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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Interconnected Nanoporous Polysulfone by the Self-Assembly of Randomly Linked Copolymer Networks and Linear Multiblocks

Porous materials have attracted considerable attention due to their versatile applications, especially in water purification. Interconnected nanoporous structures are distinguished by their high degree of porosity and resistance to clogging, as well as their insensitivity to nanostructural orientation. Previous works on randomly linked copolymer systems have shown that they can effectively produce disordered cocontinuous nanostructures, which upon removal of one component yield interconnected nanoporous materials. However, the cocontinuous nanomaterials previously developed using polystyrene (PS) and poly(d,l-lactic acid) (PLA) strands, and the resulting interconnected nanoporous PS monoliths, were far too brittle to enable practical use as membranes. Here, we study the self-assembly of randomly linked copolymer networks prepared using blocks of the engineering polymer polysulfone (PSU). A wide cocontinuous regime (spanning 40 wt %) was found for randomly end-linked copolymer networks (RECNs) constructed from PSU and PLA strands, via a combination of mechanical testing, gravimetry, small-angle X-ray scattering, and scanning electron microscopy. The PSU/PLA cocontinuous nanomaterial with symmetric composition showed 2.4 times higher Young’s modulus and ~100 times greater toughness than the corresponding PS/PLA sample. The interconnected nanoporous PSU fabricated after etching of PLA even exhibited 1.6 times greater toughness than PS/PLA prior to PLA removal. To facilitate the production of thin films of cocontinuous nanomaterials, we applied solution-processable randomly linked linear PSU/PLA multiblock polymers onto ultrafiltration membranes. Here, the interconnected nanoporous PSU thin film generated by etching PLA was found to effectively reject 50 nm diameter particles without significantly compromising permeability. This discovery presents a valuable addition to the existing techniques used to fabricate PSU membranes. In contrast to traditional methods, which are sensitive to processing conditions, produce a wide range of pore sizes, and offer limited adjustability of pore size, the current technique is anticipated to enable interconnected PSU membranes with more uniform and tailorable porosity.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Self-Assembling Microgrids for Resilient Distribution Systems of the Future: Implementation in a Commercial DERMS Platform

Microgrids have long provided resilience to critical facilities such as hospitals and military installations, and they are now increasingly being looked at as a building block for future grids to support the energy resilience needs of the grid of the future. State-of-the-art technologies, such as blackstart algorithms using renewable distributed energy resources (DERs) to effectively and seamlessly form microgrids, have been produced by national labs over the years. Their adoption by the utility industry would be critical to reap the most benefits toward energy and climate resilience, and the pathway is via commercialization of these self-assembling microgrid algorithms by integrating them in a commercial product platform. This project brings a national labs team (LLNL, LANL) together with a vendor (Smarter Grid Solutions) to perform proof-of-concept integration of the algorithms into the vendor’s commercial Distributed Energy Resources Management System (DERMS). The project provides a strong pathway to commercialization of the algorithms thereby promoting adoption of resilient microgrid technology by utilities to offer resilience benefits to all customers and especially to disadvantaged and underserved communities.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2020

Giant Domain Wall Conductivity in Self‐Assembled BiFeO 3 Nanocrystals

Abstract Ever‐increasing demand on electronic devices with ultrahigh‐density non‐volatile data storage has attracted great interest in novel ferroelectric memories based on conductive ferroelectric domain walls. Embedded in an insulating material, ferroelectric domain walls have the capability of being (re)created, displaced, erased, and altered in their spatial configurations and electronic characteristics. However, the domain wall conductivities are in most cases not yet sufficiently high to ensure the current density required to drive read‐out circuits operating at high speeds. In this work, a giant domain wall current (>10 µA) of a single charged domain wall is obtained through conductive atomic force microscopy with a bias field of 4 V. This is achieved in self‐assembled BiFeO 3 nanocrystals grown by sol‐gel method on Nb‐doped SrTiO 3 substrates. Local configurations of domains and domain wall types are studied using vector piezoresponse force microscopy and high‐resolution transmission electronic microscopy. The enhancement of the wall current is shown to be due to the formation of conducting pathways of charged defects accumulated along domain walls and traversing the nanocrystals. The diverse domain walls can be manipulated by electric field in a perpendicular architecture. The perpendicular array structure of BiFeO 3 nanocrystals should have great potentials for developing perpendicular nanoelectronic prototypes.

