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At least 613 records · Page 34

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NASA NTRS1986

Nebulization Reflux Concentrator

Nebulization reflux concentrator extracts and concentrates trace quantities of water-soluble gases for subsequent chemical analysis. Hydrophobic membrane and nebulizing nozzles form scrubber for removing trace quantities of soluble gases or other contaminants from atmosphere. Although hydrophobic membrane virtually blocks all transport of droplets, it offers little resistance to gas flow; hence, device permits relatively large volumes of gas scrubbed efficiently with very small volumes of liquid. This means analyzable quantities of contaminants concentrate in extracting solutions in much shorter times than with conventional techniques.

Cofer, Wesley R., III↗

NASA NTRS1984

Influence of aluminum oxide film on thermocompression bonding of gold wire to evaporated aluminum film

The influence of Al surface condition on the thermocompression bonding of Au wires to Al electrodes for integrated electric circuits was studied. Au wires were connected to Al electrodes by nail-head bonding after various Al surface treatments. Bonding was evaluated by measuring the wire pull strength and fraction of the number of failures at Au-Al bonds to the total number of failures. Dependence of the fraction on applied load was derived theoretically with a parameter named critical load to take into consideration the differences in Al surface condition. The relation also held explicately for various surface treatments. Characterization of the Al surface was carried out by electron microscopy for chemical analysis.

Iwata, S.↗

NASA NTRS1985

Microstructure of reaction-bonded silicon nitride consolidated by isostatic hot-pressing

A microstructural examination and chemical analysis are conducted for reaction-bonded Si3N4 specimens that were isostatically hot pressed at 1850, 1950, and 2050 C. The present observations indicate that the previously reported increase in the 1200 C bend strength of reaction-bonded Si3N4, after pressing at 2050 C exclusively, is due to the relative oxygen levels of the isostatically hot pressed specimens; calculations show that an SiO2 content of less than about 2.2 vol pct is needed to yield the 1200 C strength increase.

Mieskowski, D. M.↗

NASA NTRS1986

Batch Gas-Sampling System

Sampler collects air or other gases in consistent way and stabilizes them for later chemical analysis. Device used for concentrations ranging from few parts per million to 100 percent. Also separates and collects particles in gas for analysis. Gas flows into vacuum sphere when solenoid valve opened. As it passes through conversion tube, constituent of gas forms stable compound that remains in conversion tube for analysis at later time. Sampler parts made of glass, polytetrafluoroethylene, and stainless steel so they do not react with sample.

Diaz, Vernon, Jr.↗

NASA NTRS1985

Effects of high energy radiation on the mechanical properties of epoxy-graphite fiber reinforced composites

In an effort to elucidate the changes in molecular structural and mechanical properties of epoxy/graphite fiber composites upon exposure to ionizing radiation in a simulated space environment, spectroscopic and surface properties of tetraglycidyl-4,4'-diamino diphenyl methane (TGDDM) red with diamino diphenyl sulfone (DDS) and T-300 graphite fiber were investigated following exposure to ionizing radiation. Cobalt-60 gamma radiation and 1/2 MeV electrons were used as radiation sources. The system was studied using electron spin resonance (ESR) spectroscopy, infrared absorption spectroscopy, contact angle measurements, and electron spectroscopy for chemical analysis.

Fornes, R. E.↗

NASA NTRS1985

Samples at the Apollo 15 landing site: Types and distribution

Samples, consisting of more than 350 individually numbered samples of rock and regolith, were collected during the three EVAs on the Apollo 15 mission. Samples consisted of rock specimens, and scooped, trenched, and cored regolith samples. Petrographic and chemical analysis are discussed.

