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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 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Soot formation in pyrolysis of acetylene, allene and 1,3-butadiene

The formation of soot behind reflected shock waves in argon-diluted mixtures of acetylene, allene, and 1,3-butadiene was investigated by monitoring the attenuation of a laser beam in both the visible (632.8 nm) and the infrared (3.39 microns) regions of the spectrum. The experiments utilized temperatures ranging from 1500-3100 K, reflected shock pressures of 0.3-7.0 bar, and total carbon atom concentrations of 2-20 x 10 to the 17th atoms/cu cm. A bell-shaped dependence of soot yield on temperature was observed during the pyrolysis of all three compounds, which was similar to that previously found for toluene. For acetylene, the decrese in total pressure was found to shift the soot bell to higher temperatures with a significant increase in the maximum soot yield. A computer simulation for acetylene pyrolysis suggested that the reactions between C2H3, C4H3, and C4H4 may be those which lead to the formation of aromatic structures. In addition, it was found that soot is formed much faster and in much larger quantities from allene than from 1,3-butadiene.

Frenklach, M.↗
NASA NTRS1989

Experimental studies of gas trapping in amorphous ice and thermal modelling of comets: Implications for Rosetta

The trapping of mixtures of CO, CH4, N2 and Ar in amorphous water ice was studied experimentally. It is shown that the ice particles could not have been formed at a higher temperature and, subsequently, cool down. Experiments where ice was deposited at elevated temperatures, then cooled down and gas was flowed into the ice, showed that the amount of trapped gas depends only on the highest temperature at which the ice was formed, or resided, prior to cooling and gas flow into it. Consequently, the cometary ice had to be formed at approx. 48 K and the ice is therefore amorphous. The thermal profile of a comet in Halley's orbit was calculated, including the build-up of an insulating dust layer. It was found that an insulating dust layer a few cm thick is enough to choke most of the water emission from the surface. A similar thermal model was calculated for comet P/Temple-1, a candidate for both CRAF and Rosetta (CNSR) missions. The temperature at a depth of 10 m is approx. 160 K for all models considered and, hence, the ice at this depth is crystalline. A crystalline ice layer 40 to 240 m thick was found to overly the gas-laden amorphous ice. Consequently, it should be difficult for the probes of the two comet missions to sample pristine amorphous ice, unless they are aimed at the bottom of an active crater.

Bar-Nun, Akiva↗
NASA NTRS1991

A comparative flow visualization study of thermocapillary flow in drops in liquid-liquid systems

Experiments are performed to visualize thermocapillary flow in drops in an immiscible host liquid. The host liquid used is silicone oil. Drops of three different liquids are used, viz, vegetable oil, water-methanol mixture anad pure methanol. Clear evidence of thermocapillary flow is seen in vegetable oil drops. For a mixture of water and methanol (approximately 50-50 by weight), natural convection is seen to dominate the flow outside the drop. Pure methanol drops exhibit thermocapillary flow, but dissolve in silicone oil. A small amount of water added to pure methanol significantly reduces the dissolution. Flow oscillations occur in this system for both isothermal and non-isothermal conditions.

Balasubramaniam, R.↗
NASA NTRS1992

Lunar mining of oxygen using fluorine

Experiments during the first year of the project were directed towards generating elemental fluorine via the electrolysis of anhydrous molten fluorides. Na2SiF6 was dissolved in either molten NaBF4 or a eutectic (minimum-melting) mixture of KF-LiF-NaF and electrolyzed between 450 and 600 C to Si metal at the cathode and F2 gas at the anode. Ar gas was continuously passed through the system and F2 was trapped in a KBr furnace. Various anode and cathode materials were investigated. Despite many experimental difficulties, the capability of the process to produce elemental fluorine was demonstrated.

Burt, Donald M.↗
NASA NTRS1994

Biotransformation of an uncured composite material

The feasibility of biologically degrading prepreg wastes was studied. The work was conducted with the intention of obtaining baseline data that would facilitate the achievement of two long-range goals. These goals are: (1) the biological remediation of the hazardous components in the prepreg wastes, and (2) providing the potential for recycling the prepreg waste fibers. The experiments examined a prepreg that employs an bismaleimide resin system. Initial results demonstrated an obvious deterioration of the prepreg material when incubated with several bacterial strains. The most active cultures were identified as a mixture of 'Bacillus cereus' and 'Pseudomonas sp'. Gas chromatography analyses revealed seven primary compounds in the resin mixture. Biotransformation studies, using the complete prepreg material, demonstrated on obvious loss of all seven organic compounds. Gas chromatography-mass spectrometry analyses resulted in structure assignments for the two primary components of the resin. Both were analogs of Bisphenol A; one being bismaleimide, and the other being Bisphenol A containing a diglycidyl moiety. The 'diglycidyl analog' was purified using thin-layer chromatography and the biotransformation of this compound (at 27 ug/ml bacterial culture) was monitored. After a seven-day incubation, approximately 40% of the organic compound was biotransformed. These results demonstrate the biotransformation of the prepreg resin and indicate that biological remediation of the prepreg wastes is feasible.

