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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Sn2As2H22C7(ClO2)2 by Materials Project

C2H3Sn2AsH8(CO)4CAsH6Cl(H2)2HCl crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of one ethylene molecule, one hydrochloric acid molecule, two hydrogen molecules, one CAsH6Cl cluster, and one Sn2AsH8(CO)4 cluster. In the CAsH6Cl cluster, C+1.71- is bonded in a distorted water-like geometry to one As3-, two H1+, and one Cl1- atom. The C–As bond length is 1.97 Å. Both C–H bond lengths are 1.10 Å. The C–Cl bond length is 2.23 Å. As3- is bonded in a distorted T-shaped geometry to one C+1.71- and two H1+ atoms. Both As–H bond lengths are 1.55 Å. There are six inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C+1.71- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one As3- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one As3- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one Cl1- atom. The H–Cl bond length is 1.30 Å. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one Cl1- atom. The H–Cl bond length is 1.58 Å. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C+1.71- atom. Cl1- is bonded in a distorted T-shaped geometry to one C+1.71- and two H1+ atoms. In the Sn2AsH8(CO)4 cluster, there are two inequivalent Sn3+ sites. In the first Sn3+ site, Sn3+ is bonded in a distorted tetrahedral geometry to two C+1.71- and two O2- atoms. There are one shorter (2.18 Å) and one longer (2.32 Å) Sn–C bond lengths. There are one shorter (2.01 Å) and one longer (2.20 Å) Sn–O bond lengths. In the second Sn3+ site, Sn3+ is bonded in a 4-coordinate geometry to two C+1.71- and two O2- atoms. There are one shorter (2.15 Å) and one longer (2.48 Å) Sn–C bond lengths. There are one shorter (2.04 Å) and one longer (2.29 Å) Sn–O bond lengths. There are four inequivalent C+1.71- sites. In the first C+1.71- site, C+1.71- is bonded in a distorted bent 120 degrees geometry to one Sn3+, one H1+, and one O2- atom. The C–H bond length is 1.11 Å. The C–O bond length is 1.22 Å. In the second C+1.71- site, C+1.71- is bonded in a distorted trigonal non-coplanar geometry to one Sn3+ and three H1+ atoms. There is two shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. In the third C+1.71- site, C+1.71- is bonded in a distorted trigonal planar geometry to one Sn3+ and two H1+ atoms. There is one shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. In the fourth C+1.71- site, C+1.71- is bonded in a distorted bent 120 degrees geometry to one Sn3+, one As3-, one H1+, and one O2- atom. The C–As bond length is 2.04 Å. The C–H bond length is 1.11 Å. The C–O bond length is 1.28 Å. As3- is bonded in a 3-coordinate geometry to one C+1.71-, one H1+, and one O2- atom. The As–H bond length is 1.56 Å. The As–O bond length is 1.88 Å. There are eight inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C+1.71- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C+1.71- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C+1.71- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C+1.71- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one C+1.71- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C+1.71- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one C+1.71- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one As3- atom. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a water-like geometry to two Sn3+ atoms. In the second O2- site, O2- is bonded in a single-bond geometry to one C+1.71- atom. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to two Sn3+ and one As3- atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+1.71- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeB18H42C8(SN)2 by Materials Project

