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Full-Text Articles in Engineering

Identification And Characterization Of The Iron-Zinc Intermetallics Formed In Galvanneal Steel, Richard Frederick George Grant Apr 1995

Identification And Characterization Of The Iron-Zinc Intermetallics Formed In Galvanneal Steel, Richard Frederick George Grant

Physics Theses & Dissertations

The demand to improve the corrosion resistance of steel sheet, particularly for use within the automotive industry, has led to a dramatic increase in the use of coated steels in place of cold-rolled sheet steel. Galvanneal steel results from the post annealing of the zinc-coated steel sheet, in which iron and zinc are interdiffused to form an iron-zinc alloy coating. Within this alloy coating, four main iron-zinc phases, Zeta, Delta, Gamma-1, and Gamma may be present. Manufacture of the most suitable coating requires identifying which phases form during the galvannealing process, an understanding of the properties of each phase and ...


Growth Optimization And Characterization Of Gallium Indium Nitride Grown By Electron-Cyclotron-Resonance Plasma-Assisted Molecular-Beam Epitaxy , William O. Liners Jan 1995

Growth Optimization And Characterization Of Gallium Indium Nitride Grown By Electron-Cyclotron-Resonance Plasma-Assisted Molecular-Beam Epitaxy , William O. Liners

Retrospective Theses and Dissertations

The various alloys of gallium indium nitride (GaInN) form a technologically important semiconductor materials system, with potential uses in optoelectronic devices operating in the blue and blue-green region of the visible light spectrum. There has been little work reported on the growth of these materials, and this research addresses fundamental issues related to the epitaxial growth of the nitrides. Our first step in this project was to install an electron cyclotron resonance (ECR) apparatus into our molecular beam epitaxy system. This provided a source for atomic nitrogen needed to grow the nitride materials. We also put together a photoluminescence (PL ...


Stability Of A Eutectic Interface During Directional Solidification , Seung Hoon Han Jan 1995

Stability Of A Eutectic Interface During Directional Solidification , Seung Hoon Han

Retrospective Theses and Dissertations

Directional solidification of eutectic alloys shows different types of eutectic morphologies. These include lamellar, rod, oscillating and tilting modes. The growth of these morphologies occurs with a macroscopically planar interface. However, under certain conditions, the planar eutectic front becomes unstable and gives rise to a cellular or a dendritic structure. This instability leads to the cellular/dendritic structure of either a primary phase or a two-phase structure. The objective of this work is to develop a fundamental understanding of the instability of eutectic structure into cellular/dendritic structures of a single phase and of two-phases;Experimental studies have been carried ...


Oxidation Studies On Small Atom Doped Ti5si3 , Andrew Jason Thom Jan 1995

Oxidation Studies On Small Atom Doped Ti5si3 , Andrew Jason Thom

Retrospective Theses and Dissertations

Several Ti5Si3Zx compositions (Z = B,C,N,O and 0 ≤ x ≤ 1) were arc-melted, and powder x-ray diffraction indicates the materials maintain the Mn5Si3-type structure of undoped Ti5Si3. Single crystal x-ray diffraction verifies that the ternary additions occupy the normally vacant interstitial sites in the Mn5Si3-type structure. Interstitial nitrogen and oxygen also significantly increase the density of Ti5Si3;Coefficient of thermal expansion (CTE) of Ti5Si3 was measured by the method of high temperature x-ray diffraction. CTE along the c-axis is substantially larger than along the a-axis ([alpha] a = 8.68 ± 0.14 and [alpha] c = 20.4 ± 0.4 ppm ...


Oxidation And Creep Behavior Of Mo5si3 Based Materials , Mitchell Karl Meyer Jan 1995

Oxidation And Creep Behavior Of Mo5si3 Based Materials , Mitchell Karl Meyer

Retrospective Theses and Dissertations

Mo[subscript]5 Si[subscript]3 shows promise as a high temperature creep resistant material. The high temperature oxidation resistance of Mo[subscript]5 Si[subscript]3 has been found to be poor, however, limiting its use in oxidizing atmospheres. Mo [subscript]5Si[subscript]3 exhibits mass loss during oxidation at 800°-1200° C due to volatilization of molybdenum oxide, indicating that the silica scale that forms does not provide a passivating layer. Catastrophic 'pest' oxidation occurs at 800° C. The oxidation rate at 1200° C is on the order of 10[superscript]3 mg cm[superscript]-2 hr[superscript ...


