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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

The Evaluation of Mechanical Properties of LB650 Cavities

The 650 MHz cavities have a stronger requirement of niobium mechanical properties because of the geometric shape of the cavity due to reduced beta. The mechanical property of the niobium half-cell was measured following various heat treatments. The 5-cell cavities were tested in a controlled drop test fashion and the real-world road test. The result showed that the 900C heat treatment was compatible with cavity handling and transportation during production. The test provides the bases of the transportation specification and shipping container design guidelines.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Laser Powder Bed Fusion of ODS 14YWT from Gas Atomization Reaction Synthesis Precursor Powders

Abstract Laser powder bed fusion (LPBF) additive manufacturing (AM) is a promising route for the fabrication of oxide dispersion strengthened (ODS) steels. In this study, 14YWT ferritic steel powders were produced by gas atomization reaction synthesis (GARS). The rapid solidification resulted in the formation of stable, Y-containing intermetallic Y 2 Fe 17 on the interior of the powder and a stable Cr-rich oxide surface. The GARS powders were consolidated with LPBF. Process parameter maps identified a stable process window resulting in a relative density of 99.8%. Transmission electron microscopy and high-energy x-ray diffraction demonstrated that during LPBF, the stable phases in the powder dissociated in the liquid melt pool and reacted to form a high density (1.7 × 10 20 /m 3 ) of homogeneously distributed Ti 2 Y 2 O 7 pyrochlore dispersoids ranging from 17 to 57 nm. The use of GARS powder bypasses the mechanical alloying step typically required to produce ODS feedstock. Preliminary mechanical tests demonstrated an ultimate tensile and yield strength of 474 MPa and 312 MPa, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Autonomous hybrid optimization of a SiO 2 plasma etching mechanism

Computational modeling of plasma etching processes at the feature scale relevant to the fabrication of nanometer semiconductor devices is critically dependent on the reaction mechanism representing the physical processes occurring between plasma produced reactant fluxes and the surface, reaction probabilities, yields, rate coefficients, and threshold energies that characterize these processes. The increasing complexity of the structures being fabricated, new materials, and novel gas mixtures increase the complexity of the reaction mechanism used in feature scale models and increase the difficulty in developing the fundamental data required for the mechanism. This challenge is further exacerbated by the fact that acquiring these fundamental data through more complex computational models or experiments is often limited by cost, technical complexity, or inadequate models. In this paper, we discuss a method to automate the selection of fundamental data in a reduced reaction mechanism for feature scale plasma etching of SiO 2 using a fluorocarbon gas mixture by matching predictions of etch profiles to experimental data using a gradient descent (GD)/Nelder–Mead (NM) method hybrid optimization scheme. These methods produce a reaction mechanism that replicates the experimental training data as well as experimental data using related but different etch processes.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Summary of Geometric Parameters and Their Effects on Performance of U-10Mo Fuel Plates

A monolithic plate-type fuel system has been under development to convert high-performance test reactors from highly enriched uranium to low-enrichment uranium fuels and is now moving into the qualification phase, a predecessor to the timely conversion of the target reactors. To qualify this fuel system, the plates must meet safety standards and perform well in a reactor. The plates must maintain mechanical integrity, exhibit geometric stability, and have stable and predictable in-reactor behavior. The requirement to maintain mechanical integrity under normal operating conditions is primarily demonstrated by successful testing. However, each high-performance reactor employs a distinct design, resulting in distinct plate geometries, with unique features, attributes, irregularities, and tolerances. Due to the abundance of such distinct geometric varieties, a single “generic” plate geometry capturing all extremes is not achievable. It is also impractical to test each of these proposed designs in a reactor. This limitation necessitates cautious evaluations since the thermomechanical response of a plate with a certain geometry may not be representative for a plate with a significantly different geometry. To address concerns related to in-reactor plate performance, large set of sensitivity studies were performed. These parametric studies aimed to better understand irradiation performance, while evaluating the sensitivity of results to various modeling inputs, including geometric, operational, and material parameters. This work studied selected geometric parameters based on provided fuel specifications and performed a series of parametric simulations. The resulting temperature, displacement, and stress strains were comparatively evaluated to determine the effects of various geometric parameters. This draft provides a “high-level summary” of our parametric sensitivity studies and summarizes the key findings.

