The kinetics of SiO vapor ammonolysis to produce nano-sized silicon nitride powder was studied with an 80-mm-diameter vertical tubular flow reactor operated at temperatures ranging from 1300 degrees C to 1400 degrees C. The molar feed rate of NH3 was maintained 2-3 orders of magnitude in excess of stoichiometric ratio over SiO. The rate of reaction to form nano-sized powder was represented by a pseudo-first-order rate expression with respect to SiO concentration, independently of NH3 concentration. The temperature dependency of the pseudo-first-order rate constant was determined. The effects of mean residence time as well as the reaction temperature on the growth of nano-sized particles were investigated, and the minimum residence time to produce particles of critical size was estimated. (c) 2005 Elsevier B.V. All rights reserved.