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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Introduction to the special issue on smart transportation

Transportation is getting smarter and smarter, with the prominence of connected automated vehicle technologies in the global auto industry’s near-term growth strategies, of big data analytics and unprecedented access to sensing data of mobility, and of integration of this analytics into the optimization of mobility and transport. Further, these developments are setting off a wave of smart transportation innovations, which are featured by new methods and applications driven by various forms of sensor data such as GPS, CAN bus, LIDA, images, etc. At the same time, complexities surrounding the use, conflation, and processing of disparate data in near real-time is of essence for the design and development of futuristic smart transportation.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2024

Template Assisted Lithium Superoxide Growth for Lithium-Oxygen Batteries

Developing batteries with energy densities comparable to internal combustion technology is essential for a worldwide transition to electrified transportation. Li-O2 batteries are seen as the ‘holy grail’ of battery technologies since they have the highest theoretical energy density of all battery technologies. Current lithium-oxygen (Li-O2) batteries suffer from large charge overpotentials related to electronic resistivity of the insulating lithium peroxide (Li2O2) discharge product. One potential solution is the formation and stabilization of a lithium superoxide (LiO2) discharge intermediate that exhibits good electronic conductivity. However, LiO2 is reported to be unstable at ambient temperature despite its favorable formation energy at -1.0 eV/atom. In this paper, based on our recent work on the development of cathode materials for aprotic lithium oxygen batteries including two intermetallic compounds, LiIr3 and LiIr, that are found to form good template interfaces with LiO2, a simple goodness of fit R factor to gauge how well a template surface structure can support LiO2 growth is developed. The R factor is a quantitative measurement to calculate the geometric difference in the unit cells of specific Miller Index 2D planes of the template surface and LiO2. Using this as a guide, the R factors for LiIr3, LiIr, and La2NiO4+, are found to be good. This guide is attested by simple extension to other noble metal intermetallics with electrochemical cycling data including LiRh3, LiRh, and Li2Pd. Finally, the template concept is extended to main group elements and the R factors for LiO2 (111) and Li2Ca suggest that Li2Ca is a possible candidate for the template assisted LiO2 growth strategy.

Intermetallics↗
DOE OSTI2024

Improving luminescence response in ZnGeN 2 /GaN superlattices: defect reduction through composition control

Abstract Color-mixed (cm) light-emitting diodes (LEDs) are theoretically the most efficient white light emitters, projected to improve white light luminous efficacy by 34% compared to incumbent phosphor converted LEDs. Since white light technology is pervasive and essential, small improvements in LED technology can result in energy savings. However, cm-LEDs are not yet realized due to poor efficacy in green and amber emitting materials, a spectral region colloquially referred to as the Green Gap. ZnGeN 2 is nearly isostructural and closely lattice-matched to GaN and can be heteroepitaxially integrated with existing GaN devices; ZnGeN 2 /GaN hybrid structures are theorized to emit green (~530 nn) light with a spontaneous emission rate 4.6–4.9 times higher than traditional InGaN LEDs when incorporated into III-N LED structures. In this report we demonstrate the molecular beam epitaxy (MBE) growth of GaN and ZnGeN 2 superlattices, an important step towards realizing multiple quantum well structures required for efficient LEDs. Elemental analysis, including atom probe tomography, shows that Ga and Ge are observed in both ZnGeN 2 and GaN layers, degrading the structural uniformity. The lack of elemental abruptness also leads to increased defect luminescence and reabsorption of band edge luminescence. The source of unintentional Ga distributed throughout the ZnGeN 2 layers was identified as excess flux escaping from around the closed MBE shutter. The source of unintentional Ge, which tended to incorporate as a single delta-doped layer in GaN, was identified as Ge riding along the cyclical metal-rich Ga adlayer used for high quality GaN, incorporating during subsequent nitrogen-rich growth step. Modifying the growth strategy results in improved structural quality, elemental abruptness, and luminescence response. This realization of structurally and elementally abrupt interfaces demonstrates the potential of heteroepitaxially integrated binary and ternary nitrides for energy-relevant devices.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Microbiome Aggregated Traits and Assembly Are More Sensitive to Soil Management than Diversity

