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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 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Studying Crystal Growth With the Peltier Effect

Peltier interface demarcation (PID) shown useful as aid in studying heat and mass transfer during growth of crystals from molten material. In PID, two dissimilar "metals" solid and liquid phases of same material. Current pulse passed through unidirectionally solidifying sample to create rapid Peltier thermal disturbance at liquid/solid interface. Disturbance, measured by thermocouple stationed along path of solidification at or near interface, provides information about position and shape of interface.

Larsen, David J., Jr.↗
NASA NTRS1991

Uranium droplet core nuclear rocket

Uranium droplet nuclear rocket is conceptually designed to utilize the broad temperature range ofthe liquid phase of metallic uranium in droplet configuration which maximizes the energy transfer area per unit fuel volume. In a baseline system dissociated hydrogen at 100 bar is heated to 6000 K, providing 2000 second of Isp. Fission fragments and intense radian field enhance the dissociation of molecular hydrogen beyond the equilibrium thermodynamic level. Uranium droplets in the core are confined and separated by an axisymmetric vortex flow generated by high velocity tangential injection of hydrogen in the mid-core regions. Droplet uranium flow to the core is controlled and adjusted by a twin flow nozzle injection system.

Anghaie, Samim↗
NASA NTRS1992

A shear sensitive monomer-polymer liquid crystal system for wind tunnel applications

Characteristics of a liquid crystal system, comprised of a shear-sensitive cholesteric-monomer liquid crystal thin-film coated on a liquid-crystal polymer substrate, are described. The system provides stable Grandjean texture, a desirable feature for shear-stress measurements using selective reflection from the monomer liquid-crystal helix structure. Impingement of gas or air flow on the monomer liquid-crystal free surface changes the wavelength of the selective reflection for an incident white light from red toward blue with increase in the rate of gas flow. The contrast of the selectively reflected light improves considerably by providing a thin black coating of about 5 microns at the monomer-polymer interface. The coating thickness is such that the steric interactions are still sufficiently strong to maintain Grandjean texture. For a small angle of incidence of a monochromatic light, the measurement of the reflected light intensity normal to the monomer-polymer liquid-crystal interface enables the determination of the wavelength for selective reflection as a function of the gas-flow differential pressure applied in the plane of the interface. The variation of the wavelength with the pressure is linear with a slope of about 2 nm/mmHg. Furthermore, the shear-stress effects are reversible unlike for monomer liquid crystal-metal systems used for flow visualization on wind-tunnel model surfaces. The present system offers a suitable method for direct on-line measurement of shear stress field from measurements of the wavelength for selective reflection for an incident white light.

Parmar, D. S.↗
NASA NTRS1993

Explosive volcanism and the compositions of cores of differentiated asteroids

Eleven iron meteorite groups show correlations between Ni and siderophile trace elements that are predictable by distribution coefficients between liquid and solid metal in fractionally crystallizing metal magmas. These meteorites are interpreted to be fragments of the fractionally crystallized cores of eleven differentiated asteroids. Many of these groups crystallized from S-depleted magmas which we propose resulted from removal of the first partial melt (the Fe,Ni-FeS cotectic melt) by explosive pyroclastic volcanism of the type envisaged by Wilson and Keil (1991). We show that these dense, negatively buoyant melts can be driven to asteroidal surfaces due to the presence of excess pressure in the melt and the presence of buoyant bubbles of gas which decrease the density of the melt. We also show that, in typical asteroidal materials, veins will form which grow into dikes and serve as pathways for migration of melt and gas to asteroidal surfaces. Since cotectic Fe, Ni-FeS melt consists of about 85 wt pct FeS and 15 wt pct Fe, Ni, removal of small volumes of eutectic melts results in major loss of S but only minor loss of Fe,Ni, thus leaving sufficient Fe,Ni to form sizeable asteroidal cores.

