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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Thermodynamic Analysis of Thermo-vacuum Clothes Drying Operation

Clothes drying accounts for a significant amount of energy consumed in residential and commercial sectors. A thermal vacuum clothes drying technology (TVCD) is proposed as an advanced clothes dryer which can significantly reduce the energy requirements by expediting the drying process. In the conventional convective clothes dryer, hot dry air is introduced into the drum which gets in direct contact to dry the clothes. This process is energy inefficient since the significant amount of heat and the water carried out with the exhaust stream are wasted. In contrast to the conventional convective drying technique, the drying mechanism of TVCD is through nucleate boiling at low temperature due to reduced vessel pressure. The process is not only efficient but also reduces the required time for drying. The objective of this paper is to develop a comprehensive thermodynamic model to predict the transient drying process of TVCD. The three-stage system model including the detail analysis of individual components is capable of simulating the variation of the water content in the textile under various operational conditions. The preliminary results show that the drying time of 3 lb textile from 70% to 2.5% in TVCD is approximately four times less than the time required in the conventional clothes dryer. Parametric studies are carried out to understand the effect of operation conditions and component geometry on the system performance. Energy consumption of the system is also analyzed.

Yang, Cheng-Min↗
DOE OSTI2023

Recent advances in describing and driving crystal nucleation using machine learning and artificial intelligence

With the advent of faster computer processors and especially graphics processing units (GPUs) over the last few decades, the use of data-intensive machine learning (ML) and artificial intelligence (AI) has increased greatly, and the study of crystal nucleation has been one of the beneficiaries. In this study, we outline how ML and AI have been applied to address four outstanding difficulties of crystal nucleation: how to discover better reaction coordinates (RCs) for describing accurately non-classical nucleation situations; the development of more accurate force fields for describing the nucleation of multiple polymorphs or phases for a single system; more robust identification methods for determining crystal phases and structures; and as a method to yield improved course-grained models for studying nucleation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2012

Buckyball Nucleation of HiPco Tubes

The purpose of this innovation is to enhance nucleation of single-wall nanotubes (SWNTs) in the HiPco process, selectively producing 10,10 tubes, something which until now has not been thought possible. This is accomplished by injecting C60, or a derivative of C60, solubilized in supercritical CO2 together with a transition metal carboneal cocatalyst into the HiPco reactor. This is a variant on the supercritical disclosure. C60 has never been used to nucleate carbon nanotubes in the gas phase. C60 itself may not have adequate solubility in supercritical CO2. However, fluorinated C60, e.g., C60F36, is easy to make cheaply and should have much enhanced solubility.

Smalley, Richard E.↗
DOE OSTI2021

Fluoropolymer Aging Assessments

Fluoropolymer (FP) binders are commonly only a few percent of polymer bonded explosive compositions but they are essential for the mechanical integrity of the part. Because we are using newly manufactured binders, we need to understand how lot variations might affect processing, aging, and mechanical properties. Time, temperature and radiation induce phase changes in fluoropolymers. These phase changes can rearrange the polymer causing crystalline domains to nucleate and grow that can alter mechanical properties. These studies quantify the aging process so that it may be cross correlated with changes in the adhesion, strength, and other properties important for performance.

36 MATERIALS SCIENCE↗
NASA NTRS2000

The Electrostatic Levitation Facility at NASA's Marshall Space Flight Center

Containerless processing is an important area of research in materials science. Electrostatic levitation (ESL) represents an emerging technology which permits containerless processing in a vacuum environment. NASA's Marshall Space Flight Center (MSFC) established a levitation facility to provide a critical resource to the microgravity materials science research community to continue and enhance ground-based research in the support of the development of flight experiments during the transition to Space Station. During ESL processing, charged specimens are levitated in the electrostatic field produced by the system's electrodes. Three sets of positioning electrodes represent the heart of the MSFC system. Two dual-axis position sensitive detectors provide input for the PID control-loop computer. Sample position is maintained by adjusting the control voltages for the power supplies of the positioning electrodes. A UV source refreshes the charge on specimens during processing via the photoelectric effect. Lasers permit sample heating independent of positioning. The processing chamber typically operates under vacuum condition approximately = 10(exp -7) Torr. Electrostatic levitation provides a materials science research tool for investigations of refractory solids and melts. Topics of investigation include thermophysical properties, phase equilibria, metastable phase formation, undercooling and nucleation, time-temperature-transformation diagrams and other aspects of materials processing. Current capabilities and recent results of processing studies for metals, alloys and oxides will be reviewed.

