The influence of different Ni contents on the radar absorbing properties of FeNi nano powders

Abstract

Firstly, Fe_100−xNi_x nano powders with different Ni contents were fabricated by a liquid phase reduction method in order to obtain an agent with excellent wave-absorbing properties. Then the electromagnetic parameters in the range 1–18 GHz were measured by a vector network analyzer through coaxial cable law. The influences of Ni content on the organizational structure and radar-absorbing features of Fe_100−xNi_x powders were systematically investigated. The results showed that the peak intensity of Ni₃Fe phase significantly increased with increasing Ni content, while that of Fe₂O₃ phase decreased. Magnetic loss of Fe_100−xNi_x nano powders was dominant in the frequency range of 2–14 GHz. The peak value of magnetic loss tangent (tan δ_m) moved to the higher frequency band with the increase of Ni element content. The tan δ_m of Fe₂₀Ni₈₀ nano powders was 0.5–0.8 for 4–10 GHz and ≥0.3 for 2.5–14 GHz, which indicated excellent wave-absorbing properties. In the range 1–18 GHz, the radar wave absorption peak appeared when the thickness of the single-layer Fe₂₀Ni₈₀ material was up to 1 mm, and moved to lower frequency as the thickness increased. It was possible to effectively broaden the wave-absorbing band and improve absorbing properties though putting a fiberglass/E-51 epoxy resin layer on the surface of the Fe₂₀Ni₈₀ nano powders, which had better matching characteristics with air. After adding the fiberglass/E-51 epoxy resin layer, with a thickness of 1 mm, the bandwidth when the reflectivity was ≤−4 dB increased from 7.65 GHz to 9.35 GHz. The frequency of the wave-absorbing peak reduced from 15.62 GHz to 14.60 GHz. Meanwhile, the lowest reflectivity changed from −12.12 dB to −16.77 dB.