FeB16(H8S)2(BH)2(N(CH3)4)2 is Silicon tetrafluoride-derived structured and crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of eight boranediylradical molecules, eight tetramethylammonium molecules, and four FeB16(H8S)2 clusters. In each FeB16(H8S)2 cluster, Fe2+ is bonded in a distorted hexagonal bipyramidal geometry to six B and two equivalent S2- atoms. There are a spread of Fe–B bond distances ranging from 2.21–2.26 Å. Both Fe–S bond lengths are 2.27 Å. There are eight inequivalent B sites. In the first B site, B is bonded in a distorted single-bond geometry to one Fe2+, one B, and one H+0.95+ atom. The B–B bond length is 1.79 Å. The B–H bond length is 1.21 Å. In the second B site, B is bonded in a single-bond geometry to one B and one H+0.95+ atom. The B–B bond length is 1.78 Å. The B–H bond length is 1.20 Å. In the third B site, B is bonded in a 2-coordinate geometry to three B, one H+0.95+, and one S2- atom. There is one shorter (1.76 Å) and one longer (1.87 Å) B–B bond length. The B–H bond length is 1.20 Å. The B–S bond length is 1.93 Å. In the fourth B site, B is bonded in a distorted single-bond geometry to one B and one H+0.95+ atom. The B–B bond length is 1.73 Å. The B–H bond length is 1.20 Å. In the fifth B site, B is bonded in a 1-coordinate geometry to one Fe2+, three B, one H+0.95+, and one S2- atom. The B–B bond length is 1.84 Å. The B–H bond length is 1.20 Å. The B–S bond length is 2.00 Å. In the sixth B site, B is bonded in a distorted single-bond geometry to one Fe2+ and one H+0.95+ atom. The B–H bond length is 1.20 Å. In the seventh B site, B is bonded in a 1-coordinate geometry to two B, one H+0.95+, and one S2- atom. The B–H bond length is 1.20 Å. The B–S bond length is 1.98 Å. In the eighth B site, B is bonded in a distorted single-bond geometry to one B and one H+0.95+ atom. The B–H bond length is 1.21 Å. There are eight inequivalent H+0.95+ sites. In the first H+0.95+ site, H+0.95+ is bonded in a single-bond geometry to one B atom. In the second H+0.95+ site, H+0.95+ is bonded in a single-bond geometry to one B atom. In the third H+0.95+ site, H+0.95+ is bonded in a single-bond geometry to one B atom. In the fourth H+0.95+ site, H+0.95+ is bonded in a single-bond geometry to one B atom. In the fifth H+0.95+ site, H+0.95+ is bonded in a single-bond geometry to one B atom. In the sixth H+0.95+ site, H+0.95+ is bonded in a single-bond geometry to one B atom. In the seventh H+0.95+ site, H+0.95+ is bonded in a single-bond geometry to one B atom. In the eighth H+0.95+ site, H+0.95+ is bonded in a single-bond geometry to one B atom. S2- is bonded in a 4-coordinate geometry to one Fe2+ and three B atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1985

Containerless Studies of Nucleation and Undercooling

The long term research goals are to perform experiments to determine the achievable limits of undercooling, the characteristics of heterogeneous nucleation, and the physical properties of significantly undercooled melts. The techniques used are based on the newly developed containerless manipulation methods afforded by acoustic levitation. Ground based investigations involved 0.1 to 2 mm specimens of pure metals and alloys (In, Ga, Sn, Ga-In, ...) as well as glass-forming organic compounds (O-Terphenyl). A currently operating ultrasonic high temperature apparatus has allowed the ground-based levitation of 1 to 2 mm samples of solid aluminum at 550 deg C in an argon atmosphere. Present work is concentrating on the undercooling of pure metal samples (In, Sn), and on the measurements of surface tension and viscosity of the undercooled melts via shape oscillation techniques monitored through optical detection methods. The sound velocity of undercooled O-Terphenyl is being measured in an immiscible liquid levitation cells.

Trinh, E. H.↗
DOE OSTI2024

Impact of Sugarcane Cultivation on C Cycling in Southeastern United States Following Conversion From Grazed Pastures

ABSTRACT The expansion of sugarcane, a tropical high‐yielding feedstock, will likely reshape the Southeastern United States (SE US) bioenergy landscape. However, the sustainability of sugarcane, particularly as it displaces grazed pastures, is highly uncertain. Here, we investigated how pasture conversion to sugarcane in subtropical Florida impacts net ecosystem CO 2 exchange (NEE) and net ecosystem carbon (C) balance (NECB). Measurements were made over three full growth cycles (> 3 years) in sugarcane—plant cane, PC; first ratoon cane, FRC; second ratoon cane, SRC—and in improved (IM) and semi‐native (SN) pastures, which make up ca. 37% of agricultural land in the region. Immediately following conversion, PC was a stronger net source of CO 2 than pastures, indicating the importance of CO 2 losses related to land disturbance. Sugarcane, however, shifted to a strong net sink of CO 2 after first regrowth, and overall sugarcane was a stronger net CO 2 sink than pastures. Both stand age and low water availability during cane emergence and tillering substantially decreased its potential gross CO 2 uptake. Accounting for all C gains and removals (i.e., NECB), greater frequency of burn events and repeated harvest increased removals and overall made sugarcane a stronger C source relative to pastures despite substantial C inputs from the previous land use and a stronger CO 2 sink strength. Time since conversion substantially reduced C losses from sugarcane, and the NECB of SRC was similar to that of IM pasture but lower than that of SN pasture, indicating a rapid shift in the NECB of cane. We conclude that the C‐balance implications following conversion will depend on the proportion of IM versus SN pastures converted to sugarcane. Furthermore, our findings suggest that no‐burn harvest management strategies will be critical to the development of a sustainable bioenergy landscape in SE US.

