A kind of Fe3N alloy powders prepared by high-temperature chemical nitriding treatment with excellent wave-absorbing properties in C band

Abstract

Firstly, the flake Fe95Si1B2P0.5Cu1.5 alloy powders were prepared by the combined technology of “medium frequency melting + 3D printing + high energy ball milling”, and then the flake single phase ε-Fe3(SiBPCu)-N powders were prepared by the chemical high temperature nitriding reaction using the flake alloy powders prepared as the precursors. The samples were characterized by Field Emission Scanning Electron Microscope (FESEM), X-ray Diffractometer(XRD) and Vector Network Analyzer, and the electromagnetic parameters and electromagnetic loss mechanism of the alloy powders prepared by different nitriding processes in 0.3–8.5 GHz band were focused, and wave-absorbing properties were optimized according to the transmission line theory finally. FESEM showed that holes were formed on the surface of the powders after nitriding, which was easy for electromagnetic waves to be absorbed. XRD confirmed that the physical phase structure of the alloy powder prepared after salt bath nitriding was ε-Fe3N, and average crystallite size of ε-Fe3N increased with the complete nitriding reaction. The generation of ε-Fe3N phase lead to an increase in the real part of the complex permittivity of the alloy powder, and the real part of the permeability decreases slightly, however, larger average crystallite size of ε-Fe3N is beneficial for the improvement of the permeability. After the nitriding reaction at 580 °C *1h, the loss mechanism of alloy powders is changed from magnetic loss dominated to a dual loss mechanism of dielectric loss dominated and magnetic loss supplemented, and the loss angle tangent value increased from 0.6 to 0.7 to 2.3–1.0, and the thickness values of interference absorption decreased significantly, which is conducive to the realization of the effect of strong absorption of thin material. Taking a multilayer laminate thickness of 5.0 mm as the design index, the optimized GF/FeSiBPCu-N powders (thickness of 1 mm)/GF composite plate has excellent wave absorption in the C-band with reflectivity R < −10 dB in the frequency band of 5.52 ∼ 8.5 GHz and a bandwidth of nearly 3 GHz, which has achieved a breakthrough.