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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 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Graph-based Compact Modeling (GCM) of CMOS transistors for efficient parameter extraction: A machine learning approach

Parameter extraction of compact transistor models is an expensive process, heavily relying on engineering knowledge and experience. To automate such a process, we propose a novel approach, Graph-based Compact Model (GCM), that integrates physical modeling and data-driven learning. GCM utilizes Graph Neural Networks (GNNs) to establish the model structure, while retaining the physicality in compact models. Here, we implement our GCM in Verilog-A to support circuit simulations. As demonstrated with an academic 7 nm FinFET PDK, the new approach automatically generates a GCM model within a minute, and achieves excellent accuracy and efficiency in SPICE.

42 ENGINEERING↗
DOE OSTI2022

Overcoming significant challenges in extracting off-stoichiometric thermodynamics using the compound energy formalism through complementary use of experimental and first principles data: A case study of Ba 1-x Sr x FeO 3-δ

The compound energy formalism (CEF) is a powerful framework to describe the thermodynamics of metal oxides as a function of off-stoichiometry, temperature, and composition. The thermodynamic properties are crucial materials design attributes in metal oxide-based oxygen-exchange chemical processes. Despite the richness of information an accurate CEF model provides, a method to determine a unique and accurate fit for oxygen exchange materials remains elusive. This contribution details a method for fitting the CEF model that overcomes the current fitting challenges through three innovations: 1) the combination of density functional theory calculations with experimental data decorrelates excess terms and delineates the enthalpic/entropic contributions to the Gibbs free energy; 2) a systematic determination of the important CEF model terms, removing thermodynamic predetermining human intervention; 3) a self-consistent solution of the starting oxygen offstoichiometry (δ 0 ) of thermogravimetric measurements. Thus, our method enables the reliable extraction of off-stoichiometric metal oxide thermodynamic properties and facilitates rapid materials compositional screening, and reliable process design of systems dependent on off-stoichiometric redox-active metal oxides. We apply this method to a Ba x Sr 1-x FeO 3-δ test case. We find by systematically examining the performance of the CEF model fit with and without each innovation that all three innovations are necessary for an accurate fit. We determined that reduction enthalpy is higher and more sensitive to off-stoichiometry when the Sr fraction is large (139.5 and 185.3 kJ/mol O 2 for SrFeO 3 at δ = 0 and δ = 0.5, respectively vs. nearly constant 83 kJ/mol O 2 for BaFeO 3 ). However, the reduction entropy is mostly insensitive to Sr fraction, but highly dependent on δ suggesting larger contributions in the non-configurational entropy parameters.

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

Extraction and selective promotion of zero-group velocity and cutoff frequency resonances in bi-dimensional waveguides using the electromechanical impedance method

This study showcases the electromechanical impedance (EMI) technique for extracting and promoting zero-group velocity (ZGV) and cutoff frequency resonances in a waveguide structure. Here, we identify the mechanisms of multiple resonances in the EMI spectra via a wave propagation perspective. Both simulation and experiments reveal the fact that sharp resonances in the conductance spectra are associated with either ZGV or cutoff frequency points. Consequently, we design four test configurations to enhance local resonances by aligning induced motions with considered mode shapes. Reasonable agreement between simulation and experiment results is observed. We evaluate the performance of considered configurations in terms of mode enhancement, and configurations that can selectively promote certain mode families are summarized. This study also shines the light on the EMI technique for quantitative non-destructive evaluation (NDE) by potentially supporting the inverse characterization of mechanical properties of host structures.

