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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

The influence of Preslip Sealing on the Permeability Evolution of Fractures and Faults

The evolution of permeability on fractures and faults during the full earthquake cycle is shown to be sensitive to sealing during the repose phase. We explore the combined effect of static loading followed by fracture reactivation on permeability evolution via slide-hold-slide experiments. During the hold periods, permeability exhibits a slow but continuous reduction. The permeability decay is consistent with power law compaction of the aperture coupled with cubic law flow. With increasing hold periods, permeability evolves following reactivation from net reduction to net increase with the magnitude of the permeability change dependent on the hold period. This implies that the tight interlocking of asperities during interseismic repose primes the fault for permeability enhancement following reactivation. The inferred mechanism is via shear dilation with the probable involvement of unclogging. This result identifies that preslip sealing during repose is an essential component in the cyclic permeability evolution throughout the seismic cycle.

58 GEOSCIENCES↗
DOE OSTI2017

Transient Traceability Analysis of Land Carbon Storage Dynamics: Procedures and Its Application to Two Forest Ecosystems

Abstract Uptake of anthropogenically emitted carbon (C) dioxide by terrestrial ecosystem is critical for determining future climate. However, Earth system models project large uncertainties in future C storage. To help identify sources of uncertainties in model predictions, this study develops a transient traceability framework to trace components of C storage dynamics. Transient C storage ( X ) can be decomposed into two components, C storage capacity ( X c ) and C storage potential ( X p ). X c is the maximum C amount that an ecosystem can potentially store and X p represents the internal capacity of an ecosystem to equilibrate C input and output for a network of pools. X c is codetermined by net primary production (NPP) and residence time (τ N ), with the latter being determined by allocation coefficients, transfer coefficients, environmental scalar, and exit rate. X p is the product of redistribution matrix (τ ch ) and net ecosystem exchange. We applied this framework to two contrasting ecosystems, Duke Forest and Harvard Forest with an ecosystem model. This framework helps identify the mechanisms underlying the responses of carbon cycling in the two forests to climate change. The temporal trajectories of X are similar between the two ecosystems. Using this framework, we found that different mechanisms lead to a similar trajectory between the two ecosystems. This framework has potential to reveal mechanisms behind transient C storage in response to various global change factors. It can also identify sources of uncertainties in predicted transient C storage across models and can therefore be useful for model intercomparison.

58 GEOSCIENCES↗
DOE OSTI2019

Source-sink relationships

Life on earth depends on the growth and survival of plants. In order for plants to grow and develop effectively, coordination between sources and sinks is required. Source organs provide a net uptake of resources whilst sink organs have a net drawdown of resources. Molecular mechanisms regulate the relationship between sources and sinks. These molecular mechanisms include carbon- and nitrogen-containing metabolites, plant hormones, and genes. Sources and sinks for both carbon and nitrogen are key contributors to plant growth, and these regulate themselves and one another via feedback, feedforward, and crosstalk mechanisms. Our understanding of the relationships between sources and sinks is increased by experimental manipulations of the source-sink balance. To bring about increases in crop growth and yield, a holistic view of sources and sinks must be developed, including the molecular mechanisms underpinning the relationships between them. Mathematical modelling can be an effective tool for providing this unified perspective.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Low‐Volume Cores for Fabrication of Compact, Versatile, and Intelligent Soft Systems

Abstract This study introduces the low‐volume core (LVC) fabrication method, which enables the monolithic molding of compact, complex, versatile, and intelligent soft robotic systems. This method uses thin and flexible thermoplastic sheets to mold internal chambers in soft fluidic actuators, valves, and circuits. The LVC fabrication method creates low‐volume networks in soft actuators (LV‐net actuators) that can be made with compact and complex geometries, enabling both low actuation volume input and multi‐degree‐of‐freedom actuators. LVC fabrication can also be used for compact, completely soft, and monolithic logic components (valves with low‐volume core, also called as LV valves) to provide directional resistance as well as a switching mechanism that enables fluidic logic in soft systems. The compatibility of the fabrication methods for both soft actuators and valves facilitates the creation of compact, integrated, and versatile soft robotic systems with embodied intelligence. This study introduces two examples of such intelligent soft robotic systems that integrate both LV‐net actuators and LV valves to demonstrate capability for complex system fabrication.

