Agglomeration of α-Al2O3 powders prepared by gel combustion

Ultrafine alpha-Al2O3 powders were prepared by a gel combustion method and the agglomeration characteristic of the resultant powders was studied. A variety of fine crystallite alpha-Al2O3 powders with different agglomeration structures could be obtained by altering the citrate-to-nitrate ratio gamma and calcining the precursors at 1050 degrees C for 2 h. All the powders were of nearly equivalent crystallite size (60-80 nm) except for the P1 powder (113 nm) from the gel with gamma = 0.033. The primary crystallites of the obtained alpha-Al2O3 Powders were formed into large secondary particles with different degree of agglomeration. Except for the powder P1, the mean particle sizes from specific surface area and particle size distribution measurement increase with increasing citrate-to-nitrate ratio in the fuel-lean condition and decrease in the fuel-rich condition. Densities of alumina ceramics from powders P4 and P5 sintered at different temperatures were relatively low due to the wide particle size distribution. (C) 2007 Elsevier Ltd and Techna Group S.r.l. All rights reserved.