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13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Co(PO2)2 by Materials Project

Co(PO2)2 crystallizes in the orthorhombic Pmma space group. The structure is two-dimensional and consists of one Co(PO2)2 sheet oriented in the (0, 0, 1) direction. Co4+ is bonded to six O2- atoms to form edge-sharing CoO6 octahedra. There are two shorter (2.01 Å) and four longer (2.21 Å) Co–O bond lengths. There are two inequivalent P2+ sites. In the first P2+ site, P2+ is bonded in a bent 120 degrees geometry to two equivalent O2- atoms. Both P–O bond lengths are 1.53 Å. In the second P2+ site, P2+ is bonded in a water-like geometry to two equivalent O2- atoms. Both P–O bond lengths are 1.54 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Co4+ and one P2+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Co4+ and one P2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn(PO2)2 by Materials Project

Zn(PO2)2 crystallizes in the orthorhombic Pmma space group. The structure is two-dimensional and consists of one Zn(PO2)2 sheet oriented in the (0, 0, 1) direction. Zn2+ is bonded to six O2- atoms to form edge-sharing ZnO6 octahedra. There are two shorter (1.98 Å) and four longer (2.26 Å) Zn–O bond lengths. There are two inequivalent P3+ sites. In the first P3+ site, P3+ is bonded in a water-like geometry to two equivalent O2- atoms. Both P–O bond lengths are 1.54 Å. In the second P3+ site, P3+ is bonded in a bent 120 degrees geometry to two equivalent O2- atoms. Both P–O bond lengths are 1.53 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Zn2+ and one P3+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Zn2+ and one P3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co(PO2)2 by Materials Project

Co(PO2)2 crystallizes in the monoclinic P2/c space group. The structure is two-dimensional and consists of one Co(PO2)2 sheet oriented in the (0, 1, 0) direction. Co4+ is bonded to six O2- atoms to form edge-sharing CoO6 octahedra. There are a spread of Co–O bond distances ranging from 2.01–2.28 Å. There are two inequivalent P2+ sites. In the first P2+ site, P2+ is bonded in a bent 120 degrees geometry to two equivalent O2- atoms. Both P–O bond lengths are 1.53 Å. In the second P2+ site, P2+ is bonded in a water-like geometry to two equivalent O2- atoms. Both P–O bond lengths are 1.54 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Co4+ and one P2+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Co4+ and one P2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ge(PO2)3 by Materials Project

Ge(PO2)3 crystallizes in the trigonal R-3 space group. The structure is one-dimensional and consists of three Ge(PO2)3 ribbons oriented in the (0, 0, 1) direction. there are two inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded in an octahedral geometry to six equivalent O2- atoms. All Ge–O bond lengths are 2.33 Å. In the second Ge4+ site, Ge4+ is bonded in an octahedral geometry to six equivalent O2- atoms. All Ge–O bond lengths are 1.92 Å. P+2.67+ is bonded in a bent 120 degrees geometry to two O2- atoms. There is one shorter (1.51 Å) and one longer (1.55 Å) P–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Ge4+ and one P+2.67+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Ge4+ and one P+2.67+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PO2 by Materials Project

PO2 crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of four tetraphosphorus octoxide molecules. there are two inequivalent P4+ sites. In the first P4+ site, P4+ is bonded to four O2- atoms to form corner-sharing PO4 tetrahedra. There are a spread of P–O bond distances ranging from 1.46–1.63 Å. In the second P4+ site, P4+ is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. There is one shorter (1.65 Å) and two longer (1.70 Å) P–O bond length. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent P4+ atoms. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to two P4+ atoms. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to two P4+ atoms. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent P4+ atoms. In the fifth O2- site, O2- is bonded in a single-bond geometry to one P4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PO2 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 OSTI2023

High pO2 Flux Growth and Characterization of NdNiO3 Crystals

Single crystals of the perovskite nickelate NdNiO3 with dimensions of up to 50 μm on edge have been successfully grown using the flux method at a temperature of 400 °C and oxygen pressure of 200 bar. The crystals were investigated by a combination of techniques, including high-resolution synchrotron X-ray single-crystal and powder diffraction and physical property measurements such as magnetic susceptibility and resistivity. Resistivity measurements revealed a metal-insulator transition (MIT) at TMIT~180 K with apparent thermal hysteresis; however, no superlattice peaks or peak splitting below TMIT, which corresponds to a structural transition from Pbnm to P21/n, was observed. The successful growth of NdNiO3 crystals at relatively low temperatures and oxygen pressure provides an alternative approach for preparing single crystals of interesting perovskites such as RNiO3 (R = Sm-Lu) and parent phases of superconducting square planar nickelates.

