Synthesis, Structure And Magnetic Properties Of Mesoporous Silica And CoFe₂O₄/SBA-15 Nanocomposite

Ordered mesoporous materials with large surface area and uniform hexagonal channels, have attracted considerable attention due to its potential applications in catalysis,adsorption/ separation,biology and other fields.The most common synthetic route of the mesoporous materials is based on the corporative interaction between inorganic precursors and supra-molecular surfactants through self-assembly process.On the other hand,the interest in nanocomposites consisting of nanosized magnetic particles embedded in an immiscible insulating non-magnetic matrix has grown considerably in recent years.The SBA-15 mesoporous silica is an excellent host for supporting different types of guest nanoparticles due to its large surface area,ordered channels and excellent thermal stability.And the porous of the SBA-15 mesoporous silica can provide nucleation sites for magnetic nanoparticles,which can control the size of the particles and minimize the aggregation phenomena.Therefore,the SBA-15-based magnetic nanocomposites can be obtained using SBA-15 mesoporous silica as template.Mesoporous thin films can be seen as the development of mesoporous materials, which have potential applications in future due to their special properties.In this work,SBA-15 mesoporous silica and mesoporous silica thin film with hexagonally ordered pore array structure were prepared first of all.Then,the CoFe₂O₄ ferrite was introduced into the pores of the SBA-15 by templated synthesis,and the CoFe₂O₄/SBA-15 nanocomposite was obtained.The structures of CoFe₂O₄/SBA-15 nanocomposites with different content were characterized and magnetic properties of the nanocomposites were discussed.The main results are shown as follows:(1) The SBA-15 mesoporous silica and mesoporous silica thin film were prepared by sol-gel process using TEOS as silicon source and P123 as structure-directing agent under the acidic condition.The structure of mesoporous silica materials were characterized by X-ray diffraction,nitrogen adsorption-desorption measurements,FTIR,TEM and SEM measurements. The SBA-15 mesoporous silica and mesoporous silica thin film both showed a hexagonally ordered pore array structure and the frameworks were consisted of non-crystalline silica.The pore array period a₀ of each was 12.89 nm and 7.4 nm.(2) The cobalt and iron nitrates with molar ratio of 1:2 were introduced into SBA-15 mesoporous silica via "two-solvent" route.And the CoFe₂O₄/SBA-15 nanocomposite was obtained after calcination at 800℃for 5 h.The structure of the CoFe₂O₄/SBA-15 nanocomposite was monitored by XRD,TEM and N₂ adsorption-desorption.The results showed that the composite had a hexagonally ordered pore array nanostructure,and the spinel CoFe₂P₄ was mainly distributed in the mesoporous channels.The CoFe₂O₄/SBA-15 nanocomposite exhibited relatively small coercivity at room temperature compared to the bulk counterpart,the spontaneous magnetization of CoFe₂O₄/SBA-15 nanocomposite was increased with the increasing content of CoFe₂O₄ in SBA-15 mesoporous silica.