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13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

In situ characterization of metastable Pb3O5 and Pb2O3 phases during thermal decomposition of PbO2 to PbO

Nonstoichiometric lead oxides play a key role in the formation and cycling of the positive electrodes in a lead acid battery. These phases have been linked to the underutilization of the positive active material but also play a key role in the battery’s cycle life, providing inter-particle adhesion and the connection to the underlying lead grid. Similar phases have previously been identified by mass loss or color change during thermal annealing of PbO2 to PbO, suggesting that at least two intermediate PbOx phases exist. Using multiple in situ analysis techniques (powder diffraction, x-ray absorption, x-ray photoelectron spectroscopy) and ex situ nuclear magnetic resonance measurements, the structural conversion and changes in the lead oxidation states were identified during this process. Isolation of the PbOx phases enabled confirmation of Pb3O5 and Pb2O3 by diffraction and the first 207Pb NMR measurement of these intermediates.

Kinnibrugh, Tiffany L.↗
DOE OSTI2020

Materials Data on PbO2 by Materials Project

PbO2 is Hydrophilite-like structured and crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. Pb4+ is bonded to six equivalent O2- atoms to form a mixture of edge and corner-sharing PbO6 octahedra. The corner-sharing octahedra tilt angles range from 54–55°. There are a spread of Pb–O bond distances ranging from 2.18–2.27 Å. O2- is bonded in a distorted trigonal planar geometry to three equivalent Pb4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PbO2 by Materials Project

PbO2 is Rutile structured and crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Pb4+ is bonded to six equivalent O2- atoms to form a mixture of edge and corner-sharing PbO6 octahedra. The corner-sharing octahedral tilt angles are 51°. All Pb–O bond lengths are 2.21 Å. O2- is bonded in a trigonal planar geometry to three equivalent Pb4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BH(PbO2)2 by Materials Project

BH(PbO2)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.37–1.41 Å. There are two inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a 3-coordinate geometry to three O2- atoms. There are one shorter (2.25 Å) and two longer (2.32 Å) Pb–O bond lengths. In the second Pb2+ site, Pb2+ is bonded in a 3-coordinate geometry to three O2- atoms. There are one shorter (2.28 Å) and two longer (2.34 Å) Pb–O bond lengths. H1+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.02 Å) and one longer (1.61 Å) H–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one B3+, one Pb2+, and one H1+ atom. In the second O2- site, O2- is bonded in a distorted water-like geometry to one B3+ and one H1+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one B3+ and one Pb2+ atom. In the fourth O2- site, O2- is bonded to four Pb2+ atoms to form edge-sharing OPb4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sn(PbO2)2 by Materials Project

Pb2SnO4 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are two inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a distorted rectangular see-saw-like geometry to four O2- atoms. There are a spread of Pb–O bond distances ranging from 2.24–2.86 Å. In the second Pb2+ site, Pb2+ is bonded in a distorted rectangular see-saw-like geometry to four O2- atoms. There are a spread of Pb–O bond distances ranging from 2.24–2.84 Å. Sn4+ is bonded to six O2- atoms to form edge-sharing SnO6 octahedra. There are two shorter (2.08 Å) and four longer (2.14 Å) Sn–O bond lengths. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Pb2+ and two equivalent Sn4+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Pb2+ and two equivalent Sn4+ atoms. In the third O2- site, O2- is bonded in a trigonal planar geometry to two Pb2+ and one Sn4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pt(PbO2)2 by Materials Project

Pb2PtO4 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. Pt4+ is bonded to six O2- atoms to form edge-sharing PtO6 octahedra. There are two shorter (2.04 Å) and four longer (2.07 Å) Pt–O bond lengths. There are two inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a 4-coordinate geometry to three O2- atoms. There are two shorter (2.24 Å) and one longer (2.37 Å) Pb–O bond lengths. In the second Pb2+ site, Pb2+ is bonded in a rectangular see-saw-like geometry to four O2- atoms. There are a spread of Pb–O bond distances ranging from 2.23–2.69 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Pt4+ and two equivalent Pb2+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two equivalent Pt4+ and one Pb2+ atom. In the third O2- site, O2- is bonded in a trigonal planar geometry to one Pt4+ and two Pb2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BiP(PbO2)4 by Materials Project

