Influence of activity of CaSO4 · 2H2O on hydrothermal formation of CaSO4 · 0.5H2O whiskers

Abstract

The influence of the activity of calcium sulfate dihydrate (CaSO 4·2H2O) on the hydrothermal formation of CaSO 4·0.5H2O whiskers was investigated in this paper, using commercial CaSO4·2H2O as the raw material. The experimental results indicated that the activity of CaSO4· 2H2O was improved after calcination of the commercial CaSO 4·2H2O at 150°C for 6.0 h followed by hydration at room temperature for 1.0 h, corresponding to the decrease of the agglomerated particle sizes from 29.7 m to 15.1 m, the increase of the specific surface areas (BET) from 4.75 m2·g-1 to 19.12 m2·g-1 and the grain sizes from 95 nm to 40 nm. The active CaSO4·2H2O produced by the calcination-hydration treatment favored the hydrothermal dissolution of CaSO4·2H2O, promoting the formation of hemihydrate calcium sulfate (CaSO4·0.5H2O) whiskers with high aspect ratios. © 2013 S. C. Hou and L. Xiang.