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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Fiscal Year 2020 Filtration of Hanford Tank Waste 241-AP-105

Bench-scale filtration testing of 15 liters of 241-AP-105 supernatant was conducted using a Mott inline filter Model 6610 (media grade 5) backpulsed dead-end filter (BDEF) in the hot cells of the Radiochemical Processing Laboratory at Pacific Northwest National Laboratory. The as-received samples were diluted with raw water from the Hanford Site to assess the propensity for solids to form upon dilution and to assess the impact those solids have on filtration performance. The feed was split into two batches. The first batch was settled and decanted as planned in Tank Side Cesium Removal operations. The BDEF was used to filter this AP-105 feed at a targeted flux of 0.065 gpm/ft 2 and exhibited no measurable pressure increase during filtration. The second batch was fed to the BDEF with solids resuspended. This was also operated at the targeted flux of 0.065 gpm/ft 2 . In this case, the target pressure differential of 2 psid (resistance of 6.24 × 10 10 m -1 ) was reached in slightly more than 12 h. A backpulse restored the filter flux; however, the time to the next backpulse was slightly shorter. These tests indicate that after the addition of raw water, settle and decant effectively removed solids from the feed. It is not possible to assess the time required for these solids to settle based on the result from these tests. However, if sufficient time is allowed for the solids to settle, no measurable filter fouling was observed in current testing. In contrast, if insufficient time is allowed for solids to settle, filter fouling will occur relatively quickly and will likely require backpulses more frequently than every 12 hours (1.91 m 3 /m 2 volume filtered). Solids concentrated from backpulse solutions displayed large variability in composition with Al-silicates and mixed chromium-aluminum oxide phases. Amounts of Mg, Fe, and Ca were also found in the presence of Na and O. These solids could be grouped in three categories: (1) soluble Na-salts that formed large block-like particles but were made up of fibrous materials, (2) amorphous Al-phases, and (3) colloidal iron oxides with an average particle diameter of 4.2 µm.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Friction extrusion of ODS copper rod made from powder

Meters-long oxide dispersion strengthened copper rods were manufactured directly from powder by a single-step process, called friction extrusion. The average grain size was 880 nm, which was refined 40 times from powder precursor due to extensive shear deformation. Meanwhile, the average size of alumina particles was 60 nm which retains a decent oxide dispersion strengthening. Here, mechanical properties, including hardness, tensile strength, and ductility, were tested and found to have better or similar values than conventional sintered-then-extruded oxide dispersion strengthened copper materials. The presented technique promises a convenient avenue for the fabrication of oxide dispersion strengthened copper from powder.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Sub-volt conversion of activated biochar and water for H 2 production near equilibrium via biochar-assisted water electrolysis

Sluggish water oxidation reactions limit water electrolysis for H 2 production, which can be alleviated by the use of carbon-based ma- terials like agricultural wastes as reducing agents. Biochar from such biomass can reduce equilibrium cell potentials at standard condi- tions from 1.23 V to 0.21 V by avoiding direct water splitting at the anode. However, some challenges hinder biochar oxidation, including poor biochar binding, electrode caking, and surface passivation. We find that enhanced C/O ratio, crystallinity, and negative zeta potential improve biochar oxidation kinetics at mod- erate temperatures. Smaller particle sizes and better mixing pre- vent electrode caking, enhancing biochar stability. Here, we report sub-volt biochar-coupled H 2 production, often referred to as a bio- char-assisted water electrolysis (BAWE), yielding 250 mA/g cat H 2 current at 100% Faradaic efficiency. Over 1 mA current was observed at a near-equilibrium cell potential of 0.2 V cell potential. Using a single-junction solar cell-powered BAWE, 15 mA H 2 is generated at 1 Sun, resulting in 4.8% solar-to-hydrogen efficiency, equivalent to 35% when the energy of H 2 relative to H 2 O (without biochar) is assumed.

