Multi-Modal In Situ Characterizations for Phase Transformations of Nanomaterials

Understanding the dynamic processes of materials synthesis and phase transformation is indispensable for most applications as these processes determine the microstructure and thus the properties of materials.<i> In situ </i>techniques can uniquely capture short-lived transient states and time-dependent changes in structure-property relations during the synthesis and phase transformation, thus providing important information and opportunities to engineer the dynamic processes and ultimately material properties.<br/><br/>In this talk, I will discuss several examples of nanoscale phase transformations and syntheses in which the changes in structure and properties were systematically and directly probed by <i>in situ</i> TEM (cooling, liquid synthesis, heating, and electrical biasing), <i>in stiu</i> Raman spectroscopy, and <i>in situ</i> electron transport measurements. These examples will include discovery of metastable and transient intermediate phases during synthesis of metal and metal oxide nanostructures, emergence of new electronic phases via intercalation of metal ions in two-dimensional materials, effects of heterointerface and nanoscale confinement on the thermodynamics of phase transformations in various two-dimensional and quantum materials. In each example, unexpected nanoscale effects and the unique advantages of <i>in situ</i> techniques to capture the nanoscale effects will be highlighted. In particular, the importance of multi-modal <i>in situ</i> characterization approach will be emphasized, which is necessary to establish structure-property relationships during these dynamic processes.