Methodologies in determining mechanical properties of energy material using nanoindentation

Abstract

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 revea...