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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 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Precursor-Derived Nanostructured Silicon Carbide Based Materials for Magnetohydrodynamic Electrode Applications

Development of suitable materials for use in the MHD generator is one of the most challenging tasks. Extremely high temperatures coupled with highly corrosive seed-laden atmosphere limit choice of the materials in contact with the high temperature plasma to just a few materials. These materials are simultaneously subjected to stresses of mechanical, thermal, chemical, electrical and high temperature-electicalmagnetic nature. In this work, novel class of SiC based ceramic composite materials with tailored compositions through a polymer precursor derived synthesis route was developed. SiC has a strong covalent bonding character, resulting in high values of mechanical strength, high hardness and chemical stability while retaining good electrical properties at elevated temperatures. A unique feature of the precursor-derived materials was the presence of nanostructured crystalline SiC domains separated by nanoscale carbon which made these materials excellent candidates for the electrodes that withstands at extremely high temperatures while maintaining good mechanical and electrical properties.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2018

Precursor-Derived Nanostructured Silicon Carbide Based Materials for Magnetohydrodynamic Electrode Applications

Development of suitable materials for use in a magneto-hydro-dynamic (MHD) generator is a challenging task. Extremely high temperatures coupled with highly corrosive seed-laden atmosphere limit the choice of materials in contact with the high temperature plasma to just a few materials. These materials are simultaneously subjected to stresses of mechanical, thermal, chemical, electrical and high temperature-electromagnetic nature. In this work, a novel class of silicon carbide (SiC) based ceramic composite materials with compositions tailored through a polymer precursor derived synthesis route was developed. SiC has a strong covalent bonding character, resulting in high values of mechanical strength, high hardness and chemical stability while retaining good electrical properties at elevated temperatures. Since a unique feature of the precursor-derived materials was the presence of crystalline SiC domains separated by nanoscale carbon, feasibility of materials for electrodes that need to withstand at extremely high temperatures while maintaining good mechanical and electrical properties was investigated.

20 FOSSIL-FUELED POWER PLANTS↗
NASA NTRS2004

Thermal and Environmental Barrier Coatings for Advanced Propulsion Engine Systems

Ceramic thermal and environmental barrier coatings (TEBCs) are used in gas turbine engines to protect engine hot-section components in the harsh combustion environments, and extend component lifetimes. For future high performance engines, the development of advanced ceramic barrier coating systems will allow these coatings to be used to simultaneously increase engine operating temperature and reduce cooling requirements, thereby leading to significant improvements in engine power density and efficiency. In order to meet future engine performance and reliability requirements, the coating systems must be designed with increased high temperature stability, lower thermal conductivity, and improved thermal stress and erosion resistance. In this paper, ceramic coating design and testing considerations will be described for high temperature and high-heat-flux engine applications in hot corrosion and oxidation, erosion, and combustion water vapor environments. Further coating performance and life improvements will be expected by utilizing advanced coating architecture design, composition optimization, and improved processing techniques, in conjunction with modeling and design tools.

Zhu, Dong-Ming↗
NASA NTRS1941

Relief of Residual Stress in Streamline Tie Rods by Heat Treatment

About two-thirds of the residual stress in cold-worked SAE 1050 steel tie rods was relieved by heating 30 minutes at 600 degrees Fahrenheit. Cold-worked austenitic stainless-steel tie rods could be heated at temperatures up to 1000 degrees Fahrenheit without lowering the important physical properties. The corrosion resistance, in laboratory corrosion test, of straight 18:8 and titanium-treated 18:8 materials appeared to be impaired after heating at temperatures above 800 degrees or 900 degrees fahrenheit. Columbium-treated and molybdenum-treated 18:8 steel exhibited improved stability over a wide range of temperatures. Tie rods of either material could be heated 30 minutes with safety at any temperature up to 1000 degrees Fahrenheit. At this temperature most of the residual stress would be relieved.

