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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Computational flow modeling of triply periodic minimal surfaces as feed channel spacers in ultra-high pressure reverse osmosis applications

Triply periodic minimal surfaces (TPMS) are a special class of mathematical surfaces characterized by a high surface area-to-volume ratio. They have generated considerable interest in fields such as acoustics, heat transfer, and membrane-based filtration processes. This study evaluates the performance of four different TPMS designs—Schoen Gyroid, Schoen Crossed Layers of Parallels (CLP), Schoen Transverse Crossed Layers of Parallels (tCLP), and Schwarz-Primitive—when used as feed channel spacers under ultra-high pressure reverse osmosis (UHPRO) conditions, at approximately 200 bar. Our experimentally validated computational fluid dynamics model reveal different flow patterns within the feed channels for each of the four TPMS designs, leading to varying hydrodynamic and permeation properties. Under the simulated UHPRO conditions, the Gyroid and tCLP designs yield up to a 23% increase in average permeate velocity and a 14% reduction in average membrane-surface concentration relative to a non-woven spacer of the same porosity. Furthermore, the enhanced performance comes with an increased feed channel pressure drop, although it only constitutes less than 4% of the operating pressure when extrapolated for a meter-long membrane module. Additionally, the study analyzes the effects of varying inlet velocity and spacer porosity on membrane performance. Overall, this research provides valuable insights into the potential use of TPMS spacers in UHPRO applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Tuning transport in graphene oxide membrane with single-site copper ($\mathrm{II}$) cations

Controlling the ion transport through graphene oxide (GO) membrane is challenging, particularly in the aqueous environment due to its strong swelling tendency. Fine-tuning the interlayer spacing and chemistry is critical to create highly selective membranes. We investigate the effect of single-site divalent cations in tuning GO membrane properties. Competitive ionic permeation test indicates that Cu 2+ cations dominate the transport through the 2D channels of GO membrane over other cations (Mg 2+ /Ca 2+ /Co 2+ ). Without/With the single-site M 2+ modifications, pristine GO, Mg-GO, Ca-GO, and Cu-GO membranes show interlayer spacings of ~13.6, 15.6, 14.5, and 12.3 Å in wet state, respectively. The Cu-GO membrane shows a two-fold decrease of NaCl (1 M) permeation rate comparing to pristine GO, Mg-GO, and Ca-GO membranes. In reverse osmosis tests using 1000 ppm NaCl and Na 2 SO 4 as feeds, Cu-GO membrane shows rejection of ~78% and ~94%, respectively, which are 5%–10% higher than its counterpart membranes.

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

Acceleration of Pd-V intermetallic diffusion by hydrogen

Vanadium-based membranes have great potential for hydrogen purification due to their perfect selectivity, high permeability, and relatively low cost. With appropriate surface cleaning, V efficiently permeates hydrogen at elevated temperature, but performance declines due to its affinity to absorb impurities. Here, the application of palladium thin films maintains a clean surface that catalyzes hydrogen dissociation and recombination. Hydrogen permeation in Pd-V-Pd membranes initially reach theoretical permeability, but declines due to Pd-V interdiffusion. The objective of this work was to quantify the intermetallic diffusion process as a function of temperature and ambient. Pd-V composites were subjected to various annealing treatments and characterized using Auger electron spectroscopy, X-ray diffraction, and energy dispersive X-ray spectroscopy, as well as correlated to measurements of membrane permeability. In an inert environment Pd-V interdiffusion was observable as low as 300 °C, and the diffusion coefficient had an activation energy of 44 kJ/mol. Furthermore, the presence of hydrogen at partial pressures > 10 kPa accelerated interdiffusion six-fold at T = 400 °C. Membrane performance degraded with an activation energy 75 kJ/mol, suggesting that intermetallic diffusion leads to both a loss of catalytic activity and as well as degradation of bulk permeability. These findings provide a baseline for evaluating hydrogen permeable interdiffusion barriers to overcome these challenges.

