54 Matching Results

Search Results

Advanced search parameters have been applied.

in creator/contributor: "Boatner, L. A."

open access

Promethium (Pm/sup 3 +/) solid state laser

The achievement of stimulated emission from the trivalent promethium ion is reported. (DLC)

Date: January 1, 1987

Creator: Shinn, M. D.; Krupke, W. F.; Kirchoff, T. A.; Finch, C. B. & Boatner, L. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

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

open access

The Structure of Lead-Indium Phosphate Glass

Lead-indium phosphate-lasses exhibit a number of useful properties such as a hi-h index-of-refraction, low preparation temperature and melt viscosity, and good chemical durability. The structure of such a glass (composition in wt.%: 65 PbO, 29 P{sub 2}O{sub 5}, 6 In{sub 2}O{sub 3}) has been investigated by total neutron scattering using the GLAD diffractometer at Argonne`s spallation neutron source IPNS. Peaks corresponding to the P-0, Pb-O/ln-O, and O-O pairs were observed in the radial distri… more

Date: December 1, 1994

Creator: Suzuya, K.; Price, D. L.; Loong, C. K.; Sales, B. C. & Boatner, L. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

X-ray Absorption Spectroscopy of the Rare Earth orthophosphates

X-ray Absorption Spectroscopy (XAS) of the Rare Earth (RE) 3d levels yields sharp peaks near the edges as a result of strong, quasi-atomic 3d{sup 10}4f{sup n} {yields} 3d-{sup 9}4f{sup n+1} transitions and these transitions exhibit a wealth of spectroscopic features. The XAS measurements of single crystal REPO{sub 4} (RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er) at the 3d edge were performed in the total yield mode at beam line 8-2 at the Stanford Synchrotron Radiation Laboratory (SSRL). The XA… more

Date: June 1, 1993

Creator: Shuh, D. K.; Terminello, L. J.; Boatner, L. A. & Abraham, M. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Passive sensor systems for nuclear material monitoring

Passive fiber optic sensor systems capable of confirming the presence of special nuclear materials in storage or process facilities are being developed at Oak Ridge National Laboratory (ORNL). These sensors provide completely passive, remote measurement capability. No power supplies, amplifiers, or other active components that could degrade system reliability are required at the sensor location. ORNL, through its research programs in scintillator materials, has developed a variety of materials … more

Date: September 1, 1993

Creator: Simpson, M. L.; Boatner, L. A.; Holcomb, D. E.; McElhaney, S. A.; Mihalczo, J. T.; Muhs, J. D. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Evaluation of Large Volume SrI2(Eu) Scintillator Detectors

There is an ever increasing demand for gamma-ray detectors which can achieve good energy resolution, high detection efficiency, and room-temperature operation. We are working to address each of these requirements through the development of large volume SrI{sub 2}(Eu) scintillator detectors. In this work, we have evaluated a variety of SrI{sub 2} crystals with volumes >10 cm{sup 3}. The goal of this research was to examine the causes of energy resolution degradation for larger detectors and t… more

Date: November 18, 2010

Creator: Sturm, B. W.; Cherepy, N. J.; Drury, O. B.; Thelin, P. A.; Fisher, S. E.; Magyar, A. F. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Solidification microstructures in single-crystal stainless steel melt pools

Development of microstructure of stationary melt pools of oriented stainless steel single crystals (70%Fe-15%Ni-15%Cr was analyzed. Stationary melt pools were formed by electron-beam and gas-tungsten-arc heating on (001), (011), and (111) oriented planes of the austenitic, fcc-alloy crystals. Characterization and analysis of resulting microstructure was carried out for each crystallographic plane and welding method. Results showed that crystallography which favors ``easy growth`` along the <100… more

Date: March 1, 1994

Creator: Sipf, J. B.; Boatner, L. A. & David, S. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Modeling of single-crystal laser-weld microstructures

A heat and fluid-flow model has been used to calculate the weld-pool size and shape for a high-speed, single-pass, autogenous laser weld as a function of time. Based on the calculated weld-pool shape, and with the use of a geometric model relating the dendritic growth to the weld-pool shape, the dendritic growth pattern was calculated for a single-crystal laser weld with an (001) surface that was welded along the [100] direction. The calculated results were compared to an actual experimental la… more

Date: July 1, 1993

Creator: Vitek, J. M.; Zacharia, T.; David, S. A.; Boatner, L. A. & Rappaz, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Gravitational effects on the development of weld-pool and solidification microstructures

This research effort has as its objective the development of a quantitative understanding of the effects of both low- and high-g environments on the solidification microstructures and morphologies that are produced in alloy single crystals during a variety of melting and solidification processes. The overall goal of the effort is to delineate the nature of the roles played by natural convection, surface-tension-driven convection, and mass transport effects due to interactions associated with va… more

Date: September 1, 1994

Creator: Boatner, L. A.; David, S. A. & Workman, G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Anomalous temperature dependence of the lattice parameters in HoPO{sub 4} and HoVO{sub 4}: Rare earth quadrupolar effects

