Shape-controllable Synthesis Of ?-Fe₂O₃@SiO₂ Magnetite Hammer Colloid Particles

In this paper,hammer hematite??-Fe₂O₃?magnetic nanoparticles with different shapes and sizes were synthesized by hydrothermal method,which were used as precursors to grow silicon dioxide?SiO₂?semiconductors,and finally formed ?-Fe₂O₃@SiO₂ Magnetic Nanocomposites.The effects of synthesis condition,including the type and concentration of reagents,reaction time on the shape and size of hematite nanoparticles prepared by hydrothermal method,and the effects of reaction time on the shape control of ?-Fe₂O₃@ SiO₂ Magnetic Nanocomposites,such as the length and width of silicon segment,were studied.The results of this work provide an efficient,simple,and large-scale preparation method for further expanding the synthesis and application of ?-Fe₂O₃ magnetic composite.The specific research results are as follows:?-Fe₂O₃ magnetic nanoparticles were synthesized by a simple hydrothermal method.The effects of solvent concentration,sulfate anion concentration and reaction time on the size and morphology of ?-Fe₂O₃ were discussed.The hematite nanoparticles were characterized by scanning electron microscopy and optical microscopy.The experimental results showed that the obtained ?-Fe₂O₃ magnetic nanoparticles had different morphology such as pseudo cube,rod,peanut,and the particle length is 2-10 ?m,and the particle size gradually increased with the extension of reaction time.On the other hand,the influence of sulfate ion(SO₄^2-anion)on the morphology of hematite particles was discussed.Sulfate ion could significantly change the particle shape of hematite??-Fe₂O₃?.The effect of sulfate ions on the morphology of hematite particles,it was clearly that the amount of sulfate ions increased in the mixture of solution,the particles became increasingly an isometric particle.It could be seen that particles became elongated with the increasing concentration of sulfate ions,finally,attained peanut like shape particles.The major role of sulfate ions in the system of reaction to control the morphology of hematite particles.When increase the amount of sulfate ions in the standard conditions obtained different morphologies of hematite particles.Synthetic time is a necessary for the solid phase to be entirely transformed in to hematite particles.The morphology and size of hematite particles were affected by the reaction time.When the reaction time increased from 8 to 10 days,the particle size increased from 2 to 10 ?m to obtain different morphologies of hematite particles.In this study,the influence of synthesis conditions including the type and concentration of reagents,reaction time on the shape and size of hematite nanoparticles prepared by hydrothermal method was confirmed.The hammered ?-Fe₂O₃@SiO₂ magnetic composite nanoparticles were successfully synthesized by using the ?-Fe₂O₃ magnetic nanoparticles as the precursor.This method is suitable for the preparation of metal oxides,especially silicon oxides.In the reaction system,different temperature,different time,different water quantity and different crystal seed quantity had certain influence on the growth of silicon peanut.In addition,for hammers grown from the same emulsion drop,the change of temperature always led to the relevant change of hammer diameter.The diameter of silicon peanut was 460 nm and the length was 500 nm at a high temperature.At a low temperature,the diameter of silicon peanut segment in the composite system was larger than 510 nm,and the length was smaller than 340 nm.