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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
NASA NTRSDate not supplied

Numerical Investigation of Heat Transfer on the NASA SIDRM Model

NASA has developed a Simulated Inter-Duct Research Model (SIDRM) to study ice crystal icing in aircraft engines. A numerical investigation has been completed using the NASA in-house code, GlennHT. For each flow condition, many different wall thermal boundary conditions were imposed. Six uniform wall temperature cases were generated, with wall temperature relative to the freestream total temperature of 0.85, 0.90, 0.95, 1.05, 1.10, and 1.15. In addition, five cases with uniform heat flux were generated. Heat fluxes were chosen to generate average wall temperatures in the range explored by the uniform wall temperature cases. Included in the uniform heat flux cases is the adiabatic case where heat flux equals zero. The results of these simulations are then used to quantify the degree to which the heat transfer coefficient depends on wall thermal boundary condition. It is seen that the heat transfer coefficient is fairly independent of wall thermal boundary condition, as expected. However, it would appear that, at least in some locations, it may be prudent to attempt to correlate a variation of heat transfer coefficient with wall thermal boundary condition.

Ice Crystal Icing↗
DOE OSTI2020

Thermal conductivity of (Ge 2 Sb 2 Te 5 ) 1–x Cx phase change films

Germanium–antimony–telluride has emerged as a nonvolatile phase change memory material due to the large resistivity contrast between amorphous and crystalline states, rapid crystallization, and cyclic endurance. Improving thermal phase stability, however, has necessitated further alloying with optional addition of a quaternary species (e.g., C). In this work, the thermal transport implications of this additional species are investigated using frequency-domain thermoreflectance in combination with structural characterization derived from x-ray diffraction and Raman spectroscopy. Specifically, the room temperature thermal conductivity and heat capacity of (Ge 2 Sb 2 Te 5 ) 1–x C x are reported as a function of carbon concentration (x ≤ 0:12) and anneal temperature (T ≤ 350 °C) with results assessed in reference to the measured phase, structure, and electronic resistivity. Phase stability imparted by the carbon comes with comparatively low thermal penalty as materials exhibiting similar levels of crystallinity have comparable thermal conductivity despite the addition of carbon. The additional thermal stability provided by the carbon does, however, necessitate higher anneal temperatures to achieve similar levels of structural order.

42 ENGINEERING↗
DOE OSTI2021

New Mechanism for Yield Point Phenomena

Yield point phenomena (YPP) are widely attributed to discrete dislocation locking by solute atmospheres. An alternate YPP mechanism was recently suggested by simulations of Ta single crystals without any influence of solutes or discrete dislocations. The general meso-scale (GM) simulations consist of crystal plasticity (CP) plus accounting for internal stresses of geometrically necessary dislocation content. GM predicted the YPP while CP did not, suggesting a novel internal stress mechanism. The predicted YPP varied with crystal orientation and boundary conditions, contrary to expectations for a solute mechanism. The internal stress mechanism was probed by experimentally deforming oligocrystal Ta samples and comparing the results with independent GM simulations. Strain distributions of the experiments were observed with high-resolution digital image correlation. A YPP stress–strain response occurred in the 0–2% strain range in agreement with GM predictions. Shear bands appeared concurrent with the YPP stress–strain perturbation in agreement with GM predictions. At higher strains, the shear bands grew at progressively slower rates in agreement with GM predictions. It was concluded that the internal stress mechanism can account for the existence of YPP in a wide variety of materials including ones where interstitial-dislocation interactions and dislocation transient avalanches are improbable. Furthermore, the internal stress mechanism is a CP analog of various micro-scale mechanisms of discrete dislocations such as pile-up or bow-out. It may operate concurrently with strain aging, or either mechanism may operate alone. A suggestion was made for a future experiment to answer this question.

