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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Polymer grafted aramid nanofiber reinforces immiscible waste polypropylene/poly(ethylene terephthalate)

Polypropylene (PP) and poly(ethylene terephthalate) (PET) are plastics commonly used for packaging because of their excellent barrier and mechanical properties. The properties of these plastics are often diminished after mechanical recycling, inevitably causing down-cycling. Furthermore, this problem is exacerbated when different kinds of polymers mix. Aramid nanofibers have the potential to improve the mechanical properties of polymers due to their excellent mechanical properties but their poor dispersion in polymers is a challenge. Grafting polymers onto nanofibers can help address this challenge. In this work, different loading levels (1%, 2%, and 5%) of polymer grafted aramid nanofibers (ANFs) are blended with waste PP/PET (90/10), simulating a PP waste stream containing traces of PET contaminants. Scanning electronic microscopy, rheology, and differential scanning calorimetry results show the affinity of PP functionalized aramid nanofibers (PP_ANF) towards the PP matrix. At 1 wt% of the nanofiber, the size of the PET droplets in the PP matrix of the PP_ANF blend range from 0.2 to 2.0 μm while that of unmodified ANF and PET_ANF blends are in the range of 0.1–6.2 and 0.5–7.4 μm, respectively. In summary, polymer grafted ANFs have the tendency of improving properties of its like polymers due to similarity in the grafting polymer and the polymer matrix.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Correlating processing variables to material properties in recycled polypropylene: A data‐driven approach

Abstract Polypropylene (PP) is one of the most widely used plastics, yet its recycling remains limited, with less than 1% of solid waste PP being reprocessed. Mechanical recycling through extrusion is the most practical method, but inconsistent reprocessing conditions introduce variability in material properties. While temperature, screw speed, and residence time influence the thermomechanical stress applied during reprocessing, there are no standardized guidelines for optimizing these parameters. This study examines how these factors shape the properties of recycled PP, using conditions designed to mimic post‐industrial recycled (PIR) scrap. Residence time was measured using colorimetric tracking and correlated with molecular weight, viscosity, and mechanical properties over multiple extrusion cycles. Data‐driven modeling, including response surface methodology, support vector machines, and artificial neural networks, identified processing temperature as the dominant factor in material degradation, followed by residence time. Mechanical properties remained stable, while viscosity decreased predictably with increasing residence time. By linking reprocessing conditions to property evolution, this study provides a method to optimize processing parameters and reduce variability in recycled PP. These findings help manufacturers improve process control, making recycled PP more predictable for reuse in manufacturing. Highlights Study of PIR‐quality PP without additives or compatibilizers. Residence time analysis shows processing temperature drives PP property changes. Mark‐Houwink enables quick molecular weight checks for quality control. Models predict mechanical and rheological shifts in reprocessing. Optimized processing parameters minimize property degradation in recycling.

Estela‐García, John E. [Polymer Engineering Center↗
DOE OSTI2024

Melt compounding of spray-dried cellulose nanofibrils/polypropylene and their application in 3D printing

Abstract Micro- and nano-scale cellulosic fillers exhibit excellent dispersion and distribution within a thermoplastic matrix during the process of melt compounding or injection molding. In this study, spray-dried cellulose nanofiber (SDCNF) powders were manufactured using a pilot-scale rotating disk atomizer spray dryer. Bleached Kraft pulp (BKP), unbleached Kraft pulp (UKP), and old corrugated cardboard pulp (OCC) fibrillated at a fines level of 90% were used as feedstock materials for spray-drying. BKP-, UKP-, and OCC- SDCNFs were compounded with polypropylene using a twin screw co-rotating extruder. Maleic anhydride grafted polypropylene (MAPP) was used as a coupling agent in the composite formulations. The tensile, flexural, and impact properties of SDCNF-filled PP composites increased at 10 wt% SDCNF loading. The presence of SDCNFs in the PP matrix resulted in faster crystallization and a 12% reduction in the degree of crystallinity of the neat PP. The coefficient of thermal expansion (CTE) of neat PP was reduced by up to 31% attributable to the presence of the SDCNFs. Application of the SDCNF-reinforced PP composites in 3D printing reduced the shrinkage rate of the printed neat PP by 39%, and the printability of the PP was significantly improved with the addition of the SDCNFs.

