use of metal templates for microcavity formation in alumina

Titanium advanced through alumina approximately 100µm at 1350 o C in 4 hours
of soaking time.
Figure 4.16 shows the phase equilibrium diagram of alumina and titanium oxide.
In general, Al2TiO5 is obtained by the solid state reaction between Al2O3 and TiO2,
which is only thermodynamically possible at temperatures above 1280 o C (Low, et al.,
2008). Below this temperature, at a range between 900 and 1280 o C, metastable Al2TiO5
undergoes eutectoid decomposition, forming α-Al2O3 and TiO2 (rutile).
Figure 4.16. Phase equilibrium diagram of Al2O3 – TiO2 system
(Source: Goldenberg, 1968).
Figure 4.17 shows the SEM microstructure of cross section of alumina sample,
that used Ti wire. It is noticed that Ti +4 was diffused into the surrounding alumina, so
the phase of Al2TiO5 occured in the middle of the diffusion zone. The Kirkendall
porosity is observed in the center and around the boundary between the Ti and alumina
samples.
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