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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 1,207 records · Page 67
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Atomically dispersed metal–nitrogen–carbon catalysts for fuel cells: advances in catalyst design, electrode performance, and durability improvement

The urgent need to address the high-cost issue of proton-exchange membrane fuel cell (PEMFC) technologies, particularly for transportation applications, drives the development of simultaneously highly active and durable platinum group metal-free (PGM-free) catalysts and electrodes. The past decade has witnessed remarkable progress in exploring PGM-free cathode catalysts for the oxygen reduction reaction (ORR) to overcome sluggish kinetics and catalyst instability in acids. Among others, scientists have identified the newly emerging atomically dispersed transition metal (M: Fe, Co, or/and Mn) and nitrogen co-doped carbon (M–N–C) catalysts as the most promising alternative to PGM catalysts. Here, we provide a comprehensive review of significant breakthroughs, remaining challenges, and perspectives regarding the M–N–C catalysts in terms of catalyst activity, stability, and membrane electrode assembly (MEA) performance. A variety of novel synthetic strategies demonstrated effectiveness in improving intrinsic activity, increasing active site density, and attaining optimal porous structures of catalysts. Rationally designing and engineering the coordination environment of single metal MN x sites and their local structures are crucial for enhancing intrinsic activity. Increasing the site density relies on the innovative strategies of restricting the migration and agglomeration of single metal sites into metallic clusters. Relevant understandings provide the correlations among the nature of active sites, nanostructures, and catalytic activity of M–N–C catalysts at the atomic scale through a combination of experimentation and theory. Current knowledge of the transferring catalytic properties of M–N–C catalysts to MEA performance is limited. Rationally designing morphologic features of M–N–C catalysts play a vital role in boosting electrode performance through exposing more accessible active sites, realizing uniform ionomer distribution, and facilitating mass/proton transports. We outline future research directions concerning the comprehensive evaluation of M–N–C catalysts in MEAs. The most considerable challenge of current M–N–C catalysts is the unsatisfied stability and rapid performance degradation in MEAs. Therefore, we further discuss practical methods and strategies to mitigate catalyst and electrode degradation, which is fundamentally essential to make M–N–C catalysts viable in PEMFC technologies.

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

TriGORank: A Gene Ontology Enriched Learning-to-Rank Framework for Trigenic Fitness Prediction

Machine learning (ML) has been gaining interest in the metabolic engineering community as a means to automate prediction tasks. In this work, we introduce and study the task of using ML to recommend high-fitness triplet mutants as candidates for wet-lab experiments. We first utilize individual fitness and digenic fitness scores as features and train machine learning models that produce a ranked list, from high to low fitness scores, for triplet gene mutants of S. cerevisiae. Then, we incorporate prior metabolic knowledge from an existing gene ontology, by designing a novel graph representation and deducing features that can capture gene similarity and gene interactions. Lastly, experimental results show that our proposed gene ontology enriched model, termed TriGORank, improves both performance and explainability.

Labhishetty, Sahiti↗
DOE OSTI2014

ACDT: Architected Composite Data Types Trading-in Unfettered Data Access for Improved Execution

With Exascale performance and its challenges in mind, one ubiquitous concern among architects is energy efficiency. Petascale systems projected to Exascale systems are unsustainable at current power consumption rates. One major contributor to system-wide power consumption is the number of memory operations leading to data movement and management techniques applied by the runtime system. To address this problem, we present the concept of the Architected Composite Data Types (ACDT) framework. The framework is made aware of data composites, assigning them a specific layout, transformations and operators. Data manipulation overhead is amortized over a larger number of elements and program performance and power efficiency can be significantly improved. We developed the fundamentals of an ACDT framework on a massively multithreaded adaptive runtime system geared towards Exascale clusters. Showcasing the capability of ACDT, we exercised the framework with two representative processing kernels - Matrix Vector Multiply and the Cholesky Decomposition – applied to sparse matrices. As transformation modules, we applied optimized compress/decompress engines and configured invariant operators for maximum energy/performance efficiency. Additionally, we explored two different approaches based on transformation opaqueness in relation to the application. Under the first approach, the application is agnostic to compression and decompression activity. Such approach entails minimal changes to the original application code, but leaves out potential applicationspecific optimizations. The second approach exposes the decompression process to the application, hereby exposing optimization opportunities that can only be exploited with application knowledge. The experimental results show that the two approaches have their strengths in HW and SW respectively, where the SW approach can yield performance and power improvements that are an order of magnitude better than ACDT-oblivious, hand-optimized implementations.We consider the ACDT runtime framework an important component of compute nodes that will lead towards power efficient Exascale clusters.

