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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Interfacial Strength Evaluation of Oxide Films on Carbon Steel by Using the Laser Shock Adhesion Test

We investigate the adhesion strength (interfacial strength) of the oxide film formed on a carbon steel substrate by using a laser shock adhesion test (LaSAT). A rolled carbon steel (SS400) plate is first heated at high temperature (700 °C) under the atmosphere (heat treatment) to cause the formation of oxide films about 20-50 μm thick on the steel surface. The film consisted of multiple layers, including wustite (FeO), magnetite (Fe{sub 3}O{sub 4}), and hematite (Fe{sub 2}O{sub 3}). Next, the x-ray diffraction method was used to measure the residual stress in the film. We find that compression stress develops in the film because of a mismatch of thermal strain in between the film and substrate after the heat treatment. With LaSAT, strong elastic wave generates by a pulsed laser ablation of the substrate backside, and results in interfacial fractures in the oxide films. To monitor the normal (out-of-plane) displacement of the top surface film, a laser ultrasonic interferometer is simultaneously utilized, such that we detect film delamination and determine the critical laser energy for interfacial fracture to obtain the critical stress (interfacial strength). Furthermore, additional pulsed laser irradiation is conducted against a pre-delaminated specimen in order to examine the growth of delamination area and evaluate the interfacial fracture toughness. Finally, elastic wave propagation in the sample is computed using the finite element method (FEM) in order to evaluate the interfacial stress field, accurately. For the FEM, multiple layers in the oxide film are modeled, and the residual stress due to thermal strain mismatch is introduced. The FEM computations reveal the stress distribution around the interface and evaluate the critical stress and critical stress intensity factor for delamination. We thus quantitatively evaluate the interfacial strength and interfacial fracture toughness of the oxide film formed on carbon steel. The mechanism of interfacial fracture is also discussed on the basis of microstructures in a film with multiple layers. This result may be useful for understanding the adhesion quality of oxide film during the hot-rolling process.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Aging of Limestones and Silane–Siloxane-Based Protective Hydrophobics: The Impact of Heating–Cooling and Freeze–Thaw Cycles

Stones are traditionally used in construction and architectural applications as building elements due to their aesthetic and technical/structural performance. Like other environmental factors (rain, humidity, moisture, salt presence, biological activity, etc.), heating–cooling and freeze–thaw cycles significantly threaten the longevity of stone materials. Hence, considering the socio-economic and cultural value of stones, preventive actions such as hydrophobic coatings are applied to prevent or mitigate damage. The scope of this study is the performance assessment of limestones with different characteristics and the efficiency of various commercial silane/siloxane-based hydrophobic coatings when exposed to thermal variation and freeze–thaw. For that purpose, the standards EN 14066:2013 (determination of resistance to aging by thermal shock) and EN 12371:2010 (determination of frost resistance) were followed. Open porosity and static contact angles were estimated to assess the stone durability and water protection capabilities of the hydrophobics. Additionally, sound speed propagation velocity, quality of building material index, elastic modulus and flexural strength were measured to evaluate the variation of mechanical properties. Static contact angle revealed that the coatings maintained an efficient level of hydrophobicity even after thermal-shock and freeze–thaw weathering tests. The study also revealed a critical interaction between freeze–thaw cycles, hydrophobic coatings and structural integrity of the stones, mostly on more porous ones. When they are subjected to harsh environmental conditions, untreated porous limestones keep structural cohesion, allowing for the natural absorption and release of water during freezing and thawing. On the contrary, when limestones are treated, the hydrophobic coatings can moderately obstruct the water release due to the partial saturation of the porous framework by the products. It also probably resulted from the different mechanical behavior between the inner matrix and layer of stone coated, resulting in a premature breakout and mechanical damage of the stone.

