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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

All‐Liquid Reconfigurable Electronics Using Jammed MXene Interfaces

Abstract Rigid, solid‐state components represent the current paradigm for electronic systems, but they lack post‐production reconfigurability and pose ever‐increasing challenges to efficient end‐of‐life recycling. Liquid electronics may overcome these limitations by offering flexible in‐the‐field redesign and separation at end‐of‐life via simple liquid phase chemistries. Up to now, preliminary work on liquid electronics has focused on liquid metal components, but these devices still require an encapsulating polymer and typically use alloys of rare elements like indium. Here, using the self‐assembly of jammed 2D titanium carbide (Ti 3 C 2 T x ) MXene nanoparticles at liquid–liquid interfaces, “all‐liquid” electrically conductive sheets, wires, and simple functional devices are described including electromechanical switches and photodetectors. These assemblies combine the high conductivity of MXene nanosheets with the controllable form and reconfigurability of structured liquids. Such configurations can have applications not only in electronics, but also in catalysis and microfluidics, especially in systems where the product and substrate have affinity for solvents of differing polarity.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Extended spin relaxation times of optically addressed vanadium defects in silicon carbide at telecommunication frequencies

Optically interfaced solid-state defects are promising candidates for quantum communication technologies. The ideal defect system would feature bright telecom emission, long-lived spin states, and a scalable material platform, simultaneously. Here, in this study, we use one such system, vanadium (V 4+ ) in silicon carbide, to establish a potential telecom spin-photon interface within a mature semiconductor host. This demonstration of efficient optical spin polarization and readout facilitates all-optical measurements of temperature-dependent spin relaxation times (T 1 ). By using this technique, and lowering the temperature from approximately 2 K to approximately 100 mK, we observe a remarkable 4-orders-of-magnitude increase in spin T 1 across all measured sites, with site-specific values ranging from 57.1 ms to 27.9 s. Furthermore, we identify the underlying relaxation mechanisms, which involve a two-phonon Orbach process, indicating the opportunity for strain tuning to enable qubit operation at higher temperatures. These results position V 4+ in SiC as a prime candidate for scalable quantum nodes in future quantum networks.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Dynamics of quantum Hall interfaces

A quantum Hall (QH) interface is different from an ordinary QH edge, as the latter has its location determined by the confining potential, while the former can be unpinned and behave like a free string. In this paper, we demonstrate this difference by studying three different interfaces formed by (i) the Laughlin state and the vacuum, (ii) the Pfaffian state and the vacuum, and (iii) the Pfaffian and the anti-Pfaffian states. We find that stringlike interfaces propagating freely in the QH system lead to very different dynamical properties from edges. This qualitative difference gives rise to fascinating physics and suggests a different direction for future research on QH physics. We also discuss briefly possible analogies between QH interfaces and concepts in string theory.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2001

Decohesion Elements using Two and Three-Parameter Mixed-Mode Criteria

An eight-node decohesion element implementing different criteria to predict delamination growth under mixed-mode loading is proposed. The element is used at the interface between solid finite elements to model the initiation and propagation of delamination. A single displacement-based damage parameter is used in a softening law to track the damage state of the interface. The power law criterion and a three-parameter mixed-mode criterion are used to predict delamination growth. The accuracy of the predictions is evaluated in single mode delamination and in the mixed-mode bending tests.

Davila, Carlos G.↗
NASA NTRS1980

Chemical depth profiles of the GaAs/native oxide interface

The final-state oxidation products and their distribution in thin native oxides (30-40 A) on GaAs have been studied using X-ray photoelectron spectroscopy in conjunction with chemical depth profiling. Extended room-temperature-oxidation conditions have been chosen to allow the native oxide to attain its equilibrium composition and structure. The work emphasizes the use of chemical depth-profiling methods which make it possible to examine the variation in chemical reactivity of the oxide structure. A minimum of two distinct regions of Ga2O3 with differing chemical reactivity is observed. Chemical shift data indicate the presence of As2O3 in the oxide together with an elemental As overlayer at the interface. A change in relative charge transfer between oxygen and both arsenic and gallium-oxide species is observed in the region of the interface.

