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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Growth, structural, and magnetic properties of single-crystal full-Heusler Co 2 TiGe thin films

This paper presents the growth, structural characterization, and measurement of magnetic properties of Co 2 TiGe thin films grown by molecular beam epitaxy on insulating MgO (001) substrates and conductive lattice matched InAlAs/InGaAs/InAlAs epitaxial layers grown on n-InP (001) substrates. A GdAs diffusion barrier was used to minimize interfacial reactions during Co 2 TiGe growth on InAlAs. The surface morphology, structural quality, and magnetic behavior were examined by reflection high-energy electron diffraction, scanning tunneling microscopy, X-ray diffraction, and superconducting quantum interference device magnetometry. The results reveal high quality Co 2 TiGe thin films with a saturation magnetization of ~1.8 μ B /formula unit and a Curie temperature of ~375 K. Finally, the magnetic easy axis was found to lie in the [110] direction but magnetometry also reveals that there is only a small difference in energy between the [110] and [010] magnetization directions.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Morphology, structure, and mechanical properties of the surface of PbTe crystals after etching with H{sub 2}O{sub 2}–HBr–ethylene glycol solutions

The morphology and microstructure of PbTe surfaces polished with H{sub 2}O{sub 2}–HBr–ethylene glycol solutions have been studied by atomic force and electron microscopy techniques. The surface of PbTe single crystals after chemical–mechanical and dynamic chemical polishing with bromine-releasing etchants has been examined by optical microscopy and profilometry. The structural perfection and composition of the PbTe surface after chemical treatment have been determined by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. The mechanical properties of the crystals have been studied using microindentation. Using X-ray microanalysis, we have monitored the concentrations of the host elements (Pb and Te) and possible contamination with chemical compounds present in the etchants and the solutions used to rinse the samples.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Microstructural and Oxidation Effects of Nb Additions to U3Si2

U3Si2 is a long term, accident-tolerant nuclear fuel candidate for light-water reactors because of its superior thermal conductivity and increased uranium density when compared to traditional uranium dioxide (UO2). While reducing internal thermal stresses and increasing efficiency, U3Si2 exhibits energetic oxidation during certain off-normal and accident scenarios, which include coolant or steam exposure. To mitigate this, Nb is investigated as an alloy constituent to enhance corrosion resistance and increase mechanical strength. The work presented investigates the response of Nb-alloyed U3Si2 to steam atmospheres. A thermogravimetric analysis is conducted in flowing steam to T > 1000 °C to assess oxidation resistance. The phase characterization of as-melted, thermally annealed and post-oxidation compositions with up to 12 vol% Nb by powder X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy is reported.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Microstructure and Properties of Fe{sub 3}Al-Fe{sub 3}AlC{sub x} Composite Prepared by Reactive Liquid Processing

A Fe{sub 3}Al-Fe{sub 3}AlC{sub x} composite was prepared using reactive liquid processing (RLP) through controlled mixture of carbon steel and aluminum in the liquid state. The microstructure and phases of the composite were assessed using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, optical microscopy, and differential scanning calorimetry. In addition, the density, hardness, microhardness, and elastic modulus were evaluated. The Fe{sub 3}Al-Fe{sub 3}AlC{sub x} composite consisted of 65 vol pct Fe{sub 3}Al and 35 vol pct Fe{sub 3}AlC{sub x} (κ). The κ phase contained 10.62 at. pct C, resulting in the stoichiometry Fe{sub 3}AlC{sub 0.475}. The elastic modulus of the Fe{sub 3}Al-Fe{sub 3}AlC{sub 0.475} composite followed the rule of mixtures. The RLP technique was shown to be capable of producing Fe{sub 3}Al-Fe{sub 3}AlC{sub 0.475} with a microstructure and properties similar to those achieved using other processing techniques reported in the literature.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Electrodeposition and Characterization of Cr-MoS{sub 2} Composite Coatings

