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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

Relationship Between Filler Type, Thermomechanical Properties, and Aging of RTV Silicone Foams

Room-temperature vulcanizing (RTV) silicone foams are used in many industrial applications that require the material to perform over long time periods. However, mechanical properties tend to deteriorate when these foams age under a compressive load. The chemical aging is attributed to the presence of unreacted functional groups of the prepolymers, residues from acid, and catalytically active tin (II) species. Here, an optimized thermal treatment of an RTV foam that achieves completion of curing reactions and deactivation of reactive species is proposed. Foams that were thermally aged for three months under compressive load showed no signs of compression set, indicative of the effectiveness of the implemented post-curing approach. In addition, the effects of fillers (diatomaceous earth, fumed silica, and carbon nanofibers) on thermomechanical properties were investigated. Tensile strength, tear strength, and thermal conductivity increased when these fillers were added to the unfilled RTV formulation, with carbon nanofibers (CNFs) being the most effective filler. Rheological studies of RTV formulations indicated that 2.5 wt.% of CNFs is the upper limit that can be added to the RTV formulation.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Atmospheric processing and aerosol aging responsible for observed increase in absorptivity of long-range-transported smoke over the southeast Atlantic

Biomass burning aerosol (BBA) from agricultural fires in southern Africa contributes about one-third of the global carbonaceous aerosol load. These particles have strong radiative effects in the southeast Atlantic (SEA), which depend in part on the radiative contrast between the aerosol layer in the free troposphere (FT) and the underlying cloud layer. However, there is large disagreement in model estimates of aerosol-driven climate forcing due to uncertainties in the vertical distribution, optical properties, and life cycle of these particles. This study applies a novel method combining remote sensing observations with regional model outputs to investigate the aging of the BBA and its impact on the optical properties during transatlantic transport from emission sources in Africa to the SEA. Results show distinct variations in extinction Ångström exponent (EAE) and single-scattering albedo (SSA) as aerosols age. Near the source, fresh aerosols are characterized by low mean SSA (0.84) and high EAE (1.85), indicating smaller, highly absorbing particles. By isolating marine contributions from the total column during BBA transport across the SEA, our analysis reveals an initial decrease in BBA absorptivity, with mean FT SSA of 0.87 after 6–7 d, followed by increased absorptivity with mean FT SSA of 0.84 after 10 d, suggesting enhanced absorption due to chemical aging. These findings indicate that BBA becomes more absorbing during extended transport across the SEA, with implications for reducing model uncertainties. Our remote-sensing-based results agree well with previous in situ studies and offer new insights into aerosol–radiation interactions and the energy balance over the SEA.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Cosmogenic 21 Ne exposure ages on late Pleistocene moraines in Lassen Volcanic National Park, California, USA

We report new cosmogenic 21 Ne in quartz exposure ages from 18 samples on three distinct moraines deposited in the Lost Creek drainage, approximately 3–7 km down-valley from Lassen Peak in Lassen Volcanic National Park. Although measuring 21 Ne in quartz is generally straightforward, accurate 21Ne exposure dating of deposits of late Pleistocene is rarely possible due to the significant quantities of non-cosmogenic 21 Ne present in most lithologies. Young quartz-bearing volcanic rocks have been observed to be an exception. We take advantage of moraine boulders sourced from the ~28 ka dacite of Lassen Peak to generate a chronology of alpine deglaciation in Lassen Volcanic National Park. Ages from three distinct moraines are in stratigraphic order at 22.1 ± 3.8, 20.2 ± 2.4, and 15.3 ± 3.8 ka and generally agree with other terminal and some recessional moraine ages across the Cascade Range and Sierra Nevada of the western United States. To date, these are among the youngest surfaces ever dated using cosmogenic 21 Ne and provide a cost-effective proof-of-concept approach to dating moraines where applicable.

