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Results for “coherent diffraction microscopy”

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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Influence of CO{sub 2} activation on hydrogen storage behaviors of platinum-loaded activated carbon nanotubes

In this work, platinum (Pt) metal loaded activated multi-walled carbon nanotubes (MWNTs) were prepared with different structural characteristics for hydrogen storage applications. The process was conducted by a gas phase CO{sub 2} activation method at 1200 {sup o}C as a function of the CO{sub 2} flow time. Pt-loaded activated MWNTs were also formulated to investigate the hydrogen storage characteristics. The microstructures of the Pt-loaded activated MWNTs were characterized by XRD and TEM measurements. The textural properties of the samples were analyzed using N{sub 2} adsorption isotherms at 77 K. The BET, D-R, and BJH equations were used to observe the specific surface areas and the micropore and mesopore structures. The hydrogen storage capacity of the Pt-loaded activated MWNTs was measured at 298 K at a pressure of 100 bar. The hydrogen storage capacity was increased with CO{sub 2} flow time. It was found that the micropore volume of the activated MWNTs plays a key role in the hydrogen storage capacity. -- Graphical abstract: The hydrogen storage capacities of the Pt-loaded activated MWNTs as a function of CO{sub 2} flow time are described. Display Omitted

36 MATERIALS SCIENCE↗
DOE OSTI2011

Tunable photoluminescence of NaYF{sub 4}:Eu nanocrystals by Sr{sup 2+} codoping

NaYF{sub 4}:Eu/Sr nanocrystals were synthesized by a hydrothermal method. Tunable photoluminescence of the NaYF{sub 4}:Eu nanocrystals was successfully achieved by codoping with Sr{sup 2+} ions. With increasing Sr{sup 2+} concentration, not only the X-ray diffraction peaks of the nanocrystals become broader, but also the positions of them shift toward larger lattice parameters. Eu{sup 3+} and Eu{sup 2+} have been found to coexist in an NaYF{sub 4}:Eu/Sr. The Eu{sup 3+}/Eu{sup 2+} emission intensity ratio changed with the Sr{sup 2+} concentration and excitation wavelength. More interestingly, the spectral configurations of Eu{sup 2+} and Eu{sup 3+} also varied with the excitation wavelength, indicating that the nanocrystals have multiple luminescence centers or emitting states. -- Graphical abstract: (a) TEM and (b) HRTEM images of NaYF{sub 4}:Sr(30%)/Eu(10%) nanocrystals. (c) TEM image of NaYF{sub 4}:Sr(70%)/Eu(10%) nanocrystals. (d) EDXA pattern of NaYF{sub 4}:Sr(30%)/Eu(10%) nanocrystals. Display Omitted

36 MATERIALS SCIENCE↗
DOE OSTI2011

Bismuth titanate pyrochlore microspheres: Directed synthesis and their visible light photocatalytic activity

Bismuth titanates, Bi{sub 2}Ti{sub 2}O{sub 7} (BIT), with well-defined spherical structures were synthesized by a facile hydrothermal process without the use of any surfactant or template. XRD and SEM studies have shown that spheres could be fabricated in high yields by simply manipulating the concentrations of hydroxide ions. In this case, hydroxide ions seem to play a pivotal role in controlling the formation of seeds and growth rates of the BIT particles. On the basis of structural analysis of samples obtained at different concentrations of OH{sup -}, we also proposed a plausible mechanism to account for the formation of these distinctive morphologies under different conditions. The as-prepared BIT microspheres with good stability exhibited higher photocatalytic activities in the degradation of Rhodamine B (RhB) under visible light irradiation than that in commercial P25 TiO{sub 2}. Furthermore, the enhanced photocatalytic performance for RhB degradation was also investigated with assistance of a small amount of H{sub 2}O{sub 2}. -- Graphical abstract: Bismuth titanate pyrochlore microspheres were synthesized by a facile hydrothermal process without the use of any surfactant or template, and the effects of concentration of OH{sup -} on the diameter of microspheres, growth mechanism and photocatalytic properties were investigated. Display Omitted Research Highlights: Bismuth titanate pyrochlore microspheres with different diameters were synthesized by a facile hydrothermal process without the use of any surfactant or template. The BIT microspheres with good stability exhibited higher photocatalytic activities in the degradation of RhB under visible light irradiation than that in commercial P25 TiO{sub 2}. Further enhanced photocatalytic activity for RhB degradation was ascribed to the assistance of a small amount of H{sub 2}O{sub 2}.

