Microstructures of porous Al2O3-50 wt.% ZrO2 composites using in-situ synthesized Al2O3-ZrO2 composite powders

Abstract

Al2O3–50 wt.% ZrO2 composite powder was synthesized using the sol–gel process with aluminum iso-propoxide and zirconium butoxide as precursors. The as-received composite powders were in an amorphous phase. By calcinating them at 900 °C, the cubic (c)-ZrO2 phase, which was 5 nm average in diameter, was crystallized. As the calcination temperature increased up to 1100 °C, a small amount of tetragonal (t)-ZrO2 phase was detected, although the main phase was c-ZrO2. However, the Al2O3 particles in the Al2O3–50 wt.% ZrO2 mixed powders existed in an amorphous phase up to 1100 °C. The porous Al2O3–ZrO2 composite having ranged from 400 to 1000 nm in pore size was successfully obtained using the Al2O3–50 wt.% ZrO2 composite powders. The distribution of pores was homogeneous and it was closely related to the calcination temperature. The major phases of the porous composites were an m-ZrO2 and α-Al2O3 although a t-ZrO2 phase also was detected as a minor phase. The pore frames of the Al2O3–50 wt.% ZrO2 composite were less than 400 nm thick and they were nanocrystalline with dense structure.