Sonochemical effect and pore structure tuning of silica xerogel by ultrasonic irradiation of semi-solid hydrogel

• Published in: Ultrasonics sonochemistry 2021-05, Vol.73, p.105476-105476, Article 105476
• Main Authors: Maeda, Yuki, Hayashi, Yamato, Fukushima, Jun, Takizawa, Hirotsugu
• Format: Article
• Language: English
• Subjects: Aging; Ambient pressure drying; Hydrophobization; Original; Silica xerogel; Ultrasonic irradiation
• ISSN: 1350-4177; 1873-2828
• DOI: 10.1016/j.ultsonch.2021.105476

•A landmark synthesis method of silica xerogel was proposed by ultrasonic irradiation.•Semi-solid hydrogel was irradiated ultrasonic for aging and hydrophobization.•Ultrasonic cavitation greatly accelerates aging and hydrophobization reactions.•The pore structure and density can be easily controlled by ultrasonic irradiation.•Low-density xerogels were prepared in less than 1/5 of the usual time by ultrasonic. Silica xerogels were prepared by the sol-gel method under ultrasonic irradiation, using tetraethylorthosilicate (TEOS) as the starting material. Hexamethyldisiloxane (HMDSO) was used as the hydrophobizing agent. When preparing silica xerogel, it is necessary to perform aging and hydrophobization to suppress shrinkage during ambient pressure drying, however, such treatments are time-consuming. In this study, the semi-solid hydrogel was irradiated with ultrasonic for the first time in order to accelerate aging and hydrophobic treatment, and the effect of ultrasonic frequency on structure was investigated. Firstly, ultrasonic irradiation was performed at frequencies of 100 kHz and 500 kHz, followed by hydrophobic treatment at a frequency of 500 kHz, in order to promote aging. The results identify optimum conditions for ultrasonic irradiation to promote aging and hydrophobization reactions, and it was found to be possible to prepare silica xerogels in less than 1/5 of the conventional time. The silica xerogels had a low density and the shrinkage was suppressed. In this study, it was found that ultrasonic irradiation of semi-solid hydrogel was very effective for promoting the reaction.