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At least 1,333 records · Page 74
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on KLu3F10 by Materials Project

KLu3F10 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. K1+ is bonded to sixteen F1- atoms to form distorted edge-sharing KF16 tetrahedra. There are four shorter (2.72 Å) and twelve longer (3.16 Å) K–F bond lengths. Lu3+ is bonded in a 8-coordinate geometry to eight F1- atoms. There are four shorter (2.16 Å) and four longer (2.32 Å) Lu–F bond lengths. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a bent 150 degrees geometry to two equivalent K1+ and two equivalent Lu3+ atoms. In the second F1- site, F1- is bonded to one K1+ and three equivalent Lu3+ atoms to form a mixture of edge and corner-sharing FKLu3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2RuO4 by Materials Project

K2RuO4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to six O2- atoms to form distorted KO6 octahedra that share corners with six equivalent RuO4 tetrahedra and edges with two equivalent KO6 octahedra. There are a spread of K–O bond distances ranging from 2.74–2.86 Å. In the second K1+ site, K1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of K–O bond distances ranging from 2.64–3.36 Å. Ru6+ is bonded to four O2- atoms to form RuO4 tetrahedra that share corners with six equivalent KO6 octahedra. The corner-sharing octahedra tilt angles range from 19–67°. There are a spread of Ru–O bond distances ranging from 1.78–1.81 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to four K1+ and one Ru6+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two K1+ and one Ru6+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to four K1+ and one Ru6+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1984

Shuffle-exchanges on augmented meshes

A mesh connected array of size N = two to the Kth power, K an integer, can be augmented by adding at most one edge per node such that it can perform a shuffle-exchange of size N/2 in constant time. A shuffle-exchange of size N is performed on this augmented array in constant time. This is done by combining the available perfect shuffle of size N/2 with the existing nearest neighbor connections of the mesh. By carefully scheduling the different permutations that are composed in order to achieve the shuffle, the time required is reduced to 5 steps, which is optimal for this network.

Bokhari, S. H.↗
NASA NTRS1992

Evidence for an ionized reprocessor in NGC 6814

A detailed spectroscopic analysis of a Ginga observation of the Seyfert galaxy NGC 6814 is reported. It is shown that the X-ray data are consistent with a scenario in which the continuum radiation is reprocessed in a highly ionized medium, which can either be an accretion disk or a shell of absorbing material. Both of these can produce the strong observed iron K-alpha line, which must originate within 200 lt-sec of the continuum source. Significant iron K-beta and nickel K-alpha are predicted, based on the iron K-alpha line strength, and these lines partially conceal the iron edge in this source. The spectral variability below about 4 keV, where the apparent absorption increases as the continuum flux decreases, is probably caused by a warm absorber covering the reprocessing system.

Turner, T. J.↗
NASA NTRS2004

An Experimental Investigation Into the Temperature Profile of a Compliant Foil Air Bearing

A series of tests was performed to determine the internal temperature profile in a compliant bump-type foil journal air bearing operating at room temperature under various speeds and load conditions. The temperature profile was collected by instrumenting a foil bearing with nine, type K thermocouples arranged in the center and along the bearing s edges in order to measure local temperatures and estimate thermal gradients in the axial and circumferential directions. To facilitate the measurement of maximum temperatures from viscous shearing in the air film, the thermocouples were tack welded to the backside of the bumps that were in direct contact with the top foil. The mating journal was coated with a high temperature solid lubricant that, together with the bearing, underwent high temperature start-stop cycles to produce a smooth, steady-state run-in surface. Tests were conducted at speeds from 20 to 50 krpm and loads ranging from 9 to 222 N. The results indicate that, over the conditions tested, both journal rotational speed and radial load are responsible for heat generation with speed playing a more significant role in the magnitude of the temperatures. The temperature distribution was nearly symmetric about the bearing center at 20 and 30 krpm but became slightly skewed toward one side at 40 and 50 krpm. Surprisingly, the maximum temperatures did not occur at the bearing edge where the minimum film thickness is expected but rather in the middle of the bearing where analytical investigations have predicted the air film to be much thicker. Thermal gradients were common during testing and were strongest in the axial direction from the middle of the bearing to its edges, reaching 3.78 8C/mm. The temperature profile indicated the circumferential thermal gradients were negligible.

