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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 1,783 records · Page 99
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Synthesis and characterization of polyaniline coated gold nanocomposites

Considerable attention has been drawn during the last two decades to prepare nanocomposites consists of conducting polymer and noble metal due to their potential ability to generate a new class of material with novel optical, chemical, electronic or mechanical properties for various applications. In this work, an attempt has been made to synthesize nanocomposite of polyaniline (PANI) coated with gold nanoparticles (AuNPs) chemically with various types of surfactants such as polyvinylpyrrolidone (PVP), and sodium dodecyl sulphate (SDS) which act as stabilizing agents to help in stabilization of the PANI/Gold nanocomposites system. The synthesized nanocomposites were characterized by UV-Visible, field emission scanning electron microscope (FESEM) and particle size analyzer (PSA). The formation of finger like structure can be seen in the FESEM images when the AuNPs were incorporated into the polymer matrix. The EDX data showed that 18.66% and 12.67% of AuNPs atoms were present in the composite system thus proved the incorporation of AuNPs into the polymer matrix. A small red shift of the absorption peak in the UV-Vis of both PANI/AuNPs composites system may be due to the incorporation of AuNPs in the PANI matrix.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Hydrogen response of porous palladium nano-films

Palladium nanoparticles were synthesized by reducing sodium tetrachloropalladate at 100°C using Ethylene Glycol as reducing agent. The nanoparticles were characterized by TEM (Transmission Electron Microscopy), and optical absorption spectroscopy. The average particle size (<10 nm) was obtained from TEM images, and the palladium SPR (Surface Plasmon Resonance) absorption maxima was observed at ∼220 nm. The porous sensing films were prepared by drying the nanoparticles precipitate on cleaned glass substrates. The high porosity of these films, as revealed by Atomic Force Microscopy (AFM) studies, made these films suitable for hydrogen sensor applications. The resistance of the films, measured by making silver paste contacts on the porous surface, changed upon exposure to 1000 ppm hydrogen in nitrogen. Optimum sensor response was obtained at 50°C, beyond which it deteriorated. The total response comprising of initial rise and subsequent fall in resistance, is due to the formation of Pd-hydrides (whose resistivity is higher relative to Pd), and closure of interparticle gaps due to lattice expansion of palladium, respectively. A detailed analysis of the results based on the sensing mechanism has been discussed in the paper.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Photocatalytic behaviour of CdS/ZnS nanocomposite for dye degradation in presence of visible light

In the present work ZnS-CdS composite was prepared by hydrothermal method. The prepared samples were characterized by X-ray diffraction (XRD) to confirm formation of nano particles, Scanning electron microscopy (SEM) images exhibit nanoscale dimensions of as synthesized individual phases. UV/VIS spectra were recorded for evaluation of photophysical properties. The composite was explored as photocatalysts to study dye degradation using methylene blue in aqueous slurry under irradiation of 663 nm wavelength and congo red under irradiation of 493 nm wavelength. Under the same conditions the photocatalytic activity of the individual phases ZnS and CdS were also examined. The ZnS-CdS composite is found in enhancing the rate of photo degradation of toxic dyes as compare to ZnS and CdS individually in presence of visible light. This ZnS based metal sulphide/oxide semiconductor nanocomposites are high potential material for Photo-degradation of toxic dyes, and act as good photocatalyst in visible light.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Probing the properties of event-by-event distributions in Hanbury-Brown–Twiss radii

Hanbury-Brown–Twiss interferometry is a method which yields effective widths (i.e., “HBT radii”) of homogeneity regions in the fireballs produced in heavy ion collisions. Because the initial conditions of these collisions are stochastically fluctuating, the measured HBT radii also exhibit variation on an event-by-event basis. Yet, HBT measurements have, to date, been performed only on an ensemble-averaged basis, due to inherent limitations of finite particle statistics. Here, we show that experimental measurements to date are best characterized theoretically as weighted averages of the event-by-event HBT radii, and we propose a new method for extracting experimentally both the arithmetic mean and the variance of the event-by-event distribution of HBT radii. We demonstrate the extraction of the mean and variance of this distribution for a particular ensemble of numerically generated events, and offer some ideas to extend and generalize the method to enable measurement of higher moments of the HBT distribution as well.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Lifetimes of negative parity states in 162 Dy