Gomez‐Casanovas, Nuria↗
DOE OSTI2024

A Sulfide‐Based Solid Electrolyte With High Humid Air Tolerance for Long Lifespan All‐Solid‐State Sodium Batteries

Abstract Sulfide‐based superionic conductors present great promise to achieve high energy density and safety for all‐solid‐state sodium batteries (ASSSBs). However, the poor electrolyte/electrode interface compatibility and humid air stability seriously hinder their deployment in ASSSBs. Herein, a series of high‐performance Na 3‐□ Sb 1‐4x (SnWCaTi) x S 4 sulfide‐based solid electrolytes (SSEs) are reported by coupling the vacancy effect with configurational entropy, which displays an excellent interface stability against sodium metal and an extraordinary tolerance toward the moist atmosphere, even for water. The optimized electrolyte effectively inhibits the detrimental mixed ion‐electron conducting interphase formation, achieving the ultra‐stable operation of Na–Na symmetric cell up to 1000 h. Furthermore, the Na + diffusion kinetics is obviously enhanced by increasing the Na sites local anisotropy and Na vacancies. Eventually, the assembled TiS 2 //Na 5 Sn ASSSBs deliver a remarkable reversible capacity of 211.6 mAh g −1 at 0.5C with a long‐term cycling performance of 450 cycles at room temperature. More importantly, it achieves a steady running up to 100 cycles at 1C even if this electrolyte is placed in the air with a dew temperature of 13.8 °C for 30 min, the highest values in the state‐of‐the‐art sulfide‐based ASSSBs. The well‐designed SSEs open a new avenue for realizing the advanced and powerful ASSSBs.

Guo, Yayu↗
DOE OSTI2021

Structural and physical properties of 99 complex bulk chalcogenides crystals using first-principles calculations

Chalcogenide semiconductors and glasses have many applications in the civil and military fields, especially in relation to their electronic, optical and mechanical properties for energy conversion and in enviormental materials. However, they are much less systemically studied and their fundamental physical properties for a large class chalcogenide semiconductors are rather scattered and incomplete. Here, we present a detailed study using well defined first-principles calculations on the electronic structure, interatomic bonding, optical, and mechanical properties for 99 bulk chalcogenides including thirteen of these crytals which have never been calculated. Due to their unique composition and structures, these 99 bulk chalcogenides are divided into two main groups. The first group contains 54 quaternary crystals with the structure composition (A2BCQ4) (A = Ag, Cu; B = Zn, Cd, Hg, Mg, Sr, Ba; C = Si, Ge, Sn; Q = S, Se, Te), while the second group contains scattered ternary and quaternary chalcogenide crystals with a more diverse composition (AxByCzQn) (A = Ag, Cu, Ba, Cs, Li, Tl, K, Lu, Sr; B = Zn, Cd, Hg, Al, Ga, In, P, As, La, Lu, Pb, Cu, Ag; C = Si, Ge, Sn, As, Sb, Bi, Zr, Hf, Ga, In; Q = S, Se, Te; x=1, 2, 3; y=0, 1, 2, 5; z=0, 1, 2 and n=3, 4, 5, 6, 9). Moreover, the total bond order density (TBOD) is used as a single quantum mechanical metric to characterize the internal cohesion of these crystals enabling us to correlate them with the calculated properties, especially their mechanical properties. This work provides a very large database for bulk chalcogenides crucial for the future theoretical and experimental studies, opening opportunities for study the properties and potential application of a wide variety of chalcogenides.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Materials Data on FeSn4H24C8(Se5N)2 by Materials Project

