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29 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Si(NiO2)2 by Materials Project

Ni2SiO4 is Ilmenite-like structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Ni2+ sites. In the first Ni2+ site, Ni2+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with eight NiO6 octahedra, corners with four equivalent SiO4 tetrahedra, edges with two equivalent NiO6 octahedra, and an edgeedge with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–61°. There are a spread of Ni–O bond distances ranging from 2.06–2.19 Å. In the second Ni2+ site, Ni2+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with four equivalent NiO6 octahedra, corners with two equivalent SiO4 tetrahedra, edges with four NiO6 octahedra, and edges with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–61°. There are four shorter (2.09 Å) and two longer (2.13 Å) Ni–O bond lengths. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with six NiO6 octahedra and edges with three NiO6 octahedra. The corner-sharing octahedra tilt angles range from 55–60°. There are a spread of Si–O bond distances ranging from 1.63–1.67 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Ni2+ and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Ni2+ and one Si4+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Ni2+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba2Na(NiO2)3 by Materials Project

NaBa2Ni3O6 crystallizes in the orthorhombic Fmmm space group. The structure is three-dimensional. Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are four shorter (2.43 Å) and two longer (2.44 Å) Na–O bond lengths. There are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are four shorter (2.77 Å) and four longer (2.81 Å) Ba–O bond lengths. In the second Ba2+ site, Ba2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ba–O bond distances ranging from 2.86–3.11 Å. There are two inequivalent Ni+2.33+ sites. In the first Ni+2.33+ site, Ni+2.33+ is bonded in a square co-planar geometry to four O2- atoms. All Ni–O bond lengths are 1.89 Å. In the second Ni+2.33+ site, Ni+2.33+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Ni–O bond lengths are 1.85 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 6-coordinate geometry to one Na1+, three Ba2+, and two Ni+2.33+ atoms. In the second O2- site, O2- is bonded in a 6-coordinate geometry to one Na1+, three Ba2+, and two equivalent Ni+2.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(NiO2)2 by Materials Project

NiOCaONiO2 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of two nickel dihydroxide molecules and one NiOCaO sheet oriented in the (0, 1, -1) direction. In the NiOCaO sheet, Ca2+ is bonded in a 1-coordinate geometry to three O2- atoms. There are a spread of Ca–O bond distances ranging from 1.40–2.43 Å. There are two inequivalent Ni3+ sites. In the first Ni3+ site, Ni3+ is bonded in a linear geometry to two equivalent O2- atoms. Both Ni–O bond lengths are 1.41 Å. In the second Ni3+ site, Ni3+ is bonded in a distorted linear geometry to two equivalent O2- atoms. Both Ni–O bond lengths are 1.34 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Ca2+ and one Ni3+ atom. In the second O2- site, O2- is bonded in a distorted L-shaped geometry to one Ca2+ and one Ni3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al(NiO2)2 by Materials Project

Ni2AlO4 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Ni+2.50+ sites. In the first Ni+2.50+ site, Ni+2.50+ is bonded in a square co-planar geometry to four O2- atoms. There is two shorter (1.84 Å) and two longer (1.88 Å) Ni–O bond length. In the second Ni+2.50+ site, Ni+2.50+ is bonded in a square co-planar geometry to four O2- atoms. There is two shorter (1.84 Å) and two longer (1.88 Å) Ni–O bond length. Al3+ is bonded in a 4-coordinate geometry to four O2- atoms. All Al–O bond lengths are 1.89 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two Ni+2.50+ and one Al3+ atom. In the second O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two Ni+2.50+ and one Al3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na7(NiO2)10 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li3Cr(NiO2)4 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li3Ti(NiO2)4 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2025

Effects of stoichiometry and epitaxial strain on the stabilization of infinite-layer nickelates

