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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Finely tunable dynamical coloration using bicontinuous micrometer-domains

Nanostructures similar to those found in the vividly blue wings of Morpho butterflies and colorful photonic crystals enable structural color through constructive interference of light waves. Different from commonly studied structure-colored materials using periodic structures to manipulate optical properties, we report a previously unrecognized approach to precisely control the structural color and light transmission via a novel photonic colloidal gel without long-range order. Nanoparticles in this gel form micrometer-sized bicontinuous domains driven by the microphase separation of binary solvents. This approach enables dynamic coloration with a precise wavelength selectivity over a broad range of wavelengths extended well beyond the visible light that is not achievable with traditional methods. The dynamic wavelength selectivity is thermally tunable, reversible, and the material fabrication is easily scalable.

42 ENGINEERING↗
DOE OSTI2022

Matrimid substrates with bicontinuous surface and macrovoids in the bulk: A nearly ideal substrate for composite membranes in CO 2 capture

Scalable fabrication of thin-film composite (TFC) membrane for post-combustion carbon capture is often limited by the availability of high-performance nanoporous substrate. Ideally, the substrate should allow for fast gas transport at the selective layer/substrate interface as well as in the bulk of the substrate. In this study, highly permeable Matrimid substrates were prepared via vapor- and nonsolvent-induced phase separations. The phase separation mechanism of the Matrimid®/N-methyl-2-pyrrolidone casting solution was modulated by the addition of LiCl to control the solution thermodynamic stability, and nanoporous Matrimid substrates were formed with a bicontinuous surface and macrovoids in the bulk. This hierarchically optimized structure resulted in a CO 2 permeance of 2.60 × 10 5 GPU (1 GPU = 1 × 10 –6 cm 3 (STP) cm –2 s –1 cmHg –1 = 3.349 × 10 –10 mol m –2 s –1 Pa –1 ), which was ca. 11 times more permeable than a benchmark polyethersulfone substrate with cellular pores. The benefit of using this new substrate was demonstrated by coating a 170-nm amine-containing polymer to form a TFC facilitated transport membrane. The membrane exhibited a CO 2 permeance of 932 GPU at 57°C, which was 72 GPU higher than the counterpart coated on the benchmark substrate. Meanwhile, the CO 2 /N 2 selectivity was remained at 158. This permeance improvement could be well explained by the resistance-in-series model, where the improved permeance was attributed to the reductions in substrate and lateral diffusion mass transfer resistances. The upper bound (UB) analysis indicates that the Matrimid substrate is nearly ideal for the state-of-the-art polymers for CO 2 /N 2 separation. Here, the substrate improvement could also reduce the parasitic energy associated with the membrane process due to the reduced membrane cost and flue gas compression requirement.

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

Phase Behavior of Charged Star Block Copolymers at Fluids Interface

The phase behavior of block copolymers (BCPs) at the water-oil interface is influenced by the segmental interaction parameter (χ) and chain architecture. We synthesized a series of star block copolymers (s-BCPs) having polystyrene (PS) as core and poly(2-vinylpyridine) (P2VP) as corona. The interaction parameters of block-block (χ PS-P2VP ) and block-solvent (χ P2VP-solvent ) were varied by adjusting the pH of the aqueous solution. Lowering pH increased the fraction of quaternized-P2VP (Q-P2VP) with enhanced hydrophilicity. By transferring the equilibrated interfacial assemblies, morphologies ranging from bicontinuous films at pH of 7 and 3.1 to nanoporous and nanotubular structure at pH of 0.65 were observed. The nanoporous films formed hexagonally packed pores in s-BCP matrix, while nanotubes comprised Q-P2VP as corona and PS as core. Control over pore size, d-spacing between pores, and nanotube diameters was achieved by varying polymer concentration, molecular weight, volume fraction and arm number of s-BCPs. Large-scale nanoporous films were obtained by freeze-drying emulsions. Remarkably, the morphologies of linear BCPs were inverted, forming hexagonal-packed rigid spherical micelles with Q-P2VP as core and PS as corona in multilayer. Here, this work provides insights of phase behaviors of BCP at fluids interface and offer a facile approach to prepare nanoporous film with well-controlled pore structure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Tailorable Micelle Morphology in Self-Assembling Block Copolymer Gels for Templating Nanoporous Ceramics

