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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 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Influence of yttrium content on the location of rare earth ions in LYSO:Ce crystals

Single-crystal X-ray diffraction (SCD), X-ray fluorescence (XRF), inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray excited luminescence (XEL) measurements were performed to investigate structure details and segregation coefficients of (Lu{sub 1−x}Y{sub x}){sub 2}SiO{sub 5}:Ce (x=0 at%, 8.7 at%, 25.7 at%, 44.7 at%, 65.7 at%, 87.9 at% and 100 at%). Y{sup 3+} cations were found to have a preferential occupation for RE1 site (7-oxygen-coordinated) over RE2 site (6-oxygen-coordinated), which results in a greater increase of cell parameter c than that of a with increase in Y content due to LYSO's microstructure characteristics. Results presented here revealed that the less the difference in electronegativity and effective ionic radius between the two ions, the easier substitution of one ion by the other, and hence the higher segregation coefficients. Besides, the contribution of luminescence of Ce1 and Ce2 in the whole XEL was evaluated, and the location of Ce{sup 3+} ion was discussed. - Graphical abstract: Segregation coefficients of (Lu{sub 1−x}Y{sub x}){sub 2}SiO{sub 5}:Cce:italic> at RT/ce:italic>. Display Omitted.

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

Precipitation of aluminum nitride in a high strength maraging steel with low nitrogen content

In the present work, aluminum nitride (AlN) precipitation was investigated in a X23NiCoCrMoAl13-6-3 maraging steel with low nitrogen content (wt.% N = 5.5 ppm). A reliable and robust automatic method by scanning electron microscopy observations coupled with energy dispersive X-ray spectroscopy was developed for the quantification of AlN precipitates. The first stage was to identify the solvus temperature and to develop a heat treatment able to dissolve the AlN precipitates. The experimental determination of equilibrium conditions and solvus temperature show good agreement with ThermoCalc® simulation. Then, from this AlN-free state, the cooling rate, isothermal holding time and temperature were the subject of an intensive investigation in the austenite region of this maraging steel. In spite of the high temperatures used during heat treatments, the growth kinetic of the largest AlN precipitates (> 1 μm) is slow. The cooling rate has a major effect on the size and the number density of AlN due to a higher driving force for nucleation at low temperatures. At last, quenching prior to isothermal annealing at high temperatures leads to fine and dense AlN precipitation, resulting from the martensite to austenite transformation. Experimental results will be discussed and compared with kinetic data obtained with the mobility database MobFe2 implemented in Dictra® software. - Highlights: • Slow dissolution kinetic of AlN precipitates due to both their large size and small chemical driving force • Significant effects of cooling rate prior isothermal heat treatment, holding time and temperature on AlN precipitation • Size of AlN precipitates can be reduced by quenching prior isothermal holding. • Fine precipitation of AlN related to the α → γ transformation.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Solid-state transformation of Fe-rich intermetallic phases in Al–5.0Cu–0.6Mn squeeze cast alloy with variable Fe contents during solution heat treatment

The Al–5.0 wt.% Cu–0.6 wt.% Mn alloys with a variable Fe content were prepared by squeeze casting. Optical microscopy (OM), Deep etching technique, scanning electron microscopy(SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to examine the solid-state transformation of Fe-rich intermetallics during the solution heat treatment. The results showed that the Chinese script-like α-Fe, Al{sub 6}(FeMn) and needle-like Al{sub 3}(FeMn) phases transform to a new Cu-rich β-Fe (Al{sub 7}Cu{sub 2}(FeMn)) phase during solution heat treatment. The possible reaction and overall transformation kinetics of the solid-state phase transformation for the Fe-rich intermetallics were investigated. - Graphical abstract: Display Omitted - Highlights: • The α-Fe, Al{sub 6}(FeMn) and Al{sub 3}(FeMn) phases change to the β-Fe phases. • Possible reactions of Fe phases during solution heat treatment are discussed. • The overall fractional transformation rate follows an Avrami curve.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Development of high Fe content squeeze cast 2A16 wrought Al alloys with enhanced mechanical properties at room and elevated temperatures