58 GEOSCIENCES↗
DOE OSTI2024

Radiation Aging of Cable Insulation Systems to Support Extension of Cable Electrical Assessment Techniques - CRADA 562 (Final Report)

Radiation aging (primarily gamma radiation) affects a small subset of the LV cable population based on a 40-year operation. Increasing plant operating life to 60 or 80 years will result in additional cables experiencing degradation, either from radiation or from combined thermal and radiation effects. Previous research work done by EPRI and other researchers focuses on electrical diagnostics of thermal effects. However, the electrical diagnostic response of the cable system to radiation aging is minimally understood. In order to study the electrical responses from XLPE and EPR cabling and correlate these responses with radiation dose and level of thermal exposure, gamma radiation testing was performed at Pacific Northwest National Laboratory (PNNL). This report covers the radiation testing performed at PNNL, which involved irradiation of 30-foot long cables and short witness samples. The cabling was irradiated, at room temperature, using cobalt-60 gamma-rays to intervals of 10 million rads (10 Mrads), for a maximum of 70 Mrads. The results can be used to determine cable conditions (extent of damage) more accurately and localize where the degradation exists along the length of the cable (axial location). These insights can provide operators with the options to focus repair, mitigation, or replacement efforts locally.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Creating high-precision reference gas standards of 85Kr for groundwater age-dating

Absolute gas counting (AGC) was applied to two gas blends of 85Kr in argon-methane (P10) counting gas to establish a high-precision specific activity (Bq/cm3) reference value for characterizing 85Kr detection efficiency for groundwater age dating measurements. The AGC or length-compensated technique has been utilized by the metrology community for decades and is an accepted method for developing radioactive gas standards. The AGC capability at Pacific Northwest National Laboratory (PNNL) uses a set of nine unequal-length proportional counters with precisely-measured internal volumes, and a gas loading system with high-precision pressure and temperature sensors. A series of AGC measurements were collected at multiple pressures to determine the inverse pressure relationship (1/P) for 85Kr and define a wall-effect correction that accounts for events decaying into the detector wall and not depositing sufficient energy in the gas to be detected. In addition to the wall-effect, two additional corrections were evaluated and are discussed in detail. Specifically, the threshold effect which accounts for events deposited below the analysis threshold and a detection efficiency as a function of detector volume effect that was observed during analysis. A robust uncertainty model was developed using the Guide to the expression of Uncertainty in Measurements (GUM) approach. The combination of carefully scrutinized correction factors, precise measurements of pressure, temperature and detector volume, and robust counting statistics resulted in the determination of high-precision specific activity values with 0.50% or less total combined uncertainty for two Kr-in-P10 reference gas standards (KP10) that will enable new groundwater age-dating measurements at PNNL.

Kr-85↗
DOE OSTI2024

Reassessing early-age strength development of high-volume fly ash concretes for precast buildings

Increasing beneficial use of fresh or landfilled fly ash as a replacement for Portland cement can be more challenging for the construction of precast buildings or similar applications requiring rapid strength development. Therefore, the framework presented in this paper aims to reassess high-volume fly ash concretes but in the context of facilitating more sustainable precast buildings. More specifically, the framework was used to characterize strength development of concrete mixes with a target minimum 24-hour compressive strength of 24.1 MPa (3500 psi), selected as an example strength development metric to demonstrate the framework, and comprised of 40% Class C, Class F, and landfilled (harvested) fly ash – as a high-volume replacement of Type III or Type IL cement. High-early strength was driven by optimized dosages of commercial grade gypsum and accelerating admixtures, in addition to optimal aggregate packing and mix proportioning strategies. Early-age mechanical properties including compressive strength, modulus of rupture, and modulus of elasticity were reevaluated within 24 hours of batching with respect to common precast production demands. Simple data analyses were then used to highlight cases where currently accepted design provisions for the aforementioned properties are either overly-conservative or unconservative with respect to test data. Furthermore, the framework and demonstration of example mixes presented herein aim to promote confidence for using larger fractions of fresh or landfilled fly ashes for precast buildings to further enhance environmental benefits without sacrificing pertinent early-age structural performance.