Lifetimes of excited states in 162 Dy were measured using the (n,n’$γ$) reaction with the Doppler-Shift Attenuation Method (DSAM) at the University of Kentucky’s Accelerator Laboratory. A total of eighteen level lifetimes were obtained, including eleven negative-parity states, seven of which are new. These measurements significantly expand the experimental database of transition probabilities for negative-parity bands in the well-deformed rare earth region of nuclei. The extracted B(E1) and B(E2) values reveal enhanced interband E1 (10 -3 or 10 -4 ) W.u. and E2 strengths (several W.u.) between negative- and positive parity bands, particularly for the K π = $2^{-}_{1,2}$ bands decaying to the K π = $2^+_γ$ band, consistent with signatures of octupole-quadrupole coupling. In contrast, the K π = $0^{-}_1$ and K π = $1^{-}_3$ bands, which exhibit strong E1 transitions to the ground state band, are indicative of octupole-vibrational excitations built on the deformed ground state. Comparison of transition rates with Alaga rules supports this interpretation and distinguishes collective excitations from likely quasi-particle states. These new results establish 162 Dy as the most extensively characterized rare-earth nucleus for negative parity lifetimes and provide critical experimental benchmarks for theoretical models.

Aprahamian, A. [University of Notre Dame, IN (Unit↗
DOE OSTI2018

Testing of SSR1 Production Tuner for PIP-II

The PIP-II project at Fermilab is a proton driver linac calling for the use of five different, novel cavity geometries. Prototyping at Fermilab is in the advanced stages for the low-beta single-spoke resonator (SSR1) and associated technologies. A production tuner design has been fabricated and tested, both warm and cold in the Spoke Test Cryostat (STC). This paper will present the detailed studies on this tuner, including slow motor/piezoelectric tuner range and hysteresis as well as dynamic mechanical system characterization.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Taus at ATLAS

The grant "Taus at ATLAS" supported the group of Sarah Demers at Yale University over a period of 8.5 months, bridging the time between her Early Career Award and her inclusion on Yale's grant cycle within the Department of Energy's Office of Science. The work supported the functioning of the ATLAS Experiment at CERN's Large Hadron Collider and the analysis of ATLAS data. The work included searching for the Higgs Boson in a particular mode of its production (with a W or Z boson) and decay (to a pair of tau leptons.) This was part of a broad program of characterizing the Higgs boson as we try to understand this recently discovered particle, and whether or not it matches our expectations within the current standard model of particle physics. In addition, group members worked with simulation to understand the physics reach of planned upgrades to the ATLAS experiment. Supported group members include postdoctoral researcher Lotte Thomsen and graduate student Mariel Pettee.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Detection of Upwind Pathogens Using Aircraft and Ground Stations

The first reported investigations of microorganism occurrence in the air can be traced back to early 19th century. Since then the study of bioaerosols have come a long way, however, it remains a poorly understood area(Després et al. 2012). The actual identity, diversity, and abundance of distinct types of bioaerosol particles as well as their temporal and spatial variability are not well characterized. Bioaerosols play a key role in the dispersal of reproductive units from plants and microbes (pollen, spores, etc.), for which the atmosphere enables transport over geographic barriers and long distances(FröhlichNowoisky et al. 2016). The dispersal of plant, animal, and human pathogens and allergens has major implications for agriculture and public health. We hypothesized that airborne microbes can reach the upper atmosphere (i.e., above the boundary layer ~2 km in altitude) and deliver disease into downwind destinations. We utilized a unique set of bioaerosol samples from atmospheric aircraft observatories (NASA) to study the microbial diversity, abundance, and viability of bioaerosols reaching California during the springtime when the jet stream delivers the largest amount of Asian transpacific aerosols to N. America. We collaborated with a NASA Ames with unique access to upper troposphere and lower stratosphere bioaerosol samples on the Pacific Coast of California. We analyzed the aerosol samples using microbiological techniques, shotgun metagenomic sequencing and advanced bioinformatic tools to identify the viable and total microbial species that were detected. A number of bacterial and fungal species were identified. This study provided a deeper understanding of the microbial species that can survive in the upper atmospheric conditions. This study set the foundation for future studies on better understanding of the potential impact of airborne microbes on disease transmission affecting human, animal, or crop health.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

X-Ray Spectra Characterization [Slides]

This report details motivation, existing literature, methods, assumptions, failures, results and future study for the author's work in x-ray spectra characterization.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Evaluation of Radiography for TRISO Buffer Layer Density Measurement

