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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Anomalous phase separation behavior of gel-derived soda-silica glasses

The effects of retained bound hydroxyl groups on amorphous immiscibility behavior and on the kinetics of phase separation were studied in glasses containing from 10 to 19 percent sodium oxide preparaed by the gel process. Differences in behavior as functions of preliminary thermal treatment of the gel precursor and of melting conditions were studied, employing IR spectroscopy, SAXS and WAXD to monitor the variation in glass microstructure. Both the initial gel treatment and the OH concentration in the prepared glasses were found to affect the immiscibility temperatures, and the magnitude of the maximum temperature increase was also a function of the sodium oxide concentration. It is suggested that the variation in thermodynamic behavior may be caused by the structural arrangement attained by the OH groups during the gel condensation process, which in turn affects the extent of hydrogen bonding to nonbridging oxygen ions.

Neilson, G. F.↗
NASA NTRS1983

Mechanism and kinetics of the curing process in a resin system

The present investigation is concerned with the development of a cure reactivity model for a resin system consisting of tetraglycidyl diaminodiphenyl methane (TGDDM) and diaminodiphenyl sulfone (DDS), taking into account the temperature range from 153 to 177 C. Differential scanning calorimetry and FT-IR spectroscopy have been used to investigate the cure kinetics of the resin with the objective to obtain a correlation between the total conversion and the rates of formation and disappearance of specific functionalities. It was found that the overall process can be satisfactorily described in terms of two first order processes.

Moacanin, J.↗
NASA NTRS1985

Silicon carbide-silicon nitride fibers: Preparation and characterization of polycarbosilazane precursors

This study examines the effect of modifications of the chemical structure of the monomers on the properties of the polymeric precursor and and ceramic fibers. A group of silaneamines, R'-Si (NH-R) sub 3, taken from the series where R' is methyl or phenyl and R is n-propyl, n-butyl, phenyl or allyl, are converted to polycarbosilazanes by heating in excess of 500 C. Resins obtained from this polymerization are characterized by NMR and IR spectroscopy and GPC. Each resin is tested for fiber-forming properties. Resin samples and fibers are hydrolytically cured. Thermogravimetric analyses are conducted on the cured resins to compare the relative thermal stability and examine the pyrolysis process. Cured fibers are tested for tensil strength.

Crouse, D. J.↗
NASA NTRS1984

Dielectric Fabry-Perot mirror coatings for infrared astronomy

A number of Fabry-Perot (FP) coating designs have been developed specifically for IR astronomy. These have been optimized for uniform reflectance over five contiguous spectral ranges of particular astronomical interest between 1 and 5 microns. Wavelength coverage in individual designs is given by (maximum wavelength/minimum wavelength) greater than 1.4, over which reflective finesse is maintained near 35. Consideration has been made for the peculiar requirements of FP coatings. Visual alignment and testing of the FP has been made convenient by bringing the reflective finesse of the coating at 632.8 nm to the same value as the main IR reflection band. For example, a calcium fluoride FP can be aligned and tested at 632.8-nm He-Ne laser line, with the assurance of a corresponding finesse and spectral resolving power over its IR (3.6-5.1-micron) range. In addition, the FP can be used for IR spectroscopy while being simultaneously monitored and/or actively controlled at the laser wavelength. The potential for the coating itself to degrade the effective surface flatness of the FP through either mechanical stress or thickness nonuniformities is minimized by reducing to a minimum the number and thickness of coating layers. Several of these coatings have been fabricated and are actively in use at a number of observatories.

Trauger, J.↗
NASA NTRS1985

The preparation and characterization of a lithium borate glass prepared by the gel technique

The preparation of an amorphous lithium borate gel by the metal organic procedure is described. In addition, a preliminary evaluation of the behavior of the gel upon heating is given. In particular the crystallization tendency of the gel is studied with the aid of DTA and X-ray diffraction, and the structural changes in the gel are monitored with the aid of IR spectroscopy. The glass produced from the lithium borate gel is compared to both the gel precursor material and a glass of similar composition prepared by conventional techniques. Specifically, the relevant water contents, crystallization behavior, and structural features are contrasted.