Yu, Qifan↗
DOE OSTI2025

Unconventional Spintronics from Chiral Perovskites

Spintronic devices typically employ heterostructures with ferromagnets which break time-reversal symmetry and have non-vanishing magnetization. With the growing class of materials that support spin-polarized carriers, current, and excitations, it is possible to envision emerging spintronic applications that are not limited to magnetoresistance. Here, chiral perovskites with no net magnetization are considered, where the space-inversion and mirror symmetries are broken to induce chiral structure. The known importance of these perovskites is further expanded by the demonstration of the chiral-induced spin selectivity (CISS). However, the generation of the spin-polarized carriers across the interface with these chiral perovskites remains to be fully understood. These first-principles studies for 2D PbBr4-based chiral perovskites provide their electronic structure and an orbital-based symmetry analysis, which allows to establish an effective Hamiltonian to elucidate the underlying origin of their chirality. The same analysis is used for the Edelstein effect, responsible for electrical generation of the nonequilibrium spin polarization in many materials, which in chiral perovskites can be a mechanism contributing to CISS. Furthermore, by examining optical properties of chiral perovskites and the opportunity to use them to realize tunable altermagnets, another class of zero-magnetization spintronic materials, a versatile materials platform is put forth for unconventional spintronics.

14 SOLAR ENERGY↗
DOE OSTI2026

Uniaxial Strain Tuned Magnetism of the Altermagnet Candidate H-FeS

Altermagnets are a newly recognized class of magnetic materials characterized by compensated spin configurations while still breaking time-reversal symmetry and exhibiting unconventional transport phenomena. Hexagonal FeS (h-FeS) is a recently identified altermagnet candidate that shows a spontaneous anomalous Hall effect (AHE) accompanied by a tiny net magnetization. Here, we show that both the spontaneous AHE and magnetization can be effectively suppressed by an in-plane compressive strain. Since neutron diffraction measurements show that the applied uniaxial strain only modifies the in-plane domain population but does not affect the in-plane magnetic structure, the major effect of the applied strain is to tune the small 𝑐-axis ferromagnetic moment. Our results demonstrate a strong correlation between the tiny net magnetization and the spontaneous AHE in h-FeS, and show that uniaxial strain provides an effective knob to tune both properties in this altermagnet candidate for spintronic applications.

Yao, Weiliang [ORNL]↗
DOE OSTI2016

Hybrid Ultra‐Microporous Materials for Selective Xenon Adsorption and Separation

Abstract The demand for Xe/Kr separation continues to grow due to the industrial significance of high‐purity Xe gas. Current separation processes rely on energy intensive cryogenic distillation. Therefore, less energy intensive alternatives, such as physisorptive separation, using porous materials, are required. Herein we show that an underexplored class of porous materials called hybrid ultra‐microporous materials (HUMs) affords new benchmark selectivity for Xe separation from Xe/Kr mixtures. The isostructural materials, CROFOUR‐1‐Ni and CROFOUR‐2‐Ni, are coordination networks that have coordinatively saturated metal centers and two distinct types of micropores, one of which is lined by CrO 4 2− (CROFOUR) anions and the other is decorated by the functionalized organic linker. These nets offer unprecedented selectivity towards Xe. Modelling indicates that the selectivity of these nets is tailored by synergy between the pore size and the strong electrostatics afforded by the CrO 4 2− anions.

