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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 847 records · Page 47
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

A mobile system for a comprehensive online-characterization of nanoparticle aggregates based on wide-angle light scattering and laser-induced incandescence

A mobile demonstrator for the comprehensive online-characterization of gas-borne nanoparticle aggregates is presented. Two optical measurement techniques are combined, both utilizing a pulsed Nd:YAG laser as light source. Aggregate size and fractal dimension are measured by Wide-Angle Light Scattering (WALS). An ellipsoidal mirror images elastically scattered light from scattering angles between 10° and 165° onto a CCD-camera chip resulting in an almost complete scattering diagram with high angular resolution. Primary particle size and volume fraction are measured by time-resolved Laser-Induced Incandescence (TiRe-LII). Here, particles are heated up to about 3000 K by the short laser pulse, the enhanced thermal radiation signal is detected with gated photomultiplier tubes. Analysis of the signal decay time and maximum LII-signal allows for the determination of primary particle diameter and volume fraction. The performance of the system is demonstrated by combined measurements on soot nanoparticle aggregates from a soot aerosol generator. Particle and aggregate sizes are varied by using different equivalence ratios of the combustion in the generator. Soot volume fraction can be adjusted by different levels of dilution with air. Online-measurements were carried out demonstrating the favorable performance of the system and the potential for industrial applications such as process control and product development. The particle properties obtained are confirmed through transmission electron microscopy analysis on representative samples.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1989

Techniques for studying the effects of microgravity on model particle/cell systems

In an effort to learn more about the effects of a simulated low gravity environment on skeletal muscle, skeletal muscle cell cultures were grown within the lumen of XM-80 hollow fibers (i.d. = 0.5 mm) in a Clinostat rotating at 100 rpm. Cells were isolated from the thigh muscle tissue of 12 day embryos and were cultured for up to 14 days in the hollow fiber environment. Cells proliferated to confluency within several days, and fusion into multinucleated myotubes was then apparent. Fibers were stretched by a built-in spring mechanism to hold the fiber tightly at the center of rotation, and sections of the fiber were removed at 3, 7 and 14 days for electron microscopic analysis. When the Clinostat is rotated in the horizontal position, the gravity vector approaches zero and the cells are in an environment that simulates microgravity. Control experiments consist of one fiber rotated in the vertical position in the clinostat and another fiber that is held in a horizontal configuration in a comparable sized tube that is not rotated at all. Examination of skeletal muscle cells by electron microscopy revealed that myoblast fusion and myofibril accumulation were extensive. Two general conclusions were apparent. First, muscle cells undergo the normal progression of proliferation, fusion, and myofibril assembly in the presence of simulated microgravity for the first week in culture. After 14 days, however, many muscle fibers undergo degeneration such that myofibrillar structures are not extensive or well organized. Second, although no major abnormalities in myofibril assembly were detected in Clinostat-rotated cultures in comparison to controls that were not rotated in a Clinostat, the myofibrils in non-rotated controls tend to be more highly organized than those in either horizontally or vertically rotated Clinostat samples.

Young, Ronald B.↗
NASA NTRS1995

Line Profile of H Lyman (alpha) from Dissociative Excitation of H2 with Application to Jupiter

Observations of the H Lyman(alpha) (Ly-alpha) emission from Jupiter have shown pronounced emissions, exceeding solar fluorescence, in the polar aurora and equatorial "bulge" regions. The H Ly-alpha line profiles from these regions are broader than expected, indicating high-energy processes producing fast atoms as determined from the observed Doppler broadening. Toward understanding that process a high-resolution ultraviolet (UV) spectrometer was employed for the first measurement of the H Ly-alpha emission Doppler profile from dissociative excitation of H2 by electron impact. Analysis of the deconvolved line profile reveals the existence of a narrow central peak of 40 +/- 4 mA full width at half maximum and a broad pedestal base about 240 mA wide. Two distinct dissociation mechanisms account for this Doppler structure. Slow H(2p) atoms characterized by a distribution function with peak energy near 80 meV produce the peak profile, which is nearly independent of the electron impact energy. Slow H(2p) atoms arise from direct dissociation and predissociation of singly excited states which have a dissociation limit of 14.68 eV. The wings of H Ly-alpha arise from dissociative excitation of a series of doubly excited states which cross the Franck-Condon region between 23 and 40 eV. The profile of the wings is dependent on the electron impact energy, and the distribution function of fast H(2p) atoms is therefore dependent on the electron impact energy. The fast atom kinetic energy distribution at 100 eV electron impact energy spans the energy range from 1 to 10 eV with a peak near 4 eV. For impact energies above 23 eV the fast atoms contribute to a slightly asymmetric structure of the line profile. The absolute cross sections of the H Ly-alpha line peak and wings were measured over the range from 0 to 200 eV. Analytic model coefficients are given for the measured cross sections which can be applied to planetary atmosphere auroral and dayglow calculations. The dissociative excitation process, while one contributing process, appears insufficient by itself to explain the line broadening observed at Jupiter.