Welsh, Clement J.↗
NASA NTRS1998

Droplet Combustion Experiment (DCE)

The first space-based experiments were performed on the combustion of free, individual liquid fuel droplets in oxidizing atmospheres. The fuel was heptane, with initial droplet diameters ranging about from 1 mm to 4 mm. The atmospheres were mixtures of helium and oxygen, at pressures of 1.00, 0.50 and 0.25 bar, with oxygen mole fractions between 20% and 40%, as well as normal Spacelab cabin air. The temperatures of the atmospheres and of the initial liquid fuel were nominally 300 K. A total of 44 droplets were burned successfully on the two flights, 8 on the shortened STS-83 mission and 36 on STS-94. The results spanned the full range of heptane droplet combustion behavior, from radiative flame extinction at larger droplet diameters in the more dilute atmospheres to diffusive extinction in the less dilute atmospheres, with the droplet disappearing prior to flame extinction at the highest oxygen concentrations. Quasisteady histories of droplet diameters were observed along with unsteady histories of flame diameters. New and detailed information was obtained on burning rates, flame characteristics and soot behavior. The results have motivated new computational and theoretical investigations of droplet combustion, improving knowledge of the chemical kinetics, fluid mechanics and heat and mass transfer processes involved in burning liquid fuels.

Haggard, John B., Jr.↗
DOE OSTI2025

Characterization of W production during ICRF operations: experiments and modeling

For successfully heating plasma with waves in the ion cyclotron range of frequencies (ICRFs), mitigating impurity production is just as crucial as maximizing power coupling, especially in high-Z environments. ICRF can effectively deposit energy on ions, modify turbulence-driven transport, and enhance fusion reaction efficiency, but only when its power coupling has minimal impact on impurity production. To do so, one must rely on a toroidal array of at least three active elements excited with appropriate phasing and power ratio to reduce the currents induced on the antenna frame below levels critical for physical sputtering. In contrast to classic two-strap antennas, which are optimized for dipole phasing with equal power on both straps, three-strap antennas in ASDEX Upgrade (AUG)—but also four-strap antennas in JET, Alcator C-Mod, SPARC and ITER—offer the possibility to act also on the power ratio between the central and outer straps. With optimal settings, impurity production can be reduced substantially, making the ICRF compatible with the high-Z wall. This paper explores the characteristics of the AUG three-strap antennas in terms of impurity production, as well as the key role of plasma composition in this process. Numerical simulations were performed using SSWICH and Petra-M (finite element codes) to quantify impurity production and compare with experimental results. Energies of ions falling on antenna limiters (measured with probes) are well predicted by both codes. These tools are then used to further describe the source of the impurity, namely the gross erosion of tungsten from an ICRF antenna, for different plasma mixtures. Results are also compared to spectroscopy data. Ultimately, we show that deleterious effects of the ICRF on plasma surface interactions will be weaker in plasmas containing larger fractions of highly ionized heavier low-Z impurity, which is typically relevant for experiments relying on impurity seeding.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Design principles from multiscale simulations to predict nanostructure in self-assembling ionic liquids

