The critical velocity of rebound determined for sub-micron silver particles with a variable nozzle area impactor

- The critical velocity of rebound is determined for spherical silver aerosol particles.
- A new type of an impactor, a variable nozzle area impactor, is introduced.
- The results cover a wide sub-micron size range of 20-1000 nm.
- The critical velocity is proportional to the power of −1.6 of the particle size.
- The magnitude of the critical velocity may be highly dependent on the material pair.

The critical velocity of rebound was determined for spherical silver aerosol particles in the size range of 20-1000 nm. A novel instrument, a variable nozzle area impactor, was especially designed for measuring the particle-surface interaction as a function of the particle impact velocity. The experimental results were combined with a numerical model in order to obtain the impact velocities. The experiments were carried out using a plain aluminum collection substrate in the impactor. Our results show that the critical velocity of rebound decreases from 14 to 0.022 m/s as the particle size increases from 20 to 1000 nm. Furthermore, the critical velocity was found to be proportional to the power of −1.6 of the particle size, instead of the theoretical inverse proportionality. This result is in line with the previous studies for micron-sized particles. In the nanoparticle size range, the obtained values are approximately 3-10 times greater than the recent literature values. This discrepancy can most likely be explained by the different surface materials. All in all, our results give valuable information about the particle-surface interactions in the sub-micron size range.

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