Pollard, R E↗
DOE OSTI2019

High-temperature Tribological Behavior of Structural Materials after Conditioning in Impure-Helium Environments for High_temperature Gas-Cooled Reactor Applications

Incoloy 800HT and Inconel 617 have been selected as candidate structural alloys for the hightemperature gas-cooled reactor (HTGR) concept. Helium, the primary coolant, contains impurities (e.g., H2O and CH4) that can induce corrosion reactions at high temperatures, which in turn can affect the tribological behavior of components in sliding contact such as valves and control-rod drive systems. This paper presents results from the study of the tribological behavior of both alloys before and after conditioning them in either an impure-helium oxidizing environment or in an air environment. Both alloys were conditioned for 22 days at elevated temperatures in a once-through helium loop with 4 ppmv H2O and tested subsequently at elevated temperatures with a pin-on-disk tribometer in an air environment 650 degrees C and 750 degrees C for 800HT; 850 degrees C and 900 degrees C for 617 - with various applied loads - 1 N, 2 N and 5 N. SEM-EDS analysis revealed that conditioning the samples in an oxidizing environment leads to the formation of a mixed Fe/Cr-oxide on alloy 800HT and a Cr-oxide on alloy 617, both increasing the wear resistance compared to that of as-received samples. Alloy 617 exhibited lower steady-state friction coefficients compared to those of alloy 800HT. There was a significant decrease in the scatter of the steadystate friction coefficient of the conditioned samples compared to that of the unconditioned samples. The steady-state friction coefficient for alloy 800HT and 617 were found to be 0.53 +/- 0.07 and 0.25 +/- 0.04, respectively. The wear resistance of alloy 800HT is approximately one order of magnitude lower than that of alloy 617 in all cases that exhibited measurable wear. After sample conditioning, the wear volumes measured at low loads were undistinguishable from the unworn background, a result attributed to the formation of a compacted glaze layer under high temperatures and high contact stresses.

Alloys 800 and 617↗
DOE OSTI2025

Thermal shock resistance of lightweight cements developed for geothermal conditions

Cements are a critical component in well construction, as they act to prevent well fluid and gas escape, prevent corrosion of the casing, and strengthen the wellbore to prevent deformation. Under the high temperature/pressure conditions common in geothermal systems, the injection of cold water for energy production is expected to induce cyclic damage to the borehole cement through the rapid temperature fluctuations. These “thermal shocks” are expected to cause casing shrinkage, annulus formation, and cement tensile stresses. To understand the effect of cold water injection on the wellbore environment, a set of rock-cement-steel samples were created to simulate the structure of a geothermal well. Lightweight thermally-insulating cement blends were tested under thermal shock conditions in this study. In each test, the samples were pressurized to an effective pressure of ~3.5 MPa and placed at high temperatures. Thermal shocks were performed by injecting cold water (~10-15 °C) through the samples at a constant rate while keeping the samples at high temperatures until the sample temperature stopped decreasing and deformation ceased. Eight thermal shock tests were conducted with each sample – two at 100 °C and six at 200 °C. Post-tests analysis was then conducted by cutting open each sample to examine the damage in each component of the simulated wellbore. Experimental results suggest that all samples experienced similar degrees of axial and lateral contraction during cold water injection, but for the most part this contraction is recoverable when injection halts. Post-test analysis revealed that fly ash cenosphere pre-treatment had the best effect on improving thermal shock resistance in the cement blends. Thermomechanical modeling of likely stress paths experienced by the cements during heating/cooling cycles shows that elasto-plastic cement constitutive behavior results in most plastic strain occurring during the initial heating steps, with mostly elastic strain occurring during the thermal shock cycles. In conclusion, this agrees with experimental evidence, suggesting that cement damage from shocking occurs via other mechanisms such as chemical alteration, corrosion, and fatigue.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Atomistic Studies of Cation Transport in Tetragonal ZrO2 During Zirconium Corrosion

Zirconium alloys are the major fuel cladding materials in current reactors. The water-side corrosion is one of the major degradation mechanisms of these alloys. During corrosion the transport of oxidizing species in zirconium dioxide (ZrO2) determines the corrosion kinetics. Previously it has been argued that the outward diffusion of cation ions is important for forming protective oxides. In this work, the migration of Zr defects in tetragonal ZrO2 is studied with temperature accelerated dynamics and molecular dynamics simulations. The results show that Zr interstitials have anisotropic diffusion and migrate preferentially along the [001] or c direction in tetragonal ZrO2. The compressive stresses can increase the Zr interstitial migration barrier significantly. The migration barriers of some defect clusters can be much lower than those of point defects. The migration of Zr interstitials at some special grain boundaries is much slower than in a bulk oxide. The implications of these atomistic simulation results in the Zr corrosion are discussed.

36 MATERIALS SCIENCE↗
NASA NTRS1986

Reliability and engineering sciences area. Materials research: Single junction thin film

A test bench was designed and fabricated for the purpose of improving control of hot-spot test accuracy. Electrochemical corrosion research focused on corrosion mechanisms to which both crystalline and a-Si modules may be subjected in central station applications. A variety of cells and several designs were subjected to accelerated stress tests. Humiditiy degradation rates were determined and key electrochemical failure mechanisms were identified. Software was developed for the prediction of power loss resulting from open circuits in an array field of a-Si modules. Failure analysis was continued on the four ARCO Solar Genesis modules. The interactions of water on the silicon module was examined. An autocatalytic photooxidation model was proposed. The reliability and durability of bonding materials and electrical insulation were also studied.