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

Experimental demonstration of high-temperature (>1000 °C) heat extraction from a moving-bed oxidation reactor for thermochemical energy storage

Previously developed reduction-oxidation (redox) thermochemical energy storage technologies must store their products at high temperatures, complicating handling and transportation. This work describes a countercurrent, tubular, moving bed oxidation reactor at laboratory scale that produces high grade heat and allows solids to enter and exit the system at ambient temperatures. The particles implemented in the system consist of a novel magnesium manganese-oxide material well-suited for thermochemical energy storage. Output heat is obtained via a separate extraction gas flow, which exits from the middle portion of the main reactor tube. With this design, reactor temperatures in excess of 1000°C and extraction temperatures above 950°C were achieved. Deviation between the two measurements is a result of extraction thermocouple placement and losses in the reactor extraction arm; improvements to these parameters would bring the extraction temperature closer to the bed temperature. The reactor produces enough energy via oxidation to sustain both heat extraction and continued chemical reaction. During one representative steady state experiment at a particle flow rate of 1.5 g/s, an average of 447 W was extracted from the reactor out of an estimated 1083 W of released chemical energy for a duration of 70 minutes. Among the four experiments, the maximum bench-scale oxidation reactor energy efficiency of 36.2% and corresponding round-trip efficiency of 13.7% considering both redox reactors were demonstrated. Characteristics of an ideal system are considered and future improvements are proposed.

25 ENERGY STORAGE↗
DOE OSTI2020

Heterogeneous oxidation of amorphous organic aerosol surrogates by O 3 , NO 3 , and OH at typical tropospheric temperatures

Typical tropospheric temperatures render possible phase states of amorphous organic aerosol (OA) particles of solid, semisolid, and liquid. This will affect the multiphase oxidation kinetics involving the organic condensed-phase and gaseous oxidants and radicals. To quantify this effect, we determined the reactive uptake coefficients (γ) of O 3 , NO 3 , and OH by substrate films composed of single and binary OA surrogate species under dry conditions for temperatures from 213 to 313 K. A temperature-controlled coated-wall flow reactor coupled to a chemical ionization mass spectrometer was applied to determine γ with consideration of gas diffusion transport limitation and gas flow entrance effects, which can impact heterogeneous reaction kinetics. The phase state of the organic substrates was probed via the poke-flow technique, allowing the estimation of the substrates' glass transition temperatures. γ values for O 3 and OH uptake to a canola oil substrate, NO 3 uptake to a levoglucosan and a levoglucosan / xylitol substrate, and OH uptake to a glucose and glucose / 1,2,6-hexanetriol substrate have been determined as a function of temperature. We observed the greatest changes in γ with temperature for substrates that experienced the largest changes in viscosity as a result of a solid-to-liquid phase transition. Organic substrates that maintain a semisolid or solid phase state and as such a relatively higher viscosity do not display large variations in heterogeneous reactivity. From 213 to 293 K, γ values of O 3 with canola oil, of NO 3 with a levoglucosan / xylitol mixture, and of OH with a glucose / 1,2,6-hexanetriol mixture and canola oil, increase by about a factor of 34, 3, 2, and 5, respectively, due to a solid-to-liquid phase transition of the substrate. These results demonstrate that the surface and bulk lifetime of the OA surrogate species can significantly increase due to the slowed heterogeneous kinetics when OA species are solid or highly viscous in the middle and upper troposphere. This experimental study will further our understanding of the chemical evolution of OA particles with subsequent important consequences for source apportionment, air quality, and climate.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

The Influence of Mesoscale Particle Structure on the Electrode Degradation and Resultant Electrochemistry of Lithium Ion Cells With Nickel Rich Lithium Nickel Manganese Cobalt Oxide Positive Electrodes

