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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 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Heat Transfer of an Integrated Counterflow Ceramic Heat Exchanger

The ceramic-based heat exchanger is one of the leading contenders for high-efficiency concentrating solar power plants using a molten salt heat transfer fluid and a supercritical carbon dioxide Brayton power cycle operating at temperatures above 700 °C due to the excellent resistance of ceramics to corrosion, oxidation, erosion, creep, and fouling. In the present study, the thermal performance of a ceramic silicon carbide prototype heat exchanger, with semi-elliptical heat transfer channels, integrated header channels, and a counterflow configuration fabricated by using binder jetting additive manufacturing, was experimentally investigated. Experimental heat transfer tests of the prototype were conducted at high temperatures and under various test fluid flow rates and inlet temperatures. The experimental heat transfer rates compared favorably with simulation predictions.

Yu, Wenhua (ORCID:0000000219457014)↗
NASA NTRS1989

A tough performance simultaneous semi-interpenetrating polymer network

A semi-interpenetrating polyimide (semi-IPN) network and methods for making and using the same are disclosed. The semi-IPN system comprises a high performance thermosetting polyimide having an acetylene-terminated group acting as a crosslinking site and a high performance linear thermoplastic polyimide. The polymer is made by combining low viscosity precursors and low molecular weight polymers of the thermosetting and thermoplastic polyimides and allowing them to react in the immediate presence of each other to form a simultaneous semi-interpenetrating polyimide network. Provided is a high temperature system having significantly improved processability and damage tolerance while maintaining excellent thermo-oxidative stability, mechanical properties and resistance to humidity, when compared with the commercial high temperature resin, Thermid 600. This material is particularly adapted for use as a molding, adhesive and advanced composite matrix for aerospace structural and electronic applications.

Pater, Ruth H.↗
NASA NTRS2003

A Simplified Test for Blanching Susceptibility of Copper Alloys

GRCop-84 (Cu-8Cr-4Nb) is a dispersion-strengthened alloy developed for space-launch rocket engine applications, as a liner for the combustion chamber and nozzle ramp. Its main advantage over rival alloys, particularly NARloy-Z (Cu-Ag-Zr), the current liner alloy, is in high temperature mechanical properties. Further validation required that the two alloys be compared with respect to service performance and durability. This has been done, under conditions resembling those expected in reusable launch engine applications. GRCop-84 was found to have a superior resistance to static and cyclic oxidation up to approx. 700 C. In order to improve its performance above 700 C, Cu-Cr coatings have also been developed and evaluated. The major oxidative issue with Cu alloys is blanching, a mode of degradation induced by oxidation-reduction fluctuations in hydrogen-fueled engines. That fluctuation cannot be addressed with conventional static or cyclic oxidation testing. Hence, a further evaluation of the alloy substrates and Cu-Cr coating material necessitated our devising a test protocol that involves oxidaton-reduction cycles. This paper describes the test protocols used and the results obtained.

Thomas-Ogbuji, Linus U.↗
NASA NTRS1996

Temperature-Dependent Effects on the Mechanical Behavior and Deformation Substructure of Haynes 188 Under Low-Cycle Fatigue

The mechanical behavior of a cobalt-nickel-chromium-tungsten superalloy, Haynes 188, is being critically examined at the NASA Lewis Research Center. This dynamic, strain-aging (DSA) alloy is used for combustor liners in many military and commercial aircraft turbine engines and for the liquid oxygen posts in the main injectors of the space shuttle main engine. Its attractive features include a good combination of high monotonic yield and tensile strength, and excellent fabricability, weldability, and resistance to high-temperature oxidation for prolonged exposures.

Source record↗
NASA NTRS1980

Alkaline battery, separator therefore

An improved battery separator for alkaline battery cells has low resistance to electrolyte ion transfer and high resistance to electrode ion transfer. The separator is formed by applying an improved coating to an electrolyte absorber. The absorber, preferably, is a flexible, fibrous, and porous substrate that is resistant to strong alkali and oxidation. The coating composition includes an admixture of a polymeric binder, a hydrolyzable polymeric ester and inert fillers. The coating composition is substantially free of reactive fillers and plasticizers commonly employed as porosity promoting agents in separator coatings. When the separator is immersed in electrolyte, the polymeric ester of the film coating reacts with the electrolyte forming a salt and an alcohol. The alcohol goes into solution with the electrolyte while the salt imbibes electrolyte into the coating composition. When the salt is formed, it expands the polymeric chains of the binder to provide a film coating substantially permeable to electrolyte ion transfer but relatively impermeable to electrode ion transfer during use.

