Structural and morphological transformation of NaX zeolite crystals at high temperature

Nearly perfect crystalline zeolite structures could be used as proton exchangeable membranes for fuel cells, potentially offering major advantages over current separation and catalytic processes. They could also be employed as host materials for semiconductor clusters from 1 to 20 nm in diameter to create electronic and optical properties specific to the form of nano-crystals. Well-shaped NaX zeolite octahedral crystals of a large size of 30 μm were synthesized by a hydrothermal method in a mother solution having a 3.5Na2O:Al2O3:2.1SiO2:593–2000H2O composition. Thermal treatment of NaX zeolite crystals resulted in the formation of an intermediate amorphous phase at temperature above 800 and 900 °C and a crystalline phase of aluminium silicate (T < 1000 °C). Environmental scanning electron microscopy (ESEM), high resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, DTA/TGA and BET analysis were used to characterize the initial materials and the obtained products after various heat treatments.