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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Materials and Electrical Characterization of Physical Vapor Deposited LaxLu1-xO3 Thin Films on 300 mm Silicon

La{sub x}Lu{sub 1-x}O{sub 3} thin films were deposited on 300 mm silicon wafers by physical vapor deposition and fabricated into field-effect transistors using a gate-first process flow. The films were characterized using transmission electron microscopy, Rutherford backscattering spectrometry, and synchrotron x-ray diffraction. The results show the films remain amorphous even at temperatures of 1000 C. The dielectric properties of La{sub x}Lu{sub 1-x}O{sub 3} (0.125 {<=} x {<=} 0.875) thin films were evaluated as a function of film composition. The amorphous La{sub x}Lu{sub 1-x}O{sub 3} thin films have a dielectric constant (K) of 23 across the composition range. The inversion thickness (T{sub inv}) of the La{sub x}Lu{sub 1-x}O{sub 3} thin films was scaled to <1.0 nm.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Structural, microstructural and surface properties of a specific CeO{sub 2}-Bi{sub 2}O{sub 3} multiphase system obtained at 600 {sup o}C

Polycrystalline samples of (1-x) CeO{sub 2}-x/2 Bi{sub 2}O{sub 3} phases, where x is the atom fraction of bismuth have been synthesized by the precipitation process and after the thermal treatment at 600 {sup o}C, under air. Samples are first characterized by the X-ray diffraction and scanning electron microscopy. To determine the samples specific surface areas, Brunauer-Emmett-Teller (BET) analyses have been performed. In the composition range 0{<=}x{<=}0.20, a cubic solid solution with fluorite structure is obtained. For compositions x comprised between 0.30 and 0.90, two types of T' (or {beta}') and T (or {beta}) tetragonal phases, similar to the well-known {beta}' or {beta} Bi{sub 2}O{sub 3} metastable structural varieties, are observed. However, the crystal cell volumes of these {beta}' or {beta} Bi{sub 2}O{sub 3} phases increase with the composition x in bismuth: this might be due to the presence of defects or substitution by cerium atoms, in the tetragonal lattices. Using X-ray diffraction profile analyses, correlations between bismuth composition x and crystal sizes or lattice distortions have been established. The solid-gas interactions between these polycrystalline materials and air-CH{sub 4} and air-CO flows have been studied as a function of temperature and composition x, using Fourier transform infrared (FTIR) analyses of the conversions of CH{sub 4} and CO gases into the CO{sub 2} gas. The transformations of CH{sub 4} and CO molecules as a function of time and temperature are determined through the intensities of FTIR CO{sub 2} absorption bands. Using the specific surface areas determined from BET analyses, these FTIR intensities have been normalized and compared. For all bismuth compositions, a low catalytic reactivity is observed with air-CH{sub 4} gas flows, while, for the highest bismuth compositions, a high catalytic reactivity is observed with air-CO gas flows. -- Graphical abstract: Catalytic efficiencies of CeO{sub 2}-Bi{sub 2}O{sub 3}system: catalytic actions on methane (on the left) or carbon monoxide (on the right) of (1-x)CeO{sub 2}-x/2 Bi{sub 2}O{sub 3} samples, as a function of the fraction x, and for fixed temperatures: on the vertical axis, the intensities of CO{sub 2} FTIR absorption bands are reported. Strong efficiency of bismuth rich samples for CO conversion. Display Omitted Research highlights: {yields} Stabilization of metastable polymorph Bi{sub 2}O{sub 3} phases in the mix system [(1-x)CeO{sub 2}+(x/2)Bi{sub 2}O{sub 3}] at 600 {sup o}C. {yields} Solid gas interactions between this system and air-CO or air-CH{sub 4} gas flows at various temperatures and bismuth compositions. {yields} High efficiency of bismuth rich samples to convert CO into CO{sub 2}.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Fabrication of carbon microcapsules containing silicon nanoparticles-carbon nanotubes nanocomposite by sol-gel method for anode in lithium ion battery

