Porous alumina ceramics with addition of 0, 5, 10, 15, and 20 wt% Al(H 2 PO 4) 3 were sintered at 1300, 1350, and 1400°C. The effects of the Al(H 2 PO 4) 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 Al 2 O 3 ceramics increased remarkably with an increase in Al(H 2 PO 4) 3 addition. The flexural strength first increased to a maximum value when 5 wt% Al(H 2 PO 4) 3 was added and then decreased as additional Al(H 2 PO 4) 3 was further added. SEM images showed that the average Al 2 O 3 grain size in the porous ceramics changed in an opposite way as the flexural strength. The porous Al 2 O 3 ceramics with 10 wt% Al(H 2 PO 4) 3 addition exhibited comparable flexural strength to the ceramics without Al(H 2 PO 4) 3 addition, although the latter had much higher porosity.

Nanoscale amorphous AlPO 4 was synthesised via a solution combustion process using C 2 H 5 NO 2 (glycine) as fuel and NH 4 NO 3 as oxidant. The effects of molar ratios of C 2 H 5 NO 2 to NH 4 NO 3 on characteristics and sorption properties of the amorphous AlPO 4 were also studied. The experimental results showed that the Brunauer-Emmett-Teller specific surface areas of the amorphous AlPO 4 and the sorption capacities of Pb 2+ ions on AlPO 4 decreased appreciably with the molar ratio of C 2 H 5 NO 2 to NH 4 NO 3 varying from 1:9 to 1:12, while the average particle size of the amorphous AlPO 4 exhibited no appreciable change.

Low-cost and environment-friendly MgO was used as a new gelling and consolidating agent to fabricate porous Al 2 O 3 -based ceramics via a gel casting routine. Effects of 800 • C calcined additions of MgO (.5, 1.0, 1.5, and 2.0 wt%, respectively) on open porosity (OP), pore size distribution, gas flux, and microstructure of the porous ceramics were investigated deliberately. The experimental results showed that 800 • C calcined MgO exhibits excellent gelling and consolidating performance at 80 • C, mainly owing to the hydration reaction between MgO and H 2 O and thus results in high-quality porous Al 2 O 3 -based ceramics without deformation and cracking. The Al 2 O 3 -water suspensions with different MgO additions have good flowability at room temperature. Moreover, water absorption, open porosity, and gas flux of the as-prepared porous ceramics increase remarkably with rising of MgO addition. Furthermore, MgO addition significantly suppresses the abnormal growth of Al 2 O 3 grains, and thus the microstructure of the porous Al 2 O 3 -based ceramics becomes more uniform. This technique of gel casting using MgO as a new gelling and consolidating agent offers an alternative routine for a large-scale production of porous ceramics.