The self-assembly of block copolymers offers opportunities for the facile organization and templating of inorganic nanomaterials. Here, we describe a morphology map for a poly(methyl methacrylate)-b-poly(n-butyl acrylate)-b-poly(methyl methacrylate) (PMMA-b-PnBA-b-PMMA) block copolymer/polycarbosilane system that allows for tunable control over nanoscale micelle geometry via manipulation of the preceramic polymer content. We produced gels with spherical, wormlike, and bicontinuous morphologies, which were processed to create silicon carbide-based ceramic structures with tunable nanoscale porosities. The role of the constituent polymers in influencing the structure and rheology of this system is discussed. The PMMA-b-PnBA-b-PMMA block copolymer/preceramic polymer system offers a number of advantages including: (i) commercial availability, (ii) rapid self-assembly kinetics, and (iii) successful conversion of the self-assembled nanostructure to ceramic via pyrolysis. Finally, this system may be useful for catalytic, structural, or thermal applications in both industrial and academic settings because of its ease of use and relatively inexpensive reagents.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Viscoelastic relaxation and topological fluctuations in glass-forming liquids

In this study, a method for characterizing the topological fluctuations in liquids is proposed. This approach exploits the concept of the weighted gyration tensor of a collection of particles and permits the definition of a local configurational unit (LCU). The first principal axis of the gyration tensor serves as the director of the LCU, which can be tracked and analyzed by molecular dynamics simulations. Analysis of moderately supercooled Kob–Andersen mixtures suggests that orientational relaxation of the LCU closely follows viscoelastic relaxation and exhibits a two-stage behavior. The slow relaxing component of the LCU corresponds to the structural, Maxwellian mechanical relaxation. Additionally, it is found that the mean curvature of the LCUs is approximately zero at the Maxwell relaxation time with the Gaussian curvature being negative. This observation implies that structural relaxation occurs when the configurationally stable and destabilized regions interpenetrate each other in a bicontinuous manner. Finally, the mean and Gaussian curvatures of the LCUs can serve as reduced variables for the shear stress correlation, providing a compelling proof of the close connection between viscoelastic relaxation and topological fluctuations in glass-forming liquids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Design nanoporous metal thin films via solid state interfacial dealloying

Thin-film solid-state interfacial dealloying (thin-film SSID) is an emerging technique to design nanoarchitecture thin films. The resulting controllable 3D bicontinuous nanostructure is promising for a range of applications including catalysis, sensing, and energy storage. Using a multiscale microscopy approach, we combine X-ray and electron nano-tomography to demonstrate that besides dense bicontinuous nanocomposites, thin-film SSID can create a very fine (5–15 nm) nanoporous structure. Not only is such a fine feature among one of the finest fabrications by metal-agent dealloying, but a multilayer thin-film design enables creating nanoporous films on a wider range of substrates for functional applications. Through multimodal synchrotron diffraction and spectroscopy analysis with which the materials’ chemical and structural evolution in this novel approach is characterized in details, we further deduce that the contribution of change in entropy should be considered to explain the phase evolution in metal-agent dealloying, in addition to the commonly used enthalpy term in prior studies. Here, the discussion is an important step leading towards better explaining the underlying design principles for controllable 3D nanoarchitecture, as well as exploring a wider range of elemental and substrate selections for new applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Three-dimensional hierarchical nanoporous copper via direct ink writing and dealloying

Three-dimensional (3D) hierarchical nanoporous Cu (3DHNP-Cu) is synthesized using a combination of direct ink writing (DIW) based 3D printing, thermal sintering, and chemical dealloying of Mn–Cu alloys. Through tuning processing conditions such as ink composition and cooling rate (after sintering), with consideration of Mn loss during sintering, 3DHNP-Cu with fully bicontinuous nanostructures and negligible residual Mn can be produced after dealloying. The 3DHNP-Cu is comprised of structural features that span seven orders of magnitude, where DIW digitally controls macroscale porous features, thermal sintering and degradation of the binding polymer determines microscale porous features, and dealloying gives rise to nanoscale pores.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Structuring, stochastic behavior, and charge storage capacity of redox-active microemulsions formulated with mixtures of toluene and ionic liquid as oil phase

Oil/water microemulsions (µEs) are promising electrolytes for redox flow batteries (RFBs) as they simultaneously improve charge capacity and ionic conductivity. Here, we report the successful formulation of bicontinuous µEs where the oil phase is a solution of trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide ionic liquid in toluene with redox-active ferrocene. We examined the effect of supporting electrolyte anion (NO 3 – , Cl – , ClO 4 – ) on the structure, reactivity, transport, and electrolytic performance of redox-active µEs. Neutron scattering and nuclear magnetic resonance showed that the domain size increased as Cl – > NO 3 – > ClO 4 – while the ferrocene diffusion coefficient increased as NO 3 – > Cl – > ClO 4 – . Scanning electrochemical microscopy indicated anion-dependent current fluctuations during electrolysis, with ClO 4 – exhibiting the least high-frequency oscillations, which correlate to the highest charge and discharge capacity and reversibility. All ionic liquid containing systems improved the performance of toluene-based µEs, highlighting new design principles for these electrolytes.

