Research On Synthesis And Properties Of Self-assembled Magnetic And Its Composite Materials

Magnetic and semiconductor materials have excellent application performance. Among them, Fe3O4 is an excellent magnetic material, with high saturation magnetization and superparamagnetism if the particle size is less than 20 nm, which attracted attention for scientific research. TiO2 is a kind of semiconductor material with low cost and simple preparation method, having good performance in photocatalytic degradation of organic dyes.In this thesis, Fe3O4 was prepared by solvothermal method, assisted- hydrothermal method and LSS(liquid-solid-solution) interfacial reaction method. It is found that the size of magnetic nanoparticles increased(99 nm and 125 nm, 175 nm) with alkali content rose(1.2 g, 2.4 g, 3.6 g). Meanwhile, saturated magnetization increased from 53 emu/g, 57emu/g to 65 emu/g. While the saturation magnetization prepared by the assisted-hydrothermal method was more than that of the solventthermal method, reaching 80emu/g. After that, the hydrophilic/hydrophobic Fe3O4 material were coated with SiO2 was prepared for surface modification. The hydrophilic/hydrophobic Fe3O4 materials were coated with SiO2, whose thickness was 100 nm/10 nm.Fe3O4@TiO2 and Fe3O4@SiO2@TiO2 were prepared through being coated another anatase TiO2 from Fe3O4. and Fe3O4@SiO2. The hollow structure(yolk-shell structure)Fe3O4@void TiO2, which poccessed excellent physical and chemical properties, was also prepared by sllica-protected calcination method(SPC). The thickness of TiO2 layer and the hollow layer was 30-63 nm and 100 nm for the three kinds of composite. Saturation magnetization was 27, 19 and 14 emu/g and specific surface area were 40.82, 20.14, 121.88m2/g, respectively. The properties of the three kinds of composite materials were studied through the degradation of 10 ppm RhB under UV-light, which showed the results were80.3 %, 99.6 %, 99.8 % during 2 h. And the rate constants were 0.0139, 0.0485, 0.0580 min-1,respectively, which proved the good catalytic activity of yolk-shell and the improvement of the separation efficiency of the catalyst after the photocatalytic reaction. Finally, TiO2 is incorporated into the N/F element with the Fe3O4@Si O2@TiO2. The efficiency of degradation of RhB under visible light was increased from 40.1% to 53.3% compared with the undoped complex, proving the success of extending the light absorption range of magnetic-semiconductor composite material from the ultraviolet region to the visible region.