Lisci, Carla (ORCID:000000032179130X)↗
DOE OSTI2021

Reconfigurable plasma-dielectric hybrid photonic crystal as a platform for electromagnetic wave manipulation and computing

The introduction of 3D printing has enabled fabrication of photonic crystal devices with complex crystal structures that would be challenging to construct using other fabrication methods. In this paper, we construct and characterize a photonic crystal consisting of two 4 x 8 x 8 cubic lattices composed of spherical silicon nitride elements straddling a layer of 8 plasma discharge tubes, creating a 3D hybrid plasma photonic crystal device. Integrating under-dense gaseous plasma elements provides a unique coupling dynamic between the dielectric spheres and the cylindrical plasma discharges, creating a monolithic hybrid photonic crystal with solid state and reconfigurable elements. The device has resonant modes that have attenuation peaks that are either switchable, tunable in amplitude, or tunable in frequency with variations in plasma density. The response of these bands seen with varying plasma density is confirmed through simulations when effects due to the heating of the photonic crystal from the gaseous plasma elements are accounted for in the experiments. We discuss how this reconfigurable device may be used and expanded upon for applications in photonic artificial neural networks and optical computing systems.

3D printing↗
NASA NTRS1973

How to lose Rb, K, and change the K/Rb ratio - An experimental study

Thermal volatilization studies on Apollo 16 soils and crystalline rocks have been carried out to measure the depletion of K, Rb, and Na and changes in K/Rb ratios during heating under vacuum. Rubidium can be lost from both soils and rocks at temperatures as low as 1000 C. Because of the greater volatility of Rb as compared to K, the K/Rb ratio can be changed from normal values of 330-360 for the Apollo 16 samples to values as high as 1100 by thermal volatilization. Rapid heating experiments on soil samples were carried out to approximate agglutinate formation conditions in order to measure changes in alkali element abundances. Equal changes in K/Rb ratios can be produced with longer heating at lower temperatures or heating at higher temperatures for shorter times.

Gibson, E. K., Jr.↗
NASA NTRS1981

NASA five-ball fatigue tester: Over 20 years of research

Studies were conducted to determine the effect on rolling-element fatigue life of contact angle, material hardness, chemistry, heat treatment and processing, lubricant type and chemistry, elastohydrodynamic film thickness, deformation and wear, vacuum, and temperature as well as Hertzian and residual stresses. Correlation was established between the results obtained using the five-ball tester and those obtained with full scale rolling-element bearings.

Zaretsky, E. V.↗
NASA NTRS1986

Process for detecting the likelihood of ice formation, ice warning system for carrying out the process, and utilization thereof

An ice warning system comprising a diaphragm set into vibration at one of its frequencies of resonance by a piezoelectric cell. The diaphragm is coupled thermally to a metallic plate alternately cooled and heated respectively below and above the ambient temperature by Peltier elements connected to a reversible DC current generator. A microprocessor measures any variation of the resonance frequency caused by a deposit of ice on the diaphragm during the cooling or heating periods and delivers an alarm signal if this variation of frequency reaches and/ or exceeds a predetermined value. The microprocessor controls the period, intensity and direction of the current delivered by the DC current generator as a function of the ambient temperature and the temperature of the diaphragm. The ice warning system is preferably utilized in the aeronautical field for indicating the likelihood of natural ice formation on the engines and the wings of aircraft.

Martin Lustenberger↗
NASA NTRS1981

NASA five-ball fatigue tester - Over 20 years of research

The paper reviews, from both a technical and historic perspective, the results of research conducted using the NASA Five-Ball Fatigue Tester. The test rig was conceived by W. J. Anderson in late 1958. The first data was generated in March 1959. Since then a total of approximately 500,000 test hours have been accumulated on a group of eight test rigs which are capable of running 24 hours a day, 7 days a week. Studies have been conducted to determine the effect on rolling-element fatigue life of contact angle, material hardness, chemistry, heat treatment, and processing, lubricant type and chemistry, elastohydrodynamic film thickness, deformation and wear, vacuum, and temperature as well as Hertzian and residual stresses. Correlation was established between the results obtained using the five-ball tester and those obtained with full-scale rolling-element bearings.