Grunthaner, P. J.↗
DOE OSTI2019

Distinct driven steady states emerge from diverse initial textures in rolled nanocomposites

Severe plastic deformation is a known method of making high-performance metallic materials. Single-phase polycrystalline metals undergoing severe plastic deformation develop steady-state textures that are characteristic of the mode of deformation. By contrast, we show that two-phase, Cu-Nb nano-laminate composites reach a variety of different steady-state textures under a single mode of deformation. Using molecular statics simulations and a novel algorithm for crystal rotation analysis, we observe that the final, steady state texture and interface character in these materials depends on the initial texture of the composite. This result suggests that the range of bulk Cu-Nb nano-composite textures that may be made by severe plastic deformation is larger than previously demonstrated, with multiple plastically-driven steady states accessible, depending on initial texture. We propose a modification of accumulative roll bonding with highly textured seed layers as a means of accessing different driven steady states in layered composites.

36 MATERIALS SCIENCE↗
NASA NTRS2001

Mixed-Mode Decohesion Elements for Analyses of Progressive Delamination

A new 8-node decohesion element with mixed mode capability is proposed and demonstrated. The element is used at the interface between solid finite elements to model the initiation and propagation of delamination. A single displacement-based damage parameter is used in a strain softening law to track the damage state of the interface. The method can be used in conjunction with conventional material degradation procedures to account for inplane and intra-laminar damage modes. The accuracy of the predictions is evaluated in single mode delamination tests, in the mixed-mode bending test, and in a structural configuration consisting of the debonding of a stiffener flange from its skin.

Davila, Carlos G.↗
DOE OSTI2022

Atomically thin interlayer phase from first principles enables defect-free incommensurate SnO2/CdTe interface

Advancing optoelectronic and emerging technologies increasingly requires control and design of interfaces between dissimilar materials. However, incommensurate interfaces are notoriously defective and rarely benefit from first-principles predictions, because no explicit atomic-structure models exist. Here, we adopt a bulk crystal structure prediction method to the interface geometry and apply it to SnO2/CdTe heterojunctions without and with the addition of CdCl2, a ubiquitous and beneficial, but abstruse processing step in CdTe photovoltaics. Whereas the direct SnO2/CdTe interface is highly defective, we discover a unique two-dimensional CdCl2 interphase, unrelated to the respective bulk structure. It facilitates a seamless transition from the rutile to zincblende lattices and removes defect-states from the interface bandgap. Implementing the predicted interface electronic structure in device simulations, we demonstrate the theoretical feasibility of bufferless oxide-CdTe heterojunction solar cells approaching the Shockley–Queisser limit. Our results highlight the broader potential of designing atomically thin interlayers to enable defect-free incommensurate interfaces.

14 SOLAR ENERGY↗
DOE OSTI2024

Developing a Robust Market for CHP: A Plan for Fostering Economic Development, Business Competitiveness and Resiliency in the Mid-Atlantic Region

The Department of Energy’s Mid Atlantic Combined Heat and Power Technical Assistance Partnership (MA CHP TAP) was established to develop public-private partnerships to advance the technology, policies, and programmatic support for combined heat and power (CHP), including its application in microgrids, heat to power and district energy. The MA CHP TAP’s work includes education and outreach as well as technical assistance to a variety of stakeholders including end-users (commercial, industrial, institutional and more), state decision makers, electric and gas utilities, trade associations and non-profit organizations. This assistance includes evaluating the economic, energy, reliability and environmental value of proposed systems. The MA CHP TAP represents the multi-state Mid- Atlantic region and is the CHP expert in the region who provides fact-based, un-biased information on CHP, including technologies, project development, project financing, local electric and natural gas utility interfaces, and related state best practice policies.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2025

Biogeochemical controls on iron speciation and cycling across upland to shoreline gradients in freshwater and estuarine coastal soils (Lake Erie and Chesapeake Bay, United States)