Molecular dynamics simulations (up to the nanoscale) were performed on the 3-methyl-1-pentylimidazolium ionic liquid cation paired with three anions; chloride, nitrate, and thiocyanate as aqueous mixtures, using the effective fragment potential (EFP) method, a computationally inexpensive way of modeling intermolecular interactions. The simulations provided insight (preferred geometries, radial distribution functions and theoretical proton NMR resonances) into the interactions within the ionic domain and are validated against 1 H NMR spectroscopy and small- and wide-angle X-ray scattering experiments on 1-decyl-3-methylimidazolium. Ionic liquids containing thiocyanate typically resist gelation and form poorly ordered lamellar structures upon mixing with water. Conversely, chloride, a strongly coordinating anion, normally forms strong physical gels and produces well-ordered nanostructures adopting a variety of structural motifs over a very wide range of water compositions. Nitrate is intermediate in character, whereby upon dispersal in water it displays a range of viscosities and self-assembles into nanostructures with considerable variability in the fidelity of ordering and symmetry, as a function of water content in the binary mixtures. The observed changes in the macro and nanoscale characteristics were directly correlated to ionic domain structures and intermolecular interactions as theoretically predicted by the analysis of MD trajectories and calculated RDFs. Specifically, both chloride and nitrate are positioned in the plane of the cation. Anion to cation proximity is dependent on water content. Thiocyanate is more susceptible to water insertion into the second solvent shell. Experimental 1 H NMR chemical shifts monitor the site-specific competition dependence with water content in the binary mixtures. As a result, thiocyanate preferentially sits above and below the aromatic ring plane, a state disallowing interaction with the protons on the imidazolium ring.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1996

Quick-Mixing Studies Under Reacting Conditions

The low-NO(x) emitting potential of rich-burn/quick-mix/lean-burn )RQL) combustion makes it an attractive option for engines of future stratospheric aircraft. Because NO(x) formation is exponentially dependent on temperature, the success of the RQL combustor depends on minimizing high temperature stoichiometric pocket formation in the quick-mixing section. An experiment was designed and built, and tests were performed to characterize reaction and mixing properties of jets issuing from round orifices into a hot, fuel-rich crossflow confined in a cylindrical duct. The reactor operates on propane and presents a uniform, non-swirling mixture to the mixing modules. Modules consisting of round orifice configurations of 8, 9, 10, 12, 14, and 18 holes were evaluated at a momentum-flux ratio of 57 and jet-to-mainstream mass-flaw ratio of 2.5. Temperatures and concentrations of O2, CO2, CO, HC, and NO(x) were obtained upstream, down-stream, and within the orifice plane to determine jet penetration as well as reaction processes. Jet penetration was a function of the number of orifices and affected the mixing in the reacting system. Of the six configurations tested, the 14-hole module produced jet penetration close to the module half-radius and yielded the best mixing and most complete combustion at a plane one duct diameter from the orifice leading edge. The results reveal that substantial reaction and heat release occur in the jet mixing zone when the entering effluent is hot and rich, and that the experiment as designed will serve to explore satisfactorily jet mixing behavior under realistic reacting conditions in future studies.

Leong, May Y.↗
DOE OSTI2016

Synthesis, crystal structure, and magnetism of A{sub 2}Co{sub 12}As{sub 7} (A=Ca, Y, Ce–Yb)

Ternary intermetallics, A{sub 2}Co{sub 12}As{sub 7} (A=Ca, Y, Ce–Yb), have been synthesized by annealing mixtures of elements in molten Bi at 1223 K. The materials obtained crystallize in the P6{sub 3}/m variant of the Zr{sub 2}Fe{sub 12}P{sub 7} structure type. The unit cell volume shows a monotonic decrease with the increasing atomic number of the rare-earth metal, with the exception of Ce-, Eu-, and Yb-containing compounds. An examination of these outliers with X-ray absorption near edge structures (XANES) spectroscopy revealed mixed valence of Ce, Eu, and Yb, with the average oxidation states of +3.20(1), +2.47(5), and +2.91(1), respectively, at room temperature. Magnetic behavior of A{sub 2}Co{sub 12}As{sub 7} is generally characterized by ferromagnetic ordering of Co 3d moments at 100–140 K, followed by low-temperature ordering of rare-earth 4f moments. The 3d-4f magnetic coupling changes from antiferromagnetic for A=Pr–Sm to ferromagnetic for A=Ce and Eu–Yb. Polarized neutron scattering experiments were performed to support the postulated ferro- and ferrimagnetic ground states for Ce{sub 2}Co{sub 12}As{sub 7} and Nd{sub 2}Co{sub 12}As{sub 7}, respectively. - Graphical abstract: Title arsenides were synthesized by Bi‐flux method. They exhibit mixed valence for A = Ce, Eu, Yb, ferrimagnetism for A = Ca, Y, Pr–Sm, and ferromagnetism for A = Eu–Tm. - Highlights: • A2Co12As7 (A=Ca, Y, Ce–Yb) were synthesized in Bi flux. • Ce, Eu, Yb exhibit mixed valence in the corresponding structures. • The character of 3d‐4f magnetic coupling changes at the half‐filled f shell. • Materials behave as ferrimagnets for A=Ca, Y, Pr–Sm and as ferromagnets for A=Eu–Yb.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Mechanistic Studies of Methanol Synthesis over Cu from CO/CO2/H2/H2O Mixtures: the Source of C in Methanol and the Role of Water

