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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

XPS study of the Al/SiO2 interface viewed from the SiO2 side

The first nondestructive measurement of the chemical and physical characteristics of the interface between bulk SiO2 and thick aluminum films is presented. Both X-ray photoelectron spectroscopy (XPS) and electrical measurements of unannealed resistively evaporated Al films on thermal SiO2 indicate an atomically abrupt interface. Postmetallization annealing (PMA) at 450 C induces reduction of the SiO2 by the aluminum, resulting in the layer ordering SiO2/Al2O3/Si/Al. The XPS measurement is performed from the SiO2 side after removal of the Si substrate after etching with XeF2 gas and thinning of the SiO2 layer with HF:ETOH. This represents a powerful new approach to the study of metal-insulator and other interfaces.

Hecht, M. H.↗
NASA NTRS1984

Intercomparison of stratospheric/mesospheric data; Proceedings of the Topical Meeting, Graz, Austria, June 25-July 7, 1984

Comparative analyses of various stratospheric and mesospheric species, including aerosols, ions, ozone, and some minor species, are presented, based on measurements obtained from rocket, balloon, aircraft, and satellite missions. In addition, studies concerning temperature and density characteristics of the stratosphere and mesosphere are included, as well as discussions on the various sensing and measurement techniques. Finally, dynamics and turbulence measurements are examined; consideration is given to radar winds, solar X-ray and HF radiowave absorption, and ionization irregularities.

Ghazi, A.↗
NASA NTRS1985

Detection of atomic oxygen and further line assignments in the far-infrared stratospheric spectrum

Recent progress in high-resolution measurement of sub-millimeter and far-infrared emission in the stratosphere is reviewed. Attention is given to the results of recent balloon measurements of the minor stratospheric constituents in the spectral range 40-190 per cm. Emission spectra are presented for HCl; HF; and OH. Emission spectra were also obtained for atomic oxygen; hydrobromic acid; and hydroperoxyl radical. The possibility of detecting HO2 and H2O2 in the far-infrared is also briefly discussed.

Carli, B.↗
NASA NTRS1984

The high resolution submillimetre spectrum of the stratosphere

The structure of the stratospheric spectrum, measured with a resolution of 0.0033/cm unapodized in the 7-90/cm spectral interval is described. The spectra from measurements recorded on April 24, 1979 from a balloon-borne platform at about 39 km altitude launched from the National Scientific Balloon Facility of Palestine, TX are presented. The main spectroscopic constituents include a few strong and saturated lines due to the rotational spectrum of water vapor, to magnetic dipole transitions of oxygen, and to the rotational spectrum of ozone. It is shown that the lines of ozone prevent the positive identification of the contribution to the submillimeter spectrum of several minor constituents such as HF, HCl, HCN, HNO3, and N2O. The assignments which are possible in the spectra are revised.

Carli, B.↗
NASA NTRS1985

A novel X-ray photoelectron spectroscopy study of the Al/SiO2 interface

The nondestructive measurement of the chemical and physical characteristics of the interface between bulk SiO2 and thick aluminum films is reported. Both X-ray phototelectron spectroscopy (XPS) and electrical measurements of unannealed, resistively evaporated Al films on thermal SiO2 indicate an atomically abrupt interface. Post metallization annealing at 450 C induces reduction of the SiO2 by the aluminum, at a rate consistent with the bulk reaction rate. The XPS measurement is performed from the SiO2 side after the removal of the Si substrate with XeF2 gas and thinning of the SiO2 layer with HF:ETOH. This represents a powerful new approach to the study of metal-insulator and related interfaces.

Hecht, M. H.↗
NASA NTRS1985

Unified constitutive material models for nonlinear finite-element structural analysis

Unified constitutive material models were developed for structural analyses of aircraft gas turbine engine components with particular application to isotropic materials used for high-pressure stage turbine blades and vanes. Forms or combinations of models independently proposed by Bodner and Walker were considered. These theories combine time-dependent and time-independent aspects of inelasticity into a continuous spectrum of behavior. This is in sharp contrast to previous classical approaches that partition inelastic strain into uncoupled plastic and creep components. Predicted stress-strain responses from these models were evaluated against monotonic and cyclic test results for uniaxial specimens of two cast nickel-base alloys, B1900+Hf and Rene 80. Previously obtained tension-torsion test results for Hastelloy X alloy were used to evaluate multiaxial stress-strain cycle predictions. The unified models, as well as appropriate algorithms for integrating the constitutive equations, were implemented in finite-element computer codes.

