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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 1,333 records · Page 74
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Enhanced long-term strength and durability of shotcrete with high-strength C{sub 12}A{sub 7} mineral-based accelerator

This study evaluated the performance of shotcrete using high strength C{sub 12}A{sub 7} mineral-based accelerator that has been developed to improve the durability and long-term strength. Rebound, compressive strength and flexural strength were tested in the field. Test result showed that existing C{sub 12}A{sub 7} mineral-based accelerator exhibits better early strength than the high-strength C{sub 12}A{sub 7} mineral-based accelerator until the early age, but high-strength C{sub 12}A{sub 7} mineral-based accelerator shows about 29% higher at the long-term age of 28 days. Microstructural analysis such as scanning electron microscope (SEM), X-ray diffraction (XRD) and nitrogen adsorption method was evaluated to analyze long-term strength development mechanism of high strength C{sub 12}A{sub 7} mineral-based accelerator. As analysis result, it had more dense structure due to the reaction product by adding material that used to enhanced strength. It had better resistance performance in chloride ion penetration, freezing–thawing and carbonation than shotcrete that used existing C{sub 12}A{sub 7} mineral-based accelerator.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Reinforcing blade-cast photocatalytic-titania thin film by titanate nanotubes

Highlights: • Suspension-based photocatalysts are inferior to thin-films due to separation issues. • Hydrothermal TiO{sub 2} nanotubes and sol-gel Ti(n-OBu){sub 4} blends were tape casted on glass. • Optimum blend composition yields mechanical stability due to the tubes reinforcing effect. • At optimum gel content the nanotube bundles are smoothed without stabilizers added. • Surface accessibility and mass transfer dominate the photocatalytic dye degradation. - Abstract: Titanate nanotubes/titania gel blends were prepared as composite sol-gel material, deposited on a glass substrate using a doctor blade and calcined in order to create thin films. In order to get an insight in titania nanotubes’ ability to reinforce thin films, drying control chemical agents were not used. The effects of titanate nanotubes to titanium n-butoxide ratio on surface morphology, phase composition, mechanical stability and photocatalytic activity were studied. Characterization of the thin films was carried out by means of optical and scanning electron microscopy, powder X-ray diffraction, synchrotron radiation grazing incidence X-ray diffraction and mechanical stability testing. Photocatalytic properties of the obtained thin films were evaluated on the basis of methylene blue degradation. Moderate blends exhibit favourable microstructural features while the dye degradation rate was greater for films with a greater amount of titanate nanotubes.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Influence of Austenitizing Temperature on the Microstructure and Mechanical Properties of an Fe-Cr-Ni-Mo-Ti Maraging Stainless Steel

The influence of austenitizing temperature on the microstructure and mechanical properties of an Fe-Cr-Ni-Mo-Ti maraging stainless steel was investigated. The grain size, Laves phase, and retained austenite in steels given different solution treatments were observed using optical microscopy, scanning electron microscopy, and x-ray diffraction. Relationships with mechanical properties were measured by tensile testing. The grain growth rate was relatively slow at temperatures of 800-1000 °C then rapidly increased at higher temperatures. Low-temperature austenitization augmented the retention of austenite, the fraction of which decreased with an increase in austenitizing temperature. The Laves phases, which precipitated in austenite during austenitization at 800-900 °C, were preserved after quenching. The solution treatment had a significant effect on the final tensile properties of the steel after aging, due to the presence of retained austenite and Laves phase reducing its strength.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Application of Sorghum Starch for Preparing Superabsorbent

Starch was extracted from Sorghum bicolor grains by alkali steeping method and was utilized for the production of absorbent material by grafting and crosslinking with binary mixtures of vinyl monomers viz. acrylic acid and acrylamide. Both unmodified and modified starches were characterized with Thermogravimetric analysis, Infra-Red spectroscopy, Scanning electron microscopy and X-ray diffraction analysis, to ascertain the modification of the starch. The parameters of the reaction system viz. initiator concentration, monomer concentration, starch to monomer ratio, etc. were optimized. The modified starch showed enhanced water absorption in the range of 49–85 g/g. Absorbency of the products increased after treatment with aqueous alkali solution due to saponification at higher temperature. The saponified products showed increased water absorption level in the range of 245–400 g/g. The product thus obtained using optimized condition of grafting, on saponification found to be highly superabsorbent displaying the water absorbency of 400 g/g. The influence of pH on absorption of water was also tested and best results were obtained at pH 7–8.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Study of Bronze Statues “John the Baptist” and “Dancing Cupid” from the Collections of the Pushkin State Museum

