title: Precipitation and Crystallization Kinetics in Silica Gardens.
abstract: Silica gardens are extraordinary plant-like structures resulting from the complex interplay of relatively simple inorganic components. Recent work has highlighted that macroscopic self-assembly is accompanied by the spontaneous formation of considerable chemical gradients, which induce a cascade of coupled dissolution, diffusion, and precipitation processes occurring over timescales as long as several days. In the present study, this dynamic behavior was investigated for silica gardens based on iron and cobalt chloride by means of two synchrotron-based techniques, which allow the determination of concentration profiles and time-resolved monitoring of diffraction patterns, thus giving direct insight into the progress of dissolution and crystallization phenomena in the system. On the basis of the collected data, a kinetic model is proposed to describe the relevant reactions on a fundamental physicochemical level. The results show that the choice of the metal cations (as well as their counterions) is crucial for the development of silica gardens in both the short and long term (i.e. during tube formation and upon subsequent slow equilibration), and provide important clues for understanding the properties of related structures in geochemical and industrial environments.
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstrasse 31, 93040, Regensburg, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Glaab
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstrasse 31, 93040, Regensburg, Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: Rieder
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstrasse 31, 93040, Regensburg, Germany.
authors.forename: Regina
authors.initials: R
authors.lastname: Klein
authors.affiliation: Laboratorio de Estudios Cristalográficos, IACT (CSIC-UGR), Av. de las Palmeras 4, 18100, Armilla (Granada), Spain.
authors.forename: Duane
authors.initials: D
authors.lastname: Choquesillo-Lazarte
authors.affiliation: Laboratorio de Estudios Cristalográficos, IACT (CSIC-UGR), Av. de las Palmeras 4, 18100, Armilla (Granada), Spain.
authors.forename: Emilio
authors.initials: E
authors.lastname: Melero-Garcia
authors.affiliation: Laboratorio de Estudios Cristalográficos, IACT (CSIC-UGR), Av. de las Palmeras 4, 18100, Armilla (Granada), Spain.
authors.forename: Juan-Manuel
authors.initials: JM
authors.lastname: García-Ruiz
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstrasse 31, 93040, Regensburg, Germany.
authors.forename: Werner
authors.initials: W
authors.lastname: Kunz
authors.affiliation: Material Physics, BASF SE, Carl-Bosch-Strasse 38, 67056, Ludwigshafen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Kellermeier
keywords: X-ray absorption spectroscopy; X-ray diffraction; kinetics; self-assembly; silica gardens