Nickel-rich lithium nickel manganese cobalt oxide, NMC (LiNi x Mn y Co z O 2 ), materials are desirable positive electrodes in lithium ion batteries, providing high capacity and energy density. The mesoscale structure of NMC materials is commonly a polycrystalline aggregate, providing opportunity for short lithium ion transport distance of the small primary particles, yet facile material handling due to the larger secondary particles. On (de)lithiation the NMC unit cell changes volume, where the anisotropic strain can result in secondary particle fracture. This secondary particle fracture process during cycling has been associated with several degradation modes of NMC materials in LIBs. In this work, a milling process was determined whereby the secondary particles could be pre-fractured with retention of the parent primary particle crystallographic structure, crystallite size, and morphology, providing the ability to unambiguously determine the influence of NMC secondary particle size and mesostructure on resultant functional behavior. The bulk and interfacial properties and electrochemistry of as-received commercially obtained polycrystal NMC811 (LiNi 0.8 Mn 0.1 Co 0.1 O 2 , PC NMC) and its milled MPC NMC counterpart were compared. The smaller secondary particle size, higher surface area MPC NMC was found to result in 1) greater cathode tortuosity, 2) reduced surface Ni on the cycled MPC cathodes consistent with surface reconstruction, and 3) increased Ni deposition on the anodes from cathode-anode crosstalk. These factors manifested in unfavorable electrochemical behavior of MPC with lower functional capacity at both 1C and C/10 rates and higher impedance over extended moderate voltage (dis)charge cycling.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Mapping Competitive Reduction upon Charging in LiNi 0.8 Co 0.15 Al 0.05 O 2 Primary Particles

Side reactions involving surface reduction play a critical role in the failure of LiNi 0.8 Co 0.15 Al 0.05 O 2 to reach its theoretical capacity as a cathode material for Li-ion batteries. While macroscopic consequences are known, the underlying nanoscopic mechanisms are not fully elucidated. By coupling X-ray spectroscopy with several X-ray microscopy modalities, we have spatially resolved the extent of Ni oxidation at several states of charge and uncovered heterogeneity that is hidden when considering ensemble measurements alone. The use of morphologically controlled particles enabled high-resolution imaging of these materials, uncovering gradients of Ni oxidation states within individual primary particles. At high states of charge, these gradients revealed regions of possible oxygen deficiency extending deeper into the particle than previously observed. Surface-sensitive X-ray coupled scanning tunneling microscopy allows oxidation states to be measured at the material's surface, showing predominantly Ni II in the first atomic layer and mixtures of Ni II with Ni III /Ni IV already appearing 1.5 nm into the particle. These results reveal the subtle interplay between irreversible surface transformations and the bulk reactions that ultimately define function, which will refine strategies of surface passivation that are key to overcoming current performance limitations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Corrosion-Resistant Non-Carbon Electrocatalyst Supports for PEFCS

Insufficient durability of commercial catalysts is a persistent issue for PEFC applications.1 Herein, Pt on Nb-doped-TiO 2 is reported as a highly durable electrocatalyst on which the direct 4-electron reduction of oxygen to water is more facile compared to Pt/C. All performance metrics are reported comparing Pt/Nb-TiO2 with a 15% Pt loading, against a commercial Pt/C catalyst (46.5% Pt loading, Tanaka, K. K.). Nb-doped-TiO 2 with high surface area and high electronic conductivity was synthesized using the supercritical fluid method. Initially, the durability of the catalyst was characterized using accelerated stability tests (ASTs) involving 10,000 high potential cycles (DOE/FCCJ protocol) and the Pt/Nb-TiO 2 was found to retain 78% of its initial electrochemically active surface area (ECSA) compared to the 57.6 % retained by Pt/C. These observations were in excellent agreement with previous reports that the Pt particle size of Pt/C grew from 2nm to 8nm during the AST protocol along with severe corrosion and amorphization of the carbon surface.2, 3 TEM and XPS studies of the Pt-Nb-doped-TiO 2 catalyst showed that the Pt particle size grew from 3nm to 6nm and the Nb(IV) and Ti(III) in the support were oxidized to Nb(V) and Ti(IV) after the durability test. Thus, the improvement in Pt/Nb-TiO 2 ECSA retention was attributed to the lower extent of particle growth and lack of oxidative support loss upon oxidation as compared to Pt/C. The oxygen reduction reaction (ORR) performance was characterized by linear polarization using a rotating disk electrode (RDE). The electrochemical surface areas of Pt/Nb-TiO 2 and Pt/C were found to be 48m2·g -1 and 83m2·g -1 respectively, and the mass activity for the ORR at 0.9V vs. RHE were found to be 150 mA·mg-1Pt and 124 mA·mg-1Pt respectively. The improved mass activity on Pt/Nb-TiO 2 was attributed to strong metal support interaction (SMSI) between the Nb-TiO 2 support and the Pt catalyst based on the 625 meV decrease in the binding energy of the Pt4f x-ray photo-electron spectroscopy (XPS) peaks of Pt/Nb-TiO 2 compared to Pt/C. To quantify the impact of the SMSI, a kinetic model was applied to calculate the elementary reaction rate constants for the various steps of the ORR on both catalysts. The reaction rate constant (k1) for the direct 4-electron transfer pathway to produce H 2 O was significantly larger in Pt/Nb-TiO 2 as compared to Pt/C. Thus, the reduction in the electron binding energy as observed in the XPS was found to aid the facile filling of the higher energy 2p orbitals of O 2 thereby leading to improved 4-electron transfer kinetics and improved overall activity.