Keil, Klaus↗
NASA NTRS1993

Explosive volcanism and the compositions of the cores of differentiated asteroids

Eleven iron meteorite groups showing correlations between Ni and siderophile trace elements that are predictable by distribution coefficients between liquid and solid metal of fractionally crystallizing metal magmas, are interpreted to be fragments of the fractionally crystallized cores of 11 differentiated asteroids. Many of these groups crystallized from S-depleted magmas which we propose resulted from removal of the first partial melt (a Fe,Ni-FeS cotectic) by explosive pyroclastic volcanism. It is shown that these dense, negatively buoyant melts can be driven to asteroidal surfaces by the combination of an excess pressure in the melt and the presence of buoyant bubbles of gas which decrease the bulk density of the melt. It is also shown that in typical asteroidal materials, veins will form which grow into dikes and serve as pathways for migration of melt and gas to asteroidal surfaces. Since cotectic Fe,Ni-FeS melt consists of about 85 wt. percent FeS and 15 wt. percent Fe,Ni, removal of small volumes of eutectic melts results in major loss of S but only minor loss of Fe,Ni, thus leaving sufficient Fe,Ni to form sizeable asteroidal cores.

Keil, Klaus↗
NASA NTRS2002

A Comparison of MOCLD With PLD Ba(x)Sr(1-x)TiO3 Thin Films on LaAlO3 for Tunable Microwave Applications

Historically, tunable dielectric devices using thin crystalline Ba(x)Sr(1-x)TiO3 (BST) films deposited on lattice-matched substrates, such as LaAlO3, have generally been grown using pulsed laser deposition (PLD). Highly oriented BST films can be grown by PLD but large projects are hampered by constraints of deposition area, deposition time and expense. The Metal-Organic Chemical Liquid Deposition (MOCLD) process allows for larger areas, faster turnover and lower cost. Several BST films deposited on LaAlO3 by MOCLD have been tested in 16 GHz coupled microstrip phase shifters. They can be compared with many PLD BST films tested in the same circuit design. The MOCLD phase shifter performance of 293 deg. phase shift with 53 V/micron dc bias and a figure of merit of 47 deg./dB is comparable to the most highly oriented PLD BST films. The PLD BST films used here have measured XRD full-width-at-half-maxima (FWHM) as low as 0.047 deg.. The best FWHM of these MOCLD BST films has been measured to be 0.058 deg.

VanKeuls, F. W.↗
NASA NTRS2003

A Comparison of MOCLD With PLD Ba(x)Sr(1-x)TiO3 Thin Films on LaAlO3 for Tunable Microwave Applications

Historically, tunable dielectric devices using thin crystalline Ba(x)Sr(1-x),TiO3 (BST) films deposited on lattice-matched substrates, such as LaAlO3 have generally been grown using pulsed laser deposition (PLD). Highly oriented BST films can be grown by PLD but large projects are hampered by constraints of deposition area, deposition time and expense. The Metal-Organic Chemical Liquid Deposition (MOCLD) process allows for larger areas, faster turnover and lower cost. Several BST films deposited on LaAlO, by MOCLD have been tested in 16 GHz coupled microstrip phase shifters. They can be compared with many PLD BST films tested in the same circuit design. The MOCLD phase shifter performance of 293 degree phase shift with 53 V/micron dc bias and a figure of merit of 47 degree/dB is comparable to the most highly oriented PLD BST films. The PLD BST films used here have measured XRD full-width-at-half-maxima (FWHM) as low as 0.047 degrees. The best FWHM of these MOCLD BST films has been measured to be 0.058 degrees.

