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Theses/Dissertations

Materials Science and Engineering

1993

Articles 1 - 30 of 32

Full-Text Articles in Engineering

Laser Ablation Of Silicon Surfaces : The Effects Of A Low Level Background Light, Taposh Kumar Gayen Oct 1993

Laser Ablation Of Silicon Surfaces : The Effects Of A Low Level Background Light, Taposh Kumar Gayen

Theses

The performance of high speed optoelectronic and microelectronic devices largely depends on the uniqueness and development of the fabrication technology. Laser ablation has proven to be an effective three dimensional surface patterning technology. In this thesis, we present findings on the patterning of semiconductor surfaces using laser ablation in air as well as in solutions.

In this thesis, we suggest that the depth of a pattern induced on silicon by firing a pulsed excimer laser in air varies almost linearly with the number of pulses. We report that a He-Ne laser as a background light source has virtually little or ...


The Effect Of Texture And Microstructure On Equibiaxial Fracture In Gallium Embrittled Aluminum Sheet, Michael Daniel Grah Oct 1993

The Effect Of Texture And Microstructure On Equibiaxial Fracture In Gallium Embrittled Aluminum Sheet, Michael Daniel Grah

Open Access Dissertations

No abstract provided.


Fiber Enhanced Viscoelastic Damping Polymers And Their Application To Passive Vibration Control, Houchun Xia Jul 1993

Fiber Enhanced Viscoelastic Damping Polymers And Their Application To Passive Vibration Control, Houchun Xia

Mechanical & Aerospace Engineering Theses & Dissertations

A new composite damping material is investigated, which consists of a viscoelastic matrix and high elastic modulus fiber inclusions. This fiber enhanced viscoelastic damping polymer is intended to be applied to light-weight flexible structures as surface treatment for passive vibration control. A desirable packing geometry for the composite material is proposed, which is expected to produce maximum shear strain in the viscoelastic damping matrix. Subsequently, a micromechanical model is established in which the effect of fiber segment length and relative motion between neighboring fibers are taken into account. Based on this model, closed form expressions for the effective storage and ...


Boundary Value Problems In Rectilinearly Anisotropic Thermoelastic Solids, Gilbert Kerr Jul 1993

Boundary Value Problems In Rectilinearly Anisotropic Thermoelastic Solids, Gilbert Kerr

Mathematics & Statistics Theses & Dissertations

The boundary value problems which are considered are the type that arise due to the presence of a Griffith crack (or cracks) in an anisotropic thermoelastic solid. The thermoelastic field, in such materials, when the infinitesimal theory is employed, is governed by a set of elliptic partial differential equations. The general solution of these equations is expressed in terms of arbitrary analytic functions whose real parts, in turn, are expressed in terms of Fourier type integrals or Fourier series. Integral transform techniques are then used to determine the stress intensity factors (and other pertinent information) for various crack geometries. In ...


Silicon Carbide/Electroless Nickel Composite Plating For Aluminum Substrates, Ben Charbit Apr 1993

Silicon Carbide/Electroless Nickel Composite Plating For Aluminum Substrates, Ben Charbit

Master's Theses

The effectiveness of producing a composite coating by suspending micron-sized particles in an electroless nickel bath while plating a 2024T4 aluminum alloy part was studied. The variation in the count of particles trapped in the nickel coating due to changes in the particle size, concentration of the particles in the bath, and the substrate surface texture was also studied. Particle sizes of 1 micron and 10 microns, concentrations of 15 gr/lt and 30 gr/lt, and polished and blasted textures were used. It was found that this technique is an effective way to produce composite coatings rendering a high ...


The Effects Of Electron Radiation On The Glass Transition Temperature Of A Polyetherimide, Kristen Tulloch Kern Apr 1993

The Effects Of Electron Radiation On The Glass Transition Temperature Of A Polyetherimide, Kristen Tulloch Kern

Physics Theses & Dissertations

The effects of electron radiation on a polyetherimide (PEI), Ultem*, were investigated. In particular, the changes in the glass transition temperature (Tg) with absorbed radiation dose were studied. The polymer was exposed to mono-energetic beams of 100-keV electrons and 1.0-MeV electrons for doses up to 100 megagray (MGy). Dosimetry for the exposures was based on Monte-Carlo simulations of the transfer of energy from an energetic electron to the polymer and on comparison to Nylon standards. Dynamic mechanical analysis was used to determine the (Tg) for non-exposed PEI and the changes in (Tg) resulting from irradiation. The ...


