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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 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Haze processing of atmospheric particles during wintertime in the Indo-Gangetic Plains

The impacts of haze on visibility, air quality, and climate are not well quantified due to a lack of understanding of the evolution of the mixing state and phase state of atmospheric particles during haze processing. The variability of the mixing state of atmospheric particles contributes significantly to uncertainties associated with the estimated aerosol radiative forcing. We collected particle samples in January 2018 from the highly polluted Indo-Gangetic plain during hazy conditions to study haze-processed particles. Single particle analysis using multi-modal micro-spectroscopy techniques revealed an abundance (40–70% by number) of potassium-rich sulfate particles from biomass-burning influenced smoke. Tilted view imaging showed that most of the organic particles that had inorganic potassium and sulfate inclusions were liquid-like while those without inclusions were more semi-solid. High-resolution mass spectrometry analysis revealed a significant presence of organosulfates and nitroxy-organosulfates in the morning samples (24%) compared to the afternoon samples (9%), despite higher relative humidity in the afternoon. Overall, our results highlight the significant contribution of both organic and inorganic sulfate to the total particulate sulfur budget during haze processing in winter, when anthropogenic emissions such as household burning, agricultural burning, and vehicular emissions are major contributors to particle mass.

Mathai, Susan [Pacific Northwest National Laborato↗
DOE OSTI2019

Solid-phase reactive inter-diffusion of Mg/B multilayers

A better understanding of the reaction of Mg and B in the solid-phase regime is needed for the low-temperature synthesis of MgB 2 films. Here in this paper, we study the kinetics of reactive inter-diffusion of Mg and B multilayers on glassy carbon substrates in the temperature range of 400-650°C. Results show that, at these temperatures, inter-diffusion is characterized by a single activation energy of ~0.45eV. The formation of the superconducting MgB 2 phase with critical temperatures of 25–31 K occurs at reaction temperatures of 450°C and above, with the rate of inter-diffusion obeying a power law with a kinetic exponent of ~0.3. This suggests that rate-limiting processes are the nucleation and growth of MgB 2 grains rather than diffusion and interfacial reactions. Implications of these results to the low-temperature synthesis of MgB 2 films are discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Achieving accurate energetics beyond (semi-)local density functional theory: Illustrated with transition metal disulfides, Cu 2 ZnSnS 4 , and Na 3 PS 4 related semiconductors

Understanding, designing, and processing functional metal sulfides are significant challenges partially because of the high temperatures and pressures and the number of secondary phases encountered in these complex systems. In particular, the underlying thermochemical properties are not well understood that would allow prediction of equilibrium conditions and driving forces. In addition, obtaining accurate values for the energetics of metal sulfide systems is far from complete, suggesting application of density functional theory (DFT) calculations. Here, the results of an examination of 69 phases by DFT using 12 exchange-correlation (X-C) functionals indicate that (i) the key source of error in predicting the Gibbs energy of a phase is the enthalpy calculated at 0 K rather than entropy at finite temperatures from phonon calculations and (ii) an improved prediction of the thermodynamic properties at 0 K relies on the selected nonlocal X-C functional such as the hybrid potential. Regarding metal sulfides, we conclude from the present DFT results that (1) the secondary phase Cu 2 ZnSn 3 S 8 , associated with the desired photovoltaic material Cu 2 ZnSnS 4 , is not stable at 0 K, but it becomes slightly stable with increasing temperature (i.e., >800 K), primarily due to the vibrational entropy, which makes it difficult to be detected in a typical thin-film growth process; (2) the hybrid X-C functional improves the predicted energetics for most of the layered transition-metal disulfides such as TiS 2 , MoS 2 , and WS 2 , but not for the nonlayered RuS 2 , OsS 2 , and IrS 2 as well as the layered PdS 2 ; and (3) the formation of the solid-state electrolyte Na3PS4 is thermodynamically favored. We further conclude that accurate energetics as a function of temperature for the materials of interest is feasible to be achieved beyond the semilocal DFT calculations with the key being enthalpy predicted at 0 K.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Triply-resonant sum frequency conversion with gallium phosphide ring resonators

We demonstrate quasi-phase matched, triply-resonant sum frequency conversion in 10.6-µm-diameter integrated gallium phosphide ring resonators. A small-signal, waveguide-to-waveguide power conversion efficiency of 8 ± 1.1%/mW; is measured for conversion from telecom (1536 nm) and near infrared (1117 nm) to visible (647 nm) wavelengths with an absolute power conversion efficiency of 6.3 ± 0.6%; measured at saturation pump power. For the complementary difference frequency generation process, a single photon conversion efficiency of 7.2%/mW from visible to telecom is projected for resonators with optimized coupling. Efficient conversion from visible to telecom will facilitate long-distance transmission of spin-entangled photons from solid-state emitters such as the diamond NV center, allowing long-distance entanglement for quantum networks.