Zaretsky, E. V.↗
NASA NTRS2010

Fabrication of Lanthanum Telluride 14-1-11 Zintl High-Temperature Thermoelectric Couple

The development of more efficient thermoelectric couple technology capable of operating with high-grade heat sources up to 1,275 K is key to improving the performance of radioisotope thermoelectric generators. Lanthanum telluride La3-xTe4 and 14-1-11 Zintls (Yb14MnSb11) have been identified as very promising materials. The fabrication of advanced high-temperature thermoelectric couples requires the joining of several dissimilar materials, typically including a number of diffusion bonding and brazing steps, to achieve a device capable of operating at elevated temperatures across a large temperature differential (up to 900 K). A thermoelectric couple typically comprises a heat collector/ exchanger, metallic interconnects on both hot and cold sides, n-type and ptype conductivity thermoelectric elements, and cold-side hardware to connect to the cold-side heat rejection and provide electrical connections. Differences in the physical, mechanical, and chemical properties of the materials that make up the thermoelectric couple, especially differences in the coefficients of thermal expansion (CTE), result in undesirable interfacial stresses that can lead to mechanical failure of the device. The problem is further complicated by the fact that the thermoelectric materials under consideration have large CTE values, are brittle, and cracks can propagate through them with minimal resistance. The inherent challenge of bonding brittle, high-thermal-expansion thermoelectric materials to a hot shoe material that is thick enough to carry the requisite electrical current was overcome. A critical advantage over prior art is that this device was constructed using all diffusion bonds and a minimum number of assembly steps. The fabrication process and the materials used are described in the following steps: (1) Applying a thin refractory metal foil to both sides of lanthanum telluride. To fabricate the n-type leg of the advanced thermoelectric couple, the pre-synthesized lanthanum telluride coupon was diffusion bonded to the metal foil using a thin adhesion layer. (2) Repeating a similar process for the 14-1-11 Zintl p-type leg of the advanced thermoelectric couple. (3) Bonding thick CTE-matched metal plates on the metallized lanthanum telluride and Yb14MnSb11 to form the hot and cold sides of the thermoelectric couple. The calculated conversion efficiency of such an advanced couple would be about 10.5 percent, about 35 percent better than heritage radioisotope thermoelectric technology that relies on Si-Ge alloys. In addition, unlike Si-Ge alloys, these materials can be combined with many other thermoelectric materials optimized for operation at lower temperatures to achieve conversion efficiency in excess of 15 percent (a factor of 2 increase over heritage technology).

Ravi, Vilupanur A.↗
NASA NTRS1995

Thermal behavior spiral bevel gears

An experimental and analytical study of the thermal behavior of spiral bevel gears is presented. Experimental data were taken using thermocoupled test hardware and an infrared microscope. Many operational parameters were varied to investigate their effects on the thermal behavior. The data taken were also used to validate the boundary conditions applied to the analytical model. A finite element-based solution sequence was developed. The three-dimensional model was developed based on the manufacturing process for these gears. Contact between the meshing gears was found using tooth contact analysis to describe the location, curvatures, orientations, and surface velocities. This information was then used in a three-dimensional Hertzian contact analysis to predict contact ellipse size and maximum pressure. From these results, an estimate of the heat flux magnitude and the location on the finite element model was made. The finite element model used time-averaged boundary conditions to permit the solution to attain steady state in a computationally efficient manner.Then time- and position-varying boundary conditions were applied to the model to analyze the cyclic heating and cooling due to the gears meshing and transferring heat to the surroundings, respectively. The model was run in this mode until the temperature behavior stabilized. The transient flash temperature on the surface was therefore described. The analysis can be used to predict the overall expected thermal behavior of spiral bevel gears. The experimental and analytical results were compared for this study and also with a limited number of other studies. The experimental and analytical results attained in the current study were basically within 10% of each other for the cases compared. The experimental comparison was for bulk thermocouple locations and data taken with an infrared microscope. The results of a limited number of other studies were compared with those obtained herein and predicted the same basic behavior.