Mohamed, Mona H.↗
DOE OSTI2019

Interpenetration Isomerism in Triptycene‐Based Hydrogen‐Bonded Organic Frameworks

Abstract We describe an example of “interpenetration isomerism” in three‐dimensional hydrogen‐bonded organic frameworks. By exploiting the crystallization conditions for a peripherally extended triptycene H 6 PET, we can modulate the interpenetration of the assembled frameworks, yielding a two‐fold interpenetrated structure PETHOF‐ 1 and a five‐fold interpenetrated structure PETHOF‐ 2 as interpenetration isomers. In PETHOF‐ 1 , two individual nets are related by inversion symmetry and form an interwoven topology with a large guest‐accessible volume of about 80 %. In PETHOF‐ 2 , five individual nets are related by translational symmetry and are stacked in an alternating fashion. The activated materials show permanent porosity with Brunauer‐Emmett‐Teller surface areas exceeding 1100 m 2 g −1 . Synthetic control over the framework interpenetration could serve as a new strategy to construct complex supramolecular architectures from simple organic building blocks.

Li, Penghao↗
DOE OSTI2023

Resolving the Heat Generated from ZrO 2 Atomic Layer Deposition Surface Reactions

Abstract In situ pyroelectric calorimetry and spectroscopic ellipsometry were used to investigate surface reactions in atomic layer deposition (ALD) of zirconium oxide (ZrO 2 ). Calibrated and time‐resolved in situ ALD calorimetry provides new insights into the thermodynamics and kinetics of saturating surface reactions for tetrakis(dimethylamino)zirconium(IV) (TDMAZr) and water. The net ALD reaction heat ranged from 0.197 mJ cm −2 at 76 °C to 0.155 mJ cm −2 at 158 °C, corresponding to an average of 4.0 eV/Zr at all temperatures. A temperature dependence for reaction kinetics was not resolved over the range investigated. The temperature dependence of net reaction heat and distribution among metalorganic and oxygen source exposure is attributed to factors including growth rate, equilibrium surface hydroxylation, and the extent of the reaction. ZrO 2 ‐forming surface reactions were investigated computationally using DFT methods to better understand the influence of surface hydration on reaction thermodynamics.

Bielinski, Ashley R.↗
DOE OSTI2018

“Interpenetration Isomerism” of Triptycene-Based Hydrogen-Bonded Organic Frameworks

In this work, we describe an example of “interpenetration isomerism” in three-dimensional (3D) hydrogen-bonded organic frameworks (HOFs). By exploiting the crystallization conditions for a peripherally extended triptycene H6PET, we can modulate the interpenetration of the assembled frameworks, yielding a two-fold interpenetrated structure PETHOF-1 (acs-2c topology) and a five-fold interpenetrated structure PETHOF-2 (acs-5c topology) as “interpenetration isomers”. In PETHOF-1, two individual nets are related by inversion symmetry and form an interwoven topology with a strikingly large guest-accessible volume of about 80%. In PETHOF-2, five individual nets are related by translational symmetry and are stacked in an alternating fashion. Additionally, the activated materials show permanent porosity with high Brunauer–Emmett–Teller (BET) areas exceeding 1100 m2•g-1. Finally, we believe that synthetic control over the framework interpenetration can serve as a new design strategy to construct diverse and complex supramolecular architectures from simple organic building blocks.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Resolving the Heat Generated from ZrO 2 Atomic Layer Deposition Surface Reactions

Abstract In situ pyroelectric calorimetry and spectroscopic ellipsometry were used to investigate surface reactions in atomic layer deposition (ALD) of zirconium oxide (ZrO 2 ). Calibrated and time‐resolved in situ ALD calorimetry provides new insights into the thermodynamics and kinetics of saturating surface reactions for tetrakis(dimethylamino)zirconium(IV) (TDMAZr) and water. The net ALD reaction heat ranged from 0.197 mJ cm −2 at 76 °C to 0.155 mJ cm −2 at 158 °C, corresponding to an average of 4.0 eV/Zr at all temperatures. A temperature dependence for reaction kinetics was not resolved over the range investigated. The temperature dependence of net reaction heat and distribution among metalorganic and oxygen source exposure is attributed to factors including growth rate, equilibrium surface hydroxylation, and the extent of the reaction. ZrO 2 ‐forming surface reactions were investigated computationally using DFT methods to better understand the influence of surface hydration on reaction thermodynamics.

