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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Interfacial Activity of Amine‐Functionalized Polyhedral Oligomeric Silsesquioxanes (POSS): A Simple Strategy To Structure Liquids

Abstract Amine‐functionalized polyhedral oligomeric silsesquioxane (POSS), the smallest, monodisperse cage‐shaped silica cubic nanoparticle, is exceptionally interfacially active and can form assemblies that jam the toluene/water interface, locking in non‐equilibrium shapes of one liquid phase in another. The packing density of the amine‐functionalized POSS assembly at the water/toluene interface can be tuned by varying the concentration, the pH value, and the degree of POSS functionalization. Functionalized POSS gives a higher interface coverage, and hence a lower interfacial tension, than nanoparticle surfactants formed by interactions between functionalized nanoparticles and polymeric ligands. Hydrogen‐bonded POSS surfactants are more stable at the interface, offering some unique advantages for generating Pickering emulsions over typical micron‐sized colloidal particles and ligand‐stabilized nanoparticle surfactants.

Hou, Honghao↗
DOE OSTI2014

Arginine-Containing Ligands Enhance H-2 Oxidation Catalyst Performance

In H2 fuel cells, performance depends on factors controlling turnover frequency and energy efficiency in the electrocatalytic oxidation of H2. Nature uses the hydrogenase enzymes to oxidize H2 at high turnover frequencies (up to 20,000 s-1) and low overpotentials (<100 mV), while the fastest synthetic catalyst reported to date only oxidizes H2 at 50 s-1 under 1 atm H2. Here we report a water-soluble complex incorporating the amino acid arginine, [NiII(PCy2NArg2)2]6+, that operates at 210 s-1 (180 mV overpotential) under 1 atm H2 and 144,000 s-1 (460 mV overpotential) under 133 atm H2. The complex functions from pH 0-14 with rates increasing at lower pH values. The arginine groups impart water solubility and play a critical role in enhancing turnover frequency, most consistent with an intramolecular Arg-Arg interaction that controls the structure of the catalyst active site. This work was funded by the Office of Science Early Career Research Program through the US DOE, BES (AD, WJS), and the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US DOE, BES (JASR). PNNL is operated by Battelle for the US DOE.

amino acid catalyst↗
DOE OSTI2019

Interfacial Activity of Amine-Functionalized Polyhedral Oligomeric Silsesquioxanes (POSS): A Simple Strategy To Structure Liquids

Amine-functionalized polyhedral oligomeric silsesquioxane (POSS), the smallest, monodisperse cage-shaped silica cubic nanoparticle, is exceptionally interfacially active and can form assemblies that jam the toluene/water interface, locking in non-equilibrium shapes of one liquid phase in another. The packing density of the amine-functionalized POSS assembly at the water/toluene interface can be tuned by varying the concentration, the pH value, and the degree of POSS functionalization. Functionalized POSS gives a higher interface coverage, and hence a lower interfacial tension, than nanoparticle surfactants formed by interactions between functionalized nanoparticles and polymeric ligands. Here, hydrogen-bonded POSS surfactants are more stable at the interface, offering some unique advantages for generating Pickering emulsions over typical micron-sized colloidal particles and ligand-stabilized nanoparticle surfactants.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Impact of Advances in Anion Exchange Membranes and Ionomers on Alkaline Fuel Cells

Abstract The operation of low‐temperature electrochemical energy conversion systems (fuel cells, electrolyzers) at high pH values is of perennial interest due to the possibility of moving away from expensive platinum group metal catalysts and reducing cost. Historically, the anion exchange membranes (AEMs) and ionomers have been hampered by performance (ionic conductivity, mechanical strength) and chemical stability issues. In this context, select developments over the past decade in alternate AEM chemistries, water management methods, and production of membrane electrode assemblies (MEAs) that have enabled a significant leap in performance of alkaline fuel cells are examined. These developments are linked to performance improvements in alkaline H 2 /O 2 fuel cells and also consider developments in alkaline fuel cells using nitrogen‐containing fuels (ammonia, hydrazine), carbon‐containing fuels (alcohols, glycols), and boron‐containing fuels (sodium borohydride, ammonia borane). Finally, current challenges and bottlenecks are identified, and potential solutions are proposed.

