Continuous fabrication of calcium sulfate whiskers with adjustable aspect ratio in microdroplets

Abstract Hemi-hydrate and anhydrous CaSO 4 whiskers with adjustable aspect ratio were continuously synthesized by the reactive crystallization of CaCl 2 to K 2 S 2 O 8 in microdroplets. The effects of solvent and reactive temperature were examined, with SEM and XRD characterizations. Hemi-hydrate and anhydrous CaSO 4 whiskers can be, respectively, obtained in aqueous and N,N-dimethylformamide solutions at 90 °C in 180 s. The addition of ethylene glycol or glycerol as well as increasing temperature could lead to the increase in length and aspect ratio of the whiskers. Thus this preparation technique provides a simple continuous route to synthesize CaSO 4 whiskers with two kinds of crystal structures in a short time, and adjustable lengths and aspect ratios.