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in creator/contributor: "Oak Ridge Inst. for Science and Education, TN United States"

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[ALCHEMI formulated for delocalization and anti-site defects]

ALCHEMI (atom location by channeling enhanced microanalysis) provides a useful method for determining the site distributions of impurity atoms in crystals with multiple sublattices. Delocalization of low energy excitations and the dubious statistical confidence level of the technique are problems; a recent formulation of ALCHEMI analysis (Walls, 1992) addresses both problems. This paper extends this analysis for the distribution of atoms over two sublattices; expressions are derived for the fit… more

Date: June 1, 1994

Creator: Anderson, I. M. & Bentley, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Application of Z-contrast imaging to obtain column-by-column spectroscopic analysis of materials

Z-contrast imaging has been shown to be an effective method for obtaining a high-resolution image from a scanning transmission electron microscope (STEM). The incoherent nature of the high-angle scattering makes image interpretation straightforward and intuitive with the resolution limited only by the 2.2 {Angstrom} electron probe. The optimum experimental conditions for Z-contrast imaging also coincide with those used for analytical microscopy, enabling microanalysis to be performed with the s… more

Date: January 1, 1993

Creator: Browning, N. D. & Pennycook, S. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Aquifer thermal energy storage. International symposium: Proceedings

Aquifers have been used to store large quantities of thermal energy to supply process cooling, space cooling, space heating, and ventilation air preheating, and can be used with or without heat pumps. Aquifers are used as energy sinks and sources when supply and demand for energy do not coincide. Aquifer thermal energy storage may be used on a short-term or long-term basis; as the sole source of energy or as a partial storage; at a temperature useful for direct application or needing upgrade. T… more

Date: May 1, 1995

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

An atom probe investigation of the influence of trace impurities on the mechanical behavior of NiAl

Atom probe field ion microscopy (APFIM) and transmission electron microscopy (TEM) have been used to investigate the influence of trace metallic impurities on the enormous increase in the yield stress of boron-doped NiAl. Previous atom probe studies of NiAl containing 0.12 at. % boron had demonstrated that 0.026 at. % of the boron was in solid solution. The remainder reacted with trace metallic impurities, presumably present in high purity Ni, to form ultrafine MB{sub 2} precipitates ranging in… more

Date: November 1, 1993

Creator: Jayaram, R.; Liu, C. T. & Miller, M. K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Angular and charge state distributions of highly charged ions scattered during low energy surface-channeling interactions with Au(110)

The authors have measured scattered projectile angular and charge state distributions for 3.75 keV/amu O{sup q+} (3 {le} q {le} 8) and 1.2 keV/amu Ar{sup 1+} (3 {le} q {le} 14) ions grazingly incident along the [110] and [100] directions of a Au(110) single crystal target. Scattered projectile angular distribution characteristic of surface channeling are observed. For both incident species, the dominant scattered charge fraction is neutral, which varies only by a few percent as a function of in… more

Date: October 1, 1994

Creator: Meyer, F. W.; Folkerts, L. & Schippers, S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

The self-supporting disc: A specimen geometry exhibiting low secondary characteristic fluorescence

Secondary characteristic fluorescence, when expressed relative to the primary intensity of the fluorescing element, can be written as the product of three factors, which represent the probabilities of the various processes that govern the magnitude of fluorescence and thus have values between zero and one. Two of these factors are characteristic of the material being analyzed. The factor C{sub X}{sup Y} is the likelihood that the primary x ray of Y is absorbed by the element X if it is absorbed… more

Date: June 1, 1995

Creator: Anderson, I. M.; Bentley, J. & Carter, C. B.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Projectile image acceleration, neutralization and electron emission during grazing interactions of multicharged ions with Au(110)

Recent Oak Ridge work is summarized on projectile energy gain by image charge acceleration, scattered ion charge distributions, and K-Auger electron emission during low energy grazing interactions of highly charged Pb, I, O, and Ar ions with a Au(110) surface.

