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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Step-loaded creep testing of Zircaloy-4 cladding at higher temperatures in the α-phase

A refined understanding of zirconium-based cladding thermomechanical performance during rapid transients is essential for enhancing the safety and operation of light-water reactors. Traditional models for zirconium alloys under accident conditions generally assume that creep dominates fuel cladding performance. Here, these historic models have largely remained unchanged and serve as the basis for safety criteria development. As the U.S. nuclear industry pursues higher burnup levels, the increased release of fission gases during transients raises the risk of cladding failure in the low-temperature hcp α-phase, making the fidelity of these models of greater importance. Creep testing was conducted from 550–700°C with 25–120 MPa applied hoop stresses to investigate Zircaloy-4 deformation at accident-relevant temperatures in the α-phase. Step-loading was employed to capture creep behavior across a wide stress range from a single sample. The stress-strain rate data at higher temperatures (650 and 700°C) were well-described by isotropic versions of the Erbacher and Kaddour models, while the lower temperature data (550 and 600°C) were underpredicted by both anisotropic and isotropic model variants. Greater strain rates during the initial loading step at 650 and 700°C were attributed to recrystallization and grain growth of sub-micron crystallites. Yet, texture analysis revealed the basal split texture remained after testing. These observations produced results suggesting Zircaloy-4 claddings experience higher creep rates across the α-phase than previously thought, possibly related to dynamic anisotropy due to temperature dependent activation of deformation mechanisms, effects of biaxial loading, and variation in material condition between the current testing used in previous model development.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Stretch-induced prostaglandins and protein turnover in cultured skeletal muscle

The purpose of the study is to determine whether mechanical stimulation of cultured muscle cells influences prostaglandin efflux rates and whether they are related to stretch-induced alterations in protein turnover rates. The materials and methods of the experiment, including cell cultures, mechanical stimulation, protein synthesis, and degradation assays are outlined, and emphasis is placed on the effect of short-term mechanical stimulation in basal medium prostaglandin efflux from cultured skeletal muscle and stretch-induced alterations in prostaglandins efflux in complete medium. The major finding of the study is that mechanical stimulation of tissue-cultured skeletal-muscle cells under conditions inducing skeletal-muscle hypertropy increases the efflux of PGE(2) and PGE(2-alpha) but not 6-keto-PGF(1-alpha), the prostacyclin product.

Vandenburgh, Herman H.↗
NASA NTRS2006

Development of the Gecko (Pachydactylus turneri) Animal Model during Foton M-2 to Study Comparative Effects of Microgravity in Terrestrial and Aquatic Organisms

Terrestrial organisms exposed to microgravity during spaceflight experience degeneration in bone, muscle, and possibly other tissues that require gravity-mediated mechanical stimulation for normal regenerative growth. In the Gecko experiment aboard Foton M-2, we flew for the first time, five terrestrial Pachydactylus turneri specimens to develop a model of microgravity effects comparable to the newt Pleurodeles waltl, a well-established model organism for spaceflight. These lower vertebrate species have similar body plans and size, are poikilothermic, have tissue regenerative ability, and are adapted to moderate periods of fasting. Furthermore the gecko (Pachydactylus) can also survive prolonged periods without water. In pre-flight control experiments and after a 16-day Foton M-2 spaceflight without food or water, the geckos were recovered and showed no apparent negative health effects. However, detailed analysis of bone mass and architecture by micro Computed Tomography { pCT), showed that both synchronous control and spaceflight animals lost significant amounts of cancellous bone in the distal femur and humerus relative to basal controls. In addition, cell cycle analysis of 30h post-flight liver tissue reveals a shift of DNA content from G2 and S to G1, both in spaceflight and synchronous controls. Together, these results suggest that housing conditions alone induce rapid catabolism of cancellous bone and reduced normal tissue regeneration. Further use of the gecko Puchydactylus turneri as a spaceflight model requires modification of housing conditions, possibly by including water and food, or changing other factors such as eliminating housing stresses to obtain stable bone structure and tissue regeneration during spaceflight experiments.

