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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Solid-Phase Synthesis of Three-Armed Star-Shaped Peptoids and Their Hierarchical Self-Assembly

Due to the branched structure feature and unique properties, a variety of star-shaped polymers have been designed and synthesized. Despite those advances, solid-phase synthesis of star-shaped sequence-defined synthetic polymers that exhibit hierarchical self-assembly remains a significant challenge. Hence, we present an effective strategy for the solid-phase synthesis of three-armed star-shaped peptoids, in which ethylenediamine was used as the centric star pivot. Based on the sequence of monomer addition, a series of AA'A''-type and ABB'-type peptoids were synthesized and characterized by UPLC-MS (ultra-high performance liquid chromatography-mass spectrometry). By taking advantage of the easy-synthesis and large side-chain diversity, we synthesized star-shaped peptoids with tunable functions. We further demonstrated the aqueous self-assembly of some representative peptoids into biomimetic nanomaterials with well-defined hierarchical structures, such as nanofibers and nanotubes. These results indicate that star-shaped peptoids offer the potential in self-assembly of biomimetic nanomaterials with tunable chemistries and functions.

Solid-phase synthesis, star-shaped peptoids, aqueo↗
DOE OSTI2017

One-step hydrothermal synthesis and electrochemical performance of sodium-manganese-iron phosphate as cathode material for Li-ion batteries

The sodium-manganese-iron phosphate Na{sub 2}Mn{sub 1.5}Fe{sub 1.5}(PO{sub 4}){sub 3} (NMFP) with alluaudite structure was obtained by a one-step hydrothermal synthesis route. The physical properties and structure of this material were obtained through XRD and Mössbauer analyses. X-ray diffraction Rietveld refinements confirm a cationic distribution of Na{sup +} and presence of vacancies in A(2)’, Na{sup +} and small amounts of Mn{sup 2+} in A(1), Mn{sup 2+} in M(1), 0.5 Mn{sup 2+} and Fe cations (Mn{sup 2+},Fe{sup 2+} and Fe{sup 3+}) in M(2), leading to the structural formula Na{sub 2}Mn(Mn{sub 0.5}Fe{sub 1.5})(PO{sub 4}){sub 3}. The particles morphology was investigated by SEM. Several reactions with different hydrothermal reaction times were attempted to design a suitable synthesis protocol of NMFP compound. The time of reaction was varied from 6 to 48 h at 220 °C. The pure phase of NMFP particles was firstly obtained when the hydrothermal reaction of NMFP precursors mixture was maintained at 220 °C for 6 h. When the reaction time was increased from 6 to 12, 24 and 48 h, the dandelion structure was destroyed in favor of NMFP micro-rods. The combination of NMFP (NMFP-6H, NMFP-12H, NMFP-24H and NMFP-48H) structure refinement and Mössbauer characterizations shows that the increase of the reaction time leads to the progressive increment of Fe(III) and the decrease of the crystal size. The electrochemical tests indicated that NMFP is a 3 V sodium intercalating cathode. The comparison of the discharge capacity evolution of studied NMFP electrode materials at C/5 current density shows different capacities of 48, 40, 34 and 34 mA h g{sup −1} for NMFP-6H, NMFP-12H, NMFP-24H and NMFP-48H respectively. Interestingly, all samples show excellent capacity retention of about 99% during 50 cycles. - Graphical abstract: SEM micrographs (left) and evolution of the discharge on cycling with increasing rates from C/15 to 4 C (right) of NMFP material prepared by hydrothermal synthesis at 220 °C at indicated time. Display Omitted - Highlights: • One-step hydrothermal method was used to prepare sodium manganese iron phosphate NMFP. • 3D-NMFP dandelion sphere-like particles were obtained at 220 °C after 6 h. • Increasing reaction time leads to the enhancement of the crystallinity and crystal stabilility of NMFP. • The growth of the particle size and change of morphology are correlated to the reaction time. • EC performance of NMFP powders were greatly affected by the synthesis conditions.