Source record↗
NASA NTRS1986

Constitutive modelling of single crystal and directionally solidified superalloys

The trend towards improved engine efficiency and durability places increasing demands on materials that operate in the hot section of the gas turbine engine. These demands are being met by new coatings and materials such as single crystal and directionally solidified nickel-base superalloys which have greater creep/fatigue resistance at elevated temperatures and reduced susceptibility to grain boundary creep, corrosion and oxidation than conventionally cast alloys. Work carried out as part of a research program aimed at the development of constitutive equations to describe the elevated temperature stress-strain-time behavior of single crystal and directionally solidified turbine blade superalloys is discussed. The program involves both development of suitable constitutive models and their verification through elevated temperature tension-torsion testing of single crystals of PWA 1480.

Jordan, E. H.↗
DOE OSTI2023

PV encapsulant formulations and stress test conditions influence dominant degradation mechanisms

Polyethylene-based poly(ethylene-co-vinyl acetate) (EVA), polyolefin elastomer (POE), and thermoplastic polyolefin (TPO) are common polymer candidates for photovoltaic (PV) module encapsulants. The choice of encapsulant must be carefully considered in novel module designs, such as bifacial glass/glass laminates, to limit performance degradation through loss of optical transmittance, mechanical integrity, and corrosion - as well as potential-induced degradation. Encapsulant quality and resilience against environmental stressors are readily influenced by the additives in the encapsulant formulation. Here, we show that, the changes in optical transmittance after UV aging result from the discoloration caused by interactions between additives, and optical scattering from changes in the polymer crystal structure. We observed competing cross-linking and chain scission mechanisms, with their kinetics influenced by the presence of oxygen and elevated temperatures. Increasing chamber temperatures from 55 °C to 85 °C during the UV stress test amplified encapsulant discoloration and promoted polymer cross-linking, causing severe, irreversible damage that remains to be proven field relevant. Damp heat aging was found to be insufficient to produce significant encapsulant degradation; however, combining stress tests sequentially allowed detection of further degradation beyond the limitations of the damp heat test alone. Appropriate degradation screening methods are necessary to uncover potential encapsulant weaknesses.

14 SOLAR ENERGY↗
DOE OSTI2019

Anion transport as a target of adaption to perchlorate in sulfate-reducing communities

Inhibitors can be used to control the functionality of microbial communities by targeting specific metabolisms. The targeted inhibition of dissimilatory sulfate reduction limits the generation of toxic and corrosive hydrogen sulfide across several industrial systems. Sulfate-reducing microorganisms (SRM) are specifically inhibited by sulfate analogs, such as perchlorate. Previously, we showed pure culture SRM adaptation to perchlorate stress through mutation of the sulfate adenylyltransferase, a central enzyme in the sulfate reduction pathway. Here, we explored adaptation to perchlorate across unconstrained SRM on a community scale. We followed natural and bio-augmented sulfidogenic communities through serial transfers in increasing concentrations of perchlorate. Our results demonstrated that perchlorate stress altered community structure by initially selecting for innately more resistant strains. Isolation, whole-genome sequencing, and molecular biology techniques allowed us to define subsequent genetic mechanisms of adaptation that arose across the dominant adapting SRM. Changes in the regulation of divalent anion:sodium symporter family transporters led to increased intracellular sulfate to perchlorate ratios, allowing SRM to escape the effects of competitive inhibition. Thus, in contrast to pure-culture results, SRM in communities cope with perchlorate stress via changes in anion transport and its regulation. Finally, this highlights the value of probing evolutionary questions in an ecological framework, bridging the gap between ecology, evolution, genomics, and physiology.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Disposal of High-Level Nuclear Waste in Deep Horizontal Drillholes

