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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Development of tungsten-tantalum generator

The purpose of this project was to develop a useable tungsten (W)/tantalum (Ta) generator. Ta-178 is formed following the decay of its parent, W-178 (half-life: 21.7d) and has a half life of 9.3 minutes in turn yielding stable Hf-178. The decay of the parent isotope (W-178) occurs entirely by electron capture to the 9.3 minute Ta-178 state, without feeding the high spin Ta-178 isomer (half life 2.2 hours). In Ta-178 decay, 99.2% of the disintegrations proceed by electron capture and 0.18% by positron emission. Electron capture results in a 61.2% branch to the ground state of Hf-178 and 33.7% to the first excited state at 93 1KeV. The most prominent features of the radionuclide's energy spectrum are the hafnium characteristic radiation peaks with energies between 54.6 and 65.0 KeV. The radiation exposure dose of Ta-118 was calculated to be approximately one-twentieth that of Tc-99m on a per millicurie basis. A twenty-fold reduction in radiation exposure from Ta-178 compared with Tc-99m means that the usual administered dose can be increased three or four times, greatly increasing statistical accuracy while reducing radiation exposure by a factor of five.

Leblanc, A.↗
DOE OSTI2020

Materials Data on Ta2Be by Materials Project

BeTa2 is Khatyrkite structured and crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Be is bonded in a distorted q6 geometry to two equivalent Be and eight equivalent Ta atoms. Both Be–Be bond lengths are 2.45 Å. All Be–Ta bond lengths are 2.58 Å. Ta is bonded in a 4-coordinate geometry to four equivalent Be and one Ta atom. The Ta–Ta bond length is 2.75 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta3Co3C by Materials Project

Ta3Co3C crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Ta is bonded in a 2-coordinate geometry to six Co and two equivalent C atoms. There are a spread of Ta–Co bond distances ranging from 2.75–2.83 Å. Both Ta–C bond lengths are 2.16 Å. There are two inequivalent Co sites. In the first Co site, Co is bonded in a distorted q6 geometry to six equivalent Ta and six Co atoms. There are three shorter (2.42 Å) and three longer (2.52 Å) Co–Co bond lengths. In the second Co site, Co is bonded to six equivalent Ta and six equivalent Co atoms to form CoTa6Co6 cuboctahedra that share edges with six equivalent CTa6 octahedra and faces with six equivalent CoTa6Co6 cuboctahedra. C is bonded to six equivalent Ta atoms to form CTa6 octahedra that share corners with six equivalent CTa6 octahedra and edges with six equivalent CoTa6Co6 cuboctahedra. The corner-sharing octahedral tilt angles are 45°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaCo2 by Materials Project

Co2Ta is Cubic Laves structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to four equivalent Ta and twelve equivalent Co atoms. All Ta–Ta bond lengths are 2.91 Å. All Ta–Co bond lengths are 2.79 Å. Co is bonded to six equivalent Ta and six equivalent Co atoms to form a mixture of edge, face, and corner-sharing CoTa6Co6 cuboctahedra. All Co–Co bond lengths are 2.38 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaCr2 by Materials Project

Cr2Ta is Cubic Laves structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to four equivalent Ta and twelve equivalent Cr atoms. All Ta–Ta bond lengths are 3.00 Å. All Ta–Cr bond lengths are 2.88 Å. Cr is bonded to six equivalent Ta and six equivalent Cr atoms to form a mixture of face, edge, and corner-sharing CrTa6Cr6 cuboctahedra. All Cr–Cr bond lengths are 2.45 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaBe2 by Materials Project

Be2Ta is Cubic Laves structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Be is bonded to six equivalent Be and six equivalent Ta atoms to form a mixture of face, edge, and corner-sharing BeTa6Be6 cuboctahedra. All Be–Be bond lengths are 2.31 Å. All Be–Ta bond lengths are 2.70 Å. Ta is bonded in a 12-coordinate geometry to twelve equivalent Be and four equivalent Ta atoms. All Ta–Ta bond lengths are 2.82 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta3Sn by Materials Project