42 ENGINEERING↗
DOE OSTI2026

Strain age cracking in a simulated heat affected zone of Inconel 740H laser-powder bed fusion components

Inconel® 740H components produced via laser-powder-bed fusion (L-PBF) additive manufacturing are ideal for supercritical CO2 primary heat exchangers. Arc welding is often needed, and subsequent post-weld heat treatment aging at 790–840 °C is required to improve strength via gamma prime (γ’) precipitation; however, strain age cracking (SAC) can occur in the heat affected zone (HAZ) during this process. This study uses stress relaxation testing at 800 °C on simulated HAZ specimens from vertically and horizontally built L-PBF IN740H to assess SAC susceptibility across heating rates of 40–3480 °C/h and weld-induced strains of 3–10 %. Vertical builds require greater mechanical energy input and exhibit longer times to fracture than horizontal builds, and time to fracture occurs sooner at slower heating rates. Creep voids were observed in γ’-denuded regions along grain boundaries, and cracking propagated along migrated grain boundaries and at interfaces between elongated secondary phases (γ’ or carbides) and the γ-matrix.

14 SOLAR ENERGY↗
DOE OSTI2024

Rate-induced aging effects on Parallel-Plate Avalanche Counter (PPAC) caused by heavy ion beams

The Facility for Rare Isotope Beams (FRIB) is one of the premier scientific user facilities for nuclear science with radioactive beams, capable of producing most (approximately 80%) of the isotopes expected to exist, from oxygen to uranium, at energies up to 200 MeV/u. With the increase in beam power from the present 10 kW to the planned 400 kW, FRIB experiments are about to enter a new era. An unprecedented rate capability as well as stable performance of all the planned instrumentation intended for beam diagnostics and beam tuning is required at the expected high beam intensities (> 1 MHz). A summary of aging phenomena at high heavy-ion beam rates observed in the Advanced Rare Isotope Separator (ARIS) detectors for beam diagnostics, including Parallel Plate Avalanche Counters (PPAC) and plastic scintillation for time-of-flight measurements, is discussed. Current research and development project to mitigate rate-induced aging are presented.

Aging effects↗
DOE OSTI2024

A Multi-Metrics In Situ Aging Detector for SiC Power MOSFET Modules with Full Driver-Integration Capability

In this paper, the concept and prototype of an aging detector for silicon carbide (SiC) power metal oxide semiconductor field effect transistor (MOSFET) are proposed and described. It leverages the resonant peak values of gate-source voltage at different instants during the switching transients to decode the change of multiple aging indicators, such as the increases of on-state resistance and threshold voltage. Modeling-based analysis is conducted to support the idea. The detector can be fully integrated into gate drivers without any additional connection to the power stage and is functional during normal power stage operation. A prototype unit was built, and preliminary tests were conducted to validate the idea and the practicality of the detector.

aging↗
DOE OSTI2024

Diagnosis of PV Cell Passivation Degradation Resulting from Hot-Humid, High Voltage Potential Aging

