%0 Journal Article %A Fu, Hailu %A Huang, Jianshi %A Shen, Luming %A Li, Yi %A Xu, Liheng %A Wei, Fang %A Li, Jinye %A Jiang, Guangming %D 2018 %T Sodium Cation-Mediated Crystallization of α‑Hemihydrate Whiskers from Gypsum in Ethylene Glycol–Water Solutions %U https://acs.figshare.com/articles/journal_contribution/Sodium_Cation-Mediated_Crystallization_of_Hemihydrate_Whiskers_from_Gypsum_in_Ethylene_Glycol_Water_Solutions/7163360 %R 10.1021/acs.cgd.8b00947.s001 %2 https://acs.figshare.com/ndownloader/files/13179839 %K calcium sulfate dihydrate %K α- HH nucleation %K Sodium Cation-Mediated Crystallization %K α- HH nucleation accounts %K as-synthesized α- HH whiskers exhibit %K α- HH %K 0.10 M Na %K EG volume percentage %K DH -α-HH transformation %K α- HH whiskers %X This work reports a facile sodium cation (Na+)-mediated approach to synthesize α-calcium sulfate hemihydrate (α-HH) whiskers, with calcium sulfate dihydrate (DH) as the precursor, in ethylene glycol (EG)–water solutions at 95.0 °C and atmospheric pressure. The as-synthesized α-HH whiskers exhibit a width of 3–5 μm and a length of 600–700 μm, showing highly promising applications as reinforcing agents. An EG volume percentage of 22.5 vol % is necessary to drive the conversion of DH to α-HH at 95.0 °C, while the Na+ plays a crucial role in regulating both the conversion kinetics and the whisker quality. The conversion rate presents a volcano-like variation versus Na+ concentration (0.05–0.30 M) with the peak one achieved at 0.10 M Na+. Simultaneous boosting and retarding effects of the metallic cation on the DH-α-HH transformation were reported for the first time in alcohol–water systems. The tuning role of Na+ arises from its effect on the supersaturation for α-HH nucleation, the surface property of precursor DH via Na+ doping, as well as surface precipitate of the solid solution eugsterite (Na4Ca­(SO4)3·2H2O). In shape control, an increased Na+ concentration can elongate the α-HH but simultaneously raise the possibility of whisker agglomeration. The bridging action of Na+ among the crystal interfaces associated with the α-HH nucleation accounts for the morphology evolution of whiskers, and the optimal Na+ concentration is 0.075 M with an average aspect ratio of 105. This work provides a systematical investigation on the cation-mediated crystallization of α-HH whiskers, which should lead to a deeper understanding of whisker formation and advance their scale applications. %I ACS Publications