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

Energy security role of biofuels in evolving liquid fuel markets

In this work, we explore the role of biofuels in mitigating the negative impacts of oil supply shocks on fuel markets under a range of oil price trajectories and biofuel blending mandate levels. Using a partial equilibrium model of US biofuels production and petroleum fuels trade, we discuss the adjustments in light-duty vehicle fuel mix, fuel prices, and renewable identification number (RIN) prices following each shock as well as the distribution of shock costs across market participants. Ethanol is used as both a complement (blend component in E10) and a substitute (in E15 and E85 blends) to gasoline. Results show that, during oil supply shocks, the role of ethanol as a substitute dominates and allows some mitigation of the shock. As US petroleum imports decrease with growing US oil production, the net economic welfare effect of sudden oil price changes and the energy security role of biofuels becomes less clear than it has been in the past. Although fuel consumers lose when oil price increases due to an external shock, domestic fuel producers gain. In some cases, depending on import share and supply and demand elasticities, we show that the gain to producers could more than offset consumer losses. However, in most cases evaluated here, sudden oil-price increases remain costly.

09 BIOMASS FUELS↗
DOE OSTI2021

Environmental and cost benefits of multi‐purpose buffers in an agricultural watershed for biomass production

Abstract The cost‐benefit of riparian buffers to landowners has not been fully understood despite its ecosystem benefits. This study investigates the environmental and economic value of multi‐purpose buffers for biomass production under alternative land‐management scenarios at the watershed scale. The work incorporates the Soil and Water Assessment Tool with a field‐scale tool, the Agriculture Conservation Practice Framework, and cost‐benefit analysis. Our work took place in the agriculturally dominant Raccoon River watershed (RRW) in Iowa. The cost analysis includes implementing and harvesting the switchgrass buffers, the value of nitrogen and phosphorus fertilizer, and the forgone income of cropland to determine the net return under 12 alternative feedstock scenarios. We estimated that 14 603 Mg of nitrogen and 2563 Mg of phosphorus runoffs can be intercepted by riparian buffers in the RRW, representing a nutrient loss reduction of 11% of nitrogen and 26% of phosphorus. These nutrients are valued at $1.31 million (M) for phosphorus and $1.24 M for nitrogen as fertilizers. The trapped nutrients account for 12% of the riparian buffers’ total cost. We found that net economic returns increase with biomass market price, increase with maintenance fertilizer application, and decrease with the cropland areas that are converted to buffers. Under current land management, a biomass market price at $60 per dry ton of biomass would be economically viable at the sub‐basin level when maintenance fertilizers are applied. At $80 per dry ton, all 108 sub‐basins in the RRW would be profitable up to $517 a year. The results highlight the trade‐offs between water quality and profitability. Published 2021. This article is a U.S. Government work and is inthe public domain in the USA. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.

09 BIOMASS FUELS↗
DOE OSTI2015

Inactivation of nitrate reductase alters metabolic branching of carbohydrate fermentation in the cyanobacterium Synechococcus sp. strain PCC 7002