Radil, Kevin↗
NASA NTRSDate not supplied

Training and Validation of Spectral Gap Filling Algorithm for Cpf-Ceres Intercalibration

The Climate Absolute Radiance and Refractivity Observatory (CLARREO) Pathfinder (CPF) mission is set to launch an SI-traceable reflective solar (RS) spectrometer aboard the International Space Station to measure Earth-reflected solar radiation with a radiometric uncertainty of 0.3% (k=1). The CPF intercalibration team has devised a cutting-edge methodology to accurately transfer the benchmark CPF calibration reference to the shortwave (SW) channel (200-5000 nm) of the Clouds and the Earth’s Radiant Energy System (CERES) instrument. The spectral range of CPF measurements spans from 350-2300 nm, while the CERES SW channel measures the Earth-reflected broadband solar radiances between 200 nm to 5 μm. To conduct precise CPF-CERES intercalibration analysis, the CPF-like spectral radiances outside the CPF spectral range need to be estimated to match the CERES SW spectral range. In response, the team has developed a fast algorithm that leverages spectrally redundant information within the CPF-measured portion through principal component analysis (PCA) and utilizes pre-established spectral correlation relationships among wavelengths to extend the CPF spectrum below 350 nm and above 2300 nm. Our results show that the algorithm achieves excellent accuracy in generating the missing energy in the UV and IR portions. The RMS error in the UV region is less than 4.5x10-3 W/m2/sr/nm, while in the IR region, it is smaller than 8x10-5 W/m2/sr/nm. Our methodology was validated using measured EMIT radiance data, which covers the spectral range from 0.381 μm to 2.493 μm. We employed EMIT radiances within the wavelength range of 0.43 – 2.25 μm to generate radiances for both the shorter wavelength range (0.381 – 0.43 μm) and longer wavelength range (2.25 – 2.493 μm). The generated radiances agree very well with the measured EMIT radiances. The standard deviation in the integrated broadband radiances was about 0.1%, and the bias is less than 0.004% for over 1.5 million EMIT measured samples. These statistics show that the spectral gap filling algorithm is robust and effective in substantially reducing the spectral difference-induced uncertainty in the CPF-CERES intercalibration samples.

Qiguang Yang↗
DOE OSTI2026

Emissive Colloidal GaAs Quantum Dots

Colloidal quantum dots offer tunable optical properties for optoelectronic applications, but the synthesis of high-quality III–V quantum dots (QDs) other than indium pnictides, and particularly GaAs, has remained elusive due to synthetic challenges. Colloidal GaAs QDs have been reported very recently and have shown only weak band-edge photoluminescence. Here, we demonstrate a large-scale synthesis of colloidal GaAs QDs in molten salts, followed by a high-temperature surface treatment with K 2 S, which removes native oxide and enables uniform zinc chalcogenide shell growth on GaAs. These QDs demonstrate bright band-edge photoluminescence and electroluminescence in QD LED devices. Low-temperature spectroscopy reveals a well-resolved exciton fine structure with distinct bright-state splitting and temperature-independent decay dynamics from 4 to 100 K. These results establish a practical pathway for the preparation of high-quality colloidal GaAs QDs from molten salts with potential applications in quantum technologies and optoelectronics.

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

Materials Data on KBiSe2 by Materials Project

KBiSe2 is Caswellsilverite-like structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. K1+ is bonded to six Se2- atoms to form KSe6 octahedra that share corners with six equivalent KSe6 octahedra, edges with four equivalent KSe6 octahedra, and edges with eight equivalent BiSe6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (3.03 Å) and four longer (3.13 Å) K–Se bond lengths. Bi3+ is bonded to six Se2- atoms to form BiSe6 octahedra that share corners with six equivalent BiSe6 octahedra, edges with four equivalent BiSe6 octahedra, and edges with eight equivalent KSe6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (3.03 Å) and four longer (3.13 Å) Bi–Se bond lengths. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to two equivalent K1+ and four equivalent Bi3+ atoms to form a mixture of edge and corner-sharing SeK2Bi4 octahedra. The corner-sharing octahedral tilt angles are 0°. In the second Se2- site, Se2- is bonded to four equivalent K1+ and two equivalent Bi3+ atoms to form SeK4Bi2 octahedra that share corners with six equivalent SeK4Bi2 octahedra and edges with twelve SeK2Bi4 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KBiS2 by Materials Project

