SEARCH · Engineering Papers

Results for “Atomic techniques”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,009 records · Page 56

All sources NASA NTRS DOE OSTI

NASA NTRS1978

Studies of volatiles in Apollo 17 samples and their implication to vapor transport processes

Flameless atomic absorption (FLAA), X-ray photoemission spectroscopy (XPS) and grain size separation techniques were adopted to analyze Pb, Cd, Zn and S in orange and black droplets from Apollo 17 samples. The FLAA and XPS investigations show volatile trace metal enrichment in smaller grain fractions (broken droplets); thus a part of the volatiles was probably deposited after break-up of the droplets. In addition, redistribution of the volatiles by a cratering event is indicated by continuous decreases in Pb and Cd with core depth. Studies of Zn on individual regolith grains are also reported.

Cirlin, E. H.↗

NASA NTRS1980

Studies of laser and laser devices

The generation of tunable, infrared, and ultraviolet light, and the control of this light by mode-locking and modulation techniques are discussed. Particular emphasis is given to energy storage and extraction using atomic levels, the development of a tunable narrowband vacuum ultraviolet light source, and to the generation and applications of ultrashort optical pulses.

Harris, S. E.↗

NASA NTRS1981

Progress of the LASSO experiment

The LASSO (Later Synchronisation from Stationary Orbit) experiment, designed to demonstrate the feasibility of achieving time synchronization between remote atomic clocks with an accuracy of one nanosecond or better by using laser techniques for the first time is described. The experiment uses groundbased laser stations and the SIRIO-2 geostationary satellite to be launched towards the end of 1981. The qualification of the LASSO on-board equipment is discussed with a brief description of the electrical and optical test equipment used. The progress of the operational organization is included.

Serene, B. E. H.↗

NASA NTRS1983

Electron-photon coincidence technique for the absolute calibration of VUV detectors

A method is described whereby VUV photon detectors can be accurately calibrated. This method is illustrated by taking the 58.4-nm transition of He as an example. The technique consists of crossing a monoenergetic electron beam with a beam of He atoms. When inelastically scattered electrons which have excited the 2 1P state are detected in coincidence with the 58.4-nm photons emitted in the decay of the excited state, the interaction volume formed by the crossed beams constitutes a standard source of photons. By comparing the number of detected coincidences with the predicted number the calibration can be made. A total detector efficiency of 0.024 + or - 0.003 is obtained for a Galileo 4830 channeltron.

Mcadams, R.↗

NASA NTRS1989

Velocity mapping in a 30-kW arcjet plume using laser-induced fluorescence

A method for measuring the axial and transverse plume velocities and internal energy distributions in rarified thruster plumes by using pulsed laser-induced fluorescence (LIF) of atomic hydrogen Balmer lines is described. The results of an application of this technique for velocity mapping of a 30-kW ammonia arc-jet plume generated in the JPL arc-jet testing facility (which is uniquely suited for these measurements due to the end-on optical access provided by its ninety-degree-bent diffuser) are described. A schematic diagram of the JPL facility with LIF setup is included.

Pham-Van-diep, Gerald↗

NASA NTRS1992

Structural ceramics

This presentation gives a brief history of the field of materials sciences and goes on to expound the advantages of the fastest growing area in that field, namely ceramics. Since ceramics are moving to fill the demand for lighter, stronger, more corrosion resistant materials, advancements will rely more on processing and modeling from the atomic scale up which is made possible by advanced analytical, computer, and processing techniques. All information is presented in viewgraph format.

Craig, Douglas F.↗

NASA NTRS1993

Low earth simulation and materials characterization

Oxygen plasma ashers and an electron cyclotron resonance (ECR) sources are currently being used for low Earth orbit (LEO) simulation. The suitability of each of these simulation techniques is considered. Thin film coatings are characterized by optical techniques, including variable-angle spectroscopic ellipsometry, optical spectrophotometry, and laser light scatterometry. Atomic force microscopy (AFM) has been used to characterize the surface morphology of thin aluminum films as a function of substrate temperature during deposition. Results on diamondlike carbon (DLC) films show that DLC degrades with simulated atomic oxygen (AO) exposure at a rate comparable to Kapton polyimide. Since DLC is not as susceptible as Kapton to environmental factors such as moisture absorption, it could potentially provide more accurate measurements of AO fluence on short space flights.

