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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Facile synthesis of flower-like Pd/BiOCl/BiOI composites and photocatalytic properties

Highlights: • Flower-like Pd/BiOCl/BiOI Composites were synthesized. • Pd/BiOCl/BiOI showed better photocatalytic performance than pure BiOI. • The Pd content of the Pd/BiOCl/BiOI composites strongly affects their photocatalytic activities. - Abstract: In this study, through the BiOI and different quality of PdCl{sub 2} reactions, preparation of Pd/BiOCl/BiOI photocatalyst with diffident content of Pd by ultraviolet light reduction method. The synthesis of BiOI from Bi(NO{sub 3}){sub 3}·5H{sub 2}O and KI by solvent thermal method. The as-synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, Transmission electron microscopy, ultraviolet-visible diffuse reflectance spectroscopy, photoluminescence and X-ray photoelectron spectroscopy. The Photodegradation performence of the photocatalysts were assessed by photodegradation of rhodamine B illuminating with a 350W Xe lamp. The results showed that 3%Pd/BiOCl/BiOI photocatalyst exhibited good photocatalytic activity.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Novel of core-shell AlOOH/Cu nanostructures: Synthesis, characterization, antimicrobial activity and in vitro toxicity in Neuro-2a cells

Core-shell micro/nanostructures were fabricated by the reaction of Al/Cu bimetallic nanoparticles with water. Al/Cu nanoparticles have been obtained using the method of simultaneous electrical explosion of a pair of the corresponding metal wires in an argon atmosphere. The nanoparticles are chemically active and interact with water at 60°C to form core-shell micro/nanostructures. The obtained products were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy and dynamic light scattering and the nitrogen adsorption method. The antibacterial activity of the synthesized structures was investigated against E. coli and St. aureus. The toxic effect of these nanostructures against the Neuro-2a neuroblastoma cell line was investigated. AlOOH/Cu nanostructures are shown to inhibit cell proliferation. The AlOOH/Cu nanostructures are good candidates for medical applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Facile fabrication of novel silver-polypyrrole-multiwall carbon nanotubes nanocomposite for replacement of platinum in dye-sensitized solar cell

This paper demonstrates the facile synthesis of high performance silver-polypyrrole-multiwall carbon nanotubes (Ag-PPy-FMWCNTS) nanocomposites via electrodeposition method on stainless steel substrate and its application as a low cost counter electrode (CE) for the precious platinum (Pt) free DSSC. The nanocomposites were characterized by variety of techniques such as Fourier transforms infrared (FTIR), X-ray diffraction, Scanning electron microscope (SEM), cyclic voltammetry (CV) and Four probe technique respectively. The cyclic voltammetry and Tafel polymerization measurements of Ag-PPy-FMWCNTS nanocomposites CE reveal the favorable electrocatalytic activity and low charge transfer resistance R{sub ct}(2.50 Ω cm{sup 2}) for I{sub 3}{sup −}/I{sup −} redox solution. The four probe studies showed the large electrical conductivity (226S cm{sup −1}) of Ag-PPy-FMWCNTS nanocomposite. The DSSC assembled with Ag-PPy-FMWCNTS nanocomposites CE display the considerable short circuit current density (13.95 mA cm{sup −2}) and acceptable solar to electrical conversion efficiency of 7.6%, which is higher to the efficiency of DSSC with thermally decomposed Pt reference electrode 7.1%. The excellent conversion efficiency, rapid charge transfer in combination with low cost and simple fabrication method of Ag-PPy-FMWCNTS nanocomposites can be exploited as an efficient and potential candidate to replace the Pt CE for large scale production of DSSC.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Synthesis and Characterization of Hydrophobic Fe{sub 3}O{sub 4} Magnetic Nanoparticles with High Saturation Magnetization

A simple one-step solvothermal method is proposed to prepare hydrophobic Fe{sub 3}O{sub 4} nanoparticles (MNPs) using iron acetylacetonate (Fe(acac){sub 3}), oleylamine (OAm), and ethylene glycol (EG). X-ray powder diffraction, scanning electron microscope, infrared spectroscopy, transmission electron microscopy, X-ray photoelectron spectrometry, and vibrating sample magnetometer are used to characterize the structure, morphology, and properties of products. The testing results indicate that the as-synthesized products are spherical-like hydrophobic MNPs, superparamagnetic at room temperature, with a saturation magnetization up to 76.8 emu/g. The good hydrophobic property of MNPs is attributed to the coverage of oleylamine, without causing a remarkable loss of magnetic property. In addition, the influences of material ratio, aging time, oleic acid, and stearic acid used as additives are studied in our research.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Improving the Desulfurization Degree of High-Grade Nickel Matte via a Two-Step Oxidation Roasting Process

