Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Air Sampling”

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.

At least 1,387 records · Page 77
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Preparation of 110K (Bi, Pb)-Sr-Ca-Cu-O superconductor from glass precursor

The Bi1.5Pb0.5Sr2Ca2Cu3O(x) glass, prepared by rapid quenching of the melt, showed T(sub g) of 383 C, crystallization temperature of approx. 446 C, melting temperature of approx. 855 C, and bulk density of 5.69 g/cu. cm. in air. The as-quenched glass was oxygen deficient. On heating in O2, it showed a slow, irreversible, and continuous weight gain starting at approx. 530 C. The influence of annealing conditions on the formation of various phases was investigated by XRD and electrical resistivity measurements. The 110K-T(sub c) phase did not form below 840 C. The amount of this phase increased with the sintering time at 840 C. A sample annealed at 840 C for 243 h in air and furnace cooled showed the highest T(sub c) (R=0) of 107.2 K and transition width delta T(sub c) (10 to 90 percent) of approx. 2 K.

Bansal, Narottam P.↗
NASA NTRS2004

Characterization of C/Enhanced SiC Composite During Creep-Rupture Tests Using an Ultrasonic Guided Wave Scan System

An ultrasonic guided wave scan system was used to nondestructively monitor damage over time and position in a C/enhanced SiC sample that was creep tested to failure at 1200 C in air at a stress of 69 MPa (10 ksi). The use of the guided wave scan system for mapping evolving oxidation profiles (via porosity gradients resulting from oxidation) along the sample length and predicting failure location was explored. The creep-rupture tests were interrupted for ultrasonic evaluation every two hours until failure at approx. 17.5 cumulative hours.

Roth, Don J.↗
DOE OSTI2017

Secondary organic aerosol formation from in situ OH, O 3 , and NO 3 oxidation of ambient forest air in an oxidation flow reactor

Ambient pine forest air was oxidized by OH, O 3 , or NO 3 radicals using an oxidation flow reactor (OFR) during the BEACHON-RoMBAS (Bio–hydro–atmosphere interactions of Energy, Aerosols, Carbon, H 2 O, Organics and Nitrogen – Rocky Mountain Biogenic Aerosol Study) campaign to study biogenic secondary organic aerosol (SOA) formation and organic aerosol (OA) aging. A wide range of equivalent atmospheric photochemical ages was sampled, from hours up to days (for O 3 and NO 3 ) or weeks (for OH). Ambient air processed by the OFR was typically sampled every 20–30 min, in order to determine how the availability of SOA precursor gases in ambient air changed with diurnal and synoptic conditions, for each of the three oxidants. More SOA was formed during nighttime than daytime for all three oxidants, indicating that SOA precursor concentrations were higher at night. At all times of day, OH oxidation led to approximately 4 times more SOA formation than either O 3 or NO 3 oxidation. This is likely because O 3 and NO 3 will only react with gases containing C = C bonds (e.g., terpenes) to form SOA but will not react appreciably with many of their oxidation products or any species in the gas phase that lacks a C = C bond (e.g., pinonic acid, alkanes). In contrast, OH can continue to react with compounds that lack C = C bonds to produce SOA. Closure was achieved between the amount of SOA formed from O 3 and NO 3 oxidation in the OFR and the SOA predicted to form from measured concentrations of ambient monoterpenes and sesquiterpenes using published chamber yields. This is in contrast to previous work at this site (Palm et al., 2016), which has shown that a source of SOA from semi- and intermediate-volatility organic compounds (S/IVOCs) 3.4 times larger than the source from measured VOCs is needed to explain the measured SOA formation from OH oxidation. This work suggests that those S/IVOCs typically do not contain C = C bonds. O 3 and NO 3 oxidation produced SOA with elemental O : C and H : C similar to the least-oxidized OA observed in local ambient air, and neither oxidant led to net mass loss at the highest exposures, in contrast to OH oxidation. An OH exposure in the OFR equivalent to several hours of atmospheric aging also produced SOA with O : C and H : C values similar to ambient OA, while higher aging (days–weeks) led to formation of SOA with progressively higher O : C and lower H : C (and net mass loss at the highest exposures). NO 3 oxidation led to the production of particulate organic nitrates (pRONO 2 ), while OH and O 3 oxidation (under low NO) did not, as expected. These measurements of SOA formation provide the first direct comparison of SOA formation potential and chemical evolution from OH, O 3 , and NO 3 oxidation in the real atmosphere and help to clarify the oxidation processes that lead to SOA formation from biogenic hydrocarbons.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Analysis of air mass trajectories to explain observed variability of tritium in precipitation at the Southern Sierra Critical Zone Observatory, California, USA

