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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Transition metal ion-assisted photochemical generation of alkyl halides and hydrocarbons from carboxylic acids

Near-UV photolysis of aqueous solutions of propionic acid and aqueous Fe 3+ in the absence of oxygen generates a mixture of hydrocarbons (ethane, ethylene and butane), carbon dioxide, and Fe 2+ . The reaction becomes mildly catalytic (about five turnovers) in the presence of oxygen which converts a portion of alkyl radicals to oxidizing intermediates that reoxidize Fe 2+ . The photochemistry in the presence of halide ions (X - = Cl - , Br - ) generates ethyl halides via halogen atom abstraction from FeXn3-n by ethyl radicals. Near-quantitative yields of C 2 H 5 X are obtained at ≥0.05 M X - . Competition experiments with Co(NH 3 ) 5 Br 2+ provided kinetic data for the reaction of ethyl radicals with FeCl 2+ (k = (4.0 ± 0.5) × 10 6 M -1 s -1 ) and with FeBr 2+ (k = (3.0 ± 0.5) × 10 7 M -1 s -1 ). Photochemical decarboxylation of propionic acid in the presence of Cu 2+ generates ethylene and Cu + . Longer-chain acids also yield alpha olefins as exclusive products. These reactions become catalytic under constant purge with oxygen which plays a dual role. It reoxidizes Cu + to Cu 2+ , and removes gaseous olefins to prevent accumulation of Cu + (olefin) complexes and depletion of Cu 2+ . The results underscore the profound effect that the choice of metal ions, the medium, and reaction conditions exert on the photochemistry of carboxylic acids.

36 MATERIALS SCIENCE↗
DOE OSTI2015

A Stable Fluorinated and Alkylated Lithium Malonatoborate Salt for Lithium Ion Battery Application

A new fluorinated and alkylated lithium malonatoborate salt, lithium bis(2-methyl-2-fluoromalonato)borate (LiBMFMB), has been synthesized for lithium ion battery application. A 0.8 M LiBMFMB solution is obtained in a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (1:2 by wt.). The new LiBMFMB based electrolyte exhibits good cycling stability and rate capability in LiNi0.5Mn1.5O4 and graphite based half-cells.

25 ENERGY STORAGE↗
DOE OSTI2015

Controlling the hydrogenolysis of silica-supported tungsten pentamethyl leads to a class of highly electron deficient partially alkylated metal hydrides

The well-defined single-site silica-supported tungsten complex [( Si–O–)W(Me) 5 ], 1 , is an excellent precatalyst for alkane metathesis. The unique structure of 1 allows the synthesis of unprecedented tungsten hydrido methyl surface complexes via a controlled hydrogenolysis. Specifically, in the presence of molecular hydrogen, 1 is quickly transformed at -78 °C into a partially alkylated tungsten hydride, 4 , as characterized by 1 H solid-state NMR and IR spectroscopies. Species 4 , upon warming to 150 °C, displays the highest catalytic activity for propane metathesis yet reported. DFT calculations using model systems support the formation of [( Si–O–)WH 3 (Me) 2 ], as the predominant species at -78 °C following several elementary steps of hydrogen addition (by σ-bond metathesis or α-hydrogen transfer). Rearrangement of 4 occuring between -78 °C and room temperature leads to the formation of an unique methylidene tungsten hydride [( Si–O–)WH 3 ( CH 2 )], as determined by solid-state 1 H and 13 C NMR spectroscopies and supported by DFT. Thus for the first time, a coordination sphere that incorporates both carbene and hydride functionalities has been observed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Uranium(iii) and thorium(iv) alkyl complexes as potential starting materials

The synthesis and characterization of a rare U(iii) alkyl complex, U[η 4 -Me 2 NC(H)C 6 H 5 ] 3 , using the dimethylbenzylamine (DMBA) ligand has been accomplished. While attempting to prepare the U(iv) compound, reduction to the U(iii) complex occurred. In the analogous Th(iv) system, C-H bond activation of a methyl group of one dimethylamine was observed yielding Th[η 4 -Me 2 NC(H)C 6 H 5 ] 2 [η 5 -(CH 2 )MeNC(H)C 6 H 5 ] with a dianionic DMBA ligand. The utility of these complexes as starting materials has been analyzed using a bulky dithiocarboxylate ligand to yield tetravalent actinide species.

