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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

The Physics of Molecular Shocks in Star-Forming Regions

Molecular shocks are produced by the impact of the supersonic infall of gas and dust onto protostars and by the interaction of the supersonic outflow from the protostar with the circumstellar material. Infalling gas creates an accretion shock around the circumstellar disk which emits a unique infrared spectrum and which processes the interstellar dust as it enters the disk. The winds and jets from protostars also impact the disk, the infalling material, and the ambient molecular cloud core creating shocks whose spectrum and morphology diagnose the mass loss processes of the protostar and the orientation and structure of the star forming system. We discuss the physics of these shocks, the model spectra derived from theoretical models, and comparisons with observations of H2O masers, H2 emission, as well as other shocks tracers. We show the strong effect of magnetic fields on molecular shock structure, and elucidate the chemical changes induced by the shock heating and compression.

Hollenbach, David↗
NASA NTRS1985

r-process nucleosynthesis in dynamic helium-burning environments

The results of an extended examination of r-process nucleosynthesis in helium-burning enviroments are presented. Using newly calculated nuclear rates, dynamical r-process calculations have been made of thermal runaways in helium cores typical of low-mass stars and in the helium zones of stars undergoing supernova explosions. These calculations show that, for a sufficient flux of neutrons produced by the C-13 neutron source, r-process nuclei in solar proportions can be produced. The conditions required for r-process production are found to be 10 to the 20th-10 to the 21st neutrons per cubic centimeter for times of 0.01-0.1 s and neutron number densities in excess of 10 to the 19th per cubic centimeter for times of about 1 s. The amount of C-13 required is found to be exceedingly high - larger than is found to occur in any current stellar evolutionary model. It is thus unlikely that these helium-burning environments are responsible for producing the bulk of the r-process elements seen in the solar system.

Cowan, J. J.↗
NASA NTRS1997

Advanced Technology Composite Fuselage - Manufacturing

The goal of Boeing's Advanced Technology Composite Aircraft Structures (ATCAS) program is to develop the technology required for cost-and weight-efficient use of composite materials in transport fuselage structure. Carbon fiber reinforced epoxy was chosen for fuselage skins and stiffening elements, and for passenger and cargo floor structures. The automated fiber placement (AFP) process was selected for fabrication of stringer-stiffened and sandwich skin panels. Circumferential and window frames were braided and resin transfer molded (RTM'd). Pultrusion was selected for fabrication of floor beams and constant-section stiffening elements. Drape forming was chosen for stringers and other stiffening elements cocured to skin structures. Significant process development efforts included AFP, braiding, RTM, autoclave cure, and core blanket fabrication for both sandwich and stiffened-skin structure. Outer-mold-line and inner-mold-line tooling was developed for sandwich structures and stiffened-skin structure. The effect of design details, process control and tool design on repeatable, dimensionally stable, structure for low cost barrel assembly was assessed. Subcomponent panels representative of crown, keel, and side quadrant panels were fabricated to assess scale-up effects and manufacturing anomalies for full-scale structures. Manufacturing database including time studies, part quality, and manufacturing plans were generated to support the development of designs and analytical models to access cost, structural performance, and dimensional tolerance.

Wilden, K. S.↗
NASA NTRS2012

Observations of Nitrogen Fractionation in Prestellar Cores: Nitriles Tracing Interstellar Chemistry

Primitive materials provide important clues on the processes that occurred during the formation and early evolution of the Solar System. Space-based and ground-based observations of cometary comae show that comets appear to contain a mixture of the products of both interstellar and nebular chemistries. Significant 15-nitrogen enrichments have been measured in CN and HCN towards a number of comets and may suggest an origin of interstellar chemical fractionation. Additionally, large N-15 enhancements are found in meteorites and has also led to to the view that the N-15 traces material formed in the interstellar medium (ISM), although multiple sources cannot be excluded. Here, we show the results of observations of the nitrogen and carbon fractionation in prestellar cores for various N-bearing species to decipher the origin of primitive material isotopic enrichments.

