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Materials Science and Engineering

2009

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Articles 331 - 356 of 356

Full-Text Articles in Engineering

Investment Shell Cracking, Edward A. Druschitz Jan 2009

Investment Shell Cracking, Edward A. Druschitz

Masters Theses

"Shell cracking is the single greatest problem affecting investment casters. A clearer understanding of the factors affecting the melt profile of the wax can be gained using computational fluid dynamics (CFD) to model the interaction among 1) the thermal conductivity of the wax, 2) the thermal conductivity of the shell, and 3) the temperature of the autoclave during the autoclave de-waxing cycle. The most favorable melt profile results from a high autoclave temperature (438⁰K to 458⁰K) and saturated thermal conductivity of the shell (1.36 to 1.40 Wm⁻¹k⁻¹) in conjunction with a low wax thermal conductivity (0.33 Wm⁻¹k⁻¹). These parameters reduce …

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Inclusion Modification In Steel Castings Using Automated Inclusion Analysis, Vintee Singh Jan 2009

Inclusion Modification In Steel Castings Using Automated Inclusion Analysis, Vintee Singh

Masters Theses

"The objective of this research is to study the effects of changing the melt and ladle practices (deoxidation, slag, refractory types, etc.) in steel foundries on the cleanliness and toughness of steel castings. This study used an automated inclusion analyzer ASPEX PICA-1020, which provides a rapid and accurate method for determining the composition, size, number, and spacing of the inclusions present in steel samples. The first step in this research was to complete a series of industrial tests to benchmark the current foundry ladle practices with respect to cleanliness of the cast steel. Trials were conducted at steel foundries using …

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Synthesis Of Surface Composites Using Friction Stir Processing, Bharat Gattu Jan 2009

Synthesis Of Surface Composites Using Friction Stir Processing, Bharat Gattu

Masters Theses

"Composite materials have an edge over monolithic materials due to higher strength/stiffness - to - density ratios, improved fatigue and wear resistance and better high temperature properties. Surface composites provide improved tribological properties such as wear resistance, friction coefficient and corrosion resistance. Friction stir processing (FSP) which originated from friction stir welding (FSW - a method for joining aluminum alloys) is a solid state technique to modify the microstructure of the alloys. During FSP the frictional heat generated at the tool - work piece interface plasticizes the material allowing it to flow around the pin. The combined effect of the …

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Fatigue Of Friction Stir Welded Lap Joints With Sealants, Kenneth Doering Jan 2009

Fatigue Of Friction Stir Welded Lap Joints With Sealants, Kenneth Doering

Masters Theses

"A lack of understanding of corrosion fatigue in friction stir welded aluminum joints prevents friction stir welding from being implemented in aerospace applications. Fatigue testing reveals a 60-75% reduction in the fatigue life of friction stir welded aluminum lap joints immersed in 3.5% NaCl solution (corrosion fatigue) compared with that of lap joints tested in ambient air. The loss in fatigue life is attributed to accelerated fatigue cracking due to hydrogen environment embrittlement. Two polymer sealant candidates are investigated: silicone rubber and nylon-11. Both sealant candidates can be applied prior to welding and seal the faying surface gaps in lap …

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Quench Factor Analysis Of Wrought And Cast Aluminum Alloys, Vishwanath Gandikota Jan 2009

Quench Factor Analysis Of Wrought And Cast Aluminum Alloys, Vishwanath Gandikota

Masters Theses

"Mechanical property variation across the cross section of heat treatable aluminum alloys is a major concern. To minimize such variation, a proper understanding of kinetic transformations and estimation of mechanical properties is required. The Jominy end quench test has been used successfully to study the effect of quench rate on the final heat treated properties of wrought and cast aluminum alloys. This test produces varying cooling rates along the length of a cylindrical sample cooled with water at one end. Jominy bars of wrought and cast aluminum alloys were solutionized, endquenched, and aged to T6 temper condition after delays of …

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The Effect Of Near-Surface Metallurgy On The Machinability Of Cast Iron, William Dewey Peach Jan 2009

The Effect Of Near-Surface Metallurgy On The Machinability Of Cast Iron, William Dewey Peach