Understanding the behavior of tritium, a radioactive isotope of hydrogen, in the environment is important to evaluate the exposure risk of anthropogenic releases, and for its application as a tracer in hydrology and oceanography. To understand and predict the variability of tritium in precipitation, HYSPLIT air mass trajectories were analyzed for 16 aggregate precipitation samples collected over a 2 year period at irregular intervals at a research site located at 2000 m elevation in the southern Sierra Nevada (California, USA). Attributing the variation in tritium to specific source areas confirms the hypothesis that higher latitude or inland sources bring higher tritium levels in precipitation than precipitation originating in the lower latitude Pacific Ocean. In this case, the source of precipitation accounts for 79% of the variation observed in tritium concentrations. In conclusion, air mass trajectory analysis is a promising tool to improve the predictions of tritium in precipitation at unmonitored locations and thoroughly understand the processes controlling transport of tritium in the environment.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Fractionation of Oxygen Isotopes in Uranium Oxides during Peroxide Precipitation and Dry Air Calcination

The interaction between uranium and oxygen-containing substrates is nearly ubiquitous within the nuclear fuel cycle. Given the well-known and predictable oxygen stable isotope compositions of atmospheric oxygen and meteoric waters around the world, the use of these isotopes as a potential geolocation or processing signature of uranium compounds has been of interest within the nuclear safeguards community. This study focuses on measuring the oxygen-stable isotope composition of synthetically produced uranium oxides to determine the mechanism and extent of fractionation during materials processing relevant to the nuclear fuel cycle. Here, metastudtite [UO 2 O 2 (H 2 O) 2 ] samples were first produced using water and hydrogen peroxide of a known oxygen isotope composition. This starting material was calcined in dry air at temperatures ranging from 300 °C to 1000 °C for 20 h producing oxides ranging in composition from UO 3 +x (0 ≤ x ≤ 0.5) to U 3 O 8 . In addition, calcinations between 500 and 800 °C were performed at different time intervals to evaluate the rate of isotopic equilibration. The δ 18 O values of water bound to metastudtite were measured by thermogravimetric analysis coupled to isotope ratio infrared spectroscopy (TGA–IRIS). A redesigned fluorination manifold was constructed at the University of Utah and was used to extract the bulk oxygen from precipitated and calcined products using bromine pentafluoride (BrF 5 ). Mineralization water on metastudtite (measured by TGA–IRIS) was closely associated with the aqueous environment of precipitation with a fractionation of +3.5 ± 0.6‰. In contrast, bulk oxygen from metastudtite (measured by fluorination and gas chromatography combined with isotope ratio mass spectrometry) was found to have an inconsistent fractionation with precipitation water. Samples calcined in dry air exhibited a wide range of oxygen isotope compositions which increased from δ 18 O = +1.4 ± 0.9‰ at 300 °C to +17.3 ± 0.9‰ at 1000 °C. This variation in δ 18 O values was a result of oxygen exchange with atmospheric O 2 and was found to be rapid at calcination temperatures greater than 600°C—with equilibration occurring in less than 2 h. These results provide insights into the incorporation and exchange of oxygen isotopes during precipitation and calcination processes comparable to those employed within the nuclear fuel cycle and establish a foundation for future investigations to build upon.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2011

Soft X-Ray Spectroscopic Study of Dense Strontium-Doped Lanthanum Manganite Cathodes for Solid Oxide Fuel Cell Applications