Kaufman, A.↗
NASA NTRS1985

Role of GaAs surface clearing in plasma deposition of silicon nitride films for encapsulated annealing

The role of GaAs surface cleaning and plasma reactor cleaning prior to deposition of silicon nitride films for encapsulated annealing has been investigated. X-ray photoelectron spectroscopy was employed to determine the surface characteristics of GaAs treated with HCl, HF, and NH4OH solutions preceded by a degreasing procedure. The HCl clean left the least amount of oxygen on the surface. Fluorine contamination resulting from the CF4 plasma used to clean the reactor was found to be located at the film-substrate interface by Auger electron spectroscopy with argon-ion sputtering. A modified deposition procedure was developed to eliminate the fluorine contamination. Plasma deposition of silicon nitride encapsulating films was found to modify the I-V characteristics of Schottky diodes subsequently formed on GaAs surface. The reverse current of the diodes was slightly reduced. Substrates implanted with Si at 100 keV and a dose of 5 x 10 to the 12th/sq cm showed a peak electron concentration of 1.7 x 10 to the 17th/cu cm at a depth of 0.1-micron with 60 percent activation after encapsulation and annealing at 800 C for 7 min.

Valco, G. J.↗
NASA NTRS1985

Application of two creep fatigue life models for the prediction of elevated temperature crack initiation of a nickel base alloy

Cyclic Damage Accumulation (CDA) and Total Strain-Strain Range Partitioning (TS-SRP) models for predicting the creep-fatigue crack initiation life of high temperature alloys are presented. The models differ in their fundamental assumptions regarding the controlling parameters for fatigue crack initiation and in the amount of data required to determine model constants. The CDA model represents a ductility exhaustion approach and uses stress quantities to calculate the cyclic fatigue damage. The TS-SRP model is based on the use of total mechanical strain and earlier concepts of the Strain Range Partitioning Method. Both models were applied to a well controlled fatigue data set at a high temperature nickel base alloy, B1900 + Hf, tested at 1600 F and 1800 F. The tests were divided into a baseline data set required to determine model constants and a verification data set for evaluation of the predictive capability of the models. Both models correlated the baseline data set to within factors of two in life, and predicted the verification data set to within a factor of three or better. In addition, sample calculations to demonstrate the application of each model and discusions of the predictive capabilities and areas requiring further development are presented.

Moreno, V.↗
NASA NTRS1985

Study of the Reactive-element Effect in Oxidation of Fe-cr Alloys Using Transverse Section Analytical Electron Microscopy

The role of trace additions of reactive elements like Y, Ce, Th, or Hf to Cr bearing alloys was studied by applying a new developed technique of transverse section analytical electron microscopy. This reactive-element effect improves the high temperature oxidation resistance of alloys by strongly reducing the high temperature oxidation rate and enhancing the adhesion of the oxide scale, however, the mechanisms for this important effect remain largely unknown. It is indicated that the presence of yttrium affects the oxidation of Fe-Cr-Y alloys in at least two ways. The reactive element alters the growth mechanism of the oxide scale as evidenced by the marked influence of the reactive element on the oxide scale microstructure. The present results also suggest that reactive-element intermetallic compounds, which internally oxidize in the metal during oxidation, act as sinks for excess vacancies thus inhibiting vacancy condensation at the scale-metal interface and possibly enhancing scale adhesion.

King, W. E.↗
NASA NTRS1985

Constitutive modeling for isotropic materials (HOST)

This report presents the results of the second year of work on a problem which is part of the NASA HOST Program. Its goals are: (1) to develop and validate unified constitutive models for isotropic materials, and (2) to demonstrate their usefulness for structural analyses of hot section components of gas turbine engines. The unified models selected for development and evaluation are that of Bodner-Partom and Walker. For model evaluation purposes, a large constitutive data base is generated for a B1900 + Hf alloy by performing uniaxial tensile, creep, cyclic, stress relation, and thermomechanical fatigue (TMF) tests as well as biaxial (tension/torsion) tests under proportional and nonproportional loading over a wide range of strain rates and temperatures. Systematic approaches for evaluating material constants from a small subset of the data base are developed. Correlations of the uniaxial and biaxial tests data with the theories of Bodner-Partom and Walker are performed to establish the accuracy, range of applicability, and integability of the models. Both models are implemented in the MARC finite element computer code and used for TMF analyses. Benchmark notch round experiments are conducted and the results compared with finite-element analyses using the MARC code and the Walker model.

Lindholm, U. S.↗
NASA NTRS1986

Halogen occultation experiment intergrated test plan

The test program plan is presented for the Halogen Occultation Experiment (HALOE) instrument, which is being developed in-house at the Langley Research Center for the Upper Atmosphere Research Satellite (UARS). This comprehensive test program was developed to demonstrate that the HALOE instrument meets its performance requirements and maintains integrity through UARS flight environments. Each component, subsystem, and system level test is described in sufficient detail to allow development of the necessary test setups and test procedures. Additionally, the management system for implementing this test program is given. The HALOE instrument is a gas correlation radiometer that measures vertical distribution of eight upper atmospheric constituents: O3, HC1, HF, NO, CH4, H2O, NO2, and CO2.

