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At least 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Low cost silicon solar array project silicon materials task: Establishment of the feasibility of a process capable of low-cost, high volume production of silane (step 1) and the pyrolysis of silane to semiconductor-grade silicon (step 2)

A quartz fluid bed reactor capable of operating at temperatures of up to 1000 C was designed, constructed, and successfully operated. During a 30 minute experiment, silane was decomposed within the reactor with no pyrolysis occurring on the reactor wall or on the gas injection system. A hammer mill/roller-crusher system appeared to be the most practical method for producing seed material from bulk silicon. No measurable impurities were detected in the silicon powder produced by the free space reactor, using the cathode layer emission spectroscopic technique. Impurity concentration followed by emission spectroscopic examination of the residue indicated a total impurity level of 2 micrograms/gram. A pellet cast from this powder had an electrical resistivity of 35 to 45 ohm-cm and P-type conductivity.

Breneman, W. C.↗
NASA NTRS1978

Plasma cleaning device

High vacuum cleaning of contaminated surfaces such as hydrocarbon containment films can be accomplished by a plasma cleaning device which includes a plasma discharge housing to permit generation of a plasma in an environment having a higher pressure than the surface which is to be cleaned. A ground electrode and a radio frequency electrode partially surround a quartz plasma tube, for the introduction of an ionizable gas. These electrodes ionize the gas and help generate the plasma. This plasma flows through a non-constrictive aperture, through the plasma discharge housing and then on to the contaminated surface.

Shannon, R. L.↗
NASA NTRS1978

Measurements of material properties for solar cells

Measurements on two candidate materials for space flight are reported. The observed optical transmittance of aluminum films vapor deposited on fused quartz showed anomalously high transmittance thru 400 A and 600 A and showed an effective skin depth of 110 A in the latter part of the 1000 A thickness. KAPTON films are shown by their optical transmission spectra to have an energy gap for electron excitation of approximately 2.5 eV, which value depends on the thickness as manufactured. The resistance of KAPTON film to ionizing radiation is described by their optical spectra and their electron spin resonance spectra.

Castle, J. G., Jr.↗
NASA NTRS1978

Electronic measurement of variable torques in precision work technology

Approaches for the determination of torques on the basis of length measurements are discussed. Attention is given to torque determinations in which the deformation of a shaft is measured, an electric measurement of the torsion angle, and an approach proposed by Buschmann (1970). Methods for a torque determination conducted with the aid of force measurements make use of piezoelectric approaches. The components used by these methods include a quartz crystal and a charge amplifier.

Maehr, M.↗
NASA NTRS1978

Post-shock temperatures in minerals

Post-shock temperatures were measured in a wide variety of materials, including those of geophysical interest such as silicates by using an infrared detector to determine the brightness temperature of samples shocked to pressures in the range 5 to approximately 30 GPa. Measurements were made in the 4.5 to 5.75 micron and in the 7 to 14 micron wavelength ranges. Reproducible results, withe the temperatures in the two wavelength bands generally in excellent agreement, were obtained for aluminum-2024 (10.5 to 33 GPa; 125 to 260 C), stainless steel-304 (11.5 to 50 GPa; 80 to 350 C), crystalline quartz (5.0 to 21.5 GPa; 80 to 250 C) forsterite (7.5 to 28.0 GPa; approximately 30 to 160 C) and Bamble bronzite (6.0 to 26.0 GPa; approximately 30 to 225 C). Results are generally much higher at low pressures than the values calculated assuming a hydrodynamic rheology and isentropic release parallel to the Hugoniot but tend towards them at higher pressures.

Raikes, S. A.↗
NASA NTRS1978

The meaning of desert color in earth orbital photographs

The color of desert surfaces as seen in earth orbital photographs is indicative of soil composition. Apollo-Soyuz photographs of the Sturt and Simpson Deserts of Australia confirm that sand grains become redder as the distance from the source increases. Reddening is caused by a thin iron-oxide coating on individual sand grains and can be used, in some cases, to map relative-age zones. Photographs of the Western (Libyan) Desert of Egypt indicate three distinct and nearly parallel color zones that have been correlated in the field with: (1) arable soil composed of quartz, clay, and calcium carbonate particles; (2) relatively active sand with or without sparse vegetation; and (3) relatively inactive sand mixed with dark (desert-varnished) pebbles. The youngest sands are in the form of longitudinal dunes, which are migrating to the south-southeast along the prevailing wind direction. Some of the young dune fields are encroaching on the western boundary of the fertile Nile Valley.

