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At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on TlTcO2 by Materials Project

TcTlO2 crystallizes in the tetragonal I4_1/a space group. The structure is three-dimensional. Tc3+ is bonded in a distorted rectangular see-saw-like geometry to four equivalent O2- atoms. There are two shorter (2.06 Å) and two longer (2.07 Å) Tc–O bond lengths. Tl1+ is bonded to six equivalent O2- atoms to form edge-sharing TlO6 octahedra. There are a spread of Tl–O bond distances ranging from 2.67–3.03 Å. O2- is bonded in a 5-coordinate geometry to two equivalent Tc3+ and three equivalent Tl1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ReTc(SnO3)2 by Materials Project

Sn2TcReO6 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Re7+ is bonded to six equivalent O2- atoms to form ReO6 octahedra that share corners with six equivalent TcO6 octahedra and faces with eight equivalent SnO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All Re–O bond lengths are 1.97 Å. Tc3- is bonded to six equivalent O2- atoms to form TcO6 octahedra that share corners with six equivalent ReO6 octahedra and faces with eight equivalent SnO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All Tc–O bond lengths are 2.03 Å. Sn4+ is bonded to twelve equivalent O2- atoms to form SnO12 cuboctahedra that share corners with twelve equivalent SnO12 cuboctahedra, faces with six equivalent SnO12 cuboctahedra, faces with four equivalent ReO6 octahedra, and faces with four equivalent TcO6 octahedra. All Sn–O bond lengths are 2.83 Å. O2- is bonded in a linear geometry to one Re7+, one Tc3-, and four equivalent Sn4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TcN2 by Materials Project

TcN2 is Fluorite structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Tc6+ is bonded in a body-centered cubic geometry to eight equivalent N3- atoms. All Tc–N bond lengths are 2.12 Å. N3- is bonded to four equivalent Tc6+ atoms to form a mixture of corner and edge-sharing NTc4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on UTcO3 by Materials Project

UTcO3 is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. U4+ is bonded to twelve equivalent O2- atoms to form UO12 cuboctahedra that share corners with twelve equivalent UO12 cuboctahedra, faces with six equivalent UO12 cuboctahedra, and faces with eight equivalent TcO6 octahedra. All U–O bond lengths are 2.81 Å. Tc2+ is bonded to six equivalent O2- atoms to form TcO6 octahedra that share corners with six equivalent TcO6 octahedra and faces with eight equivalent UO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All Tc–O bond lengths are 1.98 Å. O2- is bonded in a distorted linear geometry to four equivalent U4+ and two equivalent Tc2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TcMo by Materials Project

MoTc crystallizes in the orthorhombic Cmmm space group. The structure is two-dimensional and consists of two MoTc sheets oriented in the (0, 1, 0) direction. Mo3+ is bonded in a 4-coordinate geometry to four equivalent Tc3- atoms. All Mo–Tc bond lengths are 2.70 Å. Tc3- is bonded in a 8-coordinate geometry to four equivalent Mo3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TlTcO3 by Materials Project

TcTlO3 is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Tc5+ is bonded to six equivalent O2- atoms to form TcO6 octahedra that share corners with six equivalent TcO6 octahedra and faces with eight equivalent TlO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All Tc–O bond lengths are 2.00 Å. Tl1+ is bonded to twelve equivalent O2- atoms to form TlO12 cuboctahedra that share corners with twelve equivalent TlO12 cuboctahedra, faces with six equivalent TlO12 cuboctahedra, and faces with eight equivalent TcO6 octahedra. All Tl–O bond lengths are 2.82 Å. O2- is bonded in a distorted linear geometry to two equivalent Tc5+ and four equivalent Tl1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeSi2Tc by Materials Project

TcFeSi2 crystallizes in the orthorhombic Immm space group. The structure is one-dimensional and consists of two TcFeSi2 ribbons oriented in the (1, 0, 0) direction. Tc3- is bonded in a linear geometry to two equivalent Si atoms. Both Tc–Si bond lengths are 2.31 Å. Fe3+ is bonded in a linear geometry to two equivalent Si atoms. Both Fe–Si bond lengths are 2.23 Å. Si is bonded in a linear geometry to one Tc3- and one Fe3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La2TcNiO6 by Materials Project

