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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Stress corrosion in titanium alloys and other metallic materials

Multiple physical and chemical techniques including mass spectroscopy, atomic absorption spectroscopy, gas chromatography, electron microscopy, optical microscopy, electronic spectroscopy for chemical analysis (ESCA), infrared spectroscopy, nuclear magnetic resonance (NMR), X-ray analysis, conductivity, and isotopic labeling were used in investigating the atomic interactions between organic environments and titanium and titanium oxide surfaces. Key anhydrous environments studied included alcohols, which contain hydrogen; carbon tetrachloride, which does not contain hydrogen; and mixtures of alcohols and halocarbons. Effects of dissolved salts in alcohols were also studied. This program emphasized experiments designed to delineate the conditions necessary rather than sufficient for initiation processes and for propagation processes in Ti SCC.

Harkins, C. G.↗
NASA NTRS1978

Coal thickness gauge using RRAS techniques, part 1

A noncontacting sensor having a measurement range of 0 to 6 in or more, and with an accuracy of 0.5 in or better is needed to control the machinery used in modern coal mining so that the thickness of the coal layer remaining over the rock is maintained within selected bounds. The feasibility of using the radiofrequency resonance absorption (RRAS) techniques of electron magnetic resonance (EMR) and nuclear magnetic resonance (NMR) as the basis of a coal thickness gauge is discussed. The EMR technique was found, by analysis and experiments, to be well suited for this application.

Rollwitz, W. L.↗
NASA NTRS1978

The optical absorption of triatomic carbon C3 for the wavelength range 260 to 560 nm

The spectral absorption properties of C3 have been measured in a shock tube containing a test gas mixture of acetylene diluted with argon. The absorption of a pulsed xenon light source was measured by means of eight photomultiplier channels to a spectrograph and an accompanying drum camera. The postshock test gas temperature and pressure were varied over the range 3240 to 4300 K and 37 to 229 kPa, respectively. The results showed appreciable absorption by C3 for the wavelength range 300 to 540 nm. The various reported measurements of the heat of formation of C3 which are available in the open literature were reviewed, and a value of 198 kcal/mol is recommended. This value, along with best available values for other species, was used to calculate the number density of C3 for the conditions of the present experiments in order to compute absorption cross section or electronic oscillator strength. The computed electronic oscillator strength varied from a high of 0.062 at 3300 K to a low of 0.036 at 3900 K.

Jones, J. J.↗
NASA NTRS1977

Electron-impact excitation of the low-lying electronic states of HCN

The first study of the low-energy electron-impact excitation of low-lying electronic transitions in the HCN molecule is reported. Measurements were made at incident electron energies of 11.6 and 21.6 eV in the energy-loss range of 3-10 eV, and at scattering angles of 20-130 deg. Inelastic scattering spectra were placed on the absolute cross-section scale by determining first the ratio of inelastic-to-elastic scattering cross sections, and then separately measuring the absolute elastic scattering cross section. Several new electronic transitions are observed which are intrinsically overlapped in the molecule itself. Assignments of these electronic transitions are suggested. These assignments are based on present spectroscopic and cross-sections measurements, high-energy electron scattering spectra, optical absorption spectra, and ab initio molecular orbital calculations.

Chutjian, A.↗
NASA NTRS1979

Proportional counter for X-ray analysis of lunar and planetary surfaces

A position sensitive proportional scintillation detector was developed and evaluated for use in applications involving X-ray imaging as well as spectroscopy. Topics covered include limitations of the proportional scintillation counter for use in space; purification of the xenon gas in the detector, and the operation of the detector system. Results show that the light signal in a proportional scintillation detector remains well localized. With modest electric fields in xenon, the primary electrons from a photoelectric absorption of an X-ray can be brought a distance of a few millimeters to a higher field region without spreading more than a millimeter or so. Therefore, it is possible to make a proportional scintillation detector with good position sensitivity that could be used to calibrate out the difference in light collection over its sensitive volume.

