Engineering Commons^™

Laser Treatment Of Ceramic Coatings On Defective Ceramic Glazed Tile, Gousinn Yu

Theses

Laser surface melting treatment was achieved by a 2 Kw CO2 surgical laser system.The partially defocused laser beam provided a circular spot with an annular energy distribution on the sample.

It is certain that laser surface treatment will do the job of repairing in defective ceramic tiles. All glazes provided by American Standard were tested for an ability of withstand laser treatment when coated on to a glazed tile. In order to repair the defective ceramic tile it is necessary to patch the damaged region with a cement. The cement must then be glazed in order to match that of …

A Study Of The Sintering Mechanism Of Pzt-Based Piezoceramics, Wayne Huebner, Pei Wen Lu, Wanrong Xue

Materials Science and Engineering Faculty Research & Creative Works

The densification behavior a PZT-based composition with additions of BiFeO3 as a flux was studied. Two different PZT powders were studied with varying initial particle sizes. Results clearly showed that BiFeO3 forms a low temperature liquid that aids in the densification behavior, with 3 mole% being optimum. Fine particle sizes substantially improved the density at low temperatures, with the net result that ceramics could be densified in air without the aid of a lead source. The corresponding electromechanical properties were typical of a hard PZT formulation.

Characterization Of Phase Transformation Behavior In Electrolytically Produced Indium-Thallium Shape Memory Alloy Films, Chong Ho Sonu, Thomas J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

Indium-thallium alloys in the range 15-38 at. % Tl were electrodeposited from a sulfate electrolyte by using pulsed current. The relationship between composition and phase structure of the alloys deposited was investigated with regard to the shape memory effect. To date there have been no reported experimental studies describing the electrodeposition of InTl alloys capable of undergoing such transformations. Not only did the deposited alloys exhibit the shape memory effect, but the composition-phase relationship exhibited was shown to deviate from that reported for alloys in an equilibrium condition. The results show that the temperature and the temperature interval for the …

Solid State Nmr Of Hydrogen In Thin Film Synthetic Diamond, G. Burnside, Roger M. Hawk, Richard A. Komoroski, W. D. Brown

Journal of the Arkansas Academy of Science

Thin film synthetic diamond promises to be the next semiconductor material, if the manufacturing processes which produce it can be controlled. Solid state nuclear magnetic resonance (NMR) using magic angle spinning (MAS) is used to measure the content of hydrogen in diamond which controls the resistivity of the diamond thin films. Spectral results are presented for proton NMR of thin film synthetic diamond. Experimental calibration techniques using BaF2 as the hydrogen standard will be discussed, as well as acquisition times, pulsing sequences, spinning rates, and rotor composition.

Processing And Characterization Of Samarium And Manganese Modified Lead Titanate Thin Film, Chen-Lung Fan, Wayne Huebner

Materials Science and Engineering Faculty Research & Creative Works

Samarium and manganese modified lead titanate thin films were fabricated by spin-coating an amorphous citrate precursor. These films transformed into an oxide film upon heat treatment at 400 degrees Celcius or above. Relatively large area and crack-free thin films could be obtained by this process both easily and inexpensively. The rheological behavior of the precursor solution, as well as its thermal decomposition and phase development were studied by means of DSC/TGA and XRD. The thickness and grain size of the oxide film were examined by TEM and SEM.

Reaction Of Titanocene Dichloride With Acetylenedicarboxylate, Tanya L. Hagler, Mark Draganjac, Paul M. Nave, J. Ed Bennett, Farooq Kahn, Robert Engelken, Gerard Williams, Chris Poole, Kwok Fai Yu

Journal of the Arkansas Academy of Science

The reaction of Cp2TiCl2 with either the mono- or dipotassium salt of acetylenedicarboxylic acid (ADC) gives high yields of an insoluble orange product. The insoluble compound shows potential semiconductor behavior, as evidenced by an apparent bandgap in the orange region of the visible spectrum. Under N2 ,the compound decomposes at 238° C, eventually losing approximately 46% total mass up to 1350° C. The exothermic decomposition in air, beginning at 235° C, results in the formation of titanium oxides.

