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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 OSTI2014

In Situ Observation of Directed Nanoparticle Aggregation During the Synthesis of Ordered Nanoporous Metal in Soft Templates

The prevalent approach to developing new nanomaterials is a trial and error process of iteratively altering synthesis procedures and then characterizing the resulting nanostructures. This is fundamentally limited in that the growth processes that occur during synthesis can only be inferred from the final synthetic structure. Directly observing real-time nanomaterial growth provides unprecedented insight into the relationship between synthesis conditions and product evolution, and facilitates a mechanistic approach to nanomaterial development. Here we use in situ liquid stage scanning transmission electron microscopy to observe the growth of mesoporous palladium in a solvated block copolymer (BCP) template under various synthesis conditions, and ultimately determine a refined synthesis procedure that yields ordered pores. We find that at low organic solvent (tetrahydrofuran, THF) content, the BCP assembles into a rigid, cylindrical micelle array with a high degree of short-range order, but poor long-range order. Upon slowing the THF evaporation rate using a solvent-vapor anneal step, the long-range order is greatly improved. The electron beam induces nucleation of small particles in the aqueous phase around the micelles. The small particles then flocculate and grow into denser structures that surround the micelles, forming an ordered mesoporous structure. The microscope observations revealed that template disorder can be addressed prior to reaction, and is not invariably induced by the growth process itself, allowing us to more quickly optimize the synthetic method. This work was conducted in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy under contract DE-AC05-76RL01830. This research was funded in part by: the Presidential Early Career Award for Scientist and Engineers for I.A., the University of California Academic Senate and the University of California Laboratory fee research grant, the Laboratory-Directed Research and Development program at Sandia National Laboratories, and the Chemical Imaging Initiative at Pacific Northwest National Laboratory. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

cylindrical micelle↗
DOE OSTI2013

Towards the selective modification of soft-templated mesoporous carbon materials by elemental fluorine for energy storage devices

Graphite fluoride is classified into (CF) n and (C 2 F) n types based on its structure and composition. In the former (CF) n has been widely prepared and commercially utilized as electrodes in primary lithium ion batteries (LIBs). Porous electrodes, i.e. templated mesoporous carbons, can greatly improve first Coulombic efficiencies. Furthermore, by achieving the highest discharge potentials and rate capabilities, the extent of fluorination reactions and the retention of a conductive carbon backbone are required. Thus, the choice of the starting carbon nanomaterial and of the fluorination conditions is detrimental to the design of future energy storage and conversion devices, namely LIBs and pseudosupercapacitors.

25 ENERGY STORAGE↗
DOE OSTI2019

Finding a soft spot for vanadium: a P-bound OCP ligand

Transmetallation studies with the phosphaethynolate ion, [OCP] – , have largely resulted in coordination according to classical Lewis acid–base theory. That is, for harder early transition metal ions, O-bound coordination has been observed, whereas in the case of softer late transition metal ions, P-bound coordination predominates. In this work, we report the use of a V(III) complex, namely [(nacnac)VCl(OAr)] (1) (nacnac – = [ArNC(CH 3 )] 2 CH; Ar = 2,6- i Pr 2 C 6 H 3 ), to transmetallate [OCP] – and bind via the P-atom as [(nacnac)V(OAr)(PCO)] (2), the first example of a 3d early transition metal that binds [OCP] – via the P-atom. Full characterization studies of this molecule including HFEPR spectroscopy, SQuID measurements, and theoretical studies are presented.

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

Polaronic quantum master equation theory of inelastic and coherent resonance energy transfer for soft systems

This work extends the theory of coherent resonance energy transfer [S. Jang, J. Chem. Phys. 131, 164101 (2009)] by including quantum mechanical inelastic effects due to modulation of donor-acceptor electronic coupling. Within the approach of the second order time local quantum master equation (QME) in the polaron picture and under the assumption that the bath degrees of freedom modulating the electronic coupling are independent of other modes, a general time evolution equation for the reduced system density operator is derived. Detailed expressions for the relaxation operators and inhomogeneous terms of the QME are then derived for three specific models of modulation in distance, axial angle, and dihedral angle, which are all approximated by harmonic oscillators. Numerical tests are conducted for a set of model parameters. Model calculation shows that the torsional modulation can make significant contribution to the relaxation and dephasing mechanisms.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