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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Mechanisms Engineering Test Loop (METL) Operations and Testing Report (FY2022)

This report documents the operations, testing, maintenance, and improvements that were performed at the Mechanisms Engineering Test Loop (METL) during FY2022. The METL facility had a very successful fourth year of operations and went through some new experiences such as taking the facility from its frozen state in October 2021 and thawing the facility and also recovering from an oxide plug in one of the cold trap lines. After the facility was fully thawed, the METL staff maintained the facility in a continuous molten state – either flowing sodium or a static flow condition. METL facility continued supporting the Gear Test Assembly (GTA) testing and hosted its first 28” test vessel experiment, called the Thermal Hydraulic Experimental Test Article (THETA) which was inserted into Test Vessel 4. Work to accommodate two additional experiments, a gripper test article (GrTA) and a flow sensor test article (F-STAr) continued as they are expected to make their debut in FY2023. In addition, the steam piping for the B308 scrubber unit was replaced with stainless steel piping and controls and new parts for the scrubber were purchased – such as a new pump, new storage tank, and new blower and motor. These components will ultimately replace the existing scrubber components when those 1970’s era require replacement.

42 ENGINEERING↗
DOE OSTI2023

Abstract for CRADA between NETL and Praxair Surface Technologies, Inc. (AGMT-1288)

The National Energy Technology Laboratory (NETL) and Praxair Surface Technologies (Participant) will collaborate in the design and manufacturing of new high-performance thermal barrier coatings (TBCs) for hydrogen gas turbine applications. High-throughput first-principles density functional theory (DFT) calculations will be performed to accelerate novel TBCs discovery with expanded phase field, increased temperature and erosion capabilities, low thermal conductivity, and significant toughness imparted by ferroelastic toughening for the non-transformable tetragonal oxide phase. Down-selected materials will be manufactured using solid state powder processing techniques. Testing will include isothermal aging followed by Raman and x-ray diffraction (XRD) phase analysis, indentation fracture toughness measurements, erosion testing, and thermal conductivity measurements. The collaboration will facilitate the deployment of hydrogen gas turbine technologies that are a key to the decarburization of power generation in the United States.

08 HYDROGEN↗
DOE OSTI2020

Optimal electric-distribution-grid planning considering the demand-side flexibility of thermal building systems for a test case in Singapore

The planning of district-scale electric grids, i.e., distribution grids, has traditionally relied on finding the most cost-effective design such that they are able to supply the peak loads in a district. With the advent of electric demand side flexibility (DSF), there is the opportunity to reshape peak loads such that the investment cost of the electric grid decreases in exchange for a minor increase in the operation cost. This paper formulates an optimal planning approach for the electric grid at the district scale, which incorporates the DSF from thermal building systems, e.g., heating ventilation and air-conditioning (HVAC) systems. The problem is formulated as a mixed-integer linear program (MILP) and aims at minimizing the investment cost for the grid along with the operation cost of the flexible loads. This is subjected to the fixed electricity demand and thermal comfort constraints of building occupants. To this end, linear models for the thermal comfort in the buildings and the power flow in electric grid are considered. The approach is tested on a district planning test case based in Singapore, where the results show up to 30.9 % reductions in investment cost and up to 3.7 % reduction in total annualized cost. Urban planning authorities, developers and utility companies can all benefit from the presented approach to make optimized investment decisions. For building operators, the results point to the need of adopting their control systems for DSF.

Troitzsch, Sebastian↗
DOE OSTI2023

PCB-on-DBC GaN Power Module Design with High-Density Integration and Double-Sided Cooling

Lateral gallium nitride (GaN) high-electron-mobility transistors (HEMTs) present better electrical characteristics compared to silicon or silicon carbide devices such as high switching speed and low gate charge, but also present additional challenges on the module design. Here, this paper discusses a high-density GaN power module with double-sided cooling, low inductance, on-package decoupling capacitors, and integrated gate drivers. The GaN dies as well as the gate drive are sandwiched between the printed circuit board (PCB) and direct bonded copper (DBC) substrate to achieve compact loop and double-sided cooling effect. Design considerations and thermal performance are analyzed. A module assembly procedure is presented utilizing the layer-by-layer attachment process. Finally, a 2.7 cm x 1.8 cm half-bridge GaN power module is fabricated and tested, achieving a low power-loop inductance of 1.03 nH, and the overshoot voltage of the switching waveform is less than 5% under a 400-V/25-A double-pulse test. The thermal resistance is 0.32 K/W, verified by simulation and experimental results. The design and assembly process can be generalized and applied to high power applications to achieve high power density and high performance.

