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in subjects: "Phase Studies"  
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Modeling of transformation toughening in brittle materials

Description: Results from modeling of transformation toughening in brittle materials using a discrete micromechanical model are presented. The material is represented as a two-dimensional triangular array of nodes connected by elastic springs. Microstructural effects are included by varying the spring parameters for the bulk, grain boundaries, and transforming particles. Using the width of the damage zone and the effective compliance (after the initial creation of the damage zone) as measures of fracture to… more
Date: January 24, 1992
Creator: LeSar, R.; Rollett, A.D. (Los Alamos National Lab., NM (United States)) & Srolovitz, D.J. (Michigan Univ., Ann Arbor, MI (United States). Dept. of Materials Science and Engineering)
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Microstructures and dc critical currents in textured Y-Ba-Cu-oxides

Description: Sintered bars of Y-Ba-Cu oxide were partially melted using a quartz halogen lamp zone heating apparatus. The resulting multiphase samples showed varying degrees of melt texturing.'' It was found that the addition of YBa{sub 2}CuO{sub 5} powders to the sintered YBa{sub 2}Cu{sub 3}O{sub 7} prior to the zone melting process enhanced the growth of large textured grains. The best value of the critical current density was {approximately}10{sup 3} A/cm{sup 2} at 1.0 T and 77 K for the starting composi… more
Date: September 24, 1990
Creator: Orehotsky, J.; Wiesmann, H.; Moodenbaugh, A.R.; Suenaga, M. (Brookhaven National Lab., Upton, NY (USA)); Wang, H.-G. & Herman, H. (State Univ. of New York, Stony Brook, NY (USA))
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Observations of vortex structure in YBa sub 2 Cu sub 3 O sub 7

Description: The remnant magnetic flux distribution in a single crystal and a sintered polycrystal was examined using the magnetic particle decoration technique. The single crystal, which was heavily twinned, showed only local order in the flux lattice. This was probably due to lattice distortions caused by interaction between twin boundaries and fluxons. In the polycrystal, flux pinning effectiveness was seen to vary significantly between grains, depending on size and orientation. Grains with the c axis ne… more
Date: September 24, 1990
Creator: Muller, H.; Wiesmann, H.J. & Suenaga, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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High resolution tomography of objects with access to a single side

Description: The author is developing a technique which will enable one to obtain high-contrast, high-spatial resolution, three-dimensional images in opaque objects. The only constraint will be the radiation source and detector(s) will be located on the same side of the object. The goal is to obtain images with a spatial resolution of {approximately}1 mm at depths of 10 mm and {approximately}3 mm at depths of 30 mm in materials of moderate density (brass, steel, etc.). The author`s technique uses a highly-c… more
Date: March 24, 1993
Creator: Thoe, R. S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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The analysis and minimization of oxygen contamination in the powder processing of molybdenum disilicide

Description: Problems with MoSi{sub 2} include low-temperature fracture toughness, high-temperature creep resistance, and ``pest`` phenomena. Oxygen introduced by powder processing may be the cause of some of these problems. This study led to the following conclusions: Supplied powders have significant oxygen present prior to processing (up to 2.5 %), in the form of silica on the surface. This oxygen contamination did not increase by exposure to air at room temperature. An improved powder processing method … more
Date: April 24, 1994
Creator: Shannon, K.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
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GPHS (General Purpose Heat Source) uranium oxide encapsulations supporting satellite safety tests

Description: General Purpose Heat Source (GPHS) simulant-fueled capsules were assembled, welded, nondestructively examined, and shipped to Los Alamos National Laboratory (LANL) for satellite safety tests. Simulant-fueled iridium capsules contain depleted uranium oxide pellets that serve as a stand-in for plutonium-238 oxide pellets. Information on forty seven capsules prepared during 1987 and 1988 is recorded in this memorandum along with a description of the processes used for encapsulation and evaluation.… more
Date: April 24, 1989
Creator: Kanne, W. R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Surface characterization of ceramic materials. [LEED, AES, XPS, ion scattering spectroscopy, secondary ion mass spectroscopy]

Description: In recent years several techniques have become available to characterize the structure and chemical composition of surfaces of ceramic materials. These techniques utilize electron scattering and scattering of ions from surfaces. Low-energy electron diffraction is used to determine the surface structure, Auger electron spectroscopy and other techniques of electron spectroscopy (ultraviolet and photoelectron spectroscopies) are employed to determine the composition of the surface. In addition the… more
Date: September 24, 1976
Creator: Somorjai, G. A. & Salmeron, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Advanced Conceptual Models for Unsaturated and Two-Phase Flow in Fractured Rock

Description: The Department of Energy Environmental Management Program is faced with two major issues involving two-phase flow in fractured rock; specifically, transport of dissolved contaminants in the Vadose Zone, and the fate of Dense Nonaqueous Phase Liquids (DNAPLs) below the water table. Conceptual models currently used to address these problems do not correctly include the influence of the fractures, thus leading to erroneous predictions. Recent work has shown that it is crucial to understand the top… more
Date: June 24, 2007
Creator: Rajaram, Harihar; Glass, Robert J.; Nicholl, Michael J. & Wood, Thomas R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Characterization of U9VI) Sorption-Desorption Processes and Model Upscaling

