Preparation Of Fe-Co Alloy Nanoparticles And Their Magnetic Properties Research

Fe-Co alloys have been received extensive attentions,it is because of their high saturation magnetization,high Curie temperature,high permeability,low coercivity and low magnetic anisotropy constant,and other unique soft magnetic properties.When the Fe-Co alloy particles are nanometer size,due to the surface effects of nanoparticles,small size effect,quantum size effect and macroscopic quantum tunneling effect,its electromagnetic characteristics and physical characteristics will be changed,so there are many special performances.Due to its special magnetic properties,Fe-Co alloy nanoparticles have been widely used in biomedical field,magnetic recording materials,electromagnetic wave absorbing materials and high-frequency soft magnetic materials.Therefore,preparation and properties of Fe-Co alloy nanoparticles has been a hot topic of current research.Currently,the preparation of Fe-Co alloy nanoparticles has many ways.Due to environmentally-friendly,simple,shape and size of the nanoparticles are well controlled,using polyol reduction method to Prepare Fe-Co alloy nanoparticles has been widely used.However,this,method requires strict control of the oxygen-free environment,and the nanoparticles prepared easily oxidized and the saturation magnetization is not high.In this paper,we use a simple polyol reduction method with hydrogen annealing to prepare Fe-Co alloy nanoparticles,this method is not only simple,environmentally friendly,but also the nanoparticles are very pure and have uniform particle size distribution and a high saturation magnetization.First experiment by varying the ratio of the initial salt,we obtained different components of the Fe-Co alloy nanoparticles.Then the Fe-Co alloy particles whose atomic ratio is nearly 1:1 composition were annealed at different temperatures to give the Fe-Co alloy particles having different hydrogen annealing temperatures.These samples were tested and analyzed by XRF,XRD,SEM,TEM,VSM and laser particle size analysis,the results showed that:by changing the ratio of the initial metal salt we can obtain different components of Fe-Co alloy particles;at the same annealing temperature,the average grain size of the Fe-Co alloy particles increases as the Fe in the alloy gradually increasing;Fe45CO55 alloy particles of this component annealed at 850? hydrogen has a maximum saturation magnetization?Ms?of 272 emu/g,and Fe48Co52 this component alloy with minimal residual magnetization?Mr?and the coercive force?Hc?,respectively 4 emu/g and 90 Oe;when hydrogen annealing temperature reaches 450?,we get Fe48Co52 alloy nanoparticles,the average grain size is 16.8 nm,the average particle size is 70.8 nm,the saturation magnetization is up to 231 emu/g,residual magnetization is 163 emu/g,the coercive force is 25 Oe.Since the magnetic nanoparticles embedded in magnetic nanocomposite insulator shell structure constituted in the microwave absorption,electromagnetic devices and magnetic shielding material aspect has broad application prospects,so this article also use Fe-Co alloy nanoparticles which were prepared by the above method to be coated with a layer of SiO₂.First experiment by controlling the reaction time,the Fe65Co35@SiO₂ nanocomposites which have different SiO₂ contents were prepared.Then the?Fe65Co35?0.65@?SiO₂?0.35 nanocomposites whose SiO₂ content is 35%were annealed at different temperatures,we obtained?Fe65CO35?0.65@?SiO₂?0.35 nanocomposites which are under different hydrogen annealing temperatures.Finally,the above samples were tested and analyzed by XRF,XRD,SEM,TEM,VSM and laser particle size analysis,the results showed that:under the same annealing temperature,Fe65CO35@SiO₂ composite material with increasing SiO₂ content,the saturation magnetization is gradually reduced,while the coercive force is gradually increased;the?Fe65Co35?0.65@?SiO₂?0.35 nanocomposites whose SiO₂ content is 35%with increasing annealing temperature,the saturation magnetization is first increased and then decreased,reaching a maximum at 650?,and the coercive force with increasing annealing temperature is gradually reduced;when the SiO₂ coating reaction time control at 40 min,after hydrogen annealing at 450?,we can get the composite nanoparticles material?Fe65CO35?0.65@?SiO₂?0.35,the saturation magnetization is 132 emu/g,residual magnetization is 25 emu/g,the coercive force is 420 Oe,average grain size is 20.98 nm,average particle size is 80 nm and have a uniform particle size distribution.