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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Chemical and physical transformations of carbon-based nanomaterials observed by liquid phase transmission electron microscopy

This article addresses recent advances in liquid phase transmission electron microscopy (LPTEM) for studying nanoscale synthetic processes of carbon-based materials that are independent of the electron beam—those driven by nonradiolytic chemical or thermal reactions. In particular, we focus on chemical/physical formations and the assembly of nanostructures composed of organic monomers/polymers, peptides/DNA, and biominerals. The synthesis of carbon-based nanomaterials generally only occurs at specific conditions, which cannot be mimicked by aqueous solution radiolysis. Carbon-based structures themselves are also acutely sensitive to the damaging effects of the irradiating beam, which make studying their synthesis using LPTEM a unique challenge that is possible when beam effects can be quantifi ed and mitigated. With new direct sensing, high frame rate cameras, and advances in liquid-cell holder designs, combined with a growing understanding of irradiation effects and proper experimental controls, microscopists have been able to make strides in observing traditionally problematic carbon-based materials under conditions where synthesis can be controlled, and imaged free from beam effects, or with beam effects quantified and accounted for. These materials systems and LPTEM experimental techniques are discussed, focusing on nonradiolytic chemical and physical transformations relevant to materials synthesis.

Parent, Lucas R.↗
DOE OSTI2020

Materials Data on Li7Ti12O24 by Materials Project

Li7Ti12O24 crystallizes in the monoclinic Pm space group. The structure is three-dimensional. there are seven inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with two TiO6 octahedra, corners with four equivalent LiO6 octahedra, edges with two equivalent LiO6 octahedra, and edges with eight TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–9°. There are a spread of Li–O bond distances ranging from 2.00–2.38 Å. In the second Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with two TiO6 octahedra, corners with four equivalent LiO6 octahedra, edges with two equivalent LiO6 octahedra, and edges with eight TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–14°. There are a spread of Li–O bond distances ranging from 2.00–2.35 Å. In the third Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with two TiO6 octahedra, corners with four equivalent LiO6 octahedra, and edges with eight TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–13°. There are a spread of Li–O bond distances ranging from 2.00–2.31 Å. In the fourth Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with two TiO6 octahedra, corners with four equivalent LiO6 octahedra, and edges with eight TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–11°. There are a spread of Li–O bond distances ranging from 2.00–2.43 Å. In the fifth Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with two TiO6 octahedra, corners with four equivalent LiO6 octahedra, edges with two equivalent LiO6 octahedra, and edges with eight TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–15°. There are a spread of Li–O bond distances ranging from 2.01–2.37 Å. In the sixth Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with two TiO6 octahedra, corners with four equivalent LiO6 octahedra, edges with two equivalent LiO6 octahedra, and edges with eight TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–15°. There are a spread of Li–O bond distances ranging from 2.01–2.36 Å. In the seventh Li1+ site, Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with two TiO6 octahedra, corners with four equivalent LiO6 octahedra, and edges with eight TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–15°. There are a spread of Li–O bond distances ranging from 2.01–2.36 Å. There are twelve inequivalent Ti+3.42+ sites. In the first Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four TiO6 octahedra, and edges with six LiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–19°. There are a spread of Ti–O bond distances ranging from 1.98–2.14 Å. In the second Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four equivalent LiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–18°. There are a spread of Ti–O bond distances ranging from 2.00–2.08 Å. In the third Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four TiO6 octahedra, and edges with six LiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–19°. There are a spread of Ti–O bond distances ranging from 1.95–2.15 Å. In the fourth Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four equivalent LiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–14°. There are a spread of Ti–O bond distances ranging from 2.01–2.07 Å. In the fifth Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four LiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–3°. There are a spread of Ti–O bond distances ranging from 2.00–2.08 Å. In the sixth Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four TiO6 octahedra, and edges with six LiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–19°. There are a spread of Ti–O bond distances ranging from 1.99–2.13 Å. In the seventh Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with four equivalent TiO6 octahedra, edges with four LiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedra tilt angles range from 12–13°. There are a spread of Ti–O bond distances ranging from 1.88–2.17 Å. In the eighth Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four LiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–5°. There are a spread of Ti–O bond distances ranging from 2.00–2.09 Å. In the ninth Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four LiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Ti–O bond distances ranging from 2.00–2.08 Å. In the tenth Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four LiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–12°. There are a spread of Ti–O bond distances ranging from 2.01–2.04 Å. In the eleventh Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share a cornercorner with one LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four TiO6 octahedra, and edges with six LiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–19°. There are a spread of Ti–O bond distances ranging from 1.98–2.13 Å. In the twelfth Ti+3.42+ site, Ti+3.42+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two LiO6 octahedra, corners with four equivalent TiO6 octahedra, edges with four equivalent LiO6 octahedra, and edges with four TiO6 octahedra. The corner-sharing octahedra tilt angles range from 0–16°. There are a spread of Ti–O bond distances ranging from 2.00–2.12 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded to three Li1+ and three Ti+3.42+ atoms to form OLi3Ti3 octahedra that share corners with four equivalent OLi3Ti3 octahedra, a cornercorner with one OLi2Ti3 square pyramid, edges with two equivalent OLi3Ti3 octahedra, and edges with six OLi2Ti3 square pyramids. The corner-sharing octahedra tilt angles range from 2–3°. In the second O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form OLi2Ti3 square pyramids that share corners with four equivalent OLi2Ti3 square pyramids, edges with six OLi3Ti3 octahedra, and edges with two equivalent OLi2Ti3 square pyramids. In the third O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form a mixture of edge and corner-sharing OLi2Ti3 square pyramids. In the fourth O2- site, O2- is bonded in a square co-planar geometry to one Li1+ and three Ti+3.42+ atoms. In the fifth O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form OLi2Ti3 square pyramids that share corners with four equivalent OLi2Ti3 square pyramids, edges with six OLi3Ti3 octahedra, and edges with two equivalent OLi2Ti3 square pyramids. In the sixth O2- site, O2- is bonded to three Li1+ and three Ti+3.42+ atoms to form OLi3Ti3 octahedra that share corners with four equivalent OLi3Ti3 octahedra, a cornercorner with one OLi2Ti3 square pyramid, edges with two equivalent OLi3Ti3 octahedra, and edges with six OLi2Ti3 square pyramids. The corner-sharing octahedra tilt angles range from 3–8°. In the seventh O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form OLi2Ti3 square pyramids that share a cornercorner with one OLi3Ti3 octahedra, corners with four equivalent OLi2Ti3 square pyramids, and edges with four equivalent OLi2Ti3 square pyramids. The corner-sharing octahedral tilt angles are 0°. In the eighth O2- site, O2- is bonded in a square co-planar geometry to one Li1+ and three Ti+3.42+ atoms. In the ninth O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form OLi2Ti3 square pyramids that share a cornercorner with one OLi3Ti3 octahedra, corners with four equivalent OLi2Ti3 square pyramids, and edges with four equivalent OLi2Ti3 square pyramids. The corner-sharing octahedral tilt angles are 0°. In the tenth O2- site, O2- is bonded in a square co-planar geometry to one Li1+ and three Ti+3.42+ atoms. In the eleventh O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form OLi2Ti3 square pyramids that share corners with four equivalent OLi2Ti3 square pyramids, edges with six OLi3Ti3 octahedra, and edges with two equivalent OLi2Ti3 square pyramids. In the twelfth O2- site, O2- is bonded in a square co-planar geometry to one Li1+ and three Ti+3.42+ atoms. In the thirteenth O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form a mixture of edge and corner-sharing OLi2Ti3 square pyramids. In the fourteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Li1+ and three Ti+3.42+ atoms. In the fifteenth O2- site, O2- is bonded in a square co-planar geometry to one Li1+ and three Ti+3.42+ atoms. In the sixteenth O2- site, O2- is bonded to three Li1+ and three Ti+3.42+ atoms to form OLi3Ti3 octahedra that share corners with four equivalent OLi3Ti3 octahedra, a cornercorner with one OLi2Ti3 square pyramid, edges with two equivalent OLi3Ti3 octahedra, and edges with six OLi2Ti3 square pyramids. The corner-sharing octahedra tilt angles range from 1–2°. In the seventeenth O2- site, O2- is bonded to three Li1+ and three Ti+3.42+ atoms to form OLi3Ti3 octahedra that share corners with four equivalent OLi3Ti3 octahedra, a cornercorner with one OLi2Ti3 square pyramid, edges with two equivalent OLi3Ti3 octahedra, and edges with six OLi2Ti3 square pyramids. The corner-sharing octahedral tilt angles are 2°. In the eighteenth O2- site, O2- is bonded in a square co-planar geometry to one Li1+ and three Ti+3.42+ atoms. In the nineteenth O2- site, O2- is bonded in a square co-planar geometry to one Li1+ and three Ti+3.42+ atoms. In the twentieth O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form OLi2Ti3 square pyramids that share a cornercorner with one OLi3Ti3 octahedra, corners with four equivalent OLi2Ti3 square pyramids, and edges with four equivalent OLi2Ti3 square pyramids. The corner-sharing octahedral tilt angles are 0°. In the twenty-first O2- site, O2- is bonded in a square co-planar geometry to one Li1+ and three Ti+3.42+ atoms. In the twenty-second O2- site, O2- is bonded to two equivalent Li1+ and three Ti+3.42+ atoms to form OLi2Ti3 square pyramids that share corners with four equivalent OLi2Ti3 square pyramids, ed