Date: March 1, 1995

Creator: Meyer, F. W.; Folkerts, L.; Folkerts, H. O. & Schippers, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Landscape characterization and biodiversity research

Rapid deforestation often produces landscape-level changes in forest characteristics and structure, including area, distribution, and forest habitat types. Changes in landscape pattern through fragmentation or aggregation of natural habitats can alter patterns of abundance for single species and entire communities. Examples of single-species effects include increased predation along the forest edge, the decline in the number of species with poor dispersal mechanisms, and the spread of exotic sp… more

Date: March 1, 1995

Creator: Dale, V. H.; Offerman, H.; Frohn, R. & Gardner, R. H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Landscape characterization for watershed management

Streams and rivers serve as integrators of terrestrial landscape characteristics and as recipients of pollutants from both the atmosphere and the land; thus, large rivers are especially good indicators of cumulative impacts. Landscape ecologists seek to better understand the relationships between landscape structure and ecosystem processes at various spatial scales. Understanding how scale, both data resolution and geographic extent, influences landscape characterization and how terrestrial pro… more

Date: July 1, 1996

Creator: Hunsaker, Carolyn T.; Schwartz, Paul M. & Jackson, Barbara L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Microstructural Investigations of as-Fabricated, Long-Term Thermally Aged and Neutron Irradiated RPV Materials: An Atom Probe Study

Atom probe field ton microscopy (APFIM) investigations of the microstructure of as-fabricated, long-term thermally aged ({approximately}100,000h. at 540{degrees}F (282{degrees}C)) and neutron-irradiated (6.6{times}10{sup 18} and 3.47{times}10{sup 19} n cm{sup {minus}2} (E>1 MeV) at {approximately}550{degrees}F (288{degrees}C)) surveillance materials from commercial reactor pressure vessel steels were performed This combination of materials and conditions permitted the investigation of potential… more

Date: September 1995

Creator: Pareige, P. J.; Miller, M. K. & Stoller, R. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Potential effect of natural gas wells on alluvial groundwater contamination at the Kansas City Plant

This report is the result of a request for further information about several abandoned natural gas wells at the US Department of Energy's Kansas City Plant (KCP). The request was prompted by an old map showing several, possibly eight, natural gas wells located under or near what is now the southeast corner of the Main Manufacturing Building at KCP. Volatile organic compound contamination in the alluvial aquifer surrounding the gas wells might possibly contaminate the bedrock aquifer if the gas … more

Date: May 1, 1993

Creator: Pickering, D.A.; Laase, A.D. (Oak Ridge National Lab., TN (United States)) & Locke, D.A. (Oak Ridge Inst. for Science and Education, TN (United States))

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Input shaping filter methods for the control of structurally flexible, long-reach manipulators

Within the Environmental Restoration and Waste Management Program of the US Department of Energy, the remediation of single-shell radioactive waste storage tanks is one of the areas that challenge state-of-the-art equipment and methods. Concepts that utilize long-reach manipulators are being seriously considered for this task. Due to high payload capacity and high length-to-cross-section ratio requirements, these long-reach manipulator systems are expected to exhibit significant structural flex… more

Date: November 1, 1993

Creator: Kwon, Dong-Soo; Hwang, Dong-Hwan; Babcock, S. M. & Burks, B. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Coupled finite element-Monte Carlo simulation of microstructure and texture evolution during thermomechanical processing

A novel simulation technique for predicting the microstructure and texture evolution during thermomechanical processing is presented. The technique involves coupling a finite element microstructural deformation model based on crystal plasticity with a Monte Carlo simulation of recovery and recrystallization. The finite element model captures the stored energy and the crystallographic orientation distributions in the deformed microstructure. The Monte Carlo simulation captures the microstructura… more

Date: November 1, 1998

Creator: Radhakrishnan, B.; Sarma, G. & Zacharia, T.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Atom probe field ion microscopy of titanium aluminides

Titanium aluminides have a number of potential high temperature applications due to their good elevated-temperature mechanical properties, low density, and good creep and oxidation resistance. However, fabrication of commercial components of these materials has been impeded by their poor mechanical properties at ambient temperatures. Significant efforts with various degrees of success have been made to improve the mechanical properties of these TiAl alloys by doping them with a variety of diffe… more

Date: January 1, 1998

Creator: Larson, D. J. & Miller, M. K.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Use of complementary neutron techniques in studying the effect of a solid/liquid interface on bulk solution structures

By appropriate combination of neutron scattering techniques, it is possible to obtain structural information at various distances from a solid/liquid interface and thus probe in some detail how the surface structures evolve into bulk structures. We have used neutron reflectometry (NR) with a newly developed shear cell, near surface small angle neutron scattering (NSSANS) again in combination with the new shear cell, and regular small angle neutron scattering (SANS) with a standard Couette shear… more

Date: December 31, 1996

Creator: Butler, P.D.; Hamilton, W.A. & Magid, L.J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Atomic structure of a symmetric 27{degrees}[001] tilt grain boundary in MgO

The atomic structure of a symmetric 27 degree[001] tilt grain boundary in magnesium oxide has been determined by high-resolution Z-contrast imaging using a 300kV VG HB603U scanning transmission electron microscope with a 1.3 A probe. The atomic configuration in the grain boundary core is found to be considerably less open than the structures proposed for similar materials.