Ajello, Joseph M.↗
NASA NTRS2017

A Large Ordinary Chondrite Shower in the Dominion Range

The US Antarctic Meteorite Program has visited the Dominion Range in the Transantarctic Mountains during several different seasons, including the 1985, 2003, 2008, 2010, and 2014 seasons. Total recovered meteorites from this region is over 2000. The 2008 and 2010 seasons have been fully classified and, respectively) revealing the presence of a large meteorite shower that comprises approximately 60% of all samples recovered in those two seasons. The oil immersion classification suggests that this shower is LL chondrite material, whereas published magnetic susceptibility (MS; log chi) measurements yield L chondrite values. However, usually random sampling of a large collection like this would uncover EOC material for which we have prepared thin sections. In this case, no LL chondrite materials have been found in thin section, suggesting that the shower might instead be an L chondrite. L and LL chondrites are notoriously difficult to distinguish using oil immersion techniques. To better characterize this large group of samples, we have decided to examine some of the large members of this group, using EMPA analysis of the olivines to verify the classifications. With a compositional link between this subset of samples, and the MS measurements, we can more confidently classify the samples making up this pairing group. Subsequently, more accurate and meaningful comparisons may be drawn between this pairing group and some other Antarctic pairing groups such as from the Queen Alexandra Range (QUE), and Lewis Cliffs Ice Tongue (LEW). electron microprobe analysis

Satterwhite, C. E.↗
NASA NTRS1972

The inner zone electron model AE-5

A description is given of the work performed in the development of the inner radiation zone electron model, AE-5. A complete description of the omnidirectional flux model is given for energy thresholds E sub T in the range 4.0 E sub T/(MeV) 0.04 and for L values in the range 2.8 L 1.2 for an epoch of October 1967. Confidence codes for certain regions of B-L space and certain energies are given based on data coverage and the assumptions made in the analysis. The electron model programs that can be supplied to a user are referred to. One of these, a program for accessing the model flux at arbitrary points in B-L space and arbitrary energies, includes the latest outer zone electron model and proton model. The model AE-5, is based on data from five satellites, OGO 1, OGO 3, 1963-38C, OV3-3, and Explorer 26, spanning the period December 1964 to December 1967.

Teague, M. J.↗
DOE OSTI2013

Synthesis and single-crystal structure determination of the zinc nitride halides Zn{sub 2}NX (X=Cl, Br, I)

