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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Single-Phase Jet Impingement Cooling for a Power-Dense Silicon Carbide Power Module

The adoption of silicon carbide (SiC) devices in the electric vehicle (EV) industry is increasing due to their superior performance over silicon devices. SiC devices enable further miniaturization of EV inverters, increasing their power density, which results in thermal management challenges. Here in this paper, the limits of single-phase jet impingement cooling are explored for an automotive SiC power module. We propose embedding pin fins in the direct-bonded-copper (DBC) substrate of the power module package using laser powder bed fusion additive manufacturing. The thermalhydraulic performance of the DBC-embedded pin fins is compared against folded fins that are directly soldered to the DBC substrate. A heat conduction analysis was conducted on a SiC package to determine the target heat transfer coefficient (HTC) for the heat sink. A water-ethylene glycol (WEG) jet impingement on the proposed concepts was studied using unit-cell models to achieve the target HTC. The studied designs put emphasis on the reliability and manufacturability requirements of the automotive industry. The thermal performance of DBC-embedded pin fins outperformed the DBC-soldered folded fins. The performance of the DBC-embedded pin fins is benchmarked against WEG-based cooling systems of commercial EVs. With the proposed cooling solution, we have shown a pathway of reducing the specific thermal resistance by 75% compared to BMW i3 thermal management system without any penalty on pressure drop or parasitic power.

33 ADVANCED PROPULSION SYSTEMS↗
NASA NTRS1973

Polarimetric observations of 9 Metis, 15 Eunomia, 89 Julia, and other asteroids.

White-light polarization curves for a number of asteorids are presented. All have well-developed negative branches, suggestive of relatively dark, texturally complex surfaces - possibly regoliths. Geometric albedos, estimated from the positive branch of the polarization curves, show that a significant dispersion in surface albedo exists within the asteroid belt.

Veverka, J.↗
NASA NTRS1978

Ion beam technology applications study

Specific perceptions and possible ion beam technology applications were obtained as a result of a literature search and contact interviews with various institutions and individuals which took place over a 5-month period. The use of broad beam electron bombardment ion sources is assessed for materials deposition, removal, and alteration. Special techniques examined include: (1) cleaning, cutting, and texturing for surface treatment; (2) crosslinking of polymers, stress relief in deposited layers, and the creation of defect states in crystalline material by ion impact; and (3) ion implantation during epitaxial growth and the deposition of neutral materials sputtered by the ion beam. The aspects, advantages, and disadvantages of ion beam technology and the competitive role of alternative technologies are discussed.

Sellen, J. M., Jr.↗
NASA NTRS1980

Some aerodynamic considerations related to wind tunnel model surface definition

The aerodynamic considerations related to model surface definition are examined with particular emphasis in areas of fabrication tolerances, model surface finish, and orifice induced pressure errors. The effect of model surface roughness texture on skin friction is also discussed. It is shown that at a given Reynolds number, any roughness will produce no skin friction penalty.

Gloss, B. B.↗
NASA NTRS1981

Laser annealing of ion implanted CZ silicon for solar cell junction formation

The merits of large spot size pulsed laser annealing of phosphorus implanted, Czochralski grown silicon for function formation of solar cells are evaluated. The feasibility and requirements are also determined to scale-up a laser system to anneal 7.62 cm diameter wafers at a rate of one wafer/second. Results show that laser annealing yields active, defect-free, shallow junction devices. Functional cells with AM 1 conversion efficiencies up to 15.4% for 2 x 2 cm and 2 x 4 cm sizes were attained. For larger cells, 7.62 cm dia., conversion efficiencies ranged up to 14.5%. Experiments showed that texture etched surfaces are not compatible with pulsed laser annealing due to the surface melting caused by the laser energy. When compared with furnace annealed cells, the laser annealed cells generally exhibited conversion efficiencies which were equal to or better than those furnace annealed. In addition, laser annealing has greater throughput potential.

Katzeff, J. S.↗
NASA NTRS1986

Point contact silicon solar cells

The construction of a 22.2% efficient single-crystal silicon solar cell fabricated at Stanford University is described. The cell dimensions were 3 x 5 mm and 100 microns thick with a base lifetime of 500 microseconds. The cell featured light trapping between a texturized top surface and a reflective bottom surface, small point contact diffusions, alternating between n-type and p-type in a polka-dot pattern on the bottom surface, and a surface passivation on all surfaces between contact regions.

