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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

The X-Ray Fundamental Plane of the Platinum Sample, the Kilonovae, and the SNe Ib/c Associated with GRBs

A large fraction of gamma-ray burst (GRB) lightcurves (LCs) show X-ray plateaus. We analyze all GRBs with known redshifts presenting plateaus observed by The Neil Gehrels Swift Observatory from its launch until 2019 August. The fundamental plane relation between the rest-frame time and X-ray luminosity at the end of the plateau emission and the peak prompt luminosity holds for all the GRB classes when selection biases and cosmological evolutions are applied. We have discovered two important findings: (1) a new class of long GRBs with good data coverage: the platinum sample; and (2) the platinum, the SNe-LGRB, and the KN-SGRB samples, yield the smallest intrinsic scatter with σ platinum , GRB-SNe = 0.22 ± 0.10 and σ KN-SGRB = 0.24 ± 0.12. The SNe-LGRBs are composed of GRBs associated spectroscopically with the SNe Ib,c, the KN-SGRBs are composed by eight GRBs associated with kilonovae or where there could have been such an association. The highest correlation coefficients are yielded for the SN-LGRB-ABC sample, which includes GRBs spectroscopically associated with SNe Ib/c or with a clear optical bump in the LC resembling the SNe Ib/c, ( ), the SN-LGRBs ( ), and the KN-SGRBs ( ) when the redshift evolution is considered. We find that these category planes are reliable candidates to use as cosmological tools. Furthermore, the distance from the gold fundamental plane is a crucial discriminant among classes. In fact, we find that the distributions of the distances of the SNe-LGRB, SNe-LGRB-ABC, KN-SGRB, and SGRB samples from the gold fundamental plane are statistically different from the distribution of the gold GRBs' distances from the gold fundamental plane with and without considering evolution cases. <

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

A quantum liquid of magnetic octupoles on the pyrochlore lattice

Spin liquids are highly correlated yet disordered states formed by the entanglement of magnetic dipoles. Theories define such states using gauge fields and deconfined quasiparticle excitations that emerge from a local constraint governing the ground state of a frustrated magnet. For example, the ‘2-in–2-out’ ice rule for dipole moments on a tetrahedron can lead to a quantum spin ice in rare-earth pyrochlores. However, $f$-electron ions often carry multipole degrees of freedom of higher rank than dipoles, leading to intriguing behaviours and ‘hidden’ orders. In this paper we show that the correlated ground state of a Ce 3+ -based pyrochlore, Ce 2 Sn 2 O 7 , is a quantum liquid of magnetic octupoles. Our neutron scattering results are consistent with a fluid-like state where degrees of freedom have a more complex magnetization density than that of magnetic dipoles. The nature and strength of the octupole–octupole couplings, together with the existence of a continuum of excitations attributed to spinons, provides further evidence for a quantum ice of octupoles governed by a ‘2-plus–2-minus’ rule. Our work identifies Ce 2 Sn 2 O 7 as a unique example of frustrated multipoles forming a ‘hidden’ topological order, thus generalizing observations on quantum spin liquids to multipolar phases that can support novel types of emergent fields and excitations.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3SnC7O16 by Materials Project

K3SnC7O16 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are three inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of K–O bond distances ranging from 2.64–3.24 Å. In the second K1+ site, K1+ is bonded in a distorted q6 geometry to nine O2- atoms. There are a spread of K–O bond distances ranging from 2.82–3.00 Å. In the third K1+ site, K1+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of K–O bond distances ranging from 2.73–3.36 Å. Sn2+ is bonded in a pentagonal bipyramidal geometry to seven O2- atoms. There are a spread of Sn–O bond distances ranging from 2.12–2.19 Å. There are seven inequivalent C+3.86+ sites. In the first C+3.86+ site, C+3.86+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.24 Å) and one longer (1.30 Å) C–O bond length. In the second C+3.86+ site, C+3.86+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.23 Å) and one longer (1.30 Å) C–O bond length. In the third C+3.86+ site, C+3.86+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.24 Å) and one longer (1.30 Å) C–O bond length. In the fourth C+3.86+ site, C+3.86+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.25 Å) and one longer (1.30 Å) C–O bond length. In the fifth C+3.86+ site, C+3.86+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.23 Å) and one longer (1.31 Å) C–O bond length. In the sixth C+3.86+ site, C+3.86+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.24 Å) and one longer (1.30 Å) C–O bond length. In the seventh C+3.86+ site, C+3.86+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.24 Å) and one longer (1.30 Å) C–O bond length. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to two K1+ atoms. In the second O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one Sn2+, and one C+3.86+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to two K1+ and one C+3.86+ atom. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to three K1+ atoms. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, one Sn2+, and one C+3.86+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one C+3.86+ atom. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one Sn2+, and one C+3.86+ atom. In the eighth O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one C+3.86+ atom. In the ninth O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, one Sn2+, and one C+3.86+ atom. In the tenth O2- site, O2- is bonded in a distorted single-bond geometry to three K1+ and one C+3.86+ atom. In the eleventh O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one Sn2+, and one C+3.86+ atom. In the twelfth O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one C+3.86+ atom. In the thirteenth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Sn2+, and one C+3.86+ atom. In the fourteenth O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one C+3.86+ atom. In the fifteenth O2- site, O2- is bonded in a 3-coordinate geometry to one K1+, one Sn2+, and one C+3.86+ atom. In the sixteenth O2- site, O2- is bonded in a single-bond geometry to three K1+ and one C+3.86+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1991

