Rodlike t-ZrO2 nanoparticles with aspect ratio of 1.3-8.0 and large surface area (152 m(2)/g) have been produced by two-step calcination of 1,12-diaminododecane-hydrous zirconia mesostructured composites. The two-step calcination consists of first calcination at 300 degrees C for 24 h and then at 400 degrees C for another 24 h. The resulting t-ZrO2 nanoparticles can be stored under ambient conditions for at least 2 months without discernible transformation to the monoclinic phase. Compared to one-step calcination at 400 degrees C, the two-step calcination increases the amount of hydrocarbon fragments (3.6 wt% versus 2.9 wt%) adsorbed onto the resulting t-ZrO2 nanoparticles. This increase may account for the improved phase stability of the rodlike t-ZrO2 nanoparticles. (C) 2005 Elsevier Ltd. All rights reserved.