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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Luminescent properties of Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} and its potential application in white light emitting diodes

Graphical abstract: Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} phosphor can be effectively excited by an ultraviolet and near-ultraviolet light, and produce a bright blue emission centered at 436 nm. The CIE chromaticity coordinations (x, y) of Na{sub 2}CaSiO{sub 4}:Eu{sup 2+}(NSCE)/Li{sub 2}SrSiO{sub 4}:Eu{sup 2+}(LSSE) vary with the molar ratio of the two constituents. When NSCE/LSSE is 1:3, the CIE chromaticity coordination is (0.332, 0.346), which is close to that of the natural sunlight (0.33, 0.33). The results indicate that Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} may be a promising blue phosphor for UV chip-based multi-phosphor converted white light emitting diodes. Highlights: ► Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} shows the blue emission with a peak at 436 nm and broad excitation band in the UV/n-UV range. ► White light with CIE coordinates (0.332, 0.346) is generated by mixing the blue phosphor with the Li{sub 2}SrSiO{sub 4}:Eu{sup 2+} yellow phosphor. ► Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} would be a promising blue phosphor candidate for UV chip-based multi-phosphor converted white LEDs. - Abstract: A novel blue phosphor Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} is synthesized by a high temperature solid-state reaction, and its luminescent properties are systematically studied. Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} can be effectively excited by the 354 nm radiation, and create blue emission (436 nm). The emission intensity of Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} is influenced by the Eu{sup 2+} doping content, and the optimal doping content is 1.5%, and the concentration quenching mechanism of Eu{sup 2+} in Na{sub 2}CaSiO{sub 4} can be attributed to the multipolar interaction. The white light with CIE coordinates (0.332, 0.346) is generated by mixing the blue phosphor Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} with the yellow phosphor Li{sub 2}SrSiO{sub 4}:Eu{sup 2+}. The results indicate that Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} may be a potential blue emitting phosphor for UV chip-based multi-phosphor converted white light emitting diodes.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Synthesis and luminescent properties of a white light phosphor KBa{sub 2}Nb{sub 5}O{sub 15}:Na{sup +}, Dy{sup 3+} for light-emitting-devices

Graphical abstract: - Highlights: • A novel red phosphor KBa{sub 2}Nb{sub 5}O{sub 15}:Dy{sup 3+} was synthesized and investigated firstly. • Crystal structure and characteristic luminescence properties are discussed. • The charge compensation mechanism is also investigated. • It has low color tolerance and better CIE chromaticity coordinates. - Abstract: The white light emission phosphor KBa{sub 2}Nb{sub 5}O{sub 15}:Dy{sup 3+} was synthesized by solid-state method. X-ray diffraction (XRD) study reveals that all the Dy{sup 3+} doped phosphors are single phase. Strong excitation peaks of KBa{sub 2}Nb{sub 5}O{sub 15}:Dy{sup 3+} were found around 380–400 nm, matched well with the NUV LED chip. Under 388 nm excitation, the phosphor exhibited intense white emission by combining the two emission peaks at 477 nm and 572 nm, attributed to the characteristic {sup 4}F{sub 9/2}–{sup 6}H{sub 15/2} and {sup 4}F{sub 9/2}–{sup 6}H{sub 13/2} transition of Dy{sup 3+}. The optimum doping concentration of Dy{sup 3+} is found to be 3%, whose Commission International de l’ Eclairage (CIE) chromaticity coordinates and correlated color temperature are (0.395, 0.422) and 3925 K, respectively. The results indicate that the KBa{sub 2}Nb{sub 5}O{sub 15}:Dy{sup 3+} phosphor could be considered as a potential candidate for white-LEDs.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Li doping effect on the photoluminescence behaviors of KSrPO{sub 4}:Dy{sup 3+} phosphors for WLED light