Ta3Sn crystallizes in the cubic Pm-3n space group. The structure is three-dimensional. Ta is bonded in a 6-coordinate geometry to two equivalent Ta and four equivalent Sn atoms. Both Ta–Ta bond lengths are 2.66 Å. All Ta–Sn bond lengths are 2.98 Å. Sn is bonded to twelve equivalent Ta atoms to form a mixture of face and edge-sharing SnTa12 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta6Si7Ni16 by Materials Project

Ta6Ni16Si7 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to eight Ni and four equivalent Si atoms. There are four shorter (2.69 Å) and four longer (2.75 Å) Ta–Ni bond lengths. All Ta–Si bond lengths are 2.86 Å. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded in a 12-coordinate geometry to three equivalent Ta, six Ni, and three equivalent Si atoms. There are three shorter (2.56 Å) and three longer (2.63 Å) Ni–Ni bond lengths. All Ni–Si bond lengths are 2.29 Å. In the second Ni site, Ni is bonded in a 7-coordinate geometry to three equivalent Ta, six Ni, and four Si atoms. All Ni–Ni bond lengths are 2.62 Å. There are one shorter (2.27 Å) and three longer (2.49 Å) Ni–Si bond lengths. There are two inequivalent Si sites. In the first Si site, Si is bonded in a body-centered cubic geometry to eight equivalent Ni atoms. In the second Si site, Si is bonded to four equivalent Ta and eight Ni atoms to form a mixture of corner and face-sharing SiTa4Ni8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta3SiTe6 by Materials Project

Ta3SiTe6 crystallizes in the orthorhombic Pnma space group. The structure is two-dimensional and consists of two Ta3SiTe6 sheets oriented in the (0, 0, 1) direction. there are three inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to one Si4- and six Te+1.83- atoms to form distorted TaSiTe6 pentagonal bipyramids that share an edgeedge with one SiTa4Te4 hexagonal bipyramid, edges with four TaSiTe6 pentagonal bipyramids, and a faceface with one TaSiTe6 pentagonal bipyramid. The Ta–Si bond length is 2.84 Å. There are a spread of Ta–Te bond distances ranging from 2.80–2.88 Å. In the second Ta5+ site, Ta5+ is bonded in a 8-coordinate geometry to two equivalent Si4- and six Te+1.83- atoms. There are one shorter (2.83 Å) and one longer (2.84 Å) Ta–Si bond lengths. There are a spread of Ta–Te bond distances ranging from 2.83–2.95 Å. In the third Ta5+ site, Ta5+ is bonded to one Si4- and six Te+1.83- atoms to form distorted TaSiTe6 pentagonal bipyramids that share edges with two equivalent SiTa4Te4 hexagonal bipyramids, edges with two equivalent TaSiTe6 pentagonal bipyramids, and a faceface with one TaSiTe6 pentagonal bipyramid. The Ta–Si bond length is 2.73 Å. There are a spread of Ta–Te bond distances ranging from 2.76–2.96 Å. Si4- is bonded to four Ta5+ and four Te+1.83- atoms to form distorted SiTa4Te4 hexagonal bipyramids that share corners with two equivalent SiTa4Te4 hexagonal bipyramids and edges with three TaSiTe6 pentagonal bipyramids. There are two shorter (2.71 Å) and two longer (2.76 Å) Si–Te bond lengths. There are three inequivalent Te+1.83- sites. In the first Te+1.83- site, Te+1.83- is bonded in a 3-coordinate geometry to three Ta5+ atoms. In the second Te+1.83- site, Te+1.83- is bonded in a 4-coordinate geometry to three Ta5+ and one Si4- atom. In the third Te+1.83- site, Te+1.83- is bonded in a 4-coordinate geometry to three Ta5+ and one Si4- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta3Sb by Materials Project

Ta3Sb crystallizes in the cubic Pm-3n space group. The structure is three-dimensional. Ta is bonded in a 6-coordinate geometry to two equivalent Ta and four equivalent Sb atoms. Both Ta–Ta bond lengths are 2.65 Å. All Ta–Sb bond lengths are 2.96 Å. Sb is bonded to twelve equivalent Ta atoms to form a mixture of edge and face-sharing SbTa12 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta6Fe16Si7 by Materials Project