Generally, sulfur elimination from nickel matte was incomplete in the one-step oxidation roasting process. In this work, X-ray diffraction, scanning electron microscopy/energy-dispersive X-ray spectroscopy, and chemical analysis of the roasted products were carried out to explain this phenomenon. The results indicated that the melting of heazlewoodite was the main limiting factor. Thereafter, the oxidation mechanism of high-grade nickel matte from room temperature to 1000 °C was studied. It was found that the transformation from heazlewoodite (Ni{sub 3}S{sub 2}) to nickel sulfide (NiS) took place from 400 °C to 520 °C. Considering that the melting temperature of NiS was much higher than that of Ni{sub 3}S{sub 2}, a low-temperature roasting step was suggested to suppress the melting of heazlewoodite. Under the optimum conditions (520 °C for 120 minutes followed by 800 °C for 80 minutes), the degree of desulfurization reached 99.52 pct. These results indicated that the two-step oxidation roasting method could be a promising process for producing low-sulfur calcine from high-grade nickel matte.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Interfacial Reaction During High Energy Ball Milling Dispersion of Carbon Nanotubes into Ti6Al4V

The unique thermal and mechanical properties of carbon nanotubes (CNTs) have made them choice reinforcements for metal matrix composites (MMCs). However, there still remains a critical challenge in achieving homogeneous dispersion of CNTs in metallic matrices. Although high energy ball milling (HEBM) has been reported as an effective method of dispersing CNTs into metal matrices, a careful selection of the milling parameters is important not to compromise the structural integrity of CNTs which may cause interfacial reactions with the matrix. In this study, multi-walled carbon nanotubes (MWCNTs) were purified by annealing in argon and vacuum atmospheres at 1000 and 1800 °C, respectively, for 5 h to remove possible metallic catalyst impurities. Subsequently, 1, 2 and 3 wt.% MWCNTs were dispersed by adapted HEBM into Ti6Al4V alloy metal matrix. Raman spectroscopy (RS), x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray spectrometry and transmission electron microscopy techniques were used to characterize the as-received and annealed MWCNTs, as well as the admixed MWCNT/Ti6Al4V nanocomposite powders. The experimental results showed that vacuum annealing successfully eliminated retained nickel (Ni) catalysts from MWCNTs, while the adapted HEBM method achieved a relative homogeneous dispersion of MWCNTs into the Ti6Al4V matrix and helped to control interfacial reactions between defective MWCNTs and the metal matrix.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Physicochemical properties of the Portland cement-based mortar exposed to deep seafloor conditions at a depth of 1680 m

Achieving breakthroughs in marine technologies requires the development of infrastructures submerged in deep-sea environments, whose physicochemical effects on cement-based materials considerably differ from those of shallow seas. However, very few studies focused on the cement-based materials subjected to deep-sea conditions. This work investigates the changes in the compressive strength and phase composition of the cement mortar kept on the seafloor with a depth of 1680 m for 608 d. The mortar specimens salvaged from the seafloor exhibited severe visible damages, including softened mashy structures and significantly decreased compressive strengths. The obtained X-ray diffraction, scanning electron microscopy, and nuclear magnetic resonance data revealed that the dissolution of portlandite, decalcification of calcium (alumino) silicate hydrate, and formation of brucite, magnesium (alumino) silicate hydrate, a hydrotalcite-like phase, thaumasite, and ettringite likely contributed to the disintegration of mortar, which could be further accelerated by the low temperature of the deep-sea environment.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Silver-loaded ZnO/ZnFe2O4 mesoporous hollow spheres with enhanced photocatalytic activity for 2,4-dichlorophenol degradation under visible light irradiation

