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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

The Two-Cavity Method for Characterizing Acoustical Materials—an Interlaboratory Study

This study focuses on understanding the sound absorption characteristics of porous acoustic materials, which are determined by two key parameters independent of material thickness: characteristic impedance and propagation constant. These parameters can be characterized by testing a porous sample concept in a normal incidence impedance tube using either the two-thickness or the two-cavity method. In the two-thickness method, two samples of varying thicknesses are required. In contrast, the two-cavity method requires testing one sample at two different air cavity depths behind the porous material. This method is particularly advantageous for materials that are costly or challenging to fabricate. This interlaboratory study evaluates the variability of characteristic properties determined using the two-cavity method. Porous acoustic materials were additively manufactured and tested in the Liner Technology Facility(LTF)at NASA Langley Research Center and the Mechanics, Acoustics and Dynamics Lab (MADLab) at Michigan Technological University. The characteristic properties derived from various cavity depth combinations were used to predict the surface impedance of the sample with a rigid backing. The prediction was then compared the measured impedance spectrum. It was also found that the combinations of cavity depths can significantly influence the accuracy of the deduced properties.

acoustic liners↗
DOE OSTI2023

Measuring Multicomponent Adsorption of Tracer Gases on Natural Zeolites

A natural clinoptilolite sample near the Nevada National Security Site was obtained to study adsorption and retardation on gas transport. Of interest is understanding the competition for adsorption sites that may reduce tracer gas adsorption relative to single-component measurements, which may be affected by the multi-scale pore structure of clinoptilolite. Clinoptilolite has three distinct domains of pore size distributions ranging from nanometers to micrometers: micropores with 0.4–0.7 nm diameters, measured on powders by CO2 adsorption at 273 K, representing the zeolite cages; mesopores with 4–200 nm diameters, observed using liquid nitrogen adsorption at 77 K; and macropores with 300–1000 nm diameters, measured by mercury injection on rock chips (~ 100 mesh), likely representing the microfractures. These pore size distributions are consistent with X-ray computed tomography (CT) and focused ion beam scanning electron microscope (FIB-SEM) images, which are used to construct the three-dimensional (3D) pore network to be used in future gas transport modeling. To quantify tracer gas adsorption in this multi-scale pore structure and multicomponent gas species environment, natural zeolite samples initially in equilibrium in air were exposed to a mixture of tracer gases. As the tracer gases diffuse and adsorb in the sample, the remaining tracer gases outside the sample fractionate. Using a quadrupole mass spectrometer to quantify this fractionation, the degree of adsorption of tracer gases in the multicomponent gas environment and multi-scale pore structure is assessed. The major finding is that Kr reaches equilibrium much faster than Xe in the presence of ambient air, which leads to more Kr uptake than Xe over limited exposure periods. When the clinoptilolite chips were exposed to humid air, the adsorption capability decreases significantly for both Xe and Kr with relative humidity (RH) as low as 3%. Both Xe and Kr reaches equilibrium faster at higher RH. The different, unexpected, adsorption behavior for Xe and Kr is due to their kinetic diameters similar to the micropores in clinoptilolite which makes it harder for Xe to access compared to Kr.

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

The Effect of γ Irradiation on Phase Transitions in the Polyimide–YBa{sub 2}Cu{sub 3}O{sub 6+} {sub x} System

The effect of γ irradiation on optical properties of films of the polyimide–YBa{sub 2}Cu{sub 3}O{sub 6.7} system with different concentrations of the filler in the form of the finely crystalline compound YBa{sub 2}Cu{sub 3}O{sub 6.7} (0.05 wt %, 0.10 wt %, and 0.50 wt %) has been investigated. The properties were studied on an IKS-29 infrared spectrophotometer in a spectral range of 400–4200 cm{sup –1} at room temperature. The samples were irradiated in air under room conditions on an RKhM-γ-20 by doses of 150, 250, and 600 kGy. The power of the exposure dose of the {sup 60}Co source was 0.16 rad/s. It has been established that irradiation with a dose of up to 600 kGy of the abovementioned system slightly affects the structure of the polyimide matrix but decreases the number of free radical groups in the film structure with the formation of hydrogen bonds. In the range of 400–4200 cm{sup –1} at D = 150 kGy, the most intense changes in spectra of polymeric composite samples have been revealed. In the range of 2850–3350 cm{sup –1}, the wide absorption spectrum band is preserved, which is caused by the presence of Cu, Y, and Ba crystallohydrates. The band is related to deformation vibrations of the Cu–O bond in YBa{sub 2}- Cu{sub 3}O{sub 6.7} (YBCO) chains due to properties of barium carbonate, formation of oxygen vacancies in the filler, and vibrations of the Cu(I)–O(I) bonds near one or several O(4) vacancies. Irradiation by doses of 250 and 600 kGy for different concentrations of the filler leads to a decrease in the signal intensity in the range of 1800–3600 cm{sup –1} by 20–35% on average. Peaks related to interband transitions (transitions of the Cu(I)–Cu(IY)–Cu(II) system) and bending vibrations O(I)–Cu(I) are not changed by strains of O(IY)–Cu(I) bonds. This testifies to the radiation-stimulated diffusion of oxygen atoms to O(IY) sites determining the orthorhombic phase of YBa{sub 2}Cu{sub 3}O{sub 6.7} from the occupied positions in the Cu–O sublattice.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1995

