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Low Temperature Constrained Sintering of Cerium Gadolinium OxideFilms for Solid Oxide Fuel Cell Applications

Description: Cerium gadolinium oxide (CGO) has been identified as an acceptable solid oxide fuel cell (SOFC) electrolyte at temperatures (500-700 C) where cheap, rigid, stainless steel interconnect substrates can be used. Unfortunately, both the high sintering temperature of pure CGO, >1200 C, and the fact that constraint during sintering often results in cracked, low density ceramic films, have complicated development of metal supported CGO SOFCs. The aim of this work was to find new sintering aids for … more
Date: June 30, 2007
Creator: Nicholas, Jason.D.
Partner: UNT Libraries Government Documents Department
open access

The microstructural mechanism of electromigration failure in narrow interconnects of Al alloys

Description: This thesis reports a study of the mechanism of electromigration failure in Al-2Cu-1Si thin-film conducting lines on Si. Samples were patterned from 0.5 {mu}m thick vapor-deposited films with various mean grain sizes (G), and had lines widths (W) of 1.3, 2, 4 and 6 {mu}m. The lines were aged at various conditions to change the Cu-precipitate distribution and were tested to failure at T = 225{degrees}C and j = 2.5 {times} 10{sup 6} A/cm{sup 2}. Some samples were tested over a range of substrate … more
Date: April 1, 1993
Creator: Kim, Choongun
Partner: UNT Libraries Government Documents Department
open access

A genetic algorithm approach in interface and surface structure optimization

Description: The thesis is divided into two parts. In the first part a global optimization method is developed for the interface and surface structures optimization. Two prototype systems are chosen to be studied. One is Si[001] symmetric tilted grain boundaries and the other is Ag/Au induced Si(111) surface. It is found that Genetic Algorithm is very efficient in finding lowest energy structures in both cases. Not only existing structures in the experiments can be reproduced, but also many new structures c… more
Date: January 1, 2010
Creator: Zhang, Jian
Partner: UNT Libraries Government Documents Department
open access

Grain boundary structure and solute segregation in titanium-doped sapphire bicrystals

Description: Solute segregation to ceramic grain boundaries governs material processing and microstructure evolution, and can strongly influence material properties critical to engineering performance. Understanding the evolution and implications of grain boundary chemistry is a vital component in the greater effort to engineer ceramics with controlled microstructures. This study examines solute segregation to engineered grain boundaries in titanium-doped sapphire (Al2O3) bicrystals, and explores relationsh… more
Date: May 17, 2002
Creator: Taylor, Seth T.
Partner: UNT Libraries Government Documents Department
open access

Direct measurement of anisotropy of interfacial free energy from grain boundary groove morphology in transparent organic metal analong systems

Description: Both academia and industry alike have paid close attention to the mechanisms of microstructural selection during the solidification process. The forces that give rise to and the principles which rule the natural selection of particular morphologies are important to understanding and controlling new microstructures. Interfacial properties play a very crucial role to the selection of such microstructure formation. In the solidification of a metallic alloy, the solid-liquid interface is highly mob… more
Date: August 1, 2005
Creator: Rustwick, Bryce A.
Partner: UNT Libraries Government Documents Department
open access

Thermal depinning of a single superconducting vortex

Description: Thermal depinning has been studied for a single vortex trapped in a superconducting thin film in order to determine the value of the superconducting order parameter and the superfluid density when the vortex depins and starts to move around the film. For the Pb film in Pb/Al/Al{sub 2}O{sub 3}/PbBi junction having a gold line, the vortex depins from the artificial pinning site (Au line) and reproducibly moves through the same sequence of other pinning sites before it leaves the junction area of … more
Date: October 1, 1995
Creator: Sok, J.
Partner: UNT Libraries Government Documents Department
open access

Deformation and Fracture of Polycrystalline Lithium Fluoride

Description: Techniques for forming polycrystalline LiF from the melt and for fabricating test specimens were developed and evaluated using single-crystal LiF as a control. Large -grain polycrystalline specimens tested in fourpoint loading always showed some plastic deformation (0.078 to 0.798%) before fracture, but the plastic flow was sharpiy reduced from that of single crystals. An etch was developed revealing dislocations on all crystallographic faces of LiF. Details of plastic deformation in polycrysta… more
Date: September 14, 1962
Creator: Scott, W. D.
Partner: UNT Libraries Government Documents Department
open access

Recrystallization of high temperature superconductors

Description: Currently one of the most widely used high {Tc} superconductors is the Bi-based compounds Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub z} and Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub z} (known as BSCCO 2212 and 2223 compounds) with {Tc} values of about 85 K and 110 K respectively. Lengths of high performance conductors ranging from 100 to 1000 m long are routinely fabricated and some test magnets have been wound. An additional difficulty here is that although Bi-2212 and Bi-2223 phases exist over a wide… more
Date: May 9, 1996
Creator: Kouzoudis, D.
Partner: UNT Libraries Government Documents Department
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