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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Post-Irradiation Examination (PIE) of Westinghouse-led ATF Concepts U3Si2 and U3Si2-UN. Rodlet Non-Destructive Examinations and Sectioning Diagram.

This report contains the results of non-destructive examinations of three ATF-1 rodlets, namely W01, WB2 and WB6. The rodlets are part of the series of irradiation tests led by Westinghouse within the Accident Tolerant Fuel (ATF) Phase 1 campaign. This report is intended to summarize the performed non-destructive examinations gathered so far on these rodlets and to propose a sectioning diagram before proceeding with destructive examinations.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Best Practices for Upgrading Fluorescent Troffers to LED

This fact sheet provides guidance on the various factors to consider when deciding on an LED upgrade for a fluorescent system, such as installation costs, operating costs, desired lighting levels, and performance criteria.

lighting, LED, troffer, retrofit, fluorescent, lum↗
DOE OSTI2023

High Efficiency Multijunction Devices: Solar Cells, Thermophotovoltaics, LEDs

High-efficiency III-V multijunction solar cells require multiple alloys with optimal bandgaps and excellent material quality. However, many useful alloys are lattice-mismatched to available substrates, and require strain-engineering tricks to enable efficient use. To this extent, we have developed low-dislocation density metamorphic material and optically-thick stress-balanced superlattices, enabling access to a wide variety of III-V alloys. Combined with transparent tunnel junctions, these components allow optimizing multijunction devices for a variety of applications. We have designed multijunction cells for the G173G-terrestrial and AM0-space spectra with record 39.5% and 34.2% efficiency, respectively, and also thermophotovoltaic cells for blackbody spectra that reach over 40% TPV-efficiency. Finally, using these PV components, we demonstrate a multijunction LED with high quantum efficiency.

high-efficiency↗
DOE OSTI2018

Diffusion of Magnesium in Led Structures with InGaN/GaN Quantum Wells at True Growth Temperatures 860–980°C of p-GaN

The results of an investigation of Mg diffusion in blue LED structures with InGaN/GaN quantum wells are presented for various growth temperatures of the p-GaN layer. The values of the diffusion coefficient estimated for true growth temperatures of 860, 910, and 980°C were 7.5·10{sup –17}, 2.8·10{sup –16}, and 1.2·10{sup –15} cm{sup 2}/s, respectively. The temperature values given in the work were measured on the surface of the growing layer in situ using a pyrometer. The calculated activation energy for the temperature dependence of the diffusion coefficient was 2.8 eV.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Internal Quantum Efficiency of Led Structures at Various Charge Carrier Distributions Over InGaN/GaN Quantum Wells

The results of studying the effect of the thickness of GaN barrier layers in the active region of LED structures with InGaN/GaN quantum wells on the internal quantum efficiency (IQE) of photoluminescence are presented. It is shown that a decrease in the thickness of the GaN barrier layers from 15 to 3 nm leads to an increase in the maximum value of IQE and to a shift of the maximum to the region of high excitation powers. The result obtained is explained with consideration for the decrease in the Auger recombination rate due to a more uniform distribution of charge carriers over the active region in structures with a barrier thickness of 3 nm.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Medical Student–Reported Outcomes of a Radiation Oncologist–Led Preclinical Course in Oncology: A Five-Year Analysis

Purpose: There is a recognized need for more robust training in oncology for medical students. At our institution, we have offered a core dedicated oncology block, led by a radiation oncologist course director, during the second year of the medical school curriculum since the 2008-2009 academic year. Herein, we report the outcomes of the oncology block over the past 5 years through an analysis of student perceptions of the course, both immediately after completion of the block and in the third year. Methods and Materials: We analyzed 2 separate surveys. The first assessed student impressions of how well the course met each of the course's learning objectives through a survey that was administered to students immediately after the oncology block in 2012. The second was administered after students completed the oncology block during the required radiology clerkship in the third year. All questions used a 5-level Likert scale and were analyzed by use of a Wilcoxon signed-rank test. Results: Of the 169 students who took the oncology course in 2012, 127 (75.1%) completed the course feedback survey. Over 73% of students agreed or strongly agreed that the course met its 3 learning objectives. Of the 699 medical students who took the required radiology clerkship between 2010 and 2013, 538 participated in the second survey, for a total response rate of 77%. Of these students, 368 (68.4%) agreed or strongly agreed that the course was effective in contributing to their overall medical education. Conclusion: Student perceptions of the oncology block are favorable and have improved across multiple categories since the inception of the course. Students self-reported that a dedicated preclinical oncology block was effective in helping identify the basics of cancer therapy and laying the foundation for clinical electives in oncology, including radiation oncology.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Thermostability and photostability of Sr{sub 3}SiO{sub 5}:Eu{sup 2+} phosphors for white LED applications

