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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 OSTI2026

Photoresponsive Rotaxanes Switch Lipid Bilayer Neuromorphic Behavior with Light

A rotaxane consisting of a macrocycle ring with two azobenzene units mechanically interlocked onto a bolaamphiphilic axle was incorporated into droplet interface bilayers (DIBs). The azobenzene groups on the ring underwent quasi-reversible, photoisomerization-induced cycling between 1-E and 1-Z configurations when irradiated with 370 and 467 nm light, respectively, enabling programmable access to different history-dependent electrical behaviors from the same membrane. In the 1-E configuration, bilayers exhibited type-IIactive memristance that coincided with increasingly elevated ionic conduction, associated with progressively enhanced bilayer permeability during voltage cycling. In the 1-Z configuration, bilayers displayed type-I, passive memcapacitive behavior, reflecting tighter lipid packing and reduced ionic permeability. Photoswitching also yielded a nonvolatile, photoresponsive memcapacitor that could be modulated repetitively with negligible loss, likely via reversible changes in membrane thickness. Concurrent ohmic leakage currents across the membrane were less than 0.3%. These results agree with previous studies with increasing membrane permeability using photoswitchable rotaxanes and provide new insights into the coupling between volatile and nonvolatile memcapacitance during photoisomerization. More broadly, they demonstrate a new strategy for the manipulation of neuromorphic behaviors in soft materials using light, with implications for brain-inspired computation and sensing.

droplet interface bilayers↗
DOE OSTI2020

Molecular insight into the anion effect and free volume effect of CO 2 solubility in multivalent ionic liquids

For many years, experimental and theoretical studies have investigated the solubility of CO 2 in a variety of ionic liquids (ILs), but the overarching absorption mechanism is still unclear. Currently, two different factors are believed to dominate the absorption performance: (a) the fractional free volume (FFV) accessible for absorption; and (b) the nature of the CO 2 interactions with the anion species. The FFV is often more influential than the specific choice of the anion, but neither mechanism provides a complete picture. Herein, we have attempted to decouple these mechanisms in order to provide a more definitive molecular-level perspective of CO 2 absorption in IL solvents. We simulate a series of nine different multivalent ILs comprised of imidazolium cations and sulfonate/sulfonimide anions tethered to benzene rings, along with a comprehensive analysis of the CO 2 absorption and underlying molecular-level features. We find that the CO 2 solubility has a very strong, linear correlation with respect to FFV, but only when comparisons are constrained to a common anion species. The choice of anion results in a fundamental remapping of the correlation between CO 2 solubility and FFV. Overall, the free volume effect dominates in the ILs with smaller FFV values, while the choice of anion becomes more important in the systems with larger FFVs. Our proposed mechanistic map is intended to provide a more consistent framework for guiding further IL design for gas absorption applications.

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

Ionic Precursors Transformed Into Vinyl Acetate Synthesis Catalyst via Reaction-Driven Restructuring

Conventional preparation of supported bimetallic catalysts relies on solution-mediated metal salt immobilization and pre-formation of alloy nanoparticles before reaction. Here, we report a fundamentally different synthesis strategy of using a physical mixture of salt precursors to generate an active catalyst during reaction. The catalytic structure is generated in situ from Pd3(OAc)6, Au(OH)3, and KOAc through H2 treatment and reaction-driven restructuring under vinyl acetate monomer (VAM) synthesis conditions. Ascertained from in situ X-ray diffraction and operando infrared spectroscopy analyses, reduction treatment produces segregated Pd and Au domains, and subsequent exposure to a VAM reaction mixture triggers dynamic extraction of Pd from the metal surface. This latter process, mediated by acetate-assisted redox cycles, facilitates Pd migration toward Au domains to form a near-surface localized Pd50Au50 alloy phase. Monometallic Pd domains serve as a reservoir of Pd to the alloy phase, leading to and sustaining a more Pd-enriched active surface and a higher population of accessible Pd sites, compared to a conventionally prepared K-PdAu/SiO2 catalyst. Consequently, this leads to a twofold increase in the VAM formation rate, demonstrating highly active bimetallic catalysts can be generated through the gas-phase treatment of physically mixed ionic precursors.

Cha, Byeong Jun [Rice University]↗
DOE OSTI2022

Ionic transport in electrostatic Janus Membranes. An explicit solvent molecular dynamic simulation.