Bronze statues “John the Baptist” and “Dancing Cupid” from the collections of the Pushkin State Museum of Fine Arts have been investigated at the National Research Centre “Kurchatov Institute.” These statues were previously damaged in fire. Before carrying out restoration, it was necessary to perform their complex study, including identification of statue materials; elemental and phase analysis of contaminations; estimation of the state of surfaces and internal parts; and detection of technological elements, as well as hidden defects, corroded parts, and cracks. To this end, scanning electron microscopy with X-ray microanalysis, synchrotron radiation diffraction, and neutron radiography and tomography have been used.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Features of Crystallization of Rapidly Quenched Ni{sub 45}Ti{sub 32}Hf{sub 18}Cu{sub 5} and Ni{sub 25}Ti{sub 32}Hf{sub 18}Cu{sub 25} Alloys from Melt with High-Temperature Shape Memory Effect

A comparative study of the structure and the chemical and phase composition of Ni{sub 45}Ti{sub 32}Hf{sub 18}Cu{sub 5} and Ni{sub 25}Ti{sub 32}Hf{sub 18}Cu{sub 25} amorphous alloys obtained by fast-quenching of melt stream by spinning has been carried out by transmission and scanning electron microscopy and X-ray diffraction. The critical temperatures of their devitrification were determined by the data of temperatures measurements of electrical resistance. The features of the formation of ultrafine structure and the phase transformation at the vitrification depending on the regimes of heat treatment and chemical composition of alloy have been established.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Stoichiometric Control and Optical Properties of BaTiO 3 Thin Films Grown by Hybrid MBE

BaTiO 3 is a technologically relevant material in the perovskite oxide class with above-room-temperature ferroelectricity and a very large electro-optical coefficient, making it highly suitable for emerging electronic and photonic devices. An easy, robust, straightforward, and scalable growth method is required to synthesize epitaxial BaTiO 3 thin films with sufficient control over the film's stoichiometry to achieve reproducible thin film properties. Here the growth of BaTiO 3 thin films by hybrid molecular beam epitaxy is reported. A self-regulated growth window is identified using complementary information obtained from reflection high energy electron diffraction, the intrinsic film lattice parameter, film surface morphology, and scanning transmission electron microscopy. Subsequent optical characterization of the BaTiO 3 films by spectroscopic ellipsometry revealed refractive index and extinction coefficient values closely resembling those of stoichiometric bulk BaTiO 3 crystals for films grown inside the growth window. Even in the absence of a lattice parameter change of BaTiO 3 thin films, degradation of optical properties is observed, accompanied by the appearance of a wide optical absorption peak in the IR spectrum, attributed to optical transitions involving defect states present. Therefore, the optical properties of BaTiO 3 can be utilized as a much finer and more straightforward probe to determine the stoichiometry level present in BaTiO 3 films.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Electrostatic vs steric stabilization of Fe{sub 3}O{sub 4} and Co{sub 0.5}Fe{sub 2.5}O{sub 4} nanoparticles

Magnetic nanoparticles of magnetite/maghemite and cobalt ferrite Co{sub 0.5}Fe{sub 2.5}O{sub 4} were stabilized in deionized water with perchloric acid and, respectively, sodium oleate in order to prevent agglomeration and sedimentation tendency aiming further biomedical applications. Results obtained through Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Nanoparticle Tracking Analysis (NTA), and Vibrating Sample Magnetometry (VSM) were discussed comparatively for the four suspensions highlighting specific microstructural and magnetic features of each type of soft magnetic colloidal nanomaterial on the background of coprecipitation method adjusting. The results entitled us to plan in the next research stage biological tests focused on such nanoparticle suspensions impact on cell cultures.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Microstructure evolution and electrical characterization of Lanthanum doped Barium Titanate (BaTiO{sub 3}) ceramics