Rogers, Jan R.↗
NASA NTRS1997

Emulsion Droplet Combustion in Microgravity: Water/Heptane Emulsions

This presentation reviews a series of experiments to further examine parametric effects on sooting processes of droplet flames in microgravity. The particular focus is on a fuel droplet emulsified with water, specifically emulsions of n-heptane as the fuel-phase and water as the dispersed phase. Water was selected as the additive because of its anticipated effect on soot formation, and the heptane fuel phase was chosen to theoretically reduce the likelihood of microexplosions because its boiling point is nearly the same as that of water: 100 C for water and 98 C for heptane. The water content was varied while the initial droplet diameter was kept within a small range. The experiments were carried out in microgravity to reduce the effects of buoyancy and to promote spherical symmetry in the burning process. Spherically symmetric droplet burning is a convenient starting point for analysis, but experimental data are difficult to obtain for this situation as evidenced by the fact that no quantitative data have been reported on unsupported emulsion droplet combustion in a convection-free environment. The present study improves upon past work carried out on emulsion droplet combustion in microgravity which employed emulsion droplets suspended from a fiber. The fiber can be instrusive to the emulsion droplet burning process as it can promote coalescence of the dispersed water phase and heterogeneous nucleation on the fiber. Prior work has shown that the presence of water in liquid hydrocarbons can have both beneficial and detrimental effects on the combustion process. Water is known to reduce soot formation and radiation heat transfer to combustor walls Gollahalli (1979) reduce flame temperatures and thereby NOx emissions, and encourage secondary droplet atomization or microexplosion. Water also tends to retard ignition and and promote early extinction. The former effect restricted the range of water volume fractions as discussed below.

Avedisian, C. Thomas↗
DOE OSTI2022

Engineering microstructure to improve coercivity of bulk MnBi magnet

MnBi is a candidate material for high-temperature magnets because of its increasing coercivity with increasing temperatures up to 255 °C. However, most efforts in fabricating bulk MnBi magnets have run into the problem of preserving the coercivity (H cj) of its feedstock powders. About 70% of powder’s H cj would be lost during the densification process. Our micromagnetic modeling shows that the coercivity mechanism of the MnBi bulk magnet is controlled by nucleation of the reversal magnetization domains, and the large H cj loss that occurred during the powder consolidation process can be attributed to the inter-grain magnetic coupling. To attain a high H cj , the grains in the MnBi bulk magnet must be separated with a non-magnetic grain boundary phase (GBP). To validate this GBP hypothesis, we engineered MnBi bulk magnets with two different types of GBP. The first type of GBP was created in-situ by precipitating excessive Bi from the grains; the second type was created ex-situ by coating silicates on the feedstock powders before the consolidation. While both GBP work, the ex-situ approach resulted in a better H cj due to a more uniform GBP distribution. We report the H cj loss was reduced from 70% to 15%, and the (BH)max of a warm sintered bulk magnet reached 8.9 MGOe.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Spatiotemporal Thermal Coupling in VO 2 Device Arrays

Correlated oxides such as VO 2 exhibit an electrically driven insulator–metal transition (IMT) that underlies their promise for neuromorphic and memory devices. Yet the IMT is not a uniform bulk process but a spatiotemporal phenomenon in which local heating nucleates filaments, contracts or dissolves them with the electric field, and couples to the environment. In this work, we directly image the VO 2 IMT dynamics by mid-wave infrared, thermography synchronized with electrical transport, resolving device temperature with micrometer spatial and microsecond temporal resolution. At the single-device level, we capture the full cycle of filament nucleation, contraction, and relaxation during current/voltage-driven resistive switching. At the array level, we show that heat propagates across etched gaps with an effective length scale of ∼131 µm, enabling cooperative behaviors among electrically isolated devices. Short-range distanced devices exhibit mutual filament attraction and sequential dissolution, while long-range distanced devices differentiate into distinct roles: drivers that initiate switching, cooperative responders that undergo assisted self-oscillations, and passive reporters that record the thermal field. Furthermore, these results reframe thermal crosstalk, long regarded as parasitic, as an intrinsic coupling channel and design principle for organizing collective switching behaviors, with direct implications for emergent circuit functionality in neuromorphic and unconventional computing architectures.

coupling↗
DOE OSTI2025

Soft Nanoconfinement Nucleates and Stabilizes Ultrasmall Amorphous Calcium Carbonate from Aggregation

Organisms use soft confinement structures, such as vesicles and compartments, to direct the nucleation of calcium carbonate (CaCO 3 ) and its subsequent processes during biomineralization. Despite recent efforts elucidating confinement’s effects on CaCO 3 polymorph selection, we still poorly understand how the size and distribution of CaCO 3 are controlled within soft confinement. Here, using a size-controlled nanoemulsions system made from isooctane, Span 80, Tween 80, and aqueous solutions, we studied CaCO 3 formation in soft confinement. Small angle X-ray scattering (SAXS) confirmed that a 72 nm aqueous core in nanoemulsions served as the confined space for CaCO 3 formation. Unlike the ~ 50 nm CaCO 3 particles that formed in the unconfined solution, small angle neutron scattering (SANS) and transmission electron microscope (TEM) showed that ultrasmall and amorphous calcium carbonate precipitated within soft confinement and did not exhibit any aggregation/coalescence of nanoparticles even after 24 hrs of reaction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