42 ENGINEERING↗
DOE OSTI2021

Physical-chemical-mechanical quantitative assessment of the microstructural evolution in Portland-limestone cement pastes exposed to magnesium sulfate attack at low temperature

The changes in structural integrity and microstructure of Portland-limestone cement pastes were investigated in the course of magnesium sulfate attack at low temperature. A deterioration front, consisting of three distinct layers (brucite, gypsum, leached cement matrix), swelled in time due to the expansive nature of the deterioration products, generating cracks and subsequently detaching from the sound cement matrix, continuously promoting the process. Gypsum and thaumasite characterized the leached matrix, which experienced extensive cross-linking of the aluminosilicate structures, as a result of decalcification and dealumination of the calcium silicate hydrates (C(A)SH), impairing the overall mechanical performance. CSH of low packing density was most severely affected by the process, as confirmed by the significant drop in nano-mechanical properties. The increased rate of deterioration with limestone content was tentatively attributed to the prevalent morphology of the CSH phase. Results were validated by thermodynamic simulations, indicating that the real systems did not reach equilibrium.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Oxygen reduction reaction kinetics in Sr-doped La 2 NiO 4+δ Ruddlesden-Popper phase as cathode for solid oxide fuel cells

In this study, electro-catalytic reduction of oxygen in Sr-doped lanthanum nickelates, La 2-x Sr x NiO 4+δ (0 ≤ x ≤ 0.4) Ruddlesden-Popper (R-P) phase, has been investigated. The oxygen reduction reaction (ORR) kinetics is evaluated via electrochemical impedance spectroscopy (EIS) with the symmetric cell configuration. The maximum performance is achieved with the un-doped La 2 NiO 4+δ , ~0.13 Ωcm 2 at 800°C. Sr doping decreases the electrode performance progressively. Further detailed analysis indicates that bulk ionic diffusion and surface oxygen exchange co-limit the ORR of those cathodes. Sr substitution leads to both lowered bulk diffusion and surface exchange rates. With high Sr content (x = 0.3, 0.4), oxygen ion transfer resistance between nickelate/electrolyte is observed. As for the surface exchange process, oxygen adsorption is suggested to be the main rate-limiting step (RLS) according to the reaction orders, which is retarded further by the oxidation of Ni 2+ to Ni 3+ as Sr content increases. Furthermore, the possible role of incorporation process in determining the overall reaction rate is also discussed.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2013

Monitoring Uranium Transformations Determined by the Evolution of Biogeochemical Processes: Design of Mixed Batch Reactor and Column Studies at Oak Ridge National Laboratory

With funds provided by the US DOE, Argonne National Laboratory subcontracted the design of batch and column studies to a Stanford University team with field experience at the ORNL IFRC, Oak Ridge, TN. The contribution of the Stanford group ended in 2011 due to budget reduction in ANL. Over the funded research period, the Stanford research team characterized ORNL IFRC groundwater and sediments and set up microcosm reactors and columns at ANL to ensure that experiments were relevant to field conditions at Oak Ridge. The results of microcosm testing demonstrated that U(VI) in sediments was reduced to U(IV) with the addition of ethanol. The reduced products were not uraninite but were instead U(IV) complexes associated with Fe. Fe(III) in solid phase was only partially reduced. The Stanford team communicated with the ANL team members through email and conference calls and face to face at the annual ERSP PI meeting and national meetings.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Synthesis and Crystal Structure of the Layered Lanthanide Oxychlorides Ba 3 Ln 2 O 5 Cl 2

Single crystals of a new family of layered lanthanide oxychlorides, Ba 3 Ln 2 O 5 Cl 2 (Ln = Gd–Lu), have been synthesized from a molten barium flux. This family crystallizes in the space group I4/ mmm (No. 139; Z = 2) with lattice parameters a = 4.3384(1)–4.4541(1) Å and c = 24.5108(7)–24.8448(9) Å. Ba 3 Ln 2 O 5 Cl 2 phases are built up of two different blocks: a perovskite double layer of stoichiometry Ba 2 Ln 2 O 5 formed by corner-connected LnO 5 tetragonal bipyramids and a puckered rock-salt-like interlayer of composition BaCl 2 . A complete structural study along with bond-valence-sum calculations shows that, for lanthanides larger than gadolinium, the structure becomes unstable. Density functional theory calculations show that the valence-band edge is dominated by oxygen orbitals, whereas the conduction band forms from Ba 5d orbitals. Finally, the synthesis of this family suggests a route to other potential multianion phases.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Direct characterization of the Li intercalation mechanism into α-V 2 O 5 nanowires using in-situ transmission electron microscopy

