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 center dot 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 (approximate to 40 K) temperature differences (Delta T) between the aerosol and the substrate surface. For moderate-high Delta T (>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 Delta T 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. (c) 2012 American Institute of Chemical Engineers AIChE J, 2012