A novel way to synthesize calcium sulfate whiskers with high aspect ratios from concentrated calcium nitrate solution

摘要

An innovative approach was developed to synthesize calcium sulfate whiskers by dropwise adding sulfuric acid solution into abundant concentrated calcium nitrate solution under atmospheric pressure. The effect of mixing styles of reactants on product morphology was determined by SEM. Combined with SEM, XRD, TG-DSC were used to characterize products. Dihydrate CaSO4 whiskers with high aspect ratios (approximate 93.5) could be directly synthesized at room temperature. Then, the whiskers transformed to hemi-hydrate and anhydrous CaSO4 whiskers after heat treatment using microwave at 140 degrees C and 180 degrees C, respectively. The latter whiskers also own high aspect ratios. In addition, nitric acid (concentration, 170 g/L) was regenerated in the same process of three single-phase and well crystallized CaSO4 whiskers synthesis. (C) 2018 Elsevier B.V. All rights reserved.