Preparation of P2O5-SiO2 hollow microspheres in the presence of phosphoric acid

Abstract

Silica hollow microspheres containing phosphorous have been prepared by a sol-gel/emulsion method which uses tetraethoxysilane (TEOS) as the precursor for the SiO 2 and phosphoric acid (H 3 PO 4 ) as the precursor for P 2 O 5 . The hollow structure forms an emulsion system which is composed of an oil phase (kerosene, sorbitan monooleate (Span 80)) and an aqueous phase (a viscous sol solution of ethanol, TEOS and H 3 PO 4 ). Some of the phosphorous remains in the final silica shell structure even after calcination at 650°C. The hollow structure of the P 2 O 5 -SiO 2 (silicophosphate) was characterized by X-ray diffraction (XRD), polarized optical microscopy (POM), scanning electron microscopy (SEM), nitrogen adsorption measurement and Fourier transform infrared spectroscopy (FTIR).