Search NASA⌕ Search

SEARCH · Search NASA

Results for “FERROMAGNETISM”

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.

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

At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Particle track densities in double drive tube 60009/10

Measurements are reported of particle track densities in grains from a suite of eleven samples from the Apollo 16 double drive tube 60009/10. All of the samples studied in 60009 show a clearly bimodal distribution of track densities in plagioclase. This bimodal distribution is interpreted to indicate a mixing of a relatively immature soil with a relatively mature soil. This mixing was not followed by any appreciable reworking which would have altered the distribution. The three lower samples in 60010 also show a bimodal distribution. However, the three uppermost samples show a unimodal distribution. The percentage of high track density plagioclase grains shows a good correlation with the other maturity indices of agglutinate content and the ferromagnetic resonance intensity.

Blanford, G. E.↗
NASA NTRS1977

Depositional history of core section 74001 - Depth profiles of maturity, FeO, and metal

Samples from every 0.5-cm interval of soil in core section 74001 have been studied by ferromagnetic resonance (FMR) and magnetic techniques. The values of the FMR maturity index show that the 74001 samples are very immature (the index ranges from 0.14 to 0.29 units) and have not seen appreciable, if any, surface exposure since their deposition. In fact, the small amount of fine-grained metal in the 74001 samples is probably not acquired as a result of their exposure to the micrometeoroid flux at the lunar surface. Thus, the black-glass soil of 74001 was deposited very rapidly, probably in a single episode or several closely spaced episodes of lunar fire fountaining. The average concentration of FeO and its standard deviation for all the 74001 samples are 22.5 + or - 0.3 wt.%. Since the FeO concentration is so uniform, no large variations in the major-element chemistry of 74001 are expected, with the possible exception of the volatile elements. The concentration of coarse-grained metal, which is measured magnetically, and its standard deviation are 0.15 + or - 0.01 wt.%. The coarse-grained metal probably precipitated contemporaneously with the silicate and oxide phases in the black-glass droplets.

Morris, R. V.↗
NASA NTRS1979

Infrared spectra of lunar soils

Measured data obtained by Michelson interferometer spectrometer were stored in a computer file and smoothed by being passed forward and backward through a digital four-pole low pass filter. Infrared spectra of the 10 lunar samples are presented in the format of brightness temperature versus frequency. The mol % of feldspar, pyroxene, olivine, ilmenite and ferromagnetic silicate in each sample is presented in tables. The reflectance spectra of ilmenite and enstatite are shown in graphs.

Aronson, J. R.↗
NASA NTRS1979

The Moho as a magnetic boundary

Magnetic data are presented for mantle derived rocks: peridtites from St. Pauls rocks, dunite xenoliths from the kaupulehu flow in Hawaii, as well as peridolite, dunite and eclogite xenoliths from Roberts Victor, Dutoitspan, Kilbourne Hole, and San Carlos diatremes. The rocks are paramagnetic or very weakly ferromagnetic at room temperature. Saturation magnetization values range from 0.013 emu/gm to less than 0.001 emu/gm. A review of pertinent literature dealing with analysis of the minerals in mantle xenoliths provides evidence that metals and primary Fe3O4 are absent, and that complex CR, Mg, Al, and Fe spinels dominate the oxide mineralogy. All of the available evidence supports the magnetic results, indicating that the seismic MOHO is a magnetic boundary.

Wasilewski, P. J.↗
NASA NTRS1978

Critical phenomena in a low gravity environment

Various types of critical point phenomena are discussed including the gas-liquid phase transition of a fluid, the spontaneous magnetization of a ferromagnet below the Curie temperature, and structural phase transitions of solid materials. The interrelation of thermodynamic properties by scaling laws is considered noting theories for the validity of scaling laws and the principle of universality. Gravity effects are reviewed noting that in earth-based experiments the phenomena are significantly influenced by the earth's gravitational field and that fluid samples that are spatially homogeneous cannot be realized near the gas-liquid critical point.

Sengers, J. V.↗
NASA NTRS1978

FMR and magnetic studies of Luna 24 soils and greater than 1 mm soil particles

Six Luna 24 soils (24077, 24109, 24149, 24174, 24182, 24210), their grain-size separates, and twenty-five greater than 1 mm soil particles were analyzed by ferromagnetic resonance (FMR) and static magnetic techniques. The values of the FMR maturity index for the soils ranged from 19.0 to 39.0 units; soils 24077 and 24109 are submature and soils 24149, 24174, 24182, and 24210 are immature. The metallic iron contents of the soils ranged from 0.30 to 0.51 wt % and are commensurate with their maturities. The 'best estimate' value for the concentration of metallic iron of Luna 24 mare basalts is 0.038 wt %.

