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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Pulse Radiolysis and Computational Studies on a Pyrrolidinium Dicyanamide Ionic Liquid: Detection of the Dimer Radical Anion

A pulse radiolysis study on pyrrolidinium cation based ionic liquids is presented here in this paper. Time-resolved absorption spectra for 1-methyl-1-propylpyrrolidinium dicyanamide (DCA) at 500 ns after the electron pulse show broad absorption bands at wavelengths below 440 nm and at 640 nm. In pyrrolidinium bis(trifluoromethylsulfonyl)imide (NTf 2 ) and tris(perfluoroethyl)trifluorophosphate (FAP) ILs, the transient absorption below 440 nm is much weaker. The absorption at 500 ns, which increases with wavelength from 500 nm to beyond 800 nm, was assigned to the tail of the solvated electron NIR absorption spectrum, since it disappears in the presence of N 2 O. In the DCA IL, the presence of a reducing species was confirmed by the formation of pyrene radical anion. The difference in the transient species in the case of the DCA IL compared to other two ILs should be due to the anion, with cations being similar. In pseudohalide ILs such as DCA, radicals are formed by direct hole trapping by the anion (X – + h + → X•), followed by addition to the parent anion. Prediction of the UV/vis absorption spectra of the dimer radical anion by computational calculation supports the experimental results. The oxidizing efficiency of (DCA) 2 •– and its reduction potential (E(DCA)2•–/(2DCA–)) have been determined.

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

Ionic Liquid-Enhanced Interfaces to Boost Reactive C O2 Capture

The addition of ionic liquids (ILs) to a mixture containing a molecular solvent and other ionic species can induce the heterogeneous redistribution of cations and anions at the gas–liquid interface. This nonuniform redistribution of cations and anions driven by the differences in the solvophilicity of ions can improve the thermophysical and interfacial properties of such mixtures, creating a local chemical environment that is conducive to some reactions. In this work, ILs are added to a mixture of potassium hydroxide (KOH) and ethylene glycol (EG), used as a reactive absorbent and electrolyte in the migration-assisted moisture-gradient (MAMG) process for CO 2 capture. Molecular dynamics (MD) simulations are employed to probe into the effects of complex ion–ion and ion–solvent interactions and to examine the chemical composition at the gas–liquid interface. A total of 12 systems are investigated using molecular simulations to identify trends in the performance of IL additives based on the choice of cation, anion, and IL concentration. The cation effects are studied using IL additives based on 1-ethyl-3-methylimidazolium ([EMIM] + ) and 1-butyl-3-methylimidazolium ([BMIM] + ), while the impact of anions is examined using additives based on dicyanamide [DCA] − , triflate [TfO] − , bistriflimide [NTf 2 ] − , and hexafluorophosphate [PF 6 ] − anions, respectively. The influence of the IL concentration is also evaluated at molar concentrations between 1% and 4%. The simulation results indicate that the use of IL additives can affect the physical CO 2 solubility, surface tension, and the localization of CO 2 around the [OH] − ions at the gas–liquid interface. It is also evident that the choice of cations, anions, and IL concentration determines the extent to which the IL additives impact the local physicochemical properties. Physical dissolution, diffusive transport, and interaction with [OH] − are critical intermediate steps toward reactive CO 2 capture using a liquid absorbent. Hence, the improvement in one or more of these properties, aided by IL additives, is expected to improve the overall CO 2 capture performance. Experiments reaffirmed the impact of IL additives on CO 2 capture performance and the sensitivity to the choice of the cation, anion, and concentration of the IL additive.

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

Toward Lithium Recovery Using Modular (and Membraneless) Phase Separation and Extraction (MPSE) Technology with Ionic Liquid (IL) Solvents: Effect of Coatings

In this work, a single-channel slope-plate Modular and Membrane-less Phase Separation and Extraction (MPSE) device was fabricated using 3D printing. The slope-plate was designed with an insertable glass slide to enable surface modification with coatings. Self-assembled monolayers (SAMs) and perfluoropolyether (Zdol) coatings were applied to tailor surface wettability and enhance phase separation. Using a model biphasic system of water and hexadecane, both coatings significantly improved the separation efficiency compared to the uncoated device by promoting selective wetting. Building on these results, lithium extraction from a simulated saline solution was investigated using 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf₂]) as the ionic liquid (IL) extractant. The IL effectively extracted Li⁺ from the aqueous phase in bulk extraction, demonstrating its potential for lithium recovery. However, the low interfacial tension between the IL and aqueous phases posed challenges for phase separation. The application of SAM and Zdol coatings effectively mitigated this issue. Overall, integrating tailored surface chemistry with the slope-plate MPSE design shows great promise as an efficient and scalable platform for studying liquid–liquid separation and optimizing ionic liquid–based extraction processes for lithium recovery from saline sources.

