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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Morphology and Dynamics of Bottlebrush Polymers

This thesis makes significant advances to the understanding of bottlebrush polymers. While bottlebrushes have received much attention due to the recent discovery of their unprecedented properties, including supersoftness, ultra-low viscosity, and hyperelasticity, this thesis is the first fundamental investigation at the molecular level that comprises structure and dynamics. Neutron scattering experiments, detailed within, reveal spherical or cylindrical shapes, instead of a random coil conformation. Another highlight is the analysis of the fast dynamics at the sub nm-length scale. The combination of three neutron spectrometers and the development of a new analysis technique enabled the calculation of the mean-square displacement over seven orders of magnitude in time scale. This unprecedented result can be applied to a broad class of samples, including polymers and other materials. The thesis is accessible to scientists from other fields, provides the reader with easily understandable guidelines for applying this analysis to other materials, and has the potential to make a significant impact on the analysis of neutron scattering data.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Inhibition of Micro-pitting by Tribofilm-Forming ZrO 2 Nanocrystal Lubricant Additives: A Micro-pitting Rig and Transmission Electron Microscope Study

The drive to reduce fuel consumption in transportation has encouraged the emergence of low viscosity lubricants to reduce viscous losses in the engine, drivetrain, and other components. However, viscosity reduction increases the risk of surface damage, thus motivating the development of new anti-wear (AW) additives. Capped ZrO 2 nanocrystals (NCs) in base oils have been shown to form AW tribofilms within microscale sliding contacts. However, the potential of ZrO 2 NCs to protect surfaces subjected to rolling-sliding contact from macroscale damage, such as micro-pitting, remains unexplored. Here, we explore the ability of ZrO 2 NCs to form protective tribofilms under harsh conditions using a micro-pitting rig (MPR), consisting of a three ring-on-roller configuration. The experiments were conducted in polyalphaolephin (PAO) base oil, with and without 5 nm diameter ZrO 2 NCs, at two levels of slide-to-roll ratio (SRR) (30% and 0%) and at variable test durations up to long durations (119 h). MPR results showed the use of ZrO 2 NCs gives rise to the formation of a tribofilm covering the roller surfaces and decreases the initiation and propagation of micro-pits compared to tests in pure PAO base stock. Transmission electron microscopy (TEM) performed on focused ion beam (FIB) milled cross-sectional samples of the roller surfaces revealed the growth of dense and 50–100 nm thick ZrO 2 -based tribofilms independent of (SRR), indicating the potential for robust micro-pitting fatigue protection. Nevertheless, small cracks localized within the near surface region of the roller tested at the most severe conditions (30% SRR and 119 h) were observed. The initiation of these cracks was directly related to the presence of manganese sulphide (MnS) inclusions in the steel, revealed using TEM combined with energy dispersive spectroscopy (EDS). Furthermore, the results highlight the benefits of the protective tribofilms formed by ZrO 2 NCs and suggest approaches for further optimizing their use.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Alkali-silica reaction products and cracks: X-ray micro-tomography-based analysis of their spatial-temporal evolution at a mesoscale

In this study, we propose a laboratory-scale methodology, based on X-ray micro-tomography and caesium (Cs) as a contrast agent, to advance the understanding of cracking due to alkali-silica reaction (ASR) in concrete. The methodology allows achieving a completely non-destructive and time-lapse characterization of the spatial-temporal patterns of both the cracks and the ASR products. While Cs addition slightly accelerated the ASR kinetics, the crack patterns, with and without Cs addition, were statistically equivalent. Cracks with ASR products appeared first in the aggregates, close to the interface with the cement paste. They propagated afterwards towards the aggregates interior. Some products were then extruded for several mm into air voids and cracks in the cement paste. This process suggests that, in the early stage, the ASR products may be a low-viscosity gel that can flow away from the source aggregate and may settle later elsewhere as a rigid phase, upon calcium uptake.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Water reactive polyurethane grouting for deep vadose zone contaminant immobilization