Carbon microcapsules containing silicon nanoparticles (Si NPs)-carbon nanotubes (CNTs) nanocomposite (Si-CNT-C) have been fabricated by a surfactant mediated sol-gel method followed by a carbonization process. Silicon nanoparticles-carbon nanotubes (Si-CNT) nanohybrids were produced by a wet-type beadsmill method. To obtain Si-CNT nanocomposites with spherical morphologies, a silica precursor (tetraethylorthosilicate, TEOS) and polymer (PMMA) mixture was employed as a structure-directing medium. Thus the Si-CNT/Silica-Polymer microspheres were prepared by an acid catalyzed sol-gel method. Then a carbon precursor such as polypyrrole (PPy) was incorporated onto the surfaces of pre-existing Si-CNT/silica-polymer to generate Si-CNT/Silica-Polymer-PPy microspheres. Subsequent thermal treatment of the precursor followed by wet etching of silica produced Si-CNT-C microcapsules. The intermediate silica/polymer must disappear during the carbonization and etching process resulting in the formation of an internal free space. The carbon precursor polymer should transform to carbon shell to encapsulate remaining Si-CNT nanocomposites. Therefore, hollow carbon microcapsules containing Si-CNT nanocomposites could be obtained (Si-CNT-C). The successful fabrication was confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). These final materials were employed for anode performance improvement in lithium ion battery. The cyclic performances of these Si-CNT-C microcapsules were measured with a lithium battery half cell tests. - Graphical Abstract: Carbon microcapsules containing silicon nanoparticles (Si NPs)-carbon nanotubes (CNTs) nanocomposite (Si-CNT-C) have been fabricated by a surfactant mediated sol-gel method. Highlights: > Polymeric microcapsules containing Si-CNT transformed to carbon microcapsules. > Accommodate volume changes of Si NPs during Li ion charge/discharge. > Sizes of microcapsules were controlled by experimental parameters. > Lithium storage capacity and coulombic efficiency were demonstrated. > Use of sol-gel procedure as intermediate reaction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Thermally exfoliated graphene based counter electrode for low cost dye sensitized solar cells

Graphene obtained from thermal exfoliation of graphite oxide are highly wrinkled and have large surface area. Their wrinkled nature is expected to give them excellent catalytic activity. Herein, we demonstrate the use of thermally exfoliated graphene (TEG) as cost effective electrocatalyst for the tri-iodide reduction in dye sensitized solar cells (DSSCs). X-ray diffraction, Raman and Infra red spectroscopy and electron microscopy studies confirm the defective and wrinkled nature of TEG. BET surface area measurement show a large surface area of {approx} 470 m{sup 2}/g. The counter electrode was fabricated by drop casting a slurry of TEG dispersed in a Nafion:Ethanol solution on fluorine doped tin oxide (FTO) substrates. The use of Nafion prevented film ''peel off,'' thus ensuring a good substrate adhesion. Electrochemical impedance spectroscopy reveals that TEG had a catalytic performance comparable to that of Pt, suggesting its use as counter electrode material. As expected, the DSSC fabricated with Nafion solubilized TEG/FTO as counter electrode shows an efficiency of about 2.8%, comparable to Pt counter electrode based DSSC which has an efficiency of about 3.4%.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2011

Formation of {beta}-nickel hydroxide plate-like structures under mild conditions and their optical properties

Nanostructural {beta}-nickel hydroxide ({beta}-Ni(OH){sub 2}) plates were prepared using the microwave-hydrothermal (MH) method at a low temperature and short reaction times. An ammonia solution was employed as the coordinating agent, which reacts with [Ni(H{sub 2}O){sub 6}]{sup 2+} to control the growth of {beta}-Ni(OH){sub 2} nuclei. A trigonal {beta}-Ni(OH){sub 2} single phase was observed by X-ray diffraction (XRD) analyses, and the crystal cell was constructed with structural parameters and atomic coordinates obtained from Rietveld refinement. Field emission scanning electron microscopy (FE-SEM) images revealed that the samples consisted of hexagonal-shaped nanoplates with a different particle size distribution. Broad absorption bands assigned as transitions of Ni{sup 2+} in oxygen octahedral sites were revealed by UV-vis spectra. Photoluminescence (PL) properties observed with a maximum peak centered in the blue-green region were attributed to different defects, which were produced during the nucleation process. We present a growth process scheme of the {beta}-Ni(OH){sub 2} nanoplates. - Graphical abstract: Nanostructural {beta}-Ni(OH){sub 2} crystalline powders were prepared by rapid microwave-hydrothermal method for 1, 8 and 32 min. The hexagonal-shaped nanoplates obtained presented PL emission in the blue-green region and each decomposed component represents a different type of electronic transition, which can be linked to the structural arrangement or surface defects. Highlights: > Ammonia solution to control the growth of {beta}-Ni(OH){sub 2} nuclei. > Regular plates-shape related to crystallization-dissolution-recrystallization. > The surface states and lattice defects generated in growth mechanism of crystals. > Different defects produced in the growth process responsible by photoluminescence. > Each component of photoluminescence curve linked to structural arrangement or surface defects.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2010