Highlights: • Applied pressure improved tensile properties at both room and elevated temperatures. • Experimental alloys meet the requirement of safety-critical component in automotive industry. • Increasing value of mechanical properties at elevated temperatures resulting from pressure decreases - Abstract: In this study, the evolution of iron-rich intermetallics and their effects on room and elevated-temperature tensile properties of gravity die cast and squeeze cast 2A16 wrought Al alloys with high Fe content of 0.5% after T7 heat treatment were investigated by various methods. Compared to gravity die-cast alloys, squeeze cast 2A16 wrought Al alloys showed superior tensile properties at both room and elevated temperatures, especially in terms of elongation. This can be attributed to refinement in grain size and iron-rich intermetallics, which decreased porosity and raised dispersoids in α(Al) matrix. However, the increase in mechanical properties at high temperature resulting from applied pressure was lower than that obtained at room temperature. The results were attributed to the refinement in grain size and the weakness of grain boundary at elevated temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Doping effects of Li-Sb content on the structure and electrical properties of [(Na{sub 0.5}K{sub 0.5}){sub 1-x}(Li){sub x}(Sb){sub x}(Nb){sub 1} {sub -x}O{sub 3}] lead-free piezoelectric ceramics

Highlights: Black-Right-Pointing-Pointer [Na{sub 0.5}K{sub 0.5}]{sub 1-x}(Li){sub x}(Sb){sub x}(Nb){sub 1-x}O{sub 3} were prepared by solid-state reaction method. Black-Right-Pointing-Pointer XRD analysis of the powder suggests the formation of a single-phase material. Black-Right-Pointing-Pointer The crystal structure changes from orthorhombic to tetragonal with increase in x. Black-Right-Pointing-Pointer Dielectric studies show a diffuse phase transition at 100 Degree-Sign C and 330 Degree-Sign C. Black-Right-Pointing-Pointer The composition x = 0.050 shows maximum remanent polarization (Pr {approx} 0.66 C m{sup -2}). -- Abstract: Ceramic samples of [Na{sub 0.5}K{sub 0.5}]{sub 1-x}(Li){sub x}(Sb){sub x}(Nb){sub 1-x}O{sub 3} (NKNLS) (x = 0.04-0.06) were prepared by high temperature solid-state reaction method. X-ray diffraction analysis of the powder samples suggests the formation of a single-phase material with transformation from orthorhombic to tetragonal crystal structure with increase in Sb content. Dielectric studies show a diffuse phase transition about 100 Degree-Sign C and another phase ferroelectric-paraelectric transition at 330 Degree-Sign C. Polarization vs. electric field (P-E) hysteresis studies show maximum remanent polarization (Pr {approx} 0.66 C m{sup -2}) for composition x = 0.05. AC conductivity in the compound increases with increase in temperature which may be attributed due to oxygen vacancies and show negative temperature coefficient of resistance (NTCR) effect.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Magnetic properties and homogeneous distribution of Gd{sup 3+} ions in gadolinium molybdenum borate glass with high Gd{sub 2}O{sub 3} content

Highlights: ► The magnetic susceptibility of Gd{sub 2}O{sub 3}–MoO{sub 3}–B{sub 2}O{sub 3} glass was examined in T = 1.8–300 K. ► The effective magnetic moment was μ{sub eff} = 7.87 μ{sub B}. ► The Weiss constant was θ = −0.7 K. ► Gd{sup 3+} ions are distributed homogeneously as paramagnetic ions down to T = 1.8 K. -- Abstract: The magnetic susceptibility and specific heat of 21.25Gd{sub 2}O{sub 3}–63.75MoO{sub 3}–15B{sub 2}O{sub 3} (mol%) glass showing the crystallization of ferroelastic β′-Gd{sub 2}(MoO{sub 4}){sub 3} crystals are examined in the temperature range of T = 1.8–300 K to clarify magnetic and distribution states of Gd{sup 3+} ions. The magnetic susceptibility obeys the Curie–Weiss law, giving the effective magnetic moment of μ{sub eff} = 7.87 μ{sub B} and the Weiss constant of θ = −0.7 K. Any peak such as λ-type anomaly is not observed in the temperature dependence of specific heat in T = 1.8–5 K. It is suggested that Gd{sup 3+} ions in the glass with a high Gd{sub 2}O{sub 3} content of 21.25 mol% are distributed homogeneously and randomly as paramagnetic ions down to T = 1.8 K without inducing any strong magnetic interaction. The present study suggests that glasses based on the MoO{sub 3}–B{sub 2}O{sub 3} system are good hosts for the homogeneous solubility of a large amount of rare-earth oxides.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Hydrogen production via reforming of biogas over nanostructured Ni/Y catalyst: Effect of ultrasound irradiation and Ni-content on catalyst properties and performance

