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NASA NTRS1982

Experimental determination of the spinel-garnet boundary in a Martian mantle composition

The high pressure reaction orthopyroxene + clinopyroxene + spinel to garnet + olivine is applicable to the mantle of Mars. Experimental reversals of this reaction in the system CaO-MgO-FeO-Al2O3-SiO2 have been made in the range 1000-1200 C using the bulk composition proposed by Morgan and Anders (1980). At 1000 C, 1100 C, and 1200 C the garnet-out equilibrium is bracketed at 10.8 + or - 0.5, 12.6 + or - 0.5, and 15.2 + or - 0.5 kbars, respectively. A dP/dT slope of 14.0 bar/K at 1000 C increasing to 26.0 bar/K at 1200 C has been inferred. Depending on bulk composition, the mantle of Mars is inferred to have a phase assemblage of either olivine + clinopyroxene + orthopyroxene + garnet or olivine + clinopyroxene + garnet + spinel. In the second, the partial melts will not be buffered by olivine and orthopyroxene and will have markedly lower silica activities than those of the terrestrial mantle.

Patera, E. S.↗

NASA NTRS1982

The Apollo 14 regolith - Petrology of cores 14210/14211 and 14220 and soils 14141, 14148, and 14149

New modal data are presented for continuous polished thin sections from double drive tube 14210/14211, and single drive tube 14220, and for polished grain mounts of four soils from the double drive tube, one from the single drive tube, and the soils 14148 (trench top), 14149 (trench bottom), and 14141 (Cone Crater). Modal data show that the Cone Crater soil is immature, whereas the 'smooth plains' soils are mature and rich in agglutinates and breccias. Neither core exhibits any major variations with depth. Microprobe analyses of mineral and glass fragments are consistent with derivation of the soils predominantly from the local rocks, with about 5-11% exotic mare component indicated by the modal data. About 4% of the glasses are SiO2- and K2O-rich granitic glasses which are comminuted mesostasis from the local melt rocks. The soils are depleted in feldspar relative to the source rocks. The preferred explanation for this depletion is that feldspar is concentrated in the less than 10 microns fines and is consumed in the formation of agglutinates, regolith breccias, and feldspathic glass.

Simon, S. B.↗

NASA NTRS1982

Lunar regolith - Petrology of the less than 10 micron fraction

Petrographic data for the less than 10 micron fraction from four lunar surface soils are presented in an attempt to characterize the modal mineralogy of this fraction. Individual grains were studied with a scanning/transmission electron microscope with an attached energy dispersive spectrometer. Energy dispersive analytical data are presented, and comparative modal petrology of the soils is shown. Also presented are grain size histograms and diagrammatic representation of comparative modal data for the soils, as well as the feldspathic glass/mafic glass ratio, plagioclase/mafic mineral ratio, and SiO2 modal percent for different size fractions of the four types of soil. The modal results are consistent with chemical data regarding feldspathic and KREEP enrichment in the finest fraction. Grain-size distributions are inconsistent with a fine-grained exotic component derived from distant sources.

Devine, J. M.↗

NASA NTRS1982

Sulfide saturation of basalt and andesite melts at high pressures and temperatures

When the sulfur content of an Fe-bearing magma exceeds the saturation limit for the bulk composition, an immiscible iron sulfide melt fraction separates. For an understanding of the geochemistry of sulfur-bearing magmatic systems, more information is needed regarding the solubility of metal sulfide in silicate melt at its source and the solubility changes as a function of changing intensive and extensive variables. In the present investigation, the sulfur saturation surface is determined for the pressure range from 12.5 to 30 kbar and the temperature range from 1300 to 1460 C for three silicate melt compositions representing a range of SiO2 and FeO compositions.

