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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 OSTI2017

Quantitative Analysis of the Morphology of {101} and {001} Faceted Anatase TiO 2 Nanocrystals and Its Implication on Photocatalytic Activity

The atomistic structure and morphology (shape and size) of nanomaterials have strong influences on their physical and chemical properties. However, many characterization techniques focus exclusively on one length-scale regime or another when developing quantitative morphology/structural models. In this article, we demonstrate that powder X-ray diffraction and neutron pair distribution function (PDF) can be used to obtain accurate average morphology and atomistic structure of {001} and {101} faceted anatase TiO 2 nanocrystals based on differential evolution refinements using Debye scattering equation calculations. It is also demonstrated that the morphology polydispersity of TiO 2 nanocrystals can be effectively obtained from the diffraction data via a numerical refinement routine. The morphology refinement results are in good agreement with those from transmission electron microscopy and the modeling of small angle neutron scattering data. This method is successfully used to quantify the facet-specified photocatalytic hydrogen evolution activity of anatase TiO 2 nanocrystals with different {001} to {101} ratios. It is found that the sample with an intermediate amount of both {001} and {101} facets shows the best photocatalytic hydrogen evolution reaction (HER) activity. It is expected that the simultaneous structure and morphology refinement technique can be generally used to study the relationship between morphology and functionality of nanomaterials.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Analysis of textural properties of CaO-based CO 2 sorbents by ex-situ USAXS

Here in this work, the micro-textural properties of CaO-based CO 2 sorbents prepared in a thermo-gravimetric reactor were investigated by ex situ synchrotron-based Small Angle X-ray Scattering (SAXS), Ultra Small Angle X-ray Scattering (USAXS) and Wide Angle X-ray Scattering (WAXS). Six sorbent samples were produced by calcination in vacuum at different temperatures and durations of the heating step; additionally, four partially carbonated samples were produced, after calcination in vacuum, at different CaO conversions. The scattering intensity profiles were analyzed by means of the Unified Fit model. Bimodal pore size distributions (micro-pores and meso-pores) were identified and the micro-textural properties (porosity, specific surface and pore radius of gyration) of each of the two pore populations were quantified both for the calcined and for the carbonated samples. The micro-textural properties of a few calcined samples were compared with N 2 -adsorption measurements. For each pore population, the trends of porosity, specific surface and pore radius of gyration, in addition to the pore number density and sphericity factor, were obtained versus time during the calcination and versus the CaO conversion during the carbonation. The relevance of micro-pores with respect to macro-pores was assessed both as far as the porosity impact on the CO 2 capture capacity and as far as the specific surface impact on the carbonation kinetics. For the calcined samples, the micro-textural properties of a partially calcined sample were compared with those of the completely calcined samples, and pore correlation distances were determined. Finally, for the carbonated samples, the specific surface per unit of particle volume results linearly dependent on the CaO conversion and, if expressed per unit of mass of unreacted CaO, does not change significantly for most of the CaO carbonation.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Improving the spatial dynamic range of digital inline particle holography

Digital in-line holography (DIH) has been proven to provide three-dimensional droplet position, size, and velocity distributions with a single-camera. This data is crucial for understanding multi-phase flows. In this work, we examine the performance of this diagnostic in the limit of very small particles, on the order of a pixel in diameter and smaller, and propose a post-processing method to improve them: Lanczos interpolation. The Lanczos interpolation kernel is the digital implementation of the Whittaker sinc filter, and strikes a compromise between maintaining the spatial frequency ceiling of the original digital image and computational cost of the interpolation. Without Lanczos interpolation, or super-sampling, the ultimate detectable particle size floor is on the order of 4 pixel widths. We show in this work that this limit can be reduced by 50% or more with super-sampling, depending upon the desired diameter accuracy, and examine the effect of super-sampling on the resulting accuracy of the extracted size and position of spherical particles. Extending this resolution limit increases the overall detection efficiency of the diagnostic. Since this increases the spatial dynamic range of the diagnostic, it can also allow a larger field-of-view to be captured with the same particle size floor.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Unfolding of IgG domains detected by non-reducing SDS-PAGE