Swanson, R. M.↗
NASA NTRS1987

Regional sources and sinks of dust on Mars: Viking observations of Cerberus, Solis Planum and Syrtis Major

A study of seasonal variations of albedo features in the Cerberus, Solis Planum, and Syrtis Major regions was based on Viking Orbiter data obtained over more than one complete Martian year. Contour maps of Lambert albedo and single-point thermal inertia were constructed from the Infrared Thermal Mapper (IRTM) experiment data, and Orbiter images were used to determine the pattern and variability of regional winds (inferred from wind streak orientations). Coupled with ground-based radar data, these data allow the regional sediment transport direction, surface properties (texture, morphology, and roughness), and the implications of the observed seasonal and longer term dust redistribution to be investigated. Results are outlined.

Lee, Steven W.↗
NASA NTRS1987

Regional sources and sinks of dust on Mars: Viking observations of Cerberus, Solis Planum, and Syrtis Major

A study of seasonal variation of albedo features in the Cerberus, Solis Planum, and Syrtis Major regions was based on Viking Orbiter data obtained over more than one complete Martian year. Contour maps of Lambert albedo and single point thermal inertia were constructed from the Infrared Thermal Mapper experiment data, and Orbiter images were used to determine the pattern and variability of regional winds (inferred from wind streak orientations). Coupled with ground based radar data, these data allow the regional sediment transport direction, surface properties (texture, morphology, and roughness), and the implications of the observed seasonal and longer term dust redistribution to be investigated. Results are outlined.

Lee, Steven W.↗
NASA NTRS1988

Deposition and characterization of ZnS/Si heterojunctions produced by vacuum evaporation

Isotype heterojunctions of ZnS (lattice constant 5.41 A) were grown on silicon (lattice constant 5.43 A) p-n junctions to form a minority-carrier mirror. The deposition process was vacuum evaporation from a ZnS powder source onto a heated (450 C) substrate. Both planar (100) and textured (111) surfaces were used. A reduction of the minority-carrier recombination at the surface was seen from increased short-wavelength quantum response and increased illuminated open-circuit voltage. The minority-carrier diffusion length was not degraded by the process.

Landis, Geoffrey A.↗
NASA NTRS1993

Soil texture and granulometry at the surface of Mars

Attention is given to a characterization of the physical behavior of the Martian upper surface in its first few decimeters on the basis of mutual relationships between three parameters: the linear polarization of the reflected light, the visual albedo, and the thermal inertia. Polarimetric scans raked a strip covering two contrasting regions, the dark-hued Mare Erythraeum, and the light-hued Thaumasia. Erythraeum is characterized everywhere by a uniform polarization response, despite the large geomorphological diversity of the surface. A ubiquitous coating or mantling with small dark grains of albedo 12.7 percent, with a radius of 10 to 20 microns, is indicated. Thaumasia exhibits a large variety of soil properties. A typical location with albedo of 16.3 percent has a surface covered with orange grains, probably very dispersed in size, for which the largest grains are 20 to 40 microns.

Dollfus, Audouin↗
NASA NTRS1995

Collection and review of metals data obtained from LDEF experiment specimens and support hardware

LDEF greatly extended the range of data available for metals exposed to the low-Earth-orbital environment. The effects of low-Earth-orbital exposure on metals include meteoroid and debris impacts, solar ultraviolet radiation, thermal cycling, cosmic rays, solar particles, and surface oxidation and contamination. This paper is limited to changes in surface composition and texture caused by oxidation and contamination. Surface property changes afford a means to study the environments (oxidation and contamination) as well as in-space stability of metal surfaces. We compare thermal-optical properties for bare aluminum and anodized aluminum clamps flown on LDEF. We also show that the silicon observed on the LDEF tray clamps and tray clamp bolt heads is not necessarily evidence of silicon contamination of LDEF from the shuttle. The paper concludes with a listing of LDEF reports that have been published thus far that contain significant findings concerning metals.

Bourassa, Roger↗
NASA NTRS2011

Global Roughness Texture of the Moon and Mars

Statistical measures of patterns (textures) in surface roughness are used to quantitatively differentiate regional geomorphic units on the Moon and Mars (e.g. cratered highlands, volcanic terrains and planar lowlands). The existence of vastly distinct crustal types on Mars and the Moon is well established [e.g. 1, 2, 3, & 4]. Here, a new methodology developed for differentiating terrestrial volcanic deposits using ~1 m resolution topography data [5], is tested on two global data sets where roughness pixels are much larger (1/4 of a degree).