Materials Science↗
DOE OSTI2021

Performance of hybridized bamboo-carbon fiber reinforced polypropylene composites processed using wet laid technique

The end-of-life vehicles (ELV) regulations motivate hybrid materials usage in automotive industries to optimize properties at reduced cost and increase eco-friendly designs. This research explores hybrid compositions of natural bamboo fiber and synthetic carbon fiber. The goal of hybridization was to synergistically benefit from each constituent– i.e., sustainability, energy absorption and superior damping from bamboo, and high strength and stiffness from carbon fiber. Carbon fibers (CF), bamboo fibers (BF) and polypropylene (PP) fibers were dispersed in water to produce wet-laid hybrid mats. The mats were compression molded into consolidated panels to obtain the hybrid composite(s) (BF-CF-PP). Four formulations with different fiber-resin weight percent were designed and produced including- BF-PP (30/70), BF-PP (50/50), BF-CF-PP (32/8/60), and BF-CF-PP (8/32/60). The effect of (a) fiber length, (b) surface treatment, (c) fiber content, and (d) consolidation pressure on the mechanical properties were examined. The improved mechanical (flexural strength 76.4 MPa, flexural modulus 4.1 GPa, ILSS 12.4 MPa and impact strength 49.9 KJ/m 2 ) and vibrational damping (1.05%) properties showed that the BF-CF-PP (8/32/60) provided higher properties compared to the other variants. The projected properties at various stoichiometric ratios of carbon and bamboo fiber revealed that the properties of hybrid composites could be tailored to produce desirable, cost-effective, and sustainable automotive components.

36 MATERIALS SCIENCE↗
DOE OSTI2023

High-purity Polypropylene from Disposable Face Masks via Solvent-Targeted Recovery and Precipitation

The high use of disposable face masks since the start of COVID-19 has globally generated 4.68–6.24 million tons per year of waste from personal protective equipment. Disposable face masks are generally disposed of in landfills. Polypropylene (PP) is the main component in face masks, which is one of the least recycled plastics but has a high market value. In this work, we extract high-quality PP from face masks using solvent-targeted recovery and precipitation (STRAP) with 90 wt% recovery. N,N-Dimethylacetamide removed the color from the recovered PP to produce a clear high-purity PP, as verified by CIELAB color space. The decolored PP shows similar thermochemical properties and color to virgin PP resin. Here, a techno-economic analysis of the process indicates that high-purity PP recovery can be economically viable at a scale of 5000 tons per year or higher.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

GIF Gas Cooled Fast Reactor: Proliferation Resistance and Physical Protection White Paper

This white paper represents the status of Proliferation Resistance and Physical Protection (PR&PP) characteristics for the Gas-cooled Fast reactor (GFR) reference designs selected by the Generation IV International Forum (GIF) GFR System Steering Committee (SSC). The intent is to generate preliminary information about the PR&PP features of the GFR reactor technology and to provide insights for optimizing their PR&PP performance for the benefit of GFR system designers. It updates the GFR analysis published in the 2011 report “Proliferation Resistance and Physical Protection of the Six Generation IV Nuclear Energy Systems”, prepared Jointly by the Proliferation Resistance and Physical Protection Working Group (PRPPWG) and the System Steering Committees and provisional System Steering Committees of the Generation IV International Forum, taking into account the evolution of both the systems, the GIF R&D activities, and an increased understanding of the PR&PP features. The white paper, prepared jointly by the GIF PRPPWG and the GIF GFR SSC, follows the high-level paradigm of the GIF PR&PP Evaluation Methodology to investigate the PR&PP features of the GIF GFR 2400 MWth reference design. The ALLEGRO reactor is also described. The EM2 and HEN MHR reactor are mentioned. An overview of fuel cycle for the GFR reference design and for the ALLEGRO reactor are provided. For PR, the document analyses and discusses the proliferation resistance aspects in terms of robustness against State-based threats associated with diversion of materials, misuse of facilities, breakout scenarios, and production in clandestine facilities. Similarly, for PP, the document discusses the robustness against theft of material and sabotage by non-State actors. The document follows a common template adopted by all the white papers in the updated series.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Tailoring compatibilization potential of maleic anhydride–grafted polypropylene by sequential rheochemical processing of polypropylene and polyamide 66 blends

