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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Component and Technology Development for Advanced Liquid Metal Reactors

The following report details the significant developments to Sodium Fast Reactor (SFR) technologies made throughout the course of this funding. This report will begin with an overview of the sodium loop and the improvements made over the course of this research to make it a more advanced and capable facility. These improvements have much to do with oxygen control and diagnostics. Thus a detailed report of advancements with respect to the cold trap, plugging meter, vanadium equilibration loop, and electrochemical oxygen sensor is included. Further analysis of the university’s moving magnet pump was performed and included in a section of this report. A continuous electrical resistance based level sensor was built and tested in the sodium with favorable results. Materials testing was done on diffusion bonded samples of metal and the results are presented here as well. A significant portion of this work went into the development of optical fiber temperature sensors which could be deployed in an SFR environment. Thus, a section of this report presents the work done to develop an encapsulation method for these fibers inside of a stainless steel capillary tube. High temperature testing was then done on the optical fiber ex situ in a furnace. Thermal response time was also explored with the optical fiber temperature sensors. Finally these optical fibers were deployed successfully in a sodium environment for data acquisition. As a test of the sodium deployable optical fiber temperature sensors they were installed in a sub-loop of the sodium facility which was constructed to promote the thermal striping effect in sodium. The optical fibers performed exceptionally well, yielding unprecedented 2 dimensional temperature profiles with good temporal resolution. Finally, this thermal striping loop was used to perform cross correlation velocimetry successfully over a wide range of flow rates.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2018

The Effect of γ Irradiation on Phase Transitions in the Polyimide–YBa{sub 2}Cu{sub 3}O{sub 6+} {sub x} System

The effect of γ irradiation on optical properties of films of the polyimide–YBa{sub 2}Cu{sub 3}O{sub 6.7} system with different concentrations of the filler in the form of the finely crystalline compound YBa{sub 2}Cu{sub 3}O{sub 6.7} (0.05 wt %, 0.10 wt %, and 0.50 wt %) has been investigated. The properties were studied on an IKS-29 infrared spectrophotometer in a spectral range of 400–4200 cm{sup –1} at room temperature. The samples were irradiated in air under room conditions on an RKhM-γ-20 by doses of 150, 250, and 600 kGy. The power of the exposure dose of the {sup 60}Co source was 0.16 rad/s. It has been established that irradiation with a dose of up to 600 kGy of the abovementioned system slightly affects the structure of the polyimide matrix but decreases the number of free radical groups in the film structure with the formation of hydrogen bonds. In the range of 400–4200 cm{sup –1} at D = 150 kGy, the most intense changes in spectra of polymeric composite samples have been revealed. In the range of 2850–3350 cm{sup –1}, the wide absorption spectrum band is preserved, which is caused by the presence of Cu, Y, and Ba crystallohydrates. The band is related to deformation vibrations of the Cu–O bond in YBa{sub 2}- Cu{sub 3}O{sub 6.7} (YBCO) chains due to properties of barium carbonate, formation of oxygen vacancies in the filler, and vibrations of the Cu(I)–O(I) bonds near one or several O(4) vacancies. Irradiation by doses of 250 and 600 kGy for different concentrations of the filler leads to a decrease in the signal intensity in the range of 1800–3600 cm{sup –1} by 20–35% on average. Peaks related to interband transitions (transitions of the Cu(I)–Cu(IY)–Cu(II) system) and bending vibrations O(I)–Cu(I) are not changed by strains of O(IY)–Cu(I) bonds. This testifies to the radiation-stimulated diffusion of oxygen atoms to O(IY) sites determining the orthorhombic phase of YBa{sub 2}Cu{sub 3}O{sub 6.7} from the occupied positions in the Cu–O sublattice.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Long‐Term Structural Evolution of an Intercalated Layered Semiconductor

Intercalated molecules can dramatically modify the electronic band structure of layered semiconductors, significantly altering the optical properties of the material. In the layered monochalcogenide Gallium Telluride (GaTe), exposure to air induces a nearly 1 eV reduction of its band gap due to the interlayer diffusion and chemisorption of oxygen. The effect of oxygen chemisorption at the Te‐terminated surfaces on the structure of GaTe, however, is much less known. To better understand the structure–property relationship of intercalated GaTe, a systematic, long‐term, X‐ray diffraction study has been performed on GaTe exfoliated crystals exposed to ambient conditions. It is observed that the structural changes are not limited to a previously observed short‐term increase in lattice expansion. Over the course of months and even years after exfoliation, the oxygen adsorbates continue to modify the structure of GaTe, inducing significant disorder and grain reorientation. It is estimated that approximately one out of every two grains is slightly displaced by the intercalating oxygen, demonstrating a significant increase in grain mosaicity, while still maintaining the original {−2 0 1} out‐of‐plane texture. Correlating these structural transformations to observed changes in electrical and optical properties will enable capitalization of the use of adsorbates to engineer novel properties in these layered materials.