Contaminants in the deep vadose zone (DVZ) pose a long-term threat to groundwater, human health, and the environment. Polyurethane grouting is a type of chemical grouting that is potentially advantageous in immobilizing contaminants in DVZs. Polyurethane resin has low viscosity that makes it feasible to penetrate and fill the pore space between fine particles. Here, in this study a series of laboratory pressure grouting and leaching tests were conducted to simulate and assess the effectiveness of polyurethane grouting for immobilizing contaminants in DVZs. Soil with fine particles was prepared with 127 I (as iodide) that served as a non-radioactive surrogate for radioactive 129 I. After grouting and curing, leaching tests were used to measure and compare contaminant diffusivity and leachability index values. Additionally, changes in porosity and saturated hydraulic conductivity of grouted soil were measured. X-Ray Computer Tomography (XCT) results showed that the cured polyurethane was distributed nearly homogeneously and approximately half of the voids were filled with cured polyurethane. Grouting reduced the saturated hydraulic conductivity of soil by 37 %. The effective diffusivity decreased by more than 80 % as compared with the ungrouted soil. The leachability index of the grouted soil was 6.5; meeting the criteria established by the U.S. Nuclear Regulatory Commission (NRC) standard. The results obtained in this study provide a valuable assessment of polyurethane grouting for iodide immobilization in the DVZ and indicate this approach may be a viable method for contaminant remediation in DVZ soils.

Contaminant Diffusion↗
DOE OSTI2021

Decoupling the degradation factors of Ni-rich NMC/Li metal batteries using concentrated electrolytes

Battery degradation results from multiple factors that usually correlate with each other. Electrochemical corrosion of the current collector is one of the main reasons for battery failure, leading to poor internal electrical contact and the dissolution of harmful ions into electrolytes. This phenomenon is especially evident in lithium bistrifluoromethanesulfonimidate (LiTFSI)-based electrolytes, although they have many advantages over conventional lithium hexafluorophosphate (LiPF 6 )-based electrolytes, such as low viscosity, good thermal stability, and stable to water. Recently, highly concentrated electrolytes are found hopeful of inhibiting aluminum's corrosion and boosting new electrolyte development. Here we discuss the solvation structures of liquid electrolytes and decouple the degradation mechanisms of using LiTFSI-based electrolytes in Li(Ni 0.8 Co 0.1 Mn 0.1 )O 2 /Li metal batteries. The results suggest although concentrated electrolytes inhibit the Al corrosion, the growth of lithium dendrites and the protection of the cathode-electrolyte interphase are not significantly improved. Furthermore, this paper provides a paradigm to evaluate the performance of electrolytes comprehensively.

25 ENERGY STORAGE↗
DOE OSTI2022

Carrot rhamnogalacturonan I structure and composition changed during 2017 in California

Detailed composition, fine structure, and function were determined for carrot pomace fiber remaining after commercial juice extraction from carrots harvested at four different times during 2017, in different California, USA locations. This pomace was treated with commercial enzymes and the changes in carbohydrate composition were analyzed. The enzyme-treated carrot pomace contained pectic oligosaccharides that were branched, unsaturated, partially acetylated and methylated rhamnogalacturonan I (RG-I) with arabinogalacto-oligosaccharide side chains as well as free galacto-oligosaccharides and galacturono-oligosaccharides detected by MALDI-TOF MS and NMR analysis. The molecular weight and degree of galacto-oligosaccharide polymerization decreased while water solubility increased following enzymatic treatment. While carrot soluble dietary fiber remained relatively constant, insoluble dietary fiber and total dietary fiber increased during the year. The carrot pomace fiber structure changed between the June and September harvests so that it was more susceptible to enzymatic degradation, and its shape became more linear. The diversity of carrot RG-I oligosaccharide structures was the greatest in the enzyme-treated pomace harvested in September and the RG-I became almost completely debranched by the enzyme treatment for the pomace harvested in December. The structural properties of these carrot pomace fiber fractions suggest that they can function as a low viscosity beverage food ingredient, and the rhamnogalacturonan I structure indicated the potential for anti-viral, immuno-modulatory and prebiotic properties. Furthermore, the rhamnogalacturonan structural composition changes during the growing season highlights the need for bioactivity monitoring of carrot pomace obtained from different sources, and harvested at different times during the year.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Containment strategy for subsurface H 2 storage based on time-dependent soft solids

