pressure using a variety of polymers. Moldings were made on the surface of stainless steel and silicon wafers containing features as small as 130 nm under isothermal conditions in a heated chamber by allowing polymer to spread over the features at ambient pressure. Feature replication was analyzed via AFM and SEM. Polymer behavior was characterized via melt contact angle and melt viscosity. While feature detail was well replicated, the moldings exhibited poor dimensional accuracy due to shrinkage. In general, polymers with low viscosity and surface tension comparable to the …
Dielectric Properties And Method Of Characterizing Ceramic Powders And Multiphase Composites, Ravi Kiran Kota
Dielectric Properties And Method Of Characterizing Ceramic Powders And Multiphase Composites, Ravi Kiran Kota
All Theses
Barium Titanate was the first developed ferroelectric ceramic material and even today it is widely used. It is also a well-known material used for capacitors. The only reason behind a wide range of applications is that barium titanate boasts of high dielectric properties. A phase transition from cubic to tetragonal at normal working temperatures provides enhanced dielectric properties in this electronic material. For any application and design, the most inquired property is the dielectric constant. Predicting the dielectric constant is very much required as it is the pre-requisite. This is the major objective of the present work. To estimate the …
Studies Of The Mechanism Of Electron Beam Induced Deposition (Ebid), Young Ryong Choi
Studies Of The Mechanism Of Electron Beam Induced Deposition (Ebid), Young Ryong Choi
Doctoral Dissertations
The controlled deposition of metals resulting from the passage of an ion beam through an atmosphere of a suitable precursor gas is a well-established procedure for micro scale materials manipulation. While the ion beam technique is rapid and reliable it has the disadvantage that the beam itself can ablate and contaminate the target with Gallium or other materials, and the fact that ion optics are less widely accessible than electron optical columns. We have therefore been investigating the theory and practice of depositing metal using an electron beam and variety of precursor gases. The aim of this work is to …
Thermal Stability Of Binary Cr-Cr3Si And Ternary Nial-Mo Eutectic Alloys, Aravind Gali
Thermal Stability Of Binary Cr-Cr3Si And Ternary Nial-Mo Eutectic Alloys, Aravind Gali
Doctoral Dissertations
The thermal stability of multiphase intermetallics at temperatures to 1400°C was investigated by studying two model eutectic systems: Cr-Cr3Si having a lamellar microstructure and NiAl-Mo having a fibrous microstructure. In drop cast Cr-Cr3Si, coarsening was found to be interface controlled. The coarsening rate could be significantly reduced by microalloying with Ce and Re, two elements which were chosen because they were expected to segregate to the Cr-Cr3Si interfaces and decrease their energies. Similarly, directional solidification, which is also expected to lower the Cr- Cr3Si interfacial energy, was found to dramatically decrease the …
An Investigation Of The Deposition And Characterization Of Materials Formed By Electron Beam Induced Deposition, Wei Li
Doctoral Dissertations
This dissertation deals with EBID – Electron Beam Induced Deposition – a novel bottom up nanofabrication technique. Since EBID was first employed for nano-patterning, a number of empirical factors were investigated to control deposition process. Meanwhile a few theoretical models were proposed based on some fundamental assumptions. So far little work has been done to verify the validity of these assumptions. The main objective of my PhD study, therefore, was to answer whether these assumptions are valid so that unifying the empirical factors and theoretical models would be possible. Electrical resistivity of deposited materials was another interesting topic included in …
A Study Of The Relationship Between Indentation Creep And Uniaxial Creep, James Anthony Lamanna Jr.
A Study Of The Relationship Between Indentation Creep And Uniaxial Creep, James Anthony Lamanna Jr.
Doctoral Dissertations
The purpose of this work is to further the scientific understanding of the relationship between indentation creep and uniaxial creep. The data for this study was obtained by conducting both indentation and uniaxial creep experiments on amorphous selenium. Experiments were designed to collect data over a wide range of creep rates. Specific temperatures were chosen to collect creep data above and below the glass transition temperature of 31°C. The indentation and uniaxial compression data was used to accomplish several objectives.
The first objective was to test the ability of the Oliver-Pharr stiffness equation to predict contact area. The current contact …
Pseudoelasticity And Shape Memory Effect In Single Crystal Fe3Al, Saurabh Kabra
Pseudoelasticity And Shape Memory Effect In Single Crystal Fe3Al, Saurabh Kabra
Doctoral Dissertations
Fe3Al is an intermetallic compound which has shown some excellent engineering properties and has been widely studied for this reason. It also shows interesting mechanical phenomenon like yield stress anomaly and pseudoelasticity. Mechanical behavior and diffraction studies on the pseudoelastic aspect of Fe3Al have been presented in this work.