Almeida, E. A.↗
DOE OSTI2024

Stable Pentagonal Layered Palladium Diselenide Enables Rapid Electrosynthesis of Hydrogen Peroxide

Electrosynthesis of hydrogen peroxide (H 2 O 2 ) via the two-electron oxygen reduction reaction (2e – ORR) is promising for various practical applications, such as wastewater treatment. However, few electrocatalysts are active and selective for 2e – ORR yet are also resistant to catalyst leaching under realistic operating conditions. Here, a joint experimental and computational study reveals active and stable 2e – ORR catalysis in neutral media over layered PdSe 2 with a unique pentagonal puckered ring structure type. Computations predict active and selective 2e – ORR on the basal plane and edge of PdSe 2 , but with distinct kinetic behaviors. Further, electrochemical measurements of hydrothermally synthesized PdSe 2 nanoplates show a higher 2e – ORR activity than other Pd–Se compounds (Pd 4 Se and Pd 17 Se 15 ). PdSe 2 on a gas diffusion electrode can rapidly accumulate H 2 O 2 in buffered neutral solution under a high current density. The electrochemical stability of PdSe 2 is further confirmed by long device operational stability, elemental analysis of the catalyst and electrolyte, and synchrotron X-ray absorption spectroscopy. This work establishes a new efficient and stable 2e – ORR catalyst at practical current densities and opens catalyst designs utilizing the unique layered pentagonal structure motif.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1991

The high temperature creep behavior of oxides and oxide fibers

A thorough review of the literature was conducted on the high-temperature creep behavior of single and polycrystalline oxides which potentially could serve as fiber reinforcements in ceramics or metal matrix applications. Sapphire when oriented with the basal plane perpendicular to the fiber axis (c-axis oriented) is highly creep resistant at temperatures in excess of 1600 C and applied loads of 100 MPa and higher. Pyramidal slip is preferentially activated in sapphire under these conditions and steady-state creep rates in the range of 10(exp -7) to 10 (exp -8)/s were reported. Data on the creep resistance of polycrystalline beryllia suggest that C-axiz oriented single crystal beryllia may be a viable candidate as a fiber reinforcement material; however, the issure of fabricability and moisture sensitivity must be addressed for this material. Yttrium aluminum garnet (YAG) also appears to be a fiber candidate material having a high resistance to creep which is due to it's complex crystal structure and high Peierl resistance. The high creep resistance of garnet suggests that there may be other complex ternary oxides such as single crystal mullite which may also be candidate materials for fiber reinforcements. Finally, CVD and single crystal SiC, although not oxides, do possess a high resistance to creep in the temperature range between 1550 and 1850 C and under stresses of 110 to 220 MPa. From a review of the literature, it appears that for high creep resistant applications sapphire, silicon carbide, yttrium aluminum garnet, mullite, and beryllia are desirable candidate materials which require further investigation.

Jones, Linda E.↗
DOE OSTI2024

Effect of relative humidity on the interlayer spacing of phosphate intercalated Mg, Al layered double hydroxide (hydrotalcite‐like) crystals

Abstract The availability of water and the type of interlayer anions present affect the arrangement and interlayer spacing of layered double hydroxide (LDH). A systematic study of the effect of relative humidity (RH) on the basal spacing of phosphate intercalated, magnesium aluminum LDHs (MgAl–PO 4 LDH) was conducted, confirming that MgAl‐PO 4 LDH exhibit distinct interlayer spacing corresponding to separate low‐ and high‐hydration states produced when exposed to low and high humidity conditions. The transition from the low‐ to high‐hydration form begins when RH exceeds 33% and is accompanied by the transition from one to two interlayers of water. An improved understanding of the effect of RH on MgAl–PO 4 LDHs will enable more accurate atomistic modeling and experimental characterization of MgAl–PO 4 LDHs and may lead to improvements in the tunability of MgAl‐PO 4 LDHs for commercial applications such as slow‐release fertilizer.