3D printing↗
DOE OSTI2019

Charge Transport in Imidazolium-Based Homo- and Triblock Poly(ionic liquid)s

Ion dynamics in a series of imidazolium-based triblock copolymers (triblock co-PILs) are investigated using broadband dielectric spectroscopy (BDS) and differential scanning calorimetry (DSC) and compared to their homopolymer counterparts (homo-PILs). Two calorimetric glass transition temperatures (T g ) are observed corresponding to the charged poly(ionic liquid) (PIL) blocks and noncharged polystyrene (PS) blocks. Varying the counterion from Br – to NTf 2 – decreases the T g of the charged block by over 50 °C, thereby increasing the room-temperature ionic dc conductivity by over 6 orders of magnitude. Interestingly, for a given anion, varying the volume fraction of the charged block, from ~0.5 to ~0.8, has very minimal effect on the dc ionic conductivity, indicating that the choice of counterion is the key factor influencing charge transport in these systems.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A Dicopper Nitrenoid by Oxidation of a Cu'Cu' Core: Synthesis, Electronic Structure, and Reactivity

A dicopper nitrenoid complex was prepared by formal oxidative addition of the nitrenoid fragment to a dicopper(I) center by reaction with the iminoiodinane PhINTs (Ts = tosylate). This nitrenoid complex, (DPFN)Cu 2 (μ-NTs)[NTf 2 ] 2 (DPFN = 2,7-bis(fluorodi(2-pyridyl)methyl)-1,8-naphthyridine), is a powerful H atom abstractor that reacts with a range of strong C–H bonds to form a mixed-valence Cu(I)/Cu(II) μ-NHTs amido complex in the first example of a clean H atom transfer to a dicopper nitrenoid core. In line with this reactivity, DFT calculations reveal that the nitrenoid is best described as an iminyl (NR radical anion) complex. The nitrenoid was trapped by the addition of water to form a mixed-donor hydroxo/amido dicopper(II) complex, which was independently obtained by reaction of a Cu 2 (μ-OH) 2 complex with an amine through a protonolysis pathway. Furthermore, this mixed-donor complex is an analogue for the proposed intermediate in copper-catalyzed Chan–Evans–Lam coupling, which proceeds via C–X (X = N or O) bond formation. Treatment of the dicopper(II) mixed donor complex with MgPh 2 (THF) 2 resulted in generation of a mixture that includes both phenol and a previously reported dicopper(I) bridging phenyl complex, illustrating that both reduction of dicopper(II) to dicopper(I) and concomitant C–X bond formation are feasible.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

How Does the Ionic Liquid Organizational Landscape Change when Nonpolar Cationic Alkyl Groups Are Replaced by Polar Isoelectronic Diethers?

The X-ray scattering experiments and molecular dynamics simulations have been performed to investigate the structure of four room temperature ionic liquids (ILs) comprising the bis(trifluoromethylsulfonyl)amide (NTf 2 – ) anion paired with the triethyloctylammonium (N 2228 + ) and triethyloctylphosphonium (P 2228 + ) cations and their isoelectronic diether analogs, the (2-ethoxyethoxy)ethyltriethylammonium (N 222(2O2O2) + ) and (2-ethoxyethoxy)ethyltriethylphosphonium (P 222(2O2O2) + ) cations. Agreement between simulations and experiments is good and permits a clear interpretation of the important topological differences between these systems. The first sharp diffraction peak (or prepeak) in the structure function S(q) that is present in the case of the liquids containing the alkyl-substituted cations is absent in the case of the diether substituted analogs. Using different theoretical partitioning schemes for the X-ray structure function, we show that the prepeak present in the alkyl-substituted ILs arises from polarity alternations between charged groups and nonpolar alkyl tails. In the case of the diether substituted ILs, we find considerable curling of tails. Anions can be found with high probability in two different environments: close to the cationic nitrogen (phosphorus) and also close to the two ether groups. Moreover, for the two diether systems, anions are found in locations from which they are excluded in the alkyl-substituted systems. This removes the longer range (polar/nonpolar) pattern of alternation that gives rise to the prepeak in alkyl-substituted systems.

