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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Steam-Induced Coarsening of Single-Unit-Cell MFI Zeolite Nanosheets and Its Effect on External Surface Brønsted Acid Catalysis

Commonly used methods to assess crystallinity, micro-/mesoporosity, Brønsted acid site density and distribution (in micro- vs. mesopores), and catalytic activity suggest nearly invariant structure and function for aluminosilicate zeolite MFI two-dimensional nanosheets before and after superheated steam treatment. Yet, pronounced reaction rate decrease for benzyl alcohol alkylation with mesitylene, a reaction that cannot take place in the zeolite micropores, is observed. Transmission electron microscopy images reveal pronounced changes in nanosheet thickness, aspect ratio and roughness indicating that nanosheet coarsening and the associated changes in the external (mesoporous) surface structure are responsible for the changes in the external surface catalytic activity. Finally, superheated steam treatment of hierarchical zeolites can be used to alter nanosheet morphology and regulate external surface catalytic activity while preserving micro- and mesoporosity, and micropore reaction rates.

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

Large Photothermal Effect in Sub-40 nm h-BN Nanostructures Patterned Via High-Resolution Ion Beam

The controlled nanoscale patterning of 2D materials is a promising approach for engineering the optoelectronic, thermal, and mechanical properties of these materials to achieve novel functionalities and devices. Herein, high-resolution patterning of hexagonal boron nitride (h-BN) is demonstrated via both helium and neon ion beams and an optimal dosage range for both ions that serve as a baseline for insulating 2D materials is identified. Through this nanofabrication approach, a grating with a 35 nm pitch, individual structure sizes down to 20 nm, and additional nanostructures created by patterning crystal step edges are demonstrated. Raman spectroscopy is used to study the defects induced by the ion beam patterning and is correlated to scanning probe microscopy. Photothermal and scanning near-field optical microscopy measure the resulting near-field absorption and scattering of the nanostructures. These measurements reveal a large photothermal expansion of nanostructured h-BN that is dependent on the height to width aspect ratio of the nanostructures. This effect is attributed to the large anisotropy of the thermal expansion coefficients of h-BN and the nanostructuring implemented. Finally, the photothermal expansion should be present in other van der Waals materials with large anisotropy and can lead to applications such as nanomechanical switches driven by light.

2D materials↗
DOE OSTI2019

Nanoarchitectonics of Biofunctionalized Metal–Organic Frameworks with Biological Macromolecules and Living Cells

The formation of biofunctionalized metal–organic frameworks (MOFs) by growing them on a variety of macromolecular biological species, particularly on enzymes and living cells, offers exciting opportunities for a wide range of applications, including biocatalysis, biosensing, and diagnoses. MOFs are commonly subjected to biofunctionalization and biomimetic mineralization, owing to their good chemical and thermal stabilities and easy preparation in aqueous medium under ambient conditions. The functionalization of MOFs with biological substances, such as enzymes, nonenzymatic proteins, and living cells promotes the formation of MOF-based biocomposites which retain the biological functions of the embedded biological substances. The most common method to construct these biofunctionalized MOFs is either by directly growing the MOF on the biological moiety or by postsynthetic modification of the exterior surface of the MOF with the desired biological species. In particular, hierarchically porous MOFs (containing both mesopores and micropores) are ideal candidates for hosting enzymes and for the translocation of nonenzymatic proteins. This review covers various advanced strategies for developing MOF-based biocomposites for a wide range of bioapplications, such as biomedical storage, tumor cell targeting, and drug delivery. Finally, the influence of MOFs on the biological activity of living cells and future prospects for developing novel MOF-based biorefinery are discussed.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

H-D Exchange of Simple Aromatics as a Measure of Brønsted-Acid Site Strengths in Solids

The relative Brønsted-acid strengths of H-[Al]ZSM-5, H-[Fe]ZSM-5, H-[B]ZSM-5, silicalite, P-SPP, tungstated zirconia, ZrO2, and γ-Al2O3 were studied using H-D exchange with toluene and chlorobenzene. Temperature programmed desorption (TPD) of toluene-h8 and chlorobenzene-h5 from the deuterated forms of H-[Al]ZSM-5, H-[Fe]ZSM-5, and P-SPP demonstrated that the temperature at which H-D exchange rates become significant change with the proton affinity of the aromatic molecule and the strength of the Brønsted sites. The steady-state, gas-phase reaction between D2O and the aromatic molecules were consistent with the TPD results and allowed the Brønsted-acid site strengths to be ordered as follows: H-[Al]ZSM-5 > H-[Fe]ZSM-5 > tungstated zirconia > P-SPP > H-[B]ZSM-5. H-D exchange was also observed at high temperatures with ZrO2 and γ-Al2O3 but it appears that the reaction mechanism with these Lewis acids is different because reaction with toluene and chlorobenzene occur at nearly the same temperature. It is suggested that the H-D exchange reaction with simple aromatic molecules is a useful way to probe Brønsted acidity in solids

bio-inspired↗
DOE OSTI2019

Microkinetic modeling of aqueous phase biomass conversion: Application to ethylene glycol reforming

In this communication, we develop automatically a reaction network for ethylene glycol reforming on Pt. We employ a recently introduced group additivity scheme for estimation of thermochemistry over metal catalysts in vapor phase and in solution along with Brønsted-Evans-Polanyi (BEP) relations for vapor phase kinetics to parameterize microkinetic models for vapor and aqueous phases. Unlike vapor-phase reforming, we show that solvent occupies a significant fraction of surface sites and by doing this, it shifts the water-gas shift reaction to CO2 and H2 and avoids poisoning of the catalyst by CO. The model is found to be in reasonable agreement with the experimental data.

bio-inspired↗