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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 1,333 records · Page 74
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Photo-induced halide redistribution in 2D halide perovskite lateral heterostructures

An improved understanding of the degradation pathways under external stimuli is needed to address stability challenges in two-dimensional (2D) perovskite semiconductor materials. Here, in this study, in situ synchrotron nanoprobe X-ray fluorescence (nano-XRF) is used to investigate the evolution of halide redistribution within various 2D halide perovskite (n = 1–3) lateral heterostructures under ultraviolet (UV) exposure. Further, the results show that iodine (I) experiences a loss in all cases, with the rate of change following the perovskite dimensionality monotonically. In contrast, bromine (Br) is relatively more stable than I in n = 2 and 3 heterostructures, with no significant change in the total Br concentration but a visible amount of Br diffusion to the previously I-rich regime. Combining nano-XRF and X-ray absorption spectroscopy (XAS), we found a reduction of dimensionality in crystals with n > 1 after UV exposure, indicating significant structural reconfiguration beyond ion migration.

2D halide perovskites↗
DOE OSTI2021

Unraveling the hysteretic behavior at double cations-double halides perovskite - electrode interfaces

Despite over a decade of research on metal halide perovskites (MHPs) in the context of photovoltaic applications, understanding the nature of electronic and ionic processes associated with current-voltage (I-V) hysteretic behavior has been limited. Here, we explore the hysteretic behavior in (FAPbI 3 ) 0.85 (MAPbBr 3 ) 0.15 perovskite devices with lateral Cr electrodes by applying first order reversal curve (FORC) bias waveform in I-V, Kelvin probe force microscopy (KPFM) measurements, and in-situ chemical imaging by time-resolved time-of-flight secondary ion mass spectrometry (tr-ToF-SIMS). In dark, we reveal pronounced hysteretic behaviors of charge dynamics in the off-field by probing time-dependent current and contact potential difference (CPD). Under illumination, transient and hysteretic behaviors are significantly reduced. The tr-ToF-SIMS results reveal that the hysteretic behaviors are strongly associated with accumulation of Br- ions at the interfaces. In addition, the low mobility MA + ions result in transient behavior and contribute to the hysteretic phenomena. It was shown that Pb 2+ ions can be reduced at the interfaces due to electrochemical reactions with the electrode in the presence of charge injection and photogenerated charges. Furthermore, these hysteretic behaviors associated with charge dynamics, ion migration, and interfacial electrochemical reaction are critical to further improve the performance and stability of MHPs photovoltaics and optoelectronics.

42 ENGINEERING↗
DOE OSTI2024

Integrated modeling of boron powder injection for real-time plasma-facing component conditioning

An integrated modeling framework for investigating the application of solid boron (B) powder injection for real-time surface conditioning of plasma-facing components (PFCs) in tokamak environments is presented. Utilizing the DIII-D impurity powder dropper (IPD) setup, this study simulates B powder injection scenarios ranging from milligrams to tens of milligrams per second, corresponding to boron flux rates of 10 20 –10 21 B/s in standard L-mode conditions. The comprehensive modeling approach combines EMC3-EIRENE for simulating the deuterium plasma background and the Dust Injection Simulator (DIS) for the ablation and transport of the boron powder particles. EMC3 trace impurity fluid modeling results show substantial boron transport to the inboard lower divertor, predominantly influenced by the main ion plasma flow. The dependency on powder particle size (5-250 µm) was found to be insignificant for the scenario considered. The effects of erosion and redeposition were considered to reconcile the discrepancies with experimental observations, which saw substantial deposition on the outer divertor plasma-facing components. For this purpose, the WallDYN3D code was updated to include boron sources within the plasma domain and integrated into the modeling framework. The mixed-material migration modeling shows evolving boron deposition patterns, suggesting the formation of mixed B-C layers or predominantly B coverage depending on the powder mass flow rate. While the modeling outcomes at lower B injection rates tend to align with DIII-D experimental observations, the prediction of near-pure boron layers at higher rates has yet to be experimentally verified in the carbon environment of the DIII-D tokamak. The extensive reach of boron layers found in the modeling suggests the need for modeling that encompasses the entire wall geometry for more accurate experimental correlations. This integrated approach sets a precedent for analyzing and applying real-time in-situ boron coating techniques in advanced tokamak scenarios, potentially extendable to ITER.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Preparation of illite coated geomaterial microfluidic surfaces: Effect of salinity and heat treatment