Synowicki, R. A.↗

NASA NTRS1993

Transition probabilities for the 3s2 3p(2P0)-3s3p2(4P) intersystem lines of Si II

Intensity ratios of lines of the spin-changing 'intersystem' multiplet of S II (4P yields 2P0) at 234 nm have been used to determine electron densities and temperatures in a variety of astrophysical environments. However, the accuracy of these diagnostic calculations have been limited by uncertainties associated with the available atomic data. We report the first laboratory measurement, using an ion-trapping technique, of the radiative lifetimes of the three metastable levels of the 3s3p2 4P term of Si II. Our results are 104 +/- 16, 406 +/- 33, and 811 +/- 77 micro-s for lifetimes of the J = 1/2, 5/2, and 3/2 levels, respectively. A-values were derived from our lifetimes by use of measured branching fractions. Our A-values, which differ from calculated values by 30 percent or more, should give better agreement between modeled and observed Si II line ratios.

Calamai, Anthony G.↗

NASA NTRS1997

A Competitive Kinetics Study of the Reaction of Cl with CS2 in Air at 298 K

The relative rate technique has been used to investigate the kinetics of the reaction of Cl atoms with carbon disulfide, CS2, at 700 Torr total pressure of air at 298 K. The decay rate of CS2 was measured relative to CH4, CH3Cl and CHF2CL. For experiments using CH4 and CH3Cl references, the decay rate of CS2 was dependent on the ratio of the concentration of the reference to that of CS2. We ascribe this behavior to the generation of OH radicals in the system leading to complicated secondary chemistry. From experiments using CHF2Cl we are able to assign an upper limit of 4 x 10(exp -15) cu cm/(molecule s) for the overall reaction, Cl + CS2 yields products.

Wallington, Timothy J.↗

NASA NTRS2003

Infrared Spectroscopy of Star Formation in Galactic and Extragalactic Regions

In this program we proposed to perform a series of spectroscopic studies, including data analysis and modeling, of star formation regions using an ensemble of archival space-based data from the Infrared Space Observatory's Long Wavelength Spectrometer and Short Wavelength Spectrometer, and to take advantage of other spectroscopic databases including the first results from SIRTF. Our emphasis has been on star formation in external, bright IR galaxies, but other areas of research have included young, low or high mass pre-main sequence stars in star formation regions, and the galactic center. The OH lines in the far infrared were proposed as one key focus of this inquiry, because the Principal Investigator (H. Smith) had a full set of OH IR lines from IS0 observations. It was planned that during the proposed 2-1/2 year timeframe of the proposal other data (including perhaps from SIRTF) would become available, and we intended to be responsive to these and other such spectroscopic data sets. The program has the following goals: 1) Refine the data analysis of IS0 observations to obtain deeper and better SNR results on selected sources. The IS0 data itself underwent pipeline 10 reductions in early 2001, and the more 'hands-on data reduction packages' have been released. The IS0 Fabry-Perot database is particularly sensitive to noise and can have slight calibration errors, and improvements are anticipated. We plan to build on these deep analysis tools and contribute to their development. Model the atomic and molecular line shapes, in particular the OH lines, using revised montecarlo techniques developed by the Submillimeter Wave Astronomy Satellite (SWAS) team at the Center for Astrophysics. 2) 3) Use newly acquired space-based SIRTF or SOFIA spectroscopic data as they become available, and contribute to these observing programs as appropriate. 4) Attend scientific meetings and workshops. 5) E&PO activities, especially as related to infrared astrophysics and/or spectroscopy.

Smith, Howard A.↗

NASA NTRS1992

Dielectric constant of liquid alkanes and hydrocarbon mixtures

The complex dielectric constants of n-alkanes with two to seven carbon atoms have been measured. The measurements were conducted using a slotted-line technique at 1.2 GHz and at atmospheric pressure. The temperature was varied from the melting point to the boiling point of the respective alkanes. The real part of the dielectric constant was found to decrease with increasing temperature and correlate with the change in the molar volume. An upper limit to all the loss tangents was established at 0.001. The complex dielectric constants of a few mixtures of liquid alkanes were also measured at room temperature. For a pentane-octane mixture the real part of the dielectric constant could be explained by the Clausius-Mosotti theory. For the mixtures of n-hexane-ethylacetate and n-hexane-acetone the real part of the dielectric constants could be explained by the Onsager theory extended to mixtures. The dielectric constant of the n-hexane-acetone mixture displayed deviations from the Onsager theory at the highest fractions of acetone. The dipole moments of ethylacetate and acetone were determined for dilute mixtures using the Onsager theory and were found to be in agreement with their accepted gas-phase values. The loss tangents of the mixtures exhibited a linear relationship with the volume fraction for low concentrations of the polar liquids.