diffusion↗
DOE OSTI2024

Impact of surface hydrophilicity on the ordering and transport properties of bicontinuous microemulsions

Microemulsions (MEs) have many industrial applications, where recent developments have shown that MEs can be utilized for electrochemical applications, including potentially in redox flow batteries. However, understanding the structure and dynamics of these systems, including at a surface, is needed to direct and rationally control their electrochemical behavior. While bulk solution measurements have provided insight into their structure, their assembly at an interface also impacts the electron (to the electrode) and ion (across the surfactant) charge transfer processes in the system. To address this shortcoming, neutron reflectivity experiments and molecular simulations have been completed that document the near surface structure of a series of deuterated water (D 2 O)/polysorbate-20/toluene MEs on hydrophilic and amphiphilic surfaces. These results show that the microemulsions form complex layered structures near a hard electrode surface, where most layers are not purely one component. Decreasing the D 2 O concentration in the ME increases the number of and purity of the layers established on the solid surface. These lamellar-type layers transition from the surface to the bulk microemulsion as a series of mixed layers (i.e., containing oil, water, and surfactant) that are consistent with perforated lamellae. Additionally, these mixed lamellae appear to become more perforated with oil and water pathways on an amphiphilic surface. Furthermore, the purity and thickness of these layers will influence the accessibility of an electrode by redox active species, as well as ion transport required to satisfy the electroneutrality condition.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

CHAPTER 9. Bijels the Easy Way

Spinodal decomposition is not the only way to make a bijel. Indeed, while spinodal decomposition produces structures with a potentially useful morphology, it can be challenging to make bijels using this method and the resulting systems can be hard to process and manipulate. Furthermore, exploiting the functional properties of the assembled particle monolayer is extremely challenging. Here, we show how the assembly of nanoparticle surfactants at the liquid–liquid interface can be used to kinetically trap liquids into a wealth of complex structures without using spinodal decomposition. We apply liquid three-dimensional printing and moulding methods, along with patterned substrates with controllable wetting properties, to build all-liquid devices with applications in chemical synthesis, separation, and purification. The functional properties of the assembled nanomaterials can be exploited to produce interfacially structured liquids that are plasmonically and magnetically responsive. Finally, we conclude by arguing that, while the field shows great promise, efforts need to be made to translate liquid bicontinuous systems out of the laboratory and into meaningful, real-world applications, as well applications in more ‘exotic’ disciplines, such as synthetic biology.

36 MATERIALS SCIENCE↗
DOE OSTI2024

N and OH-Immobilized Cu 3 Clusters In Situ Reconstructed from Single-Metal Sites for Efficient CO 2 Electromethanation in Bicontinuous Mesochannels

Cu-based catalysts hold promise for electrifying CO 2 to produce methane, an extensively used fuel. However, the activity and selectivity remain insufficient due to the lack of catalyst design principles to steer complex CO 2 reduction pathways. Herein, we develop a concept to design carbon-supported Cu catalysts by regulating Cu active sites’ atomic-scale structures and engineering the carbon support’s mesoscale architecture. This aims to provide a favorable local reaction microenvironment for a selective CO 2 reduction pathway to methane. In situ X-ray absorption and Raman spectroscopy analyses reveal the dynamic reconstruction of nitrogen and hydroxyl-immobilized Cu 3 (N,OH-Cu 3 ) clusters derived from atomically dispersed Cu–N 3 sites under realistic CO 2 reduction conditions. The N,OH-Cu 3 sites possess moderate *CO adsorption affinity and a low barrier for *CO hydrogenation, enabling intrinsically selective CO 2 -to-CH 4 reduction compared to the C–C coupling with a high energy barrier. Importantly, a block copolymer-derived carbon fiber support with interconnected mesopores is constructed. The unique long-range mesochannels offer an H 2 O-deficient microenvironment and prolong the transport path for the CO intermediate, which could suppress the hydrogen evolution reaction and favor deep CO 2 reduction toward methane formation. Thus, the newly developed catalyst consisting of in situ constructed N,OH-Cu 3 active sites embedded into bicontinuous carbon mesochannels achieved an unprecedented Faradaic efficiency of 74.2% for the CO 2 reduction to methane at an industry-level current density of 300 mA cm –2 . In conclusion, this work explores effective concepts for steering desirable reaction pathways in complex interfacial catalytic systems via modulating active site structures at the atomic level and engineering pore architectures of supports on the mesoscale to create favorable microenvironments.

