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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 1,441 records · Page 80
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Multimodal Characterization of Crystal Structure and Formation in Rubrene Thin Films Reveals Erasure of Orientational Discontinuities

Abstract Multimodal multiscale characterization provide opportunities to study organic semiconducting thin films with multiple length scales, across multiple platforms, to elucidate crystallization mechanisms of the various microstructures that impact functionality. With polarized scanning transmission X‐ray and 4D‐scanning transmission electron microscopy, hybrid crystalline structures in rubrene thin films in which large crystalline domains surround a common nucleus and transition to a spherulite morphology at larger radii is observed. These high‐resolution techniques reveal how azimuthal orientational discontinuities at smaller radii are erased as spherulite morphology takes hold. In situ crystallization in the films with optical microscopy is also captured, discovering the importance of considering the initial temperature increase of a film during thermal annealing over the crystallization timescale. This kinetic information of the radial crystallization rate and of corresponding film heating kinetics is used to estimate the temperature at which the larger crystalline regions transition into a spherulite. By combining the results obtained from the different characterization modes, it is learned that thermal conditions can sensitively affect the crystallization of rubrene and other organic thin films. The observations suggest opportunities for more complex temperature‐dependent processing to maximize hybrid structures’ functionality in organic thin films and demonstrate that multimodal studies deepen the understanding of structure‐function dynamics.

Tan, Jenna A.↗
DOE OSTI2018

Development and Characterization of 3D Printable Thermite Component Materials

Additive manufacturing (AM) has recently shown great promise as a means to tailor a wide range of material properties, both quasi-static and dynamic. An example of controlling the dynamic behavior is to tailor the chemical energy release rate in composite energetic materials such as thermites – which are a subset of pyrotechnics that use a metal fuel and a metal oxide as an oxidizer. Since these materials are most hazardous once finely mixed, the approach taken here is to formulate the fuel and oxidizer separately such that they can be mixed on-the-fly. The development, formulation, and characterization of two respective aqueous 3D printable inks consisting of Al and CuO are discussed. The rheological properties and ability of the material to span gaps are characterized. To demonstrate that the materials could be mixed and sustain a reaction, the inks are fed into a static mixing nozzle and extruded into a high-aspect ratio test strip. Upon drying, the material can be ignited and sustain a propagation through the part. These results present a facile, and safe, way to AM thermite which can be used for more detailed follow on studies looking at the role of architecture on the reactivity.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Advancing Insights into Electrochemical Pre‐Treatments of Supported Nanoparticle Electrocatalysts by Combining a Design of Experiments Strategy with In Situ Characterization

Activation, break-in, and/or pre-treatment protocols are generally applied to energy conversion devices before regular operation to reach stable performance. There remains much to understand about the relationships among physical properties, performance, and electrochemical pre-treatments. Here, a design-of-experiments (DoE) strategy is employed to address this gap by demonstrating the influence of five pre-treatment parameters for carbon-supported Pt-nanoparticle catalysts on the electrocatalytic oxygen reduction reaction (ORR). A subset of pre-treatments, developed using a central composite design, are tested in a flow cell combined with an inductively-coupled plasma mass spectrometer (on-line ICP-MS). The DoE-based approach facilitates comprehensive insights from two orders of magnitude fewer experiments than a conventional grid search. The coupled on-line ICP-MS setup enables effective catalysis and real-time catalyst dissolution data. Leveraging insights from DoE for on-line ICP-MS and additional characterization, a model is built between the degradation of a multi-dimensional supported Pt surface, its performance, and applied electrochemical parameters. These investigations identify surface modifications, such as oxidation, and subsequent restructuring of Pt during pre-treatment as a primary cause of performance deterioration during ORR. By combining DoE with advanced characterization techniques, a powerful approach is demonstrated to gain a mechanistic understanding of pre-treatment protocols that can be broadly adapted to various reaction chemistries.

