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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Orientation of acetic acid hydrogen bonded to acetate terminated TiO 2 (110)

Acetic acid is a common pollutant for which photocatalytic degradation over titania provides a mitigating strategy. Knowledge of the bonding of acetate/acetic acid to this substrate is needed to aid interpretation of the photocatalytic data. In this work we use ambient pressure near edge X-ray absorption fine structure to measure the coverage and geometry of acetate in the TiO 2 (110) contact layer as well as acetic acid in an additional layer. A saturation coverage of 0.5 monolayers in both layers is found up to an acetic acid pressure of 10 -1 Torr at 266 K. The geometry of acetate appears to be unchanged by adsorption of an additional layer of acetic acid, with the contact layer involving a majority acetate species bidentate bonded to neighboring Ti 5c sites and a minority acetate species bonded in a perpendicular geometry. Acetic acid has a similar geometry dictated by hydrogen bonding to the contact layer as well as the substrate.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on TiO by Materials Project

TiO crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent Ti2+ sites. In the first Ti2+ site, Ti2+ is bonded to five O2- atoms to form a mixture of corner and edge-sharing TiO5 square pyramids. There are a spread of Ti–O bond distances ranging from 2.00–2.15 Å. In the second Ti2+ site, Ti2+ is bonded to five O2- atoms to form a mixture of corner and edge-sharing TiO5 square pyramids. There are a spread of Ti–O bond distances ranging from 2.06–2.13 Å. In the third Ti2+ site, Ti2+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.06 Å) and two longer (2.12 Å) Ti–O bond lengths. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a square co-planar geometry to four Ti2+ atoms. In the second O2- site, O2- is bonded to five Ti2+ atoms to form a mixture of corner and edge-sharing OTi5 square pyramids. In the third O2- site, O2- is bonded to five Ti2+ atoms to form a mixture of corner and edge-sharing OTi5 square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiO by Materials Project

TiO is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ti2+ is bonded to six equivalent O2- atoms to form a mixture of edge and corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Ti–O bond lengths are 2.14 Å. O2- is bonded to six equivalent Ti2+ atoms to form a mixture of edge and corner-sharing OTi6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiOs by Materials Project

TiOs is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Ti2+ is bonded in a body-centered cubic geometry to eight equivalent Os2- atoms. All Ti–Os bond lengths are 2.68 Å. Os2- is bonded in a body-centered cubic geometry to eight equivalent Ti2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiO by Materials Project

