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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Local Structural Disorder in Metavanadates MV 2 O 6 (M = Zn and Cu) Synthesized by the Deep Eutectic Solvent Route: Photoactive Oxides with Oxygen Vacancies

Metavanadates MV 2 O 6–δ (M = Zn and Cu) are synthesized by using a deep eutectic solvent (DES), a mixture of hydrogen bond donor and acceptor, as a reaction medium. Dissolution of stable binary metal oxides in a DES followed by a heat treatment yields phase-pure vanadates. According to in situ powder X-ray diffraction, ternary phases (α-Zn 2 V 2 O 7 and β-Cu 2–x V 2 O 7 , x ~ 0.27) are intermediates in the reaction pathway taken. Identifying a polymorphic phase transformation temperature for CuV 2 O 6 as well as the narrow temperature range between formation and decomposition for both metavanadates allows for tackling the challenge of the synthesis of these materials. The oxygen vacancy introduced by the DES route is accompanied by the formation of reduced V 4+ and Cu + in the oxide matrix, based on X-ray photoelectron spectroscopy. These oxygen vacancies modify the vibrational modes in the corresponding Raman spectra and are also responsible for broad optical absorptions in the 1.8–1.1 eV range. The optical band gaps of the materials are found at 1.8 eV (CuV 2 O 6 ) and 2.2 eV (ZnV 2 O 6 ), approximately 0.1–0.3 eV below the values reported in the literature. The reduced band gaps and sub-band gap photon absorption are key features of the oxygen-deficient metavanadates. Surface photovoltage spectroscopy reveals that all the synthesized vanadates are n-type materials with electrons as the majority charge carriers, and photoelectrochemical measurements confirm photoanodic currents for methanol oxidation. Furthermore, these results provide insight into the synthesis and structure–property relationship of the metavanadates for their potential use as photoanodes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Convenient Syntheses of Trivalent Uranium Halide Starting Materials without Uranium Metal

Low-valent uranium coordination chemistry continues to rely heavily on access to trivalent starting materials, but these reagents are typically prepared from uranium turnings, which are becoming increasingly difficult to acquire. Here we report convenient syntheses of UI 3 (THF) 4 (THF = tetrahydrofuran) and UBr 3 (THF) 4 from UCl 4 , a more accessible uranium starting material that can be prepared from commercially available uranium oxides. UCl 3 (THF) 2 (1), UBr 3 (THF) 4 (2), and UI 3 (THF) 4 (3) were prepared by single-pot reductions from UCl 4 using KH and KC 8 and converted to 2 or 3 by halide exchange with the corresponding Me 3 SiX (where X = Br or I). Reduction of UI 4 (Et 2 O) 2 (4; Et 2 O = diethyl ether) and UI 4 (1,4-dioxane) 2 (5) was also shown to cleanly yield 3. Complex 1 was also synthesized separately by the addition of anhydrous HCl to U(BH 4 ) 3 (THF) 2 , which was prepared by thermal reduction of U(BH 4 ) 4 . All three trivalent uranium halide complexes were isolated in high crystalline yields (typically 85–99%) and their formulations were confirmed by single-crystal X-ray diffraction, elemental analysis, and 1 H NMR and IR spectroscopy. Elemental analysis conducted on triplicate samples of 1–3 exposed to vacuum for different time intervals revealed significant THF loss for all three complexes in as little as 15 min. Altogether, these results offer expedient entry into low-valent uranium chemistry for researchers lacking access to uranium turnings.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Green syntheses of stable and efficient organic dyes for organic hybrid light-emitting diodes