The Li-V 2 O 5 system has been well studied electrochemically, but there is a lack of systematic in-situ studies involving direct investigations of the structural changes that accompany the lithiation process. The open-cell battery setup inside a transmission electron microscope is ideal for studying the reaction pathway of intercalation of Li + into nanowire cathodes. Here, in this work, we utilize in-situ transmission electron microscopy to study the Li-V 2 O 5 system. More specifically, we employ electron beam diffraction and electron energy-loss spectroscopy (EELS) in an open-cell battery setup to examine the phase changes within α-V 2 O 5 nanowire cathodes upon in-situ lithiation. Our results suggest that the pristine α-V 2 O 5 nanowire forms a Li oxide shell which then acts as a solid state electrolyte to conduct Li + ions, and the bulk of the V 2 O 5 nanowire undergoes transformation to the γ-Li 2 V 2 O 5 phase.

25 ENERGY STORAGE↗
DOE OSTI2019

Interaction of Long-lived Reactive Species from Cold Atmospheric Pressure Plasma with Polymers: Chemical Modification by Ozone and Reactive Oxygen-Nitrogen Species

Atmospheric pressure plasma (APP) sources are able to generate a variety of reactive species that have different effects on materials, such as functionalization, etching and deposition. In this article, we study the effect of long-lived reactive neutral species on polymers using a model plasma-surface interaction (PSI) system that consists of ultra-thin (~10 nm) polystyrene (PS) films and a surface micro-discharge (SMD) reactor operated with various N 2 /O 2 working gas mixtures. We characterized and quantified the reactive species generated by SMD using IR and UV absorption, and we found that O 3 , N 2 O 5 , N 2 O and HNO 3 are the dominant long-lived reactants near the target surface. When exposing PS films to these reactive species, we observed material responses including film thickness expansion, surface and bulk oxidation, and surface organic nitrate formation. The quantity of these changes varied with the N 2 /O 2 working gas composition. By correlating material response with gas phase species, we find that the chemical modification of PS strongly depends on the density of O 3 in the gas phase, which is indicative of an essential role of O 3 in the remote APP treatment of polymers. Our results show that O 3 causes polymer surface oxidation, participates in the diffusion-reaction process in the polymer bulk, and results in aromatic ring cleavage and the formation of carbonyl groups. In contrast, we did not find a correlation between surface organic nitrate and individual long-lived reactive species mentioned above. This indicates that surface organic nitrate formation on polymer surfaces might result from the interaction of multiple reactive species, including O 3 and nitrogen containing species. A model for the interphase mass transfer of reactive species from gas to solid was also described.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Sm 0.5 Sr 0.5 CoO 3-δ Surface Modification of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ -Ce 0.9 Gd0.1 2-δ Composite Oxygen Electrodes for Solid Oxide Electrochemical Cells

La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3- δ -Ce 0.9 Gd 0.1 O 2- δ (LSCF-GDC) composite oxygen electrodes have been widely used in intermediate temperature (<700 °C) solid oxide cells, with composite usually providing better electrochemical performance than single-phase LSCF. However, LSCF-based electrodes are often observed to degrade over time due to Sr segregation. Here we present an impedance spectroscopy study comparing the degradation behaviors of LSCF-GDC and Sm 0.5 Sr 0.5 CoO 3- δ (SSC) infiltrated LSCF-GDC electrodes. The LSCF-GDC polarization resistance increases by ~5 times over ~1000 h at 650 °C. In contrast, the SSC-infiltrated electrode shows similar initial polarization resistance but much more stable performance. The impedance modeling results show that the improved stability is associated with the low frequency oxygen dissociative adsorption/desorption process. The results suggest that this adsorption/desorption process slows due to increased Sr segregation on LSCF over time, and that SSC does not degrade significantly due to Sr surface segregation.