In the current work, we investigated the structural and dielectric properties of Lanthanum oxide (La{sub 2}O{sub 3}) doped Barium Titanate (BaTiO{sub 3}) ceramics and established a correlation between them. Solid state sintering method was used to dope BaTiO{sub 3} with 0.3, 0.5 and 0.7 mole% La{sub 2}O{sub 3} under different sintering parameters. The raw materials used were La{sub 2}O{sub 3} nano powder of ~80 nm grain size and 99.995% purity and BaTiO{sub 3} nano powder of 100 nm grain size and 99.99% purity. Grain size distribution and morphology of fracture surface of sintered pellets were examined by Field Emission Scanning Electron Microscope and X-Ray Diffraction analysis was conducted to confirm the formation of desired crystal structure. The research result reveal that grain size and electrical properties of BaTiO{sub 3} ceramic significantly enhanced for small amount of doping (up to 0.5 mole% La{sub 2}O{sub 3}) and then decreased with increasing doping concentration. Desired grain growth (0.80-1.3 µm) and high densification (<90% theoretical density) were found by proper combination of temperature, sintering parameters and doping concentration. We found the resultant stable value of dielectric constant was 10000-12000 at 100-300 Hz in the temperature range of 30°-50° C for 0.5 mole% La{sub 2}O{sub 3} with corresponding shift of curie temperature around 30° C. So overall this research showed that proper La{sup 3+} concentration can control the grain size, increase density, lower curie temperature and hence significantly improve the electrical properties of BaTiO{sub 3} ceramics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Enhanced Up-Conversion Emission in Al{sup 3+} Co-Doped ZnGa{sub 2}O{sub 4}:Yb{sup 3+},Tm{sup 3+} Powder Phosphors

Yb{sup 3+}-Tm{sup 3+} co-doped up-conversion powder phosphors using Zn(Al{sub x}Ga{sub 1-x}){sub 2}O{sub 4} (ZAGO) as the host materials were synthesized via solid-state reaction successfully. In addition, the morphology, structural characterization and up-conversion luminescent properties were all investigated by scanning electron microscope (SEM), x-ray diffraction (XRD) and fluorescence spectrophotometer (F-7000), respectively. Under the excitation of a 980 nm laser, all as-prepared powders can carry out blue emission at about 477 nm (corresponding to {sup 1}G{sub 4} → {sup 3}H{sub 6} transition of Tm{sup 3+} ions), and red emission at about 691 nm (attributed to {sup 3}F{sub 3} → {sup 3}H{sub 6} transition of Tm{sup 3+} ions). Also, the influence of doping Al{sup 3+} ions were investigated. In brief, the doping of Al{sup 3+} ions has no effect on the position of emission peak. Howbeit the up-conversion efficiency and intensity of ZAGO:Yb,Tm phosphors are stronger than ZGO:Yb,Tm and ZAO:Yb,Tm phosphors, while the crystallinity is the opposite. More particularly, all as-prepared powder phosphors emit strong luminescence, which is observable by the naked eye, demonstrating the potential applications in luminous paint, luminescent dye, etc.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Effect of sodium carbonate as an additive on the morphology and photocatalytic activity of TiO{sub 2} nanotubes

Highlights: • Sodium Carbonate as an additive led to dope Sodium and Carbon doped TiO{sub 2} nanotube arrays. • In doped nanotubes the band gap energy reduced from 3.2 to 2.88 ev. • In doped nanotubes the adsorption edge increased to about 92 nm longer wavelength. • The photocurrent density in doped nanotubes was about 5 times higher than in the pure ones. - Abstract: The major purpose of this research is increasing the photocatalytic activity of TiO{sub 2} nanotube arrays by doping with sodium and carbon for using in water splitting as photoanode. The synthesized TiO{sub 2} nanotubes (TNA) were characterized using FESEM (Field Emission Scanning Electron Microscope), XRD (X-ray Diffraction), DRS (Diffraction Reflection Spectroscopy) and XPS test (X-ray Photoelectron Spectroscopy) analyses. The results of FTIR and XPS confirmed the presence of sodium and carbon in the lattice of TNA as dopants. Moreover, the DRS test showed the decrease in the band gap energy of TNA from 3.20 to ∼2.88 eV; uv-visible test exhibited extension in the absorption edge of pure TiO{sub 2} nanotubes from Uv-light (396 nm) to visible light (488 nm). In addition, the results of photoelectrochemical measurement indicated that the photocurrent density of doped TiO{sub 2} nanotubes increased about 5 times than that of the pure compounds.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Fabrication and characterization of nano-gas sensor arrays

