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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
DOE OSTI2020

A machine learning Automated Recommendation Tool for synthetic biology

Abstract Synthetic biology allows us to bioengineer cells to synthesize novel valuable molecules such as renewable biofuels or anticancer drugs. However, traditional synthetic biology approaches involve ad-hoc engineering practices, which lead to long development times. Here, we present the Automated Recommendation Tool (ART), a tool that leverages machine learning and probabilistic modeling techniques to guide synthetic biology in a systematic fashion, without the need for a full mechanistic understanding of the biological system. Using sampling-based optimization, ART provides a set of recommended strains to be built in the next engineering cycle, alongside probabilistic predictions of their production levels. We demonstrate the capabilities of ART on simulated data sets, as well as experimental data from real metabolic engineering projects producing renewable biofuels, hoppy flavored beer without hops, fatty acids, and tryptophan. Finally, we discuss the limitations of this approach, and the practical consequences of the underlying assumptions failing.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Thickness-independent scalable high-performance Li-S batteries with high areal sulfur loading via electron-enriched carbon framework

Abstract Increasing the energy density of lithium-sulfur batteries necessitates the maximization of their areal capacity, calling for thick electrodes with high sulfur loading and content. However, traditional thick electrodes often lead to sluggish ion transfer kinetics as well as decreased electronic conductivity and mechanical stability, leading to their thickness-dependent electrochemical performance. Here, free-standing and low-tortuosity N, O co-doped wood-like carbon frameworks decorated with carbon nanotubes forest (WLC-CNTs) are synthesized and used as host for enabling scalable high-performance Li-sulfur batteries. EIS-symmetric cell examinations demonstrate that the ionic resistance and charge-transfer resistance per unit electro-active surface area of S@WLC-CNTs do not change with the variation of thickness, allowing the thickness-independent electrochemical performance of Li-S batteries. With a thickness of up to 1200 µm and sulfur loading of 52.4 mg cm −2 , the electrode displays a capacity of 692 mAh g −1 after 100 cycles at 0.1 C with a low E/S ratio of 6. Moreover, the WLC-CNTs framework can also be used as a host for lithium to suppress dendrite growth. With these specific lithiophilic and sulfiphilic features, Li-S full cells were assembled and exhibited long cycling stability.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Evidence that Criegee intermediates drive autoxidation in unsaturated lipids

Significance Autoxidation leads to the slow persistent destruction of organic molecules causing oxidative stress and associated disease. The prevailing autoxidation mechanism of unsaturated lipids involves chain reactions initiated and propagated by H-atom abstraction, mediated by peroxy radicals and other reactive oxygen species. Here we report experimental evidence for an autoxidation mechanism initiated by OH, which is unanticipated and proceeds by OH addition followed by pathways involving Criegee intermediates (CIs). Although CIs are routinely encountered in atmospheric and synthetic organic chemistry, their role in autoxidation is unexpected. Our results suggest that in all likelihood these exotic species play a much more prominent and general role in the chemistry of cells, food, petrochemicals, and the environment beyond what is currently believed.

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

Synergistic effects of W–Ta alloys exposed to various ELM-like fusion events

Abstract Recently tungsten alloys have shown capabilities in suppressing morphological changes when exposed to harsh fusion conditions. Morphological changes due to He + and D + ions at high temperatures (1000–2000 K) can lead to easier erosion and sputtering of tungten (W) particles towards quenching the fusion plasma. This study investigated W–3Ta alloy as potential plasma facing materials (PFMs) exposed to different edge-localized mode (ELM)-like energies and ion loadings. Performance of W–3Ta has been tested as a function of ELM-like energies (0.6–1.5 GW m −2 ) and varying He + and D + ion concentrations (100% He + , 50% He + :50% D + ,10% He + :90% D + (similar ELM-like reactor condition), and 100% D + ions). Early-stage fuzz formation and surface pores were observed during 100% He + ion irradiation and mixed ion loadings but not observed during 100% D + ion loadings. Pores decreased in quantity and increased in size with increasing transient heat loading. Grain boundaries acted as trapping sites of helium and deuterium atoms during dual beam ion irradiations, as observed through increased pore size along the grain boundary. Qualitative erosion estimates were measured using witness plates. Increased erosion was observed with increasing D + ion concentration, which is attributed to D supersaturation in the near surface region affecting thermal and mechanical properties. More erosion was observed for W–3Ta samples compared to pure W, evident through large (>10 µ m) cracks on the surface, and an increase in W metal x-ray photoelectron spectroscopy peaks under similar loading conditions. The slight enhancement in erosion is attributed to the slightly decreased thermal properties, ∼10% thermal diffusivity drop, of W–3Ta at high temperatures. The damage threshold was impacted by ion loading, where distinct cracking was observed for 100% He + at a lower heat loading. This matrix study using reactor-like loading supports the need for extensive studies on future W alloy PFMs before selecting one as an alternative.

