IR Thermography and High Speed Imaging of Cerium Nitrate Precursor Droplets Heated by Monochromatic Irradiation

An experimental setup using radiative heating has been used to understand the thermophysical phenomena and chemical transformations inside acoustically levitated cerium nitrate precursor droplets. IR imaging in conjunction with high speed imaging shows presence of four distinct phases of heating. The droplet initially undergoes pure vaporization followed by surface precipitation. This results in a gelatinous phase due to precipitation of cerium nitrate which eventually goes though chemical transformation and forms a porous precipitate. Transmission Electron Microscopy (TEM) of the final precipitate revealed the presence of trapped gases in the form of bubbles. TEM also showed the presence of nano-ceria crystalline structures at 70°C. The current study also looks into the effect of different heating power on the process. At higher power each phase is sustained for smaller duration and higher maximum temperature. At all laser power, TEM showed the formation of nanoceria. In addition, the porosity of the final precipitate increased with power.