On this research, a development mechanism of vertically aligned carbon nanotubes (VACNT) on a nanostructured porous silicon template (NPSiT) was proposed primarily based on the experimental observations obtained. Camphor oil and ferrocene (Fe) have been used as a carbon supply and a catalyst, respectively. The NPSiT was optimised and used as a template to synthesise VACNT. The VACNT was synthesised on NPSiT by utilizing a double thermal chemical vapour deposition (DTCVD) technique. The synthesis was additionally carried out through a floated technique in a DTCVD reactor by utilizing an in-situ catalyst within the absence of any catalysts pre-treatment. Every of the expansion mechanisms was proposed primarily based on the TEM photos obtained at completely different synthesis situations. From the outcomes, a combined prime and backside development mannequin was proposed for the expansion mechanism of VACNT on the pores and pillars. Quite the opposite, the tip development mannequin was proposed for the expansion contained in the pores, whereas the valley development mannequin was proposed for the expansion inside the pillars of NPSiT. Moreover, a combined tip and valley development mannequin was proposed primarily based on the placement of Fe particles.