Fire safety experiments on MIR Orbital Station

The process of heterogeneous combustion of most materials under zero-g without forced motion of air is practically impossible. However, ventilation is required to support astronauts' life and cool equipment. The presence of ventilation flows in station compartments at accidental ignition can cause a fire. An additional, but exceedingly important parameter of the fire risk of solid materials under zero-g is the minimum air gas velocity at which the extinction of materials occurs. Therefore, the conception of fire safety can be based on temporarily lowering the intensity of ventilation and even turning it off. The information on the limiting conditions of combustion under natural conditions is needed from both scientific and practical points of view. It will enable us to judge the reliability of results of ground-based investigations and develop a conception of fire safety of inhabited sealed compartments of space stations to by provided be means of nontraditional and highly-effective methods without both employing large quantities of fire-extinguishing compounds and hard restrictions on use of polymers. In this connection, an experimental installation was created to study the process of heterogeneous combustion of solid non-metals and to determine the conditions of its extinction under microgravity. This installation was delivered to the orbital station 'Mir' and the cosmonauts Viktorenko and Kondakova performed initial experiments on it in late 1994. The experimental installation consists of a combustion chamber with an electrical systems for ignition of samples, a device for cleaning air from combustion products, an air suction unit, air pipes and a control panel. The whole experiment is controlled by telemetry and recorded with two video cameras located at two different places. Besides the picture, parameters are recorded to determine the velocity of the air flow incoming to the samples, the time points of switching on/off the devices, etc. The combustion chamber temperature is also controlled. The main objectives of experiments of this series were as follows: (1) verification of the reliability of the installation in orbital flight; (2) verification of the experimental procedure; and (3) investigation of combustion of two types of materials under microgravity at various velocities of the incoming air flow.

Egorov, S. D.↗
DOE OSTI2018

Ice Nucleating Particle Sources at Oliktok Point Field Campaign Report

The Ice Nucleating Particle Sources at Oliktok Point U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) facility field campaign focused on chemically characterizing springtime aerosol sources at Oliktok Point, Alaska. This work was completed to improve our understanding of air masses influencing the site and altering ice nucleating particle (INP) concentrations measured by Dr. Jessie Creamean of the National Oceanic and Atmospheric Administration (NOAA) during her coordinated, simultaneous ARM field campaign “Exploratory Ice Nucleation Measurements at Oliktok”. Together these ARM field campaigns comprised INPOP (Ice Nucleating Particles at Oliktok Point). The field campaign took place at the Oliktok Point Third ARM Mobile Facility (AMF3) site from March 1 to May 31, 2017. A Davis rotating uniform motion (DRUM) impactor was deployed to collect particles for offline analysis for single-particle chemical characterization (aerosol mixing state). Barring a few interruptions due to power outages at the site, daily samples (24-h duration) were collected for analysis by computer-controlled scanning electron microscopy with energy dispersive X-ray spectroscopy (CCSEM-EDX). Unfortunately our user facility grant at the Pacific Northwest National Laboratory (PNNL) Environmental Molecular Sciences Laboratory (EMSL) was placed on hold from October 2017 to February 2018, limiting our ability to do CCSEM-EDX, as our access is also limited at the Michigan Center for Materials Characterization. Therefore, only a subset of these samples were chosen in consultation with J. Creamean and analyzed by CCSEM-EDX. We have proposed to analyze additional samples, targeting samples collected during marine air masses, as part of our DOE Atmospheric System Research (ASR) proposal “Investigating marine and terrestrial aerosol processes and cloud ice nucleation during the Alaskan Arctic melt season”. The size-resolved aerosol mixing state data produced from the ARM field campaign represent the first of such observations in the springtime at Oliktok Point. Since this AMF3 site is located within the North Slope of Alaska (NSA) oil fields near Prudhoe Bay, the site is continually influenced by combustion emissions, with natural sources also contributing to the background aerosol population.

