Self-templated magnesiothermic reduction of ORMOSIL particles to monodisperse hollow spherical SiC composite particles

Abstract

Hollow silicon carbide (SiC) particles have attracted attention due to their well-defined morphology, low density, and large surface area that can be leveraged for a wide variety of applications. Here, we report the self-templated synthesis of monodisperse hollow spherical SiC composite particles with controllable shell thicknesses using magnesiothermic reduction of organically modified silica (ORMOSIL) particles. Monodisperse ORMOSIL particles containing three organic groups of methyl, vinyl, and mercaptopropyl were produced by a simple one-pot sol-gel process and then converted to hollow spherical SiC composite particles via a magnesiothermic reduction at 700 degrees C under an inert atmosphere. The spherical morphologies of the original ORMOSIL particles were well maintained through this self-templated conversion process, but the sizes of the hollow SiC particles were slightly reduced by the thermal treatment. Field emission transmission electron microscopy studies revealed that the shell of hollow particles mainly consists of primary beta-SiC particles with nanometer-scale sizes. The physical and chemical properties of the hollow SiC composite particles were investigated by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller, X-ray diffraction, Fourier transform infrared spectroscopy, Raman, and solid-state nuclear magnetic resonance analyses. The shell thickness of hollow spherical SiC composite particles can be controlled by simply changing the duration of the thermal conversion process. This study not only provides a simple and easy approach for the preparation of hollow spherical SiC particles but also opens the possibility of large-scale manufacturing of such particles for commercial applications.