Microstructure ceramic strength

S.R. Braganga and C.P. Bergmann, A View of Whitewares Mechanical Strength and Microstructure, Ceramics International 29,801-806,2003. 

Describe briefly how the tensile strength of ceramic materials is determined by their microstructures. How may the tensile strength of ceramics be improved ... 

The difficulty of obtaining pure / "-material for the electrolyte has been tackled in many production processes worked out in the past. Unless precautions are taken, sintering of a -alumina-derived / "-alumina compositions invariably results in the duplex microstructure and a low-strength ceramic. Therefore a balance has to be struck between conductivity and strength. The problem arises because the conversion from —alumina to / " -alumina is slow... 

Finally, the nature of the crystalline microstructure, ie, crystal size and morphology and the textural relationship among the crystals and glass, is the key to many mechanical and optical properties, including transparency/opacity, strength and fracture toughness, and machinability. These microstructures can be quite complex and often are distinct from conventional ceramic microstructures (6). 

This equilibrium expression links material properties to surface state. Strength will therefore reflect to some extent the microstructural impact on F (also likely on E), but to a much greater extent it is a reflection of the influence of a wide range of mechanical, thermal and chemical operations on cf. Most ceramic surfaces have various surface flaws running up to 10 [Am deep. Even in carefully prepared samples, the largest of them determines the material strength. 

Finally we can conclude that the strength of polycrystalline ceramics depends on many factors, mainly on their chemical composition (a measure for the strength of the bonds between the atoms), their microstructure and their surface condition. 

Nishimura N, Masuo E, Takita K (1991) Effect of Microstructural Oxidation on the Strength of Silicon Nitride after High Temperature Exposure. In Carlsson T, Johansson T, Kahlman T (eds) Proc 4th Int Symp Ceram Mater Components for Engines. Elsevier, London, p 1139... 

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