Coordinated regulation for -Al₂O₃ and mullite structures in the alumina-mullite fiber based on the different adding form of Fe element

The coordinated regulation for alpha-Al2O3 and mullite structures in the alumina-mullite duplex fiber poses a challenging yet crucial task in achieving a fiber with exceptional high -temperature properties. In this study, Fe element was added into the alumina-mullite fibers in the form of iron sol and ferric nitrate solution, respectively, with the aim of obtaining a fiber consisting of fine mullite grains embedded with nano alpha-Al2O3 grains. The results revealed that the addition of Fe element significantly enhances the crystallization process of mullite in aluminamullite fibers. Specifically, adding iron sol resulted in the reduce of alpha-Al2O3 formation temperature to 1300 C-degrees, while introducing Ferric nitrate solution promoted the formation of mullite phase. Simultaneous introduction of 1.3 wt% iron sol and 1.3 wt% Ferric nitrate solution contributed to achieve alumina-mullite fiber with tensile strength of 2.06 GPa. In addition, the influence mechanism of Fe source on the phase transformation and microstructures of alumina-mullite fiber were discussed.