36 MATERIALS SCIENCE↗
DOE OSTI2011

The ability of RP-type cobaltites to accommodate carbonate groups: A new layered oxide Sr{sub 4}Co{sub 2}(CO{sub 3})O{sub 5.86}

The possibility to introduce carbonate groups inside a pure cobalt based Ruddlesden Popper type matrix is demonstrated. This paper reports the synthesis as a single phase of a new layered oxycarbonate Sr{sub 4}Co{sub 2}(CO{sub 3})O{sub 5.86} and its structural characterizations at room temperature combining TEM observations and powder neutron diffraction data. Close structural relationships are observed with the homologous Sr{sub 4}Fe{sub 3-x}(CO{sub 3}){sub x}O{sub 10-4x} series and deal with the presence of two specific carbonate configurations, namely coat hanger and flag. Magnetization measurements reveal a complex antiferromagnetic behavior below 50 K with three others transitions, at 160, 210 and 250 K. Such behavior can be ascribed to the latent reactivity in air of this largely oxygen deficient phase. - Graphical abstract: Structural model of the Sr{sub 4}Co{sub 2}(CO{sub 3})O{sub 5.86} oxycarbonate. Highlights: > Partial substitution of CO groups for Co species is efficient to stabilize a new RP3 cobaltite. > HREM image combined with IR data and powder ND data confirm the structural model. > From ND data, Fourier difference analysis evidences two specific carbonate orientations.

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

Preparation, characterization and catalyst application of ternary interpenetrating networks of poly 4-methyl vinyl pyridinium hydroxide-SiO{sub 2}-Al{sub 2}O{sub 3}

In this work, Al{sub 2}O{sub 3} was mixed with SiO{sub 2} and poly 4-vinylpyridine by the sol-gel method in order to make a composite which is used as a heterogeneous basic catalyst for Knoevenagel condensation reaction. The physical and chemical properties of the composite catalyst were investigated by XRD, FT-IR, TG, BET and SEM techniques. The catalytic performance of each material was determined for the Knoevenagel condensation reaction between carbonyl compound and malononitrile. The reactions were performed in solvent-free conditions and the product was obtained in high yield and purity after a simple work-up. The effects of the amount of catalyst, amount of monomer for the synthesis of composite and recyclability of the heterogeneous composite were investigated. The composite catalyst used for this synthetically useful transformation showed considerable level of reusability besides very good activity. - Graphical abstract: In this paper, we report the synthesis of poly 4-methyl vinyl pyridinium hydroxide-SiO{sub 2}-Al{sub 2}O{sub 3}. The novelty of this procedure is at easy preparation together with using inexpensive materials. Highlights: > P4MVPH-SiO{sub 2}-Al{sub 2}O{sub 3} composite was prepared as a novel polymer-inorganic hybrid. > The composite was prepared without using any bridged organosilanes compound. > SEM photograph showed that the composite is completely uniform. > P4MVPH-SiO{sub 2}-Al{sub 2}O{sub 3} could behave as a recyclable catalyst for Knoevenagel reaction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Inversion of dynamical Bragg intensities to complex structure factors by iterated projections. For Ultramic. 2020. ("Pico" Festschrift, May 2021)

We discuss a method for recovering complex structure factors from many simultaneously excited Bragg beam intensities is described. The method is applied to simulated transmission electron diffraction data over a wide range of crystal thickness and beam energies. The method is based on iterated projections between structure and scattering matrices, which are related by a matrix unitary transformation, exponential, which we invert. The algorithm removes multiple-scattering perturbations from diffraction data and might be extended to other fields, including X-ray and neutron diffraction and cryo-electron microscopy. Because coherent multiple scattering involves interference between Bragg beams, the method also solves the phase problem. Unlike dynamical inversion from electron microscope images or ptychography data, the method, which starts with Bragg beam intensities, provides complex structure factors unaffected by focusing errors or resolution limitations imposed by lenses. We provide inversions from simulated data with 441 simultaneously excited Bragg beams over a range of thickness and beam energy. We discuss the retrieval of chirality information from enantiomorphs, the efficient incorporation of symmetry information using the irreducible representation of the group of structure matrices, and the effect of HOLZ lines to provide three-dimensional information.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

