Abstract: Using ethanol and deionized water as solvent,tetraethyl orthosilicate as raw material,and citric acid as complexing agent,ultrafine silica(SiO₂) powders were prepared by Pechini sol-gel method.The means of TG-DTG-DSC,XRD,FT-IR,and FESEM etc.were used to analyze the physical and chemical changes during the preparation process.Results showed that the prepared SiO₂ powders were amorphous phase when calcined below 1 000 ℃;the pH had a great influence on degradation combustion of organics;the SiO₂ powders with an average particle size of about 10 nm were synthesized when calcined at 500 ℃;while calcined at 600 ℃,the SiO₂ powders seriously conglomerated and the average size increased to 20 nm.

Key words: ultrafine silica, pechini sol-gel method, citrate acid