Here, we propose an innovative containment strategy based on time-dependent soft solids, namely 2 wt% Laponite suspensions, to reinforce natural subsurface seals and engineer flow barriers, with an eye toward making H 2 subsurface storage scalable and geographically agnostic. This suspension can be injected at its initial low viscosity and elasticity into a porous medium, allowing for easy pumping and targeted delivery. Once inside the target zone, it matures into a soft solid with much higher viscosity and elasticity, acting as a potential flow barrier. We discuss the rheological properties of the suspensions and demonstrate that hydrogen does not adversely affect their microstructure, but rather increases the suspensions’ viscosity and elasticity. Moreover, the suspensions enhance the rock samples’ compressive strength, while hydrogen exposure increases their stiffness and ductility. The ability of rock samples saturated with the suspensions to contain higher injected gas pressures is enhanced by aging at higher temperatures.

08 HYDROGEN↗
DOE OSTI2023

Stable electrospray signal on a microfabricated glass chip with three-dimensional open edge and tiered depth geometries

This paper presents the microfabrication and performance of a three-dimensional electrospray ionization (ESI) emitter tip made from glass, which achieves stable current signals important for chemical analysis. Our novel microfabrication process and custom-built signal conditioning hardware provides the advantage of providing accurate features and steady signals. The fabrication process relies on standard microfabrication techniques (i.e., deposition, photolithography, and wet etching). This fabrication method involves the novel application of two layers of positive and negative photoresists in addition to Parafilm® wax tape. Open edge and tiered depth details were successfully created from a multilayer planar mask. This is a benefit for integrated miniaturized and microfluidic systems that often require micro features for their functionality but relatively large millimeter size features for their physical periphery. We demonstrate the fundamental performance of electrospray with this microfluidic chip. The emitter tip was fixed on a linear axis stage with high resolution (10 μm) to finely control the tip distance from a metal counter electrode plate. Further, a custom printed circuit board system was built to safely control four voltages applied to the microchip ports from a single high voltage power supply. To readily form the electrospray, non-aqueous solvents were used for their low viscosity and a constant voltage of +2.7 kV was applied to the sheath electrospray microchannel. The liquid being sprayed was 80/20 (v/v) methanol/acetonitrile with 0.1% acetic acid in the sheath microchannel and with ammonium acetate (10–40 mM) in its remaining microchannels. The electrospray signal was measured in response to varying the distance (1.4 to 1.6mm) between the electrospray emitter tip and a metal counter electrode plate in addition to the varying concentration of the background electrolyte, ammonium acetate. Stable and repeatable electrospray signal showed linear relationships with emitter tip distance and concentration (r 2 ≥ 0.95).

42 ENGINEERING↗
DOE OSTI2024

Amine functionalized supported ionic liquid membranes (SILMs) for CO 2 /N 2 separation

Supported ionic liquid membranes (SILMs), containing aprotic N-heterocyclic anion ionic liquids (AHA ILs) in an inorganic inert support, exhibit CO 2 /N 2 permselectivity values as high as 640 at 35.0 °C and 0.03 bar CO 2 , which represents conditions similar to post-combustion carbon capture (PCCC) from a natural gas power plant. A Fickian model fit to the experimental data estimates CO 2 permeability at direct air capture (DAC) conditions of 10,400 barrer and a CO 2 /N 2 permselectivity of 4000 for the best performing IL, triethyl(octyl)phosphonium 4-bromopyrazolide ([P 2228 ][4-BrPyra]). The most important criterion for high selectivity is a large equilibrium constant for binding between the IL and CO 2 , which results in high CO 2 solubility. ILs with smaller molar volumes and with no fluoroalkyl chains enhance N 2 rejection. As a result, low viscosity and high IL molar density also enhance CO 2 /N 2 permselectivity and CO 2 permeance.