The low temperature (403 – 453K) conversions of CO:hydrogen and CO2:hydrogen mixtures (6 bar total pressure) to methanol over copper catalysts are both assisted by the presence of small amounts of water (mole fraction ~0.04%-0.5%). For CO2:hydrogen reaction mixtures, the water product from both methanol synthesis and reverse water gas shift serves to initiate both reactions in an autocatalytic manner. In the case of CO:D2 mixtures, very little methanol is produced until small amounts of water are added. The effect of water on methanol production is more immediate than in CO2:D2, yet the steady state rates are similar. Tracer experiments in 13CO:12CO2:hydrogen (with or without added water), show that the dominant source of C in the methanol product gradually shifts from CO2 to CO as the temperature is lowered. Cu-bound formate, the major IR visible surface species under CO2:hydrogen, is not visible in CO:moist hydrogen. Though formate is visible in the tracer experiments, the symmetric stretch is absent. These results, in conjunction with recent DFT calculations on Cu(111), point to carboxyl as a common intermediate for both methanol synthesis and reverse water gas shift, with formate playing a spectator co-adsorbate role.

copper catalysts↗
DOE OSTI2018

Electrolyte Solvation Structure at Solid/Liquid Interface Probed by Nanogap Surface-Enhanced Raman Spectroscopy

Understanding the fundamental factors that drive ion solvation structure and transport is key to design high performance, stable battery electrolytes. Reversible ion solvation and desolvation are critical to the interfacial charge transfer process across the solid-liquid interface as well as the resulting stability of the solid electrolyte interphase (SEI). Here in this paper, we report the first study of Li+ salt solvation structure in aprotic solution in the immediate vicinity (~ 20 nm) of the solid electrode-liquid interface using surface-enhanced Raman spectroscopy (SERS) from a gold nanoparticle (Au NP) monolayer. The plasmonic coupling between Au NPs produces strong electromagnetic field enhancement in the gap region, leading to 5 orders of magnitude increase in Raman intensity for electrolyte components and their mixtures namely, lithium hexafluorophosphate (LiPF6), fluoroethylene carbonate (FEC), ethylene carbonate (EC) and diethyl carbonate (DEC). Further, we estimate and compare the lithium-ion solvation number derived from SERS and Infra-Red (FTIR) spectroscopy experiments to monitor and ascertain the changes in the solvation shell diameter in the confined nanogap region where there is maximum enhancement of the electric field. Our findings provide a new multi-modal spectroscopic approach to gain fundamental insights into the molecular structure of the electrolyte at the solid-liquid interface.

25 ENERGY STORAGE↗
DOE OSTI2013

Fish scale deformation analysis using scanning electron microscope: New potential biomarker in aquatic environmental monitoring of aluminum and iron contamination

Fish scale has the potential to be a rapid biomarker due to its structure and high possibility to come into contact with any pollutant in the aquatic environment. The scale structure consists of osteoblastic cells and other bone materials such as collagen where it is possible to form a molecular complex with heavy metals such as aluminum and iron. Hence, aluminum and iron in water could possibly destroy the scale material and marked as a scale deformation that quantitatively could be analyzed by comparing it to the normal scale structure. Water sampling and fish cage experiment were performed between June and July 2011 in Porong river which represented the water body that has high aluminum and iron contamination. The filtered water samples were preserved and extracted using the acid-mixture procedure prior to measurement of the aluminum and iron concentrations using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), while samples for total suspended solid (TSS) analysis were kept at 4 °C in cool-boxes. The scales were cleaned with sterile water, then dehydrated in 30, 50, 70, and 90% ethanol and dried on filter papers. They were then mounted on an aluminum stub and coated with gold in a sputter coater prior to Scanning Electron Microscope (SEM) observation. According to the SEM analysis, it was found that there were several deformations on the scale samples taken from sites that have high concentrations of aluminum and iron i.e. the increasing number of pits, deformation and decreasing number of spherules and ridges while the control scale exhibited the normal features. However, the site with higher TSS and pH indicated lower aluminum effect. A moderate correlation was found between the number of pits with aluminum (r=0.43) and iron (r=0.41) concentrations. Fish scale deformation using SEM analysis can potentially be a rapid biomarker in aquatic monitoring of aluminum and iron contamination. However, the measurement must be accompanied by pH and TSS observations.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Structural transitions of ternary imide Li{sub 2}Mg(NH){sub 2} for hydrogen storage