Physics↗
DOE OSTI2020

Corn stover harvest reduces soil CO 2 fluxes but increases overall C losses

Abstract Harvesting corn ( Zea mays L.) stover for use as bioenergy feedstock may provide short‐term economic benefits and perhaps improve grain yield in continuous corn systems, but excessive stover removal may lead to long‐term depletion of soil C stocks. To better quantify the impacts of stover harvest on the soil C balance, we investigated CO 2 fluxes under three harvest treatments (none, moderate, and high) in three continuous corn systems: (a) no tillage and no biochar applications, (b) chisel plowing with biochar amendments, and (c) chisel plowing without biochar amendments were quantified. We sampled static chambers 14, 13, and 15 times in 2010, 2011, and 2012, respectively, and the measurements were used to calibrate the Agricultural Production Systems sIMulator model. Although CO 2 ‐C emissions did not differ among the three systems, both moderate (approximately 30%) and high (approximately 60%) stover removal rates reduced simulated CO 2 ‐C emissions by nearly 10% and more than 22%, respectively. Despite these reductions in CO 2 flux, the sum of CO 2 ‐C and stover C exceeded CO 2 ‐C losses in those plots without stover removal. This finding suggested soil C depletion was occurring for the soil and crop management practices used, even though depletion was not evident after 3 years. Application of biochar increased soil C levels, suggesting it may be able to offset some C losses. We conclude that for sustainable, highly productive agroecosystems that include stover harvest, all agronomic practices must be optimized to minimize C losses and maintain soil quality.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Criteria for projected discovery and exclusion sensitivities of counting experiments

Abstract The projected discovery and exclusion capabilities of particle physics and astrophysics/cosmology experiments are often quantified using the median expected p-value or its corresponding significance. We argue that this criterion leads to flawed results, which for example can counterintuitively project lessened sensitivities if the experiment takes more data or reduces its background. We discuss the merits of several alternatives to the median expected significance, both when the background is known and when it is subject to some uncertainty. We advocate for standard use of the “exact Asimov significance” $$Z^\mathrm{A}$$ Z A detailed in this paper.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Mechanism of γ-irradiation induced phase transformations in nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramics

The structural, infrared absorption and magnetic property transformations in nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} samples irradiated with different doses (0, 15, 25 and 50 kGy) of γ-irradiation were investigated in this work and a mechanism of phase transformation/decomposition is provided based on the metastable nature of the Mn-atoms in the spinel lattice. The nano-powder sample was prepared by solution combustion route and the pellets of the sample were exposed to γ-radiation. Up to a dose of 25 kGy of γ-radiation, the sample retained the single phase cubic spinel (Fd-3m) structure, but the disorder in the sample increased. On irradiating the sample with 50 kGy γ-radiation, the spinel phase decomposed into new stable phases such as α-Fe{sub 2}O{sub 3} and ZnFe{sub 2}O{sub 4} phases along with amorphous MnO phase, leading to a change in the surface morphology of the sample. Along with the structural transformations the magnetic properties deteriorated due to breakage of the ferrimagnetic order with higher doses of γ-irradiation. Our results are important for the understanding of the stability, durability and performance of the Mn-Zn ferrite based devices used in space applications. - Graphical abstract: The nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramic sample transforms to crystalline α-Fe{sub 2}O{sub 3} and ZnFe{sub 2}O{sub 4} phases (and amorphous MnO phase) at a γ-irradiation dose of 50 kGy, as MnO goes out of the spinel lattice. The high energy γ-irradiation causes structural damage to the nanomaterials leading to change in morphology of the sample as seen in the SEM images. - Highlights: • Mn atoms are more unstable in the Mn-Zn ferrite spinel lattice than Zn-atoms. • Displacement of Mn atoms by γ-radiation from the lattice renders phase transformation. • In Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}, Mn-ferrite cell transforms to crystalline α-Fe{sub 2}O{sub 3} and amorphous MnO. • The stable ZnFe{sub 2}O{sub 4} phase retains its structure even after 50 KGy γ-irradiation. • The γ-irradiation degrades the magnetic properties of Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramics.

