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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Direct observation of oxygen vacancy ordering evolution in cerium oxide at varying concentrations via high-resolution transmission electron microscopy

Under illumination by a 300 keV electron beam, oxygen vacancy ordering structures are induced within cerium oxide grains. Here, our high-resolution transmission electron microscopy (HRTEM) study, supported by image simulation, reveals the evolution of these structures as vacancy concentration increases. The observed fluorite-type superlattice structures are identified as CeO 1.825 , CeO 1.75 , Ce 2 O 3 , displaying a gradient in oxygen vacancy concentration moving away from the grain surface. Correspondingly, the structural sequence transitions from Ce 2 O 3 to CeO 1.75 and then to CeO 1.825 . Without the constraints of surrounding grains, fluorite-type Ce 2 O 3 nanocrystals show a preference for transformation into an A-type trigonal structure. Notably, at temperatures up to 200°C, only the perfect fluorite structure is observed. Structural models were validated through both [110] and [001] projections. Our findings further confirm lattice expansion associated with local oxygen vacancy enrichment, which can be compensated by the formation of stacking faults, where a {111} oxygen plane is lost at defect sites.

Cerium oxide↗
DOE OSTI2023

Tuning the Interaction between Platinum Single Atoms and Ceria by Zirconia Doping for Efficient Catalytic Ammonia Oxidation

Aiming at the development of an efficient NH 3 oxidation catalyst to eliminate the harmful NH 3 slip from the stationary flue gas denitrification system and diesel exhaust aftertreatment system, a facile ZrO 2 doping strategy was proposed to construct Pt 1 /Ce x Zr 1–x O 2 catalysts with a tunable Pt-CeO 2 interaction strength and Pt–O–Ce coordination environment. According to the results of systematic characterizations, Pt species supported on Ce x Zr 1–x O 2 were mainly in the form of single atoms when x ≥ 0.7, and the strength of the Pt-CeO 2 interaction and the coordination number of Pt–O–Ce bond (CN Pt–O–Ce ) on Pt 1 /Ce x Zr 1–x O 2 showed a volcanic change as a function of the ZrO 2 doping amount. Here, it was proposed that the balance between the reasonable concentration of oxygen defects and limited surface Zr–O x species well accounted for the strongest Pt-CeO 2 interaction and the highest CN Pt–O–Ce on Pt/Ce 0.9 Zr 0.1 O 2 . It was observed that the Pt/Ce 0.9 Zr 0.1 O 2 catalyst exhibited much higher NH 3 oxidation activity than other Pt/Ce x Zr 1–x O 2 catalysts. The mechanism study revealed that the Pt 1 species with the stronger Pt-CeO 2 interaction and higher CN Pt–O–Ce within Pt/Ce 0.9 Zr 0.1 O 2 could better activate NH 3 adsorbed on Lewis acid sites to react with O 2 thus resulting in superior NH 3 oxidation activity. This work provides a new approach for designing highly efficient Pt/CeO 2 based catalysts for low-temperature NH 3 oxidation.

36 MATERIALS SCIENCE↗
DOE OSTI2026

One Beam, Dual Insights: Simultaneous Chemical and Structural Changes in Nanopatterned Ceria under Reaction Conditions

Ceria’s interaction with hydrogen can proceed through multiple chemical forms (hydride, hydroxyl, and oxyhydroxide-like), with consequences for the oxidation state, density, and morphology that are rarely tracked in the same evolving state. Here, in this work, we show that under mild H 2 (and H 2 and CO 2 ) environments nanopatterned ceria undergoes oxidation-state changes accompanied by hydrogen incorporation that increases the effective electron density, establishing the following order: CeO 2 Hy > CeO 2 > CeO 2–x Hy > CeO 2–x . In parallel, the surface roughens in a chemically specific manner, with the largest changes coinciding with conditions where incorporated hydrogen is driven to react with oxygen supplied either by air exposure between experiments or by added CO 2 . We obtained these insights by using a single X-ray beam to simultaneously perform ambient-pressure X-ray photoelectron spectroscopy and grazing-incidence X-ray scattering on the same sample spot. Single-mode measurements can miss key ceria–H 2 transformations relevant to optimizing ceria-based hydrogenation catalysts and supports.

