中文摘要：

采用溶胶-凝胶法，以尺寸约10nm的Fe3O4纳米粒子为种子，碱催化正硅酸已酯（TEOS）水解、缩合，制备了磁性可控的核壳结构SiO2／Fe3O4复合纳米粒子．系统研究了醇水比、NH4OH及TEOS的浓度对复合纳米粒子形貌和性能的影响，并分析了SiO2／Fe3O4复合纳米粒子的生成机理．结果表明，SiO2的生长主要是SiO2初级粒子在Fe3O4表面的聚集生长，醇水比为4：1、NH4OH浓度为0．3mol／L和TEOS浓度低于0．02mol／L时，随TEOS浓度的增大，SiO2壳层增厚，复合粒子饱和磁化强度下降，矫顽力基本不变，仍具有良好的超顺磁性．

英文摘要：

Core-shell structural SiO2/Fe3O4 nanocomposite particles with adjustable magnetic properties were prepared via a sol-gel process, in which the hydrolysis and condensation of TEOS were conducted on the surface of Fe3O4 nanoparticles under the aid of basic catalyst. The effects of the volume ratio of alcohol to water, the concentrations of ammonium and TEOS on the appearances and properties of the nanocomposite particles were investigated. The mechanism of the formation of SiO2/Fe3O4 nanocomposite particles was analyzed. Results show that silica shell is mainly formed from the aggregative growth of silica primary particles on the surface of Fe3O4 nanoparticles. With increasing the concentration of TEOS in the range of 0-0.02mol/L, the silica shell thickness increases on the condition of 0.3mol/L of NH4OH and 4：1 ratio of alcohol to water. Although the saturation magnetization of the nanocomposite particles decreases with the thickness of silica shell increasing, the coercive force of the particles is almost unchanged. And more, the nanocomposite particles remain favorable superparamagnetism.