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At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Measurements of proton capture in the A=100–110 mass region: Constraints on the In 111 (γ,p)/(γ,n) branching point relevant to the γ process

The γ process is an explosive astrophysical scenario, which is thought to be the primary source of the rare proton-rich stable p nuclei. However, current γ-process models remain insufficient in describing the observed p-nuclei abundances, with disagreements up to two orders of magnitude. A sensitivity study has identified 111 In as a model-sensitive (γ,p)/(γ,n) branching point within the γ process. Constraining the involved reaction rates may have a significant impact on the predicted p-nuclei abundances. Here we report on measurements of the cross sections for 102 Pd (p,γ) 103 Ag, 108 Cd (p,γ) 109 In, and 110 Cd (p,γ) 111 In reactions for proton laboratory energies 3–8 MeV using the high efficiency total absorption spectrometer and the γ-summing technique. These measurements were used to constrain Hauser-Feshbach parameters used in talys 1.9, which constrains the 111 In(γ,p) 110 Cd and 111 In(γ,n) 110 Ag reaction rates. The newly constrained reaction rates indicate that the 111 In(γ,p)/(γ,n) branching point occurs at a temperature of 2.71 ± 0.05 GK, well within the temperature range relevant to the γ process. These findings differ significantly from previous studies and may impact the calculated abundances.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Materials Data on Ag3BO3 by Materials Project

Ag3BO3 crystallizes in the trigonal R32 space group. The structure is three-dimensional. Ag1+ is bonded in a 2-coordinate geometry to two equivalent O2- atoms. Both Ag–O bond lengths are 2.20 Å. B3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All B–O bond lengths are 1.38 Å. O2- is bonded in a 3-coordinate geometry to two equivalent Ag1+ and one B3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ag3BO3 by Materials Project

Ag3BO3 crystallizes in the trigonal R-3c space group. The structure is three-dimensional and consists of two Ag3BO3 frameworks. Ag1+ is bonded in a distorted linear geometry to two equivalent O2- atoms. Both Ag–O bond lengths are 2.16 Å. B3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All B–O bond lengths are 1.39 Å. O2- is bonded in a 3-coordinate geometry to two equivalent Ag1+ and one B3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Ambipolar Electrochemistry of Pre‐Intercalated Ti 3 C 2 T x MXene in Ionic Liquid Electrolyte

Abstract Cation intercalation with or without redox remains the dominant charge storage mechanism for two‐dimensional (2D) Ti 3 C 2 T x MXene. Anion‐based charge storage remains unexplored due to intrinsic negative surface charge of MXenes preventing spontaneous intercalation of anions and irreversible oxidation of Ti at anodic potentials in aqueous electrolytes. In this work, we report on the ambipolar electrochemical behavior of the Ti 3 C 2 T x in ionic liquid electrolyte over a 2.5 V electrochemically stable window. The experiments are conducted on a thin Ti 3 C 2 T x film current collector coated with an electroactive layer of small flakes (∼150 nm) of Ti 3 C 2 T x pre‐intercalated with 1‐ethyl‐3‐methylimidazolium bis‐(trifluoromethylsulfonyl)‐imide (EMIM‐TFSI) ionic liquid. Couples of redox peaks with a very small potential separation during the voltage sweep are observed at high negative (−0.75 V vs. Ag wire) and high positive (+0.75 V vs. Ag wire) potentials. Our experimental electrochemical data combined with density functional theory (DFT) calculations suggest feasibility of pseudo‐intercalation of TFSI anions between Ti 3 C 2 T x flakes. This study provides a pathway for elucidating anion intercalation for different MXene chemistries in solvent‐free electrolytes, which can lead to development of MXene based energy storage devices with improved performance.

