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Aerosol deposition with gas phase-synthesized chain-like nanoaggregates can yield dense coatings from the impaction of particles on a substrate; however, dense coating formation is not well understood. Here, we study coating consolidation at the single nanoaggregate level. Flame spray pyrolysis-made tin oxide nanoaggregates are mobility (size) filtered, accelerated through a de Laval nozzle, and impacted on alumina substrates. TEM images obtained from low velocity collection and supersonic deposition are compared via quantitative image analysis, which reveals that upon supersonic impact nanoaggregates fragment into smaller aggregates. This suggests that fragmentation is a key step in producing coatings denser than the depositing nanoaggregates themselves. We supplement experiments with detailed particle trajectory calculations, which show that the impact energies per atom during nanoaggregate deposition are below 0.2 eV/molecule. These results suggest that fragmentation can only occur at locations where nanoaggregates bonded by van der Waals and capillary interactions.
Bibliographical noteFunding Information:
Construction of the AD system was supported by ARPA‐E IDEAS Program “High‐Throughput Discovery of Thermoelectric Materials.” S.G. and X.C. acknowledge support from National Science Foundation through the University of Minnesota MRSEC under Award Number DMR‐1420013.
Construction of the AD system was supported by ARPA-E IDEAS Program ?High-Throughput Discovery of Thermoelectric Materials.? S.G. and X.C. acknowledge support from National Science Foundation through the University of Minnesota MRSEC under Award Number DMR-1420013.
© 2019 American Institute of Chemical Engineers
- deposition methods
- particulate flows
- supersonic impaction
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