The evolution of the Mn charge state, chemical composition, and electronic structure of La{sub 0.8}Sr{sub 0.2}MnO{sub 3} (LSMO) cathodes during the catalytic activation of solid oxide fuel cell (SOFC) has been studies using X-ray spectroscopy of as-processed, exposed, and activated dense thin LSMO films. Comparison of O K-edge and Mn L{sub 3,2}-edge X-ray absorption spectra from the different stages of LSMO cathodes revealed that the largest change after the activation occurred in the Mn charge state with little change in the oxygen environment. Core-level X-ray photoemission spectroscopy and Mn L{sub 3} resonant photoemission spectroscopy studies of exposed and as-processed LSMO determined that the SOFC environment (800 C ambient pressure of O{sub 2}) alone results in La deficiency (severest near the surface with Sr doping >0.55) and a stronger Mn{sup 4+} contribution, leading to the increased insulating character of the cathode prior to activation. Meanwhile, O K-edge X-ray absorption measurements support Sr/La enrichment nearer the surface, along with the formation of mixed Sr{sub x}Mn{sub y}O{sub z} and/or passive MnO{sub x} and SrO species.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2018

Assessment of the propensity of low creep ductility for optimized Grade 92 steel

A total of twenty-five optimized Grade 92 (Opt.G92) samples were tested at 550, 600, and 650°C in air with stresses ranging from 90 to 280 MPa. Two types of Opt.G92 heats were studied in this work, with one type only fabricated by vacuum induction melting (VIM) and the other type by both VIM and electro-slag remelting (VIM+ESR). All the samples were in the as-received thermomechanical treatment (TMT) condition, except for one sample in the re-normalized and tempered (Re-N&T) condition. Three of the samples are still running, with the longest test time >39,863 h at 550°C. In general, the creep-ruptured samples exhibited consistently superior creep resistance, in terms of longer time to rupture, higher creep strength, and lower minimum creep rate, compared to Grades 92 and 91. For example, Opt.G92 with TMT increased creep strength by ~50 and ~60 MPa with minimum creep rate about two orders of magnitude lower than P92 and P91, respectively, at 550°C. The ongoing test of the Opt.G92 sample in the Re-N&T condition also showed significant enhancement in creep resistance. Although the enhancement in creep resistance of Opt.G92 over P92 and P91 became smaller at higher temperatures, the enhancement is still noticeable at 650°C.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Lewis Acid Site Assisted Bifunctional Activity of Tin Doped Gallium Oxide and Its Application in Rechargeable Zn‐Air Batteries

The enhanced safety, superior energy, and power density of rechargeable metal‐air batteries make them ideal energy storage systems for application in energy grids and electric vehicles. However, the absence of a cost‐effective and stable bifunctional catalyst that can replace expensive platinum (Pt)‐based catalyst to promote oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at the air cathode hinders their broader adaptation. Here, in this work, it is demonstrated that Tin (Sn) doped β‐gallium oxide (β‐Ga 2 O 3 ) in the bulk form can efficiently catalyze ORR and OER and, hence, be applied as the cathode in Zn‐air batteries. The Sn‐doped β‐Ga 2 O 3 sample with 15% Sn (Sn x =0.15 ‐Ga 2 O 3 ) displayed exceptional catalytic activity for a bulk, non‐noble metal‐based catalyst. When used as a cathode, the excellent electrocatalytic bifunctional activity of Sn x =0.15 ‐Ga 2 O 3 leads to a prototype Zn‐air battery with a high‐power density of 138 mW cm −2 and improved cycling stability compared to devices with benchmark Pt‐based cathode. The combined experimental and theoretical exploration revealed that the Lewis acid sites in β‐Ga 2 O 3 aid in regulating the electron density distribution on the Sn‐doped sites, optimize the adsorption energies of reaction intermediates, and facilitate the formation of critical reaction intermediate (O*), leading to enhanced electrocatalytic activity.