Chemistry↗
DOE OSTI2016

Trends in Hydrogen Evolution Activity of Metal-Modified Molybdenum Carbides in Alkaline and Acid Electrolytes

Relatively high surface area nanocrystalline molybdenum carbide (Mo 2 C) was modified with 5 w% silver, copper, nickel, platinum, and palladium nanoparticles and subsequently assessed for its hydrogen evolution reaction (HER) activity in alkaline and acid electrolytes. Density functional theory (DFT)-calculated hydrogen binding energies predicted that Pt–Mo 2 C and Pd–Mo 2 C should be most active, which was confirmed with experimental results. Similar activity trends were observed at both high and low pH values, with Cu–Mo 2 C being the least active. X-ray photoelectron spectroscopy (XPS) confirmed that metal particles remained on the sample before and after HER testing. Pt-modified nanocrystalline Mo 2 C showed superior HER activity compared with Pt-modified commercial Mo 2 C, making it a potential replacement for bulk Pt in alkaline membrane electrolyzers. Further, the positive effect on the HER activity of the metal contact with non-passivated Mo 2 C surfaces was also demonstrated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Novel Hybrid Catalyst for the Oxidation of Organic Acids: Pd Nanoparticles Supported on Mn-N-3D-Graphene Nanosheets

This paper reports the fabrication and electrochemical performance of a hybrid catalyst composed of Pd nanoparticles and atomically dispersed Mn active centers integrated into the nitrogen-doped three-dimensional graphene nanosheets (Pd/Mn-N-3D-GNS). Our results show that the synergistic integration of both Pd nanoparticles and atomically dispersed Mn can be used to enhance the activity toward the electrochemical oxidation of organic acids at biologically relevant pH values. The hybrid catalyst (Pd/Mn-N-3D-GNS) showed increased maximum currents toward the oxidation of oxalic acid when compared to its individual catalysts, namely, Pd/3D-GNS and Mn N-3D-GNS catalysts. The hybrid also showed a decreased onset potential for oxidation of mesoxalic acid as compared to Mn-N-3D-GNS and decreased onset potentials for the oxidation of glyoxalic acid when compared to both of its constituent catalysts. Oxidation of formic acid was also tested and the hybrid was shown to catalyze both dehydration and dehydrogenation mechanisms of formic acid electro-oxidation. Using density functional theory calculations, it was elucidated that a two-site catalysis most likely promotes dehydrogenation reaction for formic acid oxidation, which can explain the selectivity of Pd nanoparticles and atomically dispersed Mn towards the dehydrogenation/ dehydration pathway.

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

Polymer Nanosheet Containing Star‐Like Copolymers: A Novel Scalable Controlled Release System

Abstract Poly(ε‐caprolactone) (PCL)‐based nanomaterials, such as nanoparticles and liposomes, have exhibited great potential as controlled release systems, but the difficulties in large‐scale fabrication limit their practical applications. Among the various methods being developed to fabricate polymer nanosheets (PNSs) for different applications, such as Langmuir–Blodgett technique and layer‐by‐layer assembly, are very effort consuming, and only a few PNSs can be obtained. In this paper, poly(ε‐caprolactone)‐based PNSs with adjustable thickness are obtained in large quantity by simple water exposure of multilayer polymer films, which are fabricated via a layer multiplying coextrusion method. The PNS is also demonstrated as a novel controlled guest release system, in which release kinetics are adjustable by the nanosheet thickness, pH values of the media, and the presence of protecting layers. Theoretical simulations, including Korsmeyer–Peppas model and Finite‐element analysis, are also employed to discern the observed guest‐release mechanisms.