VanKeuls, F. W.↗
NASA NTRS2004

New Gas Polarographic Hydrogen Sensor

Polarography is the measurement of the current that flows in solution as a function of an applied voltage. The actual form of the observed polarographic current depends upon the manner in which the voltage is applied and on the characteristics of the working electrode. The new gas polarographic H2 sensor shows a current level increment with concentration of the gaseous H2 similar to those relating to metal ions in liquid electrolytes in well-known polarography. This phenomenon is caused by the fact that the diffusion of the gaseous H2 through a gas diffusion hole built in the sensor is a rate-determining step in the gaseous-hydrogen sensing mechanism. The diffusion hole artificially limits the diffusion of the gaseous H2 toward the electrode located at the sensor cavity. This gas polarographic H2 sensor. is actually an electrochemical-pumping cell since the gaseous H2 is in fact pumped via the electrochemical driving force generated between the electrodes. Gaseous H2 enters the diffusion hole and reaches the first electrode (anode) located in the sensor cavity to be transformed into an H+ ions or protons; H+ ions pass through the electrolyte and reach the second electrode (cathode) to be reformed to gaseous H2. Gas polarographic 02 sensors are commercially available; a gas polarographic 02 sensor was used to prove the feasibility of building a new gas polarographic H2 sensor.

Dominguez, Jesus A.↗
NASA NTRS2012

Liquid Droplet Dynamics in Gravity Compensating High Magnetic Field

Numerical models are used to investigate behavior of liquid droplets suspended in high DC magnetic fields of various configurations providing microgravity-like conditions. Using a DC field it is possible to create conditions with laminar viscosity and heat transfer to measure viscosity, surface tension, electrical and thermal conductivities, and heat capacity of a liquid sample. The oscillations in a high DC magnetic field are quite different for an electrically conducting droplet, like liquid silicon or metal. The droplet behavior in a high magnetic field is the subject of investigation in this paper. At the high values of magnetic field some oscillation modes are damped quickly, while others are modified with a considerable shift of the oscillating droplet frequencies and the damping constants from the non-magnetic case.

Bojarevics, V.↗
NASA NTRS2012

Fabrication of Single Crystal MgO Capsules

A method has been developed for machining MgO crystal blocks into forms for containing metallic and silicate liquids at temperatures up to 2,400 C, and pressures up to at least 320 kilobars. Possible custom shapes include tubes, rods, insulators, capsules, and guides. Key differences in this innovative method include drilling along the crystallographic zone axes, use of a vibration minimizing material to secure the workpiece, and constant flushing of material swarf with a cooling medium/lubricant (water). A single crystal MgO block is cut into a section .5 mm thick, 1 cm on a side, using a low-speed saw with a 0.004 blade. The cut is made parallel to the direction of cleavage. The block may be cut to any thickness to achieve the desired length of the piece. To minimize drilling vibrations, the MgO block is mounted on a piece of adhesive putty in a vise. The putty wad cradles the bottom half of the entire block. Diamond coring tools are used to drill the MgO to the desired custom shape, with water used to wet and wash the surface of swarf. Compressed air may also be used to remove swarf during breaks in drilling. The MgO workpiece must be kept cool at all times with water. After all the swarf is rinsed off, the piece is left to dry overnight. If the workpiece is still attached to the base of the MgO block after drilling, it may be cut off by using a diamond cutoff wheel on a rotary hand tool or by using a low-speed saw.

Danielson, Lisa↗
NASA NTRS2006

H2 Detection via Polarography

Polarography is the measurement of the current that flows in solution as a function of an applied voltage. The actual form of the observed polarographic current depends upon the manner in which the voltage is applied and on the characteristics of the working electrode. The new gas polarographic H2 sensor shows a current level increment with concentration of the gaseous H2 similar to those relating to metal ions in liquid electrolytes in well-known polarography. This phenomenon is caused by the fact that the diffusion of the gaseous H2 through a gas diffusion hole built in the sensor is a rate-determining step in the gaseous-hydrogen sensing mechanism. The diffusion hole artificially limits the diffusion of the gaseous H2 toward the electrode located at the sensor cavity. This gas polarographic H2 sensor is actually an electrochemical-pumping cell since the gaseous H2 is in fact pumped via the electrochemical driving force generated between the electrodes. Gaseous H2 enters the diffusion hole and reaches the first electrode (anode) located in the sensor cavity to be transformed into an H ions or protons; H ions pass through the electrolyte and reach the second electrode (cathode) to be reformed to gaseous H2. Gas polarographic O2 sensors are commercially available; a gas polarographic O2 sensor was used to prove the feasibility of building a new gas polarographic H2 sensor.

