SEARCH · Search NASA

Results for “spinels”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16

All sources NASA NTRS DOE OSTI

NASA NTRS1980

Occurrence and mineral chemistry of high pressure phases, Portrillo basalt, southcentral New Mexico

Inclusions of clinopyroxenite, kaersutiteclinopyroxenite, kaersutite-rich inclusions, wehrlite and olivine-clinopyroxenite together with megacrysts of feldspar, kaersutite and spinel are found loose on the flanks of cinder cones, as inclusions within lava flows and within the cores of volcanic bombs in the Quaternary alkali-olivine basalt of the West Potrillo Mountains, southcentral New Mexico. Based on petrological and geochemical evidence the megacysts are interpreted to be phenocrysts which formed at great depth rather that xenocrysts of larger crystal aggregates. These large crystals are believed to have formed as stable phases at high temperature and pressure and have partially reacted with the basalt to produce subhedral to anhedral crystal boundaries. It can be demonstrated that the mafic and ultramafic crystal aggregates were derived from an alkali-basalt source rock generated in the mantle. The inclusions are believed to represent a cumulus body or bodies injected within the lower crust or upper mantle.

Hoffer, J. M.↗

NASA NTRS1980

Mineralogic and petrologic studies of lunar samples and meteorites

Experimental and thermodynamic research on the pressure temperature limits of the stability of the mineral assemblages found in pristine, spinel bearing lunar highland lithologies demonstrated the likelihood that the minerals originated in the lower stratigraphic levels of the primordial crust. The phase equilibrium in silicate solid/liquid systems of planetary importance were thermochemically interpreted in order to model the early formation of the crusts and maneles of Earth and Moon sized planets. The petrography and chemical composition of coarse grained gabbro, the chemical analysis and age dating of clasts from Apollo 16 breccia, the analysis of glass particles from Apollo 16 soil samples, the study of Allende and Mokoia meteorites as a source of information about events in the solar nebula, and the hydrothermal alteration of amorphous materials were also investigated. The capabilities of a model for addressing the problem of the origin of the Earth's moon by the disruptive capture mechanism are examined as well as models of the thermal evolution of hypothetical meteorite bodies. Progress in determining the composition of stony meteorite specimens collected at the Allan Hills site during the Antarctic field exploration is reported.

Wood, J. A.↗

NASA NTRS1979

Some TEM observations of Al2O3 scales formed on NiCrAl alloys

The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids have been observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. It was postulated that the voids resulted from an excess number of oxygen vacancies near the oxide-metal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidations of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al,Cr)2O3 and Ni(Al,Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationships between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

Smialek, J.↗

NASA NTRS1979

Stellar condensates in meteorites - Isotopic evidence from noble gases

The Murchison carbonaceous chondrite contains three isotopically anomalous noble-gas components of apparently presolar origin: two kinds of Ne-E, (Ne-20)/(Ne-22) less than 0.6, and s-process Kr + Xe (enriched in the even isotopes 82, 84, 86, 128, 130, 132). Their carriers are tentatively identified as spinel and two carbonaceous phases, the principal high-temperature stellar condensates at low and high C/O ratios, respectively.

Lewis, R. S.↗

NASA NTRS1980

Isotopic anomalies of noble gases in meteorites and their origins. VI Presolar components in the Murchison C2 chondrite

Rare gases were analyzed by stepped heating in five fractions of a chemically resistant residue from Murchison that had been separated according to grain size and resistance to HClO4. Nine gas components were recognized, of which three appear to be presolar: (1) Ne-E(H) released at 1000-1600 C and located in spinel; (2) Ne-E(L) released at less than 800 C and apparently located in a carbonaceous phase of grain size up to 10 microns; and (3) s-process Xe and Kr released at 1200-1600 C and located in a poorly characterized, possibly carbonaceous phase, distinct from the host phase of Ne-E(L).

Alaerts, L.↗

NASA NTRS1979

The petrology of the Apollo 12 pigeonite basalt suite

A study of the petrology of the Apollo 12 pigeonite basalt samples 12011, 12043, and 12007 is presented. In this suite, the abundances of olivine and Cr-spinel decrease with increasing grain size, while the abundances of plagioclase and ilmenite increase. The petrochemical and textural variations indicate that the pigeonite basalts were derived from the olivine basalts, but the compositional gap between the olivine and pigeonite basalts indicates that they could not have crystallized together from a single, initially homogeneous magma body.

Baldridge, W. S.↗

NASA NTRS1979

A summary of the petrology and geochemistry of pristine highlands rocks

The petrology and geochemistry of pristine lunar highlands rock samples consisting of ferroan anorthosites, norites, troctolites, spinel troctolites/dunite/lherzolite, and KREEP, are described. In addition, petrographic and chemical evidence is presented which shows that low-siderophile rocks are the result of endogenous igneous activity and not impact melt differentiation. For example, these rocks contain Fe-metal as a late-crystallizing phase, and have W/La ratios higher than polymict breccias.

