Mg0.5Zn0.5Fe2O4-polyurethane thin nanocomposite coating as broadband microwave absorber

We report the synthesis of Mg0.5Zn0.5Fe2O4 (MZF) nanoparticles by gel combustion technique followed by fabrication of thin layer (~ 100 μm) of ferrite–polymer nanocomposite on aluminum substrate and its application on broadband absorption properties over the microwave frequency range of 4–15 GHz. The particle size of ferrite powder was controlled by changing citrate to nitrate molar ratios of precursors, which exhibit different adiabatic isotherms. XRD analysis showed that ferrite phase formation occurred for all systems and the system with lowest crystallite size (~ 30 nm) was obtained for the stoichiometric citrate to nitrate molar ratio. The nanocomposite coating showed excellent broadband absorption properties with absorptivity greater than 88%. This implied that the real and imaginary part of the surface impedance values of the nanocomposite coatings are close to 377 Ω and 0 Ω respectively, which is impedance of free space over the significant region of the frequency band of interest. The stoichiometric fuel based MZF of smallest average particle size showed best microwave absorption properties. The as-developed MZF nanocomposite coating showed minimum reflection from the coating over this frequency band, which can solve various electromagnetic interference issues, stealth technology, and the radiated EMI management in on board spacecraft and several others.