42 ENGINEERING↗
DOE OSTI2024

Surface Atomic Rearrangement with High Cation Ordering for Ultra-Stable Single-Crystal Ni-Rich Co-Less Cathode Materials

It is crucial to minimize cobalt content in Ni-rich layered single-crystal cathodes due to their high price and limited availability, yet it will inevitably lead to cation disordering, capacity degradation, and thermal issues. Herein, to overcome the intrinsic trade-off between performance and composition of Ni-rich Co-less single-crystal cathodes, a precursor engineering strategy with an epitaxially grown cobalt enrichment on the surface is innovatively proposed. In contrast to traditional coating modifications with random orientation and rigid surface-bulk boundary, the epitaxially enriched surface cobalt layer on the precursor undergoes rapid interdiffusion with the internal Ni 3+ during the optimized sintering process. This interdiffusion eliminates the surface-bulk boundary, promoting the uniform distribution of cobalt and synergistically addressing the Li/Ni intermixing. Moreover, an enhanced surface Li + diffusion is obtained, thereby suppressing the Li + concentration gradient and intragranular cracks generation. Consequently, the modified LiNi 0.7 Co 0.07 Mn 0.23 O 2 exhibits impressive cycling stability with increased capacity retention in both coin-type half-cells and pouch-type full-cells (91% after 1000 cycles), even under the harsh condition of high-temperature, surpassing the majority of previously reported Ni-rich cathodes. Finally, this work opens new avenues toward the low cost, high energy density, thermal stability, and long cyclic life for Ni-rich Co-less cathodes and sheds light on large-scale commercial production.

25 ENERGY STORAGE↗
NASA NTRS2013

Advanced Optical Diagnostics for Ice Crystal Cloud Measurements in the NASA Glenn Propulsion Systems Laboratory

A light extinction tomography technique has been developed to monitor ice water clouds upstream of a direct connected engine in the Propulsion Systems Laboratory (PSL) at NASA Glenn Research Center (GRC). The system consists of 60 laser diodes with sheet generating optics and 120 detectors mounted around a 36-inch diameter ring. The sources are pulsed sequentially while the detectors acquire line-of-sight extinction data for each laser pulse. Using computed tomography algorithms, the extinction data are analyzed to produce a plot of the relative water content in the measurement plane. To target the low-spatial-frequency nature of ice water clouds, unique tomography algorithms were developed using filtered back-projection methods and direct inversion methods that use Gaussian basis functions. With the availability of a priori knowledge of the mean droplet size and the total water content at some point in the measurement plane, the tomography system can provide near real-time in-situ quantitative full-field total water content data at a measurement plane approximately 5 feet upstream of the engine inlet. Results from ice crystal clouds in the PSL are presented. In addition to the optical tomography technique, laser sheet imaging has also been applied in the PSL to provide planar ice cloud uniformity and relative water content data during facility calibration before the tomography system was available and also as validation data for the tomography system. A comparison between the laser sheet system and light extinction tomography resulting data are also presented. Very good agreement of imaged intensity and water content is demonstrated for both techniques. Also, comparative studies between the two techniques show excellent agreement in calculation of bulk total water content averaged over the center of the pipe.

Bencic, Timothy J.↗
DOE OSTI2023

Effect of sample size on the maximum value distribution of fatigue driving forces in metals and alloys

An analytical framework is presented to predict the effects of sample size on the maximum value distribution (MVD) of the driving forces for fatigue crack formation in metals and alloys. The distribution of the maximum driving force for fatigue crack formation over the domain follows the generalized extreme value theory in the limit as the domain size increases to infinity. Here, a simulation-based analysis of microstructure influences on fatigue resistance for polycrystalline metals and alloys is very costly, and reaching those limits is intractable. This work models the MVD of Fatigue Indicator Parameters (FIPs), which serve as surrogate measures for the driving force for fatigue crack formation, at finite sample sizes prior to their convergence to a limiting extreme value distribution. Large-scale crystal plasticity finite element (CPFE) simulations of FCC Al 7075-T6 with microstructure realizations of various sizes are incorporated to calibrate and evaluate the developed framework, and a total of ∼6.5 million grains of Al 7075-T6 are examined. The calibrated analytical solution agrees well with the brute force Monte Carlo simulation results extracted from the CPFE simulations. Furthermore, the developed formulation can predict the MVD of FIPs for different sample sizes using a size-dependent parameter, and it is capable of accurately extrapolating the MVD of FIPs for much larger microstructure sample sizes than the size used for its calibration.

