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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 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Hematite homogeneous core/shell hierarchical spheres: Surfactant-free solvothermal preparation and their improved catalytic property of selective oxidation

Solvothermal synthesis is an efficient synthetic method for preparing nano and micromaterials. Preparation of hematite through alcoholysis of ferric ion under solvothermal condition has been carried out at low concentrations. In this paper, Fe{sub 2}O{sub 3} homogeneous core/shell hierarchical nanostructures were synthesized via solvothermal treatment of FeCl{sub 3}{center_dot}6H{sub 2}O and ethanol. The achievements of such structures can be attributed to two important factors: high temperature and high concentration. Besides, the crystal water and reaction time were also important factors to the synthesis of hematite. The prepared samples were characterized using X-ray powder diffraction, Raman spectra, scanning electron microscopy equipped with an energy-dispersive X-ray spectrometer, transmission electron microscopy and Brunauer-Emmett-Teller surface area and pore size distribution. X-ray photoelectron spectroscopy showed a satellite peak at 719.8 eV, which is the characteristic peak of Fe(III). The formation mechanism of the spheres and the effects of the reactant concentrations and reaction temperatures have been discussed. Moreover, the enhanced catalytic activity of the spheres has also been investigated through oxidation of benzyl alcohol to benzaldehyde with high conversion (42%) and selectivity (95%). - Graphical abstract: Fe{sub 2}O{sub 3} homogeneous core/shell hierarchical microspheres were synthesized by solvothermal method. Owing to the special structure, the synthesized Fe{sub 2}O{sub 3} microspheres exhibit a superior catalytic activity in benzyl oxidation. Highlights: Black-Right-Pointing-Pointer Hierarchical Fe{sub 2}O{sub 3} core/shell microspheres were synthesized. Black-Right-Pointing-Pointer Microspheres were assembled by {beta}-FeOOH. Black-Right-Pointing-Pointer The sample exhibits a superior catalytic activity and selectivity. Black-Right-Pointing-Pointer The high activity and selectivity are due to the hierarchical core/shell structure.

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

Synthesis of crystalline carbon nanofern-like structure by dc-PECVD and study of its electrical and field emission properties

Graphical abstract: Display Omitted Highlights: ► Branched, carbon nanofern like structure have been synthesized on glass substrate via PECVD. ► Ni catalyst played important role in growing such structure. ► The as prepared sample shows good field emission property with turn on field as low as 4.8 V/mm. ► Temperature dependent conductivity of the sample showed non-linearity. -- Abstract: Carbon nanofern-like structure was synthesized by direct current plasma enhanced chemical vapor deposition at 400 °C using acetylene as carbon precursor and nickel particle as seed. High resolution transmission electron microscopy (HRTEM) study confirmed the fern-like structure of the as-synthesized sample. It was seen that when nickel was not used a cluster deposition took place without forming any structure. Atomic force microscopy study showed the surface topology of the as-prepared samples. X-ray photoelectron spectroscopy as well as HRTEM studies confirmed the presence of nickel in the carbon matrix. Current (I)–voltage (V) characteristics have been taken for three different temperatures. A non-linear I–V characteristic was obtained for the fern like sample. Field emission study showed that carbon nanofern showed efficient field emission with a turn-on field as low as 4.8 V/μm. Also, the field emission has been studied for different inter-electrode distances.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Processability evaluation of a Mo-containing FeCrAl alloy for seamless thin-wall tube fabrication

The processability of a Mo-containing FeCrAl alloy (Fe-13Cr-5.2Al-2Mo base, in wt%), developed for accident-tolerant nuclear fuel claddings, was evaluated through a stepwise rolling process at 400 °C under two different inter-pass annealing conditions (i.e., 650 °C for 1 h and at 870 °C for 30 min). The inter-pass annealing at 870 °C easily softened the FeCrAl alloy; however, it led to the formation of coarse grains of ~200 µm. On the other hand, the FeCrAl alloy maintained elongated, deformed grains with the inter-pass annealing at 650 °C, but the annealed samples showed relatively high deformation resistance and strong texture. Important aspects concerning the processability and microstructural control of FeCrAl alloys, such as deformation inhomogeneity, texture development, and grain coarsening, were discussed. Optimized processing conditions were recommended, based on the results, to achieve desirable microstructures with balanced processability and mechanical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2025

DNA viruses from different stages of a wastewater treatment plant in southwest Ohio