Date: April 1, 1997

Creator: Yan, Yanfa; Chisholm, M.F. & Pennycook, S.J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Effects of interlayers on the scratch adhesion performance of ultra-thin films of copper and gold on silicon substrates

Scratch testing has long been used to assess the adhesion of a film to its substrate. As film thicknesses have decreased, the need for greater precision and sensitivity in the scratch testing apparatus has increased. To this end, a nanoindenter was modified to make finely controlled, low-load scratches. Scratches at various loads and two orientations of a Berkovich scratching diamond were made in films of 100 nm of gold and 200 nm of copper, each on single crystal silicon. For each film type, s… more

Date: February 1, 1995

Creator: McAdams, S. D.; Tsui, T. Y.; Pharr, G. M. & Oliver, W. C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Atom probe field ion microscopy of high resistivity materials

Over the last 30 years the atom probe has proved to be a powerful tool for studying nanometer-sized compositional fluctuations in a wide range of metallic alloys but has had only limited applications to semiconductors and ceramics. One of the primary reasons for this difference is the higher resistivity of semiconducting and ceramic specimens. Because of this high resistivity, the high voltage field evaporation pulse is attenuated before it reaches the apex of the specimen thereby making the pu… more

Date: February 1, 1998

Creator: Sibrandij, S. J.; Larson, D. J. & Miller, M. K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Atom probe field ion microscopy of polysynthetically twinned titanium aluminide

Two phase {gamma}-based TiAl alloys are attractive for structural applications at high temperatures because they possess good elevated-temperature mechanical properties, low density, and good creep and oxidation resistance. The microstructures of these alloys consist of plates of the near equiatomic {gamma} phase (L1{sub 0}-ordered structure) and the Ti{sub 3}Al {alpha}{sub 2} phase (D0{sub 19}-ordered structure). It is of great interest to study the details of the lamellar {alpha}{sub 2} + {ga… more

Date: February 1, 1998

Creator: Larson, D. L.; Miller, M. K.; Inui, H. & Yamaguchi, M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Cooperative chemical rebonding in the segregation of impurities in silicon grain boundaries

With ab initio calculations the authors show that the experimentally observed large segregation energies of As at Si grain boundaries can be explained by the formation of isolated dimers or ordered chains of dimers of threefold-coordinated As along the cores of grain boundary dislocations. They also find the intriguing possibility that As segregation may drive structural transformation of certain grain boundaries. Recently, they have obtained the first atomic-resolution STEM images of As in a S… more

Date: December 1996

Creator: Maiti, A.; Chisholm, M. F.; Pennycook, S. J. & Pantelides, S. T.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Digital field ion microscopy

Due to environmental concerns, there is a trend to avoid the use of chemicals needed to develop negatives and to process photographic paper, and to use digital technologies instead. Digital technology also offers the advantages that it is convenient, as it enables quick access to the end result, allows image storage and processing on computer, allows rapid hard copy output, and simplifies electronic publishing. Recently significant improvements have been made to the performance and cost of came… more

Date: January 1, 1998

Creator: Sijbrandij, S. J.; Russell, K. F.; Miller, M. K. & Thomson, R. C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The atomic-scale origins of grain boundary superconducting properties

Due to the extremely short coherence lengths of the high-{Tc} superconductors, defects such as grain boundaries are obvious barriers to the flow of supercurrent. Within a few months of the discovery of these materials, it was shown how the critical current dropped four orders of magnitude as the grain boundary misorientation increased from zero to 45{degree}. Even today, there is no quantitative understanding of this behavior. A qualitative understanding is however possible through atomic resol… more

Date: February 1, 1998

Creator: Pennycook, S. J.; Chisholm, M. F.; Buban, J.; Browning, N. D.; Prouteau, C. & Nellist, P. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Proceedings of the workshop on the production and use of intense radioactive beams at the Isospin Laboratory

These proceedings report the deliberations of a 3 1/2 day workshop on the Production and Use of Intense Radioactive Ion Beams at the Isospin Laboratory, which was held at the Joint Institute for Heavy Ion Research in Oak Ridge, Tennessee, October 1992. The purpose of this workshop was not to duplicate the programs of other recent radioactive ion beam workshops or international conferences that have focused on the scientific concepts which radioactive beams can, and in fact already are, addressi… more

Date: December 31, 1992

Creator: Garrett, J. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department