| Abstract Scope |
TiO2 nanocrystals can be fabricated by carving bulk TiO2 polycrystals using reductive H2-bearing gases, yielding single-crystal [001] nanowire arrays [Yoo et al., Adv. Mater., 16 (2004) 260; J. Mater. Res., 21 (2006) 1822]. However, the origin of the strongly anisotropic nanowire morphology remains largely unexplored. In this study, we formulate a phase-field model to investigate the TiO2 morphology evolution during nanocarving. The model incorporates TiO2 reduction reaction, Ti3+ diffusion, and anisotropies in surface energy, diffusivity and reaction rate. Through systematic simulations, we elucidate the roles of different anisotropy factors in nanocrystal morphologies at different carving stages, identifying the strong reaction rate anisotropy as the dominant factor for experimentally observed nanowire morphologies. We further explore the effect of grain misorientation angle, generating a nanocarving morphology map to guide grain orientation control. This study provides insights into microstructure evolution mechanisms during nanocarving and guidances for related microstructure control. |