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

Pressure-stable supported ionic liquid membranes using isoporous supports for evaluating pure- and mixed-gas light paraffin fractionation

Advances in horizontal drilling and hydraulic fracturing have spurred the growth of domestic U.S. energy production. Membranes, typically silicone rubbers, have found utility in shale gas treatment as fuel gas conditioning units to selectively remove C 2 + hydrocarbons at pressures up to 30 bar, producing clean CH 4 for gas engines. However, more selective materials could be beneficial for broader shale gas treatment applications, such as dew point control units. Supported ionic liquid membranes (SILMs) offer a potential opportunity for improving C 3 H 8 /CH 4 selectivity, but they lack pressure-stability. Here, we report C 3 H 8 /CH 4 selective and pressure-stable SILMs using isoporous supports. SILMs with supports that had minimal defects remained stable up to 15 bar of transmembrane pressure. This stability allowed for pure- and mixed-gas testing of the resulting membranes at elevated pressures. Furthermore, these tests revealed that low viscosity ILs (<100 cp) may display mixed-gas permeances and permselectivity nearly identical to pure-gas results. On the other hand, higher viscosity ILs may display increasing permeances and permselectivity with increasing C 3 H 8 fugacity, similar to rubbery polymers. Ultimately, the SILMs demonstrated relatively high pressure-stability due to the isoporous supports and competitive mixed-gas C 3 H 8 /CH 4 permselectivity compared to silicone rubber.

Rosenthal, Justin J. [University of Texas at Austi↗
DOE OSTI2021

Crowded electrolytes containing redoxmers in different states of charge: Solution structure, properties, and fundamental limits on energy density

Nonaqueous redox flow batteries use liquid electrolytes containing redox-active organic molecules (redoxmers) as their energy storage medium. To maximize energy density, the redoxmer concentration needs to be maximized while maintaining low viscosity and high ionic conductivity. During charge, a redoxmer molecule pairs with an ion in the electrolyte while another ion migrates across the membrane to maintain electric neutrality. In a crowded electrolyte, this reconstitution changes physical and chemical properties of the solution. To explore these behaviors, a phenothiazine redoxmer fully miscible with acetonitrile was used, and electrochemical charge was mimicked by chemical oxidation. The solutions were examined using small-angle X-ray scattering, nuclear magnetic resonance, and conductometry and modeled using classical molecular dynamics. Overall, our study indicates that physical and structural properties of redoxmer solutions in both states of charge make it exceedingly difficult to increase the redoxmer concentrations over 2 M at any temperature without compromising dynamic properties of such solutions. The cause for this limitation is proximity to a gel-like regime in which fluidity, diffusivity, and ionic conductivity exponentially decrease with increasing concentration. This tendency is compounded by non-Arrhenius behavior of the electrolyte: a small increase in the concentration outruns gains in fluidity and conductivity at a higher temperature. Thus the properties of crowded electrolytes generally make it impossible to operate when gel-like behavior sets in. Pushing the redoxmer concentration to 2.5-3 M might be possible for small redoxmer molecules, but it would require the use of ionic liquid electrolytes at 340-360 K. (C) 2021 Elsevier B.V. All rights reserved.