NASA Program Exobiology↗

NASA NTRS2008

NASA Tech Briefs, May 2008

Topics covered inclde: Deployable Wireless Camera Penetrators; Hand-Held Units for Short-Range Wireless Biotelemetry; Wearable Wireless Telemetry System for Implantable BioMEMS Sensors; Electronic Escape Trails for Firefighters; Architecture for a High-to-Medium-Voltage Power Converter; 24-Way Radial Power Combiner/Divider for 31 to 36 GHz; Three-Stage InP Submillimeter-Wave MMIC Amplifier; Fast Electromechanical Switches Based on Carbon Nanotubes; Solid-State High-Temperature Power Cells; Fast Offset Laser Phase-Locking System; Fabricating High-Resolution X-Ray Collimators; Embossed Teflon AF Laminate Membrane Microfluidic Diaphragm Valves; Flipperons for Improved Aerodynamic Performance; System Estimates Radius of Curvature of a Segmented Mirror; Refractory Ceramic Foams for Novel Applications; Self-Deploying Trusses Containing Shape-Memory Polymers; Fuel-Cell Electrolytes Based on Organosilica Hybrid Proton Conductors; Molecules for Fluorescence Detection of Specific Chemicals; Cell-Detection Technique for Automated Patch Clamping; Redesigned Human Metabolic Simulator; Compact, Highly Stable Ion Atomic Clock; LiGa(OTf)(sub 4) as an Electrolyte Salt for Li-Ion Cells; Compact Dielectric-Rod White-Light Delay Lines; Single-Mode WGM Resonators Fabricated by Diamond Turning; Mitigating Photon Jitter in Optical PPM Communication; MACOS Version 3.31; Fiber-Optic Determination of N2, O2, and Fuel Vapor in the Ullage of Liquid-Fuel Tanks; Spiking Neurons for Analysis of Patterns; Symmetric Phase-Only Filtering in Particle-Image Velocimetry; Efficient Coupler for a Bessel Beam Dispersive Element; and Attitude and Translation Control of a Solar Sail Vehicle.

Source record↗

DOE OSTI2024

Atomic structure of different surface terminations of polycrystalline ZnPd

The intermetallic compound ZnPd has been found to have desirable characteristics as a catalyst for the steam reforming of methanol. The understanding of the surface structure of ZnPd is important to optimize its catalytic behavior. However, due to the lack of bulk single-crystal samples and the complexity of characterizing surface properties in the available polycrystalline samples using common experimental techniques, all previous surface science studies of this compound have been performed on surface alloy samples formed through thin-film deposition. In this study, we present findings on the chemical and atomic structure of the surfaces of bulk polycrystalline ZnPd studied by a variety of complementary experimental techniques, including scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy (XPS), low energy electron microscopy (LEEM), photoemission electron microscopy (PEEM), and microspot low-energy electron diffraction ( μ -LEED). These experimental techniques, combined with density functional theory (DFT)-based thermodynamic calculations of surface free energy and detachment kinetics at the step edges, confirm that surfaces terminated by atomic layers composed of both Zn and Pd atoms are more stable than those terminated by only Zn or Pd layers. DFT calculations also demonstrate that the primary contribution to the tunneling current arises from Pd atoms, in agreement with the STM results. The formation of intermetallics at surfaces may contribute to the superior catalyst properties of ZnPd over Zn or Pd elemental counterparts. Published by the American Physical Society 2024

36 MATERIALS SCIENCE↗

DOE OSTI2026

Insights into Native Single-Atom Electrocatalyst Site Structures

Single-atom electrocatalysts consisting of metal atoms embedded in a carbon matrix are promising next-generation catalysts for green hydrogen production and utilization, CO2 reduction, low-temperature CO oxidation, ammonia production, plastic decomposition, and electrochemical energy storage. The origins of activity and stability for the single-atom sites are still debatable, however, because of constrained insights into their local structure resulting from idealized models and experiments derived from a large number of individual sites. Insights into structural variations around single atomic sites are therefore critical for the continued development of these next-generation catalysts. While electron microscopy commonly provides atomic-scale information about these materials, the beam sensitivity of individual sites makes structural determination by conventional low-voltage (60 keV) techniques challenging. Here, we introduce ultralow-voltage electron ptychography, performed at 30 keV, that enables determination of the lattice structure around individual metal sites in a well-defined single-atom electrocatalyst system while essentially eliminating knock-on structural modifications. Pairing these atomic-scale, site-specific measurements with computational methods will broaden our understanding of the activity and stability of these materials, which will accelerate the development of the next generation of catalysts.

