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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Bulk, rare earth and other trace elements in Apollo 14 and 15 and Luna 16 samples

The chemical abundances were measured by instrumental and radiochemical neutron activation analysis in a variety of lunar specimens. Apollo 14 soils are characterized by significant enrichments of Al2O3, Na2O and K2O and depletions of TiO2, FeO, MnO and Cr2O3 relative to Apollo 11 and to most of Apollo 12 soils. The uniform abundances in 14230 core tube soils and three other Apollo 14 soils indicate that the regolith is uniform to at least 22 cm depth and within approximately 200 m from the lunar module. Two Luna 16 breccias are similar in composition to Luna 16 soils. Four Apollo 15 soils (LM, STA 4, 9, and 9a) have variable compositions. Interelement correlations between MnO-FeO, Sc-FeO, V-Cr2O3 and K2O-Hf negate the hypothesis that howardite achondrites may be primitive lunar matter, argue against the fission hypothesis for the origin of the moon, and precludes any selective large scale volatilization of alkalies during lunar magmatic events.

Laul, J. C.↗
NASA NTRS1972

Bulk and rare earth abundances in the Luna 16 soil levels A and D.

Determination of the abundances of major, minor, and trace elements by means of sequential INAA (instrumental neutron activation analysis) in two Luna 16 soils, at levels A (about 7 cm depth) and D (about 30 cm depth). Abundances of the bulk elements in Luna 16 soils generally agree with the values reported by Vinogradov (1971). Elemental abundances of both bulk and trace elements are nearly the same for the two A and D soil levels. Overall, the chemical compositions of the two Luna 16 soils are more closely related to Apollo 11 soil 10084 than to Apollo 12 and 14 soils, with the exception of TiO2 abundances.-

Gillum, D. E.↗
NASA NTRS1972

Bulk, rare earth, and other trace elements in Apollo 14 and 15 and Luna 16 samples.

Measurement of 24 and 34 bulk, minor, and trace elements in lunar specimens by instrumental and radiochemical neutron activation analysis shows greater Al2O3, Na2O, and K2O abundances and higher TiO2, FeO, MnO and Cr2O3 depletions in Apollo 14 soil samples as compared to Apollo 11 samples and to most of Apollo 12 samples. The uniform abundances in 14230 core tube soils and three other Apollo 14 soils indicate that the regolith is uniform to at least 22 cm depth and within about 200 m from the lunar module.

Laul, J. C.↗
NASA NTRS1972

Rare earths and other trace elements in Apollo 14 samples.

REE and other trace elements have been determined in igneous rocks 14053, 14072, and 14310, in breccias 14063 and 14313, and in fines 14163. All materials analyzed have typical depletions of Eu except for feldspar fragments from the breccias and igneous fragments from 14063. Igneous rocks 14072 and 14053 have REE concentrations very similar to Apollo 12 basalts; 14310 has the highest REE concentrations yet observed for a large fragment of lunar basalt. The effects of crystallization of a basaltic liquid as a closed system on the concentrations of Sm and Eu in feldspar are considered. Small anorthositic fragments may have originated by simple crystallization from very highly differentiated basalt (KREEP) or by closed-system crystallization in a less differentiated starting material. Application of independent models of igneous differentiation to Sm and Eu in massive anorthosite 15415 and to Sm and Eu in lunar basalts suggests a common starting material with a ratio of concentrations of Sm and Eu about the same as that in chondrites and with concentrations of those elements about 15 times enriched over chondrites.

Helmke, P. A.↗
NASA NTRS1973

Suitability of the rare-earth compounds Dy2Ti2O7 and Gd3Al5O12 for low temperature (4K-20K) magnetic refrigeration cycle

Measurements were made of the magnetic entropy and magnetization of powered samples of the compounds Dy2Ti2O7 and Gd3Al5O12. The magnetization was measured for temperatures at and below 4.2 K, in applied fields ranging to 7.0 tesla. Isothermal changes in magnetic entropy were measured for temperatures from 1.2 to 20 K, in applied fields up to 10 tesla. The results of the measurements are consistent with a doublet ground state for Dy2Ti2O7, and an eight-fold degenerate ground state for Gd3Al5O12. Absolute values of magnetic entropy have been obtained at the lower temperatures, permitting the isotherms to be properly located in the S-H plane with the use of adiabatic magnetization data. The iso-field lines in the S-T plane were determined. The results indicate that Dy2Ti2O7 can absorb a maximum of 71 + or - 4 joules/kg of heat at 4.2 K, while Gd3Al5O12 can absorb 233 + or - joules/kg at the same temperature. The large difference between the two is most likely a result of crystal field interactions in the dysoprosium compound. Both materials can be cycled adiabatically between 4.2 and 20 K.

Flood, D. J.↗
NASA NTRS1974

Rb-Sr age and content of potassium, rubidium strontium, barium, and rare earths in surface material from the Sea of Fertility

The Luna 16 automatic station returned from the Sea of Fertility a 35 cm long column of lunar surface material. 1 g of the Luna 16 lunar surface material, taken at a depth of 22 cm, consists of fine material: surface material and fine fragments of rocks from 1 to 4 mm in diameter. Analyses made on 17 mg of the fine lunar surface material are presented. The results obtained for the Luna 16 surface material are plotted on the diagram of the isotopic evolution of strontium and show that this surface material is most depleted of radiogenic Sr-87 of all the known lunar surface materials and that the point characterizing Lunar 16 lies somewhat to the right of the line corresponding to an age of 4.6 billion years.

Allegre, C. J.↗
NASA NTRS1979

Studies of magnetostriction and spin polarized band structures of rare earth intermetallics

Anisotropic magnetostriction measurements of R6Fe23, R = (Tb, Dy, Ho, and Er) were carried out from 77 K to room temperature. Magnetic fields up to 2.1 Tesla were applied. All the compounds exhibited large magnetostrictions at 77 K, the largest effect being obtained for Tb6Fe23. Saturation magnetostriction values for the compounds were also determined for 77 K and room temperature. Results of the temperature dependence of magnetostriction for Er6Fe23 are in good agreement with Callen and Callen's single ion theory. Therefore, the main sources of magnetostriction in this compound is the Er ion. The spin-up and spin-down electronic energy bands, the density of states and the magnetic moments of YCo5, SmCo5, and GdCo5 were calculated by the spin polarized augmented plane wave technique. The calculations obtained show the origin of the moment, provide good estimates of its magnitude and variation, and the reasons for those variations. They also show the important role of partial charge transfer and of d-d electronic coupling. Calculations for LaNi5 and GdNi5 systems are discussed.

Wallace, W. E.↗
NASA NTRS1980

Experimental mineral/liquid partition coefficients of the rare earth elements /REE/, Sc and Sr for perovskite, spinel and melilite

Experimental determinations of the mineral/liquid partition coefficients of REE (La, Sm, Eu, Gd, Tb, Yb and Lu), Sc and Sr are reported for the minerals perovskite, spinel and melilite in synthetic systems. Perovskite concentrates light REE with respect to the residual liquid but shows no preference for heavy REE. Spinel greatly discriminates against the incorporation of REE, especially light REE, into its crystal structure. The partition of REE into melilite from a silicate liquid is quite dependent upon both the bulk melt and melilite solid-solution (gehlenite and akermanite components) compositions. As such, melilite can be enriched in REE or will reject REE with corresponding strong negative or strong positive Eu anomalies, respectively.

Nagasawa, H.↗