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High-Temperature Corrosion of Aluminum Alloys: Oxide-Alloy Interactions and Sulfur Interface Chemistry

Description: The spallation of aluminum, chromium, and iron oxide scales is a chronic problem that critically impacts technological applications like aerospace, power plant operation, catalysis, petrochemical industry, and the fabrication of composite materials. The presence of interfacial impurities, mainly sulfur, has been reported to accelerate spallation, thereby promoting the high-temperature corrosion of metals and alloys. The precise mechanism for sulfur-induced destruction of oxides, however, is amb… more
Date: December 2000
Creator: Addepalli, Swarnagowri
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Characterization and Mechanical Properties of Nanoscale Precipitates in Modified Al-Si-Cu Alloys Using Transmission Electron Microscopy and 3D Atom Probe Tomography.

Description: Among the commercial aluminum alloys, aluminum 319 (Al-7wt%Si-4wt%Cu) type alloys are popularly used in automobile engine parts. These alloys have good casting characteristics and excellent mechanical properties resulting from a suitable heat treatment. To get a high strength in the 319 type alloys, grain refining, reducing the porosity, solid solution hardening, and precipitation hardening are preferred. All experimental variables such as solidification condition, composition, and heat treatme… more
Date: May 2007
Creator: Hwang, Junyeon
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Formation and Quantification of Corrosion Deposits in the Power Industry

Description: The presence of deposits on the secondary side of pressurized water reactor (PWR) steam generator systems is one of the main contributors to the high maintenance costs of these generators. Formation and transport of corrosion products formed due to the presence of impurities, metals and metallic oxides in the secondary side of the steam generator units result in formation of deposits. This research deals with understanding the deposit formation and characterization of deposits by studying the s… more
Date: May 2007
Creator: Namduri, Haritha
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Amorphization and De-vitrification in Immiscible Copper-Niobium Alloy Thin Films

Description: While amorphous phases have been reported in immiscible alloy systems, there is still some controversy regarding the reason for the stabilization of these unusual amorphous phases. Direct evidence of nanoscale phase separation within the amorphous phase forming in immiscible Cu-Nb alloy thin films using 3D atom probe tomography has been presented. This evidence clearly indicates that the nanoscale phase separation is responsible for the stabilization of the amorphous phase in such immiscible sy… more
Date: May 2007
Creator: Puthucode Balakrishnan, Anantharamakrishnan
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Diffusion Barriers/Adhesion Promoters. Surface and Interfacial Studies of Copper and Copper-Aluminum Alloys

Description: The focus of this research is to study the interaction between copper and the diffusion barrier/adhesion promoter. The behavior of copper sputter-deposited onto sputter-cleaned tantalum nitride is investigated. The data show that copper growth on tantalum nitride proceeds with the formation of 3-D islands, indicating poor adhesion characteristics between copper and Ta0.4N. Post-annealing experiments indicate that copper will diffuse into Ta0.4N at 800 K. Although the data suggests that Ta0.4N i… more
Date: August 2000
Creator: Shepherd, Krupanand Solomon
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Oxidation of alloys targeted for advanced steam turbines

Description: Ultra supercritical (USC) power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This research examines the steamside oxidation of alloys for use in USC systems, with emphasis placed on applications in high- and intermediate-pressure turbines.
Date: March 12, 2006
Creator: Holcomb, G. R.; Covino, B. S., Jr.; Bullard, S. J.; Ziomek-Moroz, M. & Alman, D. E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Environmentally Assisted Cracking in Light Water Reactors - Annual Report, January-December 2001.

Description: This report summarizes work performed by Argonne National Laboratory on fatigue and environmentally assisted cracking (EAC) in light water reactors (LWRs) from January to December 2001. Topics that have been investigated include (a) environmental effects on fatigue S-N behavior of austenitic stainless steels (SSs), (b) irradiation-assisted stress corrosion cracking (IASCC) of austenitic SSs, and (c) EAC of Alloy 600. The effects of key material and loading variables, such as strain amplitude, s… more
Date: June 1, 2003
Creator: Chopra, O. K.; Chung, H. M.; Clark, R. W.; Gruber, E. E; Hiller, R. W.; Shack, W. J. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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AN EVALUATION OF POTENTIAL LINER MATERIALS FOR ELIMINATING FCCI IN IRRADIATED METALLIC NUCLEAR FUEL ELEMENTS