Fe16Ta6Si7 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to eight Fe and four equivalent Si atoms. There are four shorter (2.74 Å) and four longer (2.77 Å) Ta–Fe bond lengths. All Ta–Si bond lengths are 2.85 Å. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded in a 1-coordinate geometry to three equivalent Ta, six Fe, and four Si atoms. There are three shorter (2.47 Å) and three longer (2.68 Å) Fe–Fe bond lengths. There are one shorter (2.32 Å) and three longer (2.46 Å) Fe–Si bond lengths. In the second Fe site, Fe is bonded in a 12-coordinate geometry to three equivalent Ta, six Fe, and three equivalent Si atoms. All Fe–Fe bond lengths are 2.43 Å. All Fe–Si bond lengths are 2.29 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded to four equivalent Ta and eight Fe atoms to form a mixture of corner and face-sharing SiTa4Fe8 cuboctahedra. In the second Si site, Si is bonded in a body-centered cubic geometry to eight equivalent Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta9Pb12O20F29 by Materials Project

Pb12Ta9O20F29 crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. there are three inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to five O2- and one F1- atom to form corner-sharing TaO5F octahedra. The corner-sharing octahedra tilt angles range from 4–19°. There are a spread of Ta–O bond distances ranging from 1.91–2.00 Å. The Ta–F bond length is 2.11 Å. In the second Ta5+ site, Ta5+ is bonded to four O2- and two F1- atoms to form corner-sharing TaO4F2 octahedra. The corner-sharing octahedra tilt angles range from 4–19°. There are a spread of Ta–O bond distances ranging from 1.88–1.99 Å. There are one shorter (2.09 Å) and one longer (2.10 Å) Ta–F bond lengths. In the third Ta5+ site, Ta5+ is bonded to four equivalent O2- and two equivalent F1- atoms to form corner-sharing TaO4F2 octahedra. The corner-sharing octahedra tilt angles range from 0–6°. All Ta–O bond lengths are 1.94 Å. Both Ta–F bond lengths are 1.96 Å. There are three inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a 6-coordinate geometry to six F1- atoms. There are a spread of Pb–F bond distances ranging from 2.32–2.77 Å. In the second Pb2+ site, Pb2+ is bonded in a 8-coordinate geometry to eight F1- atoms. There are a spread of Pb–F bond distances ranging from 2.48–2.82 Å. In the third Pb2+ site, Pb2+ is bonded in a 5-coordinate geometry to five F1- atoms. There are a spread of Pb–F bond distances ranging from 2.32–2.57 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Ta5+ atoms. In the second O2- site, O2- is bonded in a distorted linear geometry to two equivalent Ta5+ atoms. In the third O2- site, O2- is bonded in a linear geometry to two Ta5+ atoms. In the fourth O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the fifth O2- site, O2- is bonded in a linear geometry to two Ta5+ atoms. There are eight inequivalent F1- sites. In the first F1- site, F1- is bonded to four Pb2+ atoms to form a mixture of edge and corner-sharing FPb4 tetrahedra. In the second F1- site, F1- is bonded in a trigonal planar geometry to three equivalent Pb2+ atoms. In the third F1- site, F1- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the fourth F1- site, F1- is bonded in a distorted single-bond geometry to one Ta5+ and two equivalent Pb2+ atoms. In the fifth F1- site, F1- is bonded in a 3-coordinate geometry to three Pb2+ atoms. In the sixth F1- site, F1- is bonded in a distorted single-bond geometry to one Ta5+ and two equivalent Pb2+ atoms. In the seventh F1- site, F1- is bonded in a distorted single-bond geometry to one Ta5+ and two equivalent Pb2+ atoms. In the eighth F1- site, F1- is bonded in a distorted trigonal non-coplanar geometry to three Pb2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaV2 by Materials Project

TaV2 is Cubic Laves structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to four equivalent Ta and twelve equivalent V atoms. All Ta–Ta bond lengths are 3.09 Å. All Ta–V bond lengths are 2.95 Å. V is bonded to six equivalent Ta and six equivalent V atoms to form a mixture of corner, edge, and face-sharing VTa6V6 cuboctahedra. All V–V bond lengths are 2.52 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta3Au by Materials Project

AuTa3 crystallizes in the cubic Pm-3n space group. The structure is three-dimensional. Ta is bonded in a 6-coordinate geometry to two equivalent Ta and four equivalent Au atoms. Both Ta–Ta bond lengths are 2.62 Å. All Ta–Au bond lengths are 2.93 Å. Au is bonded to twelve equivalent Ta atoms to form a mixture of edge and face-sharing AuTa12 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta6Co16Si7 by Materials Project

