The Santa Catharina Meteorite and the Equilibrium State of FeNi Alloys

Jago, R. A.; Clark, Paul; Rossiter, P. L.

doi:10.1002/pssa.2210740129

Cited by 25 publications

(9 citation statements)

References 22 publications

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“…The higher Ni Santa Catharina specimens studied by Saito and Takeda (1988), and the Brazil sample studied by Danon et al (1985) show a very similar microstructure to that ofUSNM#3043. The samples used by Lovering and Anderson (1965), Bowles et al (1978) and Jago et al (1982) have the same composition as USNM#3043. The optical micrograph in Jago (1980) is essentially the same as that of sample USNM#3043 (Fig.…”

Section: Difference In Santa Catharina Bulk Compositionmentioning

confidence: 99%

“…They reported -8 wt.% a and -45 wt.% Ni in these regions, more Ni than in the surrounding metal (-31 wt.%). These results have been confirmed in later studies (Bowles et al, 1978;Albertsen et aI., 1978;Jago et al, 1982;Clarke, 1984;Saito and Takeda, 1988). The interest in Santa Catharina has been further increased by the discovery of the mineral tetrataenite, i.e., tetragonally ordered FeNi.…”

Section: Introductionmentioning

confidence: 99%

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Electron microscopy study of the iron meteorite Santa Catharina

et al. 1990

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Abstract— Characterization of the microstructural features of the metal of the Santa Catharina meteorite was performed using a variety of electron optical techniques. Sample USNM#6293 is chemically homogeneous on the micron scale and has a Ni content of 28.2 wt.%. Its microstructure is similar to that of the Twin City ataxite and contains clear taenite II, i.e., fcc taenite with domains of tetrataenite, < 10 nm in size. Sample USNM#3043 is a more typical Santa Catharina specimen with dark and light regions as observed with the light optical microscope. The dark regions are inhomogeneous and contain 45–50 wt.% Ni and 7–12 wt.% O. The light regions are homogeneous and contain 35 wt.% Ni and no detectable oxygen. The microstructure is that of cloudy zone, i.e., islands of tetrataenite, ∼20 nm in size, in a honeycomb matrix. The honeycomb phase contains Ni rich oxide in the dark regions and contains metal, fcc taenite, in the light regions. The original metal structure of USNM#3043 is cloudy zone which formed during cooling into the low temperature miscibility gap of the Fe‐Ni phase diagram. The dark regions were developed from the metal by selective corrosion of the honeycomb structure, transforming it into Ni containing oxides, possibly non‐stoichiometric Fe2NiO4 while retaining the tetrataenite islands. Using the results of this study, many of the existing discrepancies concerning the microstructure of Santa Catharina can be explained.

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Section: Difference In Santa Catharina Bulk Compositionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electron microscopy study of the iron meteorite Santa Catharina

et al. 1990

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“…Iron is appearing in the austhenitic phase and alloyed with nickel. An analysis of the Mössbauer spectra at room temperature indicates that the Fe-Ni phase is homogeneously distributed in the matrix, although variations in the composition between different regions are observed.Since the early studies of the microstructure and chemical composition of meteorites the formation of magnetic phases has attracted the attention of metallurgists [1][2][3][4][5][6][7][8][9][10][11]. Most of the metallic specimens presented high contents of nickel and iron as major constituents, and thus the Fe-Ni alloys formed under such special conditions have been the subject of several investigations with a variety of experimental techniques.…”

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confidence: 99%

A Mössbauer effect study of the Soledade meteorite

Paduani

Pérez²,

Ardisson

2005

Braz. J. Phys.