Cao, Peng‐Fei↗
DOE OSTI2018

Hydrometallurgical Extraction of Rare Earth Elements from Coal

Rare earth elements (REEs) contained in coal and associated mineral matter exist in several forms including micro-dispersed minerals, ion adsorption onto clay surfaces, and chemically bound. Tests found that REEs can be effectively recovered from certain components of three coal sources by leaching under mild conditions followed by solvent extraction. A range of pH values were evaluated at solution temperatures of 25°C and 75°C. When using 1.2 mol/L of sulfuric acid, nearly 85% recovery of the REEs was extracted from the middlings material collected from an operating plant. Acid leaching of a second middling source from another plant resulted in 60% of the total REEs being recovered under the same leaching conditions. Solvent extraction treatment of the leachate produced from six different coal sources resulted in products containing up to 50% total REEs from feedstocks starting with around 300 ppm.

Coal↗
DOE OSTI2018

A Novel Bio-based Polyaspartic Acid Copolymer: Synthesis, Structure and Performance of Degradation

A novel bio-based polyaspartic acid copolymer, as a multifunctional polymer was fabricated via in-site melting polymerization method using L-aspartic acid, γ-aminobutyric acid, L-phenylalanine and L-alanine as raw materials. The synthetic conditions were studied in detail, and the structure and degradation assays of these copolymers were investigated by FT-IR, XRD, weight loss rate, pH values, intrinsic viscosity and SEM. According to the results, all of the copolymers were found to have similar structure and excellent degradability. Additionally, the optimized copolymer C7 [L-aspartic acid (0.45 mol), γ-aminobutyric acid (0.35 mol), L-phenylalanine (0.05 mol) and L-alanine (0.15 mol)] exhibited the highest weight loss rate among all the copolymers. The weight loss rates on the 28th day in aqueous medium, phosphate buffered saline solution, 5.0 wt% trypsin solution and soil culture medium reached up to 44.74 wt%, 99.75 wt%, 90.67 wt% and 83.58 wt%, respectively. And the appropriate introduction of bio-based amino acids could control the degradation of polyaspartic acid distinctly. All of these results indicated that the bio-based polyaspartic acid copolymer could be used for reference as a good understanding of description the degradation of other environmentally friendly bio-based polymers.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Preparation and Dewatering Property of Two Sludge Conditioners Chitosan/AM/AA and Chitosan/AM/AA/DMDAAC

Two new chitosan-grafting copolymers (chitosan-g-PAM-AA and C-chitosan-g-PAM-AA) as sludge conditioners (flocculation and aggregation) have been prepared by employing ceric sulfate as a free radical initiator under nitrogen atmosphere in aqueous solution. The optimum condition for synthesizing chitosan-grafting copolymer was determined by orthogonal experiments. The structure, morphology and property of the obtained graft polymers were characterized by FT-IR, XRD, SEM, TGA and contact angle. Further, the municipal activated sludge dewatering performance of the synthesized copolymers was evaluated by the filter cake moisture content. Herein, the effects of pH value and dewatering temperatures of activated sludge, loading dosage or cationic degree of C-chitosan-g-PAM-AA on the filter cake moisture content were investigated. The synthesized amphoteric flocculant C-chitosan-g-PAM-AA showed a highly effective flocculation capability for activated sludge compared with chitosan-g-PAM-AA, chitosan, polyacrylamide (PAM). Also, the lowest filter cake moisture content was up to 61.41%.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Uptake of arsenic and selenium on iron-doped Pb resin

We report the uptake of the radioisotopes 73 As and 75 Se was characterized on Fe 3+ -doped Pb resin (Eichrom Technologies) from pH 1 to 12. There is good uptake of arsenic and selenium over a wide pH range (~ 1 to 10) with a decrease only at high pH (~ 12). Column experiments were performed to demonstrate the separations of these elements from solutions with near neutral pH values (~ 6 to 8) with high yields and high radiopurity. These separations may be relevant for a wide variety of applications especially isotope harvesting research.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2017

An improved crystal structure of C-phycoerythrin from the marine cyanobacterium Phormidium sp. A09DM

