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Low-voltage cathodoluminescence of europium-activated yttrium orthovanadate

Description: Emissive flat panel display systems operating in full color demand higher performance at low voltages (ca. 501000 V) from cathodoluminescent (CL) phosphors than cathode ray tubes require. Hydrothermal synthesis has been suggested as a route to phosphors with improved efficiencies, lower voltage thresholds, and increased saturation power. This hypothesis was tested in europium-doped yttrium orthovanadate (YVO{sub 4}:Eu), an efficient, red emitting CL phosphor. The CL efficiency of YVO{sub 4}:Eu crystallized from aqueous solution at 200{degrees}C is relatively low until it is annealed. The distribution of particle sizes in the low-temperature phosphor is similar to that in material made via a solid-state route, but crystallites remain much smaller (ca. 400 {Angstrom}) until they are annealed. These observations, along with the anomalously strong dependence of CL intensity on europium concentration, support a model in which efficiency principally depends on crystallite size. CL efficiency of both solid state and hydrothermal YVO{sub 4}:Eu increases with voltage at constant power. Surface-bound electrons are likely the dominant influence on efficiency at voltages near threshold. Saturation power is independent of synthetic route. It is apparent that the CL properties of hydrothermally synthesized YVO{sub 4}:Eu are essentially the same as those of YVO{sub 4}:Eu produced via conventional, high-temperature routes.
Date: March 1, 1995
Creator: Phillips, M.L.F.
Partner: UNT Libraries Government Documents Department

High beta and second stability region transport and stability analysis: Technical progress report

Description: This report summarizes MHD equilibrium and stability studies carried out at Northrop Grumman`s Advanced Technology and Development Center during the 12 month period starting March 1, 1994. Progress is reported in both ideal and resistive MHD modeling of TFTR plasmas. The development of codes to calculate the significant effects of highly anisotropic pressure distributions is discussed along with results from this model.
Date: March 1, 1995
Creator: Hughes, M.H. & Phillips, M.W.
Partner: UNT Libraries Government Documents Department

Infrared emission spectra or uranium and thorium

Description: The region between 1 and 5.5 ..mu..m has been observed with a high-resolution Fourier transform spectrometer. See-through hollow cathode lamps with calcium fluoride windows were operated at high current. Special precautions were required to minimize interference by blackbody radiation from the hot cathode. Observed lines were measured to an absolute accuracy of about 0.001 cm/sup -1/ and about 5% relative intensity accuracy. The argon carrier gas lines were readily distinguished by their much wider Doppler-broadened linewidths. Many lines were assigned to neutral or singly-ionized thorium on the basis of predicted transition wavenumbers calculated from accurate level lists. However, many lines remain to be assigned. This new spectral data connects to, and extends similar, spectral information given in our uranium and thorium atlases which cover the ultraviolet and visible regions.
Date: January 1, 1983
Creator: Palmer, B.A.; Phillips, M.V. & Engleman, R. Jr.
Partner: UNT Libraries Government Documents Department

Phosphor synthesis routes and their effect on the performance of garnet phosphorus at low-voltages

Description: Garnet phosphors have potential for use in field emission displays (FEDs). Green-emitting Gd{sub 3}Ga{sub 5}O{sub 12}:Tb (GGG:Tb) and Y{sub 3}Al{sub 5}O{sub 12}:Tb (YAG:Tb) are possible alternatives to ZnO:Zn, because of their excellent resistance to burn, low-voltage efficiency, (3.5 lm/W from GGG:Tb at 800 V), and saturation resistance at high power densities. Hydrothermal and combustion synthesis techniques were employed to improve the low-voltage efficiency of YAG:Tb, and Y{sub 3}Ga{sub 5}O{sub 12}:Tb (YGG:Tb). Synthetic technique did not affect low-voltage (100--1,000 V) efficiency, but affected the particle size, morphology, and burn resistance. The small particle size phosphors obtained via hydrothermal (<1 {micro}m) and combustion reactions (<1 {micro}m) would benefit projection TV, high-definition TV (HDTV), and heads-up displays (HUDs), where smaller pixel sizes are required for high resolution.
Date: July 1, 1996
Creator: Shea, L.E.; McKittrick, J. & Phillips, M.L.F.
Partner: UNT Libraries Government Documents Department

