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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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9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Laboratory infrared spectra of predicted condensates in carbon-rich stars

Laboratory spectra and mass absorption coefficients of MgS, CaS, FeS, SiS2, FeS2, Fe3C, and a commercial iron carbide are presented over the wavelength range 125-15 microns. These spectra confirm that MgS is the most likely source of the unidentified 30-micron emission in carbon-rich sources and that FeS, Fe3C, and 'iron carbide' cannot be responsible for this feature although they could contribute to the continuum in this region. CaS and FeS2 may contribute to the 30-micron feature; however, both higher resolution and higher precision astronomical observations are needed before their presence can be established. SiS2 has a peak near 22 microns and therefore cannot be a significant component of the dust in such regions.

Nuth, J. A.↗
NASA NTRS1975

The effect of C/O ratio on the condensation of planetary material

The condensation temperatures of refractory silicates and oxides in a gas of cosmic composition are strongly dependent on the C/O ratio. As the ratio increases from 0.4 to 0.9, condensation temperatures of compounds such as Al2O3, Ca2Al2SiO7, MgAl2O4, Mg2SiO4, and MgSiO3 decrease by 50-100 degrees. As C/O increases from 0.9 to 1.0, these temperatures drop an additional 300-400 degrees. Other chemical differences result when C/O approximately equals or exceeds 0.9. A new suite of high-temperature minerals appears (graphite, CaS, Fe3C, SiC and TiN); the reaction CO + 3H2 yields CH4 + H2O proceeds to the right at higher temperatures; and iron, whose condensation temperature is unaffected, condenses at higher temperatures than any silicate or oxide.

Larimer, J. W.↗
NASA NTRS1979

Iron and the formation of astrophysical dust grains

Condensation of metallic iron or the iron carbide cohenite Fe3C is proposed as the source of the approximately 1000 K dust condensate in nova shells, Wolf-Rayet stars, and other objects. Iron grains may serve as nucleation sites for carbon in carbon-star ejecta; however, nucleation of graphite at its equilibrium saturation temperature is almost certainly kinetically inhibited. A gas phase rich in CO, C2H2, and HCN is produced instead.

Lewis, J. S.↗
NASA NTRS1984

Intermediate phases in some rare earth-ruthenium systems

The phase equilibria and crystal structures of intermediate phases were investigated in eight representative RE-Ru systems using powder X-ray diffraction and metallographic techniques. The Fe3C, Mn5C2 and Er5Ru3 structures occur in all but the Ce-Ru systems. Phases analogous to Er5Ru3 possess an unknown crystal structure similar to Er5Rh3(I). MgCu2 and MgZn2 type Laves phases are encountered in the light rare earth and heavy rare earth systems, respectively, and RERu2 phases, where RE = Nd and Sm, possess both the Laves phase structures. An intermediate phase, NdRu, with an unknown structure, occurs only in the Nd-Ru system. A bcc structure with 40 atoms per unit cell is encountered in the phases Er3Ru2 and Y3Ru2. The behavior of cerium in Ce-Ru alloys is unique in that four unidentified structures, not encountered in other RE-Ru systems, have been encountered. Also a phase designated as Ce3Ru is found with the Th7Fe3 type structure.

Sharifrazi, P.↗
NASA NTRS2002

A New Analytical Approach to Predict Spacing Selection in Lamellar and Rod Eutectic Systems

The Jackson and Hunt (JH) theory has been modified to relax the assumption of isothermal solid/liquid interface(SLI) used in their treatment. Based on the predictions of this modified theory the traditional definitions of regular and irregular eutectics are revised. For regular eutectics the new model identifies a range of spacing within the limits defined by the minimum undercooling of the alpha and beta phase. For the irregular Al-Si eutectic system two different spacing selection mechanisms were identified: a) for a particular growth rate, a nearly isothermal interface can be achieved at a unique minimum spacing lambda(sub I); b) the average spacing (lambda(sub av) greater than lambda(sub I)) is essentially dictated by the undercooling of the faceted phase. Based on the modified theoretical model a semiempirical expression has been developed to account for the influence of the temperature gradient, which is dominant in the irregular Al-Si system. The behavior of the Fe-Fe3C eutectic is also discussed The theoretical calculations have been found to be in good agreement with the published experimental measurements.