A novel structures of Nanomaterials gas sensors array constructed using ZnO, and ZnO doped with Al via sol-gel technique. Two structure arrays are developed; the first one is a double sensor array based on doping with percentages of 1% and 5%. The second is a quadrature sensor array based on several doping ratios concentrations (0%, 1%, 5% and 10%). The morphological structures of prepared ZnO were revealed using scanning electron microscope (SEM). X-ray diffraction (XRD) patterns reveal a highly crystallized wurtzite structure and used for identifying phase structure and chemical state of both ZnO and ZnO doped with Al under different preparation conditions and different doping ratios. Chemical composition of Al-doped ZnO nanopowders was performed using energy dispersive x-ray (EDS) analysis. The electrical characteristics of the sensor are determined by measuring the two terminal sensor’s output resistance for O{sub 2}, H{sub 2} and CO{sub 2} gases as a function of temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A Study on Thermal Conductivity and Stability of Nanofluids Containing Chemically Synthesized Nanoparticles for Advanced Thermal Applications

This study presents easy methods of synthesizing silver (Ag) and copper (Cu) nanoparticles through chemical route in an aqueous medium under atmospheric condition at ambient temperature. The synthesized nanoparticles have been characterized with different techniques, such as x-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, high-resolution transmission electron microscopy, UV–visible spectroscopy and dynamic light scattering measurements. Experimental observations have revealed the absence of any metal oxide layer around the nanoparticles which are found to remain stable under ambient conditions. The featured properties, such as narrow size distribution, stability, make these nanoparticles potential candidates for the synthesis of effective nanofluids. The nanofluids have been prepared by dispersing the nanoparticles synthesized through chemical route in a suitable base fluid. The thermal conductivity of nanofluids with different nanoparticles loading has been measured by transient hot-wire method, and the results have shown that the increasing trend of enhancement in thermal conductivity with respect to nanoparticles concentration is attainable only when the nanoparticles concentration is below some limiting value depending on the type of nanofluid. Beyond this limiting value of loading, the thermal conductivity of the nanofluid decreases due to pronounced agglomeration effect. The measurements of thermal conductivity of nanofluids over varying temperatures for a given volume fraction loading of nanoparticles have shown that the thermal conductivity increases markedly with the increase in temperature. Hence, nanofluids are likely to be much more promising at high-temperature applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Hydrothermal synthesis of molybdenum trioxide, characterization and photocatalytic activity

Highlights: • α-MoO{sub 3} micro-belts were synthesized hydrothermally. • Micro-belts were found very rich in surface oxygen vacancies. • CR-F3BS photocatalytic degradation was promising. • The cytotoxicity and mutagenicity were reduced significantly of CR-F3BS. - Abstract: α-MoO{sub 3} micro-belts were synthesized via hydrothermal technique and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), energy dispersive X-ray analysis (EDX) and particle size analyzer. Photo-catalytic activity was evaluated by degrading Coralene Red F3BS (CR-F3BS) dye and process variables i.e., pH, photocatalyst dose, concentration of CR-F3BS and UV exposure time were optimized using response surface methodology (RSM) under central composite design (CCD). Under optimized conditions, up to 95% degradation of CR-F3BS (10 mg/L) was achieved for 120 min UV irradiation time at pH 7 using 2.75 g/L catalyst dose. The obtained RSM model revealed a satisfactory correlation between experimental and predicted CR-F3BS degradation values. Ames and heamolytic tests revealed that the toxicity was reduced significantly as a result of photo-catalytic treatment. In view of promising efficiency, α-MoO{sub 3} micro-belts could possibly be used for the degradation of dyes in textile effluents.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Development of Multilayer Films Obtained From Epoxidized Methyl Esters, Polyhydroxyalkanoates and Their Combinations

