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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
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↗
DOE OSTI2016

Electrical properties of films of zinc oxide nanoparticles and its hybrid with reduced graphene oxide

Free-standing films of ZnO nanoparticles (NPs) and reduced graphene oxide (rGO)-ZnO NPs hybrid are prepared at a liquid/liquid interface. The films are characterized by UV-visible spectroscopy, X-ray diffraction, scanning electron microscopy and atomic force microscopy. ZnO film consists of spherical aggregated NPs while the hybrid film contains folded sheets of rGO with embedded ZnO NPs. Electrical properties of the films and its photoresponse in presence of UV radiation are investigated using current sensing atomic force microscopy (CSAFM) at nanoscale and bulk measurements using two probe methods. Enhancement in photocurrent is observed in both cases and the current imaging reveals an inhomogeneous contribution by different ZnO grains in the film.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2025

Effects of a refractory metal protective barrier on uranium carbonitride ceramic–metallic composites exposed to a high temperature hydrogen environment

Uranium nitride has been under consideration at NASA and the Department of Energy for nuclear thermal propulsion applications intended for deep space exploration vehicles. It is critical to the success of the technology development that the behavior of the fuel system is properly characterized in operational environments. This body of work fabricated ceramic metal composites consisting of uranium ceramic fuel in a molybdenum and molybdenum–tungsten metal matrix, both with and without an exterior molybdenum barrier. Specimens were introduced to a high temperature hydrogen environment and characterized through x-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy to identify characteristic changes. A portion of the specimens was fabricated with a 1.27 mm thick molybdenum barrier in order to isolate the material from the hydrogen environment. Instability of the uranium nitride occurred as low as 2073 K, leading to aggressive instability approaching 2658 K. Carbon reactions with the metal matrix were observed as well as alloying between the uranium and metal matrix constituents. The liquid uranium resulting from the instability of the uranium nitride was observed to attack the grain boundaries of the refractory metal, resulting in the formation of a liquid uranium molybdenum eutectic melt. Specimens encased in a barrier experienced similar results. The authors conclude this is a significant challenge to applications of this cermet at these temperatures. Alternate configurations with resilient hermetic seals or lower temperature applications such as power reactors may have more success.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Cu{sub 2}O and CuO Films Produced by Chemical and Anodic Oxidation on the Surface of Copper Foil

The processes underlying the chemical and anodic oxidation of the surface of copper foil have been studied by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. It has been shown that, in the case of anodic oxidation, at a given process duration (τ) the composition and density of initially forming Cu(OH){sub 2} films depend not only on the current density (j{sub a}) but also on whether or not the electrolyte is stirred. A Cu{sub 2}O film with an optimal, coral-like structure has been produced by the anodic oxidation of copper foil for τ = 10 min at j{sub a} = 5 mA/cm{sup 2} without stirring, followed by the thermal reduction of the Cu(OH){sub 2} in a nitrogen atmosphere for 1 h at 500°C. In the case of the chemical oxidation of the copper foil surface, similar Cu{sub 2}O films with a coral-like structure can also be produced by the thermal reduction of initially forming Cu(OH){sub 2} at 500°C for 1 h.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Effect of Ag in CdSe thin films prepared using thermal evaporation

It has been a general practice to dope thin films with suitable dopants to modify the properties of the films to make them more suitable for potential applications. When the dopant concentrations are low, they do not normally affect the structure and morphology of the films. However, it may lead to drastic changes in electronic properties of the films. This might result from the dopant getting incorporated into the lattice of the material of the films. Cadmium selenide is an important compound semiconductor material with an attractive energy band gap. The present work relates to an attempt made to dope CdSe thin films with silver. CdSe:Ag (1–5%) thin films were deposited on glass substrates at an optimized substrate temperature of 453 K using thermal evaporation technique. The grown films were analyzed using X-ray diffraction, scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDX) techniques. It is observed that undoped CdSe thin films and CdSe:Ag films have hexagonal structure. The grain size was found to increase marginally with an increase in the Ag concentration. The optical band gap of the films determined by optical transmission measurements agree with that of CdSe. Electrical conductivity is observed to increase from 10{sup –4} to 3.66 (Ω cm){sup –1} on addition of silver. The variation of resistance with temperature indicates that the prepared films consist of CdSe and Ag existing as two separate phases coexisting and contributing individually to the resistivity of the films.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Sol–gel Synthesis and Upconversion Luminescent Properties of Yb{sup 3+},Er{sup 3+},Eu{sup 3+} Triply-Doped in YVO{sub 4} Phosphors

