Identification of clear taenite in meteorites as ordered FeNi

摘要: In the Fe–Ni system, face-centred cubic (f.c.c.) phase (called taenite in meteorites) is stable for all compositions above 1,185 K. Below this temperature, body-centred (kamacite) and has a maximum Ni concentration of about 7% around 720 K (ref. 1). Metal meteorites commonly found to contain kamacite with 4–7% 20–45% Ni. Taenite grains have M-shaped profiles which formed on slow cooling during diffusion-controlled growth preserve record rates. Another 49–57% was ordinary chondrites by Taylor Heymann2 identified as variety taenite. They called it clear distinguish from zoned variety, develops cloudy borders etching acid, proposed that nucleated at 660–610 edge isolated grains. We report here studies meteoritic metal reflected-light microscopy electron-probe analysis, we discovered optically anisotropic meteorite groups. use term originally defined include only alloys ∼48–57% Ni, not those ∼25–30% Lin et al.3 II. Except contains ∼30–40% looks because submicroscopic two-phase mixture, remains etching. conclude ordered, tetragonal FeNi Albertsen al.4–6 two iron using Mossbauer X-ray techniques, taenite, kamacite. This been synthesised irradiating neutrons or electrons below 593 (refs 7,8).