KBiS2 is Caswellsilverite-like structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. K1+ is bonded to six S2- atoms to form KS6 octahedra that share corners with six equivalent KS6 octahedra, edges with four equivalent KS6 octahedra, and edges with eight equivalent BiS6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.90 Å) and four longer (3.01 Å) K–S bond lengths. Bi3+ is bonded to six S2- atoms to form BiS6 octahedra that share corners with six equivalent BiS6 octahedra, edges with four equivalent BiS6 octahedra, and edges with eight equivalent KS6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.90 Å) and four longer (3.01 Å) Bi–S bond lengths. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded to two equivalent K1+ and four equivalent Bi3+ atoms to form a mixture of edge and corner-sharing SK2Bi4 octahedra. The corner-sharing octahedral tilt angles are 0°. In the second S2- site, S2- is bonded to four equivalent K1+ and two equivalent Bi3+ atoms to form SK4Bi2 octahedra that share corners with six equivalent SK4Bi2 octahedra and edges with twelve SK2Bi4 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Tl(Cl3O)2 by Materials Project

K21Tl7(OCl7)6(O2)4 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional and consists of sixteen water molecules and one K21Tl7(OCl7)6 framework. In the K21Tl7(OCl7)6 framework, there are four inequivalent K sites. In the first K site, K is bonded in an octahedral geometry to six O atoms. There are four shorter (2.85 Å) and two longer (2.98 Å) K–O bond lengths. In the second K site, K is bonded in a 8-coordinate geometry to eight Cl atoms. There are a spread of K–Cl bond distances ranging from 3.06–3.73 Å. In the third K site, K is bonded in a 8-coordinate geometry to eight Cl atoms. There are a spread of K–Cl bond distances ranging from 3.22–3.59 Å. In the fourth K site, K is bonded in a 1-coordinate geometry to one O and seven Cl atoms. The K–O bond length is 2.85 Å. There are a spread of K–Cl bond distances ranging from 3.25–3.50 Å. There are three inequivalent Tl sites. In the first Tl site, Tl is bonded in an octahedral geometry to six Cl atoms. There are four shorter (2.56 Å) and two longer (3.09 Å) Tl–Cl bond lengths. In the second Tl site, Tl is bonded in an octahedral geometry to six Cl atoms. There are two shorter (2.52 Å) and four longer (2.69 Å) Tl–Cl bond lengths. In the third Tl site, Tl is bonded in an octahedral geometry to six Cl atoms. There are two shorter (2.64 Å) and four longer (2.65 Å) Tl–Cl bond lengths. There are two inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one K atom. In the second O site, O is bonded in a trigonal planar geometry to three K atoms. There are seven inequivalent Cl sites. In the first Cl site, Cl is bonded to five K and one Tl atom to form distorted ClK5Tl octahedra that share corners with two equivalent ClK5Tl octahedra, corners with four equivalent ClK4Tl square pyramids, edges with two equivalent ClK4Tl square pyramids, faces with two equivalent ClK5Tl octahedra, and faces with two equivalent ClK4Tl square pyramids. The corner-sharing octahedra tilt angles range from 0–33°. In the second Cl site, Cl is bonded to four K and one Tl atom to form distorted ClK4Tl square pyramids that share corners with four equivalent ClK5Tl octahedra, a cornercorner with one ClK4Tl square pyramid, edges with two equivalent ClK5Tl octahedra, and edges with four ClK4Tl square pyramids. The corner-sharing octahedra tilt angles range from 49–51°. In the third Cl site, Cl is bonded in a 4-coordinate geometry to three K and one Tl atom. In the fourth Cl site, Cl is bonded in a distorted see-saw-like geometry to three K and one Tl atom. In the fifth Cl site, Cl is bonded in a distorted single-bond geometry to one Tl atom. In the sixth Cl site, Cl is bonded in a 5-coordinate geometry to four K and one Tl atom. In the seventh Cl site, Cl is bonded to four K and one Tl atom to form distorted ClK4Tl square pyramids that share a cornercorner with one ClK4Tl square pyramid, edges with four equivalent ClK4Tl square pyramids, and faces with four equivalent ClK5Tl octahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KTiS2 by Materials Project