Crystal plasticity↗
DOE OSTI2025

Erbium-Implanted WS 2 Flakes with Room-Temperature Photon Emission at Telecom Wavelengths

Optically addressable spin impurities in crystals along with device engineering provide an attractive route to realizing quantum technologies in the solid state, but reconciling disparate emitter and host material constraints for a given target application is often challenging. Rare-earth ions in two-dimensional (2D) materials could mitigate this problem given the atomic-like transitions of the emitters and the versatile nature of van der Waals systems. Here we combine ion implantation, confocal microscopy, and ab initio calculations to examine the photon emission of Er-doped WS 2 flakes. Optical spectroscopy reveals narrow, long-lived photoluminescence lines in the telecom band, which we activate after low-temperature thermal annealing. Spectroscopic and polarization-selective measurements show a uniform response across the ensemble, while the fluorescence brightness remains mostly unchanged with temperature, suggesting nonradiative relaxation channels are inefficient. Our results create opportunities for novel solid state devices coupling 2D-hosted, telecom-band emitters to photonic heterostructures separately optimized for photon manipulation.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Soft elasticity optimises dissipation in 3D-printed liquid crystal elastomers

Soft-elasticity in monodomain liquid crystal elastomers (LCEs) is promising for impact-absorbing applications where strain energy is ideally absorbed at constant stress. Conventionally, compressive and impact studies on LCEs have not been performed given the notorious difficulty synthesizing sufficiently large monodomain devices. Here, we use direct-ink writing 3D printing to fabricate bulk (>cm 3 ) monodomain LCE devices and study their compressive soft-elasticity over 8 decades of strain rate. At quasi-static rates, the monodomain soft-elastic LCE dissipated 45% of strain energy while comparator materials dissipated less than 20%. At strain rates up to 3000 s –1 , our soft-elastic monodomain LCE consistently performed closest to an ideal-impact absorber. Drop testing reveals soft-elasticity as a likely mechanism for effectively reducing the severity of impacts – with soft elastic LCEs offering a Gadd Severity Index 40% lower than a comparable isotropic elastomer. Lastly, we demonstrate tailoring deformation and buckling behavior in monodomain LCEs via the printed director orientation.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Closed-loop recycling of mixed polyesters via catalytic methanolysis and monomer separations

A sustainable plastics future will require high recycling rates and the use of biogenic feedstocks, which together are catalyzing interest in replacing fossil fuel-derived, noncircular polyolefin packaging materials with bio-based, chemically recyclable polyesters. Here, in this study, we present a catalytic methanolysis process capable of depolymerizing both fossil fuel- and bio-based polyesters, including polyethylene terephthalate (PET), polylactic acid, polybutylene adipate terephthalate and polybutylene succinate in one reactor under mild conditions with high monomer yields. We scaled this process to 1 kg and integrated separations engineering using activated carbon, crystallization, extraction and distillation to remove contaminants and recover individual monomers from depolymerized mixed polyesters with high yield and purity. PET synthesized from monomers isolated from postconsumer materials showed comparable mechanical and thermal properties to PET from commercial monomers. Techno-economic analysis and life cycle assessment show that this process is economically viable and exhibits lower environmental impacts than primary production of respective polymers.

09 BIOMASS FUELS↗
DOE OSTI2024

Electron mobility enhancement by electric field engineering of AlN/GaN/AlN quantum-well HEMTs on single-crystal AlN substrates

To enhance the electron mobility in quantum-well high-electron-mobility transistors (QW HEMTs), we investigate the transport properties in AlN/GaN/AlN heterostructures on Al-polar single-crystal AlN substrates. Theoretical modeling combined with experiment shows that interface roughness scattering due to high electric field in the quantum well limits mobility. Increasing the width of the quantum well to its relaxed form reduces the internal electric field and scattering, resulting in a binary QW HEMT with a high two-dimensional electron gas (2DEG) density of 3.68×1013 cm–2, a mobility of 823 cm2/Vs, and a record-low room temperature (RT) sheet resistance of 206 Ω/□. Further reduction of the quantum well electric field yields a 2DEG density of 2.53×1013 cm–2 and RT mobility > 1000 cm2/V s. These findings will enable future developments in high-voltage and high-power microwave applications on the ultrawide bandgap AlN substrate platform.

