250 200 150 100 50 0 1600 1400 1200 1000 Ts / K σb / MPa Figure 7: Relationship between bending strength and sintering temperature of alumina particulate Pylex glass. Opened marks show that mullite formation occurred. crystals were largely formed and polycrystalline alumina clusters still remained in the mixture of glass, alumina and fibrous mullite in the samples, which shows the interested dual structure. Figure 7 shows relationship between the bending strength and sintering temperature of alumina-glass samples. The bending strength was apparently enhanced by the use of polycrystalline alumina powder. Mullite formation usually contributes on the strengthening of glass ceramics but, in this case, the samples with mullite formation tended to have larger scatter of bending strength than those without mullite formation. CONCLUSIONS e zirconia and alumina particulate glass using polycrystalline alumina powder was the mixture of the glass eferences en, J.C ics vol.4, pp. 2. Tsuge, A. (1999). Proceedings of the 2nd International 5. 9, 974-982 0, 826-829. Alumina particulat fabricated by atmospheric sintering and composites with dual scale structures were obtained. The samples of dual scale structures where polycrystalline alumina clusters were distributed in alumina and zirconia were obtained though polycrystalline alumina clusters showed coarsening by double sintering. These samples indicated that the addition of polycrystalline alumina powder enhanced the fracture toughness while the bending strength was almost kept constant. The samples of dual scale structures where polycrystalline alumina clusters were distributed in ., Beauchamp, E. K., and Eagan, R.J. (1978). Fracture Mechanics of Ceram .S. and Yoon, H.S. (1990) J. Am. Ceram. Soc. 73, 1382-1391. matrix were obtained. When mullite formation occurred, the polycrystalline alumina clusters were distributed in the mixture of glass and fibrous mullite. The use of polycrystalline alumina powder enhanced the mullite formation and the average bending strength though mullite formation causes the increase in scatter of the bending strength. R 1. Sweareng 973-984, Plenum Press, New York. Taya, M., Hayashi, S., Kobayashi, A 3. Evans, A. G. (1986) Acta. Metall. 34, 761-800. 4. Kanzaki, S., Shimada, M., Komeya, K. and Symposium on the Science of Engineering Ceramics, pp. 437-442, Trans Tech Publications, Switzerland. Niihara K. (1990) J.Jpn. Soc. Powder and Powder Metall. 37, 348-351. 6. Niihara K. (1991) Nippoin Seramikkusu Kyokai Gakujutsu Ronbunshi 9 7. Hirosaki, N., Ando, M., Akimune, Y. and Mitomo, M. (1992) J. Ceram. Soc. Japan 10 8. Newman, J.R. and Raju, I.S. (1981) Eng. Frac. Mech. 15, 185-192
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