Lewis acid sites↗
NASA NTRS1997

Distributions of Beryllium 7 and Lead 210, and Soluble Aerosol-Associated Ionic Species Over the Western Pacific: PEM West B

Aerosol sampling for the determination of the concentrations of soluble ionic species and the natural radionuclides Be-7 and Pb-210 was conducted from the NASA DC-8 over the western Pacific as part of GTE/PEM-West B during February - March 1994. Concentrations of most soluble ionic species in the free troposphere were higher in samples collected on flights originating from Hong Kong and Japan than those collected further east over the open ocean. In both regions the measured concentrations were higher than those found during PEM-West A (fall 1991). Activities of Pb-210 tracer of air masses influenced by sources on the Asian continent, showed the same patterns. These data indicate the effect of stronger continental outflow from Asia over the western Pacific during the spring compared to fall season. For readily scavenged aerosol-associated species and soluble acidic gases the strongest indications of Asian outflow were restricted to altitudes below 6 km. The distribution of the continental tracer Pb-210 was also compared to those of a large number of gas phase species measured on the DC-8. Relatively strong correlations were found with O3 and peroxyacetylnitrate (PAN), but only during the flights over the remote Pacific. During PEM-West A, similar correlations were seen, but they were stronger near Asia. We believe that these correlations are a signature of continental air that has been processed by deep wet convection over land before being advected over the ocean. One flight over the Sea of Japan provided the opportunity to sample upper troposphere/lower stratosphere air in and around a tropopause fold. Concentrations of Be-7 reached 7 pCi/cu m STP, and peak O3, mixing ratios of 480 ppb were encountered at 10.7 km. The Be-7 data are used to estimate the fraction of stratospheric air mixed down into the troposphere by circulation in the fold.

Didd, J. E.↗
NASA NTRS1990

Type I polar stratospheric cloud particles - Concentration, shape, size, light extinction

Results from the flight on January 24, 1989 of the Airborne Arctic Stratospheric Experiment during which the ER-2 aircraft transitioned from unsaturated to ice saturated air at 20 km altitude are presented. Aerosol particles were sampled by wire impactors and examined for number density as a function of particle size by taking photomicrographs in a scanning electron microscope and visually sizing and counting the particles. Differences in the chemical, physical and optical properties of stratospheric aerosol between ice-saturated and nonsaturated air are described.

Pueschel, R. F.↗
NASA NTRS1997

Distributions of Beryllium 7 and Lead 210, and Soluble Aerosol-Associated Ionic Species Over the Western Pacific: PEM West B, February - March 1994

Aerosol sampling for the determination of the concentrations of soluble ionic species and the natural radionuclides Be-7 and Pb-210 was conducted from the NASA DC-8 over the western Pacific as part of GTE/PEM-West B during February - March 1994. Concentrations of most soluble ionic species in the free troposphere were higher in samples collected on flights originating from Hong Kong and Japan than those collected further east over the open ocean. In both regions the measured concentrations were higher than those found during PEM-West A (fall 1991). Activities of Pb-210, a tracer of air masses influenced by sources on the Asian continent, showed the same patterns. These data indicate the effect of stronger continental outflow from Asia over the western Pacific during the spring compared to fall season. For readily scavenged aerosol-associated species and soluble acidic gases the strongest indications of Asian outflow were restricted to altitudes below 6 km. The distribution of the continental tracer Pb-210 was also compared to those of a large number of gas phase species measured on the DC-8. Relatively strong correlations were found with O3, and peroxyacetylnitrate (PAN), but only during the flights over the remote Pacific. During PEM-West A, similar correlations were seen, but they were stronger near Asia. We believe that correlations are a signature of continental air that has been processed by deep wet convection over land before being advected over the ocean. One flight over the Sea of Japan provided the opportunity to sample upper troposphere/lower stratosphere air in and around a tropopause fold. Concentrations of Be-7 reached 7 pCi/cu m STP, and peak O3, mixing ratios of 480 ppb were encountered at 10.7 km. The Be-7 data are used to estimate the fraction of stratospheric air mixed down into the troposphere by circulation in the fold.

