Preparation Of Surface Magnetic Shell Of Fe₃O₄ Nanoparticles And Coated SiO₂ Research

Nano Fe₃O₄ belong to spinel type ferrite, Fe₃O₄ nanoparticles have well magnetic property and widely applied to many fields in recent years. Due to nanometer material agglomeration, were restricting its further applications. Core-shell nanoparticles have recently been the focus of a lot of scientific efforts because of the combination of different properties in one particle based on different compositions of the core and the shell. Synthetic core-shell type composite nanoparticles can well solve the defects above of Fe₃O₄ nanoparticles. Furthermore, many interesting technological applications can be foreseen for this kind of material, in addition to others in analytical chemistry (chromatography), separation technology (ion exchange), catalysis, biochemistry and medicine and so on. The synthesized products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), differential thermal analyzer (DTA), infrared spectrometer (FT-IR) and preliminarily research for the performance optimization, prepared technology and reaction mechanismFe₃O₄/CoO Core-shell nanoparticles were prepared by the hydrothermal method. The factors such as the concentration of cobalt acetate, reactant ratio and reaction time, which influenced the property of core-shall nanoparticles. Preliminarily discussed the reaction mechanism of CoO coated Fe₃O₄ magnetic nanoparticles. The results indicated that the products presented well crystal form and sphericity. The core shall nanoparticles have narrow particle size distribution(15-20nm)and show good superpammagnetism(no coercive force and residual magnetism). The optimal concentration is 0.04mol/L, the optimal mol ratio of reactants is: n (cobalt acetate): n (Fe₃O₄) =1:4, the optimal reaction time is 4h.Fe₃O₄/CoO/SiO₂ core-shell nanoparticles were prepared by the St?ber method. The factors such as the concentration of reactant ratio, ammonia concentration and ethanol/water ratio, which influenced the property of core-shall nanoparticles. Preliminarily discussed the reaction mechanism of SiO₂ coated Fe₃O₄/CoO magnetic nanoparticles. The results indicated that the products presented well crystal form and sphericity. The core shall nanoparticles have narrow particle size distribution (20-30nm) and show good superpammagnetism(no coercive force and residual magnetism). The optimal mol ratio of reactants is: n (TEOS): n (Fe₃O₄) =2:1, the optimal ammonia dosage is 0.3mol/L, the optimal ethanol/water ratio is 2:1.Fe₃O₄/Fe Core-shell nanoparticles were prepared by the chemical precipitation method. The factors such as solvent, surfactants, and reactant ratio, which influenced the property of core-shall nanoparticles. Preliminarily discussed the reaction mechanism of Fe coated Fe₃O₄ magnetic nanoparticles. The results indicated that the products presented well crystal form and sphericity. The core shall nanoparticles have narrow particle size distribution (15-20nm) and show good superpammagnetism(no coercive force and residual magnetism). Ethanol-water system for the best reaction media solution, PVP is the best surfactant, the optimal ethanol/water ratio is 4:1.Fe₃O₄/Fe/SiO₂ core-shell nanoparticles were prepared by the St?ber method. The factors such as the concentration of reactant ratio, ammonia concentration and ethanol/water ratio, which influenced the property of core-shall nanoparticles. Preliminarily discussed the reaction mechanism of SiO₂ coated Fe₃O₄/Fe magnetic nanoparticles. The results indicated that the products presented well crystal form and sphericity. The core shall nanoparticles have narrow particle size distribution (20-30nm) and show good superpammagnetism(no coercive force and residual magnetism). The optimal mol ratio of reactants is: n (TEOS): n (Fe₃O₄/Fe) =3:1, the optimal ammonia dosage is 0.15mol/L; the optimal ethanol/water ratio is 4:1.