Phenomenon of Whiskers Formation in Al2O3−C Refractories

• Published in: Advanced engineering materials Vol. 24; no. 2
• Main Authors: Wei, Xingwen, Yehorov, Anton, Storti, Enrico, Dudczig, Steffen, Fabrichnaya, Olga, Aneziris, Christos G., Volkova, Olena
• Format: Journal Article
• Language: English
• Published: 01.02.2022
• Subjects: Al2O3; Al2O3−C; interactions; iron; whiskers formations
• ISSN: 1438-1656; 1527-2648
• DOI: 10.1002/adem.202100718

Pure alumina (Al2O3) and carbon‐bonded alumina (Al2O3−C) are used to investigate their interaction with iron (Armco) at 1625 °C, applying the sessile drop method. The investigations are conducted inside a heating microscope for 1 h under argon atmosphere with low oxygen partial pressure. No whiskers formation is observed from the experiments with pure Al2O3 and molten iron. In the case of Al2O3−C/Fe system, several phenomena including the decarburization of Al2O3−C, Al2O3−C dissolution in molten iron, Al2O3 layer formation on the iron droplet, and Al2O3 whiskers formation are observed. To clarify the possible influence of iron on Al2O3 whiskers formation, blank Al2O3−C samples without the presence of iron are heated and held in a half‐sealed platinum crucible at 1550 °C for 2 h. Thereby, the Al2O3 whiskers formation is detected. Finally, the experimental investigations are supported with thermodynamic simulations. The carbothermic alumina reduction is a reaction which requires over 2000 °C at 1 atmospheric pressure. However, some researchers reported the alumina is reduced by carbon with the presence of iron at 1550 °C. The current experimental investigation and thermodynamic simulation shows that the presence of iron is not a necessary condition for releasing aluminum or alumina whiskers formation.