Pb4BiO4PO4 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one Pb4BiO4PO4 sheet oriented in the (0, 0, 1) direction. there are four inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Pb–O bond distances ranging from 2.28–3.06 Å. In the second Pb2+ site, Pb2+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Pb–O bond distances ranging from 2.26–2.97 Å. In the third Pb2+ site, Pb2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Pb–O bond distances ranging from 2.33–3.06 Å. In the fourth Pb2+ site, Pb2+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Pb–O bond distances ranging from 2.25–2.92 Å. Bi3+ is bonded in a distorted rectangular see-saw-like geometry to four O2- atoms. There are a spread of Bi–O bond distances ranging from 2.10–2.42 Å. P5+ is bonded in a tetrahedral geometry to four O2- atoms. There is two shorter (1.56 Å) and two longer (1.57 Å) P–O bond length. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to three Pb2+ and one P5+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one Bi3+ and one P5+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to four Pb2+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to four Pb2+ and one Bi3+ atom. In the fifth O2- site, O2- is bonded to four Pb2+ atoms to form a mixture of edge and corner-sharing OPb4 tetrahedra. In the sixth O2- site, O2- is bonded to four Pb2+ atoms to form a mixture of edge and corner-sharing OPb4 tetrahedra. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to one Bi3+ and one P5+ atom. In the eighth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two Pb2+ and one Bi3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Electrolyte-Induced Restructuring of Acid-Stable Oxygen Evolution Catalysts

Crystalline metal oxide catalysts operating under oxygen evolution reaction (OER) conditions invariably restructure, resulting in active sites with hydroxo/oxo species in an amorphous environment. An increase in the population of terminal hydroxo/oxo species (i.e., edge sites) facilitates proton-coupled electron-transfer (PCET) kinetics for oxygen generation and thus improves catalyst competency. While amorphous films benefit from a greater density of active sites, they suffer from diminished charge transport as compared to that of extended crystalline lattices. Managing this amorphous–crystalline dichotomy is essential when designing OER catalysts, which we highlight with the examination of electrodeposited PbO x materials, which historically are very poor OER catalysts. Along these lines, the presence of phosphate during PbO x electrodeposition truncates the growth of an extended lattice owing to its strong bonding to oxide surfaces to afford an amorphous catalyst film (A-PbO x ) with significant charge-transfer resistance (138 ± 42 Ω) and poor OER kinetics (420 ± 105 mV dec –1 Tafel slope). Conversely, electrodeposition of Pb 2+ in the presence of less coordinating electrolytes such as nitrate affords crystalline β-PbO2 with improved charge-transfer resistance (42.6 ± 1.1 Ω), though still poor OER kinetics (134 ± 36 mV dec –1 Tafel slope). By operating amorphous A-PbOx in less coordinating electrolytes, however, a new partially crystalline material can be generated (μc-PbO x ) with further reduced charge-transfer resistance (33.0 ± 1.4 Ω) and improved OER kinetics (70 ± 15 mV dec –1 Tafel slope). The enhanced OER activity of μc-PbO x is the result of coupling the high edge-site population of an amorphous PbOx phase with crystalline-like charge transport properties. Finally, the ability to use an electrolyte to induce OER activity in an inactive amorphous form of PbO x highlights the benefits of optimizing the amorphous–crystalline phase compositions in the design of active OER catalysts.

catalysts↗
NASA NTRS1973

LOX/GOX sensitivity of fluoroelastomers

The effect of formulation components and the addition of fire retardants on the impact sensitivity of Viton B fluoroelastomer in liquid oxygen was studied with the objective of developing a procedure for reliably reducing this sensitivity. Component evaluation, carried out on more than 40 combinations of components and cure cycles, showed that almost all the standard formulation agents, including carbon, MgO, Diak-3, and PbO2, will sensitize the Viton stock either singly or in combinations, some combinations being much more sensitive than others. Cure and postcure treatments usually reduced the sensitivity of a given formulation, often dramatically, but no formulated Viton was as insensitive as the pure Viton B stock. Coating formulated Viton with a thin layer of pure Viton gave some indication of reduced sensitivity, but additional tests are needed. It is concluded that sensitivity in formulated Viton arises from a variety of sources, some physical and some chemical in origin. Elemental analyses for all the formulated Vitons are reported as are the results of a literature search on the subject of LOX impact sensitivity.

