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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

The effect of non-redox promoters (AlO x , PO x , SiO x and ZrO x ) and surface sulfates on supported V 2 O 5 -WO 3 /TiO 2 catalysts in selective catalytic reduction of NO with NH 3

The SCR activity of MO x (M=Al, P, Si, Zr) promoted V 2 O 5 -WO 3 /TiO 2 was investigated before and after sulfation. In situ IR spectroscopy indicated that the VO x active sites preferentially anchor on promoter generated surface hydroxyl. In situ Raman spectroscopy confirmed that all oxides are completely dispersed on the TiO 2 surface. In situ NH 3 -IR spectroscopy showed that the oxides can increase the Lewis (AlO x and ZrO x ) and Brønsted (PO x , SiO x , VO x , WO x and SO x ) acid site concentrations. The SiO x and ZrO x promoters had little effect on NO conversion, while the AlO x and PO x promoters and surface sulfation generally inhibited it. The SiO x promoted catalyst was highly SCR active despite lacking Lewis acid sites, indicating that they are not vital for SCR. Finally, the N 2 O formation activity of the catalyst was inhibited by surface sulfation and the promoters, correlating with the promoter and SO x induced increase in the Brønsted acid sites’ strength.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1971

Development of flame resistant metal and metal-glass blended structures

A description is given of the design and fabrication of candidate flame-resistant woven and knitted fabrics, tapes, webbings, and cords as replacements for those items used in the Apollo spacecraft which were previously made of nylon and polyester. Structures made from Chromel R metal fibers (74% Ni, 20% Cr, 2-1/2% Fe, 2-1/2% Al, 1/2% Si, 1/2% Mo), Beta glass fibers and high-temperature organic fibers such as PBI (polybenzimidazole) were developed and evaluated. The feasibility of improving the performance of selected fabrics by using CNR (carboxy nitroso rubber) or other nonflammable coatings were also investigated.

Coskren, R. J.↗
DOE OSTI2020

Phase Equilibria and Thermochemistry of Advanced Fuels: Modeling Burnup Behavior (Final Report)

Achieving the goal of developing advanced fuel concepts that meet the DOE objectives of being robust, demonstrating high performance, and are more tolerant of accident conditions than current fuel systems will require a thorough understanding of the thermophysical and thermochemical properties of the constituent materials. Non-oxide fuel systems are being explored under the Advanced Fuels Program that hold significant promise for improved performance and accident tolerance, including the uranium silicide-based system considered in the current work. Prospective cladding materials currently considered that contribute to improved accident tolerance include silicon carbide composites and ferritic alloys (Fe-Cr-Al base compositions). Thus, the effort developed thermochemical models and values, supported with targeted experiments, to evaluate the ferritic alloy and silicon carbide composite cladding systems in contrast to current zirconium alloy cladding. The developed detailed understanding will serve to aid in relatively early screening of candidate systems to avoid wasted effort, guide development of new fuel forms, and to provide a basis for predicting and modeling fuel performance. Major deliverables for the project included: Thermochemical assessment and models of phases in the U-Si and U-Si-N systems; thermochemical evaluation supported by experimental measurements of fuel-cladding interactions of silicide fuel with baseline zirconium, ceramic composite, and ferritic alloy cladding; thermochemical assessment and models of phases supported by experimental measurements for silicide fuel with key fission products provided in a dataset and reported in refereed publications. Within the project a significantly refined U-Si phase diagram was developed and reported that now includes homogeneity ranges for key phases, such at the U 3 Si 2 proposed fuel phase, and settles issues with regard to uncertainty in the stability of some phases. Computational efforts together with key experiments has determined phase formation in interactions between U 3 Si 2 and Zircaloy-4 cladding material, a ferritic FeCrAlY alloy of interest as an advanced cladding material, and silicon carbide, also of interest as a fiber-reinforced composite cladding. As expected, very significant reactions occur between U3Si2 and Zircaloy-4, with much less interaction at higher temperatures for the ferritic alloy, and finally interactions with SiC only in the region of contact. A potentially major issue is the stability of U 3 Si 2 fuel that has undergone significant burnup. The result is the loss of the uranium metal, liberating silicon, and the formation of concomitant fission product elements that either dissolve in the U 3 Si 2 phase or form independent, and possibly silicide phases. A combination of experimental determinations of phase formation of U 3 Si 2 reacted with representative fission products yttrium, gadolinium, cerium, zirconium, and molybdenum and first principles calculations has helped understand the fuel chemistry. The behavior of the U 3 Si 2 phase and the partitioning of silicon to possible fission product phases with burnup was thus determined, with significant dissolution in U 3 Si 2 of cerium, gadolinium, zirconium, and plutonium predicted along with independent phase formation of a U-Mo-Si ternary phase, yttrium silicide, and elemental selenium. It can be concluded that at significant burnup there will be a very minor amount of the U 3 Si 2 fuel phase that will decompose to a lower silicide or a uranium alloy as silicon preferentially forms a secondary phase.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Materials Data on Hf9SiMo4 by Materials Project

