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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

A refractory glass chondrule in the Vigarano chondrite

Vigarano, a type 3 carbonaceous chondrite, contains a chondrule composed of highly refractory Ca- and Al-rich glass with minor spinel. The chondrule formed from material similar to the Ca-, Al-, Ti-rich aggregates that are common in Vigarano and other type 3 chondrites and formation of these refractory aggregates must predate formation of some Vigarano chondrules. Experiments with synthetic analogs and a comparison with studies in the system CaO-MgO-Al2O3-SiO2 indicate a temperature for formation of the chondrule at or above 1700 C followed by very rapid cooling.

Reid, A. M.↗
NASA NTRS1974

X-ray spectral microanalysis of composition of individual lunar regolith particles

Determinations were made of the chemical compositions of selected olivine crystals, spherical particles ranging in size from 170 to 350 micrometer, spinels, and magnetic particles. The olivines contain 30 to 50 mole percent fayalite. The spherical particles of various colors are aluminosilicate glasses, significantly enriched in CaO compared with the mean composition of the regolith. The degree of coloration depends on the FeO content and also the admixtures TiO2, MnO, and Cr2O3. Compositionally, the spinel was interpreted to be chromopicotites. Magnetic particles were shown to be complex intergrowths of nickelous iron and aluminosilicates. The composition of the metallic phase of one particle (in percent) was: Fe - 86, Ni - 13.6, and Co - 0.16 in combination with plagioclase and microinclusions of ilmenite in silicate. Kamacite was determined in another intergrowth of Fe, Ni, and Co.

Ilin, N. P.↗
NASA NTRS1975

On the composition of the lunar interior

There is now abundant geophysical and geochemical evidence suggesting that the moon has a thick plagioclase rich outer shell. This is most easily explained by early and extensive melting of a CaO and Al2O3 rich moon followed by fractional crystallization involving plagioclase flotation. Melilite is probably an important constituent of the interior. This model explains the seismic velocities, the mean density, and the moment of inertia of the moon. The moon is 73-88% high-temperature condensate.

Anderson, D. L.↗
NASA NTRS1975

A search for chemical laser action in low pressure metal vapor flames

Optical emissions were studied from low pressure (approximately 1 torr) dilute diffusion flames of Ca and Mg vapor with O2, N2O and mixtures of CCl4 and O2. The Ca flames with O2 and N2O revealed high vibrational excitation of the product CaO molecule (up to v=30). The flames with CCl4 revealed extreme nonequilibrium metal atom electronic excitation, up to the metal atom ionization limit (6.1 eV for Ca, 7.6 eV for Mg). The metal atom excited electronic state populations did not follow a Boltzmann distribution, but the excitation rates ('pumping rate') were found to obey an Arrhenius-type expression, with the electronic excitation energy playing the role of activation energy and a temperature of about 5000 K for triplet excited states and 2500 K for singlets (vs. approximately 500 K translational temperature).

Zwillenberg, M. L.↗
NASA NTRS1976

Amoeboid olivine aggregates in the Allende meteorite

Greyish-brown irregularly-shaped aggregates composed predominantly of olivine make up nearly 2% of the Allende meteorite by volume. Many of the aggregates are constructed of subspherical lumps of micron-sized crystals of olivine, pyroxene, nepheline and sodalite surrounded by coarser-grained olivine. Rarely, anorthite, spinel and perovskite are also present. The olivine ranges in composition from Fo64 to Fo99. Pyroxenes range from aluminous diopside to hedenbergite to very Al-rich and Ti-Al-rich varieties. The nepheline contains 1.6-2.4% K2O and 1.6-5.2% CaO but the sodalite is significantly poorer in these elements. The spinel contains 2.1-13.4% FeO. Textural information and oxygen isotopic data suggest that the aggregates are composed of primary, solid condensates from the solar nebula. The perovskite, spinel and Ti-Al-rich pyroxenes are the remains of high-temperature condensates, but the olivine compositions and the presence of feldspathoids indicate that some of the grains continued to react with the solar nebular vapor in the temperature range 500-900 K.

Grossman, L.↗
NASA NTRS1976

Composition and origin of Luna 16 aluminous mare basalts

The mineralogy and petrology of 58 lithic fragments, 52 of which are basaltic, in the Luna 16 samples were studied, with textures, and mineral and bulk compositions determined by petrographic and electron microprobe techniques. These mare basalt fragments differ from other mare basalts in being aluminous (11-20%) which results in plagioclase and (olivine) microphenocrysts; moreover, they have very low-FeO and MgO and high-CaO, FeO/MgO, and normative diopside contents.

Kurat, G.↗
NASA NTRS1978

Reactions of yttria-stabilized zirconia with oxides and sulfates of various elements

The reactions between partially stabilized zirconia, containing 8 weight-percent yttria, and oxides and sulfates of various elements were studied at 1200, 1300, and 1400 C for times to 800, 400, and 200 hours, respectively. These oxides and sulfates represent impurities and additives potentially present in gas turbine fuels or impurities in the turbine combustion air as well as the elements of the substrate alloys in contact with zirconia. Based on the results, these compounds can be classified in four groups: (1) compounds which did not react with zirconia (Na2SO4, K2SO4, Cr2O3, Al2O3 and NiO); (2) compounds that reached completely with both zirconia phases (CaO, BaO, and BaSO4); (3) compounds that reacted preferentially with monoclinic zirconia (Na2O, K2O, CoO, Fe2O3, MgO, SiO2, and ZnO); and (4) compounds that reacted preferentially with cubic zirconia (V2O5, P2O5).

