Preparation And Characterization Of SmCo₅/?-Fe Nanocomposite Magnet

SmCo permanent magnet attracts a lot of attention due to its excellent intrinsic magnetic energy,especially high magnetic crystal anisotropic field and Curie temperature.However,due to its low saturation magnetization and high cost of raw materials,the application for the SmCo permanent magnet is limited.In recent years,nano-biphase composite provides an effective way to improve the saturation magnetization intensity and reduce cost of SmCo-based permanent magnet.A large number of research shows that the SmCo/?-Fe department has great improvement in the preparation of magnetic powder and thin film materials.However,as the most widely used block permanent magnets,the SmCo permanent magnet still has difficulties on the two phase control,the grain size of the regulation and the formation of the texture.Therefore,it is a major technical challenge to find new methods to prepare the high-performance block nano-composite permanent magnetic materials.In recent years,the magnetic field heat treatment has been widely used in the preparation of magnetic materials.Magnetic heat treatment can reduce the crystallization temperature and crystallization time effectively.It also can enhance the exchange coupling effect between grains to improve the magnetic material.In addition,the phase temperature of SmCo₅ and other Sm-Co phase is lower than the Curie temperature.The magnetic field can make the effect in process of the crystallization of hard magnetic phase directly to reflect the influence of the magnetic field strongly at the process of magnetic heat treatment.Therefore,inspired by this,we make following research.Firstly,the SmCo₅ and SmCo₅/?-Fe amorphous magnets need to be prepared by the special treatment such as the levitation melting,rapid quenching,high energy ball milling and SPS hot-pressing process.Then crystallization processing should be applied on the the SmCo₅ and SmCo₅/?-Fe amorphous magnet.In the process of magnetic heat treatment,the magnetic field is added to explore the influence of heating rate,holding time and magnetic field.In addition,the experiment of SmCo₅/?-Fe hot pressing and deforming were carried out by SPS technology.The experiment shows that the magnetic properties of SmCo₅ magnets can be improved by increasing the heat treatment temperature,decreasing the heating rate and extending the heat preservation time.When the heat treatment temperature is increased to 500?,the residual magnetism and coercivity of the magnet are increased to a certain extent.It indicates that the hard magnetic phase grain starts to be formed at the temperature.When the heat treatment temperature of the magnetic field was700?,the coercivity H_ci reached to 16.77 kOe.Similarly,for SmCo₅/?-Fe phase magnets,the heat treatment temperature of the magnetic field is increased,the soft magnetic phase is reduced and the hard magnetic phase is increased,and the phase grains that have been formed have grown rapidly.When annealing temperature is700?,the coercive force reaches 6.20 kOe and remanent magnetism M_r/M_s becomes0.59,which show that the sample has good exchange coupling effect.Additionly,decreasing the heating rate and extending the heat preservation time can also improve the magnetic properties.SmCo₅/?-Fe samples of annealing under magnetic field were significantly higher than that of residual magnetism and coercive force compared with the samples that did not apply heat treatment at the same temperature.It is shown that the external magnetic field can reduce the crystallization temperature of the sample effectively to promote the nucleation growth of the crystal and the exchange coupling between grains.