Reed, Titus↗
NASA NTRS1971

Photovoltage inversion effect and its application to semiconductor surface studies: CdS.

Experimental results on the surface states of the basal plane of CdS are presented and discussed in the light of a model of the photovoltage inversion effect. It is found that the surface states associated with this effect are in poor communication with the bulk and under normal conditions may require long periods of time to reach equilibrium. A combination of photovoltage inversion, photovoltage quenching, and photovoltage spectroscopy is believed to constitute a very effective tool for the study of surfaces of wide energy gap semiconductors.

Lagowski, J.↗
DOE OSTI2025

Basal Melting and Oceanic Observations Beneath Central Fimbulisen, East Antarctica

Abstract Basal melting of ice shelves is fundamental to Antarctic ice sheet mass loss, yet direct observations remain sparse. We present the first year‐round melt record (2017–2021) from a phase‐sensitive radar on Fimbulisen, one of the fastest flowing ice shelves in Dronning Maud Land, East Antarctica. The observed long‐term mean ablation rate at 350 m depth below the central ice shelf was 1.0 ± 0.5 m yr −1 , marked by substantial sub‐weekly variability ranging from 0.4 to 3.5 m yr −1 . 36‐h filtered basal melt rate fluctuations closely align with ocean velocity. On seasonal time scales, melt rates peak during austral spring to autumn (September–March), driven by both elevated ocean velocities and thermal driving near the base. The combined effect of thermal driving and current speed explains the majority of the melt rate variability ( r = 0.84), highlighting the dominant role of shear‐driven turbulence. This relationship enables parameterization of melt rates for the decade‐long ocean record (2010–2021), although deviations appear under low and high forcing conditions. Both observed and parameterized melt rates show similar yearly mean magnitudes compared to satellite‐derived melt rates but with a tenfold lower seasonal amplitude and a 3‐month delay in seasonality. These detailed concurrent ice–ocean observations provide essential validation data for remote sensing and numerical models that aim to quantify and project ice‐shelf response to a change in ocean forcing. In situ measurements and continued monitoring are crucial for accurately assessing and modeling future basal melt rates, and for understanding the complex dynamics driving ice‐shelf stability and sea‐level change.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Fullerene-like defects in high-temperature neutron-irradiated nuclear graphite

Irradiation-induced defect evolution in graphite is particularly important for its application in graphite-moderated nuclear reactors. The evolution of defects directly influences macroscopically observed property changes in irradiated nuclear graphite which, in turn, can govern the lifetime of graphite components. This article reports novel defect structures and the irradiation response of microstructural features occurring in high-temperature irradiated nuclear graphite IG-110. High resolution transmission electron microscopy (HRTEM) was used to characterize specimens neutron-irradiated at a high temperature (≥ 800°C) at doses of 1.73 and 3.56 atomic displacements per atom (dpa). Concentric shelled and fullerene-like defects were found to result in swelling along the c-axis and contraction along the a/b-axis of crystallites. Furthermore, such defects are shown to occur within, and partially fill, Mrozowski cracks prior to turnaround dose. In addition, in situ TEM under similar irradiation conditions was used to capture the real-time dynamic evolution of defects, providing unambiguous analysis of the evolution of the graphite structures during irradiation. Here, the results suggest the mainstream theory for radiation damage in nuclear graphite (which assumes additional basal plane formation as the sole reason) to be an incorrect interpretation of defect evolution contributing to irradiation-induced property changes at higher temperatures.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2020

Thermal and magnetic evolution of a crystallizing basal magma ocean in Earth's mantle