25 ENERGY STORAGE↗
DOE OSTI2022

Synthesis and characterization of magnetic ionic liquids containing multiple paramagnetic lanthanide and transition metal centers and functionalized diglycolamide ligands

Magnetic ionic liquids (MILs) containing paramagnetic centers have gained widespread recognition as sustainable solvents due to their ability to respond to an external magnetic field. The physico-chemical properties of MILs are dependent on the choice of anion/cation ligands and metal centers; the search for highly tunable ligands and precursors that can confer favorable characteristics, such as low viscosity, is ongoing. Diglycolamides employed as cationic ligands have been previously shown to form hydrophobic MILs that can simultaneously incorporate multiple lanthanide metal centers in both the anion/cation. Despite their enhanced magnetic susceptibility, the effect of diglycolamide chemical structure modifications on the physico-chemical properties of MILs has not been thoroughly studied. Additionally, the possibility of forming diglycolamide-based MILs with popularly employed transition metals has not been investigated and combinations that can simultaneously embed two different types of metal centers in both the anion/cation have not been explored. In this study, thirty (30) MILs comprised of lanthanide and transition metals were synthesized by examining their chelation to both straight-chained and branched diglycolamides. Here, transition metal-based MILs were found to possess high thermal stabilities up to 235 °C compared to 192 °C for those comprised of lanthanides. While MILs comprised of rare-earth metal centers exhibited the lowest viscosities, substituting lanthanides with transition metals in just the anion or cation resulted in enhanced thermal stability and reduced viscosity. The effective magnetic moment for these MILs varied between 4.71 and 21.08 µ B and was much higher compared to all previous classes of MILs prepared using the same metals. Results from this study explore all possible modifications that can be made to these MILs in an effort to demonstrate their structural tunability, which is often highly desirable in various applications, including organic synthesis and chemical separations.

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

CO 2 -Soluble Nonionic Surfactants for Enhanced CO 2 Storage via In Situ Foam Generation

Geologic carbon storage (GCS) is a rapidly evolving technology with the potential to reduce the environmental impact of fos-sil fuels. Saline aquifers, which comprise a sandstone matrix with brine in the pores, make up much of the pore space availa-ble for CO 2 storage in the United States. When CO 2 is injected in saline aquifers, however, capillary fingering occurs and only a small percentage of the pore space is filled with CO 2 . This is due to the low viscosity of CO 2 , which is roughly ten times less viscous than brine. To address this problem, we tested the ability of inexpensive, commercially available nonionic surfactants to be dissolved in the injected CO 2 and increase the apparent viscosity of CO 2 by generating CO 2 -in-water foams in situ.

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

Protein Coatings Dictate the Dispersibility and Stability of Hydrophobic Zeolitic-Imidazolate Frameworks in Water

Metal–organic frameworks are promising materials for many biomedical technologies due to their ability to store and release large quantities of guest molecules in a predictable and tunable fashion. In biological fluids, proteins readily adsorb to the external surfaces of metal–organic framework particles through a combination of hydrophobic and electrostatic interactions. However, much remains to be understood about the nature of these protein coatings and how they influence the bulk properties of aqueous dispersions of metal–organic frameworks. Here, in this work, we show that a variety of proteins can be used to manipulate the properties of aqueous dispersions of zeolitic-imidazolate framework (ZIF) particles. Specifically, noncovalently associated protein coatings promote the formation of dispersions of hydrophobic ZIFs in water with high colloidal and hydrolytic stability, as long as the density of adsorbed proteins exceeds a critical, protein-dependent threshold. Further, these dispersions feature low viscosity and complete retention of gas carrying capacity. The wide range of properties accessible with protein coatings provides a highly modular approach to design hydrophobic metal–organic frameworks with properties tailored for specific biological applications.

adsorption↗
DOE OSTI2023

The Relationship between Ionic Conductivity and Solvation Structures of Localized High-Concentration Fluorinated Electrolytes for Lithium-Ion Batteries