Spent nuclear fuel and high-level radioactive waste can be disposed in deep horizontal drillholes in sedimentary, metamorphic or igneous rocks. Horizontal drillhole disposal has safety, operational and economic benefits: the repository is deep in the brine-saturated zone far below aquifers in a reducing environment of formations that can be shown to have been isolated from the surface for exceedingly long times; its depth provides safety against inadvertent intrusion, earthquakes and near-surface perturbations; it can be placed close to the reactors and interim storage facilities, minimizing transportation; disposal costs per ton of waste can be kept substantially lower than for mined repositories by its smaller size, reduced infrastructure needs and staged implementation; and, if desired, the waste could be retrieved using “fishing” technology. In the proposed disposal concept, corrosion-resistant canisters containing unmodified fuel assemblies from commercial reactors would be placed end-to-end in up to 50 cm diameter horizontal drillholes, a configuration that reduces mechanical stresses and keeps the temperatures below the boiling point of the brine. Other high-level wastes, such as capsules containing 137 Cs and 90 Sr, can be disposed in small-diameter horizontal drillholes. We provide an overview of this novel disposal concept and its technology, discuss some of its safety aspects and compare it to mined repositories and the deep vertical borehole disposal concept.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2026

040226_AnnularFuel_FuelPerformance_LRSv2

This slide deck summarizes a comparative fuel performance assessment of four annular fuel concepts for pressurized water reactor applications against a reference 17×17 fuel design. Overall, annular fuel geometry improves several key thermal-mechanical performance metrics, with the large-annulus configuration providing the most favorable balance of benefits. Relative to the reference design, annular fuel reduces peak fuel temperature by lowering thermal resistance through a thinner fuel pellet and smaller heat-conduction path. At the same time, the reduced fuel volume raises local burnup and correspondingly increases fission gas release. Despite this, rod internal pressure at end of life decreases because the annular geometry provides greater internal void volume. Annular designs also tend to delay fuel-cladding gap closure, although this advantage diminishes in thin-gap configurations where the smaller initial gap accelerates closure. Similarly, hoop stress and hoop strain are generally reduced for annular fuel, but both increase as the initial gap becomes smaller, indicating a potential cladding integrity concern for thin-gap designs. Corrosion performance shows no meaningful variation among the concepts considered. Taken together, the results indicate that annular fuel can offer significant performance advantages in a PWR environment, with large-annulus designs emerging as the strongest candidate while thin-gap geometries introduce more challenging mechanical margins.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Cold Spray NDE for Porosity and Other Process Anomalies

This paper describes a technology review of non-destructive examination (NDE) methods that can be applied to cold spray coatings. Cold spray is a process for depositing metal powder at high velocity so that it bonds to the substrate metal without significant heating that would be likely to cause additional residual tensile stresses. Coatings in the range from millimeters to centimeters are possible at relatively high deposition rates. Cold spray coatings that may be used for hydroelectric components that are subject to erosion, corrosion, wear, and cavitation damage are of interest. The topic of cold spray NDE is treated generally however and may be considered applicable to virtually any cold spray application except where there are constraints of the hydroelectric component application that bear special consideration. Hydroelectric turbine components are primarily made from low carbon and austenitic stainless steels. They are typically very large components that are partially assembled on-site. Transport of these components within the hydroelectric facility and away from the hydroelectric facility is challenging due to the component’s size and weight, high cost of disassembly, and the confined space of the dam. One method for prolonging component life is application of cold spray and thermal powder metal coatings to the components most susceptible to erosion, corrosion, cracking, and mechanical wear. Process controls and visual inspections have historically been applied to cold spray application; however, quantitative NDE could detect anomalies not readily apparent from such a visual examination. Optical profilometry, Eddy current, ultrasound, and hardness tests are shown for one set of good, fair, and poor Nickle-Chrome (NiCr) on 304 stainless steel (304SS) cold spray samples to demonstrate inspection possibilities. The primary indicator of cold spray quality is the cold spray porosity that is most directly measured with witness-sample destructive examinations (DE) – mostly photo-micrographs. These DE generated porosity values are correlated with optical profilometry, eddy current, ultrasound, and hardness test NDE methods to infer the porosity and other Information of interest. These parameters of interest primarily include: • Porosity primarily caused by improper process conditions (temperature, gas velocity, spray standoff, spray angle, powder size, condition, surface cleanliness, surface oxide, etc.). • Presence/absence of the cold spray coating including possible over-sprayed voids • Coating thickness Optical profilometry measurements of surface roughness trended with porosity plus if compared with a reference measurement or reference drawing would provide information on the coating thickness. Ultrasound could provide similar surface profile information plus attenuation measurements trended with porosity. The ultrasound measurements however may be limited to geometries where the substrate back-wall is normal to the cold spray surface and not too thick. Eddy current showed a strong correlation with porosity. Eddy currents can also be sensitive to cracks and do not need fluid coupling to make measurements. Eddy currents however are not sensitive to coating thicknesses in most cases. Vickers hardness measurements also tracked well with porosity. These types of hardness measurements however are also not sensitive to coating thickness. An NDE program may include multiple measurements. Acknowledgement: This work is sponsored by Bonneville Power Administration (BPA) under their technology innovation project program. Such support does not constitute BPA endorsement of views expressed in this work.