Single crystalline, D03 ordered Fe3Al is known to show pseudoelastic behavior at room temperature. Pseudoelastic behavior was seen in both tension and compression with a distinct tension-compression asymmetry. No strain hardening occurred under tension even at high applied strains as opposed to compression, …
Methylsilane Derived Sic Particle Coatings Produced By Fluid-Bed Chemical Vapor Deposition, James Henry Miller
Methylsilane Derived Sic Particle Coatings Produced By Fluid-Bed Chemical Vapor Deposition, James Henry Miller
Doctoral Dissertations
This report describes the research effort that was undertaken to develop and understand processing techniques for the deposition of both low and high density SiC coatings from a non-halide precursor, in support of the Generation IV Gas-Cooled Fast Reactor (GFR) fuel development program.
The research was conducted in two phases. In the first phase, the feasibility of producing both porous SiC coatings and dense SiC coatings on surrogate fuel particles by fluidized bed chemical vapor deposition (FBCVD) using gas mixtures of methylsilane and argon was demonstrated. In the second phase, a combined experimental and modeling effort was carried out in …
Effects Of Temperature And Grain Size On The Transformation And The Deformation Behaviors Of The Trip (Transformation Induced Plasticity) Steels, Kaixiang Tao
Doctoral Dissertations
Two types of TRIP steels, a commercial 304L stainless steel and an Fe-10%Cr-5%Ni-8%Mn steel, have been used to investigate the effects of temperature and grain size on the transformation and mechanical behaviors. 304L SS was used to investigate the effects of temperature ranging from 300K to 77K, while the Fe-10%Cr-5%Ni-8%Mn steel was used for the investigation of the effects of the grain size at 300K.
At 203K, the fcc grains of the 304L SS with {200} plane normal parallel to the loading direction are preferred for the fcc to bcc transformation and the {200} plane normals of the newly-formed bcc …
A Lifetime-Prediction Approach To Understanding Corrosion: The Corrosion-Fatigue And The Corrosion Behavior Of A Nickel-Based Superalloy And A Nanocrystalline Alloy, Rejanah Vernice Steward
A Lifetime-Prediction Approach To Understanding Corrosion: The Corrosion-Fatigue And The Corrosion Behavior Of A Nickel-Based Superalloy And A Nanocrystalline Alloy, Rejanah Vernice Steward
Doctoral Dissertations
Lifetime-prediction models are useful for simulating a material’s in-service behavior or outcome. Perhaps the greatest advantage of these models is the ability to use the predicted results to help optimize engineering designs and reduce costs. The Hastelloy® C-2000® superalloy is a single-phase material and face-centered cubic in structure at all temperatures. The C-2000® alloy is a commercially designed alloy manufactured to function in both reducing and oxidizing solutions. C-2000® is used as a fabrication material for heat exchangers, piping for chemical refineries, and storage repositories. The corrosion properties of C-2000® are excellent, and the ductility …
Ex-Situ Epitaxial Yba2Cu3O7-Δ Films: Precursor Conversion And Film Characterization, Yifei Zhang
Ex-Situ Epitaxial Yba2Cu3O7-Δ Films: Precursor Conversion And Film Characterization, Yifei Zhang
Doctoral Dissertations
BaF2-based precursors were deposited on various substrates by electron beam co- evaporation and trifluoroactates-involved metal organic deposition (TFA-MOD) for fabricating biaxially-textured YBa2Cu3O7-δ (YBCO) films. A low-pressure processing system was established for the conversion of the precursors. High critical current densities near 4 MA/cm2 (77 K, self field) were obtained for the first time through the ex-situ conversion under the total pressures as low as 10 mTorr. The viability of the low- pressure conversion may enable a large-scale, cost-effective batch production of YBCO- based high temperature superconductor (HTS) wires.
The effects of the …
A Kinetic Study Of Indentation Pop-Out In Si, Songqing Wen
A Kinetic Study Of Indentation Pop-Out In Si, Songqing Wen
Doctoral Dissertations
The kinetics of the phenomenon of pop-out during nanoindentation of silicon were studied by a variety of mechanical and structural characterization techniques. Pop- out is commonly viewed to result from the reversal of a unique pressure-induced, volume reducing phase transformation that occurs in silicon and germanium.