TiO crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are twelve inequivalent Ti2+ sites. In the first Ti2+ site, Ti2+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with four TiO6 octahedra, corners with two equivalent TiO5 square pyramids, an edgeedge with one TiO6 octahedra, and edges with nine TiO5 square pyramids. The corner-sharing octahedra tilt angles range from 9–17°. There are a spread of Ti–O bond distances ranging from 2.06–2.17 Å. In the second Ti2+ site, Ti2+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two equivalent TiO6 octahedra, corners with four equivalent TiO5 square pyramids, edges with ten TiO6 octahedra, and edges with two equivalent TiO5 square pyramids. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.11 Å) and four longer (2.14 Å) Ti–O bond lengths. In the third Ti2+ site, Ti2+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two equivalent TiO6 octahedra, corners with four equivalent TiO5 square pyramids, edges with ten TiO6 octahedra, and edges with two equivalent TiO5 square pyramids. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.13 Å) and four longer (2.14 Å) Ti–O bond lengths. In the fourth Ti2+ site, Ti2+ is bonded to five O2- atoms to form TiO5 square pyramids that share corners with two equivalent TiO6 octahedra, corners with five TiO5 square pyramids, edges with seven TiO6 octahedra, and an edgeedge with one TiO5 square pyramid. The corner-sharing octahedra tilt angles range from 17–19°. There are a spread of Ti–O bond distances ranging from 2.10–2.17 Å. In the fifth Ti2+ site, Ti2+ is bonded to five O2- atoms to form TiO5 square pyramids that share corners with two equivalent TiO6 octahedra, corners with five TiO5 square pyramids, edges with seven TiO6 octahedra, and an edgeedge with one TiO5 square pyramid. The corner-sharing octahedra tilt angles range from 16–19°. There are a spread of Ti–O bond distances ranging from 2.09–2.18 Å. In the sixth Ti2+ site, Ti2+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with six TiO6 octahedra, edges with seven TiO6 octahedra, and edges with four TiO5 square pyramids. The corner-sharing octahedra tilt angles range from 0–17°. There are a spread of Ti–O bond distances ranging from 2.08–2.23 Å. In the seventh Ti2+ site, Ti2+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with four equivalent TiO6 octahedra, edges with eight TiO6 octahedra, and edges with four TiO5 square pyramids. The corner-sharing octahedra tilt angles range from 0–3°. There are a spread of Ti–O bond distances ranging from 2.10–2.18 Å. In the eighth Ti2+ site, Ti2+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.02 Å) and two longer (2.10 Å) Ti–O bond lengths. In the ninth Ti2+ site, Ti2+ is bonded to five O2- atoms to form TiO5 square pyramids that share corners with five TiO5 square pyramids, edges with two equivalent TiO6 octahedra, and edges with five TiO5 square pyramids. There are a spread of Ti–O bond distances ranging from 2.06–2.15 Å. In the tenth Ti2+ site, Ti2+ is bonded to five O2- atoms to form TiO5 square pyramids that share corners with five TiO5 square pyramids, edges with two equivalent TiO6 octahedra, and edges with five TiO5 square pyramids. There are a spread of Ti–O bond distances ranging from 2.13–2.18 Å. In the eleventh Ti2+ site, Ti2+ is bonded to five O2- atoms to form TiO5 square pyramids that share corners with two equivalent TiO6 octahedra, corners with five TiO5 square pyramids, and edges with five TiO5 square pyramids. The corner-sharing octahedral tilt angles are 9°. There are a spread of Ti–O bond distances ranging from 2.05–2.16 Å. In the twelfth Ti2+ site, Ti2+ is bonded to five O2- atoms to form TiO5 square pyramids that share corners with five TiO5 square pyramids, an edgeedge with one TiO6 octahedra, and edges with five TiO5 square pyramids. There are a spread of Ti–O bond distances ranging from 2.01–2.14 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded to six Ti2+ atoms to form OTi6 octahedra that share corners with six OTi6 octahedra, edges with seven OTi6 octahedra, and edges with four OTi5 square pyramids. The corner-sharing octahedra tilt angles range from 0–17°. In the second O2- site, O2- is bonded to six Ti2+ atoms to form OTi6 octahedra that share corners with four equivalent OTi6 octahedra, edges with eight OTi6 octahedra, and edges with four OTi5 square pyramids. The corner-sharing octahedra tilt angles range from 0–3°. In the third O2- site, O2- is bonded to six Ti2+ atoms to form OTi6 octahedra that share corners with four OTi6 octahedra, corners with two equivalent OTi5 square pyramids, an edgeedge with one OTi6 octahedra, and edges with nine OTi5 square pyramids. The corner-sharing octahedra tilt angles range from 9–17°. In the fourth O2- site, O2- is bonded to five Ti2+ atoms to form OTi5 square pyramids that share corners with two equivalent OTi6 octahedra, corners with five OTi5 square pyramids, edges with seven OTi6 octahedra, and an edgeedge with one OTi5 square pyramid. The corner-sharing octahedral tilt angles are 16°. In the fifth O2- site, O2- is bonded to five Ti2+ atoms to form OTi5 square pyramids that share corners with two equivalent OTi6 octahedra, corners with five OTi5 square pyramids, edges with seven OTi6 octahedra, and an edgeedge with one OTi5 square pyramid. The corner-sharing octahedra tilt angles range from 15–16°. In the sixth O2- site, O2- is bonded to six Ti2+ atoms to form OTi6 octahedra that share corners with two equivalent OTi6 octahedra, corners with four equivalent OTi5 square pyramids, edges with ten OTi6 octahedra, and edges with two equivalent OTi5 square pyramids. The corner-sharing octahedral tilt angles are 0°. In the seventh O2- site, O2- is bonded to six Ti2+ atoms to form OTi6 octahedra that share corners with two equivalent OTi6 octahedra, corners with four equivalent OTi5 square pyramids, edges with ten OTi6 octahedra, and edges with two equivalent OTi5 square pyramids. The corner-sharing octahedral tilt angles are 0°. In the eighth O2- site, O2- is bonded to five Ti2+ atoms to form OTi5 square pyramids that share corners with two equivalent OTi6 octahedra, corners with five OTi5 square pyramids, and edges with five OTi5 square pyramids. The corner-sharing octahedra tilt angles range from 9–13°. In the ninth O2- site, O2- is bonded to five Ti2+ atoms to form OTi5 square pyramids that share corners with five OTi5 square pyramids, an edgeedge with one OTi6 octahedra, and edges with five OTi5 square pyramids. In the tenth O2- site, O2- is bonded to five Ti2+ atoms to form OTi5 square pyramids that share corners with five OTi5 square pyramids, edges with two equivalent OTi6 octahedra, and edges with five OTi5 square pyramids. In the eleventh O2- site, O2- is bonded to five Ti2+ atoms to form OTi5 square pyramids that share corners with five OTi5 square pyramids, edges with two equivalent OTi6 octahedra, and edges with five OTi5 square pyramids. In the twelfth O2- site, O2- is bonded in a square co-planar geometry to four Ti2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiO by Materials Project

