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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Selective adsorption removal of carbonyl molecular foulants from real fast pyrolysis bio-oils

A novel sorbent-based separation process has been developed to selectively remove target molecules from the real fast pyrolysis (FP) pine bio-oils. Specifically, zeolitic molecular sieves and functionalized polymeric resins were found to effectively reduce carbonyl content and carboxylic acid number of a real pine fast pyrolysis bio-oils, therefore enhance bio-oil stability and preserve down-stream catalyst. Our results provide the first-time evidence on the potential effectiveness of sorption technology strategy for dealing with real FP bio-oils, reducing the carbonyl-rich FP oils from 7.5 mmolg-1 down to 4 mmolg-1 at 40 ?, which has potential to enable bio-oil stabilization and enhance operation stability for down-stream upgrading/hydrotreating processes.

Church, Aimee L.↗
DOE OSTI2016

Characterisation of a complex thin walled structure fabricated by selective laser melting using a ferritic oxide dispersion strengthened steel

Oxide dispersion strengthened (ODS) alloys exhibit superior mechanical and physical properties due to the presence of nanoscopic Y(Al, Ti) oxide precipitates, but their manufacturing process is complex. The present study is aimed at further investigation of the application of an alternative, Additive Manufacturing (AM) technique, Selective Laser Melting (SLM), to the production of consolidated ODS alloy components. Mechanically alloyed PM2000 (ODS-FeCrAl) powders have been consolidated and a fine dispersion of Y-containing precipitates were observed in an as built thin-walled component, but these particles were typically poly-crystalline and contained a variety of elements including O, Al, Ti, Cr and Fe. Application of post-build heat treatments resulted in the modification of particle structures and compositions; in the annealed condition most precipitates were transformed to single crystal yttrium aluminium oxides. During the annealing treatment, precipitate distributions homogenised and localised variations in number density were diminished. The resulting volume fractions of those precipitates were 25–40% lower than have been reported in conventionally processed PM2000, which was attributed to Y-rich slag-like surface features and inclusions formed during SLM. - Highlights: • A wall structure was grown from ODS steel powder using selective laser melting. • A fine dispersion of nano-precipitates was apparent in as-build material. • Precipitates were multi-phased containing several elements, e.g. O, Ti, Al, Fe, Cr, Y. • Post-build annealing changed those into typically single-crystalline Y–Al–O. • The anneal also reduced and stabilised the volume fraction of precipitates to ~ 0.006.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Recommended Nuclear Data for the Production of Selected Therapeutic Radionuclides

Increasing interest in the treatment of human disease by means of targeted radionuclide-based therapies requires an accurate understanding of achievable yields and quantification of realisable degrees of purity. Important studies within a more extensive Coordinated Research Project of the International Atomic Energy Agency (IAEA CRP) have included in-depth assessments and evaluations of all available measured cross-section data for ten nuclear reactions leading to the formation of 131 Cs, 131 Ba, 225 Ac, 225 Ra, 227 Th, 227 Ac, 230 U and 230 Pa for various on-going and proposed therapeutic applications in nuclear medicine. Equivalent studies were also undertaken of possible reactions to produce the 178W /low-spin 178m Ta generator system that has been clinically applied in diagnosis by means of SPECT - these particular cross-section studies and recommendations are included in this paper for completeness. All available measured data have been critically reviewed and assessed to produce statistically consistent datasets. Selected datasets have been fitted by a least-squares method with Padé approximations of variable order to evaluate the production cross sections and corresponding uncertainties. New measurements have been made in some instances, and reported data have been adjusted to accommodate new nuclear decay or monitor reaction data which altered the original reported quantities adversely. Insufficient measured data are available in many cases to permit a reliable evaluation of cross sections, and these instances are discussed. Finally, recommended therapeutic radionuclide production reaction data and their uncertainties are available on the Web page of the IAEA Nuclear Data Section at www-nds.iaea.org/radionuclides/ and also at the IAEA medical portal www-nds.iaea.org/medportal/.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2018

Radiation Anomaly Detection and Classification with Bayes Model Selection

We present a new method for radiation anomaly detection that is based on Bayes Model Selection (BMS), together with models for gamma-radiation measurements from benign and threat sources. The method estimates the relative odds of pairs of such models, with the aim of supporting related hypotheses about the nature of the underlying source material. We also discuss partial optimization of the parameters in the models. The method allows measurements to be broadly categorized and screened for sources of interest in real time, a property that should improve the efficiency of mobile search or unattended monitoring operations.

