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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Rapid biodegradation of microplastics generated from bio-based thermoplastic polyurethane

The accumulation of microplastics in various ecosystems has now been well documented and recent evidence suggests detrimental effects on various biological processes due to this pollution. Accumulation of microplastics in the natural environment is ultimately due to the chemical nature of widely used petroleum-based plastic polymers, which typically are inaccessible to biological processing. One way to mitigate this crisis is adoption of plastics that biodegrade if released into natural environments. In this work, we generated microplastic particles from a bio-based, biodegradable thermoplastic polyurethane (TPU-FC1) and demonstrated their rapid biodegradation via direct visualization and respirometry. Furthermore, we isolated multiple bacterial strains capable of using TPU-FC1 as a sole carbon source and characterized their depolymerization products. Finally, to visualize biodegradation of TPU materials as real-world products, we generated TPU-coated cotton fabric and an injection molded phone case and documented biodegradation by direct visualization and scanning electron microscopy (SEM), both of which indicated clear structural degradation of these materials and significant biofilm formation.

09 BIOMASS FUELS↗
DOE OSTI2023

The autophagy receptor NBR1 directs the clearance of photodamaged chloroplasts

The ubiquitin-binding NBR1 autophagy receptor plays a prominent role in recognizing ubiquitylated protein aggregates for vacuolar degradation by macroautophagy. Here, we show that upon exposing Arabidopsis plants to intense light, NBR1 associates with photodamaged chloroplasts independently of ATG7, a core component of the canonical autophagy machinery. NBR1 coats both the surface and interior of chloroplasts, which is then followed by direct engulfment of the organelles into the central vacuole via a microautophagy-type process. The relocalization of NBR1 into chloroplasts does not require the chloroplast translocon complexes embedded in the envelope but is instead greatly enhanced by removing the self-oligomerization mPB1 domain of NBR1. The delivery of NBR1-decorated chloroplasts into vacuoles depends on the ubiquitin-binding UBA2 domain of NBR1 but is independent of the ubiquitin E3 ligases SP1 and PUB4, known to direct the ubiquitylation of chloroplast surface proteins. Compared to wild-type plants, nbr1 mutants have altered levels of a subset of chloroplast proteins and display abnormal chloroplast density and sizes upon high light exposure. We postulate that, as photodamaged chloroplasts lose envelope integrity, cytosolic ligases reach the chloroplast interior to ubiquitylate thylakoid and stroma proteins which are then recognized by NBR1 for autophagic clearance. This study uncovers a new function of NBR1 in the degradation of damaged chloroplasts by microautophagy.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Materials and Approaches for Mitigation of SOFC Cathode Degradation in SOFC Power Systems

Perovskites such as doped lanthanum manganite and cobaltite have been used successfully as a cathode material in SOFC power systems operating between 700-1000°C. The electrodes, however, remain prone to degradation in presence of Cr containing gas atmosphere under systems operating conditions. Cathode in SOFCs is considered as one of the largest contributors of electrochemical performance degradations, leading to significant increase in ohmic and non-ohmic losses as well as interfacial compound formation. These degradations are mostly irreversible due to permanent changes to chemical and morphological alterations in the electrodes, resulting in the blockage of triple phase boundary (TPB) sites and decrease in oxygen reduction reactions (ORR). Fundamental mechanistic understanding has been developed to elucidate the reaction pathways of electrode poisoning in electronically conducting electrodes (LSM) as well as mixed ionic and electronically conducting electrodes (LSCF). The overall goal of this program has been identification and development of cost effective solutions to mitigate electrode degradations under “real world” systems operating conditions. The overall technological innovations and impact from this work are: The research provides an understanding of the degradation mechanism and cost-effective approaches for implementation in SOFC systems; Develop mitigation processes utilizing low cost getters using conventional synthesis and fabrication route; Develop tailored high surface area powders and coatings for high Cr capture capacity under systems operating conditions; >Developed computational models to understand mechanistic behavior; Experimentally measure rate of Cr evaporation from chromia and alumina forming alloys under SOFC operating conditions; Developed conditions to minimize Cr evaporation from balance-of-plant alloys; This innovation will support the development of getter platform to capture both intrinsic and extrinsic impurities present in air; and, Applications under wide operating temperature range (500-900°C) as well for wide high-temperature electrochemical systems (SOFC, SOEC, and OTM). The work has been successfully developed, validated experimentally and implemented. Successful technology transfer of this knowledge with industrial partners has been accomplished and the getters have been independently tested and validated under their systems operating conditions. The innovation will also find application in related high temperature electrochemical systems such as OTM and SOEC for the prevention of Cr assisted performance degradation. The proposed approach for Cr capture can also be applied to oxy-combustion and other advanced combustion techniques for the reduction of Cr vapor in the exhaust gas stream. This fundamental knowledge gained also has led to the path forward for developing advanced getters for capturing more than one contaminant in air.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2026

