| Zr02 powder has been coated with Si02 using an alkoxide sol.
The isoelectric point of the coated powder changes to 2.5, a value
which is characteristics of Si02• The Zr02 powders coated with
different amounts of Si02 are mixed. with Al20 3 powder in an
aqueous suspension. The mixed powders, containing 10 vol%
coated Zr02 are dried, compacted and sintered to prepare Zr02
toughened Al20 3 (ZT A) composites. The composites possess
very high densities(- 98%) and, at a Si02 content of 1 mol% of
Zr02, the K.c is- 5.8 MNm-m. The Weibull modulus of the composites
improves by a factor of 2. A large improvement in the
surface smoothness of the as-sintered samples, prepared using
the coated powders, as compared to the ZT A prepared using the
uncoated powders, is obtained. These results point to a blunting
of the surface flaws in the composites prepared using the coated
powders. |