Platinum↗
DOE OSTI2017

Spectroscopic Evidence for a Monomeric Copper(I) Hydride and Crystallographic Characterization of a Monomeric Silver(I) Hydride

Abstract (1,3‐bis[2,6‐bis[di(4‐tert‐butylphenyl)methyl]‐4‐methylphenyl]imidazol‐2‐ylidene)CuOPh [(IPr**)CuOPh] reacts with poly(methylhydrosiloxane) as the hydride donor to afford the monomeric (IPr**)CuH complex, which was spectroscopically characterized. The latter is in equilibrium in solution with [(IPr**)CuH] 2 , the dimer being exclusively present in the solid state. These results support the hypothesis that copper hydride aggregates dissociate in solution. In contrast, addition of pinacolborane to [(IPr**)AgOPh] at −40 °C allows the isolation of the monomeric (IPr**)AgH complex, which was crystallographically characterized.

Romero, Erik A.↗
DOE OSTI2023

A General Autofluorescence Method to Characterize Polymerization Progress

Abstract An autofluorescence technique to characterize polymerization progress in real time/in line was developed, which functioned in the absence of typical fluorogenic groups on the monomer or polymer. The monomer dicyclopentadiene and polymer polydicyclopentadiene are hydrocarbons that lack traditional functional groups for fluorescence spectroscopy. Here, the autofluorescence of formulations containing this monomer and polymer during ruthenium‐catalyzed ring‐opening metathesis polymerization (ROMP) was harnessed for reaction monitoring. The methods fluorescence recovery after photobleaching (FRAP) and here‐developed fluorescence lifetime recovery after photobleaching (FLRAP) characterized polymerization progress in these native systems—without requiring exogenous fluorophore. (Auto)fluorescence lifetime recovery changes during polymerization correlated linearly to degree of cure, providing a quantitative link with reaction progress. These changing signals also provided relative rates of background polymerization, enabling comparison of 10 different catalyst‐inhibitor‐stabilized formulations. Multiple‐well analysis demonstrated suitability for future high‐throughput evaluation of formulations for thermosets. The central concept of the combined autofluorescence and FLRAP/FRAP method may be extendable to monitoring other polymerization reactions previously overlooked for lack of an obvious fluorescence handle.

López, Pía A.↗
DOE OSTI2017

Spectroscopic Evidence for a Monomeric Copper(I) Hydride and Crystallographic Characterization of a Monomeric Silver(I) Hydride

(1,3-bis[2,6-bis[di(4-tert-butylphenyl)methyl]-4-methylphenyl]imidazol-2-ylidene)CuOPh [(IPr**)CuOPh] reacts with poly(methylhydrosiloxane) as the hydride donor to afford the monomeric (IPr**)CuH complex, which was spectroscopically characterized. The latter is in equilibrium in solution with [(IPr**)CuH]2, the dimer being exclusively present in the solid state. In this work, these results support the hypothesis that copper hydride aggregates dissociate in solution. In contrast, addition of pinacolborane to [(IPr**)AgOPh] at –40 °C allows the isolation of the monomeric (IPr**)AgH complex, which was crystallographically characterized.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Synthesis and Characterization of Iridium(V) Coordination Complexes With an N,O-Donor Organic Ligand

Here, we have prepared and fully characterized two isomers of [IrI V (dpyp) 2 ] (dpyp=meso-2,4-di(2-pyridinyl)-2,4-pentanediolate). These complexes can cleanly oxidize to [Ir V (dpyp) 2 ] + , which to our knowledge represent the first mononuclear coordination complexes of Ir V in an N,O-donor environment. One isomer has been fully characterized in the Ir V state, including by X-ray crystallography, XPS, and DFT calculations, all of which validate metal-centered oxidation. The unprecedented stability of these Ir V complexes is ascribed to the exceptional donor strength of the ligands, their resistance to oxidative degradation, and the presence of four highly donor alkoxide groups in a plane, which breaks the degeneracy of the d-orbitals and favors oxidation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Nebulization Prior to Isolation, Ionization, and Dissociation of the Neutral Serine Octamer Allows Its Characterization

Nebulization of enantiomerically mixed serine solutions, followed by ion deflection and gentle on-line protonation, is used to isolate and characterize the strongly preferred homochiral neutral serine octamer (Ser 8 ). The separation of the nebulization and ionization steps and the use of the enantiomeric l-serine ion (l-d 3 Ser) 8 H + as a soft protonating agent ensured that neutral (d-Ser) 8 was characterized without interference from serine octamer ((d-Ser) 8 H + ) ions. MS/MS experiments showed that the ionized neutral octamer and the protonated octamer formed directly by ESI have the same structures. Experiments in which the temperature of the heated transfer tube was varied indicate dissociation of the neutral octamer to the dimer. Field-free nebulization of racemic serine forms the separate homochiral species with very high chiral selectivity. We suggest that the homochiral preference is a property of (d-Ser)8 and that the preference observed earlier for (d-Ser) 8 H + is simply an expression of this feature of the neutral cluster.

