Electromagnetic and microwave absorption properties of magnetic stainless steel powder in 2–18 GHz

Abstract

Ferritic stainless steel (FSS) powder exhibits magnetic loss, dielectric loss, and excellent resistance to corrosion and oxidation. In this study, four types of ferritic grades 409L, 410L, 430L, and 434L powders are used as magnetic fillers of microwave absorbers. Using the transmission/reflection method, the complex permittivity and permeability of the FSS-epoxy composites can be measured in 2-18 GHz. The real part of complex permittivity ɛ′ does not exhibit significant variation (∼4.0 to 6.0%) while the corresponding imaginary part ɛ″, however, exhibits relatively large variation. The magnetic susceptibility (μ′−1) of FSS-epoxy absorber is negative above 10 GHz due to the natural magnetic resonance. For FSS 430L with 40 wt.% for a thickness of 3 mm, the calculated reflection loss at 9.7 GHz reaches −11.4 dB and the corresponding 409L absorber has minimum reflection loss −5.2 dB at 11.1 GHz.