Physical properties, such as electrochemical and electromagnetic properties, of two-dimensional MXenes can be improved by enhancing their stability. However, MXenes fabricated via acid etching contain defects, which affect their physical properties. In this study, a method to effectively remove Al residues using only water during MXene fabrication while maintaining structural stability is proposed. The fabrication and intercalation of MXenes are controlled via epitaxial self-intercalation of H2O-etched Cr2(AlLi)C. On the basis of this mechanism, the room-temperature ferromagnetism of two-dimensional few-layered Cr2CTx MXenes, which has a specific saturation magnetization of ~0.26 emu/g and a Curie temperature of > 353 K, is experimentally verified. The calculated electronic band structure implies that the semimetal Cr2CTx MXene has a band gap of 0.75 eV. This study opens new possibilities for the research and applications of industrial-scale manufacturing of MXenes and 2D semiconductors.
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Highly pure and dense Ti2AlC and Ti2AlSn0.2C bulks were prepared by hot pressing with molar ratios of 1:1.1:0.9 and 1:0.9:0.2:0.85, respectively, at 1450 ℃ for 30 min with 28 MPa in Ar atmosphere. The phase compositions were investigated by X-ray diffraction (XRD); the surface morphology and topography of the crystal grains were also analyzed by scanning electron microscopy (SEM). The flexural strengths of Ti2AlC and Ti2AlSn0.2C have been measured as 430 and 410 MPa, respectively. Both Vickers hardness decreased slowly as the load increased. The tribological behavior was investigated by dry sliding a low-carbon steel under normal load of 20-80 N and sliding speed of 10-30 m/s. Ti2AlC bulk has a friction coefficient of 0.3-0.45 and a wear rate of (1.64-2.97)×10-6 mm3/(N·m), while Ti2AlSn0.2C bulk has a friction coefficient of 0.25-0.35 and a wear rate of (2.5-4.31)×10-6 mm3/(N·m). The influences of Sn incorporation on the microstructure and properties of Ti2AlC have also been discussed.