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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

All‐Solid‐State Batteries With Mechanically Stable Interfaces Consisting of a Zero‐Strain Cation‐Disordered Rocksalt Cathode

Interface stabilization is critical to the development of working all‐solid‐state batteries. Rigid cathode/solid electrolyte interfaces often disintegrate due to anisotropic volume change of cathode‐active materials, resulting in irreversible capacity loss. Herein, we demonstrate that Li 1.211 Mo 0.467 Cr 0.3 O 2 (LMCO), a pioneering cation‐disordered rocksalt oxide (DRX) cathode that has intrinsically small volume change upon lithium intercalation, can be integrated with a thiophosphate‐based solid electrolyte for all‐solid‐state batteries. Interface stability of the all‐solid LMCO cell was investigated by electrochemical impedance spectroscopy, X‐ray micro‐computed tomography, and electron microscopy. Since LMCO was initially synthesized as a layered phase exhibiting a large volume change, interface disintegration can be observable in the early cycles. As layered LMCO phase‐transformed into DRX LMCO in subsequent cycles, reintegration of the interfaces occurs within a pressurized cell as a result of its zero‐stain behavior. Consequently, the DRX LMCO cathode maintains interface integrity, and thus electrical wiring, over an extended number of cycles, leading to improved capacity retention with small internal cell resistance.

DRX↗
DOE OSTI2023

Assessing the Robustness of Arctic Sea Ice Bi‐Stability in the Presence of Atmospheric Feedbacks

Abstract Arctic sea‐ice loss is influenced by multiple positive feedbacks, sparking concerns of accelerated loss in the coming years or even a tipping point, where a sea‐ice equilibrium disappears at a given CO 2 value and sea ice rapidly evolves to a new steady state. Such a tipping point would imply a bi‐stability of the Arctic climate—where multiple steady‐state Arctic climates are possible at the same CO 2 value. Previous works have sought to establish the existence of bi‐stability using a range of models, from zero‐dimensional sea ice thermodynamic models to fully coupled global climate models, with conflicting results. Here, we present a new model of the Arctic that includes both sea‐ice thermodynamics and key atmospheric feedbacks in a simple framework. We exploit the model's simplicity to identify physical mechanisms that control the timing and extent of sea‐ice bi‐stability, and the abruptness of ice loss. We show that longwave radiation feedbacks can have a strong influence on Arctic surface climate from atmospheric temperature increases alone, even without major contributions from clear‐sky moisture or convective clouds suggested previously. While winter sea‐ice bi‐stability is robust to changes in uncertain model parameters in this study, summer sea ice is more sensitive. Finally, our model indicates that positive feedbacks may modulate the CO 2 threshold of sea‐ice loss and the width of bi‐stability much more strongly than the abruptness of loss. These results lead to a comprehensive understanding of the conditions that favor Arctic sea‐ice bi‐stability, particularly the role of atmospheric feedbacks, in both future and past climates.

Meteorology & Atmospheric Sciences↗
DOE OSTI2026

A robust framework for frictional fault contact in geological formations using a stabilized augmented Lagrangian approach

Numerical simulations are essential to evaluate the performance and safety of engineered subsurface systems such as geological carbon storage sites, enhanced geothermal fields, and oil and gas reservoirs. A key challenge lies in accurately modeling the frictional contact behavior along fault surfaces. This problem involves inequality constraints that arise from the physics of frictional slip, requiring specialized numerical methods to handle the resulting highly nonlinear and path-dependent behavior. Here, in this work, we address this challenge using an Augmented Lagrangian Method (ALM) implemented via the Uzawa algorithm. The formulation employs mixed finite element spaces, combining low-order piecewise linear displacements within the 3D domain cells with piecewise constant tractions defined on the fault surfaces. Furthermore, to ensure stability and satisfy the inf-sup condition, the discrete displacement space is enriched with face bubble functions on both sides of the contact interfaces. This approach offers several advantages over other stabilization techniques that rely on additional terms, and it integrates naturally in the Uzawa framework.