In this study, Cr-MoS{sub 2} composite coatings were electrodeposited from conventional Cr{sup +6} baths containing different amounts of MoS{sub 2} particles and various types of surfactant (cationic and anionic). The effect of bath chemical composition on the coatings properties like their microstructure, morphology, chemical composition, corrosion behavior, surface roughness and microhardness was investigated using x-ray diffraction, scanning electron microscopy (SEM), energy-dispersive x-ray analysis, potentiodynamic polarization, electrochemical impedance spectroscopy, surface profilometry and Vickers microhardness measurement techniques, respectively. The results showed that incorporation of MoS{sub 2} particles into the composite coatings is very limited and Cr matrix with very low crystallinity will be electrodeposited at various experimental conditions. The presence of MoS{sub 2} particles in the bath (up to an optimum value) leads to the formation of the composite coatings with lower surface roughness values than that of conventional chromium coating. Although more MoS{sub 2} particles will be incorporated into the electrodeposits when the solid content of the bath increases, chromium cannot be electrodeposited from baths containing high amounts of MoS{sub 2} particles. Application of cationic surfactant promotes incorporation of particles into the Cr metallic matrix. Moreover, the presence of surfactant in the bath results in the formation of coatings with less microcracks. All the composite coatings have more hardness values than that of conventional chromium coating; maximum hardness is attributed to the coatings that were electrodeposited from baths containing no surfactant. The corrosion test results revealed that the smooth coatings containing more MoS{sub 2} particles and less microcracks exhibit more corrosion resistance than the other ones.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Synthesis and control the morphology of Sr{sub 2}P{sub 2}O{sub 7}:Eu{sup 2+}/Eu{sup 2+},Mn{sup 2+} phosphors by precipitation method

Highlights: • Use facile and mild precipitation method obtained Sr{sub 2}P{sub 2}O{sub 7}:Eu{sup 2+}/Eu{sup 2+},Mn{sup 2+} phosphors. • Through controlling the morphology to tune the photoluminescence properties. • The columnar structure Sr{sub 2}P{sub 2}O{sub 7}:Eu{sup 2+} phosphor shows better emission intensity. • Self-assembled phenomenon appears by changing the Mn{sup 2+} concentration of the Sr{sub 2}P{sub 2}O{sub 7}:Eu{sup 2+},Mn{sup 2+} phosphor. - Abstract: Sr{sub 2}P{sub 2}O{sub 7}:Eu{sup 2+}/Eu{sup 2+},Mn{sup 2+} phosphors have been synthesized by the facile and mild precipitation method and they are characterized by X-ray powder diffraction, scanning electron microscopy, photoluminescence spectra. The SEM results indicate the obtained Sr{sub 2}P{sub 2}O{sub 7}:Eu{sup 2+} phosphors have the columnar structure and the Sr{sub 2}P{sub 2}O{sub 7}:Eu{sup 2+},Mn{sup 2+} phosphors is the sphere like. The effects of the stirring and sintering temperature on the morphology of Sr{sub 2}P{sub 2}O{sub 7}:Eu{sup 2+}/Eu{sup 2+},Mn{sup 2+} phosphors have been investigated. The photoluminescence spectra of Sr{sub 2}P{sub 2}O{sub 7}:Eu{sup 2+} and Sr{sub 2}P{sub 2}O{sub 7}:Eu{sup 2+},Mn{sup 2+} phosphors showed that the Sr{sub 2}P{sub 2}O{sub 7}:Eu{sup 2+} phosphors can be excited by 345 nm and exhibit blue emission around 421 nm and the Sr{sub 2}P{sub 2}O{sub 7}:Eu{sup 2+},Mn{sup 2+} phosphors can be excited by 355 nm and exhibited the emission around 420 nm and 578 nm showing the white light.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Photoluminescent properties and Judd–Ofelt analysis of novel Na0.5Sr0.25NbO3: Eu3+ red phosphor with high quantum efficiency