KTiS2 is Caswellsilverite structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. K1+ is bonded in a 6-coordinate geometry to six equivalent S2- atoms. All K–S bond lengths are 3.10 Å. Ti3+ is bonded to six equivalent S2- atoms to form edge-sharing TiS6 octahedra. All Ti–S bond lengths are 2.52 Å. S2- is bonded to three equivalent K1+ and three equivalent Ti3+ atoms to form a mixture of distorted corner and edge-sharing SK3Ti3 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2Ag4Se3 by Materials Project

K2Ag4Se3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to six Se2- atoms to form a mixture of edge, face, and corner-sharing KSe6 octahedra. The corner-sharing octahedra tilt angles range from 41–60°. There are a spread of K–Se bond distances ranging from 3.45–3.51 Å. In the second K1+ site, K1+ is bonded to six Se2- atoms to form a mixture of edge, face, and corner-sharing KSe6 octahedra. The corner-sharing octahedra tilt angles range from 41–60°. There are a spread of K–Se bond distances ranging from 3.33–3.49 Å. There are four inequivalent Ag1+ sites. In the first Ag1+ site, Ag1+ is bonded in a distorted trigonal non-coplanar geometry to three Se2- atoms. There are two shorter (2.68 Å) and one longer (2.74 Å) Ag–Se bond lengths. In the second Ag1+ site, Ag1+ is bonded in a 3-coordinate geometry to four Se2- atoms. There are a spread of Ag–Se bond distances ranging from 2.65–3.23 Å. In the third Ag1+ site, Ag1+ is bonded in a distorted trigonal non-coplanar geometry to three Se2- atoms. There are one shorter (2.67 Å) and two longer (2.80 Å) Ag–Se bond lengths. In the fourth Ag1+ site, Ag1+ is bonded in a distorted trigonal planar geometry to three Se2- atoms. There are two shorter (2.60 Å) and one longer (2.77 Å) Ag–Se bond lengths. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 7-coordinate geometry to four K1+ and four Ag1+ atoms. In the second Se2- site, Se2- is bonded in a 8-coordinate geometry to five K1+ and three Ag1+ atoms. In the third Se2- site, Se2- is bonded in a 9-coordinate geometry to three K1+ and six Ag1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Fungal organic acid uptake of mineral-derived K is dependent on distance from carbon hotspot

Fungal mineral weathering regulates the bioavailability of inorganic nutrients from mineral surfaces to organic matter and increase the bioavailable fraction of nutrients. Such weathering strategies are classified as biomechanical or biochemical. In the case of fungal uptake of mineral nutrients through biochemical weathering, it is widely hypothesized that uptake of inorganic nutrients occurs through organic acid chelation, but such processes have not been directly visualized. This is in part due to challenges in probing the complex and heterogeneous soil environment. Here, using an epoxy-based, mineral-doped soil micromodel platform, which emulates soil mineralogy and porosity, we visualize the molecular mechanisms of mineral weathering. Mass spectrometry imaging revealed differences in the distribution of fungal exudates, citric acid, and tartaric acid on the soil micromodels in presence of minerals. Citric acid was detected closer to the nutrient-rich inoculation point, whereas tartaric acid was highly abundant away from inoculation point. This suggested that the organic acid exuded by the fungi depended on the proximity from the carbon-rich organic substrate at the point of inoculation. Using a combination of X-ray fluorescence and X-ray near edge structure analysis, we identified citric acid- and tartaric acid-bound K within fungal hyphae networks grown in the presence of minerals. Combined, our results provide direct evidence that fungi uptake and transport mineral derived nutrient organic acid chelation. The results of this study provided unprecedented visualization of fungal uptake and transport of K + , while resolving the indirect weathering mechanism of fungal K uptake from mineral interfaces.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Materials Data on K9Bi5O13 by Materials Project

