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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Ortho- and clinopyroxene compositions in ordinary chondrites and related blander model calculation procedures

Chemical analyses of the orthopyroxene and clinopyroxene compositions in chondrites are reported. Standard microprobe techniques to 15 kilovolts, 0.03 microamperes, and 40 second counting time were employed. Duplicate analyses were conducted on three grains of each opx and cpx together with two different raw data correction methods as checks on analytical precision and correction procedures. Only those analytical summations of between 99.20 and 100.80 weight percent, and cation summations between 3.980 and 4.020 (based on 6 oxygens) were used.

Bunch, T. E.↗
NASA NTRS1973

Study of gas tungsten arc welding procedures for tantalum alloy T-111 (Ta-8 W-2Hf) plate

Methods of eliminating or reducing underbread cracking in multipass GTA welds in thick T-111 plate were studied. Single V butt welds prepared using experimental filler metal compositions and standard weld procedures resulted in only moderate success in reducing underbread cracking. Subsequent procedural changes incorporating manual welding, slower weld speeds, and three or fewer fill passes resulted in crack-free single V welds only when the filler metal was free of hafnium. The double V joint design with successive fill passes on opposite sides of the joint produced excellent welds. The quality of each weld was determined metallographically since the cracking, when present, was very slight and undetectable using standard NDT techniques. Tensile and bend tests were performed on selected weldments. The inherent filler metal strength and the joint geometry determined the strength of the weldment. Hardness and electron beam microprobe traverses were made on selected specimens with the result that significant filler metal-base metal dilution as well as hafnium segregation was detected. A tentative explanation of T-111 plate underbread cracking is presented based on the intrinsic effects of hafnium in the weldment.

Gold, R. E.↗
NASA NTRS1973

Effects of diffusion on aluminum depletion and degradation of NiAl coatings

Experiments were performed to critically demonstrate the effects of diffusion on the aluminum depletion and degradation of NiAl coatings on superalloys. Pack aluminized IN 100 and Mar-M200 were diffusion annealed in 0.0005 torr vacuum at 1100 C for 300 hours. Aluminum losses due to oxidation and vaporization were minimal. Metallographic and electron microprobe analyses showed considerable interdiffusion of the coating with the substrate, which caused a large decrease in the original aluminum level of the coating. Subsequent cyclic furnace oxidation tests were performed at 1100 C using 1 hour cycles on pre-diffused and as-coated specimens. The pre-diffusion treatment decreased the oxidation protection for both alloys, but more dramatically for IN 100. Identical oxidation tests of bulk NiAl, where such diffusion effects are precluded, showed no signs of degradation at twice the time needed to degrade the coated superalloys.

Smialek, J. L.↗
NASA NTRS1972

Comparative petrology of Apollo 16 sample 68415 and Apollo 14 samples 14276 and 14310.

Petrographic and electron microprobe studies of Apollo 16 igneous rock 68415 and Apollo 14 rocks 14276 and 14310 show that all three samples differ from the mare basalts and are characterized by plagioclase as the first liquidus phase and by the abundance of plagioclase which is in part cumulate in origin. Major and minor element abundances and isotopic data prohibit the derivation of rocks like any of these samples from one another by magmatic fractionation during their crystallization. They could have originated by partial melting of an old, more Al-rich source material without isotopic equilibration with the residuum, by complete melting of three independent sources, or by contamination with old radiogenic material. The existence of such feldspathic basalts indicates that the generation of Al-rich magmas may have been an important and widespread lunar process.

Gancarz, A. J.↗
NASA NTRS1972

Temperature-time relationships from lunar two phase metallic particles /14310, 14163, 14003/.

Electron-microprobe and metallographic techniques are applied in an analysis of individual phases in two-phase metallic alpha + gamma particles and phosphide-metal particles separated magnetically or mechanically from three lunar soil samples. The interface equilibrium temperatures of the two-phase particles during their lunar residence are inferred from experimental Fe-Ni and Fe-Ni-P equilibrium diagrams. Times of equilibration are determined in some cases.

Axon, H. J.↗
NASA NTRS1972

Major element composition of Luna 20 glasses.

Ten per cent of the 50 to 150-micron size fraction of Luna 20 soil is glass. A random suite of 270 of these glasses has been analyzed by electron microprobe techniques. The major glass type forms a strong cluster around a mean value corresponding to Highland basalt (anorthositic gabbro) with 70% normative feldspar. Minor glass groups have the compositions of mare basalts and of low-K Fra Mauro type basalts. The glass data indicate that Highland basalt is the major rock type in the highlands north of Mare Fecunditatis.

Warner, J.↗
NASA NTRS1972

Some textures in Apollo 12 lunar igneous rocks and in terrestrial analogs.

