In this work, an epoxy-based microwave absorbing coating (MAC) containing carbon nanotube (CNT), silicon carbide (SiC), and carbonyl iron (CI) particles was prepared. In order to achieve some optimum key properties such as high and broadband microwave absorbing properties, low density, and relatively low cost, a gradient structure and alternating multilayer structure are used simultaneously. The effect of a single layer containing one type of filler, single layer containing several types of fillers, and multilayer structures on mentioned key parameters are investigated. The electromagnetic parameters and the reflection loss (RL) versus frequency of samples were tested by network analyzer in the range of 2-18 GHz using the transmission/reflection method. As a final result, the multilayer MACs included nine layers in which each of the layers contained one type of the fillers (CNT, CI, and SiC) and three neat resin interlayers 2 mm in total thickness compared to other samples and provided a maximum return loss value of 17.6 dB at 08.50 GHz and an absorption bandwidth (RL < - 5 dB) of 16 GHz (2-18 GHz) with a density of 1.61 g/cm(3). So, it is simply possible to obtain an efficient MAC due to suitable microwave absorbing filler distribution in multilayer coatings for any respective application.