Masters Theses

"The increasing performance and durability of cutting tool inserts have created metallurgical challenges for production foundries to produce near-net shaped castings within strict dimensional tolerances. In order for foundries to take full advantage of the increased cutting speed capabilities, it becomes necessary to reduce machining allowances and produce much more stable casting surfaces. To accomplish this, a better understanding of the complex microstructures formed within the first 0.120 in. (3 mm) of the mold/metal interface (as-cast surface) is necessary. The goal of the work presented here was to examine the microstructures formed in the near-surface region of gray iron castings, …

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Microstructural Characterization And Heat Treatment Of A-286 Turbine Buckets, Christopher Michael Bradley Jan 2009

Microstructural Characterization And Heat Treatment Of A-286 Turbine Buckets, Christopher Michael Bradley

Open Access Theses & Dissertations

A-286 is an iron-based superalloy used extensively in land-based gas turbines for 2nd stage (low pressure) buckets and 1st and 2nd stage wheels. Although A-286 may appear to some as just another austenitic stainless steel, its elevated temperature properties are attributed to ' precipitate structures, effective distributions of alloy carbides in the forms of M23C6, M6C and MC, and solid solution strengthening. Unfortunately over the course of these components service lives microstructural degradation develops in the form of η-phase formation. The presence of η-phase, especially in large quantities, can have a negative effect on stress rupture properties. Resistance to creep …

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Tensile Strength And Failure Criterion Of Analog Lithophysal Rock, James A. Nott Jan 2009

Tensile Strength And Failure Criterion Of Analog Lithophysal Rock, James A. Nott

UNLV Theses, Dissertations, Professional Papers, and Capstones

This project determines the tensile strength of lithophysal analog rock and presents failure criteria that can be used by geotechnical engineers to evaluate underground structures in rock. The physical and mechanical properties that are related to the failure criterion, such as porosity, compressive strength and modulus of elasticity, are also discussed. Experimental tensile tests were made using direct uniaxial and indirect Brazilian tests. Three 4-inch specimens were fabricated and tested in direct uniaxial tensile tests using Hydro-Stone TB. The results showed that the elastic tensile modulus of elasticity was within two percent of existing data for the compressive modulus of …

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Effects Of Mechanical And Metallurgical Variables On Creep, Fracture Toughness And Crack Growth Behavior Of Alloy 617, Muhammad Hasibul Hasan Jan 2009

Effects Of Mechanical And Metallurgical Variables On Creep, Fracture Toughness And Crack Growth Behavior Of Alloy 617, Muhammad Hasibul Hasan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Nickel base Alloy 617 has been identified to be a suitable structural material for heat exchanger applications in both hydrogen and electricity generation using nuclear heat. A maximum operating temperature of 950°C has been specified by department of energy (DOE) for both applications to achieve a maximum possible efficiency. Therefore, an extensive investigation has been pursued to evaluate time-dependent-deformation (Creep) of this alloy as functions of temperature and applied load. The results indicate that this alloy exhibited severe creep deformation, characterized by development of an instantaneous tertiary creep region at 850 and 950°C under applied stresses corresponding to its 35% …

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The Functionalization Of Carbon Nanosheets, Ronald A. Quinlan Jan 2009

The Functionalization Of Carbon Nanosheets, Ronald A. Quinlan

Dissertations, Theses, and Masters Projects

Carbon nanosheets are a novel two-dimensional nanostructure made up of 2-20 graphene atomic planes oriented with their in-plane axis perpendicular to the growth substrate. Previous efforts in developing nanosheet technology have focused on the characterization of the system and their development as an electron source due to the high atomic enhancement factor (beta) and low turn on field. Further investigation of nanosheets as high surface area electrodes revealed poor wetting by polymeric material and extreme hydrophobic behavior.;Because nanosheet technology has promise as a high surface area electrode material, this thesis research has focused on three areas of interest: the enhancement …

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Corrosion And Leaching Study Of Low Copper (I) Oxide Paints For Antifouling Application, Hansika Parekh Jan 2009

Corrosion And Leaching Study Of Low Copper (I) Oxide Paints For Antifouling Application, Hansika Parekh

Material Science and Engineering Theses

Global environmental concern/economy challenges necessitate innovation of AFP's with novel additives offering improved corrosion protection, and biofouling resistance. Dispersing large proportions (40-70%) of Cu/Cu2O in paints although inexpensive produces excessive leaching & heavy accumulation of copper in marine. This study aims at formulating AFP's with reduced Cu2O levels along with novel additives, targeting controlled copper release around 15 ug/cm2/day. In the present study several formulations were prepared using Viscoplex (PAMA in mineral oil), Ionomer ED-SPAN and CuDDP. Substitute ocean water was prepared to simulate marine environmental conditions and perform leaching studies of different formulations. A variety of preliminary elimination tests …

