Date of this Version
Johnson, S.D., Surface & Coatings Technology (2017), http://dx.doi.org/10.1016/j.surfcoat.2017.06.085
We present results of barium hexaferrite powder mass consumption across a wide range of starting powder quantities and deposition times. From these results we develop a transfer efficiency figure of merit to describe deposition efficiency and growth rates applicable to aerosol deposition and similar spray deposition techniques. We find that the transfer efficiency of barium hexaferrite was 0.082% and the transfer efficiency rate coefficient was 0.056 min−1 with a decay factor of −0.773. As a means to further understanding the deposition efficiency we present flow simulations of an aerosol deposition system using different particle sizes and standoff distances. We find that impact with the substrate strongly depends on the particle size, particle location within the nozzle, and standoff distance. We find that the values in the simulation are consistent with those used to produce films with the aerosol deposition system used at the Naval Research Laboratory and consistent with values found in the literature. We find that to improve the transfer efficiency nozzle design must be optimized, particle size must be carefully selected, standoff distance must be selected, and the powder in the aerosol chamber must be delivered at an optimal rate. These factors may be individually tuned to contribute to the final transfer efficiency figure of merit that can be used to assess the efficiency of the aerosol deposition process.