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Results for “synthesis (scalable processing)”

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 847 records · Page 47
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DOE OSTI2015

Multielectron oxidation in a ferromagnetically coupled dinickel( II ) triple mesocate

Here, triple-stranded dinuclear nickel( II ) complexes of the meso-helicate type have been obtained from the new N,N'-1,3-phenylenebis(pyrazine-2-carboxamidate) ligand; they possess a multielectron redox behaviour featuring up to four stepwise, one-electron oxidation reactions of the two ferromagnetically coupled Ni II ions to afford the putative high-valent dinickel( III ) and dinickel( IV ) species, as supported by theoretical calculations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

An efficient low-temperature route to nitrogen-doping and activation of mesoporous carbons for CO 2 capture

We report an innovative strategy for post-synthesis nitrogen-doping of mesoporous carbons (MCs) with high yields (>90%) at low temperatures (230–380 °C) by using a strong base, sodium amide (NaNH 2 ), was developed. The as-prepared N-doped MCs exhibit a significantly enhanced CO 2 adsorption performance in terms of capacity and selectivity when compared to their parent MCs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

L -Aspartate links for stable sodium metal–organic frameworks

Metal–organic frameworks (MOFs) based purely on sodium are rare, typically due to large numbers of coordinating solvent ligands. In this work we designed a tetratopic aspartate-based linker with flexible carboxylate groups to enhance framework stability. We report two new air-stable sodium MOFs, MOF-705 and MOF-706, comprising 2D sodium oxide sheets.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Nickel(ii) and copper(i,ii)-based metal-organic frameworks incorporating an extended tris-pyrazolate linker

Solvothermal reactions between the tritopic pyrazole-based ligand 1,3,5-tris((1H-pyrazol-4-yl)phenyl)benzene (H 3 BTPP) and nickel(II) perchlorate or copper(II) nitrate afforded two new metal-organic frameworks, Ni 3 (BTPP) 2 ·solvent (Ni-BTPP) and Cu I 4 Cu II 2 (OH) 2 (BTPP) 2 ·solvent (Cu-BTPP). Powder diffraction structure determination methods were employed to determine the crystal and molecular structure of the copper(I,II) derivative: triangular [Cu3N6(μ3-OH)] nodes are connected to six nearby ones by the pyrazolate ligands, thus constructing flat two-dimensional layers that stack to form slit-like one-dimensional channels. Thermogravimetric analyses highlighted both the thermal stability and the permanent porosity of these two materials. Porosity was confirmed by N 2 adsorption at 77 K, yielding Langmuir specific surface areas of 1923(3) m 2 g -1 and 874(8) m 2 g -1 for Ni-BTPP and Cu-BTPP, respectively. Additionally, Ni-BTPP adsorbed 1.73 mmol g -1 (7.6 wt%) of CO 2 at the mild conditions of 298 K and 1 bar.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Branched isomeric 1,2,3-triazolium-based ionic liquids: new insight into structure–property relationships

A series of four isomeric 1,2,3-triazolium-based ionic liquids (ILs) with vary degree of branching were synthesized and characterized to investigate the effect of ion branching on thermal and physical properties of the resulting IL. Here, it was found that increased branching led to a higher ionicity and higher viscosity. The thermal properties were also altered significantly and spectral changes in the near edge X-ray absorption fine structure (NEXAFS) spectra show that branching affects intermolecular interaction. While the ionicity and viscosity varying linearly with branching, the MDSC and NEXAFS measurements show that the cation shape has a stronger influence on the melting temperature and absorptive properties than the number of branched alkyl substituents.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

A high-performance spectrally-selective solar absorber based on a yttria-stabilized zirconia cermet with high-temperature stability

Spectrally-selective solar absorbers are widely used in solar hot water and concentrating solar power (CSP) systems. However, their performance at high temperatures (>450 °C) is still not satisfactory due to high infrared (IR) emittance and lack of long-term thermal stability. In this work, we explore yttria-stabilized zirconia (YSZ) cermet-based spectrally-selective surfaces for high-temperature solar absorber applications. The developed multilayer selective surface comprises two sunlight-absorbing W–Ni–YSZ cermet layers with different W–Ni volume fractions inside the YSZ matrix, two anti-reflection coatings (ARCs), and one tungsten IR reflection layer for reduced IR emittance and improved thermal stability, deposited on a polished stainless steel (SS) substrate. The fabricated solar absorbers are tested for their long-term thermal stability at 600 °C. We find a distinct change in the surface morphology of the solar absorbers when oxygen is highly deficient in the YSZ-ARC layers. The oxygen deficiency can be effectively overcome through increasing the oxygen partial pressure during sputtering, which leads to a stable solar absorber with a solar absorptance of ~0.91 and a total hemispherical emittance of ~0.13 at 500 °C. Those values are obtained at the actual operating temperature using an absolute and direct method that measures the total hemispherical emittance with high accuracy. In contrast, most reports on solar absorber development in the literature to date use only near room-temperature spectroscopy techniques that have been shown to significantly underestimate the total hemispherical emittance. This makes our experimentally demonstrated total hemispherical emittance value the lowest ever reported for a high-temperature stable solar absorber with solar absorptance above 0.9.