exascale↗
DOE OSTI2021

CAR-T Cell Therapy: Mechanism, Management, and Mitigation of Inflammatory Toxicities

Engineered T cell therapies such as chimeric antigen receptor (CAR) expressing T cells (CAR-T cells) have great potential to treat many human diseases; however, inflammatory toxicities associated with these therapies present safety risks and can greatly limit its widespread use. This article briefly reviews our current understanding of mechanisms for inflammatory toxicities during CAR T-cell therapy, current strategies for management and mitigation of these risks and highlights key areas of knowledge gap for future research..

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

ML-ACCEPT: Machine-Learning-enhanced Automated Circuit Configuration and Evaluation of Power Converters

This project, ML-ACCEPT, took a significant step toward achieving the first objective of the DIFFERENTIATE program: to help engineers to more rapidly and cost-effectively consider a wider range of more novel concepts before selecting an engineering-optimal architecture for high-fidelity detailed design and evaluation. Compared to existing methods, the ML-ACCEPT project investigated innovative technologies to make the design of power converters more cost-effective and time-efficient by i) integrating recent breakthroughs in ML, power electronics, simulation software, and optimization to research, develop, and developed a suite of ML-enhanced hypothesis generation tools for power converter design; and ii) facilitating the integration of the proposed software tools into existing power-converter design work-flows. Some existing tools for power-converter design have a certain level of intelligence to aid the design process, but to our knowledge none of them has ML-enhanced capability of automating the electrical circuit design process by selecting, configuring, and tailoring the individual components that enable available resources (e.g., high-voltage DC power) to be converted to the desired output (e.g., lower-voltage DC power with a desired voltage ripple), subject to application-specific (e.g., plasma generation and automotive applications) thermal and packaging considerations. The state-of-the-art circuit design of power converters is still heavily reliant on human experts to select the optimal topology and search for design parameters with human’s experience and intuitions, which can be very time-consuming, inefficient, and labor intensive. The team is composed of University of Michigan-Dearborn (UM-Dearborn), Lawrence Livermore National Laboratory (LLNL), Oak Ridge National Laboratory (ORNL), Modelon Inc., and lighthouse customers.

42 ENGINEERING↗
DOE OSTI2021

Removal of As(III) by Electrically Conducting Ultrafiltration Membranes

As(III) species are the predominant form of arsenic found in groundwater. However, nanofiltration (NF) and reverse osmosis (RO) membranes are often unable to effectively reject As(III). In this study, we fabricate highly conducting ultrafiltration (UF) membranes for effective As(III) rejection. Here, these membranes consist of a hydrophilic nickel-carbon nanotubes layer deposited on a UF support, and used as cathodes. Applying cathodic potentials significantly increased As(III) rejection in synthetic/real tap water, a result of locally elevated pH that is brought upon through water electrolysis at the membrane/water interface. The elevated pH conditions convert H 3 ASO 3 to H 2 AsO 3 – /HAsO 3 2– that are rejected by the negatively charged membranes. In addition, it was found that Mg(OH) 2 that precipitates on the membrane can further trap arsenic. Importantly, almost all As(III) passing through the membranes is oxidized to As(V) by hydrogen peroxide produced on the cathode, which significantly decreased its overall toxicity and mobility. Although the high pH along the membrane surface led to mineral scaling, this scale could be partially removed by backwashing the membrane. To the best of our knowledge, this is the first report of effective As(III) removal using low-pressure membranes, with As(III) rejection higher than that achieved by NF and RO, and high water permeance.