58 GEOSCIENCES↗
DOE OSTI2020

Thermal transport in phase-stabilized lithium zirconate phosphates

The thermal properties of yttrium-stabilized lithium zirconate phosphate [LZP: Li 1+x+y Y x Zr 2-x (PO 4 ) 3 with x = 0.15, -0.2 ≤ y ≤ 0.4 and with x = 0.0, y = 0.0] are presented over a wide temperature range from 30 to 973 K, elucidating the interplay between structural phase transformations and thermal properties in a solid state superionic conducting material. At room temperature, the thermal conductivity decreases by more than 75% as the stoichiometry is changed from lithium deficient to excess and increases with increasing temperature, indicative of defect-mediated transport in the spark plasma sintered materials. The phase transformations and their stabilities are examined by x-ray diffraction and differential scanning calorimetry and indicate that the Y3 + substitution of Zr 4+ is effective in stabilizing the ionically conductive rhombohedral phase over the entire temperature range measured, the mechanism of which is found through ab initio theoretical calculations. Finally, these insights into thermal transport of LZP superionic conductors are valuable as they may be generally applicable for predicting material stability and thermal management in the ceramic electrolyte of future all-solid-state-battery devices.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Catch bond kinetics are instrumental to cohesion of fire ant rafts under load

Dynamic networks composed of constituents that break and reform bonds reversibly are ubiquitous in nature owing to their modular architectures that enable functions like energy dissipation, self-healing, and even activity. While bond breaking depends only on the current configuration of attachment in these networks, reattachment depends also on the proximity of constituents. Therefore, dynamic networks composed of macroscale constituents (not benefited by the secondary interactions cohering analogous networks composed of molecular-scale constituents) must rely on primary bonds for cohesion and self-repair. Toward understanding how such macroscale networks might adaptively achieve this, we explore the uniaxial tensile response of 2D rafts composed of interlinked fire ants ( S. invicta ). Through experiments and discrete numerical modeling, we find that ant rafts adaptively stabilize their bonded ant-to-ant interactions in response to tensile strains, indicating catch bond dynamics. Consequently, low-strain rates that should theoretically induce creep mechanics of these rafts instead induce elastic-like response. Our results suggest that this force-stabilization delays dissolution of the rafts and improves toughness. Nevertheless, above 35 % strain low cohesion and stress localization cause nucleation and growth of voids whose coalescence patterns result from force-stabilization. These voids mitigate structural repair until initial raft densities are restored and ants can reconnect across defects. However mechanical recovery of ant rafts during cyclic loading suggests that—even upon reinstatement of initial densities—ants exhibit slower repair kinetics if they were recently loaded at faster strain rates. These results exemplify fire ants’ status as active agents capable of memory-driven, stimuli-response for potential inspiration of adaptive structural materials.

Science & Technology - Other Topics↗
DOE OSTI2020

Phase Stability in U-6Nb Alloy Doped with Ti from the First Principles Theory

First-principles calculations within the density-functional-theory (DFT) approach are conducted in order to explore and explain the effect of small amounts of titanium on phase stability in the U-6Nb alloy. During rapid quenching from high to room temperature, metastable phases α' (orthorhombic), α" (monoclinic), and γ 0 (tetragonal) can form, depending on Nb concentration. Important mechanical properties depend on the crystal structure and, therefore, an understanding of the effect of impurities on phase stability is essential. Insights on this issue are obtained from quantum-mechanical DFT calculations. The DFT framework does not rely on any material-specific assumptions and is therefore ideal for an unbiased investigation of the U-Nb system.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Unveiling the Morphological and Physical Mechanism of Burn–in Loss Alleviation by Ternary Matrix Toward Stable and Efficient All–Polymer Solar Cells

All–polymer solar cells (All–PSCs) are considered the most promising candidate in achieving both efficient and stable organic photovoltaic devices, yet the field has rarely presented an in–depth understanding of corresponding device stability while efficiency is continuously boosted via the innovation of polymer acceptors. Herein, a ternary matrix is built for all–PSCs with optimized morphology, improved film ductility and importantly, boosted efficiency and better operational stability than its parental binary counterparts, as a platform to study the underlying mechanism. The target system PQM–Cl:PTQ10:PY–IT (0.8:0.2:1.2) exhibits an alleviated burn–in loss of morphology and efficiency under light soaking, which supports its promoted device lifetime. The comprehensive characterizations of fresh and light–soaked active layers lead to a clear illustration of opposite morphological and physical degradation direction of PQM–Cl and PTQ10, thus resulting in a delicate balance at the optimal ternary system. Specifically, the enlarging tendency of PQM–Cl and shrinking preference of PTQ10 in terms of phase separation leads to a stable morphology in their mixing phase; the hole transfer kinetics of PQM–Cl:PY–IT host is stabilized by incorporating PTQ10. Finally, this work succeeds in reaching a deep insight into all–PSC's stability promotion by a rational ternary design, which booms the prospect of gaining high–performance all–PSCs.