ABSTRACT To produce cellular energy, cyanobacteria reduce nitrate as the preferred pathway over proton reduction (H 2 evolution) by catabolizing glycogen under dark anaerobic conditions. This competition lowers H 2 production by consuming a large fraction of the reducing equivalents (NADPH and NADH). To eliminate this competition, we constructed a knockout mutant of nitrate reductase, encoded by narB , in Synechococcus sp. PCC 7002. As expected, Δ narB was able to take up intracellular nitrate but was unable to reduce it to nitrite or ammonia, and was unable to grow photoautotrophically on nitrate. During photoautotrophic growth on urea, Δ narB significantly redirects biomass accumulation into glycogen at the expense of protein accumulation. During subsequent dark fermentation, metabolite concentrations—both the adenylate cellular energy charge (∼ATP) and the redox poise (NAD(P)H/NAD(P))—were independent of nitrate availability in Δ narB , in contrast to the wild type (WT) control. The Δ narB strain diverted more reducing equivalents from glycogen catabolism into reduced products, mainly H 2 and d ‐lactate, by 6‐fold (2.8% yield) and 2‐fold (82.3% yield), respectively, than WT. Continuous removal of H 2 from the fermentation medium (milking) further boosted net H 2 production by 7‐fold in Δ narB , at the expense of less excreted lactate, resulting in a 49‐fold combined increase in the net H 2 evolution rate during 2 days of fermentation compared to the WT. The absence of nitrate reductase eliminated the inductive effect of nitrate addition on rerouting carbohydrate catabolism from glycolysis to the oxidative pentose phosphate (OPP) pathway, indicating that intracellular redox poise and not nitrate itself acts as the control switch for carbon flux branching between pathways. Biotechnol. Bioeng. 2016;113: 979–988. © 2015 Wiley Periodicals, Inc.

Qian, Xiao↗
DOE OSTI2018

Improving methyl ketone production in Escherichia coli by heterologous expression of NADH‐dependent FabG

Abstract We previously engineered Escherichia coli to overproduce medium‐ to long‐chain saturated and monounsaturated methyl ketones, which could potentially be applied as diesel fuel blending agents or in the flavor and fragrance industry. Recent efforts at strain optimization have focused on cofactor balance, as fatty acid‐derived pathways face the systematic metabolic challenge of net NADPH consumption (in large part, resulting from the key fatty acid biosynthetic enzyme FabG [β‐ketoacyl‐ACP reductase]) and net NADH production. In this study, we attempted to mitigate cofactor imbalance by heterologously expressing NADH‐dependent, rather than NADPH‐dependent, versions of FabG identified in previous studies. Of the four NADH‐dependent versions of FabG tested in our previously best‐reported methyl ketone‐producing strain (EGS1895), the version from Acholeplasma laidlawii (Al_FabG) showed the greatest increase in methyl ketone yield in shake flasks (35–75% higher than for an RFP negative‐control strain, depending on sugar loading). An improved strain (EGS2920) attained methyl ketone titers during fed‐batch fermentation of 5.4 ± 0.5 g/L, which were, on average, ca. 40% greater than those for the base strain (EGS1895) under fermentation conditions optimized in this study. Shotgun proteomic data for strains EGS2920 and EGS1895 during fed‐batch fermentation were consistent with the goal of alleviating NADPH limitation through expression of Al_FabG. For example, relative to strain EGS1895, strain EGS2920 significantly upregulated glucose‐6‐phosphate isomerase (directing flux into glycolysis rather than the NADPH‐producing pentose phosphate pathway) and downregulated MaeB (a NADP + ‐dependent malate dehydrogenase). Overall, the results suggest that heterologous expression of NADH‐dependent FabG in E. coli may improve sustained production of fatty acid‐derived renewable fuels and chemicals.

Goh, Ee‐Been↗
DOE OSTI2020

Cover Feature: Rational Design of a Uranyl Metal–Organic Framework for the Capture and Colorimetric Detection of Organic Dyes (Chem. Eur. J. 61/2020)

A new uranyl containing metal–organic framework was prepared and the diffraction data reveals the structure consists of interpenetrating 3D nets with a 4,3-connected tbo topology. Furthermore, each net contains large 22.8 Å pores and is constructed from monomeric, hexagonal bipyramidal uranyl nodes that are joined by 1,2,4,5-tetrakis(4-carboxyphenyl)benzene ligands. The crystalline material is stable in aqueous media and due to the large void space (constituting 76% of the unit cell by volume) can sequester organic dyes, the uptake of which induces a visible change to the color of the material.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