Description: Metallic nuclear fuels are being looked at as part of the Global Nuclear Energy Program for transmuting longlive transuranic actinide isotopes contained in spent nuclear fuel into shorter-lived fission products. In order to optimize the performance of these fuels, the concept of using liners to eliminate the fuel/cladding chemical interactions that can occur during irradiation of a fuel element has been investigated. The potential liner materials Zr and V have been tested using solid-solid diff… more
Date: September 1, 2007
Creator: Keiser, D. D. & Cole, J. I.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Linearly Scaling 3D Fragment Method for Large-Scale Electronic Structure Calculations

Description: We present a new linearly scaling three-dimensional fragment (LS3DF) method for large scale ab initio electronic structure calculations. LS3DF is based on a divide-and-conquer approach, which incorporates a novel patching scheme that effectively cancels out the artificial boundary effects due to the subdivision of the system. As a consequence, the LS3DF program yields essentially the same results as direct density functional theory (DFT) calculations. The fragments of the LS3DF algorithm can be… more
Date: July 1, 2008
Creator: Wang, Lin-Wang; Lee, Byounghak; Shan, Hongzhang; Zhao, Zhengji; Meza, Juan; Strohmaier, Erich et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Low Temperature Surface Carburization of Stainless Steels

Description: Low-temperature colossal supersaturation (LTCSS) is a novel surface hardening method for carburization of austenitic stainless steels (SS) without the precipitation of carbides. The formation of carbides is kinetically suppressed, enabling extremely high or colossal carbon supersaturation. As a result, surface carbon concentrations in excess of 12 at. % are routinely achieved. This treatment increases the surface hardness by a factor of four to five, improving resistance to wear, corrosion, and… more
Date: December 7, 2007
Creator: Collins, Sunniva R.; Heuer, Arthur H. & Sikka, Vinod K.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Next generation spindles for micromilling.

Description: There exists a wide variety of important applications for micro- and meso-scale mechanical systems in the commercial and defense sectors, which require high-strength materials and complex geometries that cannot be produced using current MEMS fabrication technologies. Micromilling has great potential to fill this void in MEMS technology by adding the capability of free form machining of complex 3D shapes from a wide variety and combination of traditional, well-understood engineering alloys, glas… more
Date: December 1, 2004
Creator: Pathak, Jay P. (Machine Tool Research Center, University of Florida, Gainesville, FL); Payne, Scott W. T. (Machine Tool Research Center, University of Florida, Gainesville, FL); Gill, David Dennis; Ziegert, John C. (Machine Tool Research Center, University of Florida, Gainesville, FL) & Jokiel, Bernhard, Jr.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Processing and Protection of Rare Earth Permanent Magnet Particulate for Bonded Magnet Applications

Description: Rapid solidification of novel mixed rare earth-iron-boron, MRE{sub 2}Fe{sub 14}B (MRE = Nd, Y, Dy; currently), magnet alloys via high pressure gas atomization (HPGA) have produced similar properties and structures as closely related alloys produced by melt spinning (MS) at low wheel speeds. Recent additions of titanium carbide and zirconium to the permanent magnet (PM) alloy design in HPGA powder (using He atomization gas) have made it possible to achieve highly refined microstructures with mag… more
Date: December 1, 2007
Creator: Sokolowski, Peter Kelly
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
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Thermo-Mechanical Processing Parameters for the INCONEL ALLOY 740

Description: In 2000, a Cooperative Research and Development Agreement (CRADA) was undertaken between the Oak Ridge National Laboratory (ORNL) and the Special Metals Corporation (SMC) to determine the mechanical property response of the IN740 alloy to help establish thermo-mechanical processing parameters for the use of this alloy in supercritical and ultra-critical boiler tubes with the potential for other end uses. SMC had developed an alloy, commercially known as INCONEL alloy 740, which exhibited variou… more
Date: November 19, 2007
Creator: Ludtka, G.M. & Smith, G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Silicon Solar Cells with Front Hetero-contact and Aluminum Alloy Back Junction (Poster)

Description: The objectives of this report are: (1) to apply industrial back Al process in efficient n-wafer cells with a-Si:H front surface passivation; and (2) to evaluate the surface recombination velocity (SRV) of the a-Si:H passivated front surface with different surface preparation procedures.
Date: May 1, 2008
Creator: Yuan, H.-C.; Page, M. R.; Iwaniczko, E.; Xu, Y.; Roybal, L.; Wang, Q. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Plastic Straining of Iridium Alloy DOP-26 During Cup Sizing Operations

Description: DOP-26 iridium alloy cups are used for fuel cladding for radioisotope power systems. The cups are deep drawn and recrystallized prior to final fabrication operations. This study characterizes the plastic deformation of cups during a sizing operation following the recrystallization heat treatment. The purpose of the sizing operation is to achieve the specified roundness, diameter, and radius dimensions of the cup. The operation introduces various levels of plastic strain in the cup. Plastic stra… more
Date: September 1, 2007
Creator: Ohriner, Evan Keith; Ulrich, George B & Sabau, Adrian S
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Soft Phonons in (delta)-Phase Plutonium Near the (delta)-(alpha)' Transition