08 HYDROGEN↗
DOE OSTI2020

PdAu/YSZ composite hydrogen separation membranes with enhanced stability in the presence of CO

The effects of gold composition on the tolerance of palladium-based composite membranes to CO exposure was studied under the presence of high CO concentrations. Membranes with PdAu compositions ranging up to 41% by mass were exposed to binary 50/50 H 2 /CO gas atmospheres and both hydrogen flux and purity were monitored over time. It was observed that the highest gold composition (41%) suffered no degradation in membrane performance in terms of permeate hydrogen purity and hydrogen permeation flux during the 48 h exposure. Furthermore, for lower gold compositions, X-ray diffraction patterns suggested that carbon entered the film and could be removed by exposure to a non-CO containing gas mixture over time. However, removal of the carbon adversely affected purity; interestingly, some of the purity decline could be reversed upon re-exposure to the CO gas mixture. It is hypothesized that carbon loading in the palladium films causes lattice expansion and may even fill pore defects, thus lowering leaks through the Pd films. Furthermore, this study suggests that a membrane exposed to a CO mixture should not be cycled between CO and non-CO environments, but rather run continuously for best performance. Additionally, the choice of Pd-alloy and metal composition should be considered in regard to its carbon solubility to best predict lifetime performance.

08 HYDROGEN↗
DOE OSTI2022

Using molecular simulation to understand the skin barrier

Skin's effectiveness as a barrier to permeation of water and other chemicals rests almost entirely in the outermost layer of the epidermis, the stratum corneum (SC), which consists of layers of corneocytes surrounded by highly organized lipid lamellae. As the only continuous path through the SC, transdermal permeation necessarily involves diffusion through these lipid layers. The role of the SC as a protective barrier is supported by its exceptional lipid composition consisting of ceramides (CERs), cholesterol (CHOL), and free fatty acids (FFAs) and the complete absence of phospholipids, which are present in most biological membranes. Molecular simulation, which provides molecular level detail of lipid configurations that can be connected with barrier function, has become a popular tool for studying SC lipid systems. We review this ever-increasing body of literature with the goals of (1) enabling the experimental skin community to understand, interpret and use the information generated from the simulations, (2) providing simulation experts with a solid background in the chemistry of SC lipids including the composition, structure and organization, and barrier function, and (3) presenting a state of the art picture of the field of SC lipid simulations, highlighting the difficulties and best practices for studying these systems, to encourage the generation of robust reproducible studies in the future. This review describes molecular simulation methodology and then critically examines results derived from simulations using atomistic and then coarse-grained models.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Pure- and mixed-gas transport properties of a microporous Tröger's Base polymer (PIM-EA-TB)

Polymers of intrinsic microporosity (PIMs) offer tantalizing combinations of high selectivity and permeability in initial gas permeation measurements. Here, we report characterization of pure- and mixed-gas permeation properties of a thick (~80 μm) PIM consisting of Tröger's Base (TB) and Ethanoanthracene (EA) films. The effects of feed pressure and temperature on pure-gas permeabilities of CH 4 , N 2 , O 2 , H 2 , and CO 2 were investigated. The physical aging behavior of the thick film was tracked via pure-gas O 2 , N 2 , and CH 4 permeability at 35 °C. Gas permeability decreased noticeably and selectivity increased as aging time increased. Particular attention was given to mixed-gas measurements of CO 2 and CH 4 (50/50) permeabilities at 35 °C and fugacities ranging from 2 to 18 atm to explore whether the rigid, bridged, bicyclic TB and EA units could resist CO 2 -induced plasticization. These results are presented along with pure-gas CO 2 and CH 4 results for membrane samples aged at different times. PIM-EA-TB aged for ~24 h did not show signs of plasticization across the fugacity range considered. Furthermore, dual-mode competitive sorption presumably caused the CO 2 /CH 4 mixed-gas selectivity to be slightly higher than its corresponding pure-gas selectivity. However, as aging time increased, aged films underwent progressively more rapid and extensive CO 2 -induced plasticization with increasing fugacity, suggesting a systematic relationship between physical aging and plasticization in PIMs. Consequently, physical aging caused less improvement in mixed-gas CO 2 /CH 4 selectivity than it did in pure-gas selectivity, due mainly to plasticization effects.