North Slope of Alaska, Oliktok Point, aerosols, or↗
DOE OSTI2012

Synthesis and characterization of anatase TiO{sub 2} nanotubes with controllable crystal size by a simple MWCNT template method

Highly crystalline phase-pure anatase TiO{sub 2} nanotubes were produced by performing a simple calcinations process in air of the TiO{sub 2} coated MWCNTs composite material prepared by an in situ sol-gel method. A homogeneous thin coating layer of TiO{sub 2} on the surface of MWCNTs is firstly obtained. Calcination in ambient air at appropriate temperatures is performed to transform phase of TiO{sub 2} into anatase and remove MWCNTs simultaneously, resulting in pure anatase TiO{sub 2} nanotubes. Both end tips of the nanotubes are observed to be closed, probably due to covering up MWCNTs with TiO{sub 2} particles. The crystallization of anatase phase was formed upon 350 Degree-Sign C, and MWCNTs are completely oxidized between 500 and 650 Degree-Sign C, leaving anatase TiO{sub 2} nanotubes with an average crystal size increasing from about 8 to 24 nm as the temperature rises. Moreover, the tubular structure was found to collapse after calcinations at 700 Degree-Sign C. - Graphical abstract: TGA analysis and TEM images of the samples after calcinations in air at different temperatures: (a) before calcinations, (b) 350 Degree-Sign C, (c) 500 Degree-Sign C, and (d) 650 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Highly crystalline and stable phase-pure anatase TiO{sub 2} nanotubes were produced by a simply MWCNT template method. Black-Right-Pointing-Pointer A homogeneous thin coating layer of TiO{sub 2} on the surface of MWCNTs could be obtained. Black-Right-Pointing-Pointer Small crystal size of anatase is formed at lower temperatures and higher temperatures cause significant increase of crystal size from 8 to 24 nm. Black-Right-Pointing-Pointer Convex closed tip structure of TiO{sub 2} nanotubes is formed owing to the good coating of TiO{sub 2}.

36 MATERIALS SCIENCE↗
NASA NTRS2000

BOREAS TGB-7 Ambient Air Herbicide and Organochlorine Concentration Data

The BOReal Ecosystem-Atmosphere Study Trace Gas Biogeochemistry (BOREAS TGB)-7 team measured the concentration and flux of several agricultural pesticides in air, rainwater, and dry deposition samples in order to determine the associated yearly deposition rates. This data set contains information on the ambient air concentration of seven herbicides [2,4- dichlorophenoxyacidic_acid (2,4-D), bromoxynil, dicamb, 2-methyl-4-chlorophenoxyacetic acid (MCPA), triallate, trifluralin, and diclop-methyl] known to appear in the atmosphere of the Canadian prairies. Also, the concentration of three herbicides (atrazine, alachlor, and metolachlor), two groups of insecticides (lindane and breakdown products and dichloro-diphenyl-trichloroethane (DDT) and breakdown products), and several polychlorinated biphenyls commonly used in the central United States was measured. All of these chemicals are reported, in the literature, to be transported in the atmosphere. Many have been reported to occur in boreal and arctic food chains. The sampling was carried out from 16-Jun to 13-Aug-1993 and 04-May to 20-Jul-1994 at the BOREAS site in the Prince Albert National Park (Waskesiu). The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884).

Waite, Don↗
DOE OSTI2011

Modeling Population Exposures to Pollutants Emitted from Natural Gas Cooking Burners

We developed a physics-based data-supported model to investigate indoor pollutant exposure distributions resulting from use of natural gas cooking appliances across households in California. The model was applied to calculate time-resolved indoor concentrations of CO, NO2 and formaldehyde resulting from cooking burners and entry with outdoor air. Exposure metrics include 1-week average concentrations and frequency of exceeding ambient air quality standards. We present model results for Southern California (SoCal) using two air-exchange scenarios in winter: (1) infiltration-only, and (2) air exchange rate (AER) sampled from lognormal distributions derived from measurements. In roughly 40percent of homes in the SoCal cohort (N=6634) the 1-hour USEPA NO2 standard (190 ?g/m3) was exceeded at least once. The frequency of exceeding this standard was largely independent of AER assumption, and related primarily to building volume, emission rate and amount of burner use. As expected, AER had a more substantial impact on one-week average concentrations.

