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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Mineral Scale Formation during Crossflow Reverse Osmosis at Constant Flux and Constant Transmembrane Pressure Conditions

Mineral scale formation on membrane surfaces is a significant challenge in reverse osmosis water purification. Laboratory fouling experiments are typically run such that the transmembrane pressure (TMP) is fixed, and the permeate flux decreases over time as scales accumulate on the membrane surface. However, this change in flux means that the hydrodynamic conditions at the membrane surface are continuously changing, which could affect crystallization and foulant deposition processes. Operating under constant permeate flux conditions, in contrast, is advantageous because it keeps the hydrodynamic conditions relatively consistent, making it possible to compare how membrane properties (e.g., surface chemistry) affect fouling propensity. Industrial reverse osmosis operations are not run strictly in either constant TMP or constant flux mode; while they may start at a constant TMP, feed pressure may be periodically adjusted to maintain permeate water production within a specified range. Here, the scarcity of constant permeate flux reverse osmosis scaling experiments reported in the literature frustrates efforts to compare membrane fouling processes under constant TMP and constant flux conditions. For the first time, the evolution of the fouling layer resistance was compared as a function of cumulative permeate volume per membrane area during constant TMP and constant flux reverse osmosis filtrations. Scaling experiments were conducted by challenging commercial reverse osmosis membranes with a model feed solution nearly saturated with calcium sulfate dihydrate (gypsum). At low fluxes, the increase in fouling layer resistance was quantitatively similar for the two operational modes. In contrast, at high fluxes, the fouling layer resistance increased more rapidly in constant flux filtration than in constant TMP filtration. The mechanism of scale formation in constant TMP and constant flux operation was self-limiting and self-reinforcing, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Linking structure to performance: Characterization of porous transport layers for high-pressure water electrolysis

Proton exchange membrane (PEM) water electrolysis is a promising technology to produce cost-efficient hydrogen. PEM electrolyzers offer a large current density range and the ability to operate at differential pressure which can be used to minimize both capital and operational expenditures. However, directly producing pressurized hydrogen at the cathode results in pushing the membrane against the anode porous transport layer (PTL). This can lead to detrimental effects, such as membrane deformation or ruptures, which depend on membrane properties as well as PTL material properties such as pore size, structure, and morphology. In this work, a range of sinter and felt-based commercial PTLs are evaluated for their contributions to the cell's electrochemical and H 2 crossover performance at cathode pressures up to 30 bar. X-ray tomography and post-operando optical microscopy are used to assess the morphology of the PTLs, and the PTL induced deformation experienced by the catalyst coated membrane (CCM), respectively. PTL samples with lower porosity were found to reduce both the cell voltage and the amount of H 2 permeating from the cathode to the anode exhaust, which was ascribed to improved catalyst layer contact and reduced membrane deformation, respectively. The best performing PTLs improved electrolyzer efficiency by ~1.5 kWh/kg H2 . Specifically, 1 kWh/kg H2 was gained due to reducing membrane deformation and decreasing H 2 crossover. The remainder 0.5 kWh/kg H2 were achieved by improving the electrical contact at the electrode/PTL interface which decreased cell voltage.

08 HYDROGEN↗
DOE OSTI2025

Optimal design of power constrained bipolar membrane electrodialysis over a wide brine range

Bipolar membrane electrodialysis enables the in-situ production of high value products (e.g., acid and base) from clean brine, which is essential for a sustainable future. A technoeconomic assessment (TEA) was conducted on extraction of value from brine using the WaterTAP framework to identify optimal cost across a wide design space. Here, in the power constrained regime, increasing supplied salt concentration does not necessarily result in reduced cost or increased NaOH concentration. A detailed analysis elucidates the critical roles of water dissociation, limiting currents, and sodium diffusion play in shaping the landscape of levelized cost. Among these, water splitting predominantly influences the TEA outcomes across most of the optimal design space. Sensitivity analysis further demonstrates that membrane properties controlling water dissociation significantly impact the unit cost. The results indicate that innovations targeting improvements in water disassociation should be prioritised to effectively reduce the levelized cost of product production.

