Two-Dimensional Nanosheets of Titanium Carbonitride Ti₃CNT_x MXene for Microwave Absorption in the X and Ku Bands

New types of microwave absorption (MA) materials are urgently demanded in military radars and communication satellites working in the frequency of 8–12 GHz (X band) and 12–18 GHz (Ku band). However, it remains a challenge to make a material completely satisfy the MA requirements in the whole frequency bands. Here, two-dimensional (2D) Ti3CNTx nanolayered flakes were produced by HF etching of the Ti3AlCN precursor and exhibited an attractive MA performance in the X and Ku bands. The minimum reflection loss (RL) of Ti3CNTx was −41.36 dB at 11.76 GHz with a sample thickness of 1.94 mm. Meanwhile, an effective absorption band (EAB) of 4.24 GHz (in the frequency range 13.76–18 GHz) was achieved when the sample thickness was 1.5 mm. Spin-polarized density functional theory calculations confirmed that Ti3CNTx possesses magnetic moments. The magnetic moments mainly originate from the severe asymmetric spin of electrons of Ti atoms located between N and functional groups induced by the unpaired electrons of N atoms. The synergetic effects of dielectric loss and magnetic loss mechanisms contribute to the MA performance of Ti3CNTx. 2D nanosheets of Ti3CNTx are a promising candidate for MA applications.