Mauldin, L. E., III↗
NASA NTRS1985

Satellite voice broadcast. Volume 1: Executive summary

An Executive Summary of the Satellite Voice Broadcast System Study designs are synthesized for direct sound broadcast satellite systems for HF-, VHF-, and Ku-bands. Methods are developed and used to predict satellite weight, volume, and RF performance for the various concepts considered. Cost and schedule risk assessments are performed to predict time and cost required to implement selected concepts. Technology assessments and tradeoffs are made to identify critical enabling technologies that require development to bring technical risk to acceptable levels for full scale development.

Bachtell, E. E.↗
NASA NTRS1985

Satellite voice broadcast. Volume 2: System study

The Technical Volume of the Satellite Broadcast System Study is presented. Designs are synthesized for direct sound broadcast satellite systems for HF-, VHF-, L-, and Ku-bands. Methods are developed and used to predict satellite weight, volume, and RF performance for the various concepts considered. Cost and schedule risk assessments are performed to predict time and cost required to implement selected concepts. Technology assessments and tradeoffs are made to identify critical enabling technologies that require development to bring technical risk to acceptable levels for full scale development.

Bachtell, E. E.↗
NASA NTRS1985

Gravity wave motions and momentum fluxes in the middle atmosphere at Adelaide, Australia

A study was made of gravity wave momentum fluxes in the middle atmosphere using data collected during June 1984 at Adelaide, Australia (35 deg S). The primary objectives were to identify that portion of the gravity wave spectrum that contributes most of the momentum transport and flux divergence and to examine the temporal variability of wave energies and momentum fluxes. The data were obtained with an HF (2 MHz) radar operated in a Doppler configuration with two coplanar off-vertical beams. This technique provides a direct measure of the vertical flux of horizontal momentum due to an arbitrary spectrum of gravity wave and other motions in the plane of the radar beams.

Vincent, R. A.↗
NASA NTRS1986

Halogen occultation experiment (HALOE) performance verification test procedure

The Performance Verification Test Procedure is given for the Halogen Occultation Experiment (HALOE) instrument, which is being developed in house at the Langley Research Center for the Upper Atmosphere Research Satellite (UARS). This procedure is used for comprehensive performance testing of the HALOE instrument which occurs before, during, and after flight environmental tests. The radiometric performance tests include noise, drift, linearity, instantaneous field-of-view, cal wheel gas cell characterization, and self thermal emissions. Pointer/tracker performance tests include sun sensor performance, gimbal performance, control system performance, and boresight alignment. In addition, the instrument is tested functionally in simulated orbit sequences and all command operating modes are exercised. The data analysis required for each test is specified and pass/fail criteria are given where applicable. This test will fully demonstrate the HALOE instrument's ability to achieve science mission requirements. The HALOE instrument is a gas correlation radiometer that measures vertical distribution of eight upper atmospheric constituents: O3, HCl, HF, NO, CH4, H2O, NO2, and CO2.

Mauldin, L. E., III↗
NASA NTRS1986

Compressive creep behavior of alloys based on B2 FeAl

Alloys based on FeAl are attractive alternate materials for environmental resistance at intermediate temperatures. Addition of small amounts of Nb, Hf, Ta, Mo, Zr, and B were shown to improve the compressive creep of this alloy at 1100 K. Boron, in particular, was found to have a synergistic effect along with Zr in providing properties substantially better than the binary alloy. This improvement seems to be related to the higher activation energy found for this alloy, suggesting a modification in the diffusion behavior due to the alloying additions.

Mantravadi, N.↗
NASA NTRS1985

Halogentated species

Stratospheric measurements of halogen containing species are reviewed and compared with model predictions. Halocarbons, HCl, HF, ClONO2, and ClO are discussed.

Molina, M. J.↗
NASA NTRS1985

Chondrules in the Qingzhen type-3 enstatite chondrite Possible precursor components and comparison to ordinary chondrite chondrules

The mineral composition of chondrules from a fragment of Qingzhen (EH3) fall was analyzed by neutron activation method. Unlike the ordinary chondrite (OC) chondrules (Gooding and Keil, 1981), the Qingzhen radial pyroxene (RP) and porphyritic pyroxene (PP) chondrules have similar bulk compositions. Porphyritic olivine-pyroxene (POP) chondrules are richer than PP and RP chondrules in refractory lithophiles and siderophiles. Elements in each of the following sets intercorrelate significantly: (1) Fe-Co-Ni-Ir-Au, probably derived from a metal component; (2) Ca-Eu-Se, which suggests an oldhamite-rich precursor; (3) Al-Sc-Hf, occurring in high concentrations in POP chondrules, this set suggesting the existence of a refractory lithophile-rich and olivine-rich component; (4) Na REE; and (5) Cl-Br. Sets (2) and (4) were not precursors of OC. The interelement ratios of refractory lithophiles such as Ca, Al, Ti, Sc, and REE are similar to CI ratios, suggesting that they originated in the earliest phases as silicates, which were sulfurized before chondrule formation.

Grossman, J. N.↗