Yb{sup 3+},Er{sup 3+},Eu{sup 3+} triply-doped in YVO{sub 4} with varying molar ratio of Er/Eu were synthesized in a sol–gel method with a subsequent heat treatment for the first time. The optimal molar ratio of Er/Eu for the maximum energy transfer efficiency was 1/39. After molar ratio, the influences of different heat treatment temperatures were also researched and the maximal heat temperature was 1300 °C. Besides, the properties of YVO{sub 4}:Yb{sup 3+},Er{sup 3+},Eu{sup 3+} upconversion phosphors were investigated by X-ray diffraction, scanning electron microscopy and photo luminescent spectra, respectively. In sum, XRD results indicate the crystal structure of as-prepared samples, which is the tetragonal phase of YVO{sub 4} with no other diffraction peaks. SEM images show the morphology of as-prepared samples, which are granular-like nanoparticles. PL spectra demonstrate the upconversion luminescence of as-prepared samples, which emit strong green lights (at 525 nm, 550 nm) and slight red lights (at 590 nm, 615 nm, 695 nm) under the NIR irradiation at 980 nm. Two strong green emissions are attributed to the {sup 2}H{sub 11/2}→{sup 4}I{sub 15/2} and {sup 4}S{sub 3/2}→{sup 4}I{sub 15/2} transitions of Er{sup 3+} ions. Meanwhile, three slight red emissions are attributed to the {sup 5}D{sub 0}→{sup 7}F{sub 1}, {sup 5}D{sub 0}→{sup 7}F{sub 2} and {sup 5}D{sub 0}→{sup 7}F{sub 4} transitions of Eu{sup 3+} ions. All in all, the colorful emissions endow YVO{sub 4}:Yb{sup 3+},Er{sup 3+},Eu{sup 3+} phosphors great potential for some applications, such as display devices, bio-labeling and infrared detection.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Complex magnetic properties associated with competing local and itinerant magnetism in \({\text {Pr}}_2 {\text {Co}}_{0.86} {\text {Si}}_{2.88}\)

Ternary intermetallic compound \({\text {Pr}}_2 {\text {Co}}_{0.86} {\text {Si}}_{2.88}\) has been synthesized in single phase and characterized by x-ray diffraction, scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDX) analysis, magnetization, heat capacity, neutron diffraction and muon spin rotation/relaxation ( \(\mu\) SR) measurements. The polycrystalline compound was synthesized in single phase by introducing necessary vacancies in Co/Si sites. Magnetic, heat capacity, and zero-field neutron diffraction studies reveal that the system undergoes magnetic transition below \(\sim\) 4 K. Neutron diffraction measurement further reveals that the magnetic ordering is antiferromagnetic in nature with an weak ordered moment. The high temperature magnetic phase has been attributed to glassy in nature consisting of ferromagnetic clusters of itinerant (3 d ) Co moments as evident by the development of internal field in zero-field \(\mu\) SR below 50 K. The density-functional theory (DFT) calculations suggest that the low temperature magnetic transition is associated with antiferromagnetic coupling between Pr 4 f and Co 3 d spins. Pr moments show spin fluctuation along with unconventional orbital moment quenching due to crystal field. The evolution of the symmetry and the crystalline electric field environment of Pr-ions are also studied and compared theoretically between the elemental Pr and when it is coupled with other elements such as Co. The localized moment of Pr 4 f and itinerant moment of Co 3 d compete with each other below \(\sim\) 20 K resulting in an unusual temperature dependence of magnetic coercivity in the system.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Reduction Mechanism of Iron Oxide Briquettes by Carbonaceous Materials Extracted from Blast Furnace Dust

The reducibility of carbonaceous powder extracted from blast furnace dust was investigated. In this study, pickling treatment was used for BF bag dust and BF gravitational dust to extract the carbonaceous material. The structural characteristics of carbonaceous material were studied by X-ray diffraction, scanning electron microscope, and energy-dispersive spectrometer. The reduction of ferric oxide and carbon gasification experiments were researched by thermogravimetry. The results show that the pickled raw coal gives the highest reducibility, which is followed by BF bag dust and BF gravitational dust. The reason for this is that the higher disordered crystalline structure leads to stronger gasification reactivity, and further results in stronger reduction reactivity. Based on the randomized nucleation model, the kinetic analysis shows that the activation energies for the reduction reaction of BF gravitational dust, BF bag dust, and raw coal after pickling are 300.14, 180.43, and 124.62 kJ mol{sup −1}, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Silicon Content on the Hardenability and Mechanical Properties of Link-Chain Steel