Electrochemistry↗
DOE OSTI2019

A Study on the Microstructures and Properties of Selective Laser Melted Babbitt Metals

Babbitt metal cubes were prepared by means of selected laser melting (SLM) process using Sn—11% Sb—6% Cu alloy powders; their microstructures were studied using optical microscope (OM), SEM, EDS, XRD and DSC; and their mechanical properties were tested using Vickers hardness and tensile methods. The results show that fully dense Babbitt metal components can be prepared by using appropriate SLM process parameters and an interlayer staggered laser scanning strategy. Anisotropy characteristics appear in both the microstructure and mechanical properties of SLM-Babbitt cubic specimens. The average hardness was in the range of 32.5 HV0.05 to 35.3 HV0.05. Both tensile strength and elongation were somewhat higher in a direction parallel to the laser scanning speed (Y axis) than in a direction perpendicular to the laser scanning speed (X axis). The strengthening mechanism is suggested to include solid solution strengthening of oversaturated Sb in the Sn matrix, as well as dispersion strengthening of finely dispersed SnSb and Cu{sub 6}Sn{sub 5} particles. The overgrown acicular Cu{sub 6}Sn{sub 5} phases at low laser scanning speeds and void formation at higher laser scanning speeds seriously deteriorate the mechanical properties of the SLM-Babbitt specimens.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Data Mining for Parameters Affecting Polymorph Selection in Contorted Hexabenzocoronene Derivatives

The macroscopic properties of molecular materials can be drastically influenced by their solid-state packing arrangements, of which there can be many (e.g., polymorphism). Strategies to controllably and predictively access select polymorphs are thus highly desired, but computationally predicting the conditions necessary to access a given polymorph is challenging with the current state of the art. Using derivatives of contorted hexabenzocoronene, cHBC, we employed data mining, rather than first-principles approaches, to find relationships between the crystallizing molecule, postdeposition solvent-vapor annealing conditions that induce polymorphic transformation, and the resulting polymorphs. This analysis yields a correlative function that can be used to successfully predict the appearance of either one of two polymorphs in thin films of cHBC derivatives. Within the postdeposition processing phase space of cHBC derivatives, we have demonstrated an approach to generate guidelines to select crystallization conditions to bias polymorph access. Finally, we believe this approach can be applied more broadly to accelerate the predictions of processing conditions to access desired molecular polymorphs, making progress toward one of the grand challenges identified by the Materials Genome Initiative.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Melts of CrCoNi-based high-entropy alloys: Atomic diffusion and electronic/atomic structure from ab initio simulation

High-entropy alloys (HEAs) are an emerging class of advanced structural alloys under extensive research; yet, the properties of the liquid states of these materials, which are relevant to their processing, have been far less explored. In this work, we utilize ab initio molecular dynamics simulations to investigate the melt properties of a representative HEA—the Cantor alloy—and its derivatives: CrMnFeCoNi, CrFeCoNi, and CrCoNi. The atomic dynamics of these melts at various temperatures are investigated, specifically to analyze their electronic and atomic structures, including charge transfer, pair distribution functions, and short-range order. Results are compared with existing information for the liquids of metallic glasses, which also typically contain multiple principal elements, but retain the amorphous state under moderate to fast cooling rates. The present results provide insights into the structural and bonding factors favoring solidification to single-phase solid solutions in HEAs.

36 MATERIALS SCIENCE↗
DOE OSTI2015

The Science of Battery Degradation

This report documents work that was performed under the Laboratory Directed Research and Development project, Science of Battery Degradation. The focus of this work was on the creation of new experimental and theoretical approaches to understand atomistic mechanisms of degradation in battery electrodes that result in loss of electrical energy storage capacity. Several unique approaches were developed during the course of the project, including the invention of a technique based on ultramicrotoming to cross-section commercial scale battery electrodes, the demonstration of scanning transmission x-ray microscopy (STXM) to probe lithium transport mechanisms within Li-ion battery electrodes, the creation of in-situ liquid cells to observe electrochemical reactions in real-time using both transmission electron microscopy (TEM) and STXM, the creation of an in-situ optical cell utilizing Raman spectroscopy and the application of the cell for analyzing redox flow batteries, the invention of an approach for performing ab initio simulation of electrochemical reactions under potential control and its application for the study of electrolyte degradation, and the development of an electrochemical entropy technique combined with x-ray based structural measurements for understanding origins of battery degradation. These approaches led to a number of scientific discoveries. Using STXM we learned that lithium iron phosphate battery cathodes display unexpected behavior during lithiation wherein lithium transport is controlled by nucleation of a lithiated phase, leading to high heterogeneity in lithium content at each particle and a surprising invariance of local current density with the overall electrode charging current. We discovered using in-situ transmission electron microscopy that there is a size limit to lithiation of silicon anode particles above which particle fracture controls electrode degradation. From electrochemical entropy measurements, we discovered that entropy changes little with degradation but the origin of degradation in cathodes is kinetic in nature, i.e. lower rate cycling recovers lost capacity. Finally, our modeling of electrode-electrolyte interfaces revealed that electrolyte degradation may occur by either a single or double electron transfer process depending on thickness of the solid-electrolyte-interphase layer, and this cross-over can be modeled and predicted.

