Controlling the Selective Formation of Calcium Sulfate Polymorphs at Room Temperature

Calcium sulfate is a naturally abundant and technologically important mineral with a broad scope of applications. However, controlling CaSO₄ polymorphism and, with it, its final material properties still represents a major challenge, and to date there is no universal method for the selective production of the different hydrated and anhydrous forms under mild conditions. Herein we report the first successful synthesis of pure anhydrite from solution at room temperature. We precipitated calcium sulfate in alcoholic media at low water contents. Moreover, by adjusting the amount of water in the syntheses, we can switch between the distinct polymorphs and fine‐tune the outcome of the reaction, yielding either any desired CaSO₄ phase in pure state or binary mixtures with predefined compositions. This concept provides full control over phase selection in CaSO₄ mineralization and may allow for the targeted fabrication of corresponding materials for use in various areas.     

In‐situ and laboratory Raman analysis in the field of cultural heritage: the case of a mural painting

The present work exemplifies, over a mural painting from the 14th century, the advantages of an initial exhaustive research using latest generation hand‐held spectrometers (Raman mainly) in order to perform the characterization of valuable objects of cultural heritage. These in‐situ techniques (meaning on‐site and non‐destructive) are very useful to study the pigments and materials, to identify the nature and causes of some of the main sources of deterioration and to examine past repaints. In addition, the in‐situ measurements are of great importance in the selection of micro‐samples for the laboratory analyses. In this particular case, the combination of these results with the chemical imaging analyses in the laboratory (such as Raman and energy dispersive X‐ray spectrometry imaging) allowed the characterization of the mural painting, including, the identification of all restoration works applied in the past. Copyright © 2014 John Wiley & Sons, Ltd.     

How Much Water Does Calcined Gypsum Contain?

Ordered water : Gypsum has been used for construction for millennia. The structure and water content of calcined gypsum, CaSO₄?0.5 H₂O, has been under discussion until now: single‐crystal structure analysis (see picture: S yellow, Ca gray, O blue, H red) provides an ordered model that is confirmed by DFT calculations.