Dibb, J. E.↗
NASA NTRS1998

Method Developed for the High-Temperature Nondestructive Evaluation of Fiber-Reinforced Silicon Carbide Ceramic Matrix Composites

Ceramic matrix composites have emerged as candidate materials to allow higher operating temperatures (1000 to 1400 C) in gas turbine engines. A need, therefore, exists to develop nondestructive methods to evaluate material integrity at the material operating temperature by monitoring thermal and mechanical fatigue. These methods would also have potential as quality inspection tools. The goal of this investigation at the NASA Lewis Research Center is to survey and correlate the temperature-dependent damping and stiffness of advanced ceramic composite materials with imposed thermal and stress histories that simulate in-service turbine engine conditions. A typical sample size of 100 by 4 by 2 cubic millimeters, along with the specified stiffness and density, placed the fundamental vibration frequencies between 100 and 2000 Hz. A modified Forster apparatus seemed most applicable to simultaneously measure both damping and stiffness. Testing in vacuum reduced the effects of air on the measurements. In this method, a single composite sample is vibrated at its fundamental tone; then suddenly, the mechanical excitation is removed so that the sample's motion freely decays with time. Typical results are illlustrated in this paper.

Goldsby, Jon C.↗
DOE OSTI2018

Production Procedure and Characterization of Zn-Doped Y-123 Superconducting Samples Prepared by Sol-Gel Method

The superconducting YBa{sub 2}Cu{sub 3−x}Zn{sub x}O{sub 7} (Y-123) bulk materials have been synthesized by using the sol-gel method. Samples are produced as undoped Y-123 and transition metal (Zn)-doped Y-123. Before the final heat treatment, the samples are calcined at 850 °C for 24 h. This process is repeated three times. Then, samples are sintered at 950 °C for 24 h in an air environment and at 500 °C for 5 h in an oxygen atmosphere. The synthesized products are characterized by XRD, R-T, and Vickers microhardness tester. The XRD investigation revealed that the prepared sample has an orthorhombic structure. According to XRD measurements, an orthorhombic structure has not changed with Zn doping. It was observed that undoped and Zn-doped samples have superconductivity properties by electrical measurements. T{sub c}{sup onset} is 89 K for undoped Y-123 sample, and the T{sub c}{sup onset} value decreases monotically with Zn addition. All samples show metallic behavior above T{sub c}{sup onset} temperature. As a result of Vickers microhardness measurements, it is observed that all samples have reverse indentation size effect (RISE) behavior.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1997

Joint US/Russian testing for track propagation

The power thresholds below which track propagation does not occur were determined in Russian spacecraft. The tests were performed in air and vacuum with direct current on different insulation and sample configurations. The examined wire insulations included 100 percent polyimide, modified polyimide-based insulations containing 7 to 8 percent and 100 percent polytetrafluoroethylene. The wires were tested in configurations consisting of seven-wire bundles. The results indicated that the track propagation thresholds were lower in vacuum than in air.

Hirsch, David↗
DOE OSTI2016

Sorption of atmospheric gases by bulk lithium metal

Lithium conditioning of plasma facing components has enhanced the performance of several fusion devices. Elemental lithium will react with air during maintenance activities and with residual gases (H 2 O, CO, CO 2 ) in the vacuum vessel during operations. We have used a mass balance (microgram sensitivity) to measure the mass gain of lithium samples during exposure of a ~1 cm 2 surface to ambient and dry synthetic air. For ambient air, we found an initial mass gain of several mg/h declining to less than 1 mg/h after an hour and decreasing by an order of magnitude after 24 h. A 9 mg sample achieved a final mass gain corresponding to complete conversion to Li 2 CO 3 after 5 days. Exposure to dry air resulted in a 30 times lower initial rate of mass gain. The results have implications for the chemical state of lithium plasma facing surfaces and for safe handling of lithium coated components.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Cleaned 5-Minute Resolution Air Quality and Meteorological Data from Nine TCEQ CAMS Sites in Houston, Texas (Nov 2021 – Oct 2022)

