A simple method for determination of fission gases trapped in irradiated fuel forms
Fission gases trapped in fuel particles, cladding and matrix of irradiated refractory metal-uranium oxide cermets determined by gamma counting
Sheibley, D. W.↗
SEARCH · Engineering Papers
Results for “Oxide Particles”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The erosion/corrosion of small superalloy turbine rotors operating in the effluent of a PFB coal combustor
The operation of a turbine in the effluent of a pressurized fluidized bed (PFB) coal combustor presents serious materials problems. Synergistic erosion/corrosion and deposition/corrosion interactions may favor the growth of erosion-resistant oxides on blade surfaces, but brittle cracking of these oxides may be an important source of damage along heavy particle paths. Integrally cast alloy 713LC and IN792 + Hf superalloy turbine rotors in a single-stage turbine with 6% partial admittance have been operated in the effluent of a PFB coal combustor for up to 164 hr. The rotor erosion pattern exhibits heavy particle separation with severe erosion at the leading edge, pressure side center, and suction side trailing edge at the tip. The erosion distribution pattern gives a spectrum of erosion/oxidation/deposition as a function of blade position. The data suggest that preferential degradation paths may exist even under the targeted lower loadings (less than 20 ppm).
Zellars, G. R.↗
Small particles in plumes of Mount St. Helens
Particles in the size range 0.1-25 microns were sampled by aircraft carrying a quartz crystal microcascade in the Mount St. Helens plume on three dates in August and September 1980. Two of the sampling dates represented 'typical' emissions of the volcano between plinian eruptions. One sampling flight was made 1-4 hours before the small plinian eruption of August 7, 1980 when the plume had become discontinuous and visibly darker. The plume sampled on August 7, before the eruption, contained mainly approximately 2-micron diameter silicic glass particles, fragments of the Mount St. Helens magma. The typical plumes sampled on September 22 and August 6 had much smaller concentrations of particles, trimodal size distributions with peaks at 10, 0.4, and 0.1 microns. The particles were largely nonsilicate and apparently represented Cu-Zn oxide (10 micron peak), Al sulfate, chloride, and oxide, and sulfuric acid (smallest size peak).
Rose, W. I.↗
Condensational growth and trace species scavenging in stratospheric sulfuric acid/water aerosol droplets
Stratospheric aerosols play a significant role in the environment. The composition of aerosols is believed to be a liquid solution of sulfuric acid and water with numerous trace species. Of these trace species, ozone in particular was recognized as being very important in its role of shielding the environment from harmful ultraviolet radiation. Also among the trace species are HCl and ClONO2, the so called chlorine reservoir species and various oxides of nitrogen. The quantity of stratospheric aerosol and its particle size distribution determines, to a large degree, the chemistry present in the stratosphere. Aerosols experience 3 types of growth: nucleation, condensation, and coagulation. The application of condensation investigations to the specific problem of stratospheric aerosols is discussed.
Tompson, Robert V., Jr.↗
The nanophase iron mineral(s) in Mars soil
Iron-enriched smectites have been suggested as important mineral compounds of the Martian soil. They were shown to comply with the chemical analysis of the Martian soil, to simulate many of the findings of the Viking Labeled Release Experiments on Mars, to have spectral reflectance in the VIS-NIR strongly resembling the bright regions on Mars. The analogy with Mars soil is based, in a number of aspects, on the nature and behavior of the iron oxides and oxyhydroxides deposited on the surface of the clay particles. A summary of the properties of these iron phases and some recent findings are presented. Their potential relevance to Mars surface processes is discussed.
Banin, A.↗
Depth Measurements Using Alpha Particles and Upsettable SRAMs
A custom designed SRAM was used to measure the thickness of integrated circuit over layers and the epi-layer thickness using alpha particles and a test SRAM. The over layer consists of oxide, nitride, metal, and junction regions.