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

Thermal and Reliability Characterization of an Epoxy Resin-Based Double-Side Cooled Power Module

Wide-Band Gap (WBG) power devices have become a promising option for high-power applications due to the superior material properties over traditional Silicon. To not limit WBG devices’ mother nature, a rugged and high-performance power device packaging solution is necessary. This study proposes a Double-Side Cooled (DSC) 1.2 kV half-bridge power module having dual epoxy resin insulated metal substrate (eIMS) for solving convectional power module challenges and providing a cost-effective solution. The thermal performance outperforms traditional Alumina (Al2O3) Direct Bonded Copper (DBC) DSC power module due to moderate thermal conductivity (10 W/mK) and thin (120 mm) epoxy resin composite dielectric working as the IMS insulation layer. This novel organic dielectric can withstand high voltage (5 kVAC @ 120 μm) and has a Glass Transition Temperature (Tg) of 300°C, which is suitable for high-power applications. In the thermal-mechanical modeling, the organic DSC power module can pass the thermal cycling test over 1,000 cycles by optimizing the mechanical properties of the encapsulant material. In conclusion, this article not only proposes a competitive organic-based power module but also a methodology of evaluation for thermal and mechanical performance.

42 ENGINEERING↗
DOE OSTI2022

High speed ultraviolet digital image correlation (UV-DIC) for dynamic strains at extreme temperatures

Digital Image Correlation (DIC) is a camera-based method of measuring full-field displacements and strains from the surface of a deforming object. It can be applied at any length scale (determined by the lenses) and any time scale (determined by the camera), and because it is non-contacting, it can also be used at temperatures much higher than can be withstood by bonded strain gauges. At extreme temperatures, materials emit light in the form of blackbody radiation, which can saturate the camera sensor. It has previously been shown that the emitted light can be effectively screened by using ultraviolet (UV) cameras, lenses, and filters; however, commercially available UV cameras are relatively slow, which limits the speed of combined UV-DIC measurements. In this study, a UV intensifier was paired with a high-speed camera, and its ability to perform UV-DIC at high temperature and high speed was investigated. The system was compared over three different experiments: (A) a quasi-static thermal expansion test at high temperature, (B) a vibration test at room temperature, and (C) the same vibration test repeated at high temperature. The system successfully performed DIC up to at least 1600 °C at frame rates of 5000 fps, which is more than 100 times faster than other examples of UV-DIC in the literature. In all cases, measurements made using the UV intensifier were much noisier than those made without the intensifier, but the intensifier enabled measurements at temperatures well above those which an unfiltered high-speed camera otherwise saturates.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Improving high temperature resilience of fiber sensor embedded smart components through laser shock peening

This study explores the use of laser shock peening (LSP) to enhance material properties and high-temperature performance of fiber-sensor-fused smart parts fabricated by additive manufacturing (AM) methods. Using embedded fiber sensors as distributed strain gauges, the study demonstrates that LSP can induce compressive strains of up to 130 µε on fiber embedded 1-mm below metal surfaces. The electron backscatter diffraction (EBSD) analysis shows that, with optimized LSP parameters, the metallic matrix undergoes substantial microstructural refinement, resulting in denser structures. Thermal cycling tests showed that the LSP process can increase fiber slippage temperatures by more than 50 °C. This work shows that the LSP process is an effective room-temperature process for enhancing both surface quality and increasing fiber slippage threshold under both thermal and mechanical stress.

Zhong, Shuda [University of Pittsburgh, PA (United↗
DOE OSTI2021

Effects of cyclic plasma heating on surface damage of micro-porous tungsten

The operating temperature window of solid tungsten (W) is dictated by its Ductile to Brittle Transition Temperature (DBTT) and re-crystallization temperature; roughly between 300-1300 °C. The brittleness of W at lower temperatures is exasperated when it undergoes recrystallization. We investigate here the thermal shock resistance of micro-porous W as a meta-material fabricated in a 3D open-cell network structure. We present experimental results for the effects of cyclic high-enthalpy arc-jet plasma on surface damage in three testing categories. Observed damage includes surface ablation of asperities, melting and solidification of W-fuzz on samples that have been exposed to a prior helium plasma, and micro-cracks at ligament triple junctions. Scanning electron microscope (SEM) observations show more micro-cracking on 54% and 23% foams compared to the 43% ones. In all tested samples, thermal expansion/contraction displacements were accommodated by ligament rotation and a network of micro-cracks. Furthermore, no large through-thickness crack were observed.