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

Protonation of CH 3 N 3 and CF 3 N 3 in Superacids: Isolation and Structural Characterization of Long‐Lived Methyl‐ and Trifluoromethylamino Diazonium Ions

Abstract The methylamino diazonium cations [CH 3 N(H)N 2 ] + and [CF 3 N(H)N 2 ] + were prepared as their low‐temperature stable [AsF 6 ] − salts by protonation of azidomethane and azidotrifluoromethane in superacidic systems. They were characterized by NMR and Raman spectroscopy. Unequivocal proof of the protonation site was obtained by the crystal structures of both salts, confirming the formation of alkylamino diazonium ions. The Lewis adducts CH 3 N 3 ⋅AsF 5 and CF 3 N 3 ⋅AsF 5 were also prepared and characterized by low‐temperature NMR and Raman spectroscopy, and also by X‐ray structure determination for CH 3 N 3 ⋅AsF 5 . Electronic structure calculations were performed to provide additional insights. Attempted electrophilic amination of aromatics such as benzene and toluene with methyl‐ and trifluoromethylamino diazonium ions were unsuccessful.

Saal, Thomas↗
DOE OSTI2023

A General Autofluorescence Method to Characterize Polymerization Progress

An autofluorescence technique to characterize polymerization progress in real time/in line was developed, which functioned in the absence of typical fluorogenic groups on the monomer or polymer. The monomer dicyclopentadiene and polymer polydicyclopentadiene are hydrocarbons that lack traditional functional groups for fluorescence spectroscopy. Here, the autofluorescence of formulations containing this monomer and polymer during ruthenium-catalyzed ring-opening metathesis polymerization (ROMP) was harnessed for reaction monitoring. The methods fluorescence recovery after photobleaching (FRAP) and here-developed fluorescence lifetime recovery after photobleaching (FLRAP) characterized polymerization progress in these native systems—without requiring exogenous fluorophore. (Auto)fluorescence lifetime recovery changes during polymerization correlated linearly to degree of cure, providing a quantitative link with reaction progress. These changing signals also provided relative rates of background polymerization, enabling comparison of 10 different catalyst–inhibitor-stabilized formulations. Multiple-well analysis demonstrated suitability for future high-throughput evaluation of formulations for thermosets. Furthermore, the central concept of the combined autofluorescence and FLRAP/FRAP method may be extendable to monitoring other polymerization reactions previously overlooked for lack of an obvious fluorescence handle.

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

Electrochemical Characterization of Isolated Nitrogenase Cofactors from Azotobacter vinelandii

The nitrogenase cofactors are structurally and functionally unique in biological chemistry. Despite a substantial amount of spectroscopic characterization of protein-bound and isolated nitrogenase cofactors, electrochemical characterization of these cofactors and their related species is far from complete. Herein we present voltammetric studies of three isolated nitrogenase cofactor species: the iron–molybdenum cofactor (M-cluster), iron–vanadium cofactor (V-cluster), and a homologue to the iron–iron cofactor (L-cluster). We observe two reductive events in the redox profiles of all three cofactors. Of the three, the V-cluster is the most reducing. The reduction potentials of the isolated cofactors are significantly more negative than previously measured values within the molybdenum–iron and vanadium–iron proteins. Finally, the outcome of this study provides insight into the importance of the heterometal identity, the overall ligation of the cluster, and the impact of the protein scaffolds on the overall electronic structures of the cofactors.

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

Accelerated Characterization of Electrode‐Electrolyte Equilibration

Operational durability is poorly characterized by traditional (photo)electrocatalyst discovery workflows, creating a barrier to scale-up and deployment. Corrosion is a prominent degradation mechanism whose thermodynamics depend on the concentration of corrosion products in electrolyte. We present an automated system for characterizing the equilibration of (photo)electrodes with dissolved metals in electrolyte for a given electrode, pH, and electrochemical potential. Automation of electrode selection, electrolyte preparation, and electrolyte aliquoting enables rapid identification of self-passivating electrodes and estimation of the equilibrium dissolved metals concentrations. The technique is demonstrated for metal oxide photoanodes in alkaline electrolyte, where BiVO 4 is found to continually corrode, in agreement the literature. An amorphous Ni−Sb−O photoanode is found to passivate with a Ni-rich coating on the order of 1 monolayer with less than 1 μM total dissolved metals in electrolyte, demonstrating its suitability for durable photoelectrochemical operation. The automation and throughput of the instrument are designed for incorporation in accelerated electrocatalyst discovery workflows so that durability can be considered on equal footing with activity.