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

Cascade alkylation and deuteration with aryl iodides via Pd/norbornene catalysis: an efficient method for the synthesis of congested deuterium-labeled arenes

An efficient approach for synthesizing congested deuterium-labeled arenes via cascade alkylation and deuteration with aryl iodides has been disclosed. Here, we found that the adoption of sodium formate-$d$ as a deuterium source is the key for achieving high deuterium incorporation >98%.

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

Alkyl decorated metal–organic frameworks for selective trapping of ethane from ethylene above ambient pressures

Here the trapping of paraffins is beneficial compared to selective olefin adsorption for adsorptive olefin purification from a process engineering point of view. Here we demonstrate the use of a series of Zn 2 (X-bdc) 2 (dabco) (where X-bdc 2- is bdc 2- = 1,4-benzenedicarboxylate with substituting groups X, DM-bdc 2- = 2,5-dimethyl-1,4-benzenedicarboxylate or TM-bdc 2- = 2,3,5,6-tetramethyl-1,4-benzenedicarboxylate and dabco = diazabicyclo[2.2.2.]octane) metal-organic frameworks (MOFs) for the adsorptive removal of ethane from ethylene streams. The best performing material from this series is Zn2(TM-bdc)2(dabco) (DMOF-TM), which shows a high ethane uptake of 5.31 mmol g -1 at 110 kPa, with a good IAST selectivity of 1.88 towards ethane over ethylene. Through breakthrough measurements a high productivity of 13.1 L/kg per breakthrough is revealed with good reproducibility over five consecutive cycles. Molecular simulations show that the methyl groups of DMOF-TM are forming a van der Waals trap with the methylene groups from dabco, snuggly fitting the ethane. Further, rarely used high pressure coadsorption measurements, in pressure regimes that most scientific studies on hydrocarbon separation on MOFs ignore, reveal an increase in ethane capacity and selectivity for binary mixtures with increased pressures. The coadsorption measurements reveal good selectivity of 1.96 at 1000 kPa, which is verified also through IAST calculations up to 3000 kPa. This study overall showcases the opportunities that pore engineering by alkyl group incorporation and pressure increase offer to improve hydrocarbon separation in reticular materials.

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

Regiospecific N -alkyl substitution tunes the molecular packing of high-performance non-fullerene acceptors

The rapid development of non-fullerene acceptors (NFAs) with strong near-infrared absorption has led to remarkably enhanced short-circuit current density (J sc ) values in organic solar cells (OSCs). NFAs based on the benzotriazole (Bz) fused-ring π-core have great potential in delivering both high J sc and decent open-circuit voltage values due to their strong intramolecular charge transfer with reasonably low energy loss. Here in this work, we have designed and synthesized a series of Bz-based NFAs, PN6SBO-4F, AN6SBO-4F and EHN6SEH-4F, via regiospecific N-alkyl engineering based on the high-performance NFA mBzS-4F that was reported previously. The molecular packing of mBzS-4F, AN6SBO-4F, and EHN6SEH-4F single crystals was analyzed using X-ray crystallography in order to provide a comprehensive understanding of the correlation between the molecular structure, the charge-transporting properties, and the solar cell performance. Compared with the typical honeycomb single-crystal structure of Y6 derivatives, these NFAs exhibit distinctly different molecular packing patterns. The strong interactions of terminal indanone groups in mBzS-4F and the J-aggregate-like packing in EHN6SEH-4F lead to the formation of ordered 3D networks in single-crystals with channels for efficient charge transport. Consequently, OSCs based on mBzS-4F and EHN6SEH-4F show efficient photon-to-current conversions, achieving the highest power conversion efficiency of 17.48% with a Jsc of 28.83 mA cm -2 .

36 MATERIALS SCIENCE↗
DOE OSTI2022

Cyclic(alkyl)(amino)carbene ruthenium complexes for Z -stereoselective (asymmetric) olefin metathesis

The first Z-stereoselective catechodithiolate ruthenium complexes containing cyclic(alkyl)(amino)carbene ligands are reported. Isolated in nearly quantitative yields or in situ generated, these catalysts demonstrated remarkable Z selectivity (Z/E ratio up to >98/2) in ring-opening metathesis polymerization (ROMP), ring-opening-cross metathesis (ROCM) and cross-metathesis (CM). Thanks to the efficient chiral HPLC resolution of racemic CAAC-complex precursors, optically pure dithiolated complexes were also synthesized allowing to produce enantioenriched Z-ROCM products in >99/1 Z/E with good levels of enantioselectivity.