Dominquez, Jesus↗
NASA NTRSDate not supplied

Comparison of In-situ Near Infrared Melt Pool Imagery to Optical Microscopy Measurements

Additive manufacturing (AM) is a rapidly growing technology. An area of major importance is the integrity and repeatability of AM parts. The goal is to reduce obstacles to certify AM built parts to allow for use in critical aerospace applications. In-situ nondestructive evaluation sensors can be used for build assessment and can potentially play a key role in certifying AM parts. For example, melt pool features are understood to have a strong correlation to microstructural defects and the use of a near infrared (NIR) camera can be used to record the melt pool, cooling areas, and temperature gradients during the build. This work explores the use of a low cost NIR camera to obtain single line track imagery of the Ti-6Al-4V melt pools for various processing parameters. The NIR camera is radiometrically calibrated and configured in-line with the laser source to obtain high resolution imagery of the melt pool shape and dynamics. The challenge to measure melt pool shapes is to identify the transition points between the metal solid to liquid phase. Factors for melt pool measurements such as thermal camera pixel resolution, surface emissivity, and blurring due to the laser beam movement are discussed. Lastly, the melt pool imagery are compared to optical microscopy measurements for validation.

additive manufacturing↗
DOE OSTI2024

High efficiency active environmental sampling of chemical traces

A method of sample collection includes collecting an analyte from a sampling surface using a rapidly curable liquid gel comprising one or more metal particles; co-aggregating the one or more metal particles from the rapidly curable liquid gel and the analyte from the sampling surface; and rapidly curing the rapidly curable liquid gel. The composition and sample preparation conditions may facilitate improved collection efficiency of analytes during environmental and forensic evidence sampling. In addition, the composition and sample preparation conditions may facilitate enhanced detection and identification of the analyte using e.g., Surface Enhanced Raman Spectrometry (SERS).

Junghans, Ann↗
DOE OSTI2025

The Chemistry, Formation and Passivation of Solid-Electrolyte Interphase (SEI) from FSI- Breakdown at Li-metal Potential

LiFSI-based liquid electrolytes are promising for realizing high Coulombic efficiency (CE) and long cycle life of next-generation high-energy Li metal battery. Nevertheless, the fundamentals of both the chemistry and formation of solid-electrolyte interphase (SEI) in these electrolytes have remained elusive. Herein, we extensively combine electrochemistry and X-ray photoelectron spectroscopy (XPS) to illustrate the reaction pathways of electrolyte decomposition, especially FSI- breakdown, as well as the dissolution trend of various inorganic SEI components. The SEI-forming reactions at Cu/electrolyte interface manifest a potential (E) dependence, driven by direct electron-transfer (ET) and Li underpotential-deposition (Li UPD) at high and low E regions, respectively. By closely correlating the XPS data obtained with and without solvent washing, we demonstrate that not all the products derived from SEI reactions are incorporated into forming a passivating surface layer, with a notable portion dissolving into liquid electrolyte instead. Importantly, high-CE electrolyte dictated by the chemical identity of solvent, is found to exhibit minimized interfacial reactivity of SEI formation enabling more effective interphasial passivation, via preferential integration of passivating ingredients such as LiF. Overall, this work formulates a systematic understating of bridging the SEI chemistry, formation and passivation while identifying key characteristics of high-performance electrolyte for guiding future design.

