Effects of the Etching Process on Infrared Emissivity Properties of Ti₃C₂T_x MXene: Implications for Infrared Stealth

Ti 3 C 2 T x MXene is expected to achieve infrared stealth by regulating its thermal radiation properties. In this study, Ti 3 C 2 T x MXene films were prepared by using the acid etching method, and the effects of etchants (HCl/LiF, HF, and NH 4 HF 2 ) on the film structure as well as the infrared radiation properties were systematically studied. The intercalation process used to exfoliate single/few-layer nanosheets was found to accelerate the oxidation and increase the resistance of MXene. The mechanism behind these effects on emissivity was explained in detail. Based on these findings, the most suitable preparation process for low-emissivity MXene was selected. The resulting Ti 3 C 2 T x film (HL-f), which used HCl/LiF as an etchant for Ti 3 AlC 2, has a high conductivity of 3119 S/cm that reflects numerous infrared waves reaching its surface while exhibiting a low emissivity of only 0.13. The colloidal solution (HL-s) made with HCl/LiF as an etchant was sprayed directly onto a PI substrate as a coating with infrared stealth capabilities, thermal stability, and Joule heating properties, reducing the emissivity from 0.87 to 0.14. This work provides guidance for improving MXene preparation methods and their applications in related fields while demonstrating the great potential of HCl/LiF-etched Ti 3 C 2 T x MXene as a low-emissivity infrared stealth material.