La2TcNiO6 is (Cubic) Perovskite-derived structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. La3+ is bonded to twelve equivalent O2- atoms to form LaO12 cuboctahedra that share corners with twelve equivalent LaO12 cuboctahedra, faces with six equivalent LaO12 cuboctahedra, faces with four equivalent TcO6 octahedra, and faces with four equivalent NiO6 octahedra. All La–O bond lengths are 2.80 Å. Tc4+ is bonded to six equivalent O2- atoms to form TcO6 octahedra that share corners with six equivalent NiO6 octahedra and faces with eight equivalent LaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All Tc–O bond lengths are 1.98 Å. Ni2+ is bonded to six equivalent O2- atoms to form NiO6 octahedra that share corners with six equivalent TcO6 octahedra and faces with eight equivalent LaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All Ni–O bond lengths are 1.99 Å. O2- is bonded in a distorted linear geometry to four equivalent La3+, one Tc4+, and one Ni2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Si2TcRh by Materials Project

TcRhSi2 crystallizes in the orthorhombic Immm space group. The structure is one-dimensional and consists of two TcRhSi2 ribbons oriented in the (1, 0, 0) direction. Tc3- is bonded in a linear geometry to two equivalent Si atoms. Both Tc–Si bond lengths are 2.28 Å. Rh3+ is bonded in a linear geometry to two equivalent Si atoms. Both Rh–Si bond lengths are 2.23 Å. Si is bonded in a distorted linear geometry to one Tc3- and one Rh3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SrTcO3 by Materials Project

SrTcO3 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Sr2+ is bonded to twelve O2- atoms to form distorted SrO12 cuboctahedra that share corners with twelve equivalent SrO12 cuboctahedra, faces with six equivalent SrO12 cuboctahedra, and faces with eight equivalent TcO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.57–3.08 Å. Tc4+ is bonded to six O2- atoms to form TcO6 octahedra that share corners with six equivalent TcO6 octahedra and faces with eight equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 12–15°. There are two shorter (2.00 Å) and four longer (2.01 Å) Tc–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to four equivalent Sr2+ and two equivalent Tc4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to four equivalent Sr2+ and two equivalent Tc4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zr2TcAu by Materials Project

Zr2TcAu crystallizes in the orthorhombic Immm space group. The structure is one-dimensional and consists of two Zr2TcAu ribbons oriented in the (1, 0, 0) direction. Zr2+ is bonded in a linear geometry to one Tc3- and one Au1- atom. The Zr–Tc bond length is 2.27 Å. The Zr–Au bond length is 2.78 Å. Tc3- is bonded in a linear geometry to two equivalent Zr2+ atoms. Au1- is bonded in a linear geometry to two equivalent Zr2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TcPt by Materials Project

TcPt crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Tc2+ is bonded in a hexagonal planar geometry to six equivalent Pt2- atoms. All Tc–Pt bond lengths are 2.78 Å. Pt2- is bonded to six equivalent Tc2+ and six equivalent Pt2- atoms to form a mixture of corner, edge, and face-sharing PtTc6Pt6 cuboctahedra. All Pt–Pt bond lengths are 2.76 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs2TcI6 by Materials Project

Cs2TcI6 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Cs1+ is bonded to twelve equivalent I1- atoms to form CsI12 cuboctahedra that share corners with twelve equivalent CsI12 cuboctahedra, faces with six equivalent CsI12 cuboctahedra, and faces with four equivalent TcI6 octahedra. All Cs–I bond lengths are 4.19 Å. Tc4+ is bonded to six equivalent I1- atoms to form TcI6 octahedra that share faces with eight equivalent CsI12 cuboctahedra. All Tc–I bond lengths are 2.75 Å. I1- is bonded in a distorted single-bond geometry to four equivalent Cs1+ and one Tc4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Tc by Materials Project

KK2Tc is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional and consists of four potassium molecules and one K2Tc framework. In the K2Tc framework, K1+ is bonded to four equivalent Tc3- atoms to form a mixture of edge and corner-sharing KTc4 tetrahedra. All K–Tc bond lengths are 3.87 Å. Tc3- is bonded in a body-centered cubic geometry to eight equivalent K1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A Boosted Critical Temperature of 166 K in Superconducting D 3 S Synthesized from Elemental Sulfur and Hydrogen

The discovery of superconductivity in H 3 S at 203 K marked an advance towards room-temperature superconductivity and demonstrated the potential of H-dominated compounds to possess a high critical temperature (T c ). There have been numerous reports of the H-S system over the last five years, but important questions remain unanswered. It is crucial to verify whether the Tc was determined correctly for samples prepared from compressed H 2 S, since they are inevitably contaminated with H-depleted byproducts. Here, we prepare stoichiometric H 3 S by direct in situ synthesis from elemental S and excess H 2 . The Im$_\bar{3}$ m phase of D 3 S samples exhibits a T c significantly higher than previously reported values (ca. 150 K), reaching a maximum T c of 166 K at 157 GPa. Furthermore, we confirm that the sharp decrease in T c below 150 GPa is accompanied by continuous rhombohedral structural distortions and demonstrate that the Cccm phase is nonmetallic, with molecular H 2 units in the crystal structure.

