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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Physical Properties of the Star-forming Regions in the Interacting Galaxies NGC 3395/NGC 3396

We report long-slit spectroscopy of the early major merger galaxies NGC 3395/NGC 3396. The spectra are consistent with those for star-forming galaxies, but there is some indication of LINER-like active galactic nucleus activity in the center of NGC 3396. The total star formation rate in the regions observed is 2.83 M {sub ⊙} yr{sup −1}, consistent with estimates for the entire galaxies. The highest abundances are in the centers of the galaxies, with the abundances decreasing with distance. There is a correlation between high abundance and high ionization parameter, both of which can be attributed to the presence of massive stars. Modeling with SB 99 indicates the star-forming regions are younger than 10 Myr. There are 1000–2000 WNL stars in the system, along with several thousand O stars, consistent with the ages of the star-forming regions. The highest electron densities are found in young regions with high star formation rates. The electron temperatures are higher than results for non-interacting galaxies, which is probably due to shock waves produced by the galaxy–galaxy interaction, the outflow of gas from massive stars, and/or collisions between gas clouds in the galaxies. There is star formation in the bridge of material between the galaxies. These regions are among the youngest in the system and have low abundances, suggesting the gas was pulled from the outer parts of the galaxies. X-ray point sources, probably high-mass X-ray binaries, are associated with several star-forming regions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Constraints on the Physical Properties of GW190814 through Simulations Based on DECam Follow-up Observations by the Dark Energy Survey

On 2019 August 14, the LIGO and Virgo Collaborations detected gravitational waves from a black hole and a 2.6 solar mass compact object, possibly the first neutron star–black hole merger. In search of an optical counterpart, the Dark Energy Survey (DES) obtained deep imaging of the entire 90% confidence level localization area with Blanco/DECam 0, 1, 2, 3, 6, and 16 nights after the merger. Objects with varying brightness were detected by the DES Pipeline, and we systematically reduced the candidate counterparts through catalog matching, light-curve properties, host-galaxy photometric redshifts, Southern Astrophysical Research spectroscopic follow-up observations, and machine-learning-based photometric classification. All candidates were rejected as counterparts to the merger. To quantify the sensitivity of our search, we applied our selection criteria to full light-curve simulations of supernovae and kilonovae as they would appear in the DECam observations. Because the source class of the merger was uncertain, we utilized an agnostic, three-component kilonova model based on tidally disrupted neutron star (NS) ejecta properties to quantify our detection efficiency of a counterpart if the merger included an NS. We find that, if a kilonova occurred during this merger, configurations where the ejected matter is greater than 0.07 solar masses, has lanthanide abundance less than 10 -8.56 , and has a velocity between 0.18c and 0.21c are disfavored at the 2σ level. Furthermore, we estimate that our background reduction methods are capable of associating gravitational wave signals with a detected electromagnetic counterpart at the 4σ level in 95% of future follow-up observations.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

The Physical Properties of Low-redshift FeLoBAL Quasars. II. The Rest-frame Optical Emission Line Properties

We report the results of an analysis of the Hβ emission line region of a sample of 30 low-redshift (z < 1) iron low-ionization broad absorption line quasars (FeLoBALQs). Eleven of these objects are newly classified as FeLoBALQs. A matched sample of 132 unabsorbed quasars was analyzed in parallel. The emission lines showed the well-known anticorrelation between the [O III ] and Fe II emission. Using a summary statistic called E1 to quantify this anticorrelation, we found that while the distribution of E1 for the unabsorbed quasars has a single peak, the FeLoBALQs have a bimodal shape in this parameter. Previous studies have shown that the line emission properties of BAL and non-BALQs are consistent; therefore, the difference in the Hβ region emission between FeLoBALQs and unabsorbed quasars is a new result. The two populations of FeLoBALQs are characterized by low and high bolometric luminosities and Eddington ratios. Some previous studies have suggested that BALQs are high accretion rate objects and therefore the discovery of the low accretion rate branch of FeLoBAL quasars was unexpected. We also found that the Hβ FWHM is systematically broader among the FeLoBALQs, implying a higher inclination viewing angle or a dearth of low velocity line emitting gas.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Tuning MXene Surface Terminations for Strategic Control of Physical Properties

Scientific Achievement • Ti3C2Tx surfaces with a higher hydroxyl group concentration play a pivotal role in surface properties and were found to be thermodynamically stable. • From the electronic bonding analysis, the charge density difference and electron localization function demonstrated a significant electron localization at the hydroxyl group, which results in a locally induced dipole on the surface. • A large tunability in the work function is found from different concentrations of functional groups on the surface which can be controlled by the concentration of HF used for etching of the MAX phase to produce the resulting MXene. Research Details • The influence of termination group distribution on the surface of Ti3C2Tx MXenes from various etching concentrations of HF was evaluated • The work functions of Ti3C2Tx MXenes with differing concentrations of functional groups were determined • The influence of termination group clustering on the surface of Ti3C2Tx MXenes was investigated by visualization of the electron localization function and charge density difference