The discovery of superconductivity in infinite-layer nickelates has sparked great interest due to their potential analogy with the unconventional cuprate superconductors. However, investigations of this system have been limited by the challenges in materials control and synthesis driven by substantial thermodynamic instability, making it difficult to reach an experimental consensus. Hence, establishing a robust synthetic route to highly crystalline infinite-layer nickelates is of paramount importance. Here, we present and discuss recent progress on the reproducible two-step synthesis of (Nd,Sr)NiO2 via the stabilization of high-quality perovskite nickelates and the subsequent topotactic transition to the infinite-layer phase. In particular, we discuss the important factors, such as cation stoichiometry and epitaxial strain, which significantly impact the crystallinity of both phases, accompanied by careful structural characterization. These results on robust synthesis can help accelerate the experimental investigation of the intrinsic physical properties of these complex strongly correlated materials.

36 MATERIALS SCIENCE↗
NASA NTRS1982

Thermodynamics of silicon nitridation - Effect of hydrogen

Equilibrium compositions for the nitridization of Si were calculated to detect the effectiveness of H2 in removal of the oxide film and in increasing the concentration of SiO and reducing the proportions of O2. Gibbs free energy for the formation of SiN2O was computed above 1685 K, and at lower temperatures. The thermodynamic properties of SiN2O2 were then considered from 1000-3000 K, taking into account the known thermodynamic data for 39 molecular combinations of the Si, Ni, and O. The gases formed were assumed ideal mixtures with pure phase condensed species. The mole fractions were obtained for a system of SiO2 with each Si particle covered with a thin layer of SiO2 before nitridation, and a system in which the nitriding atmosphere had access to the Si. The presence of H2 was determined to enhance the removal of NiO2 in the first system, decrease the partial pressure of O2, increase the partial pressures of SiO, Si, H2O, NH3, and SiH4, while its effects were negligible in the Si system.

Shaw, N. J.↗
NASA NTRS1989

Structural comparison of nickel electrodes and precursor phases

A summary of previous Raman spectroscopic results and a discussion of important structural differences in the various phases of active mass and active mass precurors are presented. Raman spectra provide unique signatures for these phases, and allow one to distinguish each phase, even when the compound is amorphous to X-rays (i.e., does not scatter X-rays because of a lack of order and/or small particle size). The structural changes incurred during formation, charge and discharge, cobalt addition, and aging will be discussed and related to electrode properties. Important structural differences include NiO2 layer stacking, nonstoichiometry (especially cation-deficit nonstoichiometry), disorder, dopant content, and water content. The results indicate that optimal nickel active mass is non-close packed and nonstoichiometric. The formation process transforms precursor phases into this structure. Therefore, the precursor disorder, or lack thereof, influences this final active mass structure and the rate of formation. Aging processes induce structural change which is believed to be detrimental. The role of cobalt addition can be appreciated in terms of structures favored or stabilized by the dopant. In recent work, the in situ Raman technique to characterize the critical structural parameters was developed. An in situ method relates structure, electrochemistry, and preparation. In situ Raman spectra of cells during charge and discharge, either during cyclic voltammetry or under constant current conditions were collected. With the structure-preparation knowledge and the in situ Raman tool, it will be possible to define the structure-property-preparation relations in more detail. This instrumentation has application to a variety of electrode systems.

Cornilsen, Bahne C.↗
NASA NTRS1993

Applications of x ray absorption fine structure to the in situ study of the effect of cobalt in nickel hydrous oxide electrodes for fuel cells and rechargeable batteries

Electronic and structural aspects of composite nickel-cobalt hydrous oxides have been examined in alkaline solutions using in situ X-ray absorption fine structure (XAFS). The results obtained have indicated that cobalt in this material is present as cobaltic ions regardless of the oxidation state of nickel in the lattice. Furthermore, careful analysis of the Co K-edge Extended X-ray absorption fine structure data reveals that the co-electrodeposition procedure generates a single phase, mixed metal hydrous oxide, in which cobaltic ions occupy nickel sites in the NiO2 sheet-like layers and not two intermixed phases each consisting of a single metal hydrous oxide.

Kim, Sunghyun↗