Highlights: • Synthesis of nanostructured Ni/Y catalyst by sonochemical and impregnation methods. • Enhancement of size distribution and active phase dispersion by employing sonochemical method. • Evaluation of biogas reforming over Ni/Y catalyst with different Ni-loadings. • Preparation of highly active and stable catalyst with low Ni content for biogas reforming. • Getting H{sub 2}/CO very close to equilibrium ratio by employing sonochemical method. - Abstract: The effect of ultrasound irradiation and various Ni-loadings on dispersion of active phase over zeolite Y were evaluated in biogas reforming for hydrogen production. X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray, Brunauer–Emmett–Teller, Fourier transform infrared analysis and TEM analysis were employed to observe the characteristics of nanostructured catalysts. The characterizations implied that utilization of ultrasound irradiation enhanced catalyst physicochemical properties including high dispersion of Ni on support, smallest particles size and high catalyst surface area. The reforming reactions were carried out at GHSV = 24 l/g.h, P = 1 atm, CH{sub 4}/CO{sub 2} = 1 and temperature range of 550–850 °C. Activity test displayed that ultrasound irradiated Ni(5 wt.%)/Y had the best performance and the activity remained stable during 600 min. Furthermore, the proposed reaction mechanism showed that there are three major reaction channels in biogas reforming.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Effect of oxygen content on transport and magnetic properties of PrBaCo{sub 2}O{sub 5.50+δ}

Samples of PrBaCo{sub 2}O{sub 5.50+δ} (δ = −0.15–0.14), synthesized by solid-state reactions, were investigated to ascertain oxygen compositional effects on transport/magnetic properties. Resistivity decreases with increasing oxygen content, indicative of p-type conduction. A metal-insulator transition was observed at 330 K only for sample PrBaCo{sub 2}O{sub 5.52}, coinciding with phase transition and spin-state transition of Co{sup 3+}. When δ deviates from zero, samples show insulator–insulator transitions, although for sample δ = 0.14, no transition occurs but only semi-conductive behavior appears. Electronic transport is governed by the hopping mechanism at lower temperatures and thermal activation at higher temperatures. All samples underwent paramagnetic–ferromagnetic–antiferromagnetic transitions, except PrBaCo{sub 2}O{sub 5.64}, which only went through a paramagnetic–ferromagnetic transition. The ferromagnetic state for δ < 0 originates with the Co{sup 3+}/Co{sup 2+} super-exchange interaction; for δ > 0, it stems from the Co{sup 3+}/Co{sup 4+} double exchange interaction.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Towards the development of new phosphors with reduced content of rare earth elements: Structural and optical characterization of Ce:Tb: Al{sub 2}SiO{sub 5}

Highlights: • A new promising inert matrix as host of luminescent ions is proposed. • Al2SiO5 matrix is free from Rare earths (critical raw materials). • Doping the matrix with Ce and Tb we obtain an efficient green emitter. • Cerium acts as sensitizer for Terbium emission. - Abstract: A new promising inert matrix as host of luminescent ions is proposed. Al2SiO5 samples, doped with rare earths (Ce, Tb single doped and co-doped) are proposed as good prospect for the development of new UV–vis converter with reduced content of rare earths elements. Structural characterization by Raman, XRD spectroscopy and TEM imaging reveals the sillimanite phase and nano sized dimension of the investigated powders. Optical characterization by steady time and time resolved emission spectroscopy for the single doped and co-doped samples allows to identify an efficient energy transfer from Ce to Tb ions under near UV excitation wavelength. The intense green emission observed in the Ce:Tb co-doped Al2SiO5 system suggests its potential application as efficient blue pumped green emitter phosphor to be exploited for white LED: to this purpose we tested the compound in combination with a red emitting doping ion recording for Ce:Tb:Cr:ASO system a correlated color temperature of 6720 K.