The temperature dependence of the lattice parameters in tetragonal HoPO{sub 4} and HoVO{sub 4} was measured using neutron powder-diffraction techniques. Below about 100K, the lattice parameter a of HoPO{sub 4} increases with decreasing temperature while c decreases. In HoVO{sub 4}, the above behavior is reversed, that is, a decreases with decreasing temperature while c increases. Similar measurements on nonmagnetic LUP0{sub 4} and LuVO{sub 4} do not show any anomaly. This observation indicates … more

Date: July 1, 1994

Creator: Skanthakumar, S.; Loong, C. K.; Soderholm, L.; Nipko, J.; Richardson, J. W. Jr.; Abraham, M. M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Nanoscale Science, Engineering and Technology Research Directions

This report describes important future research directions in nanoscale science, engineering and technology. It was prepared in connection with an anticipated national research initiative on nanotechnology for the twenty-first century. The research directions described are not expected to be inclusive but illustrate the wide range of research opportunities and challenges that could be undertaken through the national laboratories and their major national scientific user facilities with the suppo… more

Date: January 1, 1999

Creator: Lowndes, D. H.; Alivisatos, A. P.; Alper, M.; Averback, R. S.; Jacob Barhen, J.; Eastman, J. A. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Raman phonons in RPO{sub 4} crystals.

Orthophosphates formed by elements in the first half of the lanthanide transition series (La, Pr, Nd, Sm, Eu and Gd) are structural analogs to the monoclinic mineral monazite. This mineral is characterized by an almost unique combination of properties that make its synthetic forms attractive as possible hosts for the long-term storage of actinide wastes. Crystals of lanthanide orthophosphates were grown by dissolving and by reacting lanthanide oxides in molten lead pyrophosphate at high tempera… more

Date: May 15, 2002

Creator: Paschoal, C. W. A.; Ayala, A. P.; Guedes, I.; Loong, C.-K. & Boatner, L. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Luminescence Properties of ScPO{sub 4} Single Crystals

Flux-grown ScPO{sub 4} single crystals exhibit a number of luminescence bands in their x-ray-excited luminescence spectra - including sharp lines arising from rare-earth elements plus a number of broad bands at 5.6 cV, 4.4 eV, and 3 eV. The band at 5.6 eV was attributed to a self-trapped exciton (STE) [l], and it could be excited at 7 eV and higher energies. This luminescence is strongly polarized (P = 70 %) along the optical axes of the crystal and exhibits a kinetic decay time constant that v… more

Date: August 16, 1999

Creator: Boatner, L. A. & Trukhin, A. N.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The formation of Al{sub 2}O{sub 3}/V{sub 2}O{sub 3} multilayer structures by high-dose ion implantation

High-resolution TEM, RBS-channeling and x-ray-diffraction techniques have been used to characterize multilayered structures formed by the high-dose co-implantation of vanadium and oxygen into single crystals of {alpha}-Al{sub 2}O{sub 3}. Thin, two-dimensional multilayered structures have been formed by implanting c-axis and a-axis-oriented single crystals of Al{sub 2}O{sub 3} at room temperature with vanadium (10{sup 17} ions/cm{sup 2} at 300 keV) and oxygen (2 x 10{sup 17} ions/cm{sup 2}, 120 … more

Date: April 1, 1995

Creator: Gea, L. A.; Boatner, L. A.; Budai, J. D. & Rankin, J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Low Temperature Thermal Conductivity of Ktao/Sub 3/ and Ktn Single Crystals

Thermal conductivity of three KTaO/sub 3/ mixed crystals containing different impurities was measured. Specific heat data show large discrepancies with the calculated Debye contribution so the question of the existence of a phase transition below 10/sup 0/K remains open. (FS)

Date: January 1, 1979

Creator: de Gooer, A. M.; Salce, B. & Boatner, L. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Ion-Beam-Induced Defects and Defect Interactions in Perovskite-Structure Titanates

Ion-beam irradiation of perovskite structures results in the production and accumulation of defects. Below a critical temperature, irradiation also leads to a crystalline-to-amorphous transformation. The critical temperature for amorphization under 800 keV Kr{sup +} ion irradiation is 425,440 and 550 K for SrTiO{sub 3}, CaTiO{sub 3} and BaTiO{sub 3}, respectively. The results of ion-channeling studies on SrTiO{sub 3} irradiated with 1.0 MeV Au{sup 2+} ions suggest that the crystalline-to-amorph… more

Date: August 23, 1999

Creator: Boatner, L. A.; Jiang, W.; Meldrum, A.; Thevuthasan, S.; Weber, W. J. & Williford, R. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Intermediate-Range Order in Simple Metal-Phosphate Glasses: The Effect of Metal Cations on the Phosphate Anion Distribution

