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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Understanding Defect-Stabilized Noncovalent Functionalization of Graphene

The noncovalent functionalization of graphene by small molecule aromatic adsorbates, phenanthrenequinone (PQ), is investigated systematically by combining electrochemical characterization, high-resolution interfacial X-ray scattering, and ab initio density functional theory calculations. The findings in this study reveal that while PQ deposited on pristine graphene is unstable to electrochemical cycling, the prior introduction of defects and oxygen functionality (hydroxyl and epoxide groups) to the basal plane by exposure to atomic radicals (i.e., oxygen plasma) effectively stabilizes its noncovalent functionalization by PQ adsorption. The structure of adsorbed PQ molecules resembles the graphene layer stacking and is further stabilized by hydrogen bonding with terminal hydroxyl groups that form at defect sites within the graphene basal plane. The stabilized PQ/graphene interface demonstrates persistent redox activity associated with proton-coupled-electron-transfer reactions. The resultant PQ adsorbed structure is essentially independent of electrochemical potentials. These results highlight a facile approach to enhance functionalities of the otherwise chemically inert graphene using noncovalent interactions.

Functionalization↗
DOE OSTI2017

Strategy for Extending the Stability of Bio‐oil‐Derived Phenolic Oligomers by Mild Hydrotreatment with Ionic‐Liquid‐Stabilized Nanoparticles

Abstract The development of catalytic transformations and processes is essential to utilize bio‐oil and lignin derivatives. Metal nanoparticles (M‐NPs) stabilized in ionic liquids (ILs) are promising for the catalytic hydrotreatment of bio‐oil because the properties of the catalyst system can be customized by combining the appropriate IL and metal nanoparticles. Herein, we demonstrate an experimental approach to stabilize lignin‐derived phenolics isolated from bio‐oil with ruthenium NPs stabilized by an ionic copolymer in 1‐ethyl‐3‐methylimidazolium acetate ([C 2 C 1 Im][OAc]). The mild hydrotreatment of phenolic oligomers (POs) was performed with the synthesized M‐NP catalyst at 100 °C for 6 h. Hydrotreatment of the POs resulted in enhanced thermal stability of the POs by as much as a factor of three, as determined by the aging index and by reducing reactive functionalities, which was also confirmed by NMR spectroscopy and GC analysis. The results support our hypothesis that M‐NPs stabilized in ILs can effectively stabilize POs under mild conditions, which could be applicable to any lignin‐derived phenolic.

Kim, Kwang Ho↗
DOE OSTI2018

Simultaneous Stabilization of LiNi 0.76 Mn 0.14 Co 0.10 O 2 Cathode and Lithium Metal Anode by Lithium Bis(oxalato)borate as Additive

Abstract The long‐term cycling performance, rate capability, and voltage stability of lithium (Li) metal batteries with LiNi 0.76 Mn 0.14 Co 0.10 O 2 (NMC76) cathodes is greatly enhanced by lithium bis(oxalato)borate (LiBOB) additive in the LiPF 6 ‐based electrolyte. With 2 % LiBOB in the electrolyte, a Li∥NMC76 cell is able to achieve a high capacity retention of 96.8 % after 200 cycles at C/3 rate (1 C=200 mA g −1 ), which is the best result reported for a Ni‐rich NMC cathode coupled with Li metal anode. The significantly enhanced electrochemical performance can be ascribed to the stabilization of both the NMC76 cathode/electrolyte and Li‐metal‐anode/electrolyte interfaces. The LiBOB‐containing electrolyte not only facilitates the formation of a more compact solid–electrolyte interphase on the Li metal surface, it also forms a enhanced cathode electrolyte interface layer, which efficiently prevents the corrosion of the cathode interface and mitigates the formation of the disordered rock‐salt phase after cycling. The fundamental findings of this work highlight the importance of recognizing the dual effects of electrolyte additives in simultaneously stabilizing both cathode and anode interfaces, so as to enhance the long‐term cycle life of high‐energy‐density battery systems.

