Microwave absorption performance of M-type hexagonal ferrite and MXene composite in K_a and V bands (5G mmWave frequency bands)

Lightweight and thin electromagnetic interference (EMI) shielding materials with high shielding effectiveness (SE) have been investigated over the last decade to address the unreliability issue in all electronic technologies caused by EMI. Herein, we report the SE of the novel Ti₃C₂T_x MXene/doped-hexaferrite (hexagonal ferrite: BaCo_0.3Ti_0.3Fe_11.4O₁₉) composite. This composite suppresses electromagnetic (EM) waves dominantly via absorption over the frequency range from 30 to 50 GHz for millimeter-wave (mmWave) applications. Two-dimensional inorganic compound Ti₃C₂T_x MXene was synthesized using the LiF-HCl etching process, and doped-hexaferrite particles were prepared using a conventional solid-state reaction. Then, the MXene/doped-hexaferrite composite was fabricated by mixing MXene/polyvinyl-pyrrolidone (PVP) containing solution with the hexaferrite particles. The composites were characterized by a vibrating sample magnetometer for static magnetic properties and a vector network analyzer for dynamic magnetic and dielectric properties and microwave absorbing performance. A high magnetocrystalline anisotropy of hexaferrite shifted the microwave absorption peak to mmWave bands such as K_a- and V-bands, unlike spinel ferrite. The 1.5 mm thick MXene/45 wt% doped-hexaferrite composite shows a broad effective bandwidth (reflection loss (RL) less than 10 dB) of 7 GHz in the frequency range from 38 to 45 GHz. This excellent absorbing performance is mainly attributed to improved impedance matching and enhanced dielectric and magnetic losses of the composite. It was found that the SE was dominated by absorption instead of reflection. The experimental results demonstrate that the MXene/BaCo_0.3Ti_0.3Fe_11.4O₁₉ hexaferrite composite can be a promising and effective EM wave absorber material for millimeter-wave applications such as the fifth-generation (5G) network and opens up new opportunities for THz (6G network) EMI materials development.