Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics &Chemistry, Chinese Academy of Sciences, Urumqi 830011, China.
Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011, China.
Nat Commun. 2017 Feb 13;8:14462. doi: 10.1038/ncomms14462.
Experimental study of the atomic mechanism in melting and freezing processes remains a formidable challenge. We report herein on a unique material system that allows for in situ growth of bismuth nanoparticles from the precursor compound SrBiTaO under an electron beam within a high-resolution transmission electron microscope (HRTEM). Simultaneously, the melting and freezing processes within the nanoparticles are triggered and imaged in real time by the HRTEM. The images show atomic-scale evidence for point defect induced melting, and a freezing mechanism mediated by crystallization of an intermediate ordered liquid. During the melting and freezing, the formation of nucleation precursors, nucleation and growth, and the relaxation of the system, are directly observed. Based on these observations, an interaction-relaxation model is developed towards understanding the microscopic mechanism of the phase transitions, highlighting the importance of cooperative multiscale processes.
实验研究熔化和凝固过程中的原子机制仍然是一个艰巨的挑战。我们在此报告了一个独特的材料体系，该体系允许在高分辨率透射电子显微镜（HRTEM）内的电子束下，从前驱化合物 SrBiTaO 原位生长铋纳米颗粒。同时，通过 HRTEM 实时触发和成像纳米颗粒内的熔化和凝固过程。这些图像提供了原子尺度上的证据，证明了点缺陷诱导的熔化以及通过中间有序液体的结晶介导的凝固机制。在熔化和凝固过程中，可以直接观察到成核前体的形成、成核和生长以及系统的弛豫。基于这些观察结果，开发了一个相互作用弛豫模型来理解相变的微观机制，突出了协同多尺度过程的重要性。
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