Ryder, G.↗

NASA NTRS1986

Acoustic penetration and impact detector for micrometeoroid and space debris application

The Two-Stage Acoustic Penetration and Impact Detector is a simple device for measuring the impact event time, the projectile velocity, the flight path direction and the momentum. The results of laboratory tests have shown that this detector can be used in a wide range of projectile size and velocity. According to measurement purposes the size of the detection area, the distance between the front foil and the target plate and the number of microphones as well as the evaluation procedure can easily be adjusted. The target plate area can also be replaced by another foil detector, if two penetration stages are preferred. This active detector is suitable for a variety of applications in meteoroid and space debris exploration. It can also be supplied with capture cell properties for chemical analysis of inside-deposits. Therefore, this measurement principal has been taken into consideration as a possible flight experiment for instance for a later Longer Duration Exposure Facility (LDEF) flight or future space station activities.

Kuzcera, H.↗

NASA NTRS1984

Volcanic impact on stratospheric aerosol chemistry

Samples collected by the National Center for Atmospheric Research (NCAR) using the multiple-filter sampler on the U-2 were analyzed. The sampler is capable of exposing a number of 110 mm filters in sequence to ram air flow. Two types of filters, IPC cellulose and polystrene, were used, both of which have high blank levels for the trace elements determined. The levels of most trace elements in the stratosphere are so low under normal circumstances that none can be seen. Results from the eruption of Mt. St. Helens, a mystery cloud (probably volcanic in origin) in 1982, and the El Chichonal eruption in 1983 are discussed. To improve the collection of particles for chemical analysis, a new sampling system was developed for use on the U-2. The sampler consisted of an electrostatic collection of particles between 1 and 0.001 micron diameter dierectly onto electron microscopic grids, followed by a thermal precipitation for the smaller particles. The system was built and tested in the laboratory, but never flown on the U-2.

Zoller, W. H.↗

NASA NTRS1985

Rolling contact fatigue behavior of Cu and TiN coatings on bearing steel substrates

The resistance of copper and TiN coatings on various bearing substrates to high-load rolling contact fatigue (RCF) is investigated. Special attention is given to the lubricating characteristics of copper deposited by ion plating, and the wear resistant characteristics of TiN deposited by ion plating and magnetron sputtering techniques. RCF samples of 440C and AMS 5749 bearing steels were coated. Sputter deposited and ion plated films were on the RCF samples in a range of thickness from about 2000 A to 2 microns. Results showed a marked improvement of the RCF for pure copper tested on 440C, but a degradation for copper on AMS 5749. It is also found that the 2000 A TiN films behave favorably on the 440C and AMS 5749 bearing steels at RCF stress levels of 786 ksi. Scanning electron microscopy, X-ray diffraction, and electron spectroscopy for chemical analysis were used during the investigation.

Hochman, R. F.↗

NASA NTRS1986

Kinetics and mechanism of corrosion of SiC by molten salts

Corrosion of sintered alpha-SiC under thin films of Na2CO3/CO2, Na2SO4/O2, and Na2SO4/SO3 was investigated at 1000 C. Chemical analysis was used to follow silicate and silica evolution as a function of time. This information coupled with morphology observations leads to a detailed corrosion mechanism. In all cases the corrosion reactions occur primarily in the first few hours. In the Na2CO3/CO2 case, rapid oxidation and dissolution lead to a thick layer of silicate melt in about 0.25 h. After this, silica forms a protective layer on the carbide. In the Na2SO4/O2 case, a similar mechanism occurs. In the Na2SO4/SO3 case, a porous nonprotective layer of SiO2 grows directly on the carbide, and a silicate melt forms above this. In addition, SiO2 and regenerated Na2SO4 form at the melt/gas interface due to reaction of silicate with SO3 and SO2 + O2. The reaction slows when the lower silica layer becomes nonporous.