14 SOLAR ENERGY↗
DOE OSTI2015

Tandem Lewis/Brønsted homogeneous acid catalysis: conversion of glucose to 5-hydoxymethylfurfural in an aqueous chromium( iii ) chloride and hydrochloric acid solution

Here, a kinetic model for the tandem conversion of glucose to 5-hydroxymethylfurfural (HMF) through fructose in aqueous CrCl 3 –HCl solution was developed by analyzing experimental data. We show that the coupling of Lewis and Brønsted acids in a single pot overcomes equilibrium limitations of the glucose–fructose isomerization leading to high glucose conversions and identify conditions that maximize HMF yield. Adjusting the HCl/CrCl 3 concentration has a more pronounced effect on HMF yield at constant glucose conversion than that of temperature or CrCl 3 concentration. This is attributed to the interactions between HCl and CrCl 3 speciation in solution that leads to HMF yield being maximized at moderate HCl concentrations for each CrCl 3 concentration. This volcano-like behavior is accompanied with a change in the rate-limiting step from fructose dehydration to glucose isomerization as the concentration of the Brønsted acid increases. The maximum HMF yield in a single aqueous phase is only modest and appears independent of catalysts’ concentrations as long as they are appropriately balanced. However, it can be further maximized in a biphasic system. Our findings are consistent with recent studies in other tandem reactions catalyzed by different catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Lewis acid zeolites for tandem Diels–Alder cycloaddition and dehydration of biomass-derived dimethylfuran and ethylene to renewable p -xylene

In this work, Lewis acid zeolites including Zr-, Sn-, and Ti-BEA were examined for tandem [4 + 2] Diels–Alder cycloaddition of 2,5-dimethylfuran (DMF) and ethylene to oxanorbornene with subsequent dehydration to produce biorenewable p-xylene. Zr-BEA (Si/Zr = 168) exhibited superior performance with improved recalcitrance to deactivation, which was attributed to its low activity for the hydrolysis of DMF to 2,5-hexanedione and subsequent condensation. Zr-BEA also achieved the highest selectivity to p-xylene of 90% at 99% conversion of DMF. For low catalyst loading within a three-phase reactor, the reaction rate to form p-xylene was linearly proportional to the number of Lewis acid sites, while high catalyst loading exhibited zero order dependence on Lewis acid sites. A maximum achievable reaction rate was shown to be consistent with a transition in rate-limiting reactions from dehydration of oxanorbornene, the Diels–Alder product, to the Diels–Alder cycloaddition of DMF and ethylene.

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

Dislocation strain as the mechanism of phonon scattering at grain boundaries

Thermal conductivities of polycrystalline thermoelectric materials are satisfactorily calculated by replacing the commonly used Casimir model (freqeuncy-independent) with grain boundary dislocation strain model (frequency-dependent) of Klemens. It is demonstrated that the grain boundaries are better described as a collection of dislocations rather than perfectly scattering interfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Rectification of nanopores in aprotic solvents – transport properties of nanopores with surface dipoles

Nanopores have become a model system to understand transport properties at the nanoscale. In this paper, we report experiments and modeling of ionic current in aprotic solvents with different dipole moments through conically shaped nanopores in a polycarbonate film and through glass nanopipettes. We focus on solutions of the salt LiClO4, which is of great importance in modeling lithium based batteries. Results presented suggest ion current rectification observed results from two effects: (i) adsorption of Li+ ions to the pore walls, and (ii) a finite dipole moment rendered by adsorbed solvent molecules. Properties of surfaces in various solvents were probed by means of scanning ion conductance microscopy, which confirmed existence of an effectively positive surface potential in aprotic solvents with high dipole moments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Thermal conductivity reduction by isoelectronic elements V and Ta for partial substitution of Nb in half-Heusler Nb (1-x)/2 V (1-x)/2 Ta x CoSb

Recently, we found a new n-type thermoelectric half-Heusler NbCoSb with a valence electron count of 19, different from the usual 18. In this paper, we focus on the effect of partial substitution of Nb by isoelectronic elements V and Ta on the reduction of the thermal conductivity of Nb(1-x)/2V(1-x)/2TaxCoSb. We found that the isoelectronic elements V and Ta for partial substitution of Nb can dramatically decrease the thermal conductivity from 7.0 W m-1 K-1 to 3.3 W m-1 K-1 at room temperature for Nb0.44V0.44Ta0.12CoSb, but unfortunately a large power factor decrease also occurred. Consequently, a peak ZT of ~0.5 is achieved at 700 °C for Nb0.44V0.44Ta0.12CoSb, which is about 25% higher than the ~0.4 reported earlier for NbCoSb.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Increasing flame ionization detector (FID) sensitivity using post-column oxidation–methanation

The flame ionization detector (FID) is a robust tool in gas chromatography (GC) due to its sensitivity and linear response in the detection of common organic compounds. However, FID response to oxygenated or highly functionalized organic molecules is low, or in some cases non-existent, making it difficult or impossible to detect and quantify some organic compounds. In this work, the combination of a GC/FID system with a catalytic microreactor, which performs post-column combustion–methanation to convert organic compounds to methane, is shown to be an effective approach for quantifying low-response organic compounds. Molecules that were previously undetectable by conventional FID, including carbon monoxide and carbon dioxide, respond with the same high response of methane in the FID. Low-response molecules, including formaldehyde, formic acid, formamide, and ten other oxygenates also demonstrated enhanced detector response equivalent to that of methane in the FID. Here, the linear response of the FID to these molecules and the equivalent sensitivity to methane indicate that accurate quantification is possible without the usual calibration-corrections (e.g., response factors or correction factors) to the FID response.

99 GENERAL AND MISCELLANEOUS↗