Highlights: • The luminescence intensity of KSrPO{sub 4}:Dy{sup 3+} can be increased with Li{sup +} ions co-doping. • The mechanisms for the emitting enhancement with Li{sup +} ions co-doping were investigated. • The thermal stability demonstrated that KSrPO{sub 4}:0.01Dy{sup 3+}, 0.06Li{sup +} is suitable for WLEDs. • The chromaticity coordinates of KSrPO{sub 4}:Dy{sup 3+}, Li{sup +} can be tuned with Li{sup +} ions increasing. - Abstract: A novel warm-white phosphor KSrPO{sub 4} co-doped with Dy{sup 3+} and Li{sup +} ions was prepared by solid state reaction. A strategy of Li{sup +} doping was used with the aim of enhancing the luminescence of 475 nm and 570 nm emission bands under NUV excitation. Compared to lithium-free KSrPO{sub 4}:Dy{sup 3+}, the intensities of the 570 nm emission peaks were increased by 4.32 times and 2.84 times excited by 351 nm and 388 nm with 6 mol% Li{sup +} ions co-doping, respectively. The mechanism of the enhancement was discussed, that is due to the improvement of the phosphors’ crystallinity and charge compensation when the Li{sup +} ions were introduced. Furthermore, the thermal stability of KSrPO{sub 4}:0.01Dy{sup 3+}, 0.06Li{sup +} was measured and discussed, demonstrating it can be applied for high-powered LED. And the chromaticity coordinates of KSrPO{sub 4}:0.01Dy{sup 3+}, xLi{sup +} can be tuned efficiently from the cold-white region to warm-white region with Li{sup +} ions increasing, presenting its potential applied value as a new warm-white LED phosphor.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Photoluminescence and cathodoluminescence properties of Eu{sup 3+} ions activated AMoO{sub 4} (A = Mg, Ca, Sr, Ba) phosphors

Highlights: • Under 393 nm excitation, strong red emission located at 615 nm was observed in all the samples. • The Eu{sup 3+}-activated CaMoO{sub 4} phosphor exhibited the strongest PL properties. • The CIE chromaticity coordinate of Eu{sup 3+}-activated CaMoO{sub 4} phosphor was (0.647,0.352). • The color purity of Eu{sup 3+}-activated CaMoO{sub 4} phosphor was 92.8%. • Strong CL properties were observed in the Eu{sup 3+}-activated CaMoO{sub 4} phosphor. - Abstract: Eu{sup 3+}-activated AMoO{sub 4} (A = Mg, Ca, Sr, Ba) phosphors were synthesized by a solid-state reaction method. Photoluminescence and cathodoluminescence (CL) spectra as well as X-ray diffraction patterns were measured to characterize the fabricated samples. Under 393 nm excitation, strong red emissions located at ∼615 nm corresponding to the {sup 5}D{sub 0} → {sup 7}F{sub 2} transition of Eu{sup 3+} ions were observed in all the samples. Compared with other Eu{sup 3+} ions activated AMoO{sub 4} (A = Mg, Sr, Ba) phosphors, Eu{sup 3+}-activated CaMoO{sub 4} phosphor exhibited the strongest red emission intensity with better Commission Internationale de L’Eclairage chromaticity coordinate and higher color purity. Furthermore, the CL results indicated that the Eu{sup 3+}-activated CaMoO{sub 4} phosphor had excellent luminescence properties.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Solid state reaction synthesis and photoluminescence properties of Dy{sup 3+} doped Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12} phosphor

Highlights: • Ca{sub 3−x}Sc{sub 2}Si{sub 3}O{sub 12}:xDy{sup 3+} (0.01 ≤ x ≤ 0.03) was successfully synthesized under a reducing atmosphere. • The thermal stability of the Ca{sub 2.975}Sc{sub 2}Si{sub 3}O{sub 12}:0.025Dy{sup 3+} is superior to commercial phosphors in theory and experiment. • The optimal chromaticity coordinates of Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Dy{sup 3+} is (x = 0.3425, y = 0.3343) upon 350 nm excitation. - Abstract: The white emission phosphor Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Dy{sup 3+} was synthesized by the solid-state reaction. Phase analysis and characteristic luminescence properties are investigated by X-ray diffraction and photoluminescence spectra measurement. Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Dy{sup 3+} phosphor shows strong absorption in 350–410 nm region and exhibits white emission with CIE chromaticity coordinates of (0.3425, 0.3343). Its emission intensity at 250 °C remained 74% of that measured at room temperature. Moreover, the activation energy is also calculated through the Arrhenius equation. The result shows that the thermostability of Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Dy{sup 3+} is superior than that of commercial phosphor Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Ce{sup 3+}. The outstanding luminescent properties indicate that Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Dy{sup 3+} could be a potential white light emission phosphor.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Synthesis, energy transfer and luminescence properties of Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphor

