Seminar

Date 2023-06-08 
Time 10:00 
Title Towards an in-depth understanding of degradation mechanisms of functional and structural materials using micro- and nano-mechanics 

 

  • 일시: 2023년 6월 8일 (목요일) 오전 10시
  • 장소: 응용공학동 (W1-1) 1318 강의실
  • 주제: Towards an in-depth understanding of degradation mechanisms of functional and structural materials using micro- and nano-mechanics
  • 연사: 이수빈 박사 (Institute of Applied Materials, Karlsruhe Institute of Technology)
     
  • Abstract
    Focused ion beam (FIB) based small-scale fracture testing has been well established in recent years. Simple cantilever-based geometries are the most prominent geometries used for micro-fracture studies of not only structural materials but also functional materials, such as thin films or hard coatings. However, the applicability of small-scale fracture testing for extracting bulk-like fracture properties is controversially discussed. A major source of concern is the presence of FIB-induced artefacts such as residual stresses due to ion implantation, chemical interactions of gallium ions including segregation at the notch tip, or finite size of notch root radius. In this talk, we demonstrate two novel approaches which can minimize FIB-artefacts in micro-cantilever fracture tests using atomically sharp natural cracks. Firstly, a new geometry for testing interface toughness at the micron scale will be presented. The geometry is straightforward to fabricate using FIB and enables observation of stable crack growth along a film/substrate interface. The other approach is using a well-defined thin bridge notch for a single cantilever fracture test. During in situ SEM fracture test, we directly observed that extremely thin bridges fail first, generating sharp natural cracks ahead which are free from FIB-artefacts. As a result, the fracture toughness of materials can be measured more precisely with less scatters. Furthermore, from the load drops at bridge failures, additional data points of fracture toughness can be obtained which is a huge advantage for statistical analysis.
첨부: 연사 CV 및 Abstract 1부.