Source record↗
NASA NTRS1980

Deep-sea spherules from Pacific clay - Mass distribution and influx rate

From 411 kg of Pacific clay, 22 mg of stony spherules and 50 mg of iron spherules larger than 150 microns were concentrated. The extraterrestrial origin of these particles was evaluated with the aid of optical and electron microscopy and atomic absorption elemental analysis. An expression for the integral number of stony particles from this sediment in the mass range 20-300 micrograms was derived. The world-wide influx rate of stony particles in the mass range which survive atmospheric heating and ocean sediment storage is calculated to be 90 tons/yr. The relative contributions of ablation debris vs fused interplanetary dust to the influx of stony spherules is discussed, but no conclusions could be made.

Murrell, M. T.↗
NASA NTRS1983

Surfaces

Techniques for the characterization of surface cleanliness and roughness for predicting the quality of an adhesive bond are outlined. Generally, smooth surfaces are only available from cleavage of crystalline materials along a natural cleavage plane. Films must be deposited on metal surfaces to achieve the same smoothness. Once the surfaces are clean, however, reaction with the ambient atmosphere becomes likely through diffusive and absorption processes, producing asperities. Electron diffraction, Auger electron, and X ray emission spectroscopy are used to characterize surface condition. Once the surface is observed to be clean, the application of an adhesive will usually prohibit separation along the adhesive; separation is then confined to the weaker of the two materials. Finally, the use of polytetrafluorothylene adhesive to test the adhesion between polymers and metal surfaces is described.

Buckley, D. H.↗
NASA NTRS1986

Semiconductor superlattice photodetectors

Superlattice photodetectors were investigated. A few major physical processes in the quantum-well heterostructures related to the photon detection and electron conduction mechanisms, the field effect on the wave functions and the energy levels of the electrons, and the optical absorption with and without the photon assistance were studied.

Chuang, S. L.↗
NASA NTRS1989

Alkoxysilane adsorption on metal oxide substrates

Reflection-absorption infrared and inelastic electron tunneling spectroscopies have been used to study adsorption of liquid phase mono-, di-, and trialkoxysilanes on evaporated Al and Cu substrates. Spectral evidence shows that substrate properties influence the chemical and physical nature of trialkoxysilane films and that silane functionality plays a role in molecular orientation. Results show that dialkoxysilane films contain structural gradients, with adsorption at the monomolecular level influenced by surface morphology, and with organofunctionality and dosing procedure affecting the formation of thicker films. Evidence is presented that monoalkoxysilanes react with alumina surfaces, and a broad, multipeaked band from 1600 to 1900/cm has been interpreted as characteristic of the silylated AlO(x)Pb interface.

Ramsier, R. D.↗
NASA NTRS2002

Dip Spectroscopy of the Low Mass X-Ray Binary XB 1254-690

We observed the low mass X-ray binary XB 1254-690 with the Rossi X-ray Timing Explorer in 2001 May and December. During the first observation strong dipping on the 3.9-hr orbital period and a high degree of variability were observed, along with "shoulders" approx. 15% deep during extended intervals on each side of the main dips. The first observation also included pronounced flaring activity. The non-dip spectrum obtained using the PCA instrument was well-described by a two-component model consisting of a blackbody with kT = 1.30 +/- 0.10 keV plus a cut-off power law representation of Comptonized emission with power law photon index 1.10 +/- 0.46 and a cut-off energy of 5.9(sup +3.0, sub -1.4) keV. The intensity decrease in the shoulders of dipping is energy-independent, consistent with electron scattering in the outer ionized regions of the absorber. In deep dipping the depth of dipping reached 100%, in the energy band below 5 keV, indicating that all emitting regions were covered by absorber. Intensity-selected dip spectra were well-fit by a model in which the point-like blackbody is rapidly covered, while the extended Comptonized emission is progressively overlapped by the absorber, with the, covering fraction rising to 95% in the deepest portion of the dip. The intensity of this component in the dip spectra could be modeled by a combination of electron scattering and photoelectric absorption. Dipping did not occur during the 2001 December observation, but remarkably, both bursting and flaring were observed contemporaneously.

