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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Microstructure and Magnetic Properties of PrMnO{sub 3} Bulk and Thin Film

Perovskite PrMnO{sub 3}(PMO) had been prepared in bulk by solid state reaction and thin films on corning glass, fused silica and MgO (100) glass substrate by pulsed laser deposition technique. SEM micrographs show that grains with size 2{approx}3 {mu}m is observed in bulk PMO while thin films PMO show strongly connected grain structure with particle size that not larger than 100 nm. X-ray diffraction analysis shows that all samples are in single phase with orthorhombic crystal structure. Bulk PMO sample had lattice strain of 0.134% which is the lowest value among others. However, larger lattice strain was observed in thin film samples due to lattice mismatch between film-substrate and caused the MnO{sub 6} to deform. All samples shown paramagnetic or antiferromagnetic behavior, enhancement in magnetization value occurred for all PMO grew as film. We believe that larger lattice strain favor the grain growth of PMO towards more order phase. In summary, formation of structure and microstructure of thin film PMO depends on type of substrate used and it affect the magnetic property.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Coherent control of injection currents in high-quality films of Bi{sub 2}Se{sub 3}

Films of the topological insulator Bi{sub 2}Se{sub 3} are grown by molecular beam epitaxy with in-situ reflection high-energy electron diffraction. The films are shown to be high-quality by X-ray reflectivity and diffraction and atomic-force microscopy. Quantum interference control of photocurrents is observed by excitation with harmonically related pulses and detected by terahertz radiation. The injection current obeys the expected excitation irradiance dependence, showing linear dependence on the fundamental pulse irradiance and square-root irradiance dependence of the frequency-doubled optical pulses. The injection current also follows a sinusoidal relative-phase dependence between the two excitation pulses. These results confirm the third-order nonlinear optical origins of the coherently controlled injection current. Experiments are compared to a tight-binding band structure to illustrate the possible optical transitions that occur in creating the injection current.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

The interfacial orientation relationship of oxide nanoparticles in a hafnium-containing oxide dispersion-strengthened austenitic stainless steel

This work reports comprehensive investigations on the orientation relationship of the oxide nanoparticles in a hafnium-containing austenitic oxide dispersion-strengthened 316 stainless steel. The phases of the oxide nanoparticles were determined by a combination of scanning transmission electron microscopy–electron dispersive X-ray spectroscopy, atom probe tomography and synchrotron X-ray diffraction to be complex Y–Ti–Hf–O compounds with similar crystal structures, including bixbyite Y{sub 2}O{sub 3}, fluorite Y{sub 2}O{sub 3}–HfO{sub 2} solid solution and pyrochlore (or fluorite) Y{sub 2}(Ti,Hf){sub 2−x}O{sub 7−x}. High resolution transmission electron microscopy was used to characterize the particle–matrix interfaces. Two different coherency relationships along with one axis-parallel relation between the oxide nanoparticles and the steel matrix were found. The size of the nanoparticles significantly influences the orientation relationship. The results provide insight into the relationship of these nanoparticles with the matrix, which has implications for interpreting material properties as well as responses to radiation. - Highlights: • The oxide nanoparticles in a hafnium-containing austenitic ODS were characterized. • The nanoparticles are Y–Hf–Ti–O enriched phases according to APT and STEM–EDS. • Two coherency and an axis-parallel orientation relationships were found by HR-TEM. • Particle size has a prominent effect on the orientation relationship (OR). • Formation mechanism of the oxide nanoparticles was discussed based on the ORs.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Picoscale structural insight into superconductivity of monolayer FeSe/SrTiO 3

Remarkable enhancement of the superconducting transition temperature ( c ) has been observed for monolayer (ML) FeSe films grown on SrTiO 3 substrates. The atomic-scale structure of the FeSe/SrTiO 3 interface is an important determinant of both the magnetic and interfacial electron-phonon interactions and is a key ingredient to understanding its high- T c superconductivity. We resolve the atomic-scale structure of the FeSe/SrTiO 3 interface through a complementary analysis of scanning transmission electron microscopy and in situ surface x-ray diffraction. We find that the interface is more strongly bonded for a particular registration, which leads to a coherently strained ML. We also determine structural parameters, such as the distance between ML FeSe and the oxide, Se-Fe-Se bond angles, layer-resolved distances between Fe-Se, and registry of the FeSe lattice relative to the oxide. This picoscale structure determination provides an explicit structural framework and constraint for theoretical approaches addressing the high- T c mechanism in FeSe/SrTiO 3 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2011

