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Direct measurements of quasi-zero grain boundary energies in ceramics

机译：陶瓷中准零晶界能的直接测量

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摘要

Nanocrystalline bulk materials (also called nanograined materials) are intrinsically unstable due to the excess grain boundary (GB) free energies. Dopants designed to segregate to boundaries have been proposed to lower excess GB energies, increasing stability against coarsening and enabling nanostructure features to survive high temperature processing and operational environments. It has been theoretically proposed that the GB energy of a material can eventually become zero as a function of dopant concentration, signifying negligible driving force for growth-an infinitely stable nanomaterial. In this work we use ultrasensitive microcalorimetry to experimentally measure the absolute GB energy of gadolinium-doped nanocrystalline zirconia as a function of grain size and show that the energy can indeed reach a quasi-zero energy state (～0.05 J/m~2) when a critical GB dopant enrichment is achieved. This thermodynamic condition leads to unprecedented coarsening resistance, but is a temperature dependent function; since increasing temperatures deplete the GB as the dopant dissolves back in the crystalline bulk.
机译：由于过量的晶界（GB）自由能，纳米晶体块状材料（也称为纳米颗粒材料）本质上是不稳定的。已经提出了设计用于隔离到边界的掺杂剂，以降低过量的GB能量，提高抗粗化的稳定性，并使纳米结构特征能够在高温处理和操作环境中生存。从理论上讲，材料的GB能量最终可以变为零，这是掺杂剂浓度的函数，这意味着无限稳定的纳米材料的生长驱动力可忽略不计。在这项工作中，我们使用超灵敏的量热法，通过实验测量了掺杂lin的纳米晶氧化锆的绝对GB能量与晶粒尺寸的函数关系，并表明该能量确实可以达到准零能态（〜0.05 J / m〜2）。达到了关键的GB掺杂剂富集。这种热力学条件导致了前所未有的抗粗化性，但它是一个与温度有关的功能。因为升高的温度会耗尽GB，因为掺杂剂会溶解回到晶体块中。

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  • 来源
    《Journal of Materials Research》 |2017年第1期|166-173|共8页
  • 作者

    Nazia Nafsin; Ricardo H.R. Castro;

  • 作者单位

    Department of Materials Science and Engineering & NEAT ORU, University of California-Davis, Davis, CA 95616, USA;

    Department of Materials Science and Engineering & NEAT ORU, University of California-Davis, Davis, CA 95616, USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
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  • 正文语种 eng
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