How soil is managed, particularly for agriculture, exerts stresses upon soil microbiomes, resulting in altered community structures and functional states. Understanding how soil microbiomes respond to combined stresses is important for predicting system performance under different land use scenarios, aids in identification of the most environmentally benign managements, and provides insight into how system function can be recovered in degraded soils. We use a long-established field experiment to study the effects of combined chronic (press) disturbance of the magnitude of organic carbon inputs with acute (pulse) effects of physical disturbance by tillage and chemical disturbance due to inorganic fertilization and pesticide application. We show that because of the variety of ways it can be assessed, biodiversity—here based on microbial small subunit rRNA gene phylotypes—does not provide a consistent view of community change. In contrast, aggregated traits associated with soil microbiomes indicate general loss of function, measured as a reduction of average genome lengths, associated with chronic reduction of organic inputs in arable or bare fallow soils and altered growth strategies associated with rRNA operon copy number in prokaryotes, as well as a switch to pathogenicity in fungal communities. In addition, pulse disturbance by soil tillage is associated with an increased influence of stochastic processes upon prokaryote community assembly, but fungicide used in arable soils results in niche assembly of fungal communities compared to untilled grassland. Overall, bacteria, archaea, and fungi do not share a common response to land management change, and estimates of biodiversity do not capture important facets of community adaptation to stresses adequately.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1996

Strategies for "minimal growth maintenance" of cell cultures: a perspective on management for extended duration experimentation in the microgravity environment of a Space station

How cells manage without gravity and how they change in the absence of gravity are basic questions that only prolonged life on a Space station will enable us to answer. We know from investigations carried out on various kinds of Space vehicles and stations that profound physiological effects can and often to occur. We need to know more of the basic biochemistry and biophysics both of cells and of whole organisms in conditions of reduced gravity. The unique environment of Space affords plant scientists an unusual opportunity to carry out experiments in microgravity, but some major challenges must be faced before this can be done with confidence. Various laboratory activities that are routine on Earth take on special significance and offer problems that need imaginative resolution before even a relatively simple experiment can be reliably executed on a Space station. For example, scientists might wish to investigate whether adaptive or other changes that have occurred in the environment of Space are retained after return to Earth-normal conditions. Investigators seeking to carry out experiments in the low-gravity environment of Space using cultured cells will need to solve the problem of keeping cultures quiescent for protracted periods before an experiment is initiated, after periodic sampling is carried out, and after the experiment is completed. This review gives an evaluation of a range of strategies that can enable one to manipulate cell physiology and curtail growth dramatically toward this end. These strategies include cryopreservation, chilling, reduced oxygen, gel entrapment strategies, osmotic adjustment, nutrient starvation, pH manipulation, and the use of mitotic inhibitors and growth-retarding chemicals. Cells not only need to be rendered quiescent for protracted periods but they also must be recoverable and further grown if it is so desired. Elaboration of satisfactory procedures for management of cells and tissues at "near zero or minimal growth" will have great value and practical consequences for experimentation on Earth as well as in Space. All of the parameters and conditions and procedural details needed to meet all the specific objectives will be the basis of the design and fabrication of cell culture units for use in the Space environment. It is expected that this will be an evolutionary process.

STS-61A Shuttle Project↗
NASA NTRS1986

Thermal-capillary analysis of Czochralski and liquid encapsulated Czochralski crystal growth. II - Processing strategies

The pseudosteady-state heat transfer model developed in a previous paper is augmented with constraints for constant crystal radius and melt/solid interface deflection. Combinations of growth rate, and crucible and bottom-heater temperatures are tested as processing parameters for satisfying the constrained thermal-capillary problem over a range of melt volumes corresponding to the sequence occuring during the batchwise Czochralski growth of a small-diameter silicon crystal. The applicability of each processing strategy is judged by the range of existence of the solution, in terms of melt volume and the values of the axial and radial temperature gradients in the crystal.