Unique characteristics of clay (e.g., high surface area, deficiency in positive charges) make any clay abundant shales a good source of adsorbed gas. However, the presence of clay in porous media can also affect shale rock's producibility. The clay-water interaction can cause significant swelling and fines migration in the formation and impair the overall hydrocarbon recovery from shale. Geomaterial micromodels, developed by functionalizing traditional glass or PDMS surfaces with geomaterials (e.g., calcite, Quartz, clay), can represent the physicochemical properties of the natural porous media and have been used during the last few years to understand and evaluate the solid-fluid physicochemical interactions. Here, this study focuses on developing a clay-coated geomaterial surface and investigates the effect of base fluid's salinity on clay adsorption to the glass surface. Glass capillary tubes and straight channel borosilicate glass micromodels are coated with Illite clay to represent the pore-scale clay chemistry of Caney Shale, a Mississippian unconventional play in Southern Oklahoma, USA. 10 wt% of Illite clay slurries made with brines of four different salinities are used to coat the glass-capillary tubes to understand the effect of salinity in clay adsorption on the glass surface and overall coating quality. To achieve a stable coating and evaluate the impact of heat treatment on coating's stability, straight channel glass flow cells coated with Illite clay are heat-treated at low (25 °C) and high temperature (125 °C), and the results are compared with an untreated coated surface. Flooding tests were carried out with brines of different salinities on the coated surface to evaluate the stability of the coating. The experimental results indicated a strong relationship between the brine's salinity and the adsorption of clay particles on the glass surface. An increase in brine concentration resulted in improved adsorption of clay particles on the glass surface. Experiments involving heat treating the glass surface following the coating demonstrated significant improvement in the stability of the coating.

02 PETROLEUM↗
DOE OSTI2025

Toward Quality Control in Perovskite Solar Cell Fabrication: Spot-Like Processing Defects Disrupt Charge Transport Layers and Promote Ag Metal Electrode Intrusion

Metal halide perovskite (MHP) photovoltaics provide high efficiencies with less stringent processing requirements than traditional photovoltaic materials. However, processing related defects must be suppressed as they can lead to decreases in initial device efficiency and potentially compromise long-term device operation. In this work we investigate morphological defects in MHP devices using luminescence imaging followed by in-depth structural and composition analysis using electron microscopy-based methods. We identify several different classes of spot-like processing-related defects and observe that a single device structure may contain multiple types of these defects. The presence of these defects in devices with different layer structures and absorber chemistries makes them relevant to the perovskite photovoltaic community as a whole. The defects are associated with voids in the perovskite layer, inclusions (glass, migrated Ag, dust), thickness variations, hole transport layer disruption with anomalous crystal growth, and electron transport layer disruptions that could allow Ag intrusion and lead to local shunts. As perovskite photovoltaic technology matures, mitigation of such defects is critical to improving not only initial performance but also the long-term stability required for industrial applications.

14 SOLAR ENERGY↗
DOE OSTI2025

Selective Oxidation and Cr Segregation in High-Entropy Oxide Thin Films

High-entropy oxides (HEOs) offer exceptional compositional flexibility and structural stability, making them promising materials for energy and catalytic applications. Here, in this study, we investigate Sr doping effects on B-site cation oxidation states, local composition, and structure in epitaxial La 1–x Sr x (Cr 0.2 Mn 0.2 Fe 0.2 Co 0.2 Ni 0.2 )O 3 thin films. X-ray spectroscopies reveal that Sr doping preferentially promotes Cr oxidation from Cr 3+ to Cr 6+ , partially oxidizes Co and Ni, while leaving Mn 4+ and Fe 3+ unchanged. Atomic-resolution scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy shows pronounced Cr segregation, with depletion at the interface and enrichment at the surface, along with partial amorphization in heavily Sr-doped samples. This segregation is likely driven by oxidation-induced migration of smaller, high-valence Cr cations during growth. These findings highlight the critical interplay between charge compensation, local strain, and compositional fluctuations in HEOs, indicating that precise control over growth conditions is critical for tuning their surface composition and electronic structure toward more robust electrocatalyst design.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Interplay Between Cation and Anion Redox in Ni-Based Disordered Rocksalt Cathodes