Hf9Mo4Si crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Hf sites. In the first Hf site, Hf is bonded in a 2-coordinate geometry to four Mo and one Si atom. There are a spread of Hf–Mo bond distances ranging from 2.89–3.13 Å. The Hf–Si bond length is 2.71 Å. In the second Hf site, Hf is bonded in a distorted T-shaped geometry to two equivalent Mo and one Si atom. Both Hf–Mo bond lengths are 2.91 Å. The Hf–Si bond length is 3.05 Å. There are two inequivalent Mo sites. In the first Mo site, Mo is bonded in a 12-coordinate geometry to eight Hf and four Mo atoms. There are two shorter (2.74 Å) and two longer (2.86 Å) Mo–Mo bond lengths. In the second Mo site, Mo is bonded to six equivalent Hf and six equivalent Mo atoms to form face-sharing MoHf6Mo6 cuboctahedra. Si is bonded in a 9-coordinate geometry to nine Hf atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca3Si4(MoO7)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Be3Si3(MoO6)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca3Si3(MoO6)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Si3(MoO6)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti(Si3Mo)2 by Materials Project

Ti(MoSi3)2 is Titanium Disilicide-derived structured and crystallizes in the orthorhombic C222 space group. The structure is three-dimensional. Ti4+ is bonded in a distorted q6 geometry to ten Si+1.33- atoms. There are a spread of Ti–Si bond distances ranging from 2.56–2.77 Å. Mo2+ is bonded in a distorted q6 geometry to ten Si+1.33- atoms. There are a spread of Mo–Si bond distances ranging from 2.57–2.75 Å. There are two inequivalent Si+1.33- sites. In the first Si+1.33- site, Si+1.33- is bonded in a 10-coordinate geometry to three equivalent Ti4+, two equivalent Mo2+, and five Si+1.33- atoms. There are a spread of Si–Si bond distances ranging from 2.51–2.79 Å. In the second Si+1.33- site, Si+1.33- is bonded in a 10-coordinate geometry to one Ti4+, four equivalent Mo2+, and five Si+1.33- atoms. There are a spread of Si–Si bond distances ranging from 2.56–2.77 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg3Si4(MoO7)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg3Si3(MoO6)2 by Materials Project

Mg3Si3(MoO6)2 crystallizes in the cubic Ia-3d space group. The structure is three-dimensional. Mg2+ is bonded in a distorted body-centered cubic geometry to eight equivalent O2- atoms. There are four shorter (2.31 Å) and four longer (2.40 Å) Mg–O bond lengths. Mo3+ is bonded to six equivalent O2- atoms to form MoO6 octahedra that share corners with six equivalent SiO4 tetrahedra. All Mo–O bond lengths are 2.13 Å. Si4+ is bonded to four equivalent O2- atoms to form SiO4 tetrahedra that share corners with four equivalent MoO6 octahedra. The corner-sharing octahedral tilt angles are 55°. All Si–O bond lengths are 1.66 Å. O2- is bonded in a 4-coordinate geometry to two equivalent Mg2+, one Mo3+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Probing the active sites of oxide encapsulated electrocatalysts with controllable oxygen evolution selectivity

Electrocatalysts encapsulated by nanoscopic overlayers can control the rate of redox reactions at the outer surface of the overlayer or at the buried interface between the overlayer and the active catalyst, leading to complex behavior in the presence of two competing electrochemical reactions. This study investigated oxide encapsulated electrocatalysts (OECs) comprised of iridium (Ir) thin films coated with an ultrathin (2–10 nm thick) silicon oxide (SiO x ) or titanium oxide (TiO x ) overlayer. The performance of SiO x |Ir and TiO x |Ir thin film electrodes towards the oxygen evolution reaction (OER) and Fe(II)/Fe(III) redox reactions were evaluated. An improvement in selectivity towards the OER was observed for all OECs. Overlayer properties, namely ionic and electronic conductivity, were assessed using a combination of electroanalytical methods and molecular dynamics simulations. SiO x and TiO x overlayers were found to be permeable to H 2 O and O 2 such that the OER can occur at the MO x |Ir (M = Ti, Si) buried interface, which was further supported with molecular dynamics simulations of model SiO 2 coatings. In contrast, Fe(II)/Fe(III) redox reactions occur to the same degree with TiO x overlayers having thicknesses less than 4 nm as bare electrocatalyst, while SiO x overlayers inhibit redox reactions at all thicknesses. This observation is attributed to differences in electronic transport between the buried interface and outer overlayer surface, as measured with through-plane conductivity measurements of wetted overlayer materials. These findings reveal the influence of oxide overlayer properties on the activity and selectivity of OECs and suggest opportunities to tune these properties for a wide range of electrochemical reactions.