Highlights: • Aberrant artefactual mAb masses and size heterogeneity noted by non-reducing SDS-PAGE. • This effect depends on pre-electrophoresis sample heating temperatures and conditions. • These phenomena are also observed for a commercial human IgG{sub 1} polyclonal antibody. • Multiple observed bands hypothesized to reflect IgG domain thermal unfolding in SDS. • These results are likely relevant to analyses of many monoclonal and polyclonal Abs. Monoclonal antibodies are very important in modern therapeutics and constitute a substantial percentage of newly approved drugs. Every therapeutic monoclonal antibody must be analyzed for structural and functional integrity, and all protein heterogeneities need to be identified and quantified. The conformational stabilities of the monoclonal antibodies are also important for antibody storage and handling stabilities. One of the first and simplest of the structural analysis techniques utilized is SDS-PAGE, which can be performed both with and without prior reduction to break disulfide bonds. This permits sizing of both heavy and light chains in the reduced condition, and sizing of the intact antibody and any disulfide aggregates in the non-reduced condition. Analyzing our human anti-cocaine monoclonal antibody, we noted unexpectedly larger apparent molecular weights and apparent protein size heterogeneities using non-reducing SDS-PAGE. These apparent molecular weight heterogeneities are not consistent with other analysis techniques. Heterogeneities were noted using several heating and pre-electrophoretic sample preparation protocols, and are modified by the inclusion of small concentrations of certain alcohols such as propanol and butanol. All of these unexpected results were also observed for a commercial human IgG{sub 1} antibody, suggesting that these observations are applicable to IgGs in general. Thus, careful attention must be paid to the interpretation of non-reducing SDS-PAGE results for IgGs. It is hypothesized that differential thermal unfolding of the Fab, CH2 and CH3 domains of the IgGs in SDS give rise to the stable, discrete bands observed using different heating protocols prior to non-reducing SDS-PAGE.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

Hydrothermal synthesis and characteristics of anions-doped calcium molybdate red powder phosphors

Graphical abstract: - Highlights: • Four anion-doped CaMoO{sub 4}:Eu{sup 3+} red phosphors were prepared by hydrothermal approach. • Some samples exhibit nearly spherical morphology and well-distributed fine particles. • The red luminescence can be obviously enhanced after certain amount of anion doping. • The improved phosphor system is a potential candidate for white LED applications. - Abstract: Applying hydrothermal and subsequent heat-treatment process, CaMoO{sub 4}:Eu{sup 3+} was doped with four anions (SiO{sub 3}{sup 2−}, PO{sub 4}{sup 3−}, SO{sub 4}{sup 2−} and ClO{sub 3}{sup −}) to prepare fine red powder phosphors. The introduction of small amount of anions into the host had little influence on the structure, which was confirmed by X-ray diffraction patterns. The anion-doped phosphor samples (except SiO{sub 3}{sup 2−}) exhibited nearly spherical morphology, and the particle sizes were in the range of 0.3–0.4 μm for SO{sub 4}{sup 2−}-doped samples, and 0.8–1.2 μm for PO{sub 4}{sup 3−} and ClO{sub 3}{sup −}-doped samples. Excited with 395 nm near-UV light, all samples showed typical Eu{sup 3+} red emission at 615 nm, and PO{sub 4}{sup 3−}, SO{sub 4}{sup 2−} and ClO{sub 3}{sup −}-doped samples enhanced the red luminescence as compared with the individual CaMoO{sub 4}:Eu{sup 3+} sample. In particular, relative emission intensity for optimum ClO{sub 3}{sup −}-doped phosphors reached more than 6-fold that of the commercial red phosphor, which is highly desirable for the powder phosphors used in the solid-state lighting industry.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Synthesis, characterization and magnetic property of maghemite (γ-Fe{sub 2}O{sub 3}) nanoparticles and their protective coating with pepsin for bio-functionalization

Highlights: • Maghemite nanoparticles were prepared by a modified co-precipitation method. • Nanoparticles were then successfully coated with pepsin for bio-functionlization. • XRD and Mössbauer spectra confirmed the maghemite phase of the nanoparticles. • Magnetic data were analysed to evaluate particle size, anisotropy etc. - Abstract: Maghemite nanoparticles (γ-Fe{sub 2}O{sub 3}) are prepared by co-precipitation method. To obtain bio-functionalized magnetic nanoparticles for magnetically controlled drug delivery, the prepared nanoparticles are successfully coated with pepsin, a bio-compatible polymer and digestive enzyme. Crystallographic phase of the nanoparticles is confirmed by X-ray diffractograms (XRD), high resolution transmission electron microscopy (HRTEM) and {sup 57}Fe Mössbauer spectrometry. The average size of nanoparticles/nanocrystallites is estimated from the (3 1 1) peak of the XRD pattern using Debye–Scherrer formula. Results of HRTEM of coated and bare samples are in good agreement with those extracted from the XRD analysis. The dynamic magnetic properties are observed and different quantities viz., coercive field, magnetization, remanence, hysteresis losses etc., are estimated, which confirmed the presence of superparamagnetic relaxation of nanoparticles. Mössbauer spectra of the samples recorded at both 300 and 77 K, confirmed that the majority of particles are maghemite together with a very small fraction of magnetite nanoparticles.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Active learning of polarizable nanoparticle phase diagrams for the guided design of triggerable self-assembling superlattices

