Structural Characterization of Iron Meteorites through Neutron Tomography

Abstract

Abstract:In this communication, we demonstrate the use of neutron tomography for the structural characterization of iron meteorites. These materials prevalently consist of metallic iron with variable nickel content. Their study and classification is traditionally based on chemical and structural analysis. The latter requires cutting, polishing and chemical etching of large slabs of the sample in order to determine the average width of the largest kamacite lamellae. Although this approach is useful to infer the genetical history of these meteorites, it is not applicable to small or precious samples. On the base of different attenuation coefficient of cold neutrons for nickel and iron, neutron tomography allows the reconstruction of the Ni-rich (taenite) and Ni-poor (kamacite) metallic phases. Therefore, the measure of the average width of the largest kamacite lamellae could be determined in a non-destructive way. Furthermore, the size, shape, and spatial correlation between kamacite and taenite crystals were obtained more efficiently and accurately than via metallographic investigation.

A Feasible Mechanism for Appearance of Post-Post-<em>Fe</em> Elements in Solar System

“…However, if this were the case, then why do we find them as "chunks", why are they not quasi-uniformly mixed? For example, Sikhote-Alin meteorite -with ∼ 10 5 kg of total fallen mass [71] and fragments ranging from tiny to 1745 kg [13] -was composed of about 88% Fe, 5% Ni, and 2% Co [78], with "uniform internal structure" [16].…”

A structural insight into the Chelyabinsk meteorite: neutron diffraction, tomography and Raman spectroscopy study

“…The measurements of the chemical composition and spatial distribution of components of the Chelyabinsk meteorite could gain new insights into its origin [3,18,19]. Due to uniqueness of the meteoritic matter, an application of non-destructive testing methods provides particular advantages [18,20,21]. The conventional methods like the X-ray fluorescence analysis, scanning electron microscopy or X-ray diffraction have a significant limitation on the depth of penetration into the thickness of the studied samples.…”

“…The fundamental difference in the nature of neutron interactions with matter compared to X-rays provides additional benefits including sensitivity to light elements, a notable difference in contrast between neighboring elements like nickel and iron [18,21,22]. All these features make neutron methods highly demanded tool with a growing range of applications in industry [25], archeology [26,27] and geophysics [28] including studies of meteorites [18,20,21].…”

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“…Neutron computed tomography allowed discerning between Ni-rich (taenite) and Ni-poor (kamacite) metallic phases for structural classifi cation of the meteorite without any damage to the sample. The data obtained on DINGO demonstrated the capability of this technique to provide detailed structural information of this class of planetary materials, even more effi ciently and accurately than via metallographic investigation [17]. …”