Zaplatynsky, I.↗
NASA NTRS1977

Redox equilibria of multivalent ions in silicate glasses

Experimental studies were made on the compositional dependence of the redox equilibrium of Eu in synthetic silicate liquids, together with an empirical model describing the observed compositional dependence. Electron paramagnetic resonance (EPR) was used to measure the concentration ratio of Eu(2+) to Eu(3+) in various glasses formed by rapidly quenching silicate liquids. The compositional field studied comprised mixtures of SiO2, TiO2, Al2O3, CaO, MgO, and Na2O. The proposed model describes the Eu(2+)/Eu(3+) ratio over the entire compositional field in terms of parameters easily related to each glass composition. The general applicability and utility of the model is further demonstrated by its application to the Fe(2+)-Fe(3+), Ce(3+)-Ce(4+), and Cr(3+)-Cr(6+) redox reactions in binary alkali oxide silicate glasses of Li, Na, and K.

Lauer, H. V., Jr.↗
NASA NTRS1977

High-silica glass inclusions in olivine of Luna-24 samples

Optical examination of nine polished grain mounts of Luna-24 drill-core material (0.09-0.50 mm size) revealed melt inclusions in olivine crystals. Two inclusions consist of clear glass with exceptionally high Si, yet contain no visible daughter minerals and have had no reaction effects with the olivine walls. Their compositions (one has SiO2 93.8, Al2O3 1.51, FeO 2.32, MgO 1.61, CaO 0.06, Na2O less than 0.05, K2O 0.11, total 99.41%; the other is similar) are unique and quite unlike the high-Si high-K melt of granitic composition that is found as inclusions in late-stage minerals of these (and the Apollo) samples, from silicate liquid immiscibility. The host olivines are Fo73 and Fo51. The origin of the melt in the inclusions and the lack of reaction effects are perplexing unsolved problems.

Roedder, E.↗
NASA NTRS1977

Apollo 15 breccia rake samples - Mineralogy of lithic and mineral clasts

Major features of 22 Apollo 15 breccia rake samples and 30 lithic clasts in these samples are described. The range of compositions of exsolved pyroxene grains (bulk and individual lamellae) indicates a slowly cooled mare basalt source. In terms of these data the pyroxenes closely resemble pyroxenes in large anorthosite 67075. It is suggested that the pyroxene-plagioclase-olivine clast in 15146 as well as some anomalous chemical data might result from metamorphism of a mare-type basalt or from plutonic crystallization of magma with mare basalt affinity. The bulk composition of the clast in 15146 closely matches that of Apollo 15 'green glass' to which it may be related. A unique ultrabasic clast in 15360 has an unusually low CaO content and other chemical features which suggest that this sample is unlike ultrabasic samples described to date.

Steele, I. M.↗
NASA NTRS1975

Minor elements in lunar olivine as a petrologic indicator

Accurate electron microprobe analyses (approximately 50 ppm) were made for Al, Ca, Ti, Cr, Mn, and Ni in Mg-rich olivines which may derive from early lunar crust or deeper environments. Low-Ca contents consistently occur only in olivines from dunitic and troctolitic breccia: spinel troctolite and other rock types have high-Ca olivines suggesting derivation by near-surface processes. Rock 15445 has olivine with distinctly low CaO (approximately 0.01 wt.%). Chromium ranges to higher values (max.0.2 oxide wt.%) than for terrestrial harzburgites and lherzolites but is similar to the range in terrestrial komatiites. Divalent chromium may be indicated over trivalent Cr because olivines lack sufficient other elements for charge balance of the latter. NiO values in lunar specimens range from 0.00 to 0.07 wt.% and a weak anticorrelation with Cr2O3 suggests an oxidation state effect. Al2O3 values are mostly below 0.04-wt.% and show no obvious correlation with fragment type. TiO2 values lie below 0.13-wt.% and seem to correlate best with crystallization rate and plagioclase content of the host rock. High values of Al2O3 and TiO2 reported by other workers have not been confirmed, and are probably wrong.

Steele, I. M.↗
NASA NTRS1979

Refractory-element-rich inclusions in CM meteorites

Refractory-element-rich inclusions of a variety of types occur in CM meteorites. Based on detailed study of Murchison and more limited investigations of Murray, Nogoya, Cold Bokkeveld and Mighei, the most common of these inclusions are small spinel-hibonite bodies rimmed with diopside. Bulk chemical compositions are estimated to be approximately 67% Al2O3, 21% MgO, 5.5% CaO, 5.5% TiO2, and 1% SiO2. Although this chemical composition does not agree closely with current theoretically predicted compositions of early condensate assemblages, the inclusions have many features which suggest that they are indeed early condensates. These include texture, mineralogical composition, sequence of minerals and magnesium isotopic composition of hibonite. The CM refractory inclusions exhibit several differences from those observed in Allende and other CV meteorites. These probably record variations in time, place or physical conditions of origin for the two cases.

