Mechanical-chemical coupling at surfaces: prediction and experiment

表面机械化学耦合：预测和实验

• 批准号: 259138080
• 负责人: Professor Dr. Stefan Müller (†)
• 金额: --
• 依托单位: Institut für Keramische Hochleistungswerkstoffe
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/259138080?language=en
• 关键词: Mechanical; chemical; coupling; surfaces; prediction

While the partial atomic volume of foreign atoms in solid solutions or of constituents in intermetallic compounds, and hence the coupling between the stress state and the chemical potential, have been studied already for many decades by materials scientists, up to now the analogous processes at surfaces have not received much attention. The key goal of this project is the investigation of the coupling between the mechanics of surfaces and adsorption. The basic phenomenon is that a capillary force, the surface stress, is coupled to changes of state at the materials surface. Thus, the adsorption of atoms from gas or ions from solution, or the enrichment/depletion of electronic charge at the surface prompts deformation of the material. This phenomenon has recently found application in modern biosensors, whose miniaturized cantilevers deform measurably upon adsorption of atoms or molecules. Furthermore, it has been shown that the controlled reversible adsorption/desorption of atoms or ions can prompt large strain in nanoporous solids that promise application as metallic actuators with large amplitude and strain energy density. Understanding of the microscopic mechanisms behind the coupling of changes of state at materials surfaces and the stress state is still rudimentary at best. A theory that could predict the coupling strength for a given materials surface and adsorbate is still missing. Moreover, the surface stress changes upon reversible adsorption and desorption of light elements, which are particularly relevant for applications in actuation and sensing, remain poorly studied. In this context, the present proposal aims at 1.) providing for the first time quantitative values for the coupling between capillary force and adsorption from both experiment and theory and 2.) insight into the underlying microscopic mechanims. As model processes we plan to study the adsorption of H and O on Au, Pt and Ir surfaces. The theoretical method for calculation of the coupling strength is density functional theory. For efficient and exhaustive screening of the configuration space we additionally employ cluster expansion methods. In experiment, changes of the surface stress upon adsorption from gas and electrosorption are determined from cantilever bending. Complementary measurements of the variation of the electrode potential as a function of strain during different electrosorption processes are carried out with Dynamic Electro-Chemo-Mechanical Analysis, a technique developed by one of the applicants.

虽然材料科学家已经对固溶体中的外来原子或金属间化合物中的成分的部分原子体积以及应力状态和化学势之间的耦合进行了数十年的研究，但迄今为止，表面上的类似过程尚未受到太多关注。该项目的主要目标是研究表面力学与吸附之间的耦合。基本现象是毛细管力（表面应力）与材料表面的状态变化耦合。因此，气体中的原子或溶液中的离子的吸附，或表面电荷的富集/耗尽都会促使材料变形。这种现象最近在现代生物传感器中得到了应用，其微型悬臂在吸附原子或分子时会发生可测量的变形。此外，研究表明，原子或离子的受控可逆吸附/解吸可以促使纳米多孔固体产生大应变，有望用作具有大振幅和应变能密度的金属致动器。对材料表面状态变化和应力状态耦合背后的微观机制的理解充其量仍然是初级的。仍然缺乏能够预测给定材料表面和吸附物耦合强度的理论。此外，轻元素可逆吸附和解吸时的表面应力变化（这与驱动和传感应用特别相关）的研究仍然很少。在这种情况下，本提案的目的是：1.）首次从实验和理论中提供毛细管力和吸附之间耦合的定量值，2.）深入了解潜在的微观机制。作为模型过程，我们计划研究 H 和 O 在 Au、Pt 和 Ir 表面上的吸附。计算耦合强度的理论方法是密度泛函理论。为了有效且详尽地筛选配置空间，我们还采用了簇扩展方法。在实验中，通过悬臂弯曲确定气体吸附和电吸附时表面应力的变化。在不同的电吸附过程中电极电势随应变的变化的补充测量是利用动态电化学机械分析来进行的，动态电化学分析是申请人之一开发的技术。