Wetting and Melt Extraction Characteristics of ZrO2–Al2O3 Based Materials |
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| Authors: | Mehdi Allahverdi Robin A L Drew John O Strom–Olsen |
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| Affiliation: | Department of Mining and Metallurgical Engineering, McGill University, Montreal, QC H3A 2A7, Canada;Center for the Physics of Materials, Physics Department, McGill University, Montreal, QC H3A 2T8, Canada |
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| Abstract: | A melt extraction technique has been used to produce fine fibers from three eutectic compositions in the systems of ZrO2-Al2O3 (ZA), ZrO2-Al2O3-SiO2 (ZAS), and ZrO2-Al2O3-TiO2 (ZAT). The liquid surface tension of these ceramics was measured by a new method and estimated to be in the range of 400-567 mJ/m2 at similar ∼2400°C. The wetting between Mo (the extraction wheel material) and liquid ceramics was found to be poor during transient wetting; however, fiber extraction was achieved due to the shear action induced by the wheel rotation. The difficulties in the extraction of ZA fibers at speeds of <1.5 m/s, and also the formation of air pockets on these fibers, are attributed to the poor wetting of the Mo wheel by the liquid ZA. In a wide range of wheel velocities, extracted fibers exhibited alternating sections of uniform diameter and Rayleigh waves, both being the largest for ZAS fibers at any speed. The Rayleigh wave dimensions varied considerably with speed whereas the dimensions of the uniform region of the fibers remained unchanged over the wide range of extraction speeds examined. The fiber dimensions are controlled by both surface tension and viscosity of the molten ceramics at the extraction temperature. |
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