Reactive compatibilization of immiscible polymer blends using a preferred compatibilizer leaves the following question: How much loading of a compatibilizer is good enough and what maximum properties can be achieved? A good understanding of the process can help solve the reutilization of mixed waste plastics. Here, the reactive compatibilization of polypropylene-graft-maleic anhydride (PP-g-MAH) on polypropylene/polyamide 66 (PP/PA66) blends is quantitatively assessed using thermorheological, microoptical, spectroscopic, and x-ray scattering-based characterization tools. The overall compositions of all PP(60%)/PA66(30%)/PP-g-MAH(10%) blends are kept constant while systematically controlling the degree of the chemical reaction by varying the sequential addition of PP-g-MAH to the melt mixture. The first feeding of PP-g-MAH (x%, 0 ≤ x ≤ 10) is conducted at 280°C and the second feeding of (10–x)% is at 200°C. During the first step, a larger amount of chemical activity is observed up to 4%–6% addition of PP-g-MAH. Furthermore, the constant chemical composition allows a systematic comparison of the compatibilizer-dependent thermal, rheological, morphological, and mechanical properties. With an increased degree of interfacial reaction, the size of dispersed PA66 domains decreases to register improved interfacial adhesion with the PP matrix, yielding enhanced Young's modulus and absolute failure strength of the isotropic matrix.

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

Phosphonate functionalized magnetic mesoporous silica for rare earth element recovery from citrate assisted solid waste extracts

The growing high demand of rare earth elements (REEs) has prompted extensive research on REE recovery from waste streams. This study reports the synthesis and evaluation of phosphonate-functionalized magnetic mesoporous silica (MMS-PP) for REE recovery from the acidic extracts of solid wastes. MMS-PP was synthesized using surfactant template and post-synthesis methods, and tested using simulated and real extraction solutions from citrate-assisted REE extracts from municipal solid waste incineration (MSWI) ash. The organic-inorganic hybrid MMS-PP was evaluated for La recovery from 50 mM simulated citrate extract, with the adsorption capacity of 13.5 mg/g compared to ∼2.5 mg/g for non-functionalized MMS. The MMS-PP material exhibited fast adsorption within 10 min, good La selectivity against competing Na + and Ca 2+ , moderate selectivity against Al 3+ and Fe 3+ , high recyclability over multiple adsorption-desorption cycles, and equivalent efficiency for La, Ce, Nd, and Y recovery. Furthermore, the MMS-PP material also demonstrated 70–95% REE recovery from real citrate extracts of MSWI ash, and the spent MMS-PP material can be regenerated and reused for multiple cycles. Functionalized mesoporous materials in combination with organic-ligand assisted extraction can potentially provide a green, effective, and tunable solid-liquid separation platform for REE recovery from complex solid waste streams.