Graphical abstract: PL spectra of Ca{sub 2}MgWO{sub 6}:Sm{sup 3+} and Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphors with excitation at 407 nm, and the corresponding CIE chromaticity diagram and chromaticity coordinates. - Highlights: • Novel Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphor is synthesized by solid-state reaction method in air. • Emission intensity of Ca{sub 2}MgWO{sub 6}:Sm{sup 3+} phosphor is enhanced ∼2 times after co-doped Bi{sup 3+} ion. • Charge compensation and energy transfer may be explained via luminescence properties. • Luminous mechanism is analyzed by energy level diagrams of WO{sub 6}{sup 6−} group, Sm{sup 3+} and Bi{sup 3+} ions. - Abstract: Novel Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphor is synthesized by solid-state reaction method in air. Host Ca{sub 2}MgWO{sub 6} with excitation 300 nm emits blue light. Ca{sub 2}MgWO{sub 6}:Bi{sup 3+} phosphor with excitation 300 and 338 nm emits yellow light. Ca{sub 2}MgWO{sub 6}:Sm{sup 3+} phosphor with excitation 300 nm exhibits tunable emission from blue to red light by increasing Sm{sup 3+} doping concentration from 0 to 8 mol%, however, only emits red light with excitation 407 nm. Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphor with excitation 300 and 338 nm emits red light. The optimal Sm{sup 3+} doping concentration is ∼5 mol% in Ca{sub 2}MgWO{sub 6}:Sm{sup 3+} phosphor. After Bi{sup 3+} ion is co-doped, luminescence properties of Ca{sub 2}MgWO{sub 6}:Sm{sup 3+} phosphor can be improved obviously because of Bi{sub 2}O{sub 3} as fluxing agent role and energy transfer from Bi{sup 3+} to Sm{sup 3+} ions. The possible luminous mechanism of Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphor is analyzed and explained by simplified energy level diagrams of WO{sub 6}{sup 6−} group, Bi{sup 3+} and Sm{sup 3+} ions.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Analysis of coupled-bunch instabilities for the NSLS-II storage ring with a 500MHz 7-cell PETRA-III cavity

The NSLS-II storage ring is designed to operate with superconducting RF-cavities with the aim to store an average current of 500 mA distributed in 1080 bunches, with a gap in the uniform filling for ion clearing. At the early stage of the commissioning (phase 1), characterized by a bare lattice without damping wigglers and without Landau cavities, a normal conducting 7-cell PETRA-III RF-cavity structure has been installed with the goal to store an average current of 25 mA. In this paper we discuss our analysis of coupled-bunch instabilities driven by the Higher Order Modes (HOMs) of the 7-cell PETRA-III RF-cavity. As a cure of the instabilities, we apply a well-known scheme based on a proper detuning of the HOMs frequencies based upon cavity temperature change, and the use of the beneficial effect of the slow head–tail damping at positive chromaticity to increase the transverse coupled-bunch instability thresholds. In addition, we discuss measurements of coupled-bunch instabilities observed during the phase 1 commissioning of the NSLS-II storage ring. In our analysis we rely, in the longitudinal case, on the theory of coupled-bunch instability for uniform fillings, while in the transverse case we complement our studies with numerical simulations with OASIS, a novel parallel particle tracking code for self-consistent simulations of collective effects driven by short and long-range wakefields.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Optical properties of differing nanolayered structures of divalent europium doped barium fluoride thin films synthesized by pulsed laser deposition

Optically-active thin films are employed in a variety of applications, such as LEDs and photovoltaics, due to their ability to act as up- or down-photon energy converters. Their performance depends critically on their composition and structure; thus, the use of novel synthesis techniques that allow for their control at the nanoscale level can result in improved efficiency and practicality. Here, layered thin films consisting of Eu 2+ - doped BaF 2 nanocrystalline layers separated by amorphous Al 2 O 3 were synthesized via sequential pulsed laser deposition using three separate targets for the different components; this synthesis technique provides precise control of layer thickness at the nanoscale along with dopant distribution within the film. Cross-sectional transmission electron microscopy analysis verified the desired nano-layering. Post-deposition heat treatments in a nitrogen atmosphere resulted in samples exhibiting steady emission with a broad peak ranging from 400 to 600 nm and a shoulder at 410 nm. The CIE 1931 chromaticity coordinates are x = 0.26-0.29 and y = 0.32-0.35 and vary as a function of the sample configuration. Because the chromaticity coordinates are close to those of a pure white light (x = 0.33, y = 0.33), these films demonstrate advantageous properties for applications with UV-pumped white light LEDs.

