Microcellular Al 2 O 3 Ceramics from Wood for Filter Applications

Microcellular biomorphous Al 2 O 3 was produced by Al‐vapor infiltration in pyrolyzed rattan and pine wood‐derived biocarbon preforms. At 1600°C the biocarbon preforms reacted with gaseous aluminum to form Al 4 C 3 . After oxidation in air at temperatures between 1550° and 1650°C, for 3 h, the biocarbon preforms were fully converted into α‐Al 2 O 3 . Owing to the high anisotropy of biomorphous Al 2 O 3 , the compressive strength behavior was strongly dependent on the loading direction. The compressive strength of the specimens (0.1–11 MPa) is strongly dependent on their overall porosity and their behavior could be explained using the Gibson–Ashby model. The Darcian permeability ( k 1 ), as well as the non‐Darcian permeability ( k 2 ), increased with an increase of the total porosity. The Darcian permeability of biomorphous Al 2 O 3 was found to be in the range of 1–8 × 10 −9 m 2 , which is in the order of magnitude of gas filters, and, therefore, suitable for several technological applications.