Wendlandt, R. F.↗

NASA NTRS1983

Influence of the Mediterranean outflow on the isotopic composition of neodymium in waters of the North Atlantic

Measurements of the Nd-143/Nd-144 ratio, expressed as epsilon-Nd(0), made in sea water samples obtained at depths from 0 to 4850 m at stations 95, 101, and 30 of North-Atlantic cruise 109-1 of the RV Atlantis II are reported and analyzed. In the 1000-m sample at station 95, determined by salinity, O2, PO4, NO3, SiO2, potential-temperature, and pressure profiles to correspond to the core of the Mediterranean outflow, an epsilon-Nd(0) value of -9.8 + or - 0.6 was found, a significant increase over the layers above and below, where epsilon-Nd(0) is about -12. Mixing estimations give a value for pure Mediterranean waters of approximately -6; continental drainage or volcanic deep-sea sediments are considered possible sources for this more radiogenic Nd. The epsilon-Nd(0) peak in the western North Atlantic (station 30) is found at the surface, and the deep waters are less radiogenic than in the eastern North Atlantic, suggesting multiple Nd sources. Possible origins and distribution mechanisms are discussed.

Piepgras, D. J.↗

NASA NTRS1983

An ancient depleted mantle source for Archean crust in Rajasthan, India

Data from an initial set of Banded Gneiss Complex (BGC) east of the city of Udaipur are given. In this region the BGC comprises typical grey gneiss with variably abundant granitic and mafic components. Efforts to date were concentrated on the mafic components which, based on chemical data, appear to be metavolcanic. All samples examined were recrystallized under amphibolite or upper amphibolite facies conditions. Pertinent chemical data for a small number of amphibolites analyzed so far are: SiO2: 49-53%; MgO: 5.7-7.3%; K2O: 0.24-0.50%; Ni: 106-140 ppm; Zr: 37-159 ppm. From Sm/Nd data, all amphibolites show small to moderate LREE enrichments.

Macdougall, J. D.↗

NASA NTRS1984

Photodeposition of Nitride Insulators on 3-5 Substrates

Laser assisted chemical vapor deposition (LCVD) of nitride insulators, using an excimer laser operating on either KrF or ArF transitions (248 nm or 193 nm respectively) was explored. The properties of silicon nitride films Deposited with 193 nm photons on quartz and silicon substrates in a SiH4, NH3, N2 and He mixture are discussed. Aluminum films were deposited at substrate temperatures from room temperature to 200 C using 248 nm or 193 nm photons to dissociate trimethylaluminum (TMA). Deposition of Al films were investigated to isolate problems associated with TMA such as C and O contamination during AlN depositions. The Al film properties were evaluated on SiO2 and Si substrates. Preliminary results were obtained for aluminum nitride films using TMA and NH3 as the gas phase Al and N donors. The properties of Cr films deposited over areas 5 square cm using 193 nm or 248 nm photons to dissociate Cr(CO) were investigated.

Collins, G. J.↗

NASA NTRS1984

Magnetic properties of Martian surface material

The hypothesis that the magnetic properties of the Martian surface material are due to the production of a magnetic phase in the clay mineral nontronite by transient shock heating is examined. In the course of the investigation a magnetic material is produced with rather unusual properties. Heating from 900 C to 1000 C, of natural samples of nontronite leads first to the production of what appears to be Si doped maghemite gamma (-Fe2O3). Although apparently metastable, the growth of gamma -Fe2O3 at these temprtures is unexpected, and its relative persistence of several hours at 1000 C is most surprising. Continued annealing of this material for longer periods promote the crystallization of alpha Fe2O3 and cristobalite (high temperature polymorph of SiO2). All available data correlate this new magnetic material with the cristobalite hence our naming it magnetic ferri cristobalite. Formation of this magnetic cristobalite, however, may require topotactic growth from a smectite precursor.

Hargraves, R. B.↗

NASA NTRS1983

Carbon, oxygen and their interaction with intrinsic point defects in solar silicon ribbon material: A speculative approach

Some background information on intrinsic point defects is provided and on carbon and oxygen in silicon in so far as it may be relevant for the efficiency of solar cells fabricated from EFG ribbon material. The co-precipitation of carbon and oxygen and especially of carbon and silicon self interstitials are discussed. A simple model for the electrical activity of carbon-self-interstitial agglomerates is presented. The self-interstitial content of these agglomerates is assumed to determine their electrical activity and that both compressive stresses (high self-interstitial content) and tensile stresses (low self-interstitial content) give rise to electrical activity of the agglomerates. The self-interstitial content of these carbon-related agglomerates may be reduced by an appropriate high temperature treatment and enhanced by a supersaturation of self-interstitials generated during formation of the p-n junction of solar cells. Oxygen present in supersaturation in carbon-rich silicon may be induced to form SiO, precipitates by self-interstitials generated during phosphorus diffusion. It is proposed that the SiO2-Si interface of the precipates gives rise to a continuum of donor stables and that these interface states are responsible for at least part of the light inhancement effects observed in oxygen containing EFG silicon after phosphorus diffusion.