36 MATERIALS SCIENCE↗
DOE OSTI2017

A novel electron mirror pulse compressor

An electron mirror-based pulse compressor design has been developed for improving the temporal resolution of dynamic/ultrafast transmission electron microscopes and ultrafast electron diffraction cameras. The improvement will enable electron microscopes and diffraction cameras to better resolve the dynamics of reactions in the areas of solid state physics, chemistry, and biology. The design utilizes a combination of mirror optics and a magnetic beam separator, which exploits the symmetry inherent in reversing the electron trajectory in the mirror in order to compress the pulse. This system can also simultaneously correct the spherical and chromatic aberration of the objective lens for improved spatial resolution. For pulsed experiments with a practical bunch charge, the correction of the chromatic aberration coefficient counters the spread in the electron energies induced by the space charge of the pulse to make possible the probing of the sample with high spatial resolution. The pulse compressor can accommodate pulses with a range of electron densities and energy spreads. Additionally, it is designed to fit into both ultrafast electron diffraction cameras and dynamic/ultrafast transmission electron microscopes. Consequently, this instrument is suitable for enhancing the study of the structure, composition, and bonding states of new materials at ultrafast time scales.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Guanidinium-Based Ionic Covalent-Organic Nanosheets for Sequestration of Cr(VI) and As(V) Oxoanions in Water

Chromium- and arsenic-based oxoanions are among the major highly toxic and carcinogenic inorganic pollutants present in groundwater, demanding fast and selective sequestration. Efficient capturing and removal of these highly mobile oxometallates at neutral pH presents a great challenge in groundwater cleanup. In this report, a series of guanidinium-based ionic organic covalent nanosheets (iCONs) with varying hydrogen bonding, steric, and electronic properties was studied to examine the structure–activity relationship in the adsorption and removal of chromium- and arsenic-based oxoanions in water. Structural modulations in iCONs were found to alter the guanidinium acidity, thus regulating the oxoanion uptake limits via ion exchange. The hydrogen bonding, steric, and electrostatic interactions at/near the guanidinium-based anion binding site in iCONs exerted heavy influences on the uptake efficiency and selectivity of arsenate but not on those of chromate. Further analyses revealed that the parallel bidentate hydrogen bonding interactions play a key role in the weak binding of arsenate to the protonated/positively charged guanidine motifs, whereas the strong ion–ion interactions between chromate and guanidinium appear to be more tolerant to the geometric and structural perturbation.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Molecular Cursor Caliper: A Fluorescent Sensor for Dicarboxylate Dianions

We report herein the fluorescent sensing of both aromatic and linear saturated dicarboxylate anions (DC 2- ) (as their tetrabutylammonium salts) with different lengths and shapes in acetonitrile using a single fluorescent probe, i.e., the bis-calix[4]pyrrole-appended 9,14-diphenyl-9,14-dihydrodibenzo[a,c]phe¬nazine (DPAC-bisC4P) incorporating a vibration-induced emission (VIE) phenazine core. Fluorescence titration studies revealed that treating DPAC-bisC4P with dicarboxylate guests capable of forming pseudo-macrocyclic host–guest complexes via multiple hydrogen bonding interactions between the dicarboxylates and calix[4]pyrrole moieties, led to a blue-shift in the emission of the phenazine core. The binding-based fluorescence tuning features of DPAC-bisC4P allows the underlying binding events and inferred structural changes to be monitored in the form of different chromaticity outputs. The analyte-induced dif-ferences in the fluorescence response to DC 2- cover a wide range within the chromaticity diagram and can be visualized readily. The pre-sent system thus functions as a rudimentary dicarboxylate anion sensor. It illustrates the potential benefits associated with combining a tunable VIE core with non-covalent binding interactions and thus sets the stage for the development of new fluorescent chemosensors where a single chemical entity responds to different analytes with a high level of tunability.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Direct laser writing of volumetric gradient index lenses and waveguides