Norman, M. D.↗

NASA NTRS1981

Microstructure of Al2O3 scales formed on NiCrAl alloys

The structure of transient scales formed on pure and Y or Zr-doped Ni-15Cr-13Al alloys oxidized for 0.1 hr at 1100 C was studied by the use of transmission electron microscopy. Crystallographically oriented scales were found on all three alloys, but especially for the Zr-doped NiCrAl. The oriented scales consisted of alpha-(Al,Cr)2O3, Ni(Al,Cr)2O4 and gamma-Al2O3. They were often found in intimate contact with each other such that the close-packed planes and directions of one oxide phase were aligned with those of another. The prominent structural features of the oriented scales were approximately equal to micrometer subgrains; voids, antiphase domain boundaries and aligned precipitates were also prevalent. Randomly oriented alpha-Al2O3 was also found and was the only oxide ever observed at the immediate oxide metal interface. These approximately 0.15 micrometer grains were populated by intragranular voids which decreased in size and number towards the oxide metal interface. A sequence of oxidation was proposed in which the composition of the growing scale changed from oriented oxides rich in Ni and Cr to oriented oxides rich in Al. At the same time the structure changed from cubic spinels to hexagonal corundums with apparent precipitates of one phase in the matrix of the other. Eventually randomly oriented pure alpha-Al2O3 formed as the stable oxide with an abrupt transition: there was no gradual loss of orientation, no gradual compositional change or no gradual decrease in precipitate density.

Smialek, J. L.↗

NASA NTRS1981

Catalytic combustion with incompletely vaporized residual fuel

Catalytic combustion of fuel lean mixtures of incompletely vaporized residual fuel and air was investigated. The 7.6 cm diameter, graded cell reactor was constructed from zirconia spinel substrate and catalyzed with a noble metal catalyst. Streams of luminous particles exited the rector as a result of fuel deposition and carbonization on the substrate. Similar results were obtained with blends of No. 6 and No. 2 oil. Blends of shale residual oil and No. 2 oil resulted in stable operation. In shale oil blends the combustor performance degraded with a reduced degree of fuel vaporization. In tests performed with No. 2 oil a similar effect was observed.

Rosfjord, T. J.↗

NASA NTRS1981

A once-molten, coarse-grained, Ca-rich inclusion in Allende

A compact, spheroidal Type B inclusion in Allende contains melilite laths that project radially inward from the inclusion edge which show interference growth textures. The combined textural and chemical features of this object cannot be explained by independent vapor-solid condensation of grains in space, followed by random aggregation of these grains into an inclusion. Instead, it probably formed from a once-molten droplet that crystallized in response to radiative cooling from its outer surface. The crystallization sequence in this and another similar inclusion in which oxygen isotopes have been measured is melilite-spinel-anorthite-fassaite; this sequence shows that oxygen isotopic heterogeneities in coarse-grained inclusions were formed after complete solidification of these objects by partial exchange with a less O-16-rich gas, and not during or before a melting event.

Macpherson, G. J.↗

NASA NTRS1981

The mineralogy of global magnetic anomalies

Progress is reported in developing predictive abilities to evaluate the potential stabilities of magnetic minerals in the Earth crust and mantle by: (1) computing oxidation state profiling as a function of temperature and pressure; (2) compiling data on basalts to establish validity of the oxidation state profiles; (3) determining Fe-Ni alloys in association with magnetitie as a function of temperature and oxidation state; and (4) acquiring large chemical data banks on the mineral ilmenite which decomposes to mineral spinel in the presence of high sulfur or carbonate environments in the lower crust upper mantle. In addition to acquiring these data which are related to constraining Curie isotherm depths, an excellent correlation was found between MAGSAT anomaly data and the geology of West Africa.

Haggerty, S. E.↗

NASA NTRS1982

Petrology of suevitic lunar breccia 67016

The present investigation is concerned with a petrologic study of one of the largest samples of feldspathic fragmental breccia, 67016. Evidence presented indicates that 67016 (and by implication the entire suite of feldspathic fragmental breccias) was originally deposited in a single impact event, possibly in a setting geologically analogous to terrestrial suevite. 'Feldspathic fragmental breccia' is the term adopted for the friable, light-colored breccias with abundant dark clasts which are the predominant rock type on the rim and walls of North Ray crater. Macroscopically 67016 is a light-gray breccia with approximately 20% dark clasts, approximately 10% white lithic clasts, and scattered single grains of plagioclase, mafic silicates, opaques, metal, and spinel.

Norman, M. D.↗

NASA NTRS1982

Intergrown mica and montmorillonite in the Allende carbonaceous chondrite

High resolution transmission electron microscopy (HRTEM) observations were made of a mixture of mica and montmorillonite from fine-grained calcium, aluminum inclusions (CAI) in the Allende C3(V) meteorite. A petrographic thin section having a diameter of 4 mm contained CAI fragments ranging from less than 1 to 50 microns. The observed textural and chemical characteristics placed the inclusion in the fine-grained alkali-rich spinel aggregate category of Warks' (1979) classifications of CAIs and as type 3 in Kornacki's classifications of fine grains in Allende. Chemical analyses were performed on the phyllosilicate grains observed in the TEM scan by means of an X ray observed, and the proximity to the matrix boundary suggests a metamorphism which included aqueous alteration at a relatively low temperature.