El-Baz, F.↗
NASA NTRS1977

Photodecomposition of chloromethanes adsorbed on silica surfaces

Irradiation of CCl4, CFCl3, and CF2Cl2 in the presence of C2H6 in vessels containing silica sand or fused quartz tubing results in the formation of chlorine-containing products. The formation of these compounds occurs at wavelengths extending up to approximately 400 nm, that is, at wavelengths well beyond the absorption threshold of the chloromethanes in the gas phase. It is suggested that CCl4 adsorbed on silica surfaces photodissociates to yield CCl3 and CCl2 species. The poor material balance obtained in these experiments indicates that several of the chlorine-containing fragments are strongly adsorbed on the surface. At a CCl4 pressure of 13 Pa (0.1 torr), photolysis with 366 nm light in the presence of sand results in the decomposition of one molecule for every 10,000 photons striking the surface. Under otherwise identical conditions, the photon-induced breadkdown of CFCl3 and CF2Cl2 is respectively only 10% or 3% as efficient.

Ausloos, P.↗
NASA NTRS1978

The semiconductivity and stability of palladium oxide

Palladium metal films are prepared on quartz substrates by RF sputtering from a pure palladium target in an argon atmosphere. These films are then oxidized in air or in an oxygen atmosphere at 700 C for periods between 24 hr and 6 days. Either treatment is found to produce good-quality thin films of PdO with a uniform orange transmission. Attention is focused on optical and electrical conductivity measurements made on PdO films with a view toward determining their band gap, conductivity and thermal stability in vacuum and in the presence of oxygen. It is shown that hydrogen greatly reduces the thermal stability of PdO. The film decomposes to Pd metal by 350 K in the presence of hydrogen as compared to a temperature of about 580 K in vacuum.

Rey, E.↗
NASA NTRS1978

Shear strength of metal - SiO2 contacts

The strength of the bond between metals and SiO2 is studied by measuring the static coefficient of friction of metals contacting alpha-quartz in ultrahigh vacuum. It was found that copper with either chemisorbed oxygen, nitrogen or sulphur exhibited higher contact strength on stoichiometric SiO2 than did clean copper. Since the surface density of states induced by these species on copper is similar, it appears that the strength of the interfacial bond can be related to the density of states on the metal surface.

Pepper, S. V.↗
NASA NTRS1978

High-purity silicon for solar cell applications

The article discusses the production of solar cells from high-purity silicon. The process consists of reducing the level of impurities in the raw materials, preventing material contamination before and after entering the furnace, and performing orders-of-magnitude reduction of metal impurity concentrations. The high-purity raw materials are considered with reference to carbon reductants, silica, and graphite electrodes. Attention is also given to smelting experiments used to demonstrate, in an experimental-scale furnace, the production of high-purity SoG-Si. It is found that high-purity silicon may be produced from high-purity quartz and chemically purified charcoal in a 50-kVA arc furnace. The major contamination source is shown to be impurities from the carbon reducing materials.

Dosaj, V. D.↗
NASA NTRS1977

Design, fabrication and expected performance of the HEAO-B X ray telescope

The X-ray telescope of the second High Energy Astronomy Observatory (HEAO-B) is described. The design consists of four concentric paraboloid/hyperboloid pairs. Focal length is 3.44 meters, paraboloid diameters vary from 580-336 mm, grazing angles vary from 70 to 40 arcmin for paraxial rays, segment lengths are 511 mm. The reflecting surfaces are nickel-coated fused quartz and the resolution is limited by assembly errors (for small field angles) and design aberrations (for large field angles). The local slope, roundness, and surface roughness are identified as the primary optical tolerances connected with the individual elements.

Van Speybroeck, L. P.↗
NASA NTRS1977

Compositional dispersions in lunar and terrestrial basalts

The dispersions in composition observed among samples of terrestrial basalts with known field relationships are compared with those of various subgroups of lunar mare basalts. The comparison indicates that there are no substantial reasons based on trace-element data to require that large numbers of different basalts were sampled at each Apollo site. The Apollo 15 olivine and quartz normative basalts and the Apollo 12 ilmenite and olivine basalts show compositional variations which are no more pronounced than those found within single terrestrial flows, whose inhomogeneity in horizontal section has been demonstrated. The inhomogeneities of the parent rocks in the case of the Apollo 12 and 15 basalts on a scale of centimeters overshadow any differences which might exist among different general regions of the lava flows from which these samples might have derived.

Haskin, L. A.↗
NASA NTRS1977

Chemical variation and fractionation of KREEP basalt magmas

The fact that 53 Apollo 15 igneous KREEP basalts show a range of 100 Mg/(Mg + Fe) from 73 to 35, and that there are systematic variations in K2O and trace element abundances with the Mg/(Mg + Fe) ratio, suggests that the KREEP basalts are a magma series generated by fractional crystallization processes. Experimental and chemical evidence indicate that this magma series results from low-pressure, possibly subvolcanic, fractional crystallization of a magnesian parental liquid (100 Mg/(Mg + Fe) equal to approximately 72) by removal of low-Ca pyroxene and plagioclase, with eventual production of liquids similar in composition to 15405 quartz-monozodiorites. One soil sample, SAO 465-11, corresponds to the postulated parental liquid, which might have been a direct partial melt of troctolitic materials in the deep lunar crust.

