The influence of different Ni contents on the radar absorbing properties of FeNi nano powders
Firstly, Fe100−xNix 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 Fe100−xNix 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 Fe100−xNix nano powders was dominant in the frequency range of 2–14 GHz. The peak value of magnetic loss tangent (tan δm) moved to the higher frequency band with the increase of Ni element content. The tan δm 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.