These data encompass 5-minute air monitoring and meteorological observations collected in the greater Houston, Texas metropolitan region, at nine (9) Continuous Ambient Monitoring Stations (CAMS) operated by the Texas Commission on Environmental Quality (TCEQ) between November 1, 2021 and October 31, 2022. The CAMS sites (CAMS 1, 8, 35, 45, 148, 403, 405, 410, and 1052) were chosen because their instrumentation includes measurements of PM2.5. These sites also provide continuous multi-parameter air-quality and meteorological measurements. Particulate matter (PM2.5, PM10) was sampled along with several trace gases, including ozone (O3), nitrogen oxides (NO, NO2, NOx), sulfur dioxide (SO2), and carbon monoxide (CO). The data set also contains standard surface meteorological parameters (temperature, humidity, pressure, wind speed, and wind direction). Several sites also include AutoGC-based measurements of volatile organic compounds (VOCs). Air monitoring instruments deployed at the selected sites comprise the following systems: BAM-1020 or TEOM (PM2.5), Thermo Scientific TEI 49i (O3), TEI 42i (NOx), and AutoGCs (VOCs). This data set is similar to the data included within the houairq5mX1.00 datastream, except for a few additional quality control steps. A systematic data cleaning and verification process was performed on the data set to ensure its quality and preparation for analysis. Removal of non-numeric status flags (e.g., [LIM], [QAS], [SPZ], [CAL], [PMA], [AQI], [SPN], [MAL]) was accomplished by employing rule-based string parsing to extract valid numerical values. Missing entries were set to -9999; however, invalid or anomalous values (e.g., 99999) were retained as originally reported by the TCEQ to preserve data provenance. The time sequence was verified for completeness, removal of duplicates, and uniformity at 5-minute intervals. Column labeling was standardized, and corresponding values were assessed for physical plausibility. All timestamps in the data set were reported in Coordinated Universal Time (UTC) as provided by the TCEQ. Further, the latitude and longitude coordinates were added for each CAMS site. A subset of the data (June 1–September 30, 2022) has been used in the following publication: Subba et al. 2025. “Implications of sea breeze circulations on boundary layer aerosols in the southern coastal Texas region.” EGUsphere 2025: 1–49, https://doi.org/10.5194/egusphere-2025-2659.

latitude↗
NASA NTRS1978

NASA aviation safety reporting system

The study deals with 165 inadvertent operations on or into inappropriate portions of the aircraft areas at controlled airports. Pilot-initiated and controller-initiated incursions are described and discussed. It was found that a majority of the pilot-initiated occurrences involved operation without a clearance; controller-initiated occurrences usually involved failure to maintain assured separation. The factors associated with these occurrences are analyzed. It appears that a major problem in these occurrences is inadequate coordination among the various system participants. Reasons for this, and some possible solutions to various aspects of the problem, are discussed. A sample of reports from pilots and controllers is presented. These relate to undesired occurrences in air transport, general aviation, and air traffic control operations; to ATC coordination problems; and to a recurrent problem in ASRS reports, parachuting operations. A sample of alert bulletins and responses to them is presented.

Source record↗
DOE OSTI2011

Flaw detection in a multi-material multi-layered composite: using fem and air-coupled ut

Ceramic tiles are the main ingredient of a multi-layer multi-material composite being considered for the modernization of tank armors. The high stiffness, low attenuation, and precise dimensions of these uniform tiles make them remarkable resonators when driven to vibrate. This study is aimed at modeling the vibration modes of the tiles and the composite lay-up with finite element analysis and comparing the results with the resonance modes observed in air-coupled ultrasonic excitation of the tiles and armor samples. Defects in the tile, during manufacturing and/or after usage, are expected to change the resonance modes. The comparison of a pristine tile/lay-up and a defective tile/lay-up will thus be a quantitative damage metric. The understanding of the vibration behavior of the tile, both by itself and in the composite lay-up, can provide useful guidance to the nondestructive evaluation of armor panels containing ceramic tiles.

36 MATERIALS SCIENCE↗