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The Fe 3 O 4 @SiO 2 composite nanoparticles were obtained from as-synthesized magnetite (Fe 3 O 4) nanoparticles through the modified Stöber method. Then, the Fe 3 O 4 nanoparticles and Fe 3 O 4 @SiO 2 composite nanoparticles were characterized by means of X-ray diffraction (XRD), Raman spectra, scanning electron microscope (SEM) and vibrating sample magnetometer (VSM). Recently, the studies focus on how to improve the dispersion of composite particle and achieve good magnetic performance. Hence effects of the volume ratio of tetraethyl orthosilicate (TEOS) and magnetite colloid on the structural, morphological and magnetic properties of the composite nanoparticles were systematically investigated. The results revealed that the Fe 3 O 4 @SiO 2 had better thermal stability and dispersion than the magnetite nanoparticles. Furthermore, the particle size and magnetic property of the Fe 3 O 4 @SiO 2 composite nanoparticles can be adjusted by changing the volume ratio of TEOS and magnetite colloid.

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