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

Heterogeneous Morphologies and Hardness of Co-Sputtered Thin Films of Concentrated Cu-Mo-W Alloys

Heterogeneous microstructures in Cu-Mo-W alloy thin films formed by magnetron co-sputtering immiscible elements with concentrated compositions are characterized using scanning transmission electron microscopy (STEM) and nanoindentation. In this work, we modified the phase separated structure of a Cu-Mo immiscible system by adding W, which impedes surface diffusion during film growth. The heterogeneous microstructures in the Cu-Mo-W ternary system exhibited bicontinuous matrices and agglomerates composed of Mo(W)-rich phase. This is unique, as these are the slower-diffusing species, contrasting past reports of binary Cu-Mo thin films that exhibited Cu-rich agglomerates. The bicontinuous matrices comprised of Cu-rich and Mo(W)-rich phases exhibited bilayer thicknesses of less than 5 nm. The hardness of these thin films measured using nanoindentation is reported and compared to similar multilayers and nanocomposites in binary systems.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Metal-ion-controlled growth and nanoindentation response of 3D, bicontinuous Cu–Fe thin films

Bicontinuous, nanocomposite thin film morphologies depend largely on the deposition conditions applied during physical vapor deposition. With the introduction of high power impulse magnetron sputtering (HiPIMS), the range of potential morphologies achieved during deposition has been increased. In this work, we compare the deposition outcomes between traditional direct-current magnetron sputtering (DCMS) and HiPIMS for a thin film co deposit of Cu and Fe. Modular control of the columnarity, porosity and roughness was achieved by varying the Cu and Fe metal ion currents during deposition. The directionality of the nanostructured phase-separated morphology was also controlled as the ion current increased. At zero ion current for both Cu and Fe sputtered species during DCMS, the film exhibited lateral concentration modulations of Cu and Fe. The directionality of the Cu- and Fe-rich phases shifted to vertical concentration modulations at low ion currents of I Fe = 1A and I Cu = 0:1A and to lateral concentration modulations at relatively moderate ion currents of I Fe = 5A and I Cu = 2A: At high ion currents of I Fe = 18A and I Cu = 2A; a more randomized phase domain structure was observed on the nanoscale. This structural shift is rationalized using an interdiffusion model. Here, the role of different kinds of phase separated morphologies, achieved during DCMS deposition, on the mechanical properties has also been studied. Results indicated increase in hardness, indentation modulus and flow strength values with the increase in indentation strain rates. Bicontinuous Cu-Fe nanocomposites are found to be stronger than multilayer Cu-Fe samples.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Structural Heterogeneity and Hydrodynamics of an Intrinsically Disordered Protein Condensate

Biology demonstrates precise control over the free-energy landscape through the selective partitioning of biomacromolecules into membraneless organelles, enabling essential functions such as biochemical transformations, signaling cascades, and mechanical reinforcement. Although the function of these condensates depends on their underlying structure and hydrodynamics, molecular-scale information on these systems remains sparse. Here, in this study, neutron scattering is used to probe the organization and dynamics of the intrinsically disordered N-terminal domain of Galectin-3, an extracellular lectin responsible for facilitating liquid–liquid phase separation on the cellular surface, in both dilute and condensed phases. Dilute solutions contain isolated protein chains in equilibrium with mesoscopic clusters, whereas the condensed phase adopts a bicontinuous, microemulsion-like morphology. The dilute phase behavior is quantitatively described by coarse-grained polymer models from soft-matter physics, demonstrating their predictive power for complex biological proteins. At elevated concentrations, the proteins self-assemble akin to block copolymers, microphase separating through the aggregation of hydrophobic domains along the protein contour. The resulting condensate remains fluid-like despite a 25-fold increase in concentration; its internal hydrodynamics slow by only a factor of 3 relative to dilute protein chains. These results provide a molecular-level framework for how disordered proteins achieve both the structural complexity and dynamic fluidity of biomolecular condensates.