Premaximum observations of the type Ia SN 1990N

Spectroscopic and photometric observations of SN 1990N were obtained at ultraviolet and optical wavelengths, beginning 14 days before maximum light. The early observations reveal important differences from spectra of SN Ia's around maximum light. Photometry and spectroscopy obtained after maximum show that SN 1990N is a typical SN Ia and that most of the observed differences are due to the early epoch of the observations. The most significant characteristics are (1) the high velocities of Ca and Si up to 22,000 km/s; (2) the presence of Co and Fe 2 weeks before maximum; and (3) the more rapid increase in the UV flux compared to the optical. The most popular models for white dwarf deflagration that have provided the standard interpretation for SN Ia's at maximum light do not reproduce the high velocities of Ca II and Si II lines observed in SN 1990N.

Leibundgut, Bruno↗
DOE OSTI2023

Substitution of Pb with (Li 1/2 Bi 1/2 ) in PbZrO 3 -based antiferroelectric ceramics

PbZrO 3 -based antiferroelectric (AFE) ceramics are promising dielectrics for high-energy-density capacitors due to their reversible phase transitions during charge–discharge cycles. In this work, a new composition series, [Pb 0.93–x La 0.02 (Li 1/2 Bi 1/2 ) x Sr 0.04 ][Zr 0.57 Sn 0.34 Ti 0.09 ]O 3 , with Li + and Bi 3+ substitution of Pb 2+ at x=0 , 0.04, 0.08, 0.12, 0.16 is investigated for the microstructure evolution, ferroelectric (FE) and dielectric properties. It is found that Li + and Bi 3+ substitution can significantly reduce the sintering temperature and simultaneously enhance the dielectric breakdown strength. An ultrahigh energy efficiency (94.0%) and a large energy density (3.22J/cm 3 ) are achieved in the composition of x = 0.12 with a low sintering temperature (1075°C).

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SnHC2O3 by Materials Project

SnC2HO3 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of one SnC2HO3 sheet oriented in the (2, 0, -1) direction. there are two inequivalent Sn4+ sites. In the first Sn4+ site, Sn4+ is bonded in a distorted rectangular see-saw-like geometry to four O2- atoms. There are a spread of Sn–O bond distances ranging from 2.10–2.47 Å. In the second Sn4+ site, Sn4+ is bonded in a rectangular see-saw-like geometry to four O2- atoms. There are two shorter (2.15 Å) and two longer (2.58 Å) Sn–O bond lengths. There are two inequivalent C+0.50+ sites. In the first C+0.50+ site, C+0.50+ is bonded in a single-bond geometry to one O2- atom. The C–O bond length is 1.26 Å. In the second C+0.50+ site, C+0.50+ is bonded in a single-bond geometry to one O2- atom. The C–O bond length is 1.26 Å. H1+ is bonded in a single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.69 Å) H–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to one Sn4+ and one C+0.50+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one Sn4+, one C+0.50+, and one H1+ atom. In the third O2- site, O2- is bonded in a distorted water-like geometry to one Sn4+ and two equivalent H1+ atoms. In the fourth O2- site, O2- is bonded in a trigonal planar geometry to three Sn4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SnH7C2SeClO3 by Materials Project