42 ENGINEERING↗
DOE OSTI2020

Luminescence Quenching via Deep Defect States: A Recombination Pathway via Oxygen Vacancies in Ce-Doped YAG

Luminescence quenching via nonradiative recombination channels limits the efficiency of optical materials such as phosphors and scintillators and therefore has implications for conversion efficiency and device lifetimes. In materials such as Ce-doped yttrium aluminum garnet (YAG:Ce), quenching shows strong dependence on both temperature and activator concentration, limiting the fabrication of high-intensity white-light emitting diodes with high operating temperatures. Here, we reveal by means of first-principles calculations an efficient recombination mechanism in YAG:Ce that involves oxygen vacancies and gives rise to thermally activated concentration quenching. We demonstrate that the key requirements for this mechanism to be active are localized states with strong electron-phonon coupling. These conditions are commonly found for intrinsic defects such as anion vacancies in wide band gap materials. The present findings are therefore relevant to a broad class of optical materials and shine light on thermal quenching mechanisms in general.

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

Exploring the Basic Physical Mechanisms of Cathode- and Anode-Initiated High-Voltage Surface Flashover

Surface flashover in vacuum imposes a substantial physical limit on modern, large-scale pulsed power. One of the ramifications is a minimum size requirement for new machines, which in itself becomes a hard barrier to the modernization and improvement of existing infrastructure. Pulsed power topologies require the physical mechanisms of both anode- and cathode-initiated flashover to be considered. Originally, the geometrical implications of field emission at the cathode triple junction (CTJ) motivated the usage of configurations that avoid electrons impinging on the insulating material. This will largely suppress the cathode-initiated flashover, which is best described by the secondary electron avalanche mechanism, gas desorption, and final breakdown in the desorbed gas. It depends on the cascade growth of a conducting plasma along the length of the insulator from the cathode. Mitigating the cathode-initiated flashover typically comes at the cost of a significant field enhancement at the anode triple junction (ATJ). In a typical implementation, the anode field may be three times higher than the cathode field for a given voltage, making the corresponding anode-initiated flashover much more common than otherwise. In the case of pulsed, anode-initiated flashover, experimental evidence suggests that charge is directly extracted from the insulator resulting in the insulator taking on a net positive charge advancing the anode potential. Furthermore, along with accompanying gas desorption from the surface, the potential will then propagate from the anode toward the cathode until the effective length of the gap is sufficiently reduced to support flashover. The underlying physical mechanisms of cathode- and anode-directed flashover are discussed in light of previously gathered experimental data and recent experiments with pulsed, high-gradient, anode-initiated flashover.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

An Accelerated Creep Testing Program For Nickel Based Superalloys

In order to improve the energy production within the United States, new materials are developed with the goal of increased functionality. These materials are required to perform at extreme pressures and temperatures (up to and beyond 200MPa and 650â??) as well as be sustainable beyond 105 hours. Before developing these materials into components for power generation, mechanical testing is required to better understand the behavior of these materials at various loads and temperatures. The longest of these tests is the conventional creep test which is a real time test that can beyond 105 hours depending on service conditions. Hundreds of specimens must be tested before being approved for use in power generation, but it is extremely difficult to rapidly qualify when each material is required to exceed 105 hours making testing through conventional means unfeasible. While others have designed accelerated testing methods to help qualify materials, many of these experiments use an empirical approach that requires test data to fit already existing creep data. In this study, an accelerated creep test called the stepped isostress method (SSM) is then applied to wrought Inconel 718 (IN 718) specimens. A test matrix is designed using deformation mechanism maps, time-temperature-transformation diagrams, and time-temperature-precipitation diagrams, in order to ensure that microstructurally, the accelerated creep tests fail similarly to the conventional creep tests. The data from the stepped isostress method is then applied to the McVetty and Sin-hyperbolic (Sinh) constitutive models in order to generate a creep master curve. The results from the model fits are then compared to the conventional creep data done from experiments as well as from the NIMS database for Inconel 718. Optical microscopy and scanning electron microscopy are used to compare the evolution of the microstructure from the conventional creep and accelerated creep tests. It is found that using the Sinh model on the accelerated creep data provides reasonable creep rupture predictions when compared to the scatter band of creep tests. It was also observed that the microstructural evolution between the SSM experiments and creep tests were very similar in terms of the volume fraction of precipitates and phases.

