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.