Janus –or two-sided, charged membranes offer promise as ionic current rectifiers. In such systems, pores consisting of two regions of opposite charge can be used to generate a current from a gradient in salinity. The efficiency of nanoscale Janus pores increases dramatically as their diameter becomes smaller. However, little is known about the underlying transport processes, particularly under experimentally accessible conditions. In this work, we examine the molecular basis for rectification in Janus nanopores using an applied electric field. Molecular simulations with explicit water and ions are used to examine the structure and dynamics of all molecular species in aqueous electrolyte solutions. For several macroscopic observables, the results of such simulations are consistent with experimental observations on asymmetric membranes. Our analysis reveals a number of previously unknown features, including a pronounced local re-orientation of water molecules in the pores, and a segregation of ionic species that has not been anticipated by previously reported continuum analyses of Janus pores. Using these insights, a model is proposed for ionic current rectification in which electric leakage at pore entrance controls net transport.

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

CO 2 Capture with Capsules of Ionic Liquid/Amines

Carbon capture remains an urgent issue that has gained a great deal of attention over the past few decades. Aqueous amines have excellent selectivity, but present corrosion and volatility issues, whereas ionic liquids (ILs) have negligible volatility and tunable physical properties, but high viscosities. One approach to improve the practical performance of these liquids is encapsulating them in a CO 2 permeable polymer shell to enhance the accessibility of the liquid and the CO 2 absorption rate. In this work, we report the encapsulation of a mixture of amine and IL (i.e., monoethanolamine (MEA) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF 4 ])) and demonstrate enhanced carbon capture performance. A soft-template approach and interfacial polymerization are used to give capsules with liquid core (64 wt %) and polyurea shell. Compared to the bulk liquid, the encapsulated liquid shows improved thermal stability over cycles of absorption at 25 °C, and desorption at 75 °C. The capsules with core of [BMIM][BF 4 ]-MEA show 0.2 mol CO 2 /kg of capsules at 1 bar CO 2 , compared to the bulk liquid, which has 0.05 mol CO 2 /kg of sorbent. This is attributed to the limited evaporation of the amines. Alternatively, the same capsules but with 5 wt % of piperazine (Pz) in the core have doubled gravimetric CO 2 capacity of the capsules (0.4 mol CO 2 /kg of capsules); performance is evaluated over 10 capture–release cycles showing minimal mass loss. Characterization of the CO 2 uptake of the polymer shell itself reveals that the shell contributes only ~10% of the observed capacity, likely attributed to amine functionalities of the polymer. Here, this facile approach to encapsulating such “active” liquids can be applied to other CO 2 selective solvents that are volatile, viscous, and corrosive.

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

Design and characterization of hierarchical aluminosilicate composite materials for Cs entrapment: Adsorption efficiency tied to microstructure

The growing quantity of nuclear waste and the serious threats to the environment challenge researchers to innovate and target new waste form technologies. In the past decades, considerable efforts have been devoted to developing highly selective sorbents followed by safe disposal with the assurance of chemical stability and robust retention performance. Zeolite-containing geopolymers are regarded as a possible 2-in-1 material able to both capture and sequester elements such as Cs in bed fixed column application perspective. Here, these composites show promise for combining extraction properties of zeolite powder due to its crystalline structure (high capacity and selective adsorption), with the tunable microstructure and the shaping feasibility of the geopolymer binder. For the development of materials devoted to Cs immobilization, porous zeolite/geopolymer composites were prepared by dispersing NaY zeolite particles in a geopolymer binder. The influence of the structural properties of such composites on their ability to entrap a large amount of Cs by an ionic exchange process was notably studied. Composites' compositions, porosities, morphologies and crystallinity were analyzed by scanning electron microscopy coupled with energy dispersive x-ray spectroscopy (SEM-EDX), x-ray diffraction analysis (XRD) and nitrogen adsorption/desorption studies. Experimental Cs sorption in batch mode was used to follow the ionic exchange phenomenon in these materials. Along with 5 wt% amount of zeolite in geopolymer improves the Cs adsorption performance offering multiple new adsorption sites. Additionally, the geopolymer mesopores are beneficial facilitating the access of Cs and its role as a binder is advantageous to tailor granular hierarchical structure for safer industrial application.