SnC2H7SeO3Cl crystallizes in the triclinic P-1 space group. The structure is one-dimensional and consists of one SnC2H7SeO3Cl ribbon oriented in the (1, 0, 0) direction. Sn2+ is bonded in a 6-coordinate geometry to two C, three O2-, and one Cl1- atom. There are one shorter (2.12 Å) and one longer (2.13 Å) Sn–C bond lengths. There are a spread of Sn–O bond distances ranging from 2.24–2.71 Å. The Sn–Cl bond length is 2.53 Å. There are two inequivalent C sites. In the first C site, C is bonded in a distorted trigonal non-coplanar geometry to one Sn2+ and three H1+ atoms. There is two shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. In the second C site, C is bonded in a distorted trigonal non-coplanar geometry to one Sn2+ and three H1+ atoms. There is two shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. There are six inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one C atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C atom. Se2- is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. There are a spread of Se–O bond distances ranging from 1.68–1.82 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Sn2+ and one Se2- atom. In the second O2- site, O2- is bonded in a distorted water-like geometry to one H1+ and one Se2- atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Sn2+ and one Se2- atom. Cl1- is bonded in a single-bond geometry to one Sn2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Deep level transient spectroscopy and photoluminescence studies of hole and electron traps in ZnSnP 2 bulk crystals

ZnSnP 2 , an emerging inorganic material for solar cells, was characterized by deep level transient spectroscopy (DLTS) and photoluminescence (PL). Acceptor- and donor-like traps with shallow energy levels were detected by DLTS analysis. The previous study based on first-principle calculation also suggested such traps were due to antisite defects of Zn and Sn. PL measurements also revealed sub-gap transitions related to these trap levels. Furthermore, DLTS found a trap with a deep level in ZnSnP 2 . A short lifetime of minority carrier in previous work might be due to such trap, coming from phosphorus vacancies and/or zinc interstitials suggested by the first-principle study.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1985

Rapid solidification of levitation melted Ni-Sn alloy droplets with high undercooling

Experimental results obtained by high-speed optical temperature sensing for the rapid solidification of highly undercooled, levitation-melted Ni-Sn alloy droplets are presented. These data suggest a solidification model proceeding according to overlapping steps: (1) dendritic growth within the bulk undercooled melt, (2) continued recalescence as supersaturation of the interdendritic liquid dissipates, (3) fine-scale remelting within the dendrites, (4) ripening of the fine structure, and (5) solidification of remaining liquid at the end of recalescence.

Shiohara, Yuh↗
DOE OSTI2020

Iron Based Superconductors at FNAL: Ultra High-Field Superconductor at Low-Cost

The high energy physics community has been asking for a strong push towards the energy frontier beyond the LHC. Unfortunately, large rings are very expensive and with the current state-of-the-art magnet technology(NbTi, Nb 3 Sn and Cuprates),the costs are prohibitive. An emerging technology that has a great potential to provide low-cost conductor with ultra-high-field performance(>20T)is based on a new class of HTS materials discovered in 2008:Iron-Based-Superconductors (IBSs or pnictides). In view of future High Field Magnet(HFM) applications, this project is intended to the development of inexpensive high-T c Iron-Based-Superconductor (IBS) wire with high critical current density(J c > 10 5 A/cm 2 at > 20T/4.2K).

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Isolated copper–tin atomic interfaces tuning electrocatalytic CO 2 conversion

Direct experimental observations of the interface structure can provide vital insights into heterogeneous catalysis. Examples of interface design based on single atom and surface science are, however, extremely rare. Here, we report Cu–Sn single-atom surface alloys, where isolated Sn sites with high surface densities (up to 8%) are anchored on the Cu host, for efficient electrocatalytic CO 2 reduction. The unique geometric and electronic structure of the Cu–Sn surface alloys (Cu 97 Sn 3 and Cu 99 Sn 1 ) enables distinct catalytic selectivity from pure Cu 100 and Cu 70 Sn 30 bulk alloy. The Cu 97 Sn 3 catalyst achieves a CO Faradaic efficiency of 98% at a tiny overpotential of 30 mV in an alkaline flow cell, where a high CO current density of 100 mA cm –2 is obtained at an overpotential of 340 mV. Density functional theory simulation reveals that it is not only the elemental composition that dictates the electrocatalytic reactivity of Cu–Sn alloys; the local coordination environment of atomically dispersed, isolated Cu–Sn bonding plays the most critical role.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Irradiation creep measurement and microstructural analysis of chromium nitride–coated zirconium alloy using pressurized tubes