Fe(Sn2Se5)2(N(CH3)4)2 crystallizes in the tetragonal I-4 space group. The structure is three-dimensional and consists of four tetramethylammonium molecules and one Fe(Sn2Se5)2 framework. In the Fe(Sn2Se5)2 framework, Fe2+ is bonded to four equivalent Se2- atoms to form FeSe4 tetrahedra that share corners with four equivalent SnSe4 tetrahedra. All Fe–Se bond lengths are 2.41 Å. Sn4+ is bonded to four Se2- atoms to form SnSe4 tetrahedra that share a cornercorner with one FeSe4 tetrahedra and corners with three equivalent SnSe4 tetrahedra. There are a spread of Sn–Se bond distances ranging from 2.54–2.61 Å. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a water-like geometry to two equivalent Sn4+ atoms. In the second Se2- site, Se2- is bonded in a water-like geometry to two equivalent Sn4+ atoms. In the third Se2- site, Se2- is bonded in a bent 120 degrees geometry to one Fe2+ and one Sn4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnSn4H24C8(Se5N)2 by Materials Project

Mn(Sn2Se5)2(N(CH3)4)2 crystallizes in the tetragonal I-4 space group. The structure is three-dimensional and consists of four tetramethylammonium molecules and one Mn(Sn2Se5)2 framework. In the Mn(Sn2Se5)2 framework, Mn2+ is bonded to four equivalent Se2- atoms to form MnSe4 tetrahedra that share corners with four equivalent SnSe4 tetrahedra. All Mn–Se bond lengths are 2.56 Å. Sn4+ is bonded to four Se2- atoms to form SnSe4 tetrahedra that share a cornercorner with one MnSe4 tetrahedra and corners with three equivalent SnSe4 tetrahedra. There are a spread of Sn–Se bond distances ranging from 2.52–2.60 Å. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a water-like geometry to two equivalent Sn4+ atoms. In the second Se2- site, Se2- is bonded in a water-like geometry to two equivalent Sn4+ atoms. In the third Se2- site, Se2- is bonded in a bent 120 degrees geometry to one Mn2+ and one Sn4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Exploring the interfacial structure and crystallinity for direct growth of Mn 3 Sn(0001) on sapphire (0001) by molecular beam epitaxy

The Kagome antiferromagnet Mn 3 Sn has garnered a lot of attention due to the presence of interesting properties such as anomalous Hall effects and Nernst effects. Until now, few papers have been reported to grow using molecular beam epitaxy with a buffer layer or on other substrates. In this paper, we discuss the synthesis of crystalline Mn 3 Sn layers, prepared on Al 2 O 3 (0001) without a buffer layer using molecular beam epitaxy. The growth is monitored in-situ using reflection high energy electron diffraction and measured ex-situ using X-ray diffraction, Rutherford back-scattering, and cross-sectional scanning transmission electron microscopy. The samples were deposited at 524 ± 5 °C, with an Mn: Sn atomic flux ratio of 3.2:1 for 90 minutes. Orientation relationships between the Mn 3 Sn films and the sapphire substrates are determined from in-plane and out-of-plane measurements. Our analysis indicates that the resulting film is predominantly c−plane oriented. Lastly, the samples prepared in this way were found to be discontiguous, showing a 3-dimensional morphology. According to first-principles calculations, the Mn 3 Sn exhibits a displaced Kagome structure in the very first stages of growth, for 2ML and 4ML growth on Al 2 O 3 (0001). This result is corroborated by calculating the surface formation energies and explains the observed RHEED patterns.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Investigations Towards Ultra-Low Cost Nb 3 Sn SRF Fabrication via Melt Casted Bronze Route Processing

