8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Tue 611:23-14:00P2.67Role of the fluid and porosity formation duringsolvent-mediated phase transformationsChristophe Raufaste, 1 Bjørn Jamtveit, 2 Timm John, 3 Paul Meakin, 2 and Dag K.Dysthe 21 University of Nice, LPMC, LPMC, Parc Valrose 06108, Nice, France2 PGP, Oslo, Oslo, Norway3 Institut für Mineralogie, Universität Münster, Münster, GermanyWater solutions play a key role in the time evolution of solid-to-solid reactions. From rockalteration in Earth Sciences to industrial processes, such as cement hydration, pharmaceutical orexplosives formulations, the presence of the fluid phase allows an easier constituents transport andconsequently higher reaction rates. Such ”solvent-mediated phase transformations” [1] are generallyaccompanied by volume changes which contribute to the porosity of the new-formed solidmaterial. The question of the interplay between fluid transport, chemical reaction and porosityformation needs to be addressed to fully understand the underlying mechanisms of such processes.We focus on initially nonporous crystals. In that case the porosity formation is a prerequisite,since the new-formed pores allow a transport of the reactive solution through the reacted materialup to the interface between the original and reacted materials. The KBr − KCl − H 2 O systemis studied as a model system for dissolution/precipitation reaction since reaction is remarkablyquick at ambient conditions. The interface between the original crystal and the reacted phase isimaged in situ and recorded at the micron scale. Our observations reveal important insights aboutthe mechanism of porosity formation in solvent-mediated transformations. The reacted phaseexhibits a surprisingly organized pattern due to an intimate coupling, localized in space, betweendissolution and precipitation. Porosity is strongly heterogeneous and anisotropic, taking the shapeof channel-like pores connecting the interface of reaction to the bulk reactive solution [2]. Thisstudy shows that such transformations are self-organized and lead to surprising porosity patterns.This explains the high reaction rates generally observed in such systems.[1] P. T. Cardew, R. J. Davey. Proc. R. Soc. A 398, 415-428 (1985)[2] C. Raufaste, B. Jamtveit, T. John, P. Meakin, D. K. Dysthe. Proc. R. Soc. A 467, 1408-1426(2011)67