upsettable SRAMs↗
Quantifying VOC-Reaction Tracers, Ozone Production, and Continuing Aerosol Production Rates in Urban and Far-Downwind Atmospheres
We have found a surprisingly informative decomposition of the complex question of smoggy ozone production (basically, [HO2] in a more locally determined field of [NO]) in the process of linked investigations of modestly smoggy Eastern North America (by NASA aircraft, July 2004) and rather polluted Flushing, NYC (Queens College, July, 2001). In both rural and very polluted situations, we find that a simple contour graph parameterization of the local principal ozone production rate can be estimated using only the variables [NO] and j(sub rads) [HCHO]: Po(O3) = c (j(sub rads) [HCHO])(sup a) [HCHO](sup b). Here j(sub rads) is the photolysis of HCHO to radicals, presumably capturing many harder-UV photolytic processes and the principle ozone production is that due to HO2; mechanisms suggest that ozone production due to RO2 is closely correlated, often suggesting a limited range of different proportionality factors. The method immediately suggests a local interpretation for concepts of VOC limitation and NOx limitation. We believe that the product j(sub rads) [HCHO] guages the oxidation rate of observed VOC mixtures in a way that also provides [HO2] useful for the principle ozone production rate k [HO2] [NO], and indeed, all ozone chemical production. The success of the method suggests that dominant urban primary-HCHO sources may transition to secondary plume-HCHO sources in a convenient way. Are there other, simple, near-terminal oxidized VOC's which help guage ozone production and aerosol particle formation? Regarding particles, we report on, to the extent NASA Research resources allow, on appealing relationships between far-downwind (Atlantic PBL) HCHO and very fine aerosol (including sulfate. Since j(sub rads) [HCHO] provides a time-scale, we may understand distant-plume particle production in a more quantitative manner. Additionally we report on a statistical search in the nearer field for relationships between glyoxals (important near-terminal aromatic and isoprene reaction products) and aerosol production, looking for VOC's that might be most implicated. All three variables j(sub rads), [HCHO], and [NO] are relatively easily measured in widespread air pollution monitoring networks, and all are deducible form space-borne observations, though estimation of [NO] from [NO2] (the species observable from space) may require care. We report also on airborne and surface observations of HCHO, suggesting that concentrated (urban) and more diffuse (forest) sources may be distinguishable from space. The use of the 3.58 micron microwindow for HCHO remote sensing should allow much sharper resolution of HCHO than the UV. UV sensing requires large and expensive instruments, but even these seem justified since formaldehyde is so informative.
Chatfield, Robert↗
Characterization of Oxy-Coal Swirl Injector
The article presents the design and testing of a coal-slurry swirl-pintle injector for high pressure oxy-coal combustion systems. Pressurized oxy-coal combustion-based systems have the potential to improve efficiency by recovering latent heat of the steam in flue gas and achieve 90% CO2 capture. In oxy-coal combustion, coal is burned in the presence of pure oxygen, which results in higher efficiency and less greenhouse gas in the exhaust. With the advancement of pressurized oxy-coal combustor research, there is a need to investigate injector technology suitable for this unique combustion approach. Effective atomization and mixing of coal-slurry and oxidizer pose a challenge for the efficient burning of coal particles. A swirl-pintle type injector was designed and tested to enhance the atomization of the coal-water slurry spray by adding a swirl to the oxygen flow path. Although pintle type injectors are traditionally used in rocket engines, they present a promising approach in clean coal combustion technology due to higher mixing effectiveness and enhanced performance. The mixing behavior of three pintle injectors with different swirl numbers (S = 0, 0.9, and 1.2) was tested using a high-speed shadow sizing technique. Mixture ratios of 30% (by mass) coal-water slurry were studied. The droplet diameter and dispersion characteristics were determined from shadow images of coal-water spray. The jet breakup length, droplet number, total moment ratio (TMR), and Ohnesorge number were then calculated to compare the performance of different injectors. The paper presents an empirical correlation of the TMR with droplet size and spray regimes. For a pintle injector with S = 1.2 swirler, the droplets diameter was found to be in the range of 1 mm to 12 mm. The jet breakup length was also shorter in comparison to S= 0 and 0.9 injectors. A second atomization zone was also observed at 2 and 5 diameters downstream of injector exist at spray edge and jet core respectively
01 COAL, LIGNITE, AND PEAT↗
Synthesis and Characterization of Core-Shell Cu-Ru, Cu-Rh, and Cu-Ir Nanoparticles