The interpretation of immature crystallization and some lunar textures characterized by it are the principal objectives of this investigation. A comparative and selective approach is adopted, and particular reference is made to the form and textural relations of olivine in 12009 and of pyroxenes and plagioclase in 12021, and to terrestrial analogs. The optic orientation of the olivines in 12009 is determined, and their skeletal crystallization is illustrated and evaluated. Microprobe and optical data are associated in a textural analysis of an analog from the upper contact of a minor intrusion in Skye. The optic orientation of pyroxene enclosed in plagioclase cores is determined, and the results are plotted stereographically. The need for greater precision in the use of textural terms is stressed, and a new term - intrafasciculate - is introduced for textures in which pyroxene has crystallized within hollow, skeletal plagioclase. Apollo 12 pyroxene-phyric basalts are texturally reviewed, and the crystallization of the phenocrysts is discussed, emphasis being placed on size-independence of skeletal growth.

Drever, H. I.↗
NASA NTRS1972

Lunar plagioclase - A mineralogical study.

Mineralogical properties of calcic plagioclase have been analyzed using U-stage, microprobe, X-ray precession cameras, and a 650-kV electron microscope. The orientation of the optical indicatrix in lunar and eucrite anorthites is described with Euler angles. All crystals, except one, show strong b- and diffuse c-reflections in precession photographs. In 10017, b-split-reflections have been found. Dark-field electron micrographs of 14310 anorthite show both large and small b-antiphase domains, and an exsolution structure in crystals that display b-split reflections in the diffractogram. Diffuseness of c-reflections in X-ray photographs and the inability to resolve c-domains in electron micrographs in An 94 anorthite of 14310 indicate relatively rapid cooling of this rock compared to plutonic rocks.

Wenk, H.-R.↗
NASA NTRS1972

Metamorphism of Apollo 14 breccias.

All Apollo 14 breccias for which thin sections are available (27 rocks) were studied petrographically. From one sample in each of six groups, electron microprobe analyses were performed on matrix (less than 25 microns) plagioclase, pyroxene, and olivine and of rims and cores of plagioclase and pyroxene clasts (50 to 300 microns). Matrix plagioclase, pyroxene, and olivine in the high-grade rocks display a narrow range of compositions, suggesting an equilibrated or metamorphic origin. However, in the low-grade rocks a wide range of compositions, suggesting a detrital or unequilibrated origin, is observed. Partially equilibrated states are observed in medium-grade samples. It is concluded that the Apollo 14 breccias formed as part of the Imbrium Basin ejecta blanket - the Fra Mauro formation. The continuous nature of the metamorphic series suggests that the medium- and high-grade breccias were derived from unmetamorphosed equivalents by autometamorphism in the thick, hot Fra Mauro formation at the Apollo 14 site.

Warner, J. L.↗
NASA NTRS1972

Chondrules of lunar origin.

Chondrules and glass spherules from Apollo 14 breccia 14318, studied microscopically, and their bulk and mineral compositions, determined by electron microprobe, are described and discussed with respect to their implications. The similarity in texture of impact-produced lunar and meteoritic chondrules suggests that, if major impact events occurred on parent meteorite bodies, at least some meteoritic chondrules may have formed by impact melting and splattering. Several other conclusions are discussed.

Kurat, G.↗
NASA NTRS1972

Chemistry and particle track studies of Apollo 14 glasses.

The abundance and the composition of Apollo 14 glasses have been studied. Glass particles were analyzed for Si, Ti, Al, Fe, Mn, Mg, Na, and K by electron microprobe analysis. The refractive indices of 26 particles were determined by the oil immersion method. Track analyses have been carried out in order to determine the uranium content and the radiation history of glass particles. The proper identification of galactic and solar flare nuclei tracks makes it possible to estimated residence times of the glass particles in the top layer of the lunar soil.

Glass, B. P.↗
NASA NTRS1972

Structure of lunar glasses by Raman and soft X-ray spectroscopy.

X-ray spectra and Raman spectra have been measured from individual particles of lunar glasses. Each particle was analyzed separately by electron microprobe. Silicon emission shifts vary between parent rock types and can be interpreted as a range of Si-O distances from 1.612 to 1.637 A. Aluminum emission shifts relate to the amount of 4- and 6-coordinated Al in the glass. Raman spectra show broadened bands. Certain bands recur in many specimens and relate to the main normative minerals for the glass bulk composition, olivine, pyroxene, and anorthite.

Fabel, G. W.↗
NASA NTRS1972

Metallic particles in the Apollo 14 lunar soil.

The metallographic structures, silicate associations and bulk compositions (Ni, Co, P, S, and Si) were determined by microprobe analysis for 205 metal particles selected by magnetic separation from the less than 1 mm, greater than 125 micron fraction of soil samples 14003,18 and 14163,165. A small number of exotic particles were encountered but almost all the metal could be accommodated within one of four subpopulations, the characteristics and genetic significance of which may be stated as follows: (1) the major proportion has Ni and Co contents corresponding to the range of meteoritic metal; (2) small proportion (about 5%) that not only has meteoritic contents of Ni and Co but also shows still distinguishable indications of meteoritic microstructure; (3) another small population (about 10%) consists of metal excavated from lunar mare basalts by cratering events, and thrown onto the Apollo 14 site; and (4) metallic spheroids (about 5%), analogous to those encountered in the vicinity of the Barringer Meteorite Crater, Arizona.