Goesele, U.↗

NASA NTRS1983

Computer simulation of surface and film processes

Adequate computer methods, based on interactions between discrete particles, provide information leading to an atomic level understanding of various physical processes. The success of these simulation methods, however, is related to the accuracy of the potential energy function representing the interactions among the particles. The development of a potential energy function for crystalline SiO2 forms that can be employed in lengthy computer modelling procedures was investigated. In many of the simulation methods which deal with discrete particles, semiempirical two body potentials were employed to analyze energy and structure related properties of the system. Many body interactions are required for a proper representation of the total energy for many systems. Many body interactions for simulations based on discrete particles are discussed.

Tiller, W. A.↗

NASA NTRS1984

Flat-plate solar array project process development area, process research of non-CZ silicon material

The program is designed to investigate the fabrication of solar cells on N-type base material by a simultaneous diffusion of N-type and P-type dopants to form an P(+)NN(+) structure. The results of simultaneous diffusion experiments are being compared to cells fabricated using sequential diffusion of dopants into N-base material in the same resistivity range. The process used for the fabrication of the simultaneously diffused P(+)NN(+) cells follows the standard Westinghouse baseline sequence for P-base material except that the two diffusion processes (boron and phosphorus) are replaced by a single diffusion step. All experiments are carried out on N-type dendritic web grown in the Westinghouse pre-pilot facility. The resistivities vary from 0.5 (UC OMEGA)cm to 5 (UC OMEGA)cm. The dopant sources used for both the simultaneous and sequential diffusion experiments are commercial metallorganic solutions with phosphorus or boron components. After these liquids are applied to the web surface, they are baked to form a hard glass which acts as a diffusion source at elevated temperatures. In experiments performed thus far, cells produced in sequential diffusion tests have properties essentially equal to the baseline N(+)PP(+) cells. However, the simultaneous diffusions have produced cells with much lower IV characteristics mainly due to cross-doping of the sources at the diffusion temperature. This cross-doping is due to the high vapor pressure phosphorus (applied as a metallorganic to the back surface) diffusion through the SiO2 mask and then acting as a diffusant source for the front surface.

Campbell, R. B.↗

NASA NTRS1983

Process research of non-CZ silicon material

High risk, high payoff research areas associated with the Westinghouse process for producing photovoltaic modules using non- CZ sheet material were investigated. All work was performed using dendritic web silicon. The following tasks are discussed and associated technical results are given: (1) determining the technical feasibility of forming front and back junctions in non-CT silicon using dopant techniques; (2) determining the feasibility of forming a liquid applied diffusion mask to replace the more costly chemical vapor deposited SiO2 diffusion mask; (3) determining the feasibility of applying liquid anti-reflective solutions using meniscus coating equipment; (4) studying the production of uniform, high efficiency solar cells using ion implanation junction formation techniques; and (5) quantifying cost improvements associated with process improvements.

Source record↗

NASA NTRS1983

Temperatures of shock-induced shear instabilities and their relationship to fusion curves

New emission spectra for MgO and CaAl2Si2O8 (glass) are observed from 430 to 820 nm. Taken with previous data, it is suggested that transparent solids display three regimes of light emission upon shock compression to successively higher pressures: (1) characteristic radiation such as observed in MgO and previously in other minerals, (2) heterogeneous hot spot (greybody) radiation observed in CaAl2Si2O8 and previously in all transparent solids undergoing shock-induced phase transformations, and (3) blackbody emission observed in the high pressure phase regime in NaCl, SiO2, CaO, CaAl2Si2O8, and Mg2SiO4. The onset of the second regime may delineate the onset of shock-induced polymorphism whereas the onset of the third regime delineates the Hugoniot pressure required to achieve local thermal equilibrium in the shocked solid. It is also proposed that the hot spot temperatures and corresponding shock pressures determined in the second regime delineate points on the fusion curves of the high pressure phase.