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

Quantifying Energetic and Entropic Pathways in Molecular Systems

When examining dynamics occurring at nonzero temperatures, both energy and entropy must be taken into account to describe activated barrier crossing events. Furthermore, good reaction coordinates need to be constructed to describe different metastable states and the transition mechanisms between them. Here we use a physics-based machine learning method called state predictive information bottleneck (SPIB) to find nonlinear reaction coordinates for three systems of varying complexity. SPIB is able to correctly predict an entropic bottleneck for an analytical flat-energy double-well system and identify the entropy- and energy-dominated pathways for an analytical four-well system. Lastly, for a simulation of benzoic acid permeation through a lipid bilayer, SPIB is able to discover the entropic and energetic barriers to the permeation process. Given these results, we thus establish that SPIB is a reasonable and robust method for finding the important entropy, energy, and enthalpy barriers in physical systems, which can then be used to enhance the understanding and sampling of different activated mechanisms.

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

Molecular Dynamics Simulation Study of the Protonation State Dependence of Glutamic Acid Transport through a Cyclic Peptide Nanotube

The effect of the protonation state of glutamic acid on its translocation through cyclic peptide nanotubes (CPNs) was assessed by using molecular dynamics (MD) simulations. Anionic (GLU–), neutral zwitterionic (GLU0), and cationic (GLU+) forms of glutamic acid were selected as three different protonation states for an analysis of energetics and diffusivity for acid transport across a cyclic decapeptide nanotube. Based on the solubility-diffusion model, permeability coefficients for the three protonation states of the acid were calculated and compared with experimental results for CPN-mediated glutamate transport through CPNs. Potential of mean force (PMF) calculations reveal that, due to the cation-selective nature of the lumen of CPNs, GLU–, so-called glutamate, shows significantly high free energy barriers, while GLU+ displays deep energy wells and GLU0 has mild free energy barriers and wells inside the CPN. The considerable energy barriers for GLU– inside CPNs are mainly attributed to unfavorable interactions with DMPC bilayers and CPNs and are reduced by favorable interactions with channel water molecules through attractive electrostatic interactions and hydrogen bonding. Unlike the distinct PMF curves, position-dependent diffusion coefficient profiles exhibit comparable frictional behaviors regardless of the charge status of three protonation states due to similar confined environments imposed by the lumen of the CPN. The calculated permeability coefficients for the three protonation states clearly demonstrate that glutamic acid has a strong protonation state dependence for its transport through CPNs, as determined by the energetics rather than the diffusivity of the protonation state. In addition, the permeability coefficients also imply that GLU– is unlikely to pass through a CPN due to the high energy barriers inside the CPN, which is in disagreement with experimental measurements, where a considerable amount of glutamate permeating through the CPN was detected. To resolve the discrepancy between this work and the experimental observations, several possibilities are proposed, including a large concentration gradient of glutamate between the inside and outside of lipid vesicles and bilayers in the experiments, the glutamate activity difference between our MD simulations and experiments, an overestimation of energy barriers due to the artifacts imposed in MD simulations, and/or finally a transformation of the protonation state from GLU– to GLU0 to reduce the energy barriers. Altogether, our study demonstrates that the protonation state of glutamic acid has a strong effect on the transport of the acid and suggests a possible protonation state change for glutamate permeating through CPNs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Role of Elemental Substitution on Hydrogen Incorporation in Characteristic Ti/Fe-Based Oxides