03 NATURAL GAS↗
DOE OSTI2015

Femtosecond filament-laser ablation molecular isotopic spectrometry

A new remote sensing technology for real-time isotopic analysis is introduced: Femtosecond Filament-Induced Laser Ablation Molecular Isotopic Spectrometry (F 2 -LAMIS). The technique combines femtosecond (fs) laser filamentation and ablation-based molecular isotopic spectroscopy, thereby enabling isotopic analysis of samples at a distance, in ambient air and at ambient pressure conditions. Isotopic analysis of zirconium (Zr) samples by F 2 -LAMIS is demonstrated, and the molecular and atomic emission intensity, and properties of the filament-induced plasma generated at different filament propagation distances were investigated. Spectral fitting of F 2 -LAMIS spectra enabled semi-quantitative isotopic analysis without the use of calibration standards, which was independent of the filament propagation distance for the studied range. As a result, this technology provides new capabilities for direct isotopic ratio measurements at remote distances.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1987

A simplified method for determining heat of combustion of natural gas

A simplified technique for determination of the heat of combustion of natural gas has been developed. It is a variation of the previously developed technique wherein the carrier air, in which the test sample was burnt, was oxygen enriched to adjust the mole fraction of oxygen in the combustion product gases up to that in the carrier air. The new technique eliminates the need for oxygen enrichment of the experimental mixtures and natural gas samples and has been found to predict their heats of combustion to an uncertainty of the order of 1 percent.

Singh, Jag J.↗
DOE OSTI2015

High Throughput Ambient Mass Spectrometric Approach to Species Identification and Classification from Chemical Fingerprint Signatures

A high throughput method for species identification and classification through chemometric processing of direct analysis in real time (DART) mass spectrometry-derived fingerprint signatures has been developed. The method entails introduction of samples to the open air space between the DART ion source and the mass spectrometer inlet, with the entire observed mass spectral fingerprint subjected to unsupervised hierarchical clustering processing. Moreover, a range of both polar and non-polar chemotypes are instantaneously detected. The result is identification and species level classification based on the entire DART-MS spectrum. In this paper, we illustrate how the method can be used to: (1) distinguish between endangered woods regulated by the Convention for the International Trade of Endangered Flora and Fauna (CITES) treaty; (2) assess the origin and by extension the properties of biodiesel feedstocks; (3) determine insect species from analysis of puparial casings; (4) distinguish between psychoactive plants products; and (5) differentiate between Eucalyptus species. An advantage of the hierarchical clustering approach to processing of the DART-MS derived fingerprint is that it shows both similarities and differences between species based on their chemotypes. Furthermore, full knowledge of the identities of the constituents contained within the small molecule profile of analyzed samples is not required.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2004

Environment Partitioning and Reactivity of Polybrominated Diphenylethers

Polybrominated diphenyl ethers (PBDEs) are an important class of flame retardants. Annual global demand for these compounds was over 67,000 metric tons in 2001. PBDEs have recently been extensively investigated as environmental contaminants because they have been detected in air, sediment, and tissue samples from urban and remote areas. Important issues include quantifying PBDE partitioning in various environmental compartments, and elucidating transformation pathways. The partitioning of PBDE congeners to aerosols was estimated for 16 sites in the United States, Canada, and Mexico. The aerosol particles were PM2.5, the total suspended particle (TSP) concentration varied between 3.0 - 55.4 micro g/cubic meter, and the organic fraction ranged from 11 - 41%; these data are published values for each site. It is estimated that the largest fraction of each PBDE associated with the aerosol particles occurs in Mexico City, and the smallest fraction in Colorado Plateau. Although the organic fraction in Mexico City is about 60% of that observed in the Colorado Plateau, the TSP is larger by a factor of about 18.5, and it is the difference in TSP that strongly influences the fraction of particle-bound PBDE in this case. PBDE partitioning to PM2.5 particles also varies seasonally because of temperature variations. For the less brominated congeners the percentage that is particle-bound is relatively low, regardless of air temperature. In contrast, the heavier congeners exhibit a significant temperature dependence: as the temperature decreases (fall, winter) the percentage of PBDE that is particle-bound increases. The partitioning calculations complement experimental data indicating that decabromodiphenyl ether (DBDE) dissolved in hexane transforms very rapidly when irradiated with solar light. DBDE is the most highly brominated PBDE congener (10 bromine atoms) and occurs in the commercial formulation which is subject to the largest global demand.