C-Phycoerythrin (PE) from Phormidium sp. A09DM has been crystallized using different conditions and its structure determined to atomic resolution (1.14 Å). In order for the pigment present, phycoerythrobilin (PEB), to function as an efficient light-harvesting molecule it must be held rigidly (Kupka and Scheer in Biochim Biophys Acta 1777:94–103, 2008) and, moreover, the different PEB molecules in PE must be arranged, relative to each other, so as to promote efficient energy transfer between them. This improved structure has allowed us to define in great detail the structure of the PEBs and their binding sites. These precise structural details will facilitate theoretical calculations of each PEB’s spectroscopic properties. It was possible, however, to suggest a model for which chromophores contribute to the different regions of absorption spectrum and propose a tentative scheme for energy transfer. We show that some subtle differences in one of these PEB binding sites in two of the 12 subunits are caused by crystal contacts between neighboring hexamers in the crystal lattice. This explains some of the differences seen in previous lower resolution structures determined at two different pH values (Kumar et al. in Photosyn Res 129:17–28, 2016).

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Electrochemical Behavior Assessment of As-Cast Mg-Y-RE-Zr Alloy in Phosphate Buffer Solutions (X Na{sub 3}PO{sub 4} + Y Na{sub 2}HPO{sub 4}) Using Electrochemical Impedance Spectroscopy and Mott–Schottky Techniques

In the present study, electrochemical behavior of as-cast Mg-Y-RE-Zr alloy (RE: rare-earth alloying elements) was investigated using electrochemical tests in phosphate buffer solutions (X Na{sub 3}PO{sub 4} + Y Na{sub 2}HPO{sub 4}). X-ray diffraction techniques and Scanning electron microscopy equipped with energy dispersive x-ray spectroscopy were used to investigate the microstructure and phases of the experimental alloy. Different electrochemical tests such as potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) and Mott–Schottky (M–S) analysis were carried out in order to study the electrochemical behavior of the experimental alloy in phosphate buffer solutions. The PDP curves and EIS measurements indicated that the passive behavior of the as-cast Mg-Y-RE-Zr alloy in phosphate buffer solutions was weakened by an increase in the pH, which is related to formation of an imperfect and less protective passive layer on the alloy surface. The presence of the insoluble zirconium particles along with high number of intermetallic phases of RE elements mainly Mg{sub 24}Y{sub 5} in the magnesium matrix can deteriorate the corrosion performance of the alloy by disrupting the protective passive layer that is formed at pH values over 11. These insoluble zirconium particles embedded in the matrix can detrimentally influence the passivation. The M–S analysis revealed that the formed passive layers on Mg-Y-RE-Zr alloy behaved as an n-type semiconductor. An increase in donor concentration accompanying solutions of higher alkalinity is thought to result in the formation of a less resistive passive layer.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A Study on Passive and Electrochemical Response of Pure Nickel in Borate Buffer Solutions: Effect of Cold Deformation

In the present work, influences of the cold deformation on electrochemical and passive response of pure nickel in three solutions with adjusted pH values of 8.5, 9.0, and 9.5 at 298 ± 1 K (25 ± 1 °C) were investigated. A cold deformation process was applied by means of cold rolling. Implementation of the cold deformation process resulted in samples having a finer microstructure. Also, the cold work and grain refinement led to increased hardness. In addition, open-circuit potential and potentiodynamic polarization tests were performed and results showed that corrosion current density was reduced by applying the cold deformation. Moreover, the results of the electrochemical impedance spectroscopy and Mott–Schottky analyses indicated higher corrosion resistance of pure nickel after cold deformation. This behavior is attributed to the growth of much thicker, with less point defects, passive layer on the surface of cold-deformed samples.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Corrosion Behavior of Q235 Steel in Atmospheres Containing SO{sub 2} and NaCl

