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Results for “Silicates”

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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

A shock-induced phase change in iron-silicate garnet.

Hugoniot measurements on iron-silicate garnet demonstrate that above a shock pressure of about 205 kbar transition to a high-pressure phase(s), having an apparent zero-pressure density and bulk modulus of 4.44 g/cu cm and 3.3 Mbar, occurs. Crystal chemical systematics and Debye-Scherrer X-ray patterns of a recovered phase(s), which may be the shock-induced high-pressure form, suggest possible formation of a phase with a density of 4.48/cu cm. Occurrence of such a polymorph of garnet in the mantle would give rise to an increase in density and seismic velocity below 600 km in the earth.

Ahrens, T. J.↗
NASA NTRS1973

Microwave emission from granular silicates

Experimental finding is that mass absorption coefficient is independent of frequency but highly dependent on moisture content; effective conductivity increases with frequency, and low tangent is independent of frequency. Computed values of electrical properties are in rough numerical agreement with extrapolated laboratory values on other silicate materials.

Conel, J. E.↗
NASA NTRS1972

Partitioning of potassium between silicates and sulphide melts - Experiments relevant to the earth's core.

The partitioning of potassium between roedderite, K2Mg5Si12O30 and an Fe-FeS melt was investigated at temperatures about 40 C above the Fe-FeS eutectic. Roedderite was considered a prime candidate for one of the potassium-bearing phases in the primitive earth because roedderite and merrihueite are the only two silicates containing essential potassium which have been identified in stony meteorites. Application of the results to a primitive chondritic earth is discussed, and it is concluded that extraction of most of the earth's potassium into the Fe-FeS core would occur under the conditions in the early earth.-

Goettel, K. A.↗
NASA NTRS1973

Extinction and scattering by several types of silicate sphere of radius 0.05-1.0 micron, for the wavelength range 0.21-50 microns.

The exact calculation of scattering and absorption by various sub-micron sized silicate spheres is presented here, using accurately determined optical constants in the wavelength range from 50 to 0.21 microns. The extinction features near 10 and 20 microns for various samples are discussed. It is found that the ratio of peak extinction at 20 microns to that at 10 microns is constant for small particles up to 0.4-micron radius, but is less for particles of 1-micron radius. The ratio of maximum extinction in the ultraviolet to that at 10 microns decreases with increasing particle size.

Bromage, G. E.↗
NASA NTRS1973

Black silicate paints: Formulation and performance data on OSO-H

Formulations and general procedures are given for making and applying space environmentally, as well as atmospherically stable black silicate paints. Compositions are given which meet spacecraft self-contamination requirements, have excellent heat resistance, and are strongly semiconductive.

Schutt, J. B.↗
NASA NTRS1972

Partitioning of potassium between silicates and sulphide melts: Experiements relevant to the earth's core

The partitioning of potassium between roedderite, K2Mg5Si12O30 and an Fe-FeS melt was investigaged at temperatures about 40 C above the Fe-FeS eutectic. Roedderite was considered a prime candidate for one of the potassium-bearing phases in the primitive earth because roedderite and merrihueite are the only two silicates containing essential potassium which have been identified in stony meteorites. A mean K2S/FeS weight ratio of (3.340 + or - 0.015) x 0.001 was determined in these experiments; a K2S/FeS weight ratio of about 0.01 would be sufficient to extract all potassium in a chondritic earth into the core. Application of these results to a primitive chondritic earth is discussed and it is concluded that extraction of most of the earth's potassium into the Fe-FeS core would occur under the conditions in the early earth.

Goettel, K. A.↗
NASA NTRS1976

Chromium basalts - Experimental determination of redox states and partitioning among synthetic silicate phases

Experiments were performed on silicate compositions in the forsterite-anorthite-silica and forsterite-anorthite-diopside systems to determine the relative amounts of Cr(II), Cr(III), and Cr(VI) over a wide range of oxygen partial pressures from 10 to the -10th to 1 atm at 1500 and 1550 C. Redox states were measured by visible absorption spectroscopy and electron paramagnetic resonance spectroscopy and titration. It was found that Cr is present almost exclusively as Cr(III) in terrestrial basaltic liquids and as a mixture of Cr(III) and Cr(II) in lunar basaltic liquids.

Schreiber, H. D.↗