The investigation of the pore structure of fine alumina powders prepared for ceramic production by the technique of precipitation from solution

Abstract

In this study, alumina precursors were prepared in three different ways and were converted into three different alumina powders (Al2O3) by calcination. The precipitation methods of the alumina precursors were as follows: i) Addition in excess of a 25% NH3 solution dropwise for two hours, to a boiling 0.08 M A12(SO4)3 solution which was already buffered by NH3 / NH4Cl. ii) Boiling for two hours a 0.006 M Al2(SO4)S solution which contains C2H4(COOH)2, NH4Cl and (NHi)2CO. iti) Boiling for two hours a 0.2 M Al2(SO4)S solution which contains excess (NHj)2CO. In order to find out the effect of the followed procedure on the pore structure, the following determinations were realized. The powder shapes and sizes were determined by electron microscopy. The specific surface areas and the adsorption heats of these powders were calculated from the adsorption data. The mesopore size distribution curves were plotted by using the desoiption data. The specific micropore, mesopore and micropore-mesopore volumes were determined by extrapolating these curves. Finally, the dependence of the pore structure on the procedure of preparation was discussed in detail.