36 MATERIALS SCIENCE↗
DOE OSTI2025

U 4+/5+/6+ in a Conserved Pseudotetrahedral Imidophosphorane Coordination Sphere

While several ligand systems support uranium across a range of oxidation states, spanning more than two oxidation states in a conserved coordination geometry is uncommon among structurally authenticated complexes. Imidophosphorane ligands significantly stabilize high-valent lanthanide and actinide complexes. Here, we report a series of homoleptic uranium imidophosphorane complexes, spanning the +4, +5 and +6 oxidation states in a four-coordinate pseudotetrahedral ligand field. The +6 oxidation state is accessible using a mild ferrocenium oxidant, yielding a rare example of U6+ in a pseudotetrahedral coordination environment. As the formal oxidation state increases, the U–N distances gradually contract, consistent with the Shannon ionic radii of U 4+/5+/6+ . Compared to reported complexes, the short U–N distances observed in the U 6+ complex are more comparable to dianionic imido ligands than monoanionic amido ligands.

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

Predicting the synthesizability of crystalline inorganic materials from the data of known material compositions

Abstract Reliably identifying synthesizable inorganic crystalline materials is an unsolved challenge required for realizing autonomous materials discovery. In this work, we develop a deep learning synthesizability model ( SynthNN ) that leverages the entire space of synthesized inorganic chemical compositions. By reformulating material discovery as a synthesizability classification task, SynthNN identifies synthesizable materials with 7× higher precision than with DFT-calculated formation energies. In a head-to-head material discovery comparison against 20 expert material scientists, SynthNN outperforms all experts, achieves 1.5× higher precision and completes the task five orders of magnitude faster than the best human expert. Remarkably, without any prior chemical knowledge, our experiments indicate that SynthNN learns the chemical principles of charge-balancing, chemical family relationships and ionicity, and utilizes these principles to generate synthesizability predictions. The development of SynthNN will allow for synthesizability constraints to be seamlessly integrated into computational material screening workflows to increase their reliability for identifying synthetically accessible materials.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Metastable Clusters and Competitive Solvation Tune Ion Pairing at Liquid Interfaces

The balance of hydrophobic and hydrophilic interactions underlies emergent phenomena in complex multicomponent chemical systems. Here, we show that a supposedly ‘non–interacting’ nonpolar phase can be used to competitively solvate amphiphilic molecules at an oil/aqueous interface. This solvation, as probed by surface specific nonlinear spectroscopy and simulations, results in a molecularly thin corrugated phase boundary featuring metastable assemblies that alter the hydrogen bonding networks of water and the apparent ‘hard/soft’ descriptors used to describe ionic interactions. We show that competitive solvation enhances amphiphile mobility, opening up otherwise energetically inaccessible complexes that transiently interact with aqueous phase ions. These transient species impact ensemble binding affinities and may represent the molecular agents responsible for aspects of ionic transport and function. In conclusion, the result of this work highlights how seemingly unrelated nonpolar interactions feedback onto aqueous phase chemical phenomena, providing a pathway to tune phase separation and self-assembly to access new reaction pathways using interfaces for a range of chemical and biological systems.

Anions↗
DOE OSTI2024

High entropy ceramics for applications in extreme environments

Abstract Compositionally complex materials have demonstrated extraordinary promise for structural robustness in extreme environments. Of these, the most commonly thought of are high entropy alloys, where chemical complexity grants uncommon combinations of hardness, ductility, and thermal resilience. In contrast to these metal–metal bonded systems, the addition of ionic and covalent bonding has led to the discovery of high entropy ceramics (HECs). These materials also possess outstanding structural, thermal, and chemical robustness but with a far greater variety of functional properties which enable access to continuously controllable magnetic, electronic, and optical phenomena. In this experimentally focused perspective, we outline the potential for HECs in functional applications under extreme environments, where intrinsic stability may provide a new path toward inherently hardened device design. Current works on high entropy carbides, actinide bearing ceramics, and high entropy oxides are reviewed in the areas of radiation, high temperature, and corrosion tolerance where the role of local disorder is shown to create pathways toward self-healing and structural robustness. In this context, new strategies for creating future electronic, magnetic, and optical devices to be operated in harsh environments are outlined.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Evidence of a liquid–liquid transition in a glass-forming ionic liquid

