The Preparation And Performance Of Fe₃O₄, SiO₂ And Their Composite Particles

This work is mainly focused on the study of the preparation and structural, morphological,and magnetic properties of Fe₃O₄ nanomagnetic particle,SiO₂ particle and SiO₂/Fe₃O₄ composite particle.These materials have broad potential applications in biotechnology.Two kinds of materials and their composite particles are studied in this work.(1) Fe₃O₄ magnetic nanoparticles are synthesized by coprecipitation method. FeCl₂·4H₂O and FeCl₃·6H₂O are used as the raw materials and ammonia is used as the precipitator.The synthesized Fe₃O₄ is then characterized by X-ray diffraction(XRD) and vibrating sample magnetometer(VSM).The influences of reaction temperature and stirring rate on structural,magnetical propertiesy,and diameters of the Fe₃O₄ magnetic nanoparticles are carried out respectively.The results demonstrate that the structure of the magnetite nanoparticles is spinel,and they are superparamagnetic because of their magnetization and coercive force are almost zero,and the magnetization isn't saturation at 11000 Oe.(2) Monodispersed silicon dioxide spherical particles are prepared by hydrolysis of tetraethoxy silane(TEOS) in alcohol-water mixed solvents using ammonia as a catalyst.Effects of the volume of TEOS,water,the concentration of ammonia,the stirring rate and temperature of hydrolysis on the particle size and morphology of SiO₂ were investigated by scanning electron microscopy(SEM).The results show that the size of the SiO₂ particles increases with increasing concentration of ammonia and TEOS. While the temperature of hydrolysis,the amount of water and the stirring rate show no effect on the morphology of the SiO₂ particles.The formation mechanisms of the resultant SiO₂ particles under different reaction conditions are also carefully investigated and discussed.(3) Fe₃O₄/SiO₂ composite particles are synthesized using the improved St(o|¨)ber method.The morphological and magnetical properties are studied.To modify the inclination of conglomeration of magnetite in disperse phase and increase the magnetic content of the composite particles,silane coupling agent PEG is used for the surface modification of magnetite.