柔性基底上纳米金属多层膜的断裂与屈曲行为及其影响因素

The cracking and buckling behaviors of nanostructured metallic multilayer films adherent to compliant substrates strongly depend on the modulation structures, the constituent phases, and the film/substrate interfacial adhesion. However, the separate and coupling effects of their influencing factors on the cracking/buckling behaviors are still poorly understood, which limits the possibility of artificial tuning. Based on the applicant’s preliminary experimental results and the scientific point derived, here in this project two sets of polyimide-supported nanostructured metallic multilayer films, i.e., fcc/bcc Cu/Cr and fcc/hcp Cu/Zr, will be comprehensively studied to clarify the unknown issues. The cracking and buckling behaviors of the multilayer films with different modulation periods, constituents and interfacial adhesion will be systematically investigated in comparison by quantitative characterization of the cracking strain, buckling strain, fracture mode and buckling mode during uniaxial tension. This project is aimed to (i) reveal the individual and coupling effects of modulation period, constituent and interfacial adhesion, respectively; (ii) clarify the key factor predominantly controlling the cracking behaviors and buckling behaviors, respectively; (iii) develop the cracking and buckling models and propose a criterion to rationalize the transition in buckling modes. Based on these studies, the relationship of microstructures - mechanical properties - cracking and buckling behaviors of the nanostructured metallic multilayer films could be well understood. The results will be helpful for providing theoretical basis and technical guidance for structure design and property optimization in the field of flexible electronics.

柔性基底上纳米金属多层膜的断裂与屈曲行为强烈地依赖于调制结构、组元材料以及膜基界面结合等因素，这些因素对多层膜断裂与屈曲行为的单一和耦合影响目前尚不清楚，限制了人为调控的可能。基于前期初步研究结果及所提炼的科学问题，本申请将以柔性聚酰亚胺基底上的fcc/bcc类型(Cu/Cr)和fcc/hcp类型(Cu/Zr)两类纳米金属多层膜作为研究对象，分别设计调制周期、组元匹配和膜基界面结合对比实验，通过定量表征多层膜单轴拉伸断裂应变和屈曲应变，分析相关断裂模式和屈曲模式，尝试揭示尺寸效应、组元效应和膜基界面结合对多层膜断裂与屈曲行为的单一和耦合影响，阐明多层膜断裂与屈曲行为的主要影响因素。在此基础上建立相关断裂和屈曲理论模型，提出屈曲模式转变的判据，构建起微观组织/结构-力学性能-断裂与屈曲行为之间的内在关联，为柔性电子领域界面结构设计和性能优化提供理论基础和技术指导。

断裂和屈曲/褶皱是柔性基体上金属薄膜最为常见的失效形式，系统深入地研究单层膜/多层膜的失效行为具有重要的科学意义和工程价值。本项目以Cu/X (X=Cr、Nb、Zr)多层膜和Cu, Cr, Al, Ag, CuZr, SiOx单层膜作为研究对象，系统研究了金属薄膜的断裂和屈曲/褶皱行为，归纳总结了其共性规律和个性特征。.Cr薄膜的剥离行为遵循应变能准则，而Cu薄膜的剥离行为是由屈曲控制的。通过考虑界面结合和塑性耗散对屈曲行为的影响，提出一个描述Cu/Cr多层膜屈曲应变尺寸效应的模型。Cu/Nb多层膜屈曲尺寸随外加应变的演变表现出调制比依赖性；当调制比较小时，Cu/Nb多层膜屈曲宽度随应变增加逐渐增大，而调制比较大的Cu/Nb多层膜，屈曲宽度几乎不随应变的变化而变化。总体上，多层膜屈曲宽度随调制比的增大而减小，归因于塑性变形能力的差异。.CuZr非晶薄膜的断裂应变随厚度减小而增大；随厚度增加，界面应力传递方式由弹塑性转变为线弹性，这归因于CuZr非晶薄膜尺寸依赖的晶化行为。屈曲应变随厚度降低而增大，薄膜剥离是由应变能准则控制；基于实验结果构建了一个屈曲失效模式图谱，屈曲模式的转变归因于界面结合与薄膜本征变形的共同作用。.提出了金属表面多级褶皱的可控制备方法；提出了曲面膜/基体系表面褶皱的可控制备方法，建立了金属褶皱图案相图，发现了褶皱尺寸与微球曲率之间的幂律关系，揭示了褶皱特性/参量对表面微纳摩擦性能的影响；此外，基于单一膜/基材料体系，通过调控溶剂种类、表面处理工艺及机械预应变，实现了三种不同类型的溶剂响应型动态褶皱表面，证实了其在智能显示领域应用的可能。.本项目提出了提高断裂和屈曲抗力、改善膜基体系结构稳定性的有效方法，为柔性电子器件的结构设计提高器件服役寿命提供理论基础和应用指导。此外，通过合理控制薄膜屈曲/褶皱行为，实现了金属薄膜表面构型及其功能性调控，研究结果在柔性电子、生物医药、机器人等领域均有广泛的应用前景。