Overview of advanced plasma-facing materials testing for Fusion Pilot Plants at DIII-D

Characterization and testing of advanced plasma-facing materials (PFMs) for Fusion Pilot Plants (FPP) is being conducted at the DIII-D National Fusion Facility through the ongoing two-year FPP Candidate Materials Thrust. Year one tested 17 novel materials utilizing the Divertor Materials Evaluation System (DiMES), with samples analyzed pre- and post-experiment via SEM, EDS, and confocal microscopy. Repeatable reference discharges were developed to ensure uniformity between experiments, including a new strike-point rastering scenario to provide more uniform heat/particle flux across DiMES during ELMing H-mode discharges. Various sample geometries and temperatures were used to achieve FPP-relevant conditions, including samples angled 10° towards the incident plasma flux and pre-heating up to 500 °C. The first exposure of liquid lithium (Li) capillary porous structures in a tokamak demonstrated uniform emission of Li vapor and suppression of Li droplets in H-mode when preheated to 350 °C. Dispersoid-strengthened W with 1 wt% TaC, TiC, and ZrC exposed to H-mode showed cracking and dispersoid ejection for all varieties except TiC, providing a clear down-selection. Ultra-high temperature ceramic materials TiB 2 and ZrB 2 showed minimal degradation under L-mode exposure. Silicon carbide (SiC) fiber composites showed arcing along edges, while CVD SiC remained pristine. Atmospheric plasma-sprayed W and SiC coatings endured H-mode exposure without macroscopic delamination; SiC exhibited granular ejection, while W showed increased outgassing. Additional W-based alloys were stress tested in H-mode, including Ni-based W heavy alloys, W f SiC f /W composites, W multi-principle element alloys, and functionally-graded W/SiC, to varying degrees of success.

DIII-D↗
DOE OSTI2020

Mechanically robust and reprocessable imine exchange networks from modular polyester pre-polymers

Covalent adaptable networks (CANs) containing reversible cross-links impart recyclability to thermoset materials without sacrificing their desirable properties (e.g. high tensile strength and solvent resistance). In addition to thermal recycling, the sustainability of these materials may be further improved by incorporating bio-sourced monomers or by enabling alternate end-of-life fates, such as biodegradation or recovery of starting materials. The alternating ring-opening copolymerisation of epoxides and cyclic anhydrides permits the modular synthesis of polyester pre-polymers that can then be cross-linked to form dynamic imine-linked networks. In this work, we report the synthesis and characterisation of five imine exchange polyester CANs with varied cross-linking densities and pre-polymer architectures. While the materials exhibit characteristic thermoset properties at service temperatures, differences in pre-polymer architecture produce distinct dynamic mechanical effects at elevated temperatures. The networks may be thermally reprocessed with full recovery of their tensile strengths and cross-linking densities, dissociated to pre-polymer, or hydrolytically degraded.