Bao, Zhenan [SLAC National Accelerator Laboratory ↗
DOE OSTI2022

Application of Ionic Liquids for the Recycling and Recovery of Technologically Critical and Valuable Metals

Population growth has led to an increased demand for raw minerals and energy resources; however, their supply cannot easily be provided in the same proportions. Modern technologies contain materials that are becoming more finely intermixed because of the broadening palette of elements used, and this outcome creates certain limitations for recycling. The recovery and separation of individual elements, critical materials and valuable metals from complex systems requires complex energy-consuming solutions with many hazardous chemicals used. Significant pressure is brought to bear on the improvement of separation and recycling approaches by the need to balance sustainability, efficiency, and environmental impacts. Due to the increase in environmental consciousness in chemical research and industry, the challenge for a sustainable environment calls for clean procedures that avoid the use of harmful organic solvents. Ionic liquids, also known as molten salts and future solvents, are endowed with unique features that have already had a promising impact on cutting-edge science and technologies. This review aims to address the current challenges associated with the energy-efficient design, recovery, recycling, and separation of valuable metals employing ionic liquids.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Balancing solvation: stabilizing lithium metal batteries via optimized cosolvents for ionic-liquid electrolytes

In this study, we examined three cosolvents with distinct solvation capabilities for ionic-liquid electrolytes based on 1-methyl-1-propyl pyrrolidinium bis(fluorosulfonyl)imide (Py13FSI). We demonstrate that 1,1,1-trifluoro-2-(2-(2-(2,2,2-trifluoroethoxy)ethoxy)ethoxy)ethane (FDG) notably enhances the cycle life of Py13FSI-based electrolytes, outperforming 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropylether (TTE) and diglyme (DG). Electrochemical and surface analyses showed that this improvement could be attributed to the formation of a favorable cathode interphase, promoting efficient Li+ transport with reduced overpotential. Spectroscopic techniques (FTIR, Raman, and NMR spectroscopy) and molecular dynamics simulations revealed that cosolvents with varying solvation abilities can influence the solvation structures in Py13FSI-based electrolytes. The mild solvating strength and lithium stability of FDG are key contributors to its effectiveness. Conversely, DG, a strong solvating solvent, destabilized the Py13FSI-DG electrolyte at the lithium metal anode, while TTE, a non-solvating solvent, failed to enhance lithium transport or form a stable cathode interphase. Our findings highlight that balanced solvation exerted by the cosolvents is critical for forming a stable electrolyte–cathode interface, potentially through FSI decomposition. This study offers valuable insights into the development of durable ionic-liquid electrolytes, emphasizing the importance of selecting cosolvents with optimal solvation properties.

Li, Xinlin [Argonne National Laboratory (ANL), Arg↗
DOE OSTI2023

Understanding the mechanisms of anisotropic dissolution in metal oxides by applying radiolysis simulations to liquid-phase TEM

Iron-based redox-active minerals are ubiquitous in soils, sediments, and aquatic systems. Their dissolution is of great importance for microbial impacts on carbon cycling and the biogeochemistry of the lithosphere and hydrosphere. Despite its widespread significance and extensive prior study, the atomic-to-nanoscale mechanisms of dissolution remain poorly understood, particularly the interplay between acidic and reductive processes. Here, we use in situ liquid-phase-transmission electron microscopy (LP-TEM) and simulations of radiolysis to probe and control acidic versus reductive dissolution of akaganeite (β–FeOOH) nanorods. Informed by crystal structure and surface chemistry, the balance between acidic dissolution at rod tips and reductive dissolution at rod sides was systematically varied using pH buffers, background chloride anions, and electron beam dose. We find that buffers, such as bis-tris, effectively inhibited dissolution by consuming radiolytic acidic and reducing species such as superoxides and aqueous electrons. In contrast, chloride anions simultaneously suppressed dissolution at rod tips by stabilizing structural elements while promoting dissolution at rod sides through surface complexation. Dissolution behaviors were systematically varied by shifting the balance between acidic and reductive attacks. The findings show LP-TEM combined with simulations of radiolysis effects can provide a unique and versatile platform for quantitatively investigating dissolution mechanisms, with implications for understanding metal cycling in natural environments and the development of tailored nanomaterials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