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li10Sn(PSe6)2 by Materials Project

Li10Sn(PSe6)2 is Aluminum carbonitride-derived structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are twenty inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a 5-coordinate geometry to five Se2- atoms. There are a spread of Li–Se bond distances ranging from 2.67–2.85 Å. In the second Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six Se2- atoms. There are a spread of Li–Se bond distances ranging from 2.64–3.30 Å. In the third Li1+ site, Li1+ is bonded to six Se2- atoms to form distorted LiSe6 octahedra that share a cornercorner with one LiSe6 octahedra, corners with two equivalent PSe4 tetrahedra, corners with three LiSe4 tetrahedra, corners with two equivalent LiSe5 trigonal bipyramids, an edgeedge with one SnSe4 tetrahedra, an edgeedge with one PSe4 tetrahedra, and edges with three LiSe4 tetrahedra. The corner-sharing octahedral tilt angles are 53°. There are a spread of Li–Se bond distances ranging from 2.67–3.28 Å. In the fourth Li1+ site, Li1+ is bonded to six Se2- atoms to form LiSe6 octahedra that share corners with two equivalent PSe4 tetrahedra, corners with four LiSe4 tetrahedra, an edgeedge with one LiSe6 octahedra, an edgeedge with one SnSe4 tetrahedra, an edgeedge with one PSe4 tetrahedra, edges with four LiSe4 tetrahedra, and an edgeedge with one LiSe5 trigonal bipyramid. There are a spread of Li–Se bond distances ranging from 2.73–3.00 Å. In the fifth Li1+ site, Li1+ is bonded to four Se2- atoms to form LiSe4 tetrahedra that share corners with two equivalent LiSe6 octahedra, corners with two equivalent LiSe4 tetrahedra, corners with two PSe4 tetrahedra, an edgeedge with one LiSe6 octahedra, an edgeedge with one LiSe4 tetrahedra, an edgeedge with one SnSe4 tetrahedra, and an edgeedge with one LiSe5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 18–63°. There are a spread of Li–Se bond distances ranging from 2.49–2.67 Å. In the sixth Li1+ site, Li1+ is bonded in a 4-coordinate geometry to five Se2- atoms. There are a spread of Li–Se bond distances ranging from 2.67–3.37 Å. In the seventh Li1+ site, Li1+ is bonded to four Se2- atoms to form distorted LiSe4 tetrahedra that share a cornercorner with one LiSe6 octahedra, corners with two PSe4 tetrahedra, corners with four LiSe4 tetrahedra, corners with two LiSe5 trigonal bipyramids, an edgeedge with one LiSe6 octahedra, and an edgeedge with one SnSe4 tetrahedra. The corner-sharing octahedral tilt angles are 48°. There are a spread of Li–Se bond distances ranging from 2.55–2.69 Å. In the eighth Li1+ site, Li1+ is bonded to six Se2- atoms to form LiSe6 octahedra that share a cornercorner with one LiSe6 octahedra, corners with two PSe4 tetrahedra, corners with six LiSe4 tetrahedra, an edgeedge with one LiSe6 octahedra, an edgeedge with one LiSe4 tetrahedra, an edgeedge with one SnSe4 tetrahedra, and an edgeedge with one PSe4 tetrahedra. The corner-sharing octahedral tilt angles are 53°. There are a spread of Li–Se bond distances ranging from 2.68–3.24 Å. In the ninth Li1+ site, Li1+ is bonded to four Se2- atoms to form LiSe4 tetrahedra that share corners with two LiSe6 octahedra, a cornercorner with one SnSe4 tetrahedra, a cornercorner with one PSe4 tetrahedra, corners with two equivalent LiSe4 tetrahedra, an edgeedge with one LiSe4 tetrahedra, and an edgeedge with one PSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 46–71°. There are a spread of Li–Se bond distances ranging from 2.51–2.65 Å. In the tenth Li1+ site, Li1+ is bonded to five Se2- atoms to form LiSe5 trigonal bipyramids that share corners with two equivalent LiSe6 octahedra, a cornercorner with one PSe4 tetrahedra, corners with two equivalent SnSe4 tetrahedra, corners with four LiSe4 tetrahedra, a cornercorner with one LiSe5 trigonal bipyramid, an edgeedge with one PSe4 tetrahedra, and edges with two LiSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 31–37°. There are a spread of Li–Se bond distances ranging from 2.58–3.04 Å. In the eleventh Li1+ site, Li1+ is bonded to four Se2- atoms to form LiSe4 tetrahedra that share corners with four LiSe6 octahedra, a cornercorner with one SnSe4 tetrahedra, a cornercorner with one PSe4 tetrahedra, corners with two equivalent LiSe4 tetrahedra, an edgeedge with one LiSe4 tetrahedra, and an edgeedge with one PSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 9–68°. There are a spread of Li–Se bond distances ranging from 2.51–2.75 Å. In the twelfth Li1+ site, Li1+ is bonded to four Se2- atoms to form LiSe4 tetrahedra that share corners with two LiSe6 octahedra, corners with two PSe4 tetrahedra, corners with four LiSe4 tetrahedra, a cornercorner with one LiSe5 trigonal bipyramid, an edgeedge with one SnSe4 tetrahedra, and an edgeedge with one LiSe5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 53–73°. There are a spread of Li–Se bond distances ranging from 2.65–2.80 Å. In the thirteenth Li1+ site, Li1+ is bonded to four Se2- atoms to form LiSe4 tetrahedra that share corners with two SnSe4 tetrahedra, corners with three LiSe4 tetrahedra, corners with three LiSe5 trigonal bipyramids, edges with two LiSe6 octahedra, and an edgeedge with one PSe4 tetrahedra. There are a spread of Li–Se bond distances ranging from 2.58–2.66 Å. In the fourteenth Li1+ site, Li1+ is bonded to four Se2- atoms to form LiSe4 tetrahedra that share corners with two equivalent LiSe4 tetrahedra, corners with two PSe4 tetrahedra, corners with two equivalent LiSe5 trigonal bipyramids, an edgeedge with one LiSe6 octahedra, an edgeedge with one LiSe4 tetrahedra, and an edgeedge with one SnSe4 tetrahedra. There are a spread of Li–Se bond distances ranging from 2.55–2.76 Å. In the fifteenth Li1+ site, Li1+ is bonded to four Se2- atoms to form distorted LiSe4 tetrahedra that share a cornercorner with one SnSe4 tetrahedra, a cornercorner with one