Mixed-valent iron in synthetic rasvumite, KFe2S3

Abstract

cases apparently typical structures developed at the interface, d) To test the possibility of mass-transfer within the solution, a 0.5 mW helium-neon laser illuminated a small area just below the surface, and the solution mixed with different types of dusts, e.g. aluminum dust and fumed silica (Aerosil). Similarly, hydrophobic reverse-phased fumed silica (Aerosil R972) was sprinkled on the surface. Laser illumination very clearly showed individual red speckles of the dust particles [14], however no bulk or surface movements were apparent during UV illumination. e) Kafri recently developed a sensitive deflectometry-type method [15] which utilizes laser light and Ronchi rulings. Hydrodynamic movements are easily detected by this technique, yet again no such movements were seen in our case. It seems to us that the phenomenon is purely due to diffusion processes or, at the most, to microscopic movements which we have not yet been able to detect. In our forthcoming paper we have expanded the phenomenon to purely thermal systems, suggesting that symmetry breaking is due to the buildup of concentration instabilities at the interface, as postulated theoretically by several authors [16].