anions↗
DOE OSTI2020

Elucidation of the Active Sites in Single-Atom Pd 1 /CeO 2 Catalysts for Low-Temperature CO Oxidation

Supported precious metals with atomic dispersion are of great interest in catalysis due to their potentials in achieving maximum atom efficiency and unique reactivities. Herein, the active sites for low-temperature CO oxidation are elucidated over single-atom Pd 1 /CeO 2 catalysts prepared via high-temperature atom trapping (AT). The increased oxygen vacancies on CeO 2 surface induced by 800 °C air calcination result in decreased Pd–CeO 2 coordinations, i.e., the coordination-unsaturated Pd 2+ on CeO 2 . Light-off and light-out measurements coupled with CO-DRIFTS and X-ray absorption characterization confirm that these coordination-unsaturated Pd 2+ on CeO 2 are much more reactive than the fully coordinated counterpart, evidenced by a decrease of T 90 (temperature to achieve 90% conversion) by ~100 °C in CO oxidation at a gas hourly space velocity of 300 L g –1 h –1 .

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

Fine-tuned local coordination environment of Pt single atoms on ceria controls catalytic reactivity

Constructing single atom catalysts with fine-tuned coordination environments can be a promising strategy to achieve satisfactory catalytic performance. Herein, via a simple calcination temperature-control strategy, CeO 2 supported Pt single atom catalysts with precisely controlled coordination environments are successfully fabricated. The joint experimental and theoretical analysis reveals that the Pt single atoms on Pt 1 /CeO 2 prepared at 550 °C (Pt/CeO 2 -550) are mainly located at the edge sites of CeO 2 with a Pt–O coordination number of ca. 5, while those prepared at 800 °C (Pt/CeO 2 -800) are predominantly located at distorted Ce substitution sites on CeO 2 terrace with a Pt–O coordination number of ca. 4. Pt/CeO 2 -550 and Pt/CeO 2 -800 with different Pt 1 -CeO 2 coordination environments exhibit a reversal of activity trend in CO oxidation and NH 3 oxidation due to their different privileges in reactants activation and H 2 O desorption, suggesting that the catalytic performance of Pt single atom catalysts in different target reactions can be maximized by optimizing their local coordination structures.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Single-atom Zr promoter boosts oxygen activation on ceria-supported Pt catalysts

Activation of surface lattice oxygen and chemisorbed oxygen on catalyst surfaces constitutes a pivotal step in heterogeneous oxidative catalysis. Herein, we report a strategy for enhancing oxygen activation by rational design of catalysts with single-atom promoters. Single-site Zr species in CeO 2 (Zr 1 -CeO 2 ) are synthesized using the atom-trapping method. The Zr 1 -CeO 2 -supported Pt catalyst exhibits enhanced catalytic performance over the CeO 2 -supported Pt catalyst in the oxidation of CO, C 3 H 8 , and C 3 H 6 , achieving significantly lower T 50 values (temperature required to reach 50% conversion). This enhanced catalytic activity is attributed to the formation of an asymmetric Zr 1 -O-Pt 1 structure, which favors the activation of the adjacent surface lattice oxygen and chemisorbed molecular oxygen. This work exemplifies that incorporating single-site atoms into oxide support facilitates oxygen activation, providing new insights into the role of atomically dispersed promoters in heterogeneous catalysis.

Science & Technology - Other Topics↗
DOE OSTI2024

Spatiotemporal characterization of cerium monoxide in laser ablation plasmas using spectrally-resolved fast-gated imaging

