Core/shell structured novel cloud seeding materials for rain enhancement

Cloud-seeding materials as a promising water-augmentation technology have drawn more attention recently. We designed and synthesized a type of core/shell NaCl/TiO2 (CSNT) particles with controlled particle size, which successfully adsorbed more water vapor than that of pure NaCl, deliquesced at lower environmental RH of 62 - 66 % than the hygroscopic point (hg.p., 75 % RH) of NaCl, and formed larger water droplets ~ 6 - 10 times of its original measured size area, whereas the pure NaCl still remained as crystal at the same condition. The enhanced performance was attributed to the synergistic effect of the hydrophilic TiO2 shell and hygroscopic NaCl core microstructure, which attracted large amount of water vapor and turned it into liquid faster. Moreover, the critical particle size of CSNT particles (0.4 - 10 μm) as cloud-seeding materials was predicted via classical Kelvin equation based on their surface hydrophilicity. Finally, the benefits of CSNT particles for cloud-seeding application were determined visually through in-situ observation under Environmental - Scanning Electron Microscope (E-SEM) in microscale and cloud chamber experiments in macroscale, respectively. These excellent and consistent performances positively confirmed that CSNT particles could be the promising cloud-seeding materials.

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