Tristructural isotropic (TRISO) fuel particles consist of a central uranium-bearing kernel and a series of coating layers designed to retain fission products and to ensure fuel performance. Several parameters such as thickness and density must be measured for these coating layers to show that they conform with fuel specifications. Current methods for measuring the density of pyrolytic carbon and silicon carbide layers (liquid gradient density column) and the buffer layer (mercury porosimetry) generate Resource Conservation and Recovery Act (RCRA) radiological-mixed waste. In addition, measurement of buffer and inner pyrolytic carbon layer densities require hot sampling or interrupted coating runs and the mercury porosimetry method used for buffer density measurement only measures the mean buffer density, not the interparticle distribution. A new approach has been evaluated to measure the density of coating layers in TRISO particles based on the dependence of x-ray attenuation in radiographs on material density. This method does not generate RCRA mixed waste, measures density on a particle-by-particle basis, and in principle is capable of measuring the density of all coating layers in a single process. Initial results using thinned TRISO particle sections to evaluate radiography measurement of density as a quality control characterization method are reported herein. In this work, the primary focus is on measurement of the density of the buffer layer; however, with appropriate calibration the method should be applicable to other coating layers. Improvements to the initial method and a full demonstration of the method on the remaining coating layers may be pursued as a future effort.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Enhanced Feedstock Characterization and Modeling to Facilitate Optimal Preprocessing and Deconstruction of Corn Stover (Final Report)

This project addresses the challenge of processing corn stover by fractionating this biomass feedstock to both streamline processing and generate new potential co-products. Additionally, the project developed new field-deployable analytical tools that can be coupled with empirical models that were used to predict feedstock properties and processing performance. The overall scope of this project was: (1) identify conditions for optimal corn stover fractionation using a two- stage physical fractionation, (2) assess how physical fractionation impacts properties, partitioning of biomass, and response to processing, (3) further adapt, develop, and validate several advanced characterization tools for assessing biomass properties that can be linked to processing behavior, and (4) develop and validate predictive models based on measurements that can be performed “in the field” or “at the biorefinery gate” to predict feedstock processing behavior (preprocessing and deconstruction). The first objective employed pre-separation processing (size reduction) which was next subjected to enhanced separations to yield fractions enriched or depleted in select compositional components or properties. For the second objective, fractions were screened for their response to post-separation processing (pretreatment and enzymatic hydrolysis). Detailed characterization profiles were developed and dynamic image analysis to assess distribution of particle size and morphology. For the final objective, we utilized these tools to develop empirical models to assess the relative abundance of tissue type in order to assess fractionation efficacy and to predict fraction performance during pretreatment and enzymatic hydrolysis.

09 BIOMASS FUELS↗
DOE OSTI2021

Real-Time Identification of Oxygen Vacancy Centers in LiNbO 3 and SrTiO 3 during Irradiation with High Energy Particles

Oxygen vacancies are known to play a central role in the optoelectronic properties of oxide perovskites. A detailed description of the exact mechanisms by which oxygen vacancies govern such properties, however, is still quite incomplete. The unambiguous identification of oxygen vacancies has been a subject of intense discussion. Interest in oxygen vacancies is not purely academic. Precise control of oxygen vacancies has potential technological benefits in optoelectronic devices. In this review paper, we focus our attention on the generation of oxygen vacancies by irradiation with high energy particles. Irradiation constitutes an efficient and reliable strategy to introduce, monitor, and characterize oxygen vacancies. Unfortunately, this technique has been underexploited despite its demonstrated advantages. This review revisits the main experimental results that have been obtained for oxygen vacancy centers (a) under high energy electron irradiation (100 keV–1 MeV) in LiNbO 3 , and (b) during irradiation with high-energy heavy (1–20 MeV) ions in SrTiO 3 . In both cases, the experiments have used real-time and in situ optical detection. Moreover, the present paper discusses the obtained results in relation to present knowledge from both the experimental and theoretical perspectives. Our view is that a consistent picture is now emerging on the structure and relevant optical features (absorption and emission spectra) of these centers. One key aspect of the topic pertains to the generation of self-trapped electrons as small polarons by irradiation of the crystal lattice and their stabilization by oxygen vacancies. What has been learned by observing the interplay between polarons and vacancies has inspired new models for color centers in dielectric crystals, models which represent an advancement from the early models of color centers in alkali halides and simple oxides. The topic discussed in this review is particularly useful to better understand the complex effects of different types of radiation on the defect structure of those materials, therefore providing relevant clues for nuclear engineering applications.

36 MATERIALS SCIENCE↗
NASA NTRS1979

A high resolution holographic particle sizing system

This paper will review briefly the requirements of holography with respect to particle sizing techniques. A holographic construction system and the appropriate reconstruction system will be discussed regarding their characteristics and performance (i.e. system resolution, magnification, system aberration and correction of aberrations, and maximum total test volume). The capabilities of a commercial particle sizing system used to obtain particle sizes and distribution information from reconstructed holograms will be described and characterized. It will be shown that by using the methods described, high resolution throughout large test volumes can be achieved.