Derby, J. J.↗
DOE OSTI2023

Nuclear Security Mission Growth: A regional strategy for meeting operational challenges [Slides]

The nation's growing nuclear security requirements have yielded three major conclusions: (1) LANL possesses an exceptionally diversified workforce, multidimensional infrastructure and mission-focused strategy to fulfill the responsibilities entrusted to us; (2) However, amidst significant opportunity and growth, regional considerations have exposed several operational challenges; and (3) Given these challenges and the Lab's many strengths, assistance is needed to successfully execute our mission.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2020

Analysis of chemical stress and the propensity for cracking during the vertical Bridgman growth of BaBrCl:Eu

Computational models are employed to analyze residual chemical stresses arising from compositional variations in europium-doped BaBrCl crystals grown by the vertical Bridgman method. We find that significant chemical stress is produced by radial segregation of Eu in this system. In particular, the distribution of normal stresses is set by the radial concentration gradient, whose changing sign produces surface states in tension or compression. Additionally, crack opening from surface flaws will be promoted or suppressed by tensile or compressive surface stresses, respectively. Thus, crystal growth processing strategies that change the radial dopant concentration gradients are posited to affect the propensity for cracking. For this system, surface stresses are changed from states of tension to compression when the growth rate is increased, thus improving the chances to avoid cracking—a strategy that defies classical wisdom that dictates slower growth to improve outcomes. Similar strategies affecting segregation may prove beneficial to tailor chemical stress fields to reduce cracking in other crystal growth systems.

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

Crystal-growth-dominated fabrication of metal-organic frameworks with orderly distributed hierarchical porosity

Constructing architectures with hierarchical porosity has been widely considered as the most efficient way to bypass the problems related to slow mass transfer and inaccessibility of internal space in MOFs. Now, a crystal-growth-dominated strategy is proposed to fabricate hierarchically porous MOFs (HP-MOFs). When the crystal growth is dominated by the monomer attachment, the aggregation of nonionic surfactant or polymer can be easily captured and released during the crystal growth process, resulting in the formation and ordering hierarchical pores along the radial direction. Furthermore, owing to the accelerated mass diffusion and more exposed active sites of this design, HP-MOFs exhibited an enhanced catalytic efficiency in styrene oxidation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

On optical properties and scintillation performance of emerging Ga 2 O 3 : Crystal growth, emission mechanisms and doping strategies

As an emerging ultra-wide bandgap compound semiconductor, Ga 2 O 3 has attracted rapidly growing interest due to its unique physical properties for harsh condition applications. Compared to Ga 2 O 3 ’s electrical-characteristic based uses, such as power electronics, photodetectors and solar cells, a much less explored area for Ga 2 O 3 is its promising optical properties and its related scintillation capabilities. Undoped Ga 2 O 3 is a strong scintillator with excellent scintillation characteristics such as fast decay constants and encouraging light yield which is comparable to that of the classic Bi 4 Ge 3 O 12 (BGO) scintillator. The scintillation capability of Ga 2 O 3 can be precisely tuned via a series of approaches including systematic crystal growth control, post-growth annealing, targeted doping, and optimization of operation temperature. Here we summarize exciting progress of Ga 2 O 3 scintillators which have been pursued over the past few years. Our efforts cover a series of growth techniques of Ga 2 O 3 materials as well as discussion of emission mechanisms. Here we dedicate a targeted portion toward the doping strategies to improve the performance of Ga 2 O 3 . A detailed analysis is provided to compare the impact of different dopants. Through these efforts, we hope to provide useful perspectives to help accelerate the development of high performance Ga 2 O 3 scintillators.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Growth modeling to evaluate alternative cultivation strategies to enhance national microalgal biomass production

