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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 397 records · Page 22
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DOE OSTI2018

Microtube-Membrane Methodology for Electrochemical Synthesis and Study of Electroactive and Ionically Conductive Materials, and the Conductivity of MnO 2

A membrane-based methodology for electrochemical synthesis and study of electroactive and ionically conductive materials is described. The Li + -intercalation material MnO 2 was used to demonstrate this methodology. The membrane was a polymeric support containing monodisperse gold microtubes (diameter 600 nm) that span the thickness of the membrane. Bipolar electrochemical synthesis of MnO 2 , from Mn 2+ solutions, was conducted across this membrane, resulting in deposition of monodisperse, hemispherical MnO 2 particles at the open ends of the tubes on one face of the membrane. The resulting microtube/MnO 2 composite membrane makes a convenient construct for investigating the transport properties of the MnO 2 particles. This was accomplished by mounting the membrane in a U-tube cell, placing electrolyte solutions on either side, and driving an ionic current through the membrane. The ionic conductivity of MnO 2 was measured in this way, and found to be 40±10 μS cm -1 when LiCl or LiClO 4 solutions were used as the electrolyte. Finally, the mechanism of ionic conductivity through these MnO 2 particles is discussed.

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

Incorporating Heavy Alkanes in Metal–Organic Frameworks for Optimizing Adsorbed Natural Gas Capacity

Metal-Organic Frameworks (MOFs) as methane adsorbents are highly promising materials for applications such as methane-powered vehicles, flare gas capture, and field natural gas separation. Pre- and post-synthetic modification of MOFs have been known to help improve both the overall methane uptake as well as the working capacity. Herein, we introduce a post-synthetic modification strategy to non-covalently modify MOF adsorbents for the enhancement of the natural gas uptake for the MOF material. In our study, we doped PCN-250 adsorbents with C 10 alkane and C 14 fatty acid, investigating their impact on the methane uptake capabilities. We found that even trace amount of heavy hydrocarbons can considerably enhance the raw methane uptake of the MOF while still being regenerable. The doped hydrocarbons are presumably located at the mesoporous defects of PCN-250, thus optimizing the framework-methane interactions. Finally, these findings reveal a general approach which can be used to modify the MOF absorbents, improving their ability to be sustainable and renewable natural gas adsorption platforms.

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

Origin of Selectivity of a Triazinyl Ligand for Americium(III) over Neodymium(III)

[M(EtBTP) 3 ][BPh 4 ] 3 ∙3 CH 3 CN (M=Nd, Am; EtBTP=2,6-bis(5,6-diethyl-1,2,4-triazin-3-yl)pyridine) have been synthesized from reactions of MCl 3 ∙ n H 2 O with EtBTP in acetonitrile followed by anion metathesis. Structural analysis reveals that these compounds contain M 3+ cations bound by tridentate EtBTP ligands to create a tricapped trigonal prismatic geometry around the metal centers. Collection of high-resolution, single-crystal X-ray diffraction data also allowed reduction in bond lengths esd's, such that a slight contraction of Δ=0.0158(18) Å in the Am-N versus Nd-N bond lengths was observed, even though these cations ostensibly have matching ionic radii. Theoretical evaluation revealed enhanced metal–ligand bonding through back donation in the [Am(EtBTP) 3 ] 3+ complex that is absent in [Nd(EtBTP) 3 ] 3+ .

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

Molecularly Mixed Composite Membranes: Challenges and Opportunities

The fabrication of porous molecules, such as metal–organic polyhedra (MOPs), porous organic cages (POCs) and others, has given rise to the potential for creating “solid solutions” of molecular fillers and polymers. Such solid solutions circumvent longstanding interface issues associated with mixed matrix membranes (MMMs), and are referred to as molecularly mixed composite membranes (MMCMs) to distinguish them from traditional two-phase MMMs. Early investigations of MMCMs highlight the advantages of solid solutions over MMMs, including dispersion of the filler, anti-plasticization of the polymer network, and removal of deleterious interfacial issues. However, the exact microscopic structure as well as the transport modality in this new class of membrane are not well understood. Moreover, there are clear engineering challenges that need to be addressed for MMCMs to transition into the field. Finally in this Minireview, the authors outline several scientific and technological challenges associated with the aforementioned questions and their suggestions to tackle them.

