Current knowledge of toughening mechanisms in zirconia ceramics is reviewed, with particular emphasis on the transformation toughening of yttria-stabilised polycrystalline tetragonal zirconia (Y-TZP). The physics and mechanics of transformation toughening are discussed, but the main aim is to provide a comprehensive understanding of the role of the metastable tetragonal zirconia phase on stress induced transformation toughening. The focus is on the microstructural variables governing the stability of tetragonal zirconia in the context of transformation toughening. The potential for additional toughening contributions from microcracking and ferroelastic toughening is briefly addressed and the coupling of toughening mechanisms is also discussed. Finally, a perspective on the future development of Y-TZP-based high toughness materials is given.

The recognition that bulk nanoceramic materials, having grain sizes typically 100 nm or finer, possess appealing mechanical, physical and tribological properties has generated considerable recent research activity. A major challenge in the research on bulk nanoceramics and nanoceramic composites is concerned with the aspect of processing, in particular restriction of grain growth during sintering. In this regard novel processing techniques have been developed with the aim of fabricating bulk ceramic nanomaterials. The superior properties exhibited by these bulk nanoceramics and ceramic nanocomposites, compared with conventional ceramic materials, have opened up prospects for their use in applications demanding better mechanical properties. The present review highlights outstanding issues related with the processing of nanoceramics and ceramic nanocomposites, discusses the novel processing techniques currently used to develop these materials, critically analyses the property modifications resulting from microstructural refinement and provides an overview of the structure-property correlations of some recently developed bulk nanoceramic materials. Potential fields of application for ceramic nanomaterials are surveyed. In conclusion, the unresolved issues related to bulk nanoceramic processing are considered and a perspective is given of areas of future research.

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Strength reliability, one of the critical factors restricting wider use of brittle materials in various structural applications, is commonly characterized by Weibull strength distribution function. In the present work, the detailed statistical analysis of the strength data is carried out using a larger class of probability models including Weibull, normal, log-normal, gamma and generalized exponential distributions. Our analysis is validated using the strength data, measured with a number of structural ceramic materials and a glass material. An important implication of the present study is that the gamma or log-normal distribution function, in contrast to Weibull distribution, may describe more appropriately, in certain cases, the experimentally measured strength data.

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