Abstract Direct laser writing (DLW) has been shown to render 3D polymeric optical components, including lenses, beam expanders, and mirrors, with submicrometer precision. However, these printed structures are limited to the refractive index and dispersive properties of the photopolymer. Here, we present the subsurface controllable refractive index via beam exposure (SCRIBE) method, a lithographic approach that enables the tuning of the refractive index over a range of greater than 0.3 by performing DLW inside photoresist-filled nanoporous silicon and silica scaffolds. Adjusting the laser exposure during printing enables 3D submicron control of the polymer infilling and thus the refractive index and chromatic dispersion. Combining SCRIBE’s unprecedented index range and 3D writing accuracy has realized the world’s smallest (15 µm diameter) spherical Luneburg lens operating at visible wavelengths. SCRIBE’s ability to tune the chromatic dispersion alongside the refractive index was leveraged to render achromatic doublets in a single printing step, eliminating the need for multiple photoresins and writing sequences. SCRIBE also has the potential to form multicomponent optics by cascading optical elements within a scaffold. As a demonstration, stacked focusing structures that generate photonic nanojets were fabricated inside porous silicon. Finally, an all-pass ring resonator was coupled to a subsurface 3D waveguide. The measured quality factor of 4600 at 1550 nm suggests the possibility of compact photonic systems with optical interconnects that traverse multiple planes. SCRIBE is uniquely suited for constructing such photonic integrated circuits due to its ability to integrate multiple optical components, including lenses and waveguides, without additional printed supports.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Hybrid achromatic microlenses with high numerical apertures and focusing efficiencies across the visible

Abstract Compact visible wavelength achromats are essential for miniaturized and lightweight optics. However, fabrication of such achromats has proved to be exceptionally challenging. Here, using subsurface 3D printing inside mesoporous hosts we densely integrate aligned refractive and diffractive elements, forming thin high performance hybrid achromatic imaging micro-optics. Focusing efficiencies of 51–70% are achieved for 15μm thick, 90μm diameter, 0.3 numerical aperture microlenses. Chromatic focal length errors of less than 3% allow these microlenses to form high-quality images under broadband illumination (400–700 nm). Numerical apertures upwards of 0.47 are also achieved at the cost of some focusing efficiency, demonstrating the flexibility of this approach. Furthermore, larger area images are reconstructed from an array of hybrid achromatic microlenses, laying the groundwork for achromatic light-field imagers and displays. The presented approach precisely combines optical components within 3D space to achieve thin lens systems with high focusing efficiencies, high numerical apertures, and low chromatic focusing errors, providing a pathway towards achromatic micro-optical systems.

47 OTHER INSTRUMENTATION↗
DOE OSTI2011

Integrative analysis of transcriptomic and proteomic data of Shewanella oneidensis: missing value imputation using temporal datasets

Despite significant improvements in recent years, proteomic datasets currently available still suffer large number of missing values. Integrative analyses based upon incomplete proteomic and transcriptomic da-tasets could seriously bias the biological interpretation. In this study, we applied a non-linear data-driven stochastic gradient boosted trees (GBT) model to impute missing proteomic values for proteins experi-mentally undetected, using a temporal transcriptomic and proteomic dataset of Shewanella oneidensis. In this dataset, genes expression was measured after the cells were exposed to 1 mM potassium chromate for 5-, 30-, 60-, and 90-min, while protein abundance was measured only for 45- and 90-min samples. With the goal of elucidating the relationship between temporal gene expression and protein abundance data, and then using it to impute missing proteomic values for samples of 45-min (which does not have cognate transcriptomic data) and 90-min, we initially used nonlinear Smoothing Splines Curve Fitting (SSCF) to identify temporal relationships among transcriptomic data at different time points and then imputed missing gene expression measurements for the sample at 45-min. After the imputation was validated by biological constrains (i.e. operons), we used a data-driven Gradient Boosted Trees (GBT) model to uncover possible non-linear relationships between temporal transcriptomic and proteomic data, and to impute protein abundance for the proteins experimentally undetected in the 45- and 90-min sam-ples, based on relevant predictors such as temporal mRNA gene expression data, cellular roles, molecular weight, sequence length, protein length, guanine-cytosine (GC) content and triple codon counts. The imputed protein values were validated using biological constraints such as operon, regulon and pathway information. Finally, we demonstrated that such missing value imputation improved characterization of the temporal response of S. oneidensis to chromate.

