Fabrication of hollow spheres composed of nanosized ZSM-5 crystals via laser ablation

Zeolite spheres with a core-shell structure were fabricated by a combination of pulsed laser deposition (PLD) and vapor-phase crystallization. Spherical mesoporous DAM-1 or SBA-15 was used as the silicon source and substrate. After vapor phase treatment hollow spherical shells consisting of nanosized ZSM-5 crystals were formed. In addition, the size of the ZSM-5 crystals in the shell ranges from 5 to 500 run which can be adjusted by changing the crystallization time (3-5 days) or the PLD coating thickness. The deposition rate was 13 nm/min at 120 mJ and 6.5 nm/min at 70 mJ. The ZSM-5 core-shell structure was characterized by XRD, IR, SEM and N-2 absorption. The dissolution of the mesoporous silica substrate and transport of the resulting silica species to the growing ZSM-5 film during vapor-phase crystallization is discussed in terms of a solution mediated transport mechanism. (c) 2005 Elsevier Inc. All rights reserved.