Preparation And Properties Of Porous Magnetic Composites

Mesoporous materials have used in many areas, such as catalysis, adsorption/ separation, biotech and other fields owing to their high specific area, ordered channels. However, the difficulty of separation of the nano-structured materials limits their application. To solve the problem, researchers tried to integrate the mesoporous materials with other functions, such as the magnetic properties to obtain functionalized magnetic mesoporous materials. The novel magnetic mesoporous composites, which contain dual functions of mesoporous structure and magnetism show a great potential application in many fields. This thesis sheds light on the controlled preparation and assembly of magnetism mesoporous composites. The morphology of products was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption measurements and X-ray diffraction technique (XRD). The adsorption/separation ability of the magnetic mesoporous composite to organic guest molecules and the stability of the nanosized metallic Co decorations in air or in an acid environment were also investigated by ultraviolet spectrophotometer and magnet. The main points of this paper go as followings:(1) Encapsulated metal@carbon/mesoporous silica magnetic mesoporous composites. First, mesoporous precursor, such as surf-MCM-41 and surf-SBA-15, are prepared by sol-gel process, then the mesoporous surfactant-silica composites were impregnated with cobalt precursor solution and subsequently calcined under Autogenic Pressure at Elevated Temperature using a Swagelok-like high-temperature autoclave in N2 atmosphere. Characterization results demonstrated that the composites possess relatively high surface area, large pore volume, uniform accessible mesopores and also relatively high saturation magnetic properties, as well adsorption/separation ability.(2) Embedded magnetic mesoporous composites. The materials with different morphology are obtained by spraying cobalt precursor and chitosan solution with different concentration and subsequently calcined in N2 atmosphere. Test disclosed that morphology of the composites are microspheres and the cobalt nanoparticles are doped in the carbon matrix uniformly. The material showed also relatively high saturation magnetic properties and adsorption/separation ability(3) Core/shell-type magnetic mesoporous composites. This chapter prepared composites with carbon or SiO2 coated Fe3O4 being the core and mesoporous silica being the shell. Equally distributed FesO4 nanoparticles were prepared by solvo-thermal process. In order to synthesis the core (Fe3O4@C and Fe3O4@SiO2), Carbon or SiO2 was deposited on Fe3O4 by spraying or hydrothermal process respectively. Then, mesoporous silica was deposited on the core by sol-gel method using TEOS as silica precursor and CTAB as pore directing agent. The product was refluxed by acetone for 16h to remove surfactant to obtain Core/shell-type magnetic mesoporous composites. Characterization result showed that the composites possess relatively large pore volume and high magnetism.