08 HYDROGEN↗
DOE OSTI2025

SCILLA Secondary Aerosol Volume Concentration Airborne Data

This data set contains secondary aerosol volume concentration in cubic micrometers per cubic centimeter (um^3/cm^3). The aerosol was generated in an oxidation flow reactor (OFR) and its volume concentration measured with a scanning mobility particle sizer (SMPS). Both components were designed and built at the University of California Riverside. Ambient particles were removed with a Teflon filter upstream of the OFR and then pure ammonium sulfate particles were added to create a stable aerosol surface area on which low-volatility oxidation products condense. High concentrations of hydroxyl radical (OH) formed inside the OFR accelerate the oxidative chemistry that would typically occur over a period of several days in the atmosphere, resulting in the production of secondary aerosol from precursor gases present in the ambient air. Concentrations of added ozone and water vapor were controlled to produce the desired and approximately constant level of photochemical aging. The reactor temperature was controlled, while the pressure was not, and was always slightly lower than that of the sampled outside air. Sampled air was pulled from above the Naval Postgraduate School’s (NPS) Twin Otter aircraft through a rear-facing, ¼” OD PFA Teflon tube. The sample stream was split between the OFR and several gas analyzers (NOx, CO, O3, and H2O). Though not contained in these files, data from an aerosol mass spectrometer intermittently operated downstream of the OFR are also available.

{"secondary aerosol concentration",aerosol_concent↗
DOE OSTI2022

Solution combustion synthesis of iron-based alumina nanocomposites for clean production of hydrogen from fossil fuels

Iron-based alumina nanocomposites are promising materials for microwave-assisted thermocatalytic dehydrogenation of fossil fuels, which has been proposed for the production of hydrogen with no CO2 emissions. Solution combustion synthesis (SCS) is an attractive technique for the fabrication of these materials because it has been used for synthesis of many nanoscale oxides. However, SCS can be carried out using different organic fuels and different heating equipment, and it is important to determine which fuel and heating mode generate materials with the best properties for dehydrogenation, such as maximized specific surface area. In the present work, the iron-based alumina nanocomposites were obtained by SCS using two different fuels (citric acid and glycine) and two different heating modes (a hotplate and a muffle furnace). The precursors/oxidizers were iron nitrate and aluminum nitrate. They were mixed with the fuel according to stoichiometry and dissolved in water. Heating the solution resulted in combustion synthesis. The products were characterized by X-ray diffraction analysis, Brunauer-Emmett-Teller surface area analysis, laser diffraction particle size analysis, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The experiments have shown that the specific surface area of the iron-based alumina nanocomposites obtained by SCS can be dramatically increased by using citric acid instead of glycine, and additionally by using a muffle furnace instead of a hotplate.