Dissimilar Friction Stir Welds in Al5186-Al2024: The Effect of Process Parameters on Microstructures and Mechanical Properties

The effect of tool traverse and rotation speeds on the microstructures and mechanical properties are quantified for welds between non-age-hardening Al5083 and age hardening Al2024 and compared to single alloy joints made from each of the two constituents. In this paper, we report the results of microstructural, mechanical property investigations of Al5186-Al2024 friction stir welds produced using various rotations and traveling speeds of the tool to investigate the effects of the welding parameters on the joint strength. Metallographic studies by optical microscopy, electron probe microscopy, and the utilization of the X-ray diffraction technique have been conducted. It was found that the weld properties were dominated by the thermal input rather than the mechanical deformation by the tool. In particular the larger stresses under the weld tool on the AA5186 side compared to the AA2024 side are related to a transient reduction in yield stress due to dissolution of the hardening precipitates during welding prior to natural aging after welding.

36 MATERIALS SCIENCE↗
DOE OSTI2011

One-dimensional GdVO{sub 4}:Ln{sup 3+} (Ln=Eu, Dy, Sm) nanofibers: Electrospinning preparation and luminescence properties

One-dimensional GdVO{sub 4}:Ln{sup 3+} (Ln=Eu, Dy, Sm) nanofibers have been prepared by a combination method of sol-gel process and electrospinning technology. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL), quantum efficiency (QE), and cathodoluminescence (CL) spectra as well as kinetic decays were used to characterize the samples. The XRD, FT-IR, and TG-DTA results show that GdVO{sub 4}:Ln{sup 3+} nanofibers samples crystallize at 700 {sup o}C. SEM images indicate that the as prepared precursor fibers are smooth. After being calcined at 700 {sup o}C for 4 h, the fibers still maintain their fiberlike morphology with rough surface. TEM image further manifests that the GdVO{sub 4}:Ln{sup 3+} nanofibers consist of nanoparticles. Under ultraviolet excitation and low-voltage electron beam excitation, GdVO{sub 4}:Ln{sup 3+} phosphors showed their strong characteristic emission due to an efficient energy transfer from vanadate groups to dopants. The optimum doping concentration of Ln{sup 3+} in the GdVO{sub 4} nanofibers also has been investigated. -- Graphical abstract: Display Omitted Research Highlights: {yields}1D and Q-1D GdVO{sub 4} fiber-like nanostructures were prepared electrospinning technique. {yields}Under ultraviolet excitation and electron beam excitation, the Ln{sup 3+} ions show their characteristic emissions, respectively. {yields}The quantum efficiencies are 14 (Eu{sup 3+}), 6 (Dy{sup 3+}), and 5 % (Sm{sup 3+}) in GdVO{sub 4}, respectively.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2011

Chemical stability of highly (0001) textured Sm(CoCu){sub 5} thin films with a thin Ta capping layer

With the highest magnetocrystalline anisotropy constant (Ku) among practical magnetic materials, SmCo{sub 5} could be a very attractive candidate for future high areal density magnetic recording. However, its corrosion resistance is always a concern in recording media applications. In this paper, the chemical stability and microstructures of highly (0001) textured Sm(CoCu){sub 5} thin films with and without a 3 nm Ta capping layer were reported. For Sm(CoCu){sub 5} thin films without a capping layer, the coercivity decreases significantly (from 8kOe to 1kOe) within one month. Sm(CoCu){sub 5} thin films capped with a thin Ta layer (3 nm) behave differently. Even exposed to a laboratory environment (25 deg. C) over 3 years, the Ta-capped Sm(CoCu){sub 5} thin films are stable in terms of structural and magnetic properties, i.e., there were no changes in X-ray diffraction peaks and vibrating sample magnetometer hysteresis loops. Microstructure of Ta-capped Sm(CoCu){sub 5} thin films showed that Sm(CoCu){sub 5} formed a domelike particle assembly structure on a smooth Ru underlayer and were well covered by partially oxidized Ta capping layer, as shown by TEM cross-section micrographs. Accelerated corrosion treatment (130 deg. C, 95% relative humidity, 6 h) was performed on Ta-capped Sm(CoCu){sub 5} thin films. X-ray photoelectron spectroscopy (XPS) results showed that no Co was detected on the sample surface before the corrosion treatment, but strong XPS signals of CoOx and Co(OH)x were observed after treatment. Therefore, none of our Sm(CoCu){sub 5} thin films can pass the accelerated corrosion test. Hcp-phased CoPt-alloys are proposed as better capping materials for Sm(CoCu){sub 5} thin films in future high-density magnetic recording applications.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Perpendicular magnetic anisotropy and spin reorientation transition in L1{sub 0} FePt films