Ta6Co16Si7 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to eight Co and four equivalent Si atoms. There are four shorter (2.65 Å) and four longer (2.74 Å) Ta–Co bond lengths. All Ta–Si bond lengths are 2.84 Å. There are two inequivalent Co sites. In the first Co site, Co is bonded in a 7-coordinate geometry to three equivalent Ta, six Co, and four Si atoms. There are three shorter (2.52 Å) and three longer (2.64 Å) Co–Co bond lengths. There are one shorter (2.29 Å) and three longer (2.46 Å) Co–Si bond lengths. In the second Co site, Co is bonded in a 12-coordinate geometry to three equivalent Ta, six Co, and three equivalent Si atoms. All Co–Co bond lengths are 2.65 Å. All Co–Si bond lengths are 2.28 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded in a body-centered cubic geometry to eight equivalent Co atoms. In the second Si site, Si is bonded to four equivalent Ta and eight Co atoms to form a mixture of face and corner-sharing SiTa4Co8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta6Ni16Ge7 by Materials Project

Ta6Ni16Ge7 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to eight Ni and four equivalent Ge atoms. There are four shorter (2.72 Å) and four longer (2.84 Å) Ta–Ni bond lengths. All Ta–Ge bond lengths are 2.93 Å. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded in a 1-coordinate geometry to three equivalent Ta, six Ni, and four Ge atoms. There are three shorter (2.61 Å) and three longer (2.69 Å) Ni–Ni bond lengths. There are one shorter (2.33 Å) and three longer (2.54 Å) Ni–Ge bond lengths. In the second Ni site, Ni is bonded in a 12-coordinate geometry to three equivalent Ta, three equivalent Ni, and three equivalent Ge atoms. All Ni–Ge bond lengths are 2.34 Å. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a body-centered cubic geometry to eight equivalent Ni atoms. In the second Ge site, Ge is bonded to four equivalent Ta and eight Ni atoms to form a mixture of distorted face and corner-sharing GeTa4Ni8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaCoSn2 by Materials Project

TaCoSn2 crystallizes in the cubic F-43m space group. The structure is three-dimensional. Ta is bonded in a distorted body-centered cubic geometry to four equivalent Co and ten Sn atoms. All Ta–Co bond lengths are 2.91 Å. There are four shorter (2.91 Å) and six longer (3.36 Å) Ta–Sn bond lengths. Co is bonded in a distorted body-centered cubic geometry to four equivalent Ta and four equivalent Sn atoms. All Co–Sn bond lengths are 2.91 Å. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded to four equivalent Ta and four equivalent Sn atoms to form distorted edge-sharing SnTa4Sn4 tetrahedra. All Sn–Sn bond lengths are 2.91 Å. In the second Sn site, Sn is bonded in a 4-coordinate geometry to six equivalent Ta, four equivalent Co, and four equivalent Sn atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaTcPb2 by Materials Project

TaTcPb2 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. Ta is bonded in a distorted body-centered cubic geometry to four equivalent Tc and ten Pb atoms. There are a spread of Ta–Tc bond distances ranging from 2.99–3.04 Å. There are a spread of Ta–Pb bond distances ranging from 3.02–3.50 Å. Tc is bonded in a distorted body-centered cubic geometry to four equivalent Ta and four equivalent Pb atoms. There are one shorter (3.01 Å) and three longer (3.02 Å) Tc–Pb bond lengths. There are two inequivalent Pb sites. In the first Pb site, Pb is bonded to six equivalent Ta, four equivalent Tc, and four equivalent Pb atoms to form a mixture of distorted face and corner-sharing PbTa6Tc4Pb4 tetrahedra. All Pb–Pb bond lengths are 3.02 Å. In the second Pb site, Pb is bonded to four equivalent Ta and four equivalent Pb atoms to form distorted PbTa4Pb4 tetrahedra that share corners with twelve equivalent PbTa6Tc4Pb4 tetrahedra, edges with twelve equivalent PbTa4Pb4 tetrahedra, and faces with four equivalent PbTa6Tc4Pb4 tetrahedra.

36 MATERIALS SCIENCE↗