Solution combustion synthesis, Nanoscale metal oxi↗
DOE OSTI2021

High Performance non-PGM Transition Metal Oxide ORR Catalysts of PEMFCs

This project was designed to develop acid-stable PGM-free transition metal oxide oxygen reduction reaction (ORR) electrocatalysts to meet or exceed the performance and durability of the DOE 2020 Technical Targets for platinum-group metal (PGM) free electrocatalysts from first-principles to incorporation into membrane-electrode assemblies (MEAs) for polymer electrolyte membrane (PEM) fuel cells. The planned project was to accomplish this goal with a multi-step approach: 1) materials modeling and experimental screening to identify acid-stable oxides with high ORR activity, 2) optimization of catalyst particle size and catalyst/carbon/ionomer catalyst layer composition, 3) fabrication of MEAs for performance and durability testing. During the course of this project: 1) acid-stability descriptors were developed for manganese oxides; 2) a family of acid-stable multicomponent oxides based on antimony were developed; 3) a flexible synthesis for the formation of nanocrystalline nonstoichiometric oxides was developed; 4) limited ORR activity but modest and improving oxygen evolution reaction (OER) activity was measured for multicomponent antimony oxides. The project was programmed into five technical tasks: The development of acid-stable ORR electrocatalytic oxides through 1) identification and optimization of acid-stable oxide compositions, and 2) electrochemical characterization; 3) optimization of catalyst layer composition for MEAs using identified ORR electrocatalysts; 4) MEA fabrication and performance testing to result in performance of 44 mA-cm-2 at 0.9 V vs. RHE; and 5) accelerated-stress testing of optimized MEAs. Because no acid-stable oxide was identified with the requisite activity for ORR (4.4 µA-cm-2oxide intrinsic activity at 0.9 V vs. RHE) within the time and budget allotted in Tasks 1 and 2, the project was halted at the end of phase 1, with no activity in Tasks 3-5. The research output, while not succeeding in developing ORR electrocatalysts, advanced the development of acid-stable oxide materials, showing potential for further improvement as OER electrocatalysts.

08 HYDROGEN↗
DOE OSTI2020

Combustion, criteria pollutant and soot property assessment of mixing-controlled high-load engine operation with gasoline and diesel

Gasoline compression ignition (GCI) is an emerging technology that can achieve high fuel efficiency and low criteria emissions in diesel engine platforms using gasoline and gasoline-like fuels. While low- and mid-range loads are enabled with low temperature combustion (LTC) approaches, high-loads are more efficient with high temperature combustion (HTC) requiring mixing-controlled combustion (MCC). Lower soot emissions are achieved with gasoline even in high-load MCC than with diesel, but detailed soot properties from gasoline and diesel have been rarely discussed. In order to better understand how high-load operations affect soot properties, in this study gasoline and diesel were tested in a six-cylinder heavy duty engine at 14 bar brake mean effective pressure (BMEP) at similar combustion phasing. Effects of pilot mass ratio and EGR on heat release rates, cylinder temperatures, ignition delay (ID) and combustion duration (CD) were examined, relating with emissions variations with applications of the two fuels. Soot mass and particle number emissions were slightly lower with gasoline than with diesel, resulting in a more favorable NOx-soot trade-off with gasoline like other reports. Contrary to other findings in the literature, gasoline and diesel soot samples presented similar particle distribution shapes, carbon crystalline structures and primary particle sizes, regardless of fuel type and EGR rate. Consequently, the current result proposes that soot particles have undergone similar soot formation and oxidation processes despite reactivity difference and oxygen availability under the examined high-load MCC with similar combustion phases.

02 PETROLEUM↗
DOE OSTI2021

Hydroxymethanesulfonate (HMS) Formation during Summertime Fog in an Arctic Oil Field