High beta and second stability region transport and stability analysis. Final report

Description: This report describes MHD equilibrium and stability studies carried out at Northrop Grumman`s Advanced Technology and Development Center during the period March 1 to December 31, 1995. Significant progress is reported in both ideal and resistive MHD modeling of TFTR plasmas. Specifically, attention is concentrated on analysis of Advanced Tokamak experiments at TFTR involving plasmas in which the q-profiles were non-monotonic.
Date: January 1, 1996
Creator: Hughes, M.H. & Phillips, M.W.
Partner: UNT Libraries Government Documents Department

Assessment of impacts and evaluation of restoration methods on areas affected by a well blowout, Naval Petroleum Reserve No. 1, California

Description: In June 1994, an oil well on Naval Petroleum Reserve No. 1 blew-out and crude oil was deposited downwind. After the well was capped, information was collected to characterize the release and to assess effects to wildlife and plants. Oil residue was found up to 13.7 km from the well site, but deposition was relatively light and the oil quickly dried to form a thin crust on the soil surface. Elevated levels of hydrocarbons were found in livers collected from Heermann`s kangaroo rats (Dipodomys heermanni) from the oiled area but polycyclic aromatic hydrocarbons (known carcinogens or mutagens) were not detected in the livers. Restoration techniques (surface modification and bioremediation) and natural recovery were evaluated within three portions of the oiled area. Herbaceous cover and production, and survival and vigor of desert saltbush (Atriplex polycarpa) were also monitored within each trapping grid.
Date: December 1, 1996
Creator: Warrick, G.D.; Kato, T.T. & Phillips, M.V.
Partner: UNT Libraries Government Documents Department

Zeolite membranes from kaolin

Description: Zeolite films are sought as components of molecular sieve membranes. Different routes used to prepare zeolite composite membranes include growing zeolite layers from gels on porous supports, depositing oriented zeolites on supports, and dispersing zeolites in polymeric membranes. In most cases, it is very difficult to control and avoid the formation of cracks and/or pinholes. The approach to membrane synthesis is based on hydrothermally converting films of layered aluminosilicates into zeolite films. The authors have demonstrated this concept by preparing zeolite A membranes on alumina supports from kaolin films. The authors have optimized the process parameters not only for desired bulk properties, but also for preparing thin (ca. 5 {micro}m), continuous zeolite A films. Scanning electron microscopy shows highly intergrown zeolite A crystals over most of the surface area of the membrane, but gas permeation experiments indicate existence of mesoporous defects and/or intercrystalline gaps. It has been demonstrated that the thickness of the final zeolite A membrane can be controlled by limiting the amount of precursor kaolin present in the membrane.
Date: July 1, 1996
Creator: Karle, B.G.; Brinker, C.J. & Phillips, M.L.F.
Partner: UNT Libraries Government Documents Department

Inorganic materis for anomalous-dispersion phase-matched second harmonic generation: Rubidium titanyl arsenate isomorphs, Rb[Ti{sub 1-2x}Ln{sub x}Nb{sub x}]OAsO{sub 4}

Description: We report the synthesis and optical properties of Rb[Ti{sub 1-2x}Ln{sub x}Nb{sub x}]OAsO{sub 4}. The solid solubility of lanthanide ions in the materials decreases exponentially as the size of the lanthanide ion increases. The materials exhibit absorption spectra characteristic of the particular lanthanide ion in the structure. The spectral regions between absorption peaks are transparent and will allow the transmission of fundamental and second-harmonic radiation. The charge transfer band is red-shifted 0 to 27 nm relative to RbTiOAsO{sub 4} (midpoint 331 nm). Second-harmonic intensities measured at 532 nm decrease exponentially as lanthanide ion concentration increases.
Date: December 31, 1993
Creator: Anderson, M.T.; Phillips, M.L.F. & Stucky, G.D.
Partner: UNT Libraries Government Documents Department

