The Study Of Magnetic Nanoparticles On Surface Modification And Magnetic Properties

In the past few decades, many investigations have been performed on the magnetic nanoparticles, which is of great significance to not only fundamental research but also practical applications. This is mainly because that magnetic nanomaterials can be widely used in many areas such as electronics, medicine, chemical industry, aviation and so on. However, the aggregation is always a crucial problem to be solved.In this study, tetraethoxysiliane (TEOS) and titanium alkoxide are used to modify ferrite nanoparticles using in-situ and ex-situ sol-gel process, after which magnetic properties of ferrite nanoparticles are investigated further.In the case of in-situ, the influence of pH value, the order of addition of ammonia, deposition time of sodium silicate, nitrate concentration and the addition of APS on the formation of stable and homogeneous ferrite nanoparticles, the corresponding characterizations are performed by using XRD, TEM, PPMS. TEM characterization indicates that stable and homogeneous ferrite nanoparticles can be obtained with the addition of coupling agent, APS. Take nickel ferrite nanoparticles for example, the magnetic characterization indicates that NiFe2O4 nanoparticles formed in silica matrix with the addition of APS not only have the lowest blocking temperature but also hold the lowest interparticle interactions compared with the samples without the addition of APS.For ex-situ process, ferrite nanoparticles are prepared first using coprecipitation and sol-gel process, then their surfaces are modified. In this section, the effect of surface modification agent, solvents and the molar ratio of ferrite nanoparticles to surface modification agent on the morphology of samples are the change of morphology and magnetic properties between modified and...