Sr{sub 3}SiO{sub 5}:Eu{sup 2+} phosphors were synthesized by solid-state reactions, and their photoluminescence (PL) stability under the impact of heat or light was studied. The thermal degradation in air was observed for the Sr{sub 3}SiO{sub 5}:Eu{sup 2+} phosphor, furthermore, this drop in emission intensity could be accelerated by simultaneously illuminating the phosphor with a high-power blue LED during the heating process. This enhanced thermal degradation phenomenon in the blue light can be ascribed to the photo-assisted thermal oxidation of Eu{sup 2+} ions. A reversible decrease in emission intensity at room temperature was observed on illuminating the Sr{sub 3}SiO{sub 5}:Eu{sup 2+} phosphor alone by the blue light, which could be related to trapping centers in the phosphor. The existence of traps is also responsible for the anomalous increase of emission intensity with increasing temperature from 30 to 100 °C. Considering the influences of Ba{sup 2+} doping on temperature-dependent PL properties of the Sr{sub 3}SiO{sub 5}:Eu{sup 2+} phosphor, the thermal quenching origin may be ascribed to the thermally assisted photoionization process. - Graphical abstract: The photo-induced reversible decrease in emission intensity and the anomalous emission enhancement with increasing temperature are related to trapping centers in the phosphor. - Highlights: • The photo-assisted thermal degradation was observed for the Sr{sub 3}SiO{sub 5}:Eu{sup 2+} phosphor. • The phosphor showed a reversible intensity decrease under the blue light irradiation. • An anomalous emission enhancement with increasing temperature was found. • Ba{sup 2+} substitution could suppress the thermal quenching of Sr{sub 3}SiO{sub 5}:Eu{sup 2+}. • Mechanisms for photostability and thermostability were discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

An orange emitting phosphor Lu{sub 2−x}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:xCe with pure garnet phase for warm white LEDs

A new silicate garnet phosphor, Lu{sub 2−x}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:xCe was synthesized by a high temperature solid-state reaction under reductive atmosphere. X-ray diffraction (XRD) showed that the powder was pure garnet phase. The emission and excitation spectrum indicated that the Lu{sub 2−x}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:xCe phosphors could absorb blue light in the spectral range of 400–550 nm efficiently and exhibit bright yellow–orange emission in the range of 520–750 nm. With the increase of Ce{sup 3+} concentration, the emission band of Ce{sup 3+} showed a red shift. Interestingly, the concentration quenching occurred when the Ce{sup 3+} concentration exceeded 4 mol%. The temperature-dependent luminescent properties of the phosphors were discussed and the Lu{sub 1.96}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:0.04Ce phosphors showed good performances in color temperature (2430 K) and potential applications for warm white LEDs. - Graphical Abstract: This image shows that the phosphor of Lu{sub 1.96}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:0.04Ce can generate a uniform yellow tint under natural light illumination and emit orange–red light when excited by blue light. With a fixed 467 nm emission light, warm white light can be produced by this phosphor, which indicates that the phosphor is potentially applicable in warm white light emitting diodes based on GaN chips. - Highlights: • A new silicate garnet phosphor was synthesized by solid-state method. • Secondary phases can be avoided when a small amount of Si{sup 4+} were replaced by Ti{sup 4+}. • A broad emission band of Ce{sup 3+} in the phosphors was described. • The phosphors are potentially applicable in warm white light emitting diodes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

A new bismuth-based coordination polymer as an efficient visible light responding photocatalyst under white LED irradiation