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

The Synthesis, Characterization and Dehydrogenation of Sigma-Complexes of BN-Cyclohexanes

The coordination chemistry of the 1,2-BN-cyclohexanes 2,2-R 2 -1,2-B,N-C 4 H 10 (R 2 =HH, MeH, Me 2 ) with Ir and Rh metal fragments has been studied. This led to the solution (NMR spectroscopy) and solid-state (X-ray diffraction) characterization of [Ir(PCy 3 ) 2 (H) 2 (η 2 η 2 -H 2 BNR 2 C 4 H 8 )][BAr F 4 ] (NR 2 =NH 2 , NMeH) and [Rh( i Pr 2 PCH 2 CH 2 CH 2 P i Pr 2 )(η 2 η 2 -H 2 BNR 2 C 4 H 8 )][BAr F 4 ] (NR 2 =NH 2 , NMeH, NMe 2 ). For NR 2 =NH 2 subsequent metal-promoted, dehydrocoupling shows the eventual formation of the cyclic tricyclic borazine [BNC 4 H 8 ] 3 , via amino-borane and, tentatively characterized using DFT/GIAO chemical shift calculations, cycloborazane intermediates. For NR 2 =NMeH the final product is the cyclic amino-borane HBNMeC 4 H 8 . The mechanism of dehydrogenation of 2,2-H,Me-1,2-B,N-C 4 H 10 using the {Rh( i Pr 2 PCH 2 CH 2 CH 2 P i Pr 2 )} + catalyst has been probed. Catalytic experiments indicate the rapid formation of a dimeric species, [Rh 2 ( i Pr 2 PCH 2 CH 2 CH 2 P i Pr 2 ) 2 H 5 ][BAr F 4 ]. Using the initial rate method starting from this dimer, a first-order relationship to [amine-borane], but half-order to [Rh] is established, which is suggested to be due to a rapid dimer–monomer equilibrium operating.

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

Experimental and quantum mechanical characterization of an oxygen-bridged plutonium(IV) dimer

We report the synthesis and characterization of K 4 {[PuCl 2 (NO 3 ) 3 ] 2 (μ 2 -O)}·H 2 O, which contains the first known μ 2 -oxo bridge between two Pu IV metal centers. Adding to its uniqueness is the Pu-(μ 2 -O) bond length of 2.04 Å, which is the shortest of other analogous compounds. The Pu-(μ 2 -O)-Pu bridge is characterized by the mixing of s -, d -, and p -orbitals from Pu with the p -orbitals of O; the 5 f -orbitals do not participate in bonding. Natural bond orbital analysis indicates that Pu and O interact through one 3c-2e σ Pu-O-Pu and two 3c-2e π Pu-O-Pu bonding orbitals and that the electron density is highly polarized on the μ 2 -O. Bond topology properties analysis indicates that the Pu-(μ 2 -O) bond shares both ionic and covalent character. Quantum mechanical calculations also show that the dimer has multiconfigurational ground states, where the nonet, septet, quintet, triplet, and singlet are close in energy. This work demonstrates the interplay between experimental and computational efforts that is required to understand the chemical bonding of Pu compounds.

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

Characterizing Polyoxovanadate‐Alkoxide Clusters Using Vanadium K‐Edge X‐Ray Absorption Spectroscopy

Abstract A number of technologies would benefit from developing inorganic compounds and materials with specific electronic and magnetic exchange properties. Unfortunately, designing compounds with these properties is difficult because metal⋅⋅⋅metal coupling schemes are hard to predict and control. Fully characterizing communication between metals in existing compounds that exhibit interesting properties could provide valuable insight and advance those predictive capabilities. One such class of molecules are the series of Lindqvist iron‐functionalized and hexavanadium polyoxovanadate‐alkoxide clusters, which we characterized here using V K‐edge X‐ray absorption spectroscopy. Substantial changes in the pre‐edge peak intensities were observed that tracked with the V 3 d ‐electron count. The data also suggested substantial delocalization between the vanadium cations. Meanwhile, the Fe III cations were electronically isolated from the polyoxovanadate core.