Carrick, Brian R. [Massachusetts Inst. of Technolo↗
DOE OSTI2024

3D Printed Nanoporous Separators Based on Polymerization-Induced Phase Separation for Fast-Charging, High Cycling Stability Li-Ion Batteries

Fast charging and stable lithium-ion batteries (LIBs) require prompt Li ion transport between electrodes. 3D porous separators can potentially improve ion transport at both the microscale and macroscale levels. Additive manufacturing (AM) is an ideal tool to produce and study 3D porous separators of LIBs, although little work has been reported in this area. Here, we demonstrate porous structural control in layer-by-layer printed hexanediol diacrylate (HDDA) separators using a projection micro stereolithography (PμSL) AM technology and present their corresponding battery performance in lithium nickel manganese cobalt oxide (NMC)/graphite full cells. The composition of photocurable resin determines the porous morphology (e.g., bicontinuous and droplet-like), while the settings of printing layer thickness and number of exposures can be used to adjust the porosity (e.g., from 27% to 63%). Optimal resin and print conditions are determined, and the resulting separator exhibits superior Li ion conductivity and therefore higher rate performance and longer cycling life. Compared with a Celgard 2325 separator, the optimized porous HDDA separator increases the 10C-rate capacity by 34% and decreases the capacity degradation rate at the 1C-rate by 4.9%. In conclusion, this work paves the way for future AM of 3D separators for high-energy, high-power, and long-cycling-life LIBs.

25 ENERGY STORAGE↗
DOE OSTI2025

Uncovering the re-distribution mechanism of Ni in a de-alloyed Ni-Cr alloy in molten fluorinated salts

A mechanism of Ni redeposition during dealloying corrosion of Ni-Cr is investigated. A model Ni20Cr (wt%) metal alloy was exposed to molten LiF-NaF-KF eutectic (FLiNaK) at 600 °C and at an applied potential of +2.1 VK+/K, above the critical potential for onset of dealloying. Upon extended exposure times (up to 12 h), prominent salt-filled corrosion channels emerge along grain boundaries. A unique grain boundary corrosion mechanism, with respect to the exposed faces of the grains, a central focus of this investigation, is intrinsically connected to the formation of high purity Ni-rich de-alloyed regions within the salt-filled channel. We implement microscale techniques such as energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) to uncover morphological and compositional variations in relevance to the formation of bicontinuous porosity from corrosion dealloying. To rationalize our findings, a phase-field model is developed and discovers a mechanism in which dissolved Ni from one grain can be redeposited on an adjacent grain at a given difference in interfacial energies. The interaction of chemical and structural factors at the grain boundaries plays a central role in elucidating the dynamics of this phenomenon and its implications towards corrosion.

Mills, Sean H↗
DOE OSTI2021

Simulation of polymerization induced phase separation in model thermosets

Polymerization induced phase separation (PIPS) in a three component thermoset is studied using molecular dynamics simulations of a new coarse-grained thermoset model. The system includes two crosslinker molecules, which differ in their glass transition temperatures (T g ) and chain length and thus have the potential for phase separation. Here, one crosslinker has a high T g corresponding to a rubbery behavior, and simulations were performed for a short length (4 beads) and a long length (33 beads). The resin and other crosslinker have low T g . A coarse-grained model is developed with these features and with interaction parameters determined so that for either rubbery crosslinker length, the system is in the liquid state at the cure temperature. For sufficiently slow reaction rates, the long rubbery molecule exhibits PIPS into a bicontinuous array of nanoscale domains, but the short one does not, reproducing recent experimental results. The simulations demonstrate that the reaction rates must be slow enough to allow diffusion to yield phase separation. Particularly, the reaction rate corresponding to the secondary amine must be very slow, else the structure of crosslinked clusters and the substantially increased diffusion time will prevent PIPS.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Evolution of single gyroid photonic crystals in bird feathers

Vivid, saturated structural colors are conspicuous and important features of many animals. A rich diversity of three-dimensional periodic photonic nanostructures is found in the chitinaceous exoskeletons of invertebrates. Three-dimensional photonic nanostructures have been described in bird feathers, but they are typically quasi-ordered. Here, we report bicontinuous single gyroid β-keratin and air photonic crystal networks in the feather barbs of blue-winged leafbirds ( Chloropsis cochinchinensis sensu lato ), which have evolved from ancestral quasi-ordered channel-type nanostructures. Self-assembled avian photonic crystals may serve as inspiration for multifunctional applications, as they suggest efficient, alternative routes to single gyroid synthesis at optical length scales, which has been experimentally elusive.

59 BASIC BIOLOGICAL SCIENCES↗