PSe4 tetrahedra, corners with two equivalent LiSe4 tetrahedra, a cornercorner with one LiSe5 trigonal bipyramid, an edgeedge with one LiSe6 octahedra, and an edgeedge with one PSe4 tetrahedra. There are a spread of Li–Se bond distances ranging from 2.53–2.60 Å. In the sixteenth Li1+ site, Li1+ is bonded to five Se2- atoms to form distorted LiSe5 trigonal bipyramids that share a cornercorner with one PSe4 tetrahedra, corners with two SnSe4 tetrahedra, corners with seven LiSe4 tetrahedra, a cornercorner with one LiSe5 trigonal bipyramid, an edgeedge with one LiSe6 octahedra, an edgeedge with one LiSe4 tetrahedra, and an edgeedge with one PSe4 tetrahedra. There are a spread of Li–Se bond distances ranging from 2.61–3.07 Å. In the seventeenth Li1+ site, Li1+ is bonded to four Se2- atoms to form LiSe4 tetrahedra that share corners with two equivalent LiSe6 octahedra, corners with two SnSe4 tetrahedra, corners with four LiSe4 tetrahedra, a cornercorner with one LiSe5 trigonal bipyramid, an edgeedge with one LiSe6 octahedra, and an edgeedge with one PSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 21–25°. There are a spread of Li–Se bond distances ranging from 2.58–2.68 Å. In the eighteenth Li1+ site, Li1+ is bonded in a 4-coordinate geometry to four Se2- atoms. There are a spread of Li–Se bond distances ranging from 2.56–2.80 Å. In the nineteenth Li1+ site, Li1+ is bonded in a 5-coordinate geometry to five Se2- atoms. There are a spread of Li–Se bond distances ranging from 2.57–3.13 Å. In the twentieth Li1+ site, Li1+ is bonded to four Se2- atoms to form distorted LiSe4 tetrahedra that share a cornercorner with one SnSe4 tetrahedra, a cornercorner with one PSe4 tetrahedra, corners with three LiSe4 tetrahedra, a cornercorner with one LiSe5 trigonal bipyramid, an edgeedge with one LiSe6 octahedra, an edgeedge with one PSe4 tetrahedra, and an edgeedge with one LiSe5 trigonal bipyramid. There are a spread of Li–Se bond distances ranging from 2.64–2.71 Å. There are two inequivalent Sn4+ sites. In the first Sn4+ site, Sn4+ is bonded to four Se2- atoms to form SnSe4 tetrahedra that share corners with four LiSe4 tetrahedra, a cornercorner with one LiSe5 trigonal bipyramid, an edgeedge with one LiSe6 octahedra, and edges with two LiSe4 tetrahedra. There are a spread of Sn–Se bond distances ranging from 2.54–2.57 Å. In the second Sn4+ site, Sn4+ is bonded to four Se2- atoms to form SnSe4 tetrahedra that share corners with four LiSe4 tetrahedra, corners with three LiSe5 trigonal bipyramids, edges with two LiSe6 octahedra, and edges with two LiSe4 tetrahedra. There are a spread of Sn–Se bond distances ranging from 2.53–2.58 Å. There are four inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four Se2- atoms to form PSe4 tetrahedra that share corners with three LiSe6 octahedra and corners with five LiSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 46–55°. There are a spread of P–Se bond distances ranging from 2.20–2.26 Å. In the second P5+ site, P5+ is bonded to four Se2- atoms to form PSe4 tetrahedra that share corners with three LiSe6 octahedra, corners with three LiSe4 tetrahedra, edges with two LiSe4 tetrahedra, and edges with two LiSe5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 27–57°. There are a spread of P–Se bond distances ranging from 2.21–2.25 Å. In the third P5+ site, P5+ is bonded to four Se2- atoms to form PSe4 tetrahedra that share corners with two LiSe4 tetrahedra, corners with two LiSe5 trigonal bipyramids, and edges with two LiSe4 tetrahedra. There are one shorter (2.23 Å) and three longer (2.24 Å) P–Se bond lengths. In the fourth P5+ site, P5+ is bonded to four Se2- atoms to form PSe4 tetrahedra that share corners with two LiSe4 tetrahedra, edges with three LiSe6 octahedra, and edges with two LiSe4 tetrahedra. There are three shorter (2.23 Å) and one longer (2.24 Å) P–Se bond lengths. There are twenty-four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 5-coordinate geometry to four Li1+ and one P5+ atom. In the second Se2- site, Se2- is bonded to four Li1+ and one P5+ atom to form distorted SeLi4P square pyramids that share a cornercorner with one SeLi4P square pyramid, corners with two SeLi4P trigonal bipyramids, a cornercorner with one SeLi3P trigonal pyramid, an edgeedge with one SeLi4Sn square pyramid, and edges with two SeLi4P trigonal bipyramids. In the third Se2- site, Se2- is bonded in a 5-coordinate geometry to four Li1+ and one P5+ atom. In the fourth Se2- site, Se2- is bonded in a 5-coordinate geometry to four Li1+ and one P5+ atom. In the fifth Se2- site, Se2- is bonded in a 6-coordinate geometry to five Li1+ and one P5+ atom. In the sixth Se2- site, Se2- is bonded in a 5-coordinate geometry to four Li1+ and one P5+ atom. In the seventh Se2- site, Se2- is bonded to four Li1+ and one P5+ atom to form distorted SeLi4P trigonal bipyramids that share corners with two SeLi3P trigonal pyramids, an edgeedge with one SeLi4P square pyramid, and edges with two SeLi4P trigonal bipyramids. In the eighth Se2- site, Se2- is bonded in a distorted see-saw-like geometry to three Li1+ and one P5+ atom. In the ninth Se2- site, Se2- is bonded in a 5-coordinate geometry to four Li1+ and one Sn4+ atom. In the tenth Se2- site, Se2- is bonded in a 5-coordinate geometry to four Li1+ and one Sn4+ atom. In the eleventh Se2- site, Se2- is bonded in a 5-coordinate geometry to four Li1+ and one P5+ atom. In the twelfth Se2- site, Se2- is bonded to three Li1+ and one P5+ atom to form SeLi3P trigonal pyramids that share corners with two SeLi4Sn square pyramids, a cornercorner with one SeLi4Sn trigonal bipyramid, and an edgeedge with one SeLi3P trigonal pyramid. In the thirteenth Se2- site, Se2- is bonded to four Li1+ and one P5+ atom to form distorted SeLi4P trigonal bipyramids that share corners with two SeLi4Sn square pyramids, a cornercorner with one SeLi4Sn trigonal bipyramid, ed