InAlN/GaN Bragg reflectors grown by plasma-assisted molecular beam epitaxy

We report on molecular beam epitaxy growth and characterization of ten-period lattice-matched InAlN/GaN distributed Bragg reflectors (DBRs), with peak reflectivity centered around 400 nm. Thanks to the well tuned ternary alloy composition, crack-free surfaces have been obtained, as confirmed by both optical and transmission electron microscopy (TEM). Their good periodicity and well-defined interfaces have been confirmed by both x-ray diffraction and TEM measurements. Peak reflectivity values as high as 60% with stop bands of 30 nm have been demonstrated. Optical measurements revealed that discrepancy between the obtained (60%) and the theoretically expected ({approx}75%) reflectivity is a consequence of significant residual absorption ({approx}35%). TEM measurements revealed the coexistence of zinc-blende and wurtzite phases, as well as planar defects, mainly in GaN. These defects are suggested as the potential source of the undesired absorption and/or scattering effects that lowered the DBRs' peak reflectivity.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Laser-driven ultrafast transmission electron microscopy

Recent advances in lasers and electron optics technology have allowed transmission electron microscopes to achieve high spatial and temporal resolution, making them capable of tracking atoms, charges and spin motions down to the attosecond and nanometre scales. This Primer discusses the most common and practical experimental implementation of time-resolved transmission electron microscopy and the stroboscopic mode for evaluating ultrafast reversible dynamics. An in-depth discussion of photo-induced near-field electron microscopy, a technique unique to laser-assisted electron microscopy, is also provided, covering its prospective applications in the study of coherent phenomena in quantum materials. The experimental strategies and limitations in investigating the structural dynamics of materials and nanostructures by imaging, diffraction and spectroscopy are also described in detail, with a direct comparison with more conventional and established techniques. Here, we provide key information for new researchers who intend to use ultrafast transmission electron microscopy to address new challenges in specific materials science, condensed matter and nanophotonics.

Transmission electron microscopy↗
DOE OSTI2012

Microstructural and compositional change of NaOH-activated high calcium fly ash by incorporating Na-aluminate and co-existence of geopolymeric gel and C-S-H(I)

This study explores the reaction products of alkali-activated Class C fly ash-based aluminosilicate samples by means of high-resolution synchrotron X-ray diffraction (HSXRD), scanning electron microscope (SEM), and compressive strength tests to investigate how the readily available aluminum affects the reaction. Class C fly ash-based aluminosilicate raw materials were prepared by incorporating Na-aluminate into the original fly ashes, then alkali-activated by 10 M NaOH solution. Incorporating Na-aluminate reduced the compressive strength of samples, with the reduction magnitude relatively constant regardless of length of curing period. The HSXRD provides evidence of the co-existence of C-S-H with geopolymeric gels and strongly suggests that the C-S-H formed in the current system is C-S-H(I). The back-scattered electron images suggest that the C-S-H(I) phase exists as small grains in a finely intermixed form with geopolymeric gels. Despite providing extra source of aluminum, adding Na-aluminate to the mixes did not decrease the Si/Al ratio of the geopolymeric gel.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Effects of surfactants on morphology in synthesis of {alpha}-Mn{sub 2}O{sub 3} nanostructures

Cubic and chain-like structure of {alpha}-Mn{sub 2}O{sub 3} with a high surface area was prepared by air oxidation of manganese chloride through sol process by adding hexamine and mercaptosuccinic acid as wetting agent, respectively. The as-synthesized products were characterized with X-ray powder diffraction (XRD), Energy Dispersive X-ray spectroscopy (EDX), transmission electron microscope (TEM), and selected area electron diffraction (SAED). The possible formation mechanism of {alpha}-Mn{sub 2}O{sub 3} cubic and chain-like nanostructures has been proposed and discussed. -- Graphical abstract: Cubic and chain-like nanostructure of {alpha}-Mn{sub 2}O{sub 3} has been synthesized by air oxidation of manganese chloride as precursor, hexamine, and mercaptosuccinic acid as wetting agent, respectively. Display Omitted Research highlights: {yields} Cubic nanostructure of {alpha}-Mn{sub 2}O{sub 3} is obtained using hexamine as surfactant. {yields} Chain-like structure of {alpha}-Mn{sub 2}O{sub 3} is obtained using mercaptosuccinic acid as surfactant. {yields} The linking nature of mercaptosuccinic acid is proved. {yields} Mercaptosuccinic acid accelerates the growth of material.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2011

