Preparation of an Fe<sub>3</sub>O<sub>4</sub> Nanoparticle/Carbonized\nHemp Fiber Composite with Superior Microwave Absorption Performance

The increasing concern\nover the negative impact of electromagnetic\nradiation and interference on humans has led to a growing interest\nin microwave-absorbing materials that are cost-effective, have a wide\nfrequency range, and have high efficiency. In this paper, an Fe<sub>3</sub>O<sub>4</sub> nanoparticle/carbonized hemp fiber composite\nwas successfully prepared using hemp fibers as the primary material\nand template. By carefully regulating the concentration of the iron\nnitrate impregnation solution, accurate loading of Fe<sub>3</sub>O<sub>4</sub> nanoparticles onto the carbonized hemp fiber was achieved.\nDue to its unique porous structure, the balance between impedance\nmatching, and electromagnetic loss, the prepared Fe<sub>3</sub>O<sub>4</sub> nanoparticle/carbonized hemp fiber composite exhibits light\nweight, high absorption strength, and broadband absorption characteristics.\nThe broadest absorption bandwidth of 6.1 GHz can be achieved, covering\nthe entire Ku-band, and the minimum refection loss is as low as −49.7\ndB. More interestingly, the Fe3O4 nanoparticle/carbonized hemp fiber\ncomposite exhibits attractive microwave absorption performance in\nboth the X-band and Ku-band even with a wide range of Fe<sub>3</sub>O<sub>4</sub> nanoparticle loading. Furthermore, simulations of the\nradar cross section (RCS) have confirmed that the Fe<sub>3</sub>O<sub>4</sub> nanoparticle/carbonized hemp fiber composite is effective\nin attenuating electromagnetic waves in a real environment. This work\npresents an economical and efficient method for the development of\nporous carbon-based absorbents.