Department of Electrical Engineering, Stanford University, 496 Lomita Mall, Stanford, CA, 94305, USA.
Department of Materials Science and Engineering, Stanford University, 496 Lomita Mall, Stanford, CA, 94305, USA.
Nat Commun. 2018 May 2;9(1):1775. doi: 10.1038/s41467-018-04021-1.
Nanorods are promising components of energy and information storage devices that rely on solute-driven phase transformations, due to their large surface-to-volume ratio and ability to accommodate strain. Here we investigate the hydrogen-induced phase transition in individual penta-twinned palladium nanorods of varying aspect ratios with ~3 nm spatial resolution to understand the correlation between nanorod structure and thermodynamics. We find that the hydrogenated phase preferentially nucleates at the rod tips, progressing along the length of the nanorods with increasing hydrogen pressure. While nucleation pressure is nearly constant for all lengths, the number of phase boundaries is length-dependent, with stable phase coexistence always occurring for rods longer than 55 nm. Moreover, such coexistence occurs within individual crystallites of the nanorods and is accompanied by defect formation, as supported by in situ electron microscopy and elastic energy calculations. These results highlight the effect of particle shape and dimension on thermodynamics, informing nanorod design for improved device cyclability.
纳米棒由于其较大的表面积与体积比以及适应应变的能力，是在依赖溶质驱动的相变的能量和信息存储设备中有应用前景的组件。在这里，我们通过具有约 3nm 空间分辨率的、具有不同纵横比的单个五孪晶钯纳米棒来研究氢诱导的相转变，以了解纳米棒结构和热力学之间的相关性。我们发现，氢化相优先在棒的尖端形核，并随着氢压的增加沿纳米棒的长度推进。虽然对于所有长度，形核压力几乎保持不变，但相界的数量与长度有关，长度大于 55nm 的纳米棒总是存在稳定的相共存。此外，这种共存发生在纳米棒的单个晶粒内，并伴随着缺陷的形成，这得到了原位电子显微镜和弹性能量计算的支持。这些结果强调了颗粒形状和尺寸对热力学的影响，为改善器件循环稳定性的纳米棒设计提供了信息。