K9Bi5O13 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are nine inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to six O2- atoms to form distorted KO6 octahedra that share corners with two equivalent KO6 octahedra, a cornercorner with one KO5 square pyramid, a cornercorner with one BiO4 tetrahedra, a cornercorner with one KO5 trigonal bipyramid, edges with five KO6 octahedra, edges with two equivalent KO5 square pyramids, edges with two equivalent BiO4 tetrahedra, and an edgeedge with one KO5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 13°. There are a spread of K–O bond distances ranging from 2.72–3.02 Å. In the second K1+ site, K1+ is bonded to five O2- atoms to form distorted KO5 trigonal bipyramids that share corners with two KO6 octahedra, a cornercorner with one BiO4 tetrahedra, corners with two equivalent KO5 trigonal bipyramids, and edges with two equivalent KO6 octahedra. The corner-sharing octahedra tilt angles range from 37–44°. There are a spread of K–O bond distances ranging from 2.63–3.01 Å. In the third K1+ site, K1+ is bonded to five O2- atoms to form distorted KO5 square pyramids that share a cornercorner with one KO6 octahedra, corners with two equivalent KO5 square pyramids, a cornercorner with one BiO4 tetrahedra, corners with three equivalent KO5 trigonal bipyramids, and edges with four KO6 octahedra. The corner-sharing octahedral tilt angles are 9°. There are a spread of K–O bond distances ranging from 2.68–2.93 Å. In the fourth K1+ site, K1+ is bonded to six O2- atoms to form distorted KO6 octahedra that share corners with three KO6 octahedra, a cornercorner with one KO5 trigonal bipyramid, an edgeedge with one KO5 square pyramid, and edges with three KO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 19–35°. There are a spread of K–O bond distances ranging from 2.73–3.00 Å. In the fifth K1+ site, K1+ is bonded to five O2- atoms to form distorted KO5 trigonal bipyramids that share a cornercorner with one KO6 octahedra, corners with three equivalent KO5 square pyramids, corners with two equivalent BiO4 tetrahedra, a cornercorner with one KO5 trigonal bipyramid, edges with two KO6 octahedra, and an edgeedge with one KO5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 27°. There are a spread of K–O bond distances ranging from 2.68–2.85 Å. In the sixth K1+ site, K1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of K–O bond distances ranging from 2.70–3.13 Å. In the seventh K1+ site, K1+ is bonded to five O2- atoms to form distorted KO5 trigonal bipyramids that share a cornercorner with one BiO4 tetrahedra, corners with three KO5 trigonal bipyramids, edges with two equivalent KO6 octahedra, and an edgeedge with one KO5 trigonal bipyramid. There are a spread of K–O bond distances ranging from 2.60–2.99 Å. In the eighth K1+ site, K1+ is bonded to six O2- atoms to form distorted KO6 octahedra that share corners with three KO6 octahedra, corners with two equivalent BiO4 tetrahedra, a cornercorner with one KO5 trigonal bipyramid, edges with three equivalent KO6 octahedra, an edgeedge with one KO5 square pyramid, an edgeedge with one BiO4 tetrahedra, and edges with two equivalent KO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 29–35°. There are a spread of K–O bond distances ranging from 2.73–3.29 Å. In the ninth K1+ site, K1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of K–O bond distances ranging from 2.69–3.05 Å. There are five inequivalent Bi+3.40+ sites. In the first Bi+3.40+ site, Bi+3.40+ is bonded in a see-saw-like geometry to four O2- atoms. There are a spread of Bi–O bond distances ranging from 2.10–2.43 Å. In the second Bi+3.40+ site, Bi+3.40+ is bonded to four O2- atoms to form BiO4 tetrahedra that share corners with three KO6 octahedra, a cornercorner with one KO5 square pyramid, corners with four KO5 trigonal bipyramids, and edges with three KO6 octahedra. The corner-sharing octahedra tilt angles range from 11–75°. There are two shorter (2.04 Å) and two longer (2.05 Å) Bi–O bond lengths. In the third Bi+3.40+ site, Bi+3.40+ is bonded in a distorted see-saw-like geometry to four O2- atoms. There are a spread of Bi–O bond distances ranging from 2.06–2.69 Å. In the fourth Bi+3.40+ site, Bi+3.40+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Bi–O bond distances ranging from 2.09–2.91 Å. In the fifth Bi+3.40+ site, Bi+3.40+ is bonded in a distorted see-saw-like geometry to four O2- atoms. There are a spread of Bi–O bond distances ranging from 2.07–2.40 Å. There are thirteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 6-coordinate geometry to four K1+ and two Bi+3.40+ atoms. In the second O2- site, O2- is bonded to five K1+ and one Bi+3.40+ atom to form distorted OK5Bi octahedra that share corners with four OK5Bi octahedra, corners with two OK4Bi trigonal bipyramids, edges with four OK5Bi octahedra, and edges with two equivalent OK4Bi trigonal bipyramids. The corner-sharing octahedra tilt angles range from 3–13°. In the third O2- site, O2- is bonded in a 5-coordinate geometry to four K1+ and one Bi+3.40+ atom. In the fourth O2- site, O2- is bonded to four K1+ and two Bi+3.40+ atoms to form distorted OK4Bi2 octahedra that share corners with four OK5Bi octahedra, a cornercorner with one OK3Bi2 trigonal bipyramid, edges with two equivalent OK5Bi octahedra, an edgeedge with one OK3Bi2 square pyramid, and edges with three OK4Bi trigonal bipyramids. The corner-sharing octahedra tilt angles range from 5–12°. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to three K1+ and one Bi+3.40+ atom. In the sixth O2- site, O2- is bonded in a 5-coordinate geometry to three K1+ and two Bi+3.40+ atoms. In the seventh O2- site, O2- is bonded in a 5-coordinate geometry to two K1+ and three Bi+3.40+ atoms. In the eighth O2- site, O2- is bonded to four K1+ and one Bi+3.40+ atom to form distorted OK4Bi trigonal bipyramids that share a cornercorner with one OK5Bi octahedra, a cornercorner with one OK3Bi2 trigonal bipyramid, and edges with five OK5Bi octahedra. The corner-sharing octahedral tilt angles are 82°. In the ninth O2- site, O2- is bonded to five K1+ and one Bi+3.40+ atom to form distorted OK5Bi octahedra that share corners with four OK5Bi octahedra and an edgeedge with one OK4Bi trigonal bipyramid. The corner-sharing octahedra tilt angles range from 3–27°. In the tenth O2- site, O2- is bonded to three K1+ and two Bi+3.40+ atoms to form distorted OK3Bi2 square pyramids that share corners with two equivalent OK3Bi2 square pyramids, corners with two equivalent OK3Bi2 trigonal bipyramids, edges with three OK5Bi octahedra, and an edgeedge with one OK3Bi2 trigonal bipyramid. In the eleventh O2- site, O2- is bonded to five K1+ and one Bi+3.40+ atom to form distorted OK5Bi octahedra that share corners with four OK5Bi octahedra, edges with two equivalent OK3Bi2 square pyramids, and edges with two OK4Bi trigonal bipyramids. The corner-sharing octahedra tilt angles range from 12–27°. In the twelfth O2- site, O2- is bonded in a 5-coordinate geometry to four K1+ and one Bi+3.40+ atom. In the thirteenth O2- site, O2- is bonded to three K1+ and two equivalent Bi+3.40+ atoms to form distorted OK3Bi2 trigonal bipyramids that share corners with two OK5Bi octahedra, corners with two equivalent OK3Bi2 square pyramids, a cornercorner with one OK4Bi trigonal bipyramid, edges with three OK5Bi octahedra, an edgeedge with one OK3Bi2 square pyramid, and an edgeedge with one OK3Bi2 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 19–80°.