Ward, Patrick A.↗
DOE OSTI2021

Solid Phase Gradient Alloying Method via ShAPE

Alloying has been used to confer desirable properties to various metallic systems since the bronze age. For example, Ni, Mn, and Cr are alloyed into an Fe matrix to make steel, which has improved strength and corrosion resistance (as displayed in Fig. 1). In addition to the type of alloying elements, the amount of alloying elements added into a matrix is also very critical for a material’s mechanical property, physical property, machinability, and cost. Conventionally, new alloys are discovered by combining alloy precursors and elemental constituents into a mixture and melting them together. The solidified product or ingot represents a usually non-homogeneous combination of the chemistry with a microstructure dictated by the physics of solidification. It is time and energy intensive to optimize the alloying amounts via the casting process and hence, economically not conducive to rapid alloy discovery. In addition, the cast microstructure seen in the as-cast ingot is often not the ideal, nor even desired structure for optimized performance. Cast materials often need further processing such as homogenization, annealing, and deformation work put in through rolling, forging, extruding, etc. to have favorable microstructures and properties. A faster method to discover new alloy combinations and evaluate them in their worked or processed form is needed. Recently, Laser Engineered Net Shaping was applied to fabricate gradient compositional material for alloy designing. However, the mechanical properties of this gradient alloy were poor due to the existence of impurities, oxidation and cracks that are inherent in the melt-solidification process. Because of these limitations, we propose to use a solid-phase process (ShAPE) to create bulk materials (extrudates) that vary in composition from one end of the extruded solid to the other. Various manufacturing methods for alloy design including conventional casting method, laser based combinatorial method and current solid phase gradient alloying method are displayed and compared in Fig. 2. ShAPE machine and a schematic of ShAPE process are displayed in Fig. 3. Starting material is processed by a rotating and plunging die to form an extrudate. We are proposing through this methodology to invent a new, bulk-scale combinatorial technique. With this novel technique, alloying element can be dissolved into the matrix with a continued gradient without bulk melting. Formation of inter-metallics and defects originating from melt processing can be avoided. In addition, the ShAPE process creates the mixed alloy chemistry, and meanwhile subjects the material to severe plastic strain, which induces the favorable “worked” microstructure. Products from the ShAPE process can be tested in hardness directly providing a path to rapid evaluation of mechanical properties. The ability to create graded structures using friction stir processing (FSP) has been demonstrated, however using the ShAPE process we believe will lead to much faster and higher fidelity results. When combined with high throughput screening methods of physical, mechanical and microstructural property characterization, efficiency and accuracy of alloy design can be significantly improved.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Strength, deformation, and the fcc–hcp phase transition in condensed Kr and Xe to the 100 GPa pressure range

The rare gas solids exhibit systematic differences in crystal structure, phase transition conditions, bond strength, and other physical properties. The physical properties of heavy rare gas solids krypton and xenon are modified by the martensitic phase transition from face-centered cubic to hexagonal close packed structure over a broad pressure range. Crystal structure, strength, and plastic deformation of krypton and xenon have been investigated at 300 K using compression in the diamond-anvil cell with synchrotron angle-dispersive x-ray diffraction and complementary ruby fluorescence spectroscopy for Xe. Stacking faults indicative of the fcc–hcp phase transition are observed at pressures at and above 1.23 ± 0.05 and 1.9 ± 0.6 GPa in Kr and Xe, respectively. The transition remains incomplete in both solids to pressures greater than 100 GPa. Strength determined from stress measurements in Pt and ruby standards at pressures up to 111 GPa and complemented by observations of strain and texture measurements obtained by x-ray diffraction in the radial geometry to 100 GPa indicates similar or higher strength than Ar at all conditions, with significant stiffening at 15–20 GPa. Radial diffraction data reveal the persistence of broad highly textured fcc diffraction lines to 101 GPa in Xe, suggesting that the axial measurements may underestimate the metastable persistence of the fcc phase due to biased sampling of hcp crystallites resulting from preferred crystallite orientation. Kr and Xe are compared with He, Ne, and Ar for a systematic understanding of physical properties and phase equilibria of rare gas solids.

Compressive stress↗
DOE OSTI2022

Computationally optimized and manufactured acoustic metamaterials

A method, system, and apparatus for fabricating an acoustic metamaterial is provided. In an embodiment, a method for fabricating an acoustic metamaterial includes determining at least one tuned physical property for each of a plurality of micro-resonators according to a desired acoustic property of the acoustic metamaterial. For a particular physical property, a value of the tuned physical property for at least one of the plurality of micro-resonators is different from a value of the tuned physical property for at least one other of the plurality of micro-resonators. The method also includes additively forming the acoustic metamaterial such that the acoustic metamaterial comprises a first structure and the plurality of micro-resonators embedded within the first structure. Forming the acoustic metamaterial is performed such that an actual physical property of each of the plurality of micro-resonators is equal to a corresponding tuned physical property for each of the plurality of micro-resonators.