Milam, S. N.↗
NASA NTRS2018

Topological Control of Polystyrene-Silica Core-Shell Microspheres

Controllable surface morphology is requisite across a gamut of processes, industries, and applications. The surface morphology of silica-coated polystyrene microspheres was controllably modified to enable generation of both smooth and bumpy, or raspberry-like, surfaces. Although smooth and raspberry-like silica shells on polystyrene templates have been demonstrated extensively, the method described here used readily available materials to produce radical changes in surface morphology from a single polystyrene template coated in silica through a facile sol-gel reaction processes. Silica shells were deposited via a sol-gel process (using tetraethyl orthosilicate as the silica precursor) onto 1 to 2 m diameter anionic polystyrene spheres, fabricated by emulsifier-free polymerization. By varying of the concentration of silica precursor and ammonium hydroxide catalyst and altering the electrostatic surface interactions via addition of a cationic polymeric brush, an array of surface topologies was generated. The resulting silica shells ranged from 100 to 200 nm in thickness, as measured by calcination of the polystyrene template. Empirical relations between reaction conditions and the resulting silica colloid diameter were utilized to understand the resultant silica shell topology. These results may serve as a guide to generate a versatile platform for research in the multitude of applications where polystyrene-silica core-shell particles are utilized.

Zane A. Grady↗
DOE OSTI2019

r-Process Nucleosynthesis: Connecting Rare-Isotope Beam Facilities with the Cosmos

This is a pivotal time for the study of r-process nucleosynthesis. Recently, a neutron star merger GW170817 was observed in extraordinary detail with gravitational waves and electromagnetic radiation from radio to γ rays. The very red color of the associated kilonova suggests that neutron star mergers are an important r-process site. Astrophysical simulations of neutron star mergers and core collapse supernovae are making rapid progress. Detection of both electron neutrinos and antineutrinos from the next Galactic supernova will constrain the composition of neutrino-driven winds and provide unique nucleosynthesis information. Finally, FRIB and other rare-isotope beam facilities will soon have dramatic new capabilities to synthesize many neutron-rich nuclei that are involved in the r-process. The new capabilities can significantly improve our understanding of the r-process and likely resolve one of the main outstanding problems in classical nuclear astrophysics. Yet, to make best use of the new experimental capabilities and to fully interpret the results, a great deal of infrastructure is needed in many related areas of astronomy, astrophysics, and nuclear theory. We place these experiments in context by discussing astrophysical simulations and observations of r-process sites, observations of stellar abundances, Galactic chemical evolution, and nuclear theory for the structure and reactions of very neutron-rich nuclei. This review paper was initiated at a three week International Collaborations in Nuclear Theory program in June 2016, where we explored promising r-process experiments and discussed their likely impact, and their astronomical, astrophysical, and nuclear theory context.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1999

The formaldehyde ortho/para ratio as a probe of dark cloud chemistry and evolution

We present measurements of the H2CO ortho/para ratio toward four star-forming cores, L723, L1228, L1527, and L43, and one quiescent core, L1498. Combining these data with earlier results by Minh et al., three quiescent cores are found to have ortho/para ratios near 3, the ratio of statistical weights expected for gas-phase formation processes. In contrast, ortho/para ratios are 1.5-2.1 in five star-forming cores, suggesting thermalization at a kinetic temperature of 10 K. We attribute modification of the ortho/para ratio in the latter cores to formation and/or equilibration of H2CO on grains with sub-sequent release back into the gas phase due to the increased energy inputs from the forming star and outflow. We see accompanying enhancements in the H2CO abundance relative to H, to support this idea. The results suggest that the formaldehyde ortho/para ratio can differentiate between quiescent cores and those in which low-mass star formation has occurred.

Non-NASA Center↗
DOE OSTI2022

Sampling and Characterization of Coal Basins as an Alternative Rare-Earth Element Resource

Conference presentation at TechConnect World Innovation Conference & Expo, Washington, D.C., June 13–15, 2022. The University of North Dakota (UND) through the Energy & Environmental Research Center (EERC) and the Institute for Energy Studies teamed with the University of Kentucky Center for Applied Energy Research, Microbeam Technologies Inc., the Kentucky Geological Survey (KGS), the North Dakota Geological Survey (NDGS), and the mining industry to execute a contract with the U.S. Department of Energy National Energy Technology Laboratory (NETL) to obtain and characterize samples of U.S. domestic precombustion coal and coal-related materials with a minimum concentration of 300 parts per million (ppm) total rare-earth elements (TREEs) as the material is removed from the ground, with no processing other than drying.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2017