Optimizing the use of expensive precious metals is critical to developing sustainable and low-cost processes for heterogeneous catalysis or electrochemistry. Here, we report a synthesis method that yields core-shell Cu-Ru, Cu-Rh, and Cu-Ir nanoparticles with the platinum-group metals segregated on the surface. The synthesis of Cu-Ru, Cu-Rh, and Cu-Ir particles allows maximization of the surface area of these metals and improves catalytic performance. Furthermore, the Cu core can be selectively etched to obtain nanoshells of the platinum-group metal components, leading to a further increase in the active surface area. Characterization of the samples was performed with X-ray absorption spectroscopy, X-ray powder diffraction, and ex situ and in situ transmission electron microscopy. CO oxidation was used as a reference reaction: the three core-shell particles and derivatives exhibited promising catalyst performance and stability after redox cycling. Furthermore, these results suggest that this synthesis approach may optimize the use of platinum-group metals in catalytic applications.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Atmospheric Transformation of Refrigerants: Current Research Developments and Knowledge Gaps
Refrigerants have evolved through the years to reduce their global warming potential while providing sufficient cooling in refrigeration systems. Replacements for hydrofluorocarbons (HFCs) and chlorofluorocarbons (CFCs) are the hydrofluoroolefins (HFOs), which contain reactive double bonds that decrease the atmospheric lifetime of fluorinated compounds. However, the transformation of unsaturated fluorinated compounds in the atmosphere could generate persistent pollutants, particularly trifluoroacetic acid (TFA) which is the simplest Perfluoroalkyl carboxylic acids (PFCAs). Understanding the transformation of refrigerants is critical in assessing their contribution to atmospheric levels of TFA and their impact on watersheds and human health. This article will present the reactivity of the refrigerants, atmospheric oxidation source, and sink processes of fluorinated refrigerants under daytime conditions, particularly the variability of TFA from refrigerants. Moreover, the discussion will suggest experimental procedures that can quantify the low concentration (~parts per trillion) of TFA generated from the transformation of HFOs. New state-of-the-art techniques such as chemical ionization mass spectrometers (HR-CIMS) will be assessed in providing high temporal resolution (minutes to hourly) to fully capture the atmospheric sources and variability of TFA. Likewise, local, regional, and global concentrations of TFA accounted from the oxidation of refrigerants will be examined. This will include data from both experimental procedures and simulation models. Participation of TFA in critical atmospheric processes such as new particle formation will also be included in this study. Lastly, overall knowledge gaps related to the oxidation products and their dispersion in the environment will be summarized to guide future research needs.
Salvador, Christian↗
Growth and structural studies of In/Au(111) alloys and InO x /Au(111) inverse oxide/metal model catalysts
Indium oxide has received attention as an exciting candidate for catalyzing the CO 2 hydrogenation to methanol due to its high selectivity (>80%). Compared to the extent of research on the activity of indium oxide-based powder catalysts, very little is known about the phenomena associated with the formation of surface alloys involving indium or the growth mechanism for indium oxide nanoparticles. In this report, scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) were employed to elucidate the growth mode, structure, and chemical state of In/Au(111) alloys and InO x /Au(111) inverse model catalysts. Here, our study reveals distinct morphological differences between In/Au(111) and InO x /Au(111), and the InO x structure also depends strongly on the preparation conditions. In/Au surface alloy systems with extremely low coverage (0.02 ML) form islands preferentially on the elbow sites of reconstructed Au(111) herringbone, regardless of hcp and fcc stacking. At higher coverage (0.1 ML), the In islands expand over the herringbone in the <110> direction and create two dimensional domain structures over the entire surfaces. Moreover, this 2D domain structure is disturbed by temperature with high dispersion of indium atoms observed during the annealing process. Oxidation of the In/Au(111) surface alloys with O 2 at 550 K produces InO x /Au(111) systems which contain various sizes of InO x aggregates (from 0.7 to 10 nm). On the other hand, InO x /Au(111) surfaces prepared by vapor deposition of In at 550 K in an O 2 background exhibit highly dispersed and uniformly small InO x particles (~1 nm). Both InO x systems were confirmed to be partially oxidized by XPS.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Asphericity Can Cause Nonuniform Lithium Intercalation in Battery Active Particles
Uniform intercalation is desired to enable next-generation Li-ion batteries. While we expect nonuniformity in materials undergoing a phase change, single-phase intercalation materials such as nickel manganese cobalt oxide are believed to lithiate uniformly at the particle/electrolyte interface. However, recent imaging reveals nonuniform lithiation. Motivated by this discrepancy, we examine if aspherical particle shape can cause such nonuniformity since the conventional belief is based on spherical particle theory. We obtain real particle geometries using rapid lab-based X-ray computed tomography and subsequently perform physics-based calculations accounting for electrochemical reactions at the particle/electrolyte interface and lithium transport inside the particle bulk. The aspherical geometry breaks the symmetry and causes nonuniform reaction distribution. Such nonuniformity is exacerbated as the particle becomes more aspherical. We report the proposed mechanism represents a fundamental limit on achievable lithiation uniformity in aspherical particles in the absence of other mechanisms causing inhomogeneity, such as grain structure, nonuniform carbon-binder coating, etc.