Garnet phosphors prepared via hydrothermal synthesis

Description: This project studied hydrothermal synthesis as a route to producing green-emitting cathodoluminescent phosphorus isostructural with yttrium aluminum garnet (Y{sub 3}Al{sub 5}O{sub 12}, or YAG). Aqueous precipitation of Y, Gd, Al, Ga, and Tb salts produced amorphous gels, which were heated with water at 600 C and 3,200 bar to produce crystalline YAG:Tb, Y{sub 3}Ga{sub 5}O{sub 12}:Tb, Y{sub 3}Al{sub 3}Ga{sub 2}O{sub 12}:Tb, and Gd{sub 3}Ga{sub 5}O{sub 12}:Tb powders. Process parameters were identified that yielded submicron YAG:Tb and Y{sub 3}Ga{sub 5}O{sub 12}:Tb powders without grinding. Cathodoluminescent efficiencies were measured as functions of power density at 600 V, using both the hydrothermal garnets and identical phosphor compositions synthesized at high temperatures. Saturation behavior was independent of synthetic technique, however, the hydrothermal phosphorus were less susceptible to damage (irreversible efficiency loss) at very high power densities (up to 0.1 W/cm{sup 2}). The fine grain sizes available with hydrothermal synthesis make it an attractive method for preparing garnet phosphorus for field emission, projection, and head-up displays.
Date: May 1, 1996
Creator: Phillips, M.L.F.; Walko, R.J. & Shea, L.E.
Partner: UNT Libraries Government Documents Department

Effects of processing on the low-voltage performance of cathodoluminescent garnet phosphors

Description: Field emission flat panel displays place new demands on the performance of cathodoluminescent phosphors. In particular, such phosphors must be efficient at lower voltages (ca. 100-1000 V), and must withstand higher current densities than are present on cathode ray tube screens. ZnO:Zn has been studied extensively as a low-voltage phosphor, but problems such as poor chromatic saturation and temperature sensitivity of emission remain. In this work the use of terbium-doped garnet phases such as yttrium aluminum garnet (YAG) and gadolinium gallium garnet (GGG) as low voltage green-emitting phosphors is evaluated. Hydrothermal synthesis yields well-faceted YAG grains with particle diameters of less than 1 {mu}m. Cathodoluminescent efficiency at a particular voltage was not affected by synthetic route, though the hydrothermally synthesized material was less susceptible to damage at high power densities. An efficiency of 3.5 lm/W was observed for GGG:Tb at 800 V. Deposition of the phosphors onto conducting screens increased their efficiencies at very low voltages (< 200 V). These materials may be considered alternatives to reduced zinc oxide as green-emitting phosphors.
Date: August 1, 1995
Creator: Phillips, M.L.F. & Shea, L.E.
Partner: UNT Libraries Government Documents Department

Phosphors for flat panel emissive displays

Description: An overview of emissive display technologies is presented. Display types briefly described include: cathode ray tubes (CRTs), field emission displays (FEDs), electroluminescent displays (ELDs), and plasma display panels (PDPs). The critical role of phosphors in further development of the latter three flat panel emissive display technologies is outlined. The need for stable, efficient red, green, and blue phosphors for RGB fall color displays is emphasized.
Date: July 1, 1995
Creator: Anderson, M.T.; Walko, R.J. & Phillips, M.L.F.
Partner: UNT Libraries Government Documents Department

Real-time instrument for ambient monitoring of hydrogen sulfide, dimethyl sulfide, and other reduced organosulfur species using ozone chemiluminescent detection