Description: Plutonium and its alloys exhibit complex phase diagrams that imply anomalous lattice dynamics near phase stability boundaries. Specifically, the TA [111] phonon branch in Ga-stabilized {delta}-Pu at room temperature shows a pronounced soft mode at the zone boundary, which suggests a possible connection to the martensitic transformation from the fcc {delta}-phase to the monoclinic {alpha}{prime}-phase at low temperatures. This work is a study of the lattice dynamics of this system by x-ray therm… more
Date: September 13, 2007
Creator: Xu, R; Wong, J; Zshack, P; Hong, H & Chiang, T
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Advanced Water-Gas Shift Membrane Reactor

Description: The overall objectives for this project were: (1) to identify a suitable PdCu tri-metallic alloy membrane with high stability and commercially relevant hydrogen permeation in the presence of trace amounts of carbon monoxide and sulfur; and (2) to identify and synthesize a water gas shift catalyst with a high operating life that is sulfur and chlorine tolerant at low concentrations of these impurities. This work successfully achieved the first project objective to identify a suitable PdCu tri-me… more
Date: January 7, 2009
Creator: Emerson, Sean; Vanderspurt, Thomas; Opalka, Susanne; Radhakrishnan, Rakesh & Willigan, Rhonda
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Isothermal Martensitic and Pressure-Induced Delta to Alpha-Prime Phase Transformations in a Pu-Ga Alloy

Description: A well-homogenized Pu-2 at.% Ga alloy can be retained in the metastable face-centered cubic {delta} phase at room temperature. Ultimately, this metastable {delta} phase will decompose via a eutectoid transformation to the thermodynamically stable monoclinic {alpha} phase and the intermetallic compound Pu{sub 3}Ga over a period of approximately 10,000 years [1]. In addition, these low solute-containing {delta}-phase Pu alloys are metastable with respect to an isothermal martensitic phase transfo… more
Date: January 18, 2008
Creator: Schwartz, A J; Wall, M A; Farber, D L; Moore, K T & Blobaum, K M
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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M5Si3(M=Ti, Nb, Mo) Based Transition-Metal Silicides for High Temperature Applications

Description: Transition metal silicides are being considered for future engine turbine components at temperatures up to 1600 C. Although significant improvement in high temperature strength, room temperature fracture toughness has been realized in the past decade, further improvement in oxidation resistance is needed. Oxidation mechanism of Ti{sub 5}Si{sub 3}-based alloys was investigated. Oxidation behavior of Ti{sub 5}Si{sub 3}-based alloy strongly depends on the atmosphere. Presence of Nitrogen alters th… more
Date: December 1, 2007
Creator: Tang, Zhihong
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
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Overcoming residual stresses and machining distortion in the production of aluminum alloy satellite boxes.

Description: Distortion frequently occurs during machining of age hardening aluminum alloys due to residual stresses introduced during the quenching step in the heat treatment process. This report quantifies, compares, and discusses the effectiveness of several methods for minimizing residual stresses and machining distortion in aluminum alloys 7075 and 6061.
Date: November 1, 2007
Creator: Younger, Mandy S. & Eckelmeyer, Kenneth Hall
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Calculation of Reactive-evaporation Rates of Chromia

Description: A methodology is developed to calculate Cr-evaporation rates from Cr2O3 with a flat planar geometry. Variables include temperature, total pressure, gas velocity, and gas composition. The methodology was applied to solid-oxide, fuel cell conditions for metallic interconnects and to advanced-steam turbines conditions. The high velocities and pressures of the advanced steam turbine led to evaporation predictions as high as 5.18 9 10-8 kg/m2/s of CrO2(OH)2(g) at 760 °C and 34.5 MPa. This is equival… more
Date: April 1, 2008
Creator: Holcomb, G. R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Enhanced High Temperature Corrosion Resistance in Advanced Fossil Energy Systems by Nano-Passive Layer Formation

Description: Due to their excellent corrosion resistance, iron aluminum alloys are currently being considered for use as weld claddings in fossil fuel fired power plants. The susceptibility to hydrogen cracking of these alloys at higher aluminum concentrations has highlighted the need for research into the effect of chromium additions on the corrosion resistance of lower aluminum alloys. In the present work, three iron aluminum alloys were exposed to simulated coal combustion environments at 500 C and 700 C… more
Date: June 14, 2007
Creator: Marder, Arnold R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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