| Synthesis of spherical SiO2 powders from water glass and colloidal Sol through ultrasonic spray pyrolysis |
Sohyeon Kim, Seunghwan Son, Kyusung Han, Kwangtaek Hwang, Ungsoo Kim, Jinho Kim
, Junghoon Choi |
| Icheon Branch, Korea Institute of Ceramic Engineering and Technology, Icheon, Republic of Korea |
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Received: November 6, 2023; Revised: January 26, 2024 Accepted: February 11, 2024. Published online: March 25, 2024. |
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| ABSTRACT |
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Silicon dioxide (SiO2) is formed via a combination of silicon and oxygen, which are the most abundant elements on Earth. It possesses excellent heat and chemical resistance and can be developed into various types of functional materials. In particular, spherical SiO2 is extensively utilized in the pre-impregnated materials of printed circuit boards (PCBs) and as a filler in cosmetics. Among the methods used for manufacturing spherical SiO2 powders, ultrasonic spray pyrolysis (USP) involves the generation of droplets by subjecting a precursor solution to ultrasonic waves. These droplets then undergo a thermal decomposition, resulting in the formation of the final powders. In this study, a low-priced commercial sodium silicate (water glass, Na2O3Si) was employed as the starting material, and a high-purity colloidal nano-SiO2 sol was prepared via an ion-exchange resin method. The effects of the rheological properties (dispersion and viscosity), colloidal nano-SiO2 size, and concentration of the prepared high-purity nano-SiO2 sol on the shape of the spherical SiO2 powders synthesized through USP were observed through SEM, PSA, and XRD. The results confirmed that the changes in the colloidal nano-SiO2 size and surface tension, due to the addition of ethanol to the high-purity nano-SiO2 sol, had little effect on the physical properties, such as particle size, standard deviation, and roundness of the SiO2 powders synthesized by USP (USP-SiO2). Moreover, dispersibility alterations were achieved through pH control. Furthermore, concentration of the nano-SiO2 sol significantly affected the particle size and monodispersity of the final USP-SiO2 powders. |
| Key words:
High-purity nano-SiO2 sol · Spherical SiO2 powders · Ultrasonic spray pyrolysis · Rheological properties · Dispersibility |
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