Description: The chemiluminescent reactions of H/sup 2/S and other gaseous sulfides with ozone at 298/sup 0/K have been investigated, with the aim of developing a simple, selective, real-time monitor for these naturally emitted compounds. A commercial chemiluminescent ozone monitor has been adapted, for detection of the ozone/sulfide chemiluminescence between 300 and 400 nm wavelenght. Excess ozone was supplied to the reaction chamber from an electrical discharge ozone source. Response to dimethyl sulfide was enhanced by the use of air in the ozone source rather than oxygen. This effect was found to be caused by the presence of oxides of nitrogen produced in the ozonizer; a similar enhancement was not observed for the other sulfide compounds studied. Observed chemiluminescence signal decreased in the order CH/sub 3/SH > CH/sub 3/SCH/sub 3/ > H/sub 2/S > thiophene, with detection limits of 0.1, 0.3, 4, and 12 ppb respectively, at an instrument time constant of 60 sec. Calibration plots were linear at low sulfide concentrations, and showed less-than-first order dependence on sulfide at higher concentrations. A very small signal from ethylene was the only interference found from several compounds tested; sample air humidity has a small but significant effect on the instrument response.
Date: January 1, 1982
Creator: Kelly, T.J.; Phillips, M.F.; Tanner, R.L. & Gaffney, J.S.
Partner: UNT Libraries Government Documents Department

Photo- and cathodoluminescence of hydrothermally synthesized Y{sub 3}Al{sub 5}O{sub 12}:Tb and NaY(WO{sub 4}){sub 2}:Tb

Description: Cathodoluminescent (CL) phosphors with improved low-voltage characteristics are needed for use in emissive flat panel displays. Conventional high-temperature methods for phosphor synthesis yield large polycrystalline grains that must be pulverized prior to screen deposition. Grinding has been implicated in reducing phosphor efficiency by causing surface contamination and defects. Hydrothermal synthesis has been used to improve the quality of ceramic powders by producing fine, well-formed crystallites without grinding. Two green-emitting phosphors, Y{sub 3}Al{sub 5}O{sub 12}:Tb (YAG:Tb) and NaY(WO{sub 4}){sub 2}:Tb, were used to test the effects of hydrothermal. synthesis on grain size and morphology, and on low-voltage CL properties. YAG:Th prepared hydrothermally consisted of submicron crystallites with a typical garnet habit. The CL efficiency of hydrothermally synthesized YAG:Tb (3 lm/W at 800 V) was comparable to that of equivalent YAG:Tb compositions prepared via high-temperature solid state reaction. In comparison, CL intensities of Gd{sub 3}Ga{sub 5}O{sub l2}:Tb were slightly better (3.5 lm/W at 800 V), while those of NaY(WO{sub 4}){sub 2}:Tb were approximately 1/100th that of YAG:Tb. Both CL and photoluminescence data show that the difference in the cathodoluminescence of YAG and NaY(WO{sub 4}){sub 2} can be understood in terms of differences in the mechanism of activation.
Date: October 1, 1995
Creator: Phillips, M.L.F. & Potter, B.G. Jr.
Partner: UNT Libraries Government Documents Department

Towards p-type doping of ZnO by ion implantation

Description: Zinc oxide is a very attractive material for a range of optoelectronic devices including blue light-emitting diodes and laser diodes. Though n-type doping has been successfully achieved, p-type doing of ZnO is still a challenge that must be overcome before p-n junction devices can be realized. Ion implantation is widely used in the microelectronics industry for selective area doping and device isolation. Understanding damage accumulation and recrystallization processes is important for achieving selective area doping. In this study, As (potential p-type dopant) ion implantation and annealing studies were carried out. ZnO samples were implanted with high dose (1.4 x 10{sup 17} ions/cm{sup 2}) 300 keV As ions at room temperature. Furnace annealing of samples in the range of 900 C to 1200 C was employed to achieve recrystallization of amorphous layers and electrical activation of the dopant. Rutherford backscattering/channeling spectrometry, transmission electron microscopy and cathodolumiescence spectroscopy were used to monitor damage accumulation and annihilation behavior in ZnO. Results of this study have significant implications for p-type doing of ZnO by ion implantation.
Date: January 18, 2005
Creator: Coleman, V; Tan, H H; Jagadish, C; Kucheyev, S; Phillips, M & Zou, J
Partner: UNT Libraries Government Documents Department