Schmidt, George F.↗
NASA NTRS1994

Thermoplastic polymides and composites therefrom

A new class polyimide and polyimide precursors based on diaryl oxyalkylene diamines, such as 1,3-bis[4-aminophenoxy]-2,2-dimethyl propane, a process for their preparation and their use as the continuous phase for the manufacture of composites and composite laminates reinforced by reinforcing agents such as carbon fibers, Kevlar.TM., and other similar high strength reinforcing agents. The polyimides and molecular composites obtained from the diamines according to the invention show thermoplastic properties, excellent flex fatigue and fracture resistance, and excellent thermal and oxidative stability.

Harris, Frank W.↗
NASA NTRS2008

Scintillation Breakdowns in Chip Tantalum Capacitors

Scintillations in solid tantalum capacitors are momentarily local breakdowns terminated by a self-healing or conversion to a high-resistive state of the manganese oxide cathode. This conversion effectively caps the defective area of the tantalum pentoxide dielectric and prevents short-circuit failures. Typically, this type of breakdown has no immediate catastrophic consequences and is often considered as nuisance rather than a failure. Scintillation breakdowns likely do not affect failures of parts under surge current conditions, and so-called "proofing" of tantalum chip capacitors, which is a controllable exposure of the part after soldering to voltages slightly higher than the operating voltage to verify that possible scintillations are self-healed, has been shown to improve the quality of the parts. However, no in-depth studies of the effect of scintillations on reliability of tantalum capacitors have been performed so far. KEMET is using scintillation breakdown testing as a tool for assessing process improvements and to compare quality of different manufacturing lots. Nevertheless, the relationship between failures and scintillation breakdowns is not clear, and this test is not considered as suitable for lot acceptance testing. In this work, scintillation breakdowns in different military-graded and commercial tantalum capacitors were characterized and related to the rated voltages and to life test failures. A model for assessment of times to failure, based on distributions of breakdown voltages, and accelerating factors of life testing are discussed.

Teverovsky, Alexander↗
NASA NTRS2009

Gadolinia-Doped Ceria Cathodes for Electrolysis of CO2

Gadolinia-doped ceria, or GDC, (Gd(0.4)Ce(0.6)O(2-delta), where the value of delta in this material varies, depending on the temperature and oxygen concentration in the atmosphere in which it is being used) has shown promise as a cathode material for high-temperature electrolysis of carbon dioxide in solid oxide electrolysis cells. The polarization resistance of a GDC electrode is significantly less than that of an otherwise equivalent electrode made of any of several other materials that are now in use or under consideration for use as cathodes for reduction of carbon dioxide. In addition, GDC shows no sign of deterioration under typical temperature and gas-mixture operating conditions of a high-temperature electrolyzer. Electrolysis of CO2 is of interest to NASA as a way of generating O2 from the CO2 in the Martian atmosphere. On Earth, a combination of electrolysis of CO2 and electrolysis of H2O might prove useful as a means of generating synthesis gas (syngas) from the exhaust gas of a coal- or natural-gas-fired power plant, thereby reducing the emission of CO2 into the atmosphere. The syngas a mixture of CO and H2 could be used as a raw material in the manufacture, via the Fisher-Tropsch process, of synthetic fuels, lubrication oils, and other hydrocarbon prod

Adler, Stuart B.↗
NASA NTRS2021

In-Plane Tensile Properties, Creep Behavior and Failure Mechanisms of CVI and PIP SiC/SiC Composites at Temperatures to 1,650⁰C in Air

The in-plane tensile and creep properties of 2D woven CVI and PIP SiC/SiC composites with SylramicTM-iBN SiC fibers were measured at temperatures to 16500C in air and the data compared with the literature. Batch-to-batch variations in the tensile and creep properties, influence of thermal treatment on creep, creep parameters, damage mechanisms and failure modes for these composites were studied. Under the tested conditions, the CVI SiC/SiC composites exhibited both matrix and fiber dominated creep depending on stress, whereas the PIP SiC/SiC composites displayed only fiber dominated creep. Creep durability in both composite systems is controlled by the most creep resistant phase as well as oxidation of the fibers via cracked matrix. The Larson-Miller parameter and Monkman-Grant relationship were used wherever applicable for analyzing and predicting creep durability.