We investigated the thickness and composition dependence of perpendicular magnetic anisotropy (PMA) in L1{sub 0} Fe{sub 1-x}Pt{sub x} (x = 0.4, 0.5, and 0.55) films. The FePt films with different thicknesses of 35 and 70 A were grown at the substrate temperature T{sub s} = 300 deg. C by molecular beam epitaxy coevaporation technique. A (001)-oriented epitaxial L1{sub 0} FePt film was grown on the thin (001)-oriented fcc Pt layer, while a poorly crystallized FePt film was formed on the (111)-textured Pt layer. Our results showed that, at a fixed thickness of 70 A, the PMA of FePt alloy films is enhanced as Pt content increases from 40% to 55%.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Modulation periodicity dependent structure, stress, and hardness in NbN/W{sub 2}N nanostructured multilayer films

NbN/W{sub 2}N nano-multilayer films with a modulation periodicity, {Lambda}, ranging from 5.1 to 157.4 nm have been deposited on a Si(100) substrate by reactive magnetron sputtering in Ar/N{sub 2} mixtures. The {Lambda} dependent structural and mechanical properties for the resulting NbN/W{sub 2}N multilayers have been evaluated by means of low-angle x-ray reflectivity, x-ray diffraction, high-resolution transmission electron microscope, and nanoindentation measurements. The finding is that for films with {Lambda}{<=} 10.6 nm, fcc NbN layers are coherent with cubic W{sub 2}N layers, resulting in NbN layers and W{sub 2}N layers that are in the compressive and tensile states, respectively. In contrast, as {Lambda} is larger than 10.6 nm, a phase transition from W{sub 2}N to W occurs in the W{sub 2}N layer, which is a result of the coherent interface strain relaxation. For this case, all layers are in the compressive state, and the coherent interface disappears. The intrinsic compressive stress evolution with {Lambda} can be interpreted in terms of interface stress. The formation of coherent interface at small {Lambda} ({<=}10.6 nm) is helpful for releasing point defects in layers, leading to a low compressive stress ({<=}1.1 GPa). The hardness for the obtained multilayer film increases with decreasing {Lambda}, and approaches a maximum value of 43.7 GPa when {Lambda} is 7.4 nm. The maximum strengthen at lower {Lambda} is mainly attributed to coherent interface stresses and the modulus difference between the NbN and W{sub 2}N layers. The increase in hardness with a decrease in {Lambda} is interpreted by the Lehoczky model.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Magnetic and Magnetotransport Properties of (Pr{sub 0.7}Sr{sub 0.3}MnO{sub 3}){sub 1-x}/NiO{sub x} Composites

In this paper, we report the structural, magnetic and magnetotransport properties of (Pr{sub 0.7}Sr{sub 0.3}MnO{sub 3}){sub 1-x}/NiO{sub x}(x = 0, 0.05, 0.10, 0.15 and 0.20) composites samples. The composite samples have been synthesized in such a manner so that there is no reaction between Pr{sub 0.7}Sr{sub 0.3}MnO{sub 3}(PSMO) and NiO. This has been confirmed by XRD and FESEM results. The magnetic measurements show reduction in ferromagnetic ordering in the composite samples with increasing level of NiO. Furthermore, incorporation of NiO phase into Pr{sub 0.7}Sr{sub 0.3}MnO{sub 3} matrix lowers the metal-insulator transition temperature (TIM) and increases the resistance of composites. An enhancement in magnetoresistance (MR) is observed at low temperature, below 140 K, for the composites with x = 0.05, 0.10 and 0.15 and at high temperature (298K) for all the composites at applied magnetic field H = 5 kOe. It is suggested that the higher value of MR at temperature below 140 K is low field magnetoresistance (LFMR) caused by spin polarized tunneling, whereas at around room temperature it is caused by magnetic disordering.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Structural and Dielectric Properties of LiSr{sub 2}Nb{sub 5}O{sub 15} Ceramic