Polarizable nanoparticles are of interest in materials science because of their rich and complex phase behavior that can be used to engineer nanostructured materials with long-range crystalline order. To understand and rationally navigate the design space of polarizable nanoparticles for self-assembling highly ordered superlattices, we developed a coarse-grained computational model to describe the nanoparticle-nanoparticle interactions in implicit solvent and employ the computationally efficient image method to model many-body polarization interactions. We conducted high-throughput virtual screening over a five-dimensional particle design space spanned by temperature, particle size, particle charge, particle dielectric, and solvent dielectric using enhanced sampling molecular dynamics calculations within an active learning framework to efficiently map out the regions of thermodynamic stability of the self-assembled aggregates. We validate our predictions in comparisons against small angle x-ray scattering measurements of gold nanoparticles surface functionalized with metal chalcogenide ligands. Lastly, we use our validated phase maps to computationally design switchable nanostructured materials capable of triggered assembly and disassembly as a function of temperature and solvent dielectric with potential applications as sensors, smart windows, optoelectronic devices, and in medical diagnostics.

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

Stochastic, real-space, imaginary-time evaluation of third-order Feynman–Goldstone diagrams

A new, alternative set of interpretation rules of Feynman–Goldstone diagrams for many-body perturbation theory is proposed, which translates diagrams into algebraic expressions suitable for direct Monte Carlo integrations. A vertex of a diagram is associated with a Coulomb interaction (rather than a two-electron integral) and an edge with the trace of a Green's function in real space and imaginary time. With these, 12 diagrams of third-order many-body perturbation (MP3) theory are converted into 20-dimensional integrals, which are then evaluated by a Monte Carlo method. It uses redundant walkers for convergence acceleration and a weight function for importance sampling in conjunction with the Metropolis algorithm. The resulting Monte Carlo MP3 method has low-rank polynomial size dependence of the operation cost, a negligible memory cost, and a naturally parallel computational kernel, while reproducing the correct correlation energies of small molecules within a few mE{sub h} after 10{sup 6} Monte Carlo steps.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

PRECIOUS METALS IN SDSS QUASAR SPECTRA. I. TRACKING THE EVOLUTION OF STRONG, 1.5 < z < 4.5 C IV ABSORBERS WITH THOUSANDS OF SYSTEMS

We have vastly increased the C IV statistics at intermediate redshift by surveying the thousands of quasars in the Sloan Digital Sky Survey (SDSS) Data-Release 7. We visually verified over 16,000 C IV systems with 1.46 < z < 4.55-a sample size that renders Poisson error negligible. Detailed Monte Carlo simulations show that we are approximately 50% complete down to rest equivalent widths W {sub r} Almost-Equal-To 0.6 A. We analyzed the sample as a whole and in 10 small redshift bins with approximately 1500 doublets each. The equivalent width frequency distributions f(W {sub r}) were well modeled by an exponential, with little evolution in shape. In contrast with previous studies that modeled the frequency distribution as a single power law, the fitted exponential gives a finite mass density for the C IV ions. The comoving line density dN{sub CIV}/dX evolved smoothly with redshift, increasing by a factor of 2.37 {+-} 0.09 from z = 4.55-1.96, then plateauing at dN{sub CIV}/dX{approx}0.34 for z = 1.96-1.46. Comparing our SDSS sample with z < 1 (ultraviolet) and z > 5 (infrared) surveys, we see an approximately 10-fold increase in dN{sub CIV}/dX over z Almost-Equal-To 6 {yields} 0, for W {sub r} {>=} 0.6 A. This suggests a monotonic and significant increase in the enrichment of gas outside galaxies over the 12 Gyr lifetime of the universe.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Construction of a New MgB 2 Coating System for 1.3-GHz Superconducting RF Cavities at LANL