Catalina, Adrian V.↗
NASA NTRS2003

A New Analytical Approach to Predict Spacing Selection in Lamellar and Rod Eutectic Systems

The Jackson and Hunt (JH) theory has been modified to relax the assumption of isothermal solid liquid interface used in their treatment. Based on the predictions of this modified theory, the traditional definitions of regular and irregular eutectics are revised. For regular eutectics, the new model identifies a range of spacing within the limits defined by the minimum undercooling of the a and beta phases. For the irregular Al-Si eutectic system, two different spacing selection mechanisms were identified: (1) for a particular growth rate, a nearly isothermal interface can be achieved at a unique minimum spacing lambda (sub t); (2) the average spacing (lambda (sub av) greater than lambda (sub t) is essentially dictated by the undercooling of the faceted phase. Based on the modified theoretical model, a semiempirical expression has been developed to account for the influence of the temperature gradient, which is dominant in the irregular Al-Si system. The behavior of the Fe-Fe3C eutectic is also discussed. The theoretical calculations have been found to be in good agreement with the published experimental measurements.

Catalina, Adrian V.↗
NASA NTRS2004

First Report of Taenite in an Asteroidal Interplanetary Dust Particle: Flash-heating Simulates Nebular Dust Evolution

Metallic iron with a taenite structure rimmed by Fe3C carbide, kamacite with a magnetite rim, both approximately 200 nm in size, and les than 15 nm kamacite crystals embedded in equilibrated aggregates (or GEMS) were reported in IDPs. Here I report the first g-(Fe,Ni), taenite, in sulfide fragment -F6 particle with adhered patches of thermally modified aggregate IDP-like material belonging to cluster IDP L2011#21.

Rietmeijer, F. J. M.↗
NASA NTRS2000

Laser pyrolysis fabrication of ferromagnetic gamma'-Fe4N and FeC nanoparticles

Using the laser pyrolysis method, single phase gamma'-Fe4N nanoparticles were prepared by a two step method involving preparation of nanoscale iron oxide and a subsequent gas-solid nitridation reaction. Single phase Fe3C and Fe7C3 could be prepared by laser pyrolysis from Fe(CO)5 and 3C2H4 directly. Characterization techniques such as XRD, TEM and vibrating sample magnetometer were used to measure phase structure, particle size and magnetic properties of these nanoscale nitride and carbide particles. c2000 American Journal of Physics.

NASA Discipline Life Sciences Technologies↗
NASA NTRS2021

The Formation of Carbonaceous Material in the Early Solar Nebula: The Role of Metal Dusting

For many years it has been suggested that the carbonaceous material found in association with Fe/Ni metal and metal carbides in primitive bodies is linked to the Fischer–Tropsch reaction. This is especially true with chondritic-porous interplanetary dust particles, which are considered to have a cometary origin and are among some of the most primitive and least processed materials available for study. Another phenomenon which occurs under the same carburizing conditions as the Fischer–Tropsch reaction is called metal dusting and could be a possible pathway to forming some of the carbonaceous material found in primitive bodies. Metal dusting is a catastrophic corrosion of metal under these carburizing conditions that results in a porous mixture of carbonaceous material, metal, and metal carbides. In the case of pure iron, type I metal dusting results in the formation of a metastable iron carbide, typically cementite, Fe3C. While metal dusting has been studied industrially for over 50 years, it does not appear to have been applied to the formation of carbonaceous material in astrophysical settings. In this work, the general mechanism of metal dusting on iron is described and a thermodynamic analysis of the dusting phenomena applied to solar nebula conditions. Rate measurements are made with pure iron samples over the temperature range from 400°C to 950°C. In addition, the products from experimental runs at 500°C and 600°C are studied by transmission electron microscopy. Results show that iron carbide particles are formed with carbonaceous material consisting of poorly graphitized carbon.

Interplanetary dust↗