Synthesis and characterization of partially and fully stabilized zirconia fibers made from an inorganic precursor
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Continuous high-quality fibers of yttria-doped zirconia with 4 and 8 mol% yttria were blow spun using an inorganic sol precursor. The fibers were heated and analyzed using scanning electron microscopy, x-ray diffraction, differential thermal/thermogravimetric analysis, and surface area/porosity by nitrogen adsorption. The fibers were of a single-phase cubic structure after crystallization at 529 °C and typically 3.3–5.5 or 7.5–11.5 m in diameter depending on the composition. Samples of fibers were heated to various temperatures and their friability index and creep properties analyzed using the bend stress relaxation technique and compared to other fibers of similar composition prepared by different solution techniques and commercially available fibers.
I. INTRODUCTION
This work describes the preparation of yttria-doped zirconia fibers from zirconium carbonate paste, a raw material produced in the earlier stages of zircon sand processing. The fibers are directly comparable with those made from zirconium n-propoxide raw material under similar spinning and firing conditions, whose preparation has been described in a previous paper.1 The combined works demonstrate the importance of choosing a pure source of zirconia for fiber manufacture. This paper continues the program which shows how a varied range of refractory ceramic fibers can be made by aqueous sol/gel routes. Earlier papers in this series have reported the preparation of zirconium titanate, strontium zirconate, and mullite fibers.2– 4 More recently we have prepared yttrium aluminum garnet fibers5 and investigated their high-temperature creep behavior. The first zirconia fibers, partially stabilized with yttria, were developed by Union Carbide,6 whose product, Zircar, was made by impregnating rayon thread with a mixture of salts. Other early patents reported the preparation of zirconia fiber in sol/gel processes, from solutions of zirconyl acetate and chloride, combined with PVA spinning aid7 or zirconoxane polymers.8 The interest in zirconia fibers was further stimulated by the discovery of phase transformation toughening in partially stabilized tetragonal zirconia.9 Marshall10 has demonstrated that partially stabilized zirconia fibers of the highest strengths (implied strains to break 0.75 to 1.3%) could be hand drawn from a simple zirconyl acetate precursor. a)
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J. Mater. Res., Vol. 16, No. 8, Aug 2001 Downloaded: 24 Mar 2015
Much of the later work has focused on attempts to make spinnable zirconoxane polymers, which have been derived from zirconium tetrabutoxide11 or propoxide,12 combined with acetyl acetone or other chelating ligand. Most recently Abe13 has developed a convenient “onepot” process in which polyzirconoxane is prepared from the reaction of zirconyl chloride with ethyl acetoacetate. The reaction is performed in methanol solution in the presence of excess triethylamine. The spinnability of the various zirconoxanes has been demonstrated in hand-drawing experimen
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