Abstract
Plasma-sprayed molten molybdenum particles (∼40 µm in diameter) were photographed impinging at high velocity (∼140 m/s) on a glass substrate at room temperature. An optical sensor detected thermal radiation emitted by a droplet as it approached the substrate and activated a time delay unit. After a selected time interval, an Nd:YAG laser was triggered, emitting a 5 ns pulse that provided illumination for a charge-coupled device (CCD) camera to photograph the impacting droplet through a long-range microscope. By varying the delay before pulsing the laser, different stages of droplet deformation were recorded. Impacting droplets spread into a thin circular film that ruptured and broke into small fragments. An optical detector recording thermal radiation from the impacting droplet gave a signal that increased as the droplet spread out, reached a maximum when the liquid film began to rupture, and decreased as portions of the droplet recoiled because of surface tension and then flew out of view of the photodetector.
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Mehdizadeh, N.Z., Lamontagne, M., Moreau, C. et al. Photographing impact of molten molybdenum particles in a plasma spray. J Therm Spray Tech 14, 354–361 (2005). https://doi.org/10.1361/105996305X59422
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DOI: https://doi.org/10.1361/105996305X59422