【作者】 付乌有；

【导师】 杨海滨；

【作者基本信息】 吉林大学 ， 凝聚态物理， 2006， 博士

【摘要】 核-壳结构纳米复合材料是材料科学与工程领域中具有重要发展前景的一种新材料,根据人们的意愿控制合成核-壳结构纳米复合颗粒,揭示其新性质与新规律已成为材料科学研究的热点之一。本文利用各种控制方法和新的合成路线制备出一系列核-壳结构的新型纳米复合材料,对其形成机理及影响因素、微结构特征、磁性质、微波吸收特性、光催化特性进行了系统研究,获得了一些有重要意义的结果。用3-巯基丙基三甲氧基硅烷偶联剂（MPTS）对金属颗粒M （M=Ni,Co和不锈钢）进行表面改性,然后采用溶胶-凝胶法制备出核-壳结构的M/SiO₂纳米复合颗粒,厚度调整范围在2-25nm。改变SiO₂壳层厚度能够实现对纳米颗粒的饱和磁化强度的调制。SiO₂壳层对金属纳米颗粒起到抑制氧化的作用。用共沉淀法制备出核-壳结构Ni/Fe₃O₄纳米复合颗粒,其微波吸收（最大损耗为14dB）远高于其中单一组分的吸波性能。随着复合颗粒中Ni含量的提高,微波吸收增强,且微波吸收向低频段移动;吸收频宽比单质纳米Ni的情况宽二倍以上。增加涂层厚度可以增强微波吸收强度而不改变吸收频率。空心玻璃微球表面涂覆CoFe₂O₄颗粒层构成的复合材料,对微波吸收有十分明显的增强作用。其机制是,微波在贯穿玻璃微球过程中,在空心微球内部形成多次反射,使铁氧体层对微波形成多次吸收,进而使微波能量被充分损耗。用改进溶胶-凝胶法制备出核-壳结构的M（M=Sr, Ba）Fe₁₂O₁₉/TiO₂和M（M=Co, Mn）Fe₂O₄/TiO₂四种新型纳米复合颗粒。所制备的铁氧体/TiO₂纳米颗粒作为光催化剂对罗丹明B均有光降解作用,降解率可达98%。固-液磁分离实验表明,分离率可达95%以上,远好于纯`TiO₂静置的分离率49%。更多还原

【Abstract】 The preparation of nanocomposite particles is a great challenge in the fields ofsynthetic chemistry and materials science, because nanocomposite particles haveunique structural, mechanical, electronic, magnetic and optical properties. Variousnano-and micro devices were built up based on nanocomposite materials. Here, wefirst report on a synthetic route to prepare new material which is nanometer-sizemetals M (M=Ni, Co, stainless steel) particles coated with uniform silica layerutilizing wire electrical explosion technique and St?ber method. The method wasbased on the use of silane coupling agent 3-mercaptopropyltrimethoxysilane(HS-(CH2)3Si(OCH3)3, MPTS) as a primer to render the metal surface vitreophilic,thus rendered metal surface is compatible with silica. The product wascharacterized by XRD, XPS, TEM and TG-DTA spectroscopy. Measure resultsindicate that the metal/SiO2 nanocomposite particles have the core-shell structureand the thickness of SiO2 coating layer increases with the increasing reaction time.Result of the thermogravimetric analysis (TGA) and differential thermal analysis(DTA) indicate that the thermal stability of metal/silica is better than the pure metalnanoparticles. We suggest that the SiO2 shell is quite uniform and compact coatedon the surface of metal nanoparticles. Magnetic properties of these powders havebeen evaluated. These metal/silica core–shell nanoparticles can be utilized asprecursors for making property-tunable magnetic nanoparticles, thin films, andmultilayered core–shell structure nanocomposites. Core-shell structure Ni/Fe3O4nanocomposites were prepared by wire electrical explosion method andco-precipitation method. Ni/Fe3O4 nanocomposite powders with different mol rate wereuniformly dispersed in to the bakelite, respectively. The saturation magnetizationvalues (Ms) of Ni/Fe3O4 nanocomposites increased with increasing the concentrationof Ni. Ni/Fe3O4 nanocomposites showed higher values than coercivity concentrationof Ni and Fe3O4 because of the effects of shape anisotropy and exchange bias. Thebakelite resin comprised with 75 vol % Ni/Fe3O4 (3:1, 2:1, 1:1 vol %) powdersprovided good microwave absorption performances in ranges of 6-12, 8-13, and9-14GHz over the absorber thickness of1.5mm. The reflection loss (RL) valuesupper than14dB dB were obtained in the 9.5GHz with absorber thickness of 1.5mm, this values better than the RL values pure Ni(5.3 dB,8.7GHz) and pureFe3O4(6.5dB,18GHz). Spinel CoFe2O4 coating shell on the surface of hollow glassmicroballoon was synthesized by co-precipitation method and the shell thickness is 200nm.The produces were characterized by X-ray powder diffraction(XRD),energy dispersivespectrometer (EDS) and scanning electron microscopy (SEM), The as-synthesized powdermaterials were uniformly dispersed in the phenolic cement,then the mixture was painted onmetal plate with the area of 200mm×200mm as the test board. The test of microwaveabsorption was carried out by the RAM reflectivity far field RCS method. The results indicatethat notable microwave absorption performance have been obtained when the microwavefrequency is above 16GHz. This performance is much better than the pure CoFe2O4nanoparticles under the same condition. Ferrite/TiO2 (Ferrite=SrFe12O19, BaFe12O19, CoFe2O4and MnFe2O4) composite nanoparticles with core-shell structure have been obtained. In whichM type hexaferrites SrFe12O19 and BaFe12O19 nanoparticles were synthesized by citrateprecursor technique, spinel CoFe2O4 and MnFe2O4 were synthesized by co-deposition method,and then the shell TiO2 nanocrystals were derived via sol-gel technology. The presence of asmall quantity of polyethyleneimine (PEI) on the surface of the strontium ferrite nanoparticlesfacilitates this coating process. The morphology, crystalline structure, particle size and sizedistribution of ferrite/TiO2 composite nanoparticles were characterized by transmission electronmicroscopy (TEM), X-ray powder diffraction (XRD) and 3000HSA analyzer (MALVERN),respectively. Energy-dispersive spectroscopy (EDS) was utilized for the element analysis of theproducts. The as-prepared composite particles can be utilized as a magnetic photocatalystwhich can be fluidized and recovered by an applied magnetic field enhancing both separatingand mixing efficiency for recyclable fluids. Magnetic properties and photocatalytic activities ofthese powders have been evaluated. The results of the experiments show that the saturationmagnetizations of ferrite/TiO2 nanoparticles decrease with increasing the thickness of thetitania coating, while the coercivity does not show any change after coating. Photocatalyticactivities of these powders increase with increasing the thickness of TiO2 coating layer. As thethickness of TiO2 increases, the influence of the SrFe12O19 rapidly decreases and in the end thephotocatalytic activity of the composite never changes with increasing the thickness of TiO2.When the content of TiO2 is 30 % and there is enough UV illumination (5 h in our experiment)the photodegradation ratio of Procion Red MX-5B by the composite of TiO2/SrFe12O19 is 98 %similar to that of pure TiO2更多还原