Surface-controlled mechanical properties of nanoporous metals

纳米多孔金属的表面控制机械性能

基本信息

批准号：
154753614
负责人：
Dr. Julia Ivanisenko
金额：
--
依托单位：
Institut für Werkstoffphysik und Werkstofftechnologie
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2009
资助国家：
德国
起止时间：
2008-12-31 至 2013-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/154753614?language=en
关键词：
Surface controlled mechanical properties nanoporous

项目摘要

Surfaces play a significant role in plastic and elastic deformation, especially at small crystal size when the specific surface area is large. This is well documented by observations on the size-dependent strength, for instance in recent work on nanowire deformation. The proposed research aims to contribute towards identifying the processes that underlie the role of the surface in mechanical the behaviour. We propose to exploit a new and unconventional approach: rather than changing the size or the specific surface area of the sample, we shall instigate cyclic changes of state of the surface. This will be done in-situ during mechanical tests, and the consequences for the mechanical behavior will be recorded. Our main focus is on the constitutive plastic behaviour, as parametrized by yield- and flow stress, work hardening and strain rate sensitivity. Information on the elastic response will be sought as a closely related supplementary issue. As suitable model materials with large specific surface area we will study nanoporous noble metals and their alloys, using recent synthesis routes that yield millimetersized nanoporous metal samples which exhibit large (>50% strain) ductile deformation in compression. The surface modifications will use i) electrochemical experiments and ii) reversible gas adsorption studies to cycle selectively the surface chemistry (for instance, superficial oxidation/reduction or hydrogen adsorption/desorption cycles) or the superficial electric charge density. Through these variables, our approach affords control over the two relevant capillary forces, the surface tension and the surface stress, and over the surface diffusivity. We aim at i) establishing a first experimental data base for the response of plastic flow and of excess elastic behavior to the surface state, and ii) pinpointing the microscopic phenomena via which the surface affects the mechanics, for instance dislocation nucleation or egression, dislocation endpoint drag, step edge energetics, surface diffusion, or surface (excess-) elasticity.

表面在塑性和弹性变形中起着重要作用，尤其是在特定表面积大的晶体大小时尤其是在小晶体尺寸时。关于尺寸依赖强度的观察，例如在纳米线变形的最新工作中，这一观察结果很好地证明了这一点。拟议的研究旨在为确定表面在机械行为中作用的过程做出贡献。我们建议利用一种新的和非常规的方法：而不是改变样品的大小或特定表面积，而是应促进表面状态的循环变化。这将在机械测试期间原位进行，并记录机械行为的后果。我们的主要重点是通过产量和流动应力，工作硬化和应变速率灵敏度参数的组成型塑性行为。有关弹性响应的信息将作为一个密切相关的补充问题。作为具有较大特定表面积的合适模型材料，我们将使用最近的合成途径研究纳米多孔贵金属及其合金，这些途径产生毫米化的纳米多孔金属样品，这些纳米多孔金属样品在压缩中表现出较大（> 50％的菌株）延性变形。表面修饰将使用i）电化学实验和ii）可逆的气体吸附研究，以选择性地循环表面化学（例如，浅表氧化/还原/还原或氢吸附/解吸周期）或浅表电荷密度。通过这些变量，我们的方法可以控制两个相关的毛细作用力，表面张力和表面应力以及表面扩散率。我们的目的是I）建立第一个实验数据基础，以塑性流量和过量弹性行为对表面状态的响应，ii）精确指出了微观现象，通过该现象，表面会影响力学，例如位错成核或脱位端点阻力，阶跃边缘能量，表面扩散，表面扩散或表面（ - ）弹性。