In this paper, we present a model-based assessment of alternative cultivation strategies on algal biomass production within the conterminous United States. Our assessment focuses on two basic cultivation strategies: 1) seasonal rotation of three representative freshwater algal strains that are well suited for warm weather, cold weather, and all-season diverse weather conditions, respectively; and 2) variation between three open pond water depths (15cm, 20cm, and 25cm). The enhanced Biomass Assessment Tool (BAT) is applied on a site-specific, hourly basis at 5,832 North American Land Data Assimilation System Phase 2 1/8° meteorological model grid cells over a 30-year period (1980-2009) to evaluate the operational strategies. Recognizing that resource management decisions may also consider scales beyond the individual site, we also conduct a regional assessment of focused on 7 representative climate zones in the conterminous United States. Results demonstrate that the spatial variability of algal productivity is largely affected by the strain-specific growth response to light and temperature that vary significantly by climate zone and latitude. Therefore, with a limited set of alternative cultivation strategies, the BAT identified the best performing combination of cultivation strategies on a site-specific basis that considerably enhances national annual biomass productivity. Specifically, the appropriate choice of seasonal strain rotation is able to significantly dampen climate-driven seasonal and spatial variability.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

New insights into the role of constitutive bacterial rhizobiome and phenolic compounds in two Pinus spp. with contrasting susceptibility to pine pitch canker

Abstract The rhizobiome is being increasingly acknowledged as a key player in plant health and breeding strategies. The pine pitch canker (PPC), caused by the fungus Fusarium circinatum, affects pine species with varying susceptibility degrees. Our aims were to explore the bacterial rhizobiome of a susceptible (Pinus radiata) and a resistant (Pinus pinea) species together with other physiological traits, and to analyze shifts upon F. circinatum inoculation. Pinus seedlings were stem inoculated with F. circinatum spores and needle gas exchange and antioxidant-related parameters were analyzed in non-inoculated and inoculated plants. Rhizobiome structure was evaluated through 16S rRNA gene massive parallel sequencing. Species (non-inoculated plants) harbored distinct rhizobiomes (<40% similarity), where P. pinea displayed a rhizobiome with increased abundance of taxa described in suppressive soils, displaying plant growth promoting (PGP) traits and/or anti-fungal activity. Plants of this species also displayed higher levels of phenolic compounds. F. circinatum induced slight changes in the rhizobiome of both species and a negative impact in photosynthetic-related parameters in P. radiata. We concluded that the rhizobiome of each pine species is distinct and higher abundance of bacterial taxa associated to disease protection was registered for the PPC-resistant species. Furthermore, differences in the rhizobiome are paralleled by a distinct content in phenolic compounds, which are also linked to plants’ resistance against PPC. This study unveils a species-specific rhizobiome and provides insights to exploit the rhizobiome for plant selection in nurseries and for rhizobiome-based plant-growth-promoting strategies, boosting environmentally friendly disease control strategies.

Leitão, Frederico↗
DOE OSTI2023

Trophic interactions shape the spatial organization of medium-chain carboxylic acid producing granular biofilm communities

Abstract Granular biofilms producing medium-chain carboxylic acids (MCCA) from carbohydrate-rich industrial feedstocks harbor highly streamlined communities converting sugars to MCCA either directly or via lactic acid as intermediate. We investigated the spatial organization and growth activity patterns of MCCA producing granular biofilms grown on an industrial side stream to test (i) whether key functional guilds (lactic acid producing Olsenella and MCCA producing Oscillospiraceae) stratified in the biofilm based on substrate usage, and (ii) whether spatial patterns of growth activity shaped the unique, lenticular morphology of these biofilms. First, three novel isolates (one Olsenella and two Oscillospiraceae species) representing over half of the granular biofilm community were obtained and used to develop FISH probes, revealing that key functional guilds were not stratified. Instead, the outer 150–500 µm of the granular biofilm consisted of a well-mixed community of Olsenella and Oscillospiraceae, while deeper layers were made up of other bacteria with lower activities. Second, nanoSIMS analysis of 15N incorporation in biofilms grown in normal and lactic acid amended conditions suggested Oscillospiraceae switched from sugars to lactic acid as substrate. This suggests competitive-cooperative interactions may govern the spatial organization of these biofilms, and suggests that optimizing biofilm size may be a suitable process engineering strategy. Third, growth activities were similar in the polar and equatorial biofilm peripheries, leaving the mechanism behind the lenticular biofilm morphology unexplained. Physical processes (e.g., shear hydrodynamics, biofilm life cycles) may have contributed to lenticular biofilm development. Together, this study develops an ecological framework of MCCA-producing granular biofilms that informs bioprocess development.

