Search NASA⌕ Search

SEARCH · Search NASA

Results for “ALTERNATE REDUCTANT”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

In Situ Strain Evolution on Pt Nanoparticles during Hydrogen Peroxide Decomposition

Fundamental understanding of structural changes during catalytic reactions is crucial to understanding the underlying mechanisms and optimizing efficiencies. Surface energy and related catalytic mechanisms are widely studied. However, the catalyst lattice deformation induced by catalytic processes is not well understood. Here, we study the strain in an individual platinum (Pt) nanoparticle (NP) using Bragg coherent diffraction imaging under in situ oxidation and reduction reactions. When Pt NPs are exposed to H 2 O 2 , a typical oxidizer and an intermediate during the oxygen reduction reaction process, alternating overall strain distribution near the surface and inside the NP is observed at the (111) Bragg reflection. In contrast, relatively insignificant changes appear in the (200) reflection. Density functional theory calculations are employed to rationalize the anisotropic lattice strain in terms of induced stress by H 2 O 2 adsorption and decomposition on the Pt NP surface. Our study provides deeper insight into the activity-structure relationship in this system.

3D imaging↗
DOE OSTI2023

Simulation studies for beam commissioning at FRIB Advanced Rare Isotope Separator

The Facility for Rare Isotope Beams (FRIB) includes a powerful superconducting driver accelerator and an Advanced Rare Isotope Separator (ARIS). The ARIS collects and purifies the rare isotope fragments of interest for experiments in nuclear physics, nuclear astrophysics, fundamental symmetries, etc. ARIS consists of a vertical pre-separator and downstream horizontal separator section (C-Bend). Each section can provide a high-resolution separation alternatively. The resolution reduction due to the emittance induced by momentum compression can be avoided by isotope separation in different dispersive planes. Beam commissioning of ARIS for the first experiments was completed and demonstrated particle identification of fragments. The beam tuning in ARIS largely relies on numerical simulations since the limited space for diagnostics. Here, we report the result of the beam trajectory correction, transverse matching, and beam-based misalignment studies at ARIS.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Consumptive Water Use from Electricity Generation in the Southwest under Alternative Climate, Technology, and Policy Futures

This research assesses climate, technological, and policy impacts on consumptive water use from electricity generation in the Southwest over a planning horizon of nearly a century. We employed an integrated modeling framework taking into account feedbacks between climate change, air temperature and humidity, and consequent power plant water requirements. These direct impacts of climate change on water consumption by 2095 differ with technology improvements, cooling systems, and policy constraints, ranging from a 3–7% increase over scenarios that do not incorporate ambient air impacts. Upon additional factors being changed that alter electricity generation, water consumption increases by up to 8% over the reference scenario by 2095. With high penetration of wet recirculating cooling, consumptive water required for low-carbon electricity generation via fossil fuels will likely exacerbate regional water pressure as droughts become more common and population increases. Adaptation strategies to lower water use include the use of advanced cooling technologies and greater dependence on solar and wind. Water consumption may be reduced by 50% in 2095 from the reference, requiring an increase in dry cooling shares to 35–40%. Alternatively, the same reduction could be achieved through photovoltaic and wind power generation constituting 60% of the grid, consistent with an increase of over 250% in technology learning rates.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Extending quantum probabilistic error cancellation by noise scaling

Here, we propose a general framework for quantum error mitigation that combines and generalizes two techniques: probabilistic error cancellation (PEC) and zero-noise extrapolation (ZNE). Similar to PEC, the proposed method represents ideal operations as linear combinations of noisy operations that are implementable on hardware. However, instead of assuming a fixed level of hardware noise, we extend the set of implementable operations by noise scaling. By construction, this method encompasses both PEC and ZNE as particular cases and allows us to investigate a larger set of hybrid techniques. For example, gate extrapolation can be used to implement PEC without requiring knowledge of the device’s noise model, e.g., avoiding gate-set tomography. Alternatively, probabilistic error reduction can be used to estimate expectation values at intermediate virtual noise strengths (below the hardware level), leading to partially mitigated results at a lower sampling cost. Moreover, multiple results obtained with different noise-reduction factors can be further postprocessed with ZNE to better approximate the zero-noise limit.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Efficient Simulation of Welding Distortion in Large Structures and Its Reduction by Jig Constraints

