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Dislocation dynamics simulations of plasticity at small scales

Description: As metallic structures and devices are being created on a dimension comparable to the length scales of the underlying dislocation microstructures, the mechanical properties of them change drastically. Since such small structures are increasingly common in modern technologies, there is an emergent need to understand the critical roles of elasticity, plasticity, and fracture in small structures. Dislocation dynamics (DD) simulations, in which the dislocations are the simulated entities, offer a w… more
Date: December 15, 2010
Creator: Zhou, Caizhi
Partner: UNT Libraries Government Documents Department
open access

Metal thin film growth on multimetallic surfaces: From quaternary metallic glass to binary crystal

Description: The work presented in this thesis mainly focuses on the nucleation and growth of metal thin films on multimetallic surfaces. First, we have investigated the Ag film growth on a bulk metallic glass surface. Next, we have examined the coarsening and decay of bilayer Ag islands on NiAl(110) surface. Third, we have investigated the Ag film growth on NiAl(110) surface using low-energy electron diffraction (LEED). At last, we have reported our investigation on the epitaxial growth of Ni on NiAl(110) … more
Date: December 15, 2010
Creator: Jing, Dapeng
Partner: UNT Libraries Government Documents Department
open access

An improved criterion for new particle formation in diverse environments

Description: A dimensionless theory for new particle formation (NPF) was developed, using an aerosol population balance model incorporating recent developments in nucleation rates and measured particle growth rates. Based on this theoretical analysis, it was shown that a dimensionless parameter Lg, characterizing the ratio of the particle scavenging loss rate to the particle growth rate, exclusively determined whether or not NPF would occur on a particular day. This parameter determines the probability that… more
Date: March 15, 2010
Creator: Kuang, C.; Riipinen, I.; Sihto, S.-L.; Kulmala, M.; McCormick, A. & McMurry, P.
Partner: UNT Libraries Government Documents Department
open access

Nucleation and Growth of Atmospheric Particles

Description: New particle formation (NPF) in the atmospheric is a two-step process: Nucleation leads to the birth of stable nuclei that subsequently grow to sizes that can be detected and affect the atmosphere’s radiative properties. Our group is studying both of these processes. Our nucleation research is largely supported by NSF and involves measurements of neutral molecular clusters formed by nucleation with a new custom-designed mass spectrometer (the Cluster-CIMS) and measurements of nanoparticle size … more
Date: March 15, 2010
Creator: McMurry, P.; Kuang, C.; Barsanti, K.; Eisele, F.; Friedli, H.; Scheckman, J. et al.
Partner: UNT Libraries Government Documents Department
open access

Tungsten Cladding of Tungsten-Uranium Dioxide (W-UO2) Composites by Deposition from Tungsten Hexafluoride (WF6)

Description: A program is being conducted to develop a process for cladding tungsten and tungsten cermet fuels with tungsten deposited from the vapor state by the hydrogen reduction of tungsten hexafluoride. Early work was performed using recrystallized, high purity, commercial tungsten as the substrate material. Temperatures in the range 660 to 12950F (350 to 1700°C) and pressures from 10 to 350 mm Hg were investigated. Hydrogen to WF 6 ratios of 10: 1 to 150: 1 were utilized. Efforts were directed toward… more
Date: February 15, 1965
Creator: Lamartine, J.T. & Hoppe, A.W.
Partner: UNT Libraries Government Documents Department
open access

Devitrification kinetics and phase selection mechanisms in Cu-Zr metallic glasses

Description: Metallic glasses have been a promising class of materials since their discovery in the 1960s. Indeed, remarkable chemical, mechanical and physical properties have attracted considerable attention, and several excellent reviews are available. Moreover, the special group of glass forming alloys known as the bulk metallic glasses (BMG) become amorphous solids even at relatively low cooling rates, allowing them to be cast in large cross sections, opening the scope of potential applications to inclu… more
Date: December 15, 2010
Creator: Kalay, Ilkay
Partner: UNT Libraries Government Documents Department
open access