A liquid–liquid transition (LLT) is a transformation from one liquid to another through a first-order transition. The LLT is fundamental to the understanding of the liquid state and has been reported in a few materials such as silicon, phosphorus, triphenyl phosphite, and water. Furthermore, it has been suggested that the unique properties of materials such as water, which is critical for life on the planet, are linked to the existence of the LLT. However, the experimental evidence for the existence of an LLT in many molecular liquids remains controversial, due to the prevalence and high propensity of the materials to crystallize. In this work, we show evidence of an LLT in a glass-forming trihexyltetradecylphosphonium borohydride ionic liquid that shows no tendency to crystallize under normal laboratory conditions. We observe a step-like increase in the static dielectric permittivity at the transition. Furthermore, the sizes of nonpolar local domains and ion-coordination numbers deduced from wide-angle X-ray scattering also change abruptly at the LLT. We independently corroborate these changes in local organization using Raman spectroscopy. The experimental access to the evolution of local order and structural dynamics across a liquid–liquid transition opens up unprecedented possibilities to understand the nature of the liquid state.

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

Variability and origins of grain boundary electric potential detected by electron holography and atom-probe tomography

A number of grain boundary phenomena in ionic materials, in particular, anomalous (either depressed or enhanced) charge transport, have been attributed to space charge effects. Developing effective strategies to manipulate transport behaviour requires deep knowledge of the origins of the interfacial charge, as well as its variability within a polycrystalline sample with millions of unique grain boundaries. Electron holography is a powerful technique uniquely suited for studying the electric potential profile at individual grain boundaries, whereas atom-probe tomography provides access to the chemical identify of essentially every atom at individual grain boundaries. Using these two techniques, we show in this paper that the space charge potential at grain boundaries in lightly doped, high-purity ceria can vary by almost an order of magnitude. We further find that trace impurities (<25 ppm), rather than inherent thermodynamic factors, may be the ultimate source of grain boundary charge. These insights suggest chemical tunability of grain boundary transport properties. A number of grain boundary phenomena in ionic materials, such as anomalous charge transport, have been attributed to space charge effects. Space charge potential at grain boundaries in lightly doped, high-purity ceria is now shown to vary by almost an order of magnitude.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Macrocyclic β‐Sheets Stabilized by Hydrogen Bond Surrogates

Abstract Mimics of protein secondary and tertiary structure offer rationally‐designed inhibitors of biomolecular interactions. β‐Sheet mimics have a storied history in bioorganic chemistry and are typically designed with synthetic or natural turn segments. We hypothesized that replacement of terminal inter‐β‐strand hydrogen bonds with hydrogen bond surrogates (HBS) may lead to conformationally‐defined macrocyclic β‐sheets without the requirement for natural or synthetic β‐turns, thereby providing a minimal mimic of a protein β‐sheet. To access turn‐less antiparallel β‐sheet mimics, we developed a facile solid phase synthesis protocol. We surveyed a dataset of protein β‐sheets for naturally observed interstrand side chain interactions. This bioinformatics survey highlighted an over‐abundance of aromatic–aromatic, cation‐π and ionic interactions in β‐sheets. In correspondence with natural β‐sheets, we find that minimal HBS mimics show robust β‐sheet formation when specific amino acid residue pairings are incorporated. In isolated β‐sheets, aromatic interactions endow superior conformational stability over ionic or cation‐π interactions. Circular dichroism and NMR spectroscopies, along with high‐resolution X‐ray crystallography, support our design principles.

Chemistry↗
DOE OSTI2022

Simulation of methanol synthesis in a membrane-contactor reactor

In a recent paper we investigated experimentally in the laboratory the methanol synthesis (MeS) reaction in a novel high-pressure membrane reactor (MR) using tetraethylene glycol dimethyl ether (TGDE) and an ionic liquid (IL) as the sweep liquids. We reported significantly higher carbon conversion (per single-pass) compared to a traditional packed-bed reactor (PBR), as a result of the in-situ removal of methanol by the sweep liquid. Here, in this paper, a steady-state model is developed to simulate the MR behavior during MeS and is validated by the experimental data. The model is then used to study the reactor behavior for a broader range of operating conditions beyond those that can be accessed and studied experimentally in the laboratory-scale reactor. Converting the model equations into their dimensionless form helps to identify the key dimensionless groups determining reactor performance, enables one to better evaluate the efficacy of the MR system, and guides further process design and scale-up.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Local Chemical Enhancement and Gating of Organic Coordinated Ionic-Electronic Transport