Elemental substitution is well-known to benefit hydrogen storage in the intermetallic compound TiFe; however, the impact of these substituents on the native and passivating surface oxide has not been well-established. Here, we perform density functional theory calculations on several characteristic oxides that are likely to form on exposed TiFe surfaces, specifically, TiO 2 , FeO, TiFeO 3 , and Ti 4 Fe 2 O. In TiO 2 and TiFeO 3 , additional acceptor species substituting for Ti can increase the solubility of protonic hydrogen (H i + ), likely enhancing hydrogen permeation of the oxide layer. In FeO, few dopants will act as acceptors, and hydrogen will incorporate as substitutional H O + , which is likely to be less mobile and will hinder hydrogen permeation. Finally, we find that Ti 4 Fe 2 O, which is thermodynamically metastable, may be stabilized by defects under O-poor conditions, although the presence of certain substitutional elements can destabilize it. In general, Mn, V, and Cr are among the best substituents for enhancing hydrogenation through the oxide layer. In conclusion, our results help to explain what features make additional elements particularly effective for enabling reversible hydrogen storage in TiFe, and they can guide further technological development of high-performing TiFe-based alloys for future energy applications.

organic↗
DOE OSTI2025

Redox-Induced Microstructure and Phase Dynamics in Nickel: Insights from In Situ Synchrotron X-ray Diffraction

Using in situ synchrotron X-ray diffraction, we interrogate the microstructural and phase evolution of polycrystalline nickel (Ni) during redox cycling in O 2 , H 2 , and H 2 O environments. Oxidation in O 2 promotes strong (111) texturing in both the NiO overlayer and the underlying Ni substrate. However, this crystallographic alignment is lost following reduction in H 2 and subsequent reoxidation, demonstrating irreversible microstructural changes. H 2 exposure leads to proton dissolution into the Ni lattice, triggering a localized phase transition from face-centered cubic (FCC) to hexagonal close-packed (HCP) Ni in hydrogen-saturated regions. In H 2 O-containing atmospheres, dissociative H 2 O adsorption produces protons that permeate the NiO layer, forming γ-NiOOH within the NiO lattice and HCP Ni beneath the NiO overlayer as protons accumulate. Kinetic analysis via the Johnson-Mehl-Avrami–Kolmogorov model uncovers distinct growth mechanisms: preoxidized Ni surfaces follow one-dimensional (1D) kinetics for NiO, γ-NiOOH, and HCP growth, whereas pristine Ni exhibits three-dimensional (3D) kinetics due to island-like nucleation and growth of NiO. Furthermore, these results highlight the critical interplay between H 2 O dissociation, hydrogen permeation, and redox-driven phase transformations, with practical implications in engineering nickel-based catalysts and hydrogen storage systems through controlled microstructural and phase evolution.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Graphene-based sensing of oxygen transport through pulmonary membranes

Lipid-protein complexes are the basis of pulmonary surfactants covering the respiratory surface and mediating gas exchange in lungs. Cardiolipin is a mitochondrial lipid overexpressed in mammalian lungs infected by bacterial pneumonia. In addition, increased oxygen supply (hyperoxia) is a pathological factor also critical in bacterial pneumonia. In this paper we fabricate a micrometer-size graphene-based sensor to measure oxygen permeation through pulmonary membranes. Combining oxygen sensing, X-ray scattering, and Atomic Force Microscopy, we show that mammalian pulmonary membranes suffer a structural transformation induced by cardiolipin. We observe that cardiolipin promotes the formation of periodic protein–free inter–membrane contacts with rhombohedral symmetry. Membrane contacts, or stalks, promote a significant increase in oxygen gas permeation which may bear significance for alveoli gas exchange imbalance in pneumonia.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Selective partitioning and uphill transport enable effective Li/Mg ion separation by negatively charged membranes