Chew, Annabel R.↗
DOE OSTI2016

Field-induced stacking transition of biofunctionalized trilayer graphene

Trilayer graphene (TLG) is attracting a lot of attention as their stacking structures (i.e., rhombohedral vs. Bernal) drastically affect electronic and optical properties. Based on full-atom molecular dynamics simulations, we here predict electric field-induced rhombohedral-to-Bernal transition of TLG tethered with proteins. Furthermore, our simulations show that protein's electrophoretic mobility and diffusivity are enhanced on TLG surface. This phenomenon of controllable TLG stacking transition will contribute to various applications including biosensing.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Features of the structural states of KNbO{sub 3} single crystals before and after fast-neutron irradiation

Neutron irradiation is a unique tool for forming new structural states of ferroelectrics, which cannot be obtained by conventional methods. The inf luence of the irradiation by two doses of fast neutrons (F = 1 × 10{sup 17} and 3 × 10{sup 17} cm{sup –2}) on the structure and properties of KNbO{sub 3} single crystals has been considered for the first time. The developed method for taking into account the experimental correction to the diffuse scattering has been used to analyze the structural changes occurring in KNbO{sub 3} samples at T = 295 K and their correlations with the behavior of dielectric and nonlinear optical characteristics. The irradiation to the aforementioned doses retains the KNbO{sub 3} polar structure, shifting Т{sub Ð}¡ to lower temperatures and significantly affecting only the thermal parameters and microstructure of single crystals. Neutron irradiation with small atomic displacements provides a structure similar to the high-temperature modification of an unirradiated KNbO{sub 3} crystal.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Tunable optical properties and stability of lead free all inorganic perovskites (Cs 2 SnI x Cl 6-x )

Organic–inorganic hybrid lead-based perovskites experience significant environmental instability under ambient moist air and are not environmentally benign due to the usage of toxic Pb. In this paper, we report a new approach to synthesize lead-free all inorganic perovskites (Cs 2 SnI x Cl 6-x ) using hydriodic acid (HI) demonstrating greatly enhanced environmental stability and tunable optical properties by controlling the I - /Cl - ratios. Single phase perovskites can be achieved with a low iodine or chlorine content, and a phase separation occurs in the binary system with closer iodine and chlorine dopings. UV-vis diffuse reflectance and photoluminescence measurements reveal tunable band gaps of Cs 2 SnI x Cl 6-x perovskites from the UV to the infrared region. The mixed halide perovskite with a lower chloride content shows significantly higher photoluminescence intensity. The thermal stability of mixed halide all-inorganic perovskites is continuously improved as the Cl content increases. Finally, the synthesis of Sn-based perovskites with tunable optical properties and environmental stability represents one step further toward the realization of the stable lead-free all inorganic perovskites.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Role of shell composition and morphology in achieving single-emitter photostability for green-emitting “giant” quantum dots

The use of the varied chemical reactivity of precursors to drive the production of a desired nanocrystal architecture has become a common method to grow thick-shell graded alloy quantum dots (QDs) with robust optical properties. Conclusions on their behavior assume the ideal chemical gradation and uniform particle composition. In this work, advanced analytical electron microscopy (high-resolution scanning transmission electron microscopy coupled with energy dispersive spectroscopy) is used to confirm the nature and extent of compositional gradation and these data are compared with performance behavior obtained from single-nanocrystal spectroscopy to elucidate structure, chemical-composition, and optical-property correlations. In particular, the evolution of the chemical structure and single-nanocrystal luminescence was determined for a time-series of graded-alloy “CdZnSSe/ZnS” core/shell QDs prepared in a single-pot reaction. In a separate step, thick (~6 monolayers) to giant (>14 monolayers) shells of ZnS were added to the alloyed QDs via a successive ionic layer adsorption and reaction (SILAR) process, and the impact of this shell on the optical performance was also assessed. By determining the degree of alloying for each component element on a per-particle basis, we observe that the actual product from the single-pot reaction is less “graded” in Cd and more so in Se than anticipated, with Se extending throughout the structure. The latter suggests much slower Se reaction kinetics than expected or an ability of Se to diffuse away from the initially nucleated core. It was also found that the subsequent growth of thick phase-pure ZnS shells by the SILAR method was required to significantly reduce blinking and photobleaching. However, correlated single-nanocrystal optical characterization and electron microscopy further revealed that these beneficial properties are only achieved if the thick ZnS shell is complete and without large lattice discontinuities. Thus, we identify the necessary structural design features that are required for ideal light emission properties in these green-visible emitting QDs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Measurement and modeling of the multiwavelength optical properties of uncoated flame-generated soot