Macdougall, J. D.↗
NASA NTRS1979

Carbon dioxide electrolysis using a ceramic electrolyte

This paper discusses the results of an experimental study of the electrical aspects of carbon dioxide electrolysis using a ceramic electrolyte. The electrolyte compositions used in this study are 8% Y2O3 stabilized ZrO2, 7.5% CaO stabilized ZrO2, and 5% Y2O3 stabilized ThO2. Results indicate that the 8% Y2O3 stabilized ZrO2 is the best material to use for electrolysis, in terms of current as a function of voltage and temperature, and in terms of efficiency of oxide ion flow through it. The poorest results were obtained with the 5% Y2O3 stabilized ThO2 composition. An electrolysis system which might be employed to reclaim oxygen and carbon from effluents of space manufacturing, assuming that an industry would have to electrolyze 258,000 tonnes of CO2 per year, is predicted to require a total cell area of 110,000 sq m of 1 mm thickness and electrical capacity of 441 MW.

Erstfeld, T. E.↗
NASA NTRS1978

Chemistry of orange/black soils from core 74001/2

Double core 74001/2 soils were studied. Bulk soils and the 90-150 micrometer and less than 20 micrometer size fractions of 13 soils from the core for both major and trace elements by instrumental neutron activation analysis were analyzed. The orange and black glassy soils in the core 74001/2 are homogeneous in composition and due to their unusual compositional characteristics probably have derived from a single source with the same composition. The top of the core has been reworked to a depth of about 5 cm. The reworked layer is marked by compositional differences in the first 3 cm which reflect the addition (at least 10%) of materials including mare basalt and a CaO-rich component. The maturity profile (I sub s/FeO) clearly indicates reworking depth of about 5 cm. It is likely that at least some of the ferro-magnetically active component (including agglutinitic glass) has been 'inherited' with the added material.

Blanchard, D. P.↗
NASA NTRS1979

One atmosphere melting experiments on ilmenite basalt 12008

An evaluation of a crystal-fractionation model for Apollo 12 ilmenite basalts with melting experiments under controlled oxygen fugacities is reported. The crystallization sequence including olivine, chromium spinel, and pigeonite phases was determined, showing that the changes in melt composition are dominated by olivine crystallization and the decrease in MgO with a corresponding increase in CaO, Al2O3, and TiO2. It is concluded that the bulk composition of the ilmenite basalts was established by crystallization of olivine and minor spinel prior to the onset of pyroxene and plagioclase.

Rhodes, J. M.↗
NASA NTRS1980

Predicting major element mineral/melt equilibria - A statistical approach

Empirical equations have been developed for calculating the mole fractions of NaO0.5, MgO, AlO1.5, SiO2, KO0.5, CaO, TiO2, and FeO in a solid phase of initially unknown identity given only the composition of the coexisting silicate melt. The approach involves a linear multivariate regression analysis in which solid composition is expressed as a Taylor series expansion of the liquid compositions. An internally consistent precision of approximately 0.94 is obtained, that is, the nature of the liquidus phase in the input data set can be correctly predicted for approximately 94% of the entries. The composition of the liquidus phase may be calculated to better than 5 mol % absolute. An important feature of this 'generalized solid' model is its reversibility; that is, the dependent and independent variables in the linear multivariate regression may be inverted to permit prediction of the composition of a silicate liquid produced by equilibrium partial melting of a polymineralic source assemblage.

Hostetler, C. J.↗
NASA NTRS1974

High modulus invert analog glass compositions containing beryllia

Glass compositions having a Young's modulus of at least 15 million psi and a specific modulus of at least 110 million inches consisting essentially of, in mols, 10-45% SiO2, 2-15% Li2O, 3-34% BeO, 12-36% of at least one bivalent oxide selected from the group consisting of CaO, ZnO, MgO and CuO, 10-39% of at least one trivalent oxide selected from the group consisting of Al2O3, B2O3, La2O3, Y2O3 and the mixed rare earth oxides, the total number of said bivalent and trivalent oxides being at least three, and up to 10% of a tetravalent oxide selected from the group consisting of ZrO2, TiO2 and CeO2.

Bacon, J. F.↗
NASA NTRS1976

High modulus rare earth and beryllium containing silicate glass compositions

Glass compositions having a Young's modulus of at least 16 million psi and a specific modulus of at least 110 million inches consisting essentially of approximately, by weight, 20 to 43% SiO2, 8 to 21% Al2O3, 4 to 10% BeO, 27 to 58% of at least one oxide selected from a first group consisting of Y2O3, La2O3, Nd2O3, Ce2O3, Ce2O3, and the mixed rare earth oxides, and 3 to 12% of at least one oxide selected from a second group consisting of MgO, ZrO2, ZnO and CaO are described. The molar ratio of BeO to the total content of the first group oxides is from 1.0 to 3.0.

Bacon, J. F.↗