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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Effect of water frustration on water oxidation catalysis in the nanoconfined interlayers of layered manganese oxides birnessite and buserite

The role of geometric frustration of water molecules on the rate of water oxidation in the nanoconfined interlayer of manganese-oxide layered materials (birnessite, buserite) is examined in a well-controlled experiment. Calcium buserite is prepared, and used in a split-batch synthetic protocol to prepare calcium birnessite, sodium buserite, and sodium birnessite, and partially dehydrated sodium birnessite. Thus, four samples are prepared in which features effecting catalytic efficiency (defect density, average manganese oxidation state) are controlled, and the main difference is the degree of hydration of the interlayer (two layers of water in buserites vs one layer of water in birnessite). Here, molecular dynamics simulations predict birnessite samples to exhibit geometric water frustration, which facilitates redox catalysis by lowering the Marcus reorganizaiton energy of electron transfer, while buserite samples exhibit traditional intermolecular hydrogen bonding among the two-layer aqeuous region, leading to slower catalytic behavior akin to redox reactions in bulk water. Water oxdiation activity is investigated using chemical and electrochemical techniques, demonstrating and quantifying the role of water frustration in enhancing catalysis. Calculation and experiment demonstrate dehydrated sodium birnessite to be most effective, and calcium buserite the least effective, with a difference in electrocatlytic overpotential of ~750 mV and a ~20-fold difference in turnover number.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Galvanic corrosion of AZ31B joined to dual-phase steel with and without Zn layer by ultrasonic and friction stir welding

Galvanic corrosion of AZ31B joined with bare or Zn-coated DP590 steel by ultrasonic spot welding or linear friction stir welding was quantitatively studied by pre-defining anode and cathode in the lap joint samples. Corrosion volume and depth from Mg anode surfaces exposed to 0.1 M sodium chloride solution was analyzed as functions of cathode surface type and welding method. Characterization of as-welded joints was performed to identify any microstructural feature of the bonding zone that could impact galvanic corrosion behavior. COMSOL modeling with modified user subroutine was conducted to simulate the progression of Mg corrosion in the same joint and electrode configurations used for the corrosion experiments. The experimental results indicated that Zn-coated cathode surface can reduce Mg galvanic corrosion significantly as galvanic polarization and cathodic current on Zn-coated surface remained relatively low for Mg in the weld joints. COMSOL modeling described the growth of Mg galvanic corrosion in a reasonable manner but showed limitation by underestimating the corrosion volume as it did not capture self-corrosion.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A comparative study of the effectiveness of empirical potentials for molecular dynamics simulations of borosilicate glasses

Despite their practical importance, atomistic modeling of B 2 O 3 containing glasses have been challenging due to the lack of reliable empirical potentials. Fortunately, a few recent developments have shown promises to simulate these glasses where the boron coordination has complex and non-linear dependence on glass composition. This work aims to provide an evaluation of the effectiveness of three recently developed potentials by a systematic study of a series (~20) of sodium borosilicate glasses with constant K (ratio of [SiO 2 ]/[B 2 O 3 ]) =2 and varying R (ratio of [Na 2 O]/[B 2 O 3 ] ranging from 0.1 to 4) values and several sodium boroaluminosilicate glasses. A comparative assessment was established on the basis of the short- and medium-range structure features, such as boron N 4 values, total correlation functions, bond angle distribution, oxygen speciation, and mechanical properties using experimental or well-established models as criteria. Furthermore, this work provides insights on the choices of empirical potentials for MD simulations of borosilicate glasses and gives directions of future potential development and refining.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Thermal Properties of Sodium Borosilicate Glasses as a Function of Sulfur Content

SO3 additions, up to 3.0 wt%, were systematically investigated for effects on the physical properties of sodium borosilicate glass melted in air, with a sulfur-free composition of 50SiO2-10Al2O3-12B2O3-21Na2O-7CaO (wt%). Solubility measurements, using electron microscopy chemical analysis, determined the maximum loading to be ~1.5 wt% SO3. It was found that sulfur (here as sulfate) in this glass increased the glass transition temperature, thermal diffusivity, heat capacity, and thermal conductivity, and decreased the mass density. Structural analysis, performed with Raman spectroscopy, indicated that the borosilicate network polymerized with sulfur additions, presumably due to Na2O being required to charge compensate the ionic SO42- additions, thus becoming unavailable to form non-bridging oxygen in the silicate network. It is postulated that this increased crosslinking of the borosilicate backbone lead to a structure with higher dimensionality and average bond energy. This increased the mean free paths and vibration frequency of the phonons, which resulted in the observed increase in thermal properties.