Hua, Inez↗
DOE OSTI2022

Comparison of Irradiated and Unirradiated Graphite Oxidation Performance

This work examines the oxidation behavior of NBG-25 graphite using irradiated specimens and (not irradiated) companion specimens from the Advanced Graphite Creep (AGC) Experiment. Irradiated and companion specimens were quartered, split into four small samples, to enable four oxidation test runs for each (0.5 inch diameter by 0.25 inch tall) piggyback button obtained from the AGC Experiment inventory. These split samples were oxidized in air in a thermogravimetric analyzer (TGA) and benchmarked against observations with separately sourced same-grade specimens of three geometries oxidized either in the TGA or in a vertical furnace built and operated to satisfy the specifications of ASTM D7542. The study considers both irradiation damage and relief of damage by thermal annealing. A range of isothermal oxidation temperatures were tested for specimens exposed to a similar irradiation environment, nominally 6.5 dpa at 650°C. To assess the dose dependency of observed oxidation behavior, specimens with a range of irradiation exposures (up to 6.8 dpa) were tested at the single oxidation temperature of 650°C. In the conventional analysis (rate determined over the 5-10% mass loss range) any annealing effects appear to be negligible, while irradiation to ~6.5 dpa may double or triple the subsequent oxidation rate. However, examination of rate with extent of reaction (over incremental ranges from initial onset up to 5% mass loss) illustrates that (at least for ~6.5 dpa) irradiation initially inhibits oxidation. Slower rates of oxidation than companion split samples are clearly indicated across all oxidation temperatures tested up to ~0.5% mass loss. Over the range of 0.5-1% mass loss, regardless of normalization strategy, there is no statistically meaningful difference in oxidation rate. However, beyond 0.5% mass loss oxidation of the irradiated sample becomes progressively faster than the companion sample (up to the 10% mass loss level observed).

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1997

HO(x) Measurements in SONEX with the Airborne Tropospheric Hydrogen Oxides Sensor (ATHOS)

SONEX, which was delayed by aircraft inspection problems, began the second week of October and concluded in mid-November with 16 flights. These flights covered the Pacific Ocean off the western United States, transits across the United States, the western coast of Europe, and the North and Central Atlantic Ocean. Particular attention was paid to the North Atlantic Flight Corridor. ATHOS collected high-quality HO(x) data on 15 flights. Observations taken at 5 Hz were typically averaged into 20-second measurements. Each 20-second measurement has precision 1(sigma) of less than 0.01 pptv. OH measurements were generally made from the surface to flight altitudes. HO2 measurements, which require reagent NO flow, were made from flight altitudes to near the top of the planetary boundary layer. Measured OH and HO2 during SONEX was generally lower than the measured OH and HO2 during SUCCESS (April-May, 1996, central United States). Whereas during SUCCESS midday OH was 0.1-0.5 pptv and HO2 was 3-15 pptv, during SONEX midday OH was 0.02-0.2 pptv and HO2 was 0.5-8 pptv. Part of this difference results from the midday solar zenith angles, which were larger during SONEX than during SUCCESS due to both the season and the generally higher latitudes sampled during SONEX. However, some of the difference may be due to differences in HOx sources, since less air influenced by convection was sampled during SONEX. These possibilities await post-flight calibrations of ATHOS and analysis of observations of HO(x) and simultaneously measured meteorology and trace species.

Brune, William M.↗
DOE OSTI2012

NARAC Modeling During the Response to the Fukushima Dai-ichi Nuclear Power Plant Emergency

This paper summarizes the activities of the National Atmospheric Release Advisory Center (NARAC) during the Fukushima Dai-ichi nuclear power plant crisis. NARAC provided a wide range of products and analyses as part of its support including: (1) Daily Japanese weather forecasts and hypothetical release (generic source term) dispersion predictions to provide situational awareness and inform planning for U.S. measurement data collection and field operations; (2) Estimates of potential dose in Japan for hypothetical scenarios developed by the Nuclear Regulatory Commission (NRC) to inform federal government considerations of possible actions that might be needed to protect U.S. citizens in Japan; (3) Estimates of possible plume arrival times and dose for U.S. locations; and (4) Plume model refinement and source estimation based on meteorological analyses and available field data. The Department of Energy/National Nuclear Security Administration (DOE/NNSA) deployed personnel to Japan and stood up 'home team' assets across the DOE complex to aid in assessing the consequences of the releases from the Fukushima Dai-ichi Nuclear Power Plant. The DOE Nuclear Incident Team (NIT) coordinated response activities, while DOE personnel provided predictive modeling, air and ground monitoring, sample collection, laboratory analysis, and data assessment and interpretation. DOE deployed the Aerial Measuring System (AMS), Radiological Assistance Program (RAP) personnel, and the Consequence Management Response Team (CMRT) to Japan. DOE/NNSA home team assets included the Consequence Management Home Team (CMHT); National Atmospheric Release Advisory Center (NARAC); Radiation Emergency Assistance Center/Training Site (REAC/TS); and Radiological Triage. NARAC was activated by the DOE/NNSA on March 11, shortly after the Tohoku earthquake and tsunami occurred. The center remained on active operations through late May when DOE ended its deployment to Japan. Over 32 NARAC staff members, supplemented by other LLNL scientists, invested over 5000 person-hours of time and generated over 300 analyses and predictions.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
NASA NTRS1990