Efficient separation of lithium (Li + ) and magnesium (Mg 2+ ) is critical for enhancing sustainable lithium extraction from natural brines, which is vital for battery production and renewable energy technologies. Here we present a method for highly selective Li + /Mg 2+ separation driven by concentration gradients across negatively charged membranes with high charge densities. In contrast to typical electric field-driven transport in negatively charged membranes, where divalent cations generally permeate faster than monovalent cations, Li + ions in our system permeate the membrane at substantially higher rates than Mg 2+ ions. This unexpected selectivity stems from the selective ion partitioning properties of the membrane and the uphill transport of Mg 2+ ions against their external concentration gradient. We demonstrate the efficacy of this separation approach through bench-scale dialysis experiments using a model Atacama brine solution, achieving efficient separation of monovalent and divalent cations. As a result, the high separation efficiency observed in this study suggests a promising approach for monovalent/divalent ion separations, offering higher selectivity compared to current technologies.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Adsorption-based membranes for air separation using transition metal oxides

In this work, we use computational modeling to examine the viability of adsorption-based pore-flow membranes for separating gases when a purely size-based separation strategy is ineffective. Using molecular dynamics simulations of O 2 and N 2 , we model permeation through a nanoporous graphene membrane. Permeation is assumed to follow a five-step adsorption-based pathway, with desorption being the rate-limiting step. Using this model, we observe increased selectivity between O 2 and N 2 , resulting from increased adsorption energy differences. We explore the limits of this strategy, providing an initial set of constraints that need to be satisfied to allow for selectivity. Finally, we provide a preliminary exploration of some transition metal oxides that appear to satisfy those conditions. Using density functional theory calculations, we confirm that these oxides possess adsorption energies needed to operate as adsorption-based pore-flow membranes. These adsorption energies provide a suitable motivation to examine adsorption-based pore-flow membranes as a viable option for air separation.

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

Increased CO 2 /N 2 selectivity of PTMSP by surface crosslinking

The surface crosslinking of poly[1-(trimethylsilyl)-1-propyne] (PTMSP) membranes by dithiothreitol under thiol–ene click reaction conditions has yielded membranes having CO 2 /N 2 selectivities in excess of 30 with CO 2 permeances in excess of 300 GPU (gas permeation units). Here, the simplicity of this surface crosslinking strategy together with these permeation results suggests that PTMSP that is modified in such ways could lead to useful materials for the separation of CO 2 /N 2 from flue gas and for certain other gaseous mixtures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Importance of hydrogen oxidation reaction current in quantifying hydrogen crossover in PEM water electrolyzers at high differential pressure

Understanding hydrogen permeation in proton exchange membrane water electrolyzers (PEMWEs) operating at high differential pressures (>25 bar) is critical towards developing effective gas recombination strategies that enable safe operation and high efficiency. Developing this understanding relies on accurate quantification of hydrogen crossover rates in water electrolyzers operating under such conditions. In this work, we show that PEMWEs operating at high differential pressures exhibit noticeable hydrogen oxidation reaction (HOR) currents. As the HOR consumes part of the permeated hydrogen at the anode, neglecting HOR currents leads to severe underestimation of the hydrogen crossover rate. We implemented a new method combining hydrogen oxidation current with online gas chromatography measurements to accurately quantify hydrogen crossover rates as a function of operating current density in PEMWEs operating at high differential pressures (10–30 bar g ).