Highlights: • The Na{sub 0.5}Sr{sub 0.25}NbO{sub 3}: Eu{sup 3+} phosphor with high quantum efficiency has been successfully synthesized by using a molten salt synthesis method. • The effect of the crystal field surrounding the Eu{sup 3+} ions on the luminescent performance was analyzed by the Judd–Ofelt theory. • Photoluminescent properties of Na{sub 0.5}Sr{sub 0.25}NbO{sub 3}: Eu{sup 3+} phosphor were investigated for the first time. - Abstract: We report on a novel Na{sub 0.5}Sr{sub 0.25}NbO{sub 3}: Eu{sup 3+} phosphor fabricated by a molten salt synthesis method with the potential application in white light-emitting diodes (WLEDs) as a red phosphor. The crystal structure, morphology, emission/excitation spectra, as well as decay curves were characterized with X-ray diffraction, Scanning Electron Microscope and photoluminescence spectrometer, respectively. Concentration quenching occurred when the concentration of Eu{sup 3+} was beyond 5 mol% due to the dipole-dipole interaction by nonradiative energy transfer. Besides, the effect of the crystal field surrounding the Eu{sup 3+} ions on the luminescent performance under 396 nm and 466 nm excitions has been investigated by the Judd–Ofelt theory. The result indicated that the quantum efficiency of the phosphor was 62.65% excited by 466 nm, which was superior to 41.43% excited by 396 nm. The optimal sample’s CIE coordinates were (0.6471, 0.3504) with the color purity of 97%, showing a potential application in (WLEDs) illumination field.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Three-dimensional nanostructure determination from a large diffraction data set recorded using scanning electron nanodiffraction

A diffraction-based technique is developed for the determination of three-dimensional nanostructures. The technique employs high-resolution and low-dose scanning electron nanodiffraction (SEND) to acquire three-dimensional diffraction patterns, with the help of a special sample holder for large-angle rotation. Grains are identified in three-dimensional space based on crystal orientation and on reconstructed dark-field images from the recorded diffraction patterns. Application to a nanocrystalline TiN thin film shows that the three-dimensional morphology of columnar TiN grains of tens of nanometres in diameter can be reconstructed using an algebraic iterative algorithm under specified prior conditions, together with their crystallographic orientations. The principles can be extended to multiphase nanocrystalline materials as well. Thus, the tomographic SEND technique provides an effective and adaptive way of determining three-dimensional nanostructures.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Comparison of the Microstructure and Flux Pinning Properties of Polycrystalline YBa{sub 2}Cu{sub 3}O{sub 7-d} Containing Zn{sub 0.95}Mn{sub 0.05}O or Al{sub 2}O{sub 3} Nanoparticles

Here we compare the microstructure and flux pinning properties of polycrystalline YBa{sub 2}Cu{sub 3}O{sub 7-d} (Y-123 or YBCO) containing either Al{sub 2}O{sub 3} or Zn{sub 0.95}Mn{sub 0.05}O nanoparticles. Samples were prepared using a standard solid-state reaction process, and nanoparticles were added up to a concentration of 0.1 wt%. The crystal structure, microstructure, electrical and magnetic properties were analyzed using X-ray diffraction, scanning electron microscopy and transmission electron microscopy (TEM), and electrical resistivity and DC magnetization measurements, respectively. TEM observations showed that the addition of Zn{sub 0.95}Mn{sub 0.05}O resulted in a high density of fine twins and a variety of interacting microstructures, while Al{sub 2}O{sub 3} addition resulted in a high density of Al-rich nanoscale inhomogeneities embedded in the Y-123 matrix. Flux pinning forces were determined, and predominant pinning mechanisms in the prepared samples were proposed. We evaluated the superconducting properties of YBCO considering the effects of adding insulating or magnetic nanoparticles.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of Zr Content on Mechanical Properties of Diamond/Cu-Zr Composites Produced by Gas Pressure Infiltration

Diamond particle-reinforced Zr-alloyed Cu matrix (diamond/Cu-xZr) composites were produced by a gas pressure infiltration route, with x = 0.0, 0.3, 0.5, 0.75, and 1.0 wt.%. The x-ray diffraction, scanning electron microscopy, and transmission electron microscopy characterization confirms the formation of ZrC at the diamond/Cu interface. With increasing Zr content, the tensile, bending, and compressive strengths of the diamond/Cu-Zr composites are found to firstly increase and then decrease. The maximum tensile, bending, and compressive strengths at 0.75 wt.% Zr are 108, 360, and 441 MPa, respectively. The variation of the mechanical properties is attributed to the formation of interfacial ZrC. The increase in amount of ZrC strengthens the interface, but large ZrC particles formed at high Zr content are harmful to the interfacial bonding. The result suggests that the mechanical properties of diamond/Cu composites can be enhanced by Cu matrix alloying with Zr.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Cr3+ doped ZnGa2O4 far-red emission phosphor-in-glass: Toward high-power and color-stable plant growth LEDs with responds to all of phytochrome