Asynchronous domain dynamics and equilibration in layered oxide battery cathode

To improve lithium-ion battery technology, it is essential to probe and comprehend the microscopic dynamic processes that occur in a real-world composite electrode under operating conditions. The primary and secondary particles are the structural building blocks of battery cathode electrodes. Their dynamic inconsistency has profound but not well-understood impacts. In this research, we combine operando coherent multi-crystal diffraction and optical microscopy to examine the chemical dynamics in local domains of layered oxide cathode. Our results not only pinpoint the asynchronicity of the lithium (de)intercalation at the sub-particle level, but also reveal sophisticated diffusion kinetics and reaction patterns, involving various localized processes, e.g., chemical onset, reaction front propagation, domains equilibration, particle deformation and motion. These observations shed new lights onto the activation and degradation mechanisms of state-of-the-art battery cathode materials.

25 ENERGY STORAGE↗
DOE OSTI2011

Moessbauer spectroscopy and magnetic characteristics of Zn{sub 1-x}Co{sub x}Fe{sub 2}O{sub 4} (x = 0-1) nanoparticles

Zn{sub 1-x}Co{sub x}Fe{sub 2}O{sub 4} (x = 0-1 in a step of 0.2) nanoparticles with different range of particle size including 5-10 nm and 200-250 nm have been prepared by sol-gel process. Moessbauer spectra at room temperature indicated that, with increasing cobalt content, there is a transition from paramagnetic to magnetically ordered-ferrimagnetic state. Magnetic properties were measured at 300 and 10 K using a Quantum Design MPMS-5S SQUID magnetometer. It was found that with an increase in cobalt content the saturation magnetization and coercivity increase.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2011

Synthesis and magnetic properties of Co-Ti-Bi codoped M-type barium ferrite

The effects of Co{sup 2+}, Ti{sup 4+}, and Bi{sup 3+} substitution on the microstructures and properties of low-temperature fired M-type barium hexaferrites have been studied in order to adapt the development of low-temperature cofired ferrites technology and produce gyromagnetic devices with a multilayer process. It is found that Bi{sup 3+} ions can enter into the 2a sublattice and consequently enhance the grain growth and densification due to the activation of the lattice, which in turn first lead to an increase and then a decrease of M{sub s}. The substitution of Bi{sup 3+} ions is beneficial to forming the M phase and lowers the sintering temperature to about 900 deg. C, which is ideal for cofiring with silver paste. Scanning electron microscope and x-ray diffraction analysis have shown that the samples have excellent crystalline grains with a uniform size about 1-2 {mu}m. Moreover, nonmagnetic Ti{sup 4+} ions prefer to enter the 4f{sub VI} octahedral sites, giving rise to the weakening of the strong 12k-4f{sub VI} superexchange path and thus the isotropic exchange energy approaches the other second-order terms on the magnetic Hamiltonian, such as the antisymmetric interaction or even the magnetocrystalline anisotropy. With increasing the substitution content, some Co{sup 2+} ions, which locate in octahedral 12k sites, give a strong planar contribution to the anisotropy. Therefore, M{sub s} and H{sub c} decrease with the Co-Ti-substitution.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Communication: X-ray coherent diffractive imaging by immersion in nanodroplets

Lensless x-ray microscopy requires the recovery of the phase of the radiation scattered from a specimen. Here, we demonstrate a de novo phase retrieval technique by encapsulating an object in a superfluid helium nanodroplet, which provides both a physical support and an approximate scattering phase for the iterative image reconstruction. The technique is robust, fast-converging, and yields the complex density of the immersed object. As a result, images of xenon clusters embedded in superfluid helium droplets reveal transient configurations of quantum vortices in this fragile system.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Characterising the large coherence length at diamond’s beamline I13L

I13 is a 250 m long hard x-ray beamline (6 keV to 35 keV) at the Diamond Light Source. The beamline comprises of two independent experimental endstations: one for imaging in direct space using x-ray microscopy and one for imaging in reciprocal space using coherent diffraction based imaging techniques [1]. An outstanding feature of the coherence branch, due to its length and a new generation of ultra-stable beamline instrumentation [2], is its capability of delivering a very large coherence length well beyond 200 μm, providing opportunities for unique x-ray optical experiments. In this paper we discuss the challenges of measuring a large coherence length and present quantitative measurement based on analyzing diffraction patterns from a boron fiber [3]. We also discuss the limitations of this classical method in respect to detector performance, very short and long coherence lengths. Furthermore we demonstrate how a Ronchi grating setup [4] can be used to quickly establish if the beam is coherent over a large area.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

