SGER: Electrochemical Effects on Crystal Plasticity in Nanometer-Scale Samples

技术：最近，聚焦离子束加工(FIB‘D)纳米柱的压缩测试表明，在这些大表面积与体积比的结构中，屈服强度等塑性性能可以接近固体的理论剪切强度。这些最新发展的技术为研究环境诱导的固体力学性质的变化提供了一种新的实验方法。这项高风险/高回报的变革性研究计划使用材料基本力学实验方法结合电化学，研究了表面和电化学对FIB‘d Au、Ag和Cu柱的可塑性(所谓的Rehbinder效应)的影响。如果这种效应被发现，它将是变革性的，因为将出现一种理解应力腐蚀现象的新范式。Pi的研究使用了两种实验方案。其中一项涉及开发一种新技术，用于在电化学池中检查基本上无位错的直径200 nm的金属柱的压缩行为。另一种是使用晶片曲率技术来确定电解液中由于潜在沉积不足的广告层的吸附而产生的表面应力变化。这项研究中涉及的重要和实际问题涉及与小尺寸材料力学的塑性和环境影响有关的突出基本问题。众所周知，这些化学/机械效应很难研究，因此许多研究人员质疑这些现象的存在。随着纳米技术的到来，这些问题再次成为材料力学中有趣和悬而未决的问题的前沿。非技术性：如果PI证明表面应力变化影响表面位错成核，这一发现将影响对固体中裂纹的延性和脆性响应的更广泛的理解。因此，这项研究将为研究人员提供一个新的“旋钮”，以控制固体的变形和断裂特性。因此，新类别的结构材料可能具有对应力腐蚀失效的免疫力进行调整的潜力。在材料力学的化学效应方面的专门知识要求有能力整合电化学、应用力学和材料科学等学科的知识。PI正在开发这一领域的一门新的本科课程，该课程将在高级本科阶段教授，专门旨在为学生提供这一综合背景。此外，PI将通过亚利桑那州立大学的NSF资助的少数民族研究生教育@山区州联盟(MGE@MSA)计划，让本科生参与这项研究。

TECHNICAL: Recently compression testing of focused ion beam machined (FIB'd) nano-pillars have demonstrated that plastic properties such as yield strength in these large surface to volume ratio structures can approach the theoretical shear strength of a solid. These recently developed techniques offer a new experimental approach for studying environment-induced alterations of the mechanical properties of solids. This high-risk/high-payoff, transformative research program examines surface and electrochemical effects on plasticity (so-called Rehbinder effects) in FIB'd Au, Ag and Cu pillars using fundamental mechanics of materials experimental approaches combined with electrochemistry. If such an effect is discovered, it would be transformative in the sense that a new paradigm for understanding stress-corrosion phenomena would emerge. PI's study uses two experimental protocols. One involves the development of a new technique for examining the compressive behavior of essentially dislocation-free 200 nm diameter metallic pillars in an electrochemical cell. The other involves the use of wafer curvature techniques to ascertain surface stress changes in electrolytes owing to the adsorption of underpotentially deposited ad-layers. The important and practical problems addressed in this research deal with outstanding fundamental issues related to plasticity and environmental effects on mechanics of materials at small length scales. These chemical/mechanical effects have been notoriously difficult to study and consequently many researchers have questioned the very existence of these phenomena. With the advent of nano-technology, these issues are once again at the forefront of interesting and unsolved problems in the mechanics of materials. NON-TECHNICAL: If PI demonstrates that surface stress alterations affect surface dislocation nucleation, this finding would impact broader understanding of the ductile versus brittle response of a crack in a solid. Thus this research would provide researchers a new "knob to turn" in order to control the deformation and fracture properties of a solid. Consequently new classes of structural materials may have the potential to be "tuned" for immunity to stress-corrosion failure. Expertise in chemical effects on the mechanics of materials requires the ability to integrate knowledge in the disciplines of electrochemistry, applied mechanics and materials science. PI is developing a new undergraduate course in this area that will be taught at the senior undergraduate level specifically aimed at providing students with this integrated background. Additionally, the PI will be involving undergraduate students in this research through Arizona State University's NSF funded Minority Graduate Education @ Mountain State Alliance (MGE@MSA) program.