Highlights: • A high-power and color-stable far-red emission phosphor-convertor LEDs is proposed. • The Cr{sup 3+} ion as the center of luminescence not only increase choice in plant lighting but also provides far-red light. • The ZGO:Cr{sup 3+}-PiG shows a quantum efficiency of ∼52.8%. • The high-power plant growth LEDs was fabricated, triggering providing broad spectral range for plant growth LEDs. - Abstract: In present work, a series of luminescent glass ceramic plates were prepared via phosphor-in-glass (PiG) technology, in which included the phosphor of ZnGa{sub 2}O{sub 4}:Cr{sup 3+} (ZGO:Cr{sup 3+}) and glass host with composition of 30SiO{sub 2}-30ZnO-22B{sub 2}O{sub 3}-12BaO-6Al{sub 2}O{sub 3} as matrix. The structure of ZnGa{sub 2}O{sub 4}:Cr{sup 3+}-based PiG (ZGO:Cr{sup 3+}-PiG) samples are characterized by powder X-ray diffraction, scanning electron microscope, and energy dispersive spectrometer mapping. These phosphors are found to be embedded in glass matrix without interfacial reaction. In addition, the ZGO:Cr{sup 3+}-PiG sample shows a quantum efficiency of ∼52.8% and its fluorescence intensity maintains 68.2% when temperature reaching 150 °C. Finally, high-power and color-stable far-red emission plant growth LEDs was fabricated by ZGO:Cr{sup 3+}-PiG and 400 nm near-UV LED chip, which spectra matches well the absorption of plant's photosynthetic pigments. More importantly, it responds to all of phytochrome, triggering providing broad spectral range for plant growth LEDs.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A Comparative Analysis of Catalysts for the Preparation of Germanium through Hydrogen Reduction of Germanium Tetrachloride

We have synthesized catalysts for the hydrogen reduction of germanium tetrachloride: a catalyst based on multiwalled carbon nanotubes and a hybrid catalyst based on multiwalled carbon nanotubes whose surface was decorated with copper-containing nanoparticles. The hybrid catalyst has been characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results demonstrate that it consists of multiwalled carbon nanotubes whose surface is decorated with copper nanoparticles in a cuprous oxide shell (Cu{sub 2}O/Cu/MWCNTs). The catalytic activity of the hybrid catalyst exceeds that of the as-prepared MWCNTs. The use of the Cu{sub 2}O/Cu/MWCNT hybrid catalyst as a catalyst for the hydrogen reduction of germanium tetrachloride allows the reaction temperature to be lowered and ensures 95.7% germanium tetrachloride conversion at 873 K.

36 MATERIALS SCIENCE↗
DOE OSTI2019

The Structural, Electronic, and Magnetic Features of Co{sub 2}Mn{sub 1−x}Al{sub x}Ti (0 ≤ x ≤ 0.6) Heusler Alloys

The structural, electronic, and magnetic features of Co{sub 2}Mn{sub 1−x}Al{sub x}Ti (0 ≤ x ≤ 0.6) Heusler alloys (HAs) have been systematically investigated by experimental techniques (X-ray powder diffraction, scanning electron microscopy, and magnetization measurements) and ab initio theoretical calculations. Whole alloys have cubic structures at room temperature and exhibit ferromagnetic properties. The Curie temperature of Co{sub 2}Mn{sub 1−x}Al{sub x}Ti (x = 0) is approximately 790 K, which is compatible with other studies. By increasing Al content, the temperature dependence of magnetization trials has proved a linear diminishment on Curie temperature and saturation magnetization.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Formulation and Evaluation of Matrix Type Transdermal Patch Containing Silver Nanoparticles

This research aimed to prepare the silver nanoparticles (AgNPs)-loaded antimicrobial wound dressing patch using ethyl cellulose as a matrix membrane and diethyl phthalate as a plasticizer. The polymer suspension was homogeneously mixed with plasticizer, and then added to the colloidal AgNPs suspension. This mixture was poured into Petri dish and subsequently dried in a hot air oven at 80 ± 2 °C for 10 h. The minimum inhibition concentration of the colloidal AgNPs suspension was 2.5 µg/ml. The AgNPs-loaded antimicrobial wound dressing patch was evaluated for physical properties by differential scanning calorimeter, X-ray diffraction, scanning electron microscope, and in vitro study. The antimicrobial wound dressing patch did not exhibit any interaction between the matrix membrane and AgNPs. The AgNPs were evenly dispersed in the patch. The patch could control the release of silver at 102.98 ± 4.11% over 12 h. Although the AgNPs-loaded antimicrobial wound dressing patches can be easily prepared by the simple method, in future studies antimicrobial wound dressing patch will be developed by employing different types of film forming agents.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Effect of the Laser Scan Rate on the Microstructure, Magnetic Properties, and Microhardness of Selective Laser-Melted FeSiB