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Mechanism Of Wear Protection Of Al-Alloys Using Xanes, Beibei Wang Jan 2009

Mechanism Of Wear Protection Of Al-Alloys Using Xanes, Beibei Wang

Material Science and Engineering Theses

The mechanism of wear protection of Al-Si alloys in wear tests using lubricants containing Zinc dialkyl-dithiophosphate (ZDDP), Dialkyl dithiophosphate (DDP) , Amine phosphates, Thiadiazole, Antimony 0, 0-dialkylphosphorodithioate (SbDDP) was studied. Using techniques such as XANES this study examined the tribological behavior of these compounds and the characteristics of the tribofilms formed by them. High frequency reciprocating rig (HFRB) tests were conducted with lubricant containing these five antiwear additives were compared in both base oil and fully formulated oil. The tribofilms formed were then analyzed by a variety of techniques such as Scanning electron microscopy of the film and the composition …

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Negative Differential Resistance In Hydrated Deoxyribonucleic Acid Thin Films Mediated By Diffusion-Limited Redox Reaction, Hou Kuan Lee Jan 2009

Negative Differential Resistance In Hydrated Deoxyribonucleic Acid Thin Films Mediated By Diffusion-Limited Redox Reaction, Hou Kuan Lee

Material Science and Engineering Theses

The charge transport mechanisms in DNA proposed in the literature cover broad range of possibilities including molecular band conduction, superexchange, multistep hole hopping, and polaron hopping. The reason for the surprisingly diverse results is all the variables in the experiments - DNA sequence, DNA characteristic (single molecule or bundle, DNA length), the metal/DNA contacts, and the environmental dissimilarities in temperature, humidity, etc. In this study, the humidity effect on the electrical conduction in DNA was systematically investigated in a humidity chamber over the wide range of DC voltage. The exponential increase in conduction with increasing humidity was observed for the …

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Effect Of Aging On The Transformation Of Phases In Solder Joint Of Pbga Packaging, Jeong-Min Kim Jan 2009

Effect Of Aging On The Transformation Of Phases In Solder Joint Of Pbga Packaging, Jeong-Min Kim

Material Science and Engineering Theses

This study investigates the microstructural characteristics of 3.0Ag-0.5Cu-Sn (SAC305) solder joint as in assembled state, and their evolution with aging treatment at 100 and 150°C for various hours. Specific aim of the study is 1) to understand thermodynamic stability of as-reflowed microstructure (β-Sn dendrite, inner dendrite Cu6Sn5 intermetallic (IMC) compound, and the eutectic structure), 2) to find direction of their change with aging, and 3) to relate interfacial reaction to such evolution in microstructures. This investigation is spurred by the findings made in a separate study where fatigue resistance of solder joint and failure location shows markedly keen dependence on …

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Synthesis And Tribological Properties Of Dlc Film By Rf Pacvd: Effect Of Processing Parameters, Pruthul Desai Jan 2009

Synthesis And Tribological Properties Of Dlc Film By Rf Pacvd: Effect Of Processing Parameters, Pruthul Desai

Material Science and Engineering Theses

Diamond-like carbon (DLC) films, have gained grounds in many industries ranging from automobile and oil and gas to electronics and bio fields due to their low friction and wear rate, chemical inertness and high hardness. Radio Frequency (RF) plasma discharge has been widely used to produce amorphous carbon films, because this method can be applied not only for etching but also for deposition on insulators. The advantage of RF plasma discharge is the application for wide area and the stability as compared with direct current (DC) plasma. The properties of DLC films deposited by RF plasma-assisted chemical vapor deposition (PACVD) …

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Solar Selective Optical Coating Made With Metal Nanopaticles For Photovoltaic Thermal Applications, Xin Wang Jan 2009

Solar Selective Optical Coating Made With Metal Nanopaticles For Photovoltaic Thermal Applications, Xin Wang

Material Science and Engineering Theses

The goal of this research is to fabricate solar selective reflector with suitable optical properties and high thermal and chemical stability for using in the photovoltaic thermal window. While the reflector allows some transmittance in visible spectrum, the mid/far infrared light needs to be reflected back into the window minimizing the IR radiation loss. Nickel/alumina composite was proposed as the solar selective reflector. This thesis consists of two parts - one part concerning the fabrication and characterization of solar selective reflector and another dealing with an optical modeling to simulate the optical properties of the solar selective reflector. The alumina …

