Mosaic Patterns in Reaction-Diffusion Systems
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We study a variety of reaction-diffusion processes that lead to the formation of exotic patterns. 1. We carry out precipitation reactions in gel media, wherein the interdiffusion of the co-precipitates takes place from multiple diffusion sources arranged in a symmetric framework. The precipitation zones are delimited by clear polygonal boundaries in congruence with the spatial distribution of the diffusion pools. 2. A displacement reaction in a solid-gel medium is conducted as a carbonic acid diffusion front invades an agar-calcium hydroxide gel putty. The formation of calcium carbonate yields a diversity of patterns, ranging from mosaic structures to Liesegang bands. 3. A Liesegang experiment precipitating lead chromate from the interdiffusion of lead and chromate ions in 2D yields a pattern of rings exhibiting revert spacing. When the diffusion comes from a constantly fed unstirred source (or reactor, CFUR), the patterns transit to a chaotic regime which is sensitive to the concentrations used and the flow rate.
KeywordsPatterns Chaos Liesegang Portlandite Polygons Reaction-diffusion
This study was supported by a University Research Board (URB) grant of the American University of Beirut (AUB). X-ray diffraction, IR spectroscopy, freeze drying and SEM were performed at the Central Research Science Lab (CRSL) of the AUB.
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