The mechanical characteristics were examined by standard nanoindentation methods using a number of triangular pyramidal indenters with centerline-to-face angles varying in the range 35°-85°. The load at which pop-out occurs was systematically measured as a function of indenter angle, loading/unloading rate, and maximum load. Nanoindentation tests were conducted both at a constant loading rate …
Studying The Fatigue Behavior Of Zr-Based Bulk-Metallic Glasses And Composites, Gongyao Wang
Studying The Fatigue Behavior Of Zr-Based Bulk-Metallic Glasses And Composites, Gongyao Wang
Doctoral Dissertations
As excellent candidates for structural materials, the mechanical behavior of bulk metallic glasses (BMGs) is being widely studied. Although their fatigue behavior is very important for engineering applications, there are few studies on their fatigue behavior. Moreover, the understanding of the fatigue behavior is pretty limited.
High-cycle fatigue experiments were conducted on notched Zr-based BMGs under tension-tension loading in air and vacuum at room temperature. A sparking phenomenon was found by infrared camera at the final fracture moment of Zr50Al10Cu30Ni10 in air. The fatigue-endurance limit (983 MPa) of Zr50Cu37Al …
Severe Plastic Deformation Using Friction Stir Processing, And The Characterization Of Microstructure And Mechanical Behavior Using Neutron Diffraction, Wanchuck Woo
Doctoral Dissertations
Friction-stir welding (FSW) is a solid-state joining process, which utilizes a cylindrical rotating tool consisting of a concentric threaded tool pin and tool shoulder. The strong metallurgical bonding during the FSW is accomplished through: (1) the severe plastic deformation caused by the rotation of the tool pin that plunges into the material and travels along the joining line; and (2) the frictional heat generated mainly from the pressing tool shoulder. Recently, a number of variations of the FSW have been applied to modify the microstructure, for example, grain refinements and homogenization of precipitate particles, namely friction-stir processing (FSP). Applications of …
An Exploration Of Several Structural Measurement Techniques For Usage With Functionally Graded Materials, Robert A. Reuter
An Exploration Of Several Structural Measurement Techniques For Usage With Functionally Graded Materials, Robert A. Reuter
Theses and Dissertations
Titanium / titanium boride functionally graded 6"x 1"x1" beams were subjected to a four-point beam test in order to critique the value of several measurement techniques. Also, finite element analysis results were compared with experimental values and general observations about the experiment were recorded. Uniform 85% TiB /15% Ti and uniform commercially pure titanium specimens were also subjected to the same loading conditions as a control. Techniques used include digital image correlation, fiber optic strain gauging, strain gauging, and differential infrared thermography techniques. The strain data results were compared with one another and to linear finite element models. It was …
Investigation Of The Band Structures And Optical Properties Of Super Lattices, Sheikha Ahmed Awad Alnaeme
Investigation Of The Band Structures And Optical Properties Of Super Lattices, Sheikha Ahmed Awad Alnaeme
Theses
Group III nitrides are highly attractive materials because of their great potential for the development of optoelectronic devices in short wavelength, semiconductor lasers and optical light-emitters and detectors. GaN, AlN and InN are considered as the most important compounds in this class of materials. In this work, we present a theoretical investigation of the electronic properties (band structure, density of state and contour maps of the charge density distribution) and optical properties (refractive index, absorption and dielectric constants). Also, we investigate the band structures and optical properties of AlN/GaN and InN/GaN super lattices. A full-potential linearized plane-wave (FPLAPW) method is …
Characterization Of Processes Used In Nanofabrication Of Digital Electrostatic E-Beam Array Lithography (Deal) Devices, Ryan Benjamine Rucker
Characterization Of Processes Used In Nanofabrication Of Digital Electrostatic E-Beam Array Lithography (Deal) Devices, Ryan Benjamine Rucker
Masters Theses
The ultimate goal of this research was to nanofabricate an advanced field emission electron beam lithography platform using an electron beam induced deposition process (EBID) to deposit tungsten (W) nanofibers cathodes. In order to fabricate the devices, it was necessary to characterize the reactive ion etching (RIE) processes for the fabrication of the Digital Electrostatic e-beam Array Lithography (DEAL) device. To optimize the reactive ion etch processes of the silicon and silicon dioxide layers, a JMP desktop statistical discovery software from SAS® was employed to design a set of experiments. The design of experiments (DOE) employed variable conditions of R.F. …