Mach, Robert↗
DOE OSTI2023

Measurement of Magnetic Field using Doppler-Free Saturation Spectroscopy (DFSS) in C-2W FRC Plasma

The Cooperative Research and Development Agreement (CRADA) between Oak Ridge National Laboratory (ORNL) and TAE Technologies (TAE) focused on implementing an existing mobile Doppler-free saturation spectroscopy (DFSS) diagnostic to determine the direction of the equilibrium magnetic field within TAE’s C-2W field-reversed configuration (FRC) fusion device. Non-perturbative measurements of magnetic fields in the core of FRCs can provide critical information needed to constrain equilibrium models and for the continued advancement of the fusion research program at TAE. DFSS is a well-established, laser-based absorption spectroscopy technique used to suppress inhomogeneous (Doppler) broadening and reveal the Zeeman fine structure of the target emission lines. The collaboration involved the use of ORNL’s recently constructed mobile DFSS diagnostic. The DFSS diagnostic was shipped and installed on C- 2W in February 2023. TAE’s expertise was used to design and construct the mechanic support structures required to mount the optical hardware on C-2W. Additionally TAE provide critical input to minimize the noise imposed on the DFSS signal by vibrations of the mechanic support structure during operations. DFSS data was obtained for over 500 C-2W shots and will continue until the expiration of this CRADA on September 30 th 2023. Over the course of this work, significant progress was made to maximize the signal to noise (SNR) ratio. Analysis of recently acquired data is on-going, however, initial indications are highly suggestive that a DFSS signal above background has been successfully acquired in C-2W.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

A critical review of 25 years of glomalin research: a better mechanical understanding and robust quantification techniques are required

Arbuscular mycorrhizal fungi (AMF) are important contributors to both plant and soil health. Twenty-five years ago, researchers discovered ‘glomalin’, a soil component potentially produced by AMF, which was unconventionally extracted from soil and bound by a monoclonal antibody raised against Rhizophagus irregularis spores. ‘Glomalin’ can resist boiling, strong acids and bases, and protease treatment. Researchers proposed that ‘glomalin’ is a 60 kDa heat shock protein produced by AMF, while others suggested that it is a mixture of soil organic materials that are not unique to AMF. Despite disagreements on the nature of ‘glomalin’, it has been consistently associated with a long list of plant and soil health benefits, including soil aggregation, soil carbon storage and enhancing growth under abiotic stress. The benefits attributed to ‘glomalin’ have caused much excitement in the plant and soil health community; however, the mechanism(s) for these benefits have yet to be established. This review provides insights into the current understanding of the identity of ‘glomalin’, ‘glomalin’ quantification, and the associated benefits of ‘glomalin’. We invite the community to think more critically about how glomalin-associated benefits are generated. We suggest a series of experiments to test hypotheses regarding the nature of ‘glomalin’ and associated health benefits.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

An Innovative Design of High-Temperature, Sensible Molten Salt Thermal Energy Storage Systems With Geopolymer Insulation

This project aims to mitigate the risks of the current molten salt TES tank designs. The goal is to create a more reliable and cost-effective TES by (1) developing a new material solution for internal thermal insulation and (2) by designing a concrete-based tank structure to eliminate metal-related issues (e.g., corrosion, thermomechanical failure, etc.). Firstly, the project aims to engineer a composite refractory insulation material that possesses sufficient thermal insulation properties without significantly sacrificing the resistance to salt permeation and mechanical strength, which is the major trade-off in traditional refractory insulation design. The primary objective is to perform materials design and optimization of the composite refractory to achieve the required thermal and mechanical properties as suitable internal insulation for molten salt TES. Secondly, the project aims to design a concrete-based TES system with conventional low- cost Portland cement serving as the primary tank structure and the aforementioned composite refractory as the internal thermal insulation and salt containment. The objective is to investigate the technical and economical feasibilities of concrete tanks for high- temperature molten salt storage applications.