Optical properties of flame-generated black carbon (BC) containing soot particles were quantified at multiple wavelengths for particles produced using two different flames: a methane diffusion flame and an ethylene premixed flame. Measurements were made for (i) nascent soot particles,(ii) thermally denuded nascent particles, and (iii) particles that were coated and then thermally denuded, leading to the collapse of the initiallylacy, fractal-like morphology. The measured mass absorption coefficients(MACs) depended on soot maturity and generation but were similar between flames for similar conditions. For mature soot, here corresponding to particles with volume-equivalent diameters > ~ 160 nm, the MAC and absorption Ångström exponent (AAE) values were independent of particle collapse while the single-scatter albedo increased. The MAC values for these larger particles were also size-independent. The mean MAC value at 532 nm for larger particles was 9.1±1.1 m 2 g -1 , about 17 % higher than that recommended by Bond and Bergstrom (2006), and the AAE was close to unity. Effective, theory-specific complex refractive index(RI) values are derived from the observations with two widely used methods:Lorenz–Mie theory and the Rayleigh–Debye–Gans (RDG) approximation. Mietheory systematically underpredicts the observed absorption cross sections at all wavelengths for larger particles (with x >0.9 ) independent of the complex RI used, while RDG provides good agreement. (The dimensionless size parameter x = π d p / λ , where d p is particle diameter and λ is wavelength.) Importantly, this implies that the use of Mie theory within air quality and climate models, as is common, likely leads to under predictions in the absorption by BC, with the extent of underprediction depending on the assumed BC size distribution and complex RI used. We suggest that it is more appropriate to assume a constant,size-independent (but wavelength-specific) MAC to represent absorption by uncoated BC particles within models.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Conversion between triplet pair states is controlled by molecular coupling in pentadithiophene thin films

In singlet fission (SF) the initially formed correlated triplet pair state, 1 (TT), may evolve toward independent triplet excitons or higher spin states of the (TT) species. The latter result is often considered undesirable from a light harvesting perspective but may be attractive for quantum information sciences (QIS) applications, as the final exciton pair can be spin-entangled and magnetically active with relatively long room temperature decoherence times. In this study we use ultrafast transient absorption (TA) and time-resolved electron paramagnetic resonance (TR-EPR) spectroscopy to monitor SF and triplet pair evolution in a series of alkyl silyl-functionalized pentadithiophene (PDT) thin films designed with systematically varying pairwise and long-range molecular interactions between PDT chromophores. The lifetime of the (TT) species varies from 40 ns to 1.5 μs, the latter of which is associated with extremely weak intermolecular coupling, sharp optical spectroscopic features, and complex TR-EPR spectra that are composed of a mixture of triplet and quintet-like features. On the other hand, more tightly coupled films produce broader transient optical spectra but simpler TR-EPR spectra consistent with significant population in 5 (TT) 0 . These distinctions are rationalized through the role of exciton diffusion and predictions of TT state mixing with low exchange coupling J versus pure spin substate population with larger J. The connection between population evolution using electronic and spin spectroscopies enables assignments that provide a more detailed picture of triplet pair evolution than previously presented and provides critical guidance for designing molecular QIS systems based on light-induced spin coherence.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Electronic Structures and Magnetic Properties of Transition Metal Doped CsPbI{sub 3} Perovskite Compounds by First-Principles Calculation

