SEARCH · Engineering Papers

Results for “MgSn”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

20 records · Page 2

All sources NASA NTRS DOE OSTI

DOE OSTI2020

Materials Data on Ba(MgSn)2 by Materials Project

BaMg2Sn2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. there are two inequivalent Ba sites. In the first Ba site, Ba is bonded in a 12-coordinate geometry to eight Mg and eight Sn atoms. There are four shorter (3.75 Å) and four longer (3.98 Å) Ba–Mg bond lengths. There are four shorter (3.81 Å) and four longer (3.85 Å) Ba–Sn bond lengths. In the second Ba site, Ba is bonded in a 8-coordinate geometry to eight Mg and eight Sn atoms. There are four shorter (3.91 Å) and four longer (4.01 Å) Ba–Mg bond lengths. There are four shorter (3.76 Å) and four longer (3.82 Å) Ba–Sn bond lengths. There are three inequivalent Mg sites. In the first Mg site, Mg is bonded to four Ba and four Sn atoms to form MgBa4Sn4 tetrahedra that share corners with six equivalent MgBa4Sn4 tetrahedra, corners with six equivalent SnBa4Mg4 tetrahedra, an edgeedge with one SnBa4Mg4 tetrahedra, edges with five MgBa4Sn4 tetrahedra, and faces with four equivalent MgBa4Sn4 tetrahedra. There are two shorter (2.95 Å) and two longer (2.97 Å) Mg–Sn bond lengths. In the second Mg site, Mg is bonded to four equivalent Ba and four equivalent Sn atoms to form a mixture of edge, corner, and face-sharing MgBa4Sn4 tetrahedra. All Mg–Sn bond lengths are 2.95 Å. In the third Mg site, Mg is bonded in a 5-coordinate geometry to four equivalent Ba and five Sn atoms. There are one shorter (2.85 Å) and four longer (2.95 Å) Mg–Sn bond lengths. There are four inequivalent Sn sites. In the first Sn site, Sn is bonded in a 9-coordinate geometry to four equivalent Ba and five Mg atoms. In the second Sn site, Sn is bonded to four equivalent Ba and four equivalent Mg atoms to form distorted SnBa4Mg4 tetrahedra that share corners with twelve equivalent MgBa4Sn4 tetrahedra, edges with two equivalent MgBa4Sn4 tetrahedra, edges with four equivalent SnBa4Mg4 tetrahedra, and faces with four equivalent SnBa4Mg4 tetrahedra. In the third Sn site, Sn is bonded in a 9-coordinate geometry to four equivalent Ba, four equivalent Mg, and one Sn atom. The Sn–Sn bond length is 2.92 Å. In the fourth Sn site, Sn is bonded in a 9-coordinate geometry to four equivalent Ba, four equivalent Mg, and one Sn atom.

36 MATERIALS SCIENCE↗

DOE OSTI2023

Metal Sulfide Ion Exchangers: High Acid Stability of Na 2 x Mg 2 y – x Sn 4– y S 8 (NMS) and Topotactic Conversion to 2D Solid Acids with Semiconducting Character

Metal sulfide ion exchange materials (MSIEs) are of interest for nuclear waste remediation applications. Here, we report the high stability of two structurally related metal sulfide ion exchange materials, Na 2x Mg 2y–x Sn 4–y S 8 (Mg-NMS) and Na 2 SnS 3 (Na-NMS), in strongly acid media, in addition to the preparation of Na 2x Ni 2y–x Sn 4–y S 8 (Ni-NMS). Their formation progress during synthesis is studied with in-situ methods, with the target phases appearing in <15 min, reaction completion in <12 h, and high yields (75–80%). Upon contact with nitric or hydrochloric acid, these materials topotactically exchange Na + for H + , proceeding in a stepwise protonation pathway for Na 5.33 Sn 2.67 S 8 . Na-NMS is stable in 2 M HNO 3 and Mg-NMS is stable in 4 M HNO 3 for up to 4 h, while both NMS materials are stable in 6 M HCl for up to 4 days. However, the treatment of Mg-NMS and Na-NMS with 2–6 M H 2 SO 4 reveals a much slower protonation process since after 4 h of contact both NMS and HMS are present in the solution. The resultant protonated materials, H 2x Mg 2y–x Sn 4–y S 8 and H 4x [(H y Na y–1 ) 1.33x Sn 4––1.33x ]S 8 , are themselves solid acids and readily react with and intercalate a variety of organic amines, where the band gap of the resultant adduct is influenced by amine choice and can be tuned within the range of 1.88(5)–2.27(5) eV. The work function energy values for all materials were extracted from photoemission yield spectroscopy in air (PYSA) measurements and range from 5.47 (2) to 5.76 (2) eV, and the relative band alignments of the materials are discussed. DFT calculations suggest that the electronic structure of Na 2 MgSn 3 S 8 and H 2 MgSn 3 S 8 makes them indirect gap semiconductors with multi-valley band edges, with carriers confined to the [MgSn 3 S 8 ] 2– layers. Light electron effective masses indicate high electron mobilities.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