A review of in-situ high-temperature characterizations for understanding the processes in metallurgical engineering

For the rational manipulation of the production quality of high-temperature metallurgical engineering, there are many challenges in understanding the processes involved because of the black box chemical/electrochemical reactors. To overcome this issue, various in-situ characterization methods have been recently developed to analyze the interactions between the composition, microstructure, and solid-liquid interface of high-temperature electrochemical electrodes and molten salts. In this review, recent progress of in-situ high-temperature characterization techniques is discussed to summarize the advances in understanding the processes in metallurgical engineering. In-situ high-temperature technologies and analytical methods mainly include synchrotron X-ray diffraction (s-XRD), laser scanning confocal microscopy, and X-ray computed microtomography (X-ray mu-CT), which are important platforms for analyzing the structure and morphology of the electrodes to reveal the complexity and variability of their interfaces. In addition, laser-induced breakdown spectroscopy, high-temperature Raman spectroscopy, and ultraviolet-visible absorption spectroscopy provide microscale characterizations of the composition and structure of molten salts. More importantly, the combination of X-ray mu-CT and s-XRD techniques enables the investigation of the chemical reaction mechanisms at the two-phase interface. Therefore, these in-situ methods are essential for analyzing the chemical/electrochemical kinetics of high-temperature reaction processes and establishing the theoretical principles for the efficient and stable operation of chemical/electrochemical metallurgical processes.