25 ENERGY STORAGE↗
Proposal for a Universal Particle Detector Experiment
The Universal Particle Detector Experiment (UPDE), which consists of parallel planes of two diode laser beams of different wavelengths and a large surface metal oxide semiconductor (MOS) impact detector, is proposed. It will be used to perform real-time monitoring of contamination particles and meteoroids impacting the spacecraft surface with high resolution of time, position, direction, and velocity. The UPDE will discriminate between contaminants and meteoroids, and will determine their velocity and size distribution around the spacecraft environment. With two different color diode lasers, the contaminant and meteroid composition will also be determined based on laboratory calibration with different materials. Secondary particles dislodged from the top aluminum surface of the MOS detector will also be measured to determine the kinetic energy losses during energetic meteoroid impacts. The velocity range of this instrument is 0.1 m/s to more than 14 km/s, while its size sensitivity is from 0.2 microns to millimeter-sized particles. The particulate measurements in space of the kind proposed will be the first simultaneous multipurpose particulate experiment that includes velocities from very slow to hypervelocities, sizes from submicrometer- to pellet-sized diameters, chemical analysis of the particulate composition, and measurements of the kinetic energy losses after energetic impacts of meteroids. The experiment will provide contamination particles and orbital debris data that are critically needed for our present understanding of the space environment. The data will also be used to validate contamination and orbital debris models for predicting optimal configuration of future space sensors and for understanding their effects on sensitive surfaces such as mirrors, lenses, paints, and thermal blankets.
Lesho, J. C.↗
An improved semi-global intrinsic kinetics model for high temperature carbon oxidation
Measurements of the oxidation rates of various forms of carbon (soot, graphite, coal char) have often shown an unexplained attenuation with increasing temperatures in the vicinity of 2000 K, even when accounting for diffusional transport limitations and gas-phase chemical effects (e.g. CO 2 dissociation). With the development of oxy-fuel combustion approaches for pulverized coal utilization with carbon capture, high particle temperatures are readily achieved in sufficiently oxygen-enriched environments. Here, in this work, a new semi-global intrinsic kinetics model for high temperature carbon oxidation is created by starting with a previously developed 5-step mechanism that was shown to reproduce all major known trends in carbon oxidation, except for its high temperature kinetic falloff, and incorporating a recently discovered surface oxide decomposition step. The predictions of this new model are benchmarked by deploying the kinetic model in a steady-state reacting particle code (SKIPPY) and comparing the simulated results against a carefully measured set of pulverized coal char combustion temperature measurements over a wide range of oxygen concentrations in N 2 and CO 2 environments. The results show that the inclusion of the spontaneous surface oxide decomposition reaction step significantly improves predictions at high particle temperatures. Furthermore, the simulations reveal that O atoms released from the oxide decomposition step enhance the radical pool in the near-surface region and within the particle interior itself. Incorporation of literature rates for O and OH reactions with the carbon surface results in a reduction in the predicted radical pool concentrations and a very minor enhancement of the overall carbon oxidation rate.
33 ADVANCED PROPULSION SYSTEMS↗
Coordinated Mineralogical and Isotopic Analysis of a Cosmic Symplectite Identified in a Stardust Terminal Particle
Comet Wild-2 samples returned by the Stardust spacecraft contain a chemically diverse mixture of material, underscoring the complex nature of comets. Studies of entire Stardust aerogel tracks afford the opportunity to examine the fine-grained particle fragments distributed along the length of the track as well as the terminal particles. Previous TEM characterization of a terminal particle (TP) in track #147 revealed a symplectically intergrown iron sulfide and oxide assemblage. Mineralogically similar assemblages, known as cosmic symplectites (COS, formerly termed "new-PCP"), have only been identified in the primitive carbonaceous chondrite Acfer 094. Meteoritic COS have isotopically heavy O compositions (delta (sup 17), O-18 = 180per mille) that point to interactions with early solar system primordial water. In this study we report mineralogical and O isotopic measurements of the Wild-2 COS assemblage. Experimental: Track #147 is a "bulbous"-type track (4600 microns long) containing 7 terminal particles. The TPs were removed from the track, embedded in epoxy, and ultramicrotomed. A JEOL 2500SE 200 keV field-emission scanning-transmission electron microscope was used to obtain quantitative elemental maps and detailed mineralogical characterization. Following TEM analysis, two thin sections of TP4 (12 microns) were analyzed for O isotopes by raster ion imaging with the JSC NanoSIMS 50L. All three O isotopes were measured simultaneously using electron multipliers. San Carlos olivine grains were used as isotopic standards. Results and Discussion: The COS in the Wild-2 track #147 TP4 sample consists of symplectically intergrown pentlandite and nanocrystalline maghemite which coexists with high-Ca pyroxene with Na and Cr (kosmochlor component). This kosmochlor component could have a nebular origin and be precursors to type II chondrules in ordinary chondrites. Yet pentlandite is not a stable phase in the nebula. The COS in Acfer 094 also consists of pentlandite, but contains magnetite [4] rather than the more oxidized maghemite observed in the Wild-2 COS. The Acfer 094 COS display heavy O isotopic compositions that are the result of sulfidization and oxidation of Fe, Ni-metal grains and sulfides by O-17- and O-18-rich water in the solar nebula or possibly on the parent body. The O isotopic composition of the Wild-2 COS, however, is indistinguishable from terrestrial, indicating it was not altered by the same primordial aqueous reservoir as the Acfer 094 COS. The alteration could have occurred on the parent body by isotopically equilibrated ice. The mineralogy and petrography of Wild-2 samples suggests an incomplete or nascent hydration process. In future work we will analyze S isotopes in the track #147 TP4 COS and search for additional COS in Stardust samples.