Highlights: • Visible-light-driven ZnO/ZnFe{sub 2}O{sub 4}/Ag spheres were successfully synthesized. • ZnO/ZnFe{sub 2}O{sub 4}/Ag spheres have unique mesoporous hollow structures. • ZnO/ZnFe{sub 2}O{sub 4}/Ag spheres exhibit excellent photodegradation of 2,4-dichlorophenol. • ZnO/ZnFe{sub 2}O{sub 4}/Ag spheres are reusable with the aid of a magnet. - Abstract: Silver-loaded ZnO/ZnFe{sub 2}O{sub 4} (ZnO/ZnFe{sub 2}O{sub 4}/Ag) mesoporous hollow spheres were synthesized via a layer-by-layer technique followed chemical reduction method. The structures and morphologies of the as-prepared catalysts were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope and N{sub 2} adsorption/desorption porosimetry. The photodegradation activities of ZnO/ZnFe{sub 2}O{sub 4}/Ag mesoporous hollow spheres toward 2,4-dichlorophenol were investigated under UV and visible light irradiation. The experimental results indicated that our mesoporous hollow spheres exhibited much higher photodegradation activities than P25 for the loading of silver particles, the bands matching and the unique structures. There exists an optimal loading dosage of silver particles. Too high or too low loading will reduce the photodegradation activities of ZnO/ZnFe{sub 2}O{sub 4}/Ag mesoporous hollow spheres. The possible mechanism behind was proposed. Noteworthily, the ZnO/ZnFe{sub 2}O{sub 4}/Ag mesoporous hollow spheres are reusable with the aid of a magnet, which is cost effective.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Correlation between surface modification and photoluminescence properties of β-Ga{sub 2}O{sub 3} nanostructures

In this work three different growth methods have been used to grow β-Ga{sub 2}O{sub 3} nanostructures. The nanostructures were characterized by Grazing Incident X-Ray Diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy and Photoluminescence Spectroscopy. Photoluminescence spectra for all the samples of β-Ga{sub 2}O{sub 3} nanostructures exhibit an UV and blue emission band. The relative intensity of UV and blue luminescence is strongly affected by the surface defects present on the nanostructures. Our study shows that Photoluminescence intensity of UV and blue luminescence can be reliably used to determine the quality of β-Ga{sub 2}O{sub 3} nanostructures. Further the work opens up the possibility of using UV excitation and subsequent Photoluminescence analysis as a possible means for oxygen sensing. The Photoluminescence mechanism in β-Ga{sub 2}O{sub 3} nanostructures is also discussed.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

Stacking faults and mechanisms strain-induced transformations of hcp metals (Ti, Mg) during mechanical activation in liquid hydrocarbons

The evolution of the structure and substructure of metals Ti and Mg with hexagonal close-packed (hcp) lattice is studied during their mechanical activation in a planetary ball mill in liquid hydrocarbons (toluene, n-heptane) and with additions of carbon materials (graphite, fullerite, nanotubes) by X-ray diffraction, scanning electron microscopy, and chemical analysis. The temperature behavior and hydrogen-accumulating properties of mechanocomposites are studied. During mechanical activation of Ti and Mg, liquid hydrocarbons decay, metastable nanocrystalline titanium carbohydride Ti(C,H){sub x} and magnesium hydride β-MgH{sub 2} are formed, respectively. The Ti(C,H){sub x} and MgH{sub 2} formation mechanisms during mechanical activation are deformation ones and are associated with stacking faults accumulation, and the formation of face-centered cubic (fcc) packing of atoms. Metastable Ti(C,H)x decays at a temperature of 550°C, the partial reverse transformation fcc → hcp occurs. The crystalline defect accumulation (nanograin boundaries, stacking faults), hydrocarbon destruction, and mechanocomposite formation leads to the enhancement of subsequent magnesium hydrogenation in the Sieverts reactor.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

Emerging hierarchical dislocation structures: Insights from scanning electron microscopy-electron backscatter diffraction in situ tensile testing and multifractal analysis

Understanding the evolution of dislocation structures during plastic deformation is critical for predicting the mechanical performance of metallic materials. In this work, we applied in situ scanning electron microscopy/electron backscatter diffraction tensile testing combined with multifractal (MF) analysis to assess deformation-induced dislocation structure evolution in solution-annealed 304 L stainless steel, both in its as-received and neutron-irradiated states (5.4 displacements per atom). The analysis of kernel average misorientation patterns revealed the formation of hierarchical dislocation arrangements that exhibit clear MF scaling behavior. Despite pronounced visual differences between nonirradiated and irradiated specimens—most notably, the appearance of dislocation channels after irradiation—the singularity spectra suggest that both conditions give rise to similar underlying hierarchical structures. MF analysis provides a quantitative measure of the spatial complexity and self-organization of dislocation patterns, highlighting the accelerated emergence and evolution of the dislocation structures in irradiated polycrystalline materials, as well as the limitation of their spatial extent. The findings indicate that irradiation not only modifies microstructure but also alters correlation-driven dislocation organization. More generally, they demonstrate that MF analysis is a powerful tool for probing mesoscale deformation mechanisms.