Handschuh, Robert F.↗
NASA NTRS1994

Milestone 5 test report. Task 5, subtask 5.2: Tile to foam strength tests

This report summarizes work that has been performed to date on the strength of a cryotank insulation system using Rohacell foam and TUFI-coated AETB-12 ceramic tiles directly bonded to a simulated graphite-epoxy tank wall. Testing utilized a custom specimen design which consists of a long tensile specimen with eccentric loading to induce curvature similar to the curvature expected due to 'pillowing' of the tank when pressurized. A finite element model was constructed to predict the specific element strains in the test article, and to assist with design of the test specimen to meet the specific goals of curvature and laminate strain. The results indicate that the heat treated 3.25-pcf density Rohacell foam does not provide sufficient strength for the induced stresses due to curvature and stress concentration at the RTV bondline to the TUFI tile. The test was repeated using higher density non-heat treated Rohacell foam (6.9 pcf) without foam failure. The finite element model was shown to predict specimen behavior, and validation of the model was successful. It is pertinent to mention that the analyses described herein accurately predicted the failure of the heat treated foams and based on this analysis method it is expected that the untreated 3.25 pcf Rohacell foam will be successful.

Greenberg, H. S.↗
DOE OSTI2016

Magnetar heating

We examine four candidate mechanisms that could explain the high surface temperatures of magnetars. (1) Heat flux from the liquid core heated by ambipolar diffusion. It could sustain the observed surface luminosity L{sub s}≈10{sup 35} erg s{sup −1} if core heating offsets neutrino cooling at a temperature T{sub core}>6×10{sup 8} K. This scenario is viable if the core magnetic field exceeds 10{sup 16} G and the heat-blanketing envelope of the magnetar has a light-element composition. However, we find that the lifetime of such a hot core should be shorter than the typical observed lifetime of magnetars. (2) Mechanical dissipation in the solid crust. This heating can be quasi-steady, powered by gradual (or frequent) crustal yielding to magnetic stresses. We show that it obeys a strong upper limit. As long as the crustal stresses are fostered by the field evolution in the core or Hall drift in the crust, mechanical heating is insufficient to sustain persistent L{sub s}≈10{sup 35} erg s{sup −1}. The surface luminosity is increased in an alternative scenario of mechanical deformations triggered by external magnetospheric flares. (3) Ohmic dissipation in the crust, in volume or current sheets. This mechanism is inefficient because of the high conductivity of the crust. Only extreme magnetic configurations with crustal fields B>10{sup 16} G varying on a 100 meter scale could provide L{sub s}≈10{sup 35} erg s{sup −1}. (4) Bombardment of the stellar surface by particles accelerated in the magnetosphere. This mechanism produces hot spots on magnetars. Observations of transient magnetars show evidence of external heating.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1979

Primordial heating of asteroidal parent bodies

Most meteorites show evidence of thermal processing either because of metamorphic changes or as a result of melting and differentiation. Proposed mechanisms for supplying this energy generally rely upon short-lived radioisotopes or electrical induction, though accretion is sometimes mentioned, and more exotic models have been discussed. Interest in isotopic heating has been heightened by the discovery of Al-26 in Allende inclusions and also by the proposal that a lunar core and dynamo resulted from the radioactive decay of superheavy elements during the early solar system. Electrical induction as a heat source can be scaled to a broad range of solar system conditions, but corroborative evidence for these conditions is inconclusive. The accretion mechanism is probably not viable for the asteroidal and meteorite parent bodies, because the high kinetic energy requirement is inconsistent with the formation of the objects and their regoliths in the presence of a weak gravitational field.