Description: GrayQb{trademark} is a novel technology that has the potential to characterize radioactively contaminated areas such as hot cells, gloveboxes, small and large rooms, hallways, and waste tanks. The goal of GrayQb{trademark} is to speed the process of decontaminating these areas, which reduces worker exposures and promotes ALARA considerations. The device employs Phosphorous Storage Plate (PSP) technology as its primary detector material. PSPs, commonly used for medical applications and non-destructive testing, can be read using a commercially available scanner. The goal of GrayQb{trademark} technology is to locate, quantify, and identify the sources of contamination. The purpose of the work documented in this report was to better characterize the performance of GrayQb{trademark} in its ability to present overlay images of the PSP image and the associated visual image of the location being surveyed. The results presented in this report are overlay images identifying the location of hot spots in both controlled and field environments. The GrayQb{trademark} technology has been mainly tested in a controlled environment with known distances and source characteristics such as specific known radionuclides, dose rates, and strength. The original concept for the GrayQb{trademark} device involved utilizing the six faces of a cube configuration and was designed to be positioned in the center of a contaminated area for 3D mapping. A smaller single-faced GrayQb{trademark}, dubbed GrayQb SF, was designed for the purpose of conducting the characterization testing documented in this report. This lighter 2D version is ideal for applications where entry ports are too small for a deployment of the original GrayQb™ version or where only a single surface is of interest. The shape, size, and weight of these two designs have been carefully modeled to account for most limitations encountered in hot cells, gloveboxes, and contaminated areas. GrayQb{trademark} and GrayQb{trademark} SF share the same fundamental detection system design (e.g., ...
Date: December 12, 2013
Creator: Mayer, J.; Farfan, E.; Immel, D.; Phillips, M.; Bobbitt, J. & Plummer, J.
Partner: UNT Libraries Government Documents Department


Description: This report describes the development of a software tool, entitled “WildFire Ignition Resistance Estimator Wizard” (WildFIRE Wizard, Version 2.10). This software was developed within the Wildfire Ignition Resistant Home Design (WIRHD) program, sponsored by the U. S. Department of Homeland Security, Science and Technology Directorate, Infrastructure Protection & Disaster Management Division. WildFIRE Wizard is a tool that enables homeowners to take preventive actions that will reduce their home’s vulnerability to wildfire ignition sources (i.e., embers, radiant heat, and direct flame impingement) well in advance of a wildfire event. This report describes the development of the software, its operation, its technical basis and calculations, and steps taken to verify its performance.
Date: October 10, 2012
Creator: Phillips, M.; Robinson, C.; Gupta, N. & Werth, D.
Partner: UNT Libraries Government Documents Department

