Ti–O phases combined with carbon materials are attractive for applications in energy storage, photocatalysis, and gas sensing. The oxidation of Ti-based MXenes at high temperatures has been proposed as an effective synthesis method for carbon-supported anatase and rutile TiO2. Here, the thermal degradation and phase transformation of Ti3C2T2 (T = O or OH) under vacuum, air, and water vapor environments are investigated using reactive molecular dynamics simulations. Ti3C2(OH)2 is most stable under vacuum and water vapor, and is least stable in air. In contrast, Ti3C2O2 shows the lowest stability in air. In the air environment, anatase and rutile TiO2 phases are found regardless of the surface termination, while in water vapor, the water molecules disrupt the formation of a distinct phase. Under vacuum, we observe the formation of rock-salt TiO and present a comprehensive analysis of its transformation. The phase transformation temperatures for Ti3C2O2 are 700, 600, and 700 K for vacuum, air, and water vapor environments, respectively. Ti3C2(OH)2 showed phase stability up to 1100, 600, and 900 K under vacuum, air, and water vapor environments, respectively. Our comprehensive atomistic analysis provides detailed descriptions of the thermal degradation process and phase transformation of Ti3C2T2, which helps to understand the nanoscale aspects of the experimental work.

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The growing application of laser welding in the industry motivates the development of computational models to help improve and understand the details of the laser welding process. Classical molecular dynamic (MD) or finite element (FE) methods are insufficient to model the process due to several limitations. The coupling of both methods provides a unique approach for modeling the laser welding process. A laser welding model that accounts for free-electron conduction and three-dimensional laser beam growth was developed on the basis of this coupling. The model was tested on a Cu sample, and the results showed that the amount of energy required to weld the interface was much lower than the energy used in previous studies of MD laser processes. The temperatures in the weld pool and the heat-affected zones were similar to those in previous FE studies. The crystal structure near the weld pool matched the observations of the previous MD studies. Moreover, the scanning speeds associated with this model were relatively higher than those of previous MD models due to the effects of fast electron conduction.

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