SBR mercury↗
DOE OSTI2026

Chemical and morphological evolution of hybrid conversion coatings in low-Earth orbit space environment

Understanding how protective coatings respond to the harsh low-Earth orbit (LEO) environment is essential for ensuring the safety, longevity, and cost-effectiveness of spacecraft. In particular, identifying environmentally friendly, non-chromate alternatives that can maintain performance under such conditions has both technological and regulatory significance. This study investigates the environmental stability of zirconium-based hybrid conversion coatings with Cu additives (Cu10 and Cu20) applied to cold-rolled steel, tested in the Materials International Space Station Experiment (MISSE) outside the International Space Station (ISS). Chemical and morphological analyses were carried out using a combination of electron microscopy and X-ray spectroscopy techniques, including scanning electron microscopy (SEM), scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy (STEM-EDS), X-ray photoelectron spectroscopy (XPS), and X-ray absorption near-edge structure (XANES) spectroscopy. After exposure outside the ISS, all coatings remained structurally intact, with all exhibiting a uniform Zr-rich matrix and embedded Cu-rich clusters, while a thin Si-rich surface layer developed from interaction with space environments. Depth-resolved XPS showed a layered structure with CuO on the surface, Cu 2 O, and partial Zr(IV) reduction near Cu-rich sites, evidence of Atomic Oxygen (AO)-driven surface oxidation. These results demonstrate that Cu–Zr coatings maintain their chemical integrity and microstructure in harsh space environments, offering a non-chromate alternative for long-term aerospace protection. These insights provide valuable guidance for developing next-generation protective coatings that combine environmental sustainability with the reliability required for future aerospace and orbital applications.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Size-dependent emission efficiency and luminescence characteristics of YBO{sub 3}:Tb{sup 3+} nanocrystals under vacuum ultraviolet excitations

The luminous efficiency and lifetime of plasma display panels (PDPs) are directly related to the performance of phosphors used in PDPs, thus higher efficiency, higher stability against high temperature processes, and a long lifetime along with good color chromaticity against vacuum-ultraviolet radiation are major concerns in selecting suitable phosphors for PDPs. In the same pursuit, well crystallized pure hexagonal phase YBO{sub 3}:Tb{sup 3+} nanocrystals were prepared using co-precipitation method. The prepared YBO{sub 3}:Tb{sup 3+} nanocrystals showed bright green luminescence, color chromaticity (0.21, 0.61), and could be assigned to {sup 5}D{sub 4}{yields}{sup 7}F{sub j} transitions (j = 2-6) due to electric dipole-dipole interaction of Tb{sup 3+} ions. The vacuum ultraviolet photoluminescence spectroscopy of the prepared YBO{sub 3}:Tb{sup 3+} nanocrystals showed size dependent nonlinear luminescence enhancement with relatively shorter life time as compared to the commercial bulk YBO{sub 3}:Tb{sup 3+} phosphor. The quenching concentration of Tb{sup 3+} doping for ({sup 5}D{sub 4}{yields}{sup 7}F{sub 5}) transition was found significantly enhanced with the decrease in particle size suggesting it an ideal green phosphor for plasma display panels. The possible explanation for size-dependent emission efficiency and observed luminescence characteristics were proposed via charge transfer process and lowering of the structural symmetry.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

Measurement of parameters in Indus-2 synchrotron radiation source

The paper presents the measurement of optics parameters in Indus-2 synchrotron radiation source, which include betatron tune, beta function, dispersion function, natural chromaticity, corrected chromaticity, central RF frequency, momentum compaction factor, and linear betatron coupling. Two methods were used for beta function measurement; a conventional quadrupole scan method and a method using the fitting of the orbit response matrix. A robust Levenberg-Marquardt algorithm was used for nonlinear least square fitting of the orbit response matrix. In this paper, detailed methods for the parameter measurements are described. The measured results are discussed and compared with the theoretical values obtained using accelerator simulation code Accelerator Toolbox in MATLAB.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Spatial filtering with photonic crystals

Photonic crystals are well known for their celebrated photonic band-gaps—the forbidden frequency ranges, for which the light waves cannot propagate through the structure. The frequency (or chromatic) band-gaps of photonic crystals can be utilized for frequency filtering. In analogy to the chromatic band-gaps and the frequency filtering, the angular band-gaps and the angular (spatial) filtering are also possible in photonic crystals. In this article, we review the recent advances of the spatial filtering using the photonic crystals in different propagation regimes and for different geometries. We review the most evident configuration of filtering in Bragg regime (with the back-reflection—i.e., in the configuration with band-gaps) as well as in Laue regime (with forward deflection—i.e., in the configuration without band-gaps). We explore the spatial filtering in crystals with different symmetries, including axisymmetric crystals; we discuss the role of chirping, i.e., the dependence of the longitudinal period along the structure. We also review the experimental techniques to fabricate the photonic crystals and numerical techniques to explore the spatial filtering. Finally, we discuss several implementations of such filters for intracavity spatial filtering.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