Anomaly detection, Gamma-ray spectroscopy, Radiati↗
DOE OSTI2019

Selective growth of Al 2 O 3 on size-selected platinum clusters by atomic layer deposition

In heterogeneous catalysis, atomic layer deposition (ALD) has been developed as a tool to stabilize and reduce carbon deposition on supported nanoparticles. Here, we discuss use of high vacuum ALD to deposit alumina films on size-selected, sub-nanometer Pt/SiO 2 model catalysts. Mass-selected Pt 24 clusters were deposited on oxidized Si(100), to form model Pt 24 /SiO 2 catalysts with particles shown to be just under 1 nm, with multilayer three dimensional structure. Alternating exposures to trimethylaluminum and water vapor in an ultra-high vacuum chamber were used to grow alumina on the samples without exposing them to air. Here, the samples were probed in situ using X-ray photoelectron spectroscopy (XPS), low-energy ion scattering spectroscopy (ISS), and CO temperature-programmed desorption (TPD). Additional samples were prepared for ex situ experiments using grazing incidence small angle xray scattering spectroscopy (GISAXS). Alumina growth is found to initiate at least 60 times more efficiently at the Pt 24 cluster sites, compared to bare SiO 2 /Si, with a single ALD cycle depositing a full alumina layer on top of the clusters, with substantial additional alumina growth initiating on SiO 2 sites surrounding the clusters. As a result, the clusters were completely passivated, with no exposed Pt binding sites.

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

Selective Crystallization for Green Separations of Lanthanides Using 5-(Pyrimidyl)Tetrazolate

In an effort to develop facile, low-cost, and environmentally benign separations of lanthanides, the coordination chemistry and selective crystallization of Ln 3+ cations with the water-soluble ligand 5-(pyrimidyl)tetrazolate (pmtz) have been investigated. The wide range of coordination modes of pmtz allows for discrimination between these cations, and five distinct compound types can be prepared that are dependent on the lanthanide employed. La 3+ leads to the formation of [La(pmtz) 2 (H 2 O) 6 ]Cl (S1). [Ln(pmtz) 3 (H 2 O) 3 ]·(3+n)H 2 O is obtained with Ce 3+ and Pr 3+ (S2). Ce 3+ can also form [(Ce(pmtz) 2 (H 2 O) 3 ) 2 (μ-pmtz)](pmtz)·11H 2 O (S3). [(Ln(pmtz) 2 (H 2 O) 3 ) 2 (μ-pmtz)] 2 (pmtz) 2 ·14H 2 O (S4) is formed with Nd 3+ and Sm 3+ . Here, the smaller Ln 3+ cations, Dy 3+ to Lu 3+ , all yield [Ln(H 2 O) 8 ](pmtz) 3 ·3H 2 O (S5). This selective crystallization of Ln 3+ cations based primarily on ionic radii provides a simple method for achieving group separations.

Bai, Zhuanling↗
DOE OSTI2016

Selective O 2 Sorption at Ambient Temperatures via Node Distortions in Sc-MIL-100

An open pored metal–organic framework (MOF) with oxygen selectivity at exceptionally high temperatures is confirmed by synthesis, sorption, and synchrotron structural analyses. The large-pore MIL-100 framework with access to the metal center (e.g., Sc and Fe) resulted in preferential O2 over N2 gas uptake at temperatures ranging from 77 K to ambient temperatures (258, 298, and 313 K). Most notably, Sc-MIL-100 shows exceptional O2 sorption; pair distribution function analyses indicate that this is due to distortions in the framework owing to the size of Sc atoms, in particular in the trimer metal cluster. Experimental studies also correlate very well with GCMC simulations, confirming more favorable O2-framework interactions at pressures up to 1 bar, due to the close proximity of O2 to the high density of metal centers in the small tetrahedral cages. Both materials maintain their crystallinity upon gas adsorption cycling, are regenerable, and show exceptional promise for use in energy efficient oxygen purification processes, such as Pressure Swing Adsorption.