Tetraethylene Gycol-Based Electrolytes For High Temperature Electrodeposition Of Compound Semiconductors, Chris Poole, Robert Engelken, Brandon Kemp, Jason Brannen

Journal of the Arkansas Academy of Science

We report an investigation of tetraethylene glycol (TEG) solutions of chloride salts (CdCl2 ,TeCl4 ,and HgCl2 ) for electrodeposition of films of CdTe and Hg1.xCdxTe, leading II-VI semiconductors. The high boiling point (314°C), below-room temperature (T) (-6°C) melting point, adequate metal chloride solubilities, and low toxicity of TEG make it a good candidate for electrodeposition at T > 200°C. Such temperatures tend to activate growth of larger crystallites than with aqueous electrolytes at T< 100 °C, as are advantageous in optoelectronic applications. Initial results do, indeed, indicate a dramatic increase in crystallinity with deposition temperature, especially for the CdTe films which are nearly amorphous when grown at room temperature. Hg1.xCdxTe films (x< 0.5) are marginally polycrystalline when grown at room temperature but also improve in crystallinity at higher growth temperatures. There appears to be a strong decrease in film adherence and uniformity as growth temperature increases for both materials probably because the greatly increased carrier concentrations at higher temperatures increase film conductivity which, in turn, supports easy electroplating of protruding loose dendritic and/or columnar crystallites, instead of the monolayer-by monolayer growth of lower conductivity material as occurs at lower temperatures, especially in the higher bandgap/lower conductivity CdTe. The same increase in film conductivity with temperature is responsible for the decrease in the relative photosensitivity of both the CdTe and Hg1.x CdxTe with temperature. At all temperatures, the inferior adherence, uniformity, and photosensitivity as well as the superior crystallinity of Hg1.xCd xTe over that of the CdTe are also explained by its lower bandgap and higher conductivity. On balance, however, the initial results prove the utility of high temperature TEG electrolytes for electrodepositing CdTe and Hg1.xCdxTe films with much better crystallinity than for those grown at lower temperatures, notably in aqueous baths.

Evaluation Of Photodiode Arrays For Use In Rocket Plume Monitoring And Diagnostics, Dallas Snider, M. Keith Hudson, Robert B. Shanks, Reagan Cole

Journal of the Arkansas Academy of Science

The spectroscopic analysis of plume emissions is a non-intrusive method which has been used to check for fatigue and possible damage throughout the pumps and other mechanisms in a rocket motor or engine. These components are made of various alloys. Knowing the composition of the alloys and for which parts they are used, one can potentially determine from the emissions in the plume which component is failing. Currently, Optical Multichannel Analyzer systems are being used which utilize charge coupled devices, cost tens of thousands of dollars, are somewhat delicate, and usually require cooling. We have developed two rugged instruments using …

Positron Annihilation Determination Of Damage Caused By Fatigue Cycling In The Superalloy Haynes 188, D. Hoeckelman, Hollis P. Leighly

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

Liquid-Mix Synthesis Of Oxide Powders And Thin Films Using A Starch-Based Polymer, Lone Wen F. Tai, Harlan U. Anderson

Materials Science and Engineering Faculty Research & Creative Works

A commercially available water-soluble starch derivative was used as the sole organic precursor in the Liquid-Mix synthesis of mixed-cation oxide powders and thin films. The acidified polymer (by nitric acid) was able to complex metal ions through the carboxylate ligands. Loosely agglomerated fine powders as well as dense thin films of complex oxides have been prepared using the same type of polymer. Oxide powders of Cr-doped lanthanum aluminate and yttrium aluminum garnet both crystallized in a single step, without forming any intermediate or second phases, when the amorphous resin intermediates were calcined at 650 °C and 750 °C for 2 …

Density Changes During Isothermal Annealing Of A Quenched Pb–7.45 At% Sn Alloy, Hollis P. Leighly, A. Belaidi

Materials Science and Engineering Faculty Research & Creative Works

The increase in density of a Pb–7.45 at% Sn alloy annealed at 150, 165, 180, and 195 °C and quenched at 20, 21.5, 23, 25, and 30 °C is measured isothermally. This increase in density accompanies the formation of the Sn‐rich phase precipitating as a function of time at the quenching temperature. The quenching is rapid enough to retain some vacancies at equilibrium at the annealing temperature. These vacancies accelerate the early stages of precipitation. The change in density versus time obeys the kinetic law allowing the determination of the reaction rate constant for several annealing and quenching conditions. Copyright …

Synthesis And Characterization Of Ysz Thin Film Electrolytes, C. C. Chen, M. M. Nasrallah, Harlan U. Anderson