Heavy-section link-chains are increasingly required to satisfy industrial demands of shipping, lifting, and mining machinery. In this study, the hardenability of link-chain steels with different Si contents was investigated using end-quench tests. The microstructures of the end-quenched specimens were examined by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The mechanical properties were investigated by tension tests and impact tests. The effect of the Si content on the phase-transformation temperature during cooling was analyzed by differential scanning calorimetry. It was found that increasing the Si content from 0.24 to 0.74% led to a significant increase in hardenability; the ideal diameter (i.e., the diameter of given steel that would produce 50% martensite at the center when quenched in a hypothetical quenching medium that reduces the surface temperature of the heated steel to the bath temperature in zero time) increased from 187 to 248 mm. Si enhances the hardenability of link-chain steel by affecting its phase-transition behaviors during cooling, including suppressing ferrite formation, inhibiting carbide precipitation, and lowering the temperature of maximum transformation of bainite. The suggested Si content is 0.70-0.75% to produce link-chain steel with high hardenability and good mechanical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Enhanced photocatalytic degradation of methylene blue dye under UV-sunlight irradiation by cesium doped chromium oxide thin films

Highlights: • Cs doped thin films has been prepared by the low- cost spray pyrolysis technique. • Enhanced photocatalytic activity of Cr2O3 thin films for MB photogegradation(MB) dye was achieved through Cs doping. • 6 % Cs doped Cr{sub 2}O{sub 3} thin film photocatalyst with the merits of low band gap and more oxygen vacancies, exhibits the highest sun-light photocatalytic activity. • High photostability and recyclability was achieved under sun-light irradiation. - Abstract: The present contribution highlights the photocatalytic degradation of methylene blue dye over chromium oxide Cr{sub 2}O{sub 3} thin films based photocatalysts illuminated by ultraviolet and sunlight. Cr{sub 2}O{sub 3} photocatalyst was synthesized as thin film by the spray pyrolysis method on glass substrate at temperature of 350 °C. The physical properties of the thin films were studied by X-ray diffraction, scanning electron microscopy (SEM), infrared spectroscopy (IR), Raman spectroscopy, photoluminescence (PL) probing and UV–vis spectroscopy. XRD results showed that all samples were well crystallized with rhomoboedric curudum structure. Emissions of all films have been observed in visible region at 325 nm excitation. UV–vis-NIR spectrophotometry analysis showed that the band gap energy value of chromium oxide is shortened with cesium doping. Results indicate that both the cesium doping and the introduction of oxygen vacancies promote good photocatalytic activity of Cs doped Cr{sub 2}O{sub 3} thin films under sunlight for MB degradation.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Synthesis, Structural Characterization, and Growth Mechanism of Li 1+ x V 3 O 8 Submicron Fibers for Lithium-Ion Batteries

Here, we report on the synthesis of submicron Li 1+x V 3 O 8 fibers through a facile mixed ethanol/water solution-mediated solvothermal route in the absence of surfactants. All the raw materials used are commercially available, relatively inexpensive, and low-toxic, and these can be handled in an ambient atmosphere, rendering this synthetic route as reasonably facile and efficient. To ensure a desirable and acceptable sample crystallinity and purity, we introduced a postannealing treatment at 500°C. The monoclinic phase formation of the fiber sample was probed in detail using a series of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy, and selected area electron diffraction measurements. Both morphology and chemical composition could be carefully and systematically tuned in terms of generating a class of novel, pure, and well-defined motifs of Li 1+x V 3 O 8 . A plausible mechanism for the formation of submicron-diameter fibers has been discussed in addition to the expected phase transformation within our Li-V-O materials. Our comprehensive study should provide for needed fundamental insights into putting forth a viable synthesis strategy for the generation of well-defined morphological variants of layered oxide materials for battery applications.

25 ENERGY STORAGE↗
DOE OSTI2018

Oxidation Behavior of Zirconium Diboride Nanoparticles

The products of oxidation of ZrB{sub 2} powders with average particle sizes of ~100 and ~30 nm by atmospheric oxygen under isothermal conditions and during heating have been characterized by thermal analysis, X-ray diffraction, scanning electron microscopy, IR frustrated total internal reflection spectroscopy, energy dispersive X-ray analysis, and elemental analysis. The oxidation onset has been observed at 594 and 396°C, respectively. Oxidation at temperatures of ≥800°C leads to the formation of boron oxide and monoclinic ZrO{sub 2}, independent of the particle size of ZrB{sub 2}. The reaction rate constants for the oxidation of ZrB{sub 2} nanoparticles ~100 and ~30 nm in size have been determined to be 0.03, 0.15, and 0.31 h{sup –1} at 600, 650, and 700°C and 0.11, 0.35, and 0.81 h{sup –1} at 500, 600, and 700°C, respectively. The apparent activation energies for the oxidation of the ZrB{sub 2} nanoparticles ~100 and ~30 nm in size are 161 ± 4 and 62 ± 3 kJ/mol, respectively, as evaluated from the temperature dependence of the rate constants at the above temperatures.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Fabrication and Magnetic Characterization of CFO/NiO and CFO/NiS Heterostructures