Corrosion of the antireflective coating on the cell ("AR c corrosion") was previously observed in studies using hot-humid test conditions with external high voltage (HV) bias. Because AR c corrosion is not well understood, mini-modules (MiMos) were examined in a comparative experiment using PERC and PERT as well as legacy Al-BSF cells. For separate MiMos with the cell circuit electrical at +1500 V, -1500 V, or unbiased "V oc", test conditions in the comparative study included 60degrees C/60% RH for 96 h, as in IEC TS 62804-1; 70degrees C/70%RH for 200 h; and 85degrees C/85% RH for 200 h. Characterizations at each read point included: camera and electroluminescence (EL) imaging, colorimetry, and I-V curve tracing. Characterizations at the final read point included: SunsVoc; spatially mapping external quantum efficiency (EQE); high resolution: photoluminescence (PL), EL, and dark lock-in thermographic (DLIT) imaging. Forensics were performed on extracted cores, including scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) and scanning Auger microscopy (SAM). Forensics were also conducted on MiMos (stepped HV aging) and full-sized modules (outdoor aging) from previous studies. AR c corrosion was specifically observed for the glass/encapsulant/cell side of +1500 V (HV+) stressed MiMos, where appearance, color, and reflectance were the characteristics most distinguished relative to simultaneously occurring degradation modes. SEM/EDS and SAM identified conversion of silicon nitride to silicon oxide or hydrous silica, preferentially occurring at the edges and tips of the pyramidal textured cell surface.

aging↗
DOE OSTI2025

Helium bubble formation in aged plutonium metal at ambient conditions

A model of helium bubble formation is developed that assumes the initial nascent bubbles are generated when two diffusing helium atoms come within a distance of about the interatomic spacing of the plutonium atoms. These nascent bubbles are assumed to be locked in place and grow as additional helium atoms diffuse across their surfaces. Calculations of the helium-bubble number density and sizes as a function of age are compared to experiment. This leads to an inferred helium diffusion coefficient of-the-order of 10 -20 m 2 /s, supports the idea that most of the helium from alpha-decay end up in bubbles, and that previous transmission electron microscopy size estimates are biased low. The energy that helium can transfer to 40-year-old plutonium, upon expansion, is determined to be <0.1 Joules per gram of metal. The model predicts differences between the bubble properties in naturally and accelerated aged plutonium.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Impact of Lithium‐Free Borate Additives on the Cycle Life and Calendar Aging of Silicon‐Based Lithium‐Ion Batteries

Silicon-anode lithium-ion batteries (LIBs) suffer from limited cycle life and poor calendar life, constraining their large-scale commercialization. Integrating additives into electrolytes is a simple and cost-effective strategy to improve these aspects. The effects of lithium-free boron-based additives on cycling and calendar performance of high-loading Si-anode LIBs remain largely unexplored. In this work, the influence of five Li-free borate additives, each with distinct molecular structures and elemental compositions, is systematically investigated. All additives enhance cycle life to varying extents. Notably, the addition of 1 v/v% tri(2,2,2-trifluoroethyl) borate to the baseline electrolyte nearly doubles the cycle life at 50% state of health. This enhancement is attributed to three key factors. Specifically, borate additives 1) improve electrochemical activity, 2) act as anion receptors that interact with [PF6]- anions and carbonate solvents to reduce electrolyte decomposition, and 3) promote the formation of a stable and polymeric solid electrolyte interphase layer. Furthermore, these additives exhibited negligible impact in mitigating leakage current during a 180 h voltage-hold calendar-aging test, indicating their limited effect in calendar life. These findings provide insight into the role of Li-free borate additives in improving cycle life while addressing the knowledge gap regarding their influence on calendar aging.

Li, Defu↗
DOE OSTI2025

Solute Redistribution During Aging in a Laser-Based Powder Bed Fusion-Produced Fe-18Ni-9Co-5Mo-Ti Maraging Steel

Solute distribution during the laser-based powder bed fusion of metals process is highly complex because of solidification. This study builds on a previous investigation of how solute heterogeneities across different scales influence phase distribution and aging physical phenomena in a Fe-18Ni-9Co-5Mo-Ti maraging steel (Santana et al. in Addit Manuf 104494, 2024). Previous work using energy-dispersive X-ray spectroscopy revealed heterogeneous Ni and Mo enrichment at intercellular regions. Using X-ray diffraction, 8 ± 3% retained austenite was quantified in as-built samples. Additionally, electron backscatter diffraction analysis exposed the location of retained austenite along cell boundaries. In this work, scanning transmission electron microscopy results revealed the presence of non-enriched retained austenite in the as-built condition. With increased aging temperature, Ni and Mo enrichment in austenite increased, especially at the austenite/martensite boundary. Solute diffusion was simulated in DICTRA Thermo-Calc® software to assess solute redistribution between the matrix and second phases and to comprehend whether elemental diffusion processes are interconnected. Three different scenarios were considered: (1) solute diffusion in the matrix; (2) diffusion with enriched austenite in the intercellular region; (3) diffusion with non-enriched austenite in the intercellular region. Results showed that Ni partitioning controls austenite growth and that boundary regions exhibit higher element enrichment than the core.