14 SOLAR ENERGY↗
DOE OSTI2020

Holistic Measurement Driven Resilience: Combining Operational Fault and Failure Measurements and Fault Injection for Quantifying Fault Detection, Propagation and Impact. Final report

For HPC systems to date, application resilience to faults and failures has been accomplished by the brute- force method of checkpoint/restart, which allows an application to make forward progress in the face of system and application faults, errors, and failures independent of root cause or end result. It has remained the primary resilience mechanism because we lack a way to identify faults and anticipate consequences early enough to take meaningful mitigating action. However, checkpoint/restart implementations put a tremendous burden on system resources and on the applications themselves and is becoming less feasible at scale. Because we have not yet operated at scales at which checkpoint/restart fails to provide forward progress, despite increasing costs, vendors have had little motivation to provide the instrumentation necessary for early identification of faults and failures. However, as we move from petascale to exascale, component mean time to failure (MTTF) will render the existing techniques ineffectual and/or too expensive. Furthermore, fault recovery mechanisms such as failover and/or error correction introduce performance inconsistency. Instrumentation allowing early indication of problems and tools to enable use of such information by systems, operating systems, and applications offer an alternative, more scalable and less costly solution. In the HMDR project, we built on our experience and expertise developed and accumulated over years of research on design, monitoring, measurement, and assessment of resilient computing systems. Analysis of field data on the current and past generations of extreme-scale systems revealed several challenges that, if not addressed in increasingly larger and more complex systems, may hinder the effectiveness of future exascale computing systems. Specifically, i) file systems and interconnects in current-generation large-scale systems already operate at the margins of resiliency, including consistent performance, and may not scale to larger deployments; ii) automated, software-based failover mechanisms are frequently inadequate and can introduce wider failures, such that failures during recovery may lead to system/application failures, including system-wide outages; and iii) silent data corruption represents a critical fault mode and will require efficient detection mechanisms if next-generation applications are to take full advantage of exascale hardware. To address the above challenges, we assembled a team of world-renowned experts in resilient extreme- scale computing from the University of Illinois (Electrical and Computer Engineering, Computer Science, and NCSA), SNL, LANL, NERSC, and Cray. Our team includes representatives from centers that house many of the largest HPC resources in the world, both today and over the coming years. The team has a unique track record of research in i) system and application failure characterization based on the analysis of field data, ii) data-driven design of fault/error detection mechanisms, and iii) experimental characterization of system/application resiliency. The team includes system owners/operators who provide continuous data collection and access and ensure installation of appropriate analysis tools.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2021

Putting a spin on metamaterials: Mechanical incompatibility as magnetic frustration

Mechanical metamaterials present a promising platform for seemingly impossible mechanics. They often require incompatibility of their elementary building blocks, yet a comprehensive understanding of its role remains elusive. Relying on an analogy to ferromagnetic and antiferromagnetic binary spin interactions, we present a general approach to identify and analyze topological mechanical defects for arbitrary building blocks. We underline differences between two- and three-dimensional metamaterials, and show how topological defects can steer stresses and strains in a controlled and non-trivial manner and can inspire the design of materials with hitherto unknown complex mechanical response.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Si-Cr-Al-Mn Alloy for High Specific Resistivity

