Effects of composition on the microwave absorbing properties of FexNi100?x (x?=?0–25) submicro fibers

The morphology and composition of a material have important influences on its electromagnetic parameters and microwave absorbing property. In this paper, the Fe_xNi_100?x (x?=?0–40) powders were prepared by an oxalate precipitation-thermal decomposition process. When x?=?0–25, the powders show submicro fibrous morphologies, however, when x?>?25, some granular particles appear due to the weak coordination ability of ethylenediamine with Fe²⁺ in the oxalate precipitation process. The electromagnetic parameters and microwave absorbing properties of the composites of the Fe_xNi_100?x (x?=?0–25) submicro fibers with 80?wt% paraffin were studied in 2–18?GHz. Compared with the Ni/paraffin composite, enhanced electromagnetic losses and microwave absorbing properties are observed for the Fe₁₀Ni₉₀/paraffin and Fe₂₅Ni₇₅/paraffin composites. The Fe₁₀Ni₉₀/paraffin shows the best microwave absorbing property that at the composite thickness of 2.0?mm, the effective bandwidth and minimum RL reach 3.78?GHz (12.21–15.99?GHz) and ?45.37?dB at 13.90?GHz, respectively. The excellent microwave absorbing property of the Fe₁₀Ni₉₀/paraffin composite is from its high loss factor and the quarter-wavelength cancellation mechanism.