%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