42 ENGINEERING↗
DOE OSTI2016

Tomography of atomic number and density of materials using dual-energy imaging and the Alvarez and Macovski attenuation model

Dual-energy computed tomography and the Alvarez and Macovski [Phys. Med. Biol. 21, 733 (1976)] transmitted intensity (AMTI) model were used in this study to estimate the maps of density (ρ) and atomic number (Z) of mineralogical samples. In this method, the attenuation coefficients are represented [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976)] in the form of the two most important interactions of X-rays with atoms that is, photoelectric absorption (PE) and Compton scattering (CS). This enables material discrimination as PE and CS are, respectively, dependent on the atomic number (Z) and density (ρ) of materials [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976)]. Dual-energy imaging is able to identify sample materials even if the materials have similar attenuation coefficients at single-energy spectrum. We use the full model rather than applying one of several applied simplified forms [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976); Siddiqui et al., SPE Annual Technical Conference and Exhibition (Society of Petroleum Engineers, 2004); Derzhi, U.S. patent application 13/527,660 (2012); Heismann et al., J. Appl. Phys. 94, 2073–2079 (2003); Park and Kim, J. Korean Phys. Soc. 59, 2709 (2011); Abudurexiti et al., Radiol. Phys. Technol. 3, 127–135 (2010); and Kaewkhao et al., J. Quant. Spectrosc. Radiat. Transfer 109, 1260–1265 (2008)]. This paper describes the tomographic reconstruction of ρ and Z maps of mineralogical samples using the AMTI model. The full model requires precise knowledge of the X-ray energy spectra and calibration of PE and CS constants and exponents of atomic number and energy that were estimated based on fits to simulations and calibration measurements. The estimated ρ and Z images of the samples used in this paper yield average relative errors of 2.62% and 1.19% and maximum relative errors of 2.64% and 7.85%, respectively. Furthermore, we demonstrate that the method accounts for the beam hardening effect in density (ρ) and atomic number (Z) reconstructions to a significant extent.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

a-Si{sub x}C{sub 1−x}:H thin films with subnanometer surface roughness for biological applications

The characterization of a-Si{sub x}C{sub 1−x}:H thin films by plasma-enhanced chemical vapor deposition with high hydrogen dilution for biological applications is addressed. A root mean square roughness less than 1 nm was measured via atomic force microscopy for an area of 25 μm{sup 2}. Structural analysis was done using Fourier transform infrared spectroscopy in the middle infrared region. It was found that under the deposition conditions, the formation of Si–C bonds is promoted. Electrical dark conductivity measurements were performed to evaluate the effect of high hydrogen dilution and to find the relation between carrier transport properties and the structural arrangement. Conductivities of the order of 10{sup −7} to 10{sup −9} S/cm at room temperature for methane–silane gas flow ratio from 0.35 to 0.85 were achieved, respectively. UV-visible spectra were used to obtain the optical band gap and the Tauc parameter. Optical band gap as wide as 3.55 eV was achieved in the regime of high carbon incorporation. Accordingly, deposition under low power density and high hydrogen dilution reduces the roughness, improves the structure of the network, and stabilizes the film properties as a greater percentage of carbon is incorporated. The biofunctionalization of a-Si{sub x}C{sub 1−x}:H surfaces with NH{sub 2}-terminated self-assembled monolayers was obtained through silanization with 3-aminopropyltrimethoxysilane. This knowledge opens a window for the inclusion of these a-Si{sub x}C{sub 1−x}:H thin films in devices such as biosensors.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Pumped Storage Hydropower FAST Commissioning Technical Analysis

This report was developed in tandem with the Furthering Advancements to Shorten Time (FAST) to Commissioning PSH Challenge and represents the underlying technical analysis that informed the competition. Lead by Oak Ridge National Laboratory, the report is designed to address barriers and solutions to PSH development by establishing baseline project development knowledge, defining key aspects of project development, and identifying opportunities to reduce project timelines, costs, and risks. The document’s scope includes post-licensing activities and excludes factors related to permitting or licensing.