Jacobson, N. S.↗

NASA NTRS1986

Microstructure/mechanical property relationships for various thermal treatments of Al-Cu-Mg-X PM aluminum alloys

The thermal response and aging behavior of three 2XXX-series powder metallurgy aluminum alloys have been investigated, using Rockwell B hardness measurements, optical and electron microscopy, and energy-dispersive chemical analysis, in order to correlate microstructure with measured mechanical properties. Results of the thermal response study indicated that an increased solution heat treatment temperature was effective in resolutionizing large primary constituents in the alloy bearing more copper but had no apparent effect on the microconstituents of the other two. Aging studies conducted at room temperature and at 120, 150, and 180 C for times ranging up to 60 days indicated that classic aging response curves, as determined by hardness measurements, occurred at lower aging temperatures than were previously studied for these alloys, as well as at lower aging temperatures than are commonly used for ingot metallurgy alloys of similar compositions. Microstructural examination and fracture surface analysis of peak-aged tension specimens indicated that the highest tensile strengths are associated with extremely fine and homogeneous distributions of theta-prime or S-prime phases combined with low levels of both large constituent particles and dispersoids. Examination of the results suggest that refined solution heat treatments and lower aging temperatures may be necessary to achieve optimum mechanical properties for these 2XXX series alloys.

Blackburn, L. B.↗

NASA NTRS1988

Oxidation-Resistant Surfaces For Solar Reflectors

Thin films on silver provide highly-reflective, corrosion-resistant mirrors. Study evaluated variety of oxidation-resistant reflective materials for use in solar dynamic power system, one that generates electricity by focusing Sunlight onto reciever of heat engine. Thin films of platinum and rhodium deposited by ion-beam sputtering on various substrate materials. Solar reflectances measured as function of time of exposure to radio-frequency-generated air plasma. Several protective coating materials deposited on silver-coated substrates and exposed to plasma. Analyzed before and after exposure by electon spectroscopy for chemical analysis and by Auger spectroscopy.

Gulino, Daniel A.↗

NASA NTRS1987

A life test of a 22-Newton (5-lbf) hydrazine rocket

Life tests were conducted on a 22-N (5-lb) hydrazine rocket thruster which incorporates the latest technology to obtain long life from the catalyst bed. A spring mechanism surrounding the catalyst bed continually applies compression to the catalyst bed to prevent the formation of any void channels. The research rocket thruster was tested over an operational cycle of both steady state and pulse firing which simulated a possible space station duty cycle. The thruster ran as expected for about 40 hours, or 3.2 times 10 to the 6th power N-sec (7.2 times 10 to the 5th power lb-sec) total impulse. Subsequently, some thrust chamber pressure decreases were noted during long steady state test periods. After 60.2 hours of run time, tests had to be terminated due to a blockage in the propellant injector tube which occurred during heating of the thruster by a heat lamp. A chemical analysis of the catalyst indicated that iron and nickel metals had poisoned some of the catalyst, thereby causing a degradation in performance. It was determined that a contaminated barrel of hydrazine was the source of the metal poisoning.

Meng, P. R.↗

NASA NTRS1987

Surface catalytic degradation study of two linear perfluoropolyalkylethers at 345 C

Thin-liquid-film degradation studies of two commercially available perfluoropolyalkylether fluids (PFAE) were performed at 345 C, in nitrogen and air atmospheres, on iron and 440 C stainless steel surfaces. It was found that one fluid degraded on both iron and 440 C stainless steel surfaces in an air atmosphere, whereas the other fluid did not degrade. Chemical analysis revealed that the test fluid degraded to lower molecular weight products and that the degradation was accompanied by the formation of a brownish deposit on both the iron and 440 C stainless steel surfaces. Surface analysis of the deposit revealed a susbstantial amount of iron oxide (Fe2O3). It was hypothesized that the fluid which degraded did so because of its acetal structure. The other fluid, lacking the acetal structure, did not degrade.