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

Enhanced Curie temperature and piezoelectric properties of (Ba0.85Ca0.15)(Zr0.10Ti0.90)O3 lead-free ceramics after the addition of LiTaO3

Highlights: • The Curie temperature and piezoelectric properties of BCZT ceramics can be obviously enhanced by the addition of LiTaO{sub 3}. • The Curie temperature of (Ba{sub 0.85}Ca{sub 0.15})(Zr{sub 0.10}Ti{sub 0.90})O{sub 3} ceramics improved from 93 ℃ to 102 ℃. • (Ba{sub 0.85}Ca{sub 0.15})(Zr{sub 0.10}Ti{sub 0.90})O{sub 3} ceramic with x = 0.3 mol.% LiTaO{sub 3} demonstrates optimal piezoelectric properties. • The giant electrostrictive coefficients (Q{sub 33} ≈ 0.040-0.050 m{sup 4}/C{sup 2}) were also obtained in LT-doped BCZT ceramics. - Abstract: Polycrystalline (Ba{sub 0.85}Ca{sub 0.15})(Zr{sub 0.10}Ti{sub 0.90})O{sub 3}–xLiTaO{sub 3} ceramics were designed and synthesized using a solid-state reaction to improve both the Curie temperature and the electrical properties of (Ba{sub 0.85}Ca{sub 0.15})(Zr{sub 0.10}Ti{sub 0.90})O{sub 3} lead-free piezoelectric ceramics. The effect that the addition of LiTaO{sub 3} has on the structure and electrical properties of BCZT ceramics was studied systemically. The results show that the Curie temperature and the piezoelectric properties of BCZT can be substantially enhanced by adding LiTaO{sub 3.} The Curie temperature increased from 93 °C to 102 °C after adding LT of 0.3 mol.%. X-ray diffraction and Raman spectral analysis of the ceramics reveal the coexistence of orthorhombic (O) and tetragonal (T) phases. This coexistence of O and T phases at room temperature helps improve the ferroelectric and piezoelectric properties. The ceramic with x = 0.3 mol.% exhibits the highest values for d{sub 33} = 433 pC/N, d{sub 33}{sup *} = 858 pm/V (at 1 kV/mm) and k{sub p} = 44.6%. Furthermore, giant electrostrictive coefficients (Q{sub 33} ≈ 0.040–0.050 m{sup 4}/C{sup 2}) were also obtained for these LT-doped BCZT ceramics. These properties confirm that BCZT-xLT is a promising candidate system for lead-free piezoelectric ceramic materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

The Effect of Luminance Pattern on Nighttime Discomfort Glare Response - CRADA 653 (Abstract)

Light Emitting Diode (LED) adoption is critical for widespread energy savings from commercial outdoor lighting systems. A complaint from the public, concerns glare from LED light fixtures especially those with exposed LED arrays. This human factor study will examine luminance uniformity of the fixture aperture to identify parameters related to this response. The outcome will inform optical design by lighting manufacturers, retaining LED energy efficiency while mitigating glare. The results may also lead to improved industry standard glare metrics for lighting. Pacific Northwest National Laboratory’s (PNNL) Lighting Science and Technology Lab in Portland OR has a purpose-built apparatus with exposed LED arrays that have been used for prior work. It can easily be adapted for use in this experiment. Interchangeable templates will allow changing patterns for the stimulus. Glare ratings from the recruited subjects will be analyzed and reported in a peer-reviewed journal for application by luminaire manufacturers for improved products. The McClung Foundation’s interest is to better understand human perception of lighting, leading to more comfortable and effective visual environments. Members of the Foundation’s Technical Review Committee will be instrumental in reviewing the experimental design, analysis, and the final report. They will also help disseminate information about the results within the lighting community.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2021

Extreme Energy Dissipation via Material Evolution in Carbon Nanotube Mats

Abstract Thin layered mats comprised of an interconnected meandering network of multiwall carbon nanotubes (MWCNT) are subjected to a hypersonic micro‐projectile impact test. The mat morphology is highly compliant and while this leads to rather modest quasi‐static mechanical properties, at the extreme strain rates and large strains resulting from ballistic impact, the MWCNT structure has the ability to reconfigure resulting in extraordinary kinetic energy (KE) absorption. The KE of the projectile is dissipated via frictional interactions, adiabatic heating, tube stretching, and ultimately fracture of taut tubes and the newly formed fibrils. The energy absorbed per unit mass of the film can range from 7–12 MJ kg −1 , much greater than any other material.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Pareto Optimal Spectrally Selective Emitters for Thermophotovoltaics via Weak Absorber Critical Coupling

