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8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Undercooling studies on Nb-Pt and Nb-Si alloys using the 105 meter drop tube

Niobium-platinum samples of compositions ranging from 16 to 32 at. pct have been undercooled to as much as 540 K in the low gravity, containerless environment of a 105 meter drop tube. Undercooling was terminated in the Nb-Pt samples by the nucleation and growth of the Nb3Pt phase. In the 16-18 at. pct Pt samples, this resulted in samples which are completely Nb3Pt, in contrast to both the equilibrium phase diagram and the nonundercooled samples which formed with Nb dendrites and interdendritic Nb3Pt. Undercoolings for the Nb-Si samples were up to 670 K, which corresponds to 27 percent of the liquidus temperature or 80 percent of the estimated hypercooling limit. In the Nb-Si system, a coupled zone was identified as well as a metastable extension of the solubility limit of Si in Nb due to deep undercooling.

Robinson, M. B.↗
DOE OSTI2020

Materials Data on NbPt2 by Materials Project

NbPt2 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Nb4+ is bonded in a distorted q6 geometry to ten equivalent Pt2- atoms. There are eight shorter (2.83 Å) and two longer (2.88 Å) Nb–Pt bond lengths. Pt2- is bonded to five equivalent Nb4+ and seven equivalent Pt2- atoms to form a mixture of distorted corner, edge, and face-sharing PtNb5Pt7 cuboctahedra. There are a spread of Pt–Pt bond distances ranging from 2.82–2.86 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbPt3 by Materials Project

Pt3Nb is beta Cu3Ti-like structured and crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are two inequivalent Nb2+ sites. In the first Nb2+ site, Nb2+ is bonded to twelve Pt+0.67- atoms to form NbPt12 cuboctahedra that share corners with three NbPt12 cuboctahedra, corners with eight PtNb4Pt8 cuboctahedra, edges with seven NbPt12 cuboctahedra, edges with fourteen PtNb4Pt8 cuboctahedra, faces with five NbPt12 cuboctahedra, and faces with ten PtNb4Pt8 cuboctahedra. There are a spread of Nb–Pt bond distances ranging from 2.77–2.88 Å. In the second Nb2+ site, Nb2+ is bonded to twelve Pt+0.67- atoms to form NbPt12 cuboctahedra that share corners with three NbPt12 cuboctahedra, corners with eight PtNb4Pt8 cuboctahedra, edges with seven NbPt12 cuboctahedra, edges with fourteen PtNb4Pt8 cuboctahedra, faces with five NbPt12 cuboctahedra, and faces with twelve PtNb4Pt8 cuboctahedra. There are a spread of Nb–Pt bond distances ranging from 2.76–2.88 Å. There are four inequivalent Pt+0.67- sites. In the first Pt+0.67- site, Pt+0.67- is bonded to four Nb2+ and eight Pt+0.67- atoms to form distorted PtNb4Pt8 cuboctahedra that share corners with six PtNb4Pt8 cuboctahedra, corners with eight NbPt12 cuboctahedra, edges with eighteen PtNb4Pt8 cuboctahedra, faces with six NbPt12 cuboctahedra, and faces with ten PtNb4Pt8 cuboctahedra. There are a spread of Pt–Pt bond distances ranging from 2.81–2.85 Å. In the second Pt+0.67- site, Pt+0.67- is bonded in a distorted see-saw-like geometry to four Nb2+ and eight Pt+0.67- atoms. There are a spread of Pt–Pt bond distances ranging from 2.80–2.89 Å. In the third Pt+0.67- site, Pt+0.67- is bonded to four Nb2+ and eight Pt+0.67- atoms to form distorted PtNb4Pt8 cuboctahedra that share corners with two equivalent NbPt12 cuboctahedra, corners with thirteen PtNb4Pt8 cuboctahedra, edges with seven NbPt12 cuboctahedra, edges with ten PtNb4Pt8 cuboctahedra, faces with four NbPt12 cuboctahedra, and faces with twelve PtNb4Pt8 cuboctahedra. There are a spread of Pt–Pt bond distances ranging from 2.80–2.84 Å. In the fourth Pt+0.67- site, Pt+0.67- is bonded to four Nb2+ and eight Pt+0.67- atoms to form distorted PtNb4Pt8 cuboctahedra that share corners with two equivalent NbPt12 cuboctahedra, corners with eleven PtNb4Pt8 cuboctahedra, edges with seven NbPt12 cuboctahedra, edges with eleven PtNb4Pt8 cuboctahedra, faces with four NbPt12 cuboctahedra, and faces with fourteen PtNb4Pt8 cuboctahedra. There are a spread of Pt–Pt bond distances ranging from 2.79–2.83 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb3Pt by Materials Project

