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首页> 外文期刊>Philosophical magazine, B. Physics of condensed matter, electronic, optical, and magnetic properties >Structure and diffusional properties of nanocrystalline Pd
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Structure and diffusional properties of nanocrystalline Pd

机译：纳米Pd的结构与扩散性能

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摘要

Nanocrystalline (nc) solids are characterized by nanometre crystallite size and a high number of interfaces. In the present paper we report structural and diffusion studies on high purity nanocrystalline Pd (nc-Pd) that was prepared either by cluster compaction to full density or by severe plastic deformation. The size distribution of atomic free volumes in the interfaces studied by positron lifetime spectroscopy varies characteristically with the preparation technique. In pure high-density nanocrystalline metals, the crystallites grow rapidly upon annealing with an activation enthalpy of 1.1 eV determined for nc-Pd prepared by severe plastic deformation. The fast atomic diffusivity in the interfaces of nc-Pd is studied by sputter sectioning and Rutherford back scattering as a function of temperature, annealing state and type of diffusing metal atom. The diffusion process occurs at the interfaces, which migrate during diffusion annealing owing to rapid crystallite growth. Because of the high density of the specimens, the diffusivities are lower than reported earlier and similar to those in conventional grain boundaries.
机译：纳米晶体（nc）固体的特征在于纳米微晶尺寸和大量界面。在本文中，我们报告了对高纯度纳米晶Pd（nc-Pd）的结构和扩散研究，该纳米晶是通过团簇压实至全密度或严重的塑性变形制备的。通过正电子寿命光谱学研究的界面中无原子体积的尺寸分布随制备技术而变化。在纯高密度纳米晶体金属中，微晶在退火后迅速生长，其活化焓为1.1 eV，这是通过剧烈塑性变形制备的nc-Pd所确定的。通过溅射切片和卢瑟福反散射研究了nc-Pd界面中原子的快速扩散性，该扩散性是温度，退火状态和扩散金属原子类型的函数。扩散过程发生在界面处，由于快速的晶体生长，它们在扩散退火过程中迁移。由于样品的高密度，其扩散率比先前报道的要低，并且与常规晶界中的扩散率相似。

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