Georges Naessens

Search for Magnetite in Lunar Rocks and Fines

Magnetite crystals larger than 2 micrometers are absent from rocks and fines. Smaller opaque spheres in the fines can tentatively be identified as magnetite. Their concentration is not higher than 1 x 10-6 particle per particle smaller than 1 millimeter. In the fines from the sampling site, the contribution of material similar to type 1 carbonaceous meteorites is insignificant, either because it never existed, or because it was evaporated or comminuted by impact or was diluted by indigenous material. Other magnetite habits typical of carbonaceous meteorites or possibly of cosmic dust or comets were also sought without success-such as rods, platelets, framboids, spherulites, and idiomorphic crystals.

Structural properties of Zn-substituted epitaxial thin-films

We optimized the deposition of thin-films using inverted cylindrical magnetron sputtering and report here a detailed structural study, especially in relation to crystal growth, associated surface morphology, precipitation and other secondary phases important for flux pinning. We find that the epitaxial quality of the Zn-substituted films is decreased compared with high-quality pure films prepared under identical conditions. The pure films have smoother surfaces, while those of Zn-substituted films contain pinholes and outgrowths. Secondary phases and a-axis grains were observed in the Zn-substituted films. precipitates with typical dimensions of 50 - 100 A have been found in both pure and Zn-substituted samples. However, their density of about , observed in the pure films, is significantly reduced in the Zn-substituted films when increasing the Zn concentration up to 4%.

Influence of the reduction and oxidation on the morphology of iron and manganese monoxide grains

Abstract The morphology of iron and manganese monoxides reduced and oxidized in the 1073–1273 K temperature range, in equilibrium with CO/CO 2 gas mixture, was observed using electron scanning microscopy. Essential differences in the crystallization mode through the monoxide layer with the oxidation ratio gradient are presented. Particular attention is paid to evidence the relation between the chemical composition and the crystallization mode of Fe 1− y O and MnO 1+ x ,