Development of High-Performance Cast Crankshafts. Final Technical Report

The objective of this project was to develop technologies that would enable the production of cast crankshafts that can replace high performance forged steel crankshafts. To achieve this, the Ultimate Tensile Strength (UTS) of the new material needs to be 850 MPa with a desired minimum Yield Strength (YS; 0.2% offset) of 615 MPa and at least 10% elongation. Perhaps more challenging, the cast material needs to be able to achieve sufficient local fatigue properties to satisfy the durability requirements in today’s high performance gasoline and diesel engine applications. The project team focused on the development of cast steel alloys for application in crankshafts to take advantage of the higher stiffness over other potential material choices. The material and process developed should be able to produce high-performance crankshafts at no more than 110% of the cost of current production cast units, perhaps the most difficult objective to achieve. To minimize costs, the primary alloy design strategy was to design compositions that can achieve the required properties with minimal alloying and post-casting heat treatments. An Integrated Computational Materials Engineering (ICME) based approach was utilized, rather than relying only on traditional trial-and-error methods, which has been proven to accelerate alloy development time. Prototype melt chemistries designed using ICME were cast as test specimens and characterized iteratively to develop an alloy design within a stage-gate process. Standard characterization and material testing was done to validate the alloy performance against design targets and provide feedback to material design and manufacturing process models. Finally, the project called for Caterpillar and General Motors (GM) to develop optimized crankshaft designs using the final material and manufacturing processing path developed. A multi-disciplinary effort was to integrate finite element analyses by engine designers and geometry-specific casting simulations with existing materials models to optimize crankshaft cost and performance. Prototype crankshafts of the final design were to be produced and validated using laboratory bench testing and on-engine durability testing. ICME process simulation tools were used to investigate a broad range of processing concepts. These concepts included casting orientation, various mold and core materials, and various filling and feeding strategies. Each crankshaft was first simulated without gating and risers, which is termed natural solidification. The natural solidification results were used as a baseline for strategy development of each concept. Casting process simulations and ICME tools were proven to be reasonable predictors of real world results. Potential alloys were developed that could meet the project material property goals with appropriate normalization and temper treatments. For the alloys considered, post-normalization temper treatments proved to be necessary to achieve the desired yield strengths and elongations and appropriate heat treatments were designed using ICME tools. The experimental data of all the alloys were analyzed in combination with ICME tools to establish chemistry-process-structure relations. Several GM small gas engine (SGE) crankshafts were successfully cast in sand molds using two different sprue, runner, gate, riser, chill designs. These crankshafts were cast in two different steel alloys developed during the project, but casting finishing (e.g. riser removal) remains a cost challenge. A long list of future work was left unfinished when this project was unexpectedly terminated.

36 MATERIALS SCIENCE↗
DOE OSTI2025

3D Convective Urca Process in a Simmering White Dwarf

Abstract A proposed setting for thermonuclear (Type Ia) supernovae is a white dwarf that has gained mass from a companion to the point of carbon ignition in the core. In the early stages of carbon burning, called the simmering phase, energy released by the reactions in the core drive the formation and growth of a core convection zone. One aspect of this phase is the convective Urca process, a linking of weak nuclear reactions to convection, which may alter the composition and structure of the white dwarf. The convective Urca process is not well understood and requires 3D fluid simulations to properly model the turbulent convection, an inherently 3D process. Because the neutron excess of the fluid both sets and is set by the extent of the convection zone, the realistic steady state can only be determined in simulations with real 3D mixing processes. Additionally, the convection is relatively slow (Mach number less than 0.005) and thus a low Mach number method is needed to model the flow over many convective turnovers. Using the MAESTROeX low Mach number hydrodynamic software, we present the first full-star 3D simulations of the A = 23 convective Urca process, spanning hundreds of convective turnover times. Our findings on the extent of mixing across the Urca shell, the characteristic velocities of the flow, the energy-loss rates due to neutrino emission, and the structure of the convective boundary can be used to inform 1D stellar models that track the longer-timescale evolution.

Boyd, Brendan (ORCID:0000000254199751)↗
DOE OSTI2018

Bacterial endophyte communities in Pinus flexilis are structured by host age, tissue type, and environmental factors

Background and aims: Forest tree microbiomes are vital to forest dynamics, diversity, and ecosystem processes. Mature limber pines ( Pinus flexilis ) host a core microbiome of acetic acid bacteria in their foliage, but the bacterial endophyte community structure, variation, and assembly across tree ontogeny is unknown. The aims of this research were to test if the core microbiome observed in adult P. flexilis is established at the seedling stage, if seedlings host different endophyte communities in root and shoot tissues, and how environmental factors structure seedling endophyte communities. Methods: The 16S rRNA gene was sequenced to characterize the bacterial endophyte communities in roots and shoots of P. flexilis seedlings grown in plots at three elevations at Niwot Ridge, Colorado, subjected to experimental treatments (watering and heating). The data was compared to previously sequenced endophyte communities from adult tree foliage sampled in the same year and location. Results: Seedling shoots hosted a different core microbiome than adult tree foliage and were dominated by a few OTUs in the family Oxalobacteraceae , identical or closely related to strains with antifungal activity. Shoot and root communities significantly differed from each other but shared major OTUs. Watering but not warming restructured the seedling endophyte communities. Conclusions: The results indicate differences in assembly and ecological function across conifer life stages. Seedlings may recruit endophytes to protect against fungi under increased soil moisture.