Physics↗
DOE OSTI2021

Structural basis for antibody binding to adenylate cyclase toxin reveals RTX linkers as neutralization-sensitive epitopes

RTX leukotoxins are a diverse family of prokaryotic virulence factors that are secreted by the type 1 secretion system (T1SS) and target leukocytes to subvert host defenses. T1SS substrates all contain a C-terminal RTX domain that mediates recruitment to the T1SS and drives secretion via a Brownian ratchet mechanism. Neutralizing antibodies against the Bordetella pertussis adenylate cyclase toxin, an RTX leukotoxin essential for B . pertussis colonization, have been shown to target the RTX domain and prevent binding to the α M β 2 integrin receptor. Knowledge of the mechanisms by which antibodies bind and neutralize RTX leukotoxins is required to inform structure-based design of bacterial vaccines, however, no structural data are available for antibody binding to any T1SS substrate. Here, we determine the crystal structure of an engineered RTX domain fragment containing the α M β 2 -binding site bound to two neutralizing antibodies. Notably, the receptor-blocking antibodies bind to the linker regions of RTX blocks I–III, suggesting they are key neutralization-sensitive sites within the RTX domain and are likely involved in binding the α M β 2 receptor. As the engineered RTX fragment contained these key epitopes, we assessed its immunogenicity in mice and showed that it elicits similar neutralizing antibody titers to the full RTX domain. The results from these studies will support the development of bacterial vaccines targeting RTX leukotoxins, as well as next-generation B . pertussis vaccines.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Fundamental Mechanisms Controlling Dislocation-Obstacle Interactions in Metals and Alloys

This project combined modeling and experimentation across micro-meso-macro length scales to investigate the role of long-range internal stresses associated with obstacles and dislocation populations, in the deformation response of cubic metals. In addition to unique insights into the physical behavior of metals, advances were also made in modeling techniques and tools at the meso and atomistic level, and new characterization methods were developed and disseminated to the scientific community. Twenty eight journal papers, two dissertations and three theses have served as vehicles to share the gained scientific knowledge, and two opensource software packages have been developed, maintained and distributed. Additional publications are in progress.

36 MATERIALS SCIENCE↗
NASA NTRS1987

Creep and fatigue research efforts on advanced materials

Two of the more important materials problems encountered in turbine blades of aircraft engines are creep and fatigue. To withstand these high-temperature phenomena modern engines utilize single-crystal, nickel-based superalloys as the material of choice in critical applications. Recent research activities at Lewis on single-crystal blading material as well as future research initiatives on metal matrix composites related to creep and fatigue are discussed. The goal of these research efforts is improving the understanding of microstructure-property relationships and thereby guide material development.

Gayda, John↗
NASA NTRS1990

Creep and fatigue research efforts on advanced materials

Two of the more important materials problems encountered in turbine blades of aircraft engines are creep and fatigue. To withstand these high-temperature phenomena, modern engines utilize single-crystal, nickel-base superalloys as the material of choice in critical applications. This paper will present recent research activities at NASA's Lewis Research Center on single-crystal blading material, related to creep and fatique. The goal of these research efforts is to improve the understanding of microstructure-property relationships and thereby guide material development.

Gayda, John↗
NASA NTRSDate not supplied

Evaluation of a Thermodynamic Ice Crystal Accretion Model using Experimental Data from NASA’s 2nd Fundamental Ice Crystal Icing Test

A thermodynamic model describing ice crystal icing is evaluated using experimental data collected at NASA Propulsion Systems Laboratory. The model makes the distinction between ice accretions that are "freeze-dominated" and "melt-dominated". Freeze-dominated icing occurs when partially melted ice crystals impact a surface and freeze. This type of icing is characterized by strong adhesion. This contrasts with melt-dominated icing, where un-melted ice crystals adhere to a surface. This type of icing is characterized by weak adhesion. In this paper, the thermodynamic model is used to analyze the ice growth rates and facility conditions to explain possible phenomena such as mass loss as well as the melting and freezing fractions. Previous analyses assumed a collection efficiency of unity at the leading edge of the experimental model. LEWICE is used to determine a better estimate of the collection efficiency at the model leading edge as ice accretion grows in time. The result shows that the sticking efficiency could change in a greater percent with time than previously reported.

Ice Crystal Icing↗
NASA NTRS2011

Simulating Ice Accretion Effects on Engine Performance

Develop a modeling tool that can be used to predict the onset of engine icing due to ice crystal ingestion. The tool will be capable of modeling the effects of ice build up as well as its effect on engine performance. Perform a parametric study of an engine with simulated ice blockage effects at altitude conditions. Using the tool, estimate the effect of blockage in the low pressure compressor due to ice buildup (accretion), and its effects on engine performance.

Jorgenson, Philip C. E.↗