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

Preparation of silicon carbide SiC-based nanopowders by the aerosol-assisted synthesis and the DC thermal plasma synthesis methods

Highlights: • Make-up of the SiC-based nanopowders is a function of the C:Si:O ratio in precursor. • Two-stage aerosol-assisted synthesis offers conditions close to equilibrium. • DC thermal plasma synthesis yields kinetically controlled SiC products. - Abstract: Nanosized SiC-based powders were prepared from selected liquid-phase organosilicon precursors by the aerosol-assisted synthesis, the DC thermal plasma synthesis, and a combination of the two methods. The two-stage aerosol-assisted synthesis method provides at the end conditions close to thermodynamic equilibrium. The single-stage thermal plasma method is characterized by short particle residence times in the reaction zone, which can lead to kinetically controlled products. The by-products and final nanopowders were characterized by powder XRD, infrared spectroscopy FT-IR, scanning electron microscopy SEM, and {sup 29}Si MAS NMR spectroscopy. BET specific surface areas of the products were determined by standard physical adsorption of nitrogen at 77 K. The major component in all synthesis routes was found to be cubic silicon carbide β-SiC with average crystallite sizes ranging from a few to tens of nanometers. In some cases, it was accompanied by free carbon, elemental silicon or silica nanoparticles. The final mesoporous β-SiC-based nanopowders have a potential as affordable catalyst supports.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Perspective: Toward “synthesis by design”: Exploring atomic correlations during inorganic materials synthesis

Synthesis of inorganic extended solids is a critical starting point from which real-world functional materials and their consequent technologies originate. However, unlike the rich mechanistic foundation of organic synthesis, with its underlying rules of assembly (e.g., functional groups and their reactivities), the synthesis of inorganic materials lacks an underpinning of such robust organizing principles. In the latter case, any such rules must account for the diversity of chemical species and bonding motifs inherent to inorganic materials and the potential impact of mass transport on kinetics, among other considerations. Without such assembly rules, there is less understanding, less predictive power, and ultimately less control of properties. Despite such hurdles, developing a mechanistic understanding for synthesis of inorganic extended solids would dramatically impact the range of new material discoveries and resulting new functionalities, warranting a broad call to explore what is possible. Here we discuss our recent approaches toward a mechanistic framework for the synthesis of bulk inorganic extended solids, in which either embryonic atomic correlations or fully developed phases in solutions or melts can be identified and tracked during product selection and crystallization. The approach hinges on the application of high-energy x-rays, with their penetrating power and large Q-range, to explore reaction pathways in situ. We illustrate this process using two examples: directed assembly of Zr clusters in aqueous solution and total phase awareness during crystallization from K–Cu–S melts. These examples provide a glimpse of what we see as a larger vision, in which large scale simulations, data-driven science, and in situ studies of atomic correlations combine to accelerate materials discovery and synthesis, based on the assembly of well-defined, prenucleated atomic correlations.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Synthesis and Electrocatalytic Activity of [FeFe]‐Hydrogenase Model Complexes with Non‐Innocent Chelating Nitrogen‐Donor Ligands

To probe the influence of redox non‐innocent ligands on a well‐known class of [FeFe]‐hydrogenase models, three new asymmetrically disubstituted diiron complexes of the general formula (µ‐SRS)[Fe(CO) 3 ][Fe(CO)(N‐N)] {SRS = propane‐1,3‐dithiolate (pdt) or benzene‐1,2‐dithiolate (bdt), and N‐N = 2,2′‐bipyridine (bipy) or 2,2′‐bipyrimidine (bpym)} have been synthesized from their parent hexacarbonyls and characterized. The new complexes, (µ‐pdt)Fe 2 (CO) 4 (κ 2 ‐bpym) ( 2 ), (µ‐bdt)Fe 2 (CO) 4 (κ 2 ‐bipy) ( 3 ), and (µ‐bdt)Fe 2 (CO) 4 (κ 2 ‐bpym) ( 4 ), were fully characterized by spectroscopic and electrochemical techniques, and the results are compared to those of a related complex, (µ‐pdt)Fe 2 (CO) 4 (κ 2 ‐bipy) ( 1 ). The crystal structures of 2 – 4 show that, in each complex, the two iron units are in an eclipsed orientation, and the N‐N ligand lies in the basal plane. IR spectra and electrochemical analyses indicate that electron density at the iron centers decreases in the order 1 > 2 > 3 > 4 . Furthermore, compound 2 undergoes a ligand‐centered reduction at the same potential that the hexacarbonyl precursor undergoes its first reduction. However, unlike the 2,2′‐bipy derivatives 1 and 3 , the 2,2′‐bpym complexes 2 and 4 are not effective catalysts for electrochemical proton reduction from acetic acid.