Here, a novel approach to fabricating Nb 3 Sn SRF cavities and other RF components using an ultra-low-cost melt casting fabrication process has been investigated. This simple, low cost melt casting technique has the potential to be used to fabricate nearly any superconducting Nb3Sn structure using either the Bronze Route (BR), Internal Tin (IT), External Tin (ET) processes as well as normal conducting pure copper (Cu) cavities. Most of the heat treated samples that were examined using SEM/EDX seemed to show a reasonable correlation of T c onset and transition width (ΔT c ) of the ingots initial/starting Sn content to the desired stoichiometric Nb 3 Sn phase, where the lower starting Sn content coupons resulted in lower T c 's with broader transition widths and the higher starting Sn coupons resulted in higher T c 's with narrower ΔT c ’s. The best samples had T c onsets ~17-18 K and ΔT c 's < 2 K. Two samples were further tested for RF surface resistance (R s ) and Quality Factor (Q) at JLAB. Here, these RF measurements were performed at 7.4 GHz using a calorimetric technique and showed two transitions, one at ~ 8 K and another at ~ 14 K; values of R s were at least two orders of magnitude higher than similar high quality Nb 3 Sn films directly deposited substrates by JLAB and with another superconducting transition close to the superconducting transition temperature of niobium. Substantial improvements in the processing variables ranging from higher quality of the initial ingots with higher Sn content, to better electropolishing and reaction heat treatment regimens will be necessary to realize improved RF performance metrics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Crystal structure and magnetic properties in semiconducting Eu 3-δ Zn x Sn y As 3 with Eu-Eu dimers

Magnetic structure and crystal symmetry, which primarily determine the time-reversal and inversion symmetry, may give rise to numerous exotic quantum phenomena in magnetic semiconductors and semimetals when arranged in different patterns. Here, a new layered magnetic semiconductor, Eu 3-δ Zn x Sn y As 3 , was discovered and high-quality single crystals were grown using the Sn flux. According to structural characterization by x-ray diffraction and atomic-resolution scanning transmission electron microscopy, Eu 3-δ Zn x Sn y As 3 is found to crystallize in a hexagonal symmetry with the space group P6 3 /mmc (No. 194). After examining different specimens, we conclude that their stoichiometry is fixed at ~Eu 2.6 Zn 0.65 Sn 0.85 As 3 , which meets the chemical charge balance. Eu 3-δ Zn x Sn y As 3 is composed of septuple (Eu 1-δ Sn y As 2 )-Eu-(Zn x As)-Eu sequences. The shortest Eu–Eu distance in the system is between two Eu layers separated by Zn x As along the c-axis. Magnetization measurement shows an antiferromagnetic ordering in Eu 3-δ Zn x Sn y As 3 at T N ~ 12 K, where the magnetic easy-axis is along the c-axis, and Mössbauer spectroscopy observes magnetic hyperfine splitting on Eu and Sn at 6 K. Magnetic anisotropy is significantly different from the ones along the ab-plane in other layered Eu-based magnetic semimetals. Heat capacity measurements confirm the magnetic transition around 12 K. Electrical resistivity measurement indicates semiconductor behavior with a band gap of ~0.86 eV. Finally, various Eu-based magnetic semiconductors could provide a tunable platform to study potential topological and magnetic properties.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Sn doping on partially dealuminated Beta zeolite by solid state ion exchange for 5‐hydroxymethylfurfural ( 5‐HMF ) production from glucose

Abstract BACKGROUND The conversion of glucose into 5‐hydroxymethylfurfural (5‐HMF) involves the isomerization of glucose to fructose catalyzed by Lewis acid and subsequent dehydration of fructose catalyzed by Brönsted acid. In this work, in order to obtain a high yield of 5‐HMF, a series of Sn‐Al‐Beta catalysts containing both Lewis and Brönsted acid sites were prepared by a convenient solid state ion exchange (SSIE) method using partially dealuminated Beta zeolite and tin(II) acetate. RESULTS The obtained bifunctional catalysts were investigated for one‐pot production of 5‐HMF from glucose in the ionic liquid (IL) [C 4 mim]Cl. Among various catalysts, Sn‐Al‐Beta‐ 4 ‐ 8 exhibited the best catalytic performance, giving a 5‐HMF yield of 54% under optimal reaction conditions (393 K, 2 h), along with a glucose conversion of 81%. The Sn‐Al‐Beta‐ 4‐8 catalyst and IL were regenerated by the extraction of 5‐HMF, and the reactivity was reserved after five runs of recycling. In addition to glucose, the Sn‐Al‐Beta‐ 4‐8 /[C 4 mim]Cl system was also proven to have the potential to effectively convert other carbohydrates into 5‐HMF. CONCLUSION The results suggested that the catalyst is convenient to prepare and has preferable efficiency and stability in the conversion of carbohydrates into 5‐HMF. © 2022 Society of Chemical Industry (SCI).