Development of techniques for tagging precursor and essential chemicals

Description: The ability to identify the manufacturers and distributors of chemicals seized in raids of illicit drug labs would be of great value in controlling the diversion of these chemicals. We developed a tagging scheme based on the addition of sub-ppM concentrations of various combinations of rare-earth elements to the target chemicals and evaluated a number of techniques for detecting the tags. We developed soluble tags for tagging liquids and selected Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) as the preferred detection technique. We developed insoluble tags for tagging solids and developed methods to analyze them and mix them into solid precursors. We have successfully demonstrated the tagging of several solvents and two of the precursor chemicals used in one of the most popular clandestine methamphetamine syntheses (ephedrine reacting with hydriodic acid/red phosphorus). The tagging scheme is capable of yielding tens of thousands of signatures (using holmium as an internal standard and up to 9 rare-earths at up to 3 concentrations yields 3{sup 9} {minus} 1 = 19,682 signatures) and is applicable to most of the chemicals on the precursor and essential chemicals list. In the concentrations employed, the tags are safe enough to be added to pharmaceuticals and cheap enough to tag tanker loads of chemicals.
Date: January 1, 1994
Creator: Swansiger, W. A.; Shepodd, T. J. & Phillips, M. L. F.
Partner: UNT Libraries Government Documents Department

Low-voltage cathodoluminescent properties of europium-activated anion-deficient fluorites

Description: The authors examined the optical bandgap, particle size distribution, photoluminescence spectra, and cathodoluminescent response of fifteen phosphors that contain transition-metal and main-group sensitizers. They determined luminance versus applied voltage curves for electron energies from 5 to 1000 eV. Seven phosphors exhibit threshold voltages less than 110V. Y{sub 1.96} Eu{sub 0.04} O{sub 3} exhibits a threshold voltage of 13 V and, at 300 V, displays a luminance of 25 fL and a luminous efficiency of 0.02 lm/W.
Date: May 1, 1994
Creator: Anderson, M. T.; Phillips, M. L. F. & Walko, R. J.
Partner: UNT Libraries Government Documents Department

Technical requirements for the actinide source-term waste test program

Description: This document defines the technical requirements for a test program designed to measure time-dependent concentrations of actinide elements from contact-handled transuranic (CH TRU) waste immersed in brines similar to those found in the underground workings of the Waste Isolation Pilot Plant (WIPP). This test program wig determine the influences of TRU waste constituents on the concentrations of dissolved and suspended actinides relevant to the performance of the WIPP. These influences (which include pH, Eh, complexing agents, sorbent phases, and colloidal particles) can affect solubilities and colloidal mobilization of actinides. The test concept involves fully inundating several TRU waste types with simulated WIPP brines in sealed containers and monitoring the concentrations of actinide species in the leachate as a function of time. The results from this program will be used to test numeric models of actinide concentrations derived from laboratory studies. The model is required for WIPP performance assessment with respect to the Environmental Protection Agency`s 40 CFR Part 191B.
Date: October 1, 1993
Creator: Phillips, M. L. F. & Molecke, M. A.
Partner: UNT Libraries Government Documents Department

Optical properties of lanthanide-doped RbTiOAsO{sub 4} and transition metal-doped KTiOPO{sub 4}

Description: We have synthesized derivatives of potassium titanyl phosphate (KTP) and rubidium titanyl (RTA) where Ti has been replaced by transition metal or lanthanide ions, and K, Ti, P or O has laced by aliovalent counterions. Up to 5 mol % lanthanide ion can be substituted onto the Ti and 100 mol % substitution of other transition metals onto the Ti sites in KTP can be made. The visible spectra of these doped KTP phases are characteristic of the dopant ions, with sharp, narrow transitions resulting from lanthanide substitution and broader absorptions from transition-metal dopants. Powder second harmonic generation (SHG) intensities diminish with increased dopant concentration. Decreases in SHG intensities parallel those seen in previously studied systems. The choice of counterion substantially impacts some dopant solubilities, but generally affects SHG intensity and visible spectrum to a lesser degree. Single crystals doped with Er{sup 3+}, Fe{sup 3+} and Co{sup 2+} have linear absorption coefficients in the range of 1 to 5 cm{sup {minus}1}. Changes in noncritical phase matching wavelength due to anomalous dispersion are calculated to be less than 1 nm at the dopant levels tested.
Date: December 31, 1993
Creator: Phillips, M. L. F.; Anderson, M. T. & Sinclair, M. B.
Partner: UNT Libraries Government Documents Department