High purity, multi-walled carbon nanotubes (MWNTs) were synthesized by catalytic chemical vapor deposition (CCVD) using acetylene as the carbon source based on a zeolite NaX template loaded with different iron contents. Well shaped zeolite NaX nanocrystals (FAU) of 50 nm were synthesized by a hydrothermal method according to a well designed composition of 3.5Na 2 O:Al 2 O 3 :2.1SiO 2 :1000H 2 O. The ion-exchange method was used for supporting different Fe 2+ contents in the zeolite NaX

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... als to provide effective catalysts for carbon nanotube (CNT) formation. Thermal treatment of Fe 2+ -exchanged zeolite NaX nanocrystals resulted in the formation of ¡-Fe 2 O 3 phase at 450°C in air. Transmission electron microscopy (TEM) images showed that the inner and outer tube diameters of the MWNTs were in the range of 3.85.0 nm and 6.38.8 nm, respectively, which were smaller than those of conventional thick MWNTs. The yield of the MWNTs was increased up to 47.1% with increasing iron content in pores of the zeolite crystals, which allowed the pores to be defined as containers for catalysts and as a guide template for MWNT growth.