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

Multicomponent Reactions Among Alkyl Isocyanides, sp Reactants, and sp 2 Carbon Cages

We explored the reactivity and substrate scope of the reactions among an alkyl isocyanide, an sp-hybridized reactant (i.e. alkyne or allene), and a carbon cage, as a new approach to functionalize fullerenes and metallofullerenes. Furthermore, this account summarizes the key findings in our recent published work, and some original data for the reaction involving an isocyanide, allenes, and metallofullerene Lu 3 N@C 80 .

36 MATERIALS SCIENCE↗
DOE OSTI2014

Interaction and dynamics of (alkylamide + electrolyte) deep eutectics: Dependence on alkyl chain-length, temperature, and anion identity

Here we investigate the solute-medium interaction and solute-centered dynamics in (RCONH{sub 2} + LiX) deep eutectics (DEs) via carrying out time-resolved fluorescence measurements and all-atom molecular dynamics simulations at various temperatures. Alkylamides (RCONH{sub 2}) considered are acetamide (CH{sub 3}CONH{sub 2}), propionamide (CH{sub 3}CH{sub 2}CONH{sub 2}), and butyramide (CH{sub 3}CH{sub 2}CH{sub 2}CONH{sub 2}); the electrolytes (LiX) are lithium perchlorate (LiClO{sub 4}), lithium bromide (LiBr), and lithium nitrate (LiNO{sub 3}). Differential scanning calorimetric measurements reveal glass transition temperatures (T{sub g}) of these DEs are ∼195 K and show a very weak dependence on alkyl chain-length and electrolyte identity. Time-resolved and steady state fluorescence measurements with these DEs have been carried out at six-to-nine different temperatures that are ∼100–150 K above their individual T{sub g}s. Four different solute probes providing a good spread of fluorescence lifetimes have been employed in steady state measurements, revealing strong excitation wavelength dependence of probe fluorescence emission peak frequencies. Extent of this dependence, which shows sensitivity to anion identity, has been found to increase with increase of amide chain-length and decrease of probe lifetime. Time-resolved measurements reveal strong fractional power dependence of average rates for solute solvation and rotation with fraction power being relatively smaller (stronger viscosity decoupling) for DEs containing longer amide and larger (weaker decoupling) for DEs containing perchlorate anion. Representative all-atom molecular dynamics simulations of (CH{sub 3}CONH{sub 2} + LiX) DEs at different temperatures reveal strongly stretched exponential relaxation of wavevector dependent acetamide self dynamic structure factor with time constants dependent both on ion identity and temperature, providing justification for explaining the fluorescence results in terms of temporal heterogeneity and amide clustering in these multi-component melts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Electrical conductivity in Langmuir-Blodgett films of n-alkyl cyanobiphenyls using current sensing atomic force microscope

We report our studies on the nanoscale electrical conductivity in monolayers of n-alkyl cyanobiphenyl materials deposited on solid surface. Initially, the 8CB, 9CB, and 10CB monolayer films were prepared by the Langmuir technique at air-water interface and characterized by surface manometry and Brewster angle microscopy. The monolayer films were transferred on to solid substrates by the Langmuir-Blodgett (L-B) technique. The 8CB, 9CB, and 10CB monolayer L-B films were deposited on freshly cleaved mica and studied by atomic force microscope (AFM), thereby measuring the film thickness as ∼1.5 nm. The electrical conductivity measurements were carried out on 9CB and 10CB monolayer L-B films deposited onto highly ordered pyrolytic graphite using current sensing AFM. The nanoscale current-voltage (I-V) measurements show a non-linear variation. The nature of the curve indicates electron tunneling to be the mechanism for electrical conduction. Furthermore, analysis of the I-V curve reveals a transition in the electron conduction mechanism from direct tunneling to injection tunneling. From the transition voltage, we have estimated the values of barrier height for 9CB and 10CB to be 0.71 eV and 0.37 eV, respectively. For both 9CB and 10CB, the effective mass of electron was calculated to be 0.021 m{sub e} and 0.065 m{sub e}, respectively. These parameters are important in the design of molecular electronic devices.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Dielectric relaxation of alkyl chains in graphite oxide and n-alkylammonium halides

