use of metal templates for microcavity formation in alumina
use of metal templates for microcavity formation in alumina
use of metal templates for microcavity formation in alumina
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Dur<strong>in</strong>g the 4 hours soak<strong>in</strong>g time at high temperature, the Al +3 ions diff<strong>use</strong> out<br />
<strong>in</strong>to the titanium wire, while Ti +4 ions diff<strong>use</strong> <strong>in</strong>to the alum<strong>in</strong>a matrix. In the opposite<br />
direction, a counterdiffusion occurs with Al +3 and Ti +4 ions. It is noticed that Ti +4 is<br />
diff<strong>use</strong>d <strong>in</strong>to the surround<strong>in</strong>g alum<strong>in</strong>a so the phase <strong>of</strong> Al2TiO5 occured <strong>in</strong> the middle <strong>of</strong><br />
the diffusion zone. The diffusion <strong>of</strong> the Ti +4 ions is faster than Al +3 ions and the <strong>for</strong>mer<br />
is faster due to higher ionic mobility <strong>of</strong> the Ti +4 ions. In the diffusion rates <strong>of</strong> the Al2O3<br />
and Ti components, the balance ca<strong>use</strong>s the <strong>for</strong>mation <strong>of</strong> pores on the back <strong>of</strong> the Ti +4<br />
ions. This effect is named the Kirkendal effect (Kirkendall et al., 1939). Figure 2.12<br />
shows the diffusion zone <strong>of</strong> Al2O3-Ti system. Consider the diffusion couple illustrated<br />
<strong>in</strong> Figure 2.13.<br />
Ti<br />
Al2O3<br />
Figure 2.12. The diffusion zone <strong>of</strong> Al2O3-Ti system. Noticed that the arrows <strong>in</strong>dicate the<br />
pores.<br />
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