13 HYDRO ENERGY↗
DOE OSTI2021

Technical Basis for Extended Dry Storage of Aluminum-Clad Spent Nuclear Fuel

This report addresses previously identified technical knowledge and technology gaps and presents the key findings of the multiyear, EMTD-funded research efforts with the goal of evaluating whether ASNF can be safely stored dry for many decades and whether changes to existing ASNF management practices are appropriate. The findings formulate the technical basis for the extended dry storage of ASNF, leading to the main conclusion: All completed work to close the identified knowledge gaps on extended (>50 years) ASNF dry storage supports the conclusion that extended ASNF dry storage is both safe and viable.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Multimodal Instrument Platform for High-Pressure MAS-NMR and IR Spectroscopic Interrogation

This project developed and tested a high-pressure (HP) flow-through instrument platform that combines HP- magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy for interrogating reactivity at interfaces between solid materials and HP fluids with HP- infrared (IR) spectroscopy for measuring fluid composition. Solid-fluid interfacial reactivity is usually dependent on concentrations of species within the fluid; thus, knowledge of the fluid composition measured by IR is critical to understanding solid-fluid interfacial reactivity probed by NMR. This new system adds to PNNL’s core capabilities in Chemical and Material Sciences to support fundamental programs in catalysis, interfacial molecular science, and geosciences, as well as in Earth and Biological Sciences to support energy production and storage, efforts to mitigate the impacts energy production systems, attenuation of contaminant plumes, and design of subsurface engineered systems for energy production and waste disposal.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Driving biomass breakdown through engineered cellulosomes

Extraction of sugar is the rate-limiting step in converting unpretreated biomass into value-added products through microbial fermentation. Both anaerobic fungi and anaerobic bacteria have evolved to produce large multi-cellulase complexes referred to as cellulosomes, which are powerful machines for biomass deconstruction. Characterization of bacterial cellulosomes has inspired synthetic "designer" cellulosomes, consisting of parts discovered from the native system that have proven useful for cellulose depolymerization. By contrast, the multi-cellulase complexes produced by anaerobic fungi are much more poorly understood, and to date their composition, architecture, and enzyme tethering mechanism remain unknown and heavily debated. Here, we compare current knowledge pertaining to the cellulosomes produced by both bacteria and fungi, including their application to synthetic enzyme-tethered systems for tunneled biocatalysis. We highlight gaps in knowledge and opportunities for discovery, especially pertaining to the potential of fungal cellulosome-inspired systems.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Effective Selective Area Doping for GaN Vertical Power Transistors Enabled by Innovative Materials Engineering

