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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Convenient mounting method for electrical measurements of thin samples

A method for mounting thin samples for electrical measurements is described. The technique is based on a vacuum chuck concept in which the vacuum chuck simultaneously holds the sample and established electrical contact. The mounting plate is composed of a glass-ceramic insulating material and the surfaces of the plate and vacuum chuck are polished. The operation of the vacuum chuck is examined. The contacts on the sample and mounting plate, which are sputter-deposited through metal masks, are analyzed. The mounting method was utilized for van der Pauw measurements.

Matus, L. G.↗
NASA NTRS1986

Growth and characterization of epitaxial SrF2 on InP(100)

The epitaxial growth of 100-262.5-nm SrF2 films on n-type and p-type (100)InP in a conventional baked UHV system at base pressure about 200 ptorr, temperature 250-350 C, and growth rate from less than 100 to about 200 pm/s. Substrates are chemicomechanically polished, degreased, bombarded with 500-eV Ar ions for 3-4 min at 350 C, and annealed for 23-30 min at 350 C, producing a slightly In-rich (In/P = 1.02) In-island-free surface with a (4 x 1) or (1 x 1) LEED structure. Films grown at 350 C and less than 100 pm/s are found to be smooth and free of cracks in most cases, with a highly faceted (1 x 1) LEED structure. The electrical properties of the SrF2 films are found to be acceptable only when the ohmic contacts are applied prior to the substrate prior to SrF2 growth.

Sinharoy, S.↗
NASA NTRS1986

Four Antarctic ureilites - Petrology and observations on ureilite petrogenisis

New data are presented on the petrography and mineral compositions of four recently recovered Antarctic ureilites: Yamato-790981, RKPA80239, ALHA81101, and PCA82506. Thin polished sections of the ureilites were analyzed by polarized and reflected light microscopy, and by electron microprobe. The low shock characteristics of most (with the exception of the ALHA81101) Antarctic ureilites have afforded excellent opportunities for understanding the petrographic relationships between graphite and silicate minerals in ureilites. New speculations concerning the petrogenesis of ureilites are offered.

Berkley, J. L.↗
NASA NTRS1985

A prototype space flight intravenous injection system

Medical emergencies, especially those resulting from accidents, frequently require the administration of intravenous fluids to replace lost body liquids. The development of a prototype space flight intravenous injection system is presented. The definition of requirements, injectable concentrates development, water polisher, reconstitution hardware development, administration hardware development, and prototype fabrication and testing are discussed.

Colombo, G. V.↗
NASA NTRS1986

Welding torch with arc light reflector

A welding torch arc light reflector is disclosed for welding torches having optical viewing systems. A schematic of a welding torch having an internal coaxial viewing system consisting of a lens which focuses the field of view of the weld scene of the workpiece onto the end of the fiberoptic bundle is provided. The transmitted image of the fiberoptic bundle is provided to a camera lens which focuses it onto a TV sensor array for transmission. To improve the parity of the image of the monitoring system, an arc light reflector is shown fitted to the end of the torch housing or gas cup. The arc light reflector has an internal conical section portion which is polished to serve as a mirror which reflects the bright arc light back onto the darker areas of the weld area and thereby provides a more detailed image for the monitoring system. The novelty of the invention lies in the use of an arc light reflector on welding torches having optical viewing systems.

Gordon, Stephen S.↗
NASA NTRS1987

Composition optimization of chromium carbide based solid lubricant coatings for foil gas bearings at temperatures to 650 C

A test program to determine the optimum composition of chromium carbide based solid lubricant coatings for compliant gas bearings is described. The friction and wear properties of the coatings are evaluated using a foil gas bearing test apparatus. The various coatings were prepared by powder blending, then plasma sprayed onto Inconel 718 test journals and diamond ground to the desired coating thickness and surface finish. The journals were operated against preoxidized nickel-chromium alloy foils. The test bearings were subjected to repeated start/stop cycles under a 14 kPa (2 psi) bearing unit load. The bearings were tested for 9000 start/stop cycles or until the specimen wear reached a predetermined failure level. In general, the addition of silver and eutectic to the chromium carbide base stock significantly reduced foil wear and increased journal coating wear. The optimum coating composition, PS212 (70 wt% metal bonded Cr3C2, 15 wt% Ag, 15% BaF2/CaF2 eutectic), reduced foil wear by a factor of two and displayed coating wear well within acceptable limits. The load capacity of the bearing using the plasma-sprayed coating prior to and after a run-in period was ascertained and compared to polished Inconel 718 specimens.