The polycrystalline sample of LiSr{sub 2}Nb{sub 5}O{sub 15}(LSN) was prepared by a high temperature solid-state reaction technique. Studies of structural and microstructural characterizations were performed by X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. X-ray studies reveal that the material has an orthorhombic structure at room temperature. Dielectric properties were measured over a wide range of temperature (28-500 deg. C) and frequency (10{sup 2}-10{sup 6} Hz). Conductivity of the material increases with rise in temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Self-modulated nanostructures in super-large-period Bi{sub 11}(Fe{sub 5}CoTi{sub 3}){sub 10/9}O{sub 33} epitaxial thin films

Super-large-period Aurivillius thin films with a pseudo-period of ten were grown on (0 0 1) SrTiO{sub 3} substrates using the pulsed laser deposition method. The as-grown films are found to be coherently strained to the substrate and atomically smooth. X-ray diffraction indicates an average periodicity of ten, while analysis with the high resolution scanning transmission electron microscopy reveals a self-modulated nanostructure in which the periodicity changes as the film thickness increases. Finally, we discuss the magnetic and possible ferroelectric properties of the self-modulated large period Aurivillius films at the room temperature.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Phase-controlled solvothermal synthesis and characterization of nickel sulfides with good single crystalline nature

Dispersed rhombohedral NiS rods with high aspect ratios and rhombic dodecahedron-like cubic NiS{sub 2} crystals were prepared by solvothermal routes using NiCl{sub 2}.6H{sub 2}O and Na{sub 2}S{sub 2}O{sub 3}.5H{sub 2}O as reagents and ethylenediamine as a solvent, and 3D blossoming flower-like rhombohedral NiS microstructures were synthesized using different sulfur sources of thiourea. The products were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, energy dispersion spectrometry and selected area electronic diffraction. All the products were pure and had good single crystalline nature. The synthesis parameters were of great importance on the purity and morphology of the products. The possible growth mechanisms have been discussed based on the analyses of the effects of sulfur sources and solvent on the crystal structures and detailed configurations of the products. The present work is likely to help the phase-controlled synthesis of other metal chalcogenides. - Graphical abstract: Rhombohedral NiS dispersed rods and 3D flower-like microstructures are evolved from dispersed nucleus and aggregate of nucleus, respectively, and the cross-sections of such rods are in equilateral triangle-like shape. Highlights: > 3D blossoming flower-like r-NiS microstructures are obtained. > Equilateral triangle-like cross-sections of r-NiS rods are observed. > Approach based on XRD analysis to phase-controlled synthesis is presented.

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

Optical characteristics of pulsed laser deposited Ge-Sb-Te thin films studied by spectroscopic ellipsometry

Pulsed laser deposition technique was used for the fabrication of (GeTe){sub 1-x}(Sb{sub 2}Te{sub 3}){sub x} (x = 0, 0.33, 0.50, 0.66, and 1) amorphous thin films. Scanning electron microscopy with energy-dispersive x-ray analysis, x-ray diffraction, optical reflectivity, and sheet resistance temperature dependences as well as variable angle spectroscopic ellipsometry measurements were used to characterize as-deposited (amorphous) and annealed (rocksaltlike) layers. In order to extract optical functions of the films, the Cody-Lorentz model was applied for the analysis of ellipsometric data. Fitted sets of Cody-Lorentz model parameters are discussed in relation with chemical composition and the structure of the layers. The GeTe component content was found to be responsible for the huge optical functions and thickness changes upon amorphous-to-fcc phase transition.

36 MATERIALS SCIENCE↗
DOE OSTI2020

1D to 2D Transition in Tellurium Observed by 4D Electron Microscopy

A new microwave-enhanced synthesis method for the production of tellurium nanostructures is reported here—with control over products from the 1D regime (sub-5 nm diameter nanowires), to nanoribbons, to the 2D tellurene regime—along with a new methodology for local statistical quantification of the crystallographic parameters of these materials at the nanometer scale. Using a direct electron detector and image-corrected microscope, large and robust 4D scanning transmission electron microscopy datasets for accurate structural analysis are obtained. These datasets allow the adaptation of quantitative techniques originally developed for X-ray diffraction (XRD) refinement analyses to transmission electron microscopy, enabling the first demonstration of sub-picometer accuracy lattice parameter extraction while also obtaining both the size of the coherent crystallite domains and the nanostrain, which is observed to decrease as nanowires transition to tellurene. This new local analysis is commensurate with global powder XRD results, indicating the robustness of both the new synthesis approach and new structural analysis methodology for future scalable production of 2D tellurene and characterization of nanomaterials.