On AgRhO{sub 2}, and the new quaternary delafossites AgLi{sub 1/3}M{sub 2/3}O{sub 2}, syntheses and analyses of real structures

Two new quaternary delafossite type oxides with the general formula Ag(Li{sub 1/3}M{sub 2/3})O{sub 2}, M=Rh, Ir, have been synthesized, and their structures characterized. Based on X-ray and electron diffraction analyses the structural similarity with AgRhO{sub 2} delafossite, has been evidenced. The real structures of the quaternary delafossites have been revealed, which has allowed to fully explain the diffuse scattering as observed in X-ray powder diffraction. AgRhO{sub 2} is thermally stable up to 1173 K, the behavior of the two quaternary compounds AgLi{sub 1/3}Rh{sub 2/3}O{sub 2} and AgLi{sub 1/3}Ir{sub 2/3}O{sub 2} is comparable, and they decompose above 950 and 800 K, respectively. AgRhO{sub 2} shows temperature independent paramagnetism, while for the other two an effective magnetic moment of 1.77{mu}{sub B} for Ir, and 1.70{mu}{sub B} for Rh were determined, applying the Curie-Weiss law. All compounds are semiconducting with activation energies of 4.97 kJ mol{sup -1} (AgLi{sub 1/3}Rh{sub 2/3}O{sub 2}), 11.42 kJ mol{sup -1} (AgLi{sub 1/3}Ir{sub 2/3}O{sub 2}) and 17.58 kJ mol{sup -1} (AgRhO{sub 2}). -- graphical abstract: Two new quaternary delafossite type oxides with the general formula Ag(Li{sub 1/3}M{sub 2/3})O{sub 2}, M=Rh, Ir, have been synthesized, and their structures characterized. The real structures of the quaternary delafossites have been revealed, which has allowed to fully explain the diffuse scattering as observed in X-ray powder diffraction. Display Omitted Highlights: {yields}Analysis of the real structures of the Ag(Li{sub 1/3}Rh{sub 2/3})O{sub 2} and Ag(Li{sub 1/3}Ir{sub 2/3})O{sub 2}. {yields} Diffuse scattering has been rationalized by severe disorder in the stacking sequences. {yields} The oxygen atom layer stacking sequence needs to change.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Dye-coated europium monosulfide

Nanoparticles of EuS were synthesized using europium dithiocarbamate complexes. The resulting nanoparticles were coated with the dye, 1-pyrene carboxylic acid and the resulting material was characterized using X-ray powder diffraction, TEM, and UV-visible spectroscopy. Fluorescence spectroscopy was used to determine the relative energy of the conduction band edge to the excited state energy of the dye. -- Graphical abstract: Dye sensitized magnetic semiconductor materials were prepared by synthesizing EuS nanoparticles using single source precursors and coating with the dye, 1-pyrene carboxylic acid. Display Omitted highlights: > Synthesized EuS nanoparticles, 11{+-}2.4 nm characterized using XRD, TEM, and UV-vis. spect. > Grafted a dye to the surface and characterized the product using XRD, FTIR, UV-vis., and TEM. > Studied the photophysical properties using fluorescence spectroscopy. > Determined the relative dye excited state to the conduction band of the semiconductor.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Structural and optical properties of Ga{sub 2}O{sub 3}:In films deposited on MgO (1 0 0) substrates by MOCVD