Dislocation structures↗
DOE OSTI2018

Electrochemical Dissolution of Tungsten Carbide in NaCl-KCl-Na{sub 2}WO{sub 4} Molten Salt

Tungsten carbide was utilized as anode to extract tungsten in a NaCl-KCl-Na{sub 2}WO{sub 4} molten salt, and the electrochemical dissolution was investigated. Although the molten salt electrochemical method is a short process method of tungsten extraction from tungsten carbide in one step, the dissolution efficiency and current efficiency are quite low. In order to improve the dissolution rate and current efficiency, the sodium tungstate was added as the active substance. The dissolution rate, the anode current efficiency, and the cathode current efficiency were calculated with different contents of sodium tungstate addition. The anodes prior to and following the reaction, as well as the product, were analyzed through X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry. The results demonstrated that the sodium tungstate could improve the dissolution rate and the current efficiency, due to the addition of sodium tungstate decreasing the charge transfer resistance in the electrolysis system. Due to the fact that the addition of sodium tungstate could remove the carbon during electrolysis, pure tungsten powders with 100 nm diameter were obtained when the content of sodium tungstate was 1.0 pct.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Experimental Study of the Microstructure and Micromechanical Properties of Laser Cladded Ni-based Amorphous Composite Coatings

(Ni{sub 0.6}Fe{sub 0.4}){sub 65}B{sub 18}Si{sub 10}Nb{sub 4}C{sub 3} amorphous composite coating was successfully fabricated on AISI 1045 steel substrate by using laser cladding process with coaxial powder feeding equipment. The microstructure and phase distribution of the coating were investigated by using x-ray diffraction, scanning electron microscopy and transmission electron microscope. The mechanical properties of the coating were examined by using microhardness testing and nanoindentation. The experimental results indicated that the volume fraction of amorphous phase increased with the decrease in laser cladding heat input, leading to an improvement of mean microhardness and nanohardness. NbC particles in a size ranging between 150 and 1650 nm were found embedding in the amorphous composite coatings in all situations. The presence of the NbC particles can contribute to an improvement of 96.7 HV in hardness on the basis of experimental results, while theoretical prediction suggests an improvement of 92.5 HV by using Orowan-Ashby equation.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Sputtering Current on the Comprehensive Properties of (Ti,Al)N Coating and High-Speed Steel Substrate

To improve the practical property of (Ti,Al)N coating on a high-speed steel (HSS) substrate, a series of sputtering currents were used to obtain several (Ti,Al)N coatings using a magnetron sputtering equipment. The phase structure, morphology, and components of (Ti,Al)N coatings were characterized by x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy, respectively. The performance of (Ti,Al)N coatings, adhesion, hardness, and wear resistance was tested using a scratch tester, micro/nanohardness tester, and tribometer, respectively. Based on the structure–property relationships of (Ti,Al)N coatings, the results show that both the Al content and deposition temperature of (Ti,Al)N coatings increased with sputtering current. A high Al content helped to improve the performance of (Ti,Al)N coatings. However, the HSS substrate was softened during the high sputtering current treatment. Therefore, the optimum sputtering current was determined as 2.5 A that effectively increased the hardness and wear resistance of (Ti,Al)N coating.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Y{sub 2}O{sub 3} Addition on the Microstructure, Wear Resistance, and Corrosion Behavior of W-4.9Ni-2.1Fe Heavy Alloy

Binding and particle phases are the two important parameters influencing materials properties. In this study, a series of novel W-4.9Ni-2.1Fe-xY{sub 2}O{sub 3} (in weight%) alloys with different Y{sub 2}O{sub 3} contents are prepared by secondary ball milling and spark plasma sintering (SPS) techniques to obtain uniformly distributed γ-(Ni, Fe) binding phases and finer grains. The microstructure, mechanical, wear resistance, and corrosion behavior of the sintered bodies with different Y{sub 2}O{sub 3} were obtained by x-ray diffraction, scanning electron microscopy, Rockwell hardness tester, friction wear tester, and three-dimensional profile instruments. The results showed that a certain addition of Y{sub 2}O{sub 3} led to refined grains and uniformed microstructures; but, if excessive, a weak grain refinement would be appeared. Moreover, the grain size tends to be stable with enhancing of the Y{sub 2}O{sub 3} content. Considering properties such as density, hardness, compression yield strength, grain size, and uniform distribution of tungsten hard phase and γ-(Ni, Fe) binding phase, the comprehensive optimal amount of 0.7 wt.% of Y{sub 2}O{sub 3} was attained for the alloy. Meanwhile, the SPS sintered body also exhibited the best friction, wear behavior, and corrosion resistance in 3.5% of NaCl solution.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Green solid-state chemical synthesis and excellent xylene-detecting behaviors of Y-doped α-MoO{sub 3} nanoarrays

