Combining nanocalorimetry and dynamic transmission electron microscopy for in situ characterization of materials processes under rapid heating and cooling
Michael D. Grapes, Thomas LaGrange, Lawrence H. Friedman, Bryan W. Reed, Geoffrey H. Campbell, Timothy P. Weihs, David A. LaVan
Nanocalorimetry is a chip-based thermal analysis technique capable of analyzing endothermic and exothermic reactions at very high heating and cooling rates. Here we couple a nanocalorimeter with an extremely fast in situ microstructural characterization tool to identify the physical origin of rapid enthalpic signals. More specifically, we describe the development of a system to enable in situ nanocalorimetry experiments in a dynamic transmission electron microscope (DTEM), an ultra-fast transmission electron microscope capable of generating images and electron diffraction patterns with exposure times of 30 ns to 500 ns. The full experimental system consists of a modified nanocalorimeter chip, a custom-built in situ nanocalorimetry holder, a data acquisition system, and the DTEM itself, and is capable of thermodynamic and microstructural characterization of reactions over a range of heating rates (103 K/s to 105 K/s) inaccessible by conventional nanocalorimetry. To establish its ability to capture synchronized calorimetric and microstructural data during rapid transformations, this work describes measurements on the melting of an aluminum thin film. We were able to identify the phase transformation in both the nanocalorimetry traces and in electron diffraction patterns taken by the DTEM. Potential applications for the newly-developed system are described and future system improvements are discussed.