Ga{sub 2}O{sub 3}:In films with different indium (In) content x [x=In/(Ga+In) atomic ratio] have been deposited on MgO (1 0 0) substrates by metalorganic chemical vapor deposition (MOCVD). Structural analyses revealed that the film deposited with actual In content (x') of 0.09 was an epitaxial film and the films with x'=0.18 and 0.37 had mixed-phase structures of monoclinic Ga{sub 2}O{sub 3} and bixbyite In{sub 2}O{sub 3}. The absolute average transmittance of the obtained films in the visible region exceeded 95%, and the band gap was in the range of 4.74-4.87 eV. Photoluminescence (PL) measurements were performed at room temperature, in which the visible luminescences were strong and could be seen by the naked eye. The strong emissions in the visible light region were proposed to originate from the gallium vacancies, oxygen deficiencies and other defects in these films. - Graphical abstract: Low magnification XTEM (a), HRTEM (b) and SAED (c) micrographs of the interface area between Ga{sub 1.82}In{sub 0.18}O{sub 3} film and MgO substrate have showed the Ga{sub 1.82}In{sub 0.18}O{sub 3} is an epitaxial film. Highlights: > Ga{sub 1.82}In{sub 0.18}O{sub 3} epitaxial film was deposited on MgO(1 0 0) substrate. > The transmittance of the Ga{sub 2}O{sub 3}:In films in the visible region exceeded 95%. > Strong emissions were observed in the photoluminescence measurements of the films.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Insights into photoluminescence property and photocatalytic activity of cubic and rhombohedral ZnIn{sub 2}S{sub 4}

Cubic and rhombohedral ZnIn{sub 2}S{sub 4} were synthesized by thermal sulfidation of Zn-In mixed oxide precursor in H{sub 2}S atmosphere at different temperatures. Cubic ZnIn{sub 2}S{sub 4} was obtained when Zn-In mixed oxide precursor was sulfurized at 400 deg. C. With sulfidation temperature increasing from 400 to 800 deg. C, the crystal phase of ZnIn{sub 2}S{sub 4} gradually turned from cubic to rhombohedral, which was demonstrated by different analysis techniques such as XRD, Raman, SEM, etc. UV-vis absorption spectra indicated that cubic ZnIn{sub 2}S{sub 4} displayed better light absorption property than rhombohedral ZnIn{sub 2}S{sub 4}, with band gaps calculated to be 2.0 and 2.5 eV, respectively. However, under visible light irradiation, rhombohedral ZnIn{sub 2}S{sub 4} photocatalyzed H{sub 2} evolution from aqueous sodium sulfite/sulfide solution efficiently, whereas cubic ZnIn{sub 2}S{sub 4} was not active for this reaction. The photoluminescence property revealed the different dynamics of photogenerated carriers, which made a predominant contribution to the increasing photocatalytic performances of ZnIn{sub 2}S{sub 4} with crystal phase turning from cubic to rhombohedral. - Graphical Abstract: Rhombohedral ZnIn{sub 2}S{sub 4} showed a superior photocatalytic activity for H{sub 2} evolution than cubic ZnIn{sub 2}S{sub 4}, which was proved to be related with their different dynamics of photogenerated carriers. Highlights: > Cubic and rhombohedral ZnIn{sub 2}S{sub 4} were synthesized by thermal sulfidation. > Rhombohedral ZnIn{sub 2}S{sub 4} could photocatalyze H{sub 2} evolution efficiently. > The dynamics of photogenerated carriers affected the photocatalytic activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2010

Structural And Electrical Analysis Of Lead Free BZT-xBCT Ceramics

A comparative study of structural and electric properties of a recently discovered lead free electroceramic, Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}-x(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} or BZT-xBCT, was conducted in the entire range from x = 0 to x = 1. This novel ceramic composite is being seen as a genuine understudy for commercially one of the most widely used piezoelectric ceramic, PZT, which is facing worldwide criticism due to its lead toxicity. The new system can be very extensively used like PZT in transduction applications as sensor, actuator and ultrasonic devices apart from numerous other utilities. The XRD, SEM and Ferroelectric studies establish the structural transition and different phases as function of Zr /Ti and Ba /Ca ratios.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Perpendicular ferrimagnetism in strained Mn{sub 2}As film

Ferrimagnetic Mn{sub 2}As thin films with perpendicular magnetic anisotropy were successfully grown on Si(100) by molecular-beam epitaxy. From the reflection high-energy electron diffraction and X-ray diffraction patterns, the orientation of the Mn{sub 2}As film on Si was along the c-axis in the tetragonal crystal structure. Mn{sub 2}As film exhibited ferrimagnetic ordering at temperatures greater than 300 K, which differs from antiferromagnetic or paramagnetic behaviors in the bulk form. The magnetic moment of Mn{sub 2}As determined by saturated magnetization was 0.51 {mu}{sub B} per unit cell.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2011