36 MATERIALS SCIENCE↗
NASA NTRS1993

Hypersonic engine component experiments in high heat flux, supersonic flow environment

A major concern in advancing the state-of-the-art technologies for hypersonic vehicles is the development of an aeropropulsion system capable of withstanding the sustained high thermal loads expected during hypersonic flight. Even though progress has been made in the computational understanding of fluid dynamics and the physics/chemistry of high speed flight, there is also a need for experimental facilities capable of providing a high heat flux environment for testing component concepts and verifying/calibrating these analyses. A hydrogen/oxygen rocket engine heat source was developed at the NASA Lewis Research Center as one element in a series of facilities at national laboratories designed to fulfill this need. This 'Hot Gas Facility' is capable of providing heat fluxes up to 450 w/sq cm on flat surfaces and up to 5,000 w/sq cm at the leading edge stagnation point of a strut in a supersonic flow stream. Gas temperatures up to 3050 K can also be attained. Two recent experimental programs conducted in this facility are discussed. The objective of the first experiment is to evaluate the erosion and oxidation characteristics of a coating on a cowl leading edge (or strut leading edge) in a supersonic, high heat flux environment. Macrophotographic data from a coated leading edge model show progressive degradation over several thermal cycles at aerothermal conditions representative of high Mach number flight. The objective of the second experiment is to assess the capability of cooling a porous surface exposed to a high temperature, high velocity flow environment and to provide a heat transfer data base for a design procedure. Experimental results from transpiration cooled surfaces in a supersonic flow environment are presented.