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We performed a Mössbauer spectroscopy study of the iron meteorite Soledade. This meteorite, which consists of a metallic matrix, is an octahedrite with polycrystalline troilite, cohenite, schreibersite and rhabdites as major constituents. A chemical analysis indicates 6.78 % Ni, 0.46% Co, besides traces of Cu, Cr, Ga, Ge, As, Sb, W, Re, Ir and Au. No traces of silicates have been found and no oxygen was detected. Iron is appearing in the austhenitic phase and alloyed with nickel. An analysis of the Mössbauer spectra at room temperature indicates that the Fe-Ni phase is homogeneously distributed in the matrix, although variations in the composition between different regions are observed.Since the early studies of the microstructure and chemical composition of meteorites the formation of magnetic phases has attracted the attention of metallurgists [1][2][3][4][5][6][7][8][9][10][11]. Most of the metallic specimens presented high contents of nickel and iron as major constituents, and thus the Fe-Ni alloys formed under such special conditions have been the subject of several investigations with a variety of experimental techniques. This is not an easy task considering the weathering process and the distribution of oxides in the metallic matrix, which in some cases varies in composition from one region to another. However, the complexity of the mechanism of formation of the alloys in meteorites, which can take cooling rates as long as 1 K/Ma, is an interesting subject, and its comprehension may shed some light on the metastability of alloys.The category of iron meteorites corresponds to about 5 % of the modern meteorite falls. In the study of Fe-Ni-bearing meteorites, there is a recent discussion about the formation of a low-moment Fe-rich γ phase which differs from the ordinary high-spin γ phase in the electronic structure and a lower lattice parameter, but has the same crystal structure, same degree of atomic order and same composition of ordinary taenite. In fact, this has been claimed to be a new mineral called antitaenite which is common in slowly cooled meteorites [12][13][14]. This low-spin phase is proposed to occur in a thin epitaxial intergrowth with tetrataenite (ferromagnetic atomically ordered FeNi). Actually, metastable precipitates of this low-spin phase in a matrix of high-spin Fe-Ni phase of the same controlled composition have been synthetically produced near the Invar composition (≈ 35 at% Ni).In this work we applied x-ray diffraction (XRD) and Mössbauer spectroscopy (MS) to study the iron-bearing phases detected in the iron meteorite called Soledade, which is a massive metallic block [15]. Although no one knows precisely when this specimen was found, it received the name of the locality from where it proceeded near the city of Passo Fundo in the state of Rio Grande do Sul in Brazil. The first studies indicate that this metallic meteorite is an octahedrite, with polycrystalline troilite, cohenite, schreibersite and rhabdites as major constituents. It consists of a solid block weighing 68 kg, with a...

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“…17) When they collide with each other on a substrate, Fe and Ni clusters are neither fragmented nor coalesced at interfaces: Fe and Ni clusters randomly coexist on the substrate. 34) Many phase diagrams reported for Fe 1ÀX Ni X alloys to this day clearly indicate that Fe 1ÀX Ni X alloys are classified into an miscible system: 18,[35][36][37][38][39][40][41][42] bcc Fe-rich solid solution, AuCu 3 -type ordered FeNi 3 and fcc Ni-rich solid solution are the ground state structures, while Cu 3 Au-type ordered Fe 3 Ni and CuAu-type ordered FeNi have been obtained in meteorites, fine particles and neutron-or electron-irradiated specimens. On the contrary, the present Fe/Ni nano-hybrid material is a nano-scale heterogeneous mixture of bcc Fe and fcc Ni grains.…”

Section: Discussionmentioning

confidence: 99%

Fe/Ni Cluster Hybrid Material Produced by Double Glow Discharge Sources

et al. 2009

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Fe and Ni clusters have been simultaneously deposited on substrates using an improved plasma-gas-condensation cluster deposition apparatus, and investigated by transmission electron microscopy, X-ray photoelectron spectroscopy and magnetometry. In these Fe/Ni cluster hybrids Fe and Ni clusters are randomly mixed, where bcc Fe and fcc Ni diffraction rings are detected, and their lattice constants are almost same as those of pure Fe and Ni metals. The peak positions of core-levels, Fe-2p 3=2 and Ni-2p 3=2 lines, of Fe/Ni cluster hybrids are similar to those of pure Fe and Ni clusters. Since Fe and Ni are miscible with each other in bulk, equilibrium and film specimens, no nano-scale heterogeneity can be attained by other methods. Therefore, present results demonstrate formation of novel Fe/Ni nano-hybrid materials.

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The Santa Catharina Meteorite and the Equilibrium State of FeNi Alloys

Cited by 25 publications

References 22 publications

Electron microscopy study of the iron meteorite Santa Catharina

Electron microscopy study of the iron meteorite Santa Catharina

A Mössbauer effect study of the Soledade meteorite

Fe/Ni Cluster Hybrid Material Produced by Double Glow Discharge Sources

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