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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

A large-area lithium-fluoride Bragg spectrometer for stellar X-ray astronomy

A large-area Bragg spectrometer used to search for the Fe XXV X-ray emission lines of Sco X-1 is described. The device has 3400 sq cm of LiF on nine crystal panels aligned perpendicular to the longitudinal axis of the rocket. X rays satisfying the Bragg condition reflect into an array of nine companion proportional counters. A pointing system incorporating a free gyroscope with 2 degrees of freedom assures that target X rays are reflected at the required angle and produces repeated spectral scans of the X-ray continuum, which are later superimposed to correct temporal effects. The instrument is capable of detecting a narrow line flux from Sco X-1 of about .01 photons/sq cm/sec.

Stockman, H. S., Jr.↗
NASA NTRS1980

Ab initio projected-unrestricted Hartree-Fock calculation of some potential energy curves for carbonyl fluoride

Some potential energy curves for CF2O were calculated using projected-unrestricted Hartree-Fock (PUHF) theory. The calculations employed a contracted (4s 3p) Gaussian-type atomic orbital basis set. Bound states were found for the X-tilde 1A1 and 1,3A2 states while the 1,3B1 and 1,3B2 states were repulsive in the valence representation. The merits of the PUHF treatment for excited states are discussed. The results are discussed in terms of available experimental information and previous calculations with particular emphasis on the question of the photolysis channels open in the solar spectral region.

Brewer, D. A.↗
NASA NTRS1982

Producing Cryolite From Waste Sodium Fluoride

Simple chemical process makes synthetic cryolite by utilizing byproducts of one kind of silicon production process. Potential result of commercialization could be economic benefit to silicon industry or to aluminum industry, in which cryolite is used as flux.

Bartlett, R. W.↗
NASA NTRS1983

Separating Silicon and Sodium Fluoride by Melting

Silion is withdrawn from bottom of crucible, once two immiscible liquid stages form, in quasi-continuous method of separating silicon from other reaction products. Process is periodically halted to remove accumulated buildup of salts.

Nanis, L.↗
NASA NTRS1985

Role of hydroxide impurities in the thermoluminescent behavior of lithium fluoride

The influence of OH ion impurities on thermoluminescent sensitivity and supralinearity in LiF:Mg, Ti is analyzed. Available evidence is shown to be consistant with the presence of Ti-OH and Mg-OH complexes. The track interaction model is used to explain the data, with competing centers decreasing sensitivity and supralinearity at high concentrations.

Stoebe, T. G.↗
NASA NTRS1987

Efficient holmium:yttrium lithium fluoride laser longitudinally pumped by a semiconductor laser array

Optical pumping of a holmium:yttrium lithium floride (Ho:YLF) crystal with a 790-nm continuous-wave diode-laser array has generated 56 mW of 2.1-micron laser radiation with an optical-to-optical conversion slope efficiency of 33 percent while the crystal temperature is held at 77 K. The lasing threshold occurs at 7 mW of input power, and laser operation continues up to a crystal temperature of 124 K.

Hemmati, H.↗
NASA NTRS1986

Annealing of electron damage in mid-IR transmitting fluoride glass

Damage in ZrF4-BaF2-LaF3 glass induced by high-energy electrons was studied by ESR and optical spectroscopy. An optical absorption band at 314 nm in the irradiated glass annealed rapidly above about 50 C, probably by a second-order reaction at room temperature; the ESR lines annealed very slowly at room temperature.

Bansal, Narottam P.↗
NASA NTRS1988

Effect of fluoride doping on the transition temperature of YBa2Cu3O(6.5+delta)

The effects of F content on the Tc of superconducting YBa2Cu3F(x)O(6.5+delta-0.5x) (x = 0.0165-1.65) prepared by the solid-state reaction method (Bandsahl and Sandkuhl, 1988) are investigated experimentally. The results are presented in tables and graphs and characterized. Tc is found to increase steadily from 90.8 to 93.4 K as x is increased from 0.0165 to 0.066, but to decrease as x is further increased (Tc = 90.3 K at x = 1.65). The structure of the samples with x = 0.066 or lower is found to be single-phase perovskite.

Bansal, Narottam P.↗
NASA NTRS1989

The mechanical properties of fluoride salts at elevated temperatures

The deformation behavior of CaF2 and LiF single crystals compressed in the 111 and the 100 line directions, respectively, are compared with the mechanical properties of polycrystalline LiF-22 (mol pct) CaF2 eutectic mixture in the temperature range 300 to 1275 K for strain rates varying between 7 x 10 to the -7th and 0.2/s. The true stress-strain curves for the single crystals were found to exhibit three stages in an intermediate range of temperatures and strain rates, whereas those for the eutectic showed negative work-hardening rates after a maximum stress. The true stress-strain rate data for CaF2 and LiF-22 CaF2 could be represented by a power-law relation with the strain rate sensitivities lying between 0.05 and 0.2 for both materials. A similar relation was found to be unsatisfactory in the case of LiF.