Graphical abstract: Y-doped α-MoO{sub 3} arrays constructed by nanorods are firstly synthesized by facile two-step solid-state chemical reaction, which exhibited excellent xylene-sensing property. - Highlights: • The Y-doped α-MoO{sub 3} nanoarrays constructed by nanorods were simply synthesized by solid-state chemical reaction. • The α-MoO{sub 3} arrays exhibited excellent gas-sensing properties for xylene. • This study is helpful to explore the xylene gas-sensitive materials with good comprehensive performance. - Abstract: Y-doped α-MoO{sub 3} nanoarrays constructed by nanorods were simply synthesized by a facile and simple two-step solid-state chemical reaction. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy were applied to characterize the micro-structures and surface chemical composition of the as-prepared products. The results suggested that Y element had been successfully doped into the α-MoO{sub 3} nanoarrays. The gas-sensing behaviors of Y-doped nanoarrays toward seven kinds of harmful gases were also investigated. The results indicated that the Y-doped α-MoO{sub 3} nanoarrays display not only an improved response (the response value reaches 28.3 to 100 ppm xylene), but also an excellent selectivity to xylene. The good xylene-detecting behaviors were attributed to smaller size and the relative larger surface area. Furthermore, the doping of Y increased the electron donor defects and oxygen vacancies, which accelerated the mobility of oxygen ions and enhanced the conductivity of material, resulting in enhanced response to xylene.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Surfactant-free synthesis of m-BiVO4 nanoribbons and enhanced visible-light photocatalytic properties

Highlights: • m-BiVO{sub 4} nanoribbons were synthesized by solvothermal route. • m-BiVO{sub 4} exhibited enhanced photocatalytic activity and stable recyclability. • The superior performance can be ascribed to the low band gap, high surface area and unique morphology. - Abstract: Monoclinic Bismuth vanadate (m-BiVO{sub 4}) is a promising material for photocatalytic degradation of organic moieties. Uniform m-BiVO{sub 4} nanoribbons were synthesized by facile solvothermal route without using the surfactant and characterized by X-ray diffraction, scanning electron microscopy and UV–vis diffuse reflectance spectra technique. The obtained m-BiVO{sub 4} nanoribbons possess well defined 1-D architectures with homogenous morphology and surface area of 22.4 m{sup 2}/g. The prepared photocatalyst showed efficient photocatalytic activities up to 97% in 30 min against the degradation of methylene blue (MB) under visible-light irradiation. The prepared photocatalyst is recyclable and showed a very small change in activity after three consecutive cycles. This higher activity can be attributed to higher surface area and crystallinity, which signify the promising commercial application of m-BiVO{sub 4} nanoribbons as highly novel and highly efficient photocatalyst for the degradation of organic pollutants.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Synthesis of GaN:ZnO solid solution by solution combustion method and characterization for photocatalytic application

GaN-ZnO solid solution has emerged as a successful and reproducible photocatalyst for overall water splitting by one-step photoexcitation, with a bandgap in visible region. When the solid solution is formed, some of the Zn and O ions are replaced by Ga and N ions respectively and there is a narrowing of bandgap which is hypothesized as due to Zn3d-N2p repulsion. The traditional method of synthesis of GaN-ZnO solid solution is by nitridation of the starting oxides under constant ammonia flow. Here we report a solution combustion technique for the synthesis of the solid solution at a temperature about 500 ° C in a muffle furnace with metal nitrates as precursors and urea as the fuel. The as prepared samples showed change in color with the increased concentration of ZnO in the solution. The structural, microstructural, morphological and optical properties of the samples were realized by Powder X ray diffraction, Scanning electron microscopy, Energy dispersive X ray analysis, Transmission electron microscopy and Photoluminescence. Finally the hydrogen production efficiency of the GaN-ZnO nanopowders by water splitting was found, using methanol as a scavenger. The apparent quantum yield (AQY) of 0.048% is obtained for GaN-ZnO solid solution.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