Synthesis and Characterization of Mesoporous Multi-Walled Carbon Nanotubes at Low Frequencies Electromagnetic Waves

For electromagnetic absorbing and shielding applications, carbon nanotubes (CNT) are widely used due to their excellent electrical and physical properties. Fabrication of microwave absorbing materials involves the use of compounds capable of generating dielectric and/or magnetic losses when impinged by an electromagnetic wave. The presence of lattice defects e.g. vacancies and dislocations contributes to the loss and attenuation in the electromagnetic waves, which in turn remarkably enhance the absorption ability of the material. With the CVD technique which is known to produce several lattice defects in the final product, aligned MWCNTs were successfully synthesized by pyrolizing toluene and ferrocene in an inert argon environment. The morphology analysis of the aligned MWCNTs was conducted via FESEM and TEM analysis, to reveal the average length of approximately 295 μm, with diameters in the range of 60-200 nm. EDS analysis indicates the high yield of CNTs, with more than 90% in weight composition, with less than 5 % Fe impurities presence. Textural properties of MWCNTs were studied by measuring pore size and BET surface area. To understand the response of CNTs to an electromagnetic field, permeability and permittivity measurement were conducted in the frequency range of 100 Hz to 110 MHz. In conclusion, the presence of defects in MWCNTs is desirable for enhanced electromagnetic absorption ability.