Wastewater treatment plants (WWTPs) house diverse populations of microbial communities that are dynamic across treatment stages. Although viruses, especially non-pathogenic ones are relatively less studied compared to their bacterial counterparts, they are equally important players in WWTP microbiomes. In this study, we sampled influent, activated sludge, and effluent stages of a WWTP in southwest Ohio to sequence their viral population using multiple displacement amplification (MDA) and metagenomic approaches. We recovered 1003 viral genomes, the majority of which were ssDNA (single-stranded DNA) viruses that formed distinct clusters representing novel species and phylogenetic groups not closely related to known human gut or terrestrial viruses. Additionally, tracking viruses across treatment stages showed several persisted across multiple treatment stages. These results suggest that further studies are needed to understand the persistence of viral populations, particularly non-pathogenic ones, across different stages of WWTPs.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Characterization of brominated flame retardants from e-waste components in China

Highlights: • BFRs in housing plastics and PCBs from e-waste recycling enterprises in China were systematically examined. • Both PBDEs and TBBPA were detectable in most samples. • There is an apparent decreasing trend of BFRs from housing plastics and PCBs in China. • BFRs could be transferred into the recycled products those for other purpose use. - Abstract: Many studies show that high levels of many toxic metals and persistent and bio-accumulative chemicals have been found in electronic waste (e-waste) dismantling sites and their surrounding environmental media. Both flame-retardant plastic housing materials and printed circuit boards (PCBs) could be the major contributors. However, relatively little work has focused on the use or content of toxic substances and their changing in scrap housing materials and PCBs from home appliances. This study evaluated the existence of brominated flame retardants (BFRs, including polybrominated diphenyl ethers (PBDEs) and Tetrabromobisphenol-A (TBBPA)) in housing plastics and PCBs from home appliances collected from various e-waste recyclers in China. These were then analyzed for the potential migration of BFRs from the e-waste components into their recycled products. The results show that both PBDEs and TBBPA were found with high level in most of e-waste samples, indicating that the widespread use of BFRs in home appliances are entering into the end-of-life stage. For the plastics samples, CRT TVs and LCD monitors should be given priority for the control of BFRs. Regarding PBDEs, the dominant congeners of BDE-209 in the plastics samples contributed 90.72–93.54% to the total concentrations of PBDEs, yet there are large variations for PCBs samples: BDE-28, -47, -99, and -153 were also important congeners compositions, except for BDE-209. Compared with previous studies, the BFRs concentrations in current Chinese e-waste are trending to decline. This study also found that BFRs in housing plastics and PCBs will be transferred into the recycled products with other purpose use, and the new products could have highly enriched capacities for BFRs. The obtained results could be helpful to manage e-waste and their components properly in order to minimize associated environmental and health risks of BFRs, particularly for their further reuse.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2012

Influence of Polarization Setting on Gold Nanorod Signal at Nonplasmonic Wavelengths Under Differential Interference Contrast Microscopy

Researchers rely on a variety of microscopic techniques for observing and tracking anisotropic nanoparticles in real time experiments. This technical note focuses on the optical behavior exhibited by gold nanorods at nonplasmonic wavelengths under differential interference contrast microscopy (DIC). Intense diffraction patterns appear at nonplasmonic wavelengths, and the behavior of these patterns can be altered by adjusting the surrounding medium or the polarizer setting. Such patterns are absent when linear and crossed polarizations are utilized. Making polarization adjustments is important in DIC microscopy, because it affects bias retardation and image contrast. The nonplasmonic diffraction bands that were observed could potentially be exploited for rotational tracking, but more importantly, researchers should exhibit care in selecting a nanorod sample and the polarization setting when working with DIC microscopy.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Unequal {110} Facets: The Potential Role of Intraparticle Heterogeneity and Facet Termination in Photoelectrochemical Activity of Single BiVO 4 Particles