We present the thermochemical evolution of a downward crystallizing basal magma ocean (BMO) overlying the liquid outer core and probe its capability to dissipate enough power to generate and sustain an early dynamo. Furthermore, a total of 61 out of 112 scenarios for a BMO with imposed, present-day heat flux, Q BMO , values of 15, 18, and 21 TW and radiogenic heat, Q r , values of 4, 8, and 12 TW fully crystallized during the age of the Earth. Most of these models are energetically capable of inducing magnetic activity for the first 1.5 Gyrs, at least, with durations extending to 2.5 Gyrs; with final core-mantle boundary (CMB) temperatures of 4400 ±500 K-well within current best estimates for inferred temperatures. None of the models with Q BMO = 12 TW achieved a fully crystallized state, which may reflect a lower bound on the present-day heat flux across the CMB. BMO-powered dynamos exhibit strong dependence on the partition coefficient of iron into the liquid layer and its associated melting-point depression for a lower mantle composition at near-CMB conditions-parameters which are poorly constrained to date. Nonetheless, we show that a crystallizing BMO is a plausible mechanism to sustain an early magnetic field.

58 GEOSCIENCES↗
NASA NTRS2016

Diagenesis in the Murray Formation, Gale Crater, Mars

The Mars Science Laboratory (MSL) Curiosity rover began investigating the rocks of Mt. Sharp in September 2014. The Murray formation is the lowermost unit, which is mostly comprised of finely laminated mudstones, suggesting these sediments were deposited in a lacustrine environment. It is important to characterize the geochemical and mineralogical trends throughout the Murray Fm to interpret the aqueous conditions of the ancient lake, the sources of the lake sediments, and post-depositional alteration processes. Four samples have been drilled from the Murray Fm so far: Confidence Hills, Mojave 2, and Telegraph Peak were collected from the Pahrump Hills member - the basal portion of the Murray Fm, and Buckskin was collected in the Marias Pass region (Fig. 1). The drill fines were delivered to the instruments inside the rover, including the CheMin instrument, a combination X-ray diffractometer and X-ray fluorescence spectrometer. Rietveld refinements and FULLPAT analyses of 1D CheMin XRD patterns were performed to determine quantitative abundances of minerals and amor-phous phases and the unit cell parameters of minerals present in abundances greater than 4-5 wt.%.

Rampe, E. B.↗
NASA NTRS2015

NASA's Rodent Research Project: Validation of Capabilities for Conducting Long Duration Experiments in Space

Research using rodents is an essential tool for advancing biomedical research on Earth and in space. Prior rodent experiments on the Shuttle were limited by the short flight duration. The International Space Station (ISS) provides a new platform for conducting rodent experiments under long duration conditions. Rodent Research (RR)-1 was conducted to validate flight hardware, operations, and science capabilities that were developed at the NASA Ames Research Center. Twenty C57BL6J adult female mice were launched on Sept 21, 2014 in a Dragon Capsule (SpaceX-4), then transferred to the ISS for a total time of 21-22 days (10 commercial mice) or 37 days (10 validation mice). Tissues collected on-orbit were either rapidly frozen or preserved in RNAlater at -80C (n2group) until their return to Earth. Remaining carcasses on-orbit were rapidly frozen for dissection post-flight. The three controls groups at Kennedy Space Center consisted of: Basal mice euthanized at the time of launch, Vivarium controls housed in standard cages, and Ground Controls (GC) housed in flight hardware within an environmental chamber. Upon return to Earth, there were no differences in body weights between Flight (FLT) and GC at the end of the 37 days in space. Liver enzyme activity levels of FLT mice and all control mice were similar in magnitude to those of the samples that were processed under optimal conditions in the laboratory. Liver samples dissected on-orbit yielded high quality RNA (RIN8.99+-0.59, n7). Liver samples dissected post-flight from the intact, frozen FLT carcasses yielded RIN of 7.27 +- 0.52 (n6). Additionally, wet weights of various tissues were measured. Adrenal glands and spleen showed no significant differences in FLT compared to GC although thymus and livers weights were significantly greater in FLT compared to GC. Over 3,000 tissue aliquots collected post-flight from the four groups of mice were deposited into the Ames Life Science Data Archives for future Biospecimen Sharing Program. Together, the RR validation flight successfully demonstrates the capability to support long-duration experimentation on the ISS to achieve both basic science and biomedical objectives.

