Development of Analytical Approach to Fabricate Composites for Microwave Absorption

Nowadays microwave absorbing materials (MAMs) is in keen research interest because of its various applications in civil as well as in defense. Magnetic, dielectric, and polymeric composite materials are of research focus to achieve good microwave absorption with wide bandwidth (BW). The characteristics of the materials such as permittivity and permeability affect the absorption properties of MAMs. The variation in the proportion of the constituents of the composites (volume fraction ratio), size, shape, and coating thickness of composite has a drastic effect on the absorption behavior of MAMs. Hence, the engineering of absorbing materials with a desirable value of reflection loss (RL) and BW with respect to their physical properties is of great importance. Role of constituents as host or inclusion decides the properties of composites. Research on various material parameters on the microwave absorption is still hanging on a trial and error or knowledge-based experimental determination of the absorption characteristic which is very cumbersome, time consuming, and above all a costly affair. There is an urgent need of the optimization of the parameters of the composites for a desired RL over a broad frequency range for practical feasibility of microwave absorber. Thus, in this paper, an attempt has been made for the development of an analytical model to predict the selection of materials for the composite [as an inclusion ( $m_{i}$ ), volume fraction ( $V_{f}$ )], and a coating thickness ( $t$ ) of the composites for a predetermined RL and BW in-accordance with the requirement of the end user. A Mixing model for the extraction of effective permittivity ( $\varepsilon _{\mathrm {eff}}$ ), permeability ( $\mu _{\mathrm {eff}}$ ) of the composite, and Genetic algorithm as an optimization technique for the determination of $m_{i}$ , $V_{f}$ , and t for a specific RL and BW are used for proposing the algorithm. The developed model has been tested on the nanostructured NiFe 2 O 4 (NF) and TiO 2 (T) composite, which may possibly have good absorption in $C$ - and $X$ -bands. The computed results were experimentally validated and found that it is in good agreement. The proposed algorithm has been applied to other composites with different morphologies like nanostructured nickel ferrite (NF)—nickel zinc ferrite (NZF) and calcium ferrite (CF)—graphite (G).