Partic. vol. 8 no. 3 pp. 240-244 (June 2010)
doi: 10.1016/j.partic.2010.01.005

Influence of temperature and solution composition on the formation of calcium sulfates

Kangbi Luo^{a, b}, Chunmei Li^{a, b}, Lan Xiang^b,* , Huping Li^a, Ping Ning^a

xianglan@mail.tsinghua.edu.cn

Abstract

Calcium sulfates (anhydrite and hydrates) were synthesized by mixing CaCl₂ and Na₂SO₄ solutions at room temperature followed by aging the resulting slurries at elevated temperatures. The variation of the morphology and structure of the calcium sulfates with aging temperature was investigated. Experimental results indicated that CaSO₄·2H₂O plates, CaSO₄·0.5H₂O whiskers and CaSO₄ spindles were formed at ≤100 °C, 130–160 °C and ≥170 °C, respectively. The formation and conversion of the calcium sulfates were discussed on the basis of characterization of the products and chemical analysis of the solutions. Compared to NaCl solution, pure water favors one-dimensional hydrothermal growth of CaSO₄·0.5H₂O whiskers owing to lower supersaturation.

Keywords

Calcium sulfates; Ceramics; Hydrothermal technology; Crystal growth