36 MATERIALS SCIENCE↗
DOE OSTI2023

A mechanistic model for creep and thermal aging in Alloy 709

This report describes a physics-based model for creep and thermal aging in Alloy 709. Alloy 709 is an advanced austenitic alloy, targeted for use in future Sodium Fast Reactors (SFRs) and other advanced reactors. The material has superior high temperature properties compared to currently qualified 316 and 304 stainless steels. However, the available creep and thermal aging test database for Alloy 709 is significantly more limited compared to the historical materials. The physics-based model developed here is one way to accelerate the qualification of the material by providing more accurate long-term predictions for creep properties and thermal aging, compared to current empirical time-extrapolate techniques. The crystal plasticity finite element model is used to predict the deformation and failure of alloy 709. The same setup for the CPFE model is used in both the baseline model calibration process and the simulation campaigns for parameter inference. Specific constitutive choices are made for Alloy 709 to capture the primary deformation mechanisms. The dislocation creep formulation developed by Hu and Cocks is extended to account for coupled precipitation formation and the grain boundary cavitation model developed by Sham, Needleman, et al. is used to model grain boundary cavitation-induced failure. A novel update algorithm is proposed to render the semi-discrete constitutive update for the Sham-Needleman model unconditionally stable. A progressive calibration approach is adopted based on the observations that several types of material responses can be effectively decoupled. A surrogate model is trained based on full-fledged CPFE simulations to accelerate the forward model evaluations, and stochastic variational inference (SVI) is used to calibrate the unknown microstructural model parameters. The calibrated mechanistic model is used to predict the long-term creep life of Alloy 709, and the predictions are compared against classical empirical approaches.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Development of Multicomponent EAM Potential for Ni-Based Superalloy

We initiated the development of multi-component EAM potentials for Aluminides and Carbides, key phases in Ni-based Superalloys. The goal is to utilize the MD simulation to understand the deformation dynamics that contribute to the formation of voids and creep initiation. For this purpose, we constructed the raw data from ab-initio (molecular dynamics) MD simulations fed into the potential development code and used Nickel as the base metal with the addition of a number of various elements including Aluminum, Chromium, Tungsten. We then developed the EAM potentials for the aluminide and carbide phases using the force-fitting code MEAMfit. Our generated potential reproduces the fundamental properties of the Ni3Al and Mo23C6 phases. We verified further the EAM potential through the thermal stability test at different temperatures and by reproducing the elastic constants consistent with the experimental values.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Robust Dissimilar Metal Friction Welded Spool for Enhanced Capability for Steam Power Components (Final Program Report)

This project successfully demonstrated the feasibility and advantages of producing durable, friction-welded dissimilar-metal spools, both with and without transition pieces, as well as the use of advanced oxidation-protective coatings for steam power applications. The work encompassed the optimization and full-scale production of NFA tubing, overcoming manufacturing and processing challenges to achieve enhanced strength, creep, and fatigue properties validated by extensive microstructural characterization. Optimized welding techniques were developed and refined for joining dissimilar materials, resulting in defect-free welds optimized for both low- and high-pressure boiler circuits. Systematic evaluation of welding parameters, coupled with heat treatments, ensured reliable performance and minimized weld defects such as banding and cracking. Comprehensive mechanical and non-destructive testing, including tensile, bend, fatigue, and CT scanning, confirmed the superior integrity and durability of the friction-welded joints under representative service conditions. To address oxidation-related degradation, a range of protective alloy coatings—such as IN625, APMT, Duplex 2507, and FeCrAlY—were selected and evaluated for their ability to counteract oxide notch formation at dissimilar metal interfaces. These coatings demonstrated improved oxidation resistance and long-term stability under thermal cycling, thereby extending weld service life. Thermal cyclic testing and long-term studies captured the phase stability and diffusion behavior of coated and uncoated configurations. Validated models for low-cycle fatigue (LCF), creep, and thermal mechanical fatigue (TMF) were developed to predict component life and failure modes. These models confirmed that friction-welded configurations exhibited significantly enhanced performance compared to conventional gas-tungsten arc welding (GTAW), with up to 7× improvement in creep resistance and at least 2× enhancement in fatigue properties. The introduction of a tailored transition piece further reduced thermally induced strains, enhancing fatigue life. The results demonstrate a robust pathway for retrofitting existing steam fleet components and upgrading future equipment to deliver substantially improved cold-start cycling behavior and reduction of unplanned outages due to premature weld failures.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Testing fast reactor fuels in a thermal reactor: Comparison of transmutation metallic fuel alloys behavior by scanning electron microscopy