Electrochemistry↗
DOE OSTI2020

Materials Data on Ag2GeO4 by Materials Project

Ag2GeO4 crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. Ag2+ is bonded in a 4-coordinate geometry to six equivalent O2- atoms. There are a spread of Ag–O bond distances ranging from 2.14–2.82 Å. Ge4+ is bonded in a tetrahedral geometry to four equivalent O2- atoms. All Ge–O bond lengths are 1.79 Å. O2- is bonded in a 3-coordinate geometry to three equivalent Ag2+ and one Ge4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AgMo6Br13 by Materials Project

Mo6AgBr13 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are six inequivalent Mo2+ sites. In the first Mo2+ site, Mo2+ is bonded to five Br1- atoms to form a mixture of edge and corner-sharing MoBr5 square pyramids. There are a spread of Mo–Br bond distances ranging from 2.61–2.75 Å. In the second Mo2+ site, Mo2+ is bonded to five Br1- atoms to form MoBr5 square pyramids that share a cornercorner with one AgBr4 trigonal pyramid and edges with four MoBr5 square pyramids. There are a spread of Mo–Br bond distances ranging from 2.62–2.64 Å. In the third Mo2+ site, Mo2+ is bonded to five Br1- atoms to form a mixture of edge and corner-sharing MoBr5 square pyramids. There are a spread of Mo–Br bond distances ranging from 2.60–2.76 Å. In the fourth Mo2+ site, Mo2+ is bonded to five Br1- atoms to form MoBr5 square pyramids that share a cornercorner with one AgBr4 trigonal pyramid and edges with four MoBr5 square pyramids. There are a spread of Mo–Br bond distances ranging from 2.59–2.64 Å. In the fifth Mo2+ site, Mo2+ is bonded to five Br1- atoms to form MoBr5 square pyramids that share a cornercorner with one AgBr4 trigonal pyramid and edges with four MoBr5 square pyramids. There are a spread of Mo–Br bond distances ranging from 2.61–2.64 Å. In the sixth Mo2+ site, Mo2+ is bonded to five Br1- atoms to form MoBr5 square pyramids that share a cornercorner with one AgBr4 trigonal pyramid and edges with four MoBr5 square pyramids. There are a spread of Mo–Br bond distances ranging from 2.60–2.65 Å. Ag1+ is bonded to four Br1- atoms to form distorted AgBr4 trigonal pyramids that share corners with four MoBr5 square pyramids. There are a spread of Ag–Br bond distances ranging from 2.69–2.91 Å. There are thirteen inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a 12-coordinate geometry to three Mo2+ atoms. In the second Br1- site, Br1- is bonded in a 5-coordinate geometry to three Mo2+ atoms. In the third Br1- site, Br1- is bonded in a 4-coordinate geometry to three Mo2+ atoms. In the fourth Br1- site, Br1- is bonded in a 3-coordinate geometry to three Mo2+ atoms. In the fifth Br1- site, Br1- is bonded in a 5-coordinate geometry to three Mo2+ atoms. In the sixth Br1- site, Br1- is bonded in a 12-coordinate geometry to three Mo2+ atoms. In the seventh Br1- site, Br1- is bonded in a bent 120 degrees geometry to one Mo2+ and one Ag1+ atom. In the eighth Br1- site, Br1- is bonded in a distorted bent 120 degrees geometry to one Mo2+ and one Ag1+ atom. In the ninth Br1- site, Br1- is bonded in a 3-coordinate geometry to three Mo2+ atoms. In the tenth Br1- site, Br1- is bonded in a bent 120 degrees geometry to two Mo2+ atoms. In the eleventh Br1- site, Br1- is bonded in a bent 150 degrees geometry to one Mo2+ and one Ag1+ atom. In the twelfth Br1- site, Br1- is bonded in a bent 120 degrees geometry to one Mo2+ and one Ag1+ atom. In the thirteenth Br1- site, Br1- is bonded in a 3-coordinate geometry to three Mo2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Capture of Iodine from Nuclear-Fuel-Reprocessing Off-Gas: Influence of Aging on a Reduced Silver Mordenite Adsorbent after Exposure to NO/NO 2

