Griffith flaws

We referred to the formation of Griffith flaws or of a crack system in the surface film of a solid which has formed at high temperature because of its paramount importance for the mechanical strength of solids. This phenomenon, however, has some aspects which are of more direct interest to the physical chemist. 

If the liquid-forming particles in the green body are large, then when the melt and the melt is wicked away by the capillaries, a large pore will be left behind (see Figure 16.43). lliese large pores can lead to Griffith flaws in the final piece. 

Griffith flaws which have very low depths. They are characterized using decoration techniques. Griffith s equation can be written alternatively as. 

The material contains N identical, uniformly distributed, Griffith flaws per unit volume. 

Oxidation - Oxidation of a ceramic Is taken to be a surface effect governed by the parabolic diffusion law and a thermal activation process of constant activation energy, with an Arrhenius type of temperature dependence. By the assuming the Griffith flaw size to be proportional to the surface oxide thickness, we can structure the... 

D.C. Hughes and D.J. Hannant, Reinforcement of Griffith flaws incellulose reinforced cement composites , J. Mater. Soi. Letters A, 1985,101-102. 

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