Two large construction machinery structures were welded separately with and without jig constraints. The welding distortion of the entire structure was measured by a 3D coordinate measuring system and simulated by elastic FEM using the inherent deformation method. To obtain an accurate inherent deformation, a thermal elastoplastic FE analysis of simple one-side fillet joints with and without jig constraints was performed. Efficient simulation of welding distortion in large structures was accomplished by applying inherent deformation in a localized region, and the effect of jig constraint on the reduction of welding distortion was clarified. The computation of inherent deformation, the weld zone definition and the conversion of inherent deformation into inherent strain were automated. Measured and computed welding distortions in large structures had a good correspondence with respect to both tendency and magnitude. Further investigation of jig configuration was performed for enhanced reduction of welding distortion. Alternative controlling techniques for common welded structures were also addressed.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Graphene-Supported Monometallic and Bimetallic Dimers for Electrochemical CO 2 Reduction

Bimetallic catalysts are attractive alternatives to extend the parameter space that can be tuned for support interactions and catalytic performance. In this study, we have investigated the smallest bimetallic catalysts dimers supported on defective graphene for the electrochemical reduction of CO 2 to CH 4 based on a first-principles approach and the computational hydrogen electrode model. The monometallic and bimetallic dimers formed from Group 10 (Ni, Pd, Pt) and group 11 (Cu, Ag, Au) elements are characterized by a positively charged anchoring atom occupying the vacancy site of graphene and a neutral or slightly negatively charged antenna atom sticking out from the graphene surface. The strong selective binding of these dimers ensures their high stability. Possible rate-limiting steps are identified from the full reaction pathways to generate CH4. Overall, Pt-2, AgNi, Pd-2, and AgPt are the best candidates with the lowest overpotential values of 0.37, 0.69, 0.69, and 0.76 V, respectively. It is found that the alloy effect and the interaction with support help to optimize the property. These metallic dimers, however, retain nonmonotonous property relationships that give opportunity to go beyond scaling behavior and look for a few atom catalysts that have unique properties to reduce rate-limiting potentials and improve the catalytic performance.

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

Anion Exchange Membrane Electrolyzers as Alternative for Upgrading of Biomass-Derived Molecules

Upgrading biomass derived platform molecules to fuels or chemicals provides a unique alternative for the substitution of fossil sources with renewables. Electrochemical reduction (ECR) is one of the upgrading technologies, alternative to catalytic reduction, which only requires electricity as the energy input, which can be derived from carbon free energy sources. Moreover, ECR does not require external addition of hydrogen, as this can be generated in-situ. In this work an anion exchange membrane (AEM) electrolyte assembly (MEA) has been tested for the efficient reduction of biomass derived molecules, and compared with a cation exchange membrane (CEM) MEA. The cathode electrocatalyst has been modified with the addition of hydrophobicity and anion exchange ionomers, and incorporated onto an anion exchange membrane. Electrochemical experiments were performed with a metal free electrocatalyst in the presence and absence of surrogate compounds. The results showed that changes in the catalyst formulation can increase the overpotential for the competing hydrogen evolution reaction (HER), while significantly enhancing the reduction of the organic molecules. Bulk electrolysis experiments demonstrated higher efficiencies for furfural ECR in an AEM-MEA vs. AEM-CEM, reaching conversions up to 94% at 50 mA cm 2 and in the absence of supporting electrolyte. Moreover, AEM-MEA was able to facilitate water management during the reduction process and contribute to the separation of small carboxylic acids.

09 BIOMASS FUELS↗
DOE OSTI2012

Heavy ion beam probe advances from the first installation of the diagnostic on an RFP (invited)

Heavy ion beam probes have been installed on a variety of toroidal devices, but the first and only application on a reversed field pinch is the diagnostic on the Madison Symmetric Torus. Simultaneous measurements of spatially localized equilibrium potential and fluctuations of density and potential, previously inaccessible in the core of the reversed field pinch (RFP), are now attainable. These measurements reflect the unique strength of the heavy ion beam probe (HIBP) diagnostic. They will help determine the characteristics and evolution of electrostatic fluctuations and their role in transport, and determine the relation of the interior electric field and flows. Many aspects of the RFP present original challenges to HIBP operation and inference of plasma quantities. The magnetic field contributes to a number of the issues: the comparable magnitudes of the toroidal and poloidal fields and edge reversal result in highly three-dimensional beam trajectories; partial generation of the magnetic field by plasma current cause it and hence the beam trajectories to vary with time; and temporal topology and amplitude changes are common. Associated complications include strong ultraviolet radiation and elevated particle losses that can alter functionality of the electrostatic systems and generate noise on the detectors. These complexities have necessitated the development of new operation and data analysis techniques: the implementation of primary and secondary beamlines, adoption of alternative beam steering methods, development of higher precision electrostatic system models, refinement of trajectory calculations and sample volume modeling, establishment of stray particle and noise reduction methods, and formulation of alternative data analysis techniques. These innovative methods and the knowledge gained with this system are likely to translate to future HIBP operation on large scale stellarators and tokamaks.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