Materials Science and Engineering Faculty Research & Creative Works

Dense, homogeneous and crack-free thin films (0.2-2 microm in thickness) of (ZrO2)0.84(YO1.5)0.16 (YSZ) were deposited on porous or dense substrates, at temperatures not exceeding 600°C, using a solution-deposition technique. The structural evolution and microstructure of the deposited films were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Raman spectroscopy revealed the presence of fine-grain cubic YSZ at annealing temperatures as low as 600°C. Grain growth occurred at higher temperatures as detected by atomic force microscopy (AFM). ac impedance spectroscopy was used to study the electrical characteristics of the YSZ films as a function of temperature. The ionic conductivity …

Correlation Of Wettability And Interfacial Reaction To The Densification And Dielectric Properties Of Fluxed-Batio₃, Sea-Fue Wang, Wayne Huebner, Joseph P. Dougherty

Materials Science and Engineering Faculty Research & Creative Works

Reducing the sintering temperature of BaTiO3 has typically been achieved through the use of a fluxing agent to promote densification by liquid phase sintering. Liquid phase formation in these systems is due either to the melting of the flux or to the formation of a eutectic liquid between the flux and BaTiO3. In this paper, the correlation between the wettability and interfacial reactions between fluxes and BaTiO3 with respect to the densification behavior associated with liquid phase sintering, and the resulting dielectric properties is presented. Fluxes used in this study include 5ZnO*2B2O3, 5CdO*2SiO2, Pb5Ge3O11, CuO*TiO2, 3Bi2O3*B2O3, and LiF.

Fabrication Of 2-2 Connectivity Pzt/Thermoplastic Composites For High Frequency Linear Arrays, Wayne Huebner, Mary R. Reidmeyer, L. Busse, Jeffry W. Stevenson

Materials Science and Engineering Faculty Research & Creative Works

An alternate approach for fabricating PZT/polymer composites with 2-2 connectivity with fine scales is described. Thin (less than or equal to 20 micrometers) sintered PZT plates and sheets of a thermoplastic polymer film (less than or equal to 10 micrometers) were bonded together via thermal processing. Stack sintering of tape cast PZT generated the necessary PZT plates, while tape cast polymers were used to control the thermoplastic thickness. Composite blocks were cut to required dimensions for linear arrays, electroded, and poled. Electromechanical properties were measured to evaluate the composites. The significance of this fabrication technique is that it is able …

An Investigation Of Recycled High Density Polyethylene Reinforced By Short Glass Fibers, Tony Lynn Alwardt

Masters Theses

The mechanical properties of recycled high density polyethylene (HDPE) reinforced by short glass fibers were investigated. The composites formed by an injection molding process were examined in terms of tensile strength, percent elongation, and hardness. Recycled HDPE was compared to virgin HDPE regarding the effects of fiber concentrations, types, sizes, and treatments. The addition of three coupling agents at different concentrations was investigated.

The virgin HDPE composites slightly outperformed their recycled HDPE counterparts; having higher tensile strength and hardness, but were less ductile. Increase in fiber concentration generally increased the tensile strength and hardness, but the concentration of fibers was …

Neutron-Scattering Study Of Librations And Intramolecular Phonons In Rb_{2.6}K_{0.4}C_{60}, D. Reznik, W. A. Kamitakahara, D. A. Neumann, J. R. D. Copley, J. E. Fischer, Robert M. Strongin, M. A. Cichy, Amos B. Smith Iii

Chemistry Faculty Publications and Presentations

We report the results of inelastic neutron-scattering measurements on Rb_2.6K_0.4C₆₀. Librational modes were observed as broad peaks with maxima between 4.1 and 4.7 meV, as the temperature is lowered from 300 to 12 K. As in K₃C₆₀, no change in the width or position of the librational peak was observed when the sample was cooled through the superconducting transition. Thus any coupling of the librations to electronic states is small. The magnitude of the orientational potential barrier was estimated from the librational peak frequency. A flat background observed in the …

The Corrosive Effects Of Salt Spray On Electrolytic Zinc Plated Mechanical Fasteners: The Case Of Clear Chromate And Yellow Dichromate Coatings On Medium Carbon Plated Bolts, Souleymane Boukari

Dissertations and Theses @ UNI

The purpose of this study was to evaluate the relationship between plating thickness and corrosion resistance of zinc coated medium carbon steel bolts under salt spray moisture conditions. Two types of zinc coatings were chosen for the study: the clear chromate zinc and the yellow dichromate zinc. One hundred and eighty 3/8-16 x 5 3/4 inch medium carbon steel bolts were selected for the test and divided into groups of 18. Two types of salt solution were used in the study: the low salt and the high salt. Bolts with various coatings tested with low salt concentration were composed of …

Superplastic Forming System Design, Keith Bain

Honors Capstone Projects and Theses

No abstract provided.

