The gas-phase sintering kinetics of nickel nanoparticle agglomerates was investigated by a two step electrical mobility classification. The first electrostatic classifier sorted the agglomerated mono-area nickel nanoparticles generated by pulsed laser ablation, and then the subsequent heating process created the sintered nickel nanostructures. The second electrostatic classifier combined with the condensation nucleus counter scanned the shrinkage of the agglomerated mono-area nickel nanoparticles due to the sintering process. The change in the mono-area particle mobility size measured by the electrical mobility classification technique was compared with the results of the existing coalescence model to extract the kinetic parameters for the sintering of nickel particles. The optimum activation energy found in this study was similar to 63 kJ/moL which falls between the diffusion of nickel atoms (similar to 49 kJ/mol) and the migration and coalescence of nickel particles (similar to 78 kJ/mol). (C) 2008 Elsevier B.V. All rights reserved.