| Autor: |
Grapes MD; Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA., LaGrange T; Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA., Friedman LH; Materials Measurement Science Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA., Reed BW; Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA., Campbell GH; Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA., Weihs TP; Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA., LaVan DA; Materials Measurement Science Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA. |
| Abstrakt: |
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 the dynamic transmission electron microscope (DTEM), a time-resolved TEM capable of generating images and electron diffraction patterns with exposure times of 30 ns-500 ns. The full experimental system consists of a modified nanocalorimeter sensor, 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 (10(2) K/s-10(5) K/s) accessible by conventional (DC) 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. |