Goldstein, J. I.↗
NASA NTRS1972

The Oro Grande, New Mexico, chondrite and its lithic inclusion.

The Oro Grande, New Mexico, U.S.A., chondrite was found in 1971. Electron microprobe analyses and microscopic examination show the following mineralogy: olivine (Fa 19.3 mole %), orthopyroxene (Fs 16.2 mole %), diopside, feldspar (An 13.6 mole %), chlorapatite, whitlockite, kamacite, taenite, troilite, chromite, and an iron-bearing terrestrial weathering product. A bulk chemical analysis of the meteorite shows the following results (weight %): Fe 0.84, Ni 1.46, Co 0.07, FeS 3.62, SiO2 34.18, TiO2 0.14, Al2O3 1.83, Cr2O3 0.55, Fe2O3 21.25, FeO 9.13, MnO 0.31, MgO 21.52, CaO 1.72, Na2O 0.70, K2O 0.08, P2O5 0.25, H2O(+) 2.14, H2O(-) 0.40, C 0.22, sum 100.41. On the basis of composition and texture the Oro Grande meteorite is classified as an H5 chondrite.

Fodor, R. V.↗
NASA NTRS1973

Diffusion in a unidirectional filament reinforced metal composite.

A theoretical analysis has been developed to describe composition changes resulting from exposure of a unidirectional filament reinforced metal composite to an elevated temperature environment. The analysis was based on a simple superposition of finite-difference solutions of the diffusion equation, and was applicable to the case for which the filament and matrix metals comprised an isomorphous binary alloy system. The possibility of chemical reaction between filaments and matrix was excluded. Excellent agreement was obtained between calculated concentration profiles and results of quantitative electron microprobe analyses of nickel filament reinforced copper samples.

Herring, H. W.↗
NASA NTRS1973

Metallic particles of high cobalt content in Apollo 15 soil samples.

Single phase alpha-kamacite containing more than 3.2 wt % Co and gamma-taenite containing from 30 to 60 wt % Ni from the Apollo 15 soils - 15031, 15071, 15081, 15261, and 15271 - have been examined by metallographic and electron microprobe techniques. In addition two phase alpha + gamma particles from soils 14003, 15071, 15261, and 15271 with Ni and Co contents well outside the meteoritic range have also been examined. Two distinct types of alpha-gamma structure occur, one analogous to 'clear taenite' in ordinary chondrites, and the other analogous to a 'Widmanstaetten' structure in Ni-rich ataxites. The measured Ni gradients in the two-phase particles are very similar to those meteorites having the same structure. However the Co content is much higher than the meteoritic samples, up to 12 wt % in the alpha phase. Approximate phase equilibria data for the Fe-Ni-Co system indicate equilibration of the two-phase particles during cooling to approximately 350 C. Estimates of cooling rates and second-phase growth times indicate that the maximum time necessary for the development of the high-Co two-phase structures is roughly 25 to 100 m.y. These estimates argue for the development of the two-phase structures during formation of the lunar crust, at a depth of 10 to 20 km beneath the moon's surface.

Axon, H. J.↗
NASA NTRS1973

Optical and chemical analysis of iron in Luna 20 plagioclase.

Review of analytical data on the iron content of Luna 20 anorthitic plagioclase, obtained by a highly sensitive technique for measuring polarized absorption related to crystal-field splittings and by automated electron microprobe analysis of oriented single crystals. The iron content is found to range from a few hundredths to a few tenths of a weight per cent from crystal to crystal. The optical and chemical properties of the iron appear to be caused by postcrystallization migration and exsolution. Postcrystallization effects may obscure evidence of the original oxidation state and iron concentration of these crystals.

Bell, P. M.↗
NASA NTRS1973

Oxide minerals in lithic fragments from Luna 20 fines.

One hundred seventy-six oxide mineral grains in the Luna 20 samples were analyzed by electron microprobe. Spinel is the most abundant oxide, occurring in troctolite fragments. Next most abundant is ilmenite, which occurs in all rock types except those containing spinel. Chromite also occurs in all rock types except those containing spinel. Minor amounts of ulvospinel, armalcolite, zirkelite, baddeleyite and an unidentified TiO2-rich phase were also found. Spinel grains are predominantly spinel-hercynite solid solutions, commonly with very minor chromite. The Fe/(Fe + Mg) ratio is generally lower than in spinel from Apollo 14 rocks. Chromites in non-mare rocks are similar to those from mare rocks. Ilmenite of mare origin is Mg-poor and Zr-rich compared to non-mare ilmenite; these elements may therefore be useful in determining the origin of ilmenite grains. Phase equilibria considerations suggest that spinel troctolite crystallized from a melt high in alumina; a likely candidate is the high-alumina basalt of Prinz et al. (1973).

Brett, R.↗