Roy, Souvik↗
DOE OSTI2017

Synthesis and electrochemical characterization of Ti{sub x}Ta{sub y}Al{sub z}N{sub 1-δ}O{sub γ} for fuel cell catalyst supports

Quinary Ti{sub x}Ta{sub y}Al{sub z}N{sub 1-δ}O{sub γ} of various compositions have been prepared by a co-precipitation method followed by ammonolysis. The nitride samples were examined as potential catalyst supports in polymer electrolyte membrane fuel cells. The nitride products crystallized in the rock salt (NaCl) structure over a wide range of compositions. The addition of Ta and Al was highly beneficial towards improving the chemical and electrochemical stability of TiN, without a significant loss of electrical conductivity. Platinum particles were successfully deposited on the (oxy)nitride samples, and the composite samples at some compositions were found to be comparable to Pt/carbon in their stability and catalytic activity even without optimizing the Pt deposition and dispersion processes. - Graphical abstract: The effect of additions of Ta and Al into TiN structure. Shifts the lattice constant, and increases its chemical stability in acidic environment.

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

Hierarchically Templated Synthesis of 3D‐Printed Crosslinked Cyclodextrins for Lycopene Harvesting

Abstract Plants produce a wide range of bioactive phytochemicals, such as antioxidants and vitamins, which play crucial roles in aging prevention, inflammation reduction, and reducing the risk of cancer. Selectively harvesting these phytochemicals, such as lycopene, from tomatoes through the adsorption method is cost‐effective and energy efficient. In this work, a templated synthesis of 3D‐printed crosslinked cyclodextrin polymers featuring nanotubular structures for highly selective lycopene harvesting is reported. Polypseudorotaxanes formed by triethoxysilane‐based telechelic polyethylene glycols and α‐cyclodextrins (α‐CDs) are designed as the template to (1) synthetically access urethane‐based nanotubular structures at the molecular level, and (2) construct 3D‐printed architectures with designed macroscale voids. The polypseudorotaxane hydrogels showed good rheological properties for direct ink writing, and the 3D‐printed hydrogels were converted to the desired α‐CD polymer network through a three‐step postprinting transformation. The obtained urethane‐crosslinked α‐CD monoliths possess nanotubular structures and 3D‐printed voids. They selectively adsorb lycopene from raw tomato juice, protecting lycopene from photo‐ or thermo‐degradations. This work highlights the hierarchically templated synthesis approach in developing functional 3D‐printing materials by connecting the bottom‐up molecular assembly and synthesis with the top‐down 3D architecture control and fabrication.

Chemistry↗
DOE OSTI2016

Lithium Assisted “Dissolution–Alloying” Synthesis of Nanoalloys from Individual Bulk Metals

We report new fundamental chemistry involved in the synthesis of bimetallic nanoalloys via dissolving the pure bulk transition metals in molten lithium. It is revealed at the atomic level that when two pure bulk transition metals such as Pd and Pt are placed in molten lithium (similar to 200 degrees C), they undergo a dissolution process in which the metal-metal bonds in pure bulk transition metals are completely ruptured, which results in the existence of individual Pd and Pt atoms surrounded by lithium atoms, as is evident by synchrotron X-ray adsorption techniques. Then, upon the conversion of metal lithium to LiOH in humid air, the Pd and Pt atoms undergo an alloying process to aggregate into nanoalloys. This method was further expanded to include PdZn, which is notoriously difficult to prepare via traditional nanoalloy synthesis methods due to the easily oxidizable Zn component. The constantly reducing environment of metallic Li allowed for preparation of PdZn nanoalloys with minimal Zn oxidation via dissolution-alloying of individual bulk transition metals in molten lithium. Additionally, this lithium assisted "dissolution-alloying" method bypasses many complications intrinsic to conventional ion reduction-based nanoalloy synthesis including the necessity of ligated metal ions, the use of proper reducing agents and dispersing surfactants, and the presence of segregated phases due to different reduction potentials of the constituent metal ions.

alloying↗
DOE OSTI2016

Polyvinylpyrrolidone-induced anisotropic growth of gold nanoprisms in plasmon-driven synthesis

