Nanosized alumina powder was prepared from a mixture of aluminium nitrate and carbon black through microwave heating (2.45 GHz and 900 W) for different times. The products were characterized by powder Xray diffraction. The results showed that gamma-Al2O3 was the main phase for powder samples heated for 4 and 6 min. When heating was extended to 8 min, weak peaks of alpha-Al2O3 also appeared. For heating times longer than 10 min, alpha-Al2O3 Was the only crystalline phase present. The resultant particles were observed by SEM and TEM methods. The average particle size was found to be 96 nm. The surface area of powder was 48 m(2)/g after 15 min heating. (C) 2009 Elsevier B.V. All rights reserved.