High‐Surface‐Area Alumina Ceramics Fabricated by the Decomposition of Al(OH) 3

Al 2 O 3 ‐based porous ceramics with high surface areas were fabricated by adding Al(OH) 3 to the starting powder, followed by pressureless sintering at temperatures >1100°C. Three types of starting powders were used in the present study: pure α‐Al 2 O 3 , α‐Al 2 O 3 + Al(OH) 3 , and α‐Al 2 O 3 + ZrO 2 + Al(OH) 3 . The addition of Al(OH) 3 considerably increased the surface area of the porous Al 2 O 3 , and the addition of ZrO 2 further increased the surface area; a surface area as high as 36.39 m 2 /g was obtained, and the high surface area was retained at higher temperature. The pore size distribution of the specimens with high surface area was bimodal, with one peak at ∼100 nm and the other, which contributed most of the surface area, at ∼10 nm. X‐ray analysis showed that in the sample with the fine pores and high surface area, there was θ‐Al 2 O 3 phase produced by the decomposition of Al(OH) 3 , presumably because the phase transformation of θ‐Al 2 O 3 to α‐Al 2 O 3 was incomplete after low‐temperature sintering. Moreover, the porous Al 2 O 3 with high surface area retained superior mechanical properties, attributed to the good sinterability of the fine α‐Al 2 O 3 powder used in the present study. The sintered specimens could be large and designed to any shape, because pressureless sintering was used for fabrication. The present approach provides a new way of fabricating porous Al 2 O 3 ceramics that could be widely used as catalyst supports in industry, especially for high‐temperature catalysis.