spaceflight↗
DOE OSTI2024

Distorted dislocation cores and asymmetric glide resistances in titanium

The determination of Critical Resolved Shear Stress (CRSS) in titanium for basal, prismatic, and pyramidal slip-planes without empirical constants is presented by combining Density Functional Theory (DFT) and anisotropic elasticity. A new mechanism leading to tension-compression (T-C) asymmetry in the CRSS levels has been revealed for the first time. The conditions for this asymmetry are established, involving a complex interplay between the dislocation core-structure and core-advance behavior. The three conditions for T-C asymmetry that need to be simultaneously satisfied can be summarized as: (1) a medium stacking fault width, d, (3 < d/b F < 10, where b F is the magnitude of the Burgers vector of the full dislocation), (2) an asymmetric core-structure of the extended dislocation (ξ 1 ≠ ξ 2 , where ξ 1 and ξ 2 are the core-widths of the first and second partials, respectively), and (3) intermittent motion of the partials (Δd/b F ≠ 0, where Δd is the magnitude of fluctuation in stacking fault width during intermittent motion). Pyramidal-slip in titanium satisfies all three conditions, resulting in significant T-C asymmetry. The CRSS theory considers a Wigner-Seitz (W-S) cell based domain area assigned to each lattice site for the calculations of core-energies accurately capturing the slip-plane lattice. The W-S based approach is essential due to the lower symmetry of the HCP crystal circumventing potential errors associated with the one-dimensional atomic-row approximation. Dislocation core structures are obtained for all the slip-systems in titanium showing significant distortion of the disregistry profile governing the core-advance behavior. The CRSS values predicted from the theory show agreement with the experimental CRSS levels reported in the literature.

Dislocation core↗
NASA NTRS2001

Hudson River Paleoclimate, Sea Level, and Human Impact: A Record From Piermont Marsh, NY

A 13.77 meter sediment core from Piermont Marsh, NY (40 00 N, 73 55W) records the local and regional vegetational and foraminiferal history of the Hudson Estuary. The sediments were sampled every 4 cm, which represents a decadal to centuryscale resolution. Basal sediment dating is in progress, and the 11-m depth represents about 4000 years. Changes in plant macrofossils and charcoal appear to indicate differences in salinIty and drought, suggesting changes in climate. Scirpus, Salicornia, and high levels of charcoal seem to indicate drier/more saline conditions, while lack of these macrofossils and increases in Chara/Nitella, aquatic leaves, and very little charcoal suggests wetter conditions. Other macrofossils include Carex, Juncus, Polygonum, Zanichellia, Ruppia. High resolution AMS dating of plant macrofossils is in progress, and will be compared with changes in Hudson River sediment cores offshore. Foraminiferal assemblages from key intervals of the core will be presented. Human impact in the upper sediments is visible from the influx of grass seeds, primarily Phragmites, and the ragweed pollen rise.

Kurdyla↗
DOE OSTI2022

Limiting velocities and transonic dislocations in Mg

To accurately predict the mechanical response of materials, especially at high strain rates, it is important to account for dislocation velocities in these regimes. Under these extreme conditions, it has been hypothesized that dislocations can move faster than the speed of sound. However, the presence of such dislocations remains elusive due to challenges associated with measuring these experimentally. In this work, molecular dynamics simulations were used to investigate the dislocation velocities for the basal edge, basal screw, prismatic edge, and prismatic screw dislocations in Mg in the sub-, trans-, and supersonic regimes. Also, our results show that only prismatic edge dislocations achieve supersonic velocities. Furthermore, this work demonstrates that the discrepancy between the theoretical limiting velocity and the MD results for Mg is due to its sensitivity to large hydrostatic stress around the dislocation core, which was not the case for fcc metals such as Cu.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Subglacial Discharge Effects on Antarctic Ice‐Shelf Basal Melt and the Southern Ocean in a Global, Coupled Ocean—Sea‐Ice Model