Schmitt, D. R.↗

NASA NTRS1984

Silicon nitride films deposited with an electron beam created plasma

The electron beam assisted chemical vapor deposition (EBCVD) of silicon nitride films using NH3, N2, and SiH4 as the reactant gases is reported. The films have been deposited on aluminum, SiO2, and polysilicon film substrates as well as on crystalline silicon substrates. The range of experimental conditions under which silicon nitrides have been deposited includes substrate temperatures from 50 to 400 C, electron beam currents of 2-40 mA, electron beam energies of 1-5 keV, total ambient pressures of 0.1-0.4 Torr, and NH3/SiH4 mass flow ratios of 1-80. The physical, electrical, and chemical properties of the EBCVD films are discussed.

Bishop, D. C.↗

NASA NTRS1984

Two forsterite-bearing FUN inclusions in the Allende meteorite

Two forsterite-, fassaite-, spinel-rich inclusions in Allende which share common mineralogy and texture with three previously described inclusions are described. These inclusions were at least partially molten at temperatures over 1400 C, and their crystallization sequence was spinel, olivine, fassaite, and Mg-rich melilite. At least some of them experienced partial volatilization of MgO and SiO2 from their outer margins. At least one of the inclusions is highly enriched in MgO relative to CaO and Al2O3 compared to Allende coarse-grained inclusions, although it is just as strongly enriched in refractory trace elements as the latter, relative to C1 chondrites. Two of the objects are FUN inclusions on the basis of their oxygen, magnesium, and silicon isotopic compositions.

Clayton, R. N.↗

NASA NTRS1984

Chemical and physical studies of type 3 chondrites. III Chondrules from the Dhajala H3.8 chondrite

Thermoluminescence (TL) properties have been measured in 58 chondrules separated from the Dhajala H3.8 chondrite. The pyrolytic chondrules are noted to have higher mass-normalized TL values than nonpyrolytic ones. Significant correlations are noted between log(TL) and the bulk CaO, Al2O3, and MnO content of the chondrules. These, together with correlations of log(TL) with the CaO, Al2O3, SiO2 and normative anorthite content of the chondrule glass, indicate an association of the TL and the abundance and position of mesostasis. It is suggested that the TL level in a given chondrule is governed by its bulk composition and metamorphism, and it is hypothesized that the devitrification resistance of unequilibrated chondrule mesostasis explains the unequilibration of certain chondrules in type 3 ordinary chondrites.

Sears, D. W. G.↗

NASA NTRS1983

Description of the containerless melting of glass in low gravity

A brief description is given of a single-axis, acoustic levitator/furnace apparatus used to position, heat, melt, and quench multicomponent oxide, glass-forming compositions in low gravity. This apparatus is capable of processing eight approximately spherical samples (about 6 mm diameter) at temperatures up to 1550 C in a dry air atmosphere. Results are also presented for a containerless melting experiment conducted on SPAR VI where a ternary CaO-Ga2O3-SiO2 composition was levitated and quenched to a glass. Selected properties of the glass prepared on SPAR VI are compared with the properties of glass samples of identical composition prepared on earth.

Ray, C. S.↗

NASA NTRS1984

Major element chemical compositions of chondrules in unequilibrated chondrites

The chemical compositions (except for metals and sulfides in chondrules) of more than 500 chondrules from unequilibrated E, H, L, LL, and C chondrites were measured using a broad beam of an electron-probe microanalyzer. The compositions of chondrules can be represented by various mixtures of normative compositions of olivine, low-Ca pyroxene, plagioclase, and high-Ca pyroxene with minor amounts of spinel, feldspathoid, SiO2-minerals, etc., indicating that the chondrule precursor materials consisted of aggregates of these minerals. The Al, Na, and K contents of most chondrules reflect the compositions of the ternary feldspar (An-Ab-Kf) of the chondrule precursor materials, and chemical types of chondrules (KF, SP, IP, and CP) are defined on the basis of the atomic proportion of Al, Na, and K.

Ikeda, Y.↗