36 MATERIALS SCIENCE↗
DOE OSTI2012

CO2/light gas separation performance of cross-linked poly(vinylimidazolium) gel membranes as a function of ionic liquid loading and cross-linker content

A series of cross-linked poly(vinylimidazolium)-RTIL gel membranes was synthesized and evaluated for room-temperature, ideal CO2/N-2, CO2/CH4, and CO2/H-2 separation performance. The membranes were formed by photo-polymerization of oligo(ethylene glycol)-functionalized cross-linking (i.e., di-functional) and non-cross-linking (i.e., mono-functional) vinylimidazolium RTIL monomers with nonpolymerizable, "free RTIL." The effect of free RTIL ([emim][Tf2N]) loading on CO2 separation performance was evaluated by varying RTIL loading at three levels (45, 65, and 75 wt.%). The effect of cross-linker content on CO2 separation performance was also evaluated by varying the copolymer composition of cross-linked membranes from 5 to 100 mol% di-functional monomer. The substituent on the monofunctional RTIL monomer was also varied to investigate the effect of substituent structure and chemistry on CO2 separation performance. CO2 permeability was dramatically increased with higher loading of free RTIL. Increased RTIL loading had no effect on CO2/N-2 or CO2/CH4 permeability selectivity, but significantly improved CO2/H-2 permeability selectivity. Reducing the cross-linking monomer concentration generally improved CO2 permeability. However, anomalous permeability and selectivity behavior was observed below critical concentrations of cross-linker. The effect of the substituent on the monofunctional monomer on CO2 separation performance was minimal compared to the effects of RTIL loading and copolymer composition. (C) 2012 Elsevier B.V. All rights reserved.

Carlisle, TK↗
DOE OSTI2024

Influence of intermediate carbon content on the microstructure and high-temperature mechanical properties of cast and wrought Ni-based superalloy nimonic 105

NIMONIC® 105 variants with three different carbon concentrations were manufactured. Here, the medium carbon content variant shows inferior creep properties due to a bimodal grain size distribution and non-uniform carbides repartition leading to plastic strain accumulation between the two domains. Here, this eventually facilitated facile cracking and void formation during high-temperature creep.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Backscatter gauge description for inspection of neutron absorber content

This paper describes design, calibration, and testing of a dual He-3 detector neutron backscatter gauge for use in the Savannah River Site Mixed Oxide Fuel project. The gauge is demonstrated to measure boron content and uniformity in concrete slabs used in the facility construction.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Determination of total plutonium content in spent nuclear fuel assemblies with the differential die-away self-interrogation instrument

As a part of the Next Generation Safeguards Initiative Spent Fuel project, we simulate the response of the Differential Die-away Self-Interrogation (DDSI) instrument to determine total elemental plutonium content in an assayed spent nuclear fuel assembly (SFA). We apply recently developed concepts that relate total plutonium mass with SFA multiplication and passive neutron count rate. In this work, the multiplication of the SFA is determined from the die-away time in the early time domain of the Rossi-Alpha distributions measured directly by the DDSI instrument. Here, we utilize MCNP to test the method against 44 pressurized water reactor SFAs from a simulated spent fuel library with a wide dynamic range of characteristic parameters such as initial enrichment, burnup, and cooling time. Under ideal conditions, discounting possible errors of a real world measurement, a root mean square agreement between true and determined total Pu mass of 2.1% is achieved.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

A new method to measure the U-235 content in fresh LWR fuel assemblies via fast-neutron passive self-interrogation