Witherow, W. K.↗
NASA NTRS1981

A study of stratospheric aerosol maturity

A sampling and analysis technique that uses the binomial distribution to characterize stratospheric aerosol populations at the 95% level of confidence is described. Particle samples obtained over Alaska during July 15-19, 1979, are used; the results show the presence of more small particles at lower altitude than at high altitudes. Calculations of the surface area and volume distributions for all aerosol samples collected are given. Evidence from these data suggests either that Aitken nuclei are injected or diffused across the tropopause and rise into the stratosphere, where they mature into larger particles, or nuclei form in the lower stratosphere and become mature aerosols at high altitude. Samples obtained at another site give the same results, supporting the view that the process of injection or nucleation and maturing of aerosols with altitude may be global and need not occur only in locations exhibiting unique meteorologic features.

Oberbeck, V. R.↗
NASA NTRS1983

Simulation of transport and removal processes of the Saharan dust

A planetary boundary layer (PBL) model has been modified to include a Saharan air layer containing the bulk of Saharan dust. The Saharan air layer is recognized as a deep mixed layer, which extends up to 4-6 km during hot summer months and is characterized by high potential temperature and high dust concentration. Microphysical processes of particle coagulation and sedimentation have been coupled with dynamic processes to simulate the evolution of dust particles. In agreement with observations, simulations indicate that dust particles greater than 10 micron radius can be produced and transported in the Sahara air layer across the Atlantic Ocean, while dust concentrations in the PBL over the Atlantic Ocean are smaller by a factor of two or more than in the Saharan air layer.

Lee, I.-Y.↗
NASA NTRS1982

Convective and interfacial instabilities during solidification of succinonitrile containing ethanol

Even though slow convective flow is difficult to detect in solidifying metals, it can readily be observed in transparent materials by observing the motion of small neutrally buoyant particles. Succinonitrile, which solidifies with an unfaceted solid/liquid interface and has well characterized physical properties, is considered an excellent material for such studies. For studies of solute-induced convection, ethanol is a useful addition to succinonitrile since it has a lower density and a somewhat similar molecular structure. Samples of high purity and ethanol-doped succinonitrile are unidirectionally solidified in a vertical temperature gradient. Latex mimcrospheres 2 microns in diameter are suspended in the liquid to reveal the convective flow. Convective and morphological stability is observed as a function of solute concentration and growth velocity. These measurements are compared with theoretical calculations that predict the transition from stability to instability as a function of solidification conditions. The predicted transitions occur at low concentrations and solidification velocities; for this reason, extreme care must be taken in order to eliminate the effects of impurities or thermally induced convection.

Schaefer, R. J.↗
NASA NTRS1988

In situ chemical analyses of extraterrestrial bodies

One of the most important tasks on any sample return mission will have to be a quick sample characterization in order to guarantee a variety of collected samples. An alpha particle instrument with alpha, proton and X-ray modes can provide a quick and almost complete chemical analysis of Mars samples. This instrument is based on three interactions of the alpha particles from a radioactive source with matter: elastic scattering of the alpha particles by nuclei (alpha mode), (alpha,p) nuclear reaction with some light elements (proton mode), and excitation of the atomic structure of atoms by alpha particles, leading to emission of characteristic X-rays of the lunar surface at three sites during the Surveyor mission of 1967 to 1968. Since then the instrument has been improved and miniaturized substantially. As shown in the past, the alpha particle instrument can operate under Martian conditions without any degradation in the performance. The alpha and proton modes can provide vital information about the light elements, while the X-ray mode with its ambient temperature X-ray detector will be useful for the heavier elements. The excitation of the atomic structure is provided by the same alpha radioactive source that is used by alpha and proton modes or by an auxiliary X-ray source that is selected to enhance the sensitivity to some important geochemical elements.

Economou, Thanasis E.↗
NASA NTRS1989

Three-dimensional quantitative flow diagnostics

The principles, capabilities, and practical implementation of advanced measurement techniques for the quantitative characterization of three-dimensional flows are reviewed. Consideration is given to particle, Rayleigh, and Raman scattering; fluorescence; flow marking by H2 bubbles, photochromism, photodissociation, and vibrationally excited molecules; light-sheet volume imaging; and stereo imaging. Also discussed are stereo schlieren methods, holographic particle imaging, optical tomography, acoustic and magnetic-resonance imaging, and the display of space-filling data. Extensive diagrams, graphs, photographs, sample images, and tables of numerical data are provided.

Miles, Richard B.↗