Bipolar membrane electrodialysis↗
NASA NTRS1985

A 4-node Bilinear Isoparametric Element in Rockwell NASTRAN

The development and evaluation of the Rockwell NASTRAN four node quadrilateral (QUAD4) element is presented. The element derivation utilizes bilinear isoparametric techniques both for membrane and bending characteristics. The QUAD4 element coordinate system, membrane properties, lumped mass matrix, and treatment of warping are based upon the COSMIC/NASTRAN QDMEMI element while the bending characteristics are based on a paper by T. J. R. Hughes. The effects of warping on the bending stiffness, consistent mass, and geometric stiffness are based upon a paper by R. H. MacNeal. Numerical integration is accomplished by Gaussian quadrature on a 2 x 2 grid. Practical user support features include variable element thickness, thermal analysis and layered composite material definitions.

Liao, C.↗
NASA NTRS2002

Cellular and Network Mechanisms Underlying Information Processing in a Simple Sensory System

Realistic, biophysically-based compartmental models were constructed of several primary sensory interneurons in the cricket cercal sensory system. A dynamic atlas of the afferent input to these cells was used to set spatio-temporal parameters for the simulated stimulus-dependent synaptic inputs. We examined the roles of dendritic morphology, passive membrane properties, and active conductances on the frequency tuning of the neurons. The sensitivity of narrow-band low pass interneurons could be explained entirely by the electronic structure of the dendritic arbors and the dynamic sensitivity of the SIZ. The dynamic characteristics of interneurons with higher frequency sensitivity required models with voltage-dependent dendritic conductances.

Jacobs, Gwen↗
NASA NTRS2005

SOLAR SAIL PROPULSION SENSITIVITY TO MEMBRANE SHAPE AND OPTICAL PROPERTIES USING THE SOLAR VECTORING EVALUATION TOOL (SVET)

Solar sail propulsive performance is dependent on sail membrane optical properties and on sail membrane shape. Assumptions of an ideal sail (flat, perfect reflector) can result in errors which can affect spacecraft control, trajectory analyses, and overall evaluation of solar sail performance. A MATLAB(R) program has been developed to generate sail shape point cloud files for two square-architecture solar sail designs. Simple parabolic profiles are assumed for sail shape under solar pressure loading. These files are then input into the Solar Vectoring Evaluation Tool (SVET) software to determine the propulsive force vector, center of pressure, and moments about the sail body axes as a function of sail shape and optical properties. Also, the impact of the center-line angle, due to non-perfect optical properties, is addressed since this constrains sail force vector cone angle and is often overlooked when assuming ideal-reflector membranes. Preliminary sensitivity analysis using these tools aids in determining the key geometric and optical parameters that drive solar sail propulsive performance.

Ewing, Anthony↗
DOE OSTI2025

Insights into determining pore size properties of ultrafiltration membranes

The selectivity of porous membranes is often characterized using solute rejection tests, where membranes are challenged with dilute aqueous solutions of neutral solutes at operating conditions that minimize concentration polarization and fouling. In single solute tests, a membrane is challenged with one molecular weight (MW) solute at a time from low to high MW. Since single solute methods are time-intensive, mixed solute tests have become more common, where a mixture of several MW solutes challenges a membrane at once. However, the presence of large solutes in a mixture increases the rejection of smaller solutes. Furthermore, there are no universally accepted operating conditions or standard methods used by membrane manufacturers or researchers for the experiments, leading to difficulty in pore size and pore characteristic comparisons. In this paper, commercial ultrafiltration membranes were challenged with single and mixed solute polyethylene glycol (PEG) and dextran aqueous solutions. First, rejection values determined using total organic carbon (TOC) and high-performance liquid chromatography (HPLC) from single solute filtration experiments are compared. Differences in rejection curves obtained by the two techniques are attributed to solute polydispersity. Mixed solute filtration experiments with binary mixtures of solutes showcased co-solute interactions, which increase with both the size and weight percent of large solute in the mixture. Mixed solute filtration experiments at varying operating conditions (i.e., stir speed and flux) were conducted to determine operating conditions that mitigate co-solute interactions. Stir speed had a minimal effect on co-solute interactions. In contrast, low flux conditions can help minimize co-solute interactions, leading to pore size distributions that closely resemble results observed in single solute filtration using narrowly dispersed solutes. Additionally, at low flux conditions, the predicted membrane pore size distributions utilizing mixed solute experiments with PEG and dextran were similar.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Bipolar Membranes Electrodialysis for Water Purification and Resource Recovery