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

Significant Improvements to Si Calendar Lifetime Using Rapid Electrolyte Screening via Potentiostatic Holds

Silicon-based lithium-ion batteries exhibit severe time-based degradation resulting in poor calendar lives. This has been identified as the major impediment towards commercialization with cycle life considered a solved issue through nanosizing and protective coatings allowing over 1000 cycles of life to be achieved. In this work, rapid screening of sixteen electrolytes for calendar life extension of Si-rich systems (70 wt% Si) is performed using the voltage hold (V-hold) protocol. V-hold significantly shortens the testing duration over the traditional open circuit voltage reference performance test allowing us to screen electrolytes within a span of two months. We find a novel ethylene carbonate (EC) free electrolyte formulation containing lithium hexafluorophosphate (LiPF 6 ) salt, and binary solvent mix of fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC) that extends calendar life of Si cells as compared to conventional EC based electrolyte. Our coupled experimental-theoretical analysis framework provides a decoupling of the parasitic currents during V-hold, allowing us to extrapolate the capacity loss to predict semiquantitative calendar lifetimes. Subsequently, cycle aging and oxidative stability tests of the EC free system also show enhanced performance over baseline electrolyte.

25 ENERGY STORAGE↗
DOE OSTI2020

In-situ and in-operando analysis of voltage losses using sense wires for proton exchange membrane water electrolyzers

Proton exchange membrane water electrolyzer development requires understanding processes at the materials and interface levels to reach the required performance and lifetime targets for increasing market penetration. To achieve the required progress, it is critical to develop advanced in-situ diagnostics that allow observation of the changes that come with the reduction of catalyst loading combined with long-term intermittent operation. This work presents an internal voltage sensing method that enables observing internal voltage drops in an operating electrolyzer cell. It allows the total cell resistance to be separated into anode, CCM, and cathode resistance. The method is demonstrated by operating cells with different anode porous transport layers (PTLs). The changing properties of the PTLs result in significant variations of the resistances. Enhancing the PTL properties with a protective coating reduces the anode resistance significantly. In addition to these observations, the method enables a real-time monitoring of resistance related values that impact performance in water electrolyzers. Long-term experiments with the method allow us to gain insights into processes that occur during operation such as conditioning or degradation. The internal voltage sensing method presented in this study is a novel technique for diagnosing, analyzing, and optimizing water electrolyzers and other energy conversion devices.

42 ENGINEERING↗
DOE OSTI2025

In Situ Surface Reconstruction via Lithium Residue Regulation for Direct Recycling of Ni-Rich Cathodes

Surface stability is crucial for the long cycling performance of Ni-rich cathodes, as it dictates and governs side reactions, preserves crystal integrity, and mitigates capacity degradation during cycling. For spent Ni-rich cathodes targeted for one-step direct recycling, constructing a robust and stable surface is particularly challenging because prior cycling induces severe structural and morphological degradation. Here, in this study, we introduce an in situ surface reconstruction strategy that converts surface lithium residues into a protective layer via a direct liquid-phase coating with ammonium dihydrogen phosphate (ADP). During the process, residual lithium remaining after the hydrothermal relithiation is removed, while a conformal lithium phosphate (Li 3 PO 4 , LPO) layer is formed to act as both a chemical barrier and a structural stabilizer. This dual function enhances cycling stability and rate capability in regenerated cathodes, and the approach is applicable to various Ni-rich compositions including spent LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) and scrap LiNi 0.866 Mn 0.066 Co 0.05 Al 0.018 O 2 (NCMA). Its scalability and compositional versatility make it a promising route for sustainable regeneration of high-performance cathode materials.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Schottky contacts to N-polar GaN with SiN interlayer for elevated temperature operation

In this Letter, we unveil the high-temperature limits of N-polar GaN Schottky contacts enhanced by a low-pressure chemical vapor deposited (LPCVD) SiN interlayer. Compared to conventional Schottky diodes, the insertion of a 5 nm SiN lossy dielectric interlayer in-between Ni and N-polar GaN increases the turn-on voltage (V ON ) from 0.4 to 0.9 V and the barrier height ($\phi_B$) from 0.4 to 0.8 eV. This modification also reduces the leakage current at zero bias significantly: at room temperature, the leakage current in the conventional Schottky diode is >103 larger than that observed in the device with the SiN interlayer, while at 200 °C, this ratio increases to 105. Thus, the rectification ratio (ION/IOFF) at ±1.5 V reduces to less than one at 250 °C for the conventional Schottky diode, whereas for SiN-coated diodes, rectification continues until 500 °C. The I–V characteristics of the diode with an SiN interlayer can be recovered after exposure to 400 °C or lower. Contact degradation occurs at 500 °C, although devices are not destroyed yet. Here, we report N-polar GaN Schottky contact operation up to 500 °C using an LPCVD SiN interlayer.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Stabilizing perovskite-substrate interfaces for high-performance perovskite modules