Irving, A. J.↗
NASA NTRS1977

Petrology of four clasts from consortium breccia 73215

One felsite ('granite') and three ANT-suite anorthositic gabbro clasts extracted from breccia 73215 are described. The felsite clast has two components - fragments of crystalline felsite and veins and patches of felsic glass. The crystalline felsite, which consists largely of a vermicular intergrowth of quartz and Ba-K-feldspar, crystallized from a highly differentiated melt between 3.90 and 4.05 b.y. The felsic glass component consists of crystallized brown and colorless glasses and uncrystallized colorless glass which are all K and Si rich. The relation of glass features to past heating and the breccia-forming event is considered. In the three anorthositic gabbros, which have similar mineralogies and gradational textures, plagioclase is dominant, and olivine and orthopyroxene are the major mafic minerals. The petrologic data suggest that the gabbros formed as heated, partly melted, and/or recrystallized polymict breccias. It is possible that the approximately 4.25 b.y. age obtained for the three rocks is the date of the melting/recrystallization event.

James, O. B.↗
NASA NTRS1977

Provenance of Apollo 15 deep drill core sediments

Modal analysis and electron probe microanalysis were performed on polished thin sections prepared from Apollo 15 deep drill core soils in an effort to characterize their provenance. The particles were in the 0.25-1.00 mm size range. The particles were classified into mineral fragments, agglutinates, glasses, rock fragments, and breccias. The results show that highland and mare material occur in the core in an approximately 60:40 ratio, with mare component generally increasing from bottom to top in the core. Quartz-normative basalts are nearly twice as abundant as olivine basalts. Nonmare sources include KREEP basalt flow units from some depth in the crust, excavated by cratering events and supplied to the site as 'rays'.

Basu, A.↗
NASA NTRS1977

Shock compression and adiabatic release of a titaniferous mare basalt

A report is presented regarding the dynamic properties of a rock indigenous to the mare basins of the moon. The reported data were obtained in a study of sample 70215, a very titanium-rich basalt (58% pyroxene, 18% ilmenite, 15% plagioclase, 6% olivine, and 3% quartz by weight). This rock is probably representative of a class of the earliest mare-filling extrusive rocks which are exposed on the present lunar surface. Two series of experiments were performed. One set of experiments involved the measuring of Hugoniot and release adiabats to 15.7 GPa with a propellant gun apparatus. In the second set of experiments, a light-gas gun was employed to yield Hugoniot data at about 120 GPa and release states at about 90 GPa. Lunar basalt 70215 appears to be among the densest rocks in the present lunar sample collection, having a crystal density of 3.38 g/cu cm and a porosity of about 1.3%. The results of the experiments have important implications for both the degree of shock metamorphism expected for impact processes and the extent of ejecta transport on mare surfaces with high-titanium basalt composition.

Ahrens, T. J.↗
NASA NTRS1978

Long-duration high-efficiency operation of a continuously pulsed copper laser utilizing copper bromide as a lasant

A copper laser utilizing copper bromide as a lasant and neon as the buffer gas has been operated at an average laser power of between 16 and 19.5 W for a period of 68 h. Lasing was attained at a pulsing rate of 16.7 kHz in a quartz discharge tube 2.5-cm in diameter with an electrode separation of 200 cm. The laser energy/pulse and peak power/pulse corresponding to an average power of 19.5 W are 1.2 mJ and 30 kW, respectively. The ratio of laser power at 510.6 and 578.2 nm varied from 3.9 to 1.1 corresponding to a total average laser power of 4 and 18 W, respectively. The highest wall plug and capacitor efficiency measured during 68 h of operation were 0.7 and 1.1%, respectively.

Chen, C. J.↗
NASA NTRS1975

Anomalous low-K silicate melt inclusions in ilmenite from Apollo 17 basalts

Primary silicate melt inclusions in ilmenite crystals in seven mare basalt samples were analyzed by electron microprobe, and analyses were made of their host and associated phases. Two distinct and restricted chemical composition ranges are drawn: high-K and low-K. The high-K samples are nearly identical with the granitic residual liquid, averaging a weight percentage of 6.27% K20, 76.3% SiO2, plus 82% normative quartz and orthoclase. It is noted that no low-K melt was found as a re-entrant or interstitial inclusion in any sample; only as isolated inclusions in illmenite.

Roedder, E.↗