Influence Of Processing Techniques On Copper Deep Levels Formation And On Photoconductivity In Silicon Doped Gallium Arsenide, Lucy M. Thomas Apr 1993

Influence Of Processing Techniques On Copper Deep Levels Formation And On Photoconductivity In Silicon Doped Gallium Arsenide, Lucy M. Thomas

Electrical & Computer Engineering Theses & Disssertations

Diffusion of copper in silicon doped gallium arsenide under different diffusion conditions is studied. Copper compensated silicon doped gallium arsenide (GaAs:Si:Cu) is used as switch material for bulk optically controlled semiconductor switch, and on-state photoconductivity of the switch is primarily due to the properties of the copper deep levels introduced in the material during diffusion. Gallium arsenide being a compound semiconductor, presence of vacancies and defects make the study of diffusion a complex process. The objective of the current research is twofold: a) to study the influence of diffusion conditions and processing techniques on copper deep level formation ...


Mechanics Of Unsaturated Granular Media , Steven Mark Levorson Jan 1993

Mechanics Of Unsaturated Granular Media , Steven Mark Levorson

Retrospective Theses and Dissertations

The objective of this study was to investigate the effect of particle size distribution on the mechanics of remolded, unsaturated, granular materials. Vibratory compaction, moisture retention, and unconfined compression tests were conducted on five power function gradations of sand and silt. Analytical studies of the equivalent pore pressure and pore size distribution were conducted to explain the mechanical behavior of the materials in terms of the effective stress Law;The exponent term in the power function used to describe the particle size distributions is shown to be a characterizing parameter of the compaction and shear strength behavior. This parameter provides ...


Identification And Verification Of The Job Duties And Tasks Of The Industrial Plastics Technician In The Greater Michiana Area Using The Dacum Process , Marcus D. Tillery Jan 1993

Identification And Verification Of The Job Duties And Tasks Of The Industrial Plastics Technician In The Greater Michiana Area Using The Dacum Process , Marcus D. Tillery

Retrospective Theses and Dissertations

The purpose of the study was to develop and verify a list of the job duties and tasks of industrial plastics technicians for use in developing plastics education and training programs which meet the needs of the greater Michiana area plastics industry;Research questions were as follows: (1) What tasks are considered to be essential to the success of the industrial plastics technician in the greater Michiana area? (2) What tasks are considered to be performed by entry-level industrial plastics technicians in the greater Michiana area? (3) What is the degree of importance of each task? (4) What is the ...


Directional Solidification Studies In Ni-Al Alloys , Je-Hyun Lee Jan 1993

Directional Solidification Studies In Ni-Al Alloys , Je-Hyun Lee

Retrospective Theses and Dissertations

Three solid phases are involved in the phase equilibria of the important intermetallic compound Ni[subscript]3Al near its melting point, [beta], [gamma][superscript]' (Ni[subscript]3Al), and [gamma]. The generally-accepted phase diagram involves a eutectic reaction between [gamma][superscript]' and [gamma], but some recent studies agree with an older diagram due to Schramm, which has a eutectic reaction between the [beta] and [gamma][superscript]' phases. The phase equilibria near Ni[subscript]3Al compositions was evaluated using quenched directional solidification experiments, that preserve the microstructures formed at the solidification front, and using diffusion couple experiments. These experiments show that the ...


Flexural And Tensile Characteristics Of Steel And Polypropylene Fiber Hybrid Reinforced Concrete Composite , Shahram Varzavand Jan 1993

Flexural And Tensile Characteristics Of Steel And Polypropylene Fiber Hybrid Reinforced Concrete Composite , Shahram Varzavand

Retrospective Theses and Dissertations

This research was conducted to analyze the flexural and tensile strengths of steel and polypropylene fiber hybrid concrete composite. The concrete used in fabrication of flexural beams and tensile cylinders consisted of type I portland cement, fine aggregate, and 3/4 inch coarse aggregate. The investigation involved 56 beams and 56 cylinders each divided into eight groups. Hooked steel fiber with an aspect ratio of 100 and volume fraction of 1.0% in conjunction with collated and fiberlated polypropylene fiber with volume fractions of 0.1, 0.2, and 0.3 percent was utilized. The center point loading and splitting ...