Smale, Alan P.↗
NASA NTRS2005

Nanotube/Quantum Dot-Polymer Solar Cells

Single wall carbon nanotubes used or this study were synthesized using the pulse laser vaporization technique. The as-produced SWNTs were collected from the condensed region on the quartz tube outside the furnace and purified by modification of the previously reported procedure. Preparation of the SWNT-P3OT composite solutions was performed using a series of mixing and sonication steps as previously demonstrated for other SWNT-polymer systems. Device fabrication involved the use of commercially-obtained, high quality (i.e., less than 10 W/sq.) ITO-coated polyethylene terapthalate (PET) substrates. Initially, an intrinsic layer of pristine P3OT is spray deposited (approx. 1-2 mL of the 15 mg/mL solution) onto the masked, 1 sq in. active area of the substrate. This is followed with spray deposition of the SWNT-P3OT composite solutions at similar volumes. As seen completion of the solar cell occurs when aluminum contacts (typical thicknesses of l000A) are applied to the IT0 and SWNT-P3OT composite film layers. The homogeneous distribution of SWNTs in a polymer matrix is dependent upon the ability of the polymer chain to associate with the SWNT superstructure. Stable composite dispersions of 0.1 % and 1.0% w/w SWNTs in P3OT were produced and analyzed in this study. Optical spectroscopy was conducted to observe the SWNT doping level effects on the absorption properties and infer potential electronic interactions between dopant and polymer. Shown is an overlay of these spectra where the pristine P3OT shows strong optical absorption at energies less than 2 eV. As expected, variation in absorption properties for the SWNT-P3OT composites is observed as the doping level increases. Through modification of the SWNT doping level in the polymer, it is possible to alter the absorption pattern of these composite materials. In fact, at these relatively low doping levels, the P3OT shows a significant enhancement in absorption through the near-IR and visible regions. The gray curve for purified SWNTs is offset from the other three for clarity, but indicates the typical complex pattern observed for this spectral range.

Bailey, Sheila G.↗
NASA NTRS2007

Interband cascade detectors

A device for detecting radiation, typically in the infrared. Photons are absorbed in an active region of a semiconductor device such that the absorption induces an interband electronic transition and generates photo-excited charge carriers. The charge carriers are coupled into a carrier transport region having multiple quantum wells and characterized by intersubband relaxation that provides rapid charge carrier collection. The photo-excited carriers are collected from the carrier transport region at a conducting contact region. Another carrier transport region characterized by interband tunneling for multiple stages draws charge carriers from another conducting contact and replenishes the charge carriers to the active region for photo-excitation. A photocurrent is generated between the conducting contacts through the active region of the device.

Chuang, Shun Lien↗
NASA NTRS2008

Experimental Constraints on the Partitioning and Valence of V and Cr in Garnet and Coexisting Glass

A series of experiments with garnet and coexisting melt have been carried out across a range of oxygen fugacities (near hematite-magnetite (HM) to below the iron-wustite (IW) buffers) at 1.7 GPa to study the partitioning and valence of Cr and V in both phases. Experiments were carried out in a non end loaded piston cylinder apparatus, and the run products were analyzed with electron microprobe and xray absorption near edge structure (XANES) analysis at beamline 13-ID at the Advanced Photon Source of Argonne National Lab. The valence of vanadium and chromium were determined using the position and intensity of the Ka pre-edge peaks, calibrated on a series of Cr and Vbearing standard glasses. This technique has been applied to V and Cr in glasses and V in spinels previously, and in these isotropic phases there are no orientational effects on the XANES spectra (Righter et al., 2006, Amer. Mineral. 91, 1643-1656). We also now demonstrate this to be true for V and Cr in garnet. Also, previous work has shown that V has a higher valence in the glass (or melt) than in the coexisting spinel. This is also true for V in garnet-glass pairs in this study. Vanadium valence in garnets varies from 2.7 below the IW buffer to 3.7 near HM, and for coexisting glass it varies from 3.2 to 4.3. Vanadium valence measured in some natural garnets from mantle localities indicates V in the more reduced range at 2.5. Comparisons will be made between fO2 estimated from V valence and other methods for garnet-bearing mantle samples. In contrast, Cr valence measured in garnet and coexisting glass for all experimental and natural samples is 2.9- 3.0, suggesting that the valence of Cr does not vary within either phase across a large fO2 range. These results demonstrate that while V varies from 2+ to 3+ to 4+ in garnet-melt systems, Cr does not, and this will ultimately affect the partitioning behavior of these two elements in natural systems. Garnet/melt D(Cr) are between 12 and 17 across this range of fO2, whereas D(V) has the highest partition coefficient approx.3, near the IW buffer where the valence of V is almost entirely 3+.