Dellacorte, Christopher↗
NASA NTRS1985

Construction of a multilayered X-ray telescope for solar coronal studies from space

The construction and testing of soft x-ray Ritchey-Chretien aplanatic telescope which is to be flown on a NASA sounding rocket in 1986 for very high resolution studies of the solar corona are discussed. Goals include figuring, polishing and measuring the mirror surfaces to tolerances exceding the 5000 A wavelength diffraction limit while achieving a superpolished surface finish, and the development of a structural design to withstand the rigors of the launch. Multilayer coatings are used to achieve usable reflectivity in the soft X-ray regime, and the design goal is for spatial resolution of 1/4 sec. Future applications are discussed.

Golub, L.↗
NASA NTRS1986

Thermal stability of lightweight graphite glass sandwich reflectors for far infrared astronomy

Graphite fiber-reinforced glass matrix composites are being developed for a variety of structural applications requiring excellent thermomechanical stability. These materials are ideally suited for lightweight, high strength, thermally stable infrared mirrors because of their low density, low thermal expansion, high strength and stiffness, and their ability to be machined, replicated and figured using standard polishing techniques. These properties are particularly promising for applications such as a 3-meter balloon-borne far-infrared and submillimeter telescope mirror which must be both very lightweight and able to retain its figure accuracy when cycled between room temperature and its operating temperature of -50 C. This paper presents the results of a set of low temperature optical tests conducted to determine the figure stability of a 30-cm diameter, frit-bonded graphite/glass mirror in the +20 to -60 C temperature range using a 10.6 micron laser interferometer. The results indicate that the residual change in figure was less than 0.3 microns, rms.

Bluege, J. H.↗
NASA NTRS1986

Photoelectrochemical fabrication of sawtooth gratings in n-GaAs

A photoelectrochemical approach is employed to fabricate exceptionally smooth low-pitch grating structures consisting of polished single crystals of (100) oriented n-GaAs in a sawtooth profile. The depth of the edged features is controlled by monitoring the total coulombs passed, and the rate of etching is precisely controlled by the light intensity, minimizing diffusional gradients in the liquid which may impair the uniformity. Symmetrical grooves spaced 10 microns apart will have a depth of 7.14 microns, and typically, 10-20 percent less total charge is required.

Carrabba, Michael M.↗
NASA NTRS1986

The effect of gravity level on the average primary dendritic spacing of a directionally solidified superalloy

The effect of alternating low (0.01 g) and high (1.8 g) gravity force on the primary spacings in the dendrite structure in a directionally solidified Ni-based superalloy (PWA 1480, containing 5 pct Co, 10 pct Cr, 4 pct W, 12 pct Ta, 5 pct Al, 1.5 pct Ti, and the balance Ni) was investigated using samples solidified in a directional solidification furnace aboard the NASA KC-135 aircraft that made a series of low-g parabolas. The cross-section slices for each growth rate were polished and etched with Kallings II, and the primary dendritic arm spacings were measured using the method of Jacobi and Schwerdtfeger (1976). The arm spacings were found to fluctuate with gravity force, increasing as the gravity level decreased, and growing finer as gravity increased.

Mccay, M. H.↗
NASA NTRS1987

Barred olivine chondrules in ordinary chondrites

The characteristics of 125 barred olivine chondrules identified in polished thin sections of 26 H-L-LL3-6 chondrites were studied, using an electron microprobe for determining mineral abundances and a broad-beam electron microprobe for determining bulk compositions. Compared with all chondrule types in the H-L-LL3 ordinary chondrites, the barred olivine chondrules were found to be enriched in FeO, Al2O3, Na2O, and K2O and depleted in SiO2 and MgO; they were also found to be enriched in the feldspathic component. It is concluded that the precursor components of barred olivine chondrules consisted of a mixture of an olivine-rich component, a refractory-rich component containing Al2O3, TiO2, and CaO, and a volatile-rich alkalic component. This unusual combination implies high temperatures of melting for the refractory component and low temperatures for the volatile component, supporting the hypothesis of Grossman and Wasson (1983) that the alkalies condensed on the alumina already available.

Weisberg, Michael K.↗
NASA NTRS1986

The Extreme Ultraviolet Explorer - Optics fabrication and performance

The fabrication methods, testing and evaluation techniques, and performance results are presented for the mirrors for the Extreme Ultraviolet Explorer (EUVE). The finest mirror produced to date has a measured half energy width of 8 arcsec at optical wavelengths. With a polished nickel surface, the telescope throughput was 35 percent at 44 A and 60 percent at 256 A. The surface roughness is 20 A rms.

