Design, fabrication and characteristic of two-layer microwave absorbers composed of magnetic micropowder-rubber composites in X-band frequency range

Both experimentally and theoretically, a two-layer microwave absorber exhibits the possibility of meeting the demand for effective radar absorbing materials. The design methodology is based on the modulus of permittivity (permeability) which obeys a logarithmic law of mixtures, and the loss tangent is related through a linear law of mixtures. A linear regression analysis performed on the data points provides constants that can be used to predict the effective parameters at different frequencies, and a program is presented that computes the optimum amount of magnetic micropowder and the required thickness for each layer. A two-step sulfur treatment is then applied to preparation of the two-layer absorber, vulcanized firstly by heating at 165 °C for 15 min and then at 150 °C for 4 h. Finally, tensile strength is experimentally investigated as well as power reflection coefficient. Test results indicate the two-layer absorber has excellent mechanical and microwave attenuation properties for X-band frequency.