14 SOLAR ENERGY↗
DOE OSTI2020

Rhizosphere Carbon Turnover from Cradle to Grave: The Role of Microbe–Plant Interactions

Plant roots are the primary source of organic materials that become stabilized in soil. While most root carbon is decomposed into carbon dioxide (CO 2 ), the remainder typically undergoes multiple microbial transformations before it forms longer-term associations with soil minerals. However, the mechanisms by which roots affect microbial utilization of organic materials and subsequent mineral stabilization processes are poorly understood. It is well known that living roots increase the biomass of nearby microbial communities, and shape their population dynamics, diversity, and interactions. Community assembly and metabolic potential of these rhizosphere-enriched microorganisms are strongly influenced by the chemical composition of the exudates released by the host plant. The root exudate pools of plants undergo compositional changes as they grow, reproduce, and senesce. In the well-studied annual grasses Avena barbata and Avena fatua, this changing rhizosphere substrate pool and the “bloom” of organisms that respond are phylogenetically coherent; Acidobacteria and Actinobacteria are consistently depleted, whereas Alpha and Betaproteobacteria and Bacteroidetes are reliably enriched. When compared to non-root-influenced bulk soils, the responsive community is predictably less taxon-rich, yet forms more complex networks. Finally, these rhizosphere dynamics have significant downstream effects on the colonization of nearby soil minerals, degradation of prior season’s root litters, and the balance of stabilized versus lost soil carbon.

Pett-Ridge, Jennifer↗
DOE OSTI2025

Large scale polymer toughening of two-dimensional materials revealed by in situ TEM fracture tests and multiscale simulations

Two-dimensional (2D) materials offer significant potential for applications in energy-harvesting devices, batteries, sensors, and transistors. However, their intrinsic brittleness makes them prone to mechanical failure, limiting their practical use. In this work, we perform in situ transmission electron microscopy (TEM) fracture tests on monolayer MoSe2 and uncover an extrinsic toughening effect induced by an ultrathin adsorbed polystyrene adlayer. This adlayer substantially enhances the fracture resistance of the 2D flakes. Through a combination of molecular dynamics simulations and finite element analysis, we elucidate the molecular mechanism behind this toughening effect. Further, it arises from the active crack-bridging behavior of entangled polymer chains and the formation of a fracture process zone that stabilizes crack propagation and increases the energy required for crack extension. The proposed toughening mechanism offers a pathway to improving the mechanical reliability of 2D material-based devices by mitigating the risk of sudden failure.

2D materials↗
DOE OSTI2023

Structure-mechanical properties correlation in bulk LiPON glass produced by nitridation of metaphosphate melts

The glassy solid electrolyte Lithium phosphorous oxynitride (LiPON) has been widely researched in thin film solid state battery format due to its outstanding stability when cycled against lithium. In addition, recent reports show thin film LiPON having interesting mechanical behaviors, especially its ability to resist micro-scale cracking via densification and shear flow. Here, in the present study, we have produced bulk LiPON glasses with varying nitrogen contents by ammonolysis of LiPO 3 melts. The resulting compositions were determined to be LiPO 3-3z/2 N z , where 0 ≤ z ≤ 0.75, and the z value of 0.75 is among the highest ever reported for this series of LiPON glasses. The short-range order structures of the different resulting compositions were characterized by infrared, Raman, 31 P magic angle spinning nuclear magnetic resonance, and X-ray photoelectron spectroscopies. Instrumented nano-indentation was used to measure mechanical properties. It was observed that similar to previous studies, both trigonally coordinated (N t ) and doubly bonded (N d ) N co-exist in the glasses in about the same amounts for z ≤ 0.36, the limit of N content in most previous studies. For glasses with z > 0.36, it was found that the fraction of the N t increased significantly while the fraction of N d correspondingly decreased. The incorporation of nitrogen increased both the elastic modulus and hardness of the glass by approximately a factor of 1.5 when N/P ratio reaches 0.75. At the same time, an apparent embrittlement of the glass was observed due to nitridation, which was revealed by nanoindentation with an extra sharp nanoindenter tip.