Reverse osmosis concentrate (ROC) from inland brackish water desalination and wastewater recycling presents moderate salinity, posing significant challenges for treatment and disposal. Existing treatment technologies predominantly rely on energy-intensive thermal methods, large-area evaporation strategies, or deep-well disposal, which often result in the loss of water value. Electrified membrane brine treatment offers a promising alternative by utilizing renewable energy sources, enabling complete water recycling. This work proposes the development of next-generation bipolar membrane electrodialysis (BMED) systems capable of desalinating brine while simultaneously recovering valuable resources. However, several critical challenges remain in the areas of membrane engineering for BMED. These include: 1) decreased current efficiency during desalination due to the low conductivity of feed chambers, 2) fouling and scaling from multivalent ions and contaminants in the feed, and 3) the retention and carryover of ROC contaminants, including PFAS compounds. Our research focuses on the development of novel anion exchange membranes (AEMs) and cation exchange membranes (CEMs) based on synthesized multiblock copolymers. We investigate the effects of block length, ion exchange capacity (IEC), and polymer backbone structure on cation and anion transport (e.g., Na+, Cl-, OH-, H+) for both our synthesized membranes and commercial membranes. Fundamental properties of these membranes, such as water uptake, IEC, and ionic conductivity, are also evaluated to optimize performance for BMED applications.

08 HYDROGEN↗
NASA NTRS1984

Rationale for two phase polymer system microgravity separation experiments

The two-phase systems that result when aqueous solutions of dextran and poly(ethylene glycol) are mixed at concentrations above a few percent are discussed. They provide useful media for the partition and isolation of macromolecules and cell subpopulations. By manipulating their composition, separations based on a variety of molecular and surface properties are achieved, including membrane hydrophobic properties, cell surface charge, and membrane antigenicity. Work on the mechanism of cell partition shows there is a randomizing, nonthermal energy present which reduces separation resolution. This stochastic energy is probably associated with hydrodynamic interactions present during separation. Because such factors should be markedly reduced in microgravity, a series of shuttle experiments to indicate approaches to increasing the resolution of the procedure are planned.

Brooks, D. E.↗
NASA NTRS1972

The effect of membrane parameters on the properties of the nerve impulse.

The effect of varying some membrane parameters is explored, basing the investigation on computer simulation of the Hodgkin-Huxley equations for the squid giant axon, including variations in the membrane capacitance, conductances, and the rate constants. It is shown that by reducing the degree of regeneration in the excitable membrane, the character of the nerve signal can be smoothly changed from that of the axonal spike to essentially electrotonic spread, with all gradations in between. The reduction in the degree of regeneration can most simply be brought about by a decrease in the density of active membrane patches.

Sabah, N. H.↗
NASA NTRS1987

Electrochemical performance and transport properties of a Nafion membrane in a hydrogen-bromine cell environment

The overall energy conversion efficiency of a hydrogen-bromine energy storage system is highly dependent upon the characteristics and performance of the ion-exchange membrane utilized as a half-cell separator. The electrochemical performance and transport properties of a duPont Nafion membrane in an aqueous HBr-Br2 environment were investigated. Membrane conductivity data are presented as a function of HBr concentration and temperature for the determination of ohmic voltage losses across the membrane in an operational cell. Diffusion-controlled bromine permeation rates and permeabilities are presented as functions of solution composition and temperature. Relationships between the degree of membrane hydration and the membrane transport characteristics are discussed. The solution chemistry of an operational hydrogen-bromine cell undergoing charge from 45% HBr to 5% HBr is discussed, and, based upon the experimentally observed bromine permeation behavior, predicted cell coulombic losses due to bromine diffusion through the membrane are presented as a function of the cell state-of-charge.

Baldwin, Richard S.↗
NASA NTRS1971

The properties of an ion selective enzymatic asymmetric synthetic membrane.