Thermal properties, Borosilicate glass, Sulfur sol↗
DOE OSTI2020

Materials Data on Na9Hg by Materials Project

(Na)3Na6Hg crystallizes in the orthorhombic Cmmm space group. The structure is two-dimensional and consists of six sodium molecules and one Na6Hg sheet oriented in the (0, 0, 1) direction. In the Na6Hg sheet, there are two inequivalent Na sites. In the first Na site, Na is bonded in a distorted single-bond geometry to one Na and one Hg atom. The Na–Na bond length is 3.29 Å. The Na–Hg bond length is 3.39 Å. In the second Na site, Na is bonded in a linear geometry to two equivalent Na atoms. Hg is bonded in a distorted rectangular see-saw-like geometry to four equivalent Na atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

CO 2 Hydrogenation: Na Doping Promotes CO and Hydrocarbon Formation over Ru/m-ZrO 2 at Elevated Pressures in Gas Phase Media

Sodium-promoted monoclinic zirconia supported ruthenium catalysts were tested for CO 2 hydrogenation at 20 bar and a H 2 :CO 2 ratio of 3:1. Although increasing sodium promotion, from 2.5% to 5% by weight, slightly decreased CO 2 conversion (14% to 10%), it doubled the selectivity to both CO (~36% to ~71%) and chain growth products (~4% to ~8%) remarkably and reduced the methane selectivity by two-thirds (~60% to ~21%). For CO 2 hydrogenation during in situ DRIFTS under atmospheric pressure, it was revealed that Na increases the catalyst basicity and suppresses the reactivity of Ru sites. Higher basicity facilitates CO 2 adsorption, weakens the C–H bond of the formate intermediate promoting CO formation, and inhibits methanation occurring on ruthenium nanoparticle surfaces. The suppression of excessive hydrogenation increases the chain growth probability. Decelerated reduction during H 2 -TPR/TPR-MS and H 2 -TPR-EXAFS/XANES at the K-edge of ruthenium indicates that sodium is in contact with ruthenium. A comparison of the XANES spectra of unpromoted and Na-promoted catalysts after H 2 reduction showed no evidence of a promoting effect involving electron charge transfer.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na3As by Materials Project

Na3As is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 4-coordinate geometry to four equivalent As3- atoms. There are one shorter (2.99 Å) and three longer (3.32 Å) Na–As bond lengths. In the second Na1+ site, Na1+ is bonded in a trigonal planar geometry to three equivalent As3- atoms. All Na–As bond lengths are 2.94 Å. As3- is bonded in a 5-coordinate geometry to eleven Na1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Sb by Materials Project

K3Sb is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 1-coordinate geometry to four equivalent Sb3- atoms. There are one shorter (3.60 Å) and three longer (3.99 Å) K–Sb bond lengths. In the second K1+ site, K1+ is bonded in a trigonal planar geometry to three equivalent Sb3- atoms. All K–Sb bond lengths are 3.54 Å. Sb3- is bonded in a 5-coordinate geometry to eleven K1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3As by Materials Project

K3As is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a distorted single-bond geometry to four equivalent As3- atoms. There are one shorter (3.42 Å) and three longer (3.82 Å) K–As bond lengths. In the second K1+ site, K1+ is bonded in a trigonal planar geometry to three equivalent As3- atoms. All K–As bond lengths are 3.38 Å. As3- is bonded to eleven K1+ atoms to form a mixture of distorted edge and face-sharing AsK11 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na3P by Materials Project