Wang, Xiaoli↗
DOE OSTI2022

Sorbent-based oxygen separation with YBC114 for energy storage systems

In our report we aimed to design, build, and evaluate an oxygen separation system to provide an inert sweep gas with low oxygen partial pressure (pO2) to redox-active thermochemical energy conversion reactors for a range of applications, including two-step redox cycles for thermochemical energy storage, water splitting, and carbon-dioxide splitting. The separation is based on an oxygen-selective sorbent, YBaCo4O7+δ (YBC114), which has excellent oxygen sorption and desorption properties demonstrated in our previous work. The oxygen separation performance of YBC114 was comprehensively studied by thermogravimetric analysis, sorption breakthrough experiments, and temperature swing sorption - desorption cycles. The results reveal that YBC114 can produce inert sweep gas with an oxygen concentration of less than 100 ppmv for at least 20 min during the thermal swing adsorption (TSA) cycle with the current sorption bed configuration, and the performance is consistent from cycle to cycle. The optimal sorption and desorption temperatures for the TSA process with YBC114 are determined to be 300 °C and 500 °C, respectively. Although challenges remain for the current separation system (e.g., high sorption temperature and slow kinetics), this study demonstrates the potential to use the oxygen-selective sorbent to produce an inert sweep gas, the feasibility of the oxygen separation concept, and guides new sorbent material development to make this application economically practical. A simple procedure is described for designing the YBC114 oxygen separation process.

42 ENGINEERING↗
DOE OSTI2021

Calibration of the Diffusivity Predictions of Centipede Using Approximate Bayesian Computation and Applications in Nyx (Engineering Scale) and Xolotl-MARMOT (Meso-Scale) Simulations

Fission gas evolution and release in UO 2 nuclear fuel are important fuel performance metrics and occur in several distinct stages: 1) nucleation, growth and resolution of intra-granular bubbles, 2) diffusion to grain boundaries and 3) nucleation and growth of bubbles at grain boundaries, which eventually form a connected network (percolation) enabling release of gas from grain boundaries through connections to triple junctions, grain edges or free surfaces. The NE-SciDAC project is developing several computational tools to model this problem, which are connected in a hierarchical multi-scale framework. The information transfer in the multi-scale framework is a critical step that, in addition to best-estimates, should include uncertainty quantification. Despite taking a first-principles multi-scale approach, there is a need to perform parameter calibration to ensure consistency with available experimental data. In the present study, uncertainty quantification (UQ) and parameter calibration is demonstrated for one of the lower length scale codes in the multi-scale framework (Centipede) and then the results, including instances of the propagated uncertainties, are used in other codes within the framework, specifically Nyx and Xolotl-MARMOT. We calibrated the model parameters in Centipede, a computer code used to predict diffusivities of uranium (U) and xenon (Xe) in the context of the simulation of fission gas in uranium oxide (UO 2 ) nuclear fuel. The Centipede code depends on 183 parameters, all of which are subject to uncertainty. The three data sets used in our calibration effort are taken from the literature. This data is available as a set of measurements, including measurement errors. Our goal is to calibrate a statistical model that predicts both the value of the measurement and the uncertainty associated with the measurement. We perform a Bayesian calibration of the model parameters using a dedicated approximate Bayesian computation (ABC) likelihood function. To avoid excessive computational costs, we replace the expensive Centipede simulation code by a higher-order surrogate model, constructed using only the 9 most important parameters. These important parameters are identified by a preliminary global sensitivity analysis (GSA) study. Among the important parameters are T0 (the temperature at which UO 2 is perfectly stoichiometric) and Hf_pO2 (the temperature dependence of the oxygen (O) partial pressure) that should be considered as operating conditions to be estimated along with the other parameters. We consider two different cases: one where we define one set of these operating conditions for all data sets, and one where we define distinct operating condition parameters for each data set. The Xe diffusivities predicted by the latter case show distinct features that could not be observed in the former. Next, we use the diffusivity predictions by Centipede as input to Nyx, a reduced order fuel performance code focused on gas behavior alone, in order to estimate quantities associated with inter-granular bubble formation at conditions specified by the experiments. Finally, the diffusivities obtained from the calibrated Centipede runs were used in coupled Xolotl-MARMOT simulations of intra- and inter-granular gas evolution. The results are compared to simulations using the baseline diffusivities from Turnbull et al.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

