(158a) Fabrication of Monodisperse Silica Microspheres by Sol-Emulsion-Gel Method: Synthesis and Characterization

To fabricate monodispersed silica microspheres, a sol-emulsion-gel process combined with a T-shaped junction microfluidic technology was developed. The microfluidic system consisted of two T-shaped microchannels, one of which was used to mix partial hydrolyzed TEOS sol with dilute ammonia, the other was to generate sol emulsion droplets. The generated sol emulsions were transported into heat silicon oil to obtain gelled microspheres. The gel microspheres were characterized by optical and scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR), x-ray diffraction (XRD) analysis and thermal gravimetric analysis (TGA). The results show that monodisperse silica gel microspheres can be obtained based on the uniform reactions in the monosized sol droplets. The size of the droplets can be controlled by adjusting the flow rates of the continuous phase and disperse phase. Micrographs of the microspheres illustrate the uniform diameter and good sphericity. SEM images of the microspheres reveal the smooth surface and the dense structure. FT-IR measurements show the existence of residual hydrocarbon groups, which can be oxidized and removed by calcinations, in the gel microspheres. XRD analysis indicates that the microspheres are in a amorphous state. A weight loss of 7% during calcination was detected by the TGA measurement. The droplet formation process have been stablized by using the milimixer, which benefits the formation of monosized droplets. The present method is also characterized by using no surfactant. The microfluidic device in the present experiment can be extended to synthesize other particles by sol-emulsion-gel process .