Synthesis of zirconia toughened alumina (ZTA) fibers for high performance materials

Polycrystalline zirconia toughened alumina (ZTA) fibers were prepared from aqueous solutions of aluminum hydroxide chloride 2.5-hydrate and zirconium oxychloride octahydrate. Fiber processing was accomplished via dry spinning. Poly(vinylpyrrolidone) (PVP) was used as spinning aid. Polycrystalline ZTA fibers were obtained by calcination of the green fibers followed by sintering at defined temperatures in air. Ceramic fibers were 10 μm in diameter and had an average tensile strength of 1010 (±363) MPa with peak values reaching 1535 MPa. Differential scanning calorimetry/thermogravimetric analysis coupled with mass spectrometry (DSC/TGA-MS) showed an exothermic peak at 1156 °C assigned to the crystallization of α-Al2O3 and tetragonal ZrO2 and an overall ceramic yield of 41.7% at 1400 °C. X-ray diffraction (XRD) analysis showed that tetragonal ZrO2 can be obtained at 1350 °C directly from the amorphous precursor whereas pure-phase α-Al2O3 is formed stepwise via transition alumina phases.