Iodine radioisotopes released during nuclear fuel reprocessing must be removed from the off-gas stream before discharge. One promising material for iodine capture is reduced silver mordenite (Ag 0 Z). Nevertheless, the adsorbent’s capacity will degrade, or age, over time when the material is exposed to other off-gas constituents. Though the overall impact of aging is known, the underlying physical and chemical processes are not. To examine these processes, Ag 0 Z samples were prepared and aged in 2% NO 2 in dry air and in 1% NO in N 2 gas streams at 150 °C for up to six months. Aged samples were then characterized using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray absorption spectroscopy. These techniques show that aging involves two overarching processes: (i) oxidation of the silver nanoparticles present in Ag 0 Z and (ii) migration of oxidized silver into the mordenite’s inner network. Silver on the nanoparticle’s surface is oxidized through adsorption of O 2 , NO, and NO 2 . Additionally, Raman spectroscopy and X-ray absorption spectroscopy indicate that nitrates are the primary products of this adsorption. Most of these nitrates migrate into the interior of the mordenite and exchange at framework binding sites, returning silver to its unreduced state (AgZ). The remaining nitrates exist at a persistent concentration without aggregating into bulk-phase AgNO 3 . X-ray absorption spectroscopy results further indicate that iodine adsorption occurs on not just Ag 0 Z but also on AgZ and a portion of the nitrates in the system. AgZ adsorbs a sizable quantity of iodine early in the aging process, but its capacity drops rapidly over time. For well-aged samples, nitrates are responsible for up to 95% of mordenite’s iodine capacity. Overall, these results have enhanced our understanding of the aging process in silver mordenite and are expected to guide the development of superior adsorbents for the capture of radioactive iodine from reprocessing off-gas.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Materials Data on K2Ag(AsSe2)3 by Materials Project

K2Ag(AsSe2)3 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of K–Se bond distances ranging from 3.44–3.60 Å. In the second K1+ site, K1+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of K–Se bond distances ranging from 3.45–3.99 Å. Ag1+ is bonded to four Se2- atoms to form distorted edge-sharing AgSe4 tetrahedra. There are a spread of Ag–Se bond distances ranging from 2.66–2.84 Å. There are three inequivalent As3+ sites. In the first As3+ site, As3+ is bonded in a distorted trigonal non-coplanar geometry to three Se2- atoms. There are one shorter (2.41 Å) and two longer (2.46 Å) As–Se bond lengths. In the second As3+ site, As3+ is bonded in a trigonal non-coplanar geometry to three Se2- atoms. There are a spread of As–Se bond distances ranging from 2.38–2.51 Å. In the third As3+ site, As3+ is bonded in a trigonal non-coplanar geometry to three Se2- atoms. There are a spread of As–Se bond distances ranging from 2.36–2.50 Å. There are six inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to two K1+ and two As3+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to three K1+, one Ag1+, and one As3+ atom. In the third Se2- site, Se2- is bonded to three K1+ and two As3+ atoms to form distorted SeK3As2 square pyramids that share corners with two equivalent SeK3As2 square pyramids, a cornercorner with one SeK2As2 trigonal pyramid, and an edgeedge with one SeK2As2 trigonal pyramid. In the fourth Se2- site, Se2- is bonded in a 4-coordinate geometry to two K1+, one Ag1+, and one As3+ atom. In the fifth Se2- site, Se2- is bonded to two equivalent K1+ and two As3+ atoms to form distorted SeK2As2 trigonal pyramids that share a cornercorner with one SeK3As2 square pyramid, corners with two equivalent SeK2As2 trigonal pyramids, and an edgeedge with one SeK3As2 square pyramid. In the sixth Se2- site, Se2- is bonded in a 5-coordinate geometry to three K1+, two equivalent Ag1+, and one As3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er7(AgTe)2 by Materials Project

Er7(AgTe)2 crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. there are four inequivalent Er sites. In the first Er site, Er is bonded in a 4-coordinate geometry to two equivalent Ag and two equivalent Te atoms. Both Er–Ag bond lengths are 3.01 Å. Both Er–Te bond lengths are 3.10 Å. In the second Er site, Er is bonded in a 3-coordinate geometry to three Te atoms. There are two shorter (3.24 Å) and one longer (3.28 Å) Er–Te bond lengths. In the third Er site, Er is bonded to two equivalent Ag and three Te atoms to form a mixture of distorted edge, corner, and face-sharing ErAg2Te3 trigonal bipyramids. Both Er–Ag bond lengths are 2.97 Å. There are one shorter (3.08 Å) and two longer (3.15 Å) Er–Te bond lengths. In the fourth Er site, Er is bonded in a 4-coordinate geometry to three equivalent Ag and one Te atom. There are two shorter (2.91 Å) and one longer (3.18 Å) Er–Ag bond lengths. The Er–Te bond length is 3.13 Å. Ag is bonded in a 7-coordinate geometry to seven Er atoms. There are two inequivalent Te sites. In the first Te site, Te is bonded in a 8-coordinate geometry to eight Er atoms. In the second Te site, Te is bonded to seven Er atoms to form distorted edge-sharing TeEr7 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn2V3(AgO4)3 by Materials Project

