Preparation and Evaluation of Carbon Black-MWCNT Nanocomposites for Microwave Absorption

Nanocomposites in toroidal shaped sample have been prepared and electromagnetic (EM) and microwave absorbing properties at different thicknesses have been studied using simulation code for metal backed single layer absorber. The vector network analyser (Model PNA E8364B, Software module 85071E) attached with coaxial measurement set up has been utilised to investigate the EM and microwave absorbing properties of the samples in the frequency range of 218 GHz. Fabrication of the sample has been carried out using carbon powder and multiwall carbon nanotubes (MWCNT) as filler in different ratios in two component polyurethane (PU) matrix. The complex permittivity of the composite is found to be frequency dependent. The findings reveals that the absorption performances of composite sample having 250mg carbon black and 50 mg MWCNT in one ml polyurethane showed minimum absorption peak of -26.2 dB (RL, min,) at a matching frequency (fm) of 11.6 GHz with more than -10 dB loss in the frequency range of 10.3 GHz to 13.5 GHz for in 2.0 mm thickness. Morphology and thermal behavior of the nanocomposites were also investigated using SEM and TGA.