Phase Diagram of Continuous Binary Nanoalloys: Size, Shape, and Segregation Effects.
Phase Diagram of Continuous Binary Nanoalloys: Size, Shape, and Segregation Effects.
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连续二元纳米合金的相图：尺寸、形状和偏析效应
DOI：
10.1038/srep41990
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发表时间：
2017-02-07
影响因子：
4.6
通讯作者：
Meng X
中科院分区：
文献类型：
--
作者：
Cui M;Lu H;Jiang H;Cao Z;Meng X
连续二元纳米合金的相图对材料设计和工业应用具有重要的指导意义。然而，纳米相图的实验测定是稀缺的，因为量热测量在纳米尺度上仍然是相当具有挑战性的。基于尺寸依赖的内聚能模型，我们建立了统一的纳米热力学模型，研究了尺寸、形状和偏析对连续二元纳米合金相图的影响。随着尺寸的减小或形状因子的增大，液固相温度降低，两相区缩小，表面偏析程度减小。随着尺寸的减小或形状因子的增大，存在偏析和不存在偏析的Cu-Au纳米合金的熔点均线性向较高的Au组分和较低的温度方向转移。通过对不同二元纳米合金表面偏析元素的分析，确定了基于固体表面能和原子尺寸的两种偏析规律。此外，所建立的模型可用于描述纳米合金的其他物理化学性质，如内聚能、催化活化能、有序-无序转变温度等，现有的理论预测、实验数据和分子动力学模拟结果均支持该模型的有效性。这将通过指导实验人员设计具有所需性能的双金属纳米晶体来帮助他们。
The phase diagrams of continuous binary nanoalloys are important in providing guidance for material designs and industrial applications. However, experimental determination of the nano-phase diagram is scarce since calorimetric measurements remain quite challenging at the nanoscale. Based on the size-dependent cohesive energy model, we developed a unified nano-thermodynamic model to investigate the effects of the size, shape, and segregation on the phase diagrams of continuous binary nanoalloys. The liquidus/solidus dropped in temperature, two-phase zone was narrowed, and the degree of surface segregation decreased with decrease in the size or increase in the shape factor. The congruent melting point of Cu-Au nanoalloys with and without segregation is linearly shifted to higher Au component and lower temperature with decreasing size or increasing shape factor. By reviewing surface segregated element of different binary nanoalloys, two segregation rules based on the solid surface energy and atomic size have been identified. Moreover, the established model can be employed to describe other physicochemical properties of nanoalloys, e.g. the cohesive energy, catalytic activation energy, and order-disorder transition temperature, and the validity is supported by available other theoretical prediction, experimental data and molecular dynamic simulations results. This will help the experimentalists by guiding them in their attempts to design bimetallic nanocrystals with the desired properties.