A new bismuth-based polymer, [Hbpe][Bi(Hpydc){sub 2}(pydc)]·H{sub 2}O (H{sub 2}pydc=pyridine-2,5-dicarboxylic acid, bpe=trans-bis(4-pyridyl) ethylene) has been hydrothermally synthesized. Transient photocurrent response and electrochemical impedance spectroscopy studies indicate that the synthesized polymer with efficient charge separation and transportation can be used as a potential photocatalyst. So we use it for the degradation of rhodamine B (RhB) dye wastewater under visible light. The comparative study on commercial Bi{sub 2}O{sub 3} shows [Hbpe][Bi(Hpydc){sub 2}(pydc)]·H{sub 2}O has the higher photocatalytic performance, with the degradation rate of 97% and 2% within 100 min for [Hbpe][Bi(Hpydc){sub 2}(pydc)]·H{sub 2}O and commercial Bi{sub 2}O{sub 3} respectively. Additionally, the five cycle reproducibility results of [Hbpe][Bi(Hpydc){sub 2}(pydc)]·H{sub 2}O implies that it can be used as a stable photocatalyst. - Graphical abstract: We report a new 1D coordination polymer [Hbpe][Bi(Hpydc){sub 2}(pydc)]·H{sub 2}O by a facile hydrothermal method. The Bi-CP shows good photoelectric property and photocatalytic activity for RhB degradation under visible white LED lamp irradiation. And the stability of the visible-light-responsive bismuth-based coordination polymer has also been examined. - Highlights: • A new Bi(III) coordination polymer is hydrothermally synthesized. • The Bi-CP shows good photoelectric and photocatalytic properties. • Bi-CP shows higher activity than the commercial Bi{sub 2}O{sub 3} for RhB degradation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

A novel red emitting phosphor of Eu{sup 3+} doped TTB-type niobate NaSr{sub 2}Nb{sub 5}O{sub 15} for white LEDs

Highlights: ► A novel red phosphor NaSr{sub 2}Nb{sub 5}O{sub 15}:Eu{sup 3+} was synthesized and investigated firstly. ► Crystal structure and characteristic luminescence properties are discussed. ► The charge compensation mechanism is also investigated. ► The intensity of NSN:0.03Eu{sup 3+}, 0.03Li{sup +} is 64.5% of the commercial Y{sub 2}O{sub 3}:Eu{sup 3+}. ► It has good color saturation, the CIE is closed to that of commercial Y{sub 2}O{sub 3}:Eu{sup 3+}. - Abstract: Eu{sup 3+} doped NaSr{sub 2}Nb{sub 5}O{sub 15} series were firstly synthesized by solid-state reaction method. Crystal structure, characteristic luminescence properties as well as charge compensation mechanism are investigated detailedly by X-ray diffraction refinement and photoluminescence spectra measurement. NaSr{sub 2}Nb{sub 5}O{sub 15}:Eu{sup 3+} exhibits strong absorption in near ultraviolet-blue region and intense red emission with CIE chromaticity coordinates (0.638, 0.355) after adding the charge compensation agent upon 398 nm excitation. The integral intensity of NSN:0.03Eu{sup 3+}, 0.03Li{sup +} is 64.5% of the commercial Y{sub 2}O{sub 3}:Eu{sup 3+} and the quantum efficiency is calculated to be 41.5%. The results show that NaSr{sub 2}Nb{sub 5}O{sub 15}:Eu{sup 3+} can be a promising red-emitting phosphor for white LEDs.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Photoluminescence investigations on Sm3+ ions doped borate glasses for tricolor w-LEDs and lasers

Highlights: • Borate glasses with Sm3+ ions were synthesized by melt quenching technique. • Under 402 nm excitation Borate glasses show reddish orange luminescence. • Energy transfer through cross-relaxation leads to fall in decay time of Sm3+ ions. • I-H model confirms energy transfer between Sm3+ ions as dipole-dipole in nature. • 1 mol% Sm3+ ions in these glasses are apt for red photonic device applications. - Abstract: This work describes mainly the optical absorption, photoluminescence (PL) and decay spectral properties of Sm{sup 3+} ions doped borate glasses to understand their possible usage in tricolor w-LEDs and lasers.The XRD spectrum recorded for an un-doped glass confirms glassy nature of the as prepared glass. The Judd-Ofelt (J-O) intensity parameters evaluated from experimental oscillator strengths were used in estimating the various radiative parameters. Under 402 nm excitation, the PL spectra exhibit intense emission at 600 nm for which the decay spectral profiles were recorded.The decay profiles are converting from single exponential to non-exponential with increase in Sm{sup 3+} ion concentration ensuing decrease in experimental lifetimes which may be attributed to the efficient energy transfer through cross-relaxation process. The non-exponential decay curves fitted to I-H model reveals the interaction between the Sm{sup 3+} ions as dipole-dipole in nature. From the evaluated emission cross-sections, quantum efficiency, branching ratios and CIE co-ordinates, it is concluded that 1 mol% Sm{sup 3+} ions in these glasses are aptly suitable to fabricate reddish-orange luminescent devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Near UV based LED fabricated with K2Ba3Si8O20:Eu2+ and energy transfer between Ce3+ and Eu2+

