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in subjects: "Structure And Phase Studies"

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The influence of waste variability on the properties and phase stability of the West Valley reference glass

A year long study of the effects of waste variability on properties and phase stability of the West Valley reference glass has been conducted. Viscosity, electrical conductivity, glass transition temperature, density, and liquidus temperature have been measured for a series of glasses where the weight fraction of Al{sub 2}0{sub 3}, Fe{sub 2}0{sub 3}, NiO, MnO{sub 2}, Cr{sub 2}O{sub 3}, and P{sub 2}0{sub 5}, was varied systematically around the reference glass composition. A computer program for… more

Date: September 1, 1987

Creator: McPherson, D.; Joseph, I.; Mathur, A.; Capozzi, C.; Armstrong, S. & Pye, L. D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

The origins of ordering in CuPt

The alloy CuPt is one of the few that order into a L1{sub 1} crystal structure, i.e. planes of copper and planes of planes of planes of platinum perpendicular to the < 111 > direction. For disordered CuPt, the calculated Warren-Cowley short-range order parameter indicates an instability to concentration fluctuations with a wave-vector of ({1/2}, {1/2}, {1/2}), consistent with L1{sub 1} ordering. We show that this rare tendency is due to this ordering vector arising from the large joint density … more

Date: August 4, 1993

Creator: Clark, J. F.; Pinski, F. J.; Sterne, P. A.; Johnson, D. D.; Staunton, J. B. & Ginatempo, B.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A comparison of the evolution of cold and hot deformation microstructures and textures in fcc metals

Microstructures and textures which develop during cold deformation are compared to those which develop during hot deformation. This comparison is made using the evolutionary framework of grain subdivision and the formation of low energy dislocation structures. During deformation grains are subdivided into differently deforming regions separated by geometrically necessary dislocation boundaries. These boundaries include dense dislocation walls, microbands, lamellar boundaries and subgrains. Grai… more

Date: December 31, 1993

Creator: Hughes, D. A. & Hansen, N.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

[Aluminum Coordination and Active Sites on Aluminas, Y-Zeolites and Pillared Layered Silicates]. Progress Report

This report is organized in four sections. In the first the authors will outline structural features which are common to all fine grained alumina, as well as to non-framework alumina in zeolites. This section will be followed by a study of the surface vs. bulk coordination of aluminum. The third section will deal with measurement of the number of acid sites and the scaling of their strength. The fourth and last section will describe three model reactions: the isomerization of 1-butene and of 2 … more

Date: February 1, 1994

Creator: Fripiat, J. J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Stability and precipitation kinetics in Si{sub 1{minus}y}C{sub y}/Si and Si{sub 1{minus}x{minus}y}Ge{sub x}C{sub y}/Si heterostructures prepared by solid phase epitaxy

This study investigates the stability of metastable Si{sub 1{minus}y}C{sub y}/Si heterostructures during rapid thermal annealing (RTA) over a temperature range of 1,000--1,150 C. Heterostructures of Si{sub 1{minus}y}C{sub y}/Si and Si{sub 1{minus}x{minus}y}Ge{sub x}C{sub y}/Si (x {equals} 0.77, Y {<=} .0014) were formed by solid phase epitaxy from C implanted, preamorphized substrates using a 30 minute 700 C anneal in N{sub 2}. The occupancy of C in substitution lattice sites was monitored by F… more

Date: December 31, 1993

Creator: Strane, J. W.; Picraux, S. T.; Stein, H. J.; Lee, S. R.; Candelaria, J.; Theodore, D. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Experimental and theoretical studies on the C15 intermetallic compounds MV{sub 2} (M = Zr, Hf and Ta): Elasticity and phase stability

The phase stability of C15 HfV{sub 2} was studied by specific heat measurements. The elastic constants of C15 HfV{sub 2} were measured by the resonant ultrasound spectroscopy. Total energy and electronic structure of C15 intermetallic compounds MV{sub 2} (M = Zr, Hf and Ta) were calculated using the linear muffin tin orbital (LMTO) method. The band structures at X-point near the Fermi level were used to understand the anomalous shear moduli of the C15 HfV{sub 2} and ZrV{sub 2}. It was found tha… more

Date: December 1, 1994

Creator: Chu, F.; Mitchell, T. E.; Chen, S. P.; Sob, M.; Siegl, R. & Pope, D. P.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Epitaxial growth of bcc transition metal films and superlattices onto MgO (111), (011) and (001) substrates

We demonstrate epitaxial growth of the bcc transition metals Nb, Mo, Fe, and Cr via sputtering onto single crystal MgO substrates. The epitaxial growth orientations are (011), (112) and (001) when grown onto MgO (111), (011) and (001), respectively. Further we demonstrate that under appropriate growth conditions, superlattices of these materials (e.g., Fe/Cr, Fe/V and Mo/V) can be grown with the same epitaxial order as the films.