Liu, Lisha↗
DOE OSTI2020

Self-Assembled Solute Networks in Crowded Electrolyte Solutions and Nanoconfinement of Charged Redoxmer Molecules

Redoxmers are electrochemically active organic molecules storing charge and energy in electrolyte fluids circulating through redox flow batteries (RFBs). Such molecules typically have solvent-repelling cores and solvent-attracting pendant groups introduced to increase solubility in liquid electrolytes. These two features can facilitate nanoscale aggregation of the redoxmer molecules in crowded solutions. In some cases, this aggregation leads to the emergence of continuous networks of solute molecules in contact, and the solution becomes microscopically heterogeneous. In this study, we used small-angle X-ray scattering (SAXS) and molecular dynamics modeling to demonstrate formation of such networks and examine structural factors controlling this self-assembly. We also show that salt ions become excluded from these solute aggregates into small pockets of electrolytes, where these ions strongly associate. This confinement by exclusion is also likely to occur to charged redoxmer molecules in a “sea” of neutral precursors coexisting in the same solution. Here, we demonstrate that the decay lifetime of the confined charged molecules in such solutions can increase several fold compared to dilute solutions. We attribute this behavior to a “microreactor effect” on reverse reactions of the confined species during their decomposition.

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

Tuning Self-Assembly of Gold Nanoparticles Grafted with Charged Polymers by Varying Temperature and Electrolytes

Here, we report on the assembly of gold nanoparticles (AuNPs, 5 and 10 nm core diameters) grafted with poly(ethylene glycol) (PEG) terminated with either positively (–NH 2 ) or negatively charged (–COOH) end groups. We employ synchrotron-based small-angle X-ray scattering (SAXS) techniques to investigate the effect of electrolytes and temperature on the assembly and crystallization behavior of these grafted AuNPs. Our studies reveal that –NH 2 -grafted AuNPs spontaneously assemble into a layered hexagonal structure that deteriorates upon adding K 2 CO 3 to the suspension. The hexagonal structure recovers after heating the same suspension above 60 °C. On the other hand, the COOH-terminated AuNPs remain dispersed in the suspensions and assemble and crystallize into a face-centered cubic structure only in the presence of K 2 CO 3 at temperatures above 60 °C. Varying the pH of the –NH 2 -terminated AuNP suspensions induces short-range order (SRO) structures with a single characteristic length scale that shrinks upon heating. Similarly, SRO for the –COOH-terminated AuNP is realized only by lowering the pH. This study demonstrates the use of electrolytes and temperature on the surface charge of grafted AuNPs as knobs to tune self-assembly and crystallization.

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

Achieving High Permittivity Paraelectric Behavior in Mesogen-Free Sulfonylated Chiral Polyethers with Smectic C Liquid Crystalline Self-Assembly

Ferroelectric liquid crystalline polymers (LCPs) with a high spontaneous polarization (P s ) are of great interest for the fabrication of advanced electronic devices. However, conventional ferroelectric LCPs typically exhibit low spontaneous polarization, only around 1 mC/m 2 . To increase the orientational polarization for ferroelectric LCPs, in this work, we designed mesogen-free comb-shaped LCPs based on isotactic polyepichlorohydrin, which contained highly dipolar sulfonyl groups (dipole moment of 4.5 Debye) in the side chains. The goal was to increase dipole density and induce ferroelectric switching. In this new series of mesogen-free LCPs, the sulfonyl groups were first moved away from the main chain to mitigate strong dipole–dipole interactions. Second, methyl-branched alkyl side chains were implemented to decrease the crystallizability and induce the Smectic C (SmC) self-assembly. Intriguingly, these SmC samples, for the first time, exhibited typical paraelectric behavior (i.e., slim S-shaped single hysteresis loops) with a high dielectric constant in the range of 20–30. Finally, learning from the knowledge obtained from this study, we will be able to design new mesogen-free LCPs with tailor-made dipole–dipole interactions and realize ferroelectricity.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Ligand-induced self-assembly of twisted two-dimensional halide perovskites

