The amorphization of metal nanoparticles in graphitic shells under laser pulses
The amorphization of metal nanoparticles in graphitic shells under laser pulses
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激光脉冲下石墨壳中金属纳米粒子的非晶化
DOI：
10.1016/j.carbon.2020.01.067
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发表时间：
2020-01
期刊：
影响因子：
10.9
通讯作者：
Banhart Florian
中科院分区：
文献类型：
--
作者：
Sun Jun;Sinha Shyam Kanta;Khammari Amir;Picher Matthieu;Terrones Mauricio;Banhart Florian
结果表明，包裹金属纳米颗粒的石墨壳有利于金属的非晶化，并稳定非晶相，防止再结晶。在原位电子显微镜实验中，对象在观察过程中暴露于激光脉冲，铁和钴纳米晶体在石墨壳中的非晶化被证明。红外纳秒脉冲导致金属快速熔化，然后溶解壳中的碳原子。在脉冲之后液体溶液的快速冷却导致非晶金属-碳相的固化。非晶相是亚稳态的，可以通过重复的激光脉冲或缓慢的热退火再结晶。再结晶需要异质形核，但在金属-石墨界面处是不利的，因此稳定非晶相以防止再结晶。实验的分析解释了作为碳在过渡金属中的亚稳溶液的非晶金属-碳相的形成机制，并且示出了石墨壳的封装如何可以是朝向另外不利的非晶金属或金属-碳相的稳定化的路线。
It is shown that graphitic shells encapsulating metal nanoparticles facilitate the amorphization of metals and stabilize the amorphous phase against recrystallization. In anin-situelectron microscopy experiment, where the objects are exposed to laser pulses during their observation, the amorphization of iron and cobalt nanocrystals in graphitic shells is demonstrated. The infrared nanosecond pulses lead to fast melting of the metal which then dissolves carbon atoms from the shell. Fast cooling of the liquid solution after the pulse results in the solidification of an amorphous metal-carbon phase. The amorphous phase is metastable and can be recrystallized by repeated laser pulses or slow thermal annealing. The recrystallization needs heterogeneous nucleation but is unfavorable at the metal-graphite interface and so stabilizes the amorphous phase against recrystallization. The analysis of the experiments explains the formation mechanisms of an amorphous metal-carbon phase as a metastable solution of carbon in a transition metal and shows how that the encapsulation by a graphitic shell can be a route towards the stabilization of otherwise unfavorable amorphous metal or metal-carbon phases.
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