Abstract:
Microwave absorptive materials (MAMs), are gaining great attention due to their demand in aerospace, electronics, medical and military fields. These materials shield microwaves by absorption or reflection of the radiations. In the present study, the electromagnetic parameters of materials are determined based on the physical principle of interaction between electromagnetic field and the electromagnetic medium. Herein; polyurethane (PU) and epoxy nanocomposites i.e.; PU/SWCNT, PU/MnO2, Epoxy/SWCNT and Epoxy/MnO2 are designed and tested for their microwave absorption behavior. Maxwell Garnett effective medium theory is used to calculate the effective permittivity of the 0.4% samples of nanomaterials. Then these composite materials are modelled to find out the scattering parameters (S-Parameters) in X and Ku band region (8-18GHz) of microwave energy. The Reflection Loss, total Shielding and percentage absorption are calculated for all these samples. In X-band region, 5mm thick sample of 0.4% Epoxy/MnO2 composite showed -20.6dB reflection loss (RL), which is the highest of all the four composites. It is important to note that Epoxy/ MnO2 composite has the highest values of real part of effective permittivity, as calculated by Maxwell Garnett effective medium theory. That may be the reason for enhanced microwave absorptive property of this composite. As far as SWCNTs composite concerns, 40% PU/SWCNTs composite provides maximum RL value of -14.8dB in X-band region. The high concentration of SWCNT, and small length can be responsible for low reflection loss of SWCNTs composites.
Whereas, in Ku band region, again Epoxy/MnO2 composite with 4mm thickness furnished highest value of reflection Loss, i.e. -21.3dB. It was found that both SWCNTs and MnO2, the nanofillers, use reflection phenomenon for microwave shielding. The improved microwave absorbing properties suggested promising application of Epoxy/ MnO2 nanocomposites in high-performance microwave absorber. Outcomes of this research can lead to futuristic nature of nanocomposites to be used as microwave absorbents for military applications.