The reversibility of the redox processes plays a crucial role in the electrochemical performance of lithium-excess cation-disordered rocksalt (DRX) cathodes. Here, we report a comprehensive analysis of the redox reactions in a representative Ni-based DRX cathode. The aim of this work is to elucidate the roles of multiple cations and anions in the charge compensation mechanism that is ultimately linked to the unique electrochemical performance of Ni-based DRX cathodes. Generally, the low-voltage discharge plateau that results in the low energy efficiency and strong voltage hysteresis is associated with the low-voltage oxygen redox. However, incorporating Mo cation promotes the oxygen activity and the Mo migration between octahedral and tetrahedral sites enhances the O reduction potential as well as energy efficiency. This work highlights the important role that electrochemically inactive transition metal plays in the redox chemistry and provides useful insights into the potential pathway to further address the challenges in Ni-based DRX systems.

Yue, Yuan↗
DOE OSTI2020

Probing the Thermal-Driven Structural and Chemical Degradation of Ni-Rich Layered Cathodes by Co/Mn Exchange

The intrinsic poor thermal stability of layered LiNi x Co y Mn 1-x-y O 2 (NCM) cathodes and the exothermic side reactions triggered by the associated oxygen release are the main safety threats for their large-scale implantation. In NCM family, it is widely accepted that Ni is the stability troublemaker, while Mn has long been considered as a structure stabilizer, whereas the role of Co remains elusive. Here, via Co/Mn exchange in Ni-rich LiNi 0.83 Co 0.11 Mn 0.06 O 2 cathode, we demonstrate that, the chemical and structural stability of the deep delithiated NCM cathodes are significantly affected by Co, rather than the widely reported Mn. Operando synchrotron X-ray characterization coupling with in situ mass spectrometry reveal that the Co 4+ reduces prior to the reduction of Ni 4+ , and could thus prolong the Ni migration by occupying the tetrahedra sites, and hence postpone the oxygen release and thermal failure. In contrast, the Mn itself is stable, but barely stabilizes the Ni 4+ . Our results highlight the importance of evaluating the intrinsic role of compositional tuning on Ni-rich/Co-free layered oxide cathode materials to guarantee the safe operation of high-energy Li-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2024

Intergranular corrosion of Ni-30Cr in high-temperature hydrogenated water after removing surface passivating film

Abstract High-resolution transmission electron microscopy and atom probe tomography are used to characterize the initial passivation and subsequent intergranular corrosion of degraded grain boundaries in a model Ni-30Cr alloy exposed to 360 °C hydrogenated water. Upon initial exposure for 1000 h, the alloy surface directly above the grain boundary forms a thin passivating film of Cr 2 O 3 , protecting the underlying grain boundary from intergranular corrosion. However, the metal grain boundary experiences severe Cr depletion and grain boundary migration during this initial exposure. To understand how Cr depletion affects further corrosion, the local protective film was sputtered away using a glancing angle focused ion beam. Upon further exposure, the surface fails to repassivate, and intergranular corrosion is observed through the Cr-depleted region. Through this combination of high-resolution microscopy and localized passive film removal, we show that, although high-Cr alloys are resistant to intergranular attack and stress corrosion cracking, degradation-induced changes in the underlying metal at grain boundaries make the material more susceptible once the initial passive film is breached.

(S)TEM↗
DOE OSTI2021

Threatened salmon rely on a rare life history strategy in a warming landscape

We report that rare phenotypes and behaviours within a population are often overlooked, yet they may serve a heightened role for species imperilled by rapid warming. In threatened spring-run Chinook salmon spawning at the southern edge of the species range, we show late-migrating juveniles are critical to cohort success in years characterized by droughts and ocean heatwaves. Late migrants rely on cool river temperatures over summer, increasingly rare due to the combined effects of warming and impassable dams. Despite the dominance of late migrants, other strategies played an important role in many years. Our results suggest that further loss of phenotypic diversity will have critical impacts on population persistence in a warming climate. Predicted thermally suitable river conditions for late migrants will shrink rapidly in the future and will be largely relegated above impassable dams. Reconnecting diverse habitat mosaics to support phenotypic diversity will be integral to the long-term persistence of this species.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Unlocking anionic redox activity in O3-type sodium 3 d layered oxides via Li substitution