REE recovery↗
DOE OSTI2021

Shear reflectivity compensation in full-waveform inversion using least-squares reverse-time migration

SUMMARY The computational cost of elastic-waveform inversion is too high for inverting PP reflections, while using acoustic full-waveform inversion (FWI) is inaccurate because it does not depend on the shear modulus/velocity/impedance that affects elastic PP wavefield amplitudes. To solve this problem, we develop a waveform inversion method that uses acoustic least-squares reverse-time migration (LSRTM) to compensate the shear reflectivity for acoustic FWI. Our method is based on the quasi-elastic-wave equation developed by Chapman et al. (2014). The quasi-elastic-wave equation uses a linearized acoustic-wave equation with shear modulus μ as a virtual source to correct the acoustic PP wavefield amplitudes toward elastic ones. Our waveform inversion method inverts for elastic parameters by minimizing the L2 norm of the difference between recorded and predicted PP reflections modelled using the quasi-elastic-wave equation. Numerical tests on synthetic and field data show that our method can properly handle the amplitudes of elastic PP reflections and provides an accurate estimate of the P- and S-wave velocities/impedances and, in some cases, the density. The method does not need the computationally expensive numerical solution to the elastic-wave equation. It also gives a better estimate of elastic parameters than a pure LSRTM method for elastic PP reflections.

Feng, Zongcai↗
DOE OSTI2024

Pyrophosphate-free glycolysis in Clostridium thermocellum increases both thermodynamic driving force and ethanol titers

Background: Clostridium thermocellum is a promising candidate for production of cellulosic biofuels, however, its final product titer is too low for commercial application, and this may be due to thermodynamic limitations in glycolysis. Previous studies in this organism have revealed a metabolic bottleneck at the phosphofructokinase (PFK) reaction in glycolysis. In the wild-type organism, this reaction uses pyrophosphate (PP i ) as an energy cofactor, which is thermodynamically less favorable compared to reactions that use ATP as a cofactor. Previously we showed that replacing the PP i -linked PFK reaction with an ATP-linked reaction increased the thermodynamic driving force of glycolysis, but only had a local effect on intracellular metabolite concentrations, and did not affect final ethanol titer. Results: In this study, we substituted PP i -pfk with ATP-pfk, deleted the other PPi-requiring glycolytic gene pyruvate:phosphate dikinase (ppdk), and expressed a soluble pyrophosphatase (PPase) and pyruvate kinase (pyk) genes to engineer PP i -free glycolysis in C. thermocellum. We demonstrated a decrease in the reversibility of the PFK reaction, higher levels of lower glycolysis metabolites, and an increase in ethanol titer by an average of 38% (from 15.1 to 21.0 g/L) by using PP i -free glycolysis. Conclusions: By engineering PP i -free glycolysis in C. thermocellum, we achieved an increase in ethanol production. These results demonstrate that optimizing the thermodynamic landscape through metabolic engineering can enhance product titers. While further increases in ethanol titers are necessary for commercial application, this work represents a significant step toward engineering glycolysis in C. thermocellum to increase ethanol titers.

09 BIOMASS FUELS↗
DOE OSTI2025

Polypropylene Composites Reinforced With Recycled Waste Cellulosic Fiber/Fine Mixture: The Impact of Cellulose Sieving on Performance

This study explores how a sieving step of waste cellulosic fiber and fine (WCFF) mixture affects the performance of WCFF‐loaded polypropylene (PP) composites and whether the separation of fines from fibers offers an added benefit. The WCFF samples were downsized, and four different filler size ranges were sieved using a series of mesh sizes from 4 to 0.85 mm. The WCFF/PP composites were then compounded at 20 wt.% loading of WCFF using a twin‐screw extruder. Incorporating WCFF increased the tensile strength to 41.28 MPa and the modulus to 3207 MPa, accounting for 28% and 38% enhancements, respectively. Interestingly, the greatest improvements were associated with the nonsieved WCFF case, and the sieved WCFF fibers provided only marginal enhancements over virgin PP. The outperformance of nonsieved WCFF was attributed to the synergistic reinforcement of hybrid fibers and fines as well as the maintenance of longer fibers in the system. However, the strain at break and impact strength of PP decreased after introducing WCFF. Moreover, the complex viscosity and storage modulus increased with an increase in the filler size, due to the formation of a more effective percolative network. The PP's crystallinity exhibited a relatively strong dependency on the sieving, where WCFF samples with short‐aspect‐ratio fillers promoted the crystallinity significantly. It was also found that the WCFF degradation onset temperature increased once it was incorporated into PP. This study suggests that waste cellulosic feedstocks can be utilized as a reinforcement without additional sieving to manufacture high‐performance and cost‐effective composites.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Study of charm hadronization with prompt $ {\Lambda}_{\textrm{c}}^{+} $ baryons in proton-proton and lead-lead collisions at $ \sqrt{s_{\textrm{NN}}} $ = 5.02 TeV