SiC-SiC Composites, CVI, PIP, Creep, In-plane tens↗
NASA NTRSDate not supplied

Presolar C- and O-rich Grains in the Matrix and a Clast in Asteroid Ryugu

Presolar grains formed in the outflows of dying stars and some have been preserved in primitive meteorites, interplanetary dust particles, and comet Wild 2 samples. Presolar silicates are one of the most abundant presolar phases, but are prone to destruction by parent body hydrothermal alteration. Refractory presolar phases, such as oxides and carbides, are more resistant to such alteration. Samples from asteroid Ryugu returned by JAXA’s Haya-busa2 mission show evidence for extensive aqueous alteration. To constrain the abundance of presolar grains in Ryugu, we conducted NanoSIMS isotopic mapping of fragments of a C0002 grain from Chamber C, perhaps from the asteroid sub-surface.

A N Nguyen↗
NASA NTRS1995

Atomic oxygen dosimetry measurements made on STS-46 by CONCAP 2

With increasing flight duration and the possibility of a permanent facility in space, long-term monitoring of material degradation due to atomic oxygen is increasing in importance. Reliance on models to determine the fluence of atomic oxygen is not only necessarily complex but also imprecise due to the strong dependence of oxygen concentration on day/night, latitude and solar activity. Mass-spectroscopy, the traditional method for determining the gas phase species densities at low pressure, is not only expensive but is limited in the area that it can monitor. Our group has developed a simple and inexpensive dosimeter to measure the atomic oxygen fluence via the change in resistance as the sensor element is gradually oxidized. The sensors consisted of thin-film circuit elements deposited on a suitable substrate. Four-point resistance measurements were used to monitor the change in resistance. Results obtained using silver and carbon dosimeters flown on STS-46 (CONCAP 2-01) will be discussed.

Gregory, J. C.↗
DOE OSTI2023

Alloy designs for high temperature Mo-base systems

For high temperature applications Mo base alloy requirements include both superior structural performance and environmental resistance. To address these requirements alloys in the Mo-Si-B system and refractory multi-principal element alloys (RMPEA) are being developed that exhibit a promising potential, but also have some remaining challenges to improve ductility, lower density and enhance environmental resistance. In the Mo-Si-B system microstructures with a Mo solid solution (Moss) Mo 3 Si and Mo 5 SiB 2 (T2) phases have been the focus of attention. However, the Si solubility in the Moss phase diminishes the ductility and toughness. In order to address this issue a new design based upon Moss, Mo 2 B and T 2 phases lowers the Si solubility in the Moss to improve ductility while the T 2 phase maintains the oxidation performance. Selected additions of Al and Ti enable a density reduction to below 8 g/cm 3 . The RMPEA designs for Mo-rich alloys provide for excellent structural performance, but the complex oxidation products provide no protection. However, in this case a new coating design has been introduced that provides the required environmental resistance.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Observation of single-defect memristor in an MoS2 atomic sheet

Non-volatile resistive switching, also known as memristor effect, where an electric field switches the resistance states of a two-terminal device, has emerged as an important concept in the development of high-density information storage, computing and reconfigurable systems. The past decade has witnessed substantial advances in non-volatile resistive switching materials such as metal oxides and solid electrolytes. It was long believed that leakage currents would prevent the observation of this phenomenon for nanometre-thin insulating layers. However, the recent discovery of non-volatile resistive switching in two-dimensional monolayers of transition metal dichalcogenide and hexagonal boron nitride sandwich structures (also known as atomristors) has refuted this belief and added a new materials dimension owing to the benefits of size scaling. Here we elucidate the origin of the switching mechanism in atomic sheets using monolayer MoS 2 as a model system. Atomistic imaging and spectroscopy reveal that metal substitution into a sulfur vacancy results in a non-volatile change in the resistance, which is corroborated by computational studies of defect structures and electronic states. These findings provide an atomistic understanding of non-volatile switching and open a new direction in precision defect engineering, down to a single defect, towards achieving the smallest memristor for applications in ultra-dense memory, neuromorphic computing and radio-frequency communication systems.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
NASA NTRS1951

