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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 1,513 records · Page 84
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Direct Nanoscale Characterization of Deep Levels in AgCuInGaSe 2 Using Electron Energy–Loss Spectroscopy in the Scanning Transmission Electron Microscope

A new experimental framework for the characterization of defects in semiconductors is demonstrated. Through the direct, energy-resolved correlation of three analytical techniques spanning six orders of magnitude in spatial resolution, a critical mid-bandgap electronic trap level (E V + 0.56 eV) within Ag 0.2 Cu 0.8 In 1–x Ga x Se 2 is traced to its nanoscale physical location and chemical source. This is achieved through a stepwise, site-specific correlated characterization workflow consisting of device-scale (≈1 mm 2 ) deep level transient spectroscopy (DLTS) to survey the traps present, scanning probe–based DLTS (scanning-DLTS) for mesoscale-resolved (hundreds of nanometers) mapping of the target trap state’s spatial distribution, and scanning transmission electron microscope based electron energy-loss spectroscopy (STEM-EELS) and X-ray energy-dispersive spectroscopy for nanoscale energy-, structure, and chemical-resolved investigation of the defect source. Furthermore, this first demonstration of the direct observation of sub-bandgap defect levels via STEM-EELS, combined with the DLTS methods, provides strong evidence that the longsuspected Cu In/Ga substitutional defects are indeed the most likely source of the E V + 0.56 eV trap state and serves as a key example of this approach for the fundamental identification of defects within semiconductors, in general.

14 SOLAR ENERGY↗
DOE OSTI2016

Pillared Sn‐MWW Prepared by a Solid‐State‐Exchange Method and its Use as a Lewis Acid Catalyst

Abstract Pillared Sn‐MWW (Sn‐MWW(SP)‐SSE) was prepared through a solid‐state‐exchange (SSE) route. The pillared structure was inherited from pillared B‐MWW, and Sn was inserted in the framework by boron leaching and solid‐state‐exchange with tin tetrachloride pentahydrate. The Sn‐MWW(SP)‐SSE with framework Sn sites exhibits Lewis acidity and good catalytic performance for the Baeyer–Villiger oxidation, and mono‐ and disaccharide isomerizations.

Ren, Limin↗
DOE OSTI2015

Charged Porous Polymers using a Solid C-O Cross-Coupling Reaction

We report a green, fast, efficient mechanochemical strategy for charged porous polymers (CPPs). A cationic CPP with basic anions and an anionic CPP with Li + cations were fabricated by solid grinding under solvent- free conditions. Compared with solution-based synthesis, mechanochemical grinding can shorten the reaction time from dozens of hours to several minutes (60– 90 min) to form polymers possessing a high molecular mass and low polydispersity. During the construction of CPPs, a Pd-catalyzed solid polycondensation based on unactivated organic linkers was introduced. In particular, CPPs with basic phenolic or proline anions showed good activity and stability in SO 2 capture, and Li + -functionalized CPPs can be post-modified to CPPs with other metal ions by ion exchange, highlighting the tailorable feature of ionic-modified CPPs.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Leveraging Actinide Hydrolysis Chemistry for Targeted Th and U Separations using Amidoxime-Functionalized Poly(HIPE)s

Polymerized high internal phase emulsions (poly(HIPE)s) are porous polymer monoliths whose synthesis can easily be tailored to allow incorporation of functional units. In this work, nitrile containing poly(HIPE)s have been prepared with either acrylonitrile (AN) or 4-cyanostyrene (4CS) comonomers. Post-synthetic modification of these nitrile-containing poly(HIPE)s yields their corresponding amidoximated analogues, which were studied for actinide uptake. These amidoxime-functionalized, porous polymers were shown to adsorb 95 % Th4+ species from aqueous solution within 30 minutes. In contrast to other amidoxime containing polymers the uptake of UO22+ in these poly(HIPE)s is lower under similar conditions. A critical analysis of actinide separations and high-energy X-ray scattering data provides insight into the polymers’ selectivity, enabled by the uptake of multinuclear Th clusters.

actinides↗
DOE OSTI2019

Effect of Synthesis Method Using Varying Types of Micropore Level Sulfur Infiltration on Electrochemical Performance in Lithium–Sulfur Batteries

The role of physically restrained, noncrystalline sulfur species in rechargeable lithium–sulfur batteries is examined by electrochemical and high‐resolution material characterizations. Carbon–sulfur composites are created by melting and sublimation of sulfur in an isochoric reactor via the autogenic process. These noncrystalline sulfur cathodes demonstrate a high specific capacity of ≈1000 Ah kg −1 after 100 cycles with a gravimetric current of 557 A kg −1 . Interestingly, this high‐performance sulfur allotrope lacks a long‐range structural order: high‐resolution X‐ray diffraction, performed at the Advanced Photon Source, indicates the lack of crystalline (i.e., orthorhombic or monoclinic) sulfur in the nanoscale domain. Electrochemical and material characterizations suggest that noncrystalline sulfur is a consequence of synthesis and not necessarily evidence of electrochemical efficacy. Rather, a high rate capacity depends on sulfur distribution, in turn, controlled by synthesis pathway. At higher sulfur content, the performance of carbon–sulfur composites is limited by the available surface area in which crystalline sulfur coincides with reduced gravimetric capacity and greater charge transport impedance, suggesting suboptimal sulfur containment.

Dysart, Arthur Dence↗