engleski

Influence Of The Microstructure Of The Aluminosilicate Amorphous Precursor In The Synthesis Of Leucite And Kalsilite

Amorphous aluminosilicate gels (prepared in two ways: (A) by ion-exchange of sodium ions from zeolitic Na-aluminosilicate gel with the alkaline cation K resulting in K-gel(A) and (B) by direct precipitation from the corresponding K-aluminate and K-silicate solutions resulting in K-gels(B)) were used to synthesize ceramics after their temperature induced transformation. The process was taking place in an isothermal mode at three different temperatures and the samples taken during the crystallization as well the starting materials (gels) were investigated by powder X-ray diffraction method, FT-IR spectroscopy, SEM, light and polarizing microscopy, BET analysis and Thermogravimetry (TG) and differential scanning calorimetry (DSC) of the gels. Phase analyses of the transformation/crystallization processes have shown that: pure crystalline tetragonal leucite crystallizes from K-gel (A) in the temperature range from 1423 to 1483 K whereas pure hexagonal kalsilite crystallizes from K-gel (B) and K-exchanged zeolite A in the temperature range between 1423 and 1483 K and 1258 and 1298 K, respectively. The process of crystallization as is obtained from the calculated kinetic parameters follows for both the crystallization a zero rate equation.

leucite; kalsilite; ceramics

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