Modeling Fracture In Z-Pinned Composite Co-Cured Laminates Using Smeared Properties And Cohesive Elements In Dyna3d, Jason K. Freels
Modeling Fracture In Z-Pinned Composite Co-Cured Laminates Using Smeared Properties And Cohesive Elements In Dyna3d, Jason K. Freels
Theses and Dissertations
The purpose of the present research was three-fold: 1) gain a more sophisticated understanding of the response of co-cured composite joints with and without through-thickness reinforcement (TTR), 2) compare the behavior of specimens reinforced with various sizes and densities of reinforcement, and 3) use experimental data to verify the existing DYNA3D smeared property model. Double cantilever beam, end-notch flexure and T-section specimens reinforced with 0.011" diameter z-pins at 2% and 4% volume densities were tested to determine the mode I, mode II and mixed mode (I and II) behavior. Results were added to preliminary research in which tests were conducted …
Effects Of Polishing Shot-Peened Surfaces On Fretting Fatigue Behavior Of Ti-6al-4v, Kasey S. Scheel
Effects Of Polishing Shot-Peened Surfaces On Fretting Fatigue Behavior Of Ti-6al-4v, Kasey S. Scheel
Theses and Dissertations
The research of this thesis was done to investigate the effects of polishing a shot-peened specimen of Ti-6Al-4V on the fretting fatigue life of that specimen. The shot-peening process, though one of the most beneficial techniques in prolonging fretting fatigue life, creates a textured surface that may lead to problems on the micro level. This research was done in an attempt to further improve the peening process by examining the effects of another surface treatment to be used in conjunction, surface polishing. The rough peened surface may contain abrupt changes in surface geometry that act as stress risers, which are …
Effects Of Environment On Creep Behavior Of Two Oxide-Oxide Ceramic Matrix Composites At 1200°C, Pavlos Koutsoukos
Effects Of Environment On Creep Behavior Of Two Oxide-Oxide Ceramic Matrix Composites At 1200°C, Pavlos Koutsoukos
Theses and Dissertations
Previous studies by the advisor and graduate students examined creep behavior of the Nextel720/Alumina CMC in air and in 100% steam environments at 1200 and 1330°C. Results showed that while this oxide/oxide system exhibits an exceptionally high fatigue limit at 1200°C it also experiences substantial strain accumulation under sustained loading conditions. Furthermore, these earlier investigations revealed a significant degrading effect of 100% steam environment on material performance under both static and cyclic loadings. The present effort will investigate creep rupture behavior of Nextel720/Alumina composite in the inert gas environment. In addition, creep rupture behavior of Nextel720/Aluminosilicate CMC will be investigated …
Characterization Of Thermally Diffused Bordie Layers On Aisi 1018 Steel : Residual Stresses (By Synchrotron Radiation) And Microhardness, Joel A. Payne
Theses
Boronization is a thermal diffusion process in which needle like boride layers are formed at the surface of the metallic substrate. The boride coatings formed by the diffusion process have high hardness and strong ware and corrosion resistance. In order for coatings of this nature to be industrially successful, their service life should be long and characterization should be extensive. Measuring the residual stresses of the coatings caters to each of these aspects.
In this study, AISI 1018 steel samples were boronized by a powder-pack process for four hours at 850°C in an argon atmosphere. Characterization techniques included coating thickness, …
Submicron Patterning Using Laser Interference Lithography, Luigi Pollara Verdoni
Submicron Patterning Using Laser Interference Lithography, Luigi Pollara Verdoni
Theses
In this thesis, the theory, fabrication protocol, and initial results of an alternative nanopatterning technique called Interferometric Lithography (IL) are presented. Comprised of the identical process attributes of traditional projection photolithography, IL mirrors the wafer preparation and development procedures of our existing clean room capabilities. The main departure is solely in means of pattern delineation. IL is a "mask less" technique that employs the interference fringe pattern of two coherent beams, and can therefore be generated with a commercial laser. Due to its simplicity, Interferometric Lithography provides an attractive supplement to existing methods of nano-patterning.