Na3P is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a trigonal planar geometry to three equivalent P3- atoms. All Na–P bond lengths are 2.87 Å. In the second Na1+ site, Na1+ is bonded in a 1-coordinate geometry to four equivalent P3- atoms. There are one shorter (2.92 Å) and three longer (3.24 Å) Na–P bond lengths. P3- is bonded in a 5-coordinate geometry to eleven Na1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb3Sb by Materials Project

Rb3Sb is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Rb1+ sites. In the first Rb1+ site, Rb1+ is bonded in a trigonal planar geometry to three equivalent Sb3- atoms. All Rb–Sb bond lengths are 3.71 Å. In the second Rb1+ site, Rb1+ is bonded in a 1-coordinate geometry to four equivalent Sb3- atoms. There are one shorter (3.77 Å) and three longer (4.18 Å) Rb–Sb bond lengths. Sb3- is bonded to eleven Rb1+ atoms to form a mixture of distorted edge and face-sharing SbRb11 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li3N by Materials Project

Li3N is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a trigonal planar geometry to three equivalent N3- atoms. All Li–N bond lengths are 2.06 Å. In the second Li1+ site, Li1+ is bonded in a 1-coordinate geometry to four equivalent N3- atoms. There are one shorter (2.07 Å) and three longer (2.33 Å) Li–N bond lengths. N3- is bonded in a 5-coordinate geometry to eleven Li1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na3Bi by Materials Project

Na3Bi is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Na sites. In the first Na site, Na is bonded in a 1-coordinate geometry to four equivalent Bi atoms. There are one shorter (3.25 Å) and three longer (3.56 Å) Na–Bi bond lengths. In the second Na site, Na is bonded in a trigonal planar geometry to three equivalent Bi atoms. All Na–Bi bond lengths are 3.17 Å. Bi is bonded in a 5-coordinate geometry to eleven Na atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg3Ir by Materials Project

Mg3Ir is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a trigonal planar geometry to three equivalent Ir atoms. All Mg–Ir bond lengths are 2.64 Å. In the second Mg site, Mg is bonded in a 1-coordinate geometry to four equivalent Ir atoms. There are one shorter (2.72 Å) and three longer (3.00 Å) Mg–Ir bond lengths. Ir is bonded in a 5-coordinate geometry to eleven Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb3Bi by Materials Project

Rb3Bi is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Rb sites. In the first Rb site, Rb is bonded in a 1-coordinate geometry to four equivalent Bi atoms. There are one shorter (3.84 Å) and three longer (4.25 Å) Rb–Bi bond lengths. In the second Rb site, Rb is bonded in a trigonal planar geometry to three equivalent Bi atoms. All Rb–Bi bond lengths are 3.78 Å. Bi is bonded in a 5-coordinate geometry to eleven Rb atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg3Pt by Materials Project

Mg3Pt is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 1-coordinate geometry to four equivalent Pt atoms. There are one shorter (2.73 Å) and three longer (3.04 Å) Mg–Pt bond lengths. In the second Mg site, Mg is bonded in a trigonal planar geometry to three equivalent Pt atoms. All Mg–Pt bond lengths are 2.67 Å. Pt is bonded in a 5-coordinate geometry to eleven Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Bi by Materials Project

K3Bi is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded in a 1-coordinate geometry to four equivalent Bi atoms. There are one shorter (3.68 Å) and three longer (4.06 Å) K–Bi bond lengths. In the second K site, K is bonded in a trigonal planar geometry to three equivalent Bi atoms. All K–Bi bond lengths are 3.61 Å. Bi is bonded in a 5-coordinate geometry to eleven K atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li3P by Materials Project

Li3P is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a trigonal planar geometry to three equivalent P3- atoms. All Li–P bond lengths are 2.45 Å. In the second Li1+ site, Li1+ is bonded in a 4-coordinate geometry to four equivalent P3- atoms. There are one shorter (2.53 Å) and three longer (2.75 Å) Li–P bond lengths. P3- is bonded in a 5-coordinate geometry to eleven Li1+ atoms.

36 MATERIALS SCIENCE↗