Microstructures of porous Al 2O 3–50 wt.% ZrO 2 composites using in-situ synthesized Al 2O 3–ZrO 2 composite powders

Abstract

Al 2O 3–50 wt.% ZrO 2 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)-ZrO 2 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)-ZrO 2 phase was detected, although the main phase was c-ZrO 2. However, the Al 2O 3 particles in the Al 2O 3–50 wt.% ZrO 2 mixed powders existed in an amorphous phase up to 1100 °C. The porous Al 2O 3–ZrO 2 composite having ranged from 400 to 1000 nm in pore size was successfully obtained using the Al 2O 3–50 wt.% ZrO 2 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-ZrO 2 and α-Al 2O 3 although a t-ZrO 2 phase also was detected as a minor phase. The pore frames of the Al 2O 3–50 wt.% ZrO 2 composite were less than 400 nm thick and they were nanocrystalline with dense structure.