To optimize nuclear waste repository performance, the destruction of minor actinide elements, particularly Np and Am, in a neutron fast spectrum reactor is possible by incorporating these elements into nuclear fuel. Evaluating the performance of minor actinide containing fuel is of paramount importance to enabling this technology. However, such a task is challenging without an available domestic fast spectrum test reactor. A comparison of fuel performance tested in an available domestic thermal reactor at the Idaho National Laboratory, the Advanced Test Reactor, and in a fast spectrum reactor in France (Phénix) is presented here in this study. This study evaluates the capability of using a cadmium shrouded test position to mimic the power profile along the fuel radius present in fast spectrum reactors so that thermally driven phenomenon (e.g., constituent redistribution) can be evaluated in a thermal reactor and determined to be prototypical of a fast reactor. Thus, optical microscopy and scanning electron microscopy has been performed on irradiated 35U-29Pu-4Am-2Np-30Zr fuel samples (where the number preceding the element is the weight percent concentration) from the two mentioned reactors that present similar irradiation temperatures and power conditions. The results indicate that fuel performance phenomena are reproducible in the two irradiation conditions. The redistribution of Zr occurred in the same manner for the two samples. Similar partitioning of U-Pu-Zr phases was observed, and the behavior of Am was similar in the analyzed specimens. Finally, the overall microstructure evolution seems not to be affected by minor actinides addition compared to expected behavior of conventional U-19Pu-10Zr ternary metal fuels for both specimens. Slight differences in fuel cladding chemical interaction were, however, observed. This difference is likely driven by difference in cladding composition rather than irradiation conditions.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Nanographene Coupled with Interfacial Pyrene Derivatives for Thermally Stable Perovskite Solar Cells

Although high-efficiency perovskite solar cells (PSCs) have been achieved using a hole-extracting material, spiro-MeOTAD, thermal stability has been unattainable due to the low glass transition temperature of spiro-MeOTAD and additives therein. In this paper we report on the use of nanographene-based hole-transporting materials coupled with a pyrene derivative as an interface modifier for thermally stable and high efficiency PSCs. Asymmetric methyl and methoxy groups are introduced in the diphenylamino group that is attached to the hexa-peri-hexabenzocoronene (HBC) nanographene core, coded HBC-DPAMeOMe. 1-Pyrenemethylammonium iodide is coupled to enhance the chemical interaction between perovskite and HBC-DPAMeOMe, which leads to a power conversion efficiency over 23%. A thermal stability test at 85 degrees C for 1000 h reveals that 83.6% of the initial efficiency (23.04% --> 19.25%) is maintained for the device with HBC-DPAMeOMe, while a significant degradation from 20.69% to 5.08% is observed for the device with spiro-MeOTAD. Nanographene-based hole conductors shed light on the thermal stability issue in PSCs.

14 SOLAR ENERGY↗
DOE OSTI2024

In situ formed catalysts for active, durable, and thermally stable ammonia protonic ceramic fuel cells at 550 °C

Ammonia protonic ceramic fuel cells (NH 3 -PCFCs) are promising and attractive energy-conversion devices owing to their high energy density, zero-carbon emission, and safety. The development of NH 3 -PCFCs, however, depends largely on the insufficient activity and poor durability of typical Ni-based anodes for ammonia decomposition, especially at low temperatures such as 550 °C. Herein, we report a self-assembled heterostructured Ru 0.95 Cu 0.05 Ni x (RCN) catalyst obtained through an in situ reaction between the surface-decorated Ru 0.95 Cu 0.05 nanoparticles and the Ni grain in the anode under typical processing conditions. At 550 °C, Ni–BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3 anode-supported PCFCs with RCN catalysts exhibit a high peak power density of 0.732 W cm -2 and a significantly enhanced durability of 100 h in NH 3 . Moreover, the cells demonstrate improved thermal stability compared with the bare cell during a 31-cycle thermal cycling test in NH 3 between 550 and 700 °C. In conclusion, the enhanced performance is likely attributed to the synergistic effects of Ru and Cu in RCN for NH 3 decomposition, resulting in a more vital interaction of NH 3 than that of the bare anode surfaces, as confirmed by NH 3 thermal conversion, electrochemical performance, and theoretical simulations.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Failure analysis of field-failed bypass diodes

