Rheological behavior, molecular structure of precursor and evolution mechanism: zirconia fibers from polyaceticzirconium precursors

Abstract

Polycrystalline zirconia fibers with dense surface and good flexibility were achieved from polyaceticzirconium (abbreviated as PEZ) precursor fibers followed by steam pretreatment and post-calcination. PEZ was synthesized via a one-pot solid–liquid reaction between basic zirconium carbonate and glacial acetic acid in methanol. Rheological behavior of the precursor sol with different concentrations was investigated, the power law model was used to describe the rheological behavior more accurately, and the relationship between the rheology and the spinnability of sol was discussed particularly. For the polymeric structure of PEZ, acetic acid was used as chelating agent and the carboxyl group was acted as a bidentate bridging ligand, which was speculated by FT-IR analysis. The effect of the pretreatment atmosphere on the evolution of the precursor fibers and the microstructure of the final fibers was discussed. The acetate group was removed in the form of molecules, and the final fibers preheated under steam atmosphere had better densification and flexibility than those were not. In addition, crystallization process, phase composition and thermal decomposition were investigated by XRD, Raman spectra and TG/DSC. The preheated atmosphere exerts an important influence on the densification and flexibility of zirconia fibers. Under steam atmosphere, acetate group in the precursor fibers is removed in the form of molecules and zirconia fibers sintered at 1050 °C for 2 h have a dense surface. However, zirconia fibers not subjected to the steam pretreatment have a large number of voids on the surface due to the decomposition of the organics. Furthermore, the fibers preheated under steam atmosphere have better flexibility than those were not. Therefore, pretreatment under steam atmosphere is essential for the preparation of the dense and flexible fibers.