Transition metal doped cesium lead halide (CsPbI{sub 3}) perovskite compounds were studied for application in photovoltaic solar cells. Electronic structures, chemical shifts of {sup 207}Pb and {sup 127}I-NMR, vibration modes in infrared and Raman spectra of transition metals (Mn{sup 2+}, Fe{sup 2+} or Cu{sup 2+})-doped CsPbI{sub 3} perovskite compounds were studied by the first-principles calculation using density functional theory. The CsPb(Fe)I{sub 3} perovskite crystals had a slight perturbation of crystal field in the coordination structure. The electron density distribution was delocalized on the 5p orbital of I atom, the 3d orbital of Fe atom and the 6p orbital of Pb atom. The first excited process was based on ligand metal charge transfer from the 5p orbital on I atom to the 3d orbital of Fe atom. The chemical shifts of {sup 127}I-NMR were associated with the electron correlation of electron-nuclear spin interaction and nuclear quadrupole interactions based on electron field graduate. The asymmetric vibrations of Pb–I bonds stretching mode related to electron conductivity with scattering of the carrier diffusion as phonon effectiveness. The slight perturbation of the coordination structure in the CsPb(Fe)I{sub 3} perovskite crystal will improve the photovoltaic and optical properties.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Microstructural evolution of thin polycrystalline metallic films under extreme conditions

Thin films are materials systems that are widely used in applications ranging from electronics and optical devices to industrial and biomedical ones. However, these systems are unstable against various homogenization processes and aging mechanisms (grain growth, coarsening, surface evolution, and diffusion of species) even at low service temperatures. In this work, we examine the role of various aspects of microstructure (grain boundary types and characters, free surfaces, surface diffusion, and thermal grooves) on the thermal aging of such systems. Existing experimental tools will be leveraged to characterize thin films, i.e., in-situ quantitative thermal annealing, and provide direct comparisons to predications emerging from a recently developed meso-scale model via Precession Electron Diffraction (PED). Parametric studies will be conducted to gain insights on the role of each of the aforementioned aspects of microstructure on the dynamics. Herein, we will focus on “hard” gold thin films (with alloying elements like Co, Ni, or Fe) as they are materials of choice in a wide range of applications at Sandia. Initially, pure gold systems are examined and future studies will focus on microstructure evolution in the presence of alloying elements and second-phase particles.

36 MATERIALS SCIENCE↗
DOE OSTI2015

AWARE Shortwave Spectroradiometer Data

Shortwave spectral irradiance was measured at the West Antarctic Ice Sheet (WAIS) Divide Ice Camp as part of the ARM West Antarctic Radiation Experiment (AWARE). A Panalytical (Inc.) FieldSpec Pro Jr spectroradiometer belonging to Scripps Oceanography recorded downwelling spectral irradiance every minute covering the wavelength interval 350-2200 nm . Spectral resolution is 3 nm (10 nm) for wavelengths shorter (longer) than 1000 nm. Temporal coverage is nearly continuous between 8 December 2015 and 18 January 2016, with a few minutes of data missing during each day for data backup and optical collector hygiene. Spectral irradiances, particularly in the near infrared, are sensitive to cloud optical depth, thermodynamic phase, and effective particle size.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Microstructural, Optical, and Magnetic Properties of Vanadium-Substituted Nickel Spinel Nanoferrites

The current study investigates the impact of vanadium substitution on the structural, magnetic, and optical properties of NiFe{sub 2−x}V{sub x}O{sub 4} (x ≤ 0.3) nanoparticles (NPs) produced by the cost-effective sol-gel route. The as-prepared spinel ceramic powders were examined by X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (DRS), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). The functional groups, spinel phase, and crystal structure were confirmed by XRD and FT-IR, respectively. The crystallites size decreased from 45.24 to 36.56 nm as the doping process increases. The plots of Tauc were drawn to determine optical band gap magnitudes of 1.291, 1.302, and 1.312 eV for x = 0.0, 0.2, and 0.3, respectively. The estimated saturation magnetization is maximum for pristine NiFe{sub 2}O{sub 4} NPs and decreases to minimum for NiFe{sub 1.7}V{sub 0.3}O{sub 4} NPs. The σ-H hysteresis loops have finite coercivity (between 125 and 169 Oe) and retentivity (between 9.36 and 14.04 emu/g) values. The calculated σ{sub r}/σ{sub s} ratios are lower than 0.500, assigning the uniaxial anisotropy for NiFe{sub 2−x}V{sub x}O{sub 4}. The effective anisotropy constants (K{sub eff}) are in the range of 0.824 × 10{sup 5} and 1.303 × 10{sup 5} Erg/g. The magnetocrystalline anisotropy field (H{sub a}) values are around 5.0 kOe. The characteristics of hysteresis (σ-H) curves and the order of magnetic data reveal the soft ferrimagnetic feature of as-prepared nanoparticle samples. From Mossbauer analysis, the variations in hyperfine magnetic field, quadrupole splitting, line width, and isomer shift have been evaluated. The distribution of cations showed that the octahedral B sites are occupied by all the ions of V{sup 3+}. Mossbauer spectra are composed of four Zeeman sextets and one doublet.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