Zhao, Wengao↗
DOE OSTI2015

Chemical expansion affected oxygen vacancy stability in different oxide structures from first principles calculations

We study the chemical expansion for neutral and charged oxygen vacancies in fluorite, rocksalt, perovskite and pyrochlores materials using first principles calculations. We show that the neutral oxygen vacancy leads to lattice expansion whereas the charged vacancy leads to lattice contraction. In addition, we show that there is a window of strain within which an oxygen vacancy is stable; beyond that range, the vacancy can become unstable. Using CeO2|ZrO2 interface structure as an example, we show that the concentration of oxygen vacancies can be manipulated via strain, and the vacancies can be preferentially stabilized. These results could serve as guiding principles in predicting oxygen vacancy stability in strained systems and in the design of vacancy stabilized materials.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2015

On the mechanical stability of uranyl peroxide hydrates: Implications for nuclear fuel degradation

The mechanical properties and stability of studtite, (UO 2 )(O 2 )(H 2 O) 2 ·2H 2 O, and metastudtite, (UO 2 )(O 2 )(H 2 O) 2 , two important corrosion phases observed on spent nuclear fuel exposed to water, have been investigated using density functional perturbation theory. While (UO 2 )(O 2 )(H 2 O) 2 satisfies the necessary and sufficient Born criteria for mechanical stability, (UO 2 )(O 2 )(H 2 O) 2 ·2H 2 O is found to be mechanically metastable, which might be the underlying cause of the irreversibility of the studtite to metastudtite transformation. According to Pugh's and Poisson's ratios and the Cauchy pressure, both phases are considered ductile and shear modulus is the parameter limiting their mechanical stability. Furthermore, debye temperatures of 294 and 271 K are predicted for polycrystalline (UO 2 )(O 2 )(H 2 O) 2 ·2H 2 O and (UO 2 )(O 2 )(H 2 O) 2 , suggesting a lower micro-hardness of metastudtite.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Structure and chemical stability in perovskite–polymer hybrid photovoltaic materials

Adding polymers to methylammonium lead iodide perovskite solar cell active layers has been previously shown to increase their chemical stability, but stabilization mechanisms in these hybrid materials are poorly understood. We report here on a structural and spectroscopic analysis in a number of perovskite–polymer hybrid materials and compare their stability. We observed that perovskite crystallite sizes decrease with the addition of polymers (polyethylene glycol, polyethyleneimine, poly(acrylic acid) and polyvinylpyrrolidone), and through the use of nanomechanical AFM showed phase contrast in the perovskite–polymer mixture. NMR and single-crystal growth experiments reveal that acid–base interactions, as well as facet-dependent interfacial interactions between perovskite and polymer, contribute to differences in stabilities of these hybrid materials. The polymers investigated tend to suppress the formation of a hydrate crystal phase that accelerates the degradation reaction, and we report that adding poly(acrylic acid) increases significantly the stability of perovskite films under humid air and ambient illumination. Under these controlled degradation conditions, perovskite–poly(acrylic acid) hybrid solar cells maintain stable efficiency for the first 3 days and then slowly degrade over the next 6 days under humid air and illumination, whereas control perovskite solar cells degrade entirely within the first 2 days. Furthermore, these results highlight the importance of choosing suitable functional groups in the polymer phase of perovskite hybrid solar cells to prolong their device lifetime.

36 MATERIALS SCIENCE↗
NASA NTRS2012

MATLAB Stability and Control Toolbox Trim and Static Stability Module

MATLAB Stability and Control Toolbox (MASCOT) utilizes geometric, aerodynamic, and inertial inputs to calculate air vehicle stability in a variety of critical flight conditions. The code is based on fundamental, non-linear equations of motion and is able to translate results into a qualitative, graphical scale useful to the non-expert. MASCOT was created to provide the conceptual aircraft designer accurate predictions of air vehicle stability and control characteristics. The code takes as input mass property data in the form of an inertia tensor, aerodynamic loading data, and propulsion (i.e. thrust) loading data. Using fundamental nonlinear equations of motion, MASCOT then calculates vehicle trim and static stability data for the desired flight condition(s). Available flight conditions include six horizontal and six landing rotation conditions with varying options for engine out, crosswind, and sideslip, plus three take-off rotation conditions. Results are displayed through a unique graphical interface developed to provide the non-stability and control expert conceptual design engineer a qualitative scale indicating whether the vehicle has acceptable, marginal, or unacceptable static stability characteristics. If desired, the user can also examine the detailed, quantitative results.