Date: April 1, 1994

Creator: Mattson, J. E.; Fullerton, E. E.; Sowers, C. H. & Bader, S. D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

On the nature of striae in strontium barium niobate

Strontium barium niobate crystals were grown by the Czochralski technique. These crystals were 15--20 mm in diameter and 25 to 75 mm long. Two types stride, designated as coarse and fine, were characterized. The coarse stride are optically dense and are spaced by 100 to 500 {mu}m apart; the fine striae are optically less dense and spaced 5--50 {mu}m apart. The origins of the stride are attributed to thermal fluctuations in the melt related to the control system and to rotation of the growing cr… more

Date: December 31, 1993

Creator: Monchamp, R. R.; Mihalik, G. B. & Franks, L. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Study of nucleation and growth in Al-Zn alloys using TEM

Nucleation and growth studies were conducted on Al-Zn alloys at several temperatures using transmission electron microscopy (TEM) with an in-situ furnace. The value of the critical undercooling was established by noting the lowest temperature at which precipitates were no longer observed, following a quench into the two-phase metastable region. These results were compared with the Langer-Schwartz model of nucleation and growth in which it is predicted that the half-completion time (i.e, the tim… more

Date: December 31, 1993

Creator: Sundar, G.; Hoyt, J. J.; Kenik, E. A. & Spooner, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

High resolution energy loss research: Si compounds and ceramics. Progress report, January 2, 1991--January 1, 1992

Our current investigation of the structure and chemistry of whisker/matrix interfaces and matrix grain boundaries in SiC whisker reinforced Si{sub 3}N{sub 4} composites has been completed. We examined these interfaces and boundaries in four composites whose starting materials and processing were identical except for the SiC whiskers themselves, which were from four different sources: American matrix, Nikkei, Huber and Tokai. Thus, differences in interfaces among the composites are attributable … more

Date: February 1, 1992

Creator: Carpenter, R. W. & Lin, S. H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Microstructural development and mechanical behavior of eutectic bismuth-tin and eutectic indium-tin in response to high temperature deformation

The mechanical behavior and microstructure of eutectic Bi-Sn and In-Sn solders were studied in parallel in order to better understand high temperature deformation of these alloys. Bi-Sn solder joints were made with Cu substrates, and In-Sn joints were made with either Cu or Ni substrates. The as-cast microstructure of Bi-Sn is complex regular, with the two eutectic phases interconnected in complicated patterns. The as-cast microstructure of In-Sn depends on the substrate. In-Sn on Cu has a non-… more

Date: November 1, 1993

Creator: Goldstein, J. L. F.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

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Magnetic and structural properties of Fe/Pd multilayers studied by magnetic x-ray dichroism and x-ray absorption spectroscopy

The results of magnetic circular x-ray dichroism (MCXD) measurements and extended x-ray absorption fine structure measurements (EXAFS) of the Fe K-edges of textured Fe(110)/Pd(111) multilayers are reported. The EXAFS results indicates that the iron in the system goes from bcc to a more densely packed system as the thickness of the iron layer is decreased. The magnetic properties were measured by SQUID magnetometry from 5-350 K. For all the samples, the saturation magnetization was significantly… more

Date: December 1, 1994

Creator: Mini, S. M.; Fullerton, E. E.; Sowers, C. H.; Fontaine, A.; Pizzini, S.; Bommannavar, A. S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Microstructural development in irradiated vanadium alloys

Three simple vanadium alloys, V-5Al, V-1Ni, and V-2Ti-1Ni have been examined to determine the effects of fast neutron irradiation on microstructural evolution. Specimens were irradiated in EBR II at temperatures in the range 425 to 600{degrees}C to doses of 15 and 31 dpa. Each alloy responded very differently to irradiation. All V-5Al specimens were generally void-free and contained high densities of coherent precipitates, and moderate densities of network dislocations. Swelling was much higher… more

Date: September 1, 1993

Creator: Gelles, D. S. & Stubbins, J. F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Thin film ionic conductors based on cerium oxide

Fluorite and perovskite structure cerium oxide based ceramics are a class of materials that may exhibit good oxygen ion and/or protonic conductivity. The authors have successfully deposited thin films of these materials on a variety of substrates. Interesting orientation relationships were noticed between cerium oxide films and strontium titanate bi-crystal substrates. Near lattice site coincidence theory has been used to study these relationships.

Date: December 1, 1994

Creator: Haridoss, P.; Hellstrom, E.; Garzon, F. H.; Brown, D. R. & Hawley, M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Interdiffusion and grain-boundary migration in Au-Cu bilayers during ion-irradiation

Ion irradiation and annealing experiments have been conducted on Au/Cu bilayer films to evaluate the effect of irradiation on diffusion-induced grain boundary migration (DIGM). The Au films were prepared with a large-grained microstructure with grain boundaries perpendicular to the film surface and extending through the film thickness. Irradiations were conducted with 1.5 MeV Kr at 228{degree}C. Rutherford backscattering spectrometry of the samples revealed that interdiffusion was substantially… more

Date: November 1, 1991

Creator: Alexander, D. E.; Rehn, L. E. & Baldo, P. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Surface structure, bonding, and dynamics: The universality of zincblende (110) potential energy surfaces