The purpose of this paper is to provide a solution to a decades old safeguards problem in the verification of the fissile concentration in fresh light water reactor (LWR) fuel assemblies. The problem is that the burnable poison (e.g. Gd 2 O 3 ) addition to the fuel rods decreases the active neutron assay for the fuel assemblies. This paper presents a new innovative method for the verification of the 235 U linear mass density in fresh LEU fuel assemblies that is insensitive to the burnable poison content. The technique makes use of the 238 U atoms in the fuel rods to self-interrogate the 235 U mass. The innovation for the new approach is that the 238 U spontaneous fission (SF) neutrons from the rods induces fission reactions (IF) in the 235 U that are time correlated with the SF source neutrons. Thus, the coincidence gate counting rate benefits from both the nu-bar of the 238 U SF (2.07) and the 235 U IF (2.44) for a fraction of the IF reactions. Whereas, the 238 U SF background has no time-correlation boost. The higher the detection efficiency, the higher the correlated boost because background neutron counts from the SF are being converted to signal doubles. This time-correlation in the IF signal increases signal/background ratio that provides a good precision for the net signal from the 235 U mass. The hard neutron energy spectrum makes the technique insensitive to the burnable poison loading where a Cd or Gd liner on the detector walls is used to prevent thermal-neutron reflection back into the fuel assembly from the detector. Here, we have named the system the fast-neutron passive collar (FNPC).

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

On the physics potential to study the gluon content of proton and deuteron at NICA SPD

The Spin Physics Detector (SPD) is a future multipurpose experiment foreseen to run at the NICA collider, which is currently under construction at the Joint Institute for Nuclear Research (JINR, Dubna, Russia). The physics program of the experiment is based on collisions of longitudinally and transversely polarized protons and deuterons at √s up to 27 GeV and luminosity up to 10 32 cm –2 s –1 . SPD will operate as a universal facility for the comprehensive study of the unpolarized and polarized gluon content of the nucleon, using complementary probes such as: charmonia, open-charm, and prompt-photon production processes. Furthermore, the aim of this work is to provide a thorough review of the physics objectives that can potentially be addressed at SPD, underlining related theoretical aspects and discussing relevant experimental results when available. Among different pertinent phenomena particular attention is drawn to the study of the gluon helicity, gluon Sivers and Boer-Mulders functions in the nucleon, as well as the gluon transversity distribution in the deuteron, via the measurement of single and double spin asymmetries.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Quantification of water content by laser induced breakdown spectroscopy on Mars

Laser induced breakdown spectroscopy (LIBS), as performed by the ChemCam instrument, provides a new technique to measure hydrogen at the surface of Mars. Using a laboratory replica of the LIBS instrument onboard the Curiosity rover, different types of hydrated samples (basalts, calcium and magnesium sulfates, opals and apatites) covering a range of targets observed on Mars have been characterized and analyzed in this paper. A number of factors related to laser parameters, atmospheric conditions and differences in targets properties can affect the standoff LIBS signal, and in particular the hydrogen emission peak. Dedicated laboratory tests were run to identify a normalization of the hydrogen signal which could best compensate for these effects and enable the application of the laboratory calibration to Mars data. We check that the hydrogen signal increases linearly with water content; and normalization of the hydrogen emission peak using to oxygen and carbon emission peaks (related to the breakdown of atmospheric carbon dioxide) constitutes a robust approach. Finally, moreover, the calibration curve obtained is relatively independent of the samples types.

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

Comparison of dislocation content measured with transmission electron microscopy and micro-Laue diffraction based streak analysis

The subsurface dislocation content in a Ti-5Al-2.5Sn (wt%) uniaxial tension sample deformed at ambient temperature was characterized by peak streak analysis of micro-Laue diffraction patterns collected non-destructively by differential aperture X-raymicroscopy, and with focused ion beam transmission electron microscopy of material in the same volume. This comparison reveals that micro-Laue diffraction streak analysis based on an edge dislocation assumption can accurately identify the dominant dislocation slip system history (Burgers vector and plane observed by TEM), despite the fact that dislocations have predominantly screw character. As a result, other dislocations identified by TEM were not convincingly discernible from the peak streak analysis.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

The effect of phosphorus on the formation of grain boundary laves phase in high-refractory content Ni-based superalloys

The effect of phosphorous on the microstructure of a powder-processed, high Nb-content, Ni-based superalloy was studied and compared to a P-free variant. The P-doped sample had a lower incipient melting temperature, forming a (Ni, Co, Cr, P) 2 (Nb, Mo) laves phase along the grain boundaries. Transmission electron microscopy and atom probe tomography were used to identify the crystal structure, assess phase compositions, and determine any elemental segregation to phase boundaries. The results revealed strong partitioning of P to the laves phase and a slight Mo gradient towards the γ' phrase. Finally, a simplified laves phase was successfully modeled via density functional theory calculations.

Antonov, Stoichko↗