Kenny, Sean P.↗
NASA NTRSDate not supplied

The Influence of Yttria Content on the Thermal Stability of Yttria-Stabilized Zirconia Aerogels

Aerogels demonstrate extraordinarily low thermal conductivity and low density, presenting a promising form of lightweight insulation for aerospace applications. The primary challenge is stabilization of the highly porous structure at temperatures to 1200 °C. Upon collapse of the pore structure, the favorable thermal properties and low density are diminished. Yttria-stabilized zirconia (YSZ) aerogels are synthesized to investigate the effect of composition on morphology, phase behavior, and thermal stability (specific surface area, pore size distribution). This work demonstrates the improvement in thermal stability of zirconia aerogels with increased yttria content. To develop insight on the influence of structure on thermal stability, the effects of water content and solids loading are studied and in elucidation of the mechanism by which yttria stabilizes the pore structure. With an improved understanding of aerogel structure and performance, metal oxide aerogels can be developed to withstand the extreme environments of space exploration.

Nathaniel Olson↗
DOE OSTI2019

Impact of Inverter-Interfaced Renewable Generation on Transient Stability at Varying Levels of Penetration: Preprint

The transient dynamics of conventional power systems are dominated by synchronous generators, and low-inertia inverters serve as the primary interface between power systems and renewable energy resources. Increasing penetration levels of inverter-interfaced generation are impacting the transient dynamics of power systems. In this paper, we attempt to quantify these impacts at different penetration levels. An elementary system including one inverter, one synchronous generator, and one load is studied under different parameter variations to assess the transient dynamics of the system. To quantify transient stability, the post-fault regions of attraction of the system are estimated by the sample-based basin stability approach with parallel computing technology. The simulation results suggest that different inverter penetration levels, inertias of the generator, inverter controller gains, and phase-locked loop controller gains have a clear impact on the regions of attraction as well as on the transient dynamics of proposed systems.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2019

Enhanced Stability of Li Metal Anodes by Synergetic Control of Nucleation and the Solid Electrolyte Interphase

Use of a protective coating on a lithium (Li) metal anode (LMA) is an effective approach to enhance its coulombic efficiency and cycling stability. Here we report a facile approach to produce uniform silver (Ag) nanoparticle-decorated LMAs for high-performance Li metal batteries (LMBs). This effective treatment can lead to well controlled nucleation and the formation of a stable solid electrolyte interphase (SEI). Ag nanoparticles embedded in the surface of Li anodes induced uniform Li plating/stripping morphologies with reduced overpotential. More importantly, cross-linked lithium fluoride (LiF) networks formed during Ag+ reduction enabled a highly stable SEI layer. Based on the Ag-LiF decorated anodes, LMBs with LiNi1/3Mn1/3Co1/3O2 cathode (~1.8 mAh cm-2) can retain >80% capacity over 500 cycles. The similar results were also obtained when the same approach was applied to the design of stable sodium (Na) anodes. These results indicate that synergetic control of the nucleation and SEI is an efficient approach to stabilize rechargeable metal batteries.

anode↗
DOE OSTI2017

Balancing activity, stability and conductivity of nanoporous core-shell iridium/iridium oxide oxygen evolution catalysts [Balancing activity, stability and conductivity of nanoporous core-shell Ir/IrO 2 oxygen evolution catalysts]

The selection of oxide materials for catalyzing the Oxygen Evolution Reaction in acid-based electrolyzers must be guided by the proper balance between activity, stability and conductivity – a challenging mission of great importance for delivering affordable and environmentally friendly hydrogen. Here we report that the highly conductive nanoporous architecture of an iridium oxide shell on a metallic iridium core, formed through the fast dealloying of osmium from an Ir 25 Os 75 alloy, exhibits an exceptional balance between oxygen evolution activity and stability as quantified by the Activity-Stability FactorASF. Based on this metric, the nanoporous Ir/IrO 2 morphology of dealloyed Ir 25 Os 75 shows a factor of ~30 improvement ASFrelative to conventional Ir-based oxide materials and a ~8 times improvement over dealloyed Ir 25 Os 75 nanoparticles due to optimized stability and conductivity, respectively. Here, we propose that the Activity-Stability FactorASF is the key “metric” for determining the technological relevance of oxide-based anodic water electrolyzer catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Autonomous stabilization with programmable stabilized state

Reservoir engineering is a powerful technique to autonomously stabilize a quantum state. Traditional schemes involving multi-body states typically function for discrete entangled states. In this work, we enhance the stabilization capability to a continuous manifold of states with programmable stabilized state selection using multiple continuous tuning parameters. We experimentally achieve 84.6% and 82.5% stabilization fidelity for the odd and even-parity Bell states as two special points in the manifold. We also perform fast dissipative switching between these opposite parity states within 1.8 μs and 0.9 μs by sequentially applying different stabilization drives. Our result is a precursor for new reservoir engineering-based error correction schemes.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