Tailoring the emission spectra of a thermophotovoltaic (TPV) emitter away from that of a blackbody has the potential to minimize transmission and thermalization loss in a photovoltaic receiver. Selective TPV emitters can lead to solar energy conversion with efficiency greater than the Shockley-Queisser limit and can facilitate the generation of useful energy from waste heat. A new design is introduced to radically tune thermal emission that leverages the interplay between two resonant phenomena in simple planar nanostructures-absorption in weakly absorbing nanofilms and reflection in multilayer dielectric stacks. A virtual screening approach is employed to identify promising structures for a selective thermal emitter from a search space of millions, several of which approach the ideal values of a step-function selective thermal emitter. One of these structures is experimentally fabricated and evaluated, which includes a weakly absorbing alloy with tailored optical properties fabricated by atomic layer deposition (ALD). The versatility of the design and fabrication approach result in an emitter with excellent spectral density (0.8 W cm(-2) sr(-1)) and spectral efficiency (46.8%) at 1373 K. Future experimental challenges to a more accurate realization of the optimal structures calculated are also considered.

atomic layer deposition↗
DOE OSTI2020

Temperature dependence of nickel ion release from nitinol medical devices

Abstract Nitinol exhibits unique (thermo)mechanical properties that make it central to the design of many medical devices. However, nitinol nominally contains 50 atomic percent nickel, which if released in sufficient quantities, can lead to adverse health effects. While nickel release from nitinol devices is typically characterized using in vitro immersion tests, these evaluations require lengthy time periods. We have explored elevated temperature as a potential method to expedite this testing. Nickel release was characterized in nitinol materials with surface oxide thickness ranging from 12 to 1564 nm at four different temperatures from 310 to 360 K. We found that for three of the materials with relatively thin oxide layers, ≤ 87 nm nickel release exhibited Arrhenius behavior over the entire temperature range with activation energies of 80 to 85 kJ/mol. Conversely, the fourth ''black–oxide'' material, with a much thicker, complex oxide layer, was not well characterized by an Arrhenius relationship. Power law release profiles were observed in all four materials; however, the exponent from the thin oxide materials was approximately 1/4 compared with 3/4 for the black–oxide material. To illustrate the potential benefit of using elevated temperature to abbreviate nickel release testing, we demonstrated that a > 50 day 310 K release profile could be accurately recovered by testing for less than 1 week at 340 K. However, because the materials explored in this study were limited, additional testing and mechanistic insight are needed to establish a protective temperature scaling that can be applied to all nitinol medical device components.

Saylor, David M.↗
DOE OSTI2018

Nutrient sink limitation constrains growth in two barley species with contrasting growth strategies

Abstract Mineral nutrients exert important limitations on plant growth. Growth is limited by the nutrient source when it is constrained by nutrient availability and uptake, which may simultaneously limit investment in photosynthetic proteins, leading to carbon source limitation. However, growth may also be limited by nutrient utilization in sink tissue. The relative importance of these processes is contested, with crop and vegetation models typically assuming source limitations of carbon and mineral nutrients (especially nitrogen). This study compared the importance of source and sink limitation on growth in a slower‐growing wild perennial barley ( Hordeum bulbosum ) and a faster‐growing domesticated annual barley ( Hordeum vulgare ), by applying a mineral nutrient treatment and measuring nitrogen uptake, growth, allocation, and carbon partitioning. We found that nitrogen uptake, growth, tillering, shoot allocation, and nitrogen storage were restricted by low nutrient treatments. Multiple lines of evidence suggest that low nutrient levels do not limit growth via carbon acquisition: (a) Carbohydrate storage does not increase at high nutrient levels. (b) Ratio of free amino acids to sucrose increases at high nutrient levels. (c) Shoot allocation increases at high nutrient levels. These data indicate that barley productivity is limited by the capacity for nutrient use in growth. Models must explicitly account for sink processes in order to properly simulate this mineral nutrient limitation of growth.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Challenges to EIA consultants whilst dealing with stakeholders in Punjab, Pakistan