42 ENGINEERING↗
DOE OSTI2018

Ruta graveolens water extract inhibits cell-cell network formation in human umbilical endothelial cells via MEK-ERK1/2 pathway

Highlights: • RGWE inhibits HUVEC ability to form tubes on matrigel in vitro. • RGWE interferes, through MEK/ERK, with the VEGF-mediated signaling that leads to angiogenesis. • RGWE is proposed as a new therapeutic tool to prevent pathological angiogenesis. Angiogenesis is a process encompassing several steps such as endothelial cells proliferation, differentiation and migration to form a vascular network, involving different signal transduction pathways. Among these, ERK1/2 signaling mediates VEGF-dependent signaling pathway. Here we report that the water extract of Ruta graveolens (RGWE), widely known as a medicinal plant, is able to impair in a dose-dependent manner, cell network formation without affecting cell viability. Biochemical analysis showed that the major component of RGWE is rutin, unable to reproduce RGWE effect. We found that RGWE inhibits ERK1/2 phosphorylation and that this event is crucial in cell network formation since the transfection of HUVEC with a constitutively active MEK (caMEK), the ERK1/2 activator, induces a robust cell network formation as compared to untransfected and/or mock transfected cells and, more importantly, caMEK transfected cells became unresponsive to RGWE. Moreover, RGWE inhibits VEGF and nestin gene expression, necessary for vessel formation, and the caMEK transfection induces their higher expression. In conclusion, we report that RGWE is able to significantly impair vessels network formation without affecting cell viability, preventing ERK1/2 activation and, in turn, down-regulating VEGF and nestin expression. These findings point to RGWE as a potential therapeutic tool capable to interfere with pathologic angiogenesis.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Selective and Chemical-Free Removal of Toxic Heavy Metal Cations from Water Using Shock Ion Extraction

Electrochemical methods are known to have attractive features and capabilities when used for ion separations and water purification. In this study, we developed a new process called shock ion extraction (shock IX) for selective and chemical-free removal of toxic heavy metals from water. Shock IX is a hybrid process that combines shock electrodialysis (shock ED) and ion exchange using an ion exchange resin wafer (IERW), and this method can be thought of functionally as an electrochemically assisted variation of traditional ion exchange. In particular, shock IX exhibits greater ion removal and selectivity for longer periods of time, compared to the use of ion exchange alone. Here, the use of an IERW in shock ED also increases multivalent ion selectivity, reduces energy consumption, and improves the hydrodynamics and scalability of the system.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

Extraction, Characterization, and Stability Studies of Bistriazinyl-Derived Carboxylic Acids

Separation of An(III) and Ln(III) ions will benefit the recycling of used nuclear fuel (UNF). For this purpose, many ligands have been tested over the years, and several separation processes have been successfully demonstrated on the laboratory scale. Current research aims at the development of new ligands that are built only with carbon, hydrogen, oxygen, and nitrogen (CHON), as they can be incinerated completely without secondary waste production. Here, we tested a new class of water-soluble ligands, the bistriazinyl-octa-carboxylic acids. One member, in particular, 2,6-bis-[5,6-di(3,4-dicarboxyphenyl)-1,2,4- triazin-3-yl]-pyridine (BTPOA), was found to be suitable for the selective separation of Am(III) and Cm(III) ions from Ln(III) ions and may act as a CHON alternative to its sulfonated analogue (SO 3 -Ph-BTP). BTPOA exhibited good extraction results and a high selectivity for Am(III) over Eu(III) ions. This ligand’s complexation of metal ions was further studied using potentiometric spectroscopy, as well as time-resolved laser-induced spectroscopy with Cm(III) and Eu(III) in aqueous HClO 4 and HNO 3 media. Conditional stability constants of each formed species were determined. In the HClO 4 system, Cm(III) formed three species (1:1, 1:2, and 1:3) through the stepwise addition of a single BTPOA molecule. On the other hand, in HNO 3 , Cm(III) formed two 1:2 complexes and one 1:3 complex, while the stepwise formation of three species was observed for Eu(III). The stability constants are comparable to the values for SO 3 -Ph-BTP. The radiolytic behavior of BTPOA was also investigated using electron pulse irradiation measurements to determine absolute rate coefficients (k) under ambient temperature conditions for the reaction of BTPOA with typical UNF reprocessing radical radiolysis products the hydrated electron (e aq − , k = (1.60 ± 0.02) × 10 10 M −1 s −1 ), the hydrogen atom (H • , k = (2.17 ± 0.03) × 10 9 M −1 s −1 ), and hydroxyl ( • OH, k = (6.95 ± 0.06) × 10 9 M −1 s −1 ) and nitrate (NO 3 • , k = (0.37 ± 0.02) × 10 7 M −1 s−1) radicals. These rate coefficients indicate that the radiolytic longevity of BTPOA should increase with HNO 3 concentration, owing to the consumption of e aq − /H • , by nitrate anions, and the replacement of • OH by the less reactive NO 3 • .