Synthesis and Characterization of Ba(Zr{sub x}Ti{sub 1-x})O{sub 3} Solid Solutions Using Impedance Spectroscopic Techniques

Technologically important solid solutions of Ba(Zr{sub x}Ti{sub 1-x})O{sub 3} are synthesized using conventional solid state route. Relatively dense and single phase ceramics are confirmed using X-ray diffraction. Homogeneous and micron size grain growth is characterized using SEM. Impedance spectroscopy is used to study the electrical properties of ceramics. Broad and diffuse impedance loss peak is observed above 250 deg. C, which shifts towards higher frequency with increase in temperature. The distribution of relaxation frequency may be associated with the B-site cationic disorder due to the random distribution of (Zr{sup 4+}/Ti{sup +4}) having different ionic radii. Impedance relaxation obeys the Arrhenius relation with activation energy, E{tau} is 0.31 eV and 0.48 eV for BZT compositions with x = 0.10 and 0.15 respectively. Equivalent circuit representation using two RC element coupled in parallel is used to analyse the impedance response.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Sub-pixel high-resolution imaging of high-energy x-rays inspired by sub-wavelength optical imaging

We have developed and demonstrated an image super-resolution method—XR-UNLOC: X-Ray UNsupervised particle LOCalization—for hard x-rays measured with fast-frame-rate detectors that is an adaptation of the principle of photo-activated localization microscopy (PALM) and stochastic optical reconstruction microscopy (STORM), which enabled biological fluorescence imaging at sub-optical-wavelength scales. We demonstrate the approach on experimental coherent Bragg diffraction data measured with 52 keV x-rays from a nanocrystalline sample. From this sample, we resolve the fine fringe detail of a high-energy x-ray Bragg coherent diffraction pattern to an upsampling factor of 16 of the native pixel pitch of 30 μ m of a charge-integrating fastCCD detector. This was accomplished by analysis of individual photon locations in a series of “nearly-dark” instances of the diffraction pattern that each contain only a handful of photons. Central to our approach was the adaptation of the UNLOC photon fitting routine for PALM/STORM to the hard x-ray regime to handle much smaller point spread functions, which required a different statistical test for photon detection and for sub-pixel localization. A comparison to a photon-localization strategy used in the x-ray community (“droplet analysis”) showed that XR-UNLOC provides significant improvement in super-resolution. We also developed a metric by which to estimate the limit of reliable upsampling with XR-UNLOC under a given set of experimental conditions in terms of the signal-to-noise ratio of a photon detection event and the size of the point spread function for guiding future x-ray experiments in many disciplines where detector pixelation limits must be overcome.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

CuO-ZnO heterometallic hollow spheres: Morphology and defect structure

The Cu-ZnO hollow spheres, where CuO nanocrystals were dispersed in the shell of ZnO nanoparticals, were synthesized by using highly uniform and monodispersed Cu-embedded carbon spheres as sacrificial templates via a simple route under hydrothermal conditions. The morphology and structure of the spheres were characterized by FTIR, XRD, SEM, TEM and N{sub 2} adsorption-desorption. It was suggested that the OH and C=O groups in the surface of the Cu-embedded carbon spheres facilitated the adsorption of Zn{sup 2+} in the aqueous solution, giving rise to the final CuO-ZnO hollow structure after these Zn{sup 2+}-adsorbed spheres were calcined in air. Moreover, the photoluminescence (PL) study showed that the as-prepared CuO-ZnO hollow spheres and the annealed counterpart exhibited strong and dramatically weakened emissions, respectively. This remarkably different photoluminescent behavior afforded the evidence regarding the oxygen vacancy defects in the CuO-ZnO hollow spheres. - Graphical abstract: CuO-ZnO hollow spheres were obtained using Cu-embedded carbon spheres as template, and the photoluminescent spectra afforded the evidence regarding the oxygen vacancies in the hollow spheres. Highlights: Black-Right-Pointing-Pointer A approach was presented to prepare carbon spheres in a high yield. Black-Right-Pointing-Pointer The fabrication of CuO-ZnO hollow spheres was a simple route. Black-Right-Pointing-Pointer The photoluminescence afforded the evidence of the oxygen vacancies in the hollows. Black-Right-Pointing-Pointer The synthetic approach might be applicable to preparing other hollow structures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