Understanding Cd Nano-Whisker Growth on Ti₂CdC MAX Phase from the Perspective of Atomized Cd Migration

Cd-based coatings are prone to spontaneous Cd whisker growth, raising safety concerns, particularly short-circuit risk. Although various environmental driving forces exist, the intrinsic factors affecting whisker growth have been overlooked. Herein, we investigate the growth mechanism of Cd nano-whiskers on the Ti₂CdC MAX phase, a substrate material. Our results demonstrate that both the number and length of Cd nano-whiskers increase rapidly with rising cultivation temperatures. Furthermore, even after leaving the controlled temperature environment, the growth behavior of the whiskers continues to be influenced by the initial cultivation temperature. We speculate that this temperature dependency is related to the migration of atomized Cd, driven by the easily disrupted weak Ti-Cd bonds within the Ti₂CdC structure. Additionally, due to the thermally activated nature of atomized Cd migration, Cd nano-whiskers grow rapidly on Ti₂CdC. This work expands our understanding of Cd whisker growth by emphasizing the role of the chemical environment of Cd atoms in the substrate material, highlighting the significance of atomized Cd, and refining the growth mechanism of nano-whiskers involving atomized Cd.