H 2 -Independent Growth of the Hydrogenotrophic Methanogen Methanococcus maripaludis

Hydrogenotrophic methanogenic Archaea require reduced ferredoxin as an anaplerotic source of electrons for methanogenesis. H 2 oxidation by the hydrogenase Eha provides these electrons, consistent with an H 2 requirement for growth. Here we report the identification of alternative pathways of ferredoxin reduction in Methanococcus maripaludis that operate independently of Eha to stimulate methanogenesis. A suppressor mutation that increased expression of the glycolytic enzyme glyceraldehyde-3-phosphate:ferredoxin oxidoreductase resulted in a strain capable of H 2 -independent ferredoxin reduction and growth with formate as the sole electron donor. In this background, it was possible to eliminate all seven hydrogenases of M. maripaludis. Alternatively, carbon monoxide oxidation by carbon monoxide dehydrogenase could also generate reduced ferredoxin that feeds into methanogenesis. In either case, the reduced ferredoxin generated was inefficient at stimulating methanogenesis, resulting in a slow growth phenotype. As methanogenesis is limited by the availability of reduced ferredoxin under these conditions, other electron donors, such as reduced coenzyme F 420 , should be abundant. Indeed, when F 420 -reducing hydrogenase was reintroduced into the hydrogenase-free mutant, the equilibrium of H 2 production via an F 420 -dependent formate:H 2 lyase activity shifted markedly toward H 2 compared to the wild type.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2010

X-ray structure of the metcyano form of dehaloperoxidase from Amphitrite ornata: evidence for photoreductive dissociation of the iron-cyanide bond

X-ray crystal structures of the metcyano form of dehaloperoxidase-hemoglobin (DHP A) from Amphitrite ornata (DHPCN) and the C73S mutant of DHP A (C73SCN) were determined using synchrotron radiation in order to further investigate the geometry of diatomic ligands coordinated to the heme iron. The DHPCN structure was also determined using a rotating-anode source. The structures show evidence of photoreduction of the iron accompanied by dissociation of bound cyanide ion (CN{sup -}) that depend on the intensity of the X-ray radiation and the exposure time. The electron density is consistent with diatomic molecules located in two sites in the distal pocket of DHPCN. However, the identities of the diatomic ligands at these two sites are not uniquely determined by the electron-density map. Consequently, density functional theory calculations were conducted in order to determine whether the bond lengths, angles and dissociation energies are consistent with bound CN{sup -} or O{sub 2} in the iron-bound site. In addition, molecular-dynamics simulations were carried out in order to determine whether the dynamics are consistent with trapped CN{sup -} or O{sub 2} in the second site of the distal pocket. Based on these calculations and comparison with a previously determined X-ray crystal structure of the C73S-O{sub 2} form of DHP [de Serrano et al. (2007), Acta Cryst. D63, 1094-1101], it is concluded that CN{sup -} is gradually replaced by O{sub 2} as crystalline DHP is photoreduced at 100 K. The ease of photoreduction of DHP A is consistent with the reduction potential, but suggests an alternative activation mechanism for DHP A compared with other peroxidases, which typically have reduction potentials that are 0.5 V more negative. The lability of CN{sup -} at 100 K suggests that the distal pocket of DHP A has greater flexibility than most other hemoglobins.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Synthesis and flash sintering of (Hf 1-x Zr x )B 2 solid solution powders

(Hf 1-x Zr x )B 2 solid solution powders were synthesized by two methods. First, solution-based processing of HfCl 4 , ZrCl 4 , sucrose, and H 3 BO 3 was conducted followed by heat treatment in Argon to carry out the carbothermal reduction (CTR) reaction to form the diboride powders. Alternatively, in the so-called borohydride reduction (BHR) method, HfCl 4 , ZrCl 4 and NaBH 4 were mixed in an Argon glove box followed by heat treatment in Argon at 700-1500°C. The synthesized powders were characterized by XRD, SEM, TEM, EDS, and TGA, and the influence of different parameters such as starting composition, heat treatment temperature and time on products characteristics were revealed. Both CTR and BHR solid solution powders were then consolidated within ~5 min in a homemade flash sintering (FS) setup. Here, the composition, microstructure, hardness, and thermal-oxidation properties of flash sintered ceramics were characterized, and the implication of this study and directions for future research were discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2016

