Εξειδίκευση τύπου :	Άρθρο σε επιστημονικό περιοδικό
Τίτλος:	Nucleation pathway of calcium sulfate hemihydrate (bassanite) from solution: Implications for calcium sulfates on Mars
Δημιουργός/Συγγραφέας:	Stawski, Tomasz M. Besselink, Rogier Chatzipanagis, Konstantinos Hoevelmann, Joern Benning, Liane G. Van Briessche, Alexander E. S.
Εκδότης:	American Chemical Society
Ημερομηνία:	2020-02-06
Γλώσσα:	Αγγλικά
ISSN:	1932-7447 1932-7455
DOI:	10.1021/acs.jpcc.0c01041
Περίληψη:	CaSO4 minerals (i.e. gypsum, anhydrite and bassanite) are widespread in natural and industrial environments. During the last several years, a number of studies have revealed that nucleation in the CaSO4-H2O system is non-classical, where the formation of crystalline phases involves several steps. Based on these recent insights we have formulated a tentative general model for calcium sulfate precipitation from solution. This model involves primary species that are formed through the assembly of multiple Ca2+ and SO42- ions into nanoclusters. These nanoclusters assemble into poorly ordered (i.e. amorphous) hydrated aggregates, which in turn undergo ordering into coherent crystalline units. The thermodynamic (meta)stability of any of the three CaSO4 phases is regulated by temperature, pressure and ionic strength with gypsum being the stable form at low temperatures and low to medium ionic strengths, and anhydrite the stable phase at high temperatures and lower temperature at high salinities. Bassanite is metastable across the entire phase diagram but readily forms as the primary phase at high ionic strengths across a wide range of temperatures, and can persist up to several months. Although the physicochemical conditions leading to bassanite formation in aqueous systems are relatively well established, nanoscale insights into the nucleation mechanisms and pathways are still lacking. To fill this gap, and to further improve our general model for calcium sulfate precipitation, we have conducted in situ scattering measurements at small- and wide-angles (SAXS/WAXS) and complemented these with in situ Raman spectroscopic characterization. Based on these experiments we show that the process of formation of bassanite from aqueous solutions is very similar to the formation of gypsum: it involves the aggregation of small primary species into larger disordered aggregates.
Τίτλος πηγής δημοσίευσης:	The Journal of Physical Chemistry C
Τόμος/Κεφάλαιο:	124
Τεύχος:	15
Σελίδες:	8411–8422
Θεματική Κατηγορία:	[EL] Φυσική και θεωρητική χημεία[EN] Physical and theoretical chemistry [EL] Γεωλογία[EN] Geology [EL] Επιστήμες περιβάλλοντος[EN] Environmental sciences [EL] Φασματοσκοπία[EN] Spectroscopy
Λέξεις-Κλειδιά:	Materials science Soft condensed matter Anios Calcium Crystallization Precipitation Scattering
Κάτοχος πνευματικών δικαιωμάτων:	Copyright © 2020 American Chemical Society
Ηλεκτρονική διεύθυνση στον εκδότη (link):	http://arxiv.org/pdf/2002.02185v3 https://pubs.acs.org/doi/10.1021/acs.jpcc.0c01041
Ηλεκτρονική διεύθυνση περιοδικού (link) :	https://pubs.acs.org/journal/jpccck
Σημειώσεις:	32 pages, Supporting Information p.31-32
Εμφανίζεται στις συλλογές:	Ινστιτούτο Θεωρητικής και Φυσικής Χημείας (ΙΘΦΧ) - Επιστημονικό έργο