Preparation And Characterization Of B2s3-Based Chalcogenide Glasses , Jaephil Cho Jan 1995

Preparation And Characterization Of B2s3-Based Chalcogenide Glasses , Jaephil Cho

Retrospective Theses and Dissertations

The discovery of the fast ion conducting B[subscript]2S[subscript]3-based glasses has been one of the most significant development in the field of solid electrolytes. Considerable experimental studies have been done to maximize conductivities and chemical stabilities of these glass systems. Recently, the study of the structure and properties of these glasses compared to their oxide analog has become important;The IR spectra of M[subscript]2S + B[subscript]2S[subscript]3 (M = Li, K, Rb and Cs) and MS + B[subscript]2S[subscript]3 (M = Sr and Ba) thioborate glasses have shown the monotonic increase in tetrahedral ...


Electronic And Photonic Devices: Experimental Investigations Of Hydrogenated Amorphous Silicon Substrate N+/I/P+ Solar Cell And Fundamental Properties Of Quantum Wells With Cylindrical Geometry And Applications To Electronics And Photonics , Er-Xuan Ping Jan 1995

Electronic And Photonic Devices: Experimental Investigations Of Hydrogenated Amorphous Silicon Substrate N+/I/P+ Solar Cell And Fundamental Properties Of Quantum Wells With Cylindrical Geometry And Applications To Electronics And Photonics , Er-Xuan Ping

Retrospective Theses and Dissertations

This thesis consists of two different parts: (I) experimental investigations of hydrogenated amorphous silicon substrate n[superscript]+/i/p[superscript]+ solar cells and, (II) fundamental properties of quantum wells with cylindrical geometry and applications to electronics and photonics;Part I. The substrate structural n[superscript]+/i/p[superscript]+ solar cells based on a-Si:H materials are fabricated by a radio frequency (RF) triode geometric plasma enhanced chemical vapor deposition (PECVD) system. The solar cells have been electrically and optically tested. Two different substrates, tin-oxide coated glass and stainless steel foil, are used. An RF magnetron sputtering system is used to ...


Effect Of Agricultural Fiber Reinforcement On The Mechanical Properties Of A Recycled Polyethylene Plastic Composite Material, Michael E. Courbat Jan 1995

Effect Of Agricultural Fiber Reinforcement On The Mechanical Properties Of A Recycled Polyethylene Plastic Composite Material, Michael E. Courbat

Dissertations and Theses @ UNI

This study determined the effect of certain agricultural fiber reinforcements on the tensile and impact mechanical properties of a recycled polyethylene plastic composite material. The purpose of the study was to provide information on certain mechanical properties of a recycled polyethylene plastic material as part of a coordinated materials application process.

A prototype product run of the plastic composite material was done and test specimens were selected from this material. Notch impact, tensile, and flexure tests were conducted on test specimens. Test procedures complied with accepted standards from The American Society For Testing and Materials (ASTM). Tests were conducted on ...


Fluorinated Oxidation In Submicrometer Regions And Related Phenomena, Humberto Raposo Jan 1995

Fluorinated Oxidation In Submicrometer Regions And Related Phenomena, Humberto Raposo

Theses and Dissertations

No abstract provided.


Oxidation Enthalpy Measurements For Acceptor-Doped Perovskite Materials, Fengxia Ma Jan 1995

Oxidation Enthalpy Measurements For Acceptor-Doped Perovskite Materials, Fengxia Ma

Theses and Dissertations

No abstract provided.


Structural Integrity Of Cast-Aluminum Automotive Wheels, Ellen E. Youngblood Jan 1995

Structural Integrity Of Cast-Aluminum Automotive Wheels, Ellen E. Youngblood

Theses and Dissertations

No abstract provided.


Studies On The Chemical Composition And Thermo-Mechanical Processings Of High Performance Steels, Thomas John Todaro Jan 1995

Studies On The Chemical Composition And Thermo-Mechanical Processings Of High Performance Steels, Thomas John Todaro

Theses and Dissertations

No abstract provided.


A Quantitative Study Of Grain Growth In Copt, Ni, And Nife Thin Films, Roger A. Ristau Jan 1995

A Quantitative Study Of Grain Growth In Copt, Ni, And Nife Thin Films, Roger A. Ristau

Theses and Dissertations

No abstract provided.


Mixed-Mode Fracture Of Organic Chip Attachment Adhesives, Peter Brandenburger Jan 1995

Mixed-Mode Fracture Of Organic Chip Attachment Adhesives, Peter Brandenburger

Theses and Dissertations

No abstract provided.