A series of zinc nitride halides, Zn{sub 2}NX (X=Cl, Br, I), has been synthesized from solid–liquid reactions of zinc nitride with the respective zinc halides under vacuum, and their crystal structures were determined using single-crystal and powder X-ray diffraction. While Zn{sub 2}NCl and Zn{sub 2}NBr crystallize in the acentric orthorhombic space group Pna2{sub 1}, Zn{sub 2}NI adopts the centrosymmetric space group Pnma; Zn{sub 2}NCl and Zn{sub 2}NBr can be considered to belong to the anti-β-NaFeO{sub 2} type, and Zn{sub 2}NI is closely related. Each N{sup 3−} is tetrahedrally coordinated by zinc atoms, and the X{sup −} anions are located in the vacancies of the framework formed by corner-sharing [NZn{sub 4}] tetrahedra. According to TGA/DTA analyses, the Zn{sub 2}NX compounds exhibit good thermal stability. The electronic structure has been analyzed by employing density-functional theory and the HSE06 hybrid functional. - Graphical abstract: Zn{sub 2}NCl, Zn{sub 2}NBr, and Zn{sub 2}NI have been synthesized, and their crystal structures (Cl and Br phases: Pna2{sub 1}; I phase: Pnma) have been determined from XRD; the direct band gap of Zn{sub 2}NCl is theoretically (HSE06 hybrid functional) predicted as 3.7 eV. - Highlights: • Zn{sub 2}NCl, Zn{sub 2}NBr, and Zn{sub 2}NI have been synthesized from solid–liquid reactions. • The crystal structures of Zn{sub 2}NCl, Zn{sub 2}NBr, and Zn{sub 2}NI have been determined from single-crystal X-ray diffraction. • Zn{sub 2}NCl and Zn{sub 2}NBr crystallize in the acentric space group Pna2{sub 1} whereas Zn{sub 2}NI adopts the centrosymmetric space group Pnma. • Zn{sub 2}NCl and Zn{sub 2}NBr are stable up to 750 °C whereas Zn{sub 2}NI decays at 600 °C already. • The direct band gap of Zn{sub 2}NCl is theoretically predicted as 3.7 eV using the HSE06 hybrid functional.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Communication: Localized molecular orbital analysis of the effect of electron correlation on the anomalous isotope effect in the NMR spin-spin coupling constant in methane

We discuss the effect of electron correlation on the unexpected differential sensitivity (UDS) in the {sup 1}J(C–H) coupling constant of CH{sub 4} using a decomposition into contributions from localized molecular orbitals and compare with the {sup 1}J(N–H) coupling constant in NH{sub 3}. In particular, we discuss the well known fact that uncorrelated coupled Hartree-Fock (CHF) calculations are not able to reproduce the UDS in methane. For this purpose we have implemented for the first time a localized molecular orbital analysis for the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes—SOPPA(CCSD) in the DALTON program. Comparing the changes in the localized orbital contributions at the correlated SOPPA and SOPPA(CCSD) levels and at the uncorrelated CHF level, we find that the latter overestimates the effect of stretching the bond between the coupled atoms on the contribution to the coupling from the localized bonding orbital between these atoms. This disturbs the subtle balance between the molecular orbital contributions, which lead to the UDS in methane.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Measurements of structures and concentrations of carbon particle species in premixed flames by the use of in-situ wide angle X-ray scattering

In-situ wide-angle X-ray scattering (WAXS) measurements have been conducted on atmospheric-pressure fuel-rich premixed freely propagating ethylene/oxygen flames with argon and nitrogen dilution. In this work, a novel analysis methodology able to provide quantitative information on soot/carbon particle species and concentrations was tested under heavy sooting conditions. The particle composition and concentrations were retrieved by fitting theoretical calculations of structural components from major molecular and nanometric species to the experimental WAXS data. The results show that argon dilution yields predominantly graphenelike components that are less stacked and amorphous carbon that is less structured than under nitrogen dilution. This finding was later confirmed by electron microscopy analysis on samples extracted from similar flames. In addition, the WAXS showed that most of the carbon present in the flames was bound as particles. These results constitute some of the first in-situ observations on structures and concentrations of carbon species in laboratory burner flames operating without stabilization plates.

Concentrations↗
DOE OSTI2015

Effect of isovalent non-magnetic Fe-site doping on the electronic structure and spontaneous polarization of BiFeO{sub 3}

We report the results of our first-principles calculations on the effect of isovalent, non-magnetic, Al{sup 3+} ion doping on the electronic structure and spontaneous polarization of multiferroic BiFeO{sub 3}. Our calculations reveal that Al{sup 3+} doping in BiFeO{sub 3} results in the reduction of Fe–O–Fe bond angle, leading to the weakening of antiferromagnetic superexchange interaction, further substantiated by the reduction of exchange interaction constant with increasing doping level. Lowering of well-depth is suggestive of reduced switching potential and improved P-E loop with lowered coercivity. Chemical bonding analysis by electron localization function shows that cation–oxygen bonding is of mixed ionic–covalent character, with marginal increase in the covalent character with increasing doping concentration. Large spontaneous polarization of undoped BiFeO{sub 3} is retained with lower doping level (6.25%), while for higher doping content (31.25%), the spontaneous polarization is reduced, primarily due to larger c/a ratio at higher doping level.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1988