Highlights: • A kind of novel green-emitting phosphor K{sub 2}Ba{sub 3}Si{sub 8}O{sub 20}:Ce{sup 3+},Eu{sup 2+} has been prepared. • Energy transfer in this host is systematically investigated and their origins are to be revealed. • Commission on illumination value as well as thermal luminescence quenching properties are studied. • Results indicate that the phosphor can be served as a potential green emitting phosphor candidate for LED devices. - Abstract: K{sub 2}Ba{sub 3}Si{sub 8}O{sub 20}:Eu{sup 2+} as a new green-emitting phosphor was prepared and studied in this article. This material showed powerful absorption in near ultraviolet-visible regions from 350 to 450 and its green-emitting band peaked at 502 nm. Its photoluminescence emitting intensity affected by concentrations of K{sub 2}Ba{sub 3}Si{sub 8}O{sub 20}:Ce{sup 3+} and K{sub 2}Ba{sub 3}Si{sub 8}O{sub 20}:Eu{sup 2+} was also studied and consequently verified to be a dipole–dipole interaction. Effective energy transfer was observed in Ce{sup 3+},Eu{sup 2+} co-doped K{sub 2}Ba{sub 3}Si{sub 8}O{sub 20} phosphor, and the transfer efficiency was also obtained from the decay lifetime. The K{sub 2}Ba{sub 3}Si{sub 8}O{sub 20}:Eu{sup 2+} phosphor combined with a 380 nm near-UV chip was demonstrated to produce a diode which emitted green light. This article indicates that the phosphor prepared in this work could be used in manufacturing of white light-emitting diodes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Carrier capture efficiency in InGaN/GaN LEDs: Role of high temperature annealing

By means of time integrated (TI), time-resolved (TR) photoluminescence (PL) and PL excitation spectra, we investigate the role of an high temperature post-growth thermal annealing (TA) on a set of InGaN/GaN LED structures with different dislocation densities. We provide evidence of the nature of the radiative recombination from a wide distribution of non-interacting localised states and we show the beneficial effect of thermal annealing in reducing the contribution of non-radiative recombination in the well region.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

PVP capped CdS nanoparticles for UV-LED applications

Polyvinlypyrrolidone (PVP) capped cadmium sulphide (CdS) nanoparticles are synthesized by wet chemical method. The powder X-ray diffraction (XRD) result indicates that the nanoparticles are crystallized in cubic phase. The optical properties are characterized by UV-Vis absorption. The morphology of CdS nanoparticles are studied using Scanning electron microscope (SEM). The thermal behavior of the as prepared nanoparticles has been examined by Thermo gravimetric analysis (TGA). The optical absorption study of pvp capped CdS reveal a red shift confirms the UV-LED applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

The effect of Tb{sup +3} on α-Sr{sub 2}P{sub 2}O{sub 7} phosphor for green LED phosphor application

A series of Tb{sup +3} activated α-Sr{sub 2}P{sub 2}O{sub 7} (Strontium Pyrophosphate) phosphors were synthesized by high temperature combustion synthesis method. The structural analysis has been done by x-ray diffraction and FTIR (Fourier Transform Infrared Spectrum). The results obtained in structural characterization indicate that the doping concentration did not affect the crystal phase and structure of the phosphors. X-ray diffraction pattern reveals that the all samples were consistence with the JCPDS card No. 24-1011. The phosphor was excited at 232 nm wavelength, very intense PL green emission peak have been observed at 545 nm. This illustrates, that the phosphors could be efficiently excited because of the charge transfer band of the host as well as the energy transfer process occurred between host (Sr{sub 2}P{sub 2}O{sub 7}) and activator (Tb{sup +3}). By increasing the doping concentration of Tb{sup +3}, the intensity of 545 nm emission peak has been increased predominantly and it suggest that the phosphor prepared has very good application in green LED phosphor.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