Tomeoka, K.↗

NASA NTRS1983

NASA interdisciplinary collaboration in tribology. A review of oxidational wear

An in-depth review of oxidational wear of metals is presented. Special emphasis is given to a description of the concept of oxidational wear and the formulation of an Oxidational Wear Theory. The parallelism between the formation of an oxide film for dry contact conditions and the formation of other surface films for a lubricated contact is discussed. The description of oxidational wear is prefaced with a unification of wear modes into two major classes of mild and severe wear including both lubricated and dry contacts. Oxidational wear of metals is a class of mild wear where protective oxide films are formed at real areas of contact and during the time of contact at temperataure T sub c. When the oxide reaches a critical thickness, frequently in the range of 1 to 3 microns, the oxide breaks up and eventually appears as a wear particle. These oxides are preferentially formed on plateaux which alternately carry the load as they reach their critical thickness and are removed. If the system is operated at elevated temperatures, thick oxides can form both out of contact and between the plateaux. Temperature is important in determining the structure of the oxide film present. Spinel oxide (Fe3O4) which forms above 300 C is more protective than the lower temperature rhomobohedral (alpha-Fe2O3) oxide which is abrasive. An Oxidational Wear Theory is derived using a modified Archard wear law expressed in terms of activation energy (Qp) and Arrhenius constant (Ap).

Quinn, T. F. J.↗

NASA NTRS1982

Crystallization sequences of Ca-Al-rich inclusions from Allende - An experimental study

The results of equilibrium crystallization experiments at one atmosphere on a sample of the Type B Ca-Al-rich inclusions (CAI) of the Allende meteorite are reported. All the experiments were performed on a synthetic sample approximating the Allende CAI characteristics. The crystallization sequence observed comprised spinel at 1550 C, then melilite at 1400 C, anorthite at 1260 C, and then Ti-Al-rich clinopyroxene, formed at 1230 C. The observation that pyroxenes similar to the titaniferous fassaites found in Type B inclusions can be formed by equilibrium crystallizations of melts with Type B composition indicate that some Type B CAIs were at least partially molten. If the temperatures were not too far above the solidus, the molten condensate compositions would be similar to that occurring in gas-to-solid condensation.

Stolper, E.↗

NASA NTRS1983

Subdivision of the Mg-suite noritic rocks into Mg-gabbronorites and Mg-norites

Mg-suite noritic rocks can be divided into two groups, the Mg-gabbronorites and the Mg-norites. The rocks of these groups differ in ratios of high-Ca pyroxene to total pyroxene, compositions of pyroxene and plagioclase, assemblages of Ti-, Nb-, and Zr-bearing minerals, compositions of chrome spinel, bulk-rock Ti/Sm and Sc/Sm, and measured ages. The two groups probably crystallized from different types of parent magmas. Two hypotheses are offered for the differences in composition of the parent magmas. One hypothesis ascribes the differences to compositional heterogeneity of the mantle source areas. The other hypothesis ascribes the differences to variations in extent of partial melting of the mantle source regions and variations in extent of assimilation of the anorthosite and the highly differentiated residual liquid that were produced during the primordial lunar differentiation.

James, O. B.↗

NASA NTRS1982

The nature and origin of type B1 and B2 Ca-Al-rich inclusions in the Allende meteorite

The Type B Ca-Al-rich inclusions in the Allende carbonaceous chondrite form a continuous range from the mineralogically concentrically zoned B1 subtype to the unzoned B2 subtype. These subtypes differ in (1) structure, texture, grain size and shape, (2) mineralogical proportions and compositions, (3) accessory mineralogy, (4) relative abundance of spinel framboids, (5) rim layering, (6) major element chemistry, and (7) degree of secondary alteration. These differences, together with observations on the crystallization of synthetic melts, suggest that the B1 inclusions crystallized relatively rapidly from molten parental material while B2 types crystallized relatively slowly close to the solidus from material that had not been completely melted. The same data are used to construct an evaporative residue model for the origin of the parental Type B materials. In the model, dust in the protosolar nebula was heated with removal of more volatile elements, leaving completely melted (Type B1) residues at the highest temperatures and incompletely melted, less highly evaporated (Type B2) residues at lower temperatures.

Wark, D. A.↗

NASA NTRS1982

Evolution of Ca-Al-rich bodies in the earliest solar system Growth by incorporation

Thirty different Allende Ca-Al-rich inclusions (CAIs), 11 of type A and 19 of type B, were examined for spinel palisades and framboids, and the possible origins of these structures are discussed. Possible mechanisms for in situ formation of palisades are assessed, all of them either being rejected outright or considered highly implausible. The evidence for external formation and incorporation of palisade bodies is then assessed, and possible mechanisms are considered. It is proposed that type B CAIs are residues from the heating and incomplete evaporation of interstellar dust during the accretion of the protosolar nebula, and that type A CAIs are later condensates from completely evaporated dust whose exotic O-16-rich component became more diluted in the gas phase.

Wark, D. A.↗