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Tribological Behavior Of Nanocrystalline Metals Prepared By Surface Mechanical Attrition Treatment, Michael Frink Jan 2009

Tribological Behavior Of Nanocrystalline Metals Prepared By Surface Mechanical Attrition Treatment, Michael Frink

Material Science and Engineering Theses

Nanocrystalline materials have shown great promise for a number of engineering applications ranging from structural and electronics to biomaterials and drug delivery. Nanoscale grain structures can cause tremendous improvements in strength, hardness and other mechanical properties. This is partially due to the suppression of dislocations within nanocrystalline grains and the entirely different deformation modes active at that scale. In spite of anticipated benefits, very little work has been performed to explore nanoscale effects on the tribological behavior of materials. Surface Mechanical Attrition Treatment (SMAT) is an effective and economical method to produce nanostructured surface layers in bulk materials. The process …

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Structural, Magnetic And Surface Properties Of Rf Magnetron Sputtered Undoped Lanthanum Mangnite Thin Films, Varad Rajan Sakhalkar Jan 2009

Structural, Magnetic And Surface Properties Of Rf Magnetron Sputtered Undoped Lanthanum Mangnite Thin Films, Varad Rajan Sakhalkar

Material Science and Engineering Theses

In the present study, polycrystalline and epitaxial undoped Lanthanum Manganite (LMO) thin films were deposited by using RF magnetron sputtering on three substrates, Si (100), MgO (100) and LaAlO₃ (100) to study the influence of the misfit strain at the substrate/film interface. The effect of processing conditions on the synthesis of LMO films was studied by conducting deposition on Si wafer. Films were characterized by X-Ray Diffraction (XRD), Atomic Force Microscope (AFM), Energy Dispersive Spectroscopy (EDS) and Superconducting Quantum Interference Device (SQUID) to investigate the influence of processing parameters on their structure and properties. Based on the initial study on …

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Morphology And Cathode Optimization For Efficient Polymer Bulk Heterojunction Solar Cells, Yi Yang Jan 2009

Morphology And Cathode Optimization For Efficient Polymer Bulk Heterojunction Solar Cells, Yi Yang

Material Science and Engineering Theses

Efficiency of polymer bulk heterojunction solar cell is highly dependent on the active layer morphology and can be controlled by specific experimental conditions. In this work, the influences of P3HT:PCBM blend composition, solution concentration, and the thermal annealing on the cell performance are presented. The maximum of Jsc and FF are reached when the weight percentage of PCBM in the blend is 60 % under which both high density of donor and accepter interfaces expecting the formation of efficient percolated electron transport paths. 36 mg/ml is found to be the optimum solution concentration for P3HT:PCBM blend and it can be …

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Effect Of Reflow Variables On The Nanoscale Mechanical Properties Of Lead Free Solders, Tonye Adeogba Jan 2009

Effect Of Reflow Variables On The Nanoscale Mechanical Properties Of Lead Free Solders, Tonye Adeogba

Material Science and Engineering Theses

This study presents findings on the nano-mechanical properties of binary and ternary (Cu, Ag) - Sn Solders. Nanoindentation with a cube corner tip was used on Sn-Ag and SAC405 alloy compositions to investigate the effect of reflow process variables on the properties of hardness and reduced modulus on a nanoscale. The specimens tested were sandwich solder joints where Cu was the substrate. While the reflow variables of cooling rate and reflow time were found to cause changes in IMC morphology and solder matrix microstructure, the nano hardness and reduced modulus were independent of these variables. Low max loads coupled with …

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Thioacetamide As A Sulfur Precursor For Chalcopyrite Thin Film Solar Cells, Alex Alphonse Jan 2009

Thioacetamide As A Sulfur Precursor For Chalcopyrite Thin Film Solar Cells, Alex Alphonse

Material Science and Engineering Theses

Chalcopyrite CuInS₂ (CIS) thin films have the potential to be used in low cost terrestrial photovoltaic applications. The band gap of CIS is around 1.5 eV [1] and it well matches with the solar spectrum. However, the power conversion efficiencies in CIS solar cells are presently limited to 13.2% [2]. CIS absorber layers can be produced in a simple two-stage process consisting of the physical vapor deposition of a Cu-In bilayer - generally with Cu-rich composition - and its subsequent sulfurization under sulfur atmosphere made by either sulfur vapor or H₂S. While sulfur vapor is a safer option than H₂S …