The aim of this work was the production and characterization of films prepared from starch, gelatin and methyl esters of epoxidized macauba (Acrocomia aculeata), corn (Zea mays), pacu (Piaractus mesopotamicus), pintado (Pseudoplatystoma corruscans) and soybean (Glycine max) and also multilayer films of polyhydroxyalkanoates (PHA) conjugated with two of the epoxides that presented the best results in characterizations. The two types of films EEF (Epoxidized esters films) and EEFPHA (Epoxidized esters and PHA conjugated films) were both characterized for their visual aspects, solubility in water and acid, width, color, opacity, water vapor permeability, tensile strength and elongation. EEFPHA were also characterized by differential scanning calorimetry, scanning electron microscopy and X-ray diffraction analyses. The epoxidation reaction was successfully carried out; with the GC-MS analysis indicating the formation of epoxidized esters derived from linoleic and oleic acids. The addition of the epoxidized esters to the EEF films caused an increase in film thickness, opacity, solubility in water, tensile strength and elongation, while the solubility in acid presented the same value as compared to the blank sample. In the EEFPHA samples, addition of filmogenic solution of epoxidized esters from corn and macauba presented a value exceeding the standard in the thickness, opacity, water solubility, water vapor permeability and tensile strength analyses. In the analysis of solubility in acid these samples showed results below the standard, and the elongation test showed values very close. DSC, SEM and XRD results showed that there was a polymeric incorporation between the starch and the PHA.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Determination of density of states, conduction mechanisms and dielectric properties of nickel disulfide nanoparticles

Temperature and frequency dependent ac electrical measurements were used to explore density of states, conduction mechanisms and dielectric properties of nickel disulfide (NiS{sub 2}) nanoparticles. The NiS{sub 2} nanoparticles were prepared by conventional one step solid state reaction method at 250 °C. X-ray diffraction (XRD) confirmed cubic phase of prepared nanoparticles. Scanning electron microscope (SEM) images revealed presence of irregular shaped nanoparticles as small as 50 nm. The ac electrical measurements were carried out from 300 K to 413 K. Two depressed semicircular arcs from 20 Hz to 2 MHz showed presence of bulk and grain boundary phases in NiS{sub 2} nanoparticles at all temperatures. Small polaron hopping conduction from 300 K to 393 K and correlated barrier hopping conduction mechanism at temperatures higher than 393 K was observed. High value of density of states (of the order of 10{sup 24} eV{sup −1}cm{sup −3}) was calculated from ac conductivity. At low frequencies high values (of the order of 10{sup 4}-10{sup 7}) of real part of dielectric constant (ε′) were observed at different temperatures. These observations suggest that NiS{sub 2} nanoparticles may find applications in electronic devices.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

PEDOT:PSS/GO nanocomposites: Determination of the aspect ratio by indirect measurements

Polymer nanocomposites properties significantly depend on the average size of the fillers dispersed into the matrix and on the grade of the dispersion, the latter influenced by the process techniques. In this work, we determined the aspect ratio of graphene oxide (GO) dispersed into Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), starting from the indirect measurement of the rheological behavior of polymer/filler mixtures, as a function of the shear rate and the volumetric composition. PEDOT:PSS+GO nanocomposite films were also realized by spin coating on different substrates and characterized by Scanning electron microscopy (SEM) and X-ray diffraction (XRD), in order to analyze the quality of the dispersion, even by direct measurements.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

Metallic ferromagnetic films with magnetic damping under 1.4 × 10 -3

Low-damping magnetic materials have been widely used in microwave and spintronic applications because of their low energy loss and high sensitivity. While the Gilbert damping constant can reach 10 -4 to 10 -5 in some insulating ferromagnets, metallic ferromagnets generally have larger damping due to magnon scattering by conduction electrons. Meanwhile, low-damping metallic ferromagnets are desired for charge-based spintronic devices. In this article, we report the growth of Co 25 Fe 75 epitaxial films with excellent crystalline quality evident by the clear Laue oscillations and exceptionally narrow rocking curve in the X-ray diffraction scans as well as from scanning transmission electron microscopy. Remarkably, the Co 25 Fe 75 epitaxial films exhibit a damping constant <1.4 × 10 -3 , which is comparable to the values for some high-quality Y 3 Fe 5 O 12 films. This record low damping for metallic ferromagnets offers new opportunities for charge-based applications such as spin-transfer-torque-induced switching and magnetic oscillations.

30 DIRECT ENERGY CONVERSION↗