Walsh, Timothy F.↗
DOE OSTI2023

Understanding fundamental effects of biofuel structure on ignition and physical fuel properties

The development of biochemicals and biofuels with advantaged properties of higher combustion efficiency at lower emission levels can be aided by a priori prediction of critical global characteristics based on molecular structure. Existing predictive techniques are incomplete for comprehensive ignition and physical fuel property prediction. Here this investigation focuses on filling this knowledge gap by developing a priori prediction techniques for predicting important ignition as well as physical fuel properties of promising advantaged biofuels. We demonstrate the utility of this a priori prediction technique on saturated (≤C 5 ) alcohols, both linear and branched in nature by correlating their molecular structure with both important ignition and physical properties of the fuels. This work utilizes a semi-automated method of predicting ignition characteristics via accurate fundamental-based calculations of the fuel radical cascades that govern low-temperature combustion. This numerical methodology is supported by the relevant fuel ignition delay time (IDT) and research octane number (RON) data experimentally measured by the Advanced Fuel Ignition Delay Analyzer (AFIDA). Phyiscal fuel property trends are also analyzed by correlating the molecular structure of the fuel to its physical characteristics. Based on their molecular structure, recommendations are made on an a priori method for selecting biofuels that have advantaged properties for the selected fuel application. Lastly, the utility of this investigation is extended beyond the subset of alcohols considered by analyzing the IDT trends of i-Pentanol and n-Hexanol, revealing the fidelity of the novel kinetic modelling approach and the accuracy of the predicted trends in this study.

09 BIOMASS FUELS↗
DOE OSTI2021

Electric-field-driven octahedral rotation in perovskite

Rotation of MO 6 (M = transition metal) octahedra is a key determinant of the physical properties of perovskite materials. Therefore, tuning physical properties, one of the most important goals in condensed matter research, may be accomplished by controlling octahedral rotation (OR). In this study, it is demonstrated that OR can be driven by an electric field in Sr 2 RuO 4 . Rotated octahedra in the surface layer of Sr2RuO4 are restored to the unrotated bulk structure upon dosing the surface with K. Theoretical investigation shows that OR in Sr 2 RuO 4 originates from the surface electric field, which can be tuned via the screening effect of the overlaid K layer. This work establishes not only that variation in the OR angle can be induced by an electric field, but also provides a way to control OR, which is an important step toward in situ control of the physical properties of perovskite oxides.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Fast and stable deep-learning predictions of material properties for solid solution alloys

We present a novel deep learning (DL) approach to produce highly accurate predictions of macroscopic physical properties of solid solution binary alloys and magnetic systems. The major idea is to make use of the correlations between different physical properties in alloy systems to improve the prediction accuracy of neural network (NN) models. We use multitasking NN models to simultaneously predict the total energy, charge density and magnetic moment. These physical properties mutually serve as constraints during the training of the multitasking NN, resulting in more reliable DL models because multiple physics properties are correctly learned by a single model. Two binary alloys, copper–gold (CuAu) and iron–platinum (FePt), were studied. Our results show that once the multitasking NN's are trained, they can estimate the material properties for a specific configuration hundreds of times faster than first-principles density functional theory calculations while retaining comparable accuracy. We used a simple measure based on the root-mean-squared errors to quantify the quality of the NN models, and found that the inclusion of charge density and magnetic moment as physical constraints leads to more stable models that exhibit improved accuracy and reduced uncertainty for the energy predictions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Bacterial-Retted Hemp Fiber/PLA Composites

The push for sustainability in all facets of manufacturing has led to an increased interest in biomass as an alternative to non-renewable materials. Hemp bast fiber mats were produced from a bacterial retting process, named BFM, as the fiber reinforcement. The objective of this study was to evaluate the feasibility of laminating BFM with polylactic acid (PLA) for a composite panel product. Since both BFM and PLA are biodegradable, the resulting BFM-PLA composites will be 100% biodegradable. PLA pallets were processed into thin polymer sheets which served as the matrix. The BFM and PLA plates were laminated in five layers and compression-molded into composite panels. Experiments were conducted on the three BFM-to-PLA ratios (35/65, 45/55, and 50/50). Mechanical properties (tensile and bending properties) and physical properties (thickness swell and water absorption) were tested and compared to the currently commercial sheet molding compound (SMC) from fiber glass. The thermal behavior of the BFM/PLA composites was characterized using dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The developed BFM/PLA composite product is a sustainable alternative to existing synthetical fiber-reinforced polymer (FRP) that is biodegradable in landfill at the end of life.

Smith, Lee M. (ORCID:0000000264390357)↗