The interfaces of perovskite solar cells (PSCs) are important in determining their efficiency and stability, but the morphology and stability of imbedded perovskite-substrate interfaces have received less attention than have top interfaces. We found that dimethyl sulfoxide (DMSO), which is a liquid additive broadly applied to enhance perovskite film morphology, was trapped during film formation and led to voids at perovskite-substrate interfaces that accelerated the film degradation under illumination. Partial replacement of DMSO with solid-state carbohydrazide reduces interfacial voids. A maximum stabilized power conversion efficiency (PCE) of 23.6% was realized for blade-coated p-type/intrinsic/n-type (p-i-n) structure PSCs with no efficiency loss after 550-hour operational stability tests at 60°C. The perovskite mini-modules showed certified PCEs of 19.3 and 19.2%, with aperture areas of 18.1 and 50.0 square centimeters, respectively.

Chen, Shangshang↗
DOE OSTI2022

UV‐induced degradation of high‐efficiency silicon PV modules with different cell architectures

Abstract Degradation from ultraviolet (UV) radiation has become prevalent in the front of solar cells due to the introduction of UV‐transmitting encapsulants in photovoltaic (PV) module construction. Here, we examine UV‐induced degradation (UVID) in various commercial, unencapsulated crystalline silicon cell technologies, including bifacial silicon heterojunction (HJ), interdigitated back contact (IBC), passivated emitter and rear contact (PERC), and passivated emitter rear totally diffused (PERT) solar cells. We performed UV exposure tests using UVA‐340 fluorescent lamps at 1.24 W·m −2 (at 340 nm) and 45°C through 4.02 MJ·m −2 (2000 h). Our results showed that modern cell architectures are more vulnerable to UVID, leading to a significant power decrease (−3.6% on average; −11.8% maximum) compared with the conventional aluminum back surface field (Al‐BSF) cells (<−1% on average). The power degradation is largely caused by the decrease in short‐circuit current and open‐circuit voltage. A greater power decrease is observed in bifacial cells with rear‐side exposure compared with those with front‐side exposure, indicating that the rear side is more susceptible to UV damage. Secondary ion mass spectroscopy (SIMS) confirmed an increase in hydrogen concentration near the Si/passivation interface in HJ and IBC cells after UV exposure; the excess of hydrogen could result in hydrogen‐induced degradation and subsequently cause higher recombination losses. Additionally, surface oxidation and hot‐carrier damage were identified in PERT cells. Using a spectral‐based analysis, we obtained an acceleration factor of 5× between unpackaged cells (containing a silicon nitride antireflective coating on the front) in the UV test and an encapsulated module (with the front glass and encapsulant blocking 90% of the UV at 294 nm and 353 nm, respectively) in outdoor conditions. From the analytical calculations, we show that a UV‐blocking encapsulant can reduce UV transmission in the module by an additional factor of ~50.

14 SOLAR ENERGY↗
DOE OSTI2020

Atomic-scale tuned interface of nickel-rich cathode for enhanced electrochemical performance in lithium-ion batteries

The Ni-rich layered LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC6 22 ) is one promising cathode for lithium-ion batteries (LIBs), but suffers from poor cycling stability under high cutoff potentials. The performance degradation was reflected as capacity fading and voltage drop, having their roots in instable interface of NMC622. Aimed at improving interfacial stability, in this study, we deposited nanoscale ZrO 2 coatings conformally over NMC622 cathodes using atomic layer deposition (ALD). We found that, under a high cutoff voltage (4.5 V), the ALD ZrO 2 coatings evidently improved the performance of NMC622 cathode, showing better cyclability and higher sustainable capacity. In addition, the ALD coatings dramatically boosted the rate capability of NMC622. All these compelling performance results are ascribed to the atomic-scale tunable ZrO 2 coatings via ALD, which create stable interface and thereby inhibit unfavorable evolutions. In the study, we utilize a suite of characterization tools and various analyses to clarify the effects of ALD ZrO 2 coatings. This study will be helpful for improving the performance of nickel-rich cathodes via interfacial engineering using ALD.