Nb3Pt crystallizes in the cubic Pm-3n space group. The structure is three-dimensional. Nb is bonded in a 6-coordinate geometry to two equivalent Nb and four equivalent Pt atoms. Both Nb–Nb bond lengths are 2.60 Å. All Nb–Pt bond lengths are 2.91 Å. Pt is bonded to twelve equivalent Nb atoms to form a mixture of edge and face-sharing PtNb12 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbPt by Materials Project

NbPt is beta-prime cadmium gold structured and crystallizes in the orthorhombic Pmma space group. The structure is three-dimensional. Nb2+ is bonded to eight equivalent Pt2- atoms to form distorted NbPt8 hexagonal bipyramids that share corners with eighteen equivalent PtNb8Pt4 cuboctahedra, corners with eight equivalent NbPt8 hexagonal bipyramids, edges with four equivalent PtNb8Pt4 cuboctahedra, edges with twelve equivalent NbPt8 hexagonal bipyramids, faces with two equivalent PtNb8Pt4 cuboctahedra, and faces with six equivalent NbPt8 hexagonal bipyramids. There are a spread of Nb–Pt bond distances ranging from 2.82–2.92 Å. Pt2- is bonded to eight equivalent Nb2+ and four equivalent Pt2- atoms to form distorted PtNb8Pt4 cuboctahedra that share corners with ten equivalent PtNb8Pt4 cuboctahedra, corners with eighteen equivalent NbPt8 hexagonal bipyramids, edges with six equivalent PtNb8Pt4 cuboctahedra, edges with four equivalent NbPt8 hexagonal bipyramids, faces with twelve equivalent PtNb8Pt4 cuboctahedra, and faces with two equivalent NbPt8 hexagonal bipyramids. There are two shorter (2.83 Å) and two longer (2.92 Å) Pt–Pt bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb2Pt by Materials Project

Nb2Pt is beta Uranium-derived structured and crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. there are three inequivalent Nb sites. In the first Nb site, Nb is bonded in a 6-coordinate geometry to nine Nb and six Pt atoms. There are a spread of Nb–Nb bond distances ranging from 2.78–3.30 Å. There are two shorter (2.99 Å) and four longer (3.06 Å) Nb–Pt bond lengths. In the second Nb site, Nb is bonded in a 4-coordinate geometry to one Nb and four equivalent Pt atoms. There are a spread of Nb–Pt bond distances ranging from 2.79–2.84 Å. In the third Nb site, Nb is bonded in a 7-coordinate geometry to five Nb and five Pt atoms. There are one shorter (2.57 Å) and one longer (2.62 Å) Nb–Nb bond lengths. There are a spread of Nb–Pt bond distances ranging from 2.88–2.93 Å. There are two inequivalent Pt sites. In the first Pt site, Pt is bonded to eight Nb and four equivalent Pt atoms to form PtNb8Pt4 cuboctahedra that share corners with sixteen equivalent PtNb10Pt2 cuboctahedra, edges with two equivalent PtNb8Pt4 cuboctahedra, and faces with four equivalent PtNb10Pt2 cuboctahedra. All Pt–Pt bond lengths are 2.72 Å. In the second Pt site, Pt is bonded to ten Nb and two Pt atoms to form distorted PtNb10Pt2 cuboctahedra that share corners with eleven PtNb8Pt4 cuboctahedra, edges with three equivalent PtNb10Pt2 cuboctahedra, and faces with seven PtNb8Pt4 cuboctahedra. The Pt–Pt bond length is 2.77 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbPt4 by Materials Project

NbPt4 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Nb4+ is bonded in a hexagonal planar geometry to six equivalent Pt1- atoms. All Nb–Pt bond lengths are 2.80 Å. There are two inequivalent Pt1- sites. In the first Pt1- site, Pt1- is bonded to three equivalent Nb4+ and three equivalent Pt1- atoms to form a mixture of distorted edge and corner-sharing PtNb3Pt3 cuboctahedra. All Pt–Pt bond lengths are 2.88 Å. In the second Pt1- site, Pt1- is bonded to twelve Pt1- atoms to form PtPt12 cuboctahedra that share corners with fifteen PtNb3Pt3 cuboctahedra, edges with twenty-one PtNb3Pt3 cuboctahedra, and faces with twelve equivalent PtPt12 cuboctahedra. There are six shorter (2.83 Å) and three longer (2.84 Å) Pt–Pt bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbPt2 by Materials Project

NbPt2 crystallizes in the trigonal P-3m1 space group. The structure is two-dimensional and consists of one NbPt2 sheet oriented in the (0, 0, 1) direction. Nb4+ is bonded in a hexagonal planar geometry to six equivalent Pt2- atoms. All Nb–Pt bond lengths are 2.81 Å. Pt2- is bonded to three equivalent Nb4+ atoms to form a mixture of distorted corner and edge-sharing PtNb3 cuboctahedra.

36 MATERIALS SCIENCE↗