Preparation And Magnetic Properties Of ?-fe₂O₃ Nanoparticles Using Fumed Silica

In recent years,?-phase ferric oxide has a broad application potential in magnetic resonance imaging,magnetic sensors and permanent magnets due to its unique physical properties of high coercivity at room temperature,ferromagnetic resonance and electromagnetic coupling.Because it is very unstable,it is especially easy to be converted into stable?-phase iron trioxide,so it is extremely sensitive to the synthesis experimental conditions.For a long time,researchers have been actively seeking methods to produce high-purity?-Fe₂O₃ in large quantities.According to reports in recent years,the particle size is relatively stable and coercive at the nanometer level,but the difficulty is that it is particularly prone to agglomeration.Therefore,if you want to obtain pure?-Fe₂O₃ with high coercivity,it is necessary not only to control the particle size but also to prevent its agglomeration.For this reason,people have conducted in-depth research on the synthesis of?-Fe₂O₃,and reported some synthesis methods.Such as sol-gel method,sol-gel and reverse micelle method,microemulsion and sol-gel combination method,chemical vapor deposition method,aerogel nanoreactor method and co-precipitation method,etc.However,these methods still have some problems such as high equipment cost,complicated process,and uneven particle size.In this paper,a new synthesis method is mainly introduced,that is,the preparation of?-Fe₂O₃ nanoparticles using fumed silica as a carrier.The advantages of this method are easy operation,low cost,simple equipment,no pollution to the environment,and the prepared nanoparticles have good dispersibility and are not prone to agglomeration.The specific research content is as follows:1.Use a powder tableting machine to press the fumed silica powder under a certain pressure to form a sheet-shaped shaped carrier,and then use the impregnation technique to immerse the ferric nitrate solution into the shaped silica carrier,and finally perform annealing to prepare?-Fe₂O₃ nanoparticles.X-ray diffraction,transmission electron microscope,Raman spectroscopy,vibrating sample magnetometer were used to analyze and study the structure and morphology of the sample.The prepared?-Fe₂O₃ nanoparticles have good dispersibility,small particle size,and are not easy to agglomerate.In addition,there are hard magnetic phases and soft magnetic phases in?-Fe₂O₃ nanoparticles.The hard magnetic phase is represented by the larger?-Fe₂O₃ nanoparticles,while the soft magnetic phase is represented by the smaller?-Fe₂O₃nanoparticles.What the particles show.2.Discuss the influence of different concentrations of ferric nitrate solution on the synthesis of?-Fe₂O₃ nanoparticles.It is found that when the concentration of iron nitrate solution is 30%,the?-Fe₂O₃ nanoparticles have the characteristics of large size and large coercivity;when the concentration is 50%,the size of?-Fe₂O₃ nanoparticles is small,and the coercive force is also small.The coercivity of?-Fe₂O₃ nanoparticles is positively related to the particle size.And with the increase of the concentration of ferric nitrate solution,the presence of miscellaneous?-Fe₂O₃ in the synthesized samples becomes less and less obvious.3.The influence of the pressure of preparing SiO₂ carrier on the synthesis of?-Fe₂O₃nanoparticles is discussed.The study found that as the pressure increases,that is,the density of the silica carrier increases,the size of the?-Fe₂O₃ nanoparticles tends to decrease,and the coercive force also changes with the size of the nanoparticles.