Morris, R. V.↗
NASA NTRS1978

Particle track densities in the Luna 24 core

We report track density measurements in soil grains at six locations in the Luna 24 core. Irradiation levels are generally high precluding information on the depositional history, but indicating that the soils were exposed at the lunar surface at sometime in the past. Maturity levels determined from track density parameters disagree with those determined from ferromagnetic resonance and agglutinate contents. This discrepancy is not understood, but it could possibly indicate an ancient epoch of increased solar-flare activity.

Blanford, G. E.↗
NASA NTRS1978

Primordial Pb, radiogenic Pb and lunar soil maturation

Pb-204 is directly correlated with the reduced Fe measured by ferromagnetic resonance. A similar correlation has been noted for hydrolyzable carbon (Pillinger et al., 1974). An enrichment of these elements appears to have occurred during soil maturation. In contrast to Pb-204, radiogenic Pb is reported to be lost during soil maturation (Church et al., 1976). Radiogenic Pb is present in mineral grains and may be lost by solar wind sputtering (or volatilization) and not resupplied. Pb-204 coating grain surfaces acts as a reservoir to provide the Pb-204 being extracted in the reduced Fe formation process. Venting or some other volatile release mechanism may replenish the surface-related Pb-204.

Reed, G. W., Jr.↗
NASA NTRS1978

The surface exposure /maturity/ of lunar soils - Some concepts and I sub s/FeO compilation

Surface exposure (or, equivalently, maturity) indices of lunar soils are a measure of residence time of soil in the upper one millimeter of the regolith. Several concepts concerning the use of and terminology associated with maturity indices are discussed. For reasons which include its generally-applicable nature and large data base, the ferromagnetic resonance (FMR) surface exposure (maturity) index I sub s/FeO (the ratio of the value of the intensity in arbitrary units of the FMR resonance at g equal to about 2.1 to the FeO concentration) is particularly suitable and useful. A compilation of values of I sub s/FeO for 164 Apollo surface and trench soils and six Luna 24 core soils is given.

Morris, R. V.↗
NASA NTRS1979

Theory of global thermoremanent magnetization of planetary lithospheres in dipole fields of internal origin

A model is presented for the global thermoremanent magnetization of spherical lithospheres which cool in the presence of central dipole fields. Reversals and intensity variations of the field are incorporated in this model, which is applicable to bodies whose interiors have remained above the Curie point throughout their evolution. The model demonstrates that even considering Runcorn's (1975) magnetostatics theorems for spherical shells, a nonzero magnetic permeability and a finite cooling rate in the lithosphere permit the acquisition of a sizable global remanent dipole moment, which would be detectable by external measurements after the magnetizing field has disappeared. Preliminary application of this model to Mercury, Venus, and Mars suggests that only the combination of a nonreversing ancient source field with a surface value near 1 Oe plus a sizable concentration (about 1% by volume) of ferromagnetic material in their crusts could produce remanent planetary dipole fields as large as those measured by spacecraft. On the other hand, if ancient reversing dynamos existed in these planets, it is unlikely that large planetary-scale fields like those observed at Mercury could be due to remanence in their crusts, irrespective of their composition.

Srnka, L. J.↗
NASA NTRS1980

Space processing applications rocket project SPAR 4, engineering report

The materials processing experiments in space, conducted on the SPAR 4 Black Brant VC rocket, are described and discussed. The SPAR 4 payload configuration, the rocket performance, and the flight sequence are reported. The results, analyses, and anomalies of the four experiments are discussed. The experiments conducted were the uniform dispersions of crystallization processing, the contained polycrstalline solidification in low gravity, the containerless processing of ferromagnetic materials, and the containerless processing technology. The instrumentation operations, payload power relay anomaly, relay postflight operational test, and relay postflight shock test are reported.

Reeves, F.↗
NASA NTRS1980

Does feroxyhyte occur on the surface of Mars

The physical, chemical and paragenetic properties of delta-FeOOH in the form of the mineral feroxyhyte are discussed in relation to the possible composition of the red-brown surface coating of Mars. It is pointed out that the deep-brown ferromagnetic FeOOH polymorph will adhere to magnets such as those on the Viking Lander at Mars ambient temperatures and exhibits spectral maxima in the range 2.95-3.4 m similar to those observed in remote sensing spectra of Mars. The redox properties of the formation of feroxyhyte are shown to be compatible with postulated processes on the Martian surface, and with the results of some of the Viking biological experiments. It is thus concluded that feroxyhyte has the magnetic, chemisorption, spectral, redox and paragenetic properties to suggest its consideration as a possible component of the Martian surface.