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Synergistic And Antagonistic Effect Of Sulfur-Based Additives On The Performance Of Greases With Zddp And Ptfe, Arunya Suresh Jan 2009

Synergistic And Antagonistic Effect Of Sulfur-Based Additives On The Performance Of Greases With Zddp And Ptfe, Arunya Suresh

Material Science and Engineering Theses

Lithium-base greases constitute about 50% of the grease market. The current trend is towards developing greases with longer working life and wider application flexibility. To address this concern, greases are blended with antiwear and extreme pressure (EP) additives that serve to reduce wear and increase the operating life of the machinery by creating a low strength, shearable film on the moving surfaces. In the current study, greases were developed to address the need for both performance as prescribed by the ASTM standards D2266 and D2596, respectively. The actual bearing conditions vary significantly with load, rpm and duration of test. These …

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Synthesis And Dip-Pen Nanolithographical Patterning Of Ferrite Nanoparticles, Jingwen He Jan 2009

Synthesis And Dip-Pen Nanolithographical Patterning Of Ferrite Nanoparticles, Jingwen He

Material Science and Engineering Theses

Magnetic nanoparticles are of great interest for researchers from a wide range of disciplines, including magnetic fluids, catalysis, biotechnology/biomedicine, magnetic resonance imaging, data storage, and environmental remediation. Ferrites, a class of ferrimagnetic ceramic compounds with the chemical formula of MFe₂O₄, where M represents any one of several metallic elements such as Mg, Fe, Co, Ni, Cu and so on, are commonly used magnetic materials for nanoparticles. Magnetite (Fe3O₄) is the prototype of ferrites. Magnetite nanoparticles have been prepared through the co-precipitation of Fe²⁺ and Fe³⁺ aqueous salt solutions by addition of base. They exhibit a size distribution from 4 nm …

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Metal Induced Crystallization Of Silicon Thin Films, Sandeep Kumar Raju Sangaraju Jan 2009

Metal Induced Crystallization Of Silicon Thin Films, Sandeep Kumar Raju Sangaraju

UNLV Theses, Dissertations, Professional Papers, and Capstones

Low temperature crystallization of thin film silicon is important for many industrial applications including flat panel displays and silicon thin film solar cells. Unfortunately this remains a major challenge since crystallization temperature of silicon is above 1,000 degrees Celsius, thus limiting to substrates that can tolerate high temperatures. The inability to deposit crystalline thin films on glass substrates is the reason why flat panel display industry uses amorphous silicon for LCD active matrix displays. Thus the ability to deposit crystallized thin film silicon at low temperatures will have significant impact on thin film silicon applications. It has been observed that …

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Effectiveness Of Thermal Oxidation In Relation To Anterior Cervical Plates, Katherine A. Miyashiro Jan 2009

Effectiveness Of Thermal Oxidation In Relation To Anterior Cervical Plates, Katherine A. Miyashiro

Master's Theses

Ti-6Al-4V anterior cervical plates (ACP) are used in spinal fusion surgeries to fixate cervical vertebrae during graft adhesion. However, documented cases of implant failure and the potential for ACP corrosion raise concerns regarding any degradation of material resulting from extended implantation. In addition, abrasion during implantation may damage a section of the protective oxide layer, potentially exposing surrounding tissues to the harmful effects of bare titanium, aluminum, and vanadium. Thermal oxidation has been shown to improve corrosion-resistance and wear-resistance, depending on temperature and time. To quantify the attributes of the thermally grown oxide layer, Ti-6Al-4V coupons underwent thermal oxidation treatments …

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Cleaner Metallurgical Industry In Serbia: A Road To The Sustainable Development, Zeljko J. Kamberovic Dec 2008

Cleaner Metallurgical Industry In Serbia: A Road To The Sustainable Development, Zeljko J. Kamberovic

Zeljko J Kamberovic

Since the sustainable development has been a global and fundamental objecttive, a metallurgical industrial sector faces some of the most difficult sustainability challenges of any industrial sector. On the other hand, the metallurgical production in Serbia is a very important part of the economy. Due to present facilities and technologies, metallurgical companies face a great challenge to fulfill the requirements introduced by legislature referring to the cleaner production and sustainable development. The state of art in the production, facilities, pollution with some answers to imposed challenges is presented.

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