Meyer, Rachel L.↗
DOE OSTI2019

In-situ/operando X-ray characterization of metal hydrides

Here in this article, the capabilities of soft and hard X-ray techniques, including X-ray absorption (XAS), soft X-ray emission spectroscopy (XES), resonant inelastic soft X-ray scattering (RIXS), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), and their application to solid-state hydrogen storage materials are presented. These characterization tools are indispensable for interrogating hydrogen storage materials at the relevant length scales of fundamental interest, which range from the micron scale to nanometer dimensions.Since nanostructuring is now well established as an avenue to improve the thermodynamics and kinetics of hydrogen release and uptake, due to properties such as reduced mean free paths of transport and increased surface-to-volume ratio, it becomes of critical importance to explicitly identify structure-property relationships on the nanometer scale. X-ray diffraction and spectroscopy are effective tools for probing size-, shape-, and structure-dependent material properties at the nanoscale. This article also discusses the recent development of in-situ soft X-ray spectroscopy cells, which enable investigation of critical solid/liquid or solid/gas interfaces under more practical conditions. These unique tools are providing a window into the thermodynamics and kinetics of hydrogenation and dehydrogenation reactions and informing a quantitative understanding of the fundamental energetics of hydrogen storage processes at the microscopic level. In particular, in-situ soft X-ray spectroscopies can be utilized to probe the formation of intermediate species, byproducts, as well as the changes in morphology and effect of additives, which all can greatly affect the hydrogen storage capacity, kinetics, thermodynamics, and reversibility.A few examples using soft X-ray spectroscopies to study these materials are discussed to demonstrate how these powerful characterization tools could be helpful to further understand the hydrogen storage systems.

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

Characterizing suburban soil and microbial properties along a soil age chronosequence

Abstract Rapid urbanization is drastically altering ecosystem processes in landscapes around the world. In particular, suburban residential neighborhoods comprise novel ecosystems with water and nutrient inputs that differ greatly from the surrounding land area. These impacts generate concern over the sustainability of urban ecosystems, especially whether they will be characterized by net carbon gain or loss over time. To address this knowledge gap, we established a chronosequence of residential yards in Southern California to test how urban soils change after development. We predicted that urbanized soils would experience shifts in physical characteristics and microbial function over time consistent with ecological succession theory, but residential soils would maintain novel moisture and nutrient regimes compared to undeveloped soils, never “recovering” to a pre‐developed state. We compared different vegetation types to quantify impacts of homeowner landscaping choices and characterized yard soils and their microbial communities. We found that yard soils were nutrient‐ and moisture‐enriched compared to an adjacent undeveloped ecosystem, and turfgrass was associated with higher levels of water and nitrogen. Despite high respiration rates, yard soils accumulated carbon and nitrogen over time. We conclude that suburban residential soils comprise dynamic and heterogeneous ecosystems that are highly influenced by landscaping choices and management practices, and warrant closer study at small management‐relevant scales.

Suratt, Andie [Department of Ecology and Evolution↗
DOE OSTI2015

Synthesis and Characterization of a Triphos Ligand Derivative and the Corresponding Pd II Complexes: Triphos Ligand Derivative and Corresponding Pd II Complexes

The synthesis of the new bis(2-(diphenylphosphino)ethyl)methylhydroxyphosphine tridentate phosphine ligand, LCH2OH/Ph, is reported. The ligand reacts with [Pd(Cl)2(PhCN)2 to form [Pd(LCH2OH/Ph)Cl]Cl. Exchange of the chloride ions for triflate (OTf–) using AgOTf yielded pure [Pd(LCH2OH/Ph)OTf]OTf. In addition to spectral characterization the free ligand, LCH2OH/Ph, and Pd(II) complex, [Pd(LCH2OH/Ph)OTf]OTf, are structurally characterized. This research was supported by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Biosciences, and Geosciences. Pacific Northwest National Laboratory is a multiprogram national laboratory operated by Battelle for DOE.

Miller, Deanna L.↗