Two-dimensional (2D) halide perovskites (HPs) exhibit intriguing optoelectronic functionalities. Conventionally, 2D HPs have been synthesized with linear and planar molecular spacers, resulting in nominal modifications of their optoelectronic properties. In contrast, lower-dimensional HPs (0D and 1D) have proved accommodating to the incorporation of bulky molecular spacers. Fundamental insights into the incorporation of bulky molecular spacers in 2D HP structures remains elusive. Here, in this study, by implementing a high-throughput autonomous exploration workflow, the crystallization behaviours of 2D HPs based on a bulky 3,3-diphenylpropylammonium (DPA) spacer are comprehensively explored. Counterintuitive to conventional HP chemistry, synthesis of 2D DPA 2 PbI 4 HPs is indeed feasible when the steric hindrance is mediated by minute incorporation of 3D HP precursors. Furthermore, a moiré superlattice is observed from the DPA 2 PbI 4 flakes, indicating the spontaneous formation of twisted stacks of 2D HPs.We hypothesize that the unconventional van der Waals surface of DPA 2 PbI 4 facilitates the self-assembly of the twisted stacks of 2D HPs. This work exemplifies how high-throughput experimentation can discover unconventional material systems in which the synthetic principle lies beyond conventional chemical intuition. Furthermore, these findings provide hints for how to chemically manipulate the twist stacking in 2D HPs, thus rendering a straightforward way for bespoke realization of functionalities in exotic materials systems via a bottom-up approach.

materials chemistry↗
DOE OSTI2021

Dynamic processes in transient phases during self-assembly of organic semiconductor thin films

Understanding and manipulating crystallization processes has been an important challenge for solution-processed organic thin films, both for fundamental studies and for fabricating thin films with near-intrinsic charge transport properties. We report an in situ X-ray scattering study of the crystallization of 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-C 10 ) during its deposition from solution. At temperatures modestly below the smectic-E/crystalline phase boundary, the crystallization goes through a transient liquid crystal state before reaching the final stable crystalline phase. Significant dynamics occur in the first few seconds of the transition, which are observed through fluctuations in the X-ray scattering intensity, and are correlated with the time interval that the transient thin film coexists with the evaporating solvent. The transition to the stable crystalline phase takes minutes or even hours under these conditions, which may be a result of the asymmetry of the molecule. Transient phases are of potential interest for applications, since they can act as a route to self-assembly of organic thin films. However, our observations show that the long-lived monolayer-stacked intermediate state does not act as a template for the bilayer-stacked crystalline phase. Rather, the grain structure is replaced through nucleation, where the nucleation free-energy barrier is related to a potential barrier that prevents molecules to flip their long axis by 180°.

36 MATERIALS SCIENCE↗
DOE OSTI2023

XFEL Microcrystallography of Self-Assembling Silver n -Alkanethiolates

New synthetic hybrid materials and their increasing complexity have placed growing demands on crystal growth for single-crystal X-ray diffraction analysis. Unfortunately, not all chemical systems are conducive to the isolation of single crystals for traditional characterization. Here, small-molecule serial femtosecond crystallography (smSFX) at atomic resolution (0.833 Å) is employed to characterize microcrystalline silver n-alkanethiolates with various alkyl chain lengths at X-ray free electron laser facilities, resolving long-standing controversies regarding the atomic connectivity and odd–even effects of layer stacking. smSFX provides high-quality crystal structures directly from the powder of the true unknowns, a capability that is particularly useful for systems having notoriously small or defective crystals. We present crystal structures of silver n-butanethiolate (C4), silver n-hexanethiolate (C6), and silver n-nonanethiolate (C9). We show that an odd–even effect originates from the orientation of the terminal methyl group and its role in packing efficiency. We also propose a secondary odd–even effect involving multiple mosaic blocks in the crystals containing even-numbered chains, identified by selected-area electron diffraction measurements. Finally, we conclude with a discussion of the merits of the synthetic preparation for the preparation of microdiffraction specimens and compare the long-range order in these crystals to that of self-assembled monolayers.

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

Oxidative Self-Assembly of Au/Ag/Pt Alloy Nanoparticles into High-Surface Area, Mesoporous, and Conductive Aerogels for Methanol Electro-oxidation

