The role of stress release in shaping iron whisker morphology during oxygen removal process

Abstract

Metal growth in materials manufacturing or applications can significantly impact the efficiency and performance of processes. Despite extensive research efforts to understand dendrite and whisker growth mechanisms in various processes like battery charging and metal powder production, the growth of metal during the removal of oxygen from its oxides remains poorly understood. In this study, we investigated the role of stress release in the formation of iron whiskers. Our findings emphasized the significance of the oxygen removal process from hematite (Fe2O3) to wüstite (FeO), as a crucial step in initiating the structure for subsequent iron growth. We observed that, compared to carbon monoxide (CO), hydrogen (H2) exhibited superior stress release capabilities, leading to rapid volume shrinkage in the Fe2O3 to FeO stage. This preferential stress reduction by H2 was attributed to the development of a larger-sized nanoscale hole structure on the surface of iron oxides, effectively inhibiting the growth of filament-shaped whiskers.