25 ENERGY STORAGE↗
DOE OSTI2024

High Compression in Palladium Alloy Metal Foil Pumps

Metal foil pumps (MFPs) are key components in the direct internal recycling inner fuel cycle loop for the recovery of hydrogen isotopes from deuterium-tritium fusion exhaust. Operating under vacuum conditions, they utilize superthermal hydrogen as the feed gas in a process called superpermeation. A notable feature of MFPs is their ability to pump against a pressure gradient. This study examines the compression capabilities of PdAg and PdCu MFPs at low temperatures with a constant feed pressure of 10 Pa. At 75°C, compression ratios exceeding 200 were readily achieved, with downstream pressures exceeding 4500 Pa using PdCu. For both alloys, net fluxes decreased by only ~15% at downstream pressures of 1000 Pa, which offers potential simplifications for the downstream pump train. Performance declined markedly when the temperature was elevated to 200°C. Pump curves were constructed and advocated as the most appropriate manner to assess MFP performance. Separate pressure-driven-permeation experiments at relevant conditions were conducted, providing a direct measurement of the hydrogen dissociation constant $k$ d , which was found to be in good agreement with the previous literature. Further, these measurements were used to predict pump curves and maximum compression ratios by balancing superpermeation with pressure-driven permeation, achieving excellent agreement with experiment. Last, experiments using asymmetric MFPs revealed the detrimental impact that surface impurities have on performance in this system.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Effects of interlayer spacing and applied pressure on the lanthanide transport in MoS 2 -based two-dimensional channels

Rare-earth elements (REEs) are critical to modern industry but difficult to separate due to their subtle and monotonic changes in physicochemical properties. MoS 2 -based two-dimensional (2D) materials offer novel opportunities for enhancing REE separation, exhibiting a distinct volcano-shaped transport performance distribution that peaks at Sm 3+ . However, the specific contributions of thermodynamic and kinetic factors to ion transport within 2D confinement remain unclear. In this study, we conducted a series of non-equilibrium all-atom molecular dynamics (MD) simulations to explore the effects of interlayer spacing and external pressure on the transport of lanthanide ions in Å-scale acetate functionalized 2D MoS 2 (MoS 2 -COOH) channels. We examined ion entry and permeation rates, water flux, dehydration, and binding modes. The simulation results reveal that the transport trends of lanthanide ions are jointly driven by the dehydration degree and the relative-binding strengths of ions to water and to the acetate within the 2D channels. Notably, the dehydration pattern of lanthanide ions during permeation is closely linked to kinetic factors. Overall, this study provides a detailed atomistic understanding of the mechanisms underlying lanthanide ion transport under confinement. These findings point to the significant potential for tuning confinement and chemical functionalization within Å-scale channels for more efficient REE separation.

2D channels↗
DOE OSTI2021

Integrated model predictions on the impact of substrate damage on gas dynamics during ITER burning-plasma operations

Divertor design and choice of plasma-facing materials (PFM) will be essential to the success of next-generation fusion reactors as they operate under more powerful scenarios. Understanding and controlling interactions between the plasma and PFM is essential to making these choices. Within these plasma–material interactions and especially in tungsten (W), the interplay between the most abundant plasma species (hydrogen isotopes and helium, He) with the wall material alters fuel retention. However, this interplay is yet to be sufficiently understood to confidently project fuel retention levels to future fusion devices. The paper presents a series of integrated simulations of fusion plasmas and their interaction with tungsten. Specifically, this study assesses the impact of He plasma pre-exposure on hydrogenic species retention during 100 s of burning plasma operations (BPO) in ITER. Multiple pre-exposure scenarios are considered, including sub-surface damage resulting from exposures in the linear device PISCES and from early ITER He-operation. The predictions from these consecutive He-BPO exposures show that fuel content and spatial distribution in the material are largely determined by the He-induced damage, as manifest in: (i) changes in surface temperature expected during BPO have little effect on fuel retention in the presence of He-induced damage; (ii) gas content stabilizes quickly in substrates pre-exposed in PISCES, at levels set by the concentration of pre-existing vacancies, while it continues to increase in substrates initially pristine or pre-exposed to ITER He plasmas; (iii) the presence of He and He–V clusters in the near-surface region locally increases hydrogenic retention, but decreases its permeation; this results in hydrogenic species that remain closer to the surface in pre-damaged substrates, while the bulk content is higher for initially pristine cases. In summary, the interaction and binding of D and T with the pre-existing He–V clusters modifies retention and permeation of hydrogen species during ITER BPO.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