A Metallurgical Approach Toward Alloying In Rare-Earth Permanent Magnet Systems , Daniel James Branagan Jan 1995

A Metallurgical Approach Toward Alloying In Rare-Earth Permanent Magnet Systems , Daniel James Branagan

Retrospective Theses and Dissertations

A metallurgical approach was developed toward alloying in rare earth permanent magnet systems to allow for microstructural enhancement and control during solidification and subsequent processing. Compound additions of Group IVA, VA, or VIA transition metals (TM) along with carbon were added to the Nd[subscript]2Fe[subscript]14B system (2-14-1). Transition metal carbides will form in the quintary Nd-Fe-B-TM-C system if the phase stability of the precipitates in the specific multicomponent system is higher than the phase stability of all other phases involving the additive elements and the constituent elements. Transition metal carbide formation was found in the Group IVA ...


Vortex Lattice Melting In An Anisotropic Type Ii Superconductor , John Anton Fendrich Jan 1995

Vortex Lattice Melting In An Anisotropic Type Ii Superconductor , John Anton Fendrich

Retrospective Theses and Dissertations

The flux line lattice in superconducting single crystals of YBa [subscript]2Cu[subscript]3O[subscript]7-[delta] is shown to undergo a very abrupt melting transition as the temperature and field approach the normal state. The sharpest transitions from the vortex solid to liquid phase, as seen in resistivity measurements, are of the order of 10mK in a temperature of 85K and of the order of 10 Oe in a field of 6T. The discontinuity in the resistivity associated with vortex lattice melting is asymmetrically hysteretic with applied field in clean crystals. The melting transition width for decreasing applied magnetic ...


Ultrasonic Measurement Of Drawability (R-Values) Of Low Carbon Steel Sheets , Kaveh Forouraghi Jan 1995

Ultrasonic Measurement Of Drawability (R-Values) Of Low Carbon Steel Sheets , Kaveh Forouraghi

Retrospective Theses and Dissertations

The present research was designed to evaluate an ultrasonic technique for measuring the drawability of low carbon steel sheets nondestructively. This technique, which uses electro magnetic acoustic transducers (EMAT's) is embodied in a fully automatic ultrasonic device called Ultra-Form, which was developed by Iowa State University in 1990. EMAT transducers generate the ultrasonic pulses in the sheet (without any need for a coupling medium) whose velocities are then related to the microstructural factors (crystallographic texture) that control drawability in rolled sheets. Drawability (usually interpreted by measuring r-values of low carbon steels) is an important property indicative of the formability ...


Ultrasonic Scattering From Decorated Grain Boundaries , John Mittleman Jan 1995

Ultrasonic Scattering From Decorated Grain Boundaries , John Mittleman

Retrospective Theses and Dissertations

The microstructure of polycrystalline materials is manipulated in many ways to create materials with superior engineering properties. Alloying pure materials, for example, can alter crystallographic structure to strengthen or stiffen the material, but when impurities collect along grain boundaries, the material may become embrittled. This undesirable condition is generally associated with improper heat treatment during fabrication, but it may also occur during the service life of alloys exposed to penetrating radiation or severe thermal conditions. This dissertation studies scattering from decorated grain boundaries theoretically and experimentally, and ties results for isolated scatterers to grain noise measurements on materials composed entirely ...


Laser Machining And Its Thermal Effects On Silicon Nitride And Steel , Aloke K. Ray Jan 1995

Laser Machining And Its Thermal Effects On Silicon Nitride And Steel , Aloke K. Ray

Retrospective Theses and Dissertations

An investigation was undertaken to examine the physical and thermal processes involved in laser machining of ceramics and metals. Two types laser machining viz. milling and cutting were studied. The objective is to provide a better understanding of laser machining that in turn facilitate achieving tighter tolerances, excellent surface integrity and improved properties of the parts;A 1500 W continuous wave CO2 laser was used for this purpose to groove and mill reaction bonded silicon nitride (RBSN) and hot-isostically pressed silicon nitride (HIPSN). Experimental results showed that the material removal mechanism was essentially chemical decomposition at 2150 K leading to ...


Synthesis, Characterization And Physical Properties Of Al-Cu-Fe Quasicrystalline Plasma Sprayed Coatings , Daniel J. Sordelet Jan 1995

Synthesis, Characterization And Physical Properties Of Al-Cu-Fe Quasicrystalline Plasma Sprayed Coatings , Daniel J. Sordelet

Retrospective Theses and Dissertations

The phases and microstructures of Al-Cu-Fe powders and coatings were investigated in this study. Powders were prepared by grinding a chill cast ingot and by high pressure gas atomization. The contrasting solidification rates of these two processes yielded very different solidification structures. The cast ingot was very inhomogeneous and contained icosahedral ([psi]), cubic ([beta]), monoclinic ([lambda]) and tetragonal ([theta]) phases. The gas atomized powder had a finer scale of phase segregation and consisted primarily of the [psi] and [beta] phase; a small fraction of the [lambda] phase was present as well;Plasma arc sprayed (PAS) coatings were formed using the ...