Hydroxymethanesulfonate (HMS) is produced in the aqueous-phase reaction of formaldehyde (HCHO) and sulfur dioxide (SO 2 ) and has been proposed as a significant contributor to midlatitude wintertime pollution events. In this work, we report HMS detection within submicrometer atmospheric aerosols during frequent late summer, regional fog events in an Arctic oil field. The number fraction of individual particles containing HMS increased during fog periods, consistent with aqueous-phase formation. The single-particle mass spectra showed the primary particle signature (oil field emissions), plus secondary oxidized organics and sulfate, consistent with aqueous-phase processing. HMS mass concentrations ranged from below the ion chromatography limit of detection (0.3 ng/m 3 ) to 1.6 ng/m 3 , with sulfate concentrations of 37-222 ng/m 3 . HCHO and SO 2 measurements suggest that the fog HMS production rate is ~10 times higher in the oil fields than in the upwind Beaufort Sea. Aqueous-phase reactions of local oil field emissions during frequent summertime regional fog events likely have downwind impacts on Arctic aerosol composition. The potential for fog-based HMS production was estimated to be an order of magnitude higher in Fairbanks and Anchorage, AK, than in the oil fields and may explain the missing organosulfate source contributing to Fairbanks air quality.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Electrolyte Vapor Induced Passivation and Transition Metal Redox on Electrode Active Materials

The gaseous environment that battery electrodes are exposed to is critical to their electrochemical performance, and yet, the impact of vapor-phase components in the glovebox is relatively unexplored. In this study, we examine how the surface of Li 4 Ti 5 O 12 and LiFePO 4 composite electrodes evolve upon exposure to 1 M LiPF 6 in ethylene carbonate:dimethyl carbonate electrolyte vapors in an argon-filled glovebox. Spatially resolved X-ray photoemission electron microscopy and X-ray photoelectron spectroscopy reveal that even brief (15 minutes) contact with electrolyte vapor initiates the formation of a LiF film and changes the oxidation state of transition metals at the particle surface. Notably, these modifications occur selectively on active material particles and not on binder or conductive carbon, underscoring the specificity of vapor-induced reactions. Prolonged exposure to electrolyte vapor over the course of 1 week yields thicker, more chemically complex interphases containing both LiF and lithium oxyfluorophosphate species (Li x PO y F z ). Subsequent electrochemical testing shows that vapor-induced passivation layers influence first cycle capacities, lithium (de)insertion overpotentials, and charge-transfer resistance values. In conclusion, these results indicate that vapor–electrode interactions may be a source of variability in electrochemical behavior over time and suggest that other, more reactive electrode materials may also be susceptible to interactions with electrolyte vapor.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A Perspective on Thin-Film Perovskites as Supports for Metal Catalysts

Perovskite-supported metals have sometimes been referred to as “intelligent catalysts” because of the potential to regenerate sintered particles by driving the metal into the oxide lattice by high-temperature oxidation and releasing the metal by reduction. However, low surface areas and incomplete release of metal from the lattice have prevented the widespread application of these materials. Furthermore, we describe the preparation of thin perovskite films on stable supports by Atomic Layer Deposition (ALD) as a means for avoiding the limitations associated with bulk perovskites. Examples will be given that demonstrate many of the favorable properties of perovskite supports can be retained, while avoiding some of the shortcomings. Potential opportunities for using these materials are discussed.

36 MATERIALS SCIENCE↗
NASA NTRS1975

Value contamination avoidance devices

Mechanical redesign methods were used to minimize contamination damage of conventional fluid components and a contamination separator device was developed for long term reusable space vehicles. These were incorporated into an existing 50.8 mm poppet valve and tested for damage tolerance in a full size open loop flow system with gaseous and liquid nitrogen. Cyclic and steady flow conditions were tested with particles of 125 to 420 micrometers aluminum oxide dispersed in the test fluids. Nonflow life tests (100,000 cycles) were made with two valve configurations in gaseous hydrogen. The redesigned valve had an acceptable cycle life and improved tolerance to contamination damage when the primary sealing surfaces were coated with thin coatings of hard plastic (Teflon S and Kynar). Analytical studies and flow testing were completed of four different versions of the separator. overall separation efficiencies in the 55-90% range were measured with these non-optimum configurations.

Endicott, D. L.↗
NASA NTRS1984

Combined Silane Pyrolysis and Silicon-Particle Melt

Melter directly coupled to pyrolyzer eliminates difficulties of transport. Proposed coupling of free-space silane pyrolyzer and melter without intervening steps produce molten silicon with no problems of fine-particle movement, storage, contamination in transport, or oxide formation.

Levin, H.↗