American Recovery and Reinvestment Act: Clean Cities Project Awards

Each Clean Cities project award under the American Recovery and Reinvestment Act included a diverse group of stakeholders who worked together to lay the foundation for their communities to adopt alternative fuels and petroleum reduction strategies. This document provides a snapshot of the impact of each project and highlights the partners and Clean Cities coalitions who helped transform local and regional transportation markets through 25 projects impacting 45 states.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2018

Exploring the Effect of Gold Support on the Oxygen Reduction Reaction Activity of Metal Porphycenes

It has been a long-standing goal to find alternative, cost effective catalysts for oxygen reduction reaction (ORR) in fuel cells. Molecular complexes capable of efficiently catalyzing ORR, when supported on a conducting solid surface could provide interesting hybrid materials combining the best of homogeneous and heterogeneous catalysis. Here, we utilize density functional theory to study the ORR activity of molecular (unsupported) and gold supported 3d metal (II)-porphycenes (MPc). All the 3d metal-porphycenes adsorb strongly on the Au(111) support with negative free energy of formation ranging from 1.0–3.0 eV while solvation lowers the energy of molecular MPc by only 0.5 eV compared to the gas phase. These indicate that the 3d MPc are stable and anchored firmly to the gold surface under ORR conditions. Based on our analysis, the gold support enhances the ORR activity in some of the examined MPc systems. We find that the molecular MnPc and FePc are the best ORR electrocatalysts with theoretical overpotentials of 0.44 V and 0.36 V. Thus, this work highlights the important role of the support in preserving/increasing the activity of molecular catalyst.

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

Chemistry of Materials Underpinning Photoelectrochemical Solar Fuel Production

Since its inception, photoelectrochemistry has sought to power the generation of fuels, particularly hydrogen, using energy from sunlight. Efficient and durable photoelectrodes, however, remain elusive. Here we review the current state of the art, focusing our discussion on advances in photoelectrodes made in the past decade. We open by briefly discussing fundamental photoelectrochemical concepts and implications for photoelectrode function. We next review a broad range of semiconductor photoelectrodes broken down by material class (oxides, nitrides, chalcogenides, and mature photovoltaic semiconductors), identifying intrinsic properties and discussing their influence on performance. We then identify innovative in situ and operando techniques to directly probe the photoelectrode|electrolyte interface, enabling direct assessment of structure–property relationships for catalytic surfaces in active reaction environments. We close by considering more complex photoelectrochemical fuel-forming reactions (carbon dioxide and nitrogen reduction, as well as alternative oxidation reactions), where product selectivity imposes additional criteria on electrochemical driving force and photoelectrode architecture. By contextualizing recent literature within a fundamental framework, we seek to provide direction for continued progress toward achieving efficient and stable fuel-forming photoelectrodes.

08 HYDROGEN↗
DOE OSTI2014

Warming shifts ‘worming’: effects of experimental warming on invasive earthworms in northern North America

Climate change causes species range shifts and potentially alters biological invasions. The invasion of European earthworm species across northern North America has severe impacts on native ecosystems. Given the long and cold winters in that region that to date supposedly have slowed earthworm invasion, future warming is hypothesized to accelerate earthworm invasions into yet non-invaded regions. Alternatively, warming-induced reductions in soil water content (SWC) can also decrease earthworm performance. We tested these hypotheses in a field warming experiment at two sites in Minnesota, USA by sampling earthworms in closed and open canopy in three temperature treatments in 2010 and 2012. Structural equation modeling revealed that detrimental warming effects on earthworm densities and biomass could indeed be partly explained by warming-induced reductions in SWC. The direction of warming effects depended on the current average SWC: warming had neutral to positive effects at high SWC, whereas the opposite was true at low SWC. Our results suggest that warming limits the invasion of earthworms in northern North America by causing less favorable soil abiotic conditions, unless warming is accompanied by increased and temporally even distributions of rainfall sufficient to offset greater water losses from higher evapotranspiration.