Sodium ion batteries, because of their sustainability attributes, could be an attractive alternative to Li-ion technology for specific applications. However, it remains challenging to design high energy density and moisture stable Na-based positive electrodes. Here, we report an O3-type NaLi 1/3 Mn 2/3 O 2 phase showing anionic redox activity, obtained through a ceramic process by carefully adjusting synthesis conditions and stoichiometry. This phase shows a sustained reversible capacity of 190 mAh g -1 that is rooted in cumulative oxygen and manganese redox processes as deduced by combined spectroscopy techniques. Unlike many other anionic redox layered oxides so far reported, O3-NaLi 1/3 Mn 2/3 O 2 electrodes do not show discernible voltage fade on cycling. This finding, rationalized by density functional theory, sheds light on the role of inter- versus intralayer 3d cationic migration in ruling voltage fade in anionic redox electrodes. Another practical asset of this material stems from its moisture stability, hence facilitating its handling and electrode processing. Altogether, this work offers future directions towards designing highly performing sodium electrodes for advanced Na-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2020

Linking Small-Scale Flight Manoeuvers and Density Profiles to the Vertical Movement of Insects in the Nocturnal Stable Boundary Layer

Huge numbers of insects migrate over considerable distances in the stably-stratified night-time atmosphere with great consequences for ecological processes, biodiversity, ecosystem services and pest management. We used a combination of meteorological radar and lidar instrumentation at a site in Oklahoma, USA, to take a new look at the general assistance migrants receive from both vertical and horizontal airstreams during their long-distance flights. Movement in the nocturnal boundary layer (NBL) presents very different challenges for migrants compared to those prevailing in the daytime convective boundary layer, but we found that Lagrangian stochastic modelling is effective at predicting flight manoeuvers in both cases. A key feature for insect transport in the NBL is the frequent formation of a thin layer of fast-moving air – the low-level jet. Modelling suggests that insects can react rapidly to counteract vertical air movements and this mechanism explains how migrants are retained in the jet for long periods (e.g. overnight, and perhaps for several hours early in the morning). This results in movements over much longer distances than are likely in convective conditions, and is particularly significant for the reintroduction of pests to northern regions where they are seasonally absent due to low winter temperatures.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Electrolytic gold plating, stripping, and ion transport dynamics through a solid-state iodide perovskite

The pronounced electrochemical reactivity between halide perovskites and metal electrodes can introduce mobile extrinsic metal ions which can cause device instability or enable novel functionalities. Here we systematically investigate the kinetics of gold cation (Au + ) migration in indium tin oxide (ITO)/methylammonium lead triiodide (MAPbI 3 )/Au model devices under long-term potentiostatic biasing. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) analyses reveal that Au + ions, electrochemically generated at the Au anode, traverse the perovskite layer with diffusion coefficients on the order of 10 −11 to 10 −10 cm 2 s −1 and are subsequently reduced at the cathode as Au 0 clusters, resembling metal plating behavior in electrolytic cells and solid-state batteries during charging. Furthermore, reversing the applied bias strips the plated Au 0 , revealing reversibility suitable for bipolar resistive switching devices and providing direct evidence of the electrochemical and ionic nature of Au transport within the perovskite matrix. Quantitatively determining diffusion coefficients and ion concentrations provides foundational inputs for future drift-diffusion modelling opportunities and allows us to relate our findings to implications on long term operation of devices like photovoltaic modules. These results clearly demonstrate the solid-state electrochemical nature of perovskite devices, highlight methods to be more quantitative about ion transport properties, provide and emphasize the importance of disentangling electro-, photo-, photoelectrochemical processes for understanding device performance and unlocking new functionalities.

14 SOLAR ENERGY↗
DOE OSTI2021

Interfacial Characterization of Positive Bias Voltage Degradation in PV Modules

Degradation from high system voltage is a prevailing failure mode in fielded photovoltaic modules, and the degradation mechanism is inherently dependent on the bias polarity. Here we report the effects of positive bias. Modules under positive bias demonstrated a significant photocurrent loss caused by two routes. First, delamination and discoloration of the silicon nitride layer, leading to optical loss determined by reflectance measurements. Second, chemical discoloration of the cell gridlines and encapsulant (EVA), which is linked to an electrochemical reaction at the silver electrodes. Chemical compositional analysis using X-ray photoemission spectroscopy demonstrated that the discoloration is attributed to Ag 2 S and/or Ag 2 O. Evidence of Ag ion migration from the cell grid into the encapsulant is observed after shallow depth profiling on the EVA surface. However, Ag was not detected at the EVA/glass interface, inferring limited Ag ion transport through the EVA. The source of sulfur is believed to be ambient air, which diffused into the module through the breathable backsheet.