Static Fracture Behavior Of A Ceramic Matrix Composite At Elevated Temperatures, David M. Agins

Theses and Dissertations

This study investigated systematically the damage initiation damage progression, and failure modes of a ceramic matrix composite, Nicalon/CAS, when loaded in tension at elevated temperatures in the presence of air. A cross-ply lay-up, [0/90]_2s, was studied. The primary means of analysis were stress-strain data taken during monotonic and incremental load tests and crack density assessments. Testing was conducted at room temperature 700°C, and 850°C. The stress-strain response was consistent for monotonic and incremental loading, except for a decrease in failure load at the elevated temperatures. Initial damage progression was also consistent, but the damage leading to failure and …

Investigation Of Tension-Compression Fatigue Behavior Of A Cross-Ply Metal Matrix Composite At Room And Elevated Temperatures, Elizabeth A. Boyum

Theses and Dissertations

This research, the first load-controlled tension-compression fatigue testing to be performed on a MMC, extends the existing knowledge of MMC fatigue damage mechanisms to include the tension compression loading condition. To accomplish this, a (0/90)2, SCS-6/Ti-15-3 laminate was subjected to tension- tension fatigue at room temperature, and tension-compression fatigue at both room temperature and 427°C. Stress and strain data was taken to evaluate the macro-mechanic behavior of the material. Microscopy and fractography were performed to characterize the damage on a micro-mechanic level. On a maximum applied stress basis, the room temperature tension-tension specimens had longer fatigue lives than the room …

Influence Of Embedded Optical Fibers On Compressive Strength Of Advanced Composites, Stefan B. Dosedel

Theses and Dissertations

This study investigated the effects of embedding optical fibers into advanced composite materials. This combination was meant to simulate 'smart structures' that have been shown to sense several different variables in the composite including strain, temperature, and damage. A laminate orientation taken from an existing aircraft structure was used to fabricate sixteen groups of specimens which were subjected to compression testing in an IITRI fixture to determine the ultimate compressive strength and modulus of elasticity. Ten of these groups were fabricated with optical fibers while the other six were control groups and contained no optical fibers. This study showed that …

Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite Under Strain Controlled Tension-Tension And Tension-Compression Loading, James J. Gudaitis

Theses and Dissertations

This stuidy investigates the fatigue response of a cross-ply [0/90]_2s Nicalon/Calcium Aluminosillicate (Nicalcc/CAS) ceramic matrix composite at room temperature under strain controlled tension-tension and tension-compression fatigue loading. The primary objectives were to determine strain fatigue limits for both loading cases and to complete a fatigue life diagram (Δe-N) for all tests. Failure mechanisms were also studied. The average initial modulus value for this lay-up was 120 GPa. The ultimate tensile strain was 0.00988 mn/mm (285 MPa). Eight tests were conducted with maximum strains that ranged from 0.00300 mm/mm to 0.00722 mm/mm. The tension-tension fatigue limit was found to be …

Investigation Of Compressive Behavior For Metal Matrix Composites With A Circular Hole, Janet L. Gooder

Theses and Dissertations

This study investigated the notched and unnotched macromechanical response due to micromechanical behavior of [0/±45/90]_S SCS-6/β 21 S and [0/90] _2S Sigma/β 21S subjected to static compressive loads at room temperature. The stress-strain behavior and mechanical response in the presence of a circular hole was examined. A clear description of the progressive nature of damage, which ultimately resulted in failure, was provided. The effect of elevated temperature was shown for SCS-6/β 21S. The ultimate compressive strength and elastic modulus were reported for both MMCs. Sigma/β 21S and SCS-6/β 21S were mildly notch sensitive at room temperature. Notch sensitivity of …

Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite At Elevated Temperatures Under Tension-Tension Loading, Richard J. Tuznik

Theses and Dissertations

A study was conducted which investigated the behavior of a Nicalon/ Calcium-Aluminosilicate (Nicalon/CAS) cross-ply [0/90]_2S ceramic matrix composite at elevated temperatures under tension-tension fatigue loading. Tension-tension fatigue tests were performed with a load ratio of R = 0.10 and a frequency of 10 Hertz at 700°C and 850°C. These results were compared to results from a previous study conducted at room temperature. Material behavior and damage was recorded by fatigue life curves, elastic modulus' maximum and minimum strain, acetate replication techniques, and post-mortem fractography. Analysis of these results showed identical matrix dominated damage behavior at RT and 700°C. Ultimate …