Weinberg, M. C.↗
NASA NTRS1984

Composition and properties of the so-called 'diamond-like' amorphous carbon films

The composition of amorphous 'diamond-like' films made by direct low energy ion beam deposition, R.F. discharge and sputtering was determined by nuclear reaction analysis, IR spectroscopy and microcombustion chemical analysis. The nuclear reaction analysis showed very similar hydrogen depth profiles for all three types of samples. The atomic ratio of hydrogen to carbon was approximately 0.2 at the film surface and rose to approximately 1.0 at a depth of 500 A. The integrated intensity of the C-H stretching band at about 2900 per cm indicates that the amount of chemically bonded hydrogen is less than the total hydrogen content. Combustion analysis confirmed the overall atomic ratio of hydrogen to carbon determined by nuclear reaction analysis. The chemical state of the non-bonded hydrogen was not determined; however, the effective diffusion coefficient computed from the hydrogen depth profile was extremely low. This indicates either that the films are exceedingly impermeable or that the non-bonded hydrogen requires an additional activated step to leave the films, e.g., desorption or chemical reaction.

Angus, J. C.↗
NASA NTRS1986

Airborne infrared investigation of water in the coma of Halley's Comet

An infrared Fourier transform spectrometer on the Kuiper Airborne Observatory (KAO) was used to obtain high resolution spectra of the intense, solar-pumped infrared fluorescent emission in the (001 to 000) band of H2O near 2.6 microns. Differences between the observed H2O excitation and original expectations are discussed, and KAO water production rates are compared to those derived from International Ultraviolet Explorer observations. Possible future directions for high resolution IR spectroscopy of comets are discussed.

Weaver, Harold A.↗
NASA NTRS1986

Infrared technology and applications; Proceedings of the Meeting, Cannes, France, November 26-29, 1985

The present conference on state-of-the-art IR systems and components technologies and their applications encompasses developments in IR systems design, production technologies, IR component testing, IR systems evaluations, laboratory and industrial applications, and aerospace ranging sensor and surveillance sensor applications. Attention is given to IR zoom lens telescopes, large zinc sulphide windows for airborne applications, thermal imaging system evaluation, minimum resolvable temperature difference measurement methods, industrial use of IR spectroscopy, platinum silicide sensor imagery, and recent developments in laser rangefinders.

Baker, Lionel R.↗
NASA NTRS1987

Cure study of soluble aromatic polyimide films

Several soluble aromatic poly(amic acid) films were staged at intervals to 325 C and characterized by IR spectroscopy and various solution property techniques. A series of films in which the polymer had been endcapped in an effort to control chain extension was also examined. Much of the behavior observed is consistent with an interpretation that a reduction in molecular weight occurred during cure before the ultimate molecular weight was achieved as a polyimide.

Young, Philip R.↗
NASA NTRS1987

The helium abundance of Uranus from Voyager measurements

Voyager radio-occultation and IR spectroscopy measurements are combined to infer an He mole fraction in the upper troposphere of Uranus of 0.152 + or - 0.033; the corresponding mass fraction is Y = 0.262 + or - 0.048. This value is in agreement with recent estimates of the solar He abundance, suggesting that He differentiation has not occurred on Uranus. Comparisons with values previously obtained for Jupiter and Saturn imply that migration of He toward the core began long ago on Saturn and may also have recently begun on Jupiter. The protosolar He abundance inferred from the Uranus measurements and from recent solar evolutionary models is used along with an assumed primordial He mass fraction of 0.23-0.24 to estimate a 3-4-percent enrichment of He in the interstellar medium between the big bang and the origin of the solar system. The result is in agreement with galactic chemical evolution models which include a substantial decrease in D during the evolutionary process.

Conrath, B.↗
NASA NTRS1987

Evolution of interstellar dust

The composition, origins, and evolution of interstellar dust (ISD) are examined, reviewing the results of recent observational and theoretical investigations. Topics discussed include amorphous and polycrystalline structures; the relationship between amorphous C, graphite, and polycyclic aromatic hydrocarbons; observational techniques for determining ISD structure and composition; ISD formation in outflows from late-type giants, planetary nebulae, and novae; destruction of ISD by shocks; the formation of ISD in the ISM; and the relationship between ISD and interplanetary dust. IR spectroscopy of molecular ices and icy grain mantles is considered in detail, and it is shown that typical grain mantles consist of a 1/0.6/0.05/0.05 mixture of H2O, CH3OH, CO, and NH3.