BiVO 4 photoanodes are promising for solar water splitting, with photogenerated electrons and holes preferentially reacting at top {010} and lateral {110} facets, respectively. However, the mechanisms driving this facet-dependent reactivity remain unclear. Here, in this study, we investigate facet-dependent photocurrent and material heterogeneity using correlative scanning photoelectrochemical microscopy (SPCM), electron beam induced current (EBIC) mapping, and mid-IR scattering scanning near-field optical microscopy (s-SNOM). SPCM measurements of 62 BiVO 4 particles confirmed higher photocurrents at lateral {110} facets compared to top {010} facets, but unexpectedly revealed variations in photocurrent among lateral facets within the same particle. Variations in lateral facet surface termination could explain the intraparticle-level reactivity heterogeneity, consistent with theoretical predictions. Nano-FTIR spectroscopy and Raman microspectroscopy indicated significant materials chemistry heterogeneity within individual particles and facets that could be attributed to variations in lattice vibration distortions that enhance the overlap between Bi 6s and O 2p orbitals. The increased orbital overlap is significant as it potentially increases hole mobility in the valence band and potentially explains the lateral facet-dependent charge separation efficiency observed in photocurrent maps. Facet-dependent electrical and EBIC measurements showed no space charge regions at interfacet junctions or metal-BiVO 4 contacts under vacuum, suggesting that photogenerated holes beneath top {010} facets are unlikely to transport to lateral {110} facets to drive water/sulfite oxidation. These findings indicate the potential influence of distinct bulk properties and surface termination chemistries across different particles and facets, highlighting the importance of carefully controlling defects and surface chemistry during sample growth to optimize photocatalytic performance.

BiVO4↗
DOE OSTI2024

Use of Ionic Liquids for Hemp Fiber Degumming

Degumming or retting to remove pectin, lignin, and hemicellulose is a critical step in the production of high-quality hemp fibers. Current technologies, including traditional water or dew retting, as well as chemical, enzymatic, and physical degumming processes, have inherent environmental risks and produce fibers of varying qualities. Herein we explore the use of an ionic liquid (IL) capable of dissolving pectin, lignin, and hemicellulose, but not cellulose, in combination with different oxidating agents to degum hemp. In this study, we observed that treating raw hemp fibers with the IL choline acetate ([Cho][OAc]), alone or in combination with aqueous H 2 O 2 , led to a reduction in the gummy materials and lignin content of the resulting samples of up to 63 and 78%, respectively. More importantly, the high crystallinity and low reduction in tensile strength of the resulting fibers make these novel and relatively simple IL-based processes promising alternatives toward the sustainable preparation of hemp-based materials suitable for use in the textile industry.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Effects of scale of movement, detection probability, and true population density on common methods of estimating population density

Knowledge of population density is necessary for effective management and conservation of wildlife, yet rarely are estimators compared in their robustness to effects of ecological and observational processes, which can greatly influence accuracy and precision of density estimates. For this study, we simulate biological and observational processes using empirical data to assess effects of animal scale of movement, true population density, and probability of detection on common density estimators. We also apply common data collection and analytical techniques in the field and evaluate their ability to estimate density of a globally widespread species. We find that animal scale of movement had the greatest impact on accuracy of estimators, although all estimators suffered reduced performance when detection probability was low, and we provide recommendations as to when each field and analytical technique is most appropriately employed. The large influence of scale of movement on estimator accuracy emphasizes the importance of effective post-hoc calculation of area sampled or use of methods that implicitly account for spatial variation. In particular, scale of movement impacted estimators substantially, such that area covered and spacing of detectors (e.g. cameras, traps, etc.) must reflect movement characteristics of the focal species to reduce bias in estimates of movement and thus density.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

A six-channel pediatric coil array for detection of children spinal pathologies by MRI at 1.5 Tesla

Nowadays, magnetic resonance (MR) in Mexico has become a standard technique for clinical imaging. Although most of the times the MR systems contain only coils oriented for adults. Radiologists use these coils for children studies due to the non-availability of pediatric coils. Image quality is decreased due to the low signal to noise ratio delivered to the system. The development of RF coils is always focused towards increasing SNR and optimizing the RF penetration into the sample. Moreover, spinal pathologies in children, which are an important topic in pediatric care, cover congenital and neuromuscular disorders that occur in childhood. In this work, the design of a dedicated six-channel coil for detection of spinal pathologies at 1.5 Tesla is addressed. Numerical electromagnetic simulations were performed in order to evaluate their magnetic field performance at (63.6 MHz) 1.5 Tesla. The magnetic field uniformity as well as the RF penetration depth of the coil configurations was evaluated in order to find the best/optimized coil array configuration. The coil is comprised of three rows, one with 4 coil elements and two with only one coil element. Phantom and in vivo images were acquired with the six-channel pediatric coil array. The phantom images agree with the simulated data. In vivo images acquired with the 6-channel pediatric coil array have shown very good penetration depth and homogeneity, which allow better image quality throughout the whole FOV. In addition, the parallel imaging capabilities of the array allow the acceleration of the experiments avoiding possible motion artifacts.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Magneto-optical imaging technique for hostile environments: The ghost imaging approach