25 ENERGY STORAGE↗
DOE OSTI2013

Early age hydration of calcium sulfoaluminate (synthetic ye'elimite, C{sub 4}A{sub 3}S{sup ¯}) in the presence of gypsum and varying amounts of calcium hydroxide

Suspensions of synthetic ye'elimite (C{sub 4}A{sub 3}S{sup ¯}) in a saturated gypsum (CS{sup ¯}H{sub 2}) and calcium hydroxide (CH) solution were examined in-situ in a wet cell by soft X-ray transmission microscopy and ex-situ by scanning electron microscopy. The most voluminous hydration product observed was ettringite. Ettringite commonly displayed acicular, filiform, reticulated, and stellate crystal habits. Additionally, pastes with C{sub 4}A{sub 3}S{sup ¯}, 15% CS{sup ¯}H{sub 2}, and varying amounts of CH were prepared and examined with X-ray diffraction (XRD) and isothermal calorimetry. The XRD experiments showed that increasing CH content caused more solid solution (SO{sub 4}{sup 2−}/OH{sup −}) AFm phases to form at early ages (< 1 d) and more monosulfate to form at later ages (> 1 d). Calorimetry indicated that the increased production of solid solution AFm was accompanied with an increase in the initial (< 30 min) rate of heat evolution, and increasing CH generally reduced the time till the second maximum rate of heat evolution due to the formation of ettringite and monosulfate.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Spatial distribution of organic functional groups supported on mesoporous silica nanoparticles (2): a study by 1 H triple-quantum fast-MAS solid-state NMR

The distribution of organic functional groups attached to the surface of mesoporous silica nanoparticles (MSNs) via co-condensation was scrutinized using 1D and 2D 1 H solid-state NMR, including the triple-quantum/single-quantum (TQ/SQ) homonuclear correlation technique. The excellent sensitivity of 1 H NMR and high resolution provided by fast magic angle spinning (MAS) allowed us to study surfaces with very low concentrations of aminopropyl functional groups. The sequential process, in which the injection of tetraethyl orthosilicate (TEOS) into the aqueous mother liquor was followed by dropwise addition of the organosilane precursor, resulted in deployment of organic groups on the surface, which were highly clustered even in a sample with a very low loading of ~0.1 mmol g -1 . The underlying mechanism responsible for clustering could involve fast aggregation of the aminopropyltrimethoxysilane (APTMS) precursor within the liquid phase, and/or co-condensation of the silica-bound molecules. Understanding the deposition process and the resulting topology of surface functionalities with atomic-scale resolution, can help to develop novel approaches to the synthesis of complex inorganic–organic hybrid materials.

36 MATERIALS SCIENCE↗
DOE OSTI2019

In situ Characterization of Kinetics and Mass Transport of PbSe Nanowire Growth via LS and VLS Mechanisms

As a versatile approach, the vapor-liquid-solid (VLS) mechanism is widely used to grow nanowires. However, the details of the mass transit and mechanism of compound nanowire growth have been limited because of the complex growth process. In this study, we grew binary PbSe nanowires using an in situ gas-heating cell and elucidated two different growth mechanisms and mass transit pathways of different growth species, as well as their controlling factors, using in situ high-resolution transmission electron microscopy and composition analysis. Initial high supersaturation led to poly-nucleation and fast PbSe crystal growth through bulk diffusion of Pb and Se growth species from liquid to solid—a liquid-solid (LS) mechanism. In situ composition analysis showed that Pb dissolved in liquid catalyst at miscible atomic percentages as a precursor during growth. Se precursor was depleted after initial growth and was supplied from the vapor phase, leading to subsequently relatively slow VLS controlled mono-nuclear growth. We revealed the correlation between the nucleation mechanisms and the growth kinetics using a generalized Avrami model. Our study highlighted the key correlations among supersaturation, nucleation, mass transit, and growth kinetics, thereby enabling morphological and compositional control of nanowires.

Song, Miao↗