The production of prompt $ {\Lambda}_{\textrm{c}}^{+} $ baryons is measured via the exclusive decay channel $ {\Lambda}_{\textrm{c}}^{+}\to p{\textrm{K}}^{-}{\pi}^{+} $ at a center-of-mass energy per nucleon pair of 5.02 TeV, using proton-proton (pp) and lead-lead (PbPb) collision data collected by the CMS experiment at the CERN LHC. The pp and PbPb data were obtained in 2017 and 2018 with integrated luminosities of 252 and 0.607 nb$^{−1}$, respectively. The measurements are performed within the $ {\Lambda}_{\textrm{c}}^{+} $ rapidity interval |y| < 1 with transverse momentum (p$_{T}$) ranges of 3–30 and 6–40 GeV/c for pp and PbPb collisions, respectively. Compared to the yields in pp collisions scaled by the expected number of nucleon-nucleon interactions, the observed yields of $ {\Lambda}_{\textrm{c}}^{+} $ with p$_{T}$> 10 GeV/c are strongly suppressed in PbPb collisions. The level of suppression depends significantly on the collision centrality. The $ {\Lambda}_{\textrm{c}}^{+} $/D$^{0}$ production ratio is similar in PbPb and pp collisions at p$_{T}$> 10 GeV/c, suggesting that the coalescence process does not play a dominant role in prompt $ {\Lambda}_{\textrm{c}}^{+} $ baryon production at higher p$_{T}$.[graphic not available: see fulltext]

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Environmental exposure to industrial air pollution is associated with decreased male fertility

Objective: To understand how chronic exposure to industrial air pollution is associated with male fertility through semen parameters. Design: Retrospective cohort study. Subjects: Men in the Subfertility, Health and Assisted Reproduction cohort who underwent a semen analysis 2005-2017 with ≥1 measured semen parameter (N=21,563). Intervention(s): Residential histories for each man were constructed using locations from administrative records linked through the Utah Population Database. Industrial facilities with air emissions of nine endocrine disrupting compound chemical classes were identified from the Environmental Protection Agency Risk-Screening Environmental Indicators microdata. Chemical levels were linked with residential histories for the 5 years prior to each semen analysis. Main Outcome Measures: Semen analyses were classified as azoospermic or oligozoospermic (< 15 M/mL) using World Health Organization cutoffs for concentration. Bulk semen parameters such as concentration, total count, ejaculate volume, total motility, total motile count, and total progressive motile count were also measured. Multivariable regression models with robust standard errors were used to associate exposure quartiles for each of the nine chemical classes with each semen parameter, adjusting for age, race, and ethnicity, as well as neighborhood socioeconomic disadvantage. Results: After adjustment for demographic covariates, several chemical classes were associated with azoospermia and decreased total motility and volume. For exposure in the 4th relative to 1st quartile, significant associations were observed for acrylonitrile (β total motility = -0.87 pp), aromatic hydrocarbons (odds ratio [OR]azoospermia = 1.53; β volume = -0.14 mL), dioxins (OR azoospermia = 1.31; β volume = -0.09 mL; β total motility = -2.65 pp), heavy metals (β total motility = -2.78pp), organic solvents (OR azoospermia = 1.75; β volume = -0.10 mL), organochlorines (OR azoospermia = 2.09; β volume = -0.12 mL), phthalates (OR azoospermia = 1.44; β volume = -0.09 mL; β total motility = -1.21 pp), and silver particles (OR azoospermia = 1.64; β volume = -0.11 mL). All semen parameters significantly decreased with increasing socioeconomic disadvantage. Men who lived in the most disadvantaged areas had concentration, volume, and total motility of 6.70 M/mL, 0.13 mL, and 1.79 pp lower, respectively. Count, motile count, and total progressive motile count all decreased by 30–34 M.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2025

