Aluminum nitrate was dissolved in distilled water in the ratio 1:20 on a hot plate at 80 1C.
The pH was fixed at 8 with ammonia and measured using a Metrohm pH meter instrument, model 691, Switzerland. Hydrolyzed alumi- num nitrate aged for 24 h was separated from solution with a paper filter and washed with distilled water three times. Afterwards, nitric acid was added and condensation was fulfilled. A colloidal sol was achieved at pH 4. Then, 20 g carbon black was added to the sol containing 100 g primary aluminum nitrate. The mixture was heated at 100 1C to prepare a gel. Then, the gel was dried in oven at 120 1C. The calcination of dried gel was performed in a microwave furnace (2.45 GHz and 900 W) [13]. Finally, the residual carbon was removed by heating the resultant
powder at 650 1C in a furnace. Phase identification of the synthesized products was examined using XRD. The microstructure and particle size of synthesized alumina nanopowder were evaluated using a TEM (FEG Philips CM 200) and Zeta Sizer (Malvern HSC1330–3000), respectively