Formation of the lamellar structure in Group IA and IIID iron meteorites

Analytical EM, light microscopy, and electron microprobe analysis are used to study the lamellar plessite structure of Group IA and IIID iron meteorites. The alpha lamellae in IIID structures contained a compositional gradient from 6.1 + or - 0.7 wt pct Ni at the center of the alpha lamellae to 3.6 + or - 0.5 wt pct at the alpha/gamma interface. For the Group IA irons, compositions of 4 wt pct Ni in alpha and about 48 wt pct Ni in gamma are found. Convergent beam electron diffraction was used to characterize the orientation relations at the alpha/gamma interface in the lamellar regions of both Group IA and IIID. The phase transformations responsible for the observed lamellar structure in the IA and IIID chemical groups were also investigated.

Kowalik, J. A.↗
DOE OSTI2016

Phases and interfaces from real space atomically resolved data: Physics-based deep data image analysis

Advances in electron and scanning probe microscopies have led to a wealth of atomically resolved structural and electronic data, often with ~1–10 pm precision. However, knowledge generation from such data requires the development of a physics-based robust framework to link the observed structures to macroscopic chemical and physical descriptors, including single phase regions, order parameter fields, interfaces, and structural and topological defects. Here, we develop an approach based on a synergy of sliding window Fourier transform to capture the local analog of traditional structure factors combined with blind linear unmixing of the resultant 4D data set. This deep data analysis is ideally matched to the underlying physics of the problem and allows reconstruction of the a priori unknown structure factors of individual components and their spatial localization. We demonstrate the principles of this approach using a synthetic data set and further apply it for extracting chemical and physically relevant information from electron and scanning tunneling microscopy data. Furthermore, this method promises to dramatically speed up crystallographic analysis in atomically resolved data, paving the road toward automatic local structure–property determinations in crystalline and quasi-ordered systems, as well as systems with competing structural and electronic order parameters.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Mechanical behavior and microstructure of Ti{sub 20}Hf{sub 20}Zr{sub 20}Ta{sub 20}Nb{sub 20} high-entropy alloy loaded under quasi-static and dynamic compression conditions

The microstructure and the mechanical behavior of equimolar Ti{sub 20}Hf{sub 20}Zr{sub 20}Ta{sub 20}Nb{sub 20} high-entropy alloy in a wide range of initial strain rates between ~ 10{sup −3} s{sup −1} and ~ 3.4 × 10{sup 3} s{sup −1} were studied. A significant increment in the yield strength with increasing strain rate was observed. The yield strength at ~ 3.4 × 10{sup 3} s{sup −1} was about 40% higher than that measured at ~ 10{sup −3} s{sup −1}. Analysis by electron backscatter diffraction shows that in the low strain rate regime (up to ~ 10 s{sup −1}) the deformation occurs mainly in evenly distributed bands, while in the dynamic regime the deformation is strongly localized in macroscopic shear bands accompanied by softening even after the onset of yielding. The Kernel Average Misorientation technique reveals a high level of lattice rotation within these bands that also carries intense shear. In addition, X-ray diffraction line profile analysis indicates that the sharp increase in the flow stress is mostly related to an increase of the dislocation density. - Highlights: • Strain rate effect on the plastic behavior of Ti{sub 20}Hf{sub 20}Zr{sub 20}Ta{sub 20}Nb{sub 20} HEA was studied. • Low strain rate regime was characterized by a continuous hardening. • At high strain rates softening occurred shortly after the onset of yielding. • Intense strain localization in shear bands occurred in the high strain rate regime. • High dislocation density explained the upturn of flow stress at high strain rates.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Ag nanowire percolating network embedded in indium tin oxide nanoparticles for printable transparent conducting electrodes

Solution-based printable transparent conducting electrodes consisting of Ag nanowire (NW) and indium tin oxide (ITO) nanoparticles (NPs) were fabricated by simple brush painting at room temperature under atmospheric ambient conditions. Effectively embedding the Ag NW percolating network into the ITO NPs provided a conduction path, led to a metallic conduction behavior of the ITO NPs/Ag NW/ITO NPs multilayer and supplied electrons into the ITO NPs. The optimized ITO NPs/Ag NW/ITO NPs multilayer showed a sheet resistance of 16.57 Ω/sq and an optical transparency of 79.50% without post annealing. Based on high resolution transmission electron microscope analysis, we investigated the microstructure and interface structure of the ITO NPs/Ag NW/ITO NPs multilayer electrodes and suggested a possible mechanism to explain the low resistivity of the multilayers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Atomic resolution strain analysis in highly textured FePt thin films