Sava Gallis, Dorina F.↗
DOE OSTI2020

Optimal Orbital Selection for Full Configuration Interaction (OptOrbFCI): Pursuing the Basis Set Limit under a Budget

Full configuration interaction (FCI) solvers are limited to small basis sets due to their expensive computational costs. An optimal orbital selection for FCI (OptOrbFCI) is proposed to boost the power of existing FCI solvers to pursue the basis set limit under a computational budget. The optimization problem coincides with that of the complete active space SCF method (CASSCF), while OptOrbFCI is algorithmically quite different. OptOrbFCI effectively finds an optimal rotation matrix via solving a constrained optimization problem directly to compress the orbitals of large basis sets to one with a manageable size, conducts FCI calculations only on rotated orbital sets, and produces a variational ground-state energy and its wave function. Coupled with coordinate descent full configuration interaction (CDFCI), we demonstrate the efficiency and accuracy of the method on the carbon dimer and nitrogen dimer under basis sets up to cc-pV5Z. We also benchmark the binding curve of the nitrogen dimer under the cc-pVQZ basis set with 28 selected orbitals, which provide consistently lower ground-state energies than the FCI results under the cc-pVDZ basis set. Furthermore, the dissociation energy in this case is found to be of higher accuracy.

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

Structure Based Design of a Grp94-Selective Inhibitor: Exploiting a Key Residue in Grp94 To Optimize Paralog-Selective Binding

Grp94 and Hsp90, the ER and cytoplasmic hsp90 paralogs, share a conserved ATP-binding pocket that has been targeted for therapeutics. Paralog-selective inhibitors may lead to drugs with fewer side effects. In this work, we analyzed 1 (BnIm), a benzyl imidazole resorcinylic inhibitor, for its mode of binding. The structures of 1 bound to Hsp90 and Grp94 reveal large conformational changes in Grp94 but not Hsp90 that expose site 2, a binding pocket adjacent to the central ATP cavity that is ordinarily blocked. The Grp94:1 structure reveals a flipped pose of the resorcinylic scaffold that inserts into the exposed site 2. We exploited this flipped binding pose to develop a Grp94-selective derivative of 1. Our structural analysis shows that the ability of the ligand to insert its benzyl imidazole substituent into site 1, a different side pocket off the ATP binding cavity, is the key to exposing site 2 in Grp94.

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

Spin-Selective Oxygen Evolution Reaction in Chiral Iron Oxide Nanoparticles: Synergistic Impact of Inherent Magnetic Moment and Chirality

Electron spin polarization is identified as a promising avenue for enhancing the oxygen evolution reaction (OER), which is the bottleneck that limits the energy efficiency of water-splitting. Here, in this work, we report that both ferrimagnetic (f-Fe 3 O 4 ) and superparamagnetic iron oxide (s-Fe 3 O 4 ) catalysts can exhibit external magnetic field (Hext)-induced OER enhancement, and the activity is proportional to their intrinsic magnetic moment. Additionally, the chirality-induced spin selectivity (CISS) effect was utilized in synergy with Hext to get a maximum enhancement of up to 89% improvement in current density (at 1.8 V vs RHE) with a low onset potential of 270 mV in s-Fe 3 O 4 catalysts. Spin polarization and the resultant spin selectivity suppress the production of H 2 O 2 and promote the formation of ground state triplet O 2 during the OER. Furthermore, the design of chiral s-Fe 3 O 4 with synergistic spin potential effect demonstrates a high spin polarization of ∼42%, as measured using conductive atomic force microscopy (c-AFM).

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

Markovnikov-Selective Hydroboration of Olefins Catalyzed by a Copper N-Heterocyclic Carbene Complex

The efficient and atom-economical hydroboration of alkenes and alkynes using an N-heterocyclic carbene (NHC) copper hydroxide catalyst has been developed here. An equimolar combination of substrate and HBpin allows for the selective Markovnikov hydroboration of alkenes and alkynes. A variety of functional groups were tolerated in good to excellent yield. This system highlights a facile reaction setup, atom economy, high selectivity, and an easily synthesized copper–NHC catalyst.

