Synthesis of nickel and magnesium phyllosilicates with 1:1 and 2:1 layer structures.

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Nickel and magnesium phyllosilicates with 1:1 and 2:1 layer structures were prepared from silicic acid and metal chlorides (NiCl2 or MgCl2) in water. The phyllosilicates were allowed to crystallize at room temperature or 200°C. The 1:1 and 2:1 phyllosilicates were selectively prepared by adjusting the metal ion to silicon ratio (M/Si) in the starting mixtures. The 1:1 phyllosilicate was crystallized from the starting mixture with an M/Si ratio of 1.5 and the 2:1 phyllosilicate was crystallized from the mixture with an M/Si ratio of 0.5. The increase in the OH−/M ratio in the starting mixture accelerated the crystallization to phyllosilicates. Crystallization to the phyllosilicates occurred even at room temperature, and a hydrothermal treatment at 200°C accelerated this process. The crystal size of the 1:1 phyllosilicates was larger than that of the 2:1 phyllosilicates. The nickel phyllosilicates crystallized faster than the magnesium phyllosilicates. These results can be explained by assuming successive copolymerization reactions of silicic acid and aqua metal ions, in which an intermediate with a 1:1 structure is involved. The acidity of the aqua metal ions plays an important role in the mechanism of the copolymerization process.
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