Green, J.↗
NASA NTRS1987

The effects of gas mixtures on ion engine erosion and performance

Erosion measurements were performed on a modified J-series 30 cm ion engine operating on xenon propellant. Erosion data was obtained by measuring the trench depth etched into masked polished metal samples for test durations of up to 24 hours. The data indicates that erosion is greatest at the cathode side of the baffle, with tantalum being the material with the least erosion of all materials tested. There is a clear indication of a significant reduction in erosion of all materials tested when nitrogen is added to the propellant. The technique used in these experiments requires test samples which are extremely smooth and flat.

Garner, Charles E.↗
NASA NTRS1986

The mirrors for the Extreme Ultraviolet Explorer

Flight mirrors for the Extreme Ultraviolet Explorer satellite are currently under fabrication. The grazing incidence metal mirrors are Wolter-Schwarzschild Type I and II and are figured by diamond turning. Imaging performance is excellent, with the figure after polishing for the best mirror being such that the full width-half maximum is 1.0 arc seconds and the half energy width is 8 arc seconds measured at visible wavelengths. Surface finish, as determined from scattering measurements in the extreme ultraviolet, is about 20 A rms.

Finley, David S.↗
NASA NTRS1987

Luminal surface fabrication for cardiovascular prostheses

Methodology used for the production of highly ordered surfaces on polytetrafluoroethylene (PTFE) Teflon, for use of this material as a surface layer in small-diameter vascular prostheses, is described. Directed argon-ion beam sputter etching is used to produce highly ordered specific surface morphologies, and photolithographic techniques are used for pattern definition. The methodology also includes surface polishing of the samples, sputter deposition of the intermediary layer of gold to enhance photoresist adhesion and improve pattern resolution, and rotating of the sample to minimize the effects of ion-beam nonuniformity and asymmetry. Use of these techniques resulted in the formation of regular arrays of sharply defined hexagonal pillars with smooth vertical walls and large relief.

Deininger, William D.↗
NASA NTRS1987

Transition boiling heat transfer and the film transition regime

The Berenson (1960) flat-plate transition-boiling experiment has been recreated with a reduced thermal resistance in the heater, and an improved access to those portions of the transition boiling regime that have a steep negative slope. Tests have been made in Freon-113, acetone, benzene, and n-pentane boiling on horizontal flat copper heaters that have been mirror-polished, 'roughened', or teflon-coated. The resulting data reproduce and clarify certain features observed by Berenson: the modest surface finish dependence of boiling burnout, and the influence of surface chemistry on both the minimum heat flux and the mode of transition boiling, for example. A rational scheme of correlation yields a prediction of the heat flux in what Witte and Lienhard (1982) previously identified as the 'film-transition boiling' region. It is also shown how to calculate the heat flux at the boundary between the pure-film, and the film-transition, boiling regimes, as a function of the advancing contact angle.

Ramilison, J. M.↗
NASA NTRS1987

Shock effects and argon loss in samples of the Leedey L6 chondrite experimentally shocked to 29-70 GPa pressures

The recovery of polished 600-micron-thick 7-mm-diameter disk samples and powder samples of the Leedey L6 chondrite from 29-70-GPa experimental shocks is investigated experimentally under vacuum conditions, with a focus on the possible direct shock loss of radiogenic Ar. The results of petrographic examination of the shocked samples and Ar isotope measurements are presented in tables, graphs, and micrographs and characterized in detail. The principal damage mechanisms are identified as mechanical disaggregation and increasing cataclasis, with little melting. The degassing of radiogenic Ar is found to be relatively modest and to increase with shock pressure and sample porosity; it is attributed to a combination of mechanical grain disruption and feldspar melting. It is inferred that Ar loss in naturally shocked materials (especially those showing few signs of melting) probably occurs during extended exposure to high temperatures during impact formation.

Bogard, Donald↗
NASA NTRS1988

Sectioning Coated Specimens Without Edge Rounding

New method devised for preparation of cross sections of coated specimens for scanning electron microscopy or energy-dispersive analysis without rounding edges of coatings. After cutting and polishing, specimen section remains smooth and flat so it can be examined under high magnification out to edge of coating. Sectioned blade first electroplated with hard nickel 0.003 in., then encapsulated in two layers of material: soft conductive material at bottom and 0.25 in. of hard diallyl phthalate at top. Nickel plate provides electrical path from surface of section to conductive material below.

Mckechnie, Timothy N.↗