08 HYDROGEN↗
DOE OSTI2020

Materials Data on La3Si(Mo2O7)2 by Materials Project

La3Mo4SiO14 crystallizes in the orthorhombic Pna2_1 space group. The structure is three-dimensional. there are three inequivalent La3+ sites. In the first La3+ site, La3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of La–O bond distances ranging from 2.51–2.86 Å. In the second La3+ site, La3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of La–O bond distances ranging from 2.43–2.92 Å. In the third La3+ site, La3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of La–O bond distances ranging from 2.41–2.77 Å. There are four inequivalent Mo+3.75+ sites. In the first Mo+3.75+ site, Mo+3.75+ is bonded to six O2- atoms to form MoO6 octahedra that share a cornercorner with one SiO4 tetrahedra and edges with two MoO6 octahedra. There are a spread of Mo–O bond distances ranging from 2.00–2.17 Å. In the second Mo+3.75+ site, Mo+3.75+ is bonded to six O2- atoms to form MoO6 octahedra that share corners with two equivalent MoO6 octahedra, a cornercorner with one SiO4 tetrahedra, and edges with three MoO6 octahedra. The corner-sharing octahedra tilt angles range from 52–53°. There are a spread of Mo–O bond distances ranging from 2.09–2.18 Å. In the third Mo+3.75+ site, Mo+3.75+ is bonded to six O2- atoms to form MoO6 octahedra that share corners with two equivalent MoO6 octahedra, a cornercorner with one SiO4 tetrahedra, and edges with three MoO6 octahedra. The corner-sharing octahedra tilt angles range from 43–45°. There are a spread of Mo–O bond distances ranging from 1.99–2.16 Å. In the fourth Mo+3.75+ site, Mo+3.75+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MoO6 octahedra. The corner-sharing octahedra tilt angles range from 43–53°. There are a spread of Mo–O bond distances ranging from 1.97–2.10 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three MoO6 octahedra. The corner-sharing octahedra tilt angles range from 13–59°. There are a spread of Si–O bond distances ranging from 1.63–1.67 Å. There are fourteen inequivalent O2- sites. In the first O2- site, O2- is bonded to one La3+ and three Mo+3.75+ atoms to form distorted edge-sharing OLaMo3 trigonal pyramids. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one La3+, one Mo+3.75+, and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one La3+, one Mo+3.75+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one La3+ and three Mo+3.75+ atoms. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to two La3+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to three La3+ and one Mo+3.75+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to three La3+ and one Mo+3.75+ atom. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to two La3+ and two equivalent Mo+3.75+ atoms. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to two La3+ and two equivalent Mo+3.75+ atoms. In the tenth O2- site, O2- is bonded in a 3-coordinate geometry to one La3+ and two Mo+3.75+ atoms. In the eleventh O2- site, O2- is bonded to two La3+ and two Mo+3.75+ atoms to form distorted OLa2Mo2 trigonal pyramids that share a cornercorner with one OLa2Mo2 trigonal pyramid and edges with two OLaMo3 trigonal pyramids. In the twelfth O2- site, O2- is bonded to two La3+ and two Mo+3.75+ atoms to form a mixture of distorted edge and corner-sharing OLa2Mo2 trigonal pyramids. In the thirteenth O2- site, O2- is bonded in a 1-coordinate geometry to one La3+, one Mo+3.75+, and one Si4+ atom. In the fourteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Mo+3.75+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Hf10SiMo3 by Materials Project

Hf10Mo3Si crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are three inequivalent Hf sites. In the first Hf site, Hf is bonded in a 2-coordinate geometry to three equivalent Mo and one Si atom. There are one shorter (2.90 Å) and two longer (3.18 Å) Hf–Mo bond lengths. The Hf–Si bond length is 2.69 Å. In the second Hf site, Hf is bonded in a 3-coordinate geometry to two equivalent Mo and one Si atom. Both Hf–Mo bond lengths are 2.87 Å. The Hf–Si bond length is 3.09 Å. In the third Hf site, Hf is bonded in a 6-coordinate geometry to six equivalent Mo atoms. All Hf–Mo bond lengths are 2.79 Å. Mo is bonded in a 12-coordinate geometry to ten Hf and two equivalent Mo atoms. Both Mo–Mo bond lengths are 2.98 Å. Si is bonded in a 9-coordinate geometry to nine Hf atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn3Si3(MoO6)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn3Si4(MoO7)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Graphene as reusable substrate for bialkali photocathodes