SPUTTERED THIN FILMS FOR VERY HIGH POWER, EFFICIENT, AND LOW-COST COMMERCIAL SOFCS

The aim of this project was to leverage the low area specific resistance (ASR) of Redox’s GDC electrolyte-based cell architecture and increase solid oxide fuel cell (SOFC) efficiency (i.e., open circuit voltage, or OCV) without significantly increasing cell resistance. The key to achieving the increased SOFC efficiency is the introduction of a thin sputtered yttria stabilized zirconia (YSZ) electron-blocking layer and a thin sputtered gadolinia doped ceria (GDC) barrier layer on top of the half-cell substrate (i.e., anode and GDC electrolyte). A key initial effort of the project was to improve the quality of the half-cell substrate surface so that any remaining defects were significantly smaller than the desired film thickness. During lab-scale trials, we had to overcome challenges with film cracking during post-sputtering treatments (e.g., thermal anneals) as well as damage to the sputtering targets. After the initial lab-scale trials, the focus shifted toward the use of commercial scale sputtering equipment with a sputtering equipment manufacturer in the microelectronics industry. Using the commercial sputtering equipment, we deposited films with different variations of power, PO2, sputtering time, platen speed, etc. We then determined the combinations of sputtering conditions and post-sputtering treatments that yielded high-quality films without cracks or other significant defects. While thin films were deposited on cells as large as 10 cm by 10 cm, the processing was optimized using 4 cm by 4 cm cells. Cell performance was evaluated in stainless-steel test fixtures between 500 °C and 700 °C with hydrogen fuel fed to the anode and air fed to the cathode. Extensive studies allowed us to determine that modified cathode and cathode contact firing processes were required to achieve theoretical OCV. Moreover, use of the new firing processes resulted in the need for a modified cathode contact to achieve a low ASR. In summary, the project demonstrated the performance of high OCV (1.13 V at 650 °C) from sputtered layers and a low ASR (~0.25 Ohms-cm2 at 650 °C) resulting from a modification of cathode/contact processing and the introduction of alternative contact layers that are sufficient to yield a Gen-1 cell with a maximum power density of approximately 1.2 W/cm2. At an operating voltage of 0.74 V, this would yield a cell power density of ~1.1 W/cm2. While not utilized in this project, a Redox Gen-2 cell has a catalyst-infiltrated porous anode that reduces the ASR by more than 50% from that of the Gen-1 cells used in this project. Therefore, if the sputtered YSZ electron-blocking layer and GDC barrier layer are added to a Gen-2 half cell with a similar increase in OCV to the theoretical value of ~1.13 V at 650 °C, and if the same improvement in ASR (from that demonstrated in this project) is achieved when using the Gen-2 half-cell architecture as a sputtered cell substrate, then the power density at 0.74 Vop could be as high as ~2.6 W/cm2. The impact of such power density gains, while still maintaining high cell efficiency, and thus high system efficiency, is a dramatic decrease in system cost because the stack represents ~30-40% of the SOFC system cost.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2020

Evaluation of Doped-LaCrO3 ceramics for high temperature sensor applications

The main objective of this work was to investigate the applicability of the doped-LaCrO3 system for electrical interconnects and sensor applications at temperatures >800°C. Various A- and B-site doping strategies were investigated, and the effect on their electrical conductivity, Seebeck coefficient, and thermal coefficient of expansion were characterized up to 1500ºC. Solid-state, co-precipitation and sol gel methods were used to synthesize the compositions, and the chemical/thermal stability, microstructural evolution, sintering and grain growth kinetics were investigated for these compositions by XRD, SEM and Rietveld methods. The materials showing the greatest promise were included within thick film thermistor and thermocouple sensor designs that were tested to 1500ºC in various gas environments (various pO2 concentrations).

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2020

A Thermodynamic Investigation of Ni on Thin-Film Titanates (ATiO3)

Thin, ~1-nm films of CaTiO3, SrTiO3, and BaTiO3 were deposited onto MgAl2O4 by Atomic Layer Deposition (ALD) and then studied as catalyst supports for ~5 wt % of Ni that was added to the perovskite thin films by Atomic Layer Deposition. Scanning Transmission Electron Microscopy demonstrated that both the Ni and the perovskites uniformly covered the surface of the support following oxidation at 1073 K, even after redox cycling, but large Ni particles formed following a reduction at 1073 K. When compared to Ni/MgAl2O4, the perovskite-containing catalysts required significantly higher temperatures for Ni reduction. Equilibrium constants for Ni oxidation, as determined from Coulometric Titration, indicated that the oxidation of Ni shifted to lower PO2 on the perovskite-containing materials. Based on Ni equilibrium constants, Ni interactions are strongest with CaTiO3, followed by SrTiO3 and BaTiO3. The shift in the equilibrium constant was shown to cause reversible deactivation of the Ni/CaTiO3/MgAl2O4 catalyst for CO2 reforming of CH4 at high CO2 pressures, due to the oxidation of the Ni.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