Nguyen, A. N.↗
Correlative operando microscopy of oxygen evolution electrocatalysts
Transition metal (oxy)hydroxides are promising electrocatalysts for the oxygen evolution reaction.1–3 The properties of these materials evolve dynamically and heterogeneously4 with applied voltage through ion insertion redox reactions, converting inactive materials at open-circuit into active electrocatalysts during operation.5 Thus, the catalytic state is inherently far-from-equilibrium, complicating its direct observation. Here, we establish the link between the oxygen evolution activity and the local operational chemical, physical, and electronic nanoscale structure of single-crystalline β-Co(OH)2 platelet particles through a suite of newly developed correlative operando scanning probe and X-ray microscopy techniques. At pre-catalytic voltages, the particles swell to form an α-CoO2H1.5·0.5H2O-like structure with associated Co2.5+ oxidation state produced through hydroxide intercalation. With increasing voltage to drive oxygen evolution, interlayer water and protons de-intercalate to form contracted β-CoOOH particles with Co3+ species. While these transformations manifest heterogeneously through the bulk of the particles, the electrochemical current is primarily restricted to the particle edge facets. The observed Tafel behavior is correlated to the local concentration of Co3+ at these reactive edge sites, demonstrating the link between bulk ion-insertion and surface catalytic activity.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Low temperature hot corrosion
The reaction of Co-Cr, Ni-Cr, Co-Cr-Al, and Ni-Cr-Al alloys with Na2SO4 in the presence of SO3 at temperatures between 700 and 750 C leads to the formation of liquid CoSO4-Na2SO4 or NiSO4-Na2SO4 deposits on the alloy surface. The formation of Cr2O3 and/or Al2O3 below this deposit results in a locally low P(O2) and a higher P(S2) and P(SO2). It is noted that these conditions can prevent protective oxide formation either by sulfide formation in the alloy, which localizes the Cr and/or Al in discrete particles, or by acid fluxing involving a reaction between Al2O3 or Cr2O3 and SO2 to form a salt-soluble species and subsequent reprecipitation as porous oxides in regions of higher P(O2). These processes may occur simultaneously, although a given alloy generally exhibits features of predominantly one type. Here, the Ni-Cr and Ni-Cr-Al alloys, and to some extent the Co-Cr alloys, exhibit features indicative of the sulfidation mechanism, whereas the morphology for the Co-Cr-Al alloy is more consistent with a predominant acid fluxing mechanism.
Chiang, K. T.↗
Inclusion of Radiation Environment Variability for Reliability Estimates for SiC Power MOSFETs
Variability of the solar energetic particle environment is investigated for single-event-burnout reliability of silicon-carbide power metal-oxide-semiconductor field effect transistors. A probabilistic assessment of failure evaluates the benefits of de-rating voltage, shielding, and mission length. The Prediction of Solar particle Yields for Characterizing Integrating Circuits code is used to calculate a cumulative density function for the fluence of the environment. The lethal ion method is then used to determine what proportion of the environment will cause single-event-burnout. The operating voltage determines the lowest linear-energy-transfer particle that will cause single-event-burnout and that should be included in the environment distribution. The shielding and mission length also determine the final environment distribution of the mission fluence. Through calculating the reliability for different operating voltages, shielding, and mission length for a specific device, it is shown that shielding thickness and operating voltage have a large effect on reliability and can be traded off during the design.
Heavy ion↗