Subglacial freshwater from beneath Antarctica enters the ocean at depth, enhancing ice-shelf melting and affecting Southern Ocean properties. To study these effects in an Antarctic-wide context, we use a continental-scale subglacial hydrology model that calculates grounding line freshwater flux for a global, coupled ocean—sea-ice model. We find that subglacial discharge impacts melt rates primarily through continental shelf temperature modification, contrasting with findings from regional studies that do not permit large-scale adjustments. The consequence is that Antarctic melt rates scale with subglacial discharge more strongly than inferred from regional studies. We also find that the addition of buoyancy at depth facilitates heat upwelling to the surface, resulting in higher sea ice volume downstream of cold ice shelves and lower sea ice volume downstream of warm ice shelves. This highlights the drawbacks of simplifications in previous global studies that deposit Antarctic meltwater at the ocean surface and find uniform ocean surface cooling and sea-ice growth. While the patterns we find are robust, we conclude that the addition of subglacial discharge at present-day rates has a small effect on basal melt rates, hydrography, and sea ice. However, stronger discharge can have significant effects and can even accelerate a shift from low to high melting for ice shelves close to such a tipping point. Finally, the importance of feedbacks between enhanced cavity overturning and continental shelf conditions poses a complication for parameterizing subglacial discharge effects on melting for ice-sheet projections that do not include a coupled ocean component.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Dramatic changes in mitochondrial subcellular location and morphology accompany activation of the CO 2 concentrating mechanism

Dynamic changes in intracellular ultrastructure can be critical for the ability of organisms to acclimate to environmental conditions. Microalgae, which are responsible for ~50% of global photosynthesis, compartmentalize their Ribulose 1,5 Bisphosphate Carboxylase/Oxygenase (Rubisco) into a specialized structure known as the pyrenoid when the cells experience limiting CO 2 conditions; this compartmentalization is a component of the CO 2 Concentrating Mechanism (CCM), which facilitates photosynthetic CO 2 fixation as environmental levels of inorganic carbon (Ci) decline. Changes in the spatial distribution of mitochondria in green algae have also been observed under CO 2 limitation, although a role for this reorganization in CCM function remains unclear. We used the green microalga Chlamydomonas reinhardtii to monitor changes in mitochondrial position and ultrastructure as cells transition between high CO 2 and Low/Very Low CO 2 (LC/VLC). Upon transferring cells to VLC, the mitochondria move from a central to a peripheral cell location and orient in parallel tubular arrays that extend along the cell’s apico-basal axis. We show that these ultrastructural changes correlate with CCM induction and are regulated by the CCM master regulator CIA5. The apico-basal orientation of the mitochondrial membranes, but not the movement of the mitochondrion to the cell periphery, is dependent on microtubules and the MIRO1 protein, with the latter involved in membrane–microtubule interactions. Furthermore, blocking mitochondrial respiration in VLC-acclimated cells reduces the affinity of the cells for Ci. Overall, our results suggest that mitochondrial repositioning functions in integrating cellular architecture and energetics with CCM activities and invite further exploration of how intracellular architecture can impact fitness under dynamic environmental conditions.

CO2 concentrating mechanism↗
NASA NTRS1987

Prediction of physical workload in reduced gravity environments

The background, development, and application of a methodology to predict human energy expenditure and physical workload in low gravity environments, such as a Lunar or Martian base, is described. Based on a validated model to predict energy expenditures in Earth-based industrial jobs, the model relies on an elemental analysis of the proposed job. Because the job itself need not physically exist, many alternative job designs may be compared in their physical workload. The feasibility of using the model for prediction of low gravity work was evaluated by lowering body and load weights, while maintaining basal energy expenditure. Comparison of model results was made both with simulated low gravity energy expenditure studies and with reported Apollo 14 Lunar EVA expenditure. Prediction accuracy was very good for walking and for cart pulling on slopes less than 15 deg, but the model underpredicted the most difficult work conditions. This model was applied to example core sampling and facility construction jobs, as presently conceptualized for a Lunar or Martian base. Resultant energy expenditures and suggested work-rest cycles were well within the range of moderate work difficulty. Future model development requirements were also discussed.

Goldberg, Joseph H.↗