Defective bypass diodes are often found as the largest factor leading to power loss in solar modules. Here, we report on failure mechanisms by investigating shunted bypass diodes from a rooftop installation, using a combination of multiple characterizations including current–voltage analysis, thermal-runaway testing, X-ray computed tomography, lock-in thermography, focused ion-beam cross-section imaging, chemical decapsulation, optical microscopy, and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Differing from static discharge typically associated with lightning strikes on modules, we found diode failure by the mechanism of thermal damage under continuous, long-term overstress in forward bias. Our conclusion is based on evidence of energy dissipated—the small to medium extent of melt-through on the Schottky diode face. The diode failure shows distortions or roughening of the Schottky diode metal-semiconductor interface with the die attach, and some failures are accompanied by die-attach solder melting. We propose that nonuniform irradiance on the modules caused diode shunting due to extended periods of heat dissipation in the modules, because modules in this string were placed in two different orientations. In contrast, a second parallel module string of the same module type on the same rooftop with a unique plane of array did not show any diode failures. The thermal damage failure of melt-through was caused by the long-term current generated by overstressing of diodes that may have had crystalline and impurity defects.

14 SOLAR ENERGY↗
DOE OSTI2020

Synthesis, Crystal Growth, and Transport Properties of van der Waals Tetrel Pnictide GeAs 2

Here, bulk GeAs 2 was synthesized utilizing a vapor transport reaction with iodine. Thermal stability tests under dynamic conditions show that GeAs 2 decomposes below 700 K, in contrast to the reported congruent melting at 1029 K measured at saturated As vapor pressure. GeAs 2 is a p-type narrow bandgap (~0.4 eV) semiconductor. From a thermoelectric standpoint, GeAs 2 outperforms previous computational predictions in thermopower and thermal conductivity. Yet, electrical resistivity is significantly higher than predicted values, resulting in the low overall thermoelectric figure of merit. Aliovalent doping strategies for GeAs 2 should be developed to achieve reasonable thermoelectric performance.

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

Settling of two-way momentum and energy coupled particles subject to Boussinesq and non-Boussinesq heating

This work establishes a procedure to accurately compute heat transfer between an Eulerian fluid and Lagrangian point-particles. Recent work has focused on accurately computing momentum transfer between fluid and particles. The coupling term for momentum involves the undisturbed fluid velocity at the particle location which is not directly accessible in the simulation. Analogously, in the context of thermal coupling, the undisturbed fluid temperature at the particle location is not directly accessible in simulations and must be estimated. In this paper, we develop a scheme to accurately estimate the undisturbed fluid temperature of a point-particle exchanging thermal energy with a surrounding fluid. Furthermore, the temperature disturbance is correlated with the enhanced temperature curvature in the vicinity of the particle and is formally valid in the low heating, low convection limit. We conduct extensive verification of the correction procedure for a settling particle subject to radiation. This setup allows the simultaneous testing of thermal and momentum corrections. By considering equations of drag and Nusselt number extended to finite Péclet and Boussinesq numbers, we establish a large range over which the correction procedure can be applied.

42 ENGINEERING↗
DOE OSTI2022

Multi-cell, triple pane, vacuum insulated glazing

A novel Triple Pane Vacuum Insulated Glazing (TPVIG) architecture consisting of three panes of glass separated by two offset grids is described. The grids are made of frit-coated fibers fused with the glass panes in a vacuum to create many independent hermetic cells. Unlike traditional VIGs, which are separated by support pillars, these cells significantly increase the redundancy in sealing, and the additional bonds formed by the grid lines reduce the stresses on the edge bonds thereby increasing VIG reliability. A numerical thermal analysis was conducted to determine the thermal performance of the VIG and suggested U-values below 0.5 W/m 2 -K (greater than R=11.4 hr-ft 2 -°F/Btu) can be obtained. A prototype of the VIG unit consisting of three glass panes (5.7 mm, 1.1 mm and 5.7 mm thick with low-e coating on two surfaces) was fabricated and tested for thermal performance using the hot box method. The experimental center of glass U-value for the VIG was found to be 0.42 W/m 2 K (R=13.2 hr-ft 2 -°F/Btu). Furthermore, this U-value is about four times lower than a typical Argon filled double pane window.

14 SOLAR ENERGY↗