09 BIOMASS FUELS↗
DOE OSTI2025

Cooling-Rate-Driven Polymorphism and Vacancy Ordering in Ce 2 MnGe 6 Intergrowth Phases

Intergrowth phases in intermetallic systems provide a compelling framework for investigating structure–property relationships as a function of crystallographic subunit stacking. In this study, we examine the influence of Mn vacancy ordering on subunit stacking and reassign the structure of Ce 2 MnGe 6 to a monoclinic C2/m space group (a = 8.3486(17) Å, b = 8.6181(18) Å, c = 10.778(2) Å, β = 101.17(2)°). Additionally, we report a monoclinic polymorph of the Ln 2 MGe 6 family characterized as a tripled c-axis supercell derivative of monoclinic Ce 2 MnGe 6 , 3×c-Ce 2 MnGe 6 (a = 8.3482(16) Å, b = 8.6179(18) Å, c = 31.813(6) Å, β = 93.763(7)°). This polymorph emerges under rapid cooling conditions during the synthesis and offers insight into the structural relationship between the orthorhombic and monoclinic variants of the Ln 2 MGe 6 phases. Notably, the supercell form of Ce 2 MnGe 6 (3×c-Ce 2 MnGe 6 ) exhibits increased electrical resistivity and suggests enhanced Zintl-like behavior, potentially indicating greater thermodynamic stability relative to the parent monoclinic phase.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Sustainable Critical Minerals: Mining, Production, and Legacy

Critical minerals (CMs) are required in renewable energy systems, electric vehicles, electronics, and national defense. Global demand has increased rapidly due to energy and digital transitions, and the United States has become increasingly reliant on vulnerable supply chains. Geological scarcity, trade barriers, environmental hurdles, and processing challenges impede domestic CM production growth. Emerging strategies, including circular economy practices and advanced sustainable mining and processing techniques, can mitigate supply chain and economic risks. To advance these approaches, consistent research priorities, policy revisions, and technology investments are required to develop a resilient CM supply. Doing so with a focus on sustainability goals can simultaneously advance domestic economic and technological goals while limiting environmental impacts and supporting global environmental goals.

biomining↗
DOE OSTI2025

Facet-Dependent Hydrogen Evolution Reaction on M 2 P (M = Ni, Co, Fe) Single Crystals

Transition-metal phosphides (MPs) are promising earth-abundant catalysts for hydrogen evolution reactions (HERs) due to their remarkable activity and stability. To further improve their properties, facet control is a key strategy. The growth of shape-selected nanoparticles may substantially enhance electrocatalytic activity, but this approach requires fundamental studies of facet-specific catalytic properties. There are only a few reports on the facet effects of MPs, which leads to a limited understanding of the activity of each facet and hampers catalyst design. Here, in this study, we grew large hexagonal-prism-shaped single crystals of three representative M 2 P (M = Ni, Co, and Fe) catalysts using metal flux routes. Two facets of M 2 P single crystals were tested to study facet-dependent HER activities, and it was consistently demonstrated that for all M 2 P crystals, a tip facet [(0001) for Ni 2 P/Fe 2 P and (010) for Co 2 P] had a higher activity than the side facet [(101̅0) for Ni 2 P/Fe 2 P and (100) for Co 2 P]. HER activity between the same facet elucidated the activity ordered between different transition metals as Fe 2 P > Co 2 P > Ni 2 P under low-potential regions. At high applied potentials, this trend is reversed due to the differences in Tafel slopes, with Ni 2 P becoming the most active catalyst, such that the activity of the (0001) facet of Ni 2 P approaches that of Pt. The calculated surface density of states (DOS) of each facet and its local curvature were found to be a useful descriptor for the activity trends among different transition metals of the same facets.

Co2P↗