Designing nanoparticles: The role of process parameters in thermal plasma synthesis

This study comprehensively investigated the effects of feed and cooling rates on the formation and particle diameter of Fe nanopowders synthesized using the thermal plasma process. The particle diameters of the Fe nanopowders were analyzed by microscopic observations, X-ray diffraction, and small-angle X-ray scattering measurements. The experimental results indicated that the mean particle diameter decreased as the feed rate decreased, and quenching was applied. Numerical simulations were employed to examine the effects of the feed and cooling rates on the nanoparticle diameter and to visualize the particle growth mechanism. According to the results of the numerical study, the feed and cooling rates were identified as critical experimental parameters that significantly affect the homogeneous nucleation, total concentration of vapor atoms, and frequency of heterogeneous condensation on nuclei, ultimately determining the final diameter of the nanoparticles. This study bridges experimental and numerical analyses, clarifies particle growth mechanisms, and demonstrates the feasibility of designing nanoparticles with sizes ranging from a few to hundreds of nanometers that can be utilized in a multitude of applications using thermal plasma processes.