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

Building Blocks for High-Efficiency Organic Photovoltaics: Interplay of Molecular, Crystal, and Electronic Properties in Post-Fullerene ITIC Ensembles

Accurate single-crystal X-ray diffraction data offer a unique opportunity to compare and contrast the atomistic details of bulk heterojunction photovoltaic small-molecule acceptor structure and packing, as well as provide an essential starting point for computational electronic structure and charge transport analysis. Herein, we report diffraction-derived crystal structures and computational analyses on the n-type semiconductors which enable some of the highest efficiency organic solar cells produced to date, 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (ITIC) and seven derivatives (including three new crystal structures: 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-propylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (ITIC-C3), 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(3-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (m-ITIC-C6), and 3,9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6,7-difluoro)-indanone))-5,5,11,11-tetrakis(4-butylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (ITIC-C4-4F). IDTT acceptors typically pack in a face-to-face fashion with π–π distances ranging from 3.28–3.95 Å. Additionally, edge-to-face packing is observed with S...π interactions as short as 3.21–3.24 Å. Moreover, ITIC end group identities and side chain substituents influence the nature and strength of noncovalent interactions (e.g. H-bonding, π–π) and thus correlate with the observed packing motif, electronic structure, and charge transport properties of the crystals. Furthermore, density functional theory (DFT) calculations reveal relatively large nearest-neighbor intermolecular π-π electronic couplings (5.85–56.8 meV) and correlate the nature of the band structure with the dispersion interactions in the single crystals and core–end group polarization effects. Overall, this combined experimental and theoretical work reveals key insights into crystal engineering strategies for indacenodithienothiophene (IDTT) acceptors, as well as general design rules for high-efficiency post-fullerene small molecule acceptors.

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

Insights into the Ring‐Opening of Biomass‐Derived Furanics over Carbon‐Supported Ruthenium

Abstract The selective ring‐opening of cellulose‐derived furanic molecules is a promising pathway for the production of industrially relevant linear oxygenates, such as 1,6‐hexanediol. 2,5‐Dimethylfuran (DMF) is employed as a model compound in a combined experimental and computational investigation to provide insights into the metal‐catalyzed ring‐opening. Ring‐opening to 2‐hexanol and 2‐hexanone and ring‐saturation to 2,5‐dimethyltetrahydrofuran (DMTHF) are identified as two main parallel pathways. DFT calculations and microkinetic modeling indicate that DMF adsorbs on Ru in an open‐ring configuration, which is potentially a common surface intermediate that leads to both ring‐opening and ring‐saturation products. Although the activation barriers for the two pathways are comparable, the formation of DMTHF is more thermodynamically favorable. In addition, steric interactions with co‐adsorbed 2‐propoxyl, derived from the solvent, and the oxophilic nature of Ru play key roles to determine the product distribution: the former favors less bulky, that is, ring‐closed, intermediates, and the latter retards O−H bond formation. Finally, we show that the hydrodeoxygenation of oxygenated furanics, such as 5‐methylfurfural and (5‐methyl‐2‐furyl)methanol, on Ru occurs preferentially at oxygen‐containing side groups to form DMF, followed by either ring‐opening or ring‐saturation.

Gilkey, Matthew J.↗
DOE OSTI2019

Branched Bio-Lubricant Base Oil Production through Aldol Condensation

Currently, lubricant base oils are derived from petroleum, a nonrenewable feedstock that contributes to greenhouse gas emissions. Bioderived, renewable lubricant base oils can mitigate environmental challenges and offer superior cold flow properties by incorporating branches to the base oil's hydrocarbon backbone with an appropriate synthetic strategy. A strategy was developed to synthesize branched alkanes for lubricant base oil in two steps from 12-tricosanone, obtained from bioderived fatty acids, and furfural, obtained from lignocellulosic biomass. The reaction pathway involves carbon–carbon coupling through aldol condensation followed by hydrodeoxygenation (HDO). Various solvents (non-polar, aprotic and polar, protic) and reaction conditions were screened to achieve a maximum yield of 94.3% of aldol condensation products, containing the majority of a C 33 furan (79.5%) followed by a C 28 furan (14.8%). Subsequent HDO of aldol condensation products over an Ir-ReO x /SiO 2 catalyst produced lubricant-ranged branched alkanes (C 28 and C 33 ) with 61.4% yield and small fractions (<11%) of alkanes with carbon numbers between C 15 and C 10 . The viscous properties of the produced bio-lubricant base oil were comparable to commercial petroleum-derived Group III and Group IV base oils. Overall, this approach serves as a potential stepping-stone to replace petroleumderived base oils and, in turn, reduce greenhouse gas emissions associated with current lubricant production.

