Electromagnetic Properties of Carbon Nanotube/BaFe(12−x)Ga(x)O(19)/Epoxy Composites with Random and Oriented Filler Distributions

The microwave properties of epoxy composites filled with 30 wt.% of BaFe(12–x)Ga(x)O(19) (0.1 ≤ x ≤ 1.2) and with 1 wt.% of multi-walled carbon nanotubes (CNTs) were investigated in the frequency range 36–55 GHz. A sufficient increase in the microwave shielding efficiency was found for ternary 1 wt.%CNT/30 wt.% BaFe(12–x)Ga(x)O(19)/epoxy composites compared with binary 1% CNT/epoxy and 30 wt.% BaFe(12–x)Ga(x)O(19)/epoxy due to the complementary contributions of dielectric and magnetic losses. Thus, the addition of only 1 wt.% of CNTs along with 30 wt.% of barium hexaferrite into epoxy resin increased the frequency range where electromagnetic radiation is intensely attenuated. A correlation between the cation Ga(3+) concentration in the BaFe(12–x)Ga(x)O(19) filler and amplitude–frequency characteristics of the natural ferromagnetic resonance (NFMR) in 1 wt.%CNT/30 wt.% BaFe(12–x)Ga(x)O(19)/epoxy composites was determined. Higher values of the resonance frequency [Formula: see text] (51.8–52.4 GHz) and weaker dependence of [Formula: see text] on the Ga(3+) concentration were observed compared with pressed polycrystalline BaFe(12–x)Ga(x)O(19) ([Formula: see text] = 49.6–50.4 GHz). An increase in the NFMR amplitude on the applied magnetic field for both random and aligned 1 wt.% CNT/30 wt.% BaFe(12–x)Ga(x)O(19)/epoxy composites was found. The frequency of NFMR was approximately constant in the range of the applied magnetic field, H = 0–5 kOe, for the random 1 wt.% CNT/30 wt.% BaFe(12–x)Ga(x)O(19)/epoxy composite, and it slightly increased for the aligned 1 wt.% CNT/30 wt.% BaFe(12–x)Ga(x)O(19)/epoxy composite.