Zachman, Michael [ORNL] (ORCID:0000000319101357)↗

NASA NTRS1992

A numerical model for atomization-spray coupling in liquid rocket thrust chambers

The physical process of atomization is an important consideration in the stable operation of liquid rocket engines. Many spray combustion computational fluid dynamics (CFD) codes do not include an atomization sub-model but assume arbitrary drop size distributions, drop initial locations, and velocities. A method of coupling an atomization model with the spray model in a REFLEQS CFD code is presented. This method is based on a jet-embedding technique in which the equations governing the liquid jet core are solved separately using the surrounding gas phase conditions. The droplet initial conditions are calculated using a stability analysis appropriate for the atomization regime of liquid jet break-up. This novel coupling model is used to analyze the SSME fuel preburner single injector flow. Results of the diffusion flame characteristics in a single injection element will be presented. The effect of relative velocity, mixture ratio and droplet initial conditions will be shown. The predictions of present atomization model is compared with that of the widely used CICM correlation. The results are also compared with the predictions of volume-of-fluid method.

M. G. Giridharan↗

DOE OSTI2021

Thermodynamics of order and randomness in dopant distributions inferred from atomically resolved imaging

Abstract Exploration of structure-property relationships as a function of dopant concentration is commonly based on mean field theories for solid solutions. However, such theories that work well for semiconductors tend to fail in materials with strong correlations, either in electronic behavior or chemical segregation. In these cases, the details of atomic arrangements are generally not explored and analyzed. The knowledge of the generative physics and chemistry of the material can obviate this problem, since defect configuration libraries as stochastic representation of atomic level structures can be generated, or parameters of mesoscopic thermodynamic models can be derived. To obtain such information for improved predictions, we use data from atomically resolved microscopic images that visualize complex structural correlations within the system and translate them into statistical mechanical models of structure formation. Given the significant uncertainties about the microscopic aspects of the material’s processing history along with the limited number of available images, we combine model optimization techniques with the principles of statistical hypothesis testing. We demonstrate the approach on data from a series of atomically-resolved scanning transmission electron microscopy images of Mo x Re 1- x S 2 at varying ratios of Mo/Re stoichiometries, for which we propose an effective interaction model that is then used to generate atomic configurations and make testable predictions at a range of concentrations and formation temperatures.

25 ENERGY STORAGE↗

NASA NTRS2000

Mixing of an Airblast-atomized Fuel Spray Injected into a Crossflow of Air

The injection of a spray of fuel droplets into a crossflow of air provides a means of rapidly mixing liquid fuel and air for combustion applications. Injecting the liquid as a spray reduces the mixing length needed to accommodate liquid breakup, while the transverse injection of the spray into the air stream takes advantage of the dynamic mixing induced by the jet-crossflow interaction. The structure of the spray, formed from a model plain-jet airblast atomizer, is investigated in order to determine and understand the factors leading to its dispersion. To attain this goal, the problem is divided into the following tasks which involve: (1) developing planar imaging techniques that visualize fuel and air distributions in the spray, (2) characterizing the airblast spray without a crossflow, and (3) characterizing the airblast spray upon injection into a crossflow. Geometric and operating conditions are varied in order to affect the atomization, penetration, and dispersion of the spray into the crossflow. The airblast spray is first characterized, using imaging techniques, as it issues into a quiescent environment. The spray breakup modes are classified in a liquid Reynolds number versus airblast Weber number regime chart. This work focuses on sprays formed by the "prompt" atomization mode, which induces a well-atomized and well-dispersed spray, and which also produces a two-lobed liquid distribution corresponding to the atomizing air passageways in the injector. The characterization of the spray jet injected into the crossflow reveals the different processes that control its dispersion. Correlations that describe the inner and outer boundaries of the spray jet are developed, using the definition of a two-phase momentum-flux ratio. Cross-sections of the liquid spray depict elliptically-shaped distributions, with the exception of the finely-atomized sprays which show kidney-shaped distributions reminiscent of those obtained in gaseous jet in crossflow systems. A droplet trajectory analysis overpredicts the liquid mass penetration, and indicates a need for a more rigorous model to account for the three-dimensional mixing field induced by the jet-crossflow interaction. Nonetheless, the general procedures and criteria that are outlined can be used to efficiently assess and compare the quality of sprays formed under different conditions.

Leong, May Y.↗

NASA NTRS1973

Transition region response of the symmetric double probe and its application in the lower ionosphere.

Assessment of the floating double probe technique for in situ measurements of the plasma temperature in the D region of the ionosphere. The effects of ion-atom collisions on the current-voltage characteristic of a symmetric double-probe system are reviewed in connection with the determination of the temperature of a completely thermalized plasma. The manner in which this technique can be implemented for a rocket-borne experiment is described, and an experimental current-voltage characteristic obtained in the earth's lower atmosphere is presented and discussed.

Szuszczewicz, E. P.↗