TiO is Tungsten Carbide-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ti2+ is bonded to six equivalent O2- atoms to form a mixture of distorted corner and edge-sharing TiO6 pentagonal pyramids. All Ti–O bond lengths are 2.16 Å. O2- is bonded to six equivalent Ti2+ atoms to form a mixture of corner, edge, and face-sharing OTi6 octahedra. The corner-sharing octahedral tilt angles are 45°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiO by Materials Project

TiO is Tungsten Carbide structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Ti2+ is bonded to six equivalent O2- atoms to form a mixture of distorted corner, edge, and face-sharing TiO6 pentagonal pyramids. All Ti–O bond lengths are 2.16 Å. O2- is bonded to six equivalent Ti2+ atoms to form a mixture of distorted corner, edge, and face-sharing OTi6 pentagonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiO by Materials Project

TiO crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Ti2+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Ti–O bond lengths are 2.04 Å. O2- is bonded in a square co-planar geometry to four equivalent Ti2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiO by Materials Project

TiO crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. there are two inequivalent Ti2+ sites. In the first Ti2+ site, Ti2+ is bonded to six equivalent O2- atoms to form a mixture of distorted edge, face, and corner-sharing TiO6 pentagonal pyramids. All Ti–O bond lengths are 2.11 Å. In the second Ti2+ site, Ti2+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All Ti–O bond lengths are 1.98 Å. O2- is bonded to five Ti2+ atoms to form a mixture of distorted edge and corner-sharing OTi5 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Strain‐Driven Mixed‐Phase Domain Architectures and Topological Transitions in Pb 1− x Sr x TiO 3 Thin Films

Abstract The potential for creating hierarchical domain structures, or mixtures of energetically degenerate phases with distinct patterns that can be modified continually, in ferroelectric thin films offers a pathway to control their mesoscale structure beyond lattice‐mismatch strain with a substrate. Here, it is demonstrated that varying the strontium content provides deterministic strain‐driven control of hierarchical domain structures in Pb 1− x Sr x TiO 3 solid‐solution thin films wherein two types, c / a and a 1 / a 2 , of nanodomains can coexist. Combining phase‐field simulations, epitaxial thin‐film growth, detailed structural, domain, and physical‐property characterization, it is observed that the system undergoes a gradual transformation (with increasing strontium content) from droplet‐like a 1 / a 2 domains in a c / a domain matrix, to a connected‐labyrinth geometry of c / a domains, to a disconnected labyrinth structure of the same, and, finally, to droplet‐like c / a domains in an a 1 / a 2 domain matrix. A relationship between the different mixed‐phase modulation patterns and its topological nature is established. Annealing the connected‐labyrinth structure leads to domain coarsening forming distinctive regions of parallel c / a and a 1 / a 2 domain stripes, offering additional design flexibility. Finally, it is found that the connected‐labyrinth domain patterns exhibit the highest dielectric permittivity.