Synthesis, Rheology And Forming Of Y-Ba-Cu-O Ceramics , Timothy Myron Green Jan 1993

Synthesis, Rheology And Forming Of Y-Ba-Cu-O Ceramics , Timothy Myron Green

Retrospective Theses and Dissertations

Since the discovery of the high-Tc ceramic superconductors there has been a vast amount of work performed with regard to synthetic methods, and toward improving materials properties. Only in the last two to three years has there been significant amounts of work directed toward use of forming technologies to produce conductor shapes;A chemical synthesis route is discussed which results in a low-temperature precursor to Y-Ba-Cu-O ceramics. The synthesis is based on use of molten Ba(OH)[subscript]2·8H[subscript]2O as a molten salt flux. Two different chemical systems have been examined. The first, based on nitrate salts ...


Evaluation For Food Packaging Potential And Environmental Compatibility Of Novel Degradable Starch-Polyethylene Plastics , Meera Kim Jan 1993

Evaluation For Food Packaging Potential And Environmental Compatibility Of Novel Degradable Starch-Polyethylene Plastics , Meera Kim

Retrospective Theses and Dissertations

Linear low-density polyethylene films were prepared that contained native corn starch (7, 14, or 28%), low- or high-molecular weight oxidized- polyethylene (15%) and a pro-oxidant mixture (manganese 55 ppm and vegetable oil). Each plastic blend was first mixed in a twin-screw extruder at 195°C, pelletized, then cast into films using a single-screw extruder at 205°C. Oxidized-polyethylene addition to starch-polyethylene films did not impair transparency and thickness of the films, and relatively small reductions in film mechanical properties were observed;Thermal and photodegradation properties of each film were evaluated by 70°C forced-air oven treatment (20 days), by high-temperature ...


A Model System For The Study Of Chromized Coatings, Vishal Agarwal Jan 1993

A Model System For The Study Of Chromized Coatings, Vishal Agarwal

Theses and Dissertations

No abstract provided.


Reduced Cost 100 Ksi Minimum Yield Strength, Low Carbon, Low Alloy Steel Using Advanced Techniques, Peter T. Thompson Jan 1993

Reduced Cost 100 Ksi Minimum Yield Strength, Low Carbon, Low Alloy Steel Using Advanced Techniques, Peter T. Thompson

Theses and Dissertations

No abstract provided.


Toughening Mechanisms In A High Temperature Cyanate Ester Resin Modified With A Thermoplastic Polyimide, Michael Diberardino Jan 1993

Toughening Mechanisms In A High Temperature Cyanate Ester Resin Modified With A Thermoplastic Polyimide, Michael Diberardino

Theses and Dissertations

No abstract provided.


A Method For Introducing Marker Bands Onto A Fatigue Fracture Surface Using A Constant K (Max) Testing Procedure, Christopher Ragazzo Jan 1993

A Method For Introducing Marker Bands Onto A Fatigue Fracture Surface Using A Constant K (Max) Testing Procedure, Christopher Ragazzo

Theses and Dissertations

No abstract provided.


Investigation Into Critical Parameters Which Determine The Oxygen Refining Capability Of The Slag During Electroslag Remelting Of Alloy 718, Dwight D. Wegman Jan 1993

Investigation Into Critical Parameters Which Determine The Oxygen Refining Capability Of The Slag During Electroslag Remelting Of Alloy 718, Dwight D. Wegman

Theses and Dissertations

No abstract provided.


The Effect Of Welding Process On The Occurrence Of Weld Toe Microdiscontinuities In Hsla 80 Steel, James P. Reynolds Jan 1993

The Effect Of Welding Process On The Occurrence Of Weld Toe Microdiscontinuities In Hsla 80 Steel, James P. Reynolds

Theses and Dissertations

No abstract provided.


Characterization Of Zns-Gap Nano-Composites, Edwin T. Voiles Jan 1993

Characterization Of Zns-Gap Nano-Composites, Edwin T. Voiles

Retrospective Theses and Dissertations

It proved possible to produce consistent, high-quality nanocrystalline ZnS powders with grain sizes as small as 8 nm. These powders are nano-porous and are readily impregnated with GaP precursor, although inconsistently. Both crystal structure and small grain size of the ZnS can be maintained through the use of GaP. Heat treatment of the impregnated powders results in a ZnS-GaP composite structure where the grain sizes of the phases are on the order of 10--20 nm. Conventional powder processing should be able to produce optically dense ceramic compacts with improved mechanical properties and suitable IR transmission.