Radial Flow of Pressured Hot Water Through Narrow Cracks

Description: Geothermal wells discharging hundreds of tons/hour of steam-water mixtures may be supplied at depth from one very narrow crack of width 1 to 2 mm, or alternatively, from some hundreds of hairline cracks. In the former case, turbulent flow takes place out to tens of meters from the well while the sum of frictional and kinetic pressure-drop indicates the flashing distance to be of the order of 10 cm from the well wall for pressure-temperature equilibrium. However it is unlikely that equilibrium o… more
Date: December 15, 1983
Creator: James, Russell
Partner: UNT Libraries Government Documents Department
open access

Development of Novel Crystallizer Design and Optimization Tools for Solution Crystallization

Description: This project addresses the energy efficiency and productivity of solids manufacturing and separation processes that use crystallization. The overall objective is to develop crystallization simulation technology and software tools that significantly improve industry's ability to predict and control product quality and optimize process and equipment performance while reducing energy use. This project addresses both levels of simulation models of importance to industry: (1) Process flowsheet model… more
Date: September 15, 2004
Creator: Linz, David G.; Lythgoe, Steven C.; Anderko, Andre; Dhanasekharan, Kumar; Ring, Terry & Wang, Liguang
Partner: UNT Libraries Government Documents Department
open access

Amorphous and nanocrystalline phase formation in highly-driven Al-based binary alloys

Description: Remarkable advances have been made since rapid solidification was first introduced to the field of materials science and technology. New types of materials such as amorphous alloys and nanostructure materials have been developed as a result of rapid solidification techniques. While these advances are, in many respects, ground breaking, much remains to be discerned concerning the fundamental relationships that exist between a liquid and a rapidly solidified solid. The scope of the current disser… more
Date: October 15, 2008
Creator: Kalay, Yunus Eren
Partner: UNT Libraries Government Documents Department
open access

Influence of Thermal Aging on the Mechanical and Corrosion Properties of C-22 Alloy Welds

Description: The phase stability of C-22 alloy (UNS No. N06022) gas tungsten arc welds was studied by aging samples at 427, 482, 538, 593, 649, 704, and 760 C for times up to 40,000 hours. The tensile properties and the Charpy impact toughness of these samples were measured in the as-welded condition as well as after aging. The corrosion resistance was measured using standard immersion tests in acidic ferric sulfate (ASTM G 28 A) and 2.5% hydrochloric acid solutions at the boiling point. The microstructures… more
Date: June 15, 2000
Creator: Edgecumbe Summers, T. S.; Rebak, R. B. & Seeley, R. R.
Partner: UNT Libraries Government Documents Department
open access

Spreading of Viscous Liquids at High Temperature: Silicate Glasseson Molybdenum

Description: The spreading of Si-Ca-Al-Ti-O glasses on molybdenum has been investigated. By controlling the oxygen activity in the furnace, spreading can take place under reactive or non-reactive conditions. As the nucleation of the reaction product under reactive conditions is slow in comparison to the spreading kinetics, in both cases the glass front moves on the metal surface with similar spreading velocities. Spreading can be described using a molecular dynamics model where the main contribution to the … more
Date: December 15, 2004
Creator: Lopez-Esteban, Sonia; Saiz, Eduardo; Moya, Jose S. & Tomsia,Antoni P.
Partner: UNT Libraries Government Documents Department
open access

Enhancement of dislocation velocities by stress assisted kink nucleation at the native oxide/SiGe interface

Description: Experiments have shown that the presence of a thin native oxide layer on the surface of a strained SiGe epilayer causes an order of magnitude increase in dislocation velocities during annealing over those observed in atomically clean samples and during crystal growth. This behavior is explained herein by stress-assisted dislocation kink nucleation at the oxide/epilayer interface. Finite element models are used to estimate the magnitude of stress local to steps at this interface due to both intr… more
Date: February 15, 2001
Creator: Stach, E. A. & Hull, R.
Partner: UNT Libraries Government Documents Department
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