Abstract
The influence of NH4Cl on hydrothermal formation of CaSO4·0.5H2O whiskers from CaSO4·2H2O precursor at 135°C was investigated in this paper. Compared with the blank experiment, the presence of 3 × 10−2 mol·L−1NH4Cl led to the increase of the lengths of the whiskers from 50 to 160 μm to 150 to 300 μm and the decrease of the diameters from 1.0 to 1.5 μm to 0.2 to 0.5 μm. The dissolution of CaSO4·2H2O was accelerated by the complex interactions with NH4Cl and the soluble cations, which led to the decrease of the induction time for the occurrence ofα-CaSO4·0.5H2O from 46 minutes to 34 minutes and the formation of CaSO4·0.5H2O whiskers with high aspect ratios. Furthermore the critical supersaturation for the formation ofα-CaSO4·0.5H2O was investigated.
Highlights
The formation of calcium sulfate (CaSO4) whiskers with high aspect ratios has drawn much attention in recent years owing to their nontoxic and perfect mechanical properties and the wide applications in the fabrication of intensified composites [1–4]
Α-CaSO4⋅0.5H2O whiskers can be prepared by wet processes, including hydrothermal method, microemulsion, or acidification methods, and the hydrothermal method has been widely used owing to its high efficiency and easy control of the formation process [6–9]. α-CaSO4⋅0.5H2O whiskers were usually produced by hydrothermal conversion of CaSO4⋅2H2O at 100 to 150∘C, and the hydrothermal dissolution of CaSO4⋅2H2O and the precipitation of CaSO4⋅0.5H2O were connected with the process parameters such as the supersaturation, temperature, pH, and the organic/inorganic additives [10–15]
CaSO4⋅0.5H2O whiskers with high aspect ratios were produced by hydrothermal treatment of CaSO4⋅2H2O precursor at 135∘C in the presence of NH4Cl
Summary
The formation of calcium sulfate (CaSO4) whiskers with high aspect ratios has drawn much attention in recent years owing to their nontoxic and perfect mechanical properties and the wide applications in the fabrication of intensified composites [1–4]. Α-CaSO4⋅0.5H2O whiskers were usually produced by hydrothermal conversion of CaSO4⋅2H2O at 100 to 150∘C, and the hydrothermal dissolution of CaSO4⋅2H2O and the precipitation of CaSO4⋅0.5H2O were connected with the process parameters such as the supersaturation, temperature, pH, and the organic/inorganic additives [10–15]. The hydrothermal conversion of CaSO4⋅2H2O to CaSO4⋅0.5H2O was accelerated by the presence of CTAB and inhibited by the presence of arginine, aspartic acid, serine, glycine and sodium dodecyl sulfate, and so forth [16–. CaSO4⋅0.5H2O whiskers with high aspect ratios were produced by hydrothermal treatment of CaSO4⋅2H2O precursor at 135∘C in the presence of NH4Cl. The influences of NH4Cl on supersaturation, induction time, and morphology of the CaSO4⋅0.5H2O whiskers were investigated and the corresponding phenomena were discussed
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