Micro-Grating of Pseudomorphic Amorphous Phase and Micro-Cubic Crystalline Phase Obtained by Alkali Dissoluiton of Isothermal Treated Nh4-Zeolite A

Ammonium exchanged zeolites A were isothermally treated at 400-1000°C for durations up to 100 min in the air, and then were leached in 1 M NaOH solution at 70°C. The products were characterized by XRD, SEM, ICP-AES and ATR-FTIR. The results from isothermal treatments confirmed that the pseudomorphic transformations took place through the formations of an amorphous phase with the tweed-like patterns on the surface of the cubic solid and a subsequent recrystallization to a cubic-shaped composite of mullite and amorphous material. These characterizations supported the existence of a thin surface layer of zeolite crystals acting as a microvessel, which was consistent with a previous hypothesis. After leaching by hot alkali solution, micro-grating patterns appeared on the surfaces of the pseudomorphic amorphous phase which exhibited the tweed-like patterns. A cubic solid with fine voids were obtained from a composite of mullite and an amorphous phase. The observed differences in the surface morphology are closely related to the investigated solids.