In this paper, we develop an approach to magneto optical imaging (MOI), applying a ghost imaging (GI) protocol to perform Faraday microscopy. MOI is of the utmost importance for the investigation of magnetic properties of material samples, through Weiss domains shape, dimension and dynamics analysis. Nevertheless, in some extreme conditions such as cryogenic temperatures or high magnetic field applications, there exists a lack of domain images due to the difficulty in creating an efficient imaging system in such environments. Here, we present an innovative MOI technique that separates the imaging optical path from the one illuminating the object. The technique is based on thermal light GI and exploits correlations between light beams to retrieve the image of magnetic domains. As a proof of principle, the proposed technique is applied to the Faraday magneto-optical observation of the remanence domain structure of an yttrium iron garnet sample.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

The photocatalytic investigation of methylene blue dye with Cr doped zinc oxide nanoparticles

The present work reports eco-friendly and cost effective sol-gel technique for synthesis of Chromium doped ZnO nanoparticles at room temperature. In this process Zinc nitrate, Chromium nitrate were used as precursor. Structural as well as optical properties of Cr induced ZnO samples were analysed by X-ray diffraction technique (XRD), SEM, PL and UV-Visible spectroscopy (UV-Vis) respectively. XRD analysis shows that the samples have hexagonal (wurtzite) structure with no additional peak which suggests that Cr ions fit into the regular Zn sites of ZnO crystal structure. By using Scherrer’s formula for pure and Cr doped ZnO samples the average grain size was found to be 32 nm. Further band gap of pure and doped ZnO samples have been calculated by using UV-Vis spectra. The photo-catalytic degradation of methyl blue dye under UV irradiation was examined for synthesized samples. The results show that the concentration plays an important role in photo-catalytic activity.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Oxygen vacancy-driven evolution of structural and electrical properties in SrFeO 3₋δ thin films and a method of stabilization

Epitaxial SrFeO 3-δ (SFO) thin films have been grown on various substrates by pulsed laser deposition. The structural and electrical properties of SFO thin films are monitored with time in different atmospheres at room temperature, showing time-dependent crystal structure and electrical conductivity. The increased out-of-plane lattice parameter and resistivity over time are associated with the increased oxygen vacancies density in SFO thin films. The epitaxial strain plays an important role in determining the initial resistivity, and the sample environment determines the trend of resistivity change over time. An amorphous Al 2 O 3 passivation layer has been found to be effective in stabilizing the structure and electrical properties of SFO thin films. Lastly, this work explores time dependent structure and properties variation in oxide films and provides a way to stabilize thin film materials that are sensitive to oxygen vacancies.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Influence of growth temperature of KTiOAsO{sub 4} single crystals on their physicochemical parameters and formation of domain structures

A potassium titanyl arsenate (KTiOAsO{sub 4}, KTA) crystal 50 × 80 × 60 mm in size has been grown by upgraded Czochralski method from flux (TGGS) with a decrease in temperature from 900 to 770 °C during pulling. It is shown that the spectroscopic properties of the parts of KTA crystals grown at 900 and 770 °C are close, whereas the electrical conductivity of the low-temperature (770 °C) KTA part turned out to be an order of magnitude lower than that of the high-temperature part. Visualisation of the domain structure by second-harmonic generation microscopy revealed a more efficient domain intergrowth (throughout the sample) in the low-temperature KTA, which is important for forming a regular domain structure (RDS) in a KTA-based nonlinear optical element. It is established that the quantum efficiency of parametric generation of light in the RDS formed in low-temperature KTA is several times higher than in the case of high-temperature KTA. The results obtained are important for optimising RDS parameters. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

A tale of two planets: Disparate evolutionary models for Mars inferred from radiogenic isotope compositions of Martian meteorites