Compensation And Characterization Of Gallium Arsenide, Randy A. Roush Jan 1995

Compensation And Characterization Of Gallium Arsenide, Randy A. Roush

Electrical & Computer Engineering Theses & Disssertations

The properties of transition metals in gallium arsenide have been previously investigated extensively with respect to activation energies, but little effort has been made to correlate processing parameters with electronic characteristics. Diffusion of copper in gallium arsenide is of technological importance due to the development of GaAs:Cu bistable photoconductive devices. Several techniques are demonstrated in this work to develop and characterize compensated gallium arsenide wafers. The material is created by the thermal diffusion of copper into silicon-doped GaAs. Transition metals generally form deep and shallow acceptors in GaAs, and therefore compensation is possible by material processing such that the ...


Nonlinear Finite Element Micromechanic Analysis Of Thermoplastic Composite Of Recycled High Density Polyethylene Reinforced With Short Glass Fibers, Qiming Lou Jan 1995

Nonlinear Finite Element Micromechanic Analysis Of Thermoplastic Composite Of Recycled High Density Polyethylene Reinforced With Short Glass Fibers, Qiming Lou

Masters Theses

This thesis studied the nonlinear micromechanic behavior of thermoplastic composite of recycled high density polyethylene (HDPE) reinforced with short glass fibers using finite element method. The composite material was modeled using a micromechanic unit cell to simulate the stress distribution between the plastic matrix and the fiber in the composite. Nonlinear behavior of recycled HDPE and imperfect bonding between the fiber and matrix were investigated. Load-bearing capability of the fiber was evaluated using stress partition ratio (SPR) in the composite models. The effect of fiber aspect ratio on the stress distribution of the composite was studied to optimize the material ...


Metallization Of Polyimide Films To Enhance Dimensional Stability And To Achieve Reflective And Conductive Surfaces, David Scott Thompson Jan 1995

Metallization Of Polyimide Films To Enhance Dimensional Stability And To Achieve Reflective And Conductive Surfaces, David Scott Thompson

Dissertations, Theses, and Masters Projects

No abstract provided.


Mechanisms Of Poly(Vinyl Chloride) Fire Retardance And Smoke Suppression Induced By Copper Additives, Jong Paul Jeng Jan 1995

Mechanisms Of Poly(Vinyl Chloride) Fire Retardance And Smoke Suppression Induced By Copper Additives, Jong Paul Jeng

Dissertations, Theses, and Masters Projects

The purpose of this study was to elucidate the mechanisms of PVC fire retardance and smoke suppression induced by copper additives.;The experimental approaches involved: (1) the use of activated copper (Cu{dollar}\sp0{dollar}) to study PVC model-compound reactions and the crosslinking of PVC and (2) the pyrolysis of PVC model compounds in the presence of several copper additives in order to examine all of the possible chemical reactions involved in the formation of heavy products.;The results obtained from experiments with activated copper and allylic chloride model compounds suggest that the reductive coupling mechanism is a viable process ...


Characterization Of Composite Materials From Temporal Thermal Response, Pierre Richard Emeric Jan 1995

Characterization Of Composite Materials From Temporal Thermal Response, Pierre Richard Emeric

Dissertations, Theses, and Masters Projects

There is an increasing interest in the characterization of complex structures with thermographic techniques. Typical of these structures are multilayered systems and fiber reinforced composites where structural thermal response is a function of the combined responses of the constituents. In this work, techniques are presented for measuring the early thermal response. For multilayer structures, the response is reduced to the thermal properties of the constituents. For fiber reinforced composites, the short term response enables detection of the fibers.;A measurement system was developed consisting of an infrared detector focused on a single point on the structure. An input heat flux ...


Fabrication Of Thermoplastic Polymer Composite Ribbon, Donald Allan Sandusky Jan 1995

Fabrication Of Thermoplastic Polymer Composite Ribbon, Donald Allan Sandusky

Dissertations, Theses, and Masters Projects

The goal of this research was to develop a controllable process to convert a thermoplastic powder-coated carbon-fiber towpreg into uniform and consolidated ribbon. The approach comprised four primary activities. (1) The patent and processing literature was studied to evaluate the state of the art. (2) A functional ribbon fabrication technique was developed by scaling-up, in a novel configuration, hardware components found in the literature. (3) The ex parte ribbonizing process was characterized by calibrating equipment, determining steady state and studying cause and effect between process parameters and ribbon quality. (4) Process design and control methods were derived from heat transfer ...