V3Mn2(AgO4)3 crystallizes in the cubic Ia-3d space group. The structure is three-dimensional. V5+ is bonded to four equivalent O2- atoms to form VO4 tetrahedra that share corners with four equivalent MnO6 octahedra. The corner-sharing octahedral tilt angles are 45°. All V–O bond lengths are 1.76 Å. Mn3+ is bonded to six equivalent O2- atoms to form MnO6 octahedra that share corners with six equivalent VO4 tetrahedra. All Mn–O bond lengths are 2.08 Å. Ag1+ is bonded in a distorted body-centered cubic geometry to eight equivalent O2- atoms. There are four shorter (2.56 Å) and four longer (2.62 Å) Ag–O bond lengths. O2- is bonded in a 4-coordinate geometry to one V5+, one Mn3+, and two equivalent Ag1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ag2HgSI2 by Materials Project

Ag2HgSI2 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. Ag1+ is bonded to one S2- and three equivalent I1- atoms to form corner-sharing AgSI3 tetrahedra. The Ag–S bond length is 2.60 Å. There are a spread of Ag–I bond distances ranging from 2.85–2.93 Å. Hg2+ is bonded in a distorted linear geometry to two equivalent S2- atoms. There are one shorter (2.41 Å) and one longer (2.42 Å) Hg–S bond lengths. S2- is bonded to two equivalent Ag1+ and two equivalent Hg2+ atoms to form corner-sharing SAg2Hg2 trigonal pyramids. I1- is bonded in a 3-coordinate geometry to three equivalent Ag1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Understanding 2p core-level excitons of late transition metals by analysis of mixed-valence copper in a metal–organic framework

The L 2,3 -edge X-ray absorption spectra of late transition metals such as Cu, Ag, and Au exhibit absorption onsets lower in energy for higher oxidation states, which is at odds with the measured spectra of earlier transition metals. Time-dependent density functional theory calculations for Cu 2+ /Cu + reveal a larger 2p core-exciton binding energy for Cu 2+ , overshadowing shifts in single-particle excitation energies with respect to Cu + . Finally, we explore this phenomenon in a Cu + metal–organic framework with ~12% Cu 2+ defects and find that corrections with self-consistent excited-state total energy differences provide accurate XAS peak alignment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1978

Progress towards high efficiency polycrystalline thin-film GaAs AMOS solar cells

Results of Ge film recrystallization using focused laser beams and GaAs film growth on such layers in the making of high efficiency thin-film AMOS solar cells are discussed. Since a conversion efficiency of 14% was obtained for an AMOS cell fabricated on sliced bulk polycrystalline GaAs, high efficiency cells are being developed by chemically vapor-depositing GaAs films on previously recrystallized evaporated Ge films to minimize the grain boundary (GB) effects. Schottky barrier solar cells made on sliced polycrystalline GaAs wafers were studied to investigate the effects of grain boundaries on cell properties and the potential efficiency of GaAs thin-film cells. Ge film recrystallization and the chemical vapor deposition (CVD) of the 2 to 3 micron thick GaAs films are described. AMOS solar cells with 100 Angstrom thick Ag metallization were made on CVD GaAs/recrystallized Ge/W substrates with an energy conversion efficiency of 8%.

Yeh, Y. C. M.↗
NASA NTRS1985

A regional 17-18 MA thermal event in Southwestern Arizona

A regional thermal event in southwestern Arizona 17 to 18 Ma ago is suggested by discordances between fission track (FT) and K-Ar dates in Tertiary volcanic and sedimentary rocks, by the abundance of primary hydrothermal orthoclase in quenched volcanic rocks, and by the concentration of Mn, Ba, Cu, Ag, and Au deposits near detachment faults. A high condont alteration index (CAI) of 3 to 7 is found in Paleozoic rocks of southwestern Arizona. The high CAI may have been caused by this mid-Tertiary thermal event. Resetting of temperature-sensitive TF dates (2) 17 to 18 Ma with respect to K-Ar dates of 24 and 20 Ma has occurred in upper plate volcanic rocks at the Harcuvar and Picacho Peak detachments. Discordances between FT and K-Ar dates are most pronounced at detachment faults. However, on a regional scale Ft dates from volcanic and sedimentary rocks approach 17 to 18 Ma event in areas away from known detachment faults. Effects of detachment faulting on the K-Ar system suggest that dates of correlative rocks will be younger as the detachment fault is approached.