After many years of evaluating MgB 2 films prepared with various techniques for the application to superconducting radio-frequency (SRF) cavities, we have decided to build a system to coat full-size 1.3-GHz elliptical cavities. This paper describes the design and construction of the system. Additionally, we briefly describe experimental results with a small system and first tests with the new large system. In conclusion, we were able to obtain superconducting samples with a T c of up to 38 K with the small system, but we have not been able to get any superconducting samples with the new system yet.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Laboratory and field evaluation of the Aerosol Dynamics Inc. concentrator (ADIc) for aerosol mass spectrometry

Abstract. An air-to-air ultrafine particle concentrator (Aerosol Dynamics Inc. concentrator; ADIc) has been designed to enhance online chemical characterization of ambient aerosols using aerosol mass spectrometry. The ADIc employs a three-stage, moderated water-based condensation growth tube coupled to an aerodynamic focusing nozzle to concentrate fine particles into a portion of the flow. The system can be configured to sample between 1.0 and 1.7 L min -1 , with an output concentrated flow between 0.08 and 0.12 L min -1 , resulting in a theoretical concentration factor (sample flow/output flow) ranging from 8 to 21. Laboratory tests with monodisperse particles show that the ADIc is effective for particles as small as 10 nm. Laboratory experiments conducted with the Aerosol Mass Spectrometer (AMS) showed no shift in the particle size with the ADIc, as measured by the AMS particle time-of-flight operation. The ADIc-AMS system was operated unattended over a 1-month period near Boston, Massachusetts. Comparison to a parallel AMS without the concentrator showed concentration factors of 9.7±0.15 and 9.1±0.1 for sulfate and nitrate, respectively, when operated with a theoretical concentration factor of 10.5±0.3. The concentration factor of organics was lower, possibly due to the presence of large particles from nearby road-paving operations and a difference in aerodynamic lens cutoff between the two AMS instruments. Another field deployment was carried out in Helsinki, Finland. Two ~10 d measurement periods showed good correlation for the concentrations of organics, sulfate, nitrate and ammonium measured with an Aerosol Chemical Speciation Monitor (ACSM) with the ADIc and a parallel AMS without the concentrator. Additional experiments with an AMS alternating between the ADIc and a bypass line demonstrated that the concentrator did not significantly change the size distribution or the chemistry of the ambient aerosol particles.

47 OTHER INSTRUMENTATION↗
NASA NTRS1989

Analysis of particulates of comet nucleus samples: Possible use of olivine as indicator phase

The electron microprobe is a proven instrument for particulate analysis and modifications are possible for in situ analysis of particulates in ice at temperatures near that of liquid nitrogen. Present sample requirements allow for polished samples with 0.25 x 0.25 dimensions to be maintained in the sample chamber of a modern electron probe (CAMECA SX-50) at a temperature of -150 C; larger samples are possible but at higher temperatures as determined by thermal conductivity. The major problem is transport and insertion of samples into the instrument through vacuum interlocks. The manufacturer of the above microprobe has designed an exchange mechanism to allow storage and transport of samples previously prepared for their sample holder which attaches to their instrument allowing extraction and insertion of samples while maintaining -150 C temperature. An important test will be the capability of preparing polished surfaces of an ice-particulate sample without loss of particles and at low temperatures. While thin sections of water ice are routine, these are not examined for particulate material and are prepared at temperatures easily obtained in room-size volumes. Anticipated problems include rounding of small grains in the relatively soft ice matrix and the technical problem of dry polishing.

Steele, I. M.↗
NASA NTRS2005

Experimental Investigation of Magnesium Powder Combustion With C02 for Mars Ascent Applications

Combustion of metals with CO2 has been identified as a possible propellant for Mars ascent applications. CO2 could be condensed from the Martian atmosphere, reducing the amount of propellant that must be transported from Earth. An attractive feature of this approach compared to other in situ propellant concepts is that no chemical processing on Mars is required. Magnesium has been identified as the most promising metal for this application because it ignites and burns easily in CO2. Preliminary systems studies indicate a 2 to 1 delivered mass advantage for Mg ascent propulsion using in situ C02, as compared to a conventional storable propellant system. The Propulsion Research Center at MSFC is undertaking an experimental investigation of magnesium powder combustion with CO2 in order to provide fundamental data on the combustion performance of Mg powder + CO2 mixtures needed to assess the feasibility of developing a practical Mg powder + CO2 rocket engine. Initial combustion experiments will be carried out in a small scale atmospheric pressure dump combustor. Effects of varying the Mg particle size, firing rate and O/F ratio on combustion stability and efficiency will be investigated. The combustion process will be characterized by optical flame measurements and extraction of combustion product samples. The experimental facility is currently being prepared and combustion experiments will begin during the first quarter of 2005. The final paper will describe the test facility and initial experimental results.