36 MATERIALS SCIENCE↗
DOE OSTI2022

In Situ Plasma Processing of Superconducting Cavities at JLab

Jefferson Lab has an ongoing R&D program in plasma processing which is close to going into production pro-cessing in the CEBAF accelerator. Plasma processing is a common technique for removing hydrocarbons from surfaces, which increases the work function and reduces the secondary emission coefficient[1]. The initial focus of the effort is processing C100 cavities by injecting RF power into the HOM coupler ports. The goal will be to improve the operational gradients and the energy margin of the CEBAF linacs by processing cryomodules in situ. Results from processing cryomodule in the cryomodule test bunker as well as vertical test results will be present-ed. This work will describe the systems and methods used at JLAB for processing cavities using an argon oxygen gas mixture. Before and after plasma processing results will also be presented.

Powers, T.↗
DOE OSTI2023

Geometry Optimization for a Quadrupole Resonator at Jefferson Lab

The quadrupole resonator (QPR) is a sample characterization tool to measure the RF properties of superconducting materials using the calorime-try method at different temperatures, magnetic fields, and frequencies. Such resonators are cur-rently operating at CERN and HZB but suffer from Lorentz force detuning and modes overlap-ping, resulting in higher uncertainties in surface resistance measurement. Using the two CERN's QPR model iterations, the geometry was opti-mized via electromagnetic and mechanical simu-lations to eliminate these issues. The new QPR version was modelled for an increasing range of magnetic fields. The magnetic field is concentrat-ed at the center of the sample to reduce the un-certainty in surface resistance measurements sig-nificantly. This paper discusses the QPR geome-try optimization for the new version of QPR, which is now progressing toward fabrication.

Bira, S.↗
DOE OSTI2023

IN SITU PLASMA PROCESSING OF SUPERCONDUCTING CAVITIES AT JLAB, 2023 UPDATE

Jefferson Lab has an ongoing R&D program in plasma processing which just completed a round of production processing in the CEBAF accelerator. Plasma processing is a common technique for removing hydrocarbons from surfaces, which increases the work function and reduces the secondary emission coefficient. The initial focus of the effort was processing C100 cavities by injecting RF power into the higher order mode (HOM) coupler ports. Results from processing cryomodules in the CEBAF accelerator as well as vertical test results will be present-ed. The goal of in-situ processing is to improve the operational gradients and the energy margin of the linacs. This work will describe the systems and methods used at JLAB for processing cavities using an argon-oxygen gas mixture as well as a helium-oxygen gas mixture. Before and after plasma processing results will also be presented.

