Development of thin broad band radar absorbing materials using nanostructured spinel ferrites

Stealth applications now emphasise on development of efficient Radar Absorbing Materials of light weight, less coating thickness, broad bandwidth of absorption along with cost effective raw materials and manufacturing techniques. Therefore, in this paper an attempt has been made to develop such an efficient cost effective radar absorbing material which possesses broad band absorption with less coating thickness. Unconventionality of acquiring impedance match for a double layer absorber of nanostructured nickel ferrite (NF) with reasonably good dielectric properties and its cation substituted counterpart, nickel zinc ferrite (NZF) with enhanced magnetic properties has been thoroughly investigated for radar wave absorption for very low coating thickness. Complex permittivity and permeability of NF and NZF with crystallite sizes of 10.0 and 16.0 nm, respectively, are measured and used as the data bases. The microwave absorption properties of the ferrites are correlated with their size, morphology, permittivity, permeability, thickness and bandwidth of absorption. Multilayering has been performed using the optimization through Genetic Algorithm in order to attain suitable impedance matching layer for minimum reflection loss (RL) at lower thickness. The results indicate an enhancement in the absorption with RL value of -45.0 dB for a moderately low coating thickness of 1.72 mm. Single layers NF, NZF and multilayer NF-NZF are fabricated over the aluminium sheets and the results are experimentally verified.