The impact of oxidation chemistry on the emission characteristics and spatial structure of laser-produced Ce metal plasmas was investigated using laser-induced breakdown spectroscopy (LIBS) and time-resolved fast-gated imaging employing narrowband optical filters. Images of the plasma emission show that CeO coexists with atomic species in the periphery and vortex ring of the plasma plume. Image processing was also applied to combine independent monochromatic images of the plasma emission into a single merged image, culminating in a timelapse on the spatiotemporal evolution of atomic and molecular species within the plasma plume. The formation of CeO species was observed to proceed faster for plasmas generated in atmospheres containing larger concentrations of oxygen based on ratios of CeO-to-atomic emission intensities. Furthermore, these same ratios were shown to plateau and decrease at later times (≥25 μs), potentially indicating the depletion of CeO number densities in the plasma as the monoxide undergoes reactions to form higher polyatomic oxides. Altogether, these results provide fundamental insights into the chemical dynamics and intermixing between plasma-gas species in laser ablation cerium plasmas, advancing our understanding on optical signatures of nuclear-relevant materials to enable in-field measurement capabilities.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Response of ZrC to swift heavy ion irradiation

Zirconium carbide (ZrC) is commonly used for energy sector research, as well as a surrogate for the proposed advanced nuclear fuel candidate uranium carbide. Here this study investigates structural modifications to nanocrystalline and microcrystalline ZrC resulting from dense electronic excitations induced by swift heavy ion exposure. Samples were irradiated with 946 MeV Au ions to various fluences up to 6 × 10 13 ions cm –2 and characterized using synchrotron-based x-ray diffraction. The evolution of the unit-cell parameter and heterogeneous microstrain were evaluated as a function of fluence and compared with those of nanocrystalline and microcrystalline CeO 2 (a surrogate for UO 2 fuel) irradiated under identical conditions. Distinct differences were observed in the radiation responses of the carbide and oxide across both grain sizes. Most notably, microcrystalline ZrC exhibits swelling characterized by two distinct regimes, which does not result in saturation at the ion fluences achieved. This contrasts with CeO 2 , which exhibits the well-documented direct-impact defect accumulation mechanism, reaching a steady-state saturation of swelling at higher fluences. Nanocrystalline CeO 2 undergoes more pronounced swelling compared with microcrystalline CeO 2 , in contrast to nanocrystalline ZrC, which exhibits only minimal unit-cell changes. These results demonstrate that swift heavy ion-induced structural changes can be quite different in carbides and oxides, which must be considered when extrapolating fission-fragment type damage in current fuels to advanced fuels.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Implementing an aerosol dynamic shape factor for cerium oxide powder

The shape factor (X B ) of bulk powder CeO 2 (cerium oxide) particles is estimated to be X B = 1.34 (dimensionless). This is defined in relation to the measured aerated bulk density (0.91 g cm -3 , Hosokawa Micron, Summit NJ, 2018) of the CeO 2 powder. This information is used to determine the RRF (respirable release factor), and other parameters during drop test experiments of nuclear material storage containers at Los Alamos National Laboratory. The calculation is based on an experimental shape factor (X P = 2.66 dimensionless) for CeO 2 particles of the same (chain aggregate) morphology studied by other researchers. In that work, the shape factor was defined in terms of the maximum possible (compacted) density of CeO 2 material (7.13 g cm -3 ).

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2024

Concentrated solar thermal fuels production by electric field enhanced two step gas splitting (Final Technical Report)

Solar thermochemical CO 2 splitting (STCS) is plagued by high solar field costs due to the extraordinarily high temperatures (~1500 °C) required. In STCS, a reduction/oxidation active material, CeO 2 , is thermally reduced to CeO 2-δ generating O2 at ~1500 °C; then CeO 2-δ is re-oxidized by CO 2 to re-form CeO 2 and CO, a precursor to liquid fuels. Before this project, there were no known methods to decrease the reduction temperature while maintaining high conversion of the CO 2 to CO; thus, projected solar thermal CO costs had stagnated.