Kashyap, Hemant K.↗
DOE OSTI2018

Measurement of temperature and density using non-collective X-ray Thomson scattering in pulsed power produced warm dense plasmas

We present the first experimental measurement of temperature and density of a warm dense plasma produced by a pulsed power driver at the Nevada Terawatt Facility (NTF). In the early phases of discharge, most of the mass remains in the core, and it has been challenging to diagnose with traditional methods, e.g. optical probing, because of the high density and low temperature. Accurate knowledge of the transport coefficients as well as the thermodynamic state of the plasma is important to precisely test or develop theoretical models. Here, we have used spectrally resolved non-collective X-ray Thomson scattering to characterize the dense core region. We used a graphite load driven by the Zebra current generator (0.6 MA in 200 ns rise time) and the Ti He-α line produced by irradiating a Ti target with the Leopard laser (30 J, 0.8 ns) as an X-ray probing source. Using this configuration, we obtained a signal-to-noise ratio ~2.5 for the scattered signal. Finally, by fitting the experimental data with predicted spectra, we measured T = 2±1.9 eV, ρ = 0.6±0.5 gr/cc, 70 ns into the current pulse. The complexity of the dense core is revealed by the electrons in the dense core that are found to be degenerate and weakly coupled, while the ions remain highly coupled.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Small nickel nanoparticle arrays from long chain imidazolium ionic liquids

A series of six long chain alkyl mono- and bi-cationic imidazolium based salts with bis(trifluoromethylsulfonyl)imide (NTf 2– ) as the anion were synthesized and characterized. Single crystal structure of 1-methyl-3-octadecylimidazolium bis(trifluoromethylsulfonyl)imide could be obtained by X-ray analysis. All these long chain alkyl imidazolium based ILs were applied in the synthesis of nickel nanoparticles via chemical decomposition of an organometallic precursor of nickel. In these media, spontaneous decomposition of Ni(COD) 2 (COD = 1,5-cyclooctadiene) in the absence of H 2 occurred giving small NPs (≤4 nm) with narrow size distributions. Interestingly, formation of regularly interspaced NP arrays was also observed in long chain ILs. Lastly, such array formation could be interesting for potential applications such as carbon nanotube growth.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Electroreduction of Er 3+ in nonaqueous solvents

Here, the electroreduction of Er 3+ in propylene carbonate, N,N-dimethylformamide, or a variety of quaternary ammonium ionic liquids (ILs) was investigated using [Er(OTf) 3 ] and [Er(NTf 2 ) 3 ]. Systematic variation of the ILs' cation and anion, Er 3+ salt, and electrode material revealed a disparity in electrochemical interactions not previously seen. For most ILs at a platinum electrode, cyclic voltammetry exhibits irreversible interactions between Er 3+ salts and the electrode at potentials significantly less than the theoretical reduction potential for Er 3+ . Throughout all solvent–salt systems tested, a deposit could be formed on the electrode, though obtaining a high purity, crystalline Er 0 deposit is challenging due to the extreme reactivity of the deposit and resulting chemical interactions, often resulting in the formation of a complex, amorphous solid–electrolyte interface that slowed deposition rates. Comparison of platinum, gold, nickel, and glassy carbon (GC) working electrodes revealed oxidation processes unique to the platinum surface. While no appreciable reduction current was observed on GC at the potentials investigated, deposits were seen on platinum, gold, and nickel electrodes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Porous liquid zeolites: hydrogen bonding-stabilized H-ZSM-5 in branched ionic liquids

Porous liquids, as a newly emerging type of porous material, have great potential in gas separation and storage. However, the examples and synthetic strategies reported so far likely represent only the tip of the iceberg due to the great difficulty and challenge in engineering permanent porosity in liquid matrices. By taking advantage of the hydrogen bonding interaction between the alkane chains of branched ionic liquids and the Brønsted sites in H-form zeolites, as well as the mechanical bond of the long alkyl chain of the cation penetrated into the zeolite channel at the interface, the H-form zeolites can be uniformly stabilized in branched ionic liquids to form porous liquid zeolites, which not only significantly improve their gas sorption performance, but also change the gas sorption–desorption behavior because of the preserved permanent porosity. Furthermore, such a facile synthetic strategy can be extended to fabricate other types of H-form zeolite-based porous liquids by taking advantage of the tunability of the counter-anion (e.g., NTf 2 - , BF 4 - , EtSO 4 - , etc.) in branched ionic liquids, thus opening up new opportunities for porous liquids for specific applications in energy and environment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Spin state solvomorphism in a series of rare S = 1 manganese(III) complexes