The atmospheric corrosion of metals is a severe problem in marine environments. However, the effects of SO{sub 2} and NaCl on the atmospheric corrosion of Q235 steel have not been widely studied. In the present work, electrochemical impedance spectroscopy was conducted to exploit the initial corrosion properties of Q235 in simulated atmospheric environments containing different contents of SO{sub 2} and NaCl. The solution resistance (R{sub s}) and polarization resistance (R{sub p}) of electrodes covered with pre-deposited NaCl were continuously monitored. The results showed that both SO{sub 2} and NaCl promoted the corrosion rate of Q235 steel. The pre-deposited NaCl maintained the moisture of the metal surface to ensure continued corrosion. The thickness of the electrolyte layer on the metal surface decreased with increasing SO{sub 2} content. A thin electrolyte layer could increase the Cl{sup −} concentration and reduce the pH value of the layer. The thin electrolyte layer could also promote the mass transfer of oxygen, thereby accelerating the cathodic reduction reaction. However, the NaCl content played a more important role than that of SO{sub 2} in the simulated environments.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Pyrolysis Oil-Based Lipid Production as Biodiesel Feedstock by Rhodococcus opacus

Light oil from pyrolysis, which accounts for ~10 % carbon yield of the starting biomass, is a complex aqueous product that is difficult to utilize and usually discarded. This work presents the feasibility of light oil as a sole carbon source to support the growth of Rhodococcus opacus (R. opacus) that in turn accumulate triacylglycerols as biodiesel feedstock. Two types of bacteria (R. opacus PD630 and DSM 1069) were selected in this study. Research results showed that after short adaption periods both strains can grow well on this complex carbon source, as proved by the consumption of oligomers and monomers in light oil. Lipid content by R. opacus PD630 and DSM 1069 was observed up to 25.8 % and 22.0 % of cell dry weight, respectively. Palmitic and stearic acids were found to be the predominant fatty acids in these bacterial cells. In addition, the light oil-based lipid production can be enhanced by reducing the pH value from 7 to 4, especially in case of DSM 1069.

09 BIOMASS FUELS↗
DOE OSTI2019

Mixture of Macromolecular Crowding Agents Has a Non-additive Effect on the Stability of Proteins

The folding and unfolding of proteins inside a cell take place in the presence of macromolecules of various shapes and sizes. Such crowded conditions can significantly affect folding, stability, and biophysical properties of proteins. Thus, to logically mimic the intracellular environment, the thermodynamic stability of two different proteins (lysozyme and α-lactalbumin) was investigated in the presence of mixtures of three crowding agents (ficoll 70, dextran 70, and dextran 40) at different pH values. These crowders possess different shapes and sizes. It was observed that the stabilizing effect of mixtures of crowders is more than the sum effects of the individual crowder, i.e., the stabilizing effect is non-additive in nature. Moreover, dextran 40 (in the mixture) has been found to exhibit the greatest stabilization when compared with other crowders in the mixture. In other words, the small size of the crowder has been observed to be a dominant factor in stabilization of the proteins. .

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Assessment of shallow aquifer remediation capacity under different groundwater management conditions in CGS field

Because of unknown faults and fractures in the overlying rock, CO 2 stored deep underground may move upward, and the intrusion may impact shallow groundwater quality. After leakage of CO 2 has ceased, the affected aquifer may show remediation capacity under natural conditions and injections and extractions. Here, the reactive transport modeling software TOUGHREACT was used to simulate the remediation capacity of a study aquifer. The simulation results show that the intrusion of leaked CO 2 would decrease the pH of the target aquifer and trigger the dissolution of calcite minerals. After CO 2 leakage has ceased, the pH would increase as would the concentration of Ca because of the dissolution of calcite along the flow path. Scenario simulation results of amelioration of groundwater quality by water injection and extraction show that single injection is the best option and a combination approach of injection and extraction could control the range of the affected area. The pH value should not be regarded as the single indicator for remediation capacity assessment. Parameter sensitive analysis results show that the rates of injection and extraction affect the repair results significantly.

58 GEOSCIENCES↗