The generation of nano-sized particles was numerically investigated for the heterogeneous growth of nitrogen on homogeneously nucleated argon seed particles in a supersonic expansion. Gas dynamic equations for ID supersonic flow were solved together with the classical nucleation theory and Hill's growth model. Heterogeneous growth on homogeneously nucleated seeds effectively increased the final particle size to the range of 10-200 nm. The new process could increase the particle mass by a factor of 10 relative to the case of pure gas expansion under comparable pressure and temperature conditions. Increase in particle size resulted predominantly from the enhanced heterogeneous condensation of nitrogen, and the growth by argon condensation could even be reduced relative to the case of pure gas expansion. Final particle size easily reached 200 nm, which has been very difficult to achieve by any of die existing homogeneous growth processes. (c) 2009 Elsevier Ltd. All rights reserved.