25 ENERGY STORAGE↗
DOE OSTI2023

Understanding of three different polyvinylpyrrolidone (PVP) based battery binders blends on graphene surfaces from first principles via DFT simulations

Binders play a crucial role in binding electrodes, current collectors, and conductive agents during battery manufacturing. The selection of the binders and their blends considerably affect various properties such as mechanical durability, adhesion performance, ionic/electronic conductivities, and solid electrolyte interface stability for lithium-ion batteries. In this work, polyvinylidene di-fluoride (PVDF), polyacrylic acid (PAA), polyvinylpyrrolidone (PVP), and lithiated polyacrylic acid (Li-PAA) were selected as the model binders, and their blends were studied on graphene surfaces. Further, among them, PVDF is hardly soluble in water unlike the other binders, so in practice, the blend of PVP:PVDF is not thought to be a proper combination. However, the PVP:PVDF binder has also been included because the purpose of this work is to calculate several electronic properties such as binding energies, intermolecular interaction energies, bond critical points, electron density, and the Laplacian of electron density at critical bonding regions of all these blends at the molecular level via density functional theory (DFT) simulations in order to evaluate and compare how is the interaction strength and bonding type of three different lithium-ion batteries (LIBs) binder blends on graphene surfaces. Most stable binder pairs and their binding mechanisms on graphene surfaces were studied. The delocalization of lithium in Li-PAA was studied with the presence of water.

25 ENERGY STORAGE↗
DOE OSTI2020

Thermomagnetic Processing of Aluminum Alloys During Heat Treatment

Processing materials under magnetic fields is an underexplored technique to improve structure and mechanical properties in metals and alloys. Magnetic fields can alter phase stability, modify diffusion characteristics, and alter material flow substantially. In castings, magnetic fields can be used during melting of the alloy, during solidification, or during postprocessing operations such as heat treatment to achieve structural changes. This work investigates the effectiveness of thermomagnetic processing during heat treatment of Al alloys containing in the Al–Cu, Al–Si–Cu, and Al–Mg–Ce systems. We demonstrate an improvement in mechanical properties and a reduction in required heat treatment times for all alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Lithium Manganese Spinel Cathodes for Lithium-Ion Batteries

Spinel LiMn 2 O 4 , whose electrochemical activity was first reported by Professor John B. Goodenough’s group at Oxford in 1983, is an important cathode material for lithium-ion batteries, which attracts continuous academic and industrial interests. It is cheap and environmentally friendly, and has excellent rate performance with 3-dimensional (3D) Li + diffusion channels. However, it suffers from severe degradations, especially under extreme voltages and during high-temperature operations. In this review, the current understanding and future trends of the spinel cathode and its derivatives with cubic lattice symmetry (LiNi 0.5 Mn 1.5 O 4 that shows high-voltage stability, and Li-rich spinels that show reversible hybrid anion- and cation-redox activities) shall be discussed. Special attention is given to the degradation mechanisms, further development of spinel cathodes, and concepts of utilizing the cubic spinel structure to stabilize high-capacity layered cathodes and as robust framework for high-rate electrodes. Lastly, “Good spinel” surface phases like LiNi 0.5 Mn 1.5 O 4 are distinguished from “bad spinel” surface phases like Mn 3 O 4 .

25 ENERGY STORAGE↗
DOE OSTI2023

Coordination Stoichiometry Effects on the Binding Hierarchy of Histamine and Imidazole–M 2+ Complexes

Histidine–M 2+ coordination bonds are a recognized bond motif in biogenic materials with high hardness and extensibility, which has led to growing interest in their use in soft materials for mechanical function. However, the effect of different metal ions on the stability of the coordination complex remains poorly understood, complicating their implementation in metal-coordinated polymer materials. Herein, rheology experiments and density functional theory calculations are used to characterize the stability of coordination complexes and establish the binding hierarchy of histamine and imidazole with Ni 2+ , Cu 2+ , and Zn 2+ . It is found that the binding hierarchy is driven by the specific affinity of the metal ions to different coordination states, which can be macroscopically tuned by changing the metal-to-ligand stoichiometry of the metal-coordinated network. These findings facilitate the rational selection of metal ions for optimizing the mechanical properties of metal-coordinated materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Adaptive Control of Distributed Energy Resources for Distribution Grid Voltage Stability

