The Solvothermal Synthesis of New Layered Silicates : The Anhydrous Phyllosilicates
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The natural phyllosilicates are thermally instable due to the presence of OH group in the lattice. On the basis of the mica phlogopite type structure [KMg<SUB>3</SUB> (AlSi<SUB>3</SUB>) O<SUB>10</SUB> (OH) <SUB>2</SUB>] and through the anionic substitution OH<SUP>-</SUP> → O<SUP>2-</SUP> and the cationic substitutions (Al<SUP>3+</SUP> → Si<SUP>4+</SUP> and Mg<SUP>2+</SUP> → Al<SUP>3+</SUP>) a new composition has been proposed : K (Mg<SUB>2</SUB>Al) Si<SUB>4</SUB>O<SUB>12</SUB> . In order to get a homogeneous starting material, due to the complexity of the proposed composition [K (Mg<SUB>2</SUB>Al) Si<SUB>4</SUB>O<SUB>12</SUB>], the first step was the preparation of the process precursor through a sol-gel. The conventional treatment (high temperature) of such a precursor leading to the formation of a mixture of three-dimensional silicates, a solvothermal reaction was developed, the non-aqueous solvent required for the preparation of the sol being used in supercritical conditions. The resulting material appears to be a bidimensional oxide isostructural of the mica-type phlogopite. All the physico-chemical characterizations confirm such a structure and the absence of OH group in the lattice, in particular the IR spectroscopy. Through such an illustration, solvothermal reactions, appear a powerful way for preparing new materials.
- The Review of High Pressure Science and Technology
The Review of High Pressure Science and Technology 7, 1435-1437, 1998
The Japan Society of High Pressure Science and Technology