Effect of silane coupling agents on flowability and compressibility of compound for bonded NdFeB magnet

Based on the difference of the Y-terminal functional group of the silane coupling agent(Y-Si(X)_(3)),four different silane coupling agents were employed to pretreat the surface of the NdFeB powders.The effects of silane coupling agents on the flowability and compressibility of compounds for preparing bonded NdFeB magnets were studied.It is indicated that compounds pretreated by silane coupling agents have weaker friction and meshing force.The apparent density is increased by 0.3 g/cm^(3 )compared with the compound without silane coupling agent,and the radial crushing strength is significantly increased by about 3-4 times.In addition,the epoxy resin is more evenly distributed on the surface of the compounds treated by silane coupling agents observed by scanning electron microscopy,and some agglomerated particles are produced.Also,the compressibility of compounds with silane coupling agents is significantly improved due to the fact that hardening exponents are reduced.However,the addition of silane coupling agents has almost no effect on the magnetic properties of bonded magnets.The special energy was used to manifest the flowability of magnetic powder particles representing the macroscopic performance of the force between powder particles,providing a new direction for the study of the interface compatibility of two-phase or multiphase composite materials.

The Effect of HDDR Process on Magnetic Properties in NdFeB Type of Bonded Magnets

The present paper describes the effect of alloy composition,homogenization and dehy-drogenization procedures on magnetic properties of NdFeB type of HDDR powders and the bonded magnet.The results showed that the powders prepared by HDDR process possesses useful magnetic proper- ties and a better thermal stability than the sintered NdFeB magnet does.

Demagnetization Process and Coercivity for Anisotropic HDDR NdFeB Bonded Magnets

The demagnetization process and the coercivity mechanism for amsotropic HDDR Nd(Fe,Co)B bonded magnets were studied by comparing the dependence of coercivity on the alignment field applied while the powders were pressed. The results showed that both the remanence and the coercivity of magnet increased with increasing alignment field. The demagnetization process of the magnet can be classified as the nucleation process inside the grains and the domain-wall motion between the grains. The combined effect of two processes determines the coercivity of HDDR NdFeB bonded magnets.

Influence of Heat Treatment on Microstructures and Properties of Nd_8Fe_(78)B_6Co_4 Alloy

Melt-spun Nd8Fe78B6Co4 magnetic powders and their bonded magnets were prepared with the optimization of compositions and preparation techniques. The microstructure change of alloy NdFeB and the relation between microstruc-ture and heat-treatment were studied. The heat-treatment temperature is 200 ~ 700℃. The as-cast structure of the alloy is typically amorphous. Different melt-spun speed and different heat treatment could result in different magnetic properties of NdFeB magnets. Magnetic properties of NdFeB increase with the addition of element Co. The magnetic properties of magnet alloy get the best when the melt-spun speed reaches 23 ~ 26 m·s-1, heat treatment temperature is 690℃and time is 30 min.

Anisotropic NdFeB/SmCoCuFeZr composite bonded magnet prepared by warm compaction process

Anisotropic NdFeB/SmCoCuFeZr composite bonded magnets were prepared by warm compaction process. The effects of adding SmCoCuFeZr magnetic powder on the properties of anisotropic bonded NdFeB magnet were investigated in this work. The results show that, both magnetic properties and temperature stability of the bonded magnet can be improved by adding fine SmCoCuFeZr magnetic powder. In the present study, the optimal content of SmCoCuFeZr magnetic powder was about 20 wt.%, in this case, the Br, Hcj, and（BH）maxof the NdFeB/SmCoCuFeZr composite magnet achieved 0.943 T, 1250 kA/m, and168 kJ/m^3, respectively.