Organic hybrid light-emitting diodes (hybrid-LEDs) employ organic dyes as light converters on top of commercial blue inorganic LEDs, replacing incumbent inorganic phosphor light converters synthesized from rare-earth and/or toxic metallic elements to optimize device environmental sustainability. Here, we present two naturally derived organic dyes for hybrid-LEDs, highlighting stability and efficiency enhancement based on a novel “acceptor–acceptor” molecular design. This “acceptor–acceptor” skeleton comprises theobromine and thiadiazole, two electron-withdrawing groups that lower energy levels and suppress photooxidation. This differentiates these dyes from the widely adopted “donor–acceptor” skeleton, where photooxidation is facilitated by the presence of electron-donating units. Simultaneously, sidechains on organic dyes used to enhance solution processability, crucial for film transparency, introduce an additional photooxidation pathway. With this “acceptor–acceptor” skeleton, the destabilization from sidechains was offset by the stability enhancement from the electronic effects in the backbone. Additionally, when blended within an industrial polymer, poly(styrene-butadiene-styrene) (SBS), their enhanced solubility enables the formation of highly transparent films, crucial for reducing scattering loss in LEDs. Furthermore, resultant dye-SBS films achieved photoluminescence quantum yields (PLQYs) of around 90% under ambient conditions. Taking advantage of their transparency and solution processability, we fabricated a waveguide with this theobromine-dye-SBS composite, which was subsequentially assembled into an edge-lit LED device of no glare and enhanced aesthetics.

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

Polynitrogen High Energy Density Materials Synthesized by Nonequilibrium Plasma

Metal pentazolate compounds that contain 5-nitrogen singly charged anion rings are an interesting class of materials from a thermodynamics perspective. These compounds are believed to be equilibrium phases only at extremely high pressures, and thus, they constitute exotic states of matter at ambient pressure and temperature. Moreover, the energy released by these pentazolate compounds upon relaxation to the equilibrium state at ambient conditions is in the range 1 to 10 MJ per kg, rivaling that of combustion reactions. The synthesis of pentazolates is not an easy task, and there are only two known methods, each of which has significant challenges. Here, the development of new scalable synthesis routes could enable the production of these exotic materials in sufficient quantity to explore their properties more widely beyond the context of explosives and propellants. In this Perspective, it is argued that nonequilibrium plasma is a promising reaction medium for the synthesis of metal pentazolate compounds, for example from the corresponding metal azide and N 2 gas activated by the discharge at low background temperature.

Chemical reactions↗
DOE OSTI2021

Searching for a route to synthesize in situ epitaxial Pr 2 Ir 2 O 7 thin films with thermodynamic methods

In situ growth of pyrochlore iridate thin films has been a long-standing challenge due to the low reactivity of Ir at low temperatures and the vaporization of volatile gas species such as IrO 3 (g) and IrO 2 (g) at high temperatures and high P O2 . To address this challenge, we combine thermodynamic analysis of the Pr-Ir-O 2 system with experimental results from the conventional physical vapor deposition (PVD) technique of co-sputtering. Our results indicate that only high growth temperatures yield films with crystallinity sufficient for utilizing and tailoring the desired topological electronic properties and the in situ synthesis of Pr 2 Ir 2 O 7 thin films is fettered by the inability to grow with P O2 on the order of 10 Torr at high temperatures, a limitation inherent to the PVD process. Thus, we suggest techniques capable of supplying high partial pressure of key species during deposition, in particular chemical vapor deposition (CVD), as a route to synthesis of Pr 2 Ir 2 O 7 .

Chemistry↗
DOE OSTI2021

Phloem unloading via the apoplastic pathway is essential for shoot distribution of root-synthesized cytokinins