Powers, Thomas↗
DOE OSTI2020

Dimer description of the SU(4) antiferromagnet on the triangular lattice

In systems with many local degrees of freedom, high-symmetry points in the phase diagram can provide an important starting point for the investigation of their properties throughout the phase diagram. In systems with both spin and orbital (or valley) degrees of freedom such a starting point gives rise to SU(4)-symmetric models. Here we consider SU(4)-symmetric "spin" models, corresponding to Mott phases at half-filling, i.e. the six-dimensional representation of SU(4). This may be relevant to twisted multilayer graphene. In particular, we study the SU(4) antiferromagnetic "Heisenberg" model on the triangular lattice, both in the classical limit and in the quantum regime. Carrying out a numerical study using the density matrix renormalization group (DMRG), we argue that the ground state is non-magnetic. We then derive a dimer expansion of the SU(4) spin model. An exact diagonalization (ED) study of the effective dimer model suggests that the ground state breaks translation invariance, forming a valence bond solid (VBS) with a 12-site unit cell. Finally, we consider the effect of SU(4)-symmetry breaking interactions due to Hund's coupling, and argue for a possible phase transition between a VBS and a magnetically ordered state.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Analysis Of The Sludge Batch 7b (Macrobatch 9) DWPF Pour Stream Glass Sample (Rev. 1)

The Defense Waste Processing Facility (DWPF) began processing Sludge Batch 7b (SB7b), also referred to as Macrobatch 9 (MB9), in January 2012. SB7b is a blend of the heel of Tank 40 from Sludge Batch 7a (SB7a) and the SB7b material that was transferred to Tank 40 from Tank 51. SB7b was processed using Frit 418. During processing of each sludge batch, the DWPF is required to take at least one glass sample to meet the objectives of the Glass Product Control Program (GPCP), which is governed by the DWPF Waste Form Compliance Plan, and to complete the necessary Production Records so that the final glass product may be disposed of at a Federal Repository. Two pour stream glass samples were collected while processing SB7b. The samples were transferred to the Savannah River National Laboratory (SRNL) where one was analyzed and the other was archived. The following conclusions were drawn from the analytical results provided in this report: The sum of oxides for the official SB7b pour stream glass is within the Product Composition Control System (PCCS) limits (95-105 wt%); The average calculated Waste Dilution Factor (WDF) for SB7b is 2.3. In general, the measured radionuclide content of the official SB7b pour stream glass is in good agreement with the calculated values from the Tank 40 dried sludge results from the SB7b Waste Acceptance Program Specification (WAPS) sample; As in previous pour stream samples, ruthenium and rhodium inclusions were detected by Scanning Electron Microscopy-Electron Dispersive Spectroscopy (SEM-EDS) in the SB7b pour stream sample; The Product Consistency Test (PCT) results indicate that the official SB7b pour stream glass meets the waste acceptance criteria for durability with a normalized boron release of 0.8 g/L, which is an order of magnitude less than the Environmental Assessment (EA) glass; The measured density of the SB7b pour stream glass was 2.70 g/cm 3 ; The Fe 2+ /ΣFe ratio of the SB7b pour stream samples was 0.07.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

V28 Test Report

The V28 containment vessel was procured by the US Army Recovered Chemical Material Directorate (RCMD) as a replacement vessel for use on the P2 Explosive Destruction Systems. It is the fourth EDS vessel to be fabricated under Code Case 2564 of the ASME Boiler and Pressure Vessel Code, which provides rules for the design of impulsively loaded vessels. The explosive rating for the vessel, based on the Code Case, is nine (9) pounds TNT- equivalent for up to 637 detonations. This report documents the results of explosive tests that were done on the vessel at Sandia National Laboratories in Albuquerque New Mexico to qualify the vessel for explosive use. The primary qualification test consisted of six, 1.5 pounds charges of Composition C-4 (equivalent to 11.25 pounds TNT) distributed around the vessel in accordance with the User Design Specification. This test was repeated due to a lack of proper clamp settings. Two additional tests using less explosive were performed, one identical in configuration to a test performed in the V27 qualification series as a baseline for comparison, and one where the separation distance of the charges was increased to extend the V27 analysis of distributed load effects on the P2 vessel. All vessel acceptance criteria were met.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2020

Highly-Active and Contaminant-Tolerant Cathodes for Durable Solid Oxide Fuel Cells (Final Report)

The objective of this project is to investigate the fundamental degradation methods occurring in solid oxide fuel cell (SOFC) cathodes when exposed to chromium and carbon dioxide contamination and to rationally design alkaline earth-based catalysts to increase stability and tolerance to contaminate poisoning. With a mechanistic and fundamental understanding of the degradation methods, advanced catalytic surface modifications can be applied to reduce degradation. The specific technical objectives are: (1) To identify/develop new catalysts (alkaline-earth based-) that are compatible chemically with the state-of-the-art cathode materials at high temperatures required for fabrication and with contaminates commonly encountered under operating conditions; (2) To improve the infiltration process for optimal control of the thickness, composition, and uniformity of the catalyst coatings; (3) To evaluate the electro-catalytic activity toward ORR of the chemically-stable materials when exposed to different types of contaminants using electrical conductivity relaxation measurements on bar samples and performance evaluation of catalyst-infiltrated cathodes; (4) To unravel the contamination-tolerant mechanisms of the new catalyst coatings under realistic environmental conditions (with different types of contaminants) using powerful in situ and in operando characterization techniques performed on model cells with thin-film/pattern electrodes, as guided by modeling and simulation; (5) To establish scientific basis for rational design of new catalysts of high tolerance to contaminants; (6) To validate the long term stability of modified LSCF cathodes in commercially available cells/stacks under ROC. Alkaline earth-based catalysts have been systematically explored and tested under various contamination conditions. BaCoO 3-δ (BCO) was shown to produce the best catalytic activity enhancement as well as stability in a variety of contaminating conditions, including CO 2 and chromium. The microstructural evolution was investigated with SEM, EDS, and Raman spectroscopy, showing the BCO catalyst prevents the formation of insulating SrCrO 4 by forming electrically conductive BaCrO 4 . Electrochemical relaxation measurements determined the BCO catalyst coatings increased the surface diffusion coefficient but did not significantly affect the diffusion coefficient and determined an optimum surface modification layer of 100 nm. A novel Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O x (BCFN) catalyst was also shown to have excellent stability in chromium containing atmospheres. A novel surface sol-gel (SSG) surface modification, which offers superior thickness and compositional control, was applied to SOFCs to produce BaO catalyst coatings. SSG BaO coatings were shown to produce conformal coatings on the electrode surface, greatly increasing stability in chromium containing atmospheres. An atomic level mechanistic approach was applied to investigate the stability of PrBa 0.8 Ca 0.2 Co2O 5+δ (PBCC) with respect to a variety of common contaminants, demonstrating thermodynamically its superior stability in CO2 containing atmospheres. Finally, the best catalyst coatings demonstrated in this project, BCO and PBCC, were applied to full cells which demonstrated superior stability for over 300 hours in CO 2 and Cr atmospheres.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

