Hardness advanced structural ceramics

It can be seen that ceramic multilayer structures have been produced with increments of the hardness of up to 60 GPa, increasing the hardness by up to a factor of almost 3. Initial work in this area has developed a number of ideas, such as the effect of modulus mismatch, which in some cases give good agreement with the models suggested but in many others do not. It is suggested that at least some of this discrepancy can be accounted for by differences in the microstructure and residual stress-state of the film, both of which are often poorly characterized. Furthermore there is very little direct evidence about how these structures deform and in particular about how different layers must be strained in order to accommodate the indenter when it is pressed into the sample. Further advances in this area will require the greater use of numerical techniques to analyse the complex stress and strain behaviour under the indentation, coupled with the use of recently developed techniques that allow the localized deformation behaviour to be observed in detail. 

Krell A (1998) The effects of load, grain size, and grain boundaries on the hardness of alumina. In Bray D (ed) 22nd annual conference on composites, advanced ceramics, materials, and structures B, pp 159-68... 

Construction of transparent armors follows the principles that have been well established for their opaque counterparts. Armor against advanced threats has a typically structure as shown in Fig. 10.19 [165]. The front-face layer should be as hard as possible, in order to damage the projectiles in maximum range. Ideally, it should be harder than the projectile core. Currently, several hardened glasses or glass ceramics are being used. This layer is the weak point of present transparent... 

Biomimesis clearly will have an important role in new biomedical devices and in new devices that try to combine biological structures or organisms with electronics in sensors and actuators. In structural materials, the obvious place for advance is the introduction of more toughness into synthetic composites and ceramics. In electronics there are not yet many signs of a conjunction between the hard, high-resolution, two-dimensional world of silicon and the soft, larger scale, three-dimensional design of the brain and nervous system. 

Ceramic Structural Materials Replacing Metals An important category of advanced ceramic materials comprise stmctural materials, developed, still in the spirit of the Industrial Revolution, to replace metals in all applications where higher rigidity, hardness and resistance to wear and an aggressive environment is required... 

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