Zhang, Wei↗
DOE OSTI2020

Synthesis and characterization of Pt(Cu 0.67 Sn 0.33 )

Pt(Cu 0.67 Sn 0.33 ) has recently been found in a natural sample. In order to be able to characterize this new ternary compound, we synthesized it from the elements. Samples were characterized by X-ray powder diffraction, differential scanning calorimetry, thermal relaxation calorimetry, and scanning electron microscopy studies. Density functional theory-based model calculations complemented the experimental studies. Pt(Cu 0.67 Sn 0.33 )was already formed at a relatively low temperature of 773 K. Rietveld refinement of Pt(Cu 0.67 Sn 0.33 ) has been carried out in CuAu-type or L1 0 -type structure, space group P4/mmm, with Pt on 0,0,0 and disordered Cu and Sn on 1/2, 1/2, 1/2 and Z = 1. The lattice parameters are a = 2.823(1) Å, c = 3.64(1) Å, and V = 29.00(4) Å which are in good agreement with values obtained earlier on the natural sample and with the results of DFT calculations. The vibrational entropy for Pt(Cu 0.67 Sn 0.33 ) is $S_{298.15}^{vib}$ = 79.9(7) J mol -1 K -1 . The pressure dependence up to 36(2) GPa of the unit-cell volume and the lattice parameters and unit-cell volume have been obtained by synchrotron based powder diffraction using a diamond anvil cell. A fit of a 3rd-order Birch–Murnaghan equation of state to the Pt(Cu 0.67 Sn 0.33 )) (p,V)-data results in a bulk modulus of B 0 = 215(27) GPa and B' = 5(2).

36 MATERIALS SCIENCE↗
NASA NTRS1985

Search for a shock wave around the Crab Nebula

The region surrounding the Crab Nebula is searched for the existence of a shock wave with the imaging instruments of the Einstein Observatory. The search is complicated by the scattering of nebula and pulsar X-rays from the imperfectly polished surfaces of the telescope mirror, as well as from interstellar grains along the line of sight. Both of these effects lead to the appearance of X-ray emission, in the form of an X-ray halo, beyond the boundaries of the nebula filaments. It is shown that the size, shape, and intensity of the halo around the Crab Nebula, above the contribution of mirror scattering, is consistent with what is expected from the scattering from interstellar grains. The upper limit on the X-ray emission from a shock wave is about 1 percent of the total 0.5-4 keV luminosity of the Crab, or about 2 x 10 to the 35th ergs/sec (assuming a distance of 2.2 kpc). This figure applies to a shell whose angular radius is 9 arcminutes. The upper limit is smaller (larger) for a shell of larger (smaller) size. This upper limit is an order of magnitude or more below the flux of Cas A, Tycho, and Kepler SNRs, which are 2 to 3 times younger, but it is still above that of SN 1006.

Mauche, C. W.↗
DOE OSTI2020

Electrochemical Separation of Alkaline-Earth Elements from Molten Salts Using Liquid Metal Electrodes

Closing the nuclear fuel cycle requires recycling used nuclear fuel. Additional waste is generated during recycling due to fission products accumulating in processing salts (LiCl-KCl). Reducing waste generated during recycling entails recovering alkaline-earth fission products (Ba 2+ /Sr 2+ ) from molten chlorides with a minimal loss of bulk electrolyte constituents (Li + /K + ). Electrochemical co-deposition of Ba 2+ /Li + and Sr 2+ /Li + into liquid metal (Bi, Sb, Sn, Pb) and alloy (Bi-Sb) electrodes was investigated in LiCl-KCl-(BaCl 2 , SrCl 2 ) electrolytes at 500 °C and 650 °C. For the pure Bi (500 °C) and Sb (650 °C) electrodes, the greatest percentage of charge was used to deposit Ba and Sr. Effective recovery of Ba/Sr by liquid Bi and Sb electrodes is supported via experimentally determined activity values of Ba/Sr in Bi and Sb. Alloying Sb with Bi increased Ba recovery but decreased Sr recovery, as compared to recovery using the liquid Bi electrode. Here, the results suggest that alkaline-earth fission products can be recovered from molten chlorides by liquid metal electrodes via electrochemical separation, thereby providing a methodology to reduce the generation of nuclear waste from nuclear fuel recycling.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