After more than a decade, it is still unknown whether the plasmon-mediated growth of silver nanostructures can be extended to the synthesis of other noble metals, as the molecular mechanisms governing the growth process remain elusive. In this paper, we demonstrate the plasmon-driven synthesis of gold nanoprisms and elucidate the details of the photochemical growth mechanism at the single-nanoparticle level. Our investigation reveals that the surfactant polyvinylpyrrolidone preferentially adsorbs along the nanoprism perimeter and serves as a photochemical relay to direct the anisotropic growth of gold nanoprisms. This discovery confers a unique function to polyvinylpyrrolidone that is fundamentally different from its widely accepted role as a crystal-face-blocking ligand. Additionally, we find that nanocrystal twinning exerts a profound influence on the kinetics of this photochemical process by controlling the transport of plasmon-generated hot electrons to polyvinylpyrrolidone. Finally, these insights establish a molecular-level description of the underlying mechanisms regulating the plasmon-driven synthesis of gold nanoprisms.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Facile diamond synthesis from lower diamondoids

Carbon-based nanomaterials have exceptional properties that make them attractive for a variety of technological applications. Here, we report on the use of diamondoids (diamond-like, saturated hydrocarbons) as promising precursors for laser-induced high-pressure, high-temperature diamond synthesis. The lowest pressure and temperature $(P-T)$ conditions that yielded diamond were 12 GPa (at ~2000 K) and 900 K (at ~20 GPa), respectively. This represents a substantially reduced transformation barrier compared with diamond synthesis from conventional (hydro)carbon allotropes, owing to the similarities in the structure and full sp 3 hybridization of diamondoids and bulk diamond. At 20 GPa, diamondoid-to-diamond conversion occurs rapidly within <19 μs. Molecular dynamics simulations indicate that once dehydrogenated, the remaining diamondoid carbon cages reconstruct themselves into diamond-like structures at high $P-T$. This study is the first successful mapping of the $P-T$ conditions and onset timing of the diamondoid-to-diamond conversion and elucidates the physical and chemical factors that facilitate diamond synthesis.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Zeolitic Imidazolate Framework Membranes: Novel Synthesis Methods and Progress Toward Industrial Use

In the last decade, zeolitic imidazolate frameworks (ZIFs) have been studied extensively for their potential as selective separation membranes. In this review, we highlight unique structural properties of ZIFs that allow them to achieve certain important separations, like that of propylene from propane, and summarize the state of the art in ZIF thin-film deposition on porous substrates and their modification by postsynthesis treatments. We also review the reported membrane performance for representative membrane synthesis approaches and attempt to rank the synthesis methods with respect to potential for scalability. To compare the dependence of membrane performance on membrane synthesis methods and operating conditions, we map out fluxes and separation factors of selected ZIF-8 membranes for propylene/propane separation. Finally, we provide future directions considering the importance of further improvements in scalability, cost effectiveness, and stable performance under industrially relevant conditions.

Chemistry↗
DOE OSTI2018

Controlled synthesis of highly-branched plasmonic gold nanoparticles through peptoid engineering

Inspired by peptide- and protein-controlled formation of hierarchical inorganic nanostructures in nature, herein we report the design of sequence-defined peptoids for biomimetic synthesis of flower-like gold nanosuperstruc-tures. We demonstrate that the peptoid-induced morphosyn-thesis of gold nanoflowers is sequence-dependent. By varying the hydrophobicity, number of carboxylate and amino groups, and side-chain positions of peptoids, we develop a rule of thumb for designing peptoids that yield gold nanoflowers. Through a combination of hyperspectral UV-Vis absorption micro-spectroscopy (H-UVVIS-AMS) and three-photon photoemission electron microscopy (TP-PEEM), we measured the plasmonic properties of individual nanoflowers. Whereas H-UVVIS-AMS experiments revealed well-defined plasmon resonances centered at ~528 nm, TP-PEEM measurements showed an unprecedented plasmonic enhancement as high as 105 for a single nanoflower. A com-bination of the unique plasmonic property and the high sta-bility endows the peptoid-engineered nanoflowers with po-tential applications in chemical and biological imaging. FY, YC, HJ and C-LC acknowledge support by the Materials Synthesis and Simulation Across Scales (MS3) Initiative, through the Laboratory Directed Research & Development (LDRD) fund at Pacific Northwest National Laboratory (PNNL). FY was also partially supported by fellowships from Shandong Provincial Education Association for International Exchanges. YG was supported by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. PZE acknowledges support from the Laboratory Directed Research and Development Program through a Linus Pauling Fellowship at PNNL. PNNL is multi-program national laboratory operated for the Department of Energy by Battelle under Contracts No. DE-AC05-76RL01830. The authors are most grateful to Alan Joly and Wayne Hess (PNNL) for their support with the PEEM measurements and several useful discussions.

Yan, Feng↗