Recently, there is an increasing use of new, nanostructured materials in various devices to enhance the device performances. With increasing interests in utilizing nanoscale materials in different devices, understand-ing the mechanical properties of these nanostructured materials is crucial in avoiding any mechanical failure and reliability issues. Mechanical properties of materials are known to differ significantly as the length scale of the structure is reduced from the bulk down to submicron dimensions. The nanoindentation is a powerful tool for evaluating mechanical properties such as hardness and modulus in small scale volumes. Although nanoindentation is a widely used method, several limitations exist for using it to various nanoscale materials with different geometry and structure. In this study, we attempt to address some of these limitations as we study mechanical properties of nanoporous polymer material as well as metal nanowires. First, we studied me-chanical properties of the metal-organic frameworks (MOFs). MOFs are composed of polymer and metal cluster with large surface area that has been identified as potential high capacity gas storage/separation material. The mechanical stability of the MOF structure is therefore of interest, especially since it is known that the MOF structure is unstable in the ambient air condition. In this study, we studied mechanical properties and stability of MOF-5 using reliable nanoindentation methods to pose a stability window for MOF-5 operations under high pressures. Secondly, nanoindentation method was used to evaluate the hardness of silver nanowires with varying diameters. The mechanical properties of silver nanowires for flexible transparent electrode application is of interest, but evaluation of hardness using nanoindentation cannot be done with Oliver and Pharr method and thus requires in depth analysis. In this study, we used the double contact model to correctly analyze the nanowire indentation that revealed an interesting size dependent strength behavior arising from the five-fold twin structure of Ag nanowire. We expect the methodologies presented here to be applicable to many new energy materials that involve nanostructures such as nanowires or nanoporpous materials, and this study can serve as a foundation for reliable testing methodologies for evaluating the mechanical behavior of nanostructured energy materials.
최근 디바이스의 성능 향상을 위하여 그래핀, 폴리머, 다공성 물질 등의 다양한 재료가 쓰이고 있으며, 특히 재료의 나노스트럭쳐링을 통하여 그 성능을 향상시키는 연구들은 많은 주목을 받고 있다. 이들의 기계적인 성질은 디바이스의 성능 및 기계적인 신뢰도를 평가하는데 중요한 기준으로 제시되기 때문에, 이에 대한 연구는 필수적이라고 할 수 있다. 기계적 성질은 물질의 크기에 따라서 영향을 받기 때문에, 나노스케일에서는 그에 적합하게 기계적 성질이 측정되고 분석되어야 한다. 이에 가장 적합한 방법으로 나노인덴테이션이 제시되고 있는데, 이는 시료 준비의 간편성, 미세한 힘과 압입깊이 조절 등의 이점을 갖고 있다. 하지만 최근에 소개된 다공성 재료나 그래핀 등 다양한 에너지 재료의 인덴테이션 측정 연구는 미흡한 실정이며, 나노 구조에서는 새로운 분석 모델을 제시 및 적용해야 하는 등의 어려운 점을 갖고 있다. 이러한 한계를 극복하고자, 우리는 이번 연구에서 다양한 에너지 재료에서 나노인덴테이션법을 이용, 그 기계적인 성질을 측정하는 방법에 대한 연구를 진행하였다.