In this work, we present a detailed investigation of FePt-substrate interfaces and their influence towards the microstructural and magnetic configurations of the resulting metallic films. Discontinuous FePt films of roughly 15 nm thickness are deposited at 750 °C on MgO, MgAl{sub 2}O{sub 4}, SrTiO{sub 3}, and (La,Sr)(Al,Ta)O{sub 3} single-crystalline substrates. All of these films mainly show out-of-plane textured FePt islands; however, fractions of L1{sub 2} and in-plane oriented crystals are observed for the films on substrates with reduced lattice mismatch. Reduced easy axis coercivities and enhanced hard axis remanence values affirm this observation. Moreover, quantitative high-resolution transmission electron microscope analysis reveals that the reduced lattice mismatch results in a decreased density of dislocations, especially misfit dislocations, at the FePt-substrate interface. To further extend the research, carbon-doped FePt+32%C films are deposited on single-crystalline and sputtered MgO at 750 °C and 650 °C, respectively, to characterize the influence of a segregating media and reduced grain size. A comparison to the pure FePt sample reveals that the presence of seed layer grain boundaries leads to an increased fraction of in-plane oriented material, while the density of misfit dislocations solely depends on the degree of lattice mismatch.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Visualization of bacteriophage P1 infection by cryo-electron tomography of tiny Escherichia coli

Bacteriophage P1 has a contractile tail that targets the conserved lipopolysaccharide on the outer membrane surface of the host for initial adsorption. The mechanism by which P1 DNA enters the host cell is not well understood, mainly because the transient molecular interactions between bacteriophage and bacteria have been difficult to study by conventional approaches. Here, we engineered tiny E. coli host cells so that the initial stages of P1-host interactions could be captured in unprecedented detail by cryo-electron tomography. Analysis of three-dimensional reconstructions of frozen-hydrated specimens revealed three predominant configurations: an extended tail stage with DNA present in the phage head, a contracted tail stage with DNA, and a contracted tail stage without DNA. Comparative analysis of various conformations indicated that there is uniform penetration of the inner tail tube into the E. coli periplasm and a significant movement of the baseplate away from the outer membrane during tail contraction.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Thermal Stability of Quasi-1D NbS 3 Nanoribbons and Their Transformation to 2D NbS 2 : Insights from in Situ Electron Microscopy and Spectroscopy

Here in situ electron microscopy imaging and spectroscopy enabled us to study the evolution of quasi-1D NbS 3 -IV nanoribbons with respect to morphology and chemical structure at temperatures between room temperature and 1000 °C. Scanning transmission electron microscopy (STEM) experiments included imaging in the secondary electron, (transmitted) bright field, and high-angle annular dark-field modes while operating in the low kV regime. The results showed that NbS 3 -IV samples transform dramatically from smooth nanoribbons into highly textured configurations featuring polyhedral divots and steps. Similar in situ heating experiments conducted with aberration-corrected STEM revealed that bilayers of NbS 3 -IV chains convert topotactically into aligned 2H-NbS 2 sheets upon loss of sulfur. Atomic resolution imaging, fast Fourier transform analysis, and electron energy loss spectroscopy confirmed these chemical changes, from which we propose an atomistic mechanism for the NbS 3 -IV → 2H-NbS 2 conversion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Optimization of processing parameters on the controlled growth of c-axis oriented ZnO nanorod arrays

Optimization of the growth time parameter was conducted to synthesize high-quality c-axis ZnO nanorod arrays. The effects of the parameter on the crystal growth and properties were systematically investigated. Our studies confirmed that the growth time influence the properties of ZnO nanorods where the crystallite size of the structures was increased at higher deposition time. Field emission scanning electron microsope analysis confirmed the morphologies structure of the ZnO nanorods. The ZnO nanostructures prepared under the optimized growth conditions showed an intense XRD peak which reveal a higher c-axis oriented ZnO nanorod arrays thus demonstrating the formation of defect free structure.

77 NANOSCIENCE AND NANOTECHNOLOGY↗