Laboratory material produced in budget period one met the target resistivity, mechanical and magnetic requirements for the Go/No-Go decision to move to industrial trials. The chosen chemistry settled on a high Cr strategy, with moderate Mn and Al additions, providing a good comprise on core loss and induction with minimal impact on mechanical properties, important to successful downstream processing. Industrial trials began in budget period two with the chosen chemistry, referred to as Alloy X. Difficulties occurred during initial hot rolling trials. Reheating the material using the standard NOES practice caused slab cracking from high thermal gradients in areas exposed to the roof burners, this was solved using a modified reheat practice. High Cr caused poor dynamic recrystallization during hot rolling, which was solved using a modified hot rolling practice. The high Cr content of the steel also caused poor decarburization during final annealing, which necessitated lowering the melt carbon aim for the final heat, together with a modified decarburization practice. Steel was finished to final thicknesses of 0.20 – 0.50 mm and evaluated for magnetic and mechanical properties. Although the target core loss for the 0.25 and 0.35 mm material was not achieved, significant reductions in high frequency core loss were measured, compared to equivalent commercially available material. Alloy X at 0.35 mm showed a 26 % and 23 % improvement at 400 HZ and 1000 Hz respectively, over Cliffs’ M-19 (0.35 mm) commercially available NOES. At 0.25 mm, Alloy X showed a 23 % and a 26 % improvement at 400 HZ and 1000 Hz respectively, over Cliffs’ HF-10 (0.25 mm) commercially available NOES. The 0.25 mm product was chosen for motor efficiency evaluation. ORNL collaborated with Cleveland-Cliffs (CC) to build, assemble, and test two 5HP motors: a baseline motor with M19 steel and a motor made with high efficiency steel (Alloy X) developed for the project. Overall, results were as expected with comparable performance at low speeds, and with more than 8% efficiency improvement for high speeds. Increased motor steel efficiency at high frequencies not only results in direct efficiency improvements but can yield reductions in motor size and cost by facilitating higher operation speeds, or by increasing the number of poles in the machine. This allows the production of more power-dense motors which are sometimes avoided with conventional material due to increased core losses. The material developed on this project provides more viable options for achieving improved motor efficiency or reduced motor size and cost.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Hall instability driven seeding of helical magneto-Rayleigh–Taylor instabilities in axially premagnetized thin-foil liner Z-pinch implosions

Helical magneto-Rayleigh–Taylor instability (MRTI) structures have been observed in z-pinch-driven liner implosion experiments with a pre-imposed axial magnetic field. We show that the formation of these helical structures can be described by a Hall magnetohydrodynamical (HMHD) model. We used the 3D extended magnetohydrodynamics simulation code PERSEUS (which includes Hall physics) [Seyler and Martin, Phys. Plasmas 18, 012703 (2011)] to study these helical instabilities and show that a Hall interchange instability in low-density coronal plasma immediately surrounding the dense liner is responsible for producing helically oriented effects in the magnetic field and current density within the coronal layer. Here, this seeds the helical pitch angle of the MRTI even when other proposed helical seeding mechanisms are either not present in the experiments or not accounted for in the simulations. For example, this mechanism does not require low-density power-feed plasmas to be swept in from large radius or the development of electrothermal instabilities. The Hall Instability is, thus, a new, independent explanation for the origin of the helical instabilities observed in axially premagnetized liner experiments. Simulation results supporting this mechanism are presented.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

MatCal Users Guide: Release 1.3.0

Any continuum mechanics model will require three components: (1) a discretized geometry of the boundary value problem being studied, (2) the partial differential equations to be solved, and (3) the initial conditions and boundary conditions for the problem. To describe material behavior in these computational models, material models contribute to (2) the underlying equations and, occasionally, to (3) the initial conditions for the simulation. These material models can exhibit a mathematical form that is empirically based, based on first principles, or developed from both empirical observations and known physics. In general, these models are meant to represent a class of materials with well understood behavior. As a result, material models have parameters that must be tuned or calibrated so that the model response matches characterization data available for the specific material it is intended to represent when used to simulate a specific system. For simple models, such as isotropic, linear elastic materials in solid mechanics, this calibration process can be a simple analytical calculation directly extracting the parameters from experimental measurements. For complex models that have many inputs and require many characterization datasets to adequately identify the material behavior, the model calibration process can require an inverse problem approach where an optimization is performed to tune the model parameters to the available data.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Seismic source characterization of the Arabian Peninsula and Zagros Mountains from regional moment tensor and coda envelopes

