Flame spray pyrolysis synthesis and aerosol deposition of nanoparticle films

The assembly of nanoparticle films by flame spray pyrolysis (FSP) synthesis and deposition on temperature‐controlled substrates (323–723 K) was investigated for several application‐relevant conditions. An exemplary SnO2 nanoparticle aerosol was generated by FSP and its properties (e.g., particle size distribution), and deposition dynamics were studied in details aiming to a simple correlation between process settings and film growth rate. At high precursor concentrations (0.05–0.5·mol/L), typically used for FSP synthesis, the nanoparticles agglomerated rapidly in the aerosol leading to large (>100 nm) fractal‐like structures with low diffusivity. As a result, thermophoresis was confirmed as the dominant nanoparticle deposition mechanism down to small (≈40 K) temperature differences (ΔT) between the aerosol and the substrate surface. For moderate‐high ΔT (>120 K), thermal equilibrium was rapidly obtained yielding a constant thermophoretic flux and film growth rate. A model was developed to predict the nanoparticle deposition rates by FSP synthesis at moderate‐high ΔT that does not require detailed analysis of the aerosol composition. Comparison with previous studies having similar nozzle geometries showed that the deposition rates of FSP‐made aerosols can be reasonably well predicted for various materials and flame conditions. © 2012 American Institute of Chemical Engineers AIChE J, 2012