Utilizing a 325 nm HeCd …
Processing And Characterization Of Oxide Dispersion Strengthened 14ywt Ferritic Alloys, Michael Keith West
Processing And Characterization Of Oxide Dispersion Strengthened 14ywt Ferritic Alloys, Michael Keith West
Doctoral Dissertations
Oxide dispersion strengthened (ODS) ferritic steels are currently being investigated as candidate materials for nuclear applications due to their increased high temperature strength and low activation characteristics. Recent studies have shown that ODS ferritic steels containing Ti exhibit enhanced high temperature properties due to the formation of a very fine dispersion of nanometer-sized oxide clusters based on Ti, Y, and O. Studies are currently underway to examine so called 14YWT alloys with nominal compositions of Fe-14Cr-3W-0.4Ti (wt. %) mechanically alloyed with 0.25 (wt.%) Y2O3. The focus of this study was to investigate how the early stages …
On The Measurement Of Yield Strength By Spherical Indentation, Erik G. Herbert
On The Measurement Of Yield Strength By Spherical Indentation, Erik G. Herbert
Masters Theses
Over the past 10 years, a number of investigators have proposed methods to measure the yield strength of metals using instrumented indentation experiments performed with a sphere [1-6]. Among the proposed methods that are easy to implement experimentally and do not require any additional novel characterization techniques or proprietary software analysis are those of Field and Swain, Yu and Blanchard, Ma et al., Cao and Lu, Kogut and Komvopoulos, and Lee, Lee, and Pharr. However, these methods have yet to be rigorously verified experimentally. The objectives of this work are twofold: first, identify the basic principles, predictions, data analysis routine, …
Automatización De Un Termohigrógrafo Mecánico, Ivan Dario Robertson Rojas
Automatización De Un Termohigrógrafo Mecánico, Ivan Dario Robertson Rojas
Ingeniería en Automatización
No abstract provided.
Numerical Modeling Of Concrete Masonry Walls Strengthened By Fiber Reinforced Polymers Under Lateral Loads, Mohamed Salama
Numerical Modeling Of Concrete Masonry Walls Strengthened By Fiber Reinforced Polymers Under Lateral Loads, Mohamed Salama
Archived Theses and Dissertations
The use of fiber reinforced polymers (FRP) for the seismic retrofit of masonry walls is on the rise. Design formulae are available to estimate the lateral load capacity of the strengthened walls. However, recent experimental data from tests conducted on full scale concrete masonry walls under cyclic lateral loads have shown that these design capacities have not been reached because of the occurrence of other failure modes not accounted for in the design formulae. The limiting failure mode in all test samples referred to in this work was due to premature compression failure of the masonry units at the wall …
A Comparative Study Of Athletic Apparel Made From Cotton/Flax, Cotton/Polyester, And Polyester/Flax Blends, Elizabeth Skomra
A Comparative Study Of Athletic Apparel Made From Cotton/Flax, Cotton/Polyester, And Polyester/Flax Blends, Elizabeth Skomra
Master's Theses and Doctoral Dissertations
The desired attributes of sports apparel garments are to have durability characteristics, such as tearing and tensile strength, and comfort characteristics, such as wicking, vapor transmission, and air permeability. Currently, most sports apparel is made from a blend of polyester or other synthetic fibers. Through examining the uniqueness of natural fibers, such as cotton and flax, the advantages and benefits of using a higher percentage of natural fibers when manufacturing comfortable and functional high performance athletic wear can be obtained.
Results from this study, regarding durability, determined that for both tearing and breaking strength, traditional sports apparel made with polyester/cotton …
Characterization Of Passivated Indium Antimonide, Catherine Ann Taylor
Characterization Of Passivated Indium Antimonide, Catherine Ann Taylor
Theses and Dissertations
Infrared absorption and photoluminescence measurements have been used to optically characterize bulk-grown, 680-μm thick, indium antimonide (InSb), both as-grown and after passivation by either anodization or a 700-Å layer of silicon oxide (SiOx). Spectra were obtained using Fourier transform infrared (FT-IR) spectroscopy. Results include the effects of sample temperature in the range of 10 to 300 K and 4.636 μm laser pump power in the range of 28 mW to 1.43 W for the photoluminescence spectrum.
Effect Of Environment On Creep Behavior Of An Oxide/Oxide Cfcc With ±45° Fiber Orientation, Gregory T. Siegert
Effect Of Environment On Creep Behavior Of An Oxide/Oxide Cfcc With ±45° Fiber Orientation, Gregory T. Siegert
Theses and Dissertations
Aerospace applications require materials capable of maintaining superior mechanical properties while operating at high temperatures and oxidizing environments. Nextel™ 720/A (N720/A), an oxide/oxide ceramic matrix composite (CMC) with a porous alumina matrix was developed specifically to provide improved long-term properties and performance at 1200°C. This research evaluated the creep behavior of N720/A with a ±45° fiber orientation at 1200°C in: laboratory air, steam, and argon environments. Creep-rupture tests at the creep stress levels of: 45, 40, 35, and 15 MPa were conducted in each environment.
The ultimate tensile strength of N720/A with ±45° fiber orientation was 55 MPa, the elastic …