Coastal environments are dynamic interfaces that mediate carbon and nutrient exchanges between terrestrial landscapes and open waters, and understanding the biogeochemical factors controlling these exchanges, particularly iron (Fe) redox transformations, is crucial for predicting coastal ecosystem functions. Here, we investigated the mechanisms controlling Fe speciation changes across upland-to-shoreline gradients in freshwater and estuarine soils using Fe K-edge X-ray absorption spectroscopy, solid and porewater composition analysis, and 16S rRNA sequencing analysis. We show that Fe transformations depend primarily on inundation patterns. In unsaturated uplands, Fe occurs as Fe(III) oxyhydroxides, mainly goethite (9–35 %), Fe(II,III)-phyllosilicates (39–89 %), and Fe(III)-organic species (0–61 %). Soils influenced by estuarine waters exhibit porewater sulfide concentrations reaching up to 221 μM, Fe- and S-cycling bacteria, and up to 81 % pyrite (FeS 2 ), indicating that sulfur-driven redox dynamics control Fe transformations. In lacustrine wetlands, Fe(III) reduction is indicated by porewater Fe(II) concentrations increasing to 1.0–2.1 mM, and ~10–15 % of Fe as Fe(II,III)-(hydr)oxides (green rust), vivianite (Fe 3 (PO 4 ) 2 ·8H 2 O), and/or adsorbed Fe(II) species. EXAFS data also indicate reduction of structural Fe(III) to Fe(II) in phyllosilicates. The presence of Fe- and S-cycling bacteria, as well as sulfide (0–10 μM), suggests that Fe-cycling is microbially driven and potentially coupled with cryptic S-cycling. Fe(II) oxidation was indicated above/near the water table by the presence of Fe(III) oxyhydroxides (ferrihydrite, lepidocrocite). Furthermore, negligible Fe(III) or sulfate reduction was observed at some water-saturated sites located at the upland-wetland transition, likely due to oxic (sub-)surface water inputs. Overall, our results highlight the importance of considering both Fe-speciation and hydro-biogeochemical dynamics when predicting Fe-cycling at coastal interfaces.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1995

How far away is plug 'n' play? Assessing the near-term potential of sonification and auditory display

The commercial music industry offers a broad range of plug 'n' play hardware and software scaled to music professionals and scaled to a broad consumer market. The principles of sound synthesis utilized in these products are relevant to application in virtual environments (VE). However, the closed architectures used in commercial music synthesizers are prohibitive to low-level control during real-time rendering, and the algorithms and sounds themselves are not standardized from product to product. To bring sound into VE requires a new generation of open architectures designed for human-controlled performance from interfaces embedded in immersive environments. This presentation addresses the state of the sonic arts in scientific computing and VE, analyzes research challenges facing sound computation, and offers suggestions regarding tools we might expect to become available during the next few years. A list of classes of audio functionality in VE includes sonification -- the use of sound to represent data from numerical models; 3D auditory display (spatialization and localization, also called externalization); navigation cues for positional orientation and for finding items or regions inside large spaces; voice recognition for controlling the computer; external communications between users in different spaces; and feedback to the user concerning his own actions or the state of the application interface. To effectively convey this considerable variety of signals, we apply principles of acoustic design to ensure the messages are neither confusing nor competing. We approach the design of auditory experience through a comprehensive structure for messages, and message interplay we refer to as an Automated Sound Environment. Our research addresses real-time sound synthesis, real-time signal processing and localization, interactive control of high-dimensional systems, and synchronization of sound and graphics.

Bargar, Robin↗
DOE OSTI2024

Developing Materials for High-Energy-Density Solid State Li-S Batteries

Solid-state lithium-sulfur batteries are considered to be the next-generation power source for vehicle applications due to their high energy density (up to 3 times more than current Li-ion) and low cost of sulfur (100 times less than conventional cobalt oxide). However, issues with solid-state electrolyte stability, conduction pathways in the sulfur cathode, and the interface between solid-state electrolyte and sulfur cathode must be solved in order to allow commercialization. This project demonstrates the creation of new, advanced materials which overcome these inherent issues. Current approaches based on polymer or liquid electrolyte with additives have been able to improve stability at the cost of efficiency. In contrast, by creating new hybrid materials it is possible to achieve both stability and efficiency. We developed a novel sulfide-based solid electrolyte, a sulfur-carbon composite cathode, and explored various additives to stabilize the interface of solid electrolyte and cathode. After the desired properties were achieved, these materials were integrated into a high-performance solid-state battery, bringing low-cost high-energy solid-state lithium-sulfur batteries one step closer to reality.