The effect of the distance between acidic site and basic site immobilized on mesoporous solid on the activity in catalyzing aldol condensation

Acid-base bifunctional heterogeneous catalysts containing carboxylic and amine groups, which were immobilized at defined distance from one another on the mesoporous solid were synthesized by immobilizing lysine onto carboxyl-SBA-15. The obtained materials were characterized by X-ray diffraction (XRD), N{sub 2} adsorption, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron micrographs (SEM), transmission electron micrographs (TEM), elemental analysis, and back titration. Proximal-C-A-SBA-15 with a proximal acid-base distance was more active than maximum-C-A-SBA-15 with a maximum acid-base distance in aldol condensation reaction between acetone and various aldehydes. It appears that the distance between acidic site and basic site immobilized on mesoporous solid should be an essential factor for catalysis optimization. -- Graphical abstract: Proximal-C-A-SBA-15 with a proximal acid-base distance and maximum-C-A-SBA-15 with a maximum acid-base distance were synthesized by immobilizing lysine onto carboxyl-SBA-15. Display Omitted Research highlights: {yields} Proximal-C-A-SBA-15 with a proximal acid-base distance. {yields} Maximum-C-A-SBA-15 with a maximum acid-base distance. {yields} Compared to maximum-C-A-SBA-15, proximal-C-A-SBA-15 was more active toward aldol condensation reaction between acetone and various aldehydes.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2011

One-step synthesis and stabilization of gold nanoparticles and multilayer film assembly

Au nanoparticles (NPs) were synthesized in the one-pot procedure in water at room temperature with the wheel-shaped V{sup V}-V{sup IV} mixed-valence tungstovanadate [P{sub 8}W{sub 48}O{sub 184{l_brace}}V{sub 4}{sup V}V{sub 2}{sup IV}O{sub 12}(H{sub 2}O){sub 2{r_brace}2}]{sup 32-} (V12) acting as both reducing and stabilizing agents. The V12 stabilized Au NPs (Au-V12 NPs) were characterized by SEM, TEM, DLS, UV-vis spectroscopy, XPS, and XRD analyses and the negatively charged surface of the Au-V12 NPs was proved by the zeta potential analysis. Based on the layer-by-layer assembly (LbL), the Au-V12 NPs-containing multilayer films have been fabricated on ITO-coated glass slide and quartz substrates with poly(ethyleneimine) (PEI). The regular growth of the multilayer films was monitored by UV-vis spectroscopy and cyclic voltammetry, the composition was characterized by XPS. The Au-V12 NPs based composite films showed electrocatalytic activities towards the reduction of dioxygen and the oxidation of methanol. This approach is expected to open the way towards procedures aimed at the one-step fabrication of Au NPs and polyoxometalates (POMs) into the multilayer films. -- Graphical abstract: The wheel-shaped V{sup V}-V{sup IV} mixed-valence tungstovanadate [P{sub 8}W{sub 48}O{sub 184{l_brace}}V{sub 4}{sup V}V{sub 2}{sup IV}O{sub 12}(H{sub 2}O){sub 2{r_brace}2}]{sup 32-} (V12) stabilized Au nanoparticles (Au-V12 NPs) have been synthesized and characterized. The multilayer films containing Au-V12 NPs were fabricated and their electrocatalytic properties were studied. Display Omitted Research highlights: {yields} Au core-V12 shell nanostructures, Au-V12 NPs, were synthesized and characterized. {yields} The negatively charged Au NPs were fabricated and catalytic properties were studied. {yields} This study opens the way to the fabrication of multifunctional thin-film materials.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2011

Self-assembly of Fe{sub 3}O{sub 4} nanocrystal-clusters into cauliflower-like architectures: Synthesis and characterization