Benchmark Solutions for Radiation Transport in Stochastic Media with Inhomogeneous Material Statistics

Accurately solving implicit Monte Carlo (IMC) thermal photon transport problems with mixed material cells is important in realistic applications. The production IMC package at LLNL treats mixed material cells arising from ALE remap and hydrodynamics using the same approximate model. The new Imp IMC thermal photon transport package currently under development has both a material interface reconstruction (MIR) algorithm and a Levermore-Pomraning (LP) stochastic medium algorithm for treating mixed material cells. Existing stochastic medium algorithms for treating mixed material cells in IMC lack a complete theoretical basis. The IMC LP algorithm implementation has been demonstrated to reproduce published deterministic LP solutions for the particular case of spatially homogeneous material statistics. Realistic simulations will include spatially inhomogeneous material statistics (material mean chord lengths). In a previous investigation, the LP-model for transport in binary stochastic media in rod geometry was generalized to accommodate spatially varying material chord lengths, i.e., the mixing statistics were allowed to be nonhomogeneous. Analytical solutions were obtained and used to produce a verifi cation suite for the Imp IMC Levermore-Pomraning implementation for different spatial variations of the chord lengths. However, the accuracy of the LP model when the mixing statistics are nonhomogeneous has not been assessed and leaves open the question of whether local accuracy is improved or further degraded when chord lengths are not uniform. This shortcoming is rectifi ed here by developing benchmark analytic solutions for transport in binary Markovian stochastic mixtures in rod geometry with nonhomogeneous mixing statistics, using spatially varying chord lengths considered in the previous investigation based on the LP model. Methods for sampling a nonhomogeneous Poisson process (NHPP) are first described and used to construct individual realizations of the binary mixtures in rod geometry. Analytic solutions are then obtained for the forward and backward directed fluxes on a given realization, now viewed as a deterministic medium with alternating layers of the two materials with known interface locations. Finally, material averaged scalar fluxes are obtained using these sampling schemes with spatially linear and quadratic chord lengths and used to assess the accuracy of the previously obtained LP-model results.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

MSTAR2019 Code Description and User's Manual

This report describes an ideal cascade model of uranium enrichment that includes side feed and side product streams and flexible input options. It is based on the original MSTAR model developed by Ed Von Halle and implemented in a Visual Basic code. The current version allows the user to specify integer numbers of stages or the stage numbers of external flows instead of assays in those flows. The computational engine is written in FORTRAN-90 and is invoked by a user-friendly GUI written in C++. This version of MSTAR has been demonstrated to operate on Linux, Mac, and Windows platforms, and has undergone significant testing and quality analysis. A number of examples are presented to illustrate the operation of the code and guide the user. The code is extremely fast, and results are returned immediately. The input and output have been specially configured for analysis by the environmental sampling team of the International Atomic Energy Agency (IAEA). A number of additional output features are included to assist the user in visualizing computational results and downloading data to files for use in other analysis software.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Second Annual Progress Report on Correlation Between Microstructure and Mechanical Properties of Neutron-Irradiated Ferritic-Martensitic and Austenitic Steels

Ferritic-martensitic steels G92-2b (an optimized Grade 92 heat), NF616 and T91, and austenitic stainless steel 800H and its Grain Boundary Engineering (GBE)-treated version 800H-TMP (ThermoMechanical Processing) were irradiated in the High Flux Isotope Reactor (HFIR) of Oak Ridge National Laboratory (ORNL) and the Advanced Test Reactor (ATR) of Idaho National Laboratory (INL). Selected G92-2b samples were irradiated up to 14.66 dpa in the HFIR at two temperature ranges: 400–496.7°C and 683.3– 720°C. NF616 and T91 were irradiated in the ATR up to 8.16 dpa with the irradiation temperatures ranged from 241°C to 447.5°C. Alloy 800H and 800H-TMP samples were irradiated in both the HFIR and the ATR. Selected 800H and 800H-TMP samples had HFIR irradiation to 1.28 dpa at 580°C and ATR irradiation up to 9.12 dpa at 359°C to 431°C. Vickers hardness measurements, fractography, and microstructural characterization were performed on the selected samples in the Low Activation Materials Design and Analysis (LAMDA) laboratory. Radiation-hardening of G92-2b was observed at the lower doses and lower irradiation temperatures (400- 496.7°C), with GB03 (0.52 dpa at 400°C) and GB04 (7.44 dpa at ~490°C) showing ~12% and ~8% hardening, respectively. Softening by ~14% was observed for GB05 (14.66 dpa at 496.7°C). Radiationsoftening of G92-2b was more prevalent at the higher irradiation temperatures (683.3-~720°C), with GB10 (0.46 dpa at 683.3°C), GB11 (7.44 dpa at ~720°C), and GB12 (14.63 dpa at ~720°C) showing ~8%, ~8%, and ~40% softening, respectively. Radiation-hardening of NF616 and T91 was observed with the hardness increased by ~37% to ~65% depending on the irradiation doses and irradiation temperatures. Within the studied irradiation conditions of NF616 and T91, samples with a higher dose had a larger hardness after irradiation. All the tested alloy 800H and 800H-TMP samples in this work showed radiation-hardening by ~96±7% to ~152±10%. Alloy 800H-TMP tended to have slightly smaller radiation-hardening than alloy 800H. The fractography results of G92-2b sample GB03, GB10, and GB11, together with the previously characterized fractography of GB04, GB05, and GB12, indicated that the ductility of G92-2b was maintained up to 14.66 dpa at the lower irradiation temperatures of 400-496.7°C, while some loss of ductility (less necking) was observed for higher doses at the higher irradiation temperatures of 683.3-720°C. This agrees with the previously reported tensile test results of G92-2b, where the elongation of G92-2b was reduced at higher doses at the higher irradiation temperatures. Dimple sizes increased at higher doses, which are more evident at the higher irradiation temperatures of 683.3-~720°C. The fractography of NF616 sample D2 (2.96 dpa at 291.5°C), D4 (5.91 dpa at 359°C), and D6 (8.16 dpa at 431°C) indicated loss of ductility with negligible necking for sample D2, while ductile failure for samples D4 and D6. Fractography of alloy 800H and 800H-TMP samples in various irradiation conditions showed ductile failure with obvious necking. Dimples were observed, with some of them containing large Ti-rich particles, in all the 800H/800H-TMP samples. Electron backscatter diffraction characterization of GB12 indicated the recovery of the lath structure, which was generally replaced by an equiaxed grain structure. Transmission electron microscopy (TEM) characterization showed the presence of frequent M 23 C 6 (M = primarily Cr), MX (M = primarily V), spherical Nb(C,N) precipitates, and occasional Laves phase precipitates in the G92-2b samples. MX precipitates with sizes of 20-30 nm were observed at boundaries of smaller grains, indicating the pinning effect of the V-rich precipitates. The lath structure recovery was more evident at the higher irradiation temperatures (683.3-~720°C), with decreased densities of line dislocations and M23C6 precipitates. The irradiated T91 (TA04) showed the growth of M23C6 precipitates to 101 ± 40 nm from the initial 68 ± 22 nm in the unirradiated condition. Dislocation loops of both {100} and {111} types were present in TA04. TEM characterization was also performed on the irradiated 800H (N4, N5, N6, and AR2) and 800H-TMP (P4, P5, P6, and HG1). Accumulation of M 23 C 6 precipitates at grain boundaries was observed in all the xii 800H/800H-TMP samples, and the presence of Ti(C,N) precipitates at grain boundaries and in the matrix was observed in the irradiated 800H-TMP. Some Ti(C,N) precipitates are embedded in the M 23 C 6 precipitates, maintaining specific orientation relationships between the precipitates and between the precipitate and matrix. In addition, nanoscale Si-rich clusters were observed in the matrix of all the 800H/800H-TMP samples, with EDS Si maps tending to have a lower contrast in 800H-TMP samples. Atom probe tomography was conducted on the same samples, supported by a Rapid Turnaround Examination project under Nuclear Science User Facilities. The results are being analyzed to be integrated with the TEM results for a confident description of the γ’ precipitates. Dislocation loops also formed in all the 800H/800H-TMP samples. The density and the average size of dislocation loops were quantified to be in the order of 10 22 – 10 23 m -3 and 11.7 – 15.9 nm, respectively, in the ATR-irradiated 800H/800H-TMP samples. The loop densities in irradiated 800H were higher than that in irradiated 800H-TMP under the same irradiation conditions. Further systematic data analyses, together with some complementary experiments, will be pursued for these samples to foster peer-reviewed journal article publications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Highly-Active and Contaminant-Tolerant Cathodes for Durable Solid Oxide Fuel Cells