Highlights: • EIA in Punjab is subject to influence by elites as a result of which projects are implemented prior to EIA. • Proponents consider EIA as hindrance to project development • Lack of EPA resources lead to delayed decision making • Consultants tend to compromise the EIA quality in order to profitably run their setup. • EIA implementation is weak because Environmental Protection Agency (EPA) lacks capacity to enforce legislation - Abstract: Consultants play a pivotal role in the Environmental Impact Assessment (EIA) process because they are the ones who carry out assessments, deal with multiple stakeholders and thus face the most pressure. Considering the ineffectiveness of the EIA process, the current study attempts to identify the challenges faced by consultants in Punjab whilst dealing with stakeholders. Participant observation, professional practice and unstructured interviews were employed as data collection methods. Key challenges identified include the lack of equal treatment, insufficient capability of Environmental Protection Agency (EPA) and consultants, and the lack of awareness on the parts of the proponents and the public. Legislations accompanied with procedural controls exist in Punjab regarding EIA but the implementation is weak. A strong political will is necessary for implementation of EIA rules and regulation, awareness of the proponents and the public and capacity building of EPA. Registration and accreditation can help bring competent consultants in the field who can improve the process.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Understanding the formation of nanocomposites consisting of silver sulfide and platinum hollow nanostructures

Highlights: • Reacting core-shell [email protected] particles with Na{sub 2}S leads to hollow Pt nanostructures. • Reacting core-shell [email protected] particles with sulfur leads to Ag{sub 2}S-hPt nanocomposites. • The mechanism determining the formation of Ag{sub 2}S-hPt nanocomposites was elucidated. • Additional experiments were designed to rationalize the formation mechanism. - Abstract: Structural conversion using core-shell silver (Ag)-platinum (Pt) nanoparticles as starting materials is a promising way to produce nanocomposites consisting of silver sulfide (Ag{sub 2}S) and hollow Pt nanostructures (Ag{sub 2}S-hPtNCs). However, the mechanism behind the structural conversion process is yet to be understood. In this study, we use transmission electron microscope (TEM) as a typical tool to characterize the products formed in different structural conversion processes, and interpret the experimental observations by proposing mechanisms behind the reactions between core-shell Ag-Pt nanoparticles and sulfur precursors from different sources. We then design additional experiments to rationalize the formation mechanism we proposed. The mechanistic understanding of the structural conversion from bimetallic core-shell nanostructures to heterogeneous nanocomposites may extend the fabrication of heterogeneous nanocomposites for a given technological application.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Nanostructured aluminium titanate (Al{sub 2}TiO{sub 5}) particles and nanofibers: Synthesis and mechanism of microstructural evolution

In this study, aluminium titanate (AT) particles and nanofibers were synthesized through citrate sol gel and sol gel-assisted electrospinning methods in both nanostructured powder and nanofiber forms. The results of X-ray diffraction analysis, field-emission scanning electron microscopy and differential thermal analysis showed that the synthetic products benefit a nanostructured nature with a grain size less than 70 nm. The optimal values for time and temperature at which a roughly pure AT is attained were determined as 2 h and 900 °C, respectively. It was found that the sol gel precursor bears an amorphous structure till 700 °C and begins to be crystallized to alumina, anatase and AT at higher temperatures. Moreover, AT tends to decompose into rutile and alumina at temperatures higher than 900 °C and its degradation rate reaches a maximum at temperatures near to 1100 °C. In this synthesis, citric acid was used as a chelating agent for Al{sup 3} {sup +} and Ti{sup 4} {sup +} ions and it was shown that a low citric acid-to-metal cation ratio leads to larger numbers of nuclei during crystallization and smaller grain size. Finally, a model was suggested to describe the microstructural evolution of AT compound based on a nucleation and growth regime. - Graphical abstract: Display Omitted - Highlights: • We synthesized aluminium titanate ceramic in both powder and nanofiber forms. • The methods in use were citrate sol gel and sol gel-assisted electrospinning. • Powders and nanofibers bear a nanostructured nature with a grain size less than 70 nm. • A model is suggested to describe microstructural evolution of synthetic products.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Relating CMIP5 Model Biases to Seasonal Forecast Skill in the Tropical Pacific

Abstract We examine links between tropical Pacific mean state biases and El Niño/Southern Oscillation forecast skill, using model‐analog hindcasts of sea surface temperature (SST; 1961–2015) and precipitation (1979–2015) at leads of 0–12 months, generated by 28 different models from the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Model‐analog forecast skill has been demonstrated to match or even exceed traditional assimilation‐initialized forecast skill in a given model. Models with the most realistic mean states and interannual variability for SST, precipitation, and 10‐m zonal winds in the equatorial Pacific also generate the most skillful precipitation forecasts in the central equatorial Pacific and the best SST forecasts at 6‐month or longer leads. These results show direct links between model climatological biases and seasonal forecast errors, demonstrating that model‐analog hindcast skill—that is, how well a model can capture the observed evolution of tropical Pacific anomalies—is an informative El Niño/Southern Oscillation metric for climate simulations.

Ding, Hui↗