Superior properties in organic mixed ionic-electronic conductors (OMIECs) over inorganic counterparts have inspired intense interest in biosensing, soft-robotics, neuromorphic computing, and smart medicine. However, slow ion transport relative to charge transport in these materials is a limiting factor. Here, it is demonstrated that hydrophilic molecules local to an interfacial OMIEC nanochannel can accelerate ion transport with ion mobilities surpassing electrophoretic transport by more than an order of magnitude. Furthermore, ion access to this interfacial channel can be gated through local surface energy. This mechanism is applied in a novel sensing device, which electronically detects and characterizes chemical reaction dynamics local to the buried channel. The ability to enhance ion transport at the nanoscale in OMIECs as well as govern ion transport through local chemical signaling enables new functionalities for printable, stretchable, and biocompatible mixed conduction devices.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Electrostatic Superlattices Beyond 1:1 Stoichiometry

ABSTRACT Exotic nanoparticle superstructures can be accessed by harnessing nanoparticle softness and charge regulation, features often viewed as obstacles to structural control. Here, we show that regulated charge mismatch in polymer‐grafted nanoparticles enables the assembly of high‐stoichiometry cubic superlattices. By co‐tuning grafting density, particle size, and bulk composition, we realize ionic‐lattice analogues, such as and , as well as single‐component and superlattices without atomic counterparts. The superlattice has recently been identified theoretically as a photonic band‐gap lattice. These phases emerge from a 1:1 “parent” lattice when local charge neutrality cannot be satisfied, driving either progressive interstitial filling or reorganization into a larger basis. For instance, the systematic occupation of ZnS tetrahedral sites yields , while ligand‐swapping symmetry breaking converts CsCl into . Upon heating, the assemblies exhibit reversible lattice contraction and pronounced negative thermal expansion. Furthermore, the energetic penalty for defects increases with nanoparticle size, facilitating the scalable production of high‐quality, open superlattices for photonic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Optical Absorption-Based In Situ Characterization of Halide Perovskites

Halide perovskites have emerged as materials for high-performance optoelectronic devices. Often, progress made to date in terms of higher efficiency and stability is based on increasing material complexity, i.e., formation of multicomponent halide perovskites with multiple cations and anions. In this review article, the use of in situ optical methods, namely, photoluminescence (PL) and UV-vis, that provide access to the relevant time and length scales to ascertain chemistry–property relationships by monitoring evolving properties is discussed. Additionally, because halide perovskites are electron/ion conductors and prone to solid-state ion transport under various external stimuli, application of these optical methods in the context of ionic movement is described to reveal mechanistic insights. In conclusion, examples of using in situ PL and UV-vis to study degradation and phase transitions are reviewed to demonstrate the wealth of information that can be obtained regarding many different aspects of ongoing research activities in the field of halide perovskites.

36 MATERIALS SCIENCE↗
DOE OSTI2020

The Concept of Negative Capacitance in Ionically Conductive Van der Waals Ferroelectrics

Negative capacitance (NC) provides a path to overcome the Boltzmann limit that dictates operating voltages in transistors and, therefore, may open up a path to the challenging proposition of lowering energy consumption and waste heat in nanoelectronic integrated circuits. Typically, NC effects in ferroelectric materials are based on either stabilizing a zero-polarization state or slowing down ferroelectric switching in order to access NC regimes of the free-energy distribution. Here, a fundamentally different mechanism for NC, based on CuInP 2 S 6 , a van der Waals layered ferrielectric, is demonstrated. Using density functional theory and piezo-response force microscopy, it is shown that an unusual combination of high Cu-ion mobility and its crucial role in determining polarization magnitude and orientation (P) leads to a negative slope of the polarization versus the electric field E, dP/dE < 0, which is a requirement for NC. This mechanism for NC is likely to occur in a wide class of materials, offering new possibilities for NC-based devices. Finally, the nanoscale demonstration of this mechanism can be extended to the device-level by increasing the regions of homogeneous polarization and polarization switching, for example, through strain engineering and carefully selected electric field pulses.

36 MATERIALS SCIENCE↗