Whelley, P. L.↗
NASA NTRS2020

Barefoot Rover: a Sensor-Infused Rover Wheel Demonstrating In-Situ Engineering and Science Extractions using Machine Learning

In this work, we demonstrate an instrumented wheel concept which utilizes a 2D pressure grid, an electrochemical impedance spectroscopy (EIS) sensor and machine learning (ML) to extract meaningful metrics from the interaction between the wheel and surface terrain. These include continuous slip/skid estimation, balance, and sharpness for engineering applications. Estimates of surface hydration, texture, terrain patterns, and regolith physical properties such as cohesion and angle of internal friction are additionally calculated for science applications. Traditional systems rely on post-processing of visual images and vehicle telemetry to estimate these metrics. Through in-situ sensing, these metrics can be calculated in near real time and made available to onboard science and engineering autonomy applications. This work aims to provide a deployable system for future planetary exploration missions to increase science and engineering capabilities through increased knowledge of the terrain.

Marchetti, Yuliya↗
NASA NTRS2026

Evaluation of Superalloy 718 Additively Manufactured Lattice Blocks

Lattice block structures made up of high temperature superalloys could offer advantages in density, efficiency, and tailored properties. Three candidate lattice designs were screened through additive manufacturing of superalloy 718. Laser powder bed fusion was applied with 718 powder to produce lattice blocks for three-dimensional octahedral unit cell designs of three heights. As-designed versus additively manufactured 718 lattices were compared, including structural dimensions, densities, defects, grain structures, crystallographic texture, and surface residual stresses. Manufactured lattice I diverged the most from its design, with both corner and center nodes merged into continuous columns. Manufactured lattice III came closest to its design, though the actual nodes and struts were still larger in cross section than in the design. Only modest grain coarsening and negligible chemical segregation were observed for all three designs, suggesting uniform thermo-physical and mechanical properties are possible. Significant tensile residual stresses were present at the surface of the manufactured blocks, with highest stresses in the building direction. Current findings indicate this concept could produce useful superalloy structures for high-temperature-capable static components requiring tailored density, and thermo-physical/mechanical properties.

super alloys↗
NASA NTRSDate not supplied

Evaluations of Additively Manufactured Superalloy Lattice Blocks

Cast lattice block structures made up of high-temperature superalloys were previously shown to offer advantages in density, efficiency, and tailored properties. However, inconsistencies in casting die-fill, composition, and microstructure were identified as persistent issues with the casting process path. Three candidate lattice designs were screened through additive manufacturing of a superalloy. Laser powder bed fusion was applied with superalloy powder to produce lattice blocks for three-dimensional octahedral unit-cell designs of three heights. Properties of the structural designs versus additively manufactured lattices were compared, including structural dimensions, densities, defects, grain structures, crystallographic texture, and surface residual stresses. Findings indicate this concept could produce useful superalloy structures for high-temperature-capable static components requiring tailored density, and thermophysical and mechanical properties.

superalloy↗
DOE OSTI2021

Friction reduction for engine components

The present invention relates to techniques for lowering friction between moving surfaces of, for example, an internal combustion engine. Friction reduction is achieved by adding texture modifications to surfaces that come in contact with each other. Texture modifications that reduce friction in accordance with the present invention include dimples of varying geometries and depths ion the surfaces of components. The present invention also relates to the fabrication technique for applying the texture to the surfaces. In another embodiment, the patterned soft mask is applied onto a large surface (flat or curved including cylindrical rollers surfaces) to be followed by electrochemical etching to imprint the textures onto the component And, in another embodiment, a diamond-like-carbon (DLC) film may be applied to the turbine component to also reduce friction.

Hsu, Stephen M.↗
NASA NTRS1991

Grooved surfaces on InP

Formation of a textured or grooved front surface on a solar cell can increase the efficiency in several ways, including enhanced absorption and light trapping. In III-IV materials the (111) plane is chemically different form the (1'1'1') plane, and both etching and epitaxial deposition behave differently on these surfaces. The current state of profile etching in InP is summarized. Data are presented on novel geometries attainable as a function of etchant temperature and composition, substrate orientation and carrier concentration, and the oxide thickness between the substrate and the photoresist. Depending on dopant concentration, the same etchant can produce either anisotropic or isotropic grooves. V-grooved solar cells were manufactured on InP, and the improved optical absorption was demonstrated. Preferred parameters for various applications are listed and discussed.

Bailey, Sheila G.↗