Science & Technology - Other Topics↗
DOE OSTI2026

A rapid embodied carbon assessment tool for priority materials

Embodied carbon limits within building materials are a driving factor in global trade, generating new research and analysis tools in industry. These product assessments, which require utilizing life-cycle assessment (LCA) across broad supply chains, can be expensive, time and data-intensive, and subject to significant variations. Existing methods and tools, such as specific environmental product declarations, typically do not capture these variations and dynamics in supply and manufacturing. Moreover, models and tools must enable stakeholders to assess customized supply chains and future scenarios. In this study, we present the Rapid Embodied Carbon Assessment and Target-setting for Emissions-intensive Materials (REDuCE) tool for building materials. We developed a tool that allows users to select production technologies, transportation mode and distances, concrete carbonation, fuel sources, and regional electricity mixes to supply customization for cement and concrete produced and consumed in California. We generated and integrated a material demand model using residential building stock projections. We provide the user with a wide range of mitigation alternatives through low-carbon production pathways, material use efficiency, transportation modes, and projected electricity grid mixes. In a case study application through four mitigation scenarios, we find emission savings up to 80% by maximizing user mitigation alternatives, primarily driven by reductions in material use intensities. This work represents a foundation for expanding LCA and embodied carbon tools to better enable stakeholders to rapidly and accurately assess customized supply chains while meeting trade requirements.

building materials↗
DOE OSTI2024

Viscosities of the Baryon-Rich Quark-Gluon Plasma from Beam Energy Scan Data

Here, this work presents the first Bayesian inference study of the (3 + 1)D dynamics of relativistic heavy-ion collisions and quark-gluon plasma viscosities using an event-by-event (3 + 1)D hydrodynamics + hadronic transport theoretical framework and data from the Relativistic Heavy Ion Collider Beam energy scan program. Robust constraints on initial state nuclear stopping and the baryon chemical potential-dependent shear viscosity of the produced quantum chromodynamic (QCD) matter are obtained. The specific bulk viscosity of the QCD matter is found to exhibit a preferred maximum around $\sqrt{s_{NN}}$ = 19.6 GeV . This result allows for the alternative interpretation of a reduction (and/or increase) of the speed of sound relative to that of the employed lattice-QCD based equation of state for net baryon chemical potential μ B ~0.2(0.4) GeV .

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Bonded Bracket Assmebly for Frameless Solar Panels

In February 2011 the US Department of Energy announced their new Sunshot Initiative. The Sunshot goal is to reduce the total cost of solar energy systems by about 75 percent before the end of the decade. The DOE estimated that a total installed cost of $$1 per watt for photovoltaic systems would be equivalent to 5-6¢/kilowatt hour (kWh) for energy available from the grid. The DOE also estimated that to meet the $1 per watt goal, PV module costs would need to be reduced to $ .50 per watt, balance of systems costs would need to be reduced to $.40 per watt, and power electronic costs would need to reach $.10 per watt. To address the BOS balance of systems cost component of the $1 per watt goal, the DOE announced a funding opportunity called (BOS-X) Extreme Balance of System Hardware Cost Reductions. The DOE identified eight areas within the total BOS costs: 1) installation labor, 2) installation materials, 3) installation overhead and profit, 4) tracker, 5) permitting and commissioning, 6) site preparation, 7) land acquisition, 8) sales tax. The BOS-X funding announcement requested applications in four specific topics;Topic 1: Transformational Building Integrated Photovoltaic (BIPV) Modules; Topic 2: Roof and Ground Mount Innovations; Topic 3: Transformational Photovoltaic System Designs; and Topic 4: Development of New Wind Load Codes for PV Systems.The application submitted by ARaymond Tinnerman reflected the requirements listed in Topic #2, Roof and Ground Mount Innovations. The goal of topic #2 was to develop technologies that would result in the extreme reduction of material and labor costs associated with applications that require physical connections and attachments to roof and ground mount structures. The topics researched in this project included component cost reduction, labor reduction, weight reduction, wiring innovations, and alternative material utilization. The project objectives included; 1) The development of an innovative quick snap bracket assembly that would be bonded to frameless PV modules for commercial rooftop installations; 2) The development of a composite pultruded rail to replace traditional racking materials; 3) In partnership with a roofing company, pilot the certification of a commercial roof to be solar panel compliant, eliminating the need for structural analysis and government oversight resulting in significantly decreased permitting costs; and 4) Reduce the sum of all cost impacts in topic #2 from a baseline total of $2.05/watt to $.34/watt.

14 SOLAR ENERGY↗