Abstract Root-synthesized cytokinins are transported to the shoot and regulate the growth, development, and stress responses of aerial tissues. Previous studies have demonstrated that Arabidopsis (Arabidopsis thaliana) ATP binding cassette (ABC) transporter G family member 14 (AtABCG14) participates in xylem loading of root-synthesized cytokinins. However, the mechanism by which these root-derived cytokinins are distributed in the shoot remains unclear. Here, we revealed that AtABCG14-mediated phloem unloading through the apoplastic pathway is required for the appropriate shoot distribution of root-synthesized cytokinins in Arabidopsis. Wild-type rootstocks grafted to atabcg14 scions successfully restored trans-zeatin xylem loading. However, only low levels of root-synthesized cytokinins and induced shoot signaling were rescued. Reciprocal grafting and tissue-specific genetic complementation demonstrated that AtABCG14 disruption in the shoot considerably increased the retention of root-synthesized cytokinins in the phloem and substantially impaired their distribution in the leaf apoplast. The translocation of root-synthesized cytokinins from the xylem to the phloem and the subsequent unloading from the phloem is required for the shoot distribution and long-distance shootward transport of root-synthesized cytokinins. This study revealed a mechanism by which the phloem regulates systemic signaling of xylem-mediated transport of root-synthesized cytokinins from the root to the shoot.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Assessment the leaching characteristics and long-term leaching behavior of some radionuclides from synthesized zeolite cement matrix

Highlights: • Synthesis and characterization of zeolite cement synthesized from fly ash • Leaching tests were used to assess the release rate of {sup 85}Sr and {sup 60}Co radionuclides. • Simple mathematical models were used to detect leaching mechanisms. • Long-term leaching behavior of {sup 85}Sr and {sup 60}Co from cementitious matrix was assessed. The development of cementitious materials remains a vital goal to produce valuable products with good mechanical, physical and chemical properties suitable for the safe disposal of concentrated radionuclides resulted from the treatment of contaminated solutions. In this paper, zeolite cement with good properties was laboratory synthesized from industrial by-products fly ash and characterized using various characterization techniques. The leaching characteristics of strontium and cobalt radionuclides from the synthesized zeolite cement were scrutinized conforming with the standard leaching methodology of International Atomic Energy Authority (IAEA). A mechanical strength assessment was executed to characterize the extent of immobilization process of the solidified matrices. The cumulative leaching fraction (φ) of the two studied radionuclides was found to be less than 5% in all examined conditions, which implies the applicability of the IAEA-recommended methodology for estimating the diffusion coefficient. The experimental leaching data were regressed nonlinearly to various mathematical kinetic models to assess the controlling leaching mechanism and to determine the leaching parameters. The regression results indicated that strontium ({sup 85}Sr) and cobalt ({sup 60}Co) leaching resulted from two succeeding mechanisms: as first order kinetic reaction, and then diffusion. The calculated values of leachability indices signify that the performance of each of the studied matrices is within an acceptable range. A simplified mathematical model, rooted in the first order reaction and diffusion mechanisms, was simulated to predict the radionuclides leaching rates from zeolite cement matrices. By comparing the synthesized zeolite cement with other cementitious materials, it can be concluded that the synthesized material can be classified as an efficient material suitable to immobilize {sup 85}Sr and {sup 60}Co from radioactive wastes. The acquired findings demonstrated that the studied immobilized waste matrices have acceptable mechanical effectiveness.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Examination of Replicate Syntheses of Metal Organic Frameworks as a Window into Reproducibility in Materials Chemistry

Replicate experiments are a useful tool in understanding the repeatability of scientific measurements. In 2019, a systematic search for replicate syntheses of a collection of 130 metal–organic frameworks (MOFs) found that 89% of these materials had no reported replicate syntheses apart from the original publications identifying the material (Agrawal, M. Proc. Natl. Acad. Sci. U.S.A. 2020, 117, 877−88210.1073/pnas.1918484117). A potential weakness of that search was that only 5–11 years had elapsed since the original publication of each material. Here, this analysis is extended to all publications 11–17 years after the original publication. Although this extended time period identifies more repeat syntheses, 83% of the materials still have no reported replicate syntheses. We also consider how appropriately selected Density Functional Theory (DFT) calculations can provide corroboration for the experimentally reported crystal structures. By using data from previous high-throughput DFT studies, corroborating evidence from DFT was available for 17% of the 130 structures for which no replicate syntheses are available. In total, approximately 1/3 of the 130 MOFs have data associated with replicate synthesis experiments and/or directly corroborating DFT calculations.