10 SYNTHETIC FUELS↗
NASA NTRS2004

Overview of NASA's Earth Science Data Systems

For over the last 15 years, NASA's Earth Science Enterprise (ESE) has devoted a tremendous effort to design and build the Earth Observing System (EOS) Data and Information System (EOSDIS) to acquire, process, archive and distribute the data of the EOS series of satellites and other ESE missions and field programs. The development of EOSDIS began with an early prototype to support NASA data from heritage missions and progressed through a formal development process to today's system that supports the data from multiple missions including Landsat 7, Terra, Aqua, SORCE and ICESat. The system is deployed at multiple Distributed Active Archive Centers (DAACs) and its current holdings are approximately 4.5 petabytes. The current set of unique users requesting EOS data and information products exceeds 2 million. While EOSDIS has been the centerpiece of NASA's Earth Science Data Systems, other initiatives have augmented the services of EOSDIS and have impacted its evolution and the future directions of data systems within the ESE. ESDIS had an active prototyping effort and has continued to be involved in the activities of the Earth Science Technology Office (ESTO). In response to concerns from the science community that EOSDIS was too large and monolithic, the ESE initiated the Earth Science Information Partners (ESP) Federation Experiment that funded a series of projects to develop specialized products and services to support Earth science research and applications. Last year, the enterprise made 41 awards to successful proposals to the Research, Education and Applications Solutions Network (REASON) Cooperative Agreement Notice to continue and extend the ESP activity. The ESE has also sponsored a formulation activity called the Strategy for the Evolution of ESE Data Systems (SEEDS) to develop approaches and decision support processes for the management of the collection of data system and service providers of the enterprise. Throughout the development of its earth science data systems, NASA has had an active collaboration with a number of interagency and international partners. One of the mechanisms that has been extremely helpful in initiating and promoting this collaboration has been NASA's participation in the Committee on Earth Observation Satellites (CEOS) and its Working Group on Information Systems and Services (WGISS). The CEOS members, working together, have implemented an International Directory Network that enables users to locate collections of earth science data held by the international community and an International Catalog System to search and order specific data products. CEOS WGISS has also promoted the international interest in the Open GIS Consortium s specifications that further advance the access and use of geospatial data and the interoperation of GTS components. These are just a few highlights of the benefits that member agencies gain from CEOS participation.

McDonald, Kenneth↗
NASA NTRS2006

Meeting Report: Long Term Monitoring of Global Vegetation using Moderate Resolution Satellites

The international community has long recognized the need to coordinate observations of Earth from space. In 1984, this situation provided the impetus for creating the Committee on Earth Observation Satellites (CEOS), an international coordinating mechanism charged with coordinating international civil spaceborne missions designed to observe and study planet Earth. Within CEOS, its Working Group on Calibration and Validation (WGCV) is tasked with coordinating satellite-based global observations of vegetation. Currently, several international organizations are focusing on the requirements for Earth observation from space to address key science questions and societal benefits related to our terrestrial environment. The Global Vegetation Workshop, sponsored by the WGCV and held in Missoula, Montana, 7-10 August, 2006, was organized to establish a framework to understand the inter-relationships among multiple, global vegetation products and identify opportunities for: 1) Increasing knowledge through combined products, 2) Realizing efficiency by avoiding redundancy, and 3) Developing near- and long-term plans to avoid gaps in our understanding of critical global vegetation information. The Global Vegetation Workshop brought together 135 researchers from 25 states and 14 countries to advance these themes and formulate recommendations for CEOS members and the Global Earth Observation System of Systems (GEOSS). The eighteen oral presentations and most of the 74 posters presented at the meeting can be downloaded from the meeting website (www.ntsg.umt.edu/VEGMTG/). Meeting attendees were given a copy of the July 2006 IEEE Transactions on Geoscience and Remote Sensing Special Issue on Global Land Product Validation, coordinated by the CEOS Working Group on Calibration and Validation (WGCV). This issue contains 29 articles focusing on validation products from several of the sensors discussed during the workshop.

Morisette, Jeffrey↗
NASA NTRS2007

The CEOS/GEO Constellation Concept

The Constellation concept was first proposed during a discussion at the 19th CEOS Plenary, in London, in November 2005. The first Paper of the Constellation Concept was presented at the CEOS Strategic Implementation Team meeting (SIT-18), in Frascati, in March 2006, and strongly endorsed by the CEOS Principals. The concept attempts to provide agencies with tools for implementation of the elements that have been previously discussed in international forums (GEO Work Plan, GCOS Implementation Plan). This provides a solid foundation from the community providing requirements. Though agency spending is governed by national requirements, CEOS seeks synergies among member agency programs to fulfil GEOSS requirements, defining guidelines and standards to help agencies to determine from the outset what can be achieved. The constellations concept will allow the development of a commonalties approach among different agencies. At the heart of the application of the Constellations concept is the definition of a series of standards (specific to each Constellation) - required to be satisfied for any mission to be included in the constellation - and a process of recognition/acceptance, whereby an agency applies to SIT to have one or more of its missions (ideally from the outset of planning) recognised as meeting the constellation standards and thereby satisfying the relevant user community needs.

