Preparation of crystalline silica (quartz, cristobalite, and tridymite) and amorphous silica powder (one step)

Silica nanoparticles (SiO2 NPs) have found applications in many advanced areas. In this study, we report a powder technology route as a low cost, simple and safe method for the fabrication of SiO2 NPs. It is a promising method as it has high throughput (91.7%) for different applications. The SiO2 NPs were prepared by an ultra-sonication technique and an alkali wet chemical etching process (one step), starting from commercial silicon powder. The main factors that affect the production of crystalline (quartz, cristobalite, and tridymite) and amorphous SiO2 NPs from crystalline silicon are the etching solution (KOH) concentration and the sonication time. The particle size of the SiO2 NPs is inversely related to the sonication time for 3 wt % KOH but directly proportional to the sonication time for 6 wt % KOH. The synthesized nanoparticles were systematically characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy and scanning electron microscopy.