We present that structural, magnetic and spectroscopic data of four complex salts, [Mn(napsal 2 323)]NTf 2 , 1 ,[Mn(napsal 2 323)]ClO 4 , 2 , [Mn(napsal 2 323)]BF 4 , 3 and [Mn(napsal 2 323)]NO 3 , 4 , of the [Mn(napsal 2 323)] + complex cation indicate that the Mn 3+ ion is stabilized in the rare S = 1 spin triplet form in this ligand sphere. Zero-field splitting values of D = +19.6 cm -1 and | E | = 2.02 cm -1 for complex 1 were obtained by High Field Electron Paramagnetic Resonance (HFEPR) measurements conducted over a range of frequencies. Structural and magnetic data also indicate that co-crystallization of complexes 2 and 3 with 0.5 equivalents of ethanol yields the high spin S = 2 forms of the perchlorate and tetrafluoroborate solvates [Mn(napsal 2 323)]ClO 4 ·0.5(C 2 H 5 OH), 2·0.5EtOH and [Mn(napsal 2 323)]BF 4 ·0.5(C 2 H 5 OH), 3·0.5EtOH .

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

Valence states of cyclotron-produced thallium

The unexpected behavior of thallium atoms, produced in a reaction of gold target with accelerated 3 He ions, in liquid–liquid extraction with [C n mim][NTf 2 ] ionic liquids ( n = 2, 4, 6–8, 10) was investigated. Contrary to the general expectations, a significant proportion of thallium produced in the nuclear reaction was found in a non-monovalent state upon dissolution of the KCl aerosol collector. This finding is critical for the design and evaluation of the forthcoming chemistry experiments with the superheavy element nihonium.

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

Dynamics of fluorinated imide-based ionic liquids using nuclear magnetic resonance techniques

There is increasing interest in studying molecular motions in ionic liquids to gain better insights into their transport properties and to expand their applications. Here, in this study, we have employed the fast field cycling relaxometry and pulsed field gradient nuclear magnetic resonance techniques to investigate the rotational and translational dynamics of fluorinated imide-based ionic liquids (ILs) at different temperatures. We have studied a total of six ILs composed of the 1-butyl-3-methylimidazolium cation ([BMIM] + ) combined with chemically modified analogs of the bis((trifluoromethyl)sulfonyl)imide anion ([NTf 2 ] − or [TFSI] − ). The primary objective of this paper is to broaden the understanding of how the anion's conformational flexibility, fluorination, and mass affect the molecular dynamics of cations and anions. Our results indicate that flexibility has the most significant impact on the rotational and translational motions of ions. Meanwhile, the effect of fluorination and mass is only relevant when conformational flexibility does not change significantly between the ILs being compared.

25 ENERGY STORAGE↗
DOE OSTI2016

Communication: Nanoscale structure of tetradecyltrihexylphosphonium based ionic liquids

In a recent communication [J. J. Hettige et al., J. Chem. Phys. 140, 111102 (2014)], we investigated the anomalous temperature dependence of the X-ray first sharp diffraction peak (or prepeak) in the tetradecyltrihexylphosphonium bis(trifluoromethylsulfonyl)-amide ionic liquid. Contrary to what was expected and often observed, the first sharp diffraction peak in this system was shown to increase in intensity with increasing temperature. This implies higher intermediate-range periodicity at a higher temperature. Is this counter-intuitive behavior specific to the combination of cation and anion? The current work analyzes the structural behavior of the same cation coupled with six different anions ranging from the small and spherically symmetric Cl{sup −} to the more structurally complex and charge-diffuse NTf{sub 2}{sup −}. In all cases, the same temperature behavior trend for the prepeak is observed independent of anionic nature. We will show that the intensity increase in the prepeak region is associated with the structural behavior of charged liquid subcomponents. Instead, upon a temperature increase, the apolar subcomponents contribute to what would be an expected decrease of prepeak intensity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