Cramer, Bryant↗
NASA NTRS2012

Expedition Earth and Beyond: Using Crew Earth Observation Imagery from the International Space Station to Facilitate Student-Led Authentic Research

Student-led authentic research in the classroom helps motivate students in science, technology, engineering, and mathematics (STEM) related subjects. Classrooms benefit from activities that provide rigor, relevance, and a connection to the real world. Those real world connections are enhanced when they involve meaningful connections with NASA resources and scientists. Using the unique platform of the International Space Station (ISS) and Crew Earth Observation (CEO) imagery, the Expedition Earth and Beyond (EEAB) program provides an exciting way to enable classrooms in grades 5-12 to be active participants in NASA exploration, discovery, and the process of science. EEAB was created by the Astromaterials Research and Exploration Science (ARES) Education Program, at the NASA Johnson Space Center. This Earth and planetary science education program has created a framework enabling students to conduct authentic research about Earth and/or planetary comparisons using the captivating CEO images being taken by astronauts onboard the ISS. The CEO payload has been a science payload onboard the ISS since November 2000. ISS crews are trained in scientific observation of geological, oceanographic, environmental, and meteorological phenomena. Scientists on the ground select and periodically update a series of areas to be photographed as part of the CEO science payload.

Graff, P. V.↗
NASA NTRSDate not supplied

TPSAS-NF1676L-12770-DND

CEOS Action (Plenary 2010, Action 24-3): CEOS Chair to work with the SEO, outgoing and incoming CEO and GEO Secretariat to study possibilities for rationalisation of the multiplicity of portals provided by CEOS in support of GEO.

Brian Killough↗
NASA NTRSDate not supplied

National Aeronautics and Space Administration (NASA) Agency Report WGISS-51

The Committee on Earth Observation Satellites (CEOS) strives to enhance international coordination and data exchange and to optimize societal benefit. CEOS contributes to NASA’s core mission and is critical to NASA’s Earth Science program and to the future of Earth observations community as a whole because it advances mission planning, interagency coordination and technical implementation. Within NASA, the CEOS Working Group on Information System and Services (WGISS) is a forum for the Earth Sciences Data Systems (ESDS) Program to collaborate with other international and domestic agencies in the development of Earth observation data systems and services. NASA leads the development and demonstration of multiple prototypes supporting CEOS and Group on Earth Observations (GEO) requirements. NASA’s participation in WGISS influences NASA’s Earth Observing System Data and Information System’s (EOSDIS) ability to make high-quality data products available to the broad science community both nationally and internationally. Combined with NASA’s free and open data policy, EOSDIS’s involvement in WGISS is essential to widespread use of research satellite measurements. This presentation focuses on an overview and recent status of NASA’s EOSDIS.

Andrew Mitchell↗
NASA NTRSDate not supplied

NASA Agency Report WGISS 52

The Committee on Earth Observation Satellites (CEOS) strives to enhance international coordination and data exchange and to optimize societal benefit. CEOS contributes to NASA’s core mission and is critical to NASA’s Earth Science program and to the future of Earth observations community as a whole because it advances mission planning, interagency coordination and technical implementation. Within NASA, the CEOS Working Group on Information System and Services (WGISS) is a forum for the Earth Sciences Data Systems (ESDS) Program to collaborate with other international and domestic agencies in the development of Earth observation data systems and services. NASA leads the development and demonstration of multiple prototypes supporting CEOS and Group on Earth Observations (GEO) requirements. NASA’s participation in WGISS influences NASA’s Earth Observing System Data and Information System’s (EOSDIS) ability to make high-quality data products available to the broad science community both nationally and internationally. Combined with NASA’s free and open data policy, EOSDIS’s involvement in WGISS is essential to widespread use of research satellite measurements. This presentation focuses on an overview and recent status of NASA’s EOSDIS.

Andrew Mitchell↗