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Formation of calcium sulfate through the aggregation of sub-3 nanometre primary species.

Stawski TM, van Driessche AE, Ossorio M, Diego Rodriguez-Blanco J, Besselink R, Benning LG - Nat Commun (2016)

Bottom Line: The reaction starts through the fast formation of well-defined, primary species of <3 nm in length (stage I), followed in stage II by their arrangement into domains.The variations in volume fractions and electron densities suggest that these fast forming primary species contain Ca-SO4-cores that self-assemble in stage III into large aggregates.Within the aggregates these well-defined primary species start to grow (stage IV), and fully crystalize into gypsum through a structural rearrangement.

View Article: PubMed Central - PubMed

Affiliation: School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.

ABSTRACT
The formation pathways of gypsum remain uncertain. Here, using truly in situ and fast time-resolved small-angle X-ray scattering, we quantify the four-stage solution-based nucleation and growth of gypsum (CaSO4·2H2O), an important mineral phase on Earth and Mars. The reaction starts through the fast formation of well-defined, primary species of <3 nm in length (stage I), followed in stage II by their arrangement into domains. The variations in volume fractions and electron densities suggest that these fast forming primary species contain Ca-SO4-cores that self-assemble in stage III into large aggregates. Within the aggregates these well-defined primary species start to grow (stage IV), and fully crystalize into gypsum through a structural rearrangement. Our results allow for a quantitative understanding of how natural calcium sulfate deposits may form on Earth and how a terrestrially unstable phase-like bassanite can persist at low-water activities currently dominating the surface of Mars.

No MeSH data available.


Related in: MedlinePlus

SAXS patterns in stages I–III.(a) The first 390 s (stages I and II, excluding a frame at 30 s). The arrow points to the part of the curve affected by the structure factor; (b) Stage III as represented by the SAXS patterns between 420 and 840 s (solid lines represent best fits as described in the main text; please note that the directions of the time-axes in a and b are different); (c) progressive change in the intensities in the SAXS patterns between 750 and 5,400 s indicating the transitions from stages I–IV, and showing the I(q) dependencies and the change in scattering exponents (dashed lines).
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f2: SAXS patterns in stages I–III.(a) The first 390 s (stages I and II, excluding a frame at 30 s). The arrow points to the part of the curve affected by the structure factor; (b) Stage III as represented by the SAXS patterns between 420 and 840 s (solid lines represent best fits as described in the main text; please note that the directions of the time-axes in a and b are different); (c) progressive change in the intensities in the SAXS patterns between 750 and 5,400 s indicating the transitions from stages I–IV, and showing the I(q) dependencies and the change in scattering exponents (dashed lines).

Mentions: Stages I–III (from 0 to 1,500 s) of the process involved the formation of the primary species, the interparticle interactions between and aggregation of these well-defined primary species (Fig. 2).


Formation of calcium sulfate through the aggregation of sub-3 nanometre primary species.

Stawski TM, van Driessche AE, Ossorio M, Diego Rodriguez-Blanco J, Besselink R, Benning LG - Nat Commun (2016)

SAXS patterns in stages I–III.(a) The first 390 s (stages I and II, excluding a frame at 30 s). The arrow points to the part of the curve affected by the structure factor; (b) Stage III as represented by the SAXS patterns between 420 and 840 s (solid lines represent best fits as described in the main text; please note that the directions of the time-axes in a and b are different); (c) progressive change in the intensities in the SAXS patterns between 750 and 5,400 s indicating the transitions from stages I–IV, and showing the I(q) dependencies and the change in scattering exponents (dashed lines).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4821993&req=5

f2: SAXS patterns in stages I–III.(a) The first 390 s (stages I and II, excluding a frame at 30 s). The arrow points to the part of the curve affected by the structure factor; (b) Stage III as represented by the SAXS patterns between 420 and 840 s (solid lines represent best fits as described in the main text; please note that the directions of the time-axes in a and b are different); (c) progressive change in the intensities in the SAXS patterns between 750 and 5,400 s indicating the transitions from stages I–IV, and showing the I(q) dependencies and the change in scattering exponents (dashed lines).
Mentions: Stages I–III (from 0 to 1,500 s) of the process involved the formation of the primary species, the interparticle interactions between and aggregation of these well-defined primary species (Fig. 2).

Bottom Line: The reaction starts through the fast formation of well-defined, primary species of <3 nm in length (stage I), followed in stage II by their arrangement into domains.The variations in volume fractions and electron densities suggest that these fast forming primary species contain Ca-SO4-cores that self-assemble in stage III into large aggregates.Within the aggregates these well-defined primary species start to grow (stage IV), and fully crystalize into gypsum through a structural rearrangement.

View Article: PubMed Central - PubMed

Affiliation: School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.

ABSTRACT
The formation pathways of gypsum remain uncertain. Here, using truly in situ and fast time-resolved small-angle X-ray scattering, we quantify the four-stage solution-based nucleation and growth of gypsum (CaSO4·2H2O), an important mineral phase on Earth and Mars. The reaction starts through the fast formation of well-defined, primary species of <3 nm in length (stage I), followed in stage II by their arrangement into domains. The variations in volume fractions and electron densities suggest that these fast forming primary species contain Ca-SO4-cores that self-assemble in stage III into large aggregates. Within the aggregates these well-defined primary species start to grow (stage IV), and fully crystalize into gypsum through a structural rearrangement. Our results allow for a quantitative understanding of how natural calcium sulfate deposits may form on Earth and how a terrestrially unstable phase-like bassanite can persist at low-water activities currently dominating the surface of Mars.

No MeSH data available.


Related in: MedlinePlus