Kavle, Pravin↗
DOE OSTI2024

Flux Synthesis of A-site Disordered Perovskite La 0.5 M 0.5 TiO 3 (M$=$Li, Na, K) Nanorods Tailored for Solid Composite Electrolytes

Inorganic fillers play an important role in improving the ionic conductivity of solid composite electrolytes (SCEs) for Li-ion batteries. Among inorganic fillers, perovskite-type lithium lanthanum titanate (LLTO) stands out for its high bulk Li + conductivity on the order of 10 -3 S cm -1 at room temperature. According to a literature survey, the optimal LLTO filler should possess the following characteristics: i) a single-crystal structure to minimize grain boundaries; ii) a small particle size to increase the filler/polymer interface area; iii) a 1D morphology for efficient interface channels; and iv) cubic symmetry to facilitate rapid bulk Li + diffusion within the filler. However, the synthesis of single crystal, 1D LLTO nanomaterials with cubic symmetry is challenging. Herein, a flux strategy is developed to synthesize La 0.5 M 0.5 TiO 3 (LMTO, M$=$Li, Na, and K) single-crystal nanorods with an A-site-disordered, cubic perovskite phase. The flux media promotes the oriented growth of nanorods, prevents nanorods from sintering, and provides multiple alkali metal ion doping at M sites to stabilize the cubic phase. SCEs compositing the Li + -conducting LMTO nanorods as fillers and poly[vinylene carbonate- co -lithium sulfonyl(trifluoromethane sulfonyl)imide methacrylate] matrix exhibit more than twice the conductivity of the neat polymer electrolyte (30.6 vs 14.0 µS cm -1 at 303 K).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

The Effect of Surface Terminations on the Initial Stages of TiO 2 Deposition on Functionalized Silicon

As atomic layer deposition (ALD) emerges as a method to fabricate architectures with atomic precision, emphasis is placed on understanding surface reactions and nucleation mechanisms. ALD of titanium dioxide with TiCl 4 and water has been used to investigate deposition processes in general, but the effect of surface termination on the initial TiO 2 nucleation lacks needed mechanistic insights. Here, this work examines the adsorption of TiCl 4 on Cl–, H–, and HO– terminated Si(100) and Si(111) surfaces to elucidate the general role of different surface structures and defect types in manipulating surface reactivity of growth and non-growth substrates. The surface sites and their role in the initial stages of deposition are examined by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Density functional theory (DFT) computations of the local functionalized silicon surfaces suggest oxygen-containing defects are primary drivers of selectivity loss on these surfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Partial oxidation of isobutylene using Ni TiO x

In this work, we report an aerobic partical oxidation of isobutylene into isoprene, acetone, and p-xylene using a mesoporous Ni TiO x catalytic material. In this work, two catalysts were found to synthesize two of these three valuable products with high selectivity, with p-xylene being synthesized with a selectivity of 46.0% and isoprene being synthesized with a selectivity of 64.7%, with overall conversions of isobutylene being 34.0% and 11.9% respectively. These reactions were done at relatively low temperatures. (300°C or below) and are conducted at flow rates of 10 sccm oxygen and isobutylene. The nickel titania catalysts were studied extensively using various characterization methodologies such as TEM, Raman, XRD, and XRF.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

TiO x -supported Na-Mn-W oxides for the oxidative coupling of methane

Supported Na-Mn-W oxides are among the most studied catalysts for the oxidative coupling of methane (OCM) because of their superior thermal stability and relatively high C 2+ product yields. However, because of the structural complexity, the roles of each component in these catalysts have been controversial. In this work, WO x and MnO x sites were supported on titanate nanowires and employed in OCM studies. Compared to the commonly studied silica support, which is subject to severe restructuring due to the Na-induced crystallization, titanate support not only serves as a reservoir for alkali metals (e.g., Na), but also stabilizes isolated MnO x species. The catalytic performance of the titanate-based catalyst is similar to that of reference catalyst, MnO x /Na 2 WO 4 /SiO 2 , with a synergistic effect between MnO x and WO x sites. Further, advanced electron microscopy, X-ray diffraction, infrared spectroscopy, and X-ray absorption near edge structure spectroscopy suggest that the basic NaO x and MnO x species have strong interactions with the acidic WO x and TiO x species, which might contribute to the high selectivity toward C 2+ products and suppressed CO x formation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Influence of TiO 2 on the densification behaviour of Yb 2 O 3

