阶段过渡,化动态和固态扩散在纳米试管中
Vincent C Holmberg1, Matthew G Panthani, Brian A Korgel
1Department of Chemical Engineering, Texas Materials Institute, Center for Nano and Molecular Science and Technology, University of Texas at Austin, Austin, TX 78712, USA.
Science (New York, N.Y.)
|October 17, 2009
概括
在碳外内加热一根纳米线,揭示了黄金/的高温形成,比散热温度低15°C. 与散装材料相比,纳米级封闭改变了结晶和扩散动态.
科学领域:
- 材料科学 材料科学 材料科学
- 纳米技术 纳米技术
- 物理化学 物理化学
背景情况:
- 局限的纳米尺度几何学显著改变材料的特性和转换.
- 电子显微镜可以直接可视化纳米级的动态过程.
研究的目的:
- 为了研究一个连接到一个金 (Au) 纳米晶体的 (Ge) 纳米线的热演变和相位行为.
- 在加热过程中观察碳外对体积和界面面积的影响.
主要方法:
- 在传输电子显微镜内进行现场加热实验.
- 一个纳米线附着在一个金纳米晶体上的观测,被一个碳外封装.
- 将样品加热到 900°C.
主要成果:
- 黄金/ (Au/Ge) 脱形成的温度低于大体脱温度的15°C.
- 毛细管的压力将融的eutectic驱动到纳米线上.
- 在碳的球形尖端结晶.
- 固态扩散的Ge下纳米线发生在700°C以上,与Au扩散明显比散装Ge慢.
结论:
- 纳米尺度的封闭和保护性碳外影响了体形成温度和结晶行为.
- 封闭的纳米线中的扩散速率与散装材料有很大差异,观察到的Au扩散速度较慢.
- 电子显微镜对于理解在热应力下纳米级材料转变至关重要.
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