Bialkali photocathodes, such as cesium potassium antimonide (CsK 2 Sb), can generate a high-brightness electron beam using a high-power green laser. These photocathode materials have potential applications in advanced accelerators and electron microscopes. It is known that the quantum efficiency (QE) of these photocathodes is affected severely by their substrates; however, reusability of the substrates is not well known. Here, we use graphene, silicon (Si), and molybdenum (Mo) substrates to evaluate the effects of substrates on the QE of redeposited CsK 2 Sb photocathodes after thermal cleanings. We found the QE of CsK 2 Sb photocathodes redeposited on a graphene substrate after a thermal cleaning at 500 °C remained largely unchanged. On the other hand, the QE of redeposited photocathodes on Si and Mo substrates after thermal cleaning at the same temperature decreased drastically. We used X-ray photoelectron spectroscopy (XPS) to quantitatively evaluate the residues of photocathodes after thermal cleaning at 400 °C and 500 °C. We found that the Sb, K, and Cs are removed by thermal cleaning at 500 °C for the graphene substrate, but all or the majority of these elements remained on the Si and Mo substrates. The results were consistent with our density functional theory (DFT) calculations for the case of Si, which we investigated. Furthermore, our angle-resolved photoemission spectroscopy (ARPES) on graphene indicated that its intrinsic electronic structure is preserved after photocathode deposition and thermal cleaning at 500 °C. Hence, we attributed the difference in amount of photocathode residue to the unique dangling-bond- free surface of inert graphene. Our results provide a foundation for graphene-based reusable substrates for high-QE semiconductor photocathodes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Materials Data on Nd3Si(Mo2O7)2 by Materials Project

Nd3Si(Mo2O7)2 crystallizes in the orthorhombic Pna2_1 space group. The structure is three-dimensional. there are three inequivalent Nd3+ sites. In the first Nd3+ site, Nd3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Nd–O bond distances ranging from 2.37–2.79 Å. In the second Nd3+ site, Nd3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Nd–O bond distances ranging from 2.40–2.77 Å. In the third Nd3+ site, Nd3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Nd–O bond distances ranging from 2.44–2.75 Å. There are four inequivalent Mo+3.75+ sites. In the first Mo+3.75+ site, Mo+3.75+ is bonded to six O2- atoms to form MoO6 octahedra that share corners with two equivalent MoO6 octahedra, a cornercorner with one SiO4 tetrahedra, and edges with three MoO6 octahedra. The corner-sharing octahedra tilt angles range from 46–49°. There are a spread of Mo–O bond distances ranging from 1.99–2.13 Å. In the second Mo+3.75+ site, Mo+3.75+ is bonded to six O2- atoms to form MoO6 octahedra that share corners with two equivalent MoO6 octahedra, a cornercorner with one SiO4 tetrahedra, and edges with three MoO6 octahedra. The corner-sharing octahedra tilt angles range from 51–53°. There are a spread of Mo–O bond distances ranging from 2.07–2.19 Å. In the third Mo+3.75+ site, Mo+3.75+ is bonded to six O2- atoms to form MoO6 octahedra that share a cornercorner with one SiO4 tetrahedra and edges with two MoO6 octahedra. There are a spread of Mo–O bond distances ranging from 1.99–2.18 Å. In the fourth Mo+3.75+ site, Mo+3.75+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MoO6 octahedra. The corner-sharing octahedra tilt angles range from 46–53°. There are a spread of Mo–O bond distances ranging from 1.96–2.12 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three MoO6 octahedra. The corner-sharing octahedra tilt angles range from 17–58°. There are a spread of Si–O bond distances ranging from 1.63–1.67 Å. There are fourteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two Nd3+ and two equivalent Mo+3.75+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two Nd3+ and two equivalent Mo+3.75+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one Nd3+, one Mo+3.75+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Nd3+, one Mo+3.75+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to one Nd3+, one Mo+3.75+, and one Si4+ atom. In the sixth O2- site, O2- is bonded to one Nd3+ and three Mo+3.75+ atoms to form distorted edge-sharing ONdMo3 trigonal pyramids. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to one Nd3+ and two Mo+3.75+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Mo+3.75+ atoms. In the ninth O2- site, O2- is bonded to two Nd3+ and two Mo+3.75+ atoms to form a mixture of distorted edge and corner-sharing ONd2Mo2 trigonal pyramids. In the tenth O2- site, O2- is bonded to two Nd3+ and two Mo+3.75+ atoms to form a mixture of distorted edge and corner-sharing ONd2Mo2 trigonal pyramids. In the eleventh O2- site, O2- is bonded in a 1-coordinate geometry to two Nd3+ and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a 4-coordinate geometry to three Nd3+ and one Mo+3.75+ atom. In the thirteenth O2- site, O2- is bonded in a 4-coordinate geometry to three Nd3+ and one Mo+3.75+ atom. In the fourteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Nd3+ and three Mo+3.75+ atoms.

36 MATERIALS SCIENCE↗