Abstract We have made direct observations of the Brownian motion of individual nanosized liquid lead inclusions in solid aluminum by in-situ transmission electron microscopy. The process was found to depend strongly on the size of the inclusion and the anisotropy of the interfacial energy. The rate controlling mechanism was the nucleation of steps on facets of the equilibrium shape and the diffusion of Al along the liquid-solid interface. Because the Al-Pb interface undergoes a roughening transition at T r ≈ 820 K, the step nucleation barrier decreases with increasing temperature and vanishes completely at T r . By including the temperature dependence explicitly, we demonstrate that the contribution of the step energy to an Arrhenius plot of the data has a slope greater than the actual activation energy at temperature T by a factor T r /( T r - T ). In addition, we show that the diffusion barrier for interfacial transport makes a substantial contribution. Our analysis reconciles a large discrepancy between activation energies obtained from the temperature and size dependences of the process and solves the apparent paradox posed by the observation that some particles are frozen in non-equilibrium shapes while nearby smaller particles are sufficiently mobile to undergo rapid Brownian motion.

中文翻译：

---

固态铝基体中纳米级液态铅夹杂物的步进控制布朗运动

摘要 我们通过原位透射电子显微镜直接观察了固体铝中单个纳米级液态铅包裹体的布朗运动。发现该过程强烈依赖于夹杂物的大小和界面能的各向异性。速率控制机制是平衡形状面上台阶的成核和铝沿液固界面的扩散。由于 Al-Pb 界面在 T r ≈ 820 K 处经历粗糙化转变，阶梯形核势垒随温度升高而降低，并在 T r 处完全消失。通过明确地包括温度依赖性，我们证明了阶跃能量对数据的阿伦尼乌斯图的贡献具有比温度 T 下的实际活化能大一个因子 T r /( T r - T ) 的斜率。此外，我们表明界面传输的扩散屏障做出了重大贡献。我们的分析调和了从过程的温度和尺寸依赖性获得的活化能之间的巨大差异，并解决了观察到的明显悖论，即一些粒子以非平衡形状冻结，而附近的较小粒子则足够移动以进行快速布朗运动.