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

Disordered, Sub-Nanometer Ru Structures on CeO 2 are Highly Efficient and Selective Catalysts in Polymer Upcycling by Hydrogenolysis

We report non-degradable polyolefin plastics pose severe environmental threats, and thus demand efficient upcycling technologies. In this work, we discovered that low-loading (= 0.25 wt%) Ru/CeO 2 exhibits remarkable catalytic performance in the hydrogenolysis of polypropylene (PP), polyethylene (PE), and n-C 16 H 34 that is superior to high-loading (= 0.5 wt%) Ru/CeO 2 . They possess high PP conversion efficiency (7-fold increase over current literature reports), low selectivity towards undesired CH 4 , and good isomerization ability. In the low-loading range, the intrinsic activity of Ru in PP hydrogenolysis increases as the particle size decreases, opposite of the trend in the high-loading range. Detailed characterization revealed that the abrupt changes in catalytic behaviors coincide with Ru species transitioning from well-defined to highly disordered structures in the low-loading domain. The disordered Ru species were shown to be sub-nanometer in size and cationic. Mechanistically, the regioselectivity and the rate dependence on hydrogen pressure of C-C bond cleavage are different on low- and high-loading Ru/CeO 2 , both explained by the higher coverage of adsorbed hydrogen (*H) on low-loading Ru/CeO 2 . This work uncovers the remarkable catalytic performance of highly disordered, sub-nanometer, cationic Ru species in polyolefin hydrogenolysis, opening immense opportunities to develop effective, selective, and versatile catalysts for plastic upcycling.

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

A Combined Experimental and Theoretical Study on the Activity and Selectivity of the Electrocatalytic Hydrogenation of Aldehydes

A detailed mechanistic study of the electrochemical hydrogenation of aldehydes is presented toward the goal of identifying how organic molecules in solution behave at the interface with charged surfaces and what is the best manner to convert them. Specifically, this study focuses on designing an electrocatalytic route for ambient temperature post-pyrolysis treatment of bio-oil. Aldehyde reductions are needed to convert biomass into fuels or chemicals. A combined experimental and computational approach is taken toward catalyst design to provide testable hypotheses regarding catalyst composition, activity, and selectivity. Electrochemical hydrogenation mechanisms for benzaldehyde and pentanal reduction are found to proceed by a coupled proton-electron transfer process. Initial results show that Au, Ag, Cu, and C catalysts exhibit the highest conversion to alcohol products. These catalysts are suitable because they show high cathodic onset potentials for H2 formation and low cathodic onset potentials for organic reduction. Conversion of aromatic aldehydes is found to be appreciably higher than aliphatic ones. Classical molecular dynamics simulations of solvent and substrate mixtures in an electrolytic cell were performed to assess how species concentrations vary at the solid/liquid interface and in the bulk as a function of applied voltage. Results show that an increase in voltage in the electrolytic cell decreases organic and increases water mole fractions at the solid/liquid interface. In this current study, charged cathodic surfaces result in carbonyl orientations at the surface that do not favor electron transfer. Repulsion of organic substrates to the bulk must be compensated by strong adhesion to the electrode surface. Implications on catalyst choice and process design are discussed.

Pyrolysis Oil upgrading, Atomistic Simulations, El↗
DOE OSTI2017

Ultra-selective high-flux membranes from directly synthesized zeolite nanosheets

A zeolite with structure type MFI is an aluminosilicate or silicate material that has a three-dimensionally connected pore network, which enables molecular recognition in the size range 0.5-0.6 nm. These micropore dimensions are relevant for many valuable chemical intermediates, and therefore MFI-type zeolites are widely used in the chemical industry as selective catalysts or adsorbents. As with all zeolites, strategies to tailor them for specific applications include controlling their crystal size and shape. Nanometre-thick MFI crystals (nanosheets) have been introduced in pillared and self-pillared (intergrown) architectures, offering improved mass-transfer characteristics for certain adsorption and catalysis applications. Moreover, single (non-intergrown and nonlayered) nanosheets have been used to prepare thin membranes that could be used to improve the energy efficiency of separation processes. However, until now, single MFI nanosheets have been prepared using a multi-step approach based on the exfoliation of layered MFI9,15, followed by centrifugation to remove non-exfoliated particles. This top-down method is time-consuming, costly and low-yield and it produces fragmented nanosheets with submicrometre lateral dimensions. Alternatively, direct (bottom-up) synthesis could produce high-aspect-ratio zeolite nanosheets, with improved yield and at lower cost. Here we use a nanocrystal-seeded growth method triggered by a single rotational intergrowth to synthesize high-aspect-ratio MFI nanosheets with a thickness of 5 nanometres (2.5 unit cells). These high-aspect-ratio nanosheets allow the fabrication of thin and defect-free coatings that effectively cover porous substrates. Finally, these coatings can be intergrown to produce high-flux and ultra-selective MFI membranes that compare favourably with other MFI membranes prepared from existing MFI materials (such as exfoliated nanosheets or nanocrystals).

36 MATERIALS SCIENCE↗