外延膜中的可逆金属氢化物相变。

Reversible metal-hydride phase transformation in epitaxial films.

作者信息

Roytburd Alexander L, Boyerinas Brad M, Bruck Hugh A

机构信息

Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA. National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.

出版信息

J Phys Condens Matter. 2015 Mar 11;27(9):092201. doi: 10.1088/0953-8984/27/9/092201. Epub 2015 Feb 11.

DOI:10.1088/0953-8984/27/9/092201

PMID:25671335

Abstract

Metal-hydride phase transformations in solids commonly proceed with hysteresis. The extrinsic component of hysteresis is the result of the dissipation of energy of internal stress due to plastic deformation and fracture. It can be mitigated on the nanoscale, where plastic deformation and fracture are suppressed and the transformation proceeds through formation and evolution of coherent phases. However, the phase coherency introduces intrinsic thermodynamic hysteresis, preventing reversible transformation. In this paper, it is shown that thermodynamic hysteresis of coherent metal-hydride transformation can be eliminated in epitaxial film due to substrate constraint. Film-substrate interaction leads to formation of heterophase polydomain nanostructure with variable phase fraction which can change reversibly by varying temperature in a closed system or chemical potential in an open system.

摘要

固体中的金属氢化物相变通常伴随着滞后现象。滞后现象的外在因素是由于塑性变形和断裂导致的内应力能量耗散的结果。在纳米尺度上，塑性变形和断裂受到抑制，相变通过相干相的形成和演化进行，这种滞后现象可以得到缓解。然而，相相干性会引入内在的热力学滞后，从而阻止可逆相变。本文表明，由于衬底的约束，外延薄膜中相干金属氢化物相变的热力学滞后可以被消除。薄膜与衬底的相互作用导致形成具有可变相分数的异相多畴纳米结构，在封闭系统中通过改变温度或在开放系统中通过改变化学势，该结构可以可逆地变化。