Some Properties of Beryllium Oxide and Beryllium Oxide - Columbium Ceramals

High-temperature tensile and thermal-shock investigations were conducted on beryllium oxide and beryllium oxide plus columbium metal additions. X-ray diffraction and metallographic results are given. The tensile strength of 6150 pounds per square inch for beryllium oxide at 1800 degrees F compared favorably with the zirconia bodies previously tested. Additions of 2, 5, 8, 10, 12, and 15 percent by weight of columbium metal failed to improve the shock resistance over that of pure beryllium oxide.

Robards, C F↗
NASA NTRS1985

Ceramic oxide reactions with V2O5 and SO3

Ceramic oxides are not inert in combustion environments, but can react with, inter alia, SO3, and Na2SO4 to yield low melting mixed sulfate eutectics, and with vanadium compounds to produce vanadates. Assuming ceramic degradation to become severe only when molten phases are generated in the surface salt (as found for metallic hot corrosion), the reactivity of ceramic oxides can be quantified by determining the SO3 partial pressure necessary for molten mixed sulfate formation with Na2SO3. Vanadium pentoxide is an acidic oxide that reacts with Na2O, SO3, and the different ceramic oxides in a series of Lux-Flood type of acid-base displacement reactions. To elucidate the various possible vanadium compound-ceramic oxide interactions, a study was made of the reactions of a matrix involving, on the one axis, ceramix oxides of increasing acidity, and on the other axis, vanadium compounds of increasing acidity. Resistance to vanadium compound reaction increased as the oxide acidity increased. Oxides more acidic than ZrO2 displaced V2O5. Examination of Y2O3- and CeO2-stabilized ZrO2 sintered ceramics which were degraded in 700 C NaVO3 has shown good agreement with the reactions predicted above, except that the CeO2-ZrO2 ceramic appears to be inexplicably degraded by NaVO3.

Jones, R. L.↗
DOE OSTI2025

Mobility and threshold voltage extraction in transistors with gate-voltage-dependent contact resistance

The mobility of emerging (e.g., two-dimensional, oxide, organic) semiconductors is commonly estimated from transistor current-voltage measurements. However, such devices often experience contact gating, i.e., electric fields from the gate modulate the contact resistance during measurements, which can lead conventional extraction techniques to estimate mobility incorrectly even by a factor >2. Although this error can be minimized by measuring transistors at high gate-source bias |V gs |, this regime is often inaccessible in emerging devices that suffer from high contact resistance or early gate dielectric breakdown. Here, we propose a method of extracting mobility in transistors with gate-dependent contact resistance that does not require operation at high |V gs |, enabling accurate mobility extraction even in emerging transistors with strong contact gating. Our approach relies on updating the transfer length method (TLM) and can achieve <10% error even in regimes where conventional techniques overestimate mobility by >2×

36 MATERIALS SCIENCE↗
DOE OSTI2024

Structural basis of DNA recognition of the Campylobacter jejuni CosR regulator

Campylobacter jejuni is a foodborne pathogen commonly found in the intestinal tracts of animals. This pathogen is a leading cause of gastroenteritis in humans. Besides its highly infectious nature, C. jejuni is increasingly resistant to a number of clinically administrated antibiotics. As a consequence, the Centers for Disease Control and Prevention has designated antibiotic-resistant Campylobacter as a serious antibiotic resistance threat in the United States. The C. jejuni CosR regulator is essential to the viability of this bacterium and is responsible for regulating the expression of a number of oxidative stress defense enzymes. Importantly, it also modulates the expression of the CmeABC multidrug efflux system, the most predominant and clinically important system in C. jejuni that mediates resistance to multiple antimicrobials. Here, we report structures of apo-CosR and CosR bound with a 21 bp DNA sequence located at the cmeABC promotor region using both single-particle cryo-electron microscopy and X-ray crystallography. These structures allow us to propose a novel mechanism for CosR regulation that involves a long-distance conformational coupling and rearrangement of the secondary structural elements of the regulator to bind target DNA.

CosR-DNA complex↗