Preparation and thermal stability of zirconia-doped mullite fibers via sol-gel method

The zirconia-doped mullite fibers were prepared via a sol-gel method from aluminum isopropoxide-aluminum nitrate-tetraethyl orthosilicate system. The effects of zirconia doping on the sol spinnability, mullitization, structure and thermal stability of mullite fibers were investigated by means of Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that Zr—O—C bond was presented with the involvement of zirconium acetate, which accelerated the gelation process of the precursor sol. The mullitization process of the doped fibers was promoted by the formation of less middle-phase residues such as spinel. Among the samples investigated, the 1% ZrO₂-doped fibers exhibited the highest thermal stability with a grain growth rate of 11% (from 1 000 °C to 1 300 °C), which is only a half of that for pure mullite fibers.