An in situ tensile test device for thermo-mechanical characterisation of interfaces between carbon nanotubes and metals

Abstract

In this paper we present our recent efforts to develop an in situ tensile test device for thermo-mechanical characterization of interfaces between single-walled carbon nanotubes (SWCNTs) and metals. For the mechanical tests, the chosen loading condition is a pull-out test. After summarizing results of maximum stresses calculated from molecular dynamics simulations and obtained from in situ scanning electron microscope experiments we outline the requirement for an in situ experimental method with atomic resolution to study the mechanics of SWCNT-metal interfaces in further detail. To this purpose, we designed, fabricated and characterized a silicon-based micromechanical test stage with a thermal actuator for pull-out tests inside a transmission electron microscope. The objective is to obtain in situ images of SWCNT-metal interfaces under mechanical loads at the atomic scale for fundamental structure investigation. The design of this MEMS test stage permits also the integration of SWCNTs by wafer level technologies. First experiments with this MEMS test stage confirmed the presence of suspended thin metal electrodes to embed SWCNTs. These suspended thin metal electrodes are electron transparent at the designated SWCNT locations. Actuator movements were evaluated by digital image correlation and we observed systematic actuator movements that allow for a defined load application of SWCNTS. Although significant image drifts occured during actuation, we achieved atomic resolution of the metal electrode and stable movement in the focal plane of the electron microscope. The presented system may be also used and further developed for in situ characterization of other materials.