Localized high concentration electrolyte (LHCE) combines a diluent with high concentration electrolyte (HCE), offering promising properties. The ions, solvent, and diluent interact to form a complex heterogenous liquid structure, where high salt concentration clusters are embedded in diluent. Optimizing LHCE for desired electrolyte properties like high ionic conductivity, low viscosity, effective solid electrolyte interphase (SEI) formability, within the vast chemical and compositional design space requires deeper understanding and theoretical guidance. For this work, we investigated the structures and conductivity of LHCEs based on a fluorinated solvent with two different diluents at varying concentrations. The 2,2,3,3-tetrafluoropropyl trifluoroacetate (TFPTFA) enters the solvation cluster due to its stronger Li-ion interactions, whereas 1,1,2,2-tetrafuoroethyl 2,2,2-trifuoroethyl ether (TFETFE) enters only at extremely high diluent concentrations. The ionic conductivity increases with decreasing diluent concentrations, with a slope change during cluster percolation. Overall, TFETFE demonstrates higher effectiveness than TFPTFA, forming higher local salt concentration clusters, and resulting in higher ionic conductivity.

cluster chemistry↗
DOE OSTI2020

Dynamics of PDMS- g -PDMS Bottlebrush Polymers by Broadband Dielectric Spectroscopy

Poly(dimethylsiloxane) (PDMS)-based bottlebrush polymers, PDMS-g-PDMS, have been synthesized by anionic polymerization in combination with a condensation-based grafting reaction. Bottlebrush polymers show intriguing features, e.g., extremely low viscosities. Hereby, studies of their dynamics are rare. Therefore, we focus on the segmental relaxation by broadband dielectric spectroscopy. An increasing cross-sectional radius proportional to the increasing side chain length has been observed by small-angle neutron scattering over three samples. Here, a comparison of the segmental relaxation times of the bottlebrushes with the respective linear chains reveals slower dynamics in the former. For longer chains, this effect vanishes.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Tuning the Functionalities of Porous Liquids for Emergent Gas-Capture Properties

Type 3 Porous Liquids (PLs) are a class of materials with the potential to revolutionize gas capture, storage, and utilization. These PLs are formed by suspending sorbent nanoparticles (e.g., metal−organic frameworks) in sterically excluded solvents, creating permanent porosity for gas capture in a processable, low-viscosity phase. Herein, a computational study revealed sorbent surface functionalization strategies to enhance CO 2 sorption, and the molecular structural signatures underpinning the enhancements in gas uptake. PLs composed of a ZIF-8 surface functionalized with 3-amino-1,2,4-triazole (Atz) in glyceryl triacetate were targeted for emergent CO 2 capture, exceeding that of the unfunctionalized ZIF-8 PL. ZIF-8 was surface functionalized with Atz at various surface coverage fractions (f), and classical molecular dynamics simulations predicted an increase in CO 2 sorption capacity with increasing f, up to f = 0.75. Additionally, detailed structural analyses revealed that solvent orientational order, derived from the solvent triplet-angle distribution, can identify the gas-capture potential of a PL without requiring computationally expensive direct modeling of the CO 2 sorption. Combined with experimental validation, initial computational screening of PL compositions promises to accelerate the discovery of PL compositions for novel gas separation materials platforms.

gas capture↗
DOE OSTI2025

Electrons and Their Multiple Kinetic Fates in an Ionic Liquid

Ionic liquids (ILs) for electrochemical, nuclear, and solar energy applications operate under harsh conditions, where electrons and transient radical species can form. This communication discusses why anions such as bis(trifluoromethylsulfonyl)imide (Tf 2 N − ) are reduced at the electron-rich electrode whereas in laser photoionization or pulse radiolysis studies, where electrons are ejected from species in the bulk, we often detect long-lived electrons in cavities that interact with IL cations instead. This work argues that bulk excess electrons generated photolytically or radiolytically follow kinetically favored pathways. As such, cavity electrons may not be the most energetically favorable states, but when they form, and they do form, they are kinetically stable. Reduction reactions of anions or electron localization in cavities and subsequent reactions are all expected outcomes. Here we focus on a pyrrolidinium-based IL of the dicyanamide (N(CN) 2 − ) anion because of its large electrochemical window and very low viscosity, which are ideal for energy applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