The technique of high-performance liquid chromatography (HPLC) has been used to probe the phosphate anion distribution in a variety of metal phosphate glasses including glasses made with trivalent metal cations (Al, In, Ga, La). The composition of each glass was chosen so that the average phosphate chain length was between 2 and 4 PO{sub 4} tetrahedra. The widths of the resulting phosphate anion distributions were determined directly from an analysis of the HPLC chromatograms. Literature values… more

Date: June 1, 1997

Creator: Sales, B. C.; Boatner, L. A. & Ramey, J. O.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Growth of Large Single Crystals of Mgo

The progressive identification of new high-technology applications and requirements for MgO single crystals in the commercial realm, as well as in DOE and other government-agency project areas, has resulted in an increased demand and international market for this material. Specifically, the demand for MgO crystals in large sizes and quantities is presently increasing due to existing and developing applications that include: (a) MgO substrates for the formation of electro-optic thin films and de… more

Date: June 12, 1997

Creator: Boatner, L. A. & Urbanik, M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Growth of Large Detector Crystals. Crada Final Report

In the course of a collaborative research effort between L.A. Boatner of Oak Ridge National Laboratory and Prof. Alex Lempicki of the Department of Chemistry of Boston University, a new highly efficient and very fast scintillator for the detection of gamma-rays was discovered. This new scintillator consists of a single crystal of lutetium orthophosphate (LuPO{sub 4}) to which a small percentage of trivalent cerium is added as an activator ion. The new lutetium orthophosphate-cerium scintillator… more

Date: June 18, 1997

Creator: Boatner, L. A. & Samuelson, S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Chemical and Ceramic Methods Toward Safe Storage of Actinides Using Monazite. 1998 Annual Progress Report

'The use of ceramic monazite, (La,Ce)PO{sub 4}, for sequestering actinides, especially plutonium, and some other radioactive waste elements (rare earths e.g.) and thus isolating them from the environment has been championed by Lynn Boatner of ORNL. It may be used alone or, as it is compatible with many other minerals in nature, can be used in composite combinations. Natural monazite, which almost invariably contains Th and U, is often formed in hydrothermal pegmatites and is extremely water res… more

Date: June 1, 1998

Creator: Morgan, P. E. D. & Boatner, L. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Electrical-Conductivity Measurements of Leachates for the Rapid Assessment of Wasteform Corrosion Resistance

Measurements of the electrical conductivity of leachate solutions as a function of time can be used as an efficient, informative means of evaluation and comparison in the development of nuclear waste forms and in the preliminary analysis of their corrosion resistance in distilled water. Three separate applications of this technique are described in this work. These are: (1) its use in the optimization of the corrosion resistance of a crystalline wasteform (monazite); (2) a study of the protecti… more

Date: January 1, 1982

Creator: Sales, B. C.; Petek, M. & Boatner, L. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Chemical and Sonochemical Approaches to the Formation of Vo{Sub 2} Films and Vo{Sub 2}-Impregnated Materials

A new chemical and chemical/ultrasonic approach to the preparation of VO{sub 2} films and VO{sub 2}-impregnated bulk materials has been developed. In this approach, a V{sub 2}O{sub 5} sol prepared by quenching is used to coat SiO{sub 2} substrates. The resulting gel-film is heat treated in a reducing atmosphere to form a film identified as VO{sub 2} from the results of X-ray diffraction and both optical and resistivity measurements, which reveal the phase transition characteristic of vanadium d… more

Date: November 1, 1997

Creator: Keppens, V.; Mandrus, D. & Boatner, L. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Giant, Ultrafast Optical Switching Based on an Insulator-to-Metaltransition in vo2 Nano-Particles: Photo-Activation of Shape-Controlledplasmons at 1.55 Mu-M

A new generation of devices where the electronic, optical or magnetic state of a system can be controlled optically on the ultrafast timescale is one of the most compelling technological ramifications of the rapidly advancing field of strongly correlated electrons. However, for real-world applications it is also necessary to incorporate these compounds in appropriate environments (e.g. optical fibers or silicon-based electronics), to ensure compatibility with existing technologies (e.g. telecom… more

Date: July 1, 2004

Creator: Rini, M.; Cavalleri, A.; Schoenlein, R. W.; Lopez, R.; Feldman, C.; Haglund, R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Ferroelectric-to-Relaxor Crossover and Oxygen Vacancy Hopping in Compositionally-Disordered Perovskites - Kta(1-X)Nb(X)O(3):Ca

It is shown that lattice disorder induced by Nb and Ca substitution has a strong influence on the dielectric and relaxational properties of KTaO{sub 3}. Both substituents are believed to occupy off-center positions at the Ta site, and the difference in valence between the Ca{sup 2+} and Ta{sup 5+} ions leads to the formation of oxygen vacancies (V{sub 0}). Specifically, for a KTa{sub 1{minus}x}Nb{sub x}O{sub 3}:Ca crystal with x = 0.023 and with a 0.055 at.% Ca doping they observe: (1) a ferroe… more

Date: July 26, 1999

Creator: Samara, G. A. & Boatner, L. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department