Phase transitions and energetic properties of Li{sub 2}Mg(NH){sub 2} with different crystal structures are investigated by experiments and first-principles calculations. The Li{sub 2}Mg(NH){sub 2} with the primitive cubic and orthorhombic structure is obtained by dynamically dehydrogenating a Mg(NH{sub 2}){sub 2}-2LiH mixture up to 280 °C under an initial vacuum and 9.0 bars H{sub 2}, respectively. It is found that the obtained orthorhombic Li{sub 2}Mg(NH){sub 2} is converted to a primitive cubic structure as the dehydrogenation temperature is further increased to 400 °C or performed by a 36 h of high-energetic ball milling. Moreover, the primitive cubic phase can be converted to an orthorhombic phase after heating at 280 °C under 9.0 bars H{sub 2} for 1 h. Thermodynamic calculations show that the orthorhombic phase is the ground state structure of Li{sub 2}Mg(NH){sub 2}. The mechanism for phase transitions of Li{sub 2}Mg(NH){sub 2} is also discussed from the angle of energy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Measurements of ion velocity separation and ionization in multi-species plasma shocks

The ion velocity structure of a strong collisional shock front in a plasma with multiple ion species is directly probed in laser-driven shock-tube experiments. Thomson scattering of a 263.25 nm probe beam is used to diagnose ion composition, temperature, and flow velocity in strong shocks (M ~ 6) propagating through low-density (ρ ~ 0.1 mg/cc) plasmas composed of mixtures of hydrogen (98%) and neon (2%). Within the preheat region of the shock front, two velocity populations of ions are observed, a characteristic feature of strong plasma shocks. The ionization state of the Ne is observed to change within the shock front, demonstrating an ionization-timescale effect on the shock front structure. In conclusion, the forward-streaming proton feature is shown to be unexpectedly cool compared to predictions from ion Fokker-Planck simulations; the neon ionization gradient is evaluated as a possible cause.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Spectroscopy of the neutron-rich hypernucleus He Λ 7 from electron scattering

Here, the missing mass spectroscopy of the $^{7}_{\Lambda}$He hypernucleus was performed, using the $^{7}$Li$(e,e^{\prime}K^{+})^{7}_{\Lambda}$He reaction at the Thomas Jefferson National Accelerator Facility Hall C. The $\Lambda$ binding energy of the ground state (1/2$^{+}$) was determined with a smaller error than that of the previous measurement, being $B_{\Lambda}$ = 5.55 $\pm$ 0.10(stat.) $\pm$ 0.11(sys.) MeV. The experiment also provided new insight into charge symmetry breaking in p-shell hypernuclear systems. Finally, a peak at $B_{\Lambda}$ = 3.65 $\pm$ 0.20(stat.) $\pm$ 0.11(sys.) MeV was observed and assigned as a mixture of 3/2$^{+}$ and 5/2$^{+}$ states, confirming the "gluelike" behavior of $\Lambda$, which makes an unstable state in $^{6}$He stable against neutron emission.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Equilibrium and kinetic studies of sorption of 2.4-dichlorophenol onto 2 mixtures: bamboo biochar plus calcium sulphate (BC) and hydroxyapatite plus bamboo biochar plus calcium sulphate (HBC), in a fluidized bed circulation column

Sorption studies were carried out to investigate removal of 2.4-dichlorophenol (2.4-DCP) from aqueous solution in a fluidized bed by two types of adsorbent mixtures: BC (Bamboo char plus Calcium sulphate), and HBC (Hydroxyapatite plus Bamboo char plus Calcium sulphate); both manufactured in ball shape. The main material bamboo char was characterized by FTIR, DTA and SEM. The adsorption experiments were conducted in a fluidized bed circulation column. Adsorption, isotherms and kinetic studies were established under 180 min operating process time, at different initial 2.4-DCP solution concentrations ranging from 5–10 mg/L, and at different flow rates ranging from 0.25–0.75 L/min. The data obtained fitted well for both the Langmuir and Freundlich isotherm models; indicating favorable condition of monolayer adsorption. The kinetics of both adsorbents complies with the pseudo second-order kinetic model. BC was proven a new effective composite and low cost adsorbent which can be applied in the field of wastewater treatment, and it can also play an important role in industry water treatment

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