16S rRNA↗
DOE OSTI2017

Oxidation kinetics for conversion of U 3 O 8 to ε-UO 3 with NO 2

The oxidation kinetics of U 3 O 8 powder to ε-UO 3 in an NO 2 environment was measured by in situ x-ray diffraction (XRD). Experiments were performed at temperatures of 195, 210, 235, and 250°C using a custom designed and fabricated sample isolation stage. Data were refined to quantify phase fractions using a newly proposed structure for the ε-UO 3 polymorph. The kinetics data were modeled using a shrinking core approach. A proposed two-step reaction process is presented based on the developed models.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

A General Solution Route to Nanoporous Metal Oxide Films

Metal oxide semiconductors are of interest as efficient, stable, and low-cost photoanode materials for photoelectrochemical water splitting, but their characteristically poor charge transport properties remain a fundamental challenge to practical use. Nanoporous metal oxide films that feature open bicontinuous networks of nanocrystals and nanopores can overcome such inefficient charge transport to enable high-performance photoanodes. Here, this paper describes a general method to make high-quality nanoporous films of metal oxides by spin coating and calcining molecular inks that contain a porosity-generating block copolymer. Phase-pure nanoporous films of BiFeO 3 , FeWO 4 , WO 3 , Fe 2 O 3 , and TiO 2 serve to demonstrate the versatility of the approach. It is demonstrated that the crystallite size, film porosity, and film thickness can be independently tuned by adjusting the ink composition and film processing conditions. The method is extended to fabricate core–shell nanoporous films consisting of a nanoporous film coated in a thin shell of a second metal oxide, using WO 3 –BiVO 4 and BiFeO 3 –BiVO 4 as examples. Given its simplicity and flexibility, this solution-phase route should prove useful for making nanoporous films of many different materials for a variety of applications, including energy conversion and storage, catalysis, and chemical sensing.

coating materials↗
DOE OSTI2019

Predicted Efficient Visible-Light Driven Water Splitting and Carbon Dioxide Reduction Using Photoredox-Active UiO-NDI Metal Organic Framework

The structural and electronic properties of metal–organic frameworks (MOFs) constructed from stable Zr(IV) oxide-based nodes and naphthalenediimide-based linkers (UiO(Zr)-NDI) can be tuned to make them useful for specific photoredox processes. The NDI linker presents outside, inside, and core positions where functionalization can influence its optical properties, and such substitution in combination with suitable optical band gaps and band edge positions in UiO(Zr)-NDI offers a platform for the design of efficient MOF-based photocatalysts for water splitting and CO 2 reduction. Here, the band gaps and edge positions remain similar for UiO nodes when Zr is substituted with Ti, Th, or Ce. However, in contrast to the case for Zr-, Ti-, and Th-based UiO-NDIs, where photoexcitation remains localized on the NDI linkers owing to the very high energies of unoccupied node-based bands, for UiO(Ce)-NDI, the availability of low-lying empty f orbitals in the metal node offers the potential for energy transfer and exciton migration, which could further boost photocatalytic performance by extending exciton lifetimes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Deconvoluting XPS Spectra of La-Containing Perovskites from First-Principles

Perovskite-based oxides are used in electrochemical CO 2 and H 2 O reduction in electrochemical cells due to their compositional versatility, redox properties and stability. However limited knowledge exists on the mechanisms driving these processes. Toward this understanding, herein we probe the core level binding energy shifts of water-derived adspecies (H, O, OH, H 2 O) as well as the adsorption of CO 2 on LaCoO 3 and LaNiO 3 and we correlate the simulated peaks with experimental Temperature Programmed X-ray Photoelectron Spectroscopy (TPXPS) results. We find the strong adsorption of such chemical species can affect the antiferromagnetic ordering of LaNiO 3 . The adsorption of such adspecies is further quantified through Bader and differential charge analyses. We find the higher O 1s core level binding energy peak for both LaCoO 3 and LaNiO 3 corresponds to adsorption of water-related species and CO 2 , while the lower energy peak is due to lattice oxygen. We further correlate these DFT-based core level O 1s binding energies with the TPXPS measurements to quantify the decrease of the O 1s contribution due to desorption of adsorbates and the apparent increase of the lattice oxygen (both bulk and surface) with temperature. Finally, we quantify the influence of adsorbates on the La 4d, Co 2p and the Ni 3p core level binding energy shifts. This work demonstrates how theoretically generated XPS data can be utilized to predict species-specific binding energy shifts to assist in the deconvolution of the experimental results.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Discovery of tunable and soluble organic emitters for solid-state lasers with a self-driving laboratory