Using a tight-binding, total energy (TBTE) model we examine the hypothesis that the potential energy surfaces (PES) describing the (110) cleavage faces of the tetrahedrally coordinated, zincblende-structure compound semiconductors exhibit a common ``universal`` form if expressed in terms of suitably scaled parameters. TBTE calculations on both III-V and II-VI compounds reveal a linear scaling with bulk lattice constant of the geometric parameters of the reconstructed surfaces. This scaling is a… more

Date: November 1, 1991

Creator: Godin, T. J. & LaFemina, J. P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Microstructure and composition of electromagnetically-characterized YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} grain boundaries

The electrical character (flux-pinning, Josephson junction, or resistive) of the grain boundaries in approximately twenty flux-grown YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} bicrystals was determined in previous studies. A selection of these same bicrystals now have been thinned for study by transmission and scanning transmission electron microscopy. High-spatial resolution imaging and analytical techniques reveal microstructural differences among these boundaries that are consistent with thei… more

Date: December 1, 1991

Creator: Babcock, S. E.; Zhang, Na; Cai, Xue Yu; Larbalestier, D. C.; Gao, Yufei; Merkle, K. L. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Vacancy related defects in thin film Pb(ZrTi)O{sub 3} materials

Positron annihilation techniques have been applied to characterize vacancy-related defects in ferroelectric thin film structures. Variable energy positron beam measurements were carried out on doped and undoped Pb(ZrTi)O{sub 3} (PZT) samples subjected to different post-deposition cool down and anneal conditions. The PZT was deposited by sol-gel with either with platinum or RuO{sub 2} electrodes, or by laser ablation with La{sub 0.5}Sr{sub 0.5}CoO{sub 3} electrodes. The RuO{sub 2} and La{sub 0.5… more

Date: December 31, 1994

Creator: Krishnan, A.; Keeble, D. J.; Ramesh, R.; Warren, W. L.; Tuttle, B. A.; Pfeffer, R. L. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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High surface area, high permeability carbon monoliths

The goal of this work is to prepare carbon monoliths having precisely tailored pore size distribution. Prior studies have demonstrated that poly(acrylonitrile) can be processed into a precursor having tailored macropore structure. Since the macropores were preserved during pyrolysis, this synthetic process provided a route to porous carbon having macropores with size =0.1 to 10{mu}m. No micropores of size <2 nm could be detected in the carbon, however, by nitrogen adsorption. In the present wor… more

Date: December 31, 1994

Creator: Lagasse, R. R. & Schroeder, J. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Fiberglass material specification III

This specification describes the requirements for composite parts of fiberglass to be furnished to Martin Marietta Energy Systems, Incorporated. (JL)

Date: October 1, 1991

Creator: Frame, B. J. & Janke, C. J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Phase stability and electronic structure of transition-metal aluminides

This paper will describe the interplay between die electronic structure and structural energetics in simple, complex, and quasicrystalline Al-transition metal (T) intermetallics. The first example is the Ll{sub 2}-DO{sub 22} competition in Al{sub 3}T compounds. Ab-initio electronic total-energy calculations reveal surprisingly large structural-energy differences, and show that the phase stability of both stoichiometric and ternary-substituted compounds correlates closely with a quasigap in the … more

Date: December 31, 1992

Creator: Carlsson, A. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Densification and crystallization of zirconia thin films prepared by sol-gel processing

We have investigated the effects of precursor nature and heat treatment schedule on the densification and crystallization behavior of sol-gel derived zirconia thin films. Precursor solutions were prepared from n-propanol, zirconium (IV) n-propoxide, and either acetic acid, or 2,4-pentanedione (acac) and water additions. By controlling the ligand type and ligand-to-metal ratio, we were able to prepare films which displayed significant differences in densification behavior. We attribute the dissi… more

Date: December 31, 1993

Creator: Schwartz, R. W.; Voigt, J. A.; Buchheit, C. D. & Boyle, T. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Pore-size distributions of N-isopropylacrylamide (NIPA) hydrogels

Pore-size distributions have been measured for N-isopropylacrylamide (NIPA) hydrogels at 25 and 32{degrees}C with swelling capacities 11.3 and 6.0 g swollen gel per g dry gel. The mixed-solute-exclusion method (introduced by Kuga) was used to obtain the experimental solute-exclusion curve which represents the amount of imbibed liquid inside the gel inaccessible for a solute of radius r. The pore-size distributions were obtained by using Casassa`s Brownian-motion model and numerically solving th… more

Date: November 1, 1993

Creator: Walther, D. H.; Blanch, H. W. & Prausnitz, J. M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Structural analysis of amorphous phosphates using high performance liquid chromatography

Determining the atomic-scale structure of amorphous solids has proven to be a formidable scientific and technological problem for the past 100 years. The technique of high-performance liquid chromatography (HPLC) provides unique detailed information regarding the structure of partially disordered or amorphous phosphate solids. Applications of the experimental technique of HPLC to phosphate solids are reviewed, and examples of the type of information that can be obtained with HPLC are presented.… more

Date: December 31, 1993

Creator: Sales, B. C.; Boatner, L. A.; Chakoumakos, B. C.; McCallum, J. C.; Ramey, J. O. & Zuhr, R. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department