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Effects of Metal Ions on Crystal Morphology and Size of Calcium Sulfate Whiskers in Aqueous HCl Solutions
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文摘
The effects of metal ions such as Na+, K+, Mg2+, Cu2+, Al3+, and Fe3+ on the crystal morphology and size of calcium sulfate whiskers in aqueous HCl solutions were investigated. The average diameter, aspect ratio, length, crystal water content, phase composition, and elemental composition of the products were determined and compared. When the concentration of monovalent Na+ or K+ ions was low, with the increase in the ion concentration, the average diameter increased and the aspect ratio decreased. However, with further increase in the ion concentration, the average diameter decreased. The presence of divalent Mg2+ or Cu2+ ions increased the crystal diameter and length. All the products were calcium sulfate hemihydrate in the presence of Na+, K+, Mg2+, or Cu2+ ions within the studied concentration range. The presence of trivalent Al3+ or Fe3+ ions at low concentrations resulted in bigger and shorter crystals; furthermore, at higher ion concentrations, partial phase transformation from calcium sulfate hemihydrate to calcium sulfate dihydrate was induced. Among the metal ions investigated, only Na+ ions were found be incorporated into the crystals.

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