Diaz Gomez, Laura [Forschungszentrum Juelich (Germ↗
DOE OSTI2017

Optimization of the Electrochemical Extraction and Recovery of Metals from Electronic Waste Using Response Surface Methodology

The rapid growth of the electronic waste can be viewed both as an environmental threat and as an attractive source of minerals that can reduce the mining of natural resources, and stabilize the market of critical materials, such as rare earths. Here in this article surface response methodology was used to optimize a previously developed electrochemical recovery process for base metals from electronic waste using a mild oxidant (Fe 3+ ). Through this process an effective extraction of base metals can be achieved enriching the concentration of precious metals and significantly reducing environmental impacts and operational costs associated with the waste generation and chemical consumption. The optimization was performed using a bench-scale system specifically designed for this process. Operational parameters such as flow rate, applied current density and iron concentration were optimized to reduce the specific energy consumption of the electrochemical recovery process to 1.94 kWh per kg of metal recovered at a processing rate of 3.3 g of electronic waste per hour.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Complexation of High-Valency Mid-Actinides by a Lipophilic Schiff Base Ligand: Synthesis, Structural Characterization, and Progress toward Selective Extraction

We report that separation of U, Np, and Pu from used nuclear fuel (UNF) would result in lower long-term radiotoxicity, alleviating constraints on the storage and handling of the material. The complexity of UNF requires several industrial-scale processes with multiple waste streams. A one-step solution to the group removal of the elements, U–Pu, is desirable. Here we present a possible solution to group actinide separation utilizing the unique dioxy conformation of An(V/VI) cations and demonstrate the ability of a tetradentate lipophilic Schiff base ligand (L) to yield isostructural complexes of the general formula [(An VI O 2 )(L)(CH 3 CN)] (where An = U, Np, or Pu). Extraction of An(VI) with the ligand follows the order U > Pu > Np, likely reflecting the decreased stability of the hexavalent actinide across the series. Lastly, while the results indicate a promising path toward a one-step process, further improvement in the ligand stability and control of the redox chemistry is required.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Extracting Inelastic Scattering Cross Sections for Finite and Aperiodic Materials from Electronic Dynamics Simulations

Explicit time-dependent electronic structure theory methods are increasingly prevalent in the areas of condensed matter physics and quantum chemistry, with the broad-band optical absorptivity of molecular and small condensed-phase systems nowadays routinely studied with such approaches. Here, in this paper, it is demonstrated that electronic dynamics simulations can similarly be employed to study cross sections for the scattering-induced electronic excitations probed in nonresonant inelastic X-ray scattering and momentum-resolved electron energy loss spectroscopies. A method is put forth for evaluating the electronic dynamic structure factor, which involves the application of a momentum boost-type perturbation and transformation of the resulting reciprocal space density fluctuations into the frequency domain. Good agreement is first demonstrated between the dynamic structure factor extracted from these electronic dynamics simulations and the corresponding transition matrix elements from linear response theory. The method is then applied to some extended (quasi)one-dimensional systems, for which the wave vector becomes a good quantum number in the thermodynamic limit. Finally, the dispersion of many-body excitations in a series of hydrogen-terminated graphene flakes (and twisted bilayers thereof) is investigated to highlight the utility of the presented approach for capturing morphology-dependent effects in the inelastic scattering cross sections of nanostructured and/or noncrystalline materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Advanced Analysis of X-ray Fluorescence Measurements of the Interfacial Density of Eu Ions at Liquid–Liquid Interfaces for Solvent Back-Extraction

