Optimization of supersonic nozzle flow for titanium dioxide thin-film coating by aerosol deposition

Aerosol deposition (AD) is an efficient technique for customized coating of various substrates. The small particles of AD yield a dense coating layer with small voids. AD is amenable to rapid coating (mass production), thus, it is economically attractive. Low-temperature AD coating is desirable because it minimizes the thermal degradation of the substrate. An optimized low-cost AD coating technique is of significant interest to solar-cell engineers seeking to reduce manufacturing costs. While most previous studies ignore the importance of nozzle geometry on coating performance, this paper examines non-optimized nozzles and commensurate shockwaves using computational fluid dynamics (CFD). The optimized nozzle geometry obtained from CFD can rapidly prototype nozzles. The CFD-designed nozzles with optimized geometry yielded significantly improved coating quality over non-optimized nozzles.

► Effects of shockwaves, nozzle geometry and dimensionality, carrier-gas viscosity, and particle density.
► Nozzle geometry was adjusted to yield the optimum condition of Pe=Pamb, which significantly reduced shock formation.
► We, experimentally and numerically, showed that the correctly expanded (first) nozzle yielded a dense and void-free coating layer.
► While the under-expanded (second) nozzle yielded voids and irregularity.