Foote, John P.↗
DOE OSTI2012

Pore structure characterization of North American shale gas reservoirs using USANS/SANS, gas adsorption, and mercury intrusion

Small-angle and ultra-small-angle neutron scattering (SANS and USANS), low-pressure adsorption (N 2 and CO 2 ), and high-pressure mercury intrusion measurements were performed on a suite of North American shale reservoir samples providing the first ever comparison of all these techniques for characterizing the complex pore structure of shales. The techniques were used to gain insight into the nature of the pore structure including pore geometry, pore size distribution and accessible versus inaccessible porosity. Thus, reservoir samples for analysis were taken from currently-active shale gas plays including the Barnett, Marcellus, Haynesville, Eagle Ford, Woodford, Muskwa, and Duvernay shales.

04 OIL SHALES AND TAR SANDS↗
DOE OSTI2023

Similarity Downselection: Finding the n Most Dissimilar Molecular Conformers for Reference-Free Metabolomics

Computational methods for creating in silico libraries of molecular descriptors (e.g., collision cross sections) are becoming increasingly prevalent due to the limited number of authentic reference materials available for traditional library building. These so-called “reference-free metabolomics” methods require sampling sets of molecular conformers in order to produce high accuracy property predictions. Due to the computational cost of the subsequent calculations for each conformer, there is a need to sample the most relevant subset and avoid repeating calculations on conformers that are nearly identical. The goal of this study is to introduce a heuristic method of finding the most dissimilar conformers from a larger population in order to help speed up reference-free calculation methods and maintain a high property prediction accuracy. Finding the set of the n items most dissimilar from each other out of a larger population becomes increasingly difficult and computationally expensive as either n or the population size grows large. Because there exists a pairwise relationship between each item and all other items in the population, finding the set of the n most dissimilar items is different than simply sorting an array of numbers. For instance, if you have a set of the most dissimilar n = 4 items, one or more of the items from n = 4 might not be in the set n = 5. An exact solution would have to search all possible combinations of size n in the population exhaustively. We present an open-source software called similarity downselection (SDS), written in Python and freely available on GitHub. SDS implements a heuristic algorithm for quickly finding the approximate set(s) of the n most dissimilar items. We benchmark SDS against a Monte Carlo method, which attempts to find the exact solution through repeated random sampling. We show that for SDS to find the set of n most dissimilar conformers, our method is not only orders of magnitude faster, but it is also more accurate than running Monte Carlo for 1,000,000 iterations, each searching for set sizes n = 3–7 out of a population of 50,000. We also benchmark SDS against the exact solution for example small populations, showing that SDS produces a solution close to the exact solution in these instances. Using theoretical approaches, we also demonstrate the constraints of the greedy algorithm and its efficacy as a ratio to the exact solution.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2014

Survival Outcome After Stereotactic Body Radiation Therapy and Surgery for Stage I Non-Small Cell Lung Cancer: A Meta-Analysis

Purpose: This study compared treatment outcomes of stereotactic body radiation therapy (SBRT) with those of surgery in stage I non-small cell lung cancer (NSCLC). Methods and Materials: Eligible studies of SBRT and surgery were retrieved through extensive searches of the PubMed, Medline, Embase, and Cochrane library databases from 2000 to 2012. Original English publications of stage I NSCLC with adequate sample sizes and adequate SBRT doses were included. A multivariate random effects model was used to perform a meta-analysis to compare survival between treatments while adjusting for differences in patient characteristics. Results: Forty SBRT studies (4850 patients) and 23 surgery studies (7071 patients) published in the same period were eligible. The median age and follow-up duration were 74 years and 28.0 months for SBRT patients and 66 years and 37 months for surgery patients, respectively. The mean unadjusted overall survival rates at 1, 3, and 5 years with SBRT were 83.4%, 56.6%, and 41.2% compared to 92.5%, 77.9%, and 66.1% with lobectomy and 93.2%, 80.7%, and 71.7% with limited lung resections. In SBRT studies, overall survival improved with increasing proportion of operable patients. After we adjusted for proportion of operable patients and age, SBRT and surgery had similar estimated overall and disease-free survival. Conclusions: Patients treated with SBRT differ substantially from patients treated with surgery in age and operability. After adjustment for these differences, OS and DFS do not differ significantly between SBRT and surgery in patients with operable stage I NSCLC. A randomized prospective trial is warranted to compare the efficacy of SBRT and surgery.

62 RADIOLOGY AND NUCLEAR MEDICINE↗