Environmental barrier coatings for Zr-based materials are currently under development to reduce oxidation and embrittlement in light-water reactors. Chromium nitride is one such candidate for this application, particularly as accident-tolerant fuel cladding. However, quantifying the impact of coatings on the irradiation-induced creep of zircaloy (Zry) is critical as this mechanism often exceeds thermal creep rates under light-water reactor operating conditions and can be a limiting design characteristic. Additionally, examining irradiation effects in the microstructure at the coating interface is key to understanding the compatibility of the material system. Here, to accelerate the experimental measurement of irradiation creep and microstructure evolution in CrN-Zry, compact, pressurized creep tubes were fabricated and irradiated in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. Miniature, thin-walled rodlets fabricated from annealed Zr-Sn barstock were coated with CrN using physical vapor deposition (PVD) to nominal thicknesses of 4 and 8 μm. Coated and uncoated rodlet specimens were internally pressurized and welded, generating nominal circumferential hoop stresses of 0, 90, or 180 MPa under 300°C irradiation conditions. Twelve specimens were measured diametrically prior to irradiation using a low-cost, automated, contactless laser profilometer developed for this work. Specimens were irradiated in sealed capsules for one 25-day HFIR cycle, accumulating approximately 1.8 $\times$ 10 21 n/cm 2 fast fluence (E n > 10 MeV). The irradiated samples were retrieved and remeasured using the same profilometry system in a shielded hot cell facility. Irradiation creep between specimens was compared using standard statistical tests and showed that both thicknesses of CrN coating had a negligible effect on the irradiation creep strain of the Zry material. Microstructure characterization of pre- and post-irradiated CrN-Zry specimens showed minimal changes due to irradiation but did show a substantial O-rich region at the Zry-CrN interface.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsZnAgC4(SN)4 by Materials Project

CsAgZnC4(NS)4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Cs1+ is bonded in a 7-coordinate geometry to two N3- and five S2- atoms. There are one shorter (3.46 Å) and one longer (3.78 Å) Cs–N bond lengths. There are a spread of Cs–S bond distances ranging from 3.57–4.09 Å. Ag1+ is bonded to five S2- atoms to form corner-sharing AgS5 trigonal bipyramids. There are a spread of Ag–S bond distances ranging from 2.58–3.16 Å. Zn2+ is bonded in a tetrahedral geometry to four N3- atoms. There are a spread of Zn–N bond distances ranging from 1.96–2.00 Å. There are four inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a linear geometry to one N3- and one S2- atom. The C–N bond length is 1.18 Å. The C–S bond length is 1.63 Å. In the second C4+ site, C4+ is bonded in a distorted linear geometry to one N3- and one S2- atom. The C–N bond length is 1.18 Å. The C–S bond length is 1.63 Å. In the third C4+ site, C4+ is bonded in a distorted linear geometry to one N3- and one S2- atom. The C–N bond length is 1.19 Å. The C–S bond length is 1.62 Å. In the fourth C4+ site, C4+ is bonded in a linear geometry to one N3- and one S2- atom. The C–N bond length is 1.19 Å. The C–S bond length is 1.63 Å. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a bent 150 degrees geometry to one Cs1+, one Zn2+, and one C4+ atom. In the second N3- site, N3- is bonded in a linear geometry to one Zn2+ and one C4+ atom. In the third N3- site, N3- is bonded in a distorted linear geometry to one Cs1+, one Zn2+, and one C4+ atom. In the fourth N3- site, N3- is bonded in a linear geometry to one Zn2+ and one C4+ atom. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 2-coordinate geometry to two equivalent Cs1+, one Ag1+, and one C4+ atom. In the second S2- site, S2- is bonded in a 2-coordinate geometry to two equivalent Cs1+, one Ag1+, and one C4+ atom. In the third S2- site, S2- is bonded in a 3-coordinate geometry to one Cs1+, one Ag1+, and one C4+ atom. In the fourth S2- site, S2- is bonded in a 3-coordinate geometry to two equivalent Ag1+ and one C4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Electronic Structure, Optical Properties, and Photoelectrochemical Activity of Sn-Doped Fe 2 O 3 Thin Films

Hematite (Fe 2 O 3 ) is a well-known oxide semiconductor suitable for photoelectrochemical (PEC) water splitting and industry gas sensing. It is widely known that Sn doping of Fe 2 O 3 can enhance the device performance, yet the underlying mechanism remains elusive. In this work, we determine the relationship between electronic structure, optical properties and PEC activity of Sn doped Fe 2 O 3 by studying highly crystalline, well-controlled thin films prepared by pulsed laser deposition (PLD). We show that Sn doping substantially increases the n-type conductivity of Fe 2 O 3 , and the conduction mechanism is better described by small-polaron hoping (SPH) model. Only 0.2% Sn doping significantly reduce the activation energy barrier for SPH conduction from at least 0.5 eV for undoped Fe 2 O 3 to 0.14 eV for doped ones. A combination of X-ray photoemission, X-ray absorption spectroscopy and DFT calculations reveals the Fermi level gradually shifts toward the conduction band minimum with Sn doping. A localized Fe 2+ like gap state is observed at the top of valence band, accounting for the SPH conduction. Interestingly, in contrast to the literature, we find that only 0.2% Sn doping in Fe 2 O 3 significantly improves the PEC activity, while more Sn decreases it. The improved PEC activity is partially attributed to an increased band bending potential which facilitates the charge separation at space charge region. The reduced activation energy barrier for SPH will facilitate the transport of photo-excited carriers for the enhanced PEC, which is of interest for further carrier dynamics study.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