Glass, Samuel W.↗
DOE OSTI2018

The challenge of acquiring a satisfactory EBSD result of CWSR Zircaloy-4 cladding tube

This article presents a methodology combining SEM, EDS, conventional EBSD, and transmission-EBSD to analyse a recrystallised Zircaloy-4 sheet and cold-worked stress-relieved (CWSR) Zircaloy-4 cladding in unprecedented detail. Second-phase precipitates (SPPs) in Zircaloy-4 specimens were revealed after chemical polishing using a solution containing hydrofluoric acid (HF). Pitting corrosion of Zircaloy-4 specimens was revealed after electropolishing using an electrolyte containing HClO4. A zirconium coupon without SPPs was used to confirm the chemical response of SPPs on surface morphology. Intrinsic features of cold-worked Zircaloy-4 such as relatively small grain sizes, high dislocation density, and complex microstructure make it significantly more difficult to collect excellent EBSD results compared to recrystallised Zircaloy-4. The fine hydride structure of as-hydrided CWSR Zircaloy-4 cladding further increases the level of challenge on EBSD analysis.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1985

The structure of ion plated films in relation to coating properties

Ion plating is an ion assisted or glow discharge deposition technique, where ions or energetic atoms transfer energy, momentum and charge to the substrate and the growing film in a manner which can be controlled to favorably modify surface, subsurface chemistry, and microstructure. The glow discharge energizing effects from the initial nucleation stages to the final film growth are discussed. As a result, adherence, coherence, internal stresses, density and morphology of the coatings are significantly improved, over the conventional (nonion-assisted) techniques which in turn favorably affect the surface initiated failures caused by friction, wear, erosion, corrosion and fatigue. Ion plated films because of their graded coating/substrate interface, fine, uniform, densely packed film structure also induce a surface strengthening effect which improved the mechanical properties such as yield, tensile strength and fatigue life. Since a uniform, continuous film can be obtained at lower nominal film thickness, this effect is of great importance in solid film lubrication and in corrosion protection.

Spalvins, T.↗
NASA NTRS2020

Testing

Testing is conducted to verify that the connectors will properly perform over time (reliability) per the application requirements. Testing by the manufacturer usually involves performance testing per the datasheet requirements. However, the customer may have applications that require performance under unique operational and environmental conditions. In general, electrical tests for connectors include dielectric withstanding voltage, low-signal-level contact resistance, insulation resistance, contact resistance, and standing wave ratio. Environmental tests include humidity, temperature, and contaminating conditions, as well as mechanical stress environments including vibration, mechanical shock, and durability cycling exposures.

Connectors, testing, Dielectric Withstanding Volta↗
NASA NTRS1992

Glass corrosion in natural environments

Experiments carried out during the progress period are summarized. Experiments carried out involving glass samples exposed to solutions of Tris have shown the appearance of 'spikes' upon monitoring glass dissolution as a function of time. The periodic 'spikes' observed in Tris-based media were interpreted in terms of cracking due to excessive stress in the surface region of the glass. Studies of the interactions of silicate glasses with metal ions in buffered media were extended to systems containing Al. Caps buffer was used to establish the pH. The procedures used are described and the results are given. Preliminary studies were initiated as to the feasibility of adding a slowly dissolving solid compound of the additive to the glass-water system to maintain a supply of dissolved additive. It appears that several magnesium compounds have a suitable combination of solubility and affinity towards silicate glass surfaces to have a pronounced retarding effect on the extraction of uranium from the glass. These preliminary findings raise the possibility that introducing a magnesium source into geologic repositories for nuclear waste glass in the form of a sparingly soluble Mg-based backfill material may cause a substantial reduction in the extent of long-term glass corrosion. The studies described also provide mechanistic understanding of the roles of various metal solutes in the leachant. Such understanding forms the basis for developing long-term predictions of nuclear waste glass durability under repository conditions. From what is known about natural highly reduced glasses such as tektites, it is clear that iron is dissolved as ferrous iron with little or no ferric iron. The reducing conditions were high enough to cause metallic iron to exsolve out of the glass in the form of submicroscopic spherules. As the nuclear waste glass is much less reduced, a study was initiated on other natural glasses in addition to the nuclear waste glass. Extensive measurements were carried out on these glasses in order to characterize their magnetic properties. Results of these studies are described.

Thorpe, Arthur N.↗