Investigation Of The Phase Equilibria And Phase Transformations Associated With The Bi2sr2cacu2oy Superconductor , Terry George Holesinger Jan 1993

Investigation Of The Phase Equilibria And Phase Transformations Associated With The Bi2sr2cacu2oy Superconductor , Terry George Holesinger

Retrospective Theses and Dissertations

Compositional measurements of the Bi[subscript]2Sr[subscript]2CaCu[subscript]2O[subscript]y (2212) solid solution region were performed in the TEM in order to separate intergrowth and solid solubility effects. Most of the solid solubility is accounted for by changes in the Sr and Ca concentrations. Changes in the Bi concentration account for the rest. Based on these results, two substitution schemes were determined to occur. The first is just the interchange between Sr and Ca. The second involves the substitution of Bi for Sr or Ca. It appears to be unfavorable for Sr or Ca to substitute for ...


Phase Relations In The System Ceo2-Al2o3-Sio2 In Inert And Reducing Atmospheres , Ahmet Cuneyt Tas Jan 1993

Phase Relations In The System Ceo2-Al2o3-Sio2 In Inert And Reducing Atmospheres , Ahmet Cuneyt Tas

Retrospective Theses and Dissertations

Phase relations and microstructure development were studied in the binary systems Ce [subscript]2O[subscript]3 (CeO[subscript]2)-Ce [subscript]2Si[subscript]2O[subscript]7, Ce [subscript]2O[subscript]3(CeO[subscript]2)-Al [subscript]2O[subscript]3 and Al [subscript]2O[subscript]3-Ce [subscript]2Si[subscript]2O[subscript]7 within the ternary CeO[subscript]2-Al [subscript]2O[subscript]3-SiO[subscript]2 in inert (pure argon and vacuum) and reducing (argon + 10% H[subscript]2) atmospheres in the temperature range 900° to 1970°C. High temperature phases were quenched by conventional quenching methods to determine the high temperature phase ...


Synthesis, Characterization, Phase Diagrams And Superconducting And Normal State Magnetic Properties Of La[Subscript 2-X]Sr[Subscript X]Cuo4 (0 [Less Than Or Equal To] X [Less Than Or Equal To] 0.08) And Electrochemically Oxidized La[Subscript 2-X]Sr[Subscript X]Cuo[Subscript 4 + Delta] (0 [Less Than Or Equal To] X [Less Than Or Equal To] 0.33, 0 [Less Than Or Equal To Delta Less Than Or Equal To] 0.12) , Fangcheng Chou Jan 1993

Synthesis, Characterization, Phase Diagrams And Superconducting And Normal State Magnetic Properties Of La[Subscript 2-X]Sr[Subscript X]Cuo4 (0 [Less Than Or Equal To] X [Less Than Or Equal To] 0.08) And Electrochemically Oxidized La[Subscript 2-X]Sr[Subscript X]Cuo[Subscript 4 + Delta] (0 [Less Than Or Equal To] X [Less Than Or Equal To] 0.33, 0 [Less Than Or Equal To Delta Less Than Or Equal To] 0.12) , Fangcheng Chou

Retrospective Theses and Dissertations

La[subscript] 2-xSr[subscript] xCuO[subscript]4 (0 ≤ x ≤ 0.15) can all be intercalated with oxygen by an novel electrochemical oxidation method. Bulk superconductivity is found with an onset T[subscript] c ≈ 40 K for the whole range 0.01 ≤ x ≤ 0.15; for x = 0.25 and 0.33, the electrochemical oxidation did not improve the superconducting properties. The magnetic susceptibility [chi](T = 50-320 K) data for La[subscript]2CuO[subscript]4.11 and La[subscript]1.92Sr[subscript]0.08CuO[subscript]4.07 are nearly identical with those of conventionally prepared La[subscript]1.85Sr[subscript]0 ...


Theoretical Study Of The Noble Metals On Semiconductor Surfaces And Ti-Base Shape Memory Alloys , Yungui Ding Jan 1993

Theoretical Study Of The Noble Metals On Semiconductor Surfaces And Ti-Base Shape Memory Alloys , Yungui Ding

Retrospective Theses and Dissertations

The electronic and structural properties of the (√3 x √3) R30° Ag/Si(111) and (√3 x √3) R30° Au/Si(111) surfaces are investigated using first principles total energy calculations. We have tested almost all experimentally proposed structural models for both surfaces and found the energetically most favorable model for each of them. The lowest energy model structure of the (√3 x √3) R30° Ag/Si(111) surface consists of a top layer of Ag atoms arranged as "honeycomb-chained-trimers" lying above a distorted "missing top layer" Si(111) substrate. The coverage of Ag is 1 monolayer (ML). We find ...