Raj, S. V.↗
NASA NTRS1994

Increase of carbonyl fluoride (COF2) in the stratosphere and its contribution to the 1992 budget of inorganic fluorine in the upper stratosphere

Volume mixing ratio profiles of COF2 have been derived through most of the stratosphere between 30 deg N and 54 deg S from series of 0.01-/cm resolution infrared solar spectra recorded in the occultation mode by the atmospheric trace molecule spectroscopy (ATMOS) instrument during the ATLAS 1 space shuttle mission of March-April 1992. When compared with similar results obtained from the ATMOS/Spacelab 3 mission of April-May 1985, the cumulative increase in the burden of COF2 in the middle and upper stratosphere was found to be 67% for that 7-year time interval. By combining a subset of these COF2 results with upper stratospheric concentrations of HF also derived from the ATMOS observations, it was further found that the budget of inorganic fluorine above 35 km altitude increased by (60 +/- 10)% over the 1985-1992 time interval, which corresponds to an average exponential rate of increase of (6.7 +/- 1/1)%/yr, or a linear rate of increase reference to 1985 of (8.5 +/- 1.3)%/yr at the 1 sigma confidence level. The total inorganic F atom volume mixing ratio found in the upper stratosphere for 1985 and 1992 and the increase during this perid mirror the rise in man-made fluorine-bearing compounds at the ground during the early to mid 1980s. This demonstrates the negligible impact of natural sources of fluorine, in particular volcanic activity, on the observed change in F in the upper stratosphere. Implications of the present findings and comparison with model results are discussed.

Zander, R.↗
NASA NTRS1994

Increase of carbonyl fluoride (COF2) in the stratosphere and its contribution to the 1992 budget of inorganic fluorine in the upper stratosphere

Volume mixing ratio profiles of COF2 have been derived through most of the stratosphere between 30 deg N and 54 deg S from series of 0.01-cm(exp -1) resolution infrared solar spectra recorded in the occultation mode by the atmospheric trace molecule spectroscopy (ATMOS) instrument during the ATLAS 1 space shuttle mission of March-April 1992. When compared with similar results obtained from the ATMOS/Spacelab 3 mission of April-May 1985, the cumulative increase in the burden of COF2 in the middle and upper stratosphere was found to be 67% for that 7-year time interval. By combining a subset of these COF2 results with upper stratospheric concentrations of HF also derived from the ATMOS observations, it was further found that the budget of inorganic fluorine above 35 km altitude increased by (60 +/- 10) % over the 1985-1992 time interval, which corresponds to an average exponential rate of increase of(6.7 +/- 1.1) % /yr , or a linear rate of increase referenced to 1985 of (8.5 +/- 1.3) % /yr at the 1(sigma) confidence level. The total inorganic F atom volume mixing ratio found in the upper stratosphere for 1985 and 1992 and the increase during this period mirror the rise in man-made fluorine-bearing compounds at the ground during the early to mid 1980s. This demonstrates the negligible impact of natural sources of fluorine, in particular volcanic activity, on the observed change of F in the upper stratosphere. Implications of the present findings and comparison with model results are discussed.

Zander, R.↗
NASA NTRS1993

Relativistic Corrections to the Properties of the Alkali Fluorides

Relativistic corrections to the bond lengths, dissociation energies and harmonic frequencies of KF, RbF and CsF have been obtained at the self-consistent field level by dissociating to ions. The relativistic corrections to the bond lengths, harmonic frequencies and dissociation energies to the ions are very small, due to the ionic nature of these molecules and the similarity of the relativistic and nonrelativistic ionic radii.

Dyall, Kenneth G.↗
NASA NTRS1998

Commercial Production of Heavy Metal Fluoride Glass Fiber in Space

International Space Station Alpha (ISSA) will provide a platform not only for materials research but also a possible means to produce products in space which cannot be easily produced on the ground. Some products may even be superior to those now produced in unit gravity due to the lack of gravity induced convection effects. Our research with ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN glass) has shown that gravity does indeed play a major role in the crystallization behavior of this material. At the present time ZBLAN is being produced on earth in fiber optic form for use in surgical lasers and fiber optic lasers among other applications. High attenuation coefficients, however, have kept this material from being used in other applications such as long haul data transmission links. The high attenuation coefficients are due to impurities which can be removed through improved processing techniques and crystals which can only be removed or prevented from forming by processing in a reduced gravity environment.

Tucker, Dennis S.↗
NASA NTRS1998

Spectroscopy of Chlorosyl Fluoride, FClO

FClO has been proposed as an intermediate in reactions involving ClF, Cl2O, and ClF3O, and it has been suggested as a molecule of atmospheric interest. It has been prepared in situ by the hydrolysis of ClF3. The pure rotational spectrum of FClO has been studied by conventional millimeter wave techniques and by microwave Fourier transform spectroscopy. Selected transitions were searched for using predictions based on an analysis of the nu(sub 1) band. FClO is an asymmetric prolate top, kappa = -0.8950 for F(35)ClO, with a rather small dipole component of 0.093 (4) D along the a-axis and a larger one of 1.93 (5) D along the b-axis. Transitions with 0 <= J <= 54 and 0 <= K(sub a) <= 18 were observed. Cl hyperfine splitting was generally observable throughout the spectrum with F-19 spin-rotation splitting observable as well in the microwave region. Structural parameters, harmonic force constants, and nuclear magnetic shielding parameters were derived and will be compared with data of related molecules, such as ClF3, ClF, FClO2, and FClO3. High resolution infrared spectra were taken in the regions of the FCl stretching mode and bending mode around 600 and 310/cm, respectively. A preliminary analysis indicates that the FCl stretch, near 596.86/cm for F(35)ClO, is in resonance with the dark overtone of delta near 617/cm. A brief progress report will be given.

Mueller, Holger S. P.↗