42 ENGINEERING↗
DOE OSTI2026

A collective trigger for widespread planetesimal formation revealed by accretion ages

The formation of planetesimals was an integral part of the cascading series of processes that built the terrestrial planets. To illuminate planetesimal formation, here we develop a refined thermal evolution model to calculate the formation ages of meteorite parent planetesimals. This model includes chemical reactions and phase changes during heating, as well as natural variations in the proportions of the constituent phases of these planetesimals. We find that the parent bodies of non-carbonaceous (NC) and carbonaceous (CC) iron meteorites start forming at very similar times ( ∼ 0.95 Myr after calcium-aluminium-rich inclusion [CAI] formation) and occupy overlapping time windows. NC and CC chondrite parent bodies formed later during non-overlapping periods. We combine these ages with proportions of isotopic end-members we recover from mixing models to construct records of motion throughout the protoplanetary disk. These records argue that NC and CC material traversed the barrier in the disk after ∼ 0.95 Myr after CAI formation. The onset of this motion coincided with planetesimal formation, indicating that the phenomenon that drove motion also triggered planetesimal formation. We argue that this feature also served as the semi-permeable barrier in the disk. Although its identity is uncertain, the effects this phenomenon had on the timing of planetesimal formation and motion through the disk can now serve as constraints on models of disk evolution. Models that reproduce these effects would elucidate the nature and implications of this phenomenon, which is key to unlocking a holistic model of terrestrial planet building.

Astronomy and AstroPhysics↗
DOE OSTI2024

Glacial to periglacial transition at the end of the last ice age in the subtropical semiarid Andes

Atmospheric warming and circulation reorganization at the end of the last ice age represent the most important climate change of the last 100,000 years and provide an opportunity to uncover how the southern subtropics cryosphere responded to strong changes in the global climate system. Extensive mapping and chronologic records on cryogenic landforms to better understand the association and interactions between glaciers and viscous creep of ice-rich permafrost landforms (rock glaciers) are widely missing in the region. In this paper, we reconstruct the geomorphic imprint of the Last Glacial Maximum (LGM) and the Termination I in the high Andes of the Río Limarí Basin (30–31°S) in the subtropical semiarid Andes of Chile. 74 new 10 Be surface exposure dating ages constrain the timing of glaciation, deglaciation, and glacial to periglacial transition. Glacial advances occurred first by 41.2 ± 0.6 – 35.0 ± 0.5 ka during Marine Isotope Stage 3, but probably earlier also; then, a second advance occurred during the global LGM between 24.2 ± 0.4 and 18.6 ± 0.2 ka. Deglaciation by 17.6 ± 0.2 ka left extensive hummocky moraines on the main valleys. Characteristic patterns of furrows and ridges typical of rock glaciers and solifluction superimposed on the LGM hummocky moraine indicate ice-rich permafrost in glacial deposits likely between 15.5 ± 0.3 and 13.6 ± 0.3 ka. We propose that moraines deposited by LGM debris-covered glaciers served as a niche for strong seasonal frost and permafrost creep, which substantially modified the original landforms. Finally, our results contribute to a better understanding of major transformations in an ice-rich high mountain area of the southern hemisphere where the interplay of temperature and precipitation changes drove glacial to periglacial transitions.

10Be surface exposure dating↗