Electrical Properties Of P-Type Gainp2, Roy S. Calfas

Theses and Dissertations

The GaInP₂ n⁺—p junction diode has recently become important to the development of high efficiency GaInP₂GaAs dual junction solar cells, which have a demonstrated air mass 1.5 conversion efficiencies in excess of 27. In order to study the effects of long term exposure to the space environment, the GaInP₂ n+—p junction diodes were irradiated with a 1 MeV electron beam with a fluence of 10¹⁶ electrons/cm². Since little is known about deep level defects traps in GaInP₂, a deep level transient spectroscopy DLTS study was made to characterize the …

Experimental Analysis Of Heat Transfer Characteristics And Pressure Drop Through Screen Regenerative Heat Exchangers, Jeffrey L. Wiese

Theses and Dissertations

This study investigated the effect on heat transfer and friction characteristics for screen regenerative heat exchangers with the screen thickness reduced by rolling. The experiments were performed on 250 and 325 mesh, 304 stainless steel screen using helium gas. Reynolds numbers, based on hydraulic radius, Re, were between 10 and 100. Both the Colburn factor, StPr^2/3, and friction factor, f, decreased as the screen thickness was reduced. A correlation was found for predicting friction factor, f. The drag coefficient per screen remained nearly unchanged for thicknesses reduced not more than 30 percent. The decrease in Colburn factor was …

Nonlinear Large Deformation Theory Of Composite Arches Using Truncated Rotations, Daniel A. Miller Ii

Theses and Dissertations

This research has been directed toward capturing large cross sectional rotation during bending of composite arches. A potential energy based nonlinear finite element model that incorporates transverse shear strain was modified to include large bending rotations. Large rotation kinematics were derived in a vector format leading to nonlinear strain that was decomposed into convenient forms for inclusion in the potential energy function. Problem discretization resulted in a finite element model capable of large deformations. Riks method and displacement control solution techniques were used. Numerous problems and examples were compared and analyzed. Code vectorization and parallelization were briefly examined to improve …

The Effects Of Optical Feedback On Polarization Of Vertical Cavity Surface Emitting Lasers, Gregory J. Vansuch

Theses and Dissertations

Vertical Cavity Surface Emitting Lasers VCSELs are a type of semiconductor laser with a cavity oriented orthogonally to the planes of material growth. These lasers differ from conventional edge emitting lasers in several important ways. They have symmetric output beams and they are easily built into two dimensional arrays, making them very attractive as photonic components. The characteristic of interest in this thesis is polarization. While the asymmetric cavities of edge emitters exhibit a clear preference for light polarized in a particular direction, the cylindrically symmetric cavity of a VCSEL has no clear preference. Therefore, it should be relatively easy …

Characterization Of Fatigue Damage In A Metal Matrix Composite (Scs-6/ Ti-15-3) At Elevated Temperature, Brian P. Sanders

Theses and Dissertations

The fatigue characteristics of a unidirectional titanium based metal matrix composite (MMC) were investigated at elevated temperature (427°C). A hybrid strain controlled loading mode was used to subject the 0° and 90° laminas to fatigue. Along with the fatigue tests, microscopy and analytical modeling ware also conducted. This combination of activities led to defining the initiation and progression of damage and deformation in the MMC. Hen loading was parallel to the fiber on, the fatigue behavior was initially dominated by creep deformation of the matrix. Then, depending on the maximum strain, specimen failure was the result either fiber fractures or …

A Nonlinear Three-Dimensional Micromechanics Model For Fiber-Reinforced Laminated Composites, David D. Robertson

Theses and Dissertations

In this study, a three-dimensional micromechanics model is developed. The present capabilities of the model include both unidirectional and laminated composite layups with various types of nonlinear analysis such as a thermoelastic-plastic analysis employing the Prandtl-Reuss flow relations, a thermoviscoplastic analysis using Bodner-Partom unified constitutive theory, and an interfacial damage progression scheme based on a statistical interfacial failure criteria. Such nonlinearities are critical factors during thermomechanical fatigue TMF loading of high temperature composites. Solutions were obtained and extensive comparisons performed with existing micromechanics models, finite element analysis, and experiment with excellent results. In addition, the analysis was developed to require …