Transformation of Calcium Sulphate Hemihydrate to Insoluble Anhydrite

Ultrasonic sound speed analysis of hydrating calcium sulphate hemihydrate

This article focuses on the hydration, and associated microstructure development, of b-hemihydrate to dihydrate (gypsum). The sound velocity is used to quantify the composition of the fresh slurry as well as the hardening and hardened—porous—material. Furthermore, an overview of available hydration kinetic and volumetric models for gypsum is addressed. The presented models predict the sound vel...

In Situ Crystallization of the Insoluble Anhydrite AII Phase in Graphene Pockets.

Single-distilled water encapsulated in graphene pockets has been studied by aberration-corrected high-resolution transmission electron microscopy and electron energy loss spectroscopy at an acceleration voltage of 80 kV. Inside the graphene pockets, crystallization and in situ crystal growth are reported and identified as the insoluble AII phase of CaSO4 (anhydrite) in a quasi-two-dimensional s...

Experimental Shock Transformation of Gypsum to Anhydrite: a New Low Pressure Regime Shock Indicator

Infrared Spectroscopic Studies of Calcium Sulphate heated to High Temperatures

Infrared spectroscopic investigations have shown that on the basis of changes in the v3 , S0 4 band which occur when calcium sulphate is heated from 400° to 1400 °C, there are two forms of insoluble anhydrite, designated as ß'and /?-CaS04 . /?'-CaS04 is metastable and is completely converted into /?-CaS04 by heating above 1000 °C. With longer heating periods this conversion can even take place ...

Zinc hydroxide sulphate and its transformation to crystalline zinc oxide.

The thermal transformation of zinc hydroxide sulphate hydrate to zinc oxide has been examined using synchrotron X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and surface area measurements. By collecting X-ray diffraction data in situ, we found that the dehydration of zinc hydroxide sulphate pentahydrate proceeded in discrete steps to form anhydrous zinc hydroxide ...