Nano-composites, especially Fe (iron), and CNTs are of great interest due to their typical growth control characteristics. The ratio of Fe to CNT determines the length
and diameter of CNTs. The higher the ratio, the larger are the diameter and the length of CNTs that can be achieved. The Fe (magnetic material) is an impurity resulting from the catalyst
used during CNTs growth but it is usually removed after the synthesis is completed using HN03. The diameters of CNTs are in the order of 2nm. In this application, it would be preferable for CNTs to have the smallest diameters possible to increase the probability of CNTs being semiconductor during the synthesis and to align all the BSWCNTs in parallel to the desired direction of conduction [11 ]-[22].