Large-scale cauliflower-like Fe{sub 3}O{sub 4} architectures consist of well-assembled magnetite nanocrystal clusters have been synthesized by a simple solvothermal process. The as-synthesized Fe{sub 3}O{sub 4} samples were characterized by XRD, XPS, FT-IR, SEM, TEM, etc. The results show that the samples exhibit cauliflower-like hierarchical microstructures. The influences of synthesis parameters on the morphology of the samples were experimentally investigated. Magnetic properties of the Fe{sub 3}O{sub 4} cauliflower-like hierarchical microstructures have been detected by VSM at room temperature, showing a relatively low saturation magnetization of 65 emu/g and an enhanced coercive force of 247 Oe. - Graphical Abstract: Cauliflower-like Fe{sub 3}O{sub 4} architectures consist of well-assembled magnetite nanocrystal clusters have been synthesized by a simple solvothermal process, using FeCl{sub 3}.6H{sub 2}O and EDA as the starting materials. Highlights: > Cauliflower-like Fe{sub 3}O{sub 4} architectures were successfully prepared by a simple solvothermal route. > The cauliflower-like Fe{sub 3}O{sub 4} architectures have a size in the range of 200-300 nm. > They show a low saturation magnetization of 65 emu/g and an enhanced coercive force of 247 Oe. > These Fe{sub 3}O{sub 4} architectures may have potential applications in catalysis and biological fields.

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

Formation and Characterization of Au/TiO{sub 2} NanoComposite by Laser Irradiation

Nanosized noble metal particles and dielectric matrix composite materials have attracted extensive attention due to their large third-order nonlinear susceptibility and ultrafast response properties, and have great potential for applications in optical devices. In this study, composite Au/TiO{sub 2} nanoparticles were synthesized by laser irradiation. Characterization of the composite particles by means of UV-Vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and atomic force microscopy (AFM) was carried out. We have successfully produced composite Au/TiO{sub 2} nanoparticles by laser ablation of metal gold plate in TiO{sub 2} sol. The red shift of 30 nm in the surface plasmon band of Au is found due to the refractive index of TiO{sub 2}. The surrounding TiO{sub 2} matrix is amorphous, but upon heat treatment becomes a crystalline oxide. Various morphologies of particles are visible, including circular, hexagonal and triangular projection; circular and thus spherical particles being the most common, which were confirm by the TEM images. A large size distribution of particles is visible in TEM images; the average grain size was measured 35 nm, which was confirmed by X-ray diffraction studies.

36 MATERIALS SCIENCE↗
DOE OSTI2011

The crystallinity and mechanical properties of indium tin oxide coatings on polymer substrates

We present the relationship between the microstructure and mechanical strength of indium tin oxide (ITO) on flexible substrates. With varying thickness (h{sub f}), ITO is deposited on polyethylene terephthalate (PET) by dc magnetron sputtering. The microstructure of ITO is controlled by substrate surface conditions and sputtering parameters. The maximum substrate temperature during deposition is limited to 80 deg. C due to the low glass transition temperature (T{sub g}) of PET. The crystallinity and surface roughness (R{sub rms}) are analyzed by high resolution x-ray diffraction, high resolution transmission electron microscopy, and AFM. The crack resistance of ITO is evaluated by uniaxial tension test. The experimental results reveal that, at a fixed h{sub f}, the degree and quality of crystallinity of ITO are highly improved by increasing sputtering power and the substrate temperature. As the crystallinity is improved, the ratio of preferred growth orientations of (222) to (400) is increased and the degree of peak shifts to lower 2{theta} is decreased. They indicate that the crystallinity is improved as the lattice damage is reduced and film density is increased. The tension test results confirm that, up to a certain h{sub f}, the strength of ITO can be significantly enhanced by improving the microstructures.

36 MATERIALS SCIENCE↗
DOE OSTI2016

SHARP: a distributed GPU-based ptychographic solver

Ever brighter light sources, fast parallel detectors and advances in phase retrieval methods have made ptychography a practical and popular imaging technique. Compared to previous techniques, ptychography provides superior robustness and resolution at the expense of more advanced and time-consuming data analysis. Therefore, by taking advantage of massively parallel architectures, high-throughput processing can expedite this analysis and provide microscopists with immediate feedback. These advances allow real-time imaging at wavelength-limited resolution, coupled with a large field of view. This article describes a set of algorithmic and computational methodologies used at the Advanced Light Source and US Department of Energy light sources. These are packaged as a CUDA-based software environment named SHARP, aimed at providing state-of-the-art high-throughput ptychography reconstructions for the coming era of diffraction-limited light sources.

47 OTHER INSTRUMENTATION↗
DOE OSTI2016

Dose-dependent high-resolution electron ptychography

Recent reports of electron ptychography at atomic resolution have ushered in a new era of coherent diffractive imaging in the context of electron microscopy. We report and discuss electron ptychography under variable electron dose conditions, exploring the prospects of an approach which has considerable potential for imaging where low dose is needed.

60 APPLIED LIFE SCIENCES↗