Sholl, David S. [Oak Ridge National Laboratory (OR↗
DOE OSTI2021

Transparent silica aerogel slabs synthesized from nanoparticle colloidal suspensions at near ambient conditions on omniphobic liquid substrates

This paper presents a novel sol-gel method to synthesize large and thick silica aerogel monoliths at near ambient conditions using a commercial aqueous solution of colloidal silica nanoparticles as building blocks. To achieve slabs with high visible transmittance and low thermal conductivity, the method combines the strategies of (i) synthesizing gels on an omniphobic perfluorocarbon liquid substrate, (ii) aging at temperatures above room temperature, and (iii) performing solvent exchange with a low-surface-tension organic solvent prior to ambient drying. The omniphobic liquid substrates were used to prevent cracking and ensure an optically-smooth surface, while nanoparticle building blocks were small (<10 nm) to limit volumetric light scattering. Gels were aged at temperatures between 25 and 80 °C for up to 21 days to make them stronger and stiffer and to reduce shrinkage and cracking during ambient drying. Ambient drying was achieved by first exchanging water in the gel pores for octane, followed by drying in an octane-rich atmosphere to decrease capillary forces. The synthesized nanoparticle-based silica aerogel monoliths had thicknesses up to 5 mm, diameters up to 10 cm, porosities exceeding 80%, and thermal conductivities as low as 0.08 W m –1 K –1 . Notably, the slabs featured visible transmittance exceeding 75% even for slabs as thick as 5 mm. The as-synthesized aerogel monoliths were exposed to TMCS vapor to induce hydrophobic properties resulting in a water contact angle of 140° that prevented water infiltration into the pores and protected the aerogels from water damage. This simple synthesis route conducted at near ambient conditions produces hydrophobic aerogel monoliths with promising optically transparent and thermally insulating properties that can be adhered to glass panes for window insulation and solar-thermal energy conversion applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Multiple Arabidopsis galacturonosyltransferases synthesize polymeric homogalacturonan by oligosaccharide acceptor‐dependent or de novo synthesis

SUMMARY Homogalacturonan (HG), the most abundant pectic glycan, functions as a cell wall structural and signaling molecule essential for plant growth, development and response to pathogens. HG exists as a component of pectic homoglycans, heteroglycans and glycoconjugates. HG is synthesized by members of the GALACTURONOSYLTRANSFERASE (GAUT) family. UDP‐GalA‐dependent homogalacturonan:galacturonosyltransferase (HG:GalAT) activity has previously been demonstrated for GAUTs 1, 4 and 11, as well as the GAUT1:GAUT7 complex. Here, we show that GAUTs 10, 13 and 14 are also HG:GalATs and that GAUTs 1, 10, 11, 13, 14 and 1:7 synthesize polymeric HG in vitro . Comparison of the in vitro HG:GalAT specific activities of the heterologously‐expressed proteins demonstrates GAUTs 10 and 11 with the lowest, GAUT1 and GAUT13 with moderate, and GAUT14 and the GAUT1:GAUT7 complex with the highest HG:GalAT activity. GAUT13 and GAUT14 are also shown to de novo synthesize (initiate) HG synthesis in the absence of exogenous HG acceptors, an activity previously demonstrated for GAUT1:GAUT7. The rate of de novo HG synthesis by GAUT13 and GAUT14 is similar to their acceptor dependent HG synthesis, in contrast to GAUT1:GAUT7 for which de novo synthesis occurred at much lower rates than acceptor‐dependent synthesis. The results suggest a unique role for de novo HG synthesis by GAUTs 13 and 14. The reducing end of GAUT13‐ de novo‐ synthesized HG has covalently attached UDP, indicating that UDP‐GalA serves as both a donor and acceptor substrate during de novo HG synthesis. The functional significance of unique GAUT HG:GalAT catalytic properties in the synthesis of different pectin glycan or glycoconjugate structures is discussed.