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

Two-Dimensional Uranyl Borates: From Conventional to Extreme Synthetic Conditions: Two-Dimensional Uranyl Borates: From Conventional to Extreme Synthetic Conditions

A systematic investigation of uranyl borates under different synthetic conditions resulted in five new 2D compounds, namely, (H 3 O)[(UO 2 )(BO 3 )], Li[(UO 2 )(BO 3 )] · (H 2 O), α-K 4 [(UO 2 ) 5 (BO 3 ) 2 O 4 ], β-K 4 [(UO 2 ) 5 (BO 3 ) 2 O 4 ] and K 2.5 [(UO 2 ) 5 (BO 3 ) 2 O 2.5 (OH) 1.5 ] · (H 2 O) 2.5 . (H 3 O)[(UO 2 )(BO 3 )] and Li[(UO 2 )(BO 3 )] · (H 2 O) were obtained from hydrothermal reactions at 220 °C using the same mineralizer. Both materials possess the uranophane sheet topology with different symmetry of the unit cells. In the structure of (H 3 O)[(UO 2 )(BO 3 )] and Li[(UO 2 )(BO 3 )] · (H 2 O), UO 7 pentagonal bipyramids share edges and vertexes with four BO 3 planar triangles. α-K 4 [(UO 2 ) 5 (BO 3 ) 2 O 4 ] and β-K 4 [(UO 2 ) 5 (BO 3 ) 2 O 4 ] are polytypes. α-K 4 [(UO 2 ) 5 (BO 3 ) 2 O 4 ] was synthesized from a high-temperature solid-state reaction under ambient pressure; whereas β-K 4 [(UO 2 ) 5 (BO 3 ) 2 O 4 ] was obtained from a high-temperature/high-pressure (HT/HP) reaction. Both structures have an identical anion topology, but β-K 4 [(UO 2 ) 5 (BO 3 ) 2 O 4 ] crystallizes in space group with higher symmetry. In K 2.5 [(UO 2 ) 5 (BO 3 ) 2 O 2.5 (OH) 1.5 ] · (H 2 O) 2.5 , which was obtained from a hydrothermal reaction, UO 7 polyhedra share vertexes and edges with two independent BO 3 triangles, forming the most complex uranyl borate layers among all five compounds. The different synthetic routes, novel topologies, thermal behavior and Raman spectra are discussed.

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

Phonon scattering by dislocations at grain boundaries in polycrystalline Bi 0.5 Sb 1.5 Te 3

Reducing lattice thermal conductivity ( κ l ) of a thermoelectric material is one of the most popular strategies to improve its thermoelectric performance. Particularly, many efforts have been focused on decreasing grain size to effectively scatter low‐frequency phonons by boundary scattering. In addition to the boundary scattering, we have recently demonstrated that dense arrays of dislocations formed in grain boundaries can further reduce the κ l by dislocation scattering at room temperature and above. In order to closely examine the effect of the dislocation scattering, the κ l of polycrystalline Bi 0.5 Sb 1.5 Te 3 samples with and without dislocations were measured at low temperature ( T < 200 K). Because other phonon scattering mechanisms like Umklapp and point‐defect scatterings are not dominant at low temperature, we clearly show the presence of the dislocation scattering in the sample with the dislocations by successfully describing its low temperature experimental κ l with a theoretical model.

Kim, Hyun‐Sik↗
DOE OSTI2017

Glucose Conversion to Furans in Alcohols Catalyzed by Lewis Acidic Beta Zeolites and Brønsted Acidic Resins

Glucose was converted to 5-(hydroxymethyl)furfural (HMF) and the potential biodiesel additives 5-(ethoxymethyl)furfural (EMF) and 5-(isopropoxymethyl)furfural (IMF) by Lewis acidic zeolites and Brønsted acidic resins. The conversion occured by sequential isomerization and dehydration reactions in semiaqueous mixtures containing ethanol or isopropanol. Sn-beta and Amberlyst® 15 catalyzed the conversion of glucose to HMF and IMF in 53% yield in isopropanol containing 7.5 weight % water. The yield of undetected byproducts including humins was 7%. The moderate yield is attributed to the increased selectivity of the isomerization reaction and the suppression of further reactions of HMF to byproducts such as levullinic acid, formic acid, and humins in the alcohols.

09 BIOMASS FUELS↗
DOE OSTI2016

Ultrasmall Mode Volumes in Plasmonic Cavities of Nanoparticle‐On‐Mirror Structures

The mode volume and Purcell factor are two important parameters to assess the performance of optical nanocavities. Achieving small mode volumes and high Purcell factors for nanocavity structures while simplifying their fabrication has been a major task to realize high‐performance and large‐scale photonic devices and systems. Different optical resonators based on nanoparticle‐on‐mirror (NPoM) structures are systematically analyzed, which are easy to fabricate and flexible to use. Direct comparison of these optical resonators is made through finite‐difference time‐domain (FDTD) simulations. The achievement of ultrasmall mode volumes below 10 −7 based on the NPoM structure through FDTD simulations is demonstrated by rationally selecting the structural parameters. Such NPoM structures provide a decent Purcell factor on the order of 10 7 , which can effectively enhance spontaneous emission and facilitate a number of photonic applications. The simulation results are confirmed by dark field scattering and second‐harmonic generation measurements. This work is scientifically important and offers practical guidelines for the design of optical resonators for state‐of‐the‐art optical and photonic devices.

Huang, Shengxi↗