The São Paulo Potential and the 3 He Breakup Reaction at 130 MeV on 93 Nb and 197 Au

Nuclear reactions induced by weakly bound nuclei often result in the emission of light particles as products of the projectile breakup. The incident particle is expected to fragment before reaching the interior of the target nuclei, a characteristic that tends to favor forward angular emission. Although the first models developed for such reactions were proposed many decades ago by Udagawa and Tamura, Ichimura, Austern, Vincent, and Kasano, and Hussein and McVoy, to this date most of the attention has been dedicated to the breakup of the deuteron and other very weakly bound systems, while more strongly bound projectiles have not been fully explored. Here, we describe the production of protons and deuterons from the breakup of 3He. The breakup of 3 He on two heavy targets, 93 Nb and 197 Au, is analyzed in this study. However, the incoming energy involved is much larger than that of the standard phenomenological optical potentials available in the literature for the 3He entrance channel. We have overcome this difficulty by using the São Paulo potential and adjusting the nuclear diffusivity. The deuteron inclusive spectra were calculated at several angles and compared well with the experimental data. Theoretical proton emission predictions are also given for future reference, since no inclusive measurements were performed for the targets under study. Finally, one of our goals is to verify the description of deuteron emission from fast projectiles, for which many partial waves contribute to the scattering process.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Tuning Electrogenerated Chemiluminescence Intensity Enhancement Using Hexagonal Lattice Arrays of Gold Nanodisks

Electrogenerated chemiluminescence (ECL) microscopy shows promise as a technique for mapping chemical reactions on single nanoparticles. The technique’s spatial resolution is limited by the quantum yield of the emission and the diffusive nature of the ECL process. To improve signal intensity, ECL dyes have been coupled with plasmonic nanoparticles, which act as nanoantennas. Here, we characterize the optical properties of hexagonal arrays of gold nanodisks and how they impact the enhancement of ECL from the coreaction of tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate and tripropylamine. Here, we find that varying the lattice spacing results in a 23-fold enhancement of ECL intensity because of increased dye-array near-field coupling as modeled using finite element method simulations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Measurement and modeling of the multi-wavelength optical properties ofuncoated flame-generated soot

Abstract. Optical properties of flame-generated black carbon (BC) containing soot particles were quantified at multiple wavelengths for particles produced using two different flames, a methane diffusion flame and an ethylene premixed flame. Measurements were made for: (i) nascent soot particles, (ii) thermally denuded nascent particles, and (iii) particles that were coated then thermally denuded, leading to collapse of the initially lacy, fractal-like morphology. The measured mass absorption coefficients (MAC) depended on soot maturity and generation, but were similar between flames for similar conditions. For mature soot, here corresponding to particles with volume-equivalent diameters > ~ 160 nm, the MAC and absorption Angstrom exponent values were independent of particle collapse while the single scatter albedo increased. The MAC values for these larger particles were also size-independent. Effective, theory-specific complex refractive index ( RI ) values are derived from the observations with two widely-used methods: Lorenz-Mie theory and the Rayleigh-Debye-Gans (RDG) approximation. Mie theory systematically under-predicts the observed absorption cross-sections at all wavelengths for larger particles (with x > 0.9) independent of the complex RI used, while RDG provides good agreement. Importantly, this implies that the use of Mie theory within air quality and climate models, as is common, likely leads to under-predictions in the absorption by BC, with the extent of under-prediction depending on the assumed BC size distribution and complex RI used. We suggest that it is more appropriate to assume a constant, size-independent (but wavelength-specific) MAC to represent absorption by uncoated BC particles within models.

54 ENVIRONMENTAL SCIENCES↗