The dynamic of n-alkylammonium halides and n-alkylammonium cations (n = 12, 14, 16, 18) intercalated in graphite oxide (GO) have been investigated with complex impedance spectroscopy. X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, elemental analysis and thermogravimetry served to characterize the materials. The intercalated alkylammonium cations distributes as monolayers (when n = 12, 14 or 16) or bilayers (when n = 18), with their long axis parallel to GO layers, and with cations of headgroups bonded ionically to C-O{sup -} groups of GO; backbones of the confined molecules remain free. All halides and intercalation compounds suffer dielectric loss at low temperature. Arrhenius plots of the thermal dependence of the loss peaks, which are asymmetric, produce apparent activation energies that rise with increasing n. Ngai’s correlated-state model helps to correct for effects of dipole-dipole interaction, leading to virtually identical values for actual activation energy of 110 meV ± 5%; the values are also almost the same as the barrier energy for internal rotation in the alkyl macromolecule. We conclude that the relaxation of the alkylammonium cations arises not from C{sub 3} reorientation of the CH{sub 3} at its headgroup, but from small-angle wobbling around its major axis, an intrinsic motion.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Photodissociation dynamics of the simplest alkyl peroxy radicals, CH 3 OO and C 2 H 5 OO, at 248 nm

The photodissociation dynamics of the simplest alkyl peroxy radicals, methyl peroxy (CH 3 OO) and ethyl peroxy C 2 H 5 OO , are investigated using fast beam photofragment translational spectroscopy. A fast beam of CH 3 OO - or C 2 H 5 OO - anions is photodetached to generate neutral radicals that are subsequently dissociated using 248 nm photons. The coincident detection of the photofragment positions and arrival times allows for the determination of mass, translational energy, and angular distributions for both two-body and three-body dissociation events. CH 3 OO exhibits repulsive O loss resulting in the formation of O( 1 D) + CH 3 O with high translational energy release. Minor two-body channels leading to OH + CH 2 O and CH 3 O + O( 3 P) formation are also detected. In addition, small amounts of H + O( 3 P) + CH 2 O are observed and attributed to O loss followed by CH 3 O dissociation. C 2 H 5 OO exhibits more complex dissociation dynamics, in which O loss and OH loss occur in roughly equivalent amounts with O( 1 D) formed as the dominant O atom electronic state via dissociation on a repulsive surface. Minor two-body channels leading to the formation of O 2 + C 2 H 5 and HO 2 + C 2 H 4 are also observed and attributed to a ground state dissociation pathway following internal conversion. Additionally, C 2 H 5 OO dissociation yields a three-body product channel, CH 3 + O( 3 P) + CH 2 O, for which the proposed mechanism is repulsive O loss followed by the dissociation of C 2 H 5 O over a barrier. These results are compared to a recent study of tert-butyl peroxy (t-BuOO) in which 248 nm excitation results in three-body dissociatio n and ground state two-body dissociation but no O( 1 D) production.

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

Microstructure and heteroatom dictate the doping mechanism and thermoelectric properties of poly(alkyl-chalcogenophenes)

Heteroatom substitution can favorably alter electronic transport in conductive polymers to improve their thermoelectric performance. Here we report the spectroscopic, structural, and thermoelectric properties of poly(3–(3',7'-dimethyloctyl) chalcogenophenes) or P3RX doped with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), where the heteroatom [X = thiophene (T), selenophene (Se), tellurophene (Te)], the doping methodology, and extent of doping are systematically varied. Spectroscopic measurements reveal that while all P3RX polymers are appreciably doped, the doping mechanism is inherently different. Poly(3-hexylthiophene) (P3HT, used as a control) and poly(3–(3',7'-dimethyloctyl)tellurophene) (P3RTe) are doped primarily via integer charge transfer (ICT), whereas poly(3–(3',7'-dimethyloctyl)selenophene) (P3RSe) and poly(3–(3',7'-dimethyloctyl)thiophene) (P3RT) are doped via charge transfer complex (CTC) mechanisms. Despite these differences, all polymers saturate with roughly the same number of F4TCNQ counterions (1 dopant per 4 to 6 heterocycles), reinforcing the idea that the extent of charge transfer varies with the doping mechanism. Grazing incidence wide-angle x-ray scattering measurements provide insight into the structural driving forces behind different doping mechanisms—P3RT and P3RSe have similar microstructures in which F4TCNQ intercalates between the π-stacked backbones resulting in CTC doping (localized carriers), while P3HT and P3RTe have microstructures in which F4TCNQ intercalates in the alkyl side chain region, giving rise to ICT doping (delocalized carriers). These structural and spectroscopic observations shed light on why P3HT and P3RTe obtain electrical conductivities ca. 3 S/cm, while P3RT and P3RSe have conductivities <10–3 S/cm under the same thin film processing conditions. Ultimately, this work quantifies the effects of heteroatom, microstructural ordering, extent of doping, and doping mechanism, thereby providing rational guidance for designing future thermoelectric polymer-dopant systems.

36 MATERIALS SCIENCE↗