Sonett, C. P.↗
NASA NTRS2015

Reduced Boil-Off System Sizing

NASA is currently developing cryogenic propellant storage and transfer systems for future space exploration and scientific discovery missions by addressing the need to raise the technology readiness level of cryogenic fluid management technologies. Cryogenic propellants are baselined in many propulsion systems due to their inherently high specific impulse; however, their low boiling points can cause substantial boil-off losses over time. Recent efforts such as the Reduced Boil-off Testing and the Active Thermal Control Scaling Study provide important information on the benefit of an active cooling system applied to LH2 propellant storage. Findings show that zero-boil off technologies can reduce overall mass in LH2 storage systems when low Earth orbit loiter periods extend beyond two months. A significant part of this mass reduction is realized by integrating two stages of cooling: a 20 K stage to intercept heat at the tank surface, and a 90 K stage to reduce the heat entering the less efficient 20 K stage. A missing element in previous studies, which is addressed in this paper, is the development of a direct method for sizing the 90 K cooling stage. Such a method requires calculation of the heat entering both the 90 K and 20 K stages as compared to the overall system masses, and is reliant upon the temperature distribution, performance, and unique design characteristics of the system in question. By utilizing the known conductance of a system without active thermal control, the heat being intercepted by a 90 K stage can be calculated to find the resultant lift and mass of each active thermal control stage. Integral to this is the thermal conductance of the cooling straps and the broad area cooling shield, key parts of the 90 K stage. Additionally, a trade study is performed to show the ability of the 90 K cooling stage to reduce the lift on the 20 K cryocooler stage, which is considerably less developed and efficient than 90 K cryocoolers.

Cryogenic fluid management↗
NASA NTRS2017

Investigation of a Tricarbide Grooved Ring Fuel Element for a Nuclear Thermal Rocket

Deep space exploration, especially that of Mars, is on the horizon as the next big challenge for space exploration. Nuclear propulsion, through which high thrust and efficiency can be achieved, is a promising option for decreasing the cost and logistics of such a mission. Work on nuclear thermal engines goes back to the days of the NERVA program. Currently, nuclear thermal propulsion is under development again in various forms to provide a superior propulsion system for deep space exploration. The authors have been working to develop a concept nuclear thermal engine that uses a grooved ring fuel element as an alternative to the traditional hexagonal rod design. The authors are also studying the use of carbide fuels. The concept was developed in order to increase surface area and heat transfer to the propellant. The use of carbides would also raise the temperature limitations of the reactor. It is hoped that this could lead to a higher thrust to weight nuclear thermal engine. This paper describes the modeling of neutronics, heat transfer, and fluid dynamics of this alternative nuclear fuel element geometry. Fabrication experiments of grooved rings from carbide refractory metals are also presented along with material characterization and interactions with a hot hydrogen environment.

Taylor, Brian D.↗
NASA NTRS2018

Study of a Tricarbide Grooved Ring Fuel Element for Nuclear Thermal Propulsion

Deep space exploration, especially that of Mars, is on the horizon as the next big challenge for space exploration. Nuclear propulsion, through which high thrust and efficiency can be achieved, is a promising option for decreasing the cost and logistics of such a mission. Work on nu- clear thermal engines goes back to the days of the NERVA program. Currently, nuclear thermal propulsion is under development again in various forms to provide a superior propulsion system for deep space exploration. The authors have been working to develop a concept nuclear thermal engine that uses a grooved ring fuel element as an alternative to the traditional hexagonal rod design. The authors are also studying the use of carbide fuels. The concept was developed in order to increase surface area and heat transfer to the propellant. The use of carbides would also raise the operating temperature of the reactor. It is hoped that this could lead to a higher thrust to weight nuclear thermal engine. This paper describes the modeling of neutronics, heat transfer, and fluid dynamics of this alternative nuclear fuel element geometry. Fabrication experiments of grooved rings from carbide refractory metals are also presented along with material characterization and interactions with a hot hydrogen environment. Results of experiments and associated analysis are desired densities with some success in material distribution and reaching a solid solution. Future work is needed to improve distribution of material, minimize oxidation during the milling process, and de ne a fabrication process that will serve for constructing grooved ring fuel rods for large system tests.