25 ENERGY STORAGE↗
NASA NTRS2018

Verifying Interfaces and Generating Interface Control Documents for the Alignment and Phasing Subsystem of the Thirty Meter Telescope from a System Model in SysML

This paper presents a novel method for verifying interfaces and generating interface control documents (ICDs) from a system model in SysMLTM. In systems and software engineering, ICDs are key artifacts that specify the interface(s) to a system or subsystem, and are used to control the documentation of these interfaces. ICDs enable independent teams to develop connecting systems that use the specified interfaces. In the context of the Thirty Meter Telescope (TMT), interface control documents also act as contracts for delivered subsystems. The Alignment and Phasing system (APS) is one such subsystem. APS is required to implement a particular interface, and formulates requirements for the interfaces to be provided by other components of TMT that interface with APS. As the design of APS matures, these interfaces are frequently refined, making it necessary for related ICDs to be updated. In current systems engineering practice, ICDs are maintained manually. This manual maintenance can lead to a loss in integrity and accuracy of the documents over time, resulting in the documents no longer reflecting the actual state of the interfaces of a system. We show how a system model in SysMLTM can be used to generate ICDs automatically. The method is demonstrated through application to interface control documents pertaining to APS. Specifically, we apply the method to the interface of APS to the primary mirror control system (M1CS) and of APS to the Telescope Control System (TCS). We evaluate the newly introduced method through application to two case studies.

Troy, Mitchell↗
DOE OSTI2025

Molecular Interlocking Multidimensional Modulations of Cathode‐Electrolyte Interface for Constructing High Energy Density Quasi‐Solid‐State Batteries

Gel polymers are regarded as a promising candidate electrolyte for lithium-metal quasi-solid-state batteries, primarily due to their high ionic conductivity and solid-liquid synergistic properties. However, challenges such as interfacial side reactions, limitations in Li + transport caused by interfacial issues, and leaching of transition metals from the cathode have yet to be effectively solved. Herein, a novel gel electrolyte modulation strategy based on electrostatic filler assembly is proposed to address the issues of ineffective capacity utilization and inadequate cycling stability of high-energy-density cathode materials in solid-state lithium-ion batteries. It constructs a 3D interpenetrating charge-bridge network that effectively tackles the phase-separation challenge between fillers and electrolytes at the molecular level. Meanwhile, the molecular interlocking structure effectively inhibits the electrolyte erosion. More critically, it optimizes and stabilizes the cathode-electrolyte interface film, which facilitates the conduction of Li + -ions through a size-sieving mechanism. Consequently, this strategy enables effective adaptation across diverse high-energy-density cathode materials with satisfactory capacity performance (170.4 mAh g −1 at 4.5 V/1 C for LiNi 0.6 Co 0.2 Mn 0.2 O 2 and 194.0 mAh g −1 at 4.3 V/1 C for LiNi 0.9 Co 0.08 Mn 0.02 O 2 ). In conclusion, this investigation offers a straightforward and effective reference for addressing the critical challenges of ionic transport and interface stabilization in the design of gel electrolytes.

cathode-electrolyte interface↗
DOE OSTI2019

Interface-Dependent Radiative Lifetimes of Yb3+, Er3+ Co-doped Single NaYF4 Upconversion Nanowires

The development of upconversion nanomaterials for many photonic applications requires a detailed understanding of their radiative lifetimes that in turn depend critically on local environmental conditions. In this work, hexagonal (ß-phase) sodium-yttrium-?uoride (NaYF4) nanowires (NWs) were synthesized and substitutionally co-doped with a luminescent solid solution of trivalent erbium and ytterbium ions. A single-beam laser trapping instrument was used in tandem with a piezo-controlled, variable-temperature stage to precisely vary the nanowire’s distance from the substrate. The spontaneous photoluminescence lifetime of the 4S3/2 ? 4I15/2 transition from Er3+ ions was observed to change by >60% depending on the ions’ separation distance from a planar (water/glass) dielectric interface. The 4S3/2 state lifetime is observed to increase by a factor of 1.62 ± 0.01 as the distance from the quartz coverslip increases from ~0 nm to~40 µm. Less signi?cant changes in the luminescence lifetime (=10%) were observed over a temperature range between 25 and 50 °C. The distance dependence of the lifetime is interpreted quantitatively in the context of classical electromagnetic coupling between Er3+ ions within the nanowire and the adjacent dielectric interface. We also demonstrate potential applications of the NaYF4 NWs for both controlling and probing temperatures at nanometer scales by integrating them within a poly(dimethylsiloxane) composite matrix.

upconversion, nanowires, radiative lifetime, optic↗