FeSiB alloys have been fabricated by selective laser melting (SLM) using a laser scan rate of 0.1–1.5 m/s, laser power of 90 W, scan line spacing of 40 μ m, and layer thickness of 50 μ m. X-ray diffraction, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, atomic force microscopy, profilometer, microdurometer, and vibrating sample magnetometer have been used to investigate the structural, microstructural, roughness, microhardness, and magnetic property changes during the laser melting process. The produced samples exhibit a nanocomposite structure consisting of nanocrystalline α-Fe{sub 0.95}Si{sub 0.05} and Fe{sub 2}B phases embedded into an amorphous ε-FeSi-type matrix. The selective laser-melted samples show high density, low surface roughness, higher microhardness values (1654–2273 Hv), and soft magnetic properties (M{sub s} = 188.6–199 emu/g and H{sub c} = 43.8–73 Oe).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Effects of laser fluence on the Cd(OH){sub 2}/CdO nanostructures produced by pulsed laser ablation method

In this experimental study, Cd (OH){sub 2}/CdO nanostructures were produced by pulsed laser ablation method. The beam of a Q-switched Nd:YAG laser with wavelength of 1064 nm at different fluences was employed to irradiate the cadmium target in distilled water. The obtained products at different fluences of laser pulse were characterized by UV–Vis-NIR spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Results show that both morphology and chemical bonds of produced Cd nanostructures were changed by increasing the laser fluence. The absorption spectra shows that the Cd(OH){sub 2} nanostructures could be transformed into CdO nanostructures with increasing the laser fluence. XRD analysis showed the presence of crystalline γ-Cd(OH){sub 2}, Cd(OH){sub 2} and CdO phases, in the monoclinic, hexagonal and cubic structure, respectively. Results revealed that obtained nanostructures are particle in lowest fluence, while wire shaped nanostructures were formed with increasing the laser fluence. An increase of the laser fluence induced the synthesis of higher aspect ratio nanowires with a smaller tendency of adhesion.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Surface modification and optical properties of metal doped indium sulfide thin films

Indium sulfide (In{sub 2}S{sub 3}) thin films were prepared by chemical bath deposition method in same deposition conditions, and then doped by metals including Ag, Al and Cu. Produced films post annealed at 400 °C temperature about 1 h. The effects of different metal-doping on structural, morphological and optical properties of the films were investigated by means of X-ray diffraction, scanning electron microscopy, atomic force microscopy and UV–Vis spectroscopy analyses. Produced indium sulfide thin film was amorphous and doping process lead to shifts peaks in lower angles. Morphology and nanostructure of doped films changed completely. Compact doped films have been formed. Optical constants of the produced thin films were calculated using Kramers–Kronig relations on reflectivity curves. Different doping impurities changed optical curves and band gaps.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Effect of MgCl{sub 2} on the Corrosion Behavior of Copper Under Periodic Wet/Dry Cycle Condition

The corrosion behaviors of copper under periodic wet/dry cycle conditions were investigated. The characteristics of the corrosion product formed on copper were analyzed by x-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and in situ electrochemical impedance spectroscopy. Weight loss results showed that the corrosion of copper under an MgCl{sub 2} deposition condition was more severe than that under NaCl. The main corrosion products formed on the tested sample under NaCl deposition condition consisted of Cu{sub 2}Cl(OH){sub 3} and Cu{sub 2}O, while those under the MgCl{sub 2} deposition condition consisted of Cu{sub 2}Cl(OH){sub 3} and Mg{sub 2}(OH){sub 3}Cl·4H{sub 2}O. In the case of the NaCl deposition condition, a two-layered structure formed during the corrosion process. However, the corrosion product layer formed on copper under the MgCl{sub 2} deposition condition had an extremely loose structure. The effect of MgCl{sub 2} on the corrosion mechanism of copper is discussed.

36 MATERIALS SCIENCE↗