X-ray fluorescence near total reflection (XFNTR) is the primary technique used to measure the element-specific interfacial density of ions at liquid−liquid interfaces. Fluorescence from ions in the bulk liquids can complicate the determination of the interfacial density; consequently, measurements have been previously limited to samples without ions in the upper phase and with concentrations on the order of 10 μM or less in the lower phase. We modify the analysis of XFNTR data to account for ions in both bulk phases, then demonstrate its use in the context of rare-earth separations processes. In a model of ion stripping (i.e., back-extraction), dodecane solutions of di(2-ethylhexyl)- phosphoric acid (HDEHP) loaded with Eu(III) at the 1 mM level are placed in contact with either pure water or aqueous solutions of nitric or citric acid at pH 3. XFNTR measurements of equilibrated, quiescent samples reveal that citric acid solutions produce a disproportionately large depletion of ions from the interface compared to that from the bulk organic solution, whereas stripping by pure water or nitric acid solutions is negligible. As a result, this advance in the methodology of XFNTR may have broad applicability to the investigation of metal ions in chemical and biological processes at liquid−liquid interfaces.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Dynamic Evolution of 2D Layers within Perovskite Nanocrystals via Salt Pair Extraction and Reinsertion

Metal halide perovskite (MHP) semiconductors exhibit unprecedented optoelectronic properties coupled with low formation energies that enable scalable, cost-efficient solution processing. The low formation energies additionally facilitate dynamic transformation of the chemical composition and crystal structure of the MHP material. In this work, we show that CsBr salt is selectively extracted from CsPbBr 3 nanocrystals (NCs) to yield PbBr 2 NCs. The PbBr 2 NCs are then exposed to different glacial acetic acid ABr salt solutions to generate a variety of emissive compounds with the generic structure A' 2 A n-1 Pb n Br 3 n-1 X' 2 , where A = cesium (Cs + ), methylammonium (MA + ), formamidinium (FA+); A' = A or H+; X' = Br- or acetate (CH3COO-); and n is the number of lead halide layers, where n = 1, 2, 3, ...8. We systematically vary the ratios of PbBr 2 /ABr/CH 3 COOH and show that certain ratios result in isolable single-phase APbBr3 NCs - an effective A-site cation exchange from the parent CsPbBr 3 NCs. Importantly, time-resolved photoluminescence (PL) spectroscopy shows the dynamic evolution of many additional species as evidenced by blue-shifted emission peaks from 2.85-2.49 eV for MA + -based structures. We assign these species to n = 1, 2, 3, 4, and 5 quasi-two-dimensional network (2DN) sheets, in which CH 3 COO- anions and Br- anions compete for the c-axis X' sites separating haloplumbate(II) layers within the A' 2 A n-1 Pb n Br 3n-1 X' 2 NCs. Finally, we demonstrate the degree of CH 3 COO- incorporation, and thus the 2DN layer thickness and PL energy, is controlled in the early reaction times by kinetic factors. After a longer time (3 h), thermodynamic forces dictated by Le Chatelier's principle tune the structure in A' 2 A n-1 Pb n Br 3n-1 X' 2 NCs from exclusively n = 1 to n = 8 depending on the PbBr 2 /ABr/CH 3 COOH ratio.

14 SOLAR ENERGY↗
DOE OSTI2026

Tea ( Camellia sinensis ) Extract-Mediated Green Synthesis of Co 3 O 4 and Co 3 O 4 @Graphene Nanocomposites for Multifunctional Applications in Pollutant Degradation, Sensing, and Energy Storage