Morales, Wilfredo↗

NASA NTRS1987

The use of airborne imaging spectrometer data to determine experimentally induced variation in coniferous canopy chemistry

It was experimentally determined whether induced differences in forest canopy chemical composition can be detected using data from the Airborne Imaging Spectrometer (AIS). Treatments were applied to an even-aged forest of Douglas fir trees. Work to date has stressed wet chemical analysis of foilage samples and correction of AIS data. Plot treatments were successful in providing a range of foliar N2 concentrations. Much time was spent investigating and correcting problems with the raw AIS data. Initial problems with groups of drop out lines in the AIS data were traced to the tape recorder and the tape drive. Custom adjustment of the tape drive led to recovery of most missing lines. Remaining individual drop out lines were replaced using average of adjacent lines. Application of a notch filter to the Fourier transform of the image in each band satisfactorily removed vertical striping. The aspect ratio was corrected by resampling the image in the line direction using nearest neighbor interpolation.

Swanberg, Nancy A.↗

NASA NTRS1985

Improved silicon nitride for advanced heat engines

The AiResearch Casting Company baseline silicon nitride (92 percent GTE SN-502 Si sub 3 N sub 4 plus 6 percent Y sub 2 O sub 3 plus 2 percent Al sub 2 O sub 3) was characterized with methods that included chemical analysis, oxygen content determination, electrophoresis, particle size distribution analysis, surface area determination, and analysis of the degree of agglomeration and maximum particle size of elutriated powder. Test bars were injection molded and processed through sintering at 0.68 MPa (100 psi) of nitrogen. The as-sintered test bars were evaluated by X-ray phase analysis, room and elevated temperature modulus of rupture strength, Weibull modulus, stress rupture, strength after oxidation, fracture origins, microstructure, and density from quantities of samples sufficiently large to generate statistically valid results. A series of small test matrices were conducted to study the effects and interactions of processing parameters which included raw materials, binder systems, binder removal cycles, injection molding temperatures, particle size distribution, sintering additives, and sintering cycle parameters.

Yeh, H. C.↗

NASA NTRS1988

A fundamental approach to the sticking of insect residues to aircraft wings

The aircraft industry is concerned with the increase of drag on planes due to the sticking of insects on critical airfoil areas. The objectives of the present study were to investigate the effects of surface energy and elasticity on the number of insects sticking onto the polymer coatings on a modified aircraft wing and to determine the mechanism by which insects stick onto surfaces during high velocity impact. Analyses including scanning electron microscopy, electron spectroscopy for chemical analysis and contact angle measurements of uncoated and polymer coated aluminum surfaces were performed. A direct relation between the number of insects sticking on a sample and its surface energy was obtained. Since the sticky liquid from a burst open insect will not spread on the low energy surface, it will ball up providing poor adhesion between the insect debris and the surface. The incoming air flow can easily blow off the insect debris and thus reducing the number of insects that remain stuck on the surface. Also a direct relation between the number of insect sticking onto a surface and their modulus of elasticity was obtained.

Yi, O.↗

NASA NTRS1988

In situ chemical analyses of extraterrestrial bodies

One of the most important tasks on any sample return mission will have to be a quick sample characterization in order to guarantee a variety of collected samples. An alpha particle instrument with alpha, proton and X-ray modes can provide a quick and almost complete chemical analysis of Mars samples. This instrument is based on three interactions of the alpha particles from a radioactive source with matter: elastic scattering of the alpha particles by nuclei (alpha mode), (alpha,p) nuclear reaction with some light elements (proton mode), and excitation of the atomic structure of atoms by alpha particles, leading to emission of characteristic X-rays of the lunar surface at three sites during the Surveyor mission of 1967 to 1968. Since then the instrument has been improved and miniaturized substantially. As shown in the past, the alpha particle instrument can operate under Martian conditions without any degradation in the performance. The alpha and proton modes can provide vital information about the light elements, while the X-ray mode with its ambient temperature X-ray detector will be useful for the heavier elements. The excitation of the atomic structure is provided by the same alpha radioactive source that is used by alpha and proton modes or by an auxiliary X-ray source that is selected to enhance the sensitivity to some important geochemical elements.

Economou, Thanasis E.↗