With the aid of a simple model membrane system, the properties of cellulose enzymes and of membrane selectivity and pump-like action are considered. The model is based on materials possibly present on a primitive earth, as well as on a membrane able to sort or concentrate these materials. An overview of the model membrane system is presented in terms of how it is constructed, what its properties are, and what to expect in performance characteristics. The model system is shown to be useful for studying the selective and in some cases accelerated transfer of nutrients and metabolites.

Mitz, M. A.↗
NASA NTRS2014

Towards Co-evolution of Membrane Transport and Metabolism

Protocellular boundaries were inextricably connected to the metabolism they encapsulated: to be inheritable, early metabolism must have led to an increased rate of growth and division of vesicles and, similarly, transport through vesicle boundaries must have supported the evolution of metabolism. Even though explaining how this coupling emerged and evolved in the absence of the complex machinery of modern cells is one of the key issues in studies on the origin of life, little is known about the biochemical and biophysical processes that might have been involved. This gap in our knowledge is a major impediment in efforts to construct scenarios for the origin of life and laboratory models of protocells. A combination of experimental and computational studies carried out by us and our collaborators is aimed at helping to close this gap. Properties of membranes might have contributed to the selection of RNA as an early biopolymer. A kinetic mechanism was proposed (Sacerdote & Szostak, 2005) in which ribose was supplied more quickly than other aldopentoses to primordial cells for preferential incorporation of ribonucleotides into nucleic acids. This proposal is based on a finding that ribose permeates membranes an order of magnitude faster than its diastereomers, arabinose and xylose. Our computer simulations, which yield permeation rates in excellent agreement with experiment, and kinetic modeling explain this phenomenon in terms of inter- and intramolecular interactions involving exocyclic hydroxyl groups attached to carbon atoms of the pyranose ring (Wei and Pohorille, 2009). They also constrain scenarios for the formation of the earliest nucleic acids (Wei and Pohorille, 2013). In one scenario, sugars permeate protocellular walls and subsequently are used to synthesize nucleic acids inside protocells. As long as this process proceeds at the rate faster than 6x10(exp -3)/s, ribose derivatives will be available for synthesis easier than their diastereomers. If nucleosides or their activated derivatives are synthesized outside protocells and subsequently transported across protocellular membranes the kinetic mechanism does not apply because all diastereomers, which have their sugars in the furanose rather than pyranose form, permeate the membrane at approximately the same rate. Properties of membranes might have been also coupled to metabolism involving peptides. Recently, Adamala and Szostak (2013) have shown that a dipeptide inside fatty-acid vesicles catalyzes the formation of another dipeptide that binds to vesicle walls and, by doing so, promotes their growth at the expense of other vesicles. This coupling of metabolism, permeability of vesicles and their growth is the first demonstration of evolutionary advantage imparted by small, membrane-bound peptides. Building on this work we have calculated the rate at which different blocked amino acids are delivered to a protocell for synthesis of dipeptides. We have further shown that the dipeptides are located at the water-membrane interface rather than in the center of the bilayer. On these basis it is anticipated that other dipeptides containing aromatic, but not necessarily hydrophobic amino acids (e.g. tyrosine) could have the same catalytic effects. Insight from these studies allows for estimating the rate of vesicle growth and the rates of dipeptide synthesis required to keep the system in balance. These results, in combination with our earlier studies, lead to a general scenario for evolution from membrane-bound dipeptides to ion channels in the origin of life.

Metabolism↗
NASA NTRS2002

Protein Solvation in Membranes and at Water-Membrane Interfaces

Different salvation properties of water and membranes mediate a host of biologically important processes, such as folding, insertion into a lipid bilayer, associations and functions of membrane proteins. These processes will be discussed in several examples involving synthetic and natural peptides. In particular, a mechanism by which a helical peptide becomes inserted into a model membrane will be described. Further, the molecular mechanism of recognition and association of protein helical segments in membranes will be discussed. These processes are crucial for proper functioning of a cell. A membrane-spanning domain of glycophorin A, which exists as a helical dimer, serves as the model system. For this system, the free energy of dissociation of the helices is being determined for both the wild type and a mutant, in which dimerization is disrupted.

Pohorille, Andrew↗