GaN vertical power transistors have emerged as promising candidates for future high efficiency high power electronic applications, with the potential to outperform conventional GaN lateral power devices in terms of power, breakdown, and avalanche characteristics. However, the development of current GaN vertical power transistors is seriously hindered by the poor materials performance of selective area doped p-n junctions. A mechanistic understanding of these fundamental materials issues is essential in order to achieve high performance selective area doped p-n junctions and consequently to advance the GaN vertical power transistor technology. To address this challenge, we carried out a comprehensive research program that advance fundamental knowledge in the selective area doping for GaN materials, and which will lead to the development of high performance GaN vertical power transistors. First, we developed innovative fabrication processes, including novel surface etching, surface passivation, and metalorganic chemical vapor deposition (MOCVD) growth, which provided enhanced opportunities for solving the unique challenges of selective area doping in GaN materials. Second, we performed a fundamental materials study using powerful characterization methods including transmission electron microscopy (TEM), ultraviolet (UV-), x-ray and angle-resolved photoelectron spectroscopy (UPS/XPS/ARPES), electron holography, and cathodoluminescence (CL); Third, we investigated several related issues, including Mg incorporation, polarization effects in carrier transport, and non-ideal material effects, which have rarely been explored so far. At the end of this project, we successfully demonstrated (1) fundamental understanding of selective area etching, regrowth, and doping of GaN, and associated knowledge on defects, interface, and breakdown properties. (2) Effective etch and regrowth processing recipes to achieve etch/regrowth GaN p-n diodes with very low leakage of 3.5 nA at 600 V, which meets the ARPA-E target. (2) High performance vertical GaN p-n didoes and vertical junction termination extension (JTE) devices with breakdown voltage of ~ 2 kV, and breakdown electric field of ~ 3.5 MV/cm, which are close to the performance limit of GaN. The successful outcome has resulted in new fundamental understandings in the selective area doping and regrowth process for GaN, which will lead to groundbreaking GaN vertical transistors for high performance next generation power electronics.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2013

Development of Production-Intent Plug-In Hybrid Vehicle Using Advanced Lithium-Ion Battery Packs with Deployment to a Demonstration Fleet

The primary goal of this project was to speed the development of one of the first commercially available, OEM-produced plug-in hybrid electric vehicles (PHEV). The performance of the PHEV was expected to double the fuel economy of the conventional hybrid version. This vehicle program incorporated a number of advanced technologies, including advanced lithium-ion battery packs and an E85-capable flex-fuel engine. The project developed, fully integrated, and validated plug-in specific systems and controls by using GM’s Global Vehicle Development Process (GVDP) for production vehicles. Engineering Development related activities included the build of mule vehicles and integration vehicles for Phases I & II of the project. Performance data for these vehicles was shared with the U.S. Department of Energy (DOE). The deployment of many of these vehicles was restricted to internal use at GM sites or restricted to assigned GM drivers. Phase III of the project captured the first half or Alpha phase of the Engineering tasks for the development of a new thermal management design for a second generation battery module. The project spanned five years. It included six on-site technical reviews with representatives from the DOE. One unique aspect of the GM/DOE collaborative project was the involvement of the DOE throughout the OEM vehicle development process. The DOE gained an understanding of how an OEM develops vehicle efficiency and FE performance, while balancing many other vehicle performance attributes to provide customers well balanced and fuel efficient vehicles that are exciting to drive. Many vehicle content and performance trade-offs were encountered throughout the vehicle development process to achieve product cost and performance targets for both the OEM and end customer. The project team completed two sets of PHEV development vehicles with fully integrated PHEV systems. Over 50 development vehicles were built and operated for over 180,000 development miles. The team also completed four GM engineering development Buy-Off rides/milestones. The project included numerous engineering vehicle and systems development trips including extreme hot, cold and altitude exposure. The final fuel economy performance demonstrated met the objectives of the PHEV collaborative GM/DOE project. Charge depletion fuel economy of twice that of the non-PHEV model was demonstrated. The project team also designed, developed and tested a high voltage battery module concept that appears to be feasible from a manufacturability, cost and performance standpoint. The project provided important product development and knowledge as well as technological learnings and advancements that include multiple U.S. patent applications.