The objective of this project is to investigate the fundamental degradation methods occurring in solid oxide fuel cell (SOFC) cathodes when exposed to chromium and carbon dioxide contamination and to rationally design alkaline earth-based catalysts to increase stability and tolerance to contaminate poisoning. With a mechanistic and fundamental understanding of the degradation methods, advanced catalytic surface modifications can be applied to reduce degradation. The specific technical objectives are: (1) To identify/develop new catalysts (alkaline-earth based-) that are compatible chemically with the state-of-the-art cathode materials at high temperatures required for fabrication and with contaminates commonly encountered under operating conditions; (2) To improve the infiltration process for optimal control of the thickness, composition, and uniformity of the catalyst coatings; (3) To evaluate the electro-catalytic activity toward ORR of the chemically-stable materials when exposed to different types of contaminants using electrical conductivity relaxation measurements on bar samples and performance evaluation of catalyst-infiltrated cathodes; (4) To unravel the contamination-tolerant mechanisms of the new catalyst coatings under realistic environmental conditions (with different types of contaminants) using powerful in situ and in operando characterization techniques performed on model cells with thin-film/pattern electrodes, as guided by modeling and simulation; (5) To establish scientific basis for rational design of new catalysts of high tolerance to contaminants; (6) To validate the long term stability of modified LSCF cathodes in commercially available cells/stacks under ROC. Alkaline earth-based catalysts have been systematically explored and tested under various contamination conditions. BaCoO 3-δ (BCO) was shown to produce the best catalytic activity enhancement as well as stability in a variety of contaminating conditions, including CO 2 and chromium. The microstructural evolution was investigated with SEM, EDS, and Raman spectroscopy, showing the BCO catalyst prevents the formation of insulating SrCrO 4 by forming electrically conductive BaCrO 4 . Electrochemical relaxation measurements determined the BCO catalyst coatings increased the surface diffusion coefficient but did not significantly affect the diffusion coefficient and determined an optimum surface modification layer of 100 nm. A novel Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O x (BCFN) catalyst was also shown to have excellent stability in chromium containing atmospheres. A novel surface sol-gel (SSG) surface modification, which offers superior thickness and compositional control, was applied to SOFCs to produce BaO catalyst coatings. SSG BaO coatings were shown to produce conformal coatings on the electrode surface, greatly4 increasing stability in chromium containing atmospheres. An atomic level mechanistic approach was applied to investigate the stability of PrBa 0.8 Ca 0.2 Co 2 O 5+δ (PBCC) with respect to a variety of common contaminants, demonstrating thermodynamically its superior stability in CO 2 containing atmospheres. Finally, the best catalyst coatings demonstrated in this project, BCO and PBCC, were applied to full cells which demonstrated superior stability for over 300 hours in CO 2 and Cr atmospheres.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Scalable Geometric Modeler for Overlap Detection and Resolution (ASC IC L2 Milestone 7181 FY2020 Final Review)

The final review for the FY20 Advanced Simulation and Computing (ASC) Integrated Codes (IC) L2 Milestone #7181 was conducted on August 31, 2020 at Sandia National Laboratories in Albuquerque, New Mexico. The review panel unanimously agreed that the milestone has been successfully completed. Roshan Quadros (1543) led the milestone team and various members from the team presented the results. The review panel was comprised of staff from Sandia National Laboratories Albuquerque and California that are involved with computational engineering modeling and analysis. The panel consisted of experts in the fields of solid modeling, discretization, meshing, simulation workflows, and computational analysis including personnel Brett Clark (1543, Chair); Jay Foulk (8363); Jackie Moore (1553); Ron Kensek (1341); Ed Hoffman (8753); Dan Ibanez (1443). The presentation documented the technical approach of the team and summarized the results with sufficient detail to demonstrate both the value and the completion of the milestone. A separate SAND report was also generated with more detail to supplement the presentation. The purpose of the milestone was to advance capabilities for automatically finding, displaying, and resolving geometric overlaps in CAD models.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2020

