Whisker zirconia

Becher, P.F. and Tiegs, T.N. (1987). Toughening behavior involving multiple mechanisms whisker reinforcement and zirconia toughening. J. Am. Ceram. Soc. 70, 651-654. 

Whiskers (alumina, magnesia, thoria, zirconia. beryilia)... 

In addition to the initial work in the alumina and mullite matrix systems previously mentioned, SiC whiskers have also been used to reinforce other ceramic matrices such as silicon nitride,9-13 glass,14 15 magnesia-alumina spinel,16 cordierite,17 zirconia,18 alumina/zirconia,18 19 mullite/zirconia,18-21 and boron carbide.22 A summary of the effect of SiC whisker additions on the mechanical properties of various ceramics is given in Table 2.1. As shown, the addition of whiskers increases the fracture toughness of the ceramics in all cases as compared to the same monolithic materials. In many instances, improvements in the flexural strengths were also observed. Also important is the fact that these improvements over the monolithic materials are retained at elevated temperatures in many cases. 

As mentioned previously, the main body of research on whisker-reinforced composites was concerned with alumina, mullite, and silicon nitride matrix materials. None the less, selected work examined zirconia, cordierite, and spinel as matrix materials.16-18 The high temperature strength behavior reported for these composites is summarized in Table 2.5. As shown, the zirconia matrix composites exhibited decreases in room temperature strength with the addition of SiC whiskers. However, the retained strength at 1000°C, was significantly improved for the whisker composites over the monolithic. Claussen and co-workers attributed this behavior to loss of transformation toughening at elevated temperatures for the zirconia monolith, whereas the whisker-reinforcement contribution did not decrease at the higher temperature.17,18... 

N. Claussen and G. Petzow, Whisker-Reinforced Zirconia-Toughened Ceramics , in Tailoring Multiphase and Composite Ceramics, eds. R. E. 

P. F. Becher and T. N. Tiegs, Toughening Behavior Involving Multiple Mechanisms Whisker Reinforcement and Zirconia Toughening, J. Am. Ceram., 70[9], 651-654 (1987). 

Grade Reagent, technical, crystals, fused, whiskers, CP (99% zirconia), hydrous. The fused grade is reported to be harder than diamond (11 on Mohs scale). 

Many other methods of strengthening are based on formation of composites by inclusion of fibers or whiskers or by crystallization to form glass-ceramics. Phase separation may also affect strength by altering crack propagation mechanisms. Transformation toughening has also been attained by formation of a small concentration of zirconia crystals in glasses. 

The hydroxide suspensions were mixed with the SiC whiskers on the weight basis ofthe final fired composition ofthe mullite-zirconia or mullite matrix. Mixing was accomplished in a food blender for 12 m. The slurry-whisker mixtures were then cast into dishes and... 

N. Claussen and G. Petzow, Whisker-Reinforced Zirconia-Toughened Ceramics pp. 649-62 in Tailoring Multiphase and Composite Ceramics, Vol 20. Edited by R. E. Tiessler, G. L. Messing, C. G. Pantano, and R. E. Newnham. Plenum Press, New Yoik, 1986. 

A. Zangvil, C.-C. Lin, and R. Ruh, Microstructural Studies in Alkoxide-Derived Mullite/Zirconia/Silicon Carbide-Whisker-Composites, /. Am. Ceram. Soc., 75 [5] 1254-65 (1992). 

A. Hynes, R. H. Doremus, R. Ruh, Y. Xu, and A. Zangvil, Creep of Mullite Composites Containing Zirconia and Silicon Carbide Whiskers pp. 509-21 in Advances in Ceramic Matrix Composites III, Ceramic Transactions, Vol. 74. Edited by N. P. Bansal and J. P. Singh. The American Ceramic Society, Westerville, OH, 1996. 

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