Crystallization dynamics of supersaturated NaClO4 aerosols studied by high-speed photography

Single supersaturated NaClO₄ aerosol droplets on a quartz substrate were observed by a high-speed video camera for their morphologic changes with decreasing relative humidity (RH). The supersaturated droplets were found to form anhydrous NaClO₄ at ∼10% RH. Three stages were roughly observed in this process, i.e., the main stem appearance, primary and secondary branches growth, and the deep dehydration. The main stem grew steadily and finished in 120 ms. Affected by both crystal precipitation and water evaporation, primary branches grew for 1200 ms, accompanied by a slower growth of secondary branches. The deep dehydration was more complicated, and lasted for a longer time. Supported by the National Natural Science Foundation of China (Grant Nos. 20473012, 20673010 & 20640420450), the “111” Project (Grant No. B07012), the China Postdoctoral Science Foundation (Grant No. 20070410466), and the Incubation and Reward Foundation for Excellent Doctoral Dissertation of Beijing Institute of Technology