Highly-Active and Contaminant-Tolerant Cathodes for Durable Solid Oxide Fuel Cells

The objective of this project is to investigate the fundamental degradation methods occurring in solid oxide fuel cell (SOFC) cathodes when exposed to chromium and carbon dioxide contamination and to rationally design alkaline earth-based catalysts to increase stability and tolerance to contaminate poisoning. With a mechanistic and fundamental understanding of the degradation methods, advanced catalytic surface modifications can be applied to reduce degradation. The specific technical objectives are: (1) To identify/develop new catalysts (alkaline-earth based-) that are compatible chemically with the state-of-the-art cathode materials at high temperatures required for fabrication and with contaminates commonly encountered under operating conditions; (2) To improve the infiltration process for optimal control of the thickness, composition, and uniformity of the catalyst coatings; (3) To evaluate the electro-catalytic activity toward ORR of the chemically-stable materials when exposed to different types of contaminants using electrical conductivity relaxation measurements on bar samples and performance evaluation of catalyst-infiltrated cathodes; (4) To unravel the contamination-tolerant mechanisms of the new catalyst coatings under realistic environmental conditions (with different types of contaminants) using powerful in situ and in operando characterization techniques performed on model cells with thin-film/pattern electrodes, as guided by modeling and simulation; (5) To establish scientific basis for rational design of new catalysts of high tolerance to contaminants; (6) To validate the long term stability of modified LSCF cathodes in commercially available cells/stacks under ROC. Alkaline earth-based catalysts have been systematically explored and tested under various contamination conditions. BaCoO 3-δ (BCO) was shown to produce the best catalytic activity enhancement as well as stability in a variety of contaminating conditions, including CO 2 and chromium. The microstructural evolution was investigated with SEM, EDS, and Raman spectroscopy, showing the BCO catalyst prevents the formation of insulating SrCrO 4 by forming electrically conductive BaCrO 4 . Electrochemical relaxation measurements determined the BCO catalyst coatings increased the surface diffusion coefficient but did not significantly affect the diffusion coefficient and determined an optimum surface modification layer of 100 nm. A novel Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O x (BCFN) catalyst was also shown to have excellent stability in chromium containing atmospheres. A novel surface sol-gel (SSG) surface modification, which offers superior thickness and compositional control, was applied to SOFCs to produce BaO catalyst coatings. SSG BaO coatings were shown to produce conformal coatings on the electrode surface, greatly 4 increasing stability in chromium containing atmospheres. An atomic level mechanistic approach was applied to investigate the stability of PrBa 0.8 Ca 0.2 Co 2 O 5+δ (PBCC) with respect to a variety of common contaminants, demonstrating thermodynamically its superior stability in CO 2 containing atmospheres. Finally, the best catalyst coatings demonstrated in this project, BCO and PBCC, were applied to full cells which demonstrated superior stability for over 300 hours in CO 2 and Cr atmospheres

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2020

Advanced Anode for Internal Reforming and Thermal Management in Solid Oxide Fuel Cells

Solid oxide fuel cell (SOFC) is an efficient and clean electrical power generation system compared to conventional combustion based technologies with energy efficiency reaching as high as 85-90% in co-generation mode (electricity and heat). Other advantages of SOFCs are hybridization, modularity of construction, small CO 2 foot print per kWh of generated electricity and fuel flexibility. Hydrocarbons present in the gaseous fuel is utilized in SOFCs by internal or external reforming. There are two different internal reforming concepts: Direct Internal Reforming (DIR) and Indirect Internal Reforming (IIR). For DIR operation, the endothermic reforming reaction and the exothermic reaction from the oxidation reaction are operated together in the single unit eliminating the requirement for a separate fuel reformer. This configuration also simplifies the overall system design, making SOFC more attractive and efficient means of producing electrical power. The main advantage of the DIR type of operation is that the H 2 or CO consumption by the electrochemical reaction could directly promote the conversion of methane at the anode side of the fuel cell resulting in high conversion and high efficiency. The DIR operation, however, requires an anode material that has desired dual catalytic (hetero and electro) properties for reforming reaction and electrochemical reactions. The anode materials also need to remain resistant to carbon formation at the operating temperature and atmosphere with stable cell performance. Another requirement is to match the reforming reactions and electrochemical reactions to avoid local cooling or overheating, which can result in mechanical failure due to thermally induced stresses. Direct internal reforming (DIR) of hydrocarbon fuels simplifies the overall SOFC system design making it more attractive and efficient for producing electrical power. Low cost alloy anodes for distributed internal reforming of methane and other hydrocarbon fuels offer increased fuel-flexibility, reliability, and long term performance stability of solid oxide fuel cells (SOFC). The research program examined modification of the chemical compositions and microstructure of high entropy alloy (HEA) anode materials using thermochemical calculations and process simulation and modeling to achieve distributed reforming over the entire anode to eliminate hot zones. Cell fabrication and testing of the HEA anodes using button cell configuration has been performed to demonstrate the advantages of new anode over traditional Ni-YSZ anodes for distributed reforming and carbon free operation. Technical accomplishments include identification and synthesis of HEA carbon-resistant anode, demonstration of reduction in reforming rate confirmed by GC and modelling data validating effectiveness for thermal management in cell/stacks, electrochemical testing of HEA anode in single cell (HEA-GDC||YSZ||LSM-YSZ) and Characterization of pretest and posttest anode materials by TEM and SEM-EDS confirming carbon-free operation.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Synthesis and Flash Sintering of (Hf1-xZrx)B2 Solid Solution Fine Powders

Fine powders of (Hf1-xZrx)B2 solid solution were synthesized by two methods. In the first one, solution-based processing of HfCl4, ZrCl4, sucrose and H3BO3 was carried out followed by heat treatment (e.g., at 1500 °C for 1 h) in Argon to achieve the carbothermal reduction (CTR) reaction to form the boride solid solution. In the second one, called boron hydride reduction (BHR) method, HfCl4, ZrCl4 and NaBH4 were directly mixed in a glove box followed by heat treatment in Argon at elevated temperatures from 700 to 1500 °C. In addition, the powders synthesized via both methods were flash sintered without sample preheating in a homemade setup. The synthesized powders as well as the flash sintered bulk ceramics were characterized using different techniques including XRD, SEM, EDS, TEM, TGA-DSC, and Vickers hardness test to reveal the inter-relationships between starting materials composition, processing conditions, and the resulting materials microstructure and physical/chemical properties.

Belisario, Jose↗