25 ENERGY STORAGE↗
DOE OSTI2015

Fuel properties to enable lifted-flame combustion

The Fuel Properties to Enable Lifted-Flame Combustion project responded directly to solicitation DE-FOA-0000239 AOI 1A, Fuels and Lubricants for Advanced Combustion Regimes. This subtopic was intended to encompass clean and highly-efficient, liquid-fueled combustion engines to achieve extremely low engine-out nitrogen oxides (NOx) and particulate matter (PM) as a target and similar efficiency as state-of-the-art direct injection diesel engines. The intent of this project was to identify how fuel properties can be used to achieve controllable Leaner Lifted Flame Combustion (LLFC) with low NOx and PM emissions. Specifically, this project was expected to identify and test key fuel properties to enable LLFC and their compatibility with current fuel systems and to enhance combustion models to capture the effect of fuel properties on advanced combustion. Successful demonstration of LLFC may reduce the need for after treatment devices, thereby reducing costs and improving thermal efficiency. The project team consisted of key technical personnel from Ford Motor Company (FMC), the University of Wisconsin-Madison (UW), Sandia National Laboratories (SNL) and Lawrence Livermore National Laboratories (LLNL). Each partner had key roles in achieving project objectives. FMC investigated fuel properties relating to LLFC and sooting tendency. Together, FMC and UW developed and integrated 3D combustion models to capture fuel property combustion effects. FMC used these modeling results to develop a combustion system and define fuel properties to support a single-cylinder demonstration of fuel-enabled LLFC. UW investigated modeling the flame characteristics and emissions behavior of different fuels, including those with different cetane number and oxygen content. SNL led spray combustion experiments to quantify the effect of key fuel properties on combustion characteristics critical for LLFC, as well as single cylinder optical engine experiments to improve fundamental understanding of flame lift-off, generate model validation data, and demonstrate LLFC concurrent with FMC efforts. Additionally, LLNL was added to the project during the second year to develop a detailed kinetic mechanism for a key oxygenate to support CFD modeling. Successful completion of this project allowed the team to enhance fundamental understanding of LLFC, improve the state of current combustion models and increase understanding of desired fuel properties. This knowledge also improves our knowledge of how cost effective and environmentally friendly renewable fuels can assist in helping meet future emission and greenhouse gas regulations.

Kurtz, Eric↗
DOE OSTI2017

Understanding the mechanisms of amorphous creep through molecular simulation

Significance The individual and collective molecular displacements in an amorphous solid undergoing plastic deformation are simulated by an atomistic method that allows incremental motions to be observed over a time window of fractions of seconds. Because the timescale matches well with the conditions of experimental measurements, simulation details provide dynamical evidence for the fundamental mechanisms of amorphous creep. In particular, knowledge of the interplay between diffusion (flow) and mechanical deformation processes enables us to explain the stress and temperature behavior of the experimental data as well as the validity of model descriptions of molecular mechanisms in terms of spatially and temporally heterogeneous fluctuations.

42 ENGINEERING↗
DOE OSTI2017

Geometric prepatterning-based tuning of the period doubling onset strain during thin-film wrinkling

Wrinkling of thin films is an easy-to-implement and low-cost technique to fabricate stretch-tunable periodic micro and nanoscale structures. However, the tunability of such structures is often limited by the emergence of an undesirable period-doubled mode at high strains. Predictively tuning the onset strain for period doubling via existing techniques requires one to have extensive knowledge about the nonlinear pattern formation behavior. Herein, a geometric prepatterning-based technique is introduced that can be implemented even with limited system knowledge to predictively delay period doubling. The technique comprises prepatterning the film/base bilayer with a sinusoidal pattern that has the same period as the natural period of the system. This technique has been verified via physical and computational experiments on the polydimethylsiloxane (PDMS)/glass bilayer system. It is observed that the onset strain can be increased from the typical value of 20% for flat films to greater than 30% with a modest prepattern aspect ratio (2·amplitude/period) of 0.15. In addition, finite element simulations reveal that (i) the onset strain increases with increasing prepattern amplitude and (ii) the delaying effect can be captured entirely by the prepattern geometry. Therefore, one can implement this technique even with limited system knowledge, such as material properties or film thickness, by simply replicating pre-existing wrinkled patterns to generate prepatterned bilayers. Furthermore, geometric prepatterning is a practical scheme to increase the operating range of stretch-tunable wrinkle-based devices by at least 50%.

36 MATERIALS SCIENCE↗