The Role of Ice Splintering on Microphysics of Deep Convective Clouds Forming Under Different Aerosol Conditions: Simulations Using the Model With Spectral Bin Microphysics

Observations during the Ice in Clouds Experiment-Tropical (ICE-T) field experiment show that the ice particles concentration in a developing deep convective clouds at the level of T = -15 °C reached about 500 L -1 , that is, many orders higher than that of ice-nucleating particle. To simulate microphysics of these clouds, the 2-D Hebrew University Cloud model (HUCM) with spectral bin microphysics was used in which two main types of ice multiplication mechanisms were included in addition to the Hallet-Mossop mechanism. In the first ice multiplication mechanism ice splinters form by drop freezing and drop-ice collisions. Ice multiplication of this type dominates during developing stage of cloud evolution, when liquid water content is significant. At later stage when clouds become nearly glaciated, ice crystals are produced largely by ice splintering during ice-ice collisions (the second ice multiplication mechanism). Simulations show that droplet size distributions, as well as size distributions of ice particles, agree well with the measurements during ICE-T. Simulations with different cloud condensation nuclei concentrations show the existence of the “optimum” cloud condensation nuclei concentration (or droplet concentration), at which concentration of ice splinters reaches maximum. In these simulations ice nucleation caused by the direct formation of ice crystals upon ice-nucleating particles, as well as the Hallett-Mossop process, has a negligible contribution to the ice crystal concentration.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Effects of Pollen on Hydrometeors and Precipitation in a Convective System

Anemophilous (wind-driven) pollen is one type of primary biological aerosol particle, which can rupture under high humidity conditions and form smaller sub-pollen particles (SPPs). Both pollen and SPPs can reach the upper troposphere under convective conditions, acting as cloud condensation nuclei (CCN) and ice nucleating particles (INPs), thus influencing cloud formation and precipitation. However, the impacts of these biological aerosols on cold cloud formation and local climate remain unclear as there are large uncertainties on their emission flux and ice nucleating abilities. Here, we incorporate pollen emission and rupture processes in the Weather Research and Forecasting Model with Chemistry (WRF-Chem) simulations and update the Morrison microphysics scheme within WRF-Chem using aerosol-aware INP parameterizations to account for pollen in addition to other anthropogenic and biogenic aerosol. INP parameterizations for pollen and SPP are derived from laboratory experiments. When including pollen rupture rates as observed in a series of chamber studies, SPP concentrations increase, leading to an increase of cloud ice and water by up to 50% and potentially extending the duration of the convective system. Among all simulated hydrometeors, graupel and raindrops exhibit the largest enhancements from the inclusion of SPPs, with intensifying precipitation at the backside of the convective system and a greater spatial extent. Sensitivity simulations indicate that SPPs have a greater effect on cloud microphysical processes than whole pollen grains, and further observational evidence is needed to constrain these processes.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Investigating Aerosol Hygroscopicity in the Subcloud Transition Zone and at the Surface in the Southern Great Plains

Aerosols beneath a cloud base, a subcloud transition zone (SCTZ), are key to understand both the aerosol-cloud interaction and aerosol-radiation interactions. Lidars have been the primary means of observing aerosols in the SCTZ by virtue of enhanced light scattered by aerosol particles. The enhanced light maybe caused by several factors: the aerosol swelling effect due to hygroscopicity under high relative humidity, cloud 3-dimensional (3D) effect, aerosol nucleation into cloud droplets, etc. While each factor and process has been known, their relative contributions are much poorly quantified. This study explores the hygroscopicity and optical properties of aerosols in the SCTZ and at ground level in the Southern Great Plains (SGP) region. Utilizing comprehensive observational data from the U.S. Department of Energy's Atmospheric Radiation Measurement at the Oklahoma SGP site, including ground-based aerosol measurements and Raman lidar profiles from April 2021 to April 2022, this study extensively analyzes the influence of aerosol hygroscopic growth and cloud fragments on aerosol optical properties. Distinct seasonal variations in aerosol hygroscopic characteristics are revealed. At the ground level, aerosols in autumn and winter exhibit stronger hygroscopicity due to a higher proportion of inorganic content than summer. In the SCTZ, aerosols during summer show enhanced backscatter due to strong cloud fragmentation effects, with numerous cloud fragments elevating hygroscopicity beyond that observed in autumn and winter. These insights are crucial for understanding the interactions between aerosols at the surface and cloud layers, evaluating cloud condensation nuclei beneath clouds, and their implications for atmospheric radiation and climate modeling.