Engle, Kristen A.↗
DOE OSTI2024

In-house synthesized poly(ether ether ketone) ionenes. I. ToF-SIMS spectra in the positive ion mode

Static time-of-flight secondary ion mass spectrometry (ToF-SIMS) was performed for acquiring the high-resolution surface spectra of four types of synthesized imidazolium ionene membranes. These novel membranes have aromatic ether–ketone–ether linkages inspired by poly(ether ether ketone) (PEEK). The PEEK-ionenes synthesized for this study have imidazolium cations placed in the polymeric backbone with bistriflimide [Tf 2 N]- counterions. The attention given to synthetically modified PEEK derivatives, such as PEEK-ionenes, is considerable due to their ability to selectively capture CO 2 molecules and other light gases. Therefore, it is important to characterize the surface of these synthesized novel PEEK-ionenes. In this work, characteristic and unique peaks were identified in the positive spectra of each sample. The differences in mass spectra among the samples provide insights for optimizing or fine-tuning the PEEK-ionenes synthesis to achieve a high-performance CO 2 separation membrane with enhanced permeability, selectivity, and mechanical stability. The SIMS spectra and identified characteristic peaks of these synthesized ionenes will serve as a reference in the positive mode, complementing the corresponding spectra reported in the negative ion mode (Paper II).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Bottom‐Up Synthesized Nanoporous Graphene Transistors

Abstract Nanoporous graphene (NPG) can exhibit a uniform electronic band gap and rationally‐engineered emergent electronic properties, promising for electronic devices such as field‐effect transistors (FETs), when synthesized with atomic precision. Bottom‐up, on‐surface synthetic approaches developed for graphene nanoribbons (GNRs) now provide the necessary atomic precision in NPG formation to access these desirable properties. However, the potential of bottom‐up synthesized NPG for electronic devices has remained largely unexplored to date. Here, FETs based on bottom‐up synthesized chevron‐type NPG (C‐NPG), consisting of ordered arrays of nanopores defined by laterally connected chevron GNRs, are demonstrated. C‐NPG FETs show excellent switching performance with on–off ratios exceeding 10 4 , which are tightly linked to the structural quality of C‐NPG. The devices operate as p‐type transistors in the air, while n‐type transport is observed when measured under vacuum, which is associated with reversible adsorption of gases or moisture. Theoretical analysis of charge transport in C‐NPG is also performed through electronic structure and transport calculations, which reveal strong conductance anisotropy effects in C‐NPG. The present study provides important insights into the design of high‐performance graphene‐based electronic devices where ballistic conductance and conduction anisotropy are achieved, which could be used in logic applications, and ultra‐sensitive sensors for chemical or biological detection.

Mutlu, Zafer↗
DOE OSTI2023

Protonic Ceramic Electrochemical Cells for Synthesizing Sustainable Chemicals and Fuels

Abstract Protonic ceramic electrochemical cells (PCECs) have been intensively studied as the technology that can be employed for power generation, energy storage, and sustainable chemical synthesis. Recently, there have been substantial advances in electrolyte and electrode materials for improving the performance of protonic ceramic fuel cells and protonic ceramic electrolyzers. However, the electrocatalytic materials development for synthesizing chemicals in PCECs has gained less attention, and there is a lack of systematic and fundamental understanding of the PCEC reactor design, reaction mechanisms, and electrode materials. This review comprehensively summarizes and critically evaluates the most up‐to‐date progress in employing PCECs to synthesize a wide range of chemicals, including ammonia, carbon monoxide, methane, light olefins, and aromatics. Factors that impact the conversion, selectivity, product yield, and energy efficiencies are discussed to provide new insights into designing electrochemical cells, developing electrode materials, and achieving economically viable chemical synthesis. The primary challenges associated with producing chemicals in PCECs are highlighted. Approaches to tackle these challenges are then offered, with a particular focus on deliberately designing electrode materials, aiming to achieve practically valuable product yield and energy efficiency. Finally, perspectives on the future development of PCECs for synthesizing sustainable chemicals are provided.

03 NATURAL GAS↗