Study On The Preparation And Magnetic Properties Of Sm-Co/Fe-Co Multiphase Composite Nanoparticles By Solvothermal

With the research and development of magnetic materials, nano-composite magnetic materials as a magnetic material which becomes the most substantial increase in energy product of permanent magnets, because it combined with high coercivity of hard magnetic materials and high saturation magnetization of soft magnetic materials. In our work, we use chemical reduction method which also called solvothermal, synthesized the core-shell nanoparticles that is Sm-Co coated with the soft magnetic materials, such as Fe/Fe3O4、Co、Fe-Co. The XRD, TEM and VSM analytical methods were used to characterize the microstructure and magnetic properties of the materials. The study found that the experimental parameters have a major impact on the coating effect.（1） In ethanol system, Fe²⁺ as the precursors and the hydrazine hydrate as reducing agent were used to synthesis the core-shell structure composite magnetic particles found that the shell was Fe3O4. Because of Fe²⁺ can simultaneously be reduced and oxidized, Fe²⁺ and Fe3+ coexist to generate Fe3O4; While Fe3+ as the precursors, the resulting shell still Fe3O4, and the introduction of impurities NaCl can not be removed. In glycol system, Fe3+ reaction product detected a small amount of raw material iron phase, explained the characteristics that at the boiling point the ethylene glycol have played a role in reducing.（2） Ethylene glycol as a solvent, hydrazine hydrate as reducing agent to obtain Co-coated composite shell nanoparticles Sm-Co particles, the researchers found that incubation time on the formation of a core-shell structure of its more significant. The longer the holding time, the more severe reduction reaction pure Co particles reunion, the more bad of the coating effect.（3） Ethylene glycol as a solvent, hydrazine hydrate as reducing agent, the precursor solution while adding Fe3+ and Co²⁺, prepared Fe-Co alloy as the shell. Found that by changing the Fe3+ and Co²⁺ molar ratio of Fe-Co alloy can be obtained with different structures and components, When the molar ratio of Fe3+ and Co²⁺ was 7: 3, the composite magnetic particles was best.