Co-depolymerization of lignin and plastic waste using hydrothermal liquefaction process

Sustainable valorization of underutilized lignin and plastic waste beyond incineration is critical for producing renewable fuels. Hydrothermal liquefaction (HTL) provides a promising approach to convert wet lignin and plastics into high-quality oils without the need for prior drying of wet lignin. Here, this study examines the effects of temperature (300–400 °C), residence time, and polymer molecular weight on product yield and composition during HTL of polyethylene (PE), polypropylene (PP), and lignin under subcritical and supercritical water conditions. For PE, oil yields increased with temperature, with low molecular weight (LMW) PE achieving a maximum of ∼93 % at 400 °C for 30 min, while high molecular weight (HMW) PE reached ∼86 % at 400 °C for 1 h. Lignin and PP exhibited optimal oil yields at intermediate temperatures, decreasing at higher temperatures due to secondary reactions and char formation. Lignin yielded a maximum of ∼22 % oil at 300 °C for 30 min, LMW PP ∼88 % at 375 °C for 1 h, and HMW PP ∼83 % at 400 °C for 1 h. GC–MS analysis revealed that lignin oils were rich in phenols and alkylphenols, while PE and PP oils were dominated by paraffins and olefins. Oxygenated compounds in PE decreased at higher temperatures, improving oil quality. Co-liquefaction of lignin with plastics enhanced oil yields and energy content under specific conditions, demonstrating synergistic effects dependent on plastic type, molecular weight, and HTL conditions. These findings highlight the potential of HTL to produce high-energy, value-added fuels from lignin–plastic mixtures.

09 - BIOMASS FUELS↗
DOE OSTI2025

Effect of metal-free mesoporous silica incorporated ZSM-5 composite on thermo-catalytic pyrolysis of polypropylene

Although different zeolites impregnated with transition metals have been used in catalytic deconstruction of waste plastics to other products, the influence of hierarchical structures on conversion and product selectivity in plastic upcycling has not been thoroughly investigated. This research explores a transition metal free zeolite-based hierarchical composite, synthesized by incorporating SBA-15 in ZSM-5 framework, for efficient thermos-catalytic upcycling of polypropylene (PP). Thermogravimetric analysis reveals that ZSM-5@SBA-15 can break down PP at a significantly lower temperature, 240 °C, compared to that of pristine PP using ZSM-5 or SBA-15. In addition, pyrolysis of PP at 400 °C using ZSM-5@SBA-15 composite outperforms ZSM-5 or SBA-15 used separately and yields 90 % conversion with 70 % selectivity to propene. The presence of mesopores in the catalyst appears to reduce the diffusion resistance of intermediate products for successive scission, thereby reducing the activation energy of reaction and improving catalytic activity. In conclusion, the hierarchical composite ZSM-5@SBA-15 has significant potential for upcycling of PP into valuable monomers and lighter olefins, with lower energy demands, enhancing the economic feasibility of the process.

ZSM-5@SBA-15↗
DOE OSTI2024

Girth and groomed radius of jets recoiling against isolated photons in lead-lead and proton-proton collisions at $\sqrt{s_{NN}} = 5.02$ TeV