The effect of temperature and heating rate on the densification of ytterbia (Yb 2 O 3 ), with and without titania (TiO 2 ) doping was investigated. It is shown that up to a certain doping level, titania doping enhances the densification behaviour of ytterbia. The effect of titania doping on crystal structure confirms that titania is substitutionally incorporated in ytterbia up to the solubility limit, which corresponds well with the densification results. The increased densification rate of titania-doped ytterbia is attributed to the formation of cation vacancy and lattice distortion. Using constant heating rate experiments, the activation energy for densification has been calculated and it is shown that in the intermediate density range (60% to 85%), the activation energy is independent of the density. Furthermore, titania doping increases the activation energy for densification.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2021

The local structure of 0.5Ba(Zr 0.2 Ti 0.8 )O 3 -0.5(Ba 0.7 Ca 0.3 )TiO 3 from neutron total scattering measurements and multi-edge X-ray absorption analysis

Neutron total scattering measurements and multi-edge X-ray absorption analysis were performed on a 0.5Ba(Zr 0.2 Ti 0.8 )O 3 -0.5(Ba 0.7 Ca 0.3 )TiO 3 powder sample. The TiIII-II edges showed that titanium is distorted in the rhombohedral [111] direction (in a BaTiO 3 -like chemical and bonding environment). Extended X-ray fine structure analysis (EXAFS) was performed on the zirconium K-edge and it was found that zirconium resides in the center of the ZrO 6 octahedra in cubic symmetry. Furthermore, the local structure was initially modelled with the orthorhombic Amm2 space group with unsatisfactory results. To better model the local structure, the results from the EXAFS analysis were incorporated into the small-box pair distribution function (PDF) refinements and the best fit of the observed data was a combination of barium calcium titanate (BCT) and barium calcium zirconate (BCZ) phases.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Adsorption, charge transfer and a coverage-driven transition of alkali metals on rutile TiO 2 (110)

The interaction of alkali metals with metal oxide surfaces is central to tuning surface reactivity in heterogeneous catalysis and photocatalysis. Here we present a comprehensive DFT+U study of the adsorption of alkali metals (Li, Na, K, Rb, Cs) on the (110) surface of rutile TiO 2 . At low coverage (θ = 1/8), all alkali metals bind preferentially to bridging oxygen sites with adsorption energies in the range −4.06 to −3.33 eV, transferring nearly one full electron (0.92–0.99 |e|) to the substrate and inducing Ti 4+ → Ti 3+ reduction. The excess charge localizes preferentially at subsurface Ti sites in the form of small polarons. Diffusion barriers indicate facile motion along bridging-oxygen rows, whereas inter-row hopping is strongly hindered. Coverage effects were examined systematically for potassium: adsorption energy and charge transfer per K atom decrease monotonically with increasing θ. Strikingly, a sharp energy discontinuity occurs between θ = 4/8 and θ = 5/8 (ΔE ≈ 1 eV per atom), which we identify as a coverage-driven structural transition arising from steric packing constraints and enhanced K–K electrostatic repulsion once every (1×1) surface cell is occupied. This structural transition perfectly correlates with a dramatic drop in the work function down to an ultra-low minimum of 0.84 eV at θ=5/8, followed by a metallization- driven recovery at higher coverages. Ab initio molecular dynamics simulations confirm zigzag K arrangements at moderate coverage (θ = 1/3), while at high coverage (θ = 2/3) short-range K–K correlations emerge without long-range order. These results provide atomistic insight into the structure–activity relationships underlying alkali promotion effects on oxide-supported catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Site-Selective Atomic Layer Deposition at Thermally Generated Surface Oxygen Vacancies on Rutile TiO 2

Unique atomic arrangements (i.e., defects) on material surfaces may exhibit distinctive reactivity that affords opportunities for selective surface chemistry exclusively at those sites. While theoretically appealing, site-selective atomic layer deposition (ALD) processes remain largely unrealized experimentally. Here we provide evidence for site-selective ALD that exclusively targets oxygen vacancies thermally generated at the surface of TiO 2 single crystals. High-resolution in situ ellipsometry reveals the nucleation behavior of dimethylaluminum isopropoxide (DMAI) and water at process conditions precisely tuned for selective hydroxylation of surface defects. An island growth model for nucleation and atomic force microscopy (AFM) imaging are consistent with a site-selective growth mechanism that depends on the surface oxygen vacancy density. This approach to direct ALD reactions at defective surface sites may provide future opportunities for targeted remediation of electronically imperfect interfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