A novel solution-mixing method was proposed to synthesize Co 3 O 4 /graphene nanocomposites (Co 3 O 4 @Gr) using a green tea leaf (Camellia sinensis) extract as the reducing agent. XRD analysis shows that the as-prepared Co 3 O 4 @Gr exhibits a cubic spinel crystal structure. From morphological analysis, the obtained Co 3 O 4 NS forms spherical clusters that are uniformly distributed on the graphene surface. FT-IR and Raman analyses confirmed the strong molecular and vibrational interactions between the Co 3 O 4 NS and Gr. The suppressed PL intensity peak of the Co 3 O 4 @Gr NCs indicated significant inhibition in the recombination of charge carriers between the hybrid orbitals within the composites. As a result, the catalytic efficiency of Co 3 O 4 @Gr NCs increased to 80% compared to pristine Co 3 O 4 , which exhibited only 45% efficiency against methylene blue (MB) dye. Moreover, the as-prepared NCs exhibited a detection limit of 0.01−224 μM, demonstrating a superior low-DPA detection with high sensitivity. The Co 3 O 4 @Gr/GCE exhibits admirable selectivity for various pesticides, fungicides, and metal ions, with outstanding reproducibility and stability. From electrochemical investigations, the highest specific capacitance values of the as-synthesized Co 3 O 4 @Gr were 349 F/g at a scan rate of 5 mV/s and 158 F/g at a current density of 1 A/g.

Capacitors↗
DOE OSTI2020

Hot-Carrier Extraction in Nanowire-Nanoantenna Photovoltaic Devices

Nanowires bring new possibilities to the field of hot-carrier photovoltaics by providing flexibility in combining materials for band engineering and using nanophotonic effects to control light absorption. Previously, an open-circuit voltage beyond the Shockley–Queisser limit was demonstrated in hot-carrier devices based on InAs–InP–InAs nanowire heterostructures. However, in these first experiments, the location of light absorption, and therefore the precise mechanism of hot-carrier extraction, was uncontrolled. In this study, we combine plasmonic nanoantennas with InAs–InP–InAs nanowire devices to enhance light absorption within a subwavelength region near an InP energy barrier that serves as an energy filter. From photon-energy- and irradiance-dependent photocurrent and photovoltage measurements, we find that photocurrent generation is dominated by internal photoemission of nonthermalized hot electrons when the photoexcited electron energy is above the barrier and by photothermionic emission when the energy is below the barrier. We estimate that an internal quantum efficiency up to 0.5–1.2% is achieved. Insights from this study provide guidelines to improve internal quantum efficiencies based on nanowire heterostructures.

14 SOLAR ENERGY↗
DOE OSTI2018

Graphene-Modified Tin Dioxide for Efficient Planar Perovskite Solar Cells with Enhanced Electron Extraction and Reduced Hysteresis

Tin dioxide (SnO 2 ) as an efficient electron transport layer (ETL) has been demonstrated for emerging high-performance organic–inorganic hybrid perovskite solar cells (PSCs). However, the low-temperature solution-processed SnO 2 usually results in high trap-state density and current–voltage hysteresis. Here, we reported an effective strategy to solve this problem by incorporating graphene ink into the low-temperature processed SnO 2 for planar structure PSCs. The electron extraction efficiency has been significantly improved with graphene-doped SnO2 ETL coupled with attenuated charge recombination at the ETL/perovskite interface. The power conversion efficiency (PCE) of PSCs based on the graphene–SnO 2 ETL reached over 18% with negligible hysteresis. Incorporation of graphene into the ETL layer also enhanced the device stability retaining 90% of the initial PCE value after storing in ambient condition with a relative humidity of 40 ± 5% for 300 h. Our results provide an important insight into further efficiency boost in SnO 2 -based low-temperature processed PSCs.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Moisture-Induced Crystallographic Reorientations and Effects on Charge Carrier Extraction in Metal Halide Perovskite Solar Cells

Lead halide perovskites (LHPs) are promising semiconductors for optoelectronic applications. In LHP solar cells, the focus thus far has been mainly on compositional optimization of the MHP layer, without much understanding of the effects of compositional mixing on structure and texture. This is a serious gap in our knowledge because research has shown that texture underlies the mechanisms of charge carrier and ionic transport. Therefore, it is essential to understand the mechanisms that drive changes in texture in LHPs. Here we examine the effect of moisture and composition on the structure and texture of LHPs and their impacts on optoelectronic properties. Exposure to moisture is shown to induce a crystallographic reorientation in the polycrystalline films, which is also dependent on the amount of organic cation material present at the surface. For films with an excess of organic halide, moisture was shown to induce texture in the (001) plane contributing to the enhancement of photocurrents and long-term device stability. This work shows the importance of texture for the electronic properties of LHPs with a special emphasis on charge carrier extraction in optoelectronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Vapor-Deposited n = 2 Ruddlesden–Popper Interface Layers Aid Charge Carrier Extraction in Perovskite Solar Cells

