Metallic Whiskers Mushrooming on Mechanochemically Decomposed MAX Phases

Metallic whiskers grown on MAX phases bring concerns on their stability, and draw intense attention because of the impressing similarity they share with the troublesome tin whiskers primarily found on Sn-based solders in electronics. Herein, we report the mushrooming of tin whiskers associated with Ti2SnC, a MAX phase, and the whisker growth propensity correlated with the decomposition degree of Ti2SnC. Tin atoms, exposed as Ti2SnC mechanochemically decomposes, have high chemical potential and therefore can fast crystallize by “short-circuit” diffusion. Fascinatingly, the similar phenomenon happens to several other MAX phases, and the composition of whiskers is adjustable, boding well a paradigm-shifting means for preparing metallic whiskers. The fundamental role of active tin atoms in whisker growth manifested here shall lay foundation for developing whisker-mitigating methods for MAX phases, and furthermore, help comprehensively understand the growth mechanism of the tin whiskers haunted electronic industry for many decades.