Ultrasonic-assisted hydrothermal method

Figures 17.11-17.13 present the elimination process of these floccules on LiCo02 surface with ultrasonic-assisted hydrothermal method. According to analysis of products [53, 78,79], cavitation caused by ultrasound in hydrothermal environment cannot only lead to the production of free radicals but also the occurrence of microstreaming. The former can promote organic degradation, and the latter is able to accelerate the heat and mass transfer process accompanying the renovation process. Shock waves from cavitation in liquid-solid slurries produce high-velocity inter-particle collisions. Therefore, the agglomerates on the surface of the LiCo02 can easily be broken.

Figure 17.12 The degradation process of PVDF with ultrasonic-assisted hydrothermal method.

The hydrothermal method to synthesize perovskites thin films and powders has a number of advantages, such as high purity and high quality of the product. In order to promote hydrothermal reactions, Ohta et al. [57] developed an ultra-sonic-assisted hydrothermal method and confirmed that it produces dense and thick lead zirconate titanate (PZT) films. For this film, ultrasonic irradiation was used from the beginning of the reaction for 18h, followed by a 6h deposition without ultrasonic irradiation. These results indicate that the ultrasonic irradiation mainly promotes the nucleation process and during the ultrasonic irradiation, the number of grains increases. 

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