Reliable estimates of moment magnitude and source mechanism for seismic events in the Middle East can be challenging due to a small number of openly available stations, the complex tectonic setting, and regions of high attenuation. Access to high-quality waveform data from well-calibrated regional seismic stations is fundamental in producing robust and stable estimates of earthquake source parameters, particularly when measurements of absolute ground motion amplitudes are required. Earthquake source mechanism and moment magnitude are invaluable information in the assessment of seismic hazard, plate motions, and the characterization of faults and regional stress field. The expansion of the Kingdom of Saudi Arabia’s national seismic network in the past several decades provides an opportunity to develop the capabilities of routine focal mechanism and moment magnitude estimations. In this study, we use time-domain full waveform moment tensor inversion and coda envelope–derived amplitude measurements to solve for earthquake source mechanism, moment magnitudes, and their source type. Furthermore, we compared the moment magnitudes calculated from the two methods and publicly available earthquake catalogs and discuss the implications of the obtained source parameters.

58 GEOSCIENCES↗
DOE OSTI2021

Toward efficient single-atom catalysts for renewable fuels and chemicals production from biomass and CO 2

Transformation of biomass and CO 2 into renewable value-added chemicals and fuels has been identified as a promising strategy to fulfill high energy demands, lower greenhouse gas emissions, and exploit under-utilized resources. Cost-effective and performance-efficient catalysts are of great importance to lowering the conversion cost of biomass and CO 2 . Significant progress has been made to advance the catalyst design for these processes, with metal catalysts playing a critical role in many involved catalytic reactions. Traditional nanoparticle-based metal catalysts still require improvement in metal utilization rates, stability, and selectivity tunability. Single-atom catalysts, which have maximum atomic efficiency and a uniform and tunable metal center, as well as an adjustable metal-support interaction, provide potential opportunities to boost catalyst efficiency and thermal stability. Their well-defined and uniform structure also provides advantages to fundamental studies for understanding of the intrinsic reaction mechanism and site requirement in biomass and CO 2 conversion. In this article, we summarize and highlight the recent advances in converting biomass and CO 2 to renewable fuels and chemicals using single-atom catalysts. We discuss the design principles of single-atom catalysts and their potential applications to biomass and CO 2 upgrading as well as the origins of catalytic activity. Moreover, we compare the catalytic efficiency of various catalysts reported thus to provide a fair assessment of these catalysts. Finally, perspectives are given on the interesting fields that may guide future studies.

09 BIOMASS FUELS↗
DOE OSTI2021

The Bactrian effect: multiple resonances and light Dirac dark matter

The possibility of light dark matter (DM) annihilating through a dark photon (DP) which kinetically mixes (KM) with the Standard Model (SM) hypercharge field is a very attractive scenario. For DM in the interesting mass range below ~1 GeV, it is well known that bounds from the CMB provide a very strong model building constraint forcing the DM annihilation cross section to be roughly 3 orders of magnitude below that needed to reproduce the observed relic density. Under most circumstances this removes the possibility of an s-wave annihilation process for DM in this mass range as would be the case, e.g., if the DM were a Dirac fermion. In an extra-dimensional setup explored previously, it was found that the s-channel exchange of multiple gauge bosons could simultaneously encompass a suppressed annihilation cross section during the CMB era while also producing a sufficiently large annihilation rate during freeze-out to recover the DM relic density. In this paper, we analyze more globally the necessary requirements for this mechanism to work successfully and then realize them within the context of a simple model with two ‘dark’ gauge bosons having masses of a similar magnitude and whose contributions to the annihilation amplitude destructively interfere. We show that if the DM mass threshold lies appropriately in the saddle region of this destructive interference between the two resonance humps it then becomes possible to satisfy these requirements simultaneously provided several ancillary conditions are met. The multiple constraints on the parameter space of this setup are then explored in detail to identify the phenomenologically successful regions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