Burns, R. G.↗
NASA NTRS1979

Magnetization changes by superimposed stress pulses

The magnetization of a BiMn alloy with ferromagnetic inclusions changes at constant magnetic field, if the sample is subjected to ultrasonic pulses. The magnetization changes can be described on the basis of the Stoner-Wohlfarth theory of coherent rotation. It is possible to change the magnetization in selected volume elements by superimposing short pulses in those volume elements.

Onengut, D.↗
NASA NTRS1981

Eddy current probe response to open and closed surface flaws

A general analysis of eddy current response to certain types of open and closed surface flaws is presented for both standard low-frequency and ferromagnetic-resonance (FMR) probes. It is shown analytically that for two-dimensional and three-dimensional surface flaws interrogated by a uniform probe field, the crack opening sensitivity increases with the operating frequency of the probe, this behavior being due to the Faraday induction effect. Experiments with low-frequency probes operating at or below 1 MHz and with the FMR probe operating at approximately 1000 MHz confirm this increase of the crack mouth opening displacement for practical situations where the probe field is not uniform in the vicinity of the flaw.

Auld, B. A.↗
NASA NTRS1980

Cosmic ray production curves below reworking zones

A method is presented for calculating cosmic ray production profiles below reworking zones. The method uses an input reworking depth determined from data such as signatures in the depth profile of ferromagnetic resonance intensity and input cosmic ray production profiles for an undisturbed surface. Reworking histories are simulated using Monte Carlo techniques, and depth profiles are used to determine cosmic ray exposure age limits with a specified probability. It is shown that the track density profiles predict cosmic ray exposure ages in lunar cores that are consistent with values determined by other methods. Results applied to neutron fluence and spallation rare gases eliminate the use of reworking depth as an adjustable parameter and give cosmic ray exposure ages that are compatible with each other.

Blanford, G. E.↗
NASA NTRS1980

Origins and size distribution of metallic iron particles in the lunar regolith

The metallic iron concentration has been measured in three ranges of metal particle diameters for 79 lunar soils by a combination of static magnetic and ferromagnetic resonance techniques. Based on these measurements, a model has been developed which apportions the total metallic iron content of lunar soils between three components: (1) metallic iron particles produced from the exposure-induced reduction of ferrous iron; they range from 40 to 330 A in diameter and are predominantly associated with agglutinate glass; (2) metallic iron particles derived from the metallic phases of the micrometeorites involved in the formation of agglutinate glass; these particles are mostly greater than 300 A in diameter; and (3) metallic iron particles in the source materials such as bedrock and breccias; these are usually greater than 330 A in diameter. The maximum concentration of metallic iron in lunar regolith is estimated at about 0.7 equiv. wt% in highland regions (approximately 5.0 wt% FeO) and about 1.0 equiv. wt% in mare regions (approximately 15.0 wt% FeO).

Morris, R. V.↗
NASA NTRS1982

On the location of acid-hydrolysable carbon in lunar soil fines

Soil fines exposed on the lunar surface accumulate small metallic iron particles and solar wind-derived carbon. In previous work, it has been suggested that an intimate association exists between one particular carbon phase, hydrolysable carbon, and very fine iron droplets, where the carbon is in solid solution in the iron. The earlier hypothesis of a constant carbon in iron concentration across a broad range of droplet sizes is testable by combining hydrolysable carbon determinations with a variety of magnetic measurements sensitive to different droplet diameters. New measurements of ferromagnetic resonance response on density and magnetic separates from size fractions of soil 12023 are interpreted as evidence that hydrolysable carbon is preferentially associated with the larger, magnetically stable single-domain iron particles rather than with the smaller superparamagnetic droplets. For the former, there is a quite uniform ratio of iron to carbon both within a series of separates from a single soil, and among soils of widely varying FeO content.

Fallick, A. E.↗
NASA NTRS1982

Improved perfect-fluid energy-momentum tensor with spin in Einstein-Cartan space-time

The description of the spin given here is classical in that it is intrinsic but not quantized. The approach in this matter is similar to, for example, the work of Bailey and Israel (1973, 1975, 1979), where the fluid particles, which have intrinsic spin, may be galaxies or clusters of galaxies. The elementary particles of these objects and the 'ferromagnetic alignment' of their quantum spins are not resorted to in order to describe a fluid with spin. Physically this means that the equation of motion for the spin tensor is a modified Fermi-Walker transport equation (Misner et al., 1973), arising as a direct result of the inclusion of spin as an intrinsic variable in the thermodynamic description of the internal energy. The variables in this description are classical variables throughout and are not microscopic fields. An improved perfect-fluid energy-momentum tensor that includes spin and torsion is presented. Use is made of a Lagrangian variational principle based on the tetrad formalism of Halbwach (1960) and the method od constraints of Ray (1972).

Ray, J. R.↗