We have recently demonstrated the ability of using self-driving laboratories for AI-driven searches of organic emitters for solid-state lasing devices. Our past workflow featured solubility challenges for such large molecular moieties. In this next-generation study, we return to the drawing board to explore a family of com-pounds that are much solution processable and composed of a set of electronic cores that provide a broader color response. Out of 252 potential candidates,and with guidance from DFT calculations, we selectively perform a compre-hensive study exploring 51 fluorene-based A-B-A type organic laser oligomers, armed with our self-driving lab. The candidates range from simple hydrocarbon molecules to complex hetero atom-mixed molecules. As a result of this study, we highlight diketopyrrolopyrrole and benzodiazole derivatives for their largely red-shifted emissions. Furthermore, we investigate the effect of color change aris-ing from hetero atom permutation, fluorine addition, thiophene coupling, and a combination of fluorine addition and thiophene coupling. Amplified spontaneous emission (ASE) measurements in the solid state further corroborate the lasing potential of selected candidates, reinforcing their suitability for future device applications. The computational study with density functional theory confirms the experimental results.

fluorescence↗
DOE OSTI2025

Constraining explosive nucleosynthesis by indirect reaction methods at storage rings using unstable beams in batch mode

Nuclear reaction studies on unstable isotopes can strongly help in improving our understanding of nucleosynthesis in stars. Indirect approaches to determining astrophysical reaction rates are increasingly common-place and undergoing continuous refinement. Of particular interest is the use of such indirect techniques at storage rings, which, among other aspects, allow to recycle rare unstable beams. Here, we propose to investigate the reaction rates of astrophysical interest using indirect methods (surrogate, Trojan horse, etc.) in reverse kinematics at the IMP-CAS storage ring. Long lived radioactive ion beams, produced remotely, can be accelerated, and made to interact with light targets. The proposed reactions are 85 Kr(p, p’γ), 85 Kr(d, pγ), constraining the neutron flux in an s-process branching point, 79 Se(p, p’γ), 79 Se(d, pγ), constraining the temperature in s-process nucleosyntheses, and 59 Fe(d, pγ), constraining core collapse supernovae.

Angelis, G. de [National Inst. of Nuclear Physics ↗
DOE OSTI2017

Improvement of small to large grain A15 ratio in Nb 3 Sn PIT wires by inverted multistage heat treatments

The next generation of superconducting accelerator magnets for the Large Hadron Collider at CERN will require large amounts of Nb 3 Sn superconducting wires and the Powder-In-Tube (PIT) process, which utilizes a NbSn 2 -rich powder core within tubes of Nb(7.5wt%Ta) contained in a stabilizing Cu matrix, is a potential candidate. But, the critical current density, J c , is limited by the formation of a large grain (LG) A15 layer which does not contribute to transport current, but occupies 25-30% of the total A15 area. Thus it is important to understand how this layer forms, and if it can be minimized in favor of the beneficial small grain (SG) A15 morphology which carries the supercurrent. The ratio of SG/LG A15 is our metric here, where an increase signals improvement in the wires A15 morphology distribution. We have made a critical new observation that the initiation of the LG A15 formation can be controlled at a wide range of temperatures relative to the formation of the small grain (SG) A15. The LG A15 can be uniquely identified as a decomposition product of the Nb6Sn5(Cu x ), surrounded by a layer of rejected Cu, thus the LG A15 is not only of low pin density, but is not continuous grain to grain. We have found that in single stage reactions limited to 630 °C - 690 °C, the maximum SG A15 layer thickness prior to LG A15 formation is very sensitive to temperature, with a maximum around 670 °C. This result led to the design of four novel heat treatments which all included a short, high temperature stage early in the reaction, followed by a slow cooling to a more typical reaction temperature of 630 °C. We also found that this heat treatment (HT) modification increased the SG A15 layer thickness while simultaneously suppressing LG A15 morphology, with no additional consumption of the diffusion barrier. In the best heat treatment the SG/LG A15 ratio improved by 30%. Unfortunately, J c values suffered slightly, however further exploration of this high temperature reaction region is required to understand the limits to A15 formation in Nb3Sn PIT conductors.

36 MATERIALS SCIENCE↗