Structural and high GHz frequency EMI (electromagnetic interference) properties of carbonyl iron and boron nitride hybrid composites

Hybrid (mix of magnetic Carbonyl Iron and dielectric ceramic Boron Nitride) powders, composites and methods for making these powders that are potentially useful for high frequency EMI (electromagnetic interference) applications are described here. Comparative study of polymer composites, made using these hybrid powders by a speed mixing process and a high energy ball milling method (HEBM), has been conducted and their properties (microstructural and electromagnetic) have been characterized at high GHz frequency bands. Magnetic permittivity values of the two different samples are widely different and magnetic loss tangent values for hybrid flakes made using a HEBM process is considerably higher than speed mixed samples, especially at lower GHz frequencies. However dielectric loss tangent values are similar for both samples. EMI (Electromagnetic Interference) absorbing performance of the composites made using the two different hybrid fillers is also compared at 18-40 GHz frequency band using a radar absorption model. It was observed that the speed mixed hybrid filler composite samples show much better EMI absorber performance with a minimum reflection loss value of -12.5 dB at a frequency of 34.5 GHz which is useful for many new emerging industrial applications.