A numerical model was applied to the synthesis of iron nanoparticles and compared to experimental findings. The experiments comprised the production of iron particles from iron pentacarbonyl in a wall-heated aerosol reactor. The wall temperature of the reactor was varied between 400degreesC and 800degreesC. The size and morphology of the so-formed particles were investigated via transmission electron microscopy (TEM). The images show strongly agglomerated particles with mean primary particle diameters in the range of 10-100 nm, depending on the experimental conditions. The numerical model used accounts for the various physical and chemical processes taking place in the described aerosol reactor. Beside convection, nucleation, and coagulation, the model particularly accounts for the influence of coalescence on the particle size and morphology. With an extension of the sintering time for the nanometer size range, the experimental primary particle size could be well predicted by the computer simulations. (C) 2004 Published by Elsevier Ltd.