Gladden, Herbert J.↗
DOE OSTI2020

Materials Data on K2VCuS4 by Materials Project

K2VCuS4 crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. K1+ is bonded to eight equivalent S2- atoms to form distorted KS8 hexagonal bipyramids that share corners with four equivalent KS8 hexagonal bipyramids, corners with two equivalent VS4 tetrahedra, corners with four equivalent CuS4 tetrahedra, edges with six equivalent KS8 hexagonal bipyramids, edges with two equivalent CuS4 tetrahedra, edges with three equivalent VS4 tetrahedra, and faces with two equivalent KS8 hexagonal bipyramids. There are a spread of K–S bond distances ranging from 3.32–3.52 Å. V5+ is bonded to four equivalent S2- atoms to form VS4 tetrahedra that share corners with four equivalent KS8 hexagonal bipyramids, edges with six equivalent KS8 hexagonal bipyramids, and edges with two equivalent CuS4 tetrahedra. All V–S bond lengths are 2.18 Å. Cu1+ is bonded to four equivalent S2- atoms to form CuS4 tetrahedra that share corners with eight equivalent KS8 hexagonal bipyramids, edges with four equivalent KS8 hexagonal bipyramids, and edges with two equivalent VS4 tetrahedra. All Cu–S bond lengths are 2.31 Å. S2- is bonded in a 6-coordinate geometry to four equivalent K1+, one V5+, and one Cu1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2VCuSe4 by Materials Project

K2VCuSe4 crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. K1+ is bonded to eight equivalent Se2- atoms to form distorted KSe8 hexagonal bipyramids that share corners with four equivalent KSe8 hexagonal bipyramids, corners with two equivalent VSe4 tetrahedra, corners with four equivalent CuSe4 tetrahedra, edges with six equivalent KSe8 hexagonal bipyramids, edges with two equivalent CuSe4 tetrahedra, edges with three equivalent VSe4 tetrahedra, and faces with two equivalent KSe8 hexagonal bipyramids. There are a spread of K–Se bond distances ranging from 3.42–3.64 Å. V5+ is bonded to four equivalent Se2- atoms to form VSe4 tetrahedra that share corners with four equivalent KSe8 hexagonal bipyramids, edges with six equivalent KSe8 hexagonal bipyramids, and edges with two equivalent CuSe4 tetrahedra. All V–Se bond lengths are 2.32 Å. Cu1+ is bonded to four equivalent Se2- atoms to form CuSe4 tetrahedra that share corners with eight equivalent KSe8 hexagonal bipyramids, edges with four equivalent KSe8 hexagonal bipyramids, and edges with two equivalent VSe4 tetrahedra. All Cu–Se bond lengths are 2.43 Å. Se2- is bonded in a 6-coordinate geometry to four equivalent K1+, one V5+, and one Cu1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2TaCuSe4 by Materials Project

K2TaCuSe4 crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. K1+ is bonded to eight equivalent Se2- atoms to form distorted KSe8 hexagonal bipyramids that share corners with four equivalent KSe8 hexagonal bipyramids, corners with two equivalent TaSe4 tetrahedra, corners with four equivalent CuSe4 tetrahedra, edges with six equivalent KSe8 hexagonal bipyramids, edges with two equivalent CuSe4 tetrahedra, edges with three equivalent TaSe4 tetrahedra, and faces with two equivalent KSe8 hexagonal bipyramids. There are a spread of K–Se bond distances ranging from 3.52–3.72 Å. Ta5+ is bonded to four equivalent Se2- atoms to form TaSe4 tetrahedra that share corners with four equivalent KSe8 hexagonal bipyramids, edges with six equivalent KSe8 hexagonal bipyramids, and edges with two equivalent CuSe4 tetrahedra. All Ta–Se bond lengths are 2.43 Å. Cu1+ is bonded to four equivalent Se2- atoms to form CuSe4 tetrahedra that share corners with eight equivalent KSe8 hexagonal bipyramids, edges with four equivalent KSe8 hexagonal bipyramids, and edges with two equivalent TaSe4 tetrahedra. All Cu–Se bond lengths are 2.47 Å. Se2- is bonded in a 6-coordinate geometry to four equivalent K1+, one Ta5+, and one Cu1+ atom.

36 MATERIALS SCIENCE↗