The ability to assemble nanoparticles (NPs) into functional nanostructures is critical for the advancement of nanoscience. However, common assembling techniques utilize organic ligands or biomolecules, which are detrimental for charge transport and interparticle coupling, which impede the efficient integration of low-dimensional properties. Herein, we report a methodology for the self-supported assembly of ultra-small (3-6 nm) Au/Ag/Pt alloy NPs into large, free-standing alloy superstructures (aerogels) that exhibit direct NP connectivity, high surface area (125 ± 0.43 to142 ± 0.93 m 2 /g) and mesoporosity (21.6 ± 2.2 nm), and superior electrocatalytic activity for methanol oxidation reaction (MOR). Precursor Au/Ag/Pt alloy NPs and hydrogels were synthesized via stepwise galvanic replacement reaction (GRR) of the glutathione (GSH)-coated Ag NPs, followed by oxidative removal of the surfactant ligands. The composition of alloy aerogels was tuned by varying the oxidant/GSH molar ratio, which governs the extent of Ag dealloying with in-situ generated HNO 3 and increases the exposure of Au and Pt on the aerogel surface. The alloy aerogels exhibit superior MOR mass activity, which is 21.4 and 2.5 times higher than those of the precursor NPs and commercial Pt (40 wt.%)/C electrocatalysts, respectively. The MOR surface-specific activity (MOR-SSA) of the aerogels was improved by >17% when the Pt content was increased from 22.4% to 31.2%. The aerogels exhibit improved electronic conductivity, enhanced tolerance for carbonaceous byproducts, and maintained ~94% of the initial MOR activity at -0.3 V for 24 h in an alkaline medium. In conclusion, the interconnected porous superstructure of the aerogel provides a facile conduit for molecules to reach the pristine active surface whereas the presence of oxophilic Au promotes the dissociative adsorption of methanol, enabling the Au/Ag/Pt alloy aerogel a high efficiency, durable electrocatalyst for next generation of energy conversion studies.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Hierarchical Self-Assembly Pathways of Peptoid Helices and Sheets

Peptoids (N-substituted glycines) are a class of tailorable synthetic peptidomic polymers. Amphiphilic diblock peptoids have been engineered to assemble 2D crystalline lattices with applications in catalysis and molecular separations. Assembly is induced in an organic solvent/water mixture by evaporating the organic phase, but the assembly pathways remain uncharacterized. We conduct all-atom molecular dynamics simulations of Nbrpe6Nc6 as a prototypical amphiphilic diblock peptoid comprising an NH 2 -capped block of six hydrophobic N-((4-bromophenyl)ethyl)glycine residues conjugated to a polar NH 3 (CH 2 ) 5 CO tail. We identify a thermodynamically controlled assembly mechanism by which monomers assemble into disordered aggregates that self-order into 1D chiral helical rods then 2D achiral crystalline sheets. We support our computational predictions with experimental observations of 1D rods using small-angle X-ray scattering, circular dichroism, and atomic force microscopy and 2D crystalline sheets using X-ray diffraction and atomic force microscopy. Furthermore, this work establishes a new understanding of hierarchical peptoid assembly and principles for the design of peptoid-based nanomaterials.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Nanoparticle self-assemblies with modern complexity

Thanks to decades of tireless efforts, nanoparticle assemblies have reached at an extremely high level of controllability, sophistication, and complexity, with new insights provided by integration with graph theory, cutting-edge characterization, and machine learning (ML)-based computation and modeling, as well as with ever-diversifying applications in energy, catalysis, biomedicine, optics, electronics, magnetics, organic biosynthesis, and quantum technology. Nanoparticle assemblies can be crystalline, known as superlattices or supracrystals. Their assembly entails a transition from disorder—dispersed nanoparticles—to order, which can be achieved through classical nucleation pathways or nonclassical pathways via prenucleation precursors or particle aggregation. Further, the periodic lattices allow facile manipulations of electrons, phonons, photons, and even spins, leading to advanced device components and metamaterials. Meanwhile, aperiodic assemblies out of nanoparticles, such as gels, networks, and amorphous solids, also start to attract attentions. Despite the loss of periodicity, symmetry-lowering or symmetry-breaking three-dimensional (3D) structures emerge with unique properties, such as chiroptical activity, topological mechanical strength, and quantum entanglement. Real-space imaging such as electron microscopy and X-ray based tomography methods are utilized to characterize these complex structures, while mathematical tools such as graph theories are in need to describe such complex structures. This issue aims to provide a timely review of the efforts in this greatly broadened materials design space including experiment, simulation, theory, and applications. Nine top experts (and their teams) from four countries deliver six review papers, summarizing fundamental mechanistic understandings of nanoparticle assemblies, highlighted with the developments of state-of-the-art in situ characterization tools and ML-assisted reverse engineering, and newly emergent applications of nanoarchitectures.

36 MATERIALS SCIENCE↗