Effect of urea, NH4OH, and DCCA on texture properties of alumina prepared by ultrasonic spray pyrolysis

Mesoporous alumina particles were prepared by using a spray pyrolysis process of aluminum nitrate precursor using cetyltrimethylammonium bromide (CTAB) as a structure-directing agent. The effects of ammonium hydroxide, urea, and drying-control-chemical agent (DCCA) on the particle morphology and pore properties of alumina particles were studied by means of N2 physical adsorption, transmission electron microscopy (TEM), and small-angle X-ray diffraction (SAXS) analysis. It was found that using urea rather than NH4OH in the spray pyrolysis is effective to increase the surface area of alumina with well-organized uniform pores. The addition of NH4OH led to decrease the surface area as well as the pore regularity. Using both DCCA and urea was a helpful way to improve the surface area, the pore volume, and the pore size distribution of alumina synthesized by spray pyrolysis. The prepared alumina particles had a broad SAXS peak without further reflection peaks indicating hexagonal or cubic symmetry. According to TEM analysis, a long-range ordering of mesopores was not observed. More details on the texture properties and the morphology of alumina particles prepared by with changing the kinds of additives in spray solution were discussed.