characterization↗
DOE OSTI2021

Diffusion-mediated chemical concentration variation and void evolution in ion-irradiated NiCoFeCr high-entropy alloy

High-entropy alloys (HEAs) are proposed as potential structural materials for advanced nuclear systems, but little is known about the response of matrix chemistry in HEAs upon irradiation. Here, we reveal a substantial change of matrix chemical concentration as a function of irradiation damage (depth) in equiatomic NiCoFeCr HEA irradiated by 3 MeV Ni ions. After ion irradiation, the matrix contains more Fe/Cr in depth shallower than ~900–1000 nm but more Ni/Co from ~900–1000 nm to the end of the ion-damaged region due to the preferential diffusion of vacancies through Fe/Cr. Preferential diffusion also facilitates migration of vacancies from high radiation damage region to low radiation damage region, leading to no void formation below ~900–1000 nm and void formation around the end of the ion-damaged region at a fluence of 5 × 10 16 cm -2 (~123 dpa, displacements per atom, peak dose under full cascade mode). As voids grow significantly at an increased fluence (8 × 10 16 cm -2 , 196 dpa), the matrix concentration does not change dramatically due to new voids formed below ~900–1000 nm.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2021

Pulsed Neutron Capture for monitoring CO2 Storage with Enhanced Oil Recovery in Northern Michigan

Pulsed neutron capture (PNC) logging has been used as part of the Midwest Regional Carbon Sequestration Partnership (MRCSP) monitoring of CO2 injection and storage during assessment of enhanced oil recovery (EOR) in several northern Niagaran trend reefs in Michigan. A total of four reefs were selected for these studies to monitor CO2 migration and to test the viability and effectiveness of the PNC technology on reefs in various stages (depleted, active and new reefs) of CO2-EOR activities.

Bagley↗
DOE OSTI2024

Use of carbon electrodes to reduce mobile ion concentration and improve reliability of metal halide perovskite photovoltaics

Ion migration is one of the prime reasons for the rapid degradation of metal halide perovskite solar cells (PSCs), and we report on a method for quantifying mobile ion concentration (No) using a transient dark current measurement. We perform both ex-situ and in-situ measurements on PSCs and study the evolution of No in films and devices under a range of temperatures. We also study the effect of device architecture, top electrode chemistry, and metal halide perovskite composition and dimensionality on No. Two-dimensional perovskites are shown to reduce the ion concentration along with inert C electrodes that do not react with halides by ~99% while also improving mechanical reliability by ~250%. We believe this work can provide design guidelines for the development of stable PSCs through the lens of minimizing mobile ions and their evolution over time under operational conditions.

14 SOLAR ENERGY↗
DOE OSTI2020

Defect Kinetics and Control for Module Reliability

Potential induced degradation is currently one of the most important module degradation mechanisms. It has been suggested that stacking faults decorated with sodium from the module glass are responsible for this effect and authors have also shown the reversibility of this effect upon reverse biasing of the module. The importance of sodium in the failure mechanism is clear, however, little is known regarding the factors that control its diffusion into the wafer, making it nearly impossible to predict the performance of a given module and engineer it to be better. Sodium migration from module glass into silicon cells and the resulting module degradation is a clear example of how defect kinetics can determine overall module performance and long-term reliability. To the detriment of the industry and its bankability, no quantitative models yet exist to predict defect-assisted module degradation, limiting the progress in improving reliability. In particular, the understanding of defect behavior under high electric fields, under stresses imparted by encapsulation or temperature, and under real operating conditions over long periods of time is a crucial gap in the current state-of-the-art. In this work we developed a Defect-Device-Degradation model to predict defect behavior and its impact on device performance over the module operational lifetime using experimentally-determined defect parameterizations. The validated model will provide a platform for manufacturing process optimization across input materials and architectures to avoid deleterious defects upstream and enable enhanced module robustness.

36 MATERIALS SCIENCE↗