Defect-engineered Ni-doped α-Fe2O3@TiO2/AC nanocomposites for optimized Ka-band radar absorber

The development of radar-absorbing materials at Ka-band frequencies is highly essential, considering that radar technology in this frequency range has begun to be widely used. In this regard, radar-absorbing materials composed of a combination of Ni-doped α-Fe2O3, TiO2, and activated carbon (AC) can be promising candidates. Herein, Ni-doped α-Fe2O3@TiO2/AC nanocomposites were successfully synthesized using a coprecipitation–simultaneous calcination method by varying the Ni content. The X-ray diffraction patterns confirmed the formation of Ni-doped α-Fe2O3, TiO2 rutile, and a minor Fe2TiO5 phase, while the AC tended to be amorphous but did not form an amorphous envelope. The FTIR results revealed the formation of Ni–O, Fe–O, C=C, and Ti–O vibrations, which represent the respective constituent materials of the Ni-doped α-Fe2O3@TiO2/AC nanocomposites. Based on the resulting morphology, the Ni-doped α-Fe2O3 was successfully coated by TiO2 and uniformly distributed on the AC surface. Furthermore, the VSM results revealed that the Ni-doped α-Fe2O3@TiO2/AC nanocomposites exhibited antiferromagnetic behavior. The defects and strain generated by the Ni substitution process imparted unique characteristics to the electromagnetic parameters of the nanocomposites, as reflected in the variations in the trends of the resulting complex permittivity and permeability. This study is the first to report the potential of undoped and Ni-doped α-Fe2O3@TiO2 as radar-absorbing materials, with optimum reflection losses of –35.32 dB and –27.16 dB, respectively.