Hu, Rong [Beijing Normal University, Beijing (Chin↗
DOE OSTI2021

Dust Formation and Growth in Supernovae Explosions

Dust is a multi-messenger probe able to explore the dynamics of the Supernova Engine. The yield and composition of grains formed in the supernova explosion are dependent on the initial explosion characteristics of the progenitor and on the explosion mechanism. Using dust as a prove, the dynamics of dust formation and growth is modeled in a diverse set of Core-Collapse Supernovae Explosions (CCSNe). The progenitor mass, explosion energy engine type, and composition are varied across 72 models. The explosion is evolved using a 1-D Lagrangian Hydro-dynamical code (hydrocodes) to roughly 3 years. A multigrain nucleation and dust growth model is used to post process the hydrocode results and model grain formation and growth. The results show an earlier onset of grain formation, a larger silicate grain abundance, and smaller grain sizes in high explosion energy models.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Evaluation of UKESM aerosol size and composition using ATom measurements indicates missing marine aerosol formation mechanisms

Atmospheric aerosols influence climate through their interactions with radiation and clouds, yet large uncertainties remain in their simulation by global models. This study evaluates the United Kingdom Earth System Model version 1.1 (UKESM1.1) using global-scale aircraft observations from the Atmospheric Tomography (ATom) mission, focusing on aerosol lifecycle processes in the remote marine atmosphere. We assess model performance in simulating aerosol precursor vapours, number size distributions, chemical composition, and environmental conditions. Several process improvements are tested, including sulfuric acid-ammonia nucleation, ammonium nitrate scheme, methanesulfonic acid condensation, and low-temperature isoprene-derived secondary organic aerosol formation. Model biases differ significantly between the upper troposphere (UT) and the marine boundary layer (MBL). In the UT, UKESM1.1 overestimates nucleation and Aitken mode particles while underestimating accumulation mode, indicating insufficient growth. In the MBL, the model overestimates primary aerosols (e.g. seasalt) and precursor gases but underestimates nucleation and Aitken mode particles, even after incorporating updated nucleation and ammonium nitrate scheme. The persistence of low aerosol number concentrations, despite overestimated precursors, suggests missing formation pathways likely involving other species such as iodine, amines, and organic vapours. These limitations result in an unbalanced cloud condensation nuclei budget that over-relies on primary emissions. Sensitivity tests reveal that model outputs are strongly influenced by dimethyl sulfide emissions and vapour condensation schemes. Our results highlight the need for future model development to prioritise mechanistic representation of currently missing aerosol sources, rather than relying on empirical tuning, to improve aerosol-climate interaction estimates.

He, Xu-Cheng [Univ. of Cambridge (United Kingdom);↗
NASA NTRS1978

EPRI-NASA Cooperative Project on Stress Corrosion Cracking of Zircaloys

Examinations of the inside surface of irradiated fuel cladding from two reactors show the Zircaloy cladding is exposed to a number of aggressive substances, among them iodine, cadmium, and iron-contaminated cesium. Iodine-induced stress corrosion cracking (SCC) of well characterized samples of Zircaloy sheet and tubing was studied. Results indicate that a threshold stress must be exceeded for iodine SCC to occur. The existence of a threshold stress indicates that crack formation probably is the key step in iodine SCC. Investigation of the crack formation process showed that the cracks responsible for SCC failure nucleated at locations in the metal surface that contained higher than average concentrations of alloying elements and impurities. A four-stage model of iodine SCC is proposed based on the experimental results and the relevance of the observations to pellet cladding interaction failures is discussed.

Cubicciotti, D.↗
NASA NTRS1992

Observation of alloy solidification using high-speed video

A high-speed video instrumentation system was used to observe solidification of undercooled Ti-51 at. pct Al. The camera system developed by Battelle is capable of operation at rates up to 12,000 frames per second. The system digitizes and stores video images acquired by a 64 x 64 pixel silicon photodiode array. In a joint effort with Vanderbilt University the camera was used to observe three transformations of the undercooled alloys, using containerless processing by electromagnetic levitation. The first was solidification where nucleation was induced at an undercooling of 9 percent Tl, where Tl is the liquidus temperature of the alloy, and the second was solidification where nucleation was spontaneous at an undercooling of 15 percent Tl. The third event was a solid-state nucleation and growth transformation following the solidification at an undercooling of 15 percent Tl.

Bassler, B. T.↗
NASA NTRS1999

Composition Effects on Phase Formation and Stability

In this report, results from experimental studies of the composition dependence of nucleation are presented. A model for nucleation that takes simultaneous account of the interfacial attachment processes at the growing cluster interface and diffusion into the region surrounding the developing cluster is presented and numerical results are discussed.

Kelton, Kenneth F.↗