Alliages à structure « modulée »

Abstract

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The defect structure of Fe1−xO

“…A coarse grained specimen was made in situ in the attachment by spot welding a small sheet of iron to the heater and equilibrating in an appropriate flowing CO/COE mixture. Fel-xO recrystallizes at 1100°C in millimetersize grains with {001} planes parallel to the surface (Manenc et al 1963a) so that very strong 002 and 004 peaks can be obtained from one grain by some minor adjustment of a specimen's Orientation at temperature. Room temperature measurements of .the lattice parameter of powder specimens prepared in this way indicated that the compositions were those expected from the gas ratio employed; the parameters used by Levin & Wagner (1963) were used for this comparison.…”

“…The measured moment of 0.028 e.m.u./g, corresponded to only a very small amount (0.03 weight percent) of precipitated Fe304. No diffraction peaks from Fe304 or Fe were seen [with a detection limit 0,0,0 of about 0.1 percent from any sharp peaks from Fe304; this phase forms with cube axes parallel to those of Fel-zO (Manenc, 1963a)]. Some transmission electron microscopy and electron diffraction studies were performed on a Hitachi HU-I 1A microscope.…”

High-resolution transmission-electron-microscopy observation of the ultra-fine structure of natural magnetite

“…The satellite reflections were sensitive to electron-beam irradiation and disappeared after a short period of irradiation so the modulated structure may be metastable. The commensurate phase P" of Feo.9o20 (Manenc, 1963;Andersen & Sletnes, 1977;Ishiguro & Nagakura, 1986) has not been detected in this investigation.…”

“…W/istite has a defect NaCl-type structure and is stable above 833 K (Darken & Gurry, 1945). By X-ray diffraction, Manenc (1963) found two different types of superstructure, called P' (Feo.92oO) and P" (Feo.9o20), resulting from Fe-cation deficiency. P" is commensurate with the fundamental structure and P' is incommensurate.…”