Righter, K.↗
NASA NTRS2004

NASA Tech Briefs, February 2004

Topics include: Simulation Testing of Embedded Flight Software; Improved Indentation Test for Measuring Nonlinear Elasticity; Ultraviolet-Absorption Spectroscopic Biofilm Monitor; Electronic Tongue for Quantitation of Contaminants in Water; Radar for Measuring Soil Moisture Under Vegetation; Modular Wireless Data-Acquisition and Control System; Microwave System for Detecting Ice on Aircraft; Routing Algorithm Exploits Spatial Relations; Two-Finger EKG Method of Detecting Evasive Responses; Updated System-Availability and Resource-Allocation Program; Routines for Computing Pressure Drops in Venturis; Software for Fault-Tolerant Matrix Multiplication; Reproducible Growth of High-Quality Cubic-SiC Layers; Nonlinear Thermoelastic Model for SMAs and SMA Hybrid Composites; Liquid-Crystal Thermosets, a New Generation of High-Performance Liquid-Crystal Polymers; Formulations for Stronger Solid Oxide Fuel-Cell Electrolytes; Simulation of Hazards and Poses for a Rocker-Bogie Rover; Autonomous Formation Flight; Expandable Purge Chambers Would Protect Cryogenic Fittings; Wavy-Planform Helicopter Blades Make Less Noise; Miniature Robotic Spacecraft for Inspecting Other Spacecraft; Miniature Ring-Shaped Peristaltic Pump; Compact Plasma Accelerator; Improved Electrohydraulic Linear Actuators; A Software Architecture for Semiautonomous Robot Control; Fabrication of Channels for Nanobiotechnological Devices; Improved Thin, Flexible Heat Pipes; Miniature Radioisotope Thermoelectric Power Cubes; Permanent Sequestration of Emitted Gases in the Form of Clathrate Hydrates; Electrochemical, H2O2-Boosted Catalytic Oxidation System; Electrokinetic In Situ Treatment of Metal-Contaminated Soil; Pumping Liquid Oxygen by Use of Pulsed Magnetic Fields; Magnetocaloric Pumping of Liquid Oxygen; Tailoring Ion-Thruster Grid Apertures for Greater Efficiency; and Lidar for Guidance of a Spacecraft or Exploratory Robot.

Source record↗
NASA NTRS2018

Hybrid Theory of Scattering and Its Applications

A number of formulations have been used to investigate scattering of low-energy electrons and positrons from various targets. The hybrid theory of scattering, which takes into account the short-range correlations, and is variationally correct, is described in this article. This approach has been applied to calculate phase shifts for scattering of electrons and positrons, resonances in two-electron systems, photo detachment, and photoionization of two-electron systems. This approach has also been applied to calculate excitation of 2s state of atomic hydrogen by electron impact. In photo absorption the target can be left in 2p state instead of 1s state, resulting in the emission of Lyman-alpha radiation. Cross sections for this process are also calculated.

Bhatia, Anand K.↗
NASA NTRS2018

Application of STARFLEET Velocimetry in the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel

Selective two-photon absorptive resonance femtosecond laser electronic excitation tagging (STARFLEET) velocimetry is demonstrated for the first time in a NASA Langley wind tunnel with high repetition-rate and single-shot imaging. Experiments performed in the 0.3-meter Transonic Cryogenic Tunnel (TCT) allowed for testing at 300 K over a range of pressures (124 to 517 kPa) and Mach numbers (0.2-0.8) for freestream conditions and flow behind a cylindrical model. Measurement precision and accuracy are determined for the current set of experiments, as are signal intensity and lifetime. Precisions of 3-5 m/s (based on one standard deviation) were typical in the experiment; precisions better than 2% of the mean velocity were obtained for some of the highest velocity conditions. Agreement within a mean error of 3 m/s between STARFLEET freestream velocity measurements and facility DAS readings is demonstrated. STARFLEET is also shown to return spatially-resolved velocity profiles, though some binning of the signal is required.

STARFLEET↗