Volt-VAR and Volt-Watt functionality in photovoltaic (PV) smart inverters provide mechanisms to ensure system voltage magnitudes and power factors remain within acceptable limits. However, these control functions can become unstable, introducing oscillations in system voltages when not appropriately configured or maliciously altered during a cyberattack. In the event that Volt-VAR and Volt-Watt control functions in a portion of PV smart inverters in a distribution grid are unstable, the proposed adaptation scheme utilizes the remaining and stably-behaving PV smart inverters and other Distributed Energy Resources to mitigate the effect of the instability. The adaptation mechanism is entirely decentralized, model-free, communication-free, and requires virtually no external configuration. Here we provide a derivation of the adaptive control approach and validate the algorithm in experiments on the IEEE 37 and 8500 node test feeders.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2020

The Molybdenum Oxide Interface Limits the High-Temperature Operational Stability of Unencapsulated Perovskite Solar Cells

Here, we report on the improved operational stability of unencapsulated perovskite solar cells (PSCs) aged in an ambient atmosphere at elevated temperatures (70 °C) for >1000 h under constant illumination and bias at 30–50% relative humidity. We identify a previously unseen interfacial degradation mechanism concerning the use of a MoO x interlayer, which was originally added to increase operational stability. Specifically, the hole-transport layer/MoO x interface buckles under illumination at 70 °C, which leads to delamination and rapid losses of short-circuit current density corresponding to an average $t_{80}$ of ~55 h. By judiciously evaluating various hole-transport layers, interlayers, and contacts, we find that replacing the MoO x with a VO x interlayer, regardless of the other components in the solar cell, alleviates this buckling issue due to its higher activation barrier toward crystallization, leading to significant gains in PSC operational stability. Unencapsulated devices aged in an ambient atmosphere with a VO x interlayer retain 71% of their initial PCE on average after constant illumination and bias at 70 °C for 1100 h ($t_{80}$ ~ 645 h). Currently, this is the highest temperature reported for the operational stability of unencapsulated n-i-p PSCs aged in air. Identification of a new facet of the complex degradation mechanisms in PSCs will allow for targeted acceleration testing to speed the deployment of low-cost, long-lasting electricity generation under realistic operating temperatures.

14 SOLAR ENERGY↗
DOE OSTI2022

Mechanically strengthened heterogeneous Sm-Co sintered magnets

Samarium-cobalt sintered magnets offer excellent magnetic properties, thermal stability, and corrosion resistance. They are used in a variety of defense and civilian applications, especially when elevated operation temperatures (e.g., 200 ºC to 550 ºC) are required. However, the utilization of these materials is restricted by their brittleness. Improving their mechanical resilience would make them more cost-effective, efficient, and robust in decarbonization and other function-related applications while reducing the pressure on critical material supply chains. In this paper, we engineer a series of novel heterogeneous microstructures, such as laminated coarse grain (CG)/fine grain (FG) and core/shell CG/FG microstructures, to produce unprecedented combinations of superior mechanical and magnetic properties without altering the chemical compositions of the magnets or common heat treatment procedures. Further, a 60% flexural strength enhancement is obtained using heterogeneous Sm 2 (CoFeCuZr) 17 sintered magnets with little impact on their magnetic properties. The mechanically robust heterogeneous Sm-Co sintered magnets have a minor (e.g., less than 4.6%) reduction in the energy product (BH) max due to a slightly reduced squareness of the demagnetization curve, with no decrease in either the remanence (B r ) or the intrinsic coercivity (H ci ). The flexural strengths of these heterogeneous Sm-Co magnets depend on the volume ratios and mean grain sizes of the FG/CG regions, as well as their microstructural architectures. The fine-grained regions act as mechanical strengthening sites, which can be strategically used when designing the magnet for different applications. This technology is highly compatible with existing magnet manufacturing processes and thus can be adopted readily by the magnet industry.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Toward Higher Voltage Solid-State Batteries by Metastability and Kinetic Stability Design

The energy density of battery systems is limited largely by the electrochemical window of the electrolyte. Here, the combined thermodynamic and kinetic effects of mechanically induced metastability are shown to greatly widen the operational voltage window of solid-state batteries based on ceramic-sulfide electrolytes. Solid electrolyte voltage stability up to 10 V is achieved with minimal degradation, far beyond the capability of organic liquid electrolytes. Furthermore, combined experiment, ab initio computation, and theoretical modeling identify the nature of mechanically constrained Li 10 GeP 2 S 12 decomposition both within the bulk and at interfaces with cathode materials at very high voltages. Previously unclear kinetic processes are identified that, when properly implemented, can potentially allow solid-state full cells with remarkably high operational voltages.

25 ENERGY STORAGE↗