25 ENERGY STORAGE↗
DOE OSTI2023

High Efficiency PEM Water Electrolysis Enabled by Advanced Catalysts, Membranes and Processes

In this project, advanced membranes and catalysts were integrated into membrane electrode assembles (porous transport electrodes (PTE) or catalyst coated membranes (CCM)) leveraging precision coating methods to enable control of electrode structures and demonstration of the best component performance possible with these materials. Partner collaborations allowed for advanced characterization of the formed interfaces and degradation mechanisms. New methods of forming hydrogen recombination layers were also developed, to move away from wet chemistry processes that would have limited realization and implementation of the optimized electrode configurations in a commercial environment.

08 HYDROGEN↗
DOE OSTI2024

Unraveling the Combined Photothermal Stability of Common Perovskite Solar Cell Compositions

In halide perovskite solar cells, certain compositions, especially those with a high mixture of anions, degrade rapidly. Here, in this study, a degradation study compares the photo (exposure to light), thermal (exposure to elevated temperatures), and photo-plus-thermal (combination) stability of three representative perovskite compositions chosen for their relatively high performance and to independently test anion versus cation effects. Based upon experience and reports, the compositions studied are triple cation with a high Br ratio (Cs 0.05 (FA 0.98 MA 0.02 ) 0.95 Pb(I 0.5 Br 0.5 ) 3 ), all iodide with a moderately high Cs ratio (FA 0.8 Cs 0.2 PbI 3 ), and FA-dominated triple cation (Cs 0.05 (FA 0.98 MA 0.02 ) 0.95 Pb(I 0.98 Br 0.02 ) 3 ). Cs 0.05 (FA 0.98 MA 0.02 ) 0.95 Pb(I 0.98 Br 0.02 ) 3 displayed the best combined photo-plus-thermal stability. Degradation mechanisms were investigated by comparing the morphology, surface composition, and bulk and interface carrier dynamics. Under the harshest aging conditions (photo-plus-thermal), phase segregation and vaporization of organic cations occurred, along with the appearance of high-energy states indicating the interaction with C 60 . The findings were verified on perovskite films blade-coated in air used in devices (FTO/NiOx/SAM/Perovskite/C 60 /BCP/Cu), achieving an efficiency of 21.9% alongside correlated stability.

14 SOLAR ENERGY↗
DOE OSTI2024

Environmental Compatibility Issues for Ni-Based Alloys in Direct-Fired Supercritical CO2 Power Cycles

Direct-fired supercritical CO2 (sCO2) power cycles offer potential for high-efficiency power generation from natural gas and other fossil fuels with built-in carbon capture. Ni-based superalloys are the leading candidates for the hottest portions of these systems, where they must endure long-term exposure to high-temperature, high-pressure, high-velocity, impure CO2-rich environments. Herein we describe results of various experimental testing campaigns conduced at NETL showing that under such conditions, several simultaneously occurring degradation modes may be active including surface oxidation, alloy carburization, and oxide volatilization. It will be shown that the rates of degradation can be strongly affected by the alloy composition, impurities in the CO2, manufacturing method (wrought vs additive), and other factors. The influence of these factors in controlling alloy degradation are discussed in the context of potential compatibility issues for components in real sCO2 systems, such as compact heat exchangers. Finally, as a potential remedial measure, ongoing work involving protective coatings suitable for complex geometries is presented.

alloy oxidation↗
DOE OSTI2024

R&D to Ensure a Scientific Basis for Qualification Tests and Standards (Final Report)

