Ultra Fine Layered Silicate Synthesis from Synthetic Silicate Raw Material

This paper reports the results of experiments on ultra fine layered silicates Na-fluorotaeniolite and Na-fluorotetrasilicic mica synthesis in the melts prepared from reaction blends based on synthetic silicate raw material, namely synthetic magnesium silicate dihydrate (MSDH, MgO·SiO₂·2H₂O). The MSDH–Na₂SiF₆–LiF, MSDH–Na₂SiF₆–MgF₂ and MSDH–Na₂SiF₆–NaF blends, whose compositions are close to the stoichiometry of the Na-fluorotaeniolite (NaMg₂Li[Si₄O₁₀]F₂) and Na-fluorotetrasilicic mica (NaMg_2.5[Si₄O₁₀]F₂) were studied in the temperature range 1080–1225°C. Magnesium silicate dihydrate, the phase composition of synthesis products and layered silicates (Na-fluorotaeniolite and Na-fluorotetrasilicic mica) were examined using the crystal optical, X-ray diffraction at room and high temperatures, differential thermal and chemical analyses. It has been shown that studied blends possessed a high reactivity, owing to which the layered silicates were synthesized at lower temperatures (～180–300°C) and the duration of the synthesis was shortened severalfold. The maximal yield of the Na-fluorotetrasilicic mica was observed in the reaction blend with the Na₂SiF₆ and NaF as halogen-containing compounds. The specific effects of MSDH on the physicochemical processes proceeded during heat treatment of the reaction blends were described.