Particle in-line coating
Sometimes the properties of synthesized nanoparticles can be harmful, need to be protected, are unstable when stored under ambient conditions, or complicate subsequent processing steps. To counteract these disadvantages, the surface of the particles is functionalized or coated, i.e., core-shell nanoparticles are synthesized. In a typical inline coating process, a second reactant is introduced downstream of the spray flame via a coating nozzle into the flame exhaust gas stream, where temperatures are still high enough to decompose the secondary reactant. The arrangement can be combined with other coaxial nozzles, see Figure 1. Challenges arise because the particles may not be coated homogeneously. To overcome such challenges, flow simulations are often combined with experimental coating and kinetics tests.
Figure 1: Top: Flame reactor combined with coaxial coating nozzles for in-line surface coating/functionalization of nanoparticles. Bottom: TEM image of TiO2/SiO2 core/shell nanoparticles.
Literature:
C.-F. López-Cámara, M. Dasgupta, P. Fortugno, H. Wiggers, Proceedings of the Combustion Institute, 39 (2023) 1059-1068. doi.org/10.1021/ie3010644