2D materials↗
DOE OSTI2012

New strategy to the controllable synthesis of CuInS{sub 2} hollow nanospheres and their applications in lithium ion batteries

A new strategy has been presented to the controllable synthesis of CuInS{sub 2} hollow nanospheres based on the Cu{sub 2}O solid nanospheres as the precursor in the absence of any surfactant. Specifically, the CuInS{sub 2} hollow nanospheres result from hydrothermal transformation of the intermediate Cu{sub 7}S{sub 4} hollow nanospheres derived from Cu{sub 2}O solid nanosphere precursor by the Kirkendall effect in the conversion process. The CuInS{sub 2} hollow nanospheres with diameters of about 250 nm are assembly of nanoparticles with an average size of 20-30 nm. The composition, structure, and morphology of the Cu{sub 2}O precursor, the Cu{sub 7}S{sub 4} intermediate, and final CuInS{sub 2} product have been, respectively, characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) with selected area electron diffraction (SAED). Different from investigation of photovoltaic properties, in this work, the as-prepared CuInS{sub 2} hollow nanospheres have been explored as anode materials for rechargeable lithium ion batteries. They deliver a large initial discharge capacity of 1144 mAh g{sup -1} and exhibit good cycle performance with a discharge capacity of 265 mAh g{sup -1} after 20 cycles, which are superior to those of CuInS{sub 2} nanoparticles. The suitable surface area and relatively stable structure of the CuInS{sub 2} hollow nanospheres play an important role in their enhanced electrochemical performance as anode materials. - Graphical abstract: CuInS{sub 2} hollow nanospheres was successfully prepared from Cu{sub 2}O solid nanospheres in the absence of any surfactant, which can deliver a large initial discharge capacity of 1144 mAh g{sup -1} and exhibit good cycle performance. Highlights: Black-Right-Pointing-Pointer CuInS{sub 2} hollow nanospheres were synthesized hydrothermally from Cu{sub 2}O nanospheres. Black-Right-Pointing-Pointer The CuInS{sub 2} hollow nanospheres present high discharge capacities as anode materials. Black-Right-Pointing-Pointer Better cycling performance can be attributed to its hollow structure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Coherent growth of superconducting TiN thin films by plasma enhanced molecular beam epitaxy

We have investigated the formation of titanium nitride (TiN) thin films on (001) MgO substrates by molecular beam epitaxy and radio frequency acitvated nitrogen plasma. Although cubic TiN is stabile over a wide temperature range, superconducting TiN films are exclusively obtained when the substrate temperature exceeds 710 Degree-Sign C. TiN films grown at 720 Degree-Sign C show a high residual resistivity ratio of approximately 11 and the superconducting transition temperature (T{sub c}) is well above 5 K. Superconductivity has been confirmed also by magnetiztion measurements. In addition, we determined the upper critical magnetic field ({mu}{sub 0}H{sub c2}) as well as the corresponding coherence length ({xi}{sub GL}) by transport measurements under high magnetic fields. High-resolution transmission electron microscopy data revealed full in plane coherency to the substrate as well as a low defect density in the film, in agreement with a mean-free path length Script-Small-L Almost-Equal-To 106 nm, which is estimated from the residual resistivity value. The observations of reflection high energy electron diffraction intensity oscillations during the growth, distinct Laue fringes around the main Bragg peaks, and higher order diffraction spots in the reciprocal space map suggest the full controlability of the thickness of high quality superconducting TiN thin films.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Advances in the electron diffraction characterization of atomic clusters and nanoparticles

Nanoparticles and metallic clusters continue to make a remarkable impact on novel and emerging technologies. In recent years, there have been impressive advances in the controlled synthesis of clusters and their advanced characterization. One of the most common ways to determine the structures of nanoparticles and clusters is by means of X-ray diffraction methods. However, this requires the clusters to crystallize in a similar way to those used in protein studies, which is not possible in many cases. Novel methods based on electron diffraction have been used to efficiently study individual nanoparticles and clusters and these can overcome the obstacles commonly encountered during X-ray diffraction methods without the need for large crystals. These novel methodologies have improved with advances in electron microscopy instrumentation and electron detection. Here, we review advanced methodologies for characterizing metallic nanoparticles and clusters using a variety of electron diffraction procedures. These include selected area electron diffraction, nanobeam diffraction, coherent electron diffraction, precession electron diffraction, scanning transmission electron microcopy diffraction, and high throughput data analytics, which leverage deep learning to reduce the propensity for data errors and translate nanometer and atomic scale measurements into material data.

77 NANOSCIENCE AND NANOTECHNOLOGY↗