Magnetic analysis of different magnetic bilayers and multilayers is an important step for designing next-generation multiferroic heterostructures. In this study, we have investigated the magnetic interaction at the interface in CFO/NiO hetero-structures grown by pulsed laser deposition on sapphire substrates. The thin film heterostructure samples were characterized by means of X-ray diffraction, scanning electron microscopy (SEM), energy disruptive X-ray spectroscopy (EDS), and superconducting quantum interference device (SQUID) for magnetic measurements. The XRD analysis on different samples shows the crystalline growth of the thin films. The SEM-EDS analysis provides information about structural and elemental compositions of the heterostructure films. A SQUID magnetometer was used to investigate the temperature and field-dependent magnetic properties. To better understand the magnetic properties of the thin film heterostructure samples, zero field cool (ZFC) and field cool (FC) magnetization data were analyzed. At low temperature, ferromagnetic hysteresis loop was observed. A shift in the M-H hysteresis curve was observed for the FC data from the ZFC data, which indicates the presence of exchange bias effect. In addition, we have examined the effect of antiferromagnetic NiS thin films on ferromagnetism of CFO. This study on the magnetic interaction between a ferromagnetic layer and an antiferromagnetic layer can advance the frontier for applications in spin valves, magnetic sensors, and magnetic random access memory.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Molybdenum Content on Structural, Mechanical, and Tribological Properties of Hot Isostatically Pressed β-Type Titanium Alloys for Orthopedic Applications

Aiming to develop alloys with better properties for orthopedic applications, the focus of the present research was to evaluate the effect of Mo at.% content on structural, mechanical, and tribological properties of hot isostatically pressed Ti-xMo (x = 4, 8, 12, 15, and 20 at.%) alloys. The structural evolution, mechanical properties, and tribological behavior of the nanostructured Ti-xMo alloys were evaluated using x-ray diffraction, scanning electron microscope, and ball-on-disk tribometer. Wear tests were conducted under different applied loads of 2, 8, and 16 N. Experimental results indicated that the structural evolution and morphological changes of the milled alloys were sensitive to their molybdenum (Mo) content. The morphological characterization showed that the crystallite size and the particle size decreased with increasing Mo content (at.%) reaching the lowest values of 27 and 26 nm in the case of Ti-15Mo and Ti-20Mo, respectively. On the other hand, the coefficient of friction and wear rates were found to be decreasing with increasing Mo content.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Mesoporous ZnO microcube derived from a metal-organic framework as photocatalyst for the degradation of organic dyes

A cube-like porous ZnO architecture was synthesized by direct two-step thermolysis of a zinc-based metal-organic framework [(CH{sub 3}){sub 2}NH{sub 2}][Zn(HCOO){sub 3}]. The obtained ZnO microcube was characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption and desorption isotherms. The mesoporous ZnO microcube was comprised by many nanoparticles, and inherited the cube shape from [(CH{sub 3}){sub 2}NH{sub 2}][Zn(HCOO){sub 3}] precursor. With large surface area and mesoporous structure, the ZnO microcube exhibits excellent photocatalytic activities against methyl orange (MO) and rhodamine B (RhB) under UV irradiation, and the degradation rates reached 99.7% and 98.1% within 120 min, respectively. - Graphical abstract: Mesoporous ZnO microcube was synthesized via two-step thermolysis of metal-organic framework [(CH{sub 3}){sub 2}NH{sub 2}][Zn(HCOO){sub 3}], and exhibit excellent photocatalytic activity towards MO and RhB. Display Omitted - Highlights: • Cubic MOF [(CH{sub 3}){sub 2}NH{sub 2}][Zn(HCOO){sub 3}] was prepared by solution-precipitation method. • Mesoporous ZnO microcube was obtained by a two-step calcination of MOF precursor. • ZnO microcube shows photocatalytic activity to MO and RhB under UV irradiation. • The h{sup +} and ∙O{sub 2}{sup -} are main active species during the photodegradation process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