Brooks, W. E.↗
DOE OSTI2020

Materials Data on KMnAg3(CN)6 by Materials Project

KMnAg3(CN)6 crystallizes in the trigonal P312 space group. The structure is three-dimensional. K1+ is bonded to six equivalent N3- atoms to form distorted KN6 octahedra that share edges with three equivalent MnN6 octahedra. All K–N bond lengths are 2.94 Å. Mn2+ is bonded to six equivalent N3- atoms to form MnN6 octahedra that share edges with three equivalent KN6 octahedra. All Mn–N bond lengths are 2.23 Å. Ag1+ is bonded in a linear geometry to two equivalent C2+ atoms. Both Ag–C bond lengths are 2.06 Å. C2+ is bonded in a linear geometry to one Ag1+ and one N3- atom. The C–N bond length is 1.17 Å. N3- is bonded in a 3-coordinate geometry to one K1+, one Mn2+, and one C2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Influence of Ag metal dispersion on the thermal conversion of ethanol to butadiene over Ag-ZrO 2 /SiO 2 catalysts

Atomistic scale models were developed and coupled with experimental investigation to deliver a functional understanding of catalytic activity and selectivity in the conversion of ethanol to 1,3-butadiene over Ag/ZrO 2 /SiO 2 . A detailed evaluation of the structural and electronic properties of the resultant catalyst models led to the identification of critical active sites of the catalyst. More importantly, the extent of Ag dispersion on the SiO 2 support and relative proximity to ZrO 2 were found to vary with the oxidation state of Ag and local coordination environment (Ag-O SiO2 ) allowing for critical control of ethanol conversion towards butadiene or ethylene. Simulations revealed that less dispersed or clustered Ag contain predominantly Ag 0 charge state and promote conversion of ethanol to ethylene. The well-dispersed Ag/ZrO 2 /SiO 2 catalyst instead contain a larger fraction of cationic Ag δ+ , and predominantly promote ethanol dehydrogenation and subsequent production of butadiene. The theoretical insights drawn were validated and confirmed experimentally using TEM, XRD and reactivity measurements demonstrating the effect of Ag dispersion on the selectivity of ethanol conversion.

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

Materials Data on ScAg(PSe3)2 by Materials Project

ScAg(PSe3)2 crystallizes in the trigonal P-31c space group. The structure is two-dimensional and consists of two ScAg(PSe3)2 sheets oriented in the (0, 0, 1) direction. Sc3+ is bonded to six equivalent Se2- atoms to form ScSe6 octahedra that share edges with three equivalent AgSe6 octahedra. All Sc–Se bond lengths are 2.73 Å. Ag1+ is bonded to six equivalent Se2- atoms to form AgSe6 octahedra that share edges with three equivalent ScSe6 octahedra. All Ag–Se bond lengths are 2.95 Å. P4+ is bonded in a trigonal non-coplanar geometry to three equivalent Se2- atoms. All P–Se bond lengths are 2.22 Å. Se2- is bonded in a 3-coordinate geometry to one Sc3+, one Ag1+, and one P4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TmAg(PSe3)2 by Materials Project

TmAg(PSe3)2 crystallizes in the trigonal P-31c space group. The structure is two-dimensional and consists of two TmAg(PSe3)2 sheets oriented in the (0, 0, 1) direction. Tm3+ is bonded to six equivalent Se2- atoms to form TmSe6 octahedra that share edges with three equivalent AgSe6 octahedra. All Tm–Se bond lengths are 2.85 Å. Ag1+ is bonded to six equivalent Se2- atoms to form AgSe6 octahedra that share edges with three equivalent TmSe6 octahedra. All Ag–Se bond lengths are 2.95 Å. P4+ is bonded in a trigonal non-coplanar geometry to three equivalent Se2- atoms. All P–Se bond lengths are 2.21 Å. Se2- is bonded in a 3-coordinate geometry to one Tm3+, one Ag1+, and one P4+ atom.

36 MATERIALS SCIENCE↗