Enhancement of Porosity and Strength of Porous Al2O3 Ceramics by Al(H2PO4)3 Addition

Porous alumina ceramics with addition of 0, 5, 10, 15, and 20 wt% Al(H2PO4)(3) were sintered at 1300, 1350, and 1400 degrees C. The effects of the Al(H2PO4)(3) addition on crystal phases, water absorption, open porosity, pore size distribution, microstructures, and flexural strength were studied extensively. The experimental results revealed that only characteristic peaks of corundum were indexed in the XRD patterns of the as-prepared porous ceramics. The water absorption and open porosity of the porous Al2O3 ceramics increased remarkably with an increase in Al(H2PO4)(3) addition. The flexural strength first increased to a maximum value when 5 wt% Al(H2PO4)(3) was added and then decreased as additional Al(H2PO4)(3) was further added. SEM images showed that the average Al2O3 grain size in the porous ceramics changed in an opposite way as the flexural strength. The porous Al2O3 ceramics with 10 wt% Al(H2PO4)(3) addition exhibited comparable flexural strength to the ceramics without Al(H2PO4)(3) addition, although the latter had much higher porosity.