Failure in Ceramics and Refractories

Ceramics and refractories are inherently brittle materials. The reason for this behavior is that the bonding in them is predominantly ionic or predominantly covalent. For plastic deformation, which is required for ductile fracture, there should be dislocation movement. In ionic compounds, formation of dislocation itself is difficult, because, for neutrality of the material, a pair of dislocations should simultaneously form. One should carry negative charge, and the other, positive. This is a difficult thing. If at all a dislocation forms, it requires simultaneous movement of the oppositely charged dislocations. This is still more difficult. In the case of covalent bonds, they are directional and strong. There is no question of any line defect, such as a dislocation, forming. Therefore, any question of dislocation movement does not arise. Ceramic and refractory materials fail by the sudden fracture of their atomic or ionic bonds. Hence, the failiue of ceramic and refractory materials can be discussed in terms of the failure of brittle materials. In other words, the theory of brittle materials fracture can be applied to ceramics and refractories. 

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Failure in ceramics and refractories was discussed in Section I. Here, we shall consider the mechanical fracture resulting from the application of a load. Because ceramics are brittle materials, the fracture is fast. Fast fracture is a characteristic of brittleness. This type of fracture is sudden and occurs without any warning such as plastic deformation. 

Considers corrosion of ceramics and refractories, failures in ceramics and refractories, and the design aspects... 

This volume on ceramics and refractories is divided into three sections. The first section, "Ceramics and Refractories," is divided into seven chapters. Apart from an introductory section. Chapter 1 mainly details the applications of ceramics and refractories. Chapter 2 is on selection of materials and it describes the two stages in selection with a case study. Chapter 3 is on new developments in the ceramic and refractory fields. Chapter 4 describes the phase equilibriums in ceramic and refractory systems and outlines the three important systems, namely, unary, binary, and ternary. Corrosion of ceramics and refractories is the subject of Chapter 5. Chapter 6 discusses failures in ceramics and refractories. Design aspects are covered in Chapter 7. 

Independently of the type of erosion-protective liner installed, premature failure of the cyclone or cyclone system can occur. There are numerous causes for this. Most are unit or task specific. However, as a rule, cyclone system failure is often attributable to an increase in the feed flow rate, the particle size, the solids loading, or some combination of the three. In the case of refractory and ceramic lined cyclones, a poor refractory or ceramic liner installation can also significantly shorten a unit s run time. In addition, thermal cycling can... 

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