Impedance Spectroscopy And Nmr Studies Of Fast Ion Conducting Chalcogenide Glasses , Hitendra Kumar Patel Jan 1993

Impedance Spectroscopy And Nmr Studies Of Fast Ion Conducting Chalcogenide Glasses , Hitendra Kumar Patel

Retrospective Theses and Dissertations

Two fully automated, temperature controlled, impedance spectroscopy workstations have been developed for this project. Impedance spectroscopy studies of glasses have been performed over the wide frequency (1 Hz-1 GHz) and wide temperature (100-500 K) range;This study yields the first-ever full compositional (three decades) range examination of the Na[subscript]2S + B[subscript]2S[subscript]3 and K[subscript]2S + B[subscript]2S[subscript]3 systems. The activation energy is modeled using a modified Anderson-Stuart model that predicts well the results for the low alkali glasses. a.c. conductivity is examined through the electrical modulus formalism and the Kohlrausch-Williams-Watts decay ...


Nmr Studies Of The Structure Of Alkali Thioborate Glasses , Julia Anne Sills Jan 1993

Nmr Studies Of The Structure Of Alkali Thioborate Glasses , Julia Anne Sills

Retrospective Theses and Dissertations

The [superscript]11B NMR spectra of high purity xNa[subscript]2S + (1-x)B[subscript]2S[subscript]3 glasses (where 0 ≤ x ≤ 0.8), xK[subscript]2S + (1-x)B[subscript]2S[subscript]3 glasses (where 0 ≤ x ≤ 0.45), and mixed alkali x(Na[subscript]2S:K[subscript]2S) + (1-x) B[subscript]2S[subscript]3 glasses (where 0 ≤ x ≤ 0.25) are reported. The [superscript]11B NMR spectrum of vitreous B[subscript]2S[subscript]3 consists of a quadrupolar broadened single line and confirms a short range order of trigonally coordinated borons. As in the oxide analogs, as alkali sulfide is ...


Terfenol: A Study Of The Phase Equilibrium Diagram And The Solidification Process, Mary B. Anderson Jan 1993

Terfenol: A Study Of The Phase Equilibrium Diagram And The Solidification Process, Mary B. Anderson

Retrospective Theses and Dissertations

Terfenol is a rare earth-iron alloy that was first developed at the Naval Ordinance Laboratory because of its rare magnetostrictive properties. Terfenol is composed of terbium and dysprosium combined with iron in a composition Tb{sub x}Dy{sub 1{minus}x}Fe{sub 2}, where x{approximately}0.3. The objective of this work was to determine the growth characteristics of Terfenol and its dependence on solidification rate, temperature gradient, and stoichiometry. Specific goals of this work were to verify the phase equilibria that is currently accepted for the systems DyFe{sub 2} and TbFe{sub 2}, and establish ...


In Vivo And In Vitro Evaluations Of A Bioactive Ceramic Tooth Root Implant , Gabriele Gruss Niederauer Jan 1993

In Vivo And In Vitro Evaluations Of A Bioactive Ceramic Tooth Root Implant , Gabriele Gruss Niederauer

Retrospective Theses and Dissertations

The objective of this research was to test both the in vitro and in vivo effects of implant surface properties on soft tissue attachment to a bioactive ceramic tooth root implant. The ceramic material used for the tooth root was a composite of tricalcium phosphate and magnesium aluminate spinel, which is called "osteoceramic." For the in vitro cell attachment assays, pure tricalcium phosphate and spinel materials were used in addition to the osteoceramic. The osteoceramic was treated to produce three different surface structures: smooth, irregular and rough. Characterization of the materials included scanning electron microscopy, elemental dispersive analysis, wetting angle ...


Studies On The Optimization Of Deformation Processed Metal Metal Matrix Composites , Timothy Walter Ellis Jan 1993

Studies On The Optimization Of Deformation Processed Metal Metal Matrix Composites , Timothy Walter Ellis

Retrospective Theses and Dissertations

A methodology for the production of deformation processed metal metal matrix composites from hyper-eutectic copper-chromium alloys was developed. This methodology was derived from a basic study of the precipitation phenomena in these alloys encompassing evaluation of microstructural, electrical, and mechanical properties. The methodology developed produces material with a superior combination of electrical and mechanical properties compared to those presently available in commercial alloys;New and novel alloying procedures were investigated to extend the range of production methods available for these material. These studies focused on the use of High Pressure Gas Atomization and the development of new containment technologies for ...


Research On A Silicon Containing Electrom Beam Resist For Use In Optical Mask Manufacture, Michael William Stohl Jan 1993

Research On A Silicon Containing Electrom Beam Resist For Use In Optical Mask Manufacture, Michael William Stohl

Theses and Dissertations

No abstract provided.