Project return on investment in a photovoltaic (PV) system depends increasingly on maintaining high energy yields, and the system lifetime is a major factor in levelized cost of electricity (LCOE). Thus, the rate of PV deployment and the success of these assets depends upon reliable long-term power generation. The overarching objective of this program is to improve photovoltaic (PV) module reliability via development of tests and standards. Where reliability problems or risk are discovered, we can design tests to ensure that these liabilities don't affect future generations of products. Customers can use these tests to understand which products are susceptible to certain degradation mechanisms, and manufacturers can use the tests to design unwanted characteristics out of their products. The work under this program identifies PV reliability needs, performs characterization that provides scientific understanding of targeted degradation mechanisms, and translates those data into practical and predictive test protocols and standards. Major accomplishments include: A model for polarization-type potential induced degradation (PID-p) was developed and validated against experimental data. NREL is currently leading a new edition of IEC 62804-1 for PID detection. PID-p can cause large losses in current and voltage for some module designs on cloudy days. Finite element modeling (FEM) and experiment was used to determine when cells crack in a module. It was shown that cells in landscape orientation are much more likely to crack than those on portrait orientation. Shortly thereafter, the first products with portrait-oriented cells were introduced. Studies of how to test for light and elevated temperature degradation (LeTID) culminated with the publication of IEC TS 63342. Software to predict the progression of LeTID was developed, validated, and made publicly available. Field validated tests and international standards for durability of PV module coatings abrasion, backsheets, and encapsulants were developed. Examples are IEC 62788-1-1, IEC 62788-2 ED2, IEC TS 62788-7-2, IEC 62788-7-3 ED1, IEC 63209-2. NREL led the development a high-temperature testing technical specification, and published guidelines that enable installers to determine whether higher-temperature testing is needed, simply based on location and mounting configuration. In a number of our case studies, variations in the bills of materials or workmanship have been associated with variations in reliability. These observations emphasize the importance of quality assurance to reliability. A framework for criticality (i.e. Pareto) analysis was developed and published. The framework helps us and other researchers determine what problems should be addressed for reliability research to have the biggest industry impact. NREL continues to participate actively in international standards development and stakeholder engagement activities, including organizing an annual PV Reliability Workshop. These activities are important for ensuring we address issues that are relevant and timely, and that we convey our results to those who may benefit.

14 SOLAR ENERGY↗
DOE OSTI2023

Electrochemical mechanisms of leakage‐current in photovoltaic modules

Abstract This paper analyzes the mechanisms and pathways for leakage current flow observed in Si photovoltaic modules subjected to high temperature and humidity and a large voltage bias with respect to ground. The current inside of the frame is in the form of electron motion, but in the glass and polymer, it is in at least a large part attributable to the movement of ions. When the mode of current flow changes from electronic to ionic conduction, electrochemical reactions will take place at the interface. This can include reactions that produce volatile chemical species like H 2 , CO x , and O 2 , along with ionic species such as OH − and H 3 O + . Here, we see evidence of the importance of different charge carriers with different diffusion rates and the influence of electrochemical processes involved. The application of negative voltage to the cell circuit affects the resistivity of glass producing surfaces with poor conductivity but with some increases in the electrochemical potential producing complicated interactions that are important when the voltage is changed. In the polymer, there is the development of a space charge region and a chemical gradient providing two oppositional forces to current flow, which when released create a complicated discharge process. Here, we give a basic understanding of the charge/discharge of PV cells highlighting how the specific mechanisms are important in understanding some of the degradation processes in PV modules. We find that there is evidence of multiple significant charge carrier species with different diffusion time scales. The glass/polymer interface forms a depleted region of higher resistance after prolonged exposure to current. Charge also builds up at the polymer to cell antireflective coating interface and mostly flows to the gridlines to experience electrochemical reactions. These complexities result in non‐linear behavior where the apparent resistivities of the different layers change during charge/discharging processes, making the modeling of the current flow extremely difficult.

14 SOLAR ENERGY↗