Kirshen, N.↗
NASA NTRS1990

Effects of grain size and grain boundary on critical current density of high T(sub c) superconducting oxides

By means of adding impurity elements in high T sub c oxides, the effects were studied of grain size and grain boundary on the critical current density of the following systems: YBa2Cu3O(7-y) and Bi-Pr-Sr-Ca-Cu-O. In order to only change the microstructure instead of the superconductivity of the grains in the samples, the impurity elements were added into the systems in terms of the methods like this: (1) substituting Y with the lanthanide except Pr, Ce, and Tb in YBa2Cu3O(7-y) system to finning down grains in the samples, therefore, the effect can be investigated of the grain size on the critical current density of 1:2:3 compounds; (2) mixing the high T sub c oxides with the metal elements, such as Ag, according to the composition of (high T sub c oxide)1-xAgx to metallize the grain boundaries in the samples, studying the effect of the electric conductivity of the grain boundaries on the critical current density; (3) adding SiO2, PbO2, and SnO2 into the high T sub c oxide to form impurity phases in the grain boundaries, trying to find out the effects of the impurity phases or metalloid grain boundaries on the critical current density of the high T sub c superconductors. The experimental results indicate that in the case of of the presence of the metalloid grain boundaries finning down grains fails to enhance the j sub c, but restrains it strongly, the granular high T sub c superconductors with the small size grains coupled weakly is always the low j sub c system.

Zhao, Y.↗
NASA NTRS2019

Microstructural Characterization of TiO2-II in the Chicxulub Peak Ring

The peak ring of the approximately 180 kilometer-diameter Chicxulub impact crater on the Yucatan Peninsula, Mexico, was recently drilled during IODP-ICDP (International Ocean Discovery Program-International Continental Scientific Drilling Program) Expedition 364, producing core M0077A. The new core provides insights into the anatomy, composition, tectonic deformation, shock metamorphism, and post-impact overprint of crater-filling impactites and crystalline basement rocks. The basement rocks were shocked to approximately 12.5-17.5 gigapascals, uplifted, and hydrothermally altered. This study presents a combined Raman spectroscopic and electron backscatter diffraction (EBSD) study of TiO2-II, a high-pressure polymorph of TiO2 with an alpha-PbO2 structure (orthorhombic; space group Pbcn; density 4.34 grams per cubic centimeter, in shocked granitoid rock of the Chicxulub peak ring.

Schmieder, Martin↗
NASA NTRS2019

Outstanding Natural Occurrence of TiO2-II at the Chicxulub Crater - Anatomy of A Shock-Produced High-Pressure Polymorph

Scientific drilling of the end-Cretaceous, approximately 180 kilometers-diameter Chicxulub crater (Yucatan Peninsula, Mexico) during IODP–ICDP (Integrated Ocean Drilling Program - International Continental Scientific Drilling Program) Expedition 364 has provided new insights into the formation, shock metamorphism, structural evolution, and thermal history of peak rings in large complex impact craters. An outstanding feature in uplifted granitoid rocks of the Chicxulub peak ring is the preservation of TiO2-II, an orthorhombic high-pressure polymorph of TiO2 with an alpha-PbO2 structure, produced during the impact from rutile and/or anatase at shock pressures of approximately 12.5-17.5 gigapascals. Unlike other mostly micro- and cryptocrystalline occurrences of TiO2-II at terrestrial impact sites, ejecta deposits, and in rare ultra-high pressure metamorphic rocks, TiO2-II at Chicxulub occurs as abundant euhedral crystals greater than or equal to 70 microns in size within aggregates of altered magmatic titanite. This mode of occurrence provides an excellent opportunity to investigate the crystallography and transformation kinetics of the shock-produced high-pressure polymorph using scanning electron microscopic, micro-Raman, electron backscatter diffraction (EBSD), focused ion beam (FIB), as well as transmission-EBSD and transmission electron microscopic (TEM) techniques. Here we present refined microstructural and new crystallographic results for TiO2-II at the Chicxulub crater.

Schmieder, Martin↗