Description: Long-term sequestration of uranium at sites within the DOE complex is a significant problem that requires molecular-level information on the speciation, phase association, and spatial distribution of uranium
Date: May 24, 2007
Creator: Jr., Gordon Borwn; Catalano, Jeffrey; Singer, David & Zachara, John
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Modeling of transformation toughening in brittle materials

Description: Results from modeling of transformation toughening in brittle materials using a discrete micromechanical model are presented. The material is represented as a two-dimensional triangular array of nodes connected by elastic springs. Microstructural effects are included by varying the spring parameters for the bulk, grain boundaries, and transforming particles. Using the width of the damage zone and the effective compliance (after the initial creation of the damage zone) as measures of fracture to… more
Date: January 24, 1992
Creator: LeSar, R.; Rollett, A. D. & Srolovitz, D. J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

High temperature alkali corrosion of ceramics in coal gas. Eighth quarterly progress report, June 1, 1993--September 1, 1993

Description: Gaseous alkali corrosion kinetics of Si{sub 3}N{sub 4} were investigated from 950 to 1100{degrees}C in an atmosphere containing 0.98 vol % sodium nitrate vapors. Linear reaction rates from 950 to 1100{degrees}C indicate that the alkali reaction Of Si{sub 3}N{sub 4} is interface-controlled with an activation energy of 199 kJ/mol. Rate controlling step of overall reaction appears to be the oxidation of Si{sub 3}N{sub 4} to SiO{sub 2}.An alkali reaction mechanism, involving a complex dissolution-o… more
Date: August 24, 1993
Creator: Pickrell, G. R.; Sun, T. & Brown, J. J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Heat treatment versus properties studies associated with the Inconel 718 PBF acoustic filters

Description: PBF acoustic filter Unit No. 1 cracked when heat treatment was attempted. The effects of prior thermal cycling, solution anneal temperature, and cooling rate from solution anneals were investigated. The investigations concerned influences of the above variables upon both 1400$sup 0$F stress rupture solution- annealed properties and room temperature age-hardened properties. 1400$sup 0$F stress rupture properties were of interest to assist the prevention of cracking during heat treatments. Room t… more
Date: February 24, 1975
Creator: Smolik, G. R. & Reuter, W. G.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Nucleation of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} in the BaF{sub 2} Process.

Description: The nucleation of the c-axis aligned and non-c-axis YBa{sub 2}Cu{sub 3}O{sub {approximately}6.1} (YBCO) from precursor films on [001]-cut SrTiO{sub 3} was investigated for the so-called BaF{sub 2} process. Specimens with different thickness were quenched from 735 C, then studied by transmission electron microscopy and x-ray diffraction techniques. Preceding the formation of YBCO nuclei, three intermediate phases of (Y,Ba) oxy-fluoride and a transition phase without F were found in the precursor… more
Date: June 24, 2001
Creator: Wu, L.; Solovyov, V. F.; Wiesmann, H. J.; Zhu, Y. & Suenaga, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

MULTI-PHASE Cr-BASED ALLOYS FOR AGGRESSIVE HIGH TEMPERATURE ENVIRONMENTS

Description: Attractive high-temperature mechanical properties and oxidation/hot corrosion resistance have been achieved in a new family of Cr{sub 2}Ta-reinforced Cr alloys. However, inadequate room-temperature toughness remains a key challenge, with the best Cr-Cr{sub 2}Ta alloys exhibiting only modest toughness in the range of 12-14 MPa m{sup 1/2}. The addition of MgO has been shown to significantly improve the room-temperature mechanical properties of unalloyed Cr and was investigated as a means for impr… more
Date: August 24, 2001
Creator: Brady, MP
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Database and Interim Glass Property Models for Hanford HLW Glasses

Description: The purpose of this report is to provide a methodology for an increase in the efficiency and a decrease in the cost of vitrifying high-level waste (HLW) by optimizing HLW glass formulation. This methodology consists in collecting and generating a database of glass properties that determine HLW glass processability and acceptability and relating these properties to glass composition. The report explains how the property-composition models are developed, fitted to data, used for glass formulation… more
Date: July 24, 2001
Creator: Hrma, Pavel R; Piepel, Gregory F; Vienna, John D; Cooley, Scott K; Kim, Dong-Sang & Russell, Renee L
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Crystalline plutonium hosts derived from high-level waste formulations.

Description: The Department of Energy has selected immobilization for disposal in a repository as one approach for disposing of excess plutonium (1). Materials for immobilizing weapons-grade plutonium for repository disposal must meet the ''spent fuel standard'' by providing a radiation field similar to spent fuel (2). Such a radiation field can be provided by incorporating fission products from high-level waste into the waste form. Experiments were performed to evaluate the feasibility of incorporating hig… more
Date: April 24, 1998
Creator: O'Holleran, T. P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Characterization and testing of a {sup 238}Pu loaded ceramic waste form.

Description: This paper will describe the preparation and progress of the effort at Argonne National Laboratory-West to produce ceramic waste forms loaded with {sup 238}Pu. The purpose of this study is to determine the extent of damage, if any, that alpha decay events will play over time to the ceramic waste form under development at Argonne. The ceramic waste form is glass-bonded sodalite. The sodalite is utilized to encapsulate the fission products and transuranics which are present in a chloride salt mat… more
Date: April 24, 1998
Creator: Johnson, S. G.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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