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

Environmental remediation with functional aerogels and xerogels

Several different types of aerogel and/or xerogel scaffolds have been demonstrated as effective sorbents for the capture and immobilization of radionuclides in gaseous form [e.g., iodine gas or I2(g), Xe] as well as ionic form (e.g., Ce4+, Cs+, I–, IO3-, Rb+, Sr2+, 99Tc7+, and U6+). These scaffolds have unique properties, which include high specific surface areas, high pore volumes, varieties of pore sizes, and functionalities that provide methods for binding radionuclides through physisorption, chemisorption, or a combination thereof. This combination of properties and functionalities make these types of materials ideal scaffolds for use as sorbents for capturing radionuclides. The primary base materials that will be discussed in this chapter include Ag0-functionalized silica aerogels, Ag+-impregnated aluminosilicate aerogels, Ag0-functionalized aluminosilicate aerogels, metal-impregnated (non-Ag) aluminosilicate aerogels and xerogels, sulfide-based aerogels, and carbon-based aerogel composites. For the capture of I2(g), the materials reported herein show some of the highest iodine loadings ever reported for inorganic sorbents. For the capture of ionic species, these materials also show promise to be some of the next generations of materials for active radionuclide remediation. This progress report will describe how these materials are fabricated, the general properties of these materials, as well as an overview of how they have been used for different applications in environmental remediation of radionuclides.

aerogel, xerogel, iodine, radionuclide remediation↗
DOE OSTI2024

Characteristics and trends of Atlantic tropical cyclones that do and do not develop from African easterly waves

Abstract Atlantic tropical cyclones (TCs) are known to develop from African easterly waves (AEWs) that propagate across North Africa and out over the Atlantic Ocean. The relationship between AEWs and TCs has been the subject of numerous previous studies. There are, however, many Atlantic TCs that do not have AEW origins. In this study, we provide a novel analysis of the characteristics and trends of Atlantic TCs both with and without AEW origins using 43 years of observational and reanalysis data. To conduct this research, we identified TCs with and without AEW origins from the observational record between 1980 and 2022, and ran objective tracking algorithms on reanalysis data to identify the AEWs and TCs during this time period. We found statistically significant differences in the characteristics and environments of TCs with and without AEW origins. TCs with AEW origins are stronger and costlier, experience more favorable environmental conditions, and are more likely to make landfall in the Gulf of Mexico and the Caribbean when compared to TCs without AEW origins. Additionally, the 43‐year increasing trend in Atlantic TC activity is primarily driven by an increase in TCs with AEW origins that is associated with increasing AEW frequency and strength, with anthropogenic aerosols potentially driving this trend. In contrast, we found no trend in TCs without AEW origins.

Bercos‐Hickey, Emily↗
DOE OSTI2024

Enhanced Interfacial Electron Transfer in Photocatalyst-Natural Enzyme Coupled Artificial Photosynthesis System: Tuning Strategies and Molecular Simulations

Laccase is capable of catalyzing a vast array of reactions, but its low redox potential limits its potential applications. The use of photocatalytic materials offers a solution to this problem by converting absorbed visible light into electrons to facilitate enzyme catalysis. Herein, MIL-53(Fe) and NH 2 -MIL-53(Fe) serve as both light absorbers and enzyme immobilization carriers, and laccase is employed for solar-driven chemical conversion. Electron spin resonance spectroscopy results confirm that visible light irradiation causes rapid transfer of photogenerated electrons from MOF excitation to T1 Cu(II) of laccase, significantly increasing the degradation rate constant of tetracycline (TC) from 0.0062 to 0.0127 min -1 . Conversely, there is only minimal or no electron transfer between MOF and laccase in the physical mixture state. Theoretical calculations demonstrate that the immobilization of laccase's active site and its covalent binding to the metal-organic framework surface augment the coupled system's activity, reducing the active site accessible from 27.8 to 18.1 Å. In conclusion, the constructed photo-enzyme coupled system successfully combines enzyme catalysis’ selectivity with photocatalysis's high reactivity, providing a promising solution for solar energy use.

36 MATERIALS SCIENCE↗