Interfacial passivation with bulky organic cations such as phenetylammonium iodide has enabled high performance for metal halide perovskite optoelectronic devices. However, the homogeneity of these interfaces and their formation dynamics are poorly understood. Here we study how Ruddlesden-Popper 2D phases form at a 3D perovskite interface when the 2D precursors are introduced via solution or via vapor. When using vapor deposition, we observe uniform coverage of the capping layer and the formation of a predominantly n = 2 Ruddlesden-Popper phase. In contrast, when using solution deposition, we observe the presence of a mixture of n = 2 and n = 1 in the film and the formation of aggregates of the organic cations. As a result of the better phase purity and uniformity, vapor deposition enables higher median solar cell performance with narrower distribution compared to solution-treated films. This study provides fundamental information that the perovskite community can use to better design capping layers to achieve higher charge extraction efficiencies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Modeling the Impacts of Hydrogen Extraction on Anaerobic Fermentation Systems Using a Modified ADM1 Model

Here, this paper presents a modified ADM1 (mADM1) model for use in assessing the influence of active dissolved H 2 extraction on biogas production from anaerobic fermentation reactors, specifically in the context of high-strength brewery wastewater as the feed. The modified model adds regulation factors to account for the varying product stoichiometry of glucose degradation reactions as a function of H 2 concentration in anaerobic digestion, and incorporates the use of both lactate and ethanol as intermediates. The changes to the model are expected to better predict the effects of H 2 removal on the production of H 2 in fermentation processes. Both ADM1 and mADM1 were calibrated against experimental data from a fluidized-bed reactor containing encapsulated acidogenic-acetogenic microbial communities treating real brewery wastewater. The calibrated models were validated against another fluidized-bed reactor identical to the calibration reactor, with the addition of a hollow-fiber membrane module that was used to reduce dissolved H 2 concentrations in the validation reactor. It was found that ADM1 over-estimated the H 2 production rates of the validation reactor (117 mL/day simulated vs. 16.48 mL/day experimental), whereas mADM1 was able to successfully predict fermentation, and specifically the H 2 production rate (17 mL/day). The presented model is a first step towards a model that can predict the effects of dissolved H 2 removal on fermentation processes.

Anaerobic Digestion↗
DOE OSTI2026

Using Novosphingobium aromaticivorans for Concurrent Production of Intracellular and Extracellular Products from Aromatics Extracted from Poplar Biomass

Achieving high biochemical production in biotransformations of renewable resources requires using concentrated cultures that not only generate the product of interest but also produce abundant microbial cell waste. We explored the concept of gaining value from microbial cells by producing intracellular products in tandem with a desired extracellular product. Specifically, we engineered a strain ofNovosphingobium aromaticivorans to extracellularly produce 2-pyrone-4,6-dicarboxylic acid (PDC) from aromatic substrates and to intracellularly accumulate astaxanthin along with coenzyme Q 10 , all of which are products of industrial interest. Achieving the goal of concurrent production of intracellular and extracellular products required the creative application of bioreactor engineering principles. Although a continuously fed membrane bioreactor (MBR) maximized extracellular product biosynthesis, it had a negative effect on intracellular product accumulation. However, operating the MBR as a sequencing batch reactor (MBR-SBR) with a step-feed resulted in stable concurrent production of both extracellular and intracellular products. With aromatics extracted from poplar biomass, we achieved productivities of 1.14 g of PDC/L-h for the extracellular product and 0.04 mg of astaxanthin/L-h and 0.64 mg of CoQ 10 /L-h for intracellular products, respectively. Our findings demonstrate that the mode of operation of a bioreactor impacts the simultaneous production of intracellular and extracellular products byN. aromaticivorans.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