The radiogenic isotopic compositions of basaltic Martian meteorites (shergottites) and clinopyroxene/olivine cumulate meteorites (nakhlite/chassignites) are used to define the global evolution of Mars. However, the two main groups of meteorites demonstrate that their sources underwent divergent styles of magmatic evolution. The shergottites portray a planet that differentiated ~4.52 billion years ago via solidification of a magma ocean, producing incompatible element-depleted and -enriched reservoirs that remained isolated until melt production. In contrast, the reservoir from which the nakhlite/chassignites derive may have formed earlier, produced melts that fractionated Sm/Nd and Hf/W differently, was compositionally less variable, and experienced a significantly more complex history following primordial differentiation than the shergottite sources. The disparate histories recorded by these two groups of meteorites elucidate important questions that could be addressed by acquiring additional samples. Obtaining samples that shared the isotopic systematics of the shergottites would provide confidence that extrapolating the primordial differentiation history of Mars from shergottite radiogenic isotope systematics is reasonable. Returned samples from Mars will also constrain the physical locations of the meteorite source regions, providing insights into the general structure of the Martian mantle. In addition, they will help constrain the phases present in the martian mantle during melting and the conditions under which they are stable. Finally, identifying an evolved lithology that satisfies the geochemical and isotopic constraints placed on the incompatible element-enriched endmember observed in the shergottites would define the nature of magmatic evolution on Mars and whether it is more akin to processes on the Earth or the Moon.

Mars↗
DOE OSTI2015

Fixing the reference frame for PPMXL proper motions using extragalactic sources

In this study, we quantify and correct systematic errors in PPMXL proper motions using extragalactic sources from the first two LAMOST data releases and the Vèron-Cetty & Vèron Catalog of Quasars. Although the majority of the sources are from the Vèron catalog, LAMOST makes important contributions in regions that are not well-sampled by previous catalogs, particularly at low Galactic latitudes and in the south Galactic cap. We show that quasars in PPMXL have measurable and significant proper motions, which reflect the systematic zero-point offsets present in the catalog. We confirm the global proper motion shifts seen by Wu et al., and additionally find smaller-scale fluctuations of the QSO-derived corrections to an absolute frame. Finally, we average the proper motions of 158 106 extragalactic objects in bins of 3° × 3° and present a table of proper motion corrections.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Thermal desorption spectroscopy of high fluence irradiated ultrafine and nanocrystalline tungsten: helium trapping and desorption correlated with morphology

Here, microstructural changes due to displacement damage and helium desorption are two phenomena that occur in tungsten plasma facing materials in fusion reactors. Nanocrystalline metals are being investigated as radiation tolerant materials that can mitigate these microstructural changes and better trap helium along their grain boundaries. Here, we investigate the performance of three tungsten grades (nanocrystalline, ultrafine and ITER grade tungsten), exposed to a high fluence of 4 keV helium at both RT and 773 K, during a thermal desorption spectroscopy (TDS) experiment. An investigation of the microstructure in pre-and post-TDS sample sets was performed. The amount of desorbed helium was shown to be highest in the ITER grade tungsten and lowest in the nanocrystalline tungsten. Correlating the desorption spectra and the microstructure (grain boundaries decorated with nanopores and crack formation) and comparing with previous literature on coarse grained tungsten samples at similar irradiation and TDS conditions, revealed the importance of grain boundaries in trapping helium and limiting helium desorption up to a high temperature of 1350 K in agreement with transmission electron microscopy studies on helium irradiated tungsten which showed preferential and large facetted bubble formation along the grain boundaries in the nanocrystalline tungsten grade.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

SUPER-AGB-AGB EVOLUTION AND THE CHEMICAL INVENTORY IN NGC 2419

We follow the scenario of formation of second-generation stars in globular clusters by matter processed by hot bottom burning (HBB) in massive asymptotic giant branch (AGB) stars and super-AGB stars (SAGB). In the cluster NGC 2419 we assume the presence of an extreme population directly formed from the AGB and SAGB ejecta, so we can directly compare the yields for a metallicity Z = 0.0003 with the chemical inventory of the cluster NGC 2419. At such a low metallicity, the HBB temperatures (well above 10{sup 8} K) allow a very advanced nucleosynthesis. Masses {approx}6 M{sub Sun} deplete Mg and synthesize Si, going beyond Al, so this latter element is only moderately enhanced; sodium cannot be enhanced. The models are consistent with the observations, although the predicted Mg depletion is not as strong as in the observed stars. We predict that the oxygen abundance must be depleted by a huge factor (>50) in the Mg-poor stars. The HBB temperatures are close to the region where other p-capture reactions on heavier nuclei become possible. We show that high potassium abundance found in Mg-poor stars can be achieved during HBB by p-captures on the argon nuclei, if the relevant cross section(s) are larger than listed in the literature or if the HBB temperature is higher. Finally, we speculate that some calcium production is occurring owing to proton capture on potassium. We emphasize the importance of a strong effort to measure a larger sample of abundances in this cluster.

79 ASTRONOMY AND ASTROPHYSICS↗