Ceramic strengthening mechanisms

E. V. Clougherty, D. Kalish, in Strengthening Mechanisms. Metals and Ceramics, Syracuse Univ. Press, Syracuse, 1966, p. 431. 

Webb, W. W., H. D. Bartha, and T. B. Shaffer (1966). Strength eharacteristics of whisker crystals, macrocrystals and microcrystals, pp. 329-354. In Strengthening Mechanisms, Metals and Ceramics. Burke, J. J., N. L. Reed, and V. Weiss, Eds. Syracuse University Press, New York. 

If we compare the increase in fracture toughness that has been achieved in nacre to those obtained in technical ceramics (see table 7.4), it is rather obvious that it would be highly desirable to technically exploit the same strengthening mechanisms. This is one reason for the strong scientific interest in nacre. The main aim of these studies is to create artificial materials with similar prop>-erties. Such materials, which mimic the properties of biological materials, are called biomimetic materials. 

Nano-size dispersed particles drastically change the fracture mode from intergranular fracture to transgranular fracture, and also improve the fracture strength of ceramics markedly, especially after annealing, mentioned previously. To explain these phenomena, we consider a strengthening mechanism in nanocomposites... 

Methods for mechanical testing of materials are briefly introduced along with various strengthening mechanisms. The number and siu-face area of the slip systems in metals and in ceramics are shown to be responsible for the ductility (or the lack of it) and for ductile-to-brittle transitions. Griffith s theory of brittle fracture is used to introduce fracture mechanics and to develop the concept of fracture toughness. The viscoelastic behavior of polymers is briefly discussed. 

The strategy for employment of EX-21 is to take advantage of that strengthen increase by producing the appropriately thinner wall cell walls without sacrificing the overall mechanical integrity of the ceramic monolith. Table 3 is a comparison of the new material with the existing composition. 

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