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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Tracking Sodium-Antimonide Phase Transformations in Sodium-Ion Anodes: Insights from Operando Pair Distribution Function Analysis and Solid-State NMR Spectroscopy

Operando pair distribution function (PDF) analysis and ex situ Na-23 magic-angle spinning solid-state nuclear magnetic resonance (MAS ssNMR) spectroscopy are used to gain insight into the alloying mechanism of high-capacity antimony anodes for sodium-ion batteries. Subtraction of the PDF of crystalline NaxSb phases from the total PDF, an approach constrained by chemical phase information gained from Na-23 ssNMR in reference to relevant model compounds, identifies two previously uncharacterized intermediate species formed electro-chemically; a-Na3-xSb (x approximate to 0.4-0.5), a structure locally similar to crystalline Na3Sb (c-Na3Sb) but with significant numbers of sodium vacancies and a limited correlation length, and a-Na1.7Sb, a highly amorphous structure featuring some Sb-Sb bonding. The first sodiation breaks down the crystalline antimony to form first a-Na3-xSb and, finally, crystalline Na3Sb. Desodiation results in the formation of an electrode formed of a composite of crystalline and amorphous antimony networks. We link the different reactivity of these networks to a series of sequential sodiation reactions manifesting as a cascade of processes observed in the electrochemical profile of subsequent cycles. The amorphofis network reacts at higher voltages reforming a-Na1.7Sb, then a-Na3-xSb, whereas lower potentials are required for the sodiation of crystalline antimony, which reacts to form a-Na3-xSb without the formation of a-Na3-xSb. a-Na3-xSb is converted to crystalline Na3Sb at the end of the second discharge. We find no evidence of formation of NaSb. Variable temperature Na-23 NMR experiments reveal significant sodium mobility within c-Na3Sb; this is a possible contributing factor to the excellent rate performance of Sb anodes.

Allan, Phoebe K.↗
DOE OSTI2017

Same Precursor, Two Different Products: Comparing the Structural Evolution of In–Ga–O “Gel-Derived” Powders and Solution-Cast Films Using Pair Distribution Function Analysis

Amorphous metal oxides are central to a variety of technological applications. In particular, indium gallium oxide has garnered attention as a thin-film transistor channel layer material. In this work we examine the structural evolution of indium gallium oxide gel-derived powders and thin films using infrared vibrational spectroscopy, X-ray diffraction, and pair distribution function (PDF) analysis of X-ray total scattering from standard and normal incidence thin-film geometries (tfPDF). We find that the gel-derived powders and films from the same aqueous precursor evolve differently with temperature, forming mixtures of Ga-substituted In2O3 and In-substituted β-Ga2O3 with different degrees of substitution. X-ray total scattering and PDF analysis indicate that the majority phase for both the powders and films is an amorphous/nanocrystalline β-Ga2O3 phase, with a minor constituent of In2O3 with significantly larger coherence lengths. This amorphous β-Ga2O3 phase could not be identified using the conventional Bragg diffraction techniques traditionally used to study crystalline metal oxide thin films. The combination of Bragg diffraction and tfPDF provides a much more complete description of film composition and structure, which can be used to detail the effect of processing conditions and structure–property relationships. This study also demonstrates how structural features of amorphous materials, traditionally difficult to characterize by standard diffraction, can be elucidated using tfPDF.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Essential Function Analysis Capability

The Essential Function Analysis Capability (EFAC) is an extension of the All Hazards Knowledge Framework (AHA) and is a dynamic analytical framework that enables critical infrastructure knowledge discovery and decision support across the five mission areas – prevention, protection, mitigation, response and recovery. EFAC provides the ability to store and model infrastructure systems as a linked multigraphs providing an intuitive and natural representation. These infrastructure systems can then be tied to the organizational and essential function breakdown of an entity. This capability provides the foundation to rapidly evaluate and understand the potential consequences of manmade and natural disaster on these infrastructure systems and essential functions.

Hoover, MichaelJ.↗
DOE OSTI2023

Modeling Short-Range Order in Disordered Rocksalt Cathodes by Pair Distribution Function Analysis

Pair distribution function (PDF) analysis is a powerful technique for the characterization of short-range order (SRO) in disordered materials. Accurate interpretation of experimental PDF data is critically reliant on the development of structural models that can account for local variations in site occupancies and bond lengths. To this end, we outline an approach to model SRO using first-principles calculations based on the cluster-expansion formalism. These methods are validated on neutron scattering data from two disordered rocksalt oxyfluorides, Li 1.3 Mn 0.4 Ti 0.3 O 1.7 F 0.3 and Li 1.3 Mn 0.4 Nb 0.2 Ti 0.1 O 1.7 F 0.3 . For each composition, we demonstrate that an average structure without any SRO fails to reproduce several key features in the experimental PDF. To pinpoint the origin of the suspected SRO in these materials, configurational and displacive effects were separately investigated using two disparate models. Special quasi-random structures were relaxed using density functional theory to account for local changes in bond lengths while maintaining a near-random ionic configuration. This leads to slightly improved accuracy but still misrepresents asymmetry in the first few peaks of the PDF. Monte Carlo simulations were performed to model configurational SRO on a fixed lattice, which by itself is shown to have a minimal influence on the PDF. Instead, we find that it is the bond length relaxations within environments created by SRO which controls the details of the PDF, thereby highlighting the subtle but important coupling between configurational and displacive SRO in disordered materials.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Formalization of the functional analysis methodology to improve NPP I and C system design process - 244

Functional analysis is a universal methodology, which is able to support NPP and I and C design process. The paper proposes an approach to combining the functional analysis process and I and C design process into a single I and C functional design process. Operation of a system is considered as a set of functions providing not only the achievement of goal, but also keeping material and energy balances. A notation for graphical representation of semantic network (hierarchy of functions) describing a system is suggested. This network includes four levels, namely functional goals, abstract functions level, process functions level, and equipment level. The elements of the hierarchy are connected by three kinds of relationships, namely: parent-child, main-support, and cause-consequence. Then the semantic network (hierarchy) of functions is converted into a functional network which looks as a directed graph. This graph is used for development of control algorithm and for building of instrumentation and control functions hierarchy. Farther analysis of process functions reveals a set of criteria indicating real-time status and effectiveness of functions. The criteria are used for allocation of instruments and actuators. The process of functional analysis and design is illustrated in application to a simple heat generation system. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2011

EVENT PLANNING USING FUNCTION ANALYSIS

Event planning is expensive and resource intensive. Function analysis provides a solid foundation for comprehensive event planning (e.g., workshops, conferences, symposiums, or meetings). It has been used at Idaho National Laboratory (INL) to successfully plan events and capture lessons learned, and played a significant role in the development and implementation of the “INL Guide for Hosting an Event.” Using a guide and a functional approach to planning utilizes resources more efficiently and reduces errors that could be distracting or detrimental to an event. This integrated approach to logistics and program planning – with the primary focus on the participant – gives us the edge.

99 GENERAL AND MISCELLANEOUS↗