This Letter presents the first measurements of the groomed jet radius R g and the jet girth g in events with an isolated photon recoiling against a jet in lead-lead (PbPb) and proton-proton (pp) collisions at the LHC at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The observables R g and g provide a quantitative measure of how narrow or broad a jet is. The analysis uses PbPb and pp data samples with integrated luminosities of 1.7 nb -1 and 301 pb -1 , respectively, collected with the CMS experiment in 2018 and 2017. Events are required to have a photon with transverse momentum $p^{γ}_{T} > 100$ GeV and at least one jet back-to-back in azimuth with respect to the photon and with transverse momentum $p^{jet}_{T}$ such that $p^{jet}_{T}/p^{γ}_{T} > 0.4$ . The measured R g and g distributions are unfolded to the particle level, which facilitates the comparison between the PbPb and pp results and with theoretical predictions. It is found that jets with $p^{jet}_{T}/p^{γ}_{T} > 0.8$ , i.e., those that closely balance the photon $p^{γ}_{T}$ , are narrower in PbPb than in pp collisions. Relaxing the selection to include jets with $p^{jet}_{T}/p^{γ}_{T} > 0.4$ reduces the narrowing of the angular structure of jets in PbPb relative to the pp reference. This shows that selection bias effects associated with jet energy loss play an important role in the interpretation of jet substructure measurements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Facile Dual-Protection Layer and Advanced Electrolyte Enhancing Performances of Cobalt-free/Nickel-rich Cathodes in Lithium-Ion Batteries

Despite cobalt (Co)-free/nickel (Ni)-rich layered oxides being considered as one of the promising cathode materials due to their high specific capacity, their highly reactive surface is one of the shortcomings that still hinder their practical usages in high-energy-density batteries. Herein, a polyimide/polyvinylpyrrolidone (PI/PVP, denoted as PP) coating layer is demonstrated as dual-protection for LiNi 0.96 Mg 0.02 Ti 0.02 O 2 (NMT) cathode material to suppress surface contamination against moisty air and to prevent unwanted side reactions between cathode and electrolyte during electrochemical cycling. The optimal PP-coated NMT (PP@NMT) preserves a clean surface without generation of lithium (Li) residues, structural degradation, and gas evolution after exposure to air with ~30% humidity for 2 weeks. Contrarily, the exposed bare NMT shows severe contamination, structural shrinkage due to Li loss, and increased gas release during charging. In addition, the exposed PP@NMT significantly enhances the electrochemical performance of graphite (Gr)||NMT cells by decreasing byproducts and maintaining structural stability. Moreover, the exposed PP@NMT achieves a high capacity retention of 86.7% after 500 cycles in Gr||NMT cells using an advanced localized high-concentration electrolyte. Furthermore, this work demonstrates a promising facile approach to the protection of Co-free/Ni-rich layered cathodes for their practical applications even after exposure to moisty air.

25 ENERGY STORAGE↗
DOE OSTI2025

The Turbulent Pressure Spectrum Within the Roughness Sublayer of a Subarctic Forest Canopy

The turbulent static pressure spectrum E pp (k x ) as a function of longitudinal wavenumber k x in the roughness sublayer of forested canopies is of interest to a plethora of problems such as pressure transport in the turbulent kinetic energy budget, pressure pumping from snow or forest floor, and coupling between flow within and above canopies. Long term static pressure measurements above a sub-arctic forested canopy for near-neutral conditions during the winter and spring were collected and analyzed for three snow cover conditions: trees and ground covered with snow, trees are snow free but the ground is covered with snow, and snow free cover. In all three cases, it is shown that E pp (k x ) obeys the attached eddy hypothesis at low wavenumbers (1/δ < k x < 1/z) —with E pp (k x ) ∝ u$^4_*$k$^{-1}_x$ and Kolmogorov scaling in the inertial subrange at higher wavenumbers—with E pp (k x ) ∝ ϵ 4/3 k x -7/3 , where u * is the friction velocity at the canopy top, is the mean turbulent kinetic energy dissipation rate, z is the distance from the snow top, and is the boundary layer depth. The implications of these two scaling laws to the normalized root-mean squared pressure C p = o p /u$^2_*$ and its newly proposed logarithmic scaling with normalized wall-normal distance z/δ are discussed for snow covered and snow free vegetation conditions. The work here also shows that k$^{-1}_x$ the in the E pp (k x ) appears more extensive and robust than its longitudinal velocity counterpart.

Aslan, Toprak [Finnish Meteorological Inst., Helsi↗