Taylor, Brian↗
NASA NTRS2018

Study of a Tricarbide Grooved Ring Fuel Element for Nuclear Thermal Propulsion

Deep space exploration, especially that of Mars, is on the horizon as the next big challenge for space exploration. Nuclear propulsion, through which high thrust and efficiency can be achieved, is a promising option for decreasing the cost and logistics of such a mission. Work on nuclear thermal engines goes back to the days of the NERVA program. Currently, nuclear thermal propulsion is under development again in various forms to provide a superior propulsion system for deep space exploration. The authors have been working to develop a concept nuclear thermal engine that uses a grooved ring fuel element as an alternative to the traditional hexagonal rod design. The authors are also studying the use of carbide fuels. The concept was developed in order to increase surface area and heat transfer to the propellant. The use of carbides would also raise the operating temperature of the reactor. It is hoped that this could lead to a higher thrust to weight nuclear thermal engine. This paper describes the modeling of neutronics, heat transfer, and fluid dynamics of this alternative nuclear fuel element geometry. Fabrication experiments of grooved rings from carbide refractory metals are also presented along with material characterization and interactions with a hot hydrogen environment. Results of experiments and associated analysis are discussed. The authors demonstrated success in reaching desired densities with some success in material distribution and reaching a solid solution. Future work is needed to improve distribution of material, minimize oxidation during the milling process, and define a fabrication process that will serve for constructing grooved ring fuel rods for large system tests.

Taylor, Brian↗
DOE OSTI2018

Theoretical and Experimental Temperature Distribution along a Plate

Existing equations for the temperature distribution along a plate produced by a point heat source are analyzed. Experimental values are compared with theoretical results from a formula employed in the development of a thermoelectric element for borehole use. On that basis, the influence of the heat-transfer coefficient on the calculated temperature distribution is established. In order to ensure agreement between the distribution calculated by the proposed formula and the experimental distribution, the value of the heat-transfer must be corrected.

42 ENGINEERING↗
DOE OSTI2025

Nanoscale and Element-Specific Lattice Temperature Measurements Using Core-Loss Electron Energy-Loss Spectroscopy

Measuring nanoscale local temperatures, particularly in vertically integrated and multicomponent systems, remains challenging. Spectroscopic techniques like X-ray absorption and core-loss electron energy-loss spectroscopy (EELS) are sensitive to lattice temperature, but understanding thermal effects is nontrivial. This work explores the potential for nanoscale and element-specific core-loss thermometry by comparing the Si L2,3 edge’s temperature- dependent redshift against plasmon energy expansion thermometry (PEET) in a scanning TEM. Using density functional theory (DFT), time-dependent DFT, and the Bethe−Salpeter equation, we ab initio model both the Si L 2,3 and plasmon redshift. We find that the core-loss redshift occurs due to bandgap reduction from electron−phonon renormalization. Our results indicate that despite lower core-loss signal intensity compared to plasmon features, core-loss thermometry has key advantages and can be more accurate through standard spectral denoising. Specifically, we show that the Varshni equation easily interprets the core-loss redshift for semiconductors, which avoids plasmon spectral convolution for PEET in complex junctions and interfaces. We also find that core-loss thermometry is more accurate than PEET at modeling thermal lattice expansion in semiconductors, unless the specimen’s temperature-dependent dielectric properties are fully characterized. Furthermore, core-loss thermometry has the potential to measure nanoscale heating in multicomponent materials and stacked interfaces with elemental specificity at length scales smaller than the plasmon’s wave function.

Bethe–Salpeter equation↗