四氧化三铁(Fe3O4)因在细胞分离、靶向药物、磁共振成像等生物医学领域具有广阔的应用前景而成为研究热点。本文采用溶剂热法合成了Fe3O4纳米粒子，并详细研究了反应温度、反应时间和反应前驱体组成对Fe3O4结构和形貌的影响。实验结果表明，反应时间对球形纳米颗粒的尺寸影响不大，反应时间为12 h时，球的直径达到了最大，继续延长反应时间，球的尺寸保持不变；200 ℃容易生成大尺寸的Fe3O4纳米粒子；反应物的组成对Fe3O4纳米粒子的形貌也有一定的影响，当用水合肼代替乙二胺时，得到的是立方体形状的Fe3O4。为了增加Fe3O4纳米粒子的化学稳定性、生物相容性和作为药物载体的可能性，我们用Stber方法在Fe3O4纳米粒子的表面包覆了一层SiO2介孔分子筛，并探索了超声和机械搅拌对核壳结构形貌的影响，还研究了包覆前后样品的磁学性质。

Fe3O4 has a wide application prospect in biomedical fields such as cell separation, targeted drugs, magnetic resonance imaging and so on. In this work, Fe3O4 nanoparticles were synthesized by solvothermal method, and the effects of reaction temperature, reaction time and precursor composition on the structure and morphology of Fe3O4 were studied in detail. The reaction time had little effect on the size of the spherical nanoparticles. When the reaction time was 12 h, the diameter of the spheres reached the maximum. When the reaction time was increased, the size of the spheres kept constant. The reaction did not occur when the reaction temperature was 120 ℃. Face-centered cubic structure Fe3O4 was obtained when the reaction temperature was 160, 200, 240 ℃. The diameter of Fe3O4 was maximum when the reaction temperature was 200 ℃. Cube-shaped Fe3O4 was obtained when ethylenediamine was replaced by hydrazine hydrate. In order to improve the chemical stability, biocompatibility and the possibility using Fe3O4 nanoparticles as drug carriers, a layer of SiO2 mesoporous molecular sieve was coated on the surface of Fe3O4 by Stber method. The effects of ultrasonic and mechanical stirring on the morphology of core-shell structure were investigated. The magnetic properties of the samples before and after SiO2 coating were also studied. The samples were all superparamagnetic before and after coating.