Aerosol measurements in the stratocumulus project

Cloud Condensation Nuclei (CCN) and Condensation Nuclei (CN) were measured from the National Center for Atmospheric Research (NCAR) Electra throughout the marine stratocumulus project. The total particle concentration was measured with a condensation nucleus counter. The CCN were measured with the Desert Research Institute (DRI) instantaneous CCN spectrometer. This instrument simultaneously measures the concentration of aerosol active at up to 100 different critical supersaturations (Sc). This is accomplished by exposing the sample to a fixed supersaturation field and using the size of the droplets produced in this cloud chamber to deduce the Sc of the nuclei upon which they have grown. Droplet size is associated with Sc through a calibration which is accomplished by passing soluble aerosols of known size and composition through the cloud chamber. This procedure results in a calibration curve of Sc vs. droplet size. This then allows the channel number to be directly associated with Sc. Thus, number concentration vs. Sc is obtained and this is a CCN spectrum. Since the instrument operates continuously, the measurements at all Sc's are available simultaneously. Samples are drawn directly from the ambient air and data is displayed in nearly real time. Samples were integrated over times of about 10 seconds so that substantial spatial resolution is available. Calibrations were performed once or twice a day and were found to be consistent. Preliminary results are shown.

Hudson, James G.↗
DOE OSTI2016

Temperature-Dependent Evolution of the Oxidation States of Cobalt and Platinum in Co 1– x Pt x Clusters under H 2 and CO + H 2 Atmospheres

Co1-xPtx clusters of 2.9-nm size with a range of atomically precise Pt/Co atomic ratios (x = 0, 0.25, 0.5, 0.75, 1) were synthesized using the mass-selected low-energy cluster beam deposition (LECBD) technique and soft-landed onto an amorphous alumina thin film prepared by atomic layer deposition (ALD). Utilizing ex situ X-ray photoemission spectroscopy (XPS), the oxidation state of the as-made clusters supported on Al2O3 was determined after both a 1-h-long exposure to air and aging for several weeks while exposed to air. Next, the aged duster samples were characterized by grazing-incidence X-ray absorption spectroscopy (GIXAS) and then pretreated with diluted hydrogen and further exposed to the mixture of diluted CO and H-2 up to 225 degrees C at atmospheric pressure, and the temperature-dependent evolutions of the particle size/shape and the oxidation states of the individual metal components within the dusters were monitored using in situ grazing-incidence small-angle X-ray scattering and X-ray absorption spectroscopy (GISAXS/GIXAS). The changes in the oxidation states of Co and Pt exhibited a nonlinear dependence on the Pt/Co atomic ratio of the dusters. For example, a low Pt/Co ratio (x <= 0.5) facilitates the formation of Co(OH)(2), whereas a high Pt/Co ratio (x = 0.75) stabilizes the Co3O4 composition instead through the formation of a Co-Pt core-shell structure where the platinum shell inhibits the reduction of cobalt in the core of the Co1-xPtx alloy dusters. The obtained results indicate methods for optimizing the composition and structure of binary alloy clusters for catalysis.

Yang, Bing↗
NASA NTRS1986

Solid sorbent air sampler

A fluid sampler for collecting a plurality of discrete samples over separate time intervals is described. The sampler comprises a sample assembly having an inlet and a plurality of discreet sample tubes each of which has inlet and outlet sides. A multiport dual acting valve is provided in the sampler in order to sequentially pass air from the sample inlet into the selected sample tubes. The sample tubes extend longitudinally of the housing and are located about the outer periphery thereof so that upon removal of an enclosure cover, they are readily accessible for operation of the sampler in an analysis mode.

Galen, T. J.↗