Journal of the European Ceramic Society 36 (2016) 725–731 Contents lists available at www.sciencedirect.com Journal of the European Ceramic Society jo ur nal home p ag e: www. elsevier.com/locate/jeurceramsoc Synthesis of zirconia toughened alumina (ZTA) fibers for high performance materials Stephanie Pfeifer a,∗ , Pinar Demirci b , Rueya Duran b , Heiko Stolpmann a , Achim Renfftlen a , Sandra Nemrava c , Rainer Niewa c , Bernd Clauß a , Michael R. Buchmeiser a,b,∗∗ a Institute of Textile Chemistry and Chemical Fibers, Körschtalstraße 26, D-73770 Denkendorf, Germany b Institute of Polymer Chemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany c Institute of Inorganic Chemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany a r t i c l e i n f o Article history: Received 3 July 2015 Received in revised form 19 October 2015 Accepted 20 October 2015 Available online 1 December 2015 Keywords: Zirconia toughened alumina (ZTA) fiber Microstructure Ceramic fiber Tensile strength a b s t r a c t Polycrystalline zirconia toughened alumina (ZTA) fibers were prepared from aqueous solutions of alu- minum 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 m 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 crystal- lization of -Al 2 O 3 and tetragonal ZrO 2 and an overall ceramic yield of 41.7% at 1400 ◦ C. X-ray diffraction (XRD) analysis showed that tetragonal ZrO 2 can be obtained at 1350 ◦ C directly from the amorphous precursor whereas pure-phase -Al 2 O 3 is formed stepwise via transition alumina phases. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction The demand for innovative and high performance ceramic materials has rapidly increased in the past decades. Whereas mono- lithic ceramics have an intrinsic brittleness and correspondingly a low damage tolerance, the embedding of ceramic fibers in a ceramic matrix leads to structural materials (ceramic matrix com- posites, CMC) with outstanding features [1]. The combination of the advantages of monolithic ceramics such as high strength, high temperature stability and corrosion resistance with additional fea- tures like high damage tolerance and fracture toughness extends the application scope of high performance ceramics significantly [2,3]. Oxide ceramic fibers as reinforcement for CMC are of enor- mous interest for technical applications such as aerospace and power engineering industries because of their excellent resistance in oxidative as well as in corrosive atmospheres associated with comparatively low costs [4,5]. Furthermore, oxide ceramic fibers ∗ Corresponding author at: Institute of Textile Chemistry and Chemical Fibers, Körschtalstraße 26, D-73770 Denkendorf, Germany. ∗∗ Corresponding author at: Institute of Polymer Chemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany. E-mail addresses: stephanie.pfeifer@itcf-denkendorf.de (S. Pfeifer), michael.buchmeiser@ipoc.uni-stuttgart.de (M.R. Buchmeiser). are characterized by high temperature resistance as well as excel- lent mechanical stability and, compared to metals, their density is relatively low [4]. During the last decades, special efforts have been devoted to the development of oxide ceramic fibers based on corundum and mullite, which are now commercially available. The fibers are produced with small grain sizes in order to obtain high tensile strengths [6–12]. Since the creep rate of polycrystalline oxide ceramic fibers increases with decreasing grain size, the creep resistance of the commercially available ultrafine grained fibers is comparatively low. The so far developed oxide ceramic fibers do not only tend to creep under mechanical stress at temperatures exceeding 1100 ◦ C, but are also prone to embrittlement due to grain growth. They therefore cannot satisfy the growing requirements especially in terms of chemical and mechanical stability in long- term, high temperature use in oxidizing atmospheres [5]. That is why there is a high demand on the optimization of their creep resistance and high temperature performance. Furthermore, the commercially available oxide ceramic fibers are still too expensive for several applications and it would be advantageous if their textile processability could be improved. Zirconia toughened alumina (ZTA) is a very promising mate- rial for the optimization of the property profile of oxide ceramic fibers. The incorporation of 10–20 wt.-% zirconia in alumina leads to a structural material exhibiting considerably enhanced fracture http://dx.doi.org/10.1016/j.jeurceramsoc.2015.10.028 0955-2219/© 2015 Elsevier Ltd. All rights reserved.