Tielens, A. G. G. M.↗
NASA NTRS1988

FTIR characterization of thermally cycled PMR-15 composites

Chemical characterization results are presented for a variety of PMR-15/graphite composites, differentiated according to prepreg types and cure cycles, which were subjected to 1000 thermal cycles between 0 and 450 F. Fourier transform IR spectroscopy was used in conjunction with diffuse reflectance sampling to examine whether changes in the matrix resin chemistry due to environmental exposure may have contributed to microcracking. Analysis based on compound spectra revealed behavior associated with the oxidation of methylene groups to carbonyl groups on the composite surface; evidence of crosslinking also emerged, although the two phenomena do not appear to be related.

Young, Philip R.↗
NASA NTRS1988

The V3, V4 and V6 bands of formaldehyde: A spectral catalog from 900 cm(-1) to 1580 cm(-1)

The results of a complete high resolution study of the three vibration-rotation bands v sub 3, v sub 4, and V sub 6 using both TDLs and FT-IR spectroscopy are presented. The reults are given in terms of a table of over 8000 predicted transition frequencies and strengths. A plot of the predicted and calculated spectra is shown. Over 3000 transitions were assigned and used in the simultaneous analysis of the three bands. The simultaneous fit permitted a rigorous study of Coriolis and other type iterations among bands yielding improved molecular constants. Line intensities of 28 transitions measured by a TDL and 20 transitions from FTS data were used, along with the eigenvectors from the frequency fitting, in a least squares analysis to evaluate the band strengths.

Nadler, Shachar↗
NASA NTRS1988

Materials and formation of the Imbrium basin

A study of Imbrium basin deposits has been conducted, including geologic mapping, analysis of orbital geochemical data, earth-based near-IR spectroscopy, and analytical modeling. The morphologic facies of the deposits display an unusual bilateral symmetry with respect to the main rim of the basin, which is thought to be 1160 km in diameter and composed of Apennine-Carpathian-Alpes mountain ranges. The Imbrium ring structure consists of six concentric rings ranging from 550-3200 km in diameter. The evolution of the target for the Imbrium basin impact is discussed. It is suggested that the Imbrium impact, which occurred 3.85 Gyrs ago, formed a basin predominantly by a proportional-growth crater-forming mechanism.

Spudis, Paul D.↗
NASA NTRS1988

The condensation and vaporization behavior of H2O:CO ices and implications for interstellar grains and cometary activity

IR spectroscopy has been used to ascertain several parameters associated with CO, H2O, and H2O:CO ices' physical behavior. Since CO is noted to be capable of condensing into H2O-rich ices at temperatures that are twice as high as those required for condensation in pure CO, CO is able to condense onto H2O-rich ice grains at temperatures of up to 50 K. CO's presence in H2O ice modestly enhances the effective volatility of the H2O. Attention is given to the implications of these results for cometary models generally and the question of cometary formation specifically.

Sandford, Scott A.↗
NASA NTRS1989

Tunable diode laser measurements of absolute line strengths in the 2nu2 band of N2O near 8 microns

The absolute intensities of five rotational transitions in the 2nu2 band of N2O near 8 microns have been measured with a tunable-diode laser-spectrometer. Measurements were reproducible within an average deviation of about 3 percent, and the experimental and calculated line strengths differed by only 1.5 percent. An analysis of the line strengths has yielded a band strength of S(v) = 6.98 + or - 0.26/sq cm per atm at 296 K. The band and line strengths are in excellent agreement with two recently reported values obtained by using Fourier transform-IR spectroscopy.

Tang, Lai-Wa↗
NASA NTRS1989

Anomalous quartz from the Roter Kamm impact crater, Namibia - Evidence for post-impact hydrothermal activity?

Quartz pebbles from the Roter Kamm impact crater (the Namib Desert, SWA/Namibia) were examined for evidence of impact-induced hydrothermal activity, using results from microprobe analyses, neutron activation analyses, transmission IR spectroscopy, and X-ray diffractometry. It was found that the pebbles consisted of pure quartz, which contains three different types of fluid inclusions. These were identified as primary inclusions (5-10 microns) that record the formation conditions of the quartz, very small (less than 1 micron) secondary inclusions associated with the grain boundaries, and late inclusions of irregular size. It is concluded that the quartz and the primary inclusions may provide evidence for a postimpact phase of extensive hydrothermal activity, generated by the residual heat from the kinetic energy of the impact.

Koeberl, Christian↗