Preparation of Y-TZP/AI₂O₃ whisker preform by an in situ method

In situ growth of AI₂O₃ whiskers into the matrix of Y-TZP (yttria-doped tetragonal zirconia polycrystals) was examined in order to prepare Y-TZP/AI₂O₃ whisker preform for the composites. Various shapes of AI₂O₃ particles were grown by the reaction of AI₂O₃ and AIF₃ powders with moist nitrogen or oxygen gases at high temperature. They showed a trend to change the particle shapes from massive → rhombohedron → whisker → platelet as the processing temperature was increased. These particles, however, grew only on the surface and not inside the pellets It was found necessary to introduce the carrier gas inside the pellets for particle growth to occur internally. AI₂O₃ whiskers can be synthesized inside the pellets by mixing with an organic space-forming agent having a relatively large particle size.