A Lead‐Free Ferroelectric 2D Dion–Jacobson Tin Iodide Perovskite

2D hybrid organic–inorganic halide perovskites emerge as a new class of 2D semiconductors with the potential to combine excellent optoelectronic properties with symmetry-enabled properties such as ferroelectricity. Although many lead-based ferroelectric 2D halide perovskites are reported, there is yet to be a conclusive report of ferroelectricity in tin-based 2D perovskites. Here, the structures and properties of a new series of 2D Dion–Jacobson (DJ) Sn perovskites: (4AMP)SnI 4 , (4AMP)(MA)Sn 2 I 7 , and (4AMP)(FA)Sn 2 I 7 (4AMP = 4-(aminomethyl)piperidinium, MA = methylammonium, and FA = formamidinium), are reported. Structural characterization reveals that (4AMP)SnI 4 is polar with in-plane spontaneous polarization whereas (4AMP)(MA)Sn 2 I 7 and (4AMP)(FA)Sn 2 I 7 are centrosymmetric. Further, (4AMP)SnI 4 displays second harmonic generation (SHG) and polarization-electric field hysteresis measurements confirm it is ferroelectric with a spontaneous polarization of 10.0 µC cm −2 at room temperature. (4AMP)SnI 4 transitions into a centrosymmetric structure above 367 K. As the first direct experimental observation of the spontaneous ferroelectric polarization of a Sn-based 2D hybrid perovskite, this work opens up environmentally friendly 2D tin halide perovskites for ferroelectricity and other physical property studies.

2D↗
DOE OSTI2023

Physical and Flow Properties of Glass-Forming Chemicals (V 2 O 5 , SnO, SnO 2 , Cr 2 O 3 , FeCr 2 O 4 , and ZrSiO 4 ) and Mixtures

For an efficient nuclear waste vitrification process at the Waste Treatment and Immobilization Plant (WTP) on the Hanford Site, proper selection and consistent supply of glass-forming chemicals (GFCs) are crucial. Thorough characterization of the GFCs is required to reduce risks in operation of the vitrification facility. Low-activity waste (LAW) will be blended with GFCs to form slurry feeds and then fed to melters and vitrified. To enhance properties of waste glasses, new chemicals are being introduced to the current GFC mixture. In this study, three new GFCs were evaluated for enhanced LAW glass formulations: chromium oxide (Cr 2 O 3 ), vanadium oxide (V 2 O 5 ), and stannic oxide (SnO 2 ). These three oxide components are included in enhanced waste glass formulations, and GFCs with the appropriate physical and flow properties are needed. As a starting point, single metal oxide GFCs, Cr 2 O 3 , V 2 O 5 , and SnO 2 , were sourced and tested. Then, alternative sources of Sn and Cr (SnO and FeCr 2 O 4 ) were tested along with an alternative zircon source (ZrSiO 4 ). This report documents the work performed to collect physical and flow property data on these new GFCs and melter feed slurries generated using these GFCs and simulated low-activity wastes.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1991

A large supershell H II region complex in the Large Magellanic Cloud and the interstellar environment of SN 1987A

Results from narrow-bandpass optical imagery of the LMC, acquired prior to the supernova event are discussed, with special emphasis on the region about SN 1987A. The observations reveal the presence of an extremely large H II region complex, mostly embedded in an even larger dust ring. The H II region is roughly 1 kpc in diameter. This region is ionized by over 700 luminous OB stars that comprise the 'star clouds' dispersed throughout the region. The 1.5 x 2 kpc dimension of the large dust ring or supershell enshrouding this H II region is traced out as enhanced extinction in narrow-bandpass imagery of the continuum at 4215 A. The results also indicate that SN 1987A occurred in the cavity carved out by the combined stellar winds and the previous supernova explosions produced by the large number of massive stars in the region.

Bruhweiler, Frederick C.↗