Kaatz Forrest H, Bultheel Adhemar
Mesalands Community College, 911 South 10th Street, Tucumcari, NM 88401, United States of America.
Nanotechnology. 2018 Aug 24;29(34):345701. doi: 10.1088/1361-6528/aac6b4. Epub 2018 May 22.
Au-Cu and Pt-M (M = Fe, Co, and Ni) nanocluster alloys are currently being investigated world-wide by many researchers for their interesting catalytic and nanophase properties. The low temperature behavior of the phase diagrams is not well understood for alloys with nanometer sizes and shapes. We consider two models for low temperature ordering in the phase diagrams of Au-Cu and Pt-M nanocluster alloys. These models are valid for sizes ∼5 nm and approach bulk values for sizes ∼20 nm. We study the phase transitions in nanoclusters with cubic, octahedral, and cuboctahedral shapes, covering the compositions of interest. These models are based on studying the melting temperatures in nanoclusters using the regular solution, mixing model for alloys. From our data, experiments on nanocubes about 5 nm in size, of stoichiometric AuCu and PtM composition, could help differentiate between the models. Dispersion data shows that for the three shapes considered, octahedra have the highest percentage of surface atoms for the same relative diameter. We summarize the effects of structural ordering on the catalytic activity and suggest a method to avoid sintering during annealing of Pt-M alloys.
目前，许多研究人员正在全球范围内研究金 - 铜和铂 - 金属（M = 铁、钴和镍）纳米团簇合金，因其具有有趣的催化和纳米相特性。对于具有纳米尺寸和形状的合金，相图的低温行为尚未得到很好的理解。我们考虑了金 - 铜和铂 - 金属纳米团簇合金相图中低温有序化的两种模型。这些模型对于尺寸约为5纳米的情况有效，对于尺寸约为20纳米的情况接近体相值。我们研究了具有立方、八面体和立方八面体形状的纳米团簇中的相变，涵盖了感兴趣的成分。这些模型基于使用合金的正规溶液混合模型研究纳米团簇中的熔化温度。根据我们的数